JP5660705B2 - COMMUNICATION DEVICE, RADIO COMMUNICATION SYSTEM, AND FREQUENCY ALLOCATION METHOD - Google Patents

Description

The present invention relates to a communication device, a wireless communication system , and a frequency allocation method.

  In recent years, research on next-generation mobile communication systems has been actively conducted, and in particular, it is required to achieve a larger transmission capacity in a limited frequency band in the uplink for transmission from a mobile station to a base station. Yes. For example, as one of multiplexing schemes in an environment where a plurality of mobile stations exist in the same cell, the entire frequency band is divided into allocation units called resource blocks (RBs), and different RBs are assigned to each mobile station. There is an FDM (Frequency Division Multiplexing) type scheduling in which allocation is performed and communication is simultaneously performed. However, in this method, since an RB used by a certain mobile station is not assigned to other mobile stations, the bandwidth that can be used by each mobile station when there are many mobile stations is severely limited. In such a case, as a technique for improving the transmission capacity without changing the bandwidth, the AMC (Adaptive Modulation and Coding) that increases the transmission bit rate by changing the modulation scheme and the coding rate of the error correction code according to the channel state. : Adaptive modulation and coding system).

  However, once the modulation scheme in AMC is changed from QPSK (Quaternary Phase Shift Keying) to more multi-valued one such as 16QAM (16-ary Quadrature Amplitude Modulation). Can increase the number of bits that can be transmitted, i.e., increase the bit rate. However, since the inter-signal distance of the modulation signal point becomes narrow, a large amount of transmission energy is required per bit. Therefore, if sufficient transmission energy cannot be obtained, the error rate increases and the throughput decreases. Similarly, as the coding rate of the error correction code increases, the bit rate increases as the coding rate increases, but the error correction capability of the error correction code decreases, and the bit error rate increases. Therefore, in order to improve the throughput by AMC, after grasping the bit error rate characteristics in each modulation method and each coding rate, the bit error rate is set by using the transmission power necessary for obtaining a desired bit rate. A high signal-to-noise power ratio (SNR) is required because transmission power is limited depending on the capability of the transmission apparatus.

  When the FDM scheme is used in a multi-user environment, frequency spectrum allocation is performed so as to avoid frequencies allocated to other mobile stations. For this reason, there is a problem that a frequency spectrum with a low SNR may be assigned when the frequency spectrum is already assigned to another mobile station even though the SNR of a certain frequency spectrum is good. . In response to this problem, spectrum overlapping resources that allow allocation of a part of the frequency spectrum between mobile stations and assign an optimum frequency spectrum with a high channel gain to each mobile station. Management (SORM: Spectrum-Overlapped Resource Management) technology has been proposed (for example, Non-Patent Document 1).

  In the SORM technique, on the premise that redundant interference is removed by non-linear iterative equalization processing, each receiving device allocates a spectrum to a desired frequency by utilizing the energy of the desired signal, but the IUI (Inter- User Interference (inter-user interference) can be removed and decoded data for each mobile station can be obtained.

Yokomakura et al., “Spectrum Overlapping Resource Management Using Dynamic Spectrum Control”, IEICE Proceedings of the 2008 General Conference, B-5-51, March 2008

  However, in the SORM technique described in Non-Patent Document 1, if the allocation to each mobile station is too biased to the same band, the overlapping band becomes excessive, and the interference is separated by nonlinear iterative equalization processing on the receiving side. There is a problem that the capability is lowered and the characteristics can be deteriorated. In Non-Patent Document 1, since the number of symbols per user is “512” and the number of users is “2”, the total frequency bandwidth allocated to each mobile station is 512 × 2 = 1024. The system bandwidth, that is, the number of FFT (Fast Fourier Transform) points is “1024”, which is equal to the sum of the frequency bandwidths allocated to each mobile station. When a frequency spectrum is allocated, there is a problem that a band that cannot be allocated is generated and a part of the frequency band cannot be used effectively.

The present invention has been made in view of such circumstances, and an object without causing characteristic degradation by the spectral overlap, the communication device capable of improving the cell throughput is the total throughput of all mobile stations is to provide a wireless communication system, and a frequency allocation method.

(1) The present invention has been made to solve the above-described problems, and the wireless communication system of the present invention converts a transmission signal into a frequency signal, and arranges and transmits the signal in a frequency spectrum assigned to the device. A wireless communication system comprising: a plurality of transmission devices; and a reception device that receives signals transmitted by the plurality of transmission devices, removes interference between signals of the transmission devices, and separates the signals for each transmission device The receiving device assigns the frequency spectrum to each of the plurality of transmitting devices such that the width of the frequency spectrum assigned to each of the plurality of transmitting devices is smaller than a predetermined value. It is characterized by that.

(2) Moreover, the radio | wireless communications system of this invention is the above-mentioned radio | wireless communications system, Comprising: The said predetermined value is a bandwidth of the predetermined ratio with respect to the system bandwidth of the said radio | wireless communications system, It is characterized by the above-mentioned. .

(3) Moreover, the radio | wireless communications system of this invention is the above-mentioned radio | wireless communications system, Comprising: The said receiving apparatus accept | permits duplication of a spectrum, when the said overlapping bandwidth is less than the said predetermined value. An allocation is performed, and if the value is equal to or greater than the predetermined value, allocation that does not allow duplication is performed thereafter.

(4) Moreover, the radio | wireless communications system of this invention is the above-mentioned radio | wireless communications system, Comprising: The said predetermined value is a predetermined ratio with respect to the total bandwidth of the frequency spectrum allocated to one of the said transmitters. Bandwidth.

