KR101083227B1 - METHOD FOR ALLOCATING RADIO RESOURCE TO A PLURALITY OF USER EQUIPMENTS(UEs) CONSTITUTING A GROUP - Google Patents

Abstract

A method of allocating radio resources to a plurality of terminals forming a group is provided. The method includes adding a terminal to a group, and transmitting group scheduling information determined by the scheduling to a plurality of terminals belonging to the group. The group scheduling information includes terminal indication information and resource information. The terminal indication information indicates whether information on radio resources allocated to the terminal is changed. The resource information indicates a changed radio resource of the terminal. If there is no change in the entire terminal in the group, the base station does not transmit the MAP IE, the terminal decodes the previously allocated resources in accordance with the previous transmission format, such as the continuous allocation method, there is an effect that the MAP overhead is reduced.

Description

Method for allocating radio resources to a plurality of terminals forming a group {METHOD FOR ALLOCATING RADIO RESOURCE TO A PLURALITY OF USER EQUIPMENTS (UEs) CONSTITUTING A GROUP}

The present invention relates to wireless communication, and more particularly, to a method for allocating radio resources to a plurality of terminals forming a group.

The next generation mobile communication system is not just a wireless communication service like the previous generation mobile communication system, but has been standardized for an efficient interworking and integration service between a wired communication network and a wireless communication network. As such, a high-speed mass communication system capable of processing and transmitting a variety of information such as video and wireless data beyond a voice-oriented service is required, thereby transmitting large-capacity data approaching the capacity of a wired communication network to a wireless communication network. There is a need for technology development.

In response to these demands, technologies such as orthogonal frequency division multiplexing (OFDM) and multiple input multiple output (MIMO) have emerged, which are intended to increase the data rate. The more resources available for data transmission, the larger the amount of data can be transmitted. However, due to the characteristics of wireless communication, it is necessary to service a large number of users using a very limited radio resource, so there is some limitation in increasing the data transmission rate. Therefore, there is a need to use limited radio resources more efficiently.

Various technologies have emerged for the efficient use of radio resources, such as the Group Allocation Scheme, the Dynamic Allocation Scheme, and the Persistent Allocation Scheme. In order to reduce the overhead of control information, the group allocation method is a method of allocating resources by dividing a plurality of users into several groups according to MCS and resource size.

The dynamic allocation method allocates radio resources to users who do not have data packets to transmit and receive, and allocates radio resources to users who have data packets to transmit and receive, but allocates radio resources dynamically at regular intervals in frequency or time. .

Voice over Internet Protocol (VoIP) services continue to allocate resources until the end of the VoIP session, even if no VoIP packets are sent to the radio resources allocated to the user. As described above, an allocation method for maintaining a once allocated radio resource for a predetermined time is a continuous allocation method. According to this method, since a specific radio resource is continuously allocated only to a specific terminal, when the specific terminal does not transmit or receive data (this case is called a hole of a resource), the cause of reducing the efficiency of limited radio resources Becomes

The advantages and disadvantages of group allocation and continuous allocation are shown in the table below.

Group assignment method Persistent Allocation Method
Advantages
Dynamically change transport formats such as MCS with low overhead MAP overhead can be minimized if there is no change in transmission format or resources
Support for HARQ retransmission resource allocation
Disadvantages
Need to send separate control message for joining / leave group Reset required when changing transfer format MAP IE should be sent even when no change in transmission format or resources is required HARQ retransmission requires separate resource allocation with general MAP

Referring to Table 1, the group allocation method and the continuous allocation method have an advantage of lowering the MAP overhead compared to the conventional general MAP transmission, but also has disadvantages. The group allocation method has a problem of transmitting a separate control message for joining / leave a group and transmitting a MAP IE even when a change in transmission format or resources is not necessary. On the other hand, there is a problem that the continuous allocation method requires resetting when the transmission format is changed, and HARQ retransmission requires separate resource allocation to the general MAP.

