WO2010034354A1

WO2010034354A1 - Method of operating a user equipment and user equipment

Info

Publication number: WO2010034354A1
Application number: PCT/EP2008/063023
Authority: WO
Inventors: Thomas Malcolm Chapman; Lukasz Koszulanski; Krystian Pawlak; Malgorzata Wimmer
Original assignee: Nokia Siemens Networks Oy
Priority date: 2008-09-29
Filing date: 2008-09-29
Publication date: 2010-04-01

Abstract

A method of operating a user equipment of a communication network is provided, wherein the method comprises sending an information density indicator from the user equipment to another network element, wherein the information density indicator relates to an amount of information sent during a respective time interval.

Description

Method of operating a user equipment and user equipment

Field of invention

The present invention relates to a method of operating a user equipment, in particular a user equipment of a cellular communication network. Moreover, the invention relates to a method of transmitting data. Further, the invention relates to a user equipment. Furthermore, the invention relates to a processing unit.

Art Background

For future communication systems a plurality of different communication protocols or schemata are thought of. In general according to such protocols data are transmitted during so called time slots or time intervals. For example, Release 6/7 supports both 2 ms and 10 ms transmission time intervals (TTIs) for E-DCH including switching from one TTI to another. The benefit of longer TTI is that it improves the received energy per information bit for power-limited user equipments (UEs) because the received energy is an increasing function of the transmission time. Improved received energy per information bit for power limited UEs can contribute to better coverage. In general, it is preferable to use the 2 ms TTI, and so the 10ms TTI should only be used where the UE has become power limited. However switching to a longer TTI has some disadvantages. One of this is that switching between TTI lengths always takes some time, what may lead to unnecessary data losses if the radio channel is rapidly worsening and the user equipment is rapidly running out of power. Additionally switching to a longer TTI may have a negative impact on delay sensitive services since a longer TTI also implies larger latency. Currently, TTI switching can only be done slowly, with a risk that data packets get lost during the switching if the radio channel is changing rapidly, due to the fact that it is managed from the radio network controller (RNC) . Thus a radio link reconfiguration is required for switching the TTI length. This implies that the switching cannot keep up with fast channel variations, and the algorithm for deciding to switch must be conservative. A conservative algorithm has disadvantages such as reducing system capacity and/or increasing UE battery usage. Since the 2 ms TTI can benefit from CPC and is more link efficient, this contributes to reduced capacity and UE battery life. Also, the nodeB scheduler must manage 2 TTI lengths.

One of the alternatives proposes enhancement of the enhanced uplink (EUL) coverage by decreasing the time between retransmission by letting the UE make a certain number of repetitions without waiting for a NACK in between them. This allows the UE to transmit more repetitions before the maximum packet delay is reached.

It is therefore motivated to look to improved TTI switching or for alternative solutions which may contribute to the UL coverage enhancement.

Summary of the Invention

Thus, there may be a need for improved method of operating a user equipment, a method of transmitting data, a user equipment, a processing unit, a program element, and a computer-readable medium possibly contributing to a coverage enhancement in a communication network.

This need may be met by a method of operating a user equipment, a method of transmitting data, a user equipment, a processing unit, a program element, and a computer-readable medium according to the independent claims. Further embodiments of the present invention are described by the dependent claims.

According to an exemplary aspect of the invention a method of operating a user equipment of a communication network is provided, wherein the method comprises sending an information density indicator from the user equipment to another network element, wherein the information density indicator relates to a time interval during which an amount of information is sent .

In particular, the communication network may be an UMTS communication network which may use a WCDMA protocol, for example. For example, the another network element may be a serving nodeB, a non serving nodeB, another user equipment, a relay node, or the like. In particular, the information duration may relate to a time interval during which a number of information is transmitted. Alternatively, the information density indicator may relate to an amount of information sent during a respective time interval, wherein the information density may relate to a number of information per second. According to an exemplary aspect of the invention a method of transmitting data from a first network element to a second network element of a communication network is provided, wherein the method comprises operating a user equipment according to an exemplary aspect of the invention, and performing a transmission of a data set taking into account the information density indicator.

In particular, the first and/or the second network element may be the user equipment, a serving nodeB, a non serving nodeB, another user equipment, a relay node, or the like.

According to an exemplary aspect of the invention a user equipment for a communication network is provided, wherein the user equipment comprises a transmitting unit adapted to send an information density indicator from the user equipment to another network element, wherein the information density indicator relates to a time interval during which an amount of information is sent.

