JP6329099B2 - Radio resource scheduling apparatus, method and program - Google Patents

Description

  The present invention relates to a radio resource scheduling apparatus, method, and program for performing radio communication between a transmission point and each user terminal in a wireless network system having a plurality of transmission points.

  In order to accommodate rapidly increasing mobile traffic, it is considered to arrange small cells at high density. A small cell has a smaller transmission power and a smaller cell radius from a base station (transmission point (hereinafter abbreviated as TP) in a wireless network system) than a macro cell.

  For this reason, when a small cell is adopted, the number of mobile terminals sharing the same frequency within the small cell (user equipment in the wireless network system: User Equipment, hereinafter abbreviated as UE) is reduced, so throughput per terminal can be reduced. Can be improved.

  On the other hand, the high density arrangement of small cells causes an increase in interference power from adjacent cells. For example, when a plurality of TPs simultaneously transmit data to different UEs using the same frequency band, for the UE, a transmission signal from a TP other than the TP that transmits data addressed to itself is a desired received signal. Interference power, which may cause a reduction in throughput.

  For this reason, in next-generation wireless communication interfaces such as LTE (Long Term Evolution) / LTE-A (Advanced), in order to suppress interference power between cells in the same frequency band, multi-point coordination (Coordinated Multi Point, hereinafter) Scheduling (abbreviated as CoMP) is employed (Non-Patent Document 1). In CoMP scheduling, TP operation contents (transmission destination UE / transmission stop) in the same subband are scheduled.

  Specifically, CoMP scheduling is a technique for evaluating a combination pattern of a plurality of TPs and UEs using a predetermined evaluation function, and selecting and outputting a pattern having the maximum evaluation value as a transmission pattern. The combination pattern of the TP and UE indicates a transmission destination UE or transmission stop (blank) for each TP. The predetermined evaluation function is a total value of TP-specific lower evaluation values calculated based on external evaluation information input from the outside, and the lower evaluation value is, for example, based on the Proportional Fairness method. This is a value obtained by dividing the instantaneous throughput of the transmission destination UE by the average throughput (Non-Patent Document 2).

  Further, the external evaluation information at this time is, for example, the average throughput of each UE, the untransmitted data amount of each UE, and channel quality state information for each TP for the target subband of each UE. This channel quality state information is, for example, subband CQI (Channel Quality Indicator: channel quality information) fed back from the UE (Non-Patent Document 3, Non-Patent Document 4). CQI is a positive integer value, and the larger the value, the better the channel quality.

  FIG. 18 shows a flow of CoMP scheduling. The CoMP scheduling apparatus first acquires, as a pattern generation condition, a UE number that can be selected by each TP as a transmission destination (step S100 in FIG. 18), and then an already generated pattern and the operation content of at least one TP (transmission destination). A combination pattern of TP and UE with different UE / transmission stop) is generated and output (step S101 in FIG. 18).

  Subsequently, the CoMP scheduling apparatus acquires the external evaluation information for the target subband, and calculates the evaluation value of the pattern generated in step S101 using the predetermined evaluation function (step S102 in FIG. 18). Then, when the evaluation value calculated in step S102 is larger than the maximum value of the evaluation values of the combination pattern so far, the CoMP scheduling apparatus stores the evaluation value calculated in step S102 as the maximum value, and step S101. Is stored as a new optimum pattern (step S103 in FIG. 18).

  The CoMP scheduling apparatus repeats the processes of steps S101 to S103, and when the evaluation for the transmission patterns of all TPs and UEs is completed (Yes in step S104 in FIG. 18), determines the optimum pattern stored as the transmission pattern, This is output (step S105 in FIG. 18).

Taoka et al., “MIMO and inter-cell cooperative transmission / reception technology in LTE-Advanced”, NTT DOCOMO Technical Journal, Vol.18, No.2, Jul.2010 Tolga Giric, et al., “Proportional Fair Scheduling Algorithm in OFDMA-Based Wireless Systems with QoS Constraints”, JOURNAL OF COMMUNICATIONS AND NETWORKS, VOL.12, NO.1, FEBRUARY 2010 Sandy Fraser, “LTE Channel State Information (CSI)”, <http://www.keysight.com/upload/cmc_upload/All/31May2012_LTE.pdf?&cc=JP&lc=jpn>, 2012 3GPP, TS 36.213 (V.8.2.0), 7.2.3, “Channel quality indicator (CQI) definition”, 2008

  Since conventional CoMP scheduling is frequency scheduling for determining the TP operation content for one subband, it must be performed for each subband. However, when CoMP scheduling is performed for each subband, the number of pattern evaluations becomes enormous as Npat × Nsb (Npat is the number of combined patterns of TP and UE, Nsb is the number of subbands that can be allocated), and frequency scheduling takes time. There was a point. For example, if Npat is 10,000 and Nsb is 7, the number of pattern evaluations is 70000.

  The present invention has been made in view of such circumstances, and an object thereof is to provide a scheduling technique for each frequency resource that can reduce the number of pattern evaluations.

The present invention is a radio resource scheduling apparatus for allocating frequency resources used for radio communication between a transmission point and a destination user terminal in a radio network system having a plurality of transmission points, and is transmitted for each transmission point. from the pattern combination shows a previous user terminal, or any operation to the destination without the multipoint collaborative scheduling means for selecting a number more than a predetermined number of combination patterns of allocatable frequency resources as transmission candidate pattern, Frequency scheduling means for determining a pattern for allocating frequency resources from among the transmission candidate patterns, wherein the multipoint coordinated scheduling means allocates all the assignable frequency resources or some of the plurality of frequency resources to one virtual resource. As a frequency resource , The obtained from the channel quality information indicating the reception quality of the downlink channel measured by the user terminal, transmission point by the channel quality state information for the virtual frequency resources fed back from the user terminals included in the combination pattern of the evaluation value calculation target based on a predetermined objective function to calculate the evaluation value of the combination pattern, based on this evaluation value, selects the predetermined number of combination patterns from the combination pattern of better evaluated in order as the transmission candidate pattern, said frequency scheduling unit is obtained from the channel quality information indicating the reception quality of the downlink channel measured by the user terminal to be fed back from the user terminal included in the transmission candidate pattern evaluation value calculation target, it can be allocated frequency resources The evaluation value of the transmission candidate pattern calculated for each frequency resource according to a predetermined objective function based on the transmission point by the channel quality state information against, on the basis of the evaluation value, unallocated to order from the transmission candidate patterns good estimate Frequency resources are allocated.

Further, in one configuration example of the radio resource scheduling apparatus of the present invention, the multipoint cooperative scheduling means calculates an evaluation value of the combination pattern by a Proportional Fairness method, and the frequency scheduling means performs the transmission candidate by the Proportional Fairness method. A pattern evaluation value is calculated.
Further, in one configuration example of the radio resource scheduling apparatus of the present invention, the multipoint cooperative scheduling means sets the number of the transmission candidate patterns to be the same as the number of frequency resources that can be allocated , and the combination pattern by the Proportional Fairness method. the evaluation value is calculated, the frequency scheduling unit is obtained from the channel quality information indicating the reception quality of the downlink channel measured by the user terminal to be fed back from the user terminal included in the transmission candidate pattern evaluation value calculation target , a value obtained by adding the total transmission points included the value of the transmission point by the channel quality state information for the allocatable frequency resources in the transmission candidate pattern, and is characterized in that the evaluation value of the transmission candidate pattern .

