JP5277084B2 - Radio resource allocation radio communication apparatus - Google Patents

Description

  The present invention relates to a radio communication system having a radio base station apparatus or a radio terminal that performs data transmission / reception, and more particularly to a technique for managing radio resources for data transmission / reception.

  In general, in a digital mobile communication system using OFDMA (Orthogonal Frequency Division Multiple Access), communication is performed with a terminal using radio resource units (hereinafter referred to as slots) divided by frequency and time. As in Non-Patent Document 1, the base station measures the reception quality from the interference and reception power of each slot by scheduling, determines the slot used for communication with each terminal from the measured reception quality, and performs allocation. .

  Also, as shown in Non-Patent Documents 2 and 3, the base station notifies the terminal of the combination of the slot position and the terminal used for communication using a part of the radio resource of Dwonlink. The terminal refers to the radio resource that transmits the position information of the slot used for communication, recognizes the position of the slot allocated to itself, and performs downlink reception or uplink transmission. Therefore, in the scheduling of the base station, a terminal that performs transmission and a slot that is allocated to the terminal are determined.

Tien-Dzung Nguyen and Youngnam Han, “A Proportional Fairness Algorithm with QoS Provision in Downlink OFDMA Systems,” IEEE Commun., Vol.10, no.11, Nov. 2006 IEEE802.16, P802.16Rev2 / D9, Jan. 2009 3GPP, TR36.814 v0.4.1, Feb. 2009

  Here, in the scheduling of the base station, if many terminals are allocated in the same frame, the position information of the allocation slot notified to each terminal by the base station increases due to the slot allocation, so that the notification information requires a lot of radio resources. . Also, if the number of slots allocated per terminal is small, the amount of data that can be transmitted decreases, and the PER (Packet Error Rate) increases because the code length after error correction coding becomes shorter. In the conventional scheduling, a terminal to be assigned using a measurement value of reception quality as an index and a slot to be assigned to the terminal are determined. Therefore, increase of notification information and deterioration of PER due to the above cause occur.

  Further, in order to reduce the number of allocated terminals and increase the number of allocated slots, if the unit of radio resources allocated to each terminal is increased by, for example, 1 unit in a plurality of slots, there is a possibility that excessive radio resources may be allocated for data transmission. Increases and throughput decreases.

  As one aspect of the present invention for solving at least one of the above-described problems, the wireless base station apparatus includes a plurality of radio base station apparatuses and a plurality of terminal apparatuses, and the radio base station apparatus and the terminal apparatus use radio resources. A wireless communication system capable of communicating with each other, wherein a wireless resource is allocated to the terminal in a predetermined wireless resource allocation unit, and temporary allocation determining means for temporarily determining the number of units of the allocated wireless resource; The number of terminals allocated by the temporary allocation determining means exceeds the threshold value of the number of terminals stored in advance, or the number of radio resource units allocated to the terminals by the temporary allocation determining means is stored in advance. Distribution means for distributing the number of units of the radio resource allocated to the terminal to terminals other than the terminal when the unit number threshold is not satisfied, After means has determined radio resources to be allocated to the terminal, to distribute radio resources to the distribution means is allocated above the arrangement for determining the radio resources to be allocated to the terminal.

  According to an aspect of the present invention, it is possible to avoid an increase in radio resources required for notification information and a deterioration in PER without increasing the unit of radio resources allocated to each terminal.

FIG. 6 is a block configuration diagram of a slot allocation determination unit 1505 of the scheduling unit 603 according to the first embodiment. 1 is a diagram illustrating an example of a wireless communication system. The figure which shows one example of the base station arrangement | positioning of a communication system. The figure which shows an example of the communication frame transmitted between a terminal and a base station. The figure which shows the structure of MAP of the communication frame transmitted between a terminal and a base station. The block block diagram based on the software configuration of a base station. The block diagram of a base station. The figure which shows an example of substitution of a subcarrier. The block block diagram based on the software configuration of a terminal. The block diagram of a terminal. Sequence 1 showing an embodiment in which a base station performs resource allocation to terminals by scheduling. The figure which shows the structure of the CINR table 1503. The figure which shows the structure of the MCS table 1504. The figure which shows the structure of the transmission rate table 1506. FIG. The block block diagram of the scheduling part 603. FIG. The flowchart of the CINR measurement part 1501. The flowchart of the MCS determination part 1502. The flowchart of the allocation information generation part 1507. The figure which shows the structure of the slot allocation table. The flowchart of the initial cost function calculation part 101. FIG. The figure which shows the structure of the initial cost function table. The flowchart of the temporary slot allocation determination part 103. The flowchart 1 of the 1st allocation slot distribution part 3802. FIG. The figure which shows the structure of the allocation terminal number threshold value table. The figure which shows the structure of the MCS allocation table 1509. The figure which shows the structure of the MCS index table 1508. The figure which shows the structure of the allocation slot number threshold value table. The flowchart of the ranking part 3801. The flowchart 2 of the 1st allocation slot distribution part 3802. FIG. The flowchart 3 of the 1st allocation slot distribution part 3802. FIG. The flowchart of the 2nd allocation slot distribution part 3803. FIG. The flowchart of the allocation update part 3804. FIG. The conceptual diagram which shows an example of distribution of a slot. The conceptual diagram which shows an example of distribution of a slot. The conceptual diagram which shows an example of distribution of a slot. The sequence 2 which shows one Example in which a base station performs resource allocation to a terminal by scheduling. FIG. 9 is a block configuration diagram of a distribution unit 104 according to the second embodiment. FIG. 3 is a block configuration diagram of a distribution unit 104 according to the first embodiment.

  Hereinafter, a radio communication system in which a radio communication base station assigns a channel to a radio terminal by scheduling and transmits / receives data between the radio base station apparatus and the radio terminal, and a radio communication base station and a radio terminal in the radio communication system In particular, an embodiment to which the present invention is applied will be described by way of an example with regard to a technique in which a radio base station apparatus manages allocation of radio resources to radio terminals.