Therefore, there is a need for a method for efficiently allocating radio resources while minimizing transmission of control information for radio resource allocation.

The technical problem of the present invention is to assign radio resources to a plurality of terminals by transmitting only control information for a terminal having a changed transmission format or a resource, without transmitting control information for a terminal whose transmission format or a resource does not change. To provide a way to.

According to an embodiment of the present invention, a method for allocating radio resources to a plurality of terminals forming a group is provided. The method includes adding a terminal to a group, and transmitting group scheduling information determined by the scheduling to a plurality of terminals belonging to the group. The group scheduling information includes terminal indication information and resource information. The terminal indication information indicates whether information on radio resources allocated to the terminal is changed. The resource information indicates a changed radio resource of the terminal.

If there is no change in the entire terminal in the group, the base station does not transmit the MAP IE, the terminal decodes the previously allocated resources in accordance with the previous transmission format, such as the continuous allocation method, there is an effect that the MAP overhead is reduced.

The following technologies include code division multiple access (CDMA), frequency division multiple access (FDMA), time division multiple access (TDMA), orthogonal frequency division multiple access (OFDMA), single carrier-frequency division multiple access (SC-FDMA), and the like. Such as various wireless communication systems. CDMA may be implemented with a radio technology such as Universal Terrestrial Radio Access (UTRA) or CDMA2000. TDMA may be implemented with wireless technologies such as Global System for Mobile communications (GSM) / General Packet Radio Service (GPRS) / Enhanced Data Rates for GSM Evolution (EDGE). OFDMA may be implemented in a wireless technology such as IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802-20, Evolved UTRA (E-UTRA). UTRA is part of the Universal Mobile Telecommunications System (UMTS). 3rd Generation Partnership Project (3GPP) long term evolution (LTE) is part of an Evolved UMTS (E-UMTS) using E-UTRA, and employs OFDMA in downlink and SC-FDMA in uplink.

1 is a block diagram illustrating a wireless communication system. Wireless communication systems are widely deployed to provide various communication services such as voice, packet data, and the like.

Referring to FIG. 1, a wireless communication system includes a user equipment (UE) 10 and a base station 20 (BS). The terminal 10 may be fixed or mobile and may be called by other terms such as mobile station (MS), advanced mobile station (AMS), user terminal (UT), subscriber station (SS), and wireless device (wireless device). have. The base station 20 generally refers to a fixed station communicating with the terminal 10, and includes an advanced base station (ABS), a node-b (node-b), a base transceiver system (BTS), and an access point ( Access Point) may be called. There may be one or more cells in one base station 20.

Hereinafter, downlink (DL) means communication from the base station 20 to the terminal 10, and uplink (UL) means communication from the terminal 10 to the base station 20. In downlink, the transmitter may be part of the base station 20 and the receiver may be part of the terminal 10. In uplink, the transmitter may be part of the terminal 10 and the receiver may be part of the base station 20. For clarity, the following description focuses on IEEE 802.16m, but the technical spirit of the present invention is not limited thereto.

2 shows an example of a frame structure.

Referring to FIG. 2, a superframe includes a superframe header and four frames (frames, F0, F1, F2, and F3). In the case of using a superframe, the transmission period of control information that does not need to be transmitted frequently can be increased in units of superframes, thereby increasing the efficiency of transmission. In addition, data allocation and scheduling may be performed most frequently in units of superframes, thereby reducing delay characteristics of data transmission considering a retransmission mechanism. The size of each superframe is 20ms and the size of each frame is illustrated as 5ms, but is not limited thereto.

The superframe header may be placed at the front of the superframe, and a common control channel is assigned. The common control channel is a channel used for transmitting control information that can be commonly used by all terminals in a cell, such as information on frames constituting a superframe or system information.

