EP3804444A1

EP3804444A1 - Channel contention in wireless network

Info

Publication number: EP3804444A1
Application number: EP19727445.9A
Authority: EP
Inventors: Olli Alanen; Jari Pekka MUSTAJÄRVI; Hans Thomas HÖHNE; Janne Petteri Tervonen; Mika Kasslin
Original assignee: Nokia Technologies Oy
Current assignee: Nokia Technologies Oy
Priority date: 2018-06-11
Filing date: 2019-05-23
Publication date: 2021-04-14
Also published as: WO2019239006A1

Abstract

This document discloses a solution for selecting a contention method in a wireless network. According to an aspect, a method comprises: establishing, by an apparatus, an association with an access node of a wireless network; receiving, by the apparatus during the association, a first frame comprising a first value of a selection parameter for selection between a first contention method and a second contention method in the wireless network and select one of the first contention method and the second contention method on the basis of the first value; and receiving, by the apparatus during the association, a second frame comprising a second value, different from the first value, of the selection parameter for selection between the first contention method and the second contention method and select one of the first contention method and the second contention method on the basis of the second value.

Description

CHANNEL CONTENTION IN WIRELESS NETWORK

Field

Various embodiments described herein relate to the field of wireless networking and, particularly, to performing channel contention in a wireless network.

Background

In a wireless network, channel contention is a media access method for a shared medium such as a radio channel. A wireless device transmitting first on the radio channel gains access to the shared medium. A typical problem in such a system realizes when two devices attempt to transmit at the same time. This is known as a collision. To avoid collisions, several mechanisms have been proposed. One mechanism is carrier sensing mechanism where each device listens to the channel before attempting to transmit. If the channel is detected to be busy, a device waits until the channel is free again. Another method employs random backoff time. Upon detecting the channel to be free, a device starts a timer counting a random backoff time. If the channel remains free for the duration of the timer, the device accesses the channel.

Brief description

Some aspects of the invention are defined by the independent claims.

Some embodiments of the invention are defined in the dependent claims. According to an aspect, there is provided an apparatus comprising at least one processor and at least one memory including a computer program code, wherein the at least one memory and the computer program code are configured, with the at least one processor, to cause the apparatus to: establish an association with a station of a wireless network; transmit, during the association, a first frame comprising a first value of a selection parameter for selection between a first contention method and a second contention method in the wireless network; and transmit, during the association, a second frame comprising a second value, different from the first value, of the selection parameter for selection between the first contention method and the second contention method.

In an embodiment, the first contention method is a single-access contention method where only a single station of the wireless network gains access to a transmission medium at a time, and wherein the second contention method is a multi-access contention method where multiple stations are allowed to access the transmission medium at the same time.

In an embodiment, the first contention method is a backoff-based enhanced distributed channel access contention method of an 802.11 network, and wherein the second contention method is an uplink orthogonal frequency division multiple access random access method. In an embodiment, the at least one memory and the computer program code are configured, with the at least one processor, to cause the apparatus to transmit each of the first frame and the second frame in a broadcast frame.

In an embodiment, the at least one memory and the computer program code are configured, with the at least one processor, to cause the apparatus to transmit each of the first frame and the second frame as a beacon or trigger frame.

In an embodiment, the at least one memory and the computer program code are configured, with the at least one processor, to cause the apparatus to transmit each of the first frame and the second frame as a unicast frame.

In an embodiment, one of the first value and the second value indicates that the second contention method is preferred over the first contention method, and the other one of the first value and the second value indicates that the first contention method is preferred over the second contention method.

In an embodiment, one of the first value and the second value indicates that the second contention method is mandatory, and the other one of the first value and the second value indicates that the second contention method is not mandatory.

In an embodiment, one of the first value and the second value indicates that one of the first contention method and the second contention method is to be used for a first time interval before using the other one of the first contention method and the second contention method.

In an embodiment, the at least one memory and the computer program code are configured, with the at least one processor, to cause the apparatus to further transmit an information element indicating an estimate of density of resource allocations for the second contention method.

In an embodiment, a determined value of the information element indicates that there are currently no resource allocations to the channel contention according to the second contention method.

In an embodiment, the at least one memory and the computer program code are configured, with the at least one processor, to cause the apparatus to transmit, before the association, a third frame comprising the first value or the second value of the selection parameter.

According to another aspect, there is provided an apparatus comprising

at least one processor and at least one memory including a computer program code, wherein the at least one memory and the computer program code are configured, with the at least one processor, to cause the apparatus to: establish an association with an access node of a wireless network; receive, during the association, a first frame comprising a first value of a selection parameter for selection between a first contention method and a second contention method in the wireless network and select one of the first contention method and the second contention method on the basis of the first value; and receive, during the association, a second frame comprising a second value, different from the first value, of the selection parameter for selection between the first contention method and the second contention method and select one of the first contention method and the second contention method on the basis of the second value.

In an embodiment, the at least one memory and the computer program code are configured, with the at least one processor, to cause the apparatus to transmit to the access node an uplink buffer status report by using the second contention method while another apparatus is performing uplink data transmission to the access node.

In an embodiment, the at least one memory and the computer program code are configured, with the at least one processor, to cause the apparatus to further receive an information element indicating an estimate of density of resource allocations for the second contention method and to determine, on the basis the information element, whether or not to select the second contention method.

In an embodiment, a determined value of the information element indicates that there are currently no resource allocations to the channel contention according to the second contention method, and wherein the at least one memory and the computer program code are configured, with the at least one processor, to cause the apparatus to select the first contention method upon detecting the determined value of the information element.

In an embodiment, the at least one memory and the computer program code are configured, with the at least one processor, to cause the apparatus to: receive an information element indicating an estimate of a time interval between consecutive resource allocations for the second contention method; compare the time interval with delay requirement of a data stream in the apparatus; and select one of the first contention method and the second contention method on the basis of the comparison.

In an embodiment, the at least one memory and the computer program code are configured, with the at least one processor, to cause the apparatus to: receive an information element indicating an estimate of a bandwidth allocation for the second contention method; compare the estimate of the bandwidth allocation with a quality requirement of a data stream in the apparatus; and select one of the first contention method and the second contention method on the basis of the comparison.

In an embodiment, the first contention method is a backoff-based enhanced distributed channel access contention method of an 802.11 network, and wherein the second contention method is an uplink orthogonal frequency division multiple access random access method. In an embodiment, the first frame and the second frame are broadcast frames.

ln an embodiment, first frame and the second frame are beacon or trigger frames. ln an embodiment, the first frame and the second frame are unicast frames. ln an embodiment, one of the first value and the second value indicates that the second contention method is preferred over the first contention method, and the other one of the first value and the second value indicates that the first contention method is preferred over the second contention method.

ln an embodiment, one of the first value and the second value indicates that the second contention method is mandatory, and the other one of the first value and the second value indicates that the second contention method is not mandatory.

In an embodiment, the at least one memory and the computer program code are configured, with the at least one processor, to cause the apparatus to receive, before the association, a third frame comprising the first value or the second value of the selection parameter.

In an embodiment, the apparatus further comprises radio interface components providing the apparatus with radio communication capability.

According to another aspect, there is provided a method comprising: establishing, by an apparatus, an association with a station of a wireless network; transmitting, by the apparatus during the association, a first frame comprising a first value of a selection parameter for selection between a first contention method and a second contention method in the wireless network; and transmitting, by the apparatus during the association, a second frame comprising a second value, different from the first value, of the selection parameter for selection between the first contention method and the second contention method.

ln an embodiment, the first contention method is a single-access contention method where only a single station of the wireless network gains access to a transmission medium at a time, and wherein the second contention method is a multi-access contention method where multiple stations are allowed to access the transmission medium at the same time.

In an embodiment, the first contention method is a backoff-based enhanced distributed channel access contention method of an 802.11 network, and wherein the second contention method is an uplink orthogonal frequency division multiple access random access method.