(5) The wireless communication system of the present invention is the above-described wireless communication system, and performs allocation that allows spectrum overlap when the overlapping bandwidth ratio is less than the predetermined ratio. When the ratio is equal to or greater than the predetermined ratio, the allocation is performed without allowing duplication.

(6) Further, the wireless communication system of the present invention is any one of the wireless communication systems described above, wherein the predetermined value is obtained by separating the received signal into the signal for each transmitting device in the receiving device. It is a value calculated based on a propagation path characteristic from the transmitting device to the receiving device so that it can be performed with desired quality.

(7) Moreover, the base station apparatus of the present invention receives a signal transmitted from a plurality of mobile station apparatuses that convert a transmission signal into a frequency signal, and arrange and transmit the signal in a frequency spectrum allocated to the apparatus, A base station apparatus that removes interference between signals of mobile station apparatuses and separates the signals for each of the mobile station apparatuses, and has a width of a band in which frequency spectra assigned to each of the plurality of mobile station apparatuses overlap each other. A frequency spectrum is allocated to each of the plurality of mobile station apparatuses so as to be smaller than a predetermined value.

(8) Further, in the frequency allocation method of the present invention, a transmission signal is converted into a frequency signal, arranged in a frequency spectrum allocated to the device, and transmitted, and the plurality of transmission devices transmit A frequency allocation method in a wireless communication system comprising: a reception device that receives a signal, removes interference between signals of the transmission device, and separates the signal into signals for each transmission device, wherein the reception device The method includes a step of assigning a frequency spectrum to each of the plurality of transmission devices such that a bandwidth of a frequency spectrum assigned to each of the plurality of transmission devices is smaller than a predetermined value.

  According to the present invention, cell throughput can be improved without causing characteristic deterioration due to spectrum overlap.

It is a conceptual diagram which shows schematic structure of the radio | wireless communications system in the 1st Embodiment of this invention. It is a schematic block diagram which shows the structure of the mobile station apparatuses 11-14 and the base station apparatus 15 in the embodiment. It is a schematic block diagram which shows the structure of the transmission part 102 which is a transmitter in the embodiment. It is a schematic block diagram which shows the structure of the receiving part 503 and the control part 501 which are the receivers in the embodiment. FIG. 6 is a diagram (part 1) illustrating an operation example of a scheduling unit 308 in the embodiment. FIG. 11B is a diagram illustrating an example of an operation of the scheduling unit 308 in the embodiment (No. 2). FIG. 11 is a diagram (part 3) illustrating an operation example of the scheduling unit 308 in the embodiment. FIG. 11 is a diagram (part 4) illustrating an operation example of the scheduling unit 308 in the embodiment. It is a flowchart explaining operation | movement of the scheduling part 308 in the embodiment. It is a schematic block diagram which shows the structure of the receiving part 503 and the control part 501a in the 2nd Embodiment of this invention. FIG. 6 is a diagram (part 1) illustrating an operation example of a scheduling unit 308a in the embodiment. FIG. 8B is a diagram illustrating an example of an operation of the scheduling unit 308a in the embodiment (No. 2). FIG. 11 is a diagram (part 3) illustrating an operation example of the scheduling unit 308a in the same embodiment; FIG. 11 is a diagram (part 4) illustrating an operation example of the scheduling unit 308a in the same embodiment; It is a flowchart explaining operation | movement of the scheduling part 308a in the embodiment.

  In each of the following embodiments, the base station apparatus has one receiving antenna. However, even if the base station apparatus has a plurality of receiving antennas, “the number of spectrums allocated to the same band> the number of receiving antennas”. By defining a case as overlapping, the present invention can be applied.

[First Embodiment]
In the first embodiment, assuming that the allocation is performed so as to fill the entire system band, the allocation is performed so that the ratio of the “duplicated band” to the “system band” is equal to or less than a certain value. That is, in this embodiment, before starting scheduling, the amount of overlap that can be obtained by separating the spectrum overlap from the system bandwidth in advance and obtaining the desired communication quality is defined as “allowable overlap bandwidth” and actually assigned. It is characterized in that the allocation is performed so that the overlapped spectrums are within the value of “allowable overlapping bandwidth”.

  Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a conceptual diagram showing a schematic configuration of a wireless communication system in the present embodiment. As illustrated in FIG. 1, the wireless communication system 10 according to the present embodiment includes mobile station apparatuses 11, 12, 13, and 14 including a transmission apparatus, and a base station apparatus 15 including a reception apparatus. Here, the number U of mobile station apparatuses in the same cell is set to U = 4, but the value of U may be other values according to the situation of the cell. In the wireless communication system of FIG. 1, spectrum overlap resource management (SORM) is used for uplink communication from the mobile station apparatuses 11 to 14 to the base station apparatus 15. That is, when each mobile station apparatus 11-14 transmits a signal to the base station apparatus 15, a part of the frequency signal is transmitted between the mobile station apparatuses to transmit the signal, and the base station apparatus 15 interferes. Use the suppression function to suppress interference caused by spectrum overlap. Thereby, each mobile station apparatus 11-14 can transmit using a favorable frequency, even if the frequency with a favorable reception condition overlaps mutually.

  FIG. 2 is a schematic block diagram illustrating configurations of the mobile station apparatuses 11 to 14 and the base station apparatus 15. Since the mobile station apparatuses 11 to 14 have the same configuration, only the mobile station apparatus 11 will be described here as a representative. The mobile station apparatus 11 includes a control unit 101, a transmission unit 102, and a reception unit 103. The base station apparatus 15 includes a control unit 501, a transmission unit 502, and a reception unit 503. The control unit 101 of the mobile station device 11 controls the transmission unit 102 and the reception unit 103 to communicate with the base station device 15. The transmission unit 102 converts the transmission signal into a frequency signal, assigns the frequency signal to the frequency spectrum assigned to the mobile station device 11, and transmits the frequency signal to the base station device 15. The receiving unit 103 receives from the base station apparatus 15 spectrum allocation information indicating the frequency spectrum allocated to the mobile station apparatus 11.

