JP5033823B2 - Wireless communication system, base station, and scheduling method - Google Patents

Description

  The present invention relates to a radio communication system, a base station, and a scheduling method that perform radio resource scheduling for improving the total throughput of the entire system in a radio communication system including a base station and a relay station.

  The IEEE802.16e-2005 standard communication method standardized by IEEE802.16 (so-called mobile WiMAX (Worldwide interoperability for microwave access)) is used for various applications such as VoIP and streaming distribution in addition to high-speed data services. Designed for a wide range of applications. The use of a microwave band as a frequency band is expected to widen the service area. However, due to the undulations of buildings and hilly areas, throughput degradation and coverage holes associated with radio wave shielding occur, so there is a limit to widening the area by a single base station (hereinafter referred to as BS).

  In IEEE802.16TGj, an extension work for applying a relay station (hereinafter referred to as RS) to the IEEE802.16e-2005 standard is being performed (Non-Patent Document 1). By using RS, it can be expected to complement an area where communication quality is deteriorated due to radio wave shielding such as a building, and to expand a service area. The relay system being studied is a system in which the same frequency band is time-division multiplexed on the access line and the relay line in order to realize the relay on the same channel.

  FIG. 14 shows an example of a frame configuration that realizes relaying by time division indicated by IEEE802.16TGj. BS and RS divide one frame into downlink (DL) subframe and uplink (UL) subframe by time division duplex, and further subdivide each subframe into access section and relay section To do. The access section is a section in which both the BS and the RS communicate with a terminal station (hereinafter referred to as SS), and when the communication between the BS, the RS, and the SS interferes with each other, the resources used by the BS and the RS Divide (frequency and time). The relay section in the DL subframe is a section in which the BS transmits relay data and the RS receives the relay data. The relay section in the UL subframe is a section in which the RS transmits relay data and the BS receives the relay data. Also, in the DL subframe, at the head of the access section and BS relay section, a control signal such as a preamble for synchronizing with each SS or RS, schedule information for notifying a subchannel assigned to communication and time, etc. is transmitted. .

  In the method of realizing relaying in time division shown in FIG. 14, access resources are suppressed in order to set relay resources in each subframe. Therefore, there is a problem that the total throughput of the entire system is lowered as compared with a system configured by PMP (Point-to-Multipoint). In Non-Patent Document 2, in order to improve the total throughput by efficiently using radio resources (time / frequency of radio frame), multiplexing of frequencies used by BS and RS, and control of ratio of access zone and relay zone The application of optimal subcarrier allocation has been proposed.

  Here, multiplexing or frequency multiplexing means that one or more BSs or one or more RSs communicate with a plurality of different SSs using the same frequency at the same time. For example, in SS1 in FIG. 15, the signal wave from the BS is strong, and the interference wave from the RS does not cause a problem. In SS2, the signal from the BS is blocked by an obstacle, and only the signal from the RS is received. In such a case, the throughput can be improved by multiplexing the communication from the BS to the SS1 and the communication from the RS to the SS2.

  However, frequency multiplexing by BS and RS in Non-Patent Document 2 remains in the scheduling procedure of BS and single RS. When there are multiple RSs and BSs, the number of BS and RS combination patterns to be multiplexed (hereinafter referred to as “multiplex combination patterns”) increases, and further, the multiplex combination patterns that can be multiplexed and the total throughput can be maximized depending on the environment where each SS is located. Multiple combination patterns are different. Therefore, in order to maximize the total throughput, there is a need for a method for dynamically selecting an optimum multiple combination pattern in consideration of the SS environment in which BSs and RSs included in the multiple combination pattern respectively communicate.

  In the frame configuration shown in FIG. 14, the following two methods are used as a method of dividing the communication area (hereinafter referred to as a slot) allocated to each SS on the time axis or the frequency axis and dynamically selecting a multiple combination pattern for each slot. Conceivable.

  Method 1 determines whether or not each SS can be multiplexed for each multiple combination pattern in each slot, so that the total number of BSs and RSs (= the number of multiplexing) included in the multiple combination pattern is maximized. Select an SS to communicate in the pattern.

  In Method 2, as shown in Non-Patent Document 3, the multiple combination pattern and the SS that communicates in the pattern are selected so that the total throughput of SSs that are multiplexed and communicated in each slot is maximized.

IEEE Draft standards for Local and metropolitan area networks, Part 16: Air Interface for Fixed Broadband Wireless Access Systems, Multihop Relay Specification, 8.4.4.8 TDD frame structure of MR-BS and RS, pp.194-202, 2008 Yohei Ohno, Tatsuya Shimizu, Seiji Nakatsugawa, "Study on resource control in wireless relay access system", 2008 IEICE General Conference, B-5-186, 2008 Yohei Ohno, Tatsuya Shimizu, Seiji Nakatsugawa, "Frequency reuse effect in wireless access system with multiple relay stations", 2008 IEICE Society Conference, B-5-103, 2008

  As shown in FIG. 16, the determination of whether or not frequency multiplexing is possible in Method 1 is based on a CINR threshold value set to a level at which QPSK demodulation is possible, for example. Specifically, when the BS and the RS simultaneously transmit signals of the same frequency, the amount of radio interference from the other to the transmission signal from one of the BS or RS to the SS is not large, and the CINR of the transmission signal from one is If it is equal to or greater than the threshold, the SS determines that frequency multiplexing by the BS and RS is possible. Here, when BS, RS1, and RS2 exist and frequency is multiplexed by BS, RS1, and RS2, all of the CINRs of SS1, SS2, and SS3 located in the respective service areas are higher than a level that allows QPSK demodulation. If so, the multiple combination pattern by the BS having the maximum number of multiplexing, RS1, and RS2 is selected.

  However, in reality, there are cases where two multiple combination patterns of BS and RS1 can realize higher total throughput than multiple combination patterns of BS, RS1, and RS2. For example, SS1, SS2, and SS3 can communicate only by QPSK in the former multiple combination pattern, but SS1 and SS2 can communicate using 16QAM in the latter multiple combination pattern.