In an embodiment, the at least one memory and the computer program code are configured, with the at least one processor, to cause the apparatus to transmit each of the first frame and the second frame in a broadcast frame. In an embodiment, the at least one memory and the computer program code are configured, with the at least one processor, to cause the apparatus to transmit each of the first frame and the second frame as a beacon or trigger frame.

ln an embodiment, the at least one memory and the computer program code are configured, with the at least one processor, to cause the apparatus to transmit each of the first frame and the second frame as a unicast frame.

ln an embodiment, one of the first value and the second value indicates that the second contention method is preferred over the first contention method, and the other one of the first value and the second value indicates that the first contention method is preferred over the second contention method.

In an embodiment, the method further comprises transmitting, by the apparatus, an information element indicating an estimate of density of resource allocations for the second contention method.

ln an embodiment, a determined value of the information element indicates that there are currently no resource allocations to the channel contention according to the second contention method.

In an embodiment, the method further comprises transmitting, by the apparatus before the association, a third frame comprising the first value or the second value of the selection parameter.

According to another aspect, there is provided a method comprising: establishing, by an apparatus, an association with an access node of a wireless network; receiving, by the apparatus during the association, a first frame comprising a first value of a selection parameter for selection between a first contention method and a second contention method in the wireless network and select one of the first contention method and the second contention method on the basis of the first value; and receiving, by the apparatus during the association, a second frame comprising a second value, different from the first value, of the selection parameter for selection between the first contention method and the second contention method and select one of the first contention method and the second contention method on the basis of the second value.

In an embodiment, the method further comprises transmitting, by the apparatus to the access node, an uplink buffer status report by using the second contention method while another apparatus is performing uplink data transmission to the access node. In an embodiment, the method further comprises: receiving, by the apparatus, an information element indicating an estimate of density of resource allocations for the second contention method and determining, by the apparatus on the basis the information element, whether or not to select the second contention method.

In an embodiment, a determined value of the information element indicates that there are currently no resource allocations to the channel contention according to the second contention method, the method further comprising selecting, by the apparatus, the first contention method upon detecting the determined value of the information element.

In an embodiment, the method further comprises: receiving, by the apparatus, an information element indicating an estimate of a time interval between consecutive resource allocations for the second contention method; comparing, by the apparatus, the time interval with delay requirement of a data stream in the apparatus; and selecting, by the apparatus, one of the first contention method and the second contention method on the basis of the comparison.

In an embodiment, the method further comprises: receiving, by the apparatus, an information element indicating an estimate of a bandwidth allocation for the second contention method; comparing, by the apparatus, the estimate of the bandwidth allocation with a quality requirement of a data stream in the apparatus; and selecting, by the apparatus, one of the first contention method and the second contention method on the basis of the comparison.

In an embodiment, the first frame and the second frame are broadcast frames.

In an embodiment, first frame and the second frame are beacon or trigger frames.

In an embodiment, the first frame and the second frame are unicast frames.

In an embodiment, one of the first value and the second value indicates that the second contention method is mandatory, and the other one of the first value and the second value indicates that the second contention method is not mandatory. In an embodiment, one of the first value and the second value indicates that one of the first contention method and the second contention method is to be used for a first time interval before using the other one of the first contention method and the second contention method.

In an embodiment, the method further comprises receiving, by the apparatus before the association, a third frame comprising the first value or the second value of the selection parameter.

According to an aspect, there is provided an apparatus comprising: means for establishing an association with a station of a wireless network; means for transmitting, during the association, a first frame comprising a first value of a selection parameter for selection between a first contention method and a second contention method in the wireless network; and means for transmitting, during the association, a second frame comprising a second value, different from the first value, of the selection parameter for selection between the first contention method and the second contention method.

According to an aspect, there is provided an apparatus comprising: means for establishing, an association with an access node of a wireless network; means for receiving, during the association, a first frame comprising a first value of a selection parameter for selection between a first contention method and a second contention method in the wireless network and select one of the first contention method and the second contention method on the basis of the first value; and means for receiving, during the association, a second frame comprising a second value, different from the first value, of the selection parameter for selection between the first contention method and the second contention method and select one of the first contention method and the second contention method on the basis of the second value.

According to an aspect, there is provided a computer program product embodied on a distribution medium readable by a computer and comprising program instructions which, when loaded into an apparatus, execute a computer process comprising: establishing an association with a station of a wireless network; transmitting, during the association, a first frame comprising a first value of a selection parameter for selection between a first contention method and a second contention method in the wireless network; and transmitting, during the association, a second frame comprising a second value, different from the first value, of the selection parameter for selection between the first contention method and the second contention method.

According to an aspect, there is provided a computer program product embodied on a distribution medium readable by a computer and comprising program instructions which, when loaded into an apparatus, execute a computer process comprising: establishing an association with an access node of a wireless network; receiving, during the association, a first frame comprising a first value of a selection parameter for selection between a first contention method and a second contention method in the wireless network and select one of the first contention method and the second contention method on the basis of the first value; and receiving, during the association, a second frame comprising a second value, different from the first value, of the selection parameter for selection between the first contention method and the second contention method and select one of the first contention method and the second contention method on the basis of the second value.

List of drawings

Embodiments are described below, by way of example only, with reference to the accompanying drawings, in which

Figure 1 illustrates a wireless communication scenario to which some embodiments of the invention may be applied;

Figure 2 illustrates a process for selecting a contention method according to an embodiment of the invention;

Figure 3 illustrates an example of resource allocation when using a multiple access contention method according to an embodiment of the invention;

Figure 4 illustrates a flow diagram of a process for selecting a contention method in an access node according to an embodiment of the invention;

Figure 5 illustrates a flow diagram of a process for selecting a contention method and estimating traffic intensity in an access node according to an embodiment of the invention;

Figures 6 and 7 illustrate some examples of resource allocations in the view of resource density estimation according to some embodiments of the invention;

Figure 8 illustrates a flow diagram of a process for selecting a channel contention method in a station according to an embodiment of the invention;

Figure 9 illustrates a signalling diagram of a procedure for switching a contention method according to an embodiment of the invention; and

Figures 10 and 11 illustrate block diagrams of structures of apparatuses according to some embodiments of the invention.

Description of embodiments

The following embodiments are examples. Although the specification may refer to“an”, “one”, or“some” embodiment(s) in several locations, this does not necessarily mean that each such reference is to the same embodiment s), or that the feature only applies to a single embodiment. Single features of different embodiments may also be combined to provide other embodiments. Furthermore, words“comprising” and“including” should be understood as not limiting the described embodiments to consist of only those features that have been mentioned and such embodiments may contain also features/structures that have not been specifically mentioned.

A wireless communication scenario to which some embodiments of the invention may be applied is illustrated in Figure 1. Figure 1 illustrates a plurality of wireless devices 100, 110 112, 114. A wireless device 100 may operate as an access node managing a wireless network and providing the other wireless devices 110 to 114 with wireless access, e.g. to other networks 130 such as the Internet. The wireless devices 100 to 1 14 may employ a physical layer and a medium access control (MAC) layer that comply with wireless local area network (WLAN) specifications based on IEEE 802.11 but, in other embodiments, the wireless devices may support another wireless communication protocol as an alternative or in addition to the WLAN. In the WLAN specifications, a wireless network may be called a basic service set (BSS), the access node may be called an access point, and the wireless devices 110 to 114 served by the access point are called stations (STA). In peer networks, a wireless network operating according to the WLAN specifications may be established amongst the stations. While some embodiments of the invention are described in the context of the IEEE 802.11 , it should be appreciated that these or other embodiments of the invention may be applicable to wireless networks based on other specifications, e.g. WiMAX (Worldwide Interoperability for Microwave Access), UMTS LTE (Long-term Evolution for Universal Mobile Telecommunication System), 5G cellular communication systems, including unlicensed radio variants, Multefire, mobile ad hoc networks (MANET), mesh networks, and other networks having cognitive radio features, e.g. transmission medium sensing features and adaptive capability to coexist with radio access networks based on different specifications and/or standards. Some embodiments may be applicable to networks having features under development by other IEEE task groups. Therefore, the following description may be generalized to other systems as well.