In particular, the UE may comprise a change unit to change the information density based on the information density indicator. Furthermore, the user equipment may comprise a decision unit adapted to decide on a change of the information density indicator.

According to an exemplary aspect of the invention a processing unit for a nodeB of a communication network is provided, wherein the processing unit is adapted to process an information density indicator received from a user equipment .

In particular, the processing may relate to the decoding, interpreting, or the like of the information density indicator. For example, the nodeB may switch a state and/or may take into account the content of the information density indicator for further transmission and/or receptions in the communication network.

According to an exemplary aspect of the invention a program element is provided, which, when being executed by a processor, is adapted to control or carry out a method according to an exemplary aspect of the invention.

According to an exemplary aspect of the invention a computer- readable medium is provided, in which a computer program is stored which, when being executed by a processor, is adapted to control or carry out a method according to an exemplary aspect of the invention.

The term "information density indicator" may particularly denote an indicator associated to a time interval during which an amount of bits, data or information bits can be transmitted. In particular, the information density should be distinguished from bit transfer rates since according to the concept of this application a repeated transmission or repetition or TTI length increase would not increase the information density. That is, in case a transmission of identical information or bits is repeated or transmitted in larger TTI the information density is decreased when the bit transfer rate is held constant.

The term "time interval" may particularly denote one or a multiple of transmission time intervals used for a transmission. It may also denote a number of frames or time- slots or any other indications that can be interpreted as a time interval It should be noted that in case the "information density indicator" may relate to one parameter only, e.g. to the time duration or to a repetition rate, or to more than one parameter, e.g. switching time and number of repetitions, e.g. the TTI length and the amount of information to be transmitted during that length. In this case the value of these parameters may be contained distinctly or separately from each other or both together in the information density indicator. It may also be possible to send several information density indicators each relating to a specific parameter .

By providing a user equipment which is adapted to send or transmit an information density indicator it may be possible to provide a measure to signal a change of the state of a communication, e.g. a change of an amount of repetitions or fast transmission time interval (TTI) switching between different network elements of a communication network. Furthermore, the signalling may be performable independent from the fact which entity takes the decision on initiating the change of the state, e.g. starting repetitions or TTI switching. In particular, the method may be used for soft handover to inform non serving nodeBs .

Next, further exemplary embodiments of the method of operating a user equipment for a communication network are described. However, these embodiments also apply to the method of transmitting data, the user equipment, the processing unit for a nodeB, the program element, and the computer-readable medium.

According to another exemplary embodiment of the method the user equipment is sending the information density indicator in response to a request for changing the information density of sent information.

In particular, the request for changing the information density may be initiated by a nodeB, e.g. a serving nodeB, the user equipment, or another network element. For example, the request for changing may be implemented in HS-SCCH orders in case of a UMTS communication network. The signalling may thus be performed independently of the entity performing the decision to alter or change the communication scheme, e.g. by initiating repetitions or TTI switching to enhance the coverage. For example, the serving nodeB may make the decision to change the amount of repetitions or to change the TTI length, i.e. the information density. The serving nodeB may send this decision to the UE. This, decision may be performed by a decision unit adapted to decide the change of an information density, wherein the information density may be related to the time during which information is transmitted. Furthermore, the serving nodeB may have a reception device adapted to receive the UE power headroom from a UE. For example, in order to inform the UE about the amount of repetitions the serving nodeB may send orders via e.g. the fast Ll signalling (HS-SCCH orders) . Alternatively, the UE may decide on the amount of repetitions, in which case the UE needs to signal the number of repetitions to the serving Node B.

According to another exemplary embodiment of the method the changing request is initiated when a predetermined threshold of a parameter is reached.

In particular, the parameter may be indicative of a coverage of a respective cell of the communication network. It should be noted that the term "reaching" the threshold includes a rising above the threshold as well as falling below the threshold. By initiating the changing request depending on a predetermined threshold or criterion it may be possible to activate state changes, e.g. TTI bundling mechanism or TTI switching, in specific cases only, e.g. in power limited scenarios only.

According to another exemplary embodiment of the method the parameter is the user equipment power headroom.