One frame includes eight subframes (Subframe, SF0, SF1, SF2, SF3, SF4, SF5, SF6, SF7). Each subframe may be used for uplink or downlink transmission. The subframe may consist of 6 or 7 OFDM symbols, but this is only an example. Time division duplexing (TDD) or frequency division duplexing (FDD) may be applied to the frame. In TDD, each subframe is used in uplink or downlink at different times at the same frequency. That is, subframes in the TDD frame are divided into an uplink subframe and a downlink subframe in the time domain. In FDD, each subframe is used as uplink or downlink on a different frequency at the same time. That is, subframes in the FDD frame are divided into an uplink subframe and a downlink subframe in the frequency domain. Uplink transmission and downlink transmission occupy different frequency bands and may be simultaneously performed.

3 is an example of a MAC protocol data unit (PDU) format.

Referring to FIG. 3, the MAC PDU begins with a MAC header. Dozens of one or more extended headers are located after the MAC header. The MAC PDU may include a payload. Multiple MAC Service Data Units (SDUs) and / or SDU fragments from different unicast connections belonging to the same terminal may be multiplexed within a single MAC PDU.

On the other hand, the MAC header has two formats. One is a generic MAC PDU that contains a MAC management message and starts each downlink and uplink MAC PDU. The other is a compact MAC PDU that initiates a MAC PDU of a connection using persistent allocation or group allocation.

4 is a flowchart illustrating a resource allocation method according to an embodiment of the present invention.

Referring to FIG. 4, the base station ABS determines whether to perform scheduling by a group allocation method for the terminal AMS (S100). If the base station determines scheduling by the group assignment method, the base station adds the terminal to the most appropriate group among a plurality of groups (S110). There are several ways to divide the plurality of groups. For example, terminals having similar path loss from the base station may be configured as a group. If the plurality of groups are not all appropriate for the terminal, the base station may create a new group for the terminal.

The base station transmits group scheduling information to the terminal (S120). The group scheduling information includes any one or a combination of terminal indication information, resource information, resource format information, and the number of assigned resource information. It may include. That is, the base station may include only the terminal indication information in the group scheduling information or all the information according to the situation. The group scheduling information may be called group resource allocation A-MAP IE.

The terminal indication information is information in a bitmap format and uses 1 bit per user, and indicates which users in the frame have a change in the scheduling result in the previous frame. The terminal indication information may be called a user bitmap. Each bit position of the bitmap is mapped to each terminal. If the bit is 1, the scheduling result of transmission format, resource, etc. is changed compared to the previous scheduling for the terminal. In comparison, the scheduling is not changed.

Hereinafter, each element included in the group scheduling information will be described with reference to Tables 2 to 4 below. Table 2 is an example of parameters of group scheduling information according to the present invention.

Syntax Size in bits Description Of Notes A-MAP IE Type 4 DL Hybrid Resource Allocation A-MAP IE Resource Offset [6] [8] Indicates starting LRU for resource assignment to this group
ACK Channel Offfset TBD Indicates the start of ACK index used for scheduled allocations at this subframe in the group NDA [2] [3] Indicates the number of deleted AMSs in the group AMS indicating Information Index 5 Indicates the UE Indicating Information Index of deleted AMSs The Number of Assigned Resource Information 2 Indicates the number of assigned resource information to the group Resource Information variable (8, 16, 32, 64) Indicates which resource units are assigned to an AMS in the group AMS Indicating Information Size [2] [5] Indicates the length of AMS Indicating Information
AMS Indicating Information variable Indicates scheduled AMSs in a group. The size of the bitmap is equal to the AMS Indicating Information Size Resource Format Information variable Indicates MCS / resource size for each scheduled AMS CRC 16 16 bit mased CRC

syntax bit information A-MAP IE type 1001 Resource Offset 101101 ACK channel offset 1101 NDA 00 (NDA = 0) AMS Indicating Information Size 11 (8 bit) AMS Indicating Information 00001000 The Number of Assigned Resource Information 00 (8 units) Resource Information 00110000 Resource Format Information 0110 MCRC 16 bit

Table 4 shows another example of the state of the group scheduling information according to the present invention.