The access node 100 may be a fixed access point or a mobile access point. The wireless devices 110 to 114 may be terminal devices or stations capable of connecting or associating to the access node 100. A station 110 may establish a connection with any one of access nodes it has detected to provide a wireless connection within the neighbourhood of the terminal device. The connection establishment may include authentication in which an identity of the terminal device is established in the access node. The authentication may comprise setting up an encryption key used in the BSS. After the authentication, the access node and the station may carry out association in which the station is fully registered in the BSS, e.g. by providing the station with an association identifier (AID). The separate user authentication may follow association, which may also comprise building an encryption key used in the BSS. It should be noted that in other systems terms authentication and association are not necessarily used and, therefore, the association of the station to an access node should be understood broadly as establishing a connection between the station and the access node such that the station is in a connected state with respect to the access node and waiting for downlink frame transmissions from the access node and its own buffers for uplink frame transmissions. A station not associated to the access node is in an unassociated state. An unassociated station may still exchange some frames with the access node. Traditional WLAN networks employ a backoff-based channel contention procedure described in Background. As described in the Background, a device attempting channel access may, upon detecting the channel to be free, start a timer counting the backoff time. Upon detecting the channel to become occupied during the counting, the device may pause the timer until the channel is detected to be free again. WLAN has improved the backoff-based channel contention by introducing Enhanced Distributed Channel Access contention protocol in which the backoff time of a station is determined by priority of traffic the station is transmitting. Access classes such as background, best effort, video, and voice were introduced to define the traffic priority classes. A higher priority traffic is associated with a shorter backoff time, thus providing a higher probability of winning the contention ln the EDCA, the channel contention is carried out on a primary channel of the wireless network. A station winning the contention gains the access to the primary channel to transmit one or more frames. Upon winning the contention on the primary channel, the station may employ all the channels of the wireless network in the frame transmission. The channels may include the primary channel and one or more secondary or auxiliary channels. This type of channel contention is suitable for situations where the number of stations performing the channel contention is very limited. When the number of active stations increase, the channel contention may cause high delays to the frame transmissions.

1EEE 802.1 lax defines the next generation of the WLAN standard ft adds new features such as support for orthogonal frequency division multiple access (OFDMA) where an access node is capable of scheduling multiple stations to either receive or transmit simultaneously by dividing a frequency band of the wireless network to sub-bands and allocating different sub-bands to different stations ln this context, a sub-band refers to a group of subcarriers of a channel, which may also be called a resource unit. Sub-bands or resource units may be allocated dynamically, i.e. they may not be static over time. The protocol also defines an uplink OFDMA random access (UORA) scheme that provides an alternative to the legacy backoff-based contention protocol for uplink communication. The difference between the UORA and the legacy protocol is that UORA is based on OFDMA where multiple stations may gain channel access simultaneously. This results from the contention being performed separately per each parallel resource unit, e.g. a frequency sub-band. However, only one station may win the contention within a single resource unit. Different to this, the legacy channel contention principle allows only one station to win the contention on the whole operating frequency band of the network and, thus, gain access to the channel. Therefore, the UORA provides a better channel contention method in a situation where the wireless network is crowded.

Let us briefly describe some principles of the UORA. UORA channel contention begins when the access node transmits a trigger frame comprising an information element indicating resource units, e.g. frequency sub-bands, reserved for the UORA channel contention. The trigger frame may additionally schedule other sub-bands of the wireless network for other uplink OFDMA frame transmissions, e.g. data frame transmissions for selected one or more associated stations. UORA serves for the following exemplary purposes: unassociated stations can transmit management packets such as an association request to the access node by using the UORA; and associated stations with payload data buffered for uplink transmission can send a buffer status report (BSR) to the access node by using the UORA. A station detecting the trigger frame with the UORA allocation may start channel contention. The UORA-based channel contention may also employ the backoff factors, e.g. based on EDCA. When a backoff counter of the station reaches zero, the station may access any the sub-band(s) allocated to the station for use in UORA channel access.

As described above, the channel contention allowing multiple stations to win the contention is suitable for certain traffic situations while the legacy principle where only a single station may win the contention at a time may be more optimal to other traffic situations. The wireless network may support both channel contention methods, and the selection of the channel may be important from the perspective of the performance of a single station and the whole wireless network.

Figure 2 illustrates a signalling diagram of a procedure for performing selection of a channel contention method in a wireless network. The procedure comprises steps performed in an access node, e.g. the access node 100, and steps performed in a station such as any one of the wireless devices 110 to 114. Referring to Figure 2, the station and the access node establish an association in step 200. The association may be triggered by the station transmitting an association request to the access node. Upon establishing the association, the station is capable of carrying out data transmissions in the wireless network. In block 202, the access node performs resource allocation and determine a value of a selection parameter for selection between a first contention method and a second contention method. In step 204, the access node transmits, during the association, a first frame comprising the value. In step 204, the station receives the frame comprising the value of the selection parameter. Thereafter, the station may select in block 206 one of the first contention method and the second contention method on the basis of the first value. In step 208, the station may perform channel contention by using the selected channel contention method. Upon winning the contention, the station may transmit a frame to the access node.

Later during the association, the access node may perform a new resource allocation in block 210 and determine a different value for the selection parameter. In step 212, the access node may transmit a second frame comprising the different value of the selection parameter for the selection between the first contention method and the second contention method. The station receives the frame in step 212, and it may select one of the first contention method and the second contention method on the basis of the second value in block 214. Since the selection parameter now has a different value than in steps 202, 204, 206, the station may end up selecting a different channel contention method than in block 206. Thereafter, the station may perform a new channel contention in step 216 by using the channel contention method selected in block 214. The embodiment of Figure 2 enables the access node to select and recommend or enforce a determined channel contention method, and it also provides the station with multiple options for performing the channel contention. The provision and selection amongst multiple channel contention methods may improve the overall performance of the wireless network under various traffic scenarios.

In an embodiment, the first contention method is a single-access contention method where only a single station of the wireless network gains access to a transmission medium at a time, and the second contention method is a multi-access contention method where multiple stations are allowed to access the transmission medium at the same time. Such channel contention methods apply to the 802.11 networks where the first contention method may be the EDCA contention method, e.g. EDCA applied to a primary channel, and the second contention method may be the UORA contention method. However, in other systems, similar multiple contention methods may be employed, e.g. in MANETs a master node may carry out the functions of the access node while another node performs the functions of the station.

In an embodiment, the frames transmitted in steps 208 and 212 are broadcast frames, e.g. beacon frames or other management frames carrying management information.

In another embodiment, the frames transmitted in steps 204 and 212 are unicast or multicast frames addressed to the station. For example, in an associated state access node may transmit a dedicated selection parameter value to each station. The access node may also make the selection of the channel contention method per stations in blocks 202 and 210. This may allow flexible allocation of the stations to use any one or both channel contention methods. The access node may, for example, schedule some stations to use the first contention method while other stations are scheduled to use the second contention method.

Figure 3 illustrates a time-frequency diagram describing some embodiments of the resource allocation for the second contention method. Referring to Figure 3, the access node may divide the frequency band of the wireless network into sub-bands , for a determined time interval, and allocate, for the determined time interval, some of the sub-bands for the channel contention according to the second contention method (UORA resource 300). The access node may further allocate other sub- bands of the same channel for uplink data transmission (data resource 302). This resource allocation may be indicated in the frame transmitted in step 204 and/or 212. Whenever the access node schedules a resource for the second contention method, e.g. the UORA, the access node may select a value for the selection parameter that indicates, promotes, or recommends the use of the second contention method. Accordingly, a station receiving such a value may select the second contention method, or select the second contention method with a higher probability.

For another time interval, the access node may allocate the whole frequency band to data transmissions (data resource 304). In such a case, the access node may indicate unavailability of the second contention method or transmit a value of the selection parameter that indicates, promotes, or recommends the use of the first contention method. Accordingly, a station receiving such a value may select the first contention method, or select the first contention method with a higher probability.