Thus, the changing request may be initiated when the UE power headroom (UPH) is reaching a limit or threshold. Of course the limit may be reached by rising above or falling below the threshold. Therefore, the invention may foresee triggering of a state change mechanism, e.g. the bundling mechanism, based on uplink power headroom (UPH) reports. In case if UPH reports a UE' s power limitation, the decision may be made that consecutive TTIs are grouped and assigned to the same HARQ process. Thus, adaptation of TTI length or repetition may be based on power limit so that when UE power is reaching power limit, the UE changes the number of repetitions that are performed without waiting for respective ACK/NACK messages or changes the TTI length, e.g. when UE power headroom is above or equal to a limit. UE transmission power headroom (UPH) may be the ratio of the maximum UE transmission power and the corresponding DPCCH code power, and might be calculated as following: UPH = P_n^ /P_DPCCH wherein: P_{maXl tx} = min {Maximum allowed UL TX Power, P_max} is the UE maximum transmission power; Maximum allowed UL TX Power is set by UTRAN. Furthermore, P_max is the UE nominal maximum output power according to the UE power class and P_DPCCH is the transmitted code power on DPCCH. The reference point for the UE transmission power headroom may be the antenna connector of the UE. In particular, there can be more than one threshold, e.g. an upper threshold and a lower threshold, e.g. a lower power value. There can be for example defined a threshold that is below the UE power headroom.

According to another exemplary embodiment of the method the changing request is initiated every time when the predetermined threshold of the parameter is reached.

By sending a changing request every time when the predetermined threshold of the parameter is reached an iterative or stepwise adaptation of an information density may be enabled, e.g. a stepwise increase or decrease of a repetition rate or TTI length. That is, in a first step the information density may be increased only a small step. However, if after this small step, corresponding to a small adaptation, the corresponding information density is still not suitable a further changing request may be initiated or sent to further adapt the information density. That is, the number of repetitions may be set gradually - according to the current UPH measurements, e.g. two TTIs are grouped together when power limitation is signalled for the first time, four TTIs may be merged when UPH reports power limitation for the second time and finally eight repetitions may be utilized with third UPH alarm

According to another exemplary embodiment of the method the information density indicator relates to a repetition rate. The term "repetition rate" may particularly denote the number of times a transmission of a specific information is repeated without receiving a request of retransmitting the specific information, e.g. by a non acknowledge (NACK) message. This may correspond to a so called transmission time interval

(TTI) bundling. That is, a specific information is sent several times in order to increase the coverage and/or sureness of the transmission of the information even in cases no message indicating a failure of correct transmission is received. Thus, the request for changing the information density may be a request to change the number of repetitions, e.g. decreasing the number of repetitions or increasing the number of repetitions.

According to another exemplary embodiment of the method the information density indicator relates to a transmission time interval length.

In particular, the transmission time interval (TTI) length may be set to a specific value based on the information density indicator. For example, the information density indicator may indicate a state in which the transmission time interval has a length of 2 ms, 4 ms, 6 ms, 8 ms, or 10 ms . The changing of the TTI may also be called switching so that this process may be called TTI switching. Thus, the request for changing the information density may be a request to change the TTI length, e.g. decreasing the TTI length or increasing the TTI length.

According to another exemplary embodiment of the method the information density indicator is sent in a data frame. In particular, the data frame may be or contain a transport format combination indicator (TFCI) or an enhanced TFCI (E- TFCI) . That is, the known E-TFCI may be reinterpreted so that the information density indicator is associated to a TTI length or number of repetition, for example, may be encoded in the E-TFCI leading to a common multiplexing/transmitting of the number of repetitions and the data frames. The E-TFCI, in addition to the amount of information to be transmitted, may include the information on the TTI length or the number of repetitions.

According to another exemplary embodiment of the invention, a mapping between the chosen E-TFCI and the corresponding E-DCH transport block size is given in a transport block size table that is e.g. valid for 2ms TTI and for 10 ms TTI. In this case the E-TFCI mapping contains the information on the TTI length. The mapping may also be given in a table that contains the amount of repetitions. A user equipment may select the E-TFCI mapping based on such table. A nodeB may select the E-TFCI mapping based on such table.

For example, in order that the user equipment may select the E-TFCI mapping base on this table, there has to be a signaling from the base station or the radio network controller to the UE that UE has to use this special table.

According to another exemplary embodiment of the method the information density indicator corresponds to a signal power.

In particular, the information density indicator may correspond to a signal power ratio, e.g. a ratio between a power transmitted per TTI and an accumulated transmitted power. That is, an indication of an information density may be given by adjusting or setting a power ratio to a specific value. For example, the power ratio between E-DPDCH and E- DPCCH may be adjusted to signal the information density indicator, e.g. the power ratio between E-DPDCH or E-DPCCH and DPCCH may be adjusted to signal the information density indicator.