  The wireless communication system in the present embodiment is applied in a network configuration as shown in FIG. The wireless communication system includes a plurality of base stations (20b1, 20b2,... 20bN) and a plurality of wirelessly communicating with the base stations in cells (2c1, 2c2,... 2cN) that are within the wireless communication range of the base station. Terminal (20m1, 20m2,...). The base station is connected to an external communication network such as the Internet (NW) 203 via a router (or L3 switch) 201 and a gateway (GW) 202. However, the network configuration according to the present invention is not limited to this, and any network configuration may be used as long as the base station and the terminal can perform wireless access.

  Further, FIG. 3 shows a planar arrangement of the base stations. When the cell radius is uniform, hexagonal cell arrangement is generally performed. The base station arrangement in that case is shown in FIG. The cell of base station 302 is indicated at 301. Further, when the cell radii are not uniform, the hexagonal cell arrangement is not used, but an irregular base station arrangement as shown in FIG. The present invention is provided in each of such base station arrangements.

  An example of a frame configuration used for the wireless communication of this embodiment is shown in FIG. FIG. 4 shows a frame configuration of WiMAX (Worldwide Interoperability for Microwave Access). A frequency bandwidth that can be used for communication is called a system bandwidth 404. The system bandwidth is divided into subchannel 401 units, divided into subslots 402 in the time direction, and a time and a frequency region divided by one subchannel and one subslot are defined as slots.

  Also, a preamble 403 for use in synchronization or the like is inserted at the beginning of the Downlink 405. In the FCH 407, frame configuration information such as the frame length, the Downlink 405 length, and the Uplink 406 length is broadcast, and the MAP 408 notifies the slot allocation information to each terminal.

  As shown in FIG. 5, MAP IE # 1 501 (IE: Information Element) slot assignment information for terminal number 1 and slot assignment information MAP IE # 2 502 for terminal number 2 are notified by MAP. ... is included. The header 500 is a fixed Ph [bit] regardless of the slot assignment, and each MAP IE is a data amount Pa [bit] required to notify the assignment of one terminal. Here, if the data amount that can be transmitted by the base station by MAP is P_total [bit] and the number of allocated terminals is M, slot allocation can be performed in a range satisfying Ph + M * Pa ≦ P_total. Here, a slot divided by one subchannel and one subslot is a minimum unit that can be allocated to a terminal. Such a configuration is a resource assumed when, for example, OFDMA (Orthogonal Frequency Division Multiple Access) of TDD (Time Division Duplex) is assumed.

  Here, the subchannel is a logical division unit, and the frequency does not need to be continuous. In WiMAX, as shown in FIG. 8, the subcarriers 803 in the subchannel are spread over the entire band by a preset replacement sequence 804, and are transmitted in an actual frequency arrangement 802. By spreading the subcarriers over the entire band, frequency diversity gain can be obtained within the subchannel. In addition, since the difference in reception quality between different subchannels is reduced, the number of slots, not the position of the slot assigned to the terminal, becomes dominant in determining the throughput. Therefore, the number of allocated slots determined from the reception quality of each terminal is important in the base station.

  The number of Downlink slots is Nd, the number of Uplink slots is Nu, and slot numbers 1, 2,..., Nd, 1, 2,. The base station determines a slot to be used for communication with the terminal from the slots shown in FIG. 5, and performs downlink and uplink communication by allocating to the terminal. However, the definition of the slot is not limited to the configuration of FIG. 5 as long as it communicates using radio, such as time, frequency, code, and the like. For example, in the case of TDMA (Time Division Multiple Access), the system band is not divided into subchannels, and in the case of FDMA (Frequency Division Multiple Access), it is not divided into subslots. Further, the present invention is not limited to the configuration shown in FIG. 5, and can also be applied to a configuration using different frequencies for downlink and uplink, such as FDD (Frequency Division Duplex). In Downlink, first, data transmitted from the line interface 601 is processed by the upper layer control unit 602. Next, the scheduling unit 603 measures the reception quality of each slot using the service information from the higher layer control unit 602, the signal from the reception RF unit 607, and the signal from the Uplink baseband processing unit 605, Determine resource allocation for Downlink and Uplink. However, the information used in the scheduling unit 703 is not limited to the above, and information from other processing units may be used. Thereafter, the data is transferred to the downlink baseband processing unit 704, and the transmission RF unit 706 performs RF processing. Then, the switch 708 is switched to the transmission side, and a radio signal is transmitted from the antenna 709. The above processing operates according to a control signal from the controller 710. The controller 710 is a program module executed by the processor 701.

  In Uplink, first, the switch 708 is switched to the receiving side, and the antenna 709 receives a radio signal. Next, the received data is subjected to RF processing in the reception RF unit 707. Thereafter, the data is transferred to the uplink baseband processing unit 705, processed by the upper layer control unit 702, and transmitted from the line interface 701. The above processing operates according to a control signal from the controller 710.

  The software configuration of the base station (corresponding to 20b, 302, 304) of this embodiment will be described with reference to the block configuration diagram shown in FIG.

  The base station includes a controller 610, an antenna 609 for transmitting / receiving radio waves to / from the terminal, a transmission / reception switching switch 608 connected to the antenna 609, a line interface 601 connected to a connection line to the router 201, and a line interface. An upper layer processing unit 602 connected to 601, a transmission RF (Radio Frequency) unit 606 and a reception RF unit 607 connected to the switch 608, a downlink baseband processing unit 604 connected to the transmission RF unit 606, An uplink baseband processing unit 605 connected between the layer processing unit 602 and the reception RF unit 607 and a scheduling unit 603 connected between the upper layer control unit 602 and the downlink baseband processing unit 604 are included.

  An example of the device configuration of the base station will be described with reference to FIG.

  The transceiver 703 includes a transmission RF unit 606, a reception RF unit 607, a switch 608, and an antenna 609, and is a device that transmits and receives radio signals. The line IF 704 is connected to the network 705 and includes an interface 601. Other functional blocks shown in FIG. 6 are program modules executed by the processor 701. The memory 702 stores program modules. In the scheduling unit 603, the data memory 706 stores a table referred to by a program executed by the processor 701. As will be described later, scheduling is performed by referring to various tables formed in the data memory 706, and slots are allocated to terminals.