  In addition, there is a situation in which a higher total throughput can be secured with the multiple combination pattern of RS1 and RS2 than with the multiple combination pattern of BS and RS1. Method 2 assumes such a situation. By using the transmission rate list shown in FIG. 17, the multiplex combination pattern and the pattern are used so that the sum of the throughputs of SSs that are multiplexed and communicated is maximized. Select the SS to communicate with. That is, the total rates for all multiple combination patterns are compared. For example, the total rate of the multiple combination patterns BS, RS1, and RS2 is X1 + X2 + X3, and the total rate of the multiple combination patterns BS and RS1 is X4 + X5, and the multiple combination pattern that maximizes the total rate is selected.

  However, in method 2, the maximum total throughput can be ensured for each slot. However, considering the fairness of the throughput, when the slot size is evenly allocated to all the SSs, the total throughput is not necessarily increased over the entire frame. It may not be possible to maximize. As shown in FIG. 18, in method 1, multiple combination patterns BS, RS1, and RS2 are selected, and communication of all SSs can be assigned in one slot, so there is no need to divide the access section into slots. On the other hand, in the method 2, the multiple combination patterns BS and RS1 are selected so that the sum of the throughput is highest for each slot, and the BS and RS1 communicate with SS1 and SS2 by multiplexing the frequencies, respectively. If the slot size is assigned equally to all SSs, it is necessary to prepare a slot for SS3, and the access section is divided into two slots. Therefore, the slot size allocated to the multiple combination pattern is reduced, and the total throughput in the entire frame is reduced as compared with the method 1.

  As described above, for the purpose of maximizing the total throughput in the entire frame, the method 1 and the method 2 cannot always select the optimum combination pattern.

  The present invention provides a radio communication system including a plurality of relay stations RS, and an optimum base station BS and a base station BS and a plurality of relay stations RS, when multiplexing frequencies used for communication to a plurality of terminal stations SS, A wireless communication system capable of obtaining a combination of multiple combination patterns of a plurality of relay stations RS and terminal stations SS with which each base station BS or relay station RS communicates in the multiple combination patterns and improving the total throughput of the entire frame An object of the present invention is to provide a base station and a scheduling method.

  A first invention is a radio communication system including a base station BS, a plurality of relay stations RS, and a plurality of terminal stations SS. The base station BS includes a base station BS, a plurality of relay stations RS, and a plurality of relay stations RS. First means for collecting a CNR (carrier power to noise power ratio) with the terminal station SS and determining a base station BS or a relay station RS with which each terminal station SS communicates directly based on the information of the CNR; For each combination pattern composed of a part or all of the station BS and the plurality of relay stations RS, all base stations BS or a plurality of relay stations RS included in each combination pattern simultaneously receive signals of the same frequency respectively When transmitting to the terminal station SS, the CINR (carrier power to noise + interference power ratio) between each terminal station SS and the base station BS or relay station RS with which the terminal station SS communicates directly is calculated, and the transmission rate is calculated. A terminal having the maximum estimated transmission rate among a plurality of terminal stations SS communicating with all base stations BS or relay stations included in the combination pattern for each combination pattern and the second means to be determined The station SS is selected, and the sum of the transmission rates of the terminal stations SS selected for each group is multiplied by the multiplex number that is the total number of base stations BS and relay stations RS included in the combination pattern. Is determined as the combination pattern used for communication by the terminal station SS selected by the combination pattern, the terminal station SS determined by the combination pattern used for communication is excluded, and the terminal station SS is further selected. , Repeating the procedure of determining the combination pattern and excluding the terminal station SS, and third means for determining the combination pattern used for communication by all the terminal stations SS. .

  In the wireless communication system of the first invention, the transmission rate for each combination pattern is normalized by the transmission rate when all base stations BS and relay stations RS included in the combination pattern do not transmit signals of the same frequency at the same time. Is used.

  In the wireless communication system of the first invention, the first means includes a CNR between the base station BS and the terminal station SS, between the base station BS and the relay station RS, and between the relay station RS and the terminal station SS. From the means for estimating the transmission rate communicable in each section, and for each terminal station SS, as access radio resources necessary for direct communication with the base station BS (1 / base station BS and terminal station SS (Transmission rate) is calculated, and as a relay and access radio resource required for direct communication with the relay station RS (1 / transmission rate between the base station BS and the relay station RS + 1 / between the relay station RS and the terminal station SS) Means for calculating (transmission rate), and means for selecting a base station BS or relay station RS that minimizes radio resources.

  In the wireless communication system of the first invention, the base station BS and the relay station RS switch transmission / reception by time division duplex, an access section in which the base station BS and the relay station RS communicate with the terminal station SS, and a radio frame, The base station BS is configured to be time-divided into a relay section relayed by the BS and the relay station RS. Is configured to control the ratio between the access section and the relay section so as to be equal. Further, the base station BS sets the ratio between the access section and the relay section for each relay station RS (sum of transmission rates between the relay station RS and the terminal station SS that communicates directly with the relay station RS) / (base station BS The transmission rate between the relay station RS and the number of combination patterns determined for the communication of the terminal station SS) may be calculated, and the sum thereof may be determined based on the calculated value.

  In the wireless communication system of the first invention, the base station BS is a first base station BS having a control station function, and includes a plurality of second base stations BS instead of the plurality of relay stations RS, In this configuration, a control signal is transmitted and received between the station BS and the second base station BS via a backbone network or by wireless communication.

  A second invention is a scheduling method for a radio communication system including a base station BS, a plurality of relay stations RS, and a plurality of terminal stations SS. The base station BS includes a base station BS and a plurality of relay stations RS. First step of collecting CNR (carrier power to noise power ratio) with a plurality of terminal stations SS and determining a base station BS or a relay station RS with which each terminal station SS communicates directly based on the information of the CNR For each combination pattern composed of part or all of the base station BS and the plurality of relay stations RS, all the base stations BS or the plurality of relay stations RS included in each combination pattern simultaneously transmit signals of the same frequency. CINR (carrier power versus noise + interference power) between each terminal station SS and the base station BS or relay station RS with which the terminal station SS communicates directly when transmitted to the other terminal station SS ) And calculating a transmission rate, and, for each combination pattern, are estimated in a group of terminal stations SS that communicate with all base stations BS or relay stations included in the combination pattern A terminal station SS that maximizes the transmission rate, and a sum of the transmission rates of the terminal stations SS selected for each group and a multiplexing number that is the total number of base stations BS and relay stations RS included in the combination pattern; The combination pattern having the maximum value is determined as the combination pattern used for communication by the terminal station SS selected by the combination pattern, and the terminal station SS determined by the combination pattern used for communication is excluded. Further, the selection of the terminal station SS, the determination of the combination pattern, and the procedure of excluding the terminal station SS are repeated, and the combination pattern used by all the terminal stations SS for communication is repeated. And a third step of determining.