syntax bit information A-MAP IE type 1001 Resource Offset 101101 ACK channel offset 1101 NDA 00 (NDA = 0) AMS Indicating Information Size 11 (8 bit) AMS Indicating Information 00101000 The Number of Assigned Resource Information 00 (8 units) Resource Information 00110011 Resource Format Information 1101 1110 MCRC 16 bit

Referring to Tables 3 and 4, the number of assigned resource information is 00, indicating that the number of unit resources allocated to the group is 8 (indexes 1 to 8). If the size of the UE indication information (AMS Indicating Information Size) is 11, this indicates that the number of terminals belonging to the group is eight (indexes 1 to 8). Assuming that the number of terminals allocated to the resource is 4 (index 1, 5, 6, 8), since the number of terminals allocated to the resource is 4, eight unit resources may be divided and allocated by two. Therefore, terminals 1, 5, 6, and 8 are sequentially allocated unit resources of index combination {1,2}, {3,4}, {5,6}, and {7,8}. Of course, this is merely an example, and a different index combination may be preset between the base station and the terminal.

Here, when a change occurs in the resource allocation of the terminal having index 5, the base station transmits the group scheduling information by setting the terminal indication information (AMS Indicating Information) to 00001000, as shown in Table 3. Accordingly, the terminals 1, 6, and 8 transmit and receive data according to the existing resource allocation, and only the terminal having index 5 transmits and receives data by the new resource allocation. Since newly allocated resource information is 00110000, the terminal having index 5 may know that the unit resource having indexes {3, 4} is allocated to itself having index 5. On the other hand, the base station need to transmit the resource format information (Resource Format Information) 0110 million (4 bits) of the terminal of the index 5, and does not have to transmit the resource format information (3 AMSs × 4bits / AMS = 12bits) of the remaining terminals, The signaling burden can be reduced by 12 bits.

For example, when the number of terminals in the group is 8 as shown in Tables 3 and 4, the terminal instruction information is represented by eight bits. When the terminal instruction information is 00001000 as shown in Table 3, only the fifth user out of the eight users compares to the previous frame in the frame. It means that the transmission resource or format has been changed, and the remaining users have no change in the allocation and transmission format. (Users who have not been transmitted still do not transmit, and they transmit in a specified MCS or MIMO mode using a specific resource. The old user will send the new allocation cycle as it was previously). In the example of Table 4, when the terminal indication information is 00101000, it means that the third and fifth users have a change in scheduling result compared to the previous. Of course, what the bits 0 and 1 point to may be reversed, which is a matter of implementation.

Therefore, if the bit of the terminal indication information is 1, since there is a change in the scheduling result for the terminal, the base station should also inform the terminal of new resource information, resource format information, and the number of allocation resources. Therefore, in this case, the group scheduling information includes all of the terminal indication information, resource information, resource format information, and information on the number of allocated resources.

On the other hand, if the bit of the terminal indication information is 0, since there is no change in the scheduling result for the terminal, the base station does not have to inform the terminal of new resource information, resource format information, and the number of allocated resources. Therefore, the group scheduling information includes only terminal indication information. In this case, the terminal may receive data using resource information, resource format information, and number of allocated resources according to the previous scheduling.

The number information of allocated resources indicates the number of bits of resource information. If the resource information is any one of 8, 16, 32, and 64 bits, the number information of allocated resources is 2 bits and may indicate four cases.

Resource information is control information for indicating an allocated resource in a bitmap format. The resource information may be called a resource unit (RU) bitmap. The UE may know the size of the resource unit bitmap according to the number of allocated resources. For example, when eight resources are allocated to a group as shown in Tables 3 and 4, for example, if the resource information is 00110000 , It can be seen that the third and fourth resources represented by bit 1 are resources allocated to the terminal whose transmission format is changed at this scheduling time. If the resource information is 00110011, as shown in Table 4, the first, second, fifth and sixth resources can be seen that the resource allocation and transmission format has not changed compared to the previous scheduling time, and the third, fourth, and seventh resources. The eighth resource is a new resource allocated through this scheduling, or the resource has changed in the transmission user and transmission format. By using the resource allocation bitmap in this way, it is possible to efficiently use distant or fragmented resources that are not connected in series.