The present invention is also a radio resource scheduling method for allocating frequency resources used for radio communication between a transmission point and a destination user terminal in a radio network system having a plurality of transmission points, and for each transmission point multipoint collaborative scheduling step of selecting from among the combination patterns indicating one of the operation content of the user terminal or destination without the destination number than a predetermined number of combination patterns of allocatable frequency resources as transmission candidates pattern And a frequency scheduling step for determining a pattern for allocating frequency resources from among the transmission candidate patterns. In the multi-point coordinated scheduling step , all the frequency resources that can be allocated or a part of a plurality of frequency resources are set to 1 One provisional As frequency resources, obtained from the channel quality information indicating the reception quality of the downlink channel measured by the user terminal to be fed back from the user terminals included in the combination pattern of the evaluation value calculation target, transmission point by the channel to the virtual frequency resources based on the quality state information to calculate the evaluation value of the combination patterns by a predetermined objective function, selected on the basis of the evaluation value, the predetermined number of combination patterns in order from the combination pattern of better evaluation as the transmission candidate pattern and, in the frequency scheduling step, it is obtained from the channel quality information indicating the reception quality of the downlink channel measured by the user terminal to be fed back from the user terminal included in the transmission candidate pattern evaluation value calculation target Based on the transmission point by the channel quality state information for the allocatable frequency resources evaluation value of the transmission candidate pattern calculated for each frequency resource according to a predetermined objective function, based on the evaluation value, the transmission candidate a better evaluation This is characterized in that unallocated frequency resources are allocated in order from the pattern.

Further, in one configuration example of the radio resource scheduling method of the present invention, in the multipoint coordinated scheduling step , the evaluation value of the combination pattern is calculated by a Proportional Fairness method, and in the frequency scheduling step , the evaluation value is calculated by the Proportional Fairness method. An evaluation value of a transmission candidate pattern is calculated.
Further, in one configuration example of the radio resource scheduling method of the present invention, in the multipoint coordinated scheduling step , the number of the transmission candidate patterns is the same as the number of frequency resources that can be allocated , and the combination pattern is obtained by a Proportional Fairness method. calculating the evaluation value, in the frequency scheduling step, the channel quality information indicating the reception quality of the downlink channel measured by the user terminal to be fed back from the user terminal included in the transmission candidate pattern evaluation value calculation target obtained a value obtained by adding the total transmission points included the value of the transmission point by the channel quality state information to the transmission candidate pattern for allocatable frequency resources, characterized in that the evaluation value of the transmission candidate pattern that It is.

The present invention also provides a radio resource that causes a computer to function as a radio resource scheduling apparatus that allocates frequency resources used for radio communication between a transmission point and a destination user terminal in a radio network system having a plurality of transmission points. a scheduling program, from among the combination patterns indicating one of the operation content of the user terminal or destination without the destination for each transmission point, transmission candidate number more than a predetermined number of combination patterns of allocatable frequency resources A multipoint coordinated scheduling step for selecting as a pattern; and a frequency scheduling step for determining a pattern for allocating a frequency resource from the transmission candidate patterns. The ring step, all frequency resource allocation capable or some of the plurality of frequency resources as one virtual frequency resources, determined by the user terminal to be fed back from the user terminals included in the combination pattern of the evaluation value calculation target resulting from the channel quality information indicating the reception quality of the downlink channel that is, it calculates an evaluation value of the combination patterns by a predetermined objective function based on the transmission point by the channel quality state information for the virtual frequency resources, based on the evaluation value selects a better said predetermined number of combination patterns from the combination pattern in the order of evaluation as the transmission candidate pattern, said at frequency scheduling step, evaluation value said transmission feedback is from a user terminal included in the candidate pattern to be calculated That the the user terminal obtained from the channel quality information indicating the reception quality of the downlink channel measured, the evaluation value of the transmission candidate pattern by a predetermined objective function based on the transmission point by the channel quality state information for the allocatable frequency resources Is calculated for each frequency resource, and based on this evaluation value , unassigned frequency resources are allocated in order from the transmission candidate pattern with better evaluation .

  According to the present invention, the multipoint coordinated scheduling means feeds back all the assignable frequency resources or some of the plurality of frequency resources as one virtual frequency resource from the user terminal included in the evaluation value calculation target combination pattern. The evaluation value of the combination pattern is calculated by a predetermined objective function based on the channel quality state information for each transmission point for the virtual frequency resource obtained from the received information, and combinations of numbers equal to or greater than the number of frequency resources in order from the largest evaluation value A pattern is selected as a transmission candidate pattern, and the frequency scheduling means is predetermined based on channel quality state information for each transmission point for an assignable frequency resource fed back from a user terminal included in the transmission candidate pattern to be evaluated. Eye By calculating the evaluation value of the transmission candidate pattern for each frequency resource using a function and allocating unassigned frequency resources in order from the transmission candidate pattern with the largest evaluation value, the number of pattern evaluations can be reduced compared to conventional techniques. And the time required for frequency scheduling can be shortened. In the present invention, assuming that the number of transmission candidate patterns selected by the multipoint cooperative scheduling means is Ncand, the number of frequency resources that can be allocated is Nsb, and the number of combination patterns that can be taken by the transmission point and the user terminal is Npat, the number of pattern evaluations is Npat + Ncand. × Nsb, and the number of pattern evaluations can be reduced compared to the conventional number of pattern evaluations Npat × Nsb.

  Further, in the present invention, the transmission candidate pattern for evaluation value calculation includes the value of channel quality state information by transmission point for the assignable frequency resource fed back from the user terminal included in the transmission candidate pattern for evaluation value calculation. When using the Proportional Fairness method to calculate the pattern evaluation value, the sum of all the transmission points is used as the evaluation value of the transmission candidate pattern, so that the pattern evaluation value in the frequency scheduling means only needs to be added. Compared to the above, the time required for frequency scheduling can be further shortened.

It is a block diagram which shows the structure of the radio | wireless resource scheduling apparatus which concerns on the 1st Embodiment of this invention. It is a flowchart explaining the outline of operation | movement of the radio | wireless resource scheduling apparatus based on the 1st Embodiment of this invention. It is a block diagram which shows the structural example of the CoMP scheduling part which concerns on the 1st Embodiment of this invention. It is a flowchart explaining the whole operation | movement of the CoMP scheduling part which concerns on the 1st Embodiment of this invention. It is a figure which shows an example of the transmission candidate pattern in the 1st Embodiment of this invention. It is a flowchart explaining operation | movement of the transmission candidate pattern selection part which concerns on the 1st Embodiment of this invention. It is a block diagram which shows the structural example of the frequency scheduling part which concerns on the 1st Embodiment of this invention. It is a flowchart explaining the whole operation | movement of the frequency scheduling part which concerns on the 1st Embodiment of this invention. It is a flowchart explaining operation | movement of the pattern evaluation part classified by subband which concerns on the 1st Embodiment of this invention. It is a figure which shows an example of the pattern evaluation value for every subband in the 1st Embodiment of this invention. It is a flowchart explaining the operation | movement of the subband allocation part which concerns on the 1st Embodiment of this invention. It is a figure which shows one example of the pattern evaluation value after the process of the subband allocation part in the 1st Embodiment of this invention. It is a flowchart explaining the pattern evaluation value maximum value search process of the subband allocation part in the 1st Embodiment of this invention. It is a flowchart explaining the operation | movement of the subband allocation part which concerns on the 2nd Embodiment of this invention. It is a figure which shows an example of the pattern evaluation value after the process of the subband allocation part in the 2nd Embodiment of this invention. It is a flowchart explaining operation | movement of the pattern evaluation part classified by subband which concerns on the 3rd Embodiment of this invention. It is a flowchart explaining the pattern evaluation value maximum value search process of the subband allocation part in the 3rd Embodiment of this invention. It is a flowchart explaining the conventional CoMP scheduling.

[First Embodiment]
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing the configuration of the radio resource scheduling apparatus according to the present embodiment, and FIG. 2 is a flowchart for explaining the outline of the operation of the radio resource scheduling apparatus. The radio resource scheduling apparatus according to the present embodiment includes a CoMP scheduling unit 1 that selects a transmission candidate pattern from a combination pattern of TP and UE, and a frequency scheduling unit 2 that allocates frequency resources to the transmission candidate pattern.