  FIG. 9 is a block diagram of a software configuration example of the terminal according to the present embodiment.

  The terminal includes a controller 910, an antenna 909 that transmits and receives radio waves between the base station, a transmission / reception switching switch 908 connected to the antenna 909, an upper layer processing unit 902 connected to the interface 901, a switch RF transmission unit 906 and reception RF unit 907 connected to 908, Uplink baseband processing unit 904 connected between upper layer processing unit 902 and transmission RF unit 906, upper layer processing unit 902 and reception RF unit 907 A Downlink baseband processing unit 905 connected between the two.

  In Uplink, first, data transmitted from the user interface 1005 is processed by the upper layer control unit 902. Next, the data is transferred to the Uplink baseband processing unit 904, and RF processing is performed in the transmission RF unit 906. Then, the switch 908 is switched to the transmission side, and a radio signal is transmitted from the antenna 909. The above processing operates according to a control signal from the controller 910. The controller 910 is a program module executed by the processor 1001.

  In Downlink, first, the switch 908 is switched to the receiving side, and a radio signal is received by the antenna 909. Next, RF processing is performed by the reception RF unit 907. Thereafter, the data is transferred to the downlink baseband processing unit 905, processed by the upper layer control unit 902, and output to the user interface 901. In addition, the reception quality measurement unit 913 measures the reception quality of the slot and transmits it to the upper layer control unit 902. The above processing operates according to a control signal from the controller 910. Here, the user interface is not limited to this, and an interface with another device is also conceivable.

  The device configuration of the terminal will be described with reference to FIG.

  The transmission RF unit 906, the reception RF unit 907, the switch 908, and the antenna 909 are stored in the transceiver 1003 that transmits and receives wireless signals, and the interface 901 is stored in the IF 1004 and connected to the user interface 1005. The other functional blocks are program modules executed by the processor 1001. These program modules are stored in the memory 1002 and operate according to data from the user interface 1005.

  FIG. 11 shows a scheduling sequence diagram.

  First, in step 1101, each terminal measures reception quality. In the reception quality measurement, the preamble 403 or the assigned slot is observed, and interference power, received signal power, CINR (Carrier to Interference plus Noise Ratio), and the like are calculated. In the following, CINR is assumed as a measurement index of reception quality. In CINR measurement, averaging in the frequency and time directions is performed. The unit for averaging in the frequency direction is the entire band when measuring with the preamble 403, and the subchannel when measuring with the allocation slot. In the reception quality measurement, it is necessary to obtain the reception quality of the subchannel to be actually assigned.

  As an example of reception quality measurement, in WiMAX, since each subchannel is spread over the entire band, the reception quality averaged over the entire band can be approximated to the reception quality of each subchannel. Similarly, the reception quality averaged over a certain subchannel can be approximated to the reception quality of different subchannels. In averaging in the time direction, there are a method in which time windows are divided as in Equation 1 and a method in which a forgetting factor is used as in Equation 2. Where γave (t) is the average CINR at frame number t, T is the time window for averaging (unit is frame), γ (i) is the frequency averaged CINR at frame number i, and λ is the forgetting factor (0 ≦ λ <1). When the forgetting factor λ is increased, the past CINR weight is increased, and when λ is decreased, the current CINR weight is increased. However, the interference value averaging method is not limited to the above, and is not limited to this as long as it is a method capable of averaging in the frequency and time directions.

Next, in step 1102, the terminal reports the CINR to the base station. In the case of downlink CINR reporting, each terminal reports the CINR measured in step 1101. In the uplink CINR report, each terminal transmits a reference signal to the base station, and the base station measures the CINR, or the base station periodically measures the CINR. For reporting CINR, a reporting slot set in advance by the base station is used. However, reporting may be performed using a slot allocated for each terminal, which is not for reporting. The CINR is reported according to a request from the base station, or is periodically reported at a predetermined period.

  In step 1103, the base station aggregates the CINRs reported from each terminal, and divides them into Downlink and Uplink in the communication direction column 1201, and sets the CINR value for the terminal number column 1202 in the CINR column 1203 as shown in FIG. Update the CINR table held in step 1. The CINR table exists in the data memory 706 inside the base station.

  In step 1104, the base station refers to the CINR table created in step 1103, determines the MCS (Modulation and Coding Scheme) of each terminal by referring to the MCS table shown in FIG. 13, and transmits the transmission rate as shown in FIG. Update the table. For example, the MCS table refers to the CINR threshold value column 1301 and the terminal having a CINR of β2 or less and greater than β1 refers to the MCS column 1302, and the MCS is 2 / 3-QPSK and the terminal of β3 or less and greater than β2 has an MCS of 3 Indicates that it is / 4-QPSK. Also, when CINR is β0 or less, the reception quality is poor and transmission is not permitted. Also, the transmission rate [bps] when one slot is allocated in each MCS is called an instantaneous transmission rate, and is held in the instantaneous transmission rate column 1303.

  For example, if 1 slot is assigned with 1 / 2-QPSK, which allows 1 bit transmission with 1 symbol, and s [bps], 2 / 3-QPSK allows 4/3 bit transmission per symbol. 3 s [bps]. Here, when transmitting 30 symbols per slot, 1 * 30 = 30 bps for 1 / 2-QPSK and 4/3 * 30 = 40 bps for 2 / 3-QPSK. The MCS is determined with reference to the MCS table, and the instantaneous transmission rate column 1403 of the transmission rate table shown in FIG. 14 is updated. The average transmission rate column 1404 will be described later. The MCS table and the transmission rate table exist in the data memory 706 inside the base station. The number of symbols that can be transmitted in one slot is initialized or is instructed from the network side, for example, the GW 202, and held in the data memory 706. Further, the determined MCS is held in the MCS allocation table shown in FIG. The MCS index column 2502 of the MCS allocation table is written with reference to the MCS index table shown in FIG. The MCS index table holds the MCS index corresponding to the MCS column 2602 in the MCS index column 2601. These tables exist in the data memory 706 inside the base station.