  In the scheduling method of the wireless communication system of the second invention, the transmission rate for each combination pattern is a transmission rate when all base stations BS and relay stations RS included in the combination pattern do not simultaneously transmit signals of the same frequency. Use a normalized version.

  In the scheduling method of the wireless communication system of the second invention, the first step is between the base station BS and the terminal station SS, between the base station BS and the relay station RS, and between the relay station RS and the terminal station SS. Means for estimating the transmission rate communicable in each section from the CNR between the two, and for each terminal station SS as an access radio resource required for direct communication with the base station BS (1 / base station BS and (Transmission rate of the terminal station SS) is calculated, and as a radio resource for relay and access necessary for direct communication with the relay station RS (1 / transmission rate between the base station BS and the relay station RS + 1 / relay station RS and the terminal) (Transmission rate between stations SS) and a step of selecting a base station BS or a relay station RS that minimizes radio resources.

  In the scheduling method of the wireless communication system according to the second aspect of the invention, the base station BS and the relay station RS switch transmission / reception by time division duplex, and an access section in which the base station BS and the relay station RS communicate with the terminal station SS. And the relay section relayed by the base station BS and the relay station RS, and the base station BS has a data amount communicated between the base station BS and the relay station RS, and the relay station RS and the terminal station SS The ratio between the access section and the relay section is controlled so that the amount of data to be communicated is equal. Further, the base station BS sets the ratio between the access section and the relay section for each relay station RS (sum of transmission rates between the relay station RS and the terminal station SS that communicates directly with the relay station RS) / (base station BS May be determined based on the calculated value of the transmission rate between the relay station RS and the number of combination patterns determined for the communication of the terminal station SS).

  In the scheduling method of the wireless communication system of the second invention, the base station BS is a first base station BS having a control station function, and a plurality of second base stations BS are provided instead of the plurality of relay stations RS, Control signals are transmitted and received between the first base station BS and the second base station BS via the backbone network or by wireless communication.

  A third invention is a base station BS of a wireless communication system constituted by a base station BS, a plurality of relay stations RS, and a plurality of terminal stations SS, wherein the base station BS, the plurality of relay stations RS, and the plurality of terminals A first means for collecting a CNR (carrier power to noise power ratio) with a station SS and determining a base station BS or a relay station RS with which each terminal station SS communicates directly based on the CNR information; For each combination pattern composed of a part of or all of a BS and a plurality of relay stations RS, all base stations BS or a plurality of relay stations RS included in each combination pattern simultaneously transmit signals of the same frequency to each other terminal. The CINR (carrier power to noise + interference power ratio) between each terminal station SS and the base station BS or the relay station RS with which the terminal station SS communicates directly when transmitted to the station SS is calculated to estimate the transmission rate. And a terminal station having a maximum estimated transmission rate in a group of a plurality of terminal stations SS communicating with all base stations BS or relay stations included in the combination pattern for each combination pattern SS is selected, and the sum of the transmission rates of the terminal stations SS selected for each group is multiplied by the multiplexing number that is the total number of base stations BS and relay stations RS included in the combination pattern. Is determined as a combination pattern used for communication by the terminal station SS selected by the combination pattern, excluding the terminal station SS determined by the combination pattern used for communication, and further selecting the terminal station SS, 3rd means which repeats the procedure of determination of a combination pattern and exclusion of terminal station SS, and determines the combination pattern which all the terminal stations SS use for communication

  In the base station BS of the wireless communication system of the third invention, the transmission rate for each combination pattern is a transmission rate when all base stations BS and relay stations RS included in the combination pattern do not simultaneously transmit signals of the same frequency. Use a normalized version.

  In the base station BS of the wireless communication system of the third invention, the first means is between the base station BS and the terminal station SS, between the base station BS and the relay station RS, and between the relay station RS and the terminal station SS. Means for estimating the transmission rate communicable in each section from the CNR between the two, and for each terminal station SS as an access radio resource required for direct communication with the base station BS (1 / base station BS and (Transmission rate of the terminal station SS) is calculated, and as a radio resource for relay and access necessary for direct communication with the relay station RS (1 / transmission rate between the base station BS and the relay station RS + 1 / relay station RS and the terminal) Means for calculating (transmission rate between stations SS) and means for selecting a base station BS or relay station RS that minimizes radio resources.

  In the base station BS of the radio communication system of the third invention, the base station BS and the relay station RS switch transmission / reception by time division duplex, and the radio frame is accessed in the access section in which the base station BS and the relay station RS communicate with the terminal station SS. And a time division into relay sections relayed by the base station BS and the relay station RS, and the data amount communicated between the base station BS and the relay station RS and the data amount communicated between the relay station RS and the terminal station SS are In this configuration, the ratio between the access section and the relay section is controlled so as to be equal. Further, the base station BS sets the ratio between the access section and the relay section for each relay station RS (sum of transmission rates between the relay station RS and the terminal station SS that communicates directly with the relay station RS) / (base station BS The transmission rate between the relay station RS and the number of combination patterns determined for the communication of the terminal station SS) may be calculated, and the sum thereof may be determined based on the calculated value.

  In the base station BS of the radio communication system according to the third aspect of the invention, control for transmitting / receiving control signals to / from a plurality of base stations BS arranged in place of the plurality of relay stations RS via a backbone network or by radio communication It has a station function.