  The control unit 501 of the base station device 15 controls the transmission unit 502 and the reception unit 503 to communicate with the mobile station devices 11 to 14. In particular, the control unit 501 assigns the frequency spectrum used for the uplink to each mobile station apparatus 11-14. Transmitting section 502 transmits spectrum allocation information indicating the frequency spectrum allocated to each mobile station apparatus 11-14 by control section 501 to each mobile station apparatus 11-14. The receiving unit 503 receives signals transmitted by the mobile station apparatuses 11 to 14, removes interference between signals of the mobile station apparatuses 11 to 14, and separates the signals for the mobile station apparatuses 11 to 14.

  FIG. 3 is a schematic block diagram illustrating a configuration of the transmission unit 102 which is a transmission apparatus according to the present embodiment. The transmission unit 102 includes an encoding unit 201, an interleaving unit 202, a modulation unit 203, a DFT (Discrete Fourier Transform) unit 204, a spectrum mapping unit 205, an IDFT (Inverse DFT) unit 206, a pilot signal A generation unit 207, a pilot multiplexing unit 208, a CP (Cyclic Prefix) insertion unit 209, a D / A (Digital to Analog) conversion unit 210, a radio unit 211, and a transmission antenna 212 are provided.

  The encoding unit 201 performs error correction encoding on the transmission data bits constituting the input transmission data to generate code data bits. The interleave unit 202 rearranges the order of the code data bits (time order). Modulation section 203 maps the code bits rearranged by interleaving section 202 to signal points according to the modulation scheme, and generates a modulated signal (transmission signal). Here, the modulation scheme is BPSK (Binary PSK; two-phase phase shift keying), QPSK, or the like. The DFT unit 204 performs discrete Fourier transform on the modulated signal to convert it into a frequency signal.

  The spectrum mapping unit 205 receives the spectrum allocation information notified from the base station device 15 from the control unit 101, and arranges frequency signals in the frequency spectrum allocated to the mobile station device based on the spectrum allocation information. The IDFT unit 206 performs inverse discrete Fourier transform on the arranged frequency signal to convert it into a time signal. Pilot signal generation section 207 generates a known pilot signal for estimating propagation path characteristics in base station apparatus 15. Pilot multiplexing section 208 multiplexes the pilot signal generated by pilot signal generation section 207 with the time signal obtained from IDFT section 206. CP insertion section 209 inserts a cyclic prefix (CP) into the signal multiplexed by pilot multiplexing section 208. The D / A converter 210 converts the signal with the cyclic prefix inserted from a digital signal to an analog signal. The radio unit 211 up-converts the analog signal converted by the D / A conversion unit 210 to a radio frequency and transmits the radio signal from the transmission antenna 212 to the base station apparatus 15.

  FIG. 4 is a schematic block diagram illustrating configurations of the reception unit 503 and the control unit 501 which are reception devices in the present embodiment. The receiving unit 503 shown in FIG. 4 shows a configuration when the maximum number of mobile stations is U. The reception unit 503 includes a reception antenna 301, a radio unit 302, an A / D conversion unit 303, a CP removal unit 304, a pilot separation unit 305, a propagation path estimation unit 306, a buffer 310, a first DFT unit 311 and a spectrum demapping unit. 312 includes a first decoding processing unit 330-1 to a U-th decoding processing unit 330-U. Each of the first decoding processing unit 330-1 to the U-th decoding processing unit 330-U includes a soft cancellation unit 313, an equalization unit 314, an IDFT unit 315, a demodulation unit 316, a deinterleave unit 317, a decoding unit 318, An interleaving unit 319, a soft replica generation unit 320, a second DFT unit 321, an interference extraction unit 322, and a determination unit 323 are provided. The control unit 501 includes an allowable overlapping bandwidth calculation unit 307, a scheduling unit 308, and a spectrum allocation information generation unit 309.

  Radio section 302 receives a signal from mobile station apparatus 400 via reception antenna 301, down-converts it, and generates a baseband signal. The A / D conversion unit 303 performs analog / digital conversion of the baseband signal into a digital signal. The CP removal unit 304 removes a cyclic prefix (CP) from the digital signal converted by the A / D conversion unit 303. Pilot separation section 305 separates the pilot signals of mobile station apparatuses 11 to 14 from the digital signal from which the cyclic prefix has been removed. The propagation path estimation unit 306 estimates propagation path characteristics from each transmission antenna 212 to the base station apparatus 15 for each of the mobile station apparatuses 11 to 14 using the separated pilot signals from the mobile station apparatuses 11 to 14. To do. The propagation path estimation unit 306 outputs the estimated propagation path characteristics to the soft cancellation unit 313, the equalization unit 314, the allowable overlapping bandwidth calculation unit 307, and the scheduling unit 308.

  The allowable overlapping bandwidth calculation unit 307 obtains an allowable overlapping bandwidth allowed in the system band based on the propagation path characteristic (for example, reception SNR), and outputs it to the scheduling unit 308. For example, when a specific modulation scheme and coding rate are used, an allowable overlap bandwidth value such that the error rate is a certain value or less, and an allowable overlap bandwidth value according to the system bandwidth and the average received SNR Is set in advance in the allowable overlapping bandwidth calculation unit 307. The allowable overlapping bandwidth calculation unit 307 calculates the average value of the received SNR in the frequency direction for the received signal as the average received SNR, and uses the above setting to calculate the calculated average received SNR and the system bandwidth of the wireless communication system. The allowable overlapping bandwidth is determined in accordance with.