  The CoMP scheduling unit 1 regards all subbands (frequency resources) that can be allocated as one virtual subband (virtual frequency resource) as compared with the conventional case, and determines a pattern evaluation value based on channel quality state information for the virtual subbands. And the point that the combination pattern of the top Ncand TPs and UEs of the evaluation value is selected as a transmission candidate pattern is different (step S1 in FIG. 2). Here, Ncand is greater than or equal to Nsb and less than Npat (Nsb is the number of subbands that can be allocated, and Npat is the number of combination patterns that TP and UE can take).

  The frequency scheduling unit 2 calculates a pattern evaluation value for the transmission candidate pattern selected by the CoMP scheduling unit 1 based on channel quality state information for each subband, and the subbands in order from the transmission candidate pattern having the largest evaluation value. Is assigned (step S2 in FIG. 2).

  Hereinafter, details of the CoMP scheduling unit 1 and the frequency scheduling unit 2 in the present embodiment will be described.

[CoMP scheduling unit]
FIG. 3 is a block diagram showing a configuration example of the CoMP scheduling unit 1, and FIG. 4 is a flowchart for explaining the overall operation of the CoMP scheduling unit 1. The CoMP scheduling unit 1 according to the present embodiment includes a pattern generation condition acquisition unit 10 that acquires pattern generation conditions, a pattern generation unit 11 that generates a combination pattern of TP and UE, and pattern evaluation that calculates an evaluation value of the combination pattern Unit 12 and a transmission candidate pattern selection unit 13 that selects a combination pattern as a transmission candidate pattern in order from the pattern with the largest pattern evaluation value.

  Compared to a conventional CoMP scheduling apparatus, the CoMP scheduling unit 1 includes external evaluation information E1 input to the pattern evaluation unit 12 that includes at least average throughput for each UE, untransmitted data amount for each UE, and virtual sub information for each UE. The difference is that the channel quality state information for each TP for the band is included, and the transmission candidate pattern selection unit 13 is newly provided.

  The TP-specific channel quality state information for the virtual subband is, for example, a wideband CQI indicating the channel quality for the entire virtual subband fed back from the UE. That is, the UE measures the wideband CQI indicating the reception quality of the downlink channel for the determined virtual subband, and reports the measured wideband CQI to the TP.

As in the prior art, the pattern generation condition acquisition unit 10 acquires the number of a UE that can be selected as a transmission destination by each TP as the pattern generation condition (step S100 in FIG. 4).
The pattern generation unit 11 generates a combination pattern of TP and UE based on the pattern generation condition acquired by the pattern generation condition acquisition unit 10 (step S101 in FIG. 4). Specifically, the pattern generation unit 11 generates a combination pattern of TP and UE that is different from the already generated combination pattern and the operation content (transmission destination UE / transmission stop) of at least one TP.

  The pattern evaluation unit 12 acquires the external evaluation information E1, and calculates the evaluation value of the combination pattern of TP and UE generated by the pattern generation unit 11 using a predetermined evaluation function (object function) (step S106 in FIG. 4).

  That is, for each TP included in the combination pattern of TPs and UEs for which evaluation values are to be calculated, the pattern evaluation unit 12 uses the external evaluation information E1 (feedback from the UE defined as the transmission destination of the TP in this combination pattern). The lower evaluation value is calculated by a predetermined evaluation function (objective function) based on the average throughput for each UE, the amount of untransmitted data for each UE, and the channel quality state information for each TP for each virtual subband, and the calculation target The sum of the lower evaluation values of the TPs included in the combination pattern is used as the evaluation value of the combination pattern to be calculated. For the calculation of the pattern evaluation value, it is preferable to use a method that considers fairness between users, such as the Proportional Fairness method.

Note that the lower evaluation value of TP calculated in the Proportional Fairness method can be expressed by (R _ins [#ue]) ^α / (R _avg [#ue]) ^β . Here, R _ins [#ue] is the instantaneous throughput of the UE of number #ue specified as the transmission destination of the TP in the combination pattern to be calculated, and R _avg [#ue] is the average of the UEs of number #ue Throughput, α and β are predetermined adjustment coefficients. The instantaneous throughput R _ins [#ue] is a value obtained by converting the SINR (Signal to Interference plus Noise power Ratio) value of the UE of number #ue. The SINR corresponds to the UE of the number #ue among the values obtained by converting the channel quality state information per TP (external evaluation information E1) fed back from the UE of the number #ue into the SNR (Signal to Noise Ratio). This is a value obtained using the SNR of the TP (TP specified as the transmission source of the UE in the combination pattern to be calculated) as the numerator and the sum of the SNRs of the remaining TPs as the denominator.

  The transmission candidate pattern selection unit 13 selects a combination pattern of TPs and UEs whose evaluation values calculated by the pattern evaluation unit 12 are among the top Ncand among the combination patterns of TPs and UEs generated by the pattern generation unit 11. The pattern is selected (step S107 in FIG. 4). Needless to say, at the time when the combination pattern of TP and UE generated by the pattern generation unit 11 is Ncand or less, all these combination patterns become transmission candidate patterns.

  The CoMP scheduling unit 1 repeats the processes of steps S101, S106, and S107. When the pattern evaluation unit 12 calculates the pattern evaluation value, the transmission candidate pattern is also updated if the combination pattern of the TP and the UE whose evaluation value falls within the upper Ncand number changes. When the transmission candidate pattern selection unit 13 completes the evaluation for all transmission patterns that can be taken by the TP and the UE (Yes in step S108 in FIG. 4), the transmission candidate pattern selection unit 13 notifies the subsequent frequency scheduling unit 2 of the determined transmission candidate pattern Cand_Pat. (Step S109 in FIG. 4). Thus, the process of the CoMP scheduling unit 1 is completed.

  FIG. 5 shows an example of the transmission candidate pattern Cand_Pat. Here, it is assumed that the transmission candidate patterns whose pattern evaluation values are included in the upper Ncand patterns are Cand_Pat [0] to Cand_Pat [Ncand-1]. In the example of FIG. 5, for example, in the transmission candidate pattern Cand_Pat [0] of the transmission candidate pattern number 0, the number of the transmission destination UE of the number 0 TP is 0, the number of the transmission destination UE of the TP of number 1 is 5, The number of the TP transmission destination UE is “Blank”. “Blank” indicates that there is no transmission destination (transmission stop). Further, in the transmission candidate pattern Cand_Pat [1] of the transmission candidate pattern number 1, the number of the transmission destination UE of the number 0 TP is 3, the number of the transmission destination UE of the number 1 TP is 7, and the transmission destination of the TP of the number 3 The UE number is 8.

  FIG. 6 is a flowchart for explaining the operation of the transmission candidate pattern selection unit 13. Here, the process of FIG. 6 is executed every time the pattern evaluation value Vinput is input from the pattern evaluation unit 12.

  In FIG. 6, #cand is a transmission candidate pattern number (# cand = 0, 1,..., Ncand−1). V [#cand] is the upper Ncand pattern evaluation values stored in the transmission candidate pattern selection unit 13. V [#cand] is stored in descending order (V [0] ≧ V [1] ≧... ≧ V [Ncand−1]). Cand_Pat [#cand] is a transmission candidate pattern corresponding to V [#cand].

  When the pattern evaluation value Vinput is input from the pattern evaluation unit 12, the transmission candidate pattern selection unit 13 resets the number #cand to 0 (step S <b> 110 in FIG. 6), and if the number #cand has not reached Ncand (No in step S111 in FIG. 6), the pattern evaluation value Vinput input from the pattern evaluation unit 12 is compared with the stored pattern evaluation value V [#cand] (step S112 in FIG. 6).

  If the pattern evaluation value Vinput is less than V [#cand] (No in step S112), the transmission candidate pattern selection unit 13 increments the number #cand by 1 (step S113 in FIG. 6) and returns to step S111.