  The present invention relates to a combination pattern of an optimum base station BS and a plurality of relay stations RS, and a combination pattern thereof, when the base station BS and the plurality of relay stations RS multiplex frequencies used for communication to a plurality of terminal stations SS. , A combination of terminal stations SS with which each base station BS and relay station RS communicate is obtained, and the total throughput can be improved over the entire frame.

It is a figure which shows embodiment of the radio | wireless communications system of this invention. It is a figure which shows the structural example of the scheduler 12 of BS10. 4 is a flowchart showing a scheduling process procedure of a schedule information construction unit 32. It is a flowchart which shows an example of multiple combination setting procedure S1 of SS. 3 is a diagram illustrating an example of a propagation path information storage unit 31. FIG. It is a figure which shows an example of a grouping process. It is a flowchart which shows an example of a grouping process procedure. It is a figure which shows an example of a CINR list | wrist. It is a figure which shows an example of a transmission rate list | wrist. It is a figure which shows an example of the normalized transmission rate list | wrist. It is a figure which shows an example of a multiple | multiplex combination list | wrist. It is a flowchart which shows an example of ratio setting procedure S2 of an access area and a relay area. It is a figure which shows the structural example of the scheduler 22 of RS20. It is a figure which shows an example of the conventional frame structure. It is a figure which shows an example of the multiplexing by single BS and RS. It is a flowchart which shows the conventional frequency multiplexing possibility determination procedure. It is a figure which shows an example of the conventional multiple combination pattern selection. It is a figure which shows the comparison of the method 1 and the method 2. FIG.

(Example of wireless communication system)
FIG. 1 shows a configuration of an embodiment of a wireless communication system of the present invention.
In FIG. 1, the radio communication system of the present embodiment includes a BS 10 connected to a backbone network 1, a plurality (m) of RSs 20 (1) to 20 (m), and a plurality (n) of SS30 (1) to 30. Consists of (n).

  The data buffer unit 11 of the BS 10 inputs data from the backbone network 1. The scheduler 12 divides the frame into DL subframes and UL subframes, and further subdivides each subframe into an access section and a relay section, and based on propagation path information input from the receiving unit 17, an access section and a relay section The schedule information that divides the time into the time domain and frequency domain is constructed. Then, the data is extracted from the data buffer unit 11 in accordance with the schedule information and output to the transmission data generation unit 13. The transmission data generation unit 13 creates a frame using a control message composed of data input from the scheduler 12 and schedule information. The transmission unit 14 converts the frame created by the transmission data generation unit 13 into a radio signal by modulation and frequency conversion, and transmits a plurality of RSs 20 from the antenna 16 via the TDD switch 15 that controls transmission / reception switching based on schedule information. And transmitted to SS30 under BS.

  A radio signal received by the antenna 16 of the BS 10 is input to the receiving unit 17 via the TDD switch 15. The receiving unit 17 frequency-converts and demodulates the UL subframe radio signal, outputs the demodulated received data to the data buffer unit 11, and outputs the data to the backbone network 1.

  The RS 20 inputs a radio signal received by the antenna 26 to the receiving unit 27 via the TDD switch 25. The receiving unit 27 performs frequency conversion and demodulation on the radio signal in the DL subframe relay section and the UL subframe access section. The control message transmitted from the BS 10 or the previous hop RS is input to the scheduler 22 to grasp the frequency domain and time domain used for transmission / reception with the BS 10 and SS 30. The received data in the relay period of the DL subframe and the access period of the UL subframe demodulated by the reception unit 27 is input to the data buffer unit 21.

  The scheduler 22 of the RS 20 constructs schedule information based on the schedule information notified from the BS 10 and the propagation path information input from the receiving unit 27. Then, the data is extracted from the data buffer unit 21 in accordance with the schedule information and output to the transmission data generation unit 23. The transmission data generation unit 23 creates a frame using a control message composed of data input from the scheduler 22 and schedule information. The transmission unit 24 converts the frame created by the transmission data generation unit 23 into a radio signal by modulation and frequency conversion, and transmits from the antenna 26 to the BS 10 or SS 30 via the TDD switch 25 that controls switching between transmission and reception based on schedule information. Send to.

  The SS 30 refers to the schedule information transmitted by the BS 10 or the RS 20 via the antenna 31 and performs transmission / reception in the access period of the frame.

(Configuration example of scheduler 12 of BS 10)
FIG. 2 shows a configuration example of the scheduler 12 of the BS 10.
2, the scheduler 12 includes a propagation path information storage unit 31 that stores propagation path information input from the reception unit 17 and a schedule information construction unit 32 that constructs schedule information.

FIG. 3 shows a scheduling process procedure of the schedule information construction unit 32.
In FIG. 3, the schedule information construction unit 32 refers to the propagation path information storage unit 31 to set multiple combinations of SS (S1), and sets the ratio between the access section and the relay section (S2).

  The propagation path information storage unit 31 of the scheduler 12 of the BS 10 includes a CNR between the BS and SS (i) (BS CNR (i)) and a CNR between the RS (j) and SS (i) (RSj CNR (i) ) And the CNR (BS CNR RELAY (j)) between the BS and RS (j). i is the identification number of the SS, and j is the identification number of the RS. As an example, the state of the propagation path information storage unit 31 when the number of RSs is 2 and the number of SSs is 6 is shown in FIG. CNR (Carrier-to-Noise Ratio) is the value of the carrier power to noise power ratio received by the SS when the BS and RS are not frequency multiplexed.

  The BS CNR (i) is a control signal (preamble) transmitted by the BS when the BS receives a transmission signal of each SS (i) by the receiving unit 17 via the antenna 16 and the TDD switch 15 and grasps the CNR. Etc.) is received by SS (i), the CNR is grasped by SS (i) and the result is notified to the BS, so that it is registered in the channel information storage unit 31.

  In RSj CNR (i), RS (j) first receives the transmission signal of each SS (i) and grasps the CNR, or sends a control signal (such as a preamble) transmitted by RS (j) to SS (i). Is received in SS (i), the result is notified to RS (j), and the CNR is notified from RS (j) to the BS to be registered in the channel information storage unit 31. The At this time, when the BS receives the transmission signal of RS (j), the CNR between the BS and RS (j) is grasped.