  In step 1105, the base station determines slot allocation to each terminal using the transmission rate table updated in step 1104, and notifies the terminal of the slot allocated by the base station to the terminal in step 1106. For the slot allocation notification, a notification slot set in advance by the base station is used, but not for notification but may be notified using a slot individually allocated for each terminal.

  The scheduling sequence is not limited to this as long as the base station determines an allocation slot based on a report of information indicating reception quality from the terminal. For example, as shown in FIG. 34, after the terminal measures the CINR as in FIG. 11, the MCS may be determined in step 3402 as in step 1104, and the MCS may be reported to the base station in step 3403.

  FIG. 15 is a diagram showing details of the scheduling unit 603 in FIG. CINR measurement section 1501 measures and aggregates CINR from the received signal RF (in case of uplink scheduling) or baseband processed signal (in case of downlink scheduling). The CINR table 1503 holds measurement results. The MCS table 1504 holds MCS corresponding to CINR. The MCS index table 1508 holds an MCS index corresponding to the MCS. Allocation MCS table 1509 holds MCS allocated to each terminal. The transmission rate table 1506 holds the instantaneous transmission rate and average transmission rate of each terminal. MCS determination section 1502 refers to CINR table 1503 and MCS table 1504, determines the MCS of each terminal, and updates allocation MCS table 1509 and transmission rate table 1506. The slot allocation determination unit 1505 determines slot allocation to each terminal in response to a packet arrival in the case of Downlink and a communication request from the terminal in the case of Uplink. The allocation information generation unit 1507 generates allocation information for transmitting slot allocation to the terminal. In the sequence diagram of FIG. 11, step 1103 is performed by the CINR determination unit 1501, step 1104 is performed by the MCS determination unit 1502, and step 1105 is performed by the slot allocation determination unit 1505. Hereinafter, the operation of Downlink will be described, but the same applies to Uplink. A flowchart of the CINR measurement unit 1501 is shown in FIG.

  In step 1601, the terminal number is initialized to n = 1. In Step 1602, it is determined whether or not the terminal number n is performing a CINR report. If a report is being made, the process proceeds to step 1603. If no report is made, the process proceeds to step 1604. In step 1603, the CINR column 1203 of the terminal number n in the CINR table is updated.

  In step 1604, the terminal number is incremented. If it is determined in step 1605 that n ≦ M, that is, all the terminals have not been determined, the process returns to step 1602. If n> M, that is, if all terminals have been determined, the process ends. In step 1603, the present invention is not limited to this as long as the CINR value is updated. For example, the updated average value of CINR may be used. A flowchart of the MCS determination unit 1502 is shown in FIG. In step 1701, the terminal number is initialized to n = 1. In step 1702, the CINR column 1203 of the CINR table 1503 is referred to extract the CINR of the terminal number n. In step 1703, the instantaneous transmission rate corresponding to the CINR extracted in step 1702 is extracted from the instantaneous transmission rate column 1303 with reference to the CINR threshold column 1301 of the MCS table 1504.

  In step 1704, the MCS index column 2601 of the MCS index table 1508 is referred to, and the MCS index column 2502 of the terminal number n in the allocated MCS index table is updated. In step 1705, the instantaneous transmission rate column 1403 of terminal number n in the transmission rate table 1506 is updated from the instantaneous transmission rate extracted in step 1703. In step 1706, the terminal number is incremented.

  In step 1707, if n ≦ M, that is, if all the terminals have not been determined, the process returns to step 1702. If n> M, that is, if all terminals have been determined, the process ends.

  Slot allocation determining section 1505 determines the number of slots allocated to each terminal. The operation will be described later.

  The allocation information generation unit 1507 determines the position of the slot used by each terminal from the number of allocation slots determined by the slot allocation determination unit 1505, and generates allocation information. A flowchart is shown in FIG. In step 1801, the terminal number is initialized to n = 1 and the slot number is initialized to p = 1. In step 1802, the number of assigned slots of terminal number n in the slot assignment table 106 is extracted. The slot assignment table 106 is shown in FIG. The allocation slot number Nn of the terminal number n is assigned to the allocation slot number field 1903, the allocation start slot pn indicating the number of the slot to be allocated is allocated to the allocation start slot column 1905, and the allocation end slot qn indicating the slot number where the allocation ends Is held in the assignment end slot field 1906. That is, the terminal number n indicates that the slot numbers pn to qn are allocated.

  In step 1803, the allocation start slot column 1905 of the terminal number n in the slot allocation table is updated to p and the allocation end slot column 1906 is updated to p + Nn. In step 1804, the average transmission rate column 1404 of the transmission rate table 1506 is updated with the following formula from the number of assigned slots. However, the instantaneous transmission rate is rn, and the average transmission rate before update is Rn (0).

  Here, α is a forgetting factor (0 ≦ α <1). If the forgetting factor α is increased, the average transmission rate weight is increased, and if α is decreased, the instantaneous transmission rate weight is increased.

In step 1805, the slot number p = p + Nn is updated so that the allocation start slot number of the next terminal is immediately after. In step 1806, the terminal number is incremented.
If n ≦ M in step 1807, that is, if all the terminals have not been determined, the process returns to step 1802. If n> M, that is, if all terminals have been determined, the process ends. The flowchart in FIG. 18 is a method of sequentially assigning slots in the order of terminal numbers, but the present invention is not limited to this as long as it determines the slot position assigned to each terminal.

The terminal scheduling means in this embodiment relates to the slot allocation determination unit 1505 in FIG. 15 in the configuration of the base station.
A block configuration diagram of the slot allocation determination unit 1505 in the present embodiment is shown in FIG.