The resource format information indicates the MCS, MIMO mode, and resource size of the resource allocated to the corresponding terminal whose transmission format or allocated resource is changed through current scheduling, and each terminal decodes it and transmits the entire transmission specified in the resource information. Find out the information of the resource allocated to the terminal among the resources of the format change. The number of bits of the resource format information is determined depending on the supportable MCS level, MIMO mode, and resource size. For example, 0110 in Table 3 indicates that a transmission mode occupies two QPSK 1/2 codes, an STBC, and two resource units (RUs). As described above, each resource format information bit string has information in which a combination of a modulation method, a channel coding method, a MIMO mode, and a resource amount is previously mapped. In the example of Table 3, since only the third and fourth resources have the current allocation change indicated in the resource unit bitmap, the corresponding resources are all allocated to the user 5 specified in the user bitmap.

In the example of Table 4, when the number of resource format information bits for each terminal is 4 bits, the first 1101 of 8 bits of total resource format information is allocated to the third terminal, and 16QAM 1/2 code, STBC, and 3 resource units are allocated. Information indicating the transmission mode to occupy is shown. Therefore, the third, fourth, and seventh resource units of the third, fourth, seventh, and eighth resources designated as changes in the resource unit bitmap are allocated to the third terminal. 1110 at the end of all 8 bits of resource format information indicates allocation information for the fifth terminal as QPSK 1/4 code, two stream openloop spatial multiplexing, and a transmission mode occupying one RU. Therefore, it can be seen that the remaining eighth resource unit is allocated to the corresponding terminal.

The base station and the terminal transmit and receive data based on the group scheduling information (S130). This method basically follows the group allocation method, but if the same scheduling continues, it works like the persistent allocation method. Through this, the UE can grasp the changed resource and the unchanged resource information among the resources allocated to the group, and the overhead of the scheduling information to be transmitted to the UE by the base station can be significantly reduced in the environment where the scheduling does not change rapidly.

Simulation was performed to see the effect of the resource allocation method according to the present invention, and the results are described below.

5 is an example of a simulation result according to the present invention. As the number of terminals belonging to a group increases from 5 to 60, how the size of the group scheduling information changes is compared with the prior art.

Referring to FIG. 5, the number of unit resources N _RU allocated to a group is 8, 16, 32, and 64. The number of terminals belonging to the group is 5 to 60, and the activation factor is 0.5. The average of the probability that the resource allocation by previous scheduling will change is 0.2 (assuming 0 to 0.4 uniform distribution). In addition, it is assumed that there is no terminal NDA leaving the group.

The graph labeled Conventional is a conventional group allocation method, and the graph labeled Proposed is a resource allocation method according to the present invention, and is classified according to the number of allocated unit resources. As can be easily expected, in the present invention, the larger the number of unit resources allocated to one group, the larger the size of resource information to be transmitted. Therefore, the advantage is reduced compared to the existing group allocation method, and the smaller the number of terminals belonging to the group, The benefit is less because the number of bits saved is reduced. However, it can be seen that the present invention reduces the MAP IE size compared to the conventional group resource allocation method in a wide range of communication environments. The situation in which the size of resource information that occurs in the prior art and reversal is 64 and the number of terminals per group less than 20 corresponds to a situation in which the channel environment is bad because the resources allocated to each terminal are large. This seems to be an advantage.

6 and 7 are other examples of simulation results according to the present invention. In the resource allocation method of the present invention, how the size of the group scheduling information changes as the number of terminals belonging to the group increases from 5 to 60, compared with the continuous allocation method and the group allocation method. FIG. 6 illustrates a case where the size of the allocated unit resource is 16 and FIG. 7 illustrates a case where the size of the allocated unit resource is 32.