(Multiple combination setting procedure in step S1 in FIG. 3)
In the present invention, the total throughput when the BS and the plurality of RSs multiplex the frequencies used for communication to the plurality of SSs in the case where the slot size is equally allocated to all the SSs considering the fairness of the throughput. The purpose is to maximize. Therefore, in the multiple combination setting procedure in step S1 of FIG. 3, the optimum multiple combination pattern of the BS and the plurality of RSs and the combination of SSs that communicate with each BS and RS in the multiple combination pattern are selected.

The total throughput when the BS and the plurality of RSs multiplex the frequencies used for communication to the plurality of SSs is expressed as follows using Shannon's theorem.

の要素として表される場合、ＢＳ(1) とＳＳ(1) との通信およびＢＳ(2) とＳＳ(3) との通信が、スロット(t')において周波数を多重して行われる。Σｐ｜ｈ_k,j ｜² は、ＢＳ(l) とＳＳ(k) 間の通信時における干渉電力を示す。上記のＣ(k,l,t')の場合、多重組合せパターンはＢＳ(1) とＢＳ(2) であるので、スロット(t')でＢＳ(1) とＳＳ(1) の通信に対しては、ＲＳ(2) からＳＳ(1) への干渉電力がΣｐ｜ｈ_k,j ｜² に相当する。 Here, K is the number of SSs, L is the total number of BSs and RSs, and T is the number of slots that divide the access section. B is the frequency band possessed by the system, p is the transmission power of BS and RS, N ₀ is the noise power density, and h _{k, l} is the channel gain of BS (l) and SS (k). In the configuration of the embodiment of FIG. 1, BS (1) indicates BS, and other BS (l) corresponds to RS. C (k, l, t) is an element of an allocation matrix of K × L × T composed of 0 and 1, and is 1 when communicating from BS (l) to SS (k) in slot (t). Otherwise, it is set to 0. For example, when K = 3 and L = 3, C (k, l, t ′) in slot (t ′) is a matrix of K × L.

, The communication between BS (1) and SS (1) and the communication between BS (2) and SS (3) are performed with frequency multiplexed in slot (t ′). Σp | h _{k, j} | ² represents the interference power during communication between BS (l) and SS (k). In the case of the above C (k, l, t '), the multiple combination patterns are BS (1) and BS (2). Therefore, for the communication between BS (1) and SS (1) in slot (t') Thus, the interference power from RS (2) to SS (1) corresponds to Σp | h _{k, j} | ² .

が付加される。この場合に、Ｃ(k,l,t) が取りうる行列のパターン数は（Ｌ・Ｔ) ^K となる。また、Ｔの数は多重組合せパターンによって１〜Ｋの領域で動的に変化する。したがって、ＲＳ数またはＳＳ数が増加するに従い、Ｃ(k,l,t) の組合せ数が増え、最適な解を得るまでには膨大な計算処理が必要となる。 In order to maximize the total throughput, by selecting the optimal allocation matrix element C (k, l, t), a multiple combination pattern of BS and a plurality of RSs, and each BS and The combination of SSs with which the RS communicates can be derived. When all SSs are allocated to communication with any one RS in any one slot, the optimal allocation matrix element C (k, l, t) is a constraint condition

Is added. In this case, the number of matrix patterns that C (k, l, t) can take is (L · T) ^K. The number of T dynamically changes in the region of 1 to K depending on the multiple combination pattern. Therefore, as the number of RSs or SSs increases, the number of combinations of C (k, l, t) increases, and enormous calculation processing is required to obtain an optimal solution.

However, in an environment where the received signal power from each BS or RS in each SS changes from moment to moment due to fading, scheduling that can follow them is required, so the calculation process needs to be reduced. Therefore, formula (1) is simplified for the purpose of obtaining a suboptimal solution. Specifically, in all SSs, it is assumed that the signal power from the desired BS or RS is equally h, and the interference powers from all BSs and RSs are equally h ′. Furthermore, assuming that the number of multiplexing in the multiple combination pattern is equal to M in all SSs, the total throughput can be simplified as follows.
M · (B / (K / M)) log ₂ (1 + p | h | ² / (N ₀ B + Mp | h ′ | ² ))
= (B / K) · M ² · F (M) (2)

In this case, the slot number T can be calculated as K / M. Also,
F (M) = log ₂ (1 + p | h | ² / (N ₀ B + Mp | h ′ | ² ))
It is said. In the above assumption, in order to maximize the total throughput, it is necessary to select the multiplexing number M so as to maximize the expression (2).

Here, it compares with the method 1 and the method 2 which were described in background art. Method 1 is a method for maximizing M in equation (2). Method 2 is a method for maximizing M · F (M). Therefore, in the present invention, in order to maximize M ² · F (M) based on the equation (2), the total throughput of SSs that are multiplexed and communicated in each slot in method 2 (= M · F (M )) The multiple combination pattern and the SS that communicates in the pattern are selected so that the value obtained by weighting the multiplexing number M to the maximum is selected.

FIG. 4 shows an example of the SS multiple combination setting procedure S1.
In FIG. 4, in the SS grouping (S101), the BS or RS (j) directly communicating with the SS is determined, the SS directly communicating with the BS is classified into a BS group, and the SS communicating with the RS (j) is Classify into RS (j) groups. An example of the grouping process when the number of RSs is 2 and the number of SSs is 6 is shown in FIG. In FIG. 6, SS (1) and SS (2) are classified into BS groups, SS (3) and SS (4) are classified into RS (1) groups, and SS (5) and SS (6) are classified as RS. (2) Classified into groups. The classification here may select the BS or RS (j) group having the highest CNR for each SS (i). In addition, the radio resources required for access when communicating directly with the BS and the sum of radio resources required for relay and access when communicating via RS (j) are compared. The smallest BS or RS (j) group may be selected. An example of the grouping process procedure in the latter case is shown in FIG.