  The initial cost function calculation unit 101 refers to the transmission rate table 1506 and calculates the initial value of the cost function. The initial cost function table 102 holds the calculated initial cost function. The temporary slot allocation determination unit 103 refers to the initial cost function table 102 from the occurrence of a downlink packet or a UL request, and temporarily determines slot allocation. The allocated terminal number threshold table 107 holds the maximum number of allocated terminals that can be allocated from the MAP length. The allocation slot number threshold table 108 holds the minimum allocation slot number that is the minimum necessary for each MCS. Distribution section 104 allocates a terminal number that exceeds the maximum number of allocated terminals in the allocation slot temporarily determined by provisional slot allocation determination section 103, or when the number of allocated slots for each terminal is less than the minimum number of allocated slots In addition, the allocation slot of the terminal is distributed to other terminals. The allocation slot table 106 holds the number of allocation slots for each terminal.

  The initial cost function calculation unit 101, the temporary slot allocation determination unit 103, and the distribution unit 104 operate in response to an allocation signal instructing slot allocation in the controller 610. The temporary slot allocation determining unit 103 exists as a temporary slot allocation program 702a that is a program module inside the base station memory 702, and the distribution unit 104 exists as a distribution program 702b that is a program module inside the base station memory 702.

  Further, in FIG. 11 of the scheduling sequence diagram, the temporary slot allocation determining unit 103 operates in step 1105a in step 1105, and the distributing unit 104 in step 1105b in step 1105.

  Example 1 in this example will be described. In the first embodiment, after determining the provisional allocation resource number to each terminal from the initial value of the cost function, the number of slots allocated to the terminals whose allocation terminal number exceeds the threshold is distributed, and the allocation slot number The number of slots assigned to the terminals that are below the threshold is sequentially distributed to the terminals that are not below the threshold to determine the number of assigned slots.

  The initial cost function calculation unit 101 refers to the transmission rate table 1506, calculates a cost function for determining the priority of slot allocation to each terminal, and stores it in the initial cost function table 102. This flowchart is shown in FIG.

In step 2001, the terminal number is initialized to n = 1. In step 2002, the instantaneous transmission rate column 1403 and the average transmission rate column 1404 of the transmission rate table 1506 are referred to extract the instantaneous transmission rate rn and the average transmission rate Rn of the terminal number n.
In step 2003, the initial cost function gn is calculated by the following equation.

The calculated cost function gn is updated in the initial cost function column 2102 of the terminal number n in the initial cost function table shown in FIG.
In step 2004, the terminal number is incremented. If n ≦ M in step 2004, that is, if all the terminals have not been determined, the process returns to step 2002. If n> M, that is, if all terminals have been determined, the process ends. The calculation method of the initial cost function in step 2003 is not limited to this as long as it indicates the priority of slot allocation of each terminal.

  Temporary slot allocation determination unit 103 temporarily determines the number of slots allocated to each terminal from the initial cost function. This flowchart is shown in FIG. In step 2201, the terminal number is initialized to n = 1. In step 2202, the initial cost function column 2102 of the initial cost function table 102 is referenced to extract the initial cost function gn of the terminal number n. In step 2203, the allocated slot number Nn is obtained from the extracted initial cost function by the following formula, and the allocated slot number column 1903 of the slot allocation table 106 is updated.

Here, N is the total number of slots.

In step 2204, the terminal number is incremented. If n ≦ M in step 2204, that is, if all the terminals have not been determined, the process returns to step 2202. If n> M, that is, if all terminals have been determined, the process ends.
In the formula of Nn obtained in step 2203, it is first assumed that the total number of slots is equally allocated to each terminal (first term). After that, the average value of the reciprocal of the initial cost function is taken (second term) and offset by the reciprocal of the initial cost function of the terminal itself (third term). Since the initial cost function is offset by the reciprocal of the initial cost function, a terminal having a higher initial cost function than the average and a higher priority has a smaller reciprocal of the initial cost function and is assigned more slots than the average allocation slot. On the other hand, a terminal having a smaller initial cost function than the average and a lower priority has a larger reciprocal of the initial cost function and is assigned fewer slots than the average allocation slot. The method for determining the number of allocated slots in step 2203 is not limited to this as long as the number of allocated slots is determined in accordance with the method for obtaining the initial cost function.

In distribution section 104, when the number of terminals exceeding the maximum number of allocated terminals is allocated in the allocation slots temporarily determined by provisional slot allocation determination section 103, or when the number of allocated slots for each terminal is less than the minimum allocation slot number In addition, the allocation slot number of the terminal having a low allocation priority is distributed to other terminals having a high allocation priority. A block diagram of the distribution unit 104 is shown in FIG.
The distribution unit 104 refers to the ranking unit 3601 for determining the priority of slot allocation and the allocated terminal number threshold table 107, and updates the slot allocation so that the allocated terminal number does not exceed the maximum allocated terminal number. A distribution unit 3602, a second allocation slot distribution unit 3603 that updates slot allocation so that the number of allocation slots of each terminal does not fall below the minimum allocation slot number, and an allocation update unit 3604 that updates the allocation slot number to an integer value Become.

  The ranking unit 3601 obtains the minimum number of allocated slots from the MCS of each terminal extracted from the allocated MCS table 1509 with reference to the allocated slot number threshold table 108, and from the number of allocated slots in the slot allocation table 106, ( Numbered slots)-(Minimum number of assigned slots) ranked, and in order from the terminal with the largest value of (Number of assigned slots)-(Minimum number of assigned slots), set the assigned order column 1904 of the slot assignment table to 1, 2,. Write., M. Here, the allocation slot number threshold value table is shown in FIG. In FIG. 27, the minimum allocation slot number corresponding to each MCS index is held in the minimum allocation slot number column 2702. For example, when MCS index = 1, that is, 1 / 2-QPSK, the minimum number of allocated slots is 10, and when MCS index = 4, that is, 1 / 2-16QAM, the minimum number of allocated slots is 3. The minimum allocation slot number corresponding to each MCS is set in advance or is instructed from the network side, for example, the GW 202. The allocation slot number threshold table 108 exists in the data memory 706 inside the base station.

