JP2013009424A - Radio communications system, communication method thereof, base station, and mobile station - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radio communications system that can reduce inter-cell interference therein.SOLUTION: In a radio communications system including a first base station, a second base station, and a mobile station, the first base station transmits information on resource allocation for a random access channel (RACH) of the first base station to the second base station, the second base station determines resource allocation for the uplink communication, which is different from the resource allocation for the RACH of the first base station, and the mobile station communicates with the second base station using the resource determined for the uplink communication.

Description

The present invention relates to a wireless communication system having a plurality of wireless zones (hereinafter referred to as cells), and more particularly to a communication method, a base station, and a mobile station .

  In a mobile communication system, in order to perform data communication between a base station and a mobile station, it is necessary to establish synchronization between them in advance. In particular, since the initial access from the mobile station is not always synchronized, the base station needs some procedure for uplink synchronization of the mobile station.

  In LTE (Long Term Evolution), which is being standardized by 3GPP (3rd Generation Partnership Project), a random access channel (RACH) and an uplink shared channel (UL) are used for uplink synchronization and uplink data transmission. -SCH: Uplink-Shared Channel). The RACH is a channel for transmitting a control signal for establishing uplink synchronization and requesting resources for uplink data transmission. In order to establish uplink synchronization without a large delay, it is desirable to keep the RACH transmission collision probability as small as possible (Non-Patent Document 1). On the other hand, UL-SCH is a channel for transmitting data and layer 2 / layer 3 control packets. In particular, the transmission power of UL-SCH increases according to the transmission rate, so it is necessary to consider interference with other signals.

  FIG. 1A is a diagram schematically illustrating a general configuration of a mobile communication system based on LTE, and FIG. 1B is a resource configuration diagram schematically illustrating radio resources based on frequency division and time division. is there. Here, as shown in FIG. 1A, a mobile station UE (User Equipment) 1 located in the cell A of the base station eNB1 transmits data to the base station eNB1 by UL-SCH, and the cell of the base station eNB2 Assume that the mobile station UE2 located in B transmits a control signal to the base station eNB2 by RACH.

  In WCDMA (Wideband Code Division Multiple Access), RACH and EDCH (Enhanced Dedicated Channel) are multiplexed by different spreading and scrambling codes and share the same frequency resource. On the other hand, in LTE, a plurality of frequency-divided and time-divided resources as shown in FIG. 1B are exclusively shared by the RACH and UL-SCH. Specifically, the LTE uplink has a resource configuration in which a system bandwidth 10 MHz is time-divided at a time interval of 1 msec and further frequency-divided at a 1.25 MHz width. In FIG. 1B, t1, t2,... On the horizontal axis correspond to time resources of 1 msec, and FB # 1, FB # 2. Correspond. Hereinafter, one rectangular block specified by one time resource and one frequency resource as shown in FIG. 1B is simply referred to as “resource”.

  How to allocate such system resources to RACH and UL-SCH is determined by each base station eNB. Normally, the RACH resource is periodically allocated so that the mobile station UE can access the base station without a large delay, as shown in FIG. It is also possible to secure a sufficient RACH access capacity by assigning a plurality of RACH resources at the same time. The base station eNB normally broadcasts information indicating to which resource such RACH is allocated. Therefore, all mobile stations UE in the cell can access the RACH resource whenever necessary according to the broadcast information. As long as RACH resources and UL-SCH resources are allocated according to the frequency division and time division shown in FIG. 1B within one cell, RACH and UL-SCH do not interfere directly.

Special Table 2002-526970

3GPP TS36.300 1.0.0 (2007/3/19)

  However, when the control subject that performs resource allocation differs between adjacent cells, the RACH transmission of one cell may interfere with the UL-SCH transmission of the other cell. As described above, each base station eNB assigns the uplink resources of the cell controlled by the base station to the RACH and UL-SCH in each responsibility, so that the high-speed uplink data transmission of a certain cell is transmitted to the RACH transmission of the adjacent cell. May interfere. For example, when starting a call setup procedure, it is particularly important to avoid this RACH interference, considering that it is necessary to establish uplink synchronization by RACH transmission. This is because if data transmission of a certain cell interferes with RACH transmission of an adjacent cell, call setup is delayed in the adjacent cell. Not only in the case of call setting, but also in the case where RACH transmission is required before the start of other processing, the same effect that the processing is delayed due to strong uplink interference due to high-speed uplink data transmission occurs.