  Scheduling section 308 determines the spectrum allocation as to which subcarriers each mobile station apparatus 11 to 14 uses based on the propagation path characteristics given from propagation path estimation section 306. At this time, scheduling is performed in which spectrum allocation is determined so that the overlapping of a part of the spectrum is allowed and the width of the band in which the frequency spectrum allocated to each of the plurality of mobile station apparatuses overlaps is equal to or less than a predetermined value. In particular, in the present embodiment, the predetermined value described above is an allowable overlapping bandwidth that is a predetermined ratio of bandwidth to the system bandwidth of the wireless communication system 10. Here, the allowable overlapping bandwidth (number of spectra) is given from the allowable overlapping bandwidth calculation unit 307. Details of the scheduling unit 308 will be described later. The spectrum allocation information generation unit 309 generates spectrum allocation information indicating the spectrum allocation determined by the scheduling unit 308 and outputs the spectrum allocation information to the transmission unit 502 for feedback to the mobile station apparatuses 11 to 14. At the same time, the spectrum allocation information generation unit 309 stores the spectrum allocation information in the buffer 310 as mapping information for restoring the frequency signal in the spectrum demapping unit 312 at the next transmission opportunity.

  The first DFT unit 311 performs discrete Fourier transform on the received signal obtained by separating the pilot signal in the pilot separation unit 305 to convert it into a frequency signal. The spectrum demapping unit 312 extracts the mapping information obtained at the time of the previous transmission opportunity from the buffer 310 and, based on the mapping information, moves each movement from the frequency signal obtained by the conversion by the first DFT unit 311. The signals of the station apparatuses 11 to 14 are separated. The spectrum demapping unit 312 outputs the separated signals of the mobile devices 11 to 14 to the decoding processing units 330-1 to 330-U corresponding to the mobile station devices 11 to 14, respectively.

  At this stage, based on the mapping information, each mobile station apparatus 11-14 simply extracts the frequency spectrum signal in which the frequency signal is arranged for each mobile station apparatus 11-14, and therefore, it is duplicated during transmission. Some of the frequency signals remain as interference with each other. For example, when the mobile station apparatuses 11 and 13 place frequency signals in a certain frequency spectrum, the spectrum demapping unit 312 converts the frequency spectrum signal into a decoding processing unit corresponding to the mobile station apparatus 11. The data is output to a certain first decoding processing unit 330-1 and a third decoding processing unit 330-3 that is a decoding processing unit corresponding to the mobile station device 13.

  The first decoding processing unit 330-1 to the U-th decoding processing unit 330-U have the same configuration except for the corresponding mobile station devices. Therefore, here, the first decoding processing unit 330-1 to the U-th decoding processing unit 330-U corresponds to the mobile station device 11. Only the decoding processing unit 330-1 will be described, and description of the other decoding processing units will be omitted. The soft cancellation unit 313 of the first decoding processing unit 330-1 uses the second DFT unit 321 and the interference extraction unit from the received signal of each mobile station apparatus 11 returned to the original arrangement by the spectrum demapping unit 312. The replica of its own signal obtained from 322 and the interference replica from another mobile station apparatus are canceled, and the residual is input to the equalization unit 314. Since the replica cannot be generated for the first time, nothing is canceled.

  The equalization unit 314 reconstructs a desired component using the residual output from the soft cancellation unit 313, the replica obtained from the soft replica generation unit 320, and the channel characteristics estimated by the channel estimation unit 306, and performs radio propagation. Equalization processing is performed to compensate for signal distortion caused by the path. The IDFT unit 315 performs inverse discrete Fourier transform on the equalized signal to convert it into a time signal. The demodulator 316 demodulates the time signal to obtain a log likelihood ratio (LLR) representing the reliability of each code bit. Here, the log likelihood ratio is expressed by a natural logarithm of the ratio of the probability that the sign bit is 1 and the probability that the sign bit is 0 (base is the logarithm of e (Napier number)).

  The deinterleaving unit 317 restores the sequence of interleaving performed by the interleaving unit 202 of the mobile station apparatus 11 to the log likelihood ratio of each code bit obtained by the demodulating unit 316 and outputs the result to the decoding unit 318. The decoding unit 318 performs error correction processing based on the maximum a posteriori (MAP) estimation for the log likelihood ratio of each code bit, and performs the external LLR of the code bit with improved likelihood and the a posteriori of the information bit. Outputs LLR. Here, the external LLR subtracts the log-likelihood ratio of the code bit input to the decoding unit 318 from the a posteriori LLR of the code bit, which is the log-likelihood ratio of the code bit with improved likelihood, by error correction processing. This value represents the reliability improved only by error correction processing. The information bits are bits obtained by decoding the code bits, and are transmitted data bits constituting the transmission data of the mobile station apparatuses 11 to 14 (the mobile station apparatus 11 in the first decoding processing unit 330-1). Correspond.

  The decoding unit 318 inputs the external LLR to the interleaving unit 319 so as to be used for the iterative process, and outputs the post-LLR of the information bits to the determination unit 323 so that it is used for the determination of the transmission bits. Interleaving section 319 performs interleaving for rearrangement similar to that performed by interleaving section 202 of mobile station apparatus 11 for the external LLR. The soft replica generation unit 320 generates a soft replica having an amplitude based on the reliability obtained from the interleaved external LLR. The soft replica generation unit 320 outputs the obtained soft replica to the equalization unit 314 and also outputs it to the second DFT unit 321 for soft cancellation.