Next, further exemplary embodiments of the method of transmitting data are described. However, these embodiments also apply to the method of operating a user equipment, the user equipment, the processing unit for a nodeB, the program element, and the computer-readable medium.

According to another exemplary embodiment of the method the transmission of the data set includes a repeated transmission, and wherein in the repetition control channel information is not transmitted.

That is, control information, e.g. a DPCCH or E-DPCCH, may only be transmitted once at the beginning and in the repetition or retransmission this information is not retransmitted or repeated. Thus, the repeated transmission may be free of control channel information. Although, the transmission of E-DPCCH may be maintained in parallel to all repetitions, for the sake of the transmitted power in uplink it may be advantageous to maintain E-DPCCH only during first TTI in the bundle. The energy saved during repetitions could be utilized for data transmission. Thus, it may be possible to repeat or retransmit E-DPCCH according to special rules leading to a schema in which control signals and data are multiplexed normally but for repetition only the data are repeated. Such a schema may be in particular useful for WCDMA schemata . Next, further exemplary embodiments of the user equipment are described. However, these embodiments also apply to the method of operating a user equipment, the method of transmitting data, the processing unit for a nodeB, the program element, and the computer-readable medium.

According to another exemplary embodiment of the method the user equipment is adapted to perform a transmission time interval switching based on the information density indicator.

According to another exemplary embodiment of the method the user equipment is adapted to change a number of repetitions an information is sent based on the information density indicator.

It should be noted that the user equipment may be adapted for transmitting data to a plurality of nodeBs or base stations. Furthermore, it should be noted that a processing unit according to an exemplary aspect of the invention may be included into a nodeB or base station which may know or which may not know the decision on the information density, e.g. a base station from the active set, e.g. a non serving base station. In case that the base station does not know the decision the information density indicator may be used to signal the decision to the nodeB, e.g. the serving nodeB. According to an exemplary aspect of the invention the nodeB or base station may be adapted to perform a soft handover to another nodeB. For example, a communication network may be provided comprising a plurality of user equipments according to an exemplary aspect of the invention and a plurality of nodeBs having a processing unit according to an exemplary aspect of the invention, wherein at least one of the plurality of nodeB is adapted to perform a soft handover to another one of the plurality of nodeBs .

Summarizing an exemplary aspect of the invention may be seen in providing a method of informing network elements of a communication network over a used communication or coding scheme by using an information density indicator. This information density indicator is sent by a user equipment and may relate to a repetition number and/or a TTI length. The information density indicator may in particular be sent to a non serving nodeB in order to facilitate a soft handover in case of UMTS. Such a method may enable a TTI bundling in an UMTS communication network which still aligns with the existing number of HARQ processes, the possible number of autonomous repetitions may be limited to {0, 1, 3, 7} for 2 ms TTI and {0, 1, 3} for 10 ms TTI, which results in a total transmission burst (including the first transmission) of {1, 2, 4, 8} TTIs in the 2 ms TTI case and {1, 2, 4} TTIs in the 10 ms TTI case. It should be noted that LTE bundling solution may not require UE to nodeB signalling as the serving nodeB sets the number of retransmissions, and soft handover (SHO) is not defined for LTE.

Regardless of the TTI bundling activation by a user equipment or the serving nodeB it may also be essential to handle soft handover. In soft handover, regardless of the activation mechanism, non serving nodeBs may not be aware of the number of transmissions and/or may not be aware of the information density, e.g. the number of repetitions or the TTI length. Therefore, non serving nodeBs should be informed about applied repetition scheme. The use of Iub for this purpose would require involvement of the radio network controller

(RNC) and defeat the purpose of fast bundling, therefore a viable way for informing the non serving nodeBs of the amount of repetitions or retransmissions may be UE signalling, even if the serving nodeB configures the number of transmissions, configures the number of repetitions, and/or configures the TTI length. In general there are possible different signalling methods to inform the nodeB about the number of repetitions or the TTI length. Some of the possible signalling methods may be E-TFCI reinterpretation, offset detection on E-DPCCH, or mixture of E-TFCI reinterpretation and offset detection on E-DPCCH. Furthermore, method based on similarity of consecutive TTI or so called blind detection methods may be used. The bundling and/or TTI switching may be activated by either serving nodeB orders an UE to transmit additional retransmissions, or UE may autonomously decide about out-of-HARQ cycle transmissions. Both decisions may be taken based on the information about power headroom available at a UE.