  In addition, when the pattern evaluation value Vinput is equal to or higher than V [#cand] (Yes in step S112), the transmission candidate pattern selection unit 13 adds the combination pattern of the TP and UE having the pattern evaluation value Vinput to the transmission candidate pattern. Therefore, the currently stored pattern evaluation values V [#cand] to V [Ncand-2] and transmission candidate patterns Cand_Pat [#cand] to Cand_Pat [Ncand-2] are shifted one by one in the lower direction ( FIG. 6 steps S114 to S117).

  #Cand_tmp in FIG. 6 is an internal variable (number) for shifting the pattern evaluation value and the transmission candidate pattern in the lower direction. The transmission candidate pattern selection unit 13 initializes the number #cand_tmp to Ncand-1 (step S114 in FIG. 6), and stores the stored pattern evaluation value V [#cand_tmp] and the transmission candidate pattern Cand_Pat [#cand_tmp] in the lower direction. The process of shifting by one (step S116 in FIG. 6) is repeatedly performed while the number #cand_tmp is decreased by 1 (step S117 in FIG. 6). When the number #cand_tmp becomes equal to or less than #cand (No in step S115 in FIG. 6), the repetition process is finished.

  Then, the transmission candidate pattern selection unit 13 stores the pattern evaluation value Vinput input from the pattern evaluation unit 12 as the new pattern evaluation value V [#cand] (step S118 in FIG. 6), and the new transmission candidate pattern Cand_Pat. As [#cand], a combination pattern of TP and UE corresponding to the pattern evaluation value Vinput (a combination pattern that is a target of calculation of the pattern evaluation value Vinput and generated by the pattern generation unit 11) is stored ( FIG. 6 step S119). Above, the process of the transmission candidate pattern selection part 13 is complete | finished.

  When the transmission candidate pattern selection unit 13 repeats the size comparison process in step S112, the pattern evaluation value Vinput input from the pattern evaluation unit 12 stores the pattern evaluation values V [0] to V [ If it is smaller than any of Ncand−1], the number #cand reaches Ncand (Yes in step S111 in FIG. 16). In this case, the transmission candidate pattern selection unit 13 ends the processing of FIG. 6 without adding the combination pattern of TP and UE corresponding to the pattern evaluation value Vinput to the transmission candidate pattern Cand_Pat, and inputs the next pattern evaluation value Vinput. Wait for. The initial values of the pattern evaluation values V stored in the transmission candidate pattern selection unit 13 are all 0, and the initial values of the transmission candidate patterns Cand_Pat are all blanks.

[Frequency scheduling section]
Next, the frequency scheduling unit 2 will be described. FIG. 7 is a block diagram showing a configuration example of the frequency scheduling unit 2, and FIG. 8 is a flowchart for explaining the overall operation of the frequency scheduling unit 2.

  The frequency scheduling unit 2 includes a transmission candidate pattern acquisition unit 20 that acquires a transmission candidate pattern Cand_Pat from the CoMP scheduling unit 1, and a subband-specific pattern evaluation unit 21 that calculates a pattern evaluation value for each subband for each transmission candidate pattern Cand_Pat. The subband allocating unit 22 allocates subbands in units of transmission candidate patterns Cand_Pat based on the evaluation value.

  When the output from the CoMP scheduling unit 1 is updated, the transmission candidate pattern acquisition unit 20 of the frequency scheduling unit 2 acquires all the updated transmission candidate patterns Cand_Pat (Step S200 in FIG. 8). Then, the transmission candidate pattern acquisition unit 20 inputs all the acquired transmission candidate patterns Cand_Pat one by one to the subband-specific pattern evaluation unit 21 (step S202 in FIG. 8). #Pat in FIG. 8 is a positive integer representing a transmission candidate pattern number.

  The subband pattern evaluation unit 21 calculates and stores a pattern evaluation value for each subband for each transmission candidate pattern Cand_Pat input from the transmission candidate pattern acquisition unit 20 (step S203 in FIG. 8). When the pattern evaluation values for all transmission candidate patterns Cand_Pat have been calculated (Yes in step S204 in FIG. 8), the subband-specific pattern evaluation unit 21 displays the stored pattern evaluation value calculation results as subband allocation. To the unit 22.

  The subband allocating unit 22 allocates subbands to the transmission candidate patterns Cand_Pat in descending order of the pattern evaluation values calculated by the subband pattern evaluating unit 21 (steps S205 and S206 in FIG. 8). When the assignment of all the assignable subbands to the transmission candidate pattern Cand_Pat is completed (Yes in step S207 in FIG. 8), the subband assignment unit 22 transmits the assigned transmission candidate pattern Cand_Pat for each subband for each subband. Output as a pattern. Above, the process of the frequency scheduling part 2 is complete | finished.

  Note that subbands are assigned to transmission candidate patterns Cand_Pat by assigning numbers (0 to Nsb-1) to all subbands that can be assigned in advance and assigning the subband numbers to transmission candidate patterns Cand_Pat. . In FIG. 8, #alloc_sb_num is a positive integer representing the number of assigned subbands.

In the present embodiment, the combination pattern of the top Ncand TPs and UEs of the pattern evaluation value calculated by the CoMP scheduling unit 1 is set as the transmission candidate pattern Cand_Pat. Since Nsb ≦ Ncand <Npat as described above, in the case of Nsb <Ncand, there is no assignable subband in some transmission candidate patterns Cand_Pat whose pattern evaluation value calculated by the subband pattern evaluation unit 21 is small. Subband allocation is not performed.
Hereinafter, operations of the subband-specific pattern evaluation unit 21 and the subband allocation unit 22 will be described in detail.

[Subband pattern evaluation section]
The subband pattern evaluation unit 21 calculates a pattern evaluation value for each subband with respect to the transmission candidate pattern Cand_Pat input from the transmission candidate pattern acquisition unit 20. FIG. 9 is a flowchart for explaining the operation of the subband-specific pattern evaluation unit 21. In FIG. 9, #sb is a positive integer representing a subband number.

  First, the subband pattern evaluation unit 21 acquires external evaluation information E2 corresponding to the subband number #sb (steps S210 and S211 in FIG. 9). Next, the subband pattern evaluation unit 21 calculates a pattern evaluation value for the subband of the subband number #sb for the # pat-th transmission candidate pattern Cand_Pat [#pat] (step S212 in FIG. 9), and the calculated pattern The evaluation value is stored as Vpat [#sb] [#pat] (step S213 in FIG. 9). The subband-by-subband pattern evaluation unit 21 performs the processes of steps S210 to S213 as described above for all subbands that can be assigned.

  When the pattern evaluation value calculation processing is completed for all the assignable subbands (Yes in step S214 in FIG. 9), the processing for the # pat-th transmission candidate pattern Cand_Pat [#pat] is completed. The subband pattern evaluation unit 21 performs the processing shown in FIG. 9 for all transmission candidate patterns Cand_Pat [0] to Cand_Pat [Ncand-1] of transmission candidate pattern numbers # pat = 0 to Ncand-1. Do this for each pattern.

  Note that the external evaluation information E2 for each subband includes, for example, at least the average throughput for each UE and the channel quality state information for each TP (for example, the subband CQI) for each subband of each UE. The UE measures the subband CQI indicating the reception quality of the downlink channel for each subband, and reports the measured subband CQI to the TP.

  For each TP included in the transmission candidate pattern Cand_Pat [#pat] for which the evaluation value is to be calculated, the subband-specific pattern evaluation unit 21 starts from the UE specified as the transmission destination of the TP in the transmission candidate pattern Cand_Pat [#pat]. Based on the fed back external evaluation information E2, a lower evaluation value for the target subband of subband number #sb is calculated by a predetermined evaluation function (objective function), and each TP included in the transmission candidate pattern Cand_Pat [#pat] The sum of the lower evaluation values is set as the pattern evaluation value Vpat [#sb] [#pat] of the transmission candidate pattern Cand_Pat [#pat] for the target subband. For the calculation of the pattern evaluation value, it is preferable to use a method that considers fairness between users, such as the Proportional Fairness method.