A flowchart of the ranking unit 3601 is shown in FIG.
In step 2801, a one-dimensional array order [M], tmp_N [M] of size M is secured. Order [] stores the rank of terminal numbers according to the number of allocated slots, and tmp_N [] stores a value obtained by subtracting the minimum number of allocated slots from the number of allocated slots. These temporary memories are secured in the data memory 706 inside the base station. In step 2802, order [i] = i (i = 1, 2,..., M) is initialized. In step 2803, the terminal number n = 1 is initialized. In step 2804, the MCS index column 2502 of the MCS allocation table 1509 is referenced to extract the MCS index of the terminal number n. In step 2805, the minimum allocation slot number field 2702 of the allocation slot number threshold table 108 is referred to, and the minimum allocation slot number Nmin corresponding to the MCS index extracted in step 2804 is extracted.

In step 2806, the number of assigned slots Nn of the terminal number n is extracted with reference to the assigned slot number field 1903 of the slot assignment table 106.
In Step 2807, tmp_N [n] = Nn−Nmin is written. That is, the surplus number of assigned slots, which is obtained by subtracting the minimum number of slots from the number of assigned slots obtained by the temporary slot assignment determining unit 103, is written to tmp_N [n]. In step 2808, the terminal number is incremented. If n ≦ M in step 2809, that is, if writing to all terminals has not been completed, the processing returns to step 2804. If n> M, that is, if all terminals have finished writing, the process proceeds to step 2810.

  In step 2810, the one-dimensional array order [] is rearranged in order from the terminal number with the largest number of excess allocation slots tmp_N []. That is, the terminal with the largest tmp_N [] is stored in order [1], and the terminal with the smallest tmp_N [] is stored in order [M]. The rearranging method may be any method. For example, quick sort or bubble sort may be used. In step 2811, the rank is initialized as i = 1. In step 2812, the allocation order column 1904 of the terminal number order [i] in the slot allocation table 106 is updated to i.

In step 2813, the rank is incremented. If it is determined in step 2814 that i ≦ M, that is, all terminals have not been updated, the process returns to step 2812. If n> M, that is, if all terminals have been updated, the process proceeds to step 2815. In step 2815, the temporary memory order [], tmp_N [] is released, and the process ends.
The ranking unit 3601 is not limited to this as long as each terminal is ranked by Nn-Nmin.

  The first allocation slot distribution unit 3602 allocates notification information that increases according to the number of allocated terminals to a certain level or less, and suppresses degradation of transmission efficiency. The assigned number of slots is distributed to terminals with higher priority of allocation. This flowchart is shown in FIG.

  In Step 2302, the maximum allocated terminal number Mmax is extracted from the maximum allocated terminal number column 2403 of the allocated terminal number threshold table 107. FIG. 24 shows an allocation terminal number threshold table. The allocation terminal number threshold table 107 holds a MAP length storing information for notifying slot allocation of terminals in a frame in the MAP length column 2402, and indicates the maximum number of terminals that can be allocated corresponding to the maximum allocation terminal number column. An Index column 2401 held in 2403 represents the index of each row. For example, if the MAP length is 100 bits and 20 bits are required to notify the allocation of one terminal, the maximum number of allocated terminals is 5.

  In step 2303, the number of slots allocated to terminals having an allocation order equal to or lower than Mmax is summed up with reference to the allocation order field 1904 and the assigned slot number field 1903 of the slot assignment table 106. A flowchart of Step 2303 is shown in FIG. In step 2901, the allocation order is initialized to i = Mmax + 1, and the total number of slots is initialized to sum = 0. That is, a search is performed from the terminal with the allocation order Mmax + 1. If i ≦ M in step 2902, that is, if all terminals have not been searched, the process proceeds to step 2903. If i> M, that is, if all terminals have been searched, the process proceeds to step 2907. In step 2903, the allocation slot number L of the terminal number whose allocation order column 1904 of the slot allocation table 106 is i is extracted. In step 2904, sum = sum + L is calculated. In step 2905, the assigned slot number field 1903 in the assignment order field of the slot assignment table 106 is set to 0. That is, assignment is not performed to terminals with a low assignment order exceeding the maximum number of assigned terminals. In step 2906, the allocation order is incremented.

  In step 2907, since all terminals have been searched, sum is output and the process proceeds to step 2304. The step 2303 is not limited to this as long as the total number of allocation slots of terminals whose allocation order is Mmax + 1 or less is summed and output. In step 2304, the total number of slots in step 2303 is evenly distributed to the terminals with the highest allocation order. A flowchart of step 2304 is shown in FIG. In step 3001, the total number of slots sum obtained in step 2303 is input.

  In step 3002, in order to evenly distribute the number of slots allocated to terminals that cannot be allocated to terminals having higher allocation order, the distribution slot number D = sum / Mmax is calculated.

  In step 3003, the allocation order is initialized to i = 1.

In step 3004, D is added to the allocation slot number field 1903 corresponding to the terminal whose allocation order field 1904 of the slot allocation table 106 is i.
In step 3005, the allocation order is incremented.
If it is determined in step 3006 that i ≦ Mmax, that is, the distribution of the allocation slot to all terminals having the highest Mmax in the allocation order has not been completed, the process proceeds to step 3004. If i> M, that is, the distribution of the allocation slot to all terminals having the highest Mmax in the allocation order has been completed, the process ends.

  In step 2304, the number of slots totaled in step 2303 is not limited to this as long as it is distributed to the terminals with the highest allocation order. The first allocation slot distribution unit 104 is not limited to this as long as it distributes the number of slots allocated to terminals with a low allocation order to terminals with a high allocation order when the number of allocated terminals exceeds a threshold. . For example, instead of distributing evenly, the distribution may be performed after weighting according to reception quality or service priority.

  The second allocation slot distribution unit 105 allocates the number of slots allocated to a terminal having a low allocation priority when the number of allocation slots falls below a threshold value in order to suppress PER deterioration due to a decrease in the number of allocation slots. Distribute to terminals with higher priority. This flowchart is shown in FIG. In step 3101, the allocation order is set to i = Mmax. That is, a search is performed from the terminal with the lowest allocation order among the terminals to which slot allocation is performed. If i> M, that is, Mmax> M in step 3102, the process proceeds to step 3103. If i ≦ M, the process proceeds to step 3104.