  2A and 2B are schematic views showing an example of inter-cell interference. Here, as shown in FIG. 2 (A), it is assumed that cell A and cell B independently allocate RACH resources and UL-SCH resources to a certain frequency resource. If these cells A and B are separated so as not to affect each other, interference does not become a problem. However, as shown in FIG. 1A, cell A and cell B are adjacent to each other, the frequency band and timing of data transmission of mobile station UE1 in cell A, and the frequency of RACH transmission of mobile station UE2 in cell B When the band and timing overlap, the probability of occurrence of interference as shown in FIG. 2B increases.

  For example, in FIG. 2B, when the mobile station UE1 of the cell A tries to perform data transmission at a certain time, first, RACH transmission is performed using the RACH resource specified by the broadcast signal of the base station eNB1. Uplink data transmission is started using a UL-SCH resource permitted (GRANT) by a response from the station eNB1. At that time, if the mobile station UE2 in the cell B starts the RACH transmission with resources overlapping with the UL-SCH in the cell A in order to transmit data in the same manner, the base station eNB2 receives the UL- from the mobile station UE1 in the cell A. Due to the interference with the SCH transmission, the RACH transmission from the mobile station UE2 cannot be detected. If there is no response from the base station eNB2, the mobile station UE2 repeats RACH transmission by increasing the transmission power, and starts UL-SCH transmission after receiving a response (GRANT) from the base station eNB2. Thus, there is a high possibility that the start of communication of the mobile station UE2 is greatly delayed due to a collision with UL-SCH transmission.

  In order to avoid such interference, for example, as disclosed in Patent Document 1, a method of searching for a resource with the smallest interference and allocating the minimum interference resource to RACH transmission can be considered. However, this makes it impossible to periodically allocate RACH resources, and the access of the mobile station UE to the base station is not stable, and there is a high possibility that it will be greatly delayed. Furthermore, since data transmission is generally assigned to a resource with low interference, assigning RACH transmission to the minimum interference resource conversely increases interference and easily causes collision.

  Such a problem is not limited to LTE, and may occur in general radio communication systems using an access scheme (FTDMA) with a frequency division and time division resource configuration.

An object of the present invention is to solve the above-described problems, and to provide a radio communication system, a communication method thereof, a base station, and a mobile station that reduce inter-cell interference.

Another object of the present invention is to provide a radio communication system , a communication method thereof, a base station, and a mobile station that reduce a communication start delay.

A radio communication system according to the present invention is a radio communication system including a first base station, a second base station, and a mobile station, wherein the first base station has a random access channel ( RACH) resource allocation information is transmitted to the second base station, and the second base station determines a resource for uplink communication with a resource allocation different from the RACH resource allocation in the first base station. The mobile station communicates with the second base station using the uplink communication resource .

A communication method according to the present invention is a communication method of a wireless communication system including a first base station, a second base station, and a mobile station, wherein the first base station performs random access in the first base station. Information on channel (RACH) resource allocation is transmitted to the second base station, and the second base station has a resource allocation different from the RACH resource allocation in the first base station for uplink communication. And the mobile station communicates with the second base station using the resource for uplink communication .

A base station according to the present invention is a base station in a radio communication system including a mobile station, and includes a receiving unit that receives information on a resource arrangement of a random access channel (RACH) in another base station, and a base station in the other base station. A resource determination unit that determines a resource for uplink communication with a resource arrangement different from the resource arrangement of the RACH, and a communication unit that communicates with the mobile station using the resource for uplink communication .

A mobile station according to the present invention is a mobile station in a wireless communication system including a first base station and a second base station, and is a resource different from a random access channel (RACH) resource arrangement in the first base station. Means for receiving information regarding resources for uplink communication determined by the second base station so as to be arranged, and means for communicating with the second base station using the resources for uplink communication Features.

  According to the present invention, inter-cell interference can be reduced and communication start delay can be shortened by setting buffer area resources within a predetermined range of resources of the local station corresponding to control resources used by neighboring cells. It becomes possible to do.