The lower evaluation value of TP calculated in the Proportional Fairness method can be expressed by (R _ins [#ue]) ^α / (R _avg [#ue]) ^β as described above. Here, R _ins [#ue] is the instantaneous throughput of the UE of number #ue defined as the transmission destination of the TP in the transmission candidate pattern Cand_Pat [#pat] to be calculated, and R _avg [#ue] is the UE's Average throughput. The instantaneous throughput R _ins [#ue] is a value obtained by converting the SINR value of the UE of number #ue in the same manner as described above. The SINR is a TP corresponding to the UE of the number #ue (calculation target) among the values obtained by converting the channel quality state information by TP (external evaluation information E2) fed back from the UE of the number #ue into the SNR. This value is obtained using the SNR of the TP defined as the transmission source of the UE in the transmission candidate pattern Cand_Pat [#pat] as the numerator and the sum of the SNRs of the remaining TPs as the denominator.

  FIG. 10 shows an example of pattern evaluation values for each subband. In the example of FIG. 10, for example, in the transmission candidate pattern Cand_Pat [0] with the transmission candidate pattern number # pat = 0, the pattern evaluation value Vpat [0] [0] for the subband with the subband number # sb = 0 is 5, The pattern evaluation value Vpat [1] [0] for the subband of subband number # sb = 1 is 20, and the pattern evaluation value Vpat [2] [0] for the subband of subband number # sb = 2 is 10. It has become.

  In addition, in the transmission candidate pattern Cand_Pat [Ncand-1] with the transmission candidate pattern number # pat = Ncand-1, the pattern evaluation value Vpat [0] [Ncand-1] for the subband with the subband number # sb = 0 is 2 The pattern evaluation value Vpat [1] [Ncand-1] for the subband with subband number # sb = 1 is 15, and the pattern evaluation value Vpat [2] [Ncand− for the subband with subband number # sb = 2. 1] is 9.

[Subband allocation unit]
Next, the subband allocating unit 22 allocates subbands to the transmission candidate patterns Cand_Pat in descending order of the pattern evaluation value Vpat calculated by the subband pattern evaluating unit 21. FIG. 11 is a flowchart for explaining the operation of the subband allocating unit 22. In FIG. 11, #max_pat is the number of a transmission candidate pattern corresponding to the maximum value of the pattern evaluation value Vpat, and #alloc_sb is the number of a subband assigned to the transmission candidate pattern.

  First, the subband allocation unit 22 searches for the maximum value from the pattern evaluation values Vpat calculated by the subband pattern evaluation unit 21 (steps S220 and S221 in FIG. 11). When the number #max_pat is not NULL, that is, when the subband allocation unit 22 finds the maximum value in the pattern evaluation value Vpat calculated by the subband pattern evaluation unit 21 (Yes in step S222 in FIG. 11), this pattern A subband of subband number #alloc_sb corresponding to the maximum value of pattern evaluation value Vpat is assigned to a transmission candidate pattern of transmission candidate pattern number #max_pat corresponding to the maximum value of evaluation value Vpat (step S223 in FIG. 11).

  Then, the subband allocating unit 22 assigns all the pattern evaluation values Vpat [#all_sb] [# max_pat] of the transmission candidate pattern of the transmission candidate pattern number #max_pat to which the subband of the subband number #alloc_sb is allocated. In addition to rewriting to NULL to represent, by rewriting the pattern evaluation value Vpat [#alloc_sb] [#other_pat] for the subband of the subband number #alloc_sb of another transmission candidate pattern to NULL, the assigned transmission candidate pattern and assigned Are assigned to the subbands (step S224 in FIG. 11). Note that #all_sb represents all subband numbers, and #other_pat represents transmission candidate pattern numbers other than #max_pat.

  FIG. 12 shows an example of the pattern evaluation value after processing by the subband allocating unit 22. In the example shown in FIG. 10, among the pattern evaluation values Vpat calculated by the subband pattern evaluation unit 21, the pattern evaluation value Vpat [1] for the subband number # alloc_sb = 1 and the transmission candidate pattern number # max_pat = 1. [1] indicates a maximum value of 20. Therefore, the subband allocating unit 22 allocates the subband with the subband number # alloc_sb = 1 to the transmission candidate pattern with the transmission candidate pattern number # max_pat = 1 corresponding to the maximum value 20.

Then, as shown in FIG. 12, the subband allocating unit 22 sets all the pattern evaluation values Vpat [0] [1], Vpat [1] [1], Vpat of the transmission candidate pattern of transmission candidate pattern number # max_pat = 1. [2] [1],..., Vpat [Nsb-1] [1] is rewritten to NULL, and the pattern evaluation value Vpat [for the subband number # alloc_sb = 1 of another transmission candidate pattern 1] [0], Vpat [1] [2],..., Vpat [1] [Ncand-1] are rewritten to NULL.
The subband allocating unit 22 performs the processing shown in FIG. 11 for each transmission candidate pattern Cand_Pat in order from the largest pattern evaluation value Vpat.

  FIG. 13 is a flowchart for explaining the pattern evaluation value maximum value search process (steps S220 and S221) of the subband allocating unit 22. In FIG. 13, Vmax is the maximum value of the pattern evaluation value Vpat searched so far, and the initial value is 0. #Sb_tmp is an internal variable indicating a search subband number, and #pat_tmp is an internal variable indicating a search pattern number. The initial values of these internal variables #sb_tmp and #pat_tmp are both 0.

  The subband allocation unit 22 initializes the maximum value Vmax of the pattern evaluation value Vpat to 0 (step S230 in FIG. 13), and the pattern evaluation value pattern evaluation value Vpat [#sb] [# calculated by the subband-specific pattern evaluation unit 21 [pat], the pattern evaluation value Vpat [#sb_tmp] [#pat_tmp] is checked whether it is not NULL and whether it is equal to or larger than Vmax (steps S231 to S234 in FIG. 13).

  If the pattern evaluation value Vpat [#sb_tmp] [#pat_tmp] is not NULL and is equal to or greater than the current maximum value Vmax (Yes in step S234), the subband allocating unit 22 determines the pattern evaluation value Vpat [#sb_tmp] [# pat_tmp] is a new maximum value Vmax, search pattern number #pat_tmp is a new transmission candidate pattern number #max_pat corresponding to the maximum value Vmax, and search subband number #sb_tmp is a new subband number corresponding to the maximum value Vmax #Alloc_sb is set (step S235 in FIG. 13).

  The subband allocating unit 22 repeats the processes of steps S233 to S235 while increasing the search pattern number #pat_tmp by 1 from the initial value 0 (step S232), and after completing the process for all pattern numbers (step 13 in FIG. 13). In step S236, the search subband number #sb_tmp is incremented by 1 from the initial value 0 (step S231), and the processing in steps S232 to S236 is repeated to complete the processing for all subband numbers (FIG. 13). In step S237, Yes), the pattern evaluation value maximum value search process ends.

  Thus, based on the subband pattern evaluation values of all unassigned transmission candidate patterns, the transmission candidate pattern of the transmission candidate pattern number #max_pat corresponding to the maximum value Vmax and the subband number #alloc_sb corresponding to the maximum value Vmax Subbands can be derived.

According to the present embodiment described above, the number of pattern evaluations can be reduced as compared with the conventional technique. The number of pattern evaluations N in the present embodiment is obtained by the following equation.
N = Npat + Ncand × Nsb (1)

  As described above, Ncand is the number of transmission candidate patterns selected by the CoMP scheduling unit 1, and is a value that is equal to or greater than the number of subbands that can be allocated, Nsb, and less than the number of combined patterns Npat that TP and UE can take. For example, when Npat is 10000 and Nsb is 7, and Ncand is 14, the number of pattern evaluations N in this embodiment is 10098, which is smaller than the number of pattern evaluations 70000 of the prior art.