The advantage of TTI bundling scheduled by a nodeB may be that HARQ process management may be easily maintained. On the other hand allowing UE for autonomous repetitions may benefit in a quick reactions to the uplink power headroom fluctuations. Moreover the signalling applied by a UE may be utilized to handle soft handover. With such approach non serving nodeBs will be notified about applied retransmission or repetition scheme.

Furthermore, it should be noted that in case that a E-DPCCH power offset is used for indicating the information density, i.e. as an information density indicator" this may in particular relate to a TTI length, whereas a using of E-TFCI as information density indicator may in particular relate to a number of bits or number of repetitions. The E-TFCI, in addition to the amount of information to be transmitted, may include the information on the TTI length or the number of repetitions. However, for example the E-DPCCH power offset may also be used for indicating TTI length and/or number of repetition as well.

It has to be noted that embodiments of the invention have been described with reference to different subject matters. In particular, some embodiments and aspects have been described with reference to apparatus type claims whereas other embodiments have been described with reference to method type claims. However, a person skilled in the art will gather from the above and the following description that, unless otherwise notified, in addition to any combination of features belonging to one type of subject matter also any combination between features relating to different subject matters, in particular between features of the apparatus type claims and features of the method type claims is considered to be disclosed within this application.

The aspects and exemplary embodiments defined above and further aspects of the invention are apparent from the example of embodiment to be described hereinafter and are explained with reference to these examples of embodiment.

Brief Description of the Drawings

Fig. 1 schematically shows a TTI bundling concept.

Fig. 2 schematically illustrates effects of a gradual activation of a TTI bundling.

Fig. 3 schematically illustrates effects of a gradual deactivation of a TTI bundling. Fig. 4 schematically illustrates E-DPCCH gating during repetitions .

Fig. 5 schematically illustrates a TTI switching.

Fig. 6 schematically illustrates a communication network.

Detailed Description

The illustration in the drawings is schematic. It is noted that in different figures, similar or identical elements may be provided with the similar or identical reference signs.

Fig. 1 schematically shows a transmission time interval (TTI) bundling concept in the context of a HARQ process. In the first line 100 a transmission of data according to a normal HARQ process is shown without performing a bundling and thus corresponding to an ordinary high speed uplink packet access (HSUPA) . In particular, a retransmission is performed of eight packets 101 to 108 corresponding to a time interval of 16 ms in case a NACK is received at the sending side. In the second line 110 a HSUPA transmission implementing TTI bundling is schematically depicted. In particular, the same data packet 111 is repeated eight times before a new data packet 112 is transmitted. The repetitions are performed without waiting for a NACK message. In case a NACK message is received the whole bundle of the data packets 101 is retransmitted. In Fig. 1 the bundle size is 8. However, different bundle sizes, e.g. 2 and 4 are also possible.

Fig. 2 schematically illustrates effects of a gradual activation of a TTI bundling. TTI bundling mechanism operates in power limited scenarios, hence it may be connected to uplink power headroom (UPH) measurements. That is, the activation of additional repetitions may be triggered by the UPH measurements - as soon as power limitation at UE is reported, TTI bundling mechanism may be enabled. Furthermore, there may be implemented a gradual activation of repetitions, i.e. with each power limitation alarm, TTI bundle size is increased gradually according to the available bundle size of {1, 2, 4, 8} TTIs. The effect of a gradual activation of repetitions is schematically depicted in Fig. 2.

In particular, Fig. 2 shows the transmission power (Tx power) in dB over time. Line 201 indicates the maximum Tx power, while line 202 indicates the total Tx power showing different areas corresponding to different bundling sizes. Furthermore, line 203 indicates the accumulative Tx power and line 204 indicates the transmission power of the dedicated physical control channel (DPCCH) . Additionally, the points in time when the transmission scheme changes are labelled in Fig. 2. At 205 a first repetition is activated corresponding to a bundle size of 2 and leading to a first change of the continuous course of the total Tx power. At 206 a second repetition is activated corresponding to a bundle size of 4 and leading to a second change of the continuous course of the total Tx power. At 207 a third repetition is activated corresponding to a bundle size of 8 and leading to a third change of the continuous course of the total Tx power.