First, the transmission rates BS RATE (i) and RSj RATE (i) of the communicable access are estimated from the BS CNR (i) and RSj CNR (i) registered in the channel information storage unit 31 (S1011). . Subsequently, the relay transmission rate BS RATE RELAY (j) that can be communicated is estimated from the BS CNR RELAY (j) between the BS and RS (j) (S1012). Next, for each SS (i), the radio resource 1 / BS RATE (i) required for access when communicating directly with the BS
And radio resources required for relay and access when communicating via RS (j) 1 / BS RATE RELAY (j) + 1 / RSj RATE (i)
(S1013) and classify each SS (i) into a group of BS or RS (j) that minimizes the resource (S1014).

Subsequently, in FIG. 4, a transmission rate list is created in consideration of the amount of interference when the frequencies used by the BS and RS (j) are multiplexed (S102). In the transmission rate list, a transmission rate corresponding to the multiple combination pattern is calculated. When the RS number (including the BS number) is L, the multiple combination pattern number X is
X = 2 ^L −1
It is. First, the CINR list for each combination pattern is a true value, and CINR = (CNR from BS or RS (j) directly communicated by SS) / (CNR from BS or RS (j) causing interference in 1 + Σ multiple combination pattern)
And the value of the transmission rate list is estimated from the value of the CINR list and the multivalued number of modulation schemes capable of communication.

  As an example, FIG. 8 shows a CINR list when the number of RSs is 2 and the number of SSs is 6, and FIG. 9 shows a transmission rate list. The number of multiple combination patterns is seven. Multiplex combination pattern ID = 1 is a case where all three of BS, RS (1), and RS (2) are multiplexed. Multiple combination pattern IDs = 2 to 4 are cases where any two of BS, RS (1) and RS (2) are multiplexed. Multiplex combination pattern IDs = 5 to 7 are cases where none of BS, RS (1), and RS (2) multiplexes frequencies.

  In FIG. 8 and FIG. 9, the hatched portion indicates that the SS does not perform frequency multiplex communication. For example, in the column of the multiple combination pattern ID = 2 in FIG. 8, the CINR of each SS when BS and RS (1) are simultaneously transmitted is described. SS (1) and SS (2) are groups directly connected to the BS, and the CINR with the BS is written in the corresponding column. SS (3) and SS (4) are groups directly connected to RS (1), and CINRs with RS (1) are written in the corresponding columns. On the other hand, SS (5) and SS (6) are groups directly connected to RS (2). Since RS (2) does not transmit a signal when multiple combination pattern ID = 2, hatched lines are entered.

  Subsequently, the multiple combination pattern ID is set to x = 1 (S103), and from each group (BS group, RS (j) group) multiplexed in the multiple combination pattern ID = x from the transmission rate list created in step S102. The SS with the highest transmission rate is selected from the transmission rate list (S104). Subsequently, the sum of the transmission rates of the SSs selected in each group to be multiplexed is calculated, and the value is multiplied by the multiplexing number which is the total number of BSs and RSs included in the multiplexing combination pattern ID = x (S105). While increasing x of the multiple combination pattern ID one by one (S107), steps S104 and S105 are repeated. After repeating steps S104 and S105 for all multiple combination patterns (Yes in S106), the values multiplied in step S105 in each multiple combination pattern are compared (S108), and the SS selected in the maximum multiple combination pattern is multiplexed. The combination is confirmed and the transmission rate is saved (S109), and the transmission rate of the SS is deleted from the transmission rate list (S110). Then, Steps S103 to S110 are repeated, and when all the multiple combinations of SS are determined (Yes in S111), a multiple combination list is created and the setting of the multiple combinations is completed (S112).

  Further, in the transmission rate list, as shown in FIG. 10, the transmission rate for each multiplex combination pattern of each SS may be normalized with the transmission rate of each SS when not multiplexed. Also in this case, the processing of steps S103 to S111 in FIG. 4 is performed with reference to the normalized transmission rate, and multiple combinations are set.

  An example of the multiple combination list when the number of RSs is 2 and the number of SSs is 6 is shown in FIG. In the multiple combination list, a confirmed multiple combination is shown, and at the same time, the transmission rate of the multiple combination is shown. SS (1), SS (3), and SS (5) have multiple combination pattern ID = 1, and are multiplexed at the same frequency by BS, RS (1), and RS (2) for communication. SS (4) and SS (6) have multiple combination pattern ID = 4, and are multiplexed at the same frequency by RS (1) and RS (2) for communication. SS (2) has multiple combination pattern ID = 5, and BS occupies and communicates with RS (1) and RS (2) without multiplexing frequencies.

(Procedure for setting ratio between access section and relay section in step S2 in FIG. 3)
FIG. 12 shows an example of the ratio setting procedure S2 between the access section and the relay section.
In FIG. 12, each RS sets a ratio of sections so that either the amount of data communicated in the relay section or the amount of data communicated in the access section does not become a bottleneck. Specifically, the transmission rate BS RATE RELAY (j estimated from the multiple combination list set in step S1 and the CNR between the BS and RS (j) stored in the propagation path information storage unit 31 of the scheduler 12 ), The ratio length2 / length1 between the access section length length1 and the relay section length length2 is determined so that the amount of data that can be communicated in the access section and the relay section becomes equal.

In the access section, when a communication section equal to each multiplex combination to which SS is assigned is set, the access section is divided by each multiplex combination number (slot number T) to which SS is assigned. In FIG. 11, T = 3. The amount of data that RS (j) can communicate in the access section is the sum of the transmission rates of SS assigned to the RS (j) group in the multiple combination list,
length1 / T
Multiply by Here, the amount of data that RS (j) can communicate with SS in the access section is
ΣRSj RATE · length1 / T
It becomes. On the other hand, the amount of data that can be communicated between BS and RS (j) in the relay section is
BS RATE RELAY (j) ・ a (j) ・ length2
It is. Here, a (j) is the ratio of the communication section assigned to RS (j) to the relay section length2.

Subsequently, if the right sides of these two formulas are set to be equal,
a (j) = (ΣRSj RATE / BS RATE RELAY (j)) ・ (length1 / length2 ・ T)
It becomes. At this time, since Σa (j) = 1 (j = 1 to j = add the number of RSs), the ratio between the access section and the relay section is
length1 / length2 = Σ (ΣRSj RATE / BS RATE RELAY (j)) ・ (1 / T)
Can be determined.