  The reason why the number of pattern evaluations N is obtained by the equation (1) is as follows. In the present embodiment, CoMP scheduling and frequency scheduling are separated and pattern evaluation is performed. The CoMP scheduling unit 1 regards all subbands as one virtual subband and performs pattern evaluation. Therefore, the number of patterns evaluated by the CoMP scheduling unit 1 is the same number of Npat as that of one subband.

  On the other hand, since the frequency scheduling unit 2 performs pattern evaluation for each subband only for Ncand, the number of pattern evaluations in the frequency scheduling unit 2 is a value obtained by multiplying Ncand by Nsb. Therefore, the total number of pattern evaluations N in the present embodiment is the sum obtained by adding Npat and Ncand × Nsb because it is the sum of the number of pattern evaluations for CoMP scheduling and frequency scheduling.

  In the present embodiment, frequency scheduling is performed in units of subbands, but frequency scheduling in units of frequency resource blocks, which are defined in the radio interface and have a smaller allocation unit, may be used. In addition, the external evaluation information E1 and E2 includes CQI, but information obtained by updating other channel quality state information fed back from the UE may be used as the external evaluation information E1 and E2. . Various modifications may be made without departing from the spirit of the present embodiment.

[Second Embodiment]
Next, a second embodiment of the present invention will be described. Also in the present embodiment, the configuration of the radio resource scheduling apparatus, the operation of the CoMP scheduling unit 1, and the overall operation of the frequency scheduling unit 2 are the same as those in the first embodiment. It explains using. The radio resource scheduling apparatus according to the present embodiment is different from the first embodiment in that allocation to the same transmission candidate pattern is permitted in a plurality of subbands.

  FIG. 14 is a flowchart for explaining the operation of the subband allocating unit 22 according to the present embodiment. The same processes as those in FIG. 11 are denoted by the same reference numerals. The processing in steps S220 to S223 in FIG. 14 is as described in FIG. 11 of the first embodiment.

  The subband allocating unit 22 selects the subband number #alloc_sb among the pattern evaluation values Vpat of the transmission candidate patterns of the transmission candidate pattern number #max_pat to which the subband of the subband number #alloc_sb is allocated in the process of step S223. The pattern evaluation value Vpat [#alloc_sb] [# max_pat] for the band is rewritten to NULL, and the pattern evaluation value Vpat [#alloc_sb] [# other_pat] for the subband of the subband number #alloc_sb of another transmission candidate pattern is set. It is rewritten to NULL (step S225 in FIG. 11). Note that #other_pat represents a transmission candidate pattern number other than #max_pat.

  Other processes are as described in the first embodiment. FIG. 15 shows an example of the pattern evaluation value after processing by the subband allocating unit 22 of the present embodiment. If the pattern evaluation value Vpat calculated by the subband pattern evaluation unit 21 is the value shown in FIG. 10, the subband allocation unit 22 transmits the transmission candidate pattern number #max_pat as in the first embodiment. A subband of subband number # alloc_sb = 1 is assigned to a transmission candidate pattern of = 1.

  Then, as shown in FIG. 15, the subband allocating unit 22 uses the pattern evaluation value Vpat [1] [1] for the subband number # alloc_sb = 1 of the transmission candidate pattern of transmission candidate pattern number # max_pat = 1. To NULL, and pattern evaluation values Vpat [1] [0], Vpat [1] [2],..., Vpat [for the subband number # alloc_sb = 1 of other transmission candidate patterns. 1] Rewrite [Ncand-1] to NULL.

  Thus, in the present embodiment, only overlapping assignment of the same subband is prohibited, and it is allowed to assign a plurality of subbands to one transmission candidate pattern.

  As in the first embodiment, in this embodiment, frequency scheduling is performed in units of subbands. However, frequency scheduling in units of frequency resource blocks that are defined in the radio interface and that have finer allocation units is also possible. good. In addition, the external evaluation information E1 and E2 includes CQI, but information obtained by updating other channel quality state information fed back from the UE may be used as the external evaluation information E1 and E2. . Various modifications may be made without departing from the spirit of the present embodiment.

[Third Embodiment]
Next, a third embodiment of the present invention will be described. Also in the present embodiment, the configuration of the radio resource scheduling apparatus, the operation of the CoMP scheduling unit 1, and the overall operation of the frequency scheduling unit 2 are the same as those in the first embodiment. It explains using. Compared with the first embodiment, the radio resource scheduling apparatus according to the present embodiment limits the number of transmission candidate patterns selected by the CoMP scheduling unit 1 to the same number as the number of subbands, and the frequency scheduling unit 2 The difference is that the pattern evaluation value is based on the sum of the subband CQIs.

  As described in the first embodiment, the CoMP scheduling unit 1 applies a method that also considers fairness among users in the calculation of the pattern evaluation value. For example, the Proportional Fairness method corresponds to this method. At this time, the transmission candidate pattern selected by the CoMP scheduling unit 1 is a combination pattern of the upper Ncand TPs and UEs of the pattern evaluation value. However, in this embodiment, Ncand = Nsb, that is, Ncand is limited to the same number of subbands Nsb that can be allocated, and any of the subbands is allocated to all transmission candidate patterns.

  On the other hand, in the frequency scheduling unit 2 according to the present embodiment, in consideration of the fact that the CoMP scheduling unit 1 has selected a pattern in which fairness between users is considered as a transmission candidate pattern, the fairness between users is not considered. In order to maximize the throughput, each subband is allocated in order from the transmission candidate pattern having the largest sum of the subband CQIs. As described above, when Ncand is equal to Nsb, transmission is performed in all transmission candidate patterns, so the combination of TP-UEs does not change, and fairness between users is not impaired.

  In addition, since the calculation of the pattern evaluation value in the frequency scheduling unit 2 only needs to be added, the time required for scheduling can be further reduced as compared with the case where the Proportional Fairness method is used.

  FIG. 16 is a flowchart for explaining the operation of the subband-specific pattern evaluation unit 21 of the frequency scheduling unit 2 of the present embodiment.

  First, the subband-specific pattern evaluation unit 21 resets zero_flag [#sb] corresponding to the subband number #sb to 0 (steps S240 and S241 in FIG. 16). Zero_flag [#sb] of 0 indicates that the subband CQI is not 0. Then, the subband pattern evaluation unit 21 acquires the external evaluation information E2 corresponding to the subband number #sb (step S242 in FIG. 16).

  Subsequently, the subband-by-subband pattern evaluation unit 21 transmits the sub-band of the transmission destination UE corresponding to the TP of the TP number #tp and the subband of the subband number #sb included in the # pat-th transmission candidate pattern Cand_Pat [#pat]. It is determined whether or not the band CQI is 0 (steps S243 and S244 in FIG. 16).

  The subband-by-subband pattern evaluation unit 21, when at least one 0 exists in the subband CQI of each UE corresponding to the TP with the TP number #tp and the subband with the subband number #sb (in step S244). Yes), zero_flag [#sb] [# pat] corresponding to the subband of the # pat-th transmission candidate pattern Cand_Pat [#pat] and subband number #sb is set to 1 (step S245 in FIG. 16), and the subband If 0 does not exist in the CQI, zero_flag [#sb] [# pat] is left as 0.

  The subband pattern evaluation unit 21 repeats the processes of steps S244 and S245 while increasing the TP number #tp by 1 from 0 (step S243), and after completing the process for all TPs (in step S246 in FIG. 16). Yes), the pattern evaluation value for the subband of the subband number #sb is calculated for the # pat-th transmission candidate pattern Cand_Pat [#pat] (step S247 in FIG. 16), and the calculated pattern evaluation value is Vpat [#sb] [ #Pat] is stored (step S248 in FIG. 16).

  Here, the subband-by-subband pattern evaluation unit 21 of the present embodiment determines the subband CQI of the transmission destination UE corresponding to the TP of the TP number #tp and the subband of the subband number #sb as the #patth transmission candidate. A value obtained by adding all the TPs included in the pattern Cand_Pat [#pat] is calculated as a pattern evaluation value Vpat [#sb] [#pat].