In a situation when UPH reports power limitation at UE according to the ordinary power control behaviour when maximal transmit power is exceeded, transmit power is scaled down. According to an exemplary embodiment whenever maximal transmit power is reached for the first time, corresponding to the point 204 in Fig. 2, then eligible entity, e.g. the respective UE or the corresponding serving nodeB, triggers a decision to enable first repetition. From this point each HARQ process is repeated in two consecutive TTIs. Moreover E- DPDCH power offset (/3_eci) may be decreased by number of repetitions - in this case by factor of two (N_rep = 2) . Total power can be calculated then from equation 1 :

total _ TxPower_perTT[ = TxPower_DPCCH

( i ;

Accumulative transmit power from two consecutive TTIs is now calculated from the equation 2:

total _TxPower_all__{bundled TTh} = TxPower_DPCCH

N_Rep

A c

( 2 ) ,

wherein β_c, β_d and β_ec are abstract variables that relate to the power relationships between the transmitted channels. The ratio βd/βc is the ratio of the amplitude of the DPDCH signal to the DPCCH signal amplitude, whilst β_ed/β_c is the ratio of the E-DPDCH signal amplitude to the DPCCH signal amplitude.

The repetition of a TTI may result in a decreased transmitted power per TTI however the accumulated power is kept on the same level. This mechanism may save the resources of uplink power headroom, thus possibly maintaining the transmission in power limited conditions.

The amount of repetitions may be increased if saved power resources will be consumed again by power control mechanism. When single retransmission is insufficient, to keep total transmit power under the maximum threshold, the size of TTI bundle may be increased gradually, i.e. after second UPH alarm three repetitions should be utilized and finally after third UPH report bundle size should increase to 8 TTIs or seven repetitions. This scheme may keep the continuous level of DPCCH which results in good channel estimation and proper SIR target setting, thus possibly enables correct reception and power control behaviour.

Fig. 3 schematically illustrates effects of a gradual deactivation of a TTI bundling. In particular, on the left side of Fig. 3 Fig. 2 is repeated while on the right side the deactivation of repetitions is shown. For the activation part it is referred to the description of Fig. 2. In the deactivation part at a first point in time labelled 308 the bundle size is lowered to four TTIs. At a second point in time labelled 309 the bundle size is lowered again to two TTIs, while at point in time 310 the repetition mode is deactivated.

Thus, the mechanism of TTI bundling may also take into account that available uplink power headroom can increase. Therefore another trigger is responsible for decreasing the size of TTI bundle whenever sufficient power is reported by UPH measurements. Calculations of the trigger may utilize equation 1 taking into account lower number of repetitions, i.e. if TTI bundle comprises of 8 TTIs, N_rep should be equal to 4. The deactivation TTI bundling may also be done gradually.

Further uplink energy savings may be achieved with E-DPCCH gating during repetitions. Transmission of E-DPCCH may be kept during all of the repetitions. However for the sake of the transmitted power in uplink it is reasonable to maintain E-DPCCH only during first TTI in the bundle. The overhead energy saved during retransmissions could be utilized for data transmission, i.e. E-DPDCH power for all repetitions might be rescaled to keep power level equal to the first TTI. The maintaining of the E-DPCCH only during the first TTI in the bundle is schematically illustrated in Fig. 4, wherein the E-DPCCH 401 signal is only included into the first TTI 402 while the seven repetitions only include the data signal E-DPDCH 403.

It should be noted that the TTI bundling mechanism may be activated either by serving nodeB (NB) which orders an UE to transmit additional retransmissions, or by UE, which autonomously decides about out-of-HARQ cycle transmissions. Both decisions may be taken based on the information about power headroom available at a UE.

If the nodeB schedules the use of additional repetitions, fast Ll signalling may be utilized. The advantage of this solution may be that unnecessary delays can be avoided. There are several possibilities how to utilize Ll orders for requesting additional repetitions. In particular, specifying the number of repetitions which have to be performed instantaneously or TTI length and as long as second order will not bring the UE back to the normal mode. Alternatively, Ll orders may act as the pointer to the predefined repetition settings, defined by the RNC and delivered to the UE beforehand via RRC signalling. After receptions of the Ll order the UE starts additional repetitions.

Another option is to allow UE decide autonomously about additional repetitions. In such a case serving nodeB should be informed about retransmission scheme applied. For SHO, non serving nodeBs always need to be informed of the number of repetitions used. For informing several options are possible. In particular, possible solutions may be E-TFCI reinterpretation, offset detection on E-DPCCH, or mixture of E-TFCI reinterpretation and offset detection on E-DPCCH. Furthermore, methods based on similarity of consecutive TTI or so called blind detection methods may be used.