For another time interval, the access node may carry out no allocations 305. ln such a time interval, the channel may be free for any wireless device to access ln such a case, the access node may indicate unavailability of the second contention method or transmit a value of the selection parameter that indicates, promotes, or recommends the use of the first contention method. Accordingly, a station receiving such a value may select the first contention method with a higher probability.

As illustrated by resource allocations 306, 308, 310, the resource units may be allocated flexibly for the uplink data transmissions and uplink channel contention according to the second contention method ln this case, the uplink data resource allocation 308 is between two channel contention resource allocations 306, 310 in the frequency domain.

ln an embodiment, a resource allocation may be periodic, as illustrated by the resource allocations 312, 314 that are the same as resource allocations 300, 302, respectively.

For yet another time interval, the access node may allocate the whole frequency band to the channel contention according to the second contention method ln such a case, the access node may indicate availability of the second contention method or transmit a value of the selection parameter that indicates, promotes, or recommends the use of the second contention method. Accordingly, a station receiving such a value may select the second contention method with a higher probability.

Let us then describe some embodiments of blocks 202 and 210 with reference to Figure 4. When performing the block 202 or 210, the access node may evaluate the traffic situation in the wireless network in block 400. The evaluation may comprise evaluation of at least one of the following traffic characteristics: a number of associated stations 406, traffic load 404, quality of service (QoS) classification of traffic currently transferred, and QoS classes of the devices in the network. Regarding the last feature, the device class may indicate a priority of each device regardless of the type of data the device is transmitting. The QoS may thus be a static parameter for a device. Upon performing the evaluation, the access node may perform comparison between the result(s) of the evaluation and one or more criteria for selecting the contention method (block 408). ln the embodiment of Figure 4, the comparison involves determining whether or not the criterion/criteria for using the second contention method (e.g. UORA) have been met. Next, some examples of the criteria are described.

Regarding block 406, the criterion for using the second contention method may include a certain threshold in terms of a number of associated stations lf the number of associated station is higher than the threshold, the access node may deem that the criterion for selecting the second contention method has been met. Regarding block 404, the criterion for using the second contention method may include a certain threshold in terms of the traffic load. A measure of the traffic load may be a channel utilisation rate, a number of detected collisions, a number of traffic streams, data throughput, or available data transfer capacity in the access node lf the traffic load is higher than the threshold, the access node may deem that the criterion for selecting the second contention method has been met. Regarding block the criterion for using the second contention method may include a certain threshold in terms of the QoS for one or more associated stations or data streams lf the QoS or an average QoS is below the threshold, indicating that the average QoS is associated with lower priority than the level associated with the threshold, the access node may deem that the criterion for selecting the second contention method has been met. The comparison in block 408 may include a combination of multiple comparisons and compute an aggregation of the comparison result.

Upon determining in block 408 that the criteria for using the second contention method has been met, the process may proceed to block 410 in which the access node allocates resources to the second contention method and transmits a frame indicating the availability of the second contention method. Accordingly, the access node may transmit a frame having a value of the selection parameter that indicates, promotes, or recommends the use of the second contention method ln this case, the selected value of the selection parameter may indicate that the second contention method is preferred over the first contention method. The frame may be transmitted in step 204 or 212 when the comparison is made in block 202 or 210, respectively.

Upon determining in block 408 that the criteria for using the second contention method has not been met, the process may proceed to block 412 in which the access node transmits a frame indicating the availability of the first contention method. Accordingly, the access node may transmit a frame having a value of the selection parameter that indicates, promotes, or recommends the use of the first contention method ln this case, the value of the selection parameter indicates that the first contention method is preferred over the second contention method. The frame may be transmitted in step 204 or 212 when the comparison is made in block 202 or 210, respectively.

ln an embodiment, the access node performs the process of Figure 4 for associated stations and, separately, for unassociated stations. The access node may use different selection criteria for the associated stations than for the unassociated stations and, thus, select a different channel contention method for the associated stations than for the unassociated stations. The access node may indicate in the transmitted frame, two values of the selection parameter: one for the associated stations and another for the unassociated stations. An unassociated station may use the value of the selection parameter associated with the unassociated stations in the selection of the channel contention method. An associated station may use the value of the selection parameter associated with the associated stations in the selection of the channel contention method. In an embodiment, the access node estimates density of the resources allocated to the second contention method and transmits, in the frame in step 204 or 212 indicating the availability of the second contention method, an information element indicating an estimate of the density of the resource allocations for the second contention method. Figure 5 illustrates an embodiment of a process for such operation of the access node. Figure 5 is illustrated as an embodiment of Figure 4 and, as a consequence, the same reference numbers may refer to the same or substantially similar operations as in Figure 4. Referring to Figure 5, the access node may, upon selecting the second contention method in block 408, perform the evaluation of the density of the resource allocations for the second contention method in block 500. The estimation may be carried out by evaluating the density in the previous resource allocations the access node has made. Machine learning can also be utilized for the estimation and optimal scheduling.

In an embodiment, the density is estimated in a time domain in terms of an interval between consecutive resource allocations for the second contention method. The time interval may be measured by the access node from the previous resource allocations. In embodiments that utilize only periodic resource allocations, the time interval may have a static value. However, in other embodiments the access node may allocate resources to the second contention method in an irregular/aperiodic manner, although some allocations may be periodic. In such a case, the measured density may vary over time, and the estimated density may represent an average time interval between consecutive resource allocations for the second contention method. The average may be computed as mean or median of the time intervals between consecutive resource allocations for the second contention method, for example. In this case, the access node may also compute and maintain variance of the estimate which indicates how regular the resource allocation is in general.

In an embodiment, the density is estimated in a frequency domain in terms of bandwidth allocated for the second contention method. The bandwidth may be represented in terms of a number of frequency resource units or sub- bands, for example. The bandwidth may be measured by the access node from the previous resource allocations. In embodiments that utilize a fixed bandwidth for resource allocations of the second contention method, the bandwidth may have a static value. However, in other embodiments the access node may employ dynamic bandwidth allocation. In such a case, the measured density may vary over time, and the estimated density may represent an average bandwidth of the resource allocations for the second contention method. The average may be computed as mean or median of the bandwidths allocated to the second contention method, for example. In this case, the access node may also compute and maintain variance of the estimate which indicates how regular the bandwidth of the resource allocation is in general.

In an embodiment, the density is estimated as a combination of the above-described embodiments. The density may be estimated both in the frequency domain in terms of a (average) bandwidth allocated for the second contention method and in the time domain in terms of an (average) interval between consecutive resource allocations for the second contention method.

Upon estimating the density of the resource allocations in block 500, the access node may carry out block 502 where the access node transmits a frame indicating the estimated density to the station(s). The access node may insert also further information on the traffic situation in the frame, e.g. information used when performing the traffic evaluation in blocks 402, 404, and/or 406. Such information may thus include traffic QoS information (block 402), information on the load in the network (block 404), and/or information on the number stations in the network (block 406) The frame may be the frame transmitted in step 204 or 212, e.g. a frame indicating the availability of the second contention method. The station receiving the frame may then evaluate the density in the selection of the contention method, and, in case the further information is available, the further information in the estimation of a probability for winning the channel contention. The density and the described pieces of further information may be considered as embodiments of the value of the selection parameter.

Figures 6 and 7 illustrate some examples of different densities of the resource allocations. Referring to Figure 6, the resource allocation for the second contention method is relatively static, e.g. periodic with static bandwidth allocation. The resources 600, 604 for the second contention method thus occur with a fixed periodicity and bandwidth. The remaining bandwidth may be allocated to the uplink data transmissions 610, 614. A non-scheduled interval 606 may be provided between the allocations to allow any station to gain access to the transmission medium.