  The subband-by-subband pattern evaluation unit 21 performs the processes in steps S240 to S248 as described above for all subbands that can be assigned. When the pattern evaluation value calculation processing is completed for all subbands that can be allocated (Yes in step S249 in FIG. 16), the processing for the # pat-th transmission candidate pattern Cand_Pat [#pat] ends. The per-band pattern evaluation unit 21 performs the processing shown in FIG. 16 for all transmission candidate patterns Cand_Pat [0] to Cand_Pat [Ncand-1] with transmission candidate pattern numbers # pat = 0 to Ncand-1. Do this for each pattern.

  As described above, in the present embodiment, it is confirmed whether or not 0 exists in the subband CQI of the transmission destination UE of each TP in the input transmission candidate pattern, and the pattern evaluation value Vpat is set to the subband CQI. This is different from the first embodiment in that it is the sum of the above. When the subband CQI of the transmission destination UE is 0, the TP paired with the transmission destination UE behaves the same as the transmission stop and becomes a combination pattern of TP-UEs different from the input transmission candidate pattern.

  In order to prevent the combination pattern from being different from the transmission candidate pattern, the subband pattern evaluation unit 21 in the present embodiment sets the zero_flag according to the confirmation result of the subband CQI as described above. This zero_flag is notified to the subband allocating unit 22 in the subsequent stage together with the pattern evaluation value calculation result.

  The processing flow of the subband allocating unit 22 of the present embodiment is as described in FIG. 11 of the first embodiment. In the pattern evaluation value maximum value search process (step S221 in FIG. 11), the zero_flag described above is used. And a combination of a subband-transmission candidate pattern in which zero_flag is 0 (no 0 exists in the subband CQI corresponding to the transmission candidate pattern) is assigned high priority, and zero_flag is 1 (in the transmission candidate pattern). The difference is that the combination of subband-transmission candidate patterns (with 0 in the corresponding subband CQI) is assigned low priority.

  FIG. 17 is a flowchart for explaining the pattern evaluation value maximum value search process of the subband allocating unit 22 according to this embodiment. In FIG. 17, Vmax is the maximum value of the pattern evaluation value Vpat searched so far, and the initial value is 0. #Sb_tmp is an internal variable indicating a search subband number, and #pat_tmp is an internal variable indicating a search pattern number. The initial values of the internal variables #sb_tmp and #pat_tmp are both 0. Zero_flag_hold is the value of zero_flag of the transmission candidate pattern in which the pattern evaluation value Vpat indicates the maximum value Vmax. The initial value of zero_flag_hold is 1.

  The subband allocating unit 22 initializes the maximum value Vmax of the pattern evaluation value Vpat to 0 and initializes zero_flag_hold to 1 (step S250 in FIG. 17), and the pattern evaluation value pattern calculated by the subband-specific pattern evaluation unit 21 Among the evaluation values Vpat [#sb] [#pat], it is confirmed whether the pattern evaluation value Vpat [#sb_tmp] [#pat_tmp] is not NULL, the #pat_tmpth transmission candidate pattern Cand_Pat [#pat_tmp], and the sub It is confirmed whether zero_flag [#sb_tmp] [# pat_tmp] corresponding to the subband of the band number #sb_tmp is not 1 (steps S251 to S254 in FIG. 17).

  When the pattern evaluation value Vpat [#sb_tmp] [#pat_tmp] is not NULL, zero_flag [#sb_tmp] [#pat_tmp] is not 1, and zero_flag_hold is not 1 (Yes in step S255). Or the pattern evaluation value Vpat [#sb_tmp] [# pat_tmp] is not NULL, zero_flag [#sb_tmp] [# pat_tmp] is 1 and zero_flag [#sb_tmp] [# pat_tmp] is the same value as zero_flag_hold In step S256 of FIG. 17, Yes), it is confirmed whether or not the pattern evaluation value Vpat [#sb_tmp] [#pat_tmp] is equal to or higher than Vmax (step S257 of FIG. 17).

  When the pattern evaluation value Vpat [#sb_tmp] [#pat_tmp] is equal to or greater than the current maximum value Vmax (Yes in step S257), the subband allocation unit 22 sets the pattern evaluation value Vpat [#sb_tmp] [#pat_tmp] as a new value. The maximum value Vmax is set, the search pattern number #pat_tmp is set as a new transmission candidate pattern number #max_pat corresponding to the maximum value Vmax, the search subband number #sb_tmp is set as a new subband number #alloc_sb corresponding to the maximum value Vmax, and # The zero_flag [#sb_tmp] [# pat_tmp] corresponding to the subband of the pat_tmpth transmission candidate pattern Cand_Pat [#pat_tmp] and the subband number #sb_tmp is replaced with a new zero_flag_hol. To (17 step S258).

  The subband allocating unit 22 repeatedly performs the processing of steps S253 to S258 while increasing the search pattern number #pat_tmp by 1 from the initial value 0 (step S252), and after completing the processing for all the pattern numbers (step 17 in FIG. 17). When the search subband number #sb_tmp is incremented by 1 from the initial value 0 (step S251), the processes of steps S252 to S259 are repeated, and all the subband numbers have been processed (FIG. 17). In step S260, Yes), the pattern evaluation value maximum value search process ends.

  As described above, in this embodiment, when zero_flag is 0 and zero_flag_hold that is the value of zero_flag of the transmission candidate pattern indicating the current maximum value Vmax is 0 (Yes in step S255), step Proceeding to the processing of S257, if zero_flag is 1 and zero_flag_hold is 0 (No in step S256), the processing of steps S257 and S258 is avoided, so that zero_flag is 0 (subband CQI corresponding to the transmission candidate pattern). Subbands are preferentially assigned to a transmission candidate pattern (zero does not exist), and zero_flag is 1 (0 exists in the subband CQI corresponding to the transmission candidate pattern). Allocation It is possible to lower the priority.

  As in the first embodiment, in this embodiment, frequency scheduling is performed in units of subbands. However, frequency scheduling in units of frequency resource blocks that are defined in the radio interface and that have finer allocation units is also possible. good. In addition, the external evaluation information E1 and E2 includes CQI, but information obtained by updating other channel quality state information fed back from the UE may be used as the external evaluation information E1 and E2. . Various modifications may be made without departing from the spirit of the present embodiment.

  In the first to third embodiments, all frequency resources (subbands) that can be allocated are set as one virtual frequency resource (virtual subband). However, the present invention is not limited to this, and all frequencies that can be allocated. Some of the plurality of frequency resources may be virtual frequency resources. However, in this case, the pattern evaluation unit 12 needs to calculate the evaluation value of the combination pattern of TP and UE using the external evaluation information E2 instead of the external evaluation information E1.

  Specifically, for each TP included in the combination pattern of the TP and the UE for which the evaluation value is to be calculated, the pattern evaluation unit 12 feeds back the external evaluation fed back from the UE defined as the transmission destination of the TP in this combination pattern. A lower evaluation value is calculated based on the information E2, and a value obtained by totaling the lower evaluation values of the TPs included in the calculation target combination pattern is set as an evaluation value of the calculation target combination pattern.

The lower evaluation value of TP can be expressed by (R _ins [#ue]) ^α / (R _avg [#ue]) ^β as described above. The instantaneous throughput R _ins [#ue] of the number #ue UE defined as the transmission destination of the TP in the combination pattern to be calculated is a value obtained by converting the SINR value of the number #ue UE. In order to obtain the SINR, first, each of the values obtained by converting the channel quality state information (external evaluation information E2) for each TP fed back from the UE of the number #ue into the SNR is represented by virtual frequency resources (virtual subbands). ) Is averaged. Then, the SINR may be calculated using the average value for the virtual frequency resource of the SNR of the TP corresponding to the number #ue UE as the numerator and the sum of the average values of the virtual frequency resources of the remaining TP SNR as the denominator. .