6 and 7, the simulation environment follows the IEEE 802.16m EMD document, assuming a 1.6% probability of transition between active and inactive, and a 5% probability of changing the MCS. Assume that In the case of the continuous allocation method, the transmission period of the scheduling information is 8 frames (160 msec), and the group allocation method and the resource allocation method according to the present invention are 2 frames (40 msec). In this case, the conditions under which the persistent allocation type A-MAP IE and the group allocation type A-MAP IE are transmitted are as follows.

1. A-MAP IE Transmission Condition of Continuous Allocation Method

   -Start communication

   End allocation cycle (assuming 8 frames)

   MCS change

   -Change in resource allocation is required

2. A-MAP IE Transmission Condition of Group Assignment

   -Per resource allocation cycle (assuming 2 frames)

MAP overhead according to three schemes is shown in FIG. 6. Overall, the resource allocation scheme according to the present invention shows superior performance compared to the continuous resource allocation. As described above, the smaller the number of allocated unit resources and the larger the number of terminals per group, the greater the overhead reduction effect of the proposed method. Considering the communication environment corresponding to such a situation, it can be considered that a group composed of users having excellent channel conditions has an advantage. As described above, the resource allocation method according to the present invention can additionally obtain the advantage of continuous allocation while using the group allocation method, and shows advantages in a fairly wide range of communication environments.

The numerical values of the above-described simulation results are examples only and are not limiting. Simulation results may vary depending on the given conditions. Even if the result of the simulation is different, it does not depart from the technical spirit of the present invention as long as it is in accordance with the spirit of the present invention.

All of the above functions may be performed by a processor such as a microprocessor, a controller, a microcontroller, an application specific integrated circuit (ASIC), or the like according to software or program code coded to perform the function. The design, development and implementation of the code will be apparent to those skilled in the art based on the description of the present invention.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those skilled in the art that various changes and modifications may be made therein without departing from the spirit and scope of the invention. You will understand. Therefore, the present invention is not limited to the above-described embodiment, and the present invention will include all embodiments within the scope of the following claims.

1 is a block diagram illustrating a wireless communication system.

2 shows an example of a frame structure.

3 is an example of a MAC protocol data unit (PDU) format.

4 is a flowchart illustrating a resource allocation method according to an embodiment of the present invention.

5 is an example of a simulation result according to the present invention.

6 and 7 are other examples of simulation results according to the present invention.

Claims (11)

In a method for allocating radio resources to a terminal by a base station, Adding a terminal to the group; Transmitting group scheduling information determined by scheduling to a plurality of terminals belonging to the group, The group scheduling information includes terminal instruction information and resource information. The terminal instruction information indicates whether information on radio resources allocated to the terminal is changed. Instructing a radio resource allocation method. The method of claim 1, The group scheduling information further includes resource format information indicating a modulation and coding scheme (MCS) for the changed radio resource. The method of claim 1, And when the information on the radio resource allocated to the terminal is changed, the group scheduling information further includes information on the number of allocated resources indicating the number of unit radio resources allocated to the group. The method of claim 1, And the group scheduling information is a MAP Information Element (IE). The method of claim 4, wherein The MAP information element includes a MAP IE Type field indicating the type of the MAP information element. The method of claim 1, The group scheduling information is transmitted on a common control channel. The method of claim 1, And the number of bits of the terminal indication information is equal to the number of terminals belonging to the group. In the method for receiving a radio resource performed by the terminal, Receiving group scheduling information determined by scheduling; And Receiving data using the group scheduling information, The group scheduling information includes terminal instruction information and resource information. The terminal instruction information indicates whether information on radio resources allocated to the terminal is changed. Instructing a radio resource allocation method. The method of claim 8, If the terminal indication information is 0, the data is received according to previous resource allocation information. The method of claim 8, The group scheduling information further includes resource format information indicating a modulation and coding scheme for the changed radio resource. 11. The method of claim 10, And if the terminal indication information is 1, the data is received according to the changed radio resource and the resource format information.

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