Referring to Figure 7, the resource allocation pattern comprises multiples sets of periodic or regular resource allocations for the second contention method. Resource allocations 700 and 712 may belong a static or semi-static resource allocation pattern having fixed periodicity and bandwidth, and resource allocations 706 and 718 may belong another static or semi-static resource allocation pattern having fixed periodicity and bandwidth. The bandwidths of these two sets of regular resource allocations for the second contention method have the same periodicity and different bandwidths but, in other embodiments, the periodicities may be different as well, or the periodicities may differ while the bandwidths are equal. As described above, the bandwidth may be defined in terms of a number of resource units. Each resource unit may have a fixed bandwidth, e.g. a fixed number of consecutive sub-carriers. A single resource unit may cover a sub-band of a frequency channel, and all the allocated resource units cover a larger sub-band of the frequency channel or, in a special case, the whole frequency channel of the network. Any combination is possible in a flexible and dynamic resource allocation policy, when employed by the access node. Again, data allocations 702, 708, 714, 720 may be carried out to allow concurrent scheduled data transmissions and channel contention by using the second contention method ln some instances, the whole bandwidth may again be scheduled to data transmission (704), or no scheduling is made (716). ln the example of Figure 7, the density is an aggregate of two regular densities, and the variance of the density may be low. In other cases, the access node may employ no regular pattern when allocating resources to the second contention method and, in such a case, the variance may be substantially high.

The station may employ the information on the density of the resource allocations for the second contention method when performing the selection between the first contention method and the second contention method. Figure 8 illustrates such an embodiment in the form of a process executed by the station. Referring to Figure 8, upon detecting a resource for the second contention method in block 800, the station may record a stamp associated with the resource (block 802). The detection may be based on reception of a (beacon/trigger/probe response) frame comprising the resource allocation for the second contention method and the estimate of the resource density of the allocations for the second contention method. The stamp may be a time stamp indicating the timing of the resource, or the stamp may be a bandwidth stamp indicating the bandwidth of the resource, or the stamp may be a combination of the time stamp and the bandwidth stamp. This may serve as a reference in the selection process. In the embodiment of Figure 8, let us use the time stamp as an example. Thereafter, upon detecting the next frame containing a resource allocation for the second contention method in block 804, the station may extract from the frame the indication of the estimated density of the resources for the second contention method. Since this example uses the time stamp, the estimated density may comprise the time interval between consecutive resource allocations for the second contention method.

With the knowledge of the timing of the previous resource allocation and the estimate of the time interval between consecutive allocations and, optionally the variance also indicated in the received frame, the station is able to estimate when the next resource allocation will be available (block 806), e.g. by using the following equation:

T_t+i ⁼ T_t + TI + delay (variance)

where T, represents the timing of the previously detected resource allocation, TI is the estimate of the time interval between the consecutive allocations, and delay is a parameter proportional to the variance. The higher the variance is, the higher is the value of the delay parameter.

In block 806, the station also evaluates delay requirement, e.g. QoS classification, of data traffic the station is has acquired for transmission and, in block 808, compares the delay requirement with the estimated next resource allocation. If the next resource allocation is estimated to be so far in the future that there is a risk for not meeting the delay requirement, the station may select the first contention method and proceed to block 812. The first contention method may be the single-access contention method such as the EDCA. If the next resource allocation is estimated to be available such that the delay requirement can be met, the station may select the second contention method and proceed to block 810. The second contention method may be the multiple access contention method such as the UORA, and block 810 may comprise waiting for the next UORA resource. From blocks 810 and 812, the process may return to block 800 for detection of the next resource of the second contention method.

Further regarding the channel access in the embodiment of Figure 8, if the station has data buffered ready for transmission when executing block 800, the station may perform the channel contention in the detected UORA resource by decrementing the backoff time and accessing the UORA resource when the backoff time reaches zero. If the station acquires the data for transmission after block 800 or after the UORA resource has passed, the station may estimate the time until the next UORA resource. If the time is estimated to be acceptable, the station may perform the channel contention of block 810 in the next UORA resource.

In another example of block 804, the access node may signal the density of the UORA resource allocations in the following form: 77=20 ms +/- 5ms. The station may acquire the time stamps of a number of past UORA resource allocations, e.g. time stamps 0, 22, and 38 milliseconds (ms). The station may thus estimate that the next UORA resource allocation may be scheduled in a time window [55 ms; 65 ms]. If the station has buffered uplink data which expires (no longer meets the delay requirements of the data) at a time instant 45 ms, the station may decide to attempt the legacy channel contention in block 812 rather than wait for the next UORA resource allocation. Accordingly, the station may meet the delay requirements.

In an embodiment using the UORA, the station may estimate in block 806 a delay for transmitting the buffer status report in the next UORA resource and, thereafter, to send the data. In an embodiment where the UORA resource can be used to send uplink data, the station may estimate a delay for transmitting the data in the next UORA resource.

In a similar manner, the station may utilize the bandwidth as the resource density in blocks 806 and 808. If the station determines that the bandwidth is high enough for a sufficient probability of gaining the channel access by using the second contention method, the station may select the second contention method. The sufficiency of the bandwidth may be defined by a bandwidth threshold against which the comparison is made in block 808. The bandwidth threshold may depend on the access class of the traffic, for example. On the other hand, if the bandwidth of the estimated resource allocation is below the bandwidth threshold, the station may select the first contention method.

ln an embodiment, the access node may estimate and transmit multiple different resource intensities, e.g. one density in terms of the time interval between consecutive resource allocations and another density in terms of the bandwidth of a resource allocation. Another example based on Figure 7 would be indication of multiple different time intervals, e.g. when the access node applies multiple different periodic patterns in the resource allocation.

ln an embodiment using the 802.11 specifications, the access node may include the resource density /densities in the information element“Multiuser EDCA Parameter Set Element”. In an embodiment, the information element carrying information on the resource density in the frame may include at least one of the following pieces of the resource density information: the (mean) time interval between consecutive resource allocations for the second contention method in time units such as microseconds (us), the (mean) bandwidth of a resource allocation for the second contention method in terms of a number of resource units, and a statistical parameters such as the variance indicating the accuracy of the estimate. A special value of the information element (e.g. zero) may indicate that there are currently no resource allocations for the second contention method.

In the embodiment of Figure 8, the access node may indicate the resource density for the second contention method, and the selection of the contention method is made autonomously by each station that decides to perform channel contention. As described above, the selection may include the evaluation of the further information on the traffic situation in the network, provided that such information is available to the station.

ln some embodiments described above, the access node may transmit a recommendation of the contention method to be used in the frame, e.g. the beacon frame. The access node may recommend the use of the second contention method when the access node has allocated resources to the second contention method. However, at another instance the access node may recommend the use of the first contention method when even the access node has allocated resources to the second contention method. The recommendation may be based on the traffic situation in the wireless network, as described above ln such cases, each station may determine whether or not to obey the recommendation. However, each station may prioritize the use of the recommended contention method. Another factor such as the delay requirement of the uplink data traffic in the station may, however, cause the station to perform selection against the recommendation. Multiple recommendation classes may be provided for the access node to indicate the strength of the recommendation. The station may then assign a different weight for the second contention method in the decision-making on the bases of the recommendation class indicated by the access node.

ln an embodiment, the access node may indicate in the frame whether or not the second contention method is mandatory to the stations. Accordingly, the access node may enforce the use of the second contention method, if it chooses to do so. Accordingly, one value of the selection parameter may indicate that the second contention method is mandatory, and another value of the selection parameter indicates that the second contention method is not mandatory. A background for making the second contention method mandatory may be that the second contention method is more efficient when evaluating the performance of the whole network, while the first contention method may be more efficient for a single station. Therefore, without the enforced use of the second contention method the stations may prefer the first contention method.

ln an embodiment, the access node sets one of the first value and the second value to indicate that one of the first contention method and the second contention method is to be used for a first time interval before using the other one of the first contention method and the second contention method. Figure 9 illustrates an embodiment where the access node configures the station to first use the second contention method and, upon failing to gain channel access with a determined time interval T, to switch to the first contention method. Referring to Figure 9, the process may proceed in the above-described manner in steps 200 to 206. Accordingly, in step 204 the access node transmits a frame where the value of the selection parameter indicates to the station that the second contention method shall be used for the determined time interval before the use of the first contention method is allowed. Upon receiving the frame and extracting the value of the selection parameter, the station starts the channel contention according to the second contention method in block 206. If the station manages to gain channel access within the time interval T (block 900), the station transmits an uplink frame in step 208. Upon failing to gain channel access within the time interval T (block 900), the station switches the contention method to the first contention method in block 902. In step 904 upon winning the contention by using the first contention method, the station transmits an uplink frame to the access node.