  The second DFT unit 321 performs discrete Fourier transform on the soft replica to convert it into a frequency signal. The second DFT unit 321 inputs the obtained frequency signal to the soft cancel unit 313 for canceling its own signal, and other mobile station devices for canceling interference between signals of the mobile station device. It outputs to the interference extraction part 322 in the 2nd to Uth decoding process part 330-2-330-U which is a decoding process part corresponding to 12-14. The interference extraction unit 322 extracts the frequency signal received from the other decoding processes 330-2 to 330-U that is an interference signal for the signal of the mobile station apparatus 11 based on the spectrum allocation information, The data is output to the cancel unit 313.

  The processing by each unit included in the first decoding processing unit 330-1 is repeated a predetermined number of times for the same signal, and the determination unit 323 finally determines the a posteriori LLR of the information bits obtained by the decoding unit 318. By doing so, the transmission data of the mobile station apparatus 11 is detected. Instead of repeating a predetermined number of times, for example, repeating until the absolute value of the posterior LLR of all information bits becomes larger than a predetermined value, a repetition end condition is set, It may be repeated until the condition is satisfied.

  While each of the first decoding processing unit 330-1 to the U-th decoding processing unit 330-U performs iterative processing as described above, while assigning a desired frequency spectrum to each mobile station apparatus 11-14, In addition, IUI (Inter User Interference) between the mobile station apparatuses 11 to 14 can be removed, and transmission data for each of the mobile station apparatuses 11 to 14 can be obtained.

  5 to 8 are diagrams illustrating an operation example of the scheduling unit 308 in the present embodiment. The procedure described below is an example, and the maximum number of overlapping discrete frequency points at which desired communication quality can be obtained by separating spectrum overlap with respect to the system bandwidth is defined as “allowable overlap bandwidth”. Any other procedure may be used as long as the allocation is performed so that the bandwidth in which the frequency spectrum that is actually allocated overlaps between the mobile station apparatuses falls within the allowable overlapping bandwidth.

  In this case, as a scheduling method, a method of using SORM scheduling that allows spectrum overlap and FDM scheduling that does not allow spectrum overlap is used. The scheduling unit 308 counts the number of discrete frequencies (number of subcarriers) with overlapping spectrum in the system band at the time of scheduling, and allocates spectrum by SORM scheduling until the number of subcarriers reaches the allowable overlapping bandwidth. After the number of overlapping subcarriers reaches the allowable overlapping bandwidth, allocation is performed by FDM scheduling. Scheduling ends when all mobile stations reach an allocatable bandwidth or when there is no more free bandwidth that can be allocated.

  As a reference for allocation, the value of propagation path characteristics given by the received SINR (Signal to Interference and Noise power Ratio), communication path capacity, etc. of all system bands is used for each mobile station. The order of scheduling may be assigned in descending order of the propagation path characteristic value among the combinations of all mobile stations and frequency bands, or from the frequency band with the high propagation path characteristic value for each mobile station by one allocation unit. Allocation may be performed in order.

Here, the system band is divided into 12 allocation units in the frequency direction, and the allocation limit bandwidth determined from the transmission power of the mobile station is set to 5 for all mobile stations. Further, the allowable overlapping bandwidth given from the allowable overlapping bandwidth calculation unit 307 is 6.
FIG. 5 shows spectrum allocation when the allowable overlapping bandwidth is reached by performing the SORM scheduling. The mobile station apparatus 11 is assigned with allocation units hatched with slanting lines in the figure, ie, the fifth, ninth, tenth and eleventh allocation units from the lowest frequency. The mobile station apparatus 12 is assigned with allocation units hatched by shading in the figure, ie, 2, 5, 8, and 12th allocation units from the lowest frequency. The mobile station apparatus 13 is assigned with allocation units hatched with slanting diagonal lines in the figure, that is, allocation units 1, 2, 6, and 9 from the lowest frequency. The mobile station apparatus 14 is assigned with allocation units hatched in a diagonal lattice pattern in the figure, that is, allocation units 2, 6, 7, and 8 from the lowest frequency.

  FIG. 6 is a diagram showing an overlapping state of allocation of each allocation unit in the spectrum allocation state of FIG. If the scheduling unit 308 finally allocates the eighth allocation unit to the mobile station apparatus 14 in the scheduling so far, the overlapping bandwidths up to now are the second, fifth, sixth, ninth and tenth allocation units. Since it was 5 points, SORM scheduling was possible. However, because the 8th allocation unit also overlapped, the allowable overlapping bandwidth of 6 was reached, so the scheduling unit 308 finished the SORM scheduling, This is performed by FDM scheduling that does not allow duplication.

  FIG. 7 is a diagram illustrating an example of spectrum allocation when FDM scheduling that does not allow duplication is performed after performing the SORM scheduling of FIG. 5. FIG. 8 is a diagram showing an overlapping state of allocation of each allocation unit in the spectrum allocation state of FIG. When the SORM scheduling is completed, as shown in FIG. 5, the third, fourth, and twelfth allocation units from the lowest frequency are free bands. Therefore, the scheduling unit 308 allocates each of the mobile station apparatuses 11, 12, and 13 whose spectrum allocation has not reached the number of allocatable bands to these allocation units. As a result, there is no free bandwidth and no further FDM scheduling is possible, and the scheduling unit 308 ends the scheduling. As a result, the spectrum is assigned to all the allocation units of the system band, and the 2, 5, 6, 8, 9, and 10th allocation units are spectrum overlapping. For this reason, the overlapping bandwidth in this case is “6”, and is allocated within a range that falls within the allowable overlapping bandwidth.