  In the schedule information construction unit 32, the scheduler 12 of the BS 10 constructs scheduling information reflecting the SS combination and the ratio between the access section and the relay section as described above, and outputs the scheduling information to the transmission data generation section 14. The transmission data generation unit 13 creates a frame by a control signal constructed from data input from the scheduler 12 and schedule information. The control signal in the access section includes information on the communication area allocated from the BS 10 to the SS. The control signal for the relay section is used by the SS of each multiple combination in addition to the information necessary for a plurality of RSs to construct the scheduling information, for example, the ratio between the access section and the relay section and the information of the multiple combinations of SSs. Includes information about the communication area.

(Configuration example of the scheduler 22 of the RS 20)
FIG. 13 shows a configuration example of the scheduler 22 of the RS 20.
In FIG. 13, the scheduler 22 includes a propagation path information storage unit 33 that stores propagation path information for each subchannel under the RS, a BS schedule information holding unit 34, and a schedule information construction unit 35. In the schedule information holding unit 34 of the BS, the schedule information included in the control signal received by the RS 20 from the BS 10 in the relay section, for example, the ratio between the access section and the relay section, the information of the multiple combinations of SS, etc. Enter and save. The schedule information construction unit 35 refers to the schedule information holding unit 34 of the BS, constructs schedule information from the RS 20 to a plurality of SSs, and outputs the schedule information to the transmission data generation unit 23.

  In the above embodiment, the procedure (step S1) for setting the multiple combinations of the terminal stations SS in the scheduling process of the present invention is performed in an environment where the base station BS, the plurality of relay stations RS, and the plurality of terminal stations SS exist. The case where it implements was demonstrated. However, this procedure can be implemented by providing a control station function capable of centrally controlling a plurality of base stations BS, even in an environment where a plurality of base stations BS and a plurality of terminal stations SS exist. .

  For example, in a wireless communication system including one base station BS1 having a control station function, a plurality of other base stations BS2, and a plurality of terminal stations SS, the base station BS1 has the same configuration as the base station BS of FIG. The base station BS2 may be configured similarly to the relay station RS in FIG. However, the base station BS2 is different from the relay station RS in that each base station BS2 is connected to the backbone network. In such a system, the length of the relay section in FIG. 14 is zero when the base station BS1 and the base station BS2 transmit and receive control signals via the backbone network, or the base station BS1 and the base station BS2 When a control signal is transmitted / received by wireless communication, a constant value is obtained, so that the procedure for setting the ratio between the access section and the relay section (step S2) in FIG. 3 is not necessary.

1 Backbone network 10 Base station (BS)
20 Relay station (RS)
11, 21 Data buffer unit 12, 22 Scheduler 13, 23 Transmission data generation unit 14, 24 Transmission unit 15, 25 TDD switch 16, 26 Antenna 17, 27 Reception unit 31, 33 Propagation path information storage unit 32, 35 Schedule information construction Part 34 BS schedule information holding part

Claims (18)