In an embodiment using the 802.11 specifications, the access node may include the recommendation of the contention method in the information element“Multiuser EDCA Parameter Set Element”. In a similar manner, the indication of whether or not the second contention method is mandatory may be transmitted in the information element “Multiuser EDCA Parameter Set Element”. In a similar manner, the indication of that the second contention method shall be used for a determined time interval before switching to the first contention method may be transmitted in the information element“Multiuser EDCA Parameter Set Element”.

Figure 10 illustrates an embodiment of a structure of the above-mentioned functionalities of an apparatus executing the functions of the access node in the process of Figure 2 or any one of its embodiments. The apparatus may be the access node. The apparatus may comply with specifications of an IEEE 802.11 network and/or another wireless network. The apparatus may be or may be comprised in a computer (PC), a laptop, a tablet computer, a cellular phone, a palm computer, a sensor device, a router device, or any other apparatus provided with radio communication capability. In another embodiment, the apparatus carrying out the above-described functionalities of the service provider device is comprised in such a device, e.g. the apparatus may comprise a circuitry, e.g. a chip, a chipset, a processor, a micro controller, or a combination of such circuitries in any one of the above-described devices. The apparatus may be an electronic device comprising electronic circuitries for realizing some embodiments of the access node.

Referring to Figure 11, the apparatus may comprise radio interface components 12 configured to provide the apparatus with capability for bidirectional radio communication with other wireless devices in a wireless network. The radio interface components 12 may comprise analogue radio communication components and digital baseband processing components for processing received frames and frames to be transmitted. The radio interface components 12 may comprise standard well-known components such as a radio modem, an amplifier, filter, frequency-converter, (de)modulator, and encoder/decoder circuitries and one or more antennas.

The apparatus may further comprise a memory 20 storing one or more computer program products 22 configuring the operation of at least one processor of the apparatus, e.g. a communication circuitry described below. The memory 20 may further store a configuration database 24 storing operational configurations of the apparatus. The configuration database may, for example, store configuration parameters for the selection of the contention method according to any one of the above-described embodiments. The configuration database 24 may, for example, store traffic parameters for the execution of block 400.

The apparatus may further comprise a communication circuitry 14 configured to control or manage a wireless network operated by the access node. The communication circuitry 14 may comprise a frame handler 15 configured to manage the contents of the transmitted and received frames. The frame handler 15 may, for example, manage the contents of the frame that comprises the selection parameter. The communication circuitry may further comprise a contention method selector 18 configured to select the contention method for the wireless network. In an embodiment, the contention method selector may make the selection between the first and second contention method. The contention method selector may select only one of the contention methods to be used at a time, or the contention method selector may at some occasions enable both or all contention methods. The contention method selector 16 may employ a traffic analysis module in the selection. The traffic analysis module 16 may be configured to execute block 400, for example.

The contention method selector 18 may also determine the amount of resource to schedule for the second contention method. The contention method selector may then utilize a scheduler 17 to carry out the actual scheduling of the resources. The scheduler 17 may be configured to carry out scheduling of the resources for the second contention method in connection with scheduling resources to associated stations for uplink data transmission. The scheduler may employ any one of the above-described scheduling principles for scheduling the resources for the second contention method.

In an embodiment, the apparatus comprises at least one processor and at least one memory 20 including a computer program code 22, wherein the at least one memory and the computer program code are configured, with the at least one processor, to cause the apparatus to carry out the functionalities of the access node according to any one of the embodiments of Figures 2 to 7 and 9. According to an aspect, when the at least one processor executes the computer program code, the computer program code causes the apparatus to carry out the functionalities according to any one of the embodiments of Figures 2 to 7 and 9. According to another embodiment, the apparatus comprises the at least one processor and at least one memory 20 including a computer program code 22, wherein the at least one processor and the computer program code 22 perform the at least some of the functionalities of the access node according to any one of the embodiments of Figures 2 to 7 and 9. Accordingly, the at least one processor, the memory, and the computer program code form processing means for carrying out some embodiments in the access node. According to yet another embodiment, the apparatus carrying out some embodiments in the access node comprises a circuitry including at least one processor and at least one memory 20 including computer program code 22. When activated, the circuitry causes the apparatus to perform the at least some of the functionalities of the access node according to any one of the embodiments of Figures 2 to 7 and 9.

Figure 11 illustrates an embodiment of a structure of the above-mentioned functionalities of the apparatus executing the process of Figure 2 or any one of the embodiments performed by the station. The apparatus may be the station. The apparatus may comply with 1EEE 802.11 technology and/or another wireless networking technology. The apparatus may be or may be comprised in a computer (PC), a laptop, a tablet computer, a cellular phone, a palm computer, a sensor device, or any other apparatus provided with radio communication capability ln another embodiment, the apparatus carrying out the above-described functionalities is comprised in such a station, e.g. the apparatus may comprise a circuitry, e.g. a chip, a chipset, a processor, a micro controller, or a combination of such circuitries in any one of the above-described devices. The apparatus may be an electronic device comprising electronic circuitries for realizing some embodiments of the present invention.

Referring to Figure 11, the apparatus may comprise radio interface components 52 providing the apparatus with radio communication capability within one or more wireless networks. The radio interface components may comprise standard well-known components such as a radio modem, amplifier, filter, frequency-converter, (de)modulator, and encoder/decoder circuitries and one or more antennas.

The apparatus may further comprise a memory 60 storing one or more computer program products 62 configuring the operation of at least one processor of the apparatus. The memory 60 may further store a configuration database 64 storing operational configurations of the apparatus. The configuration database 64 may, for example, store rules for selecting a contention method on the basis of a selection parameter received from the access node, as described in the embodiments above. The memory 60 may further store an uplink data buffer for uplink data waiting for transmission.

The apparatus may further comprise a communication circuitry 54 managing wireless communications in the apparatus and controlling the operation of the radio interface according to any one of the above-described embodiments. The communication controller 54 may comprise a channel access controller 55 configured to manage channel access in the station. The channel access controller 55 may be configured to perform channel contention according to a contention method selected by a contention method selector 58. The contention method selector may be configured to select the contention method on the basis of the selection parameter received from the access node according to any one of the above-described embodiments. For example, when the selection parameter indicates the second selection method as mandatory, the contention method selector 58 may configure the channel access controller to use the second contention method without further considerations. If the selection parameter indicates availability of multiple contention methods, the contention method selector 58 may perform the selection according to current operational conditions of the station, e.g. the delay requirement of the data stored in the buffer 66. Upon selecting the contention method, the contention method selector 58 may configure the channel access controller to employ the selected contention method.

In an embodiment, the apparatus comprises at least one processor and at least one memory 60 including a computer program code 62, wherein the at least one memory and the computer program code are configured, with the at least one processor, to cause the apparatus to carry out the functionalities of the station according to any one of the embodiments of Figures 2 to 9. According to an aspect, when the at least one processor executes the computer program code, the computer program code causes the apparatus to carry out the functionalities according to any one of the embodiments of Figures 2 to 9. According to another embodiment, the apparatus comprises the at least one processor and at least one memory 60 including a computer program code 62, wherein the at least one processor and the computer program code 62 perform the at least some of the functionalities of the station according to any one of the embodiments of Figures 2 to 9. Accordingly, the at least one processor, the memory, and the computer program code form processing means for carrying out some embodiments of the present invention in the station. According to yet another embodiment, the apparatus carrying out some embodiments of the invention in the station comprises a circuitry including at least one processor and at least one memory 60 including computer program code 62. When activated, the circuitry causes the apparatus to perform the at least some of the functionalities of the station according to any one of the embodiments of Figures 2 to 9.