(A) is a figure which shows typically the general structure of the mobile communication system by LTE, (B) is a resource block diagram which shows typically the radio | wireless resource based on a frequency division and a time division. (A) And (B) is a schematic diagram which shows an example of inter-cell interference. (A), (B), and (C) are flowcharts showing resource allocation control methods according to the first, second, and third embodiments of the present invention, respectively. It is a resource block diagram which shows the example of allocation of the RACH resource and UL-SCH resource to which the resource allocation control method by 1st Embodiment of this invention is applied. It is a resource block diagram which shows the example of allocation of the RACH resource and UL-SCH resource to which the resource allocation control method by 2nd Embodiment of this invention is applied. It is a figure which shows an example of a cell structure in case a some adjacent cell exists. (A) is a resource block diagram schematically showing a buffer area resource candidate and a persistent interference avoidance pattern for explaining a resource allocation control method according to a third embodiment of the present invention, and (B) is a diagram of this embodiment. FIG. 3 is a resource configuration diagram showing an example of buffer area resource allocation to which the resource allocation control method according to FIG. It is a block diagram which shows schematic structure of the radio | wireless communications system containing the radio | wireless communication apparatus which mounted the resource allocation control apparatus by this invention. It is a block diagram which shows the structure of the radio | wireless communication apparatus which mounts the resource allocation control apparatus by this invention. It is a block diagram which shows the structure of the mobile station shown in FIG. It is a sequence diagram which shows the resource rearrangement operation | movement in the radio | wireless communications system shown in FIGS. It is a flowchart which shows the resource allocation control method by 1st Example of this invention. It is a flowchart which shows the resource allocation control method by 2nd Example of this invention. It is a block diagram which shows the structure of the radio | wireless communication apparatus which mounts the resource allocation control apparatus by 3rd Example of this invention. It is a flowchart which shows the resource allocation control method by 3rd Example of this invention.

1. Outline of Embodiment FIGS. 3A, 3B, and 3C are flowcharts showing resource allocation control methods according to the first embodiment, the second embodiment, and the third embodiment of the present invention, respectively. Here, for simplification of description, the cells controlled by the two wireless communication apparatuses are adjacent cells that may cause interference with each other, and each cell has a resource configuration by frequency division and time division as in FIG. It shall have. The RACH resources of these cells are arranged by the respective wireless communication devices. However, the present invention is not limited to LTE but can be applied to a wireless communication system using an access scheme (FTDMA) with a frequency-divided and time-divided resource configuration.

  According to the first embodiment of the present invention shown in FIG. 3A, first, the RACH resource information is exchanged between wireless communication apparatuses to share the RACH usage status between adjacent cells (step S20). Each wireless communication device sets a predetermined resource range of its own resource corresponding to the RACH resource used by another wireless communication device as a buffer area resource (step S21). This predetermined resource range (buffer area resource in the first embodiment) has a margin in the frequency direction and / or the time direction in consideration of fluctuations due to frequency and synchronization deviation between wireless communication devices, as will be described later. It is desirable to be a resource area. That is, the predetermined resource range is the resource of the own cell corresponding to the RACH resource of another cell, or the range of the resource and the resource within the predetermined range from the resource. Then, each wireless communication device executes UL-SCH scheduling so as not to allocate a buffer area resource (step S22). By not allocating the buffer area resource to UL-SCH transmission, it is possible to avoid interference with RACH transmission of other wireless communication apparatuses.

  According to the second embodiment of the present invention shown in FIG. 3B, the buffer area resource is set by steps S20 and S21 as in the first embodiment, and the interference to other radio communication apparatuses is subsequently performed. It is determined whether or not there is a small UL-SCH transmission, that is, whether or not there is a mobile station UE that performs UL-SCH transmission in which interference is within an allowable range (step S30). Each wireless communication apparatus performs UL-SCH scheduling so as to permit allocation of buffer area resources for UL-SCH transmission with low interference and not allocate buffer area resources for other UL-SCH transmissions (steps). S31). By enabling buffer area resources to be allocated to UL-SCH transmissions that satisfy certain conditions in this way, it is possible to achieve efficient use of resources while reducing inter-cell interference, and to reduce uplink communication start delay. Is possible.

  According to the third embodiment of the present invention shown in FIG. 3C, first, in the same manner as in the first embodiment, the RACH usage status between adjacent cells is shared in step S20 and used by other radio communication apparatuses. A predetermined resource range of the own station resource corresponding to the resource is set as a buffer area resource candidate (step S40). Subsequently, buffer area resources are set by excluding buffer area resource candidates non-persistently (step S41). Although a specific example will be described later, non-persistent exclusion means that buffer region resource candidates are not excluded continuously but are sparsely excluded in an arbitrary pattern. In other words, buffer area resource candidates of the own station cell are excluded with an arbitrary pattern so that interference with RACH transmission of adjacent cells does not continue. Then, each wireless communication device executes UL-SCH scheduling so as to suppress allocation of buffer area resources (step