  Note that when some of the allocatable frequency resources are set as virtual frequency resources, there are a plurality of virtual frequency resources, but the frequency scheduling unit 2 includes the first to third frequency resources. The processing described in the embodiment may be performed for each virtual frequency resource.

  The radio resource scheduling apparatus according to the first to third embodiments can be realized by a computer having a CPU (Central Processing Unit), a storage device, and an interface, and a program for controlling these hardware resources. The CPU executes the processes described in the first to third embodiments in accordance with a program stored in the storage device.

  A radio resource scheduling program for realizing the radio resource scheduling methods of the first to third embodiments is provided in a state of being recorded on a recording medium such as a flexible disk, a CD-ROM, a DVD, or a memory card. A radio resource scheduling program may be provided through a network.

  The present invention can be applied to a technique for allocating frequency resources to a combination pattern of transmission points and user terminals.

  DESCRIPTION OF SYMBOLS 1 ... CoMP scheduling part, 2 ... Frequency scheduling part, 10 ... Pattern generation condition acquisition part, 11 ... Pattern generation part, 12 ... Pattern evaluation part, 13 ... Transmission candidate pattern selection part, 20 ... Transmission candidate pattern acquisition part, 21 ... Subband pattern evaluation unit, 22... Subband allocation unit.

Claims (7)

A radio resource scheduling apparatus for allocating frequency resources used for radio communication between a transmission point and a destination user terminal in a radio network system having a plurality of transmission points,
Multipoints that select a predetermined number of combination patterns that are equal to or greater than the number of frequency resources that can be allocated as transmission candidate patterns from among the combination patterns indicating the operation contents of either the destination user terminal or no destination for each transmission point Collaborative scheduling means;
Frequency scheduling means for determining a pattern to allocate frequency resources from among the transmission candidate patterns,
The multipoint collaborative scheduling means as one virtual frequency resources multiple frequency resources of all frequency resource allocation possible or in part, the user fed back from the user terminals included in the combination pattern of the evaluation value calculation target resulting from the channel quality information indicating the reception quality of the downlink channel measured by the terminal, and calculates the evaluation value of the combination patterns by a predetermined objective function based on the transmission point by the channel quality state information for the virtual frequency resources, the evaluation based on the value, and selects the predetermined number of combination patterns in order from the combination pattern of better evaluation as the transmission candidate pattern,
Wherein the frequency scheduling unit is obtained from the channel quality information indicating the reception quality of the downlink channel measured by the user terminal to be fed back from the user terminal included in the transmission candidate pattern evaluation value calculation target, it can be allocated frequency resources based on the transmission point by the channel quality state information evaluation value of the transmission candidate pattern calculated for each frequency resource by a predetermined objective function for, based on the evaluation value, unallocated in order from the transmission candidate patterns better evaluation A radio resource scheduling apparatus characterized by allocating frequency resources. The radio resource scheduling apparatus according to claim 1, wherein
The multipoint cooperative scheduling means calculates an evaluation value of the combination pattern by a Proportional Fairness method,
The radio resource scheduling apparatus, wherein the frequency scheduling means calculates an evaluation value of the transmission candidate pattern by a Proportional Fairness method. The radio resource scheduling apparatus according to claim 1, wherein
The multipoint collaborative scheduling means, the number of the transmission candidate pattern, as same as the number of allocatable frequency resources, and calculates an evaluation value of the combination patterns by Proportional Fairness method,
Wherein the frequency scheduling unit is obtained from the channel quality information indicating the reception quality of the downlink channel measured by the user terminal to be fed back from the user terminal included in the transmission candidate pattern evaluation value calculation target, it can be allocated frequency resources radio resources scheduling apparatus, wherein a value obtained by adding the total transmission points included the value of the transmission point by the channel quality state information to the transmission candidate pattern, and the evaluation value of the transmission candidate pattern for. A radio resource scheduling method for assigning frequency resources used for radio communication between a transmission point and a destination user terminal in a radio network system having a plurality of transmission points,
Multipoints that select a predetermined number of combination patterns that are equal to or greater than the number of frequency resources that can be allocated as transmission candidate patterns from among the combination patterns indicating the operation contents of either the destination user terminal or no destination for each transmission point A cooperative scheduling step;
A frequency scheduling step of determining a pattern for allocating frequency resources from among the transmission candidate patterns,
The said in the multipoint collaborative scheduling step, as a single virtual frequency resources multiple frequency resources of all frequency resource allocation capable or partially fed back from the user terminals included in the combination pattern of the evaluation value calculation target resulting from the channel quality information indicating the reception quality of the downlink channel measured by the user terminal, and calculates the evaluation value of the combination patterns by a predetermined objective function based on the transmission point by the channel quality state information for the virtual frequency resources, the based on the evaluation value, and selects the predetermined number of combination patterns in order from the combination pattern of better evaluation as the transmission candidate pattern,
Wherein the frequency scheduling step is obtained from the channel quality information indicating the reception quality of the downlink channel measured by the user terminal to be fed back from the user terminal included in the transmission candidate pattern evaluation value calculation target, assignable frequencies based on the transmission point by the channel quality state information for the resource evaluation value of the transmission candidate pattern calculated for each frequency resource according to a predetermined objective function, based on the evaluation value, viewed from the transmission candidate patterns better evaluated in order A radio resource scheduling method characterized by allocating frequency resources for allocation. The radio resource scheduling method according to claim 4, wherein
In the multipoint coordinated scheduling step , the evaluation value of the combination pattern is calculated by the Proportional Fairness method,
In the frequency scheduling step , an evaluation value of the transmission candidate pattern is calculated by a Proportional Fairness method. The radio resource scheduling method according to claim 4, wherein
In the multipoint coordinated scheduling step , the number of transmission candidate patterns is the same as the number of allocatable frequency resources , and the evaluation value of the combination pattern is calculated by the Proportional Fairness method,
Wherein the frequency scheduling step is obtained from the channel quality information indicating the reception quality of the downlink channel measured by the user terminal to be fed back from the user terminal included in the transmission candidate pattern evaluation value calculation target, assignable frequencies a value obtained by adding the total transmission points included the value of the transmission point by the channel quality state information for the resource to the transmission candidate pattern, radio resource scheduling method, characterized in that the evaluation value of the transmission candidate pattern. A radio resource scheduling program that causes a computer to function as a radio resource scheduling device that allocates frequency resources used for radio communication between a transmission point and a destination user terminal in a radio network system having a plurality of transmission points,
Multipoints that select a predetermined number of combination patterns that are equal to or greater than the number of frequency resources that can be allocated as transmission candidate patterns from among the combination patterns indicating the operation contents of either the destination user terminal or no destination for each transmission point A cooperative scheduling step;
Causing the computer to execute a frequency scheduling step of determining a pattern for allocating frequency resources from the transmission candidate patterns,
The said in the multipoint collaborative scheduling step, as a single virtual frequency resources multiple frequency resources of all frequency resource allocation capable or partially fed back from the user terminals included in the combination pattern of the evaluation value calculation target resulting from the channel quality information indicating the reception quality of the downlink channel measured by the user terminal, and calculates the evaluation value of the combination patterns by a predetermined objective function based on the transmission point by the channel quality state information for the virtual frequency resources, the based on the evaluation value, and selects the predetermined number of combination patterns in order from the combination pattern of better evaluation as the transmission candidate pattern,
Wherein the frequency scheduling step is obtained from the channel quality information indicating the reception quality of the downlink channel measured by the user terminal to be fed back from the user terminal included in the transmission candidate pattern evaluation value calculation target, assignable frequencies based on the transmission point by the channel quality state information for the resource evaluation value of the transmission candidate pattern calculated for each frequency resource according to a predetermined objective function, based on the evaluation value, viewed from the transmission candidate patterns better evaluated in order A radio resource scheduling program characterized by allocating frequency resources for allocation.

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