For the E-TFCI reinterpretation the number of repetitions or TTI length may be encoded in the TFCI and hence the information about number of repetitions may be transmitted/multiplexed together with the data frames.

It is assumed that when making VoIP transmissions, the UE may not need to make use of the full set of TFCs defined in the specifications. Thus, a reduced set of TFCs could be defined, whose size would be smaller than the full size set. It is assumed that at the physical layer, E-DPCCH remains structured as in Release 6, hence the same amount of E-TFCI bits might be available for a reduced TFC set. This might allow for E-TFCI bits to signal in a paired manner values of TFC indicator and the number of repetitions.

An example is shown below, in which the TFC set size is reduced to 122 values, which are indicated by the first 122 E-TFCI values. The final 6 E-TFCIs indicate bundling, including the amount of repetition. Bundling is permitted in this example for TFCl and TFC2, which are assumed to be the most commonly used TFCs for VoIP signalling.

E-TFCI index Interpretation

0 TFC 0, no bundling

1 TFC 1, no bundling

2 TFC2, no bundling 121 TFC 121, no bundling

122 TFCl, bundling 1 repetition

123 TFC 2, bundling 1 repetition

124 TFCl, bundling 3 repetitions 125 TFC 2, bundling 3 repetitions

126 TFCl, bundling 7 repetitions

127 TFC 2, bundling 7 repetitions

Reinterpretation of E-TFCI may be based on the fact that information about repetition scheme will be encompassed in E- TFCI. In this case it may be advantageous for nodeB to distinguish between ordinary and redefined E-TFCI value. This might be achieved by appropriate RNC configuration of the UE and nodeB. Therefore UE may choose E-TFCI value from the not permitted range. This may be a notification for nodeB to identify the repetition scheme. The E-TFCI values need to be redefined beforehand e.g. 4 new E-TFCI values may be defined, which will indicate not only TFC but also number of possible repetitions (e.g. 0, 1, 3, 7) .

The E-TFCI re-interpretation method may best be combined with a repetition scheme transmitting E-DPCCH only in the first TTI, since the nodeB may not be aware of the number of repetitions until it has decoded E-DPCCH.

Offset detection on E-DPCCH is based on an assumption that UE can signal repetition scheme by changing power relation /3ec//3_c. If the E-DPCCH is transmitted all of the TTIs, the increase of the power offset will signal utilizing the repetition scheme, e.g. β_ec/β_c decreased by x dB means that TTI bundle size may be increased. Likewise lowering of the TTI bundle size might be signalled by increasing β_ec/β_c power relation. It should be noted that it may not necessary to adjust the E-DPCCH power offset for repetition compared to only 1 transmission when E-DPCCH is transmitted in the first TTI only, so there is some power usage for using offset signalling in this case. However, the offset detection method may best be combined with a repetition scheme in which E- DPCCH is repeated in each TTI. In that case, the E-DPCCH power offset may anyhow be reduced according to the number of repetitions. In this case, there may be no additional power usage for the signalling as the total power spent over the repeated TTIs on E-DPCCH remains the same. In the specifications, some indication to the nodeB of the relationship between E-DPCCH level and the number of repetitions may be required.

It is also possible to utilize mixture of E-TFCI reinterpretation and E-DPCCH offset detection to notify the nodeB about repetitions. In this case UE will signal TTI bundling by changing the power relation β_ec/β_c. This will be a notification for nodeB that TTI bundling is to be applied.

Then the nodeB may detect the amount of repetitions from the E-TFCI value.

Alternative to the above described signalling methods, i.e. the use of an information density indicator, would be to rely on the nodeB detecting similarity between repeated TTIs in order to determine whether repetition has been applied and the amount of repetitions. Another alternative would be a blind detection based method relying on a detection device or unit included in the nodeB. The detection may consist of making an assumption on the number of repetitions, performing despreading and decoding according to that assumption and then checking the CRC on the decoded data. A further alternative is for the UE to not make any attempt at signalling the amount of repetitions, and rely on the Node B testing a number of hypothesis on the repetition number. Fig. 5 schematically illustrates a TTI switching. On the left side a TTI 501 of 2 ms is schematically depicted corresponding to a slot including control channel DPCCH 502 and data channel E-DPDCH 503. On the right side a TTI 504 of 10 ms is depicted including also control channel DPCCH 505 and data channel E-DPDCH 506. The switching between these two states is indicated by arrow 507.