The circuitries or modules of the communication circuitries 14, 54 may be realized as sub-circuitries of the respective communication circuitries. In another embodiment, the circuitries or modules of the communication circuitries 14, 54 may be realized by computer program modules configured to execute of the respective functions of the circuitries or modules.

As used in this application, the term‘circuitry’ refers to one or more of the following: (a) hardware-only circuit implementations such as implementations in only analog and/or digital circuitry; (b) combinations of circuits and software and/or firmware, such as (as applicable): (i) a combination of processor(s) or processor cores; or (ii) portions of processor(s)/software including digital signal processor(s), software, and at least one memory that work together to cause an apparatus to perform specific functions; and (c) circuits, such as a microprocessor(s) or a portion of a microprocessor(s), that require software or firmware for operation, even if the software or firmware is not physically present.

This definition of‘circuitry’ applies to uses of this term in this application. As a further example, as used in this application, the term“circuitry” would also cover an implementation of merely a processor (or multiple processors) or portion of a processor, e.g. one core of a multi-core processor, and its (or their) accompanying software and/or firmware. The term“circuitry” would also cover, for example and if applicable to the particular element, a baseband integrated circuit, an application-specific integrated circuit (ASIC), and/or a field-programmable grid array (FPGA) circuit for the apparatus according to an embodiment of the invention.

The processes or methods described in Figures 2 to 9 may also be carried out in the form of one or more computer processes defined by one or more computer program. A separate computer program may be provided in one or more apparatuses that execute functions of the processes described in connection with the figures. The computer program(s) may be in source code form, object code form, or in some intermediate form, and it may be stored in some sort of carrier, which may be any entity or device capable of carrying the program. Such carriers include transitory and/or non-transitory computer media, e.g. a record medium, computer memory, read-only memory, electrical carrier signal, telecommunications signal, and software distribution package. Depending on the processing power needed, the computer program may be executed in a single electronic digital processing unit or it may be distributed amongst a number of processing units.

Embodiments described herein are applicable to wireless networks defined above but also to other wireless networks. The protocols used, the specifications of the wireless networks and their network elements develop rapidly. Such development may require extra changes to the described embodiments. Therefore, all words and expressions should be interpreted broadly and they are intended to illustrate, not to restrict, the embodiment. It will be obvious to a person skilled in the art that, as technology advances, the inventive concept can be implemented in various ways. Embodiments are not limited to the examples described above but may vary within the scope of the claims.

Claims

1. An apparatus comprising:

at least one processor; and

at least one memory including a computer program code, wherein the at least one memory and the computer program code are configured, with the at least one processor, to cause the apparatus to:

establish an association with a station of a wireless network; transmit, during the association, a first frame comprising a first value of a selection parameter for selection between a first contention method and a second contention method in the wireless network; and transmit, during the association, a second frame comprising a second value, different from the first value, of the selection parameter for selection between the first contention method and the second contention method.

2. The apparatus of claim 1, wherein the first contention method is a single-access contention method where only a single station of the wireless network gains access to a transmission medium at a time, and wherein the second contention method is a multi-access contention method where multiple stations are allowed to access the transmission medium at the same time.

3. The apparatus of claim 2, wherein the first contention method is a backoff-based enhanced distributed channel access contention method of an 802.11 network, and wherein the second contention method is an uplink orthogonal frequency division multiple access random access method.

4. The apparatus of any preceding claim, wherein the at least one memory and the computer program code are configured, with the at least one processor, to cause the apparatus to transmit each of the first frame and the second frame in a broadcast frame.

5. The apparatus of claim 4, wherein the at least one memory and the computer program code are configured, with the at least one processor, to cause the apparatus to transmit each of the first frame and the second frame as a beacon or trigger frame.

6. The apparatus of any preceding claim 1 to 3, wherein the at least one memory and the computer program code are configured, with the at least one processor, to cause the apparatus to transmit each of the first frame and the second frame as a unicast frame.

7. The apparatus of any preceding claim, wherein one of the first value and the second value indicates that the second contention method is preferred over the first contention method, and the other one of the first value and the second value indicates that the first contention method is preferred over the second contention method.

8. The apparatus of any preceding claim, wherein one of the first value and the second value indicates that the second contention method is mandatory, and the other one of the first value and the second value indicates that the second contention method is not mandatory.

9. The apparatus of any preceding claim, wherein one of the first value and the second value indicates that one of the first contention method and the second contention method is to be used for a first time interval before using the other one of the first contention method and the second contention method.

10. The apparatus of any preceding claim, wherein the at least one memory and the computer program code are configured, with the at least one processor, to cause the apparatus to further transmit an information element indicating an estimate of density of resource allocations for the second contention method.

11. The apparatus of claim 10, wherein a determined value of the information element indicates that there are currently no resource allocations to the channel contention according to the second contention method.

12. The apparatus of any preceding claim, wherein the at least one memory and the computer program code are configured, with the at least one processor, to cause the apparatus to transmit, before the association, a third frame comprising the first value or the second value of the selection parameter.

13. An apparatus comprising:

at least one processor; and

establish an association with an access node of a wireless network; receive, during the association, a first frame comprising a first value of a selection parameter for selection between a first contention method and a second contention method in the wireless network and select one of the first contention method and the second contention method on the basis of the first value; and receive, during the association, a second frame comprising a second value, different from the first value, of the selection parameter for selection between the first contention method and the second contention method and select one of the first contention method and the second contention method on the basis of the second value.

14. The apparatus of claim 13, wherein the at least one memory and the computer program code are configured, with the at least one processor, to cause the apparatus to transmit to the access node an uplink buffer status report by using the second contention method while another apparatus is performing uplink data transmission to the access node.

15. The apparatus of claim 13 or 14, wherein the at least one memory and the computer program code are configured, with the at least one processor, to cause the apparatus to further receive an information element indicating an estimate of density of resource allocations for the second contention method and to determine, on the basis the information element, whether or not to select the second contention method.

16. The apparatus of claim 15, wherein a determined value of the information element indicates that there are currently no resource allocations to the channel contention according to the second contention method, and wherein the at least one memory and the computer program code are configured, with the at least one processor, to cause the apparatus to select the first contention method upon detecting the determined value of the information element.

17. The apparatus of claim 15 or 16, wherein the at least one memory and the computer program code are configured, with the at least one processor, to cause the apparatus to: receive an information element indicating an estimate of a time interval between consecutive resource allocations for the second contention method; compare the time interval with delay requirement of a data stream in the apparatus; and select one of the first contention method and the second contention method on the basis of the comparison.

18. The apparatus of any preceding claim 13 to 17, wherein the at least one memory and the computer program code are configured, with the at least one processor, to cause the apparatus to: receive an information element indicating an estimate of a bandwidth allocation for the second contention method; compare the estimate of the bandwidth allocation with a quality requirement of a data stream in the apparatus; and select one of the first contention method and the second contention method on the basis of the comparison.

19. The apparatus of any preceding claim 13 to 18, wherein the first contention method is a single access contention method where only a single station of the wireless network gains access to a transmission medium at a time, and wherein the second contention method is a multi-access contention method where multiple stations are allowed to access the transmission medium at the same time.

20. The apparatus of claim 19, wherein the first contention method is a backoff-based enhanced distributed channel access contention method of an 802.11 network, and wherein the second contention method is an uplink orthogonal frequency division multiple access random access method.

21. The apparatus of any preceding claim 13 to 20, wherein the first frame and the second frame are broadcast frames.

22. The apparatus of claim 19, the first frame and the second frame are beacon or trigger frames.

23. The apparatus of any preceding claim 13 to 20, wherein the first frame and the second frame are unicast frames.

24. The apparatus of any preceding claim 13 to 23, wherein one of the first value and the second value indicates that the second contention method is preferred over the first contention method, and the other one of the first value and the second value indicates that the first contention method is preferred over the second contention method.