In the scheduling methods in FIG. 5 to FIG. 8, the PF (Proportional Fairness) is based on propagation path characteristics such as allocation priority and communication path capacity of each mobile station apparatus in consideration of average received SINR, QoS (Quality of Service), and the like. ), Max CIR (Maximum Carrier to Interference power Ratio), RR (Round Robin), or the like.
Note that the assignable bandwidth of each mobile station device may be stored in advance by the scheduling unit 308, or can be assigned when each mobile station device starts communication with the base station device 15. Information indicating the bandwidth may be notified to the base station apparatus 15, and the scheduling unit 308 may store the value indicated by the notified information.

FIG. 9 is a flowchart for explaining the operation of the scheduling unit 308 in the present embodiment. First, the scheduling unit 308 is different for each mobile station apparatus determined from the propagation path characteristics H _u (u = 1, 2,..., U) of each mobile station apparatus and the transmittable power of each mobile station apparatus. An allocatable bandwidth W _u (u = 1, 2,..., U) and an allowable overlapping bandwidth X are acquired (S1). The propagation path characteristic H _u is acquired from the propagation path estimation unit 306, the allocatable bandwidth W _u is read from the scheduling unit 308, and the allowable overlapping bandwidth X is calculated as the allowable overlapping bandwidth. What is determined in the unit 307 is acquired. Based on the acquired information, the scheduling unit 308 first performs SORM scheduling that allows spectrum overlap (S2). Here, when there is no mobile station apparatus whose allocated bandwidth has not reached W _u (S3-No), scheduling is terminated, but when there is a mobile station apparatus that has not reached W _u (S3-Yes). Then, the process proceeds to step S4 to continue scheduling.

In step S4, the scheduling unit 308 confirms the number of points of the band allocated redundantly in the system band. When the overlapping allowable bandwidth X has not been reached (S4-No), the scheduling unit 308 returns to step S2. The scheduling of the SORM is continued, and when it is reached (S4-Yes), the process proceeds to FDM scheduling that does not allow spectrum overlap, that is, step S5. In step S5, the scheduling unit 308 performs FDM scheduling only with a mobile station apparatus whose allocated bandwidth has not reached W _u . The FDM scheduling end condition is when all the free bandwidths in the system bandwidth are filled or the allocated bandwidth of all mobile stations reaches the allocatable bandwidth W _u (S6).

  As described above, in the present embodiment, while performing allocation so that the number of spectra overlapping in the system band falls within the allowable range, each mobile station apparatus can allocate a spectrum in a wide band, Since it is possible to control so that overlapping spectra can be separated, cell throughput can be improved without causing characteristic deterioration due to spectrum overlapping.

[Second Embodiment]
In the second embodiment, in order to prevent excessive duplication when scheduling ends at an arbitrary time point, scheduling is performed in consideration of the duplication rate in an already allocated band. That is, the ratio of the “duplicate bandwidth” to the “used bandwidth” in the system bandwidth is set to be equal to or less than a predetermined value.
Here, a minimum unit of allocation in the entire system band is a resource block. In general, in scheduling in the frequency domain, the base station apparatus assigns each resource block included in the system band to each mobile station apparatus one by one from the highest gain. In this embodiment, when allocating one by one, it is assumed that the resource block to be allocated next has already been allocated, and the duplication rate when duplication increases is calculated as the expected duplication rate and allowed. Assign while comparing with the overlap rate. At this time, it is defined as “expected duplication rate = (already duplicated bandwidth + resource block bandwidth) / allocated bandwidth”. If this expected duplication rate is lower than the allowable duplication rate, duplication is allowed in the next allocation, and if it is higher than the allowable duplication rate, duplication is not allowed in the next allocation.

  Note that the procedure described below is an example, and any other scheduling method can be used as long as the scheduling method allocates “the number of overlapping bands / the number of allocated bands” within an allowable overlapping rate. Good. For example, the resource block scheduled to be allocated next may be determined first by scheduling that allows overlap, and the expected overlap rate may be calculated only when the resource block has already been allocated to another mobile station apparatus.

  The wireless communication system in the present embodiment includes mobile station apparatuses 11 to 14 and a base station apparatus 15a. The configuration of mobile station apparatuses 11-14 is the same as that of mobile station apparatuses 11-14 shown in FIG. The base station apparatus 15a differs from the base station apparatus 15 shown in FIG. 2 in that the control unit 501 that performs scheduling is the control unit 501a. FIG. 10 is a schematic block diagram illustrating the configuration of the reception unit 503 and the control unit 501a in the present embodiment. 4, the same parts as those in FIG. 4 are denoted by the same reference numerals (301 to 307, 309 to 323, 330-1 to 330-U, 503), and description thereof is omitted. The control unit 501a includes an allowable duplication rate calculation unit 324a, a scheduling unit 308a, and a spectrum allocation information generation unit 309.

  The allowable duplication rate calculation unit 324a obtains the allowable duplication rate allowed in the system band based on the propagation path characteristics (for example, reception SNR), and outputs it to the scheduling unit 308a. For example, when a specific modulation scheme and coding rate are used, an allowable duplication rate value corresponding to the average received SNR is set in advance in the allowable duplication rate calculation unit 324a so that the error rate becomes a certain value or less. Keep it. The allowable duplication rate calculation unit 324a determines the allowable duplication rate according to the average value in the frequency direction of the received SNR regarding the received signal according to this setting.

  Similar to the scheduling unit 308, the scheduling unit 308a allows overlapping of a part of the spectrum so that the frequency band allocated to each of the plurality of mobile station apparatuses has a band width that is equal to or less than a predetermined value. Determine the spectrum allocation. However, in the present embodiment, the above-mentioned predetermined value is a bandwidth of a predetermined ratio (allowable overlap rate) with respect to the total bandwidth of the frequency spectrum allocated to any mobile station apparatus. More specifically, the scheduling unit 308a determines the allowable duplication rate given from the allowable duplication rate calculation unit 324a and “expected duplication rate = (already overlapping bandwidth + 1 allocation unit) / allocated bandwidth”. Judgment is made based on the expected duplication rate given in (1) or not, and if it is met, scheduling that allows duplication is performed. If not, scheduling that does not allow duplication is performed. Thus, the frequency spectrum is assigned to the mobile station apparatuses 11-14.

  11 to 14 are diagrams illustrating an operation example of the scheduling unit 308a in the present embodiment. Here, the system band is divided into 12 allocation units in the frequency direction, and the allowable duplication rate is 50%. In FIG. 11 to FIG. 14, a rectangle hatched with a diagonal line that rises to the right indicates that the resource block in which the rectangle is located is allocated to the mobile station apparatus 11. Similarly, a hatched rectangle indicates that the resource block in which the rectangle is located is allocated to the mobile station apparatus 12, and a rectangle hatched with a slanting diagonal line indicates the resource in which the rectangle is located. A block that is assigned to the mobile station apparatus 13 is indicated by a hatched rectangle, and a resource block in which the rectangle is located is assigned to the mobile station apparatus 14.

  FIG. 11 and FIG. 12 show a case where assignment that does not allow duplication is performed. In FIG. 11, while the allocation to the mobile station apparatuses 11 to 14 is being performed, the allocated band has 9 points (1, 2, 5, 6, 7, 8, 9, 10, 11th allocation). (Unit) There are 4 points (2, 5, 8, 9th allocation unit) where there are overlapping spectrums. In this case, since the expected duplication rate is “(4 (duplication multiple) +1 (allocation unit)) / 9 (allocated bandwidth) = 55.5%”, “expected duplication rate (55.5%)> allowable duplication” Rate (50%) ”and does not satisfy the above-described expected duplication rate <allowable duplication rate”, the scheduling unit 308a does not allow duplication in the next allocation. Therefore, for example, the scheduling unit 308a allocates to a third allocation unit that is a free band as illustrated in FIG. As a result, the allocated bandwidth is 10 points (1, 2, 3, 5, 6, 7, 8, 9, 10, 11th allocation unit), and the overlapping number is 4 points (2, 5, 8, 9th allocation). Therefore, the actual duplication rate is “4/10 = 40.0%”, so that “actual duplication rate (40%) <allowable duplication rate (50%)”, and excessive duplication can be avoided. it can.

  FIG. 13 and FIG. 14 show a case where assignment that allows duplication is performed. In FIG. 13, 11 points (1, 2, 4, 5, 6, 7, 8, 9, 10, 11, The twelfth allocation unit) is in a state where there are four points (2, 5, 8, and 9th allocation units) where the spectrum overlaps. In this case, since the expected duplication rate is “(4 (duplication number) +1 (allocation unit)) / 11 (allocated bandwidth) = 45.5%”, “expected duplication rate (45.5%) <allowable duplication” Rate (50%) ”, which satisfies the above-mentioned“ expected duplication rate <allowable duplication rate ”, the scheduling unit 308a allows duplication in the next allocation. Therefore, for example, as illustrated in FIG. 14, the scheduling unit 308 a allocates the mobile station apparatus 11 to the sixth allocation unit to which the mobile station apparatus 14 has already been allocated.

  The above-described allocation in FIG. 11 to FIG. 14 is repeated. For example, the allocation ends when the allocated bandwidth of all mobile stations reaches the allocatable bandwidth. In this scheduling method, since the ratio of the overlapping band is lower than the allowable overlapping ratio with respect to the total allocated band at all times, the final allocation is not performed even under other termination conditions. It is possible to always keep the ratio of overlapping bands lower than the allowable overlapping rate with respect to the total of the bands.

The scheduling methods in FIGS. 11 to 14 are based on propagation characteristics such as average received SINR, CQI (Channel Quality Indicator) and channel capacity, and PF (Proportional Fairness) or Max CIR (Maximum Carrier to Interferer). power Ratio), RR (Round Robin) or the like is used.
Note that the allocatable bandwidth of each mobile station apparatus may be stored in advance by the scheduling unit 308a as in the first embodiment, or when each mobile station apparatus starts communication with the base station apparatus 15a. In addition, the mobile station apparatus may notify the base station apparatus 15a of information indicating the allocatable bandwidth, and the scheduling unit 308a may store the value indicated by the notified information.

FIG. 15 is a flowchart for explaining the operation of the scheduling unit 308a in the present embodiment. First, the scheduling unit 308a assigns different allocable bands for each mobile station determined from the propagation path characteristics H _u (u = 1, 2,..., U) of each mobile station and the transmittable power of each mobile station. The width W _u (u = 1, 2,..., U) and the allowable overlap rate Y are acquired (S11). The propagation path characteristic H _u is acquired from the propagation path estimation unit 306, the allocatable bandwidth W _u is read from the scheduling unit 308a, and the allowable overlap rate Y is the allowable overlap rate calculation unit 324a. Get what was determined in.

  Next, the scheduling unit 308a confirms the status of the allocated bandwidth that has already been allocated, and calculates the expected overlap rate Z (S12). However, since the allocation is not yet performed for the first time, the expected overlap rate Z is set to 0%. Then, the derived expected duplication rate Z and the allowable duplication rate Y are compared (S13), and if “Z <Y” (S13-Yes), scheduling that allows duplication is performed (S14), and “Z <Y”. If not (S13-No), scheduling that does not allow duplication is performed (S15). If the scheduling satisfies an arbitrary allocation end condition, the scheduling ends (S16-Yes). If the scheduling end condition is not satisfied (S16-No), the process returns to the calculation of the expected overlap rate Z in step S12. Repeat scheduling. Here, the allocation end condition may be, for example, that all the allocatable bandwidth fields Wu corresponding to the transmission power of each mobile station are satisfied, or that all the system bandwidths have been allocated.

In the present embodiment, wideband transmission can be performed in a range where the spectrum does not overlap too much by performing allocation so that the spectrum that overlaps the band allocated within the system band is within the allowable range.
In the first and second embodiments described above, the allocatable bandwidth of each mobile station has been described as being determined by the transmission power of the mobile station, but may be determined by the bandwidth requested by the mobile station. The bandwidth may be in accordance with the service requested by the mobile station, or a combination thereof.

  Also, a program for realizing the functions of the control unit 101, the control unit 501, and the control unit 501a in FIG. 2 is recorded on a computer-readable recording medium, and the program recorded on the recording medium is stored in the computer. The processing of each unit may be performed by reading it into the system and executing it. Here, the “computer system” includes an OS and hardware such as peripheral devices.

The “computer-readable recording medium” refers to a storage device such as a flexible medium, a magneto-optical disk, a portable medium such as a ROM and a CD-ROM, and a hard disk incorporated in a computer system. Furthermore, the “computer-readable recording medium” dynamically holds a program for a short time like a communication line when transmitting a program via a network such as the Internet or a communication line such as a telephone line. In this case, a volatile memory in a computer system serving as a server or a client in that case, and a program that holds a program for a certain period of time are also included. The program may be a program for realizing a part of the functions described above, and may be a program capable of realizing the functions described above in combination with a program already recorded in a computer system.
The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and includes design changes and the like within a scope not departing from the gist of the present invention.

  The present invention is suitable for use in a mobile communication system that is a radio communication system using a mobile phone as a mobile station device, but is not limited to this.

DESCRIPTION OF SYMBOLS 10 ... Wireless communication system 11, 12, 13, 14 ... Mobile station apparatus 15 ... Base station apparatus 101 ... Control part 102 ... Transmission part 103 ... Reception part 201 ... Encoding part 202 ... Interleaving part 203 ... Modulation part 204 ... DFT part 205 ... spectrum mapping unit 206 ... IDFT unit 207 ... pilot signal generation unit 208 ... pilot multiplexing unit 209 ... CP insertion unit 210 ... D / A conversion unit 211 ... radio unit 212 ... transmission antenna 301 ... reception antenna 302 ... radio unit 303 ... A / D conversion unit 304 ... CP removal unit 305 ... pilot separation unit 306 ... propagation path estimation unit 307 ... allowable overlapping bandwidth calculation unit 308, 308a ... scheduling unit 309 ... spectrum allocation information generation unit 310 ... buffer 311 ... first DFT Unit 312 ... spectrum demapping unit 313 Canceling unit 314 ... equalizing unit 315 ... IDFT unit 316 ... demodulating unit 317 ... deinterleaving unit 318 ... decoding unit 319 ... interleaving unit 320 ... soft replica generating unit 321 ... second DFT unit 322 ... interference extracting unit 323 ... determination Unit 324a ... allowable duplication rate calculation unit 330-1 ... first decoding processing unit 330-2 ... second decoding processing unit 330-U ... Uth decoding processing unit 501, 501a ... control unit 502 ... transmission unit 503 ... Receiver

Claims (8)

A communication device including a scheduling unit that assigns a frequency band to be used for communication with its own device for each of a plurality of terminal devices,
  The scheduling unit allocates the frequency band so that overlapping bandwidths are smaller than a predetermined value when allocation is performed so that a part of the frequency band overlaps among at least some of the terminal devices. Assigning
  A communication device characterized by the above. Receiving a plurality of frequency signals that overlap with each other in a part of the frequency bands, and the bandwidths of the overlapping frequency bands are smaller than a predetermined value, and using the replica signal generated from the received frequency signals, the frequency signal A receiving unit that performs the canceling process and separates each frequency signal.
  A communication device characterized by the above. Wherein the predetermined value, the communication apparatus according to claim 1 or 2, wherein the communication device is a bandwidth of a predetermined rate in pairs on the system bandwidth available. Wherein the predetermined value, the communication apparatus according to claim 1 or 2, characterized in that in pairs the total bandwidth of the frequency band is the bandwidth of a predetermined ratio. Percentage of bandwidth that the overlap, if less than the rate that the communication device is predetermined by pairs on the system bandwidth available, allocates to permit duplication, if the predetermined ratio or more 2. The communication apparatus according to claim 1, wherein allocation is performed so as not to allow duplication thereafter. The predetermined value is
The communication device according to claim 1 , wherein the communication device is a value calculated based on a propagation path characteristic between the terminal device and the device itself . Converts the transmission signal into a frequency signal, received a plurality of terminal devices and transmits the arranged frequency spectrum allocated to the own device, a signal in which the plurality of terminal device transmits, interference between signals of the terminal device And a base station device that separates the signal into signals for each terminal device, and a wireless communication system comprising:
The base station apparatus allocates a frequency spectrum to each of the plurality of terminal apparatuses so that a width of a band in which the frequency spectrum allocated to each of the plurality of terminal apparatuses overlaps becomes smaller than a predetermined value. A wireless communication system. A frequency allocation method in a communication apparatus that allocates a frequency band to be used for communication with the own apparatus for each of a plurality of terminal apparatuses,
  A process of allocating the frequency band so that overlapping bandwidths are smaller than a predetermined value when allocating so that a part of the frequency band overlaps among at least some of the terminal devices;
  A frequency allocation method characterized by the above.

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