  In step 3103, since the terminal with the allocation order M is the lowest, i = M. In step 3104, the allocation ranking column 1904 and the allocation slot number column 1903 of the slot allocation table 106 are referred to, and the allocation slot number L and the terminal number n with the allocation ranking i are extracted. In step 3105, the MCS index column 2502 of the MCS allocation table 1509 is referenced to extract the MCS index of the terminal number n.

  In Step 3106, the minimum allocation slot number Nmin corresponding to the MCS index is extracted with reference to the minimum allocation slot number field 2702 of the allocation slot number threshold table 108. If it is determined in step 3107 that L <Nmin, that is, the minimum number of allocation slots is not allocated, the process proceeds to step 3108 in order to distribute the allocation slot number. If L ≧ Nmin, that is, if more than the minimum number of allocated slots is allocated, the slot distribution is terminated and the process is terminated. In step 3108, in order to evenly distribute the number of assigned slots for terminal number n to the terminals with the highest order of assignment, the number of distribution slots D = L / (i-1) is calculated, and slot assignment is performed for terminal number n. Therefore, the number of assigned slots in the slot assignment table 106 is set to zero.

  In step 3109, the allocation order is initialized to m = 1 for distribution. In step 3110, the allocation order column 1904 of the slot allocation table 106 adds D to the m allocated slot number column 1903. In step 3111, the allocation order is incremented. If m ≦ i in step 3112, that is, if the slot distribution has not ended, the process returns to step 3110. If m> i, that is, if the slot distribution has been completed, the process proceeds to step 3113. In step 3113, the allocation order i is decremented.

  If i = 1 is not satisfied in step 3115, that is, if all the terminals have not been searched, the process proceeds to step 3104. If i = 1, that is, if all terminals have been searched, the process ends.

  The second allocation slot distribution unit 105 allocates to terminals having a higher allocation order when the allocation slot number is less than the minimum allocation slot number, starting from the terminal having the lowest allocation order, among the terminals having the allocation slot number greater than 0. There is no limitation to this as long as the number of slots is distributed, the integer part of the number of assigned slots expressed in decimal is first determined as the number of assigned slots, and the remaining slots are distributed.

The allocation updating unit 3604 updates the allocation slot number field 1903 to an integer when the allocation slot number field 1903 of the slot allocation table 106 is expressed in decimal. A flowchart is shown in FIG.
In step 3201, a one-dimensional array order [M], tmp_l [M] of size M is secured. Order [] stores the ranking of terminal numbers according to the number of assigned slots, and tmp_l [] stores the decimal part of the number of assigned slots. In step 3202, order [i] = i (i = 1, 2,..., M) is initialized. In step 3203, the terminal number is initialized to n = 1 and the total allocated slot number is initialized to sum = 0.

  In step 3204, the allocation slot number field 1903 of the slot allocation table 106 is referred to, and the allocation slot number L of the terminal number n is extracted. In step 3205, the decimal part of the number of assigned slots is calculated as tmp_l [n] = L-floor (L), and the total number of assigned slots is calculated as sum = sum + floor (L). Here, floor (x) is a function that returns the largest integer not exceeding x.

  In step 3206, the allocated slot number field 1903 for the terminal number n in the slot allocation table 106 is updated to floor (L). In step 3207, the terminal number is incremented. If n ≦ M in step 3208, that is, if the search of all terminals has not been completed, the process returns to step 3204. If n> M, that is, if all terminals have been searched, the process proceeds to step 3209.

In step 3209, the one-dimensional array order [] is rearranged in order from the terminal number having the largest fractional part tmp_l [] of the number of assigned slots. That is, the terminal with the largest tmp_l [] is stored in order [1], and the terminal with the smallest tmp_l [] is stored in order [M]. The rearranging method may be any method. For example, quick sort or bubble sort may be used.
In step 3210, the allocation order is initialized to i = 1.
If it is determined in step 3211 that the total number of allocated slots is sum <N, that is, if all slots have not been allocated, the process proceeds to step 3212. If the total number of allocated slots sum ≧ N, that is, if all slots have been allocated, the process proceeds to step 3214.
In step 3212, 1 is added to the assigned slot number field 1903 whose terminal number in the slot assignment table 106 is order [i].

In step 3213, the allocation order is incremented, the total allocation slot number is incremented, and the process returns to step 3211.
In step 3214, the temporary memory is released and the process ends.
The allocation update unit 3604 is limited to this as long as the integer part of the allocation slot number of each terminal is first determined as the allocation slot number, and the remaining slots are distributed to the terminals whose allocation slot number is greater than 0. Not what you want.

  The operation up to the determination of the number of assigned slots in this embodiment will be described with reference to FIGS. 33A and 33B. The total number of terminals is M = 6. In this embodiment, first, from the initial cost function, the provisional slot assignment determination unit 103 obtains the number of assigned slots temporarily for each terminal, and the ranking unit 3801 first assigns the number of assigned slots Nn and the minimum number of assigned slots to each terminal. Ranking from Nmin to Nn-Nmin. Assume that the ranking is as shown in FIG. 33A. That is, it is assumed that the terminal numbers are 2, 3, 1, 6, 5, 4 in descending order of priority. Here, the size of the gray rectangle represents the number of slots currently allocated, and the dotted rectangle represents the minimum number of slots allocated to each terminal. That is, a portion obtained by subtracting a dotted rectangle from a gray rectangle represents Nn-Nmin, and Nn-Nmin is the maximum on the left side.

  Here, assuming that the maximum number of allocated terminals Mmax = 4, the first allocation slot distribution unit 3802 disables allocation of terminal numbers 5 and 4 having lower ranks, and assigns gray rectangular portions 3305 and 3304 of terminal numbers 5 and 4 to Distribute to terminal numbers 2, 3, 1, and 6.