25. The apparatus of any preceding claim 13 to 24, wherein one of the first value and the second value indicates that the second contention method is mandatory, and the other one of the first value and the second value indicates that the second contention method is not mandatory.

26. The apparatus of any preceding claim 13 to 25, wherein one of the first value and the second value indicates that one of the first contention method and the second contention method is to be used for a first time interval before using the other one of the first contention method and the second contention method.

27. The apparatus of any preceding claim 13 to 26, wherein the at least one memory and the computer program code are configured, with the at least one processor, to cause the apparatus to receive, before the association, a third frame comprising the first value or the second value of the selection parameter.

28. The apparatus of any preceding claim 1 to 27, further comprising radio interface components providing the apparatus with radio communication capability.

29. A method comprising:

establishing, by an apparatus, an association with a station of a wireless network; transmitting, by the apparatus during the association, a first frame comprising a first value of a selection parameter for selection between a first contention method and a second contention method in the wireless network; and transmitting, by the apparatus during the association, a second frame comprising a second value, different from the first value, of the selection parameter for selection between the first contention method and the second contention method.

30. The method of claim 29, wherein the first contention method is a single-access contention method where only a single station of the wireless network gains access to a transmission medium at a time, and wherein the second contention method is a multi-access contention method where multiple stations are allowed to access the transmission medium at the same time.

31. The method of claim 30, wherein the first contention method is a backoff-based enhanced distributed channel access contention method of an 802.11 network, and wherein the second contention method is an uplink orthogonal frequency division multiple access random access method.

32. The method of any preceding claim 29 to 31, wherein the at least one memory and the computer program code are configured, with the at least one processor, to cause the apparatus to transmit each of the first frame and the second frame in a broadcast frame.

33. The method of claim 32, wherein the at least one memory and the computer program code are configured, with the at least one processor, to cause the apparatus to transmit each of the first frame and the second frame as a beacon or trigger frame.

34. The method of any preceding claim 29 to 31, wherein the at least one memory and the computer program code are configured, with the at least one processor, to cause the apparatus to transmit each of the first frame and the second frame as a unicast frame.

35. The method of any preceding claim 29 to 34, wherein one of the first value and the second value indicates that the second contention method is preferred over the first contention method, and the other one of the first value and the second value indicates that the first contention method is preferred over the second contention method.

36. The method of any preceding claim 29 to 35, wherein one of the first value and the second value indicates that the second contention method is mandatory, and the other one of the first value and the second value indicates that the second contention method is not mandatory.

37. The method of any preceding claim 29 to 36, wherein one of the first value and the second value indicates that one of the first contention method and the second contention method is to be used for a first time interval before using the other one of the first contention method and the second contention method.

38. The method of any preceding claim 29 to 37, further comprising transmitting, by the apparatus, an information element indicating an estimate of density of resource allocations for the second contention method.

39. The method of claim 38, wherein a determined value of the information element indicates that there are currently no resource allocations to the channel contention according to the second contention method.

40. The method of any preceding claim 29 to 39, further comprising transmitting, by the apparatus before the association, a third frame comprising the first value or the second value of the selection parameter.

41. A method comprising: establishing, by an apparatus, an association with an access node of a wireless network; receiving, by the apparatus during the association, a first frame comprising a first value of a selection parameter for selection between a first contention method and a second contention method in the wireless network and select one of the first contention method and the second contention method on the basis of the first value; and receiving, by the apparatus during the association, a second frame comprising a second value, different from the first value, of the selection parameter for selection between the first contention method and the second contention method and select one of the first contention method and the second contention method on the basis of the second value.

42. The method of claim 41, further comprising transmitting, by the apparatus to the access node, an uplink buffer status report by using the second contention method while another apparatus is performing uplink data transmission to the access node.

43. The method of claim 41 or 42, further comprising:

receiving, by the apparatus, an information element indicating an estimate of density of resource allocations for the second contention method and determining, by the apparatus on the basis the information element, whether or not to select the second contention method.

44. The method of claim 43, wherein a determined value of the information element indicates that there are currently no resource allocations to the channel contention according to the second contention method, the method further comprising selecting, by the apparatus, the first contention method upon detecting the determined value of the information element.

45. The method of claim 43 or 44, further comprising: receiving, by the apparatus, an information element indicating an estimate of a time interval between consecutive resource allocations for the second contention method; comparing, by the apparatus, the time interval with delay requirement of a data stream in the apparatus; and selecting, by the apparatus, one of the first contention method and the second contention method on the basis of the comparison.

46. The method of any preceding claim 41 to 45, further comprising: receiving, by the apparatus, an information element indicating an estimate of a bandwidth allocation for the second contention method; comparing, by the apparatus, the estimate of the bandwidth allocation with a quality requirement of a data stream in the apparatus; and selecting, by the apparatus, one of the first contention method and the second contention method on the basis of the comparison.

47. The method of any preceding claim 41 to 46, wherein the first contention method is a single access contention method where only a single station of the wireless network gains access to a transmission medium at a time, and wherein the second contention method is a multi-access contention method where multiple stations are allowed to access the transmission medium at the same time.

48. The method of claim 47, wherein the first contention method is a backoff-based enhanced distributed channel access contention method of an 802.11 network, and wherein the second contention method is an uplink orthogonal frequency division multiple access random access method.

49. The method of any preceding claim 41 to 48, wherein the first frame and the second frame are broadcast frames.

50. The method of claim 49, the first frame and the second frame are beacon or trigger frames.

51. The method of any preceding claim 41 to 48, wherein the first frame and the second frame are unicast frames.

52. The method of any preceding claim 41 to 51, wherein one of the first value and the second value indicates that the second contention method is preferred over the first contention method, and the other one of the first value and the second value indicates that the first contention method is preferred over the second contention method.

53. The method of any preceding claim 41 to 52, wherein one of the first value and the second value indicates that the second contention method is mandatory, and the other one of the first value and the second value indicates that the second contention method is not mandatory.

54. The method of any preceding claim 13 to 25, wherein one of the first value and the second value indicates that one of the first contention method and the second contention method is to be used for a first time interval before using the other one of the first contention method and the second contention method.

55. The method of any preceding claim 41 to 44, further comprising receiving, by the apparatus before the association, a third frame comprising the first value or the second value of the selection parameter.

56. An apparatus comprising:

means for establishing an association with a station of a wireless network; means for transmitting, during the association, a first frame comprising a first value of a selection parameter for selection between a first contention method and a second contention method in the wireless network; and means for transmitting, during the association, a second frame comprising a second value, different from the first value, of the selection parameter for selection between the first contention method and the second contention method.

57. An apparatus comprising:

means for establishing, an association with an access node of a wireless network; means for receiving, during the association, a first frame comprising a first value of a selection parameter for selection between a first contention method and a second contention method in the wireless network and select one of the first contention method and the second contention method on the basis of the first value; and means for receiving, during the association, a second frame comprising a second value, different from the first value, of the selection parameter for selection between the first contention method and the second contention method and select one of the first contention method and the second contention method on the basis of the second value.

58. A computer program product embodied on a distribution medium readable by a computer and comprising program instructions which, when loaded into an apparatus, execute a computer process comprising:

establishing an association with a station of a wireless network; transmitting, during the association, a first frame comprising a first value of a selection parameter for selection between a first contention method and a second contention method in the wireless network; and transmitting, during the association, a second frame comprising a second value, different from the first value, of the selection parameter for selection between the first contention method and the second contention method.

59. A computer program product embodied on a distribution medium readable by a computer and comprising program instructions which, when loaded into an apparatus, execute a computer process comprising: establishing an association with an access node of a wireless network; receiving, during the association, a first frame comprising a first value of a selection parameter for selection between a first contention method and a second contention method in the wireless network and select one of the first contention method and the second contention method on the basis of the first value; and receiving, during the association, a second frame comprising a second value, different from the first value, of the selection parameter for selection between the first contention method and the second contention method and select one of the first contention method and the second contention method on the basis of the second value.