Summarizing according to an exemplary aspect of the invention a method may be provided which increases coverage of an EUL/HSUPA of WCDMA. The coverage may be increased by performing an adapted bundling and/or TTI switching which possibly solves the problems of: how to determine the number of TTI repetitions or TTI length, which entity should take a decision on starting the repetitions and/or TTI switching, how to inform a second network element (NB or UE) about this decision, and how to operate soft handover (SHO) .

Fig. 6 schematically illustrates a communication network 600 comprises a plurality of nodeBs 601 and 602 and a plurality of user equipments 604, 605, 606. Of course the communication network may comprise more than the shown elements. The nodeB 601 is at one point in time the serving nodeB for the user equipment 604 which is moving so that to another point in time the former non serving nodeB 602 may become the serving nodeB by a soft handover. As schematically indicated in Fig. 6 for nodeB 601 some or all nodeBs may comprise a decision unit 610 adapted to decide on a change of the information density indicator and may further comprise a receiving unit 611 and a transmission unit 612. As well as the nodeBs the user equipments 604, 605, 606 comprise a transmission unit 613, a receiving unit 614 and a decision unit 615 adapted to decide on a change of the information density indicator. Finally, it should be noted that the above-mentioned embodiments illustrate rather then limit the invention, and that those skilled in the art will be capable of designing many alternative embodiments without departing from the scope of the invention as defined by the appended claims. In the claims, any reference signs shall not be construed as limiting the claims. The word "comprising" and "comprises", and the like, does not exclude the presence of elements or steps other than those listed in any claim or the specification as a whole. The singular reference of an element does not exclude the plural reference of such elements and vice-versa. In a device claim enumerating several means, several of these means may be embodied by one and the same item of software or hardware. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

List of reference signs:

100 HARQ process

101 First packet 102 Second packet

103 Third packet

104 Fourth packet

105 Fifth packet

106 Sixth packet 107 Seventh packet

108 Eight packet

110 HARQ process bundling

111 First packet

112 Second packet 201 Max Tx power

202 Total Tx power

203 Accumulative Tx power

204 Tx power DPCCH

205 Initiate repetition first level 206 Initiate repetition second level

207 Initiate repetition third level

308 Decreasing repetition level

309 Decreasing repetition level

310 Deactivate repetition 401 E-DPCCH

402 TTI

403 E-DPDCH

501 TTI 2 ms

502 DPCCH 503 E-DPDCH

504 TTI 10 ms

505 DPCCH

506 E-DPDCH

507 Time switching

Claims

CLAIMS :

1. A method of operating a user equipment of a communication network, the method comprising: sending an information density indicator from the user equipment to another network element, wherein the information density indicator relates to a time interval during which an amount of information is sent.

2. The method according to claim 1, wherein the user equipment is sending the information density indicator in response to a request for changing the information density of sent information.

3. The method according to claim 2, wherein the changing request is initiated when a predetermined threshold of a parameter is reached.

4. The method according to claim 3, wherein the parameter is the user equipment power headroom.

5. The method according to claim 3, wherein the changing request is initiated every time that the predetermined threshold of the parameter is reached.

6. The method according to claim 1, wherein the information density indicator relates to a repetition rate.

7. The method according claim 1, wherein the information density indicator relates to a transmission time interval length.

8. The method according to claim 1, wherein the information density indicator is sent in a data frame.

9. The method according to claim 1, wherein the information density indicator corresponds to a signal power.

10. A method of transmitting data from a first network element to a second network element of a communication network, the method comprising: operating a user equipment according to the method of claim 1, and performing a transmission of a data set taking into account the information density indicator.

11. The method according to claim 10, wherein the transmission of the data set includes a repeated transmission, and wherein in the repeated control channel information is not transmitted.

12. A user equipment for a communication network, wherein the user equipment comprises: a transmitting unit adapted to send an information density indicator from the user equipment to another network element, wherein the information density indicator relates to a time interval during which an amount of information is sent.

13. The user equipment according to claim 12, wherein the user equipment is adapted to perform a transmission time interval switching based on the information density indicator.

14. The user equipment according to claim 12, wherein the user equipment is adapted to change a number of repetitions an information is sent based on the information density indicator.

15. A processing unit for a nodeB of a communication network, wherein the processing unit is adapted to process an information density indicator received from a user equipment.

16. A program element, which, when being executed by a processor, is adapted to control or carry out a method according claim 1.

17. A computer-readable medium, in which a computer program is stored which, when being executed by a processor, is adapted to control or carry out a method according claim 1.