  It is assumed that after distribution by the first allocation slot distribution unit 3802, the result is as shown in FIG. 33B. Here, the size of the black rectangle is the number of slots distributed by the 10% slot distribution unit 3802. After the distribution, the second allocation slot distribution unit 3803 then searches for terminals that are less than the minimum allocation slot number from the lower rank. Since terminal number 6 in the lowest order is less than the minimum number of assigned slots, terminal number 6 cannot be assigned, and the number of assigned slots (the sum of the sizes of the gray rectangle and the black rectangle) 3306 is assigned. Distribute to high terminal numbers 2, 3, and 1.

  After distribution is shown in FIG. 33C. Here, the size of the hatched rectangle is the number of slots distributed by the second allocation slot distribution unit 3803. Accordingly, the total number of slots after distribution is the total number of gray rectangles, black rectangles, and hatched rectangles. At this time, since terminal number 1 in the lowest order is assigned more than the minimum number of assigned slots, slot distribution is terminated. According to the first embodiment described above, the number of allocated radio resources allocated to each terminal is determined by determining the number of allocated slots so that the number of allocated terminals is kept below the maximum number of allocated terminals and the number of allocated slots is equal to or greater than the minimum number of allocated slots. Without increasing the unit, it is possible to avoid an increase in radio resources required for notification information and deterioration of PER.

  Example 2 in the present embodiment will be described below. In the second embodiment, as shown in the block configuration diagram of the base station shown in FIG. 35, the first allocation slot distribution unit 3602 and the second allocation slot distribution unit 3603 in the base station of the first embodiment are connected in reverse. Yes. In the second embodiment, when the slots are allocated so as to be allocated more than the minimum number of allocated slots and the number of allocated terminals becomes less than the maximum number of allocated terminals, the processing can be completed earlier than in the first embodiment.

  In the above-described embodiments including Example 1 and Example 2, WIMAX, which is one of wireless communication standards, has been described as an example. However, the present invention is not limited to this standard, and finite wireless resources are allocated to a plurality of terminals. You may apply also about the standard of the wireless communication allocated to.

101, 3501: Initial cost calculation unit 102, 3502: Initial cost function table 103, 3503: Temporary slot allocation determination unit 104: Distribution unit 106, 3506: Slot allocation table 107, 3507: Assigned terminal number threshold table 108, 3508: Allocation Slot number threshold table 602, 902: Upper layer control unit 603: Scheduling unit 604, 904: Downlink baseband processing unit 605, 905: Uplink baseband processing unit 1501: CINR measurement unit 1502: MCS determination unit 1503: CINR table 1504: MCS table 1505: slot allocation determination unit 1506: transmission rate table 1507: allocation information generation unit 1508: MCS index table 1509: MCS allocation table 3501, 3601: ranking units 3502, 36 2: first assigned slot distribution unit 3503,3603: second assigned slot distribution unit 3504,3604: allocation update unit

Claims (6)

A radio base station apparatus that allocates radio resources to each of one or a plurality of terminals located in the own cell area, and transmits and receives data to and from each terminal using the radio resources,
Based on a scheduling request for the radio resource to be used for data transmission / reception with the terminal, the radio resource is allocated to the terminal in a predetermined radio resource allocation unit, and the number of radio resource units to be allocated is assumed. A provisional allocation determination processing unit to be determined;
Ranking the terminals by radio resource allocation priority;
The temporary allocation determining processing terminal number radio resources are allocated by the unit, when exceeding a threshold of the number of terminals that are pre Me stored, the priority radio resources the priority order is assigned to the smaller terminal than the threshold value Distributed to terminals whose rank is equal to or higher than a threshold, or when there is a terminal in which the number of units of radio resources allocated by the temporary allocation determination means does not satisfy the threshold of the number of units stored in advance, the radio allocated to that terminal A distribution processing unit that distributes the resources to terminals whose radio resource units are allocated to a threshold or more ;
A radio base station apparatus, comprising: an allocation result notification processing unit that notifies each terminal of a radio resource allocation result based on the distributed result. The radio base station apparatus according to claim 1,
The ranking processing unit
The radio base station apparatus, wherein ranking is performed based on a difference between a unit number of radio resources allocated by the temporary allocation determination unit and a threshold value of the unit number stored in advance. The radio base station apparatus according to claim 1,
The distribution processing unit includes:
An allocation update processing unit that updates the number of units of the radio resource allocated to the terminal to an integer when the number of units of the radio resource allocated to the terminal is not an integer;
A radio base station apparatus, wherein after determining a radio resource to be allocated to the terminal, the number of units of the radio resource to be allocated to the terminal is updated to an integer. The radio base station apparatus according to claim 3,
The allocation update processing unit
Determining an integer part of the number of radio resource units to be allocated to the terminal as a radio resource unit number to be allocated, and allocating the remaining radio resources in order from a terminal having a larger fractional part of the radio resource unit to be allocated to the terminal, A radio base station apparatus that determines the number of radio resource units to be allocated to a radio base station. The radio base station apparatus according to claim 1,
When the number of terminals to which radio resources have been allocated by the temporary allocation determination processing unit exceeds a pre-stored threshold value for the number of terminals, the distribution processing unit allocates the priority ranking to a terminal that is smaller than the threshold value Wireless resources are distributed to terminals whose priority ranking is equal to or higher than a threshold, and among the distributed terminals, the number of units of the wireless resources allocated by the temporary allocation determination processing unit is set to a threshold of the number of units stored in advance. A radio base station apparatus that distributes radio resources allocated to a terminal to terminals whose number of allocated radio resources is greater than or equal to a threshold when there is a terminal that does not satisfy the condition. The radio base station apparatus according to claim 1,
The distribution processing unit is assigned the radio resource allocated to the terminal when there is a terminal in which the number of units of the radio resource allocated by the temporary allocation determination processing unit is less than the threshold of the number of units stored in advance. The number of units of the radio resource is distributed to terminals having a threshold value or more, and among the distributed terminals, the number of terminals to which the radio resource is allocated by the temporary allocation determination processing unit is a threshold value of the number of terminals stored in advance. When it exceeds, the radio base station apparatus distributes the radio resource allocated to the terminal having the priority order smaller than the threshold to the terminals having the priority order higher than the threshold.

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