In a wireless communication system including a base station, a plurality of relay stations, and a plurality of terminal stations,
The base station
Collecting CNR (carrier power to noise power ratio) between the base station and the plurality of relay stations and the plurality of terminal stations, and each terminal station directly communicates based on the information of the CNR A first means for determining a relay station;
For each combination pattern composed of a part or all of the base station and the plurality of relay stations, all base stations or a plurality of relay stations included in each combination pattern simultaneously transmit signals of the same frequency to the counterpart terminals. Second means for calculating the CINR (carrier power to noise + interference power ratio) between each terminal station and the base station or relay station with which the terminal station communicates directly when transmitting to the station, and estimating the transmission rate When,
For each combination pattern, select a terminal station that maximizes the estimated transmission rate from among a group of terminal stations that communicate with all base stations or relay stations included in the combination pattern, and Multiplying the sum of the transmission rates of the terminal stations selected for each and the multiplexing number that is the total number of base stations and relay stations included in the combination pattern, the combination pattern having the maximum value is multiplied by the combination pattern. The selected terminal station is determined as a combination pattern to be used for communication, excludes the terminal station determined by the combination pattern to be used for communication, and further selects the terminal station, determines the combination pattern, and excludes the terminal station. And a third means for determining a combination pattern used by all terminal stations for communication. The wireless communication system according to claim 1, wherein
The transmission rate for each combination pattern is the one normalized by the transmission rate when all base stations and relay stations included in the combination pattern do not transmit signals of the same frequency at the same time. system. The wireless communication system according to claim 1, wherein
The first means includes
Means for estimating a transmission rate communicable in each section from a CNR between the base station and the terminal station, between the base station and the relay station, and between the relay station and the terminal station; ,
For each terminal station, a radio resource for access necessary for direct communication with the base station is calculated as (1 / transmission rate between the base station and the terminal station), and relay necessary for direct communication with the relay station. And means for calculating (1 / transmission rate between base station and relay station + 1 / transmission rate between relay station and terminal station) as radio resources for access;
Means for selecting a base station or a relay station that minimizes the radio resource. The wireless communication system according to claim 1, wherein
The base station and the relay station switch transmission and reception by time division duplex, an access section in which the base station and the relay station communicate with the terminal station, and a relay section in which the base station and the relay station relay radio frames. And time-sharing
The base station is configured to control a ratio between the access period and the relay period so that a data amount communicated between the base station and the relay station is equal to a data amount communicated between the relay station and the terminal station. A wireless communication system, characterized in that The wireless communication system according to claim 4, wherein
The base station determines the ratio of the access section and the relay section for each relay station (sum of transmission rates between the relay station and a terminal station that communicates directly with the relay station) / (between the base station and the relay station). (Transmission rate x number of combination patterns determined for terminal station communication) and a sum of them is determined based on the calculated value. The wireless communication system according to claim 1, wherein
The base station is a first base station having a control station function, a plurality of second base stations are provided instead of the plurality of relay stations, and the base station is between the first base station and the second base station. A wireless communication system, wherein the control signal is transmitted and received via a backbone network or by wireless communication. In a scheduling method of a radio communication system including a base station, a plurality of relay stations, and a plurality of terminal stations,
The base station
Collecting CNR (carrier power to noise power ratio) between the base station and the plurality of relay stations and the plurality of terminal stations, and each terminal station directly communicates based on the information of the CNR A first step of determining a relay station;
For each combination pattern composed of a part or all of the base station and the plurality of relay stations, all base stations or a plurality of relay stations included in each combination pattern simultaneously transmit signals of the same frequency to the counterpart terminals. Second step of calculating a CINR (carrier power to noise + interference power ratio) between each terminal station and a base station or a relay station with which the terminal station communicates directly when transmitting to the station, and estimating a transmission rate When,
For each combination pattern, select a terminal station that maximizes the estimated transmission rate from among a group of terminal stations that communicate with all base stations or relay stations included in the combination pattern, and Multiplying the sum of the transmission rates of the terminal stations selected for each and the multiplexing number that is the total number of base stations and relay stations included in the combination pattern, the combination pattern having the maximum value is multiplied by the combination pattern. The selected terminal station is determined as a combination pattern to be used for communication, excludes the terminal station determined by the combination pattern to be used for communication, and further selects the terminal station, determines the combination pattern, and excludes the terminal station. And a third step of determining a combination pattern used by all terminal stations for communication. Scheduling method. The radio communication system scheduling method according to claim 7,
The transmission rate for each combination pattern is the one normalized by the transmission rate when all base stations and relay stations included in the combination pattern do not transmit signals of the same frequency at the same time. System scheduling method. The radio communication system scheduling method according to claim 7,
The first step includes
Means for estimating a transmission rate communicable in each section from a CNR between the base station and the terminal station, between the base station and the relay station, and between the relay station and the terminal station; ,
For each terminal station, a radio resource for access necessary for direct communication with the base station is calculated as (1 / transmission rate between the base station and the terminal station), and relay necessary for direct communication with the relay station. Calculating (1 / transmission rate between base station and relay station + 1 / transmission rate between relay station and terminal station) as access radio resources;
Selecting a base station or a relay station that minimizes the radio resource. The radio communication system scheduling method according to claim 7,
The base station and the relay station switch transmission and reception by time division duplex, an access section in which the base station and the relay station communicate with the terminal station, and a relay section in which the base station and the relay station relay radio frames. And time-sharing
The base station controls a ratio of the access section and the relay section so that a data amount communicated between the base station and the relay station is equal to a data amount communicated between the relay station and the terminal station. A scheduling method for a wireless communication system. The radio communication system scheduling method according to claim 10,
The base station determines the ratio of the access section and the relay section for each relay station (sum of transmission rates between the relay station and a terminal station that communicates directly with the relay station) / (between the base station and the relay station). (The transmission rate x the number of combination patterns determined for terminal station communication) and the sum thereof is determined based on the calculated value. The radio communication system scheduling method according to claim 7,
The base station is a first base station having a control station function, a plurality of second base stations are provided instead of the plurality of relay stations, and the base station is between the first base station and the second base station. A scheduling method for a wireless communication system, comprising: transmitting and receiving control signals via a backbone network or by wireless communication. In a base station of a wireless communication system composed of a base station, a plurality of relay stations, and a plurality of terminal stations,
Collecting CNR (carrier power to noise power ratio) between the base station and the plurality of relay stations and the plurality of terminal stations, and each terminal station directly communicates based on the information of the CNR A first means for determining a relay station;
For each combination pattern composed of a part or all of the base station and the plurality of relay stations, all base stations or a plurality of relay stations included in each combination pattern simultaneously transmit signals of the same frequency to the counterpart terminals. Second means for calculating the CINR (carrier power to noise + interference power ratio) between each terminal station and the base station or relay station with which the terminal station communicates directly when transmitting to the station, and estimating the transmission rate When,
For each combination pattern, select a terminal station that maximizes the estimated transmission rate from among a group of terminal stations that communicate with all base stations or relay stations included in the combination pattern, and Multiplying the sum of the transmission rates of the terminal stations selected for each and the multiplexing number that is the total number of base stations and relay stations included in the combination pattern, the combination pattern having the maximum value is multiplied by the combination pattern. The selected terminal station is determined as a combination pattern to be used for communication, excludes the terminal station determined by the combination pattern to be used for communication, and further selects the terminal station, determines the combination pattern, and excludes the terminal station. And a third means for determining a combination pattern to be used for communication by all the terminal stations. Ground station. In the base station of the wireless communication system according to claim 13,
The transmission rate for each combination pattern is the one normalized by the transmission rate when all base stations and relay stations included in the combination pattern do not transmit signals of the same frequency at the same time. System base station. In the base station of the wireless communication system according to claim 13,
The first means includes
Means for estimating a transmission rate communicable in each section from a CNR between the base station and the terminal station, between the base station and the relay station, and between the relay station and the terminal station; ,
For each terminal station, a radio resource for access necessary for direct communication with the base station is calculated as (1 / transmission rate between the base station and the terminal station), and relay necessary for direct communication with the relay station. And means for calculating (1 / transmission rate between base station and relay station + 1 / transmission rate between relay station and terminal station) as radio resources for access;
Means for selecting a base station or a relay station that minimizes the radio resource. In the base station of the wireless communication system according to claim 13,
The base station and the relay station switch transmission and reception by time division duplex, an access section in which the base station and the relay station communicate with the terminal station, and a relay section in which the base station and the relay station relay radio frames. And time-sharing
The ratio of the access section and the relay section is controlled so that the amount of data communicated between the base station and the relay station is equal to the amount of data communicated between the relay station and the terminal station. A base station of a wireless communication system. The base station of the wireless communication system according to claim 16,
The ratio between the access section and the relay section is, for each relay station, (sum of transmission rates between the relay station and a terminal station that communicates directly with the relay station) / (transmission rate between the base station and the relay station × terminal. A base station of a wireless communication system, characterized in that the number of combination patterns determined for station communication) is calculated and a sum of them is determined based on the calculated value. In the base station of the wireless communication system according to claim 13,
A base of a wireless communication system comprising a control station function for transmitting / receiving a control signal to / from a plurality of base stations arranged instead of the plurality of relay stations via a backbone network or by wireless communication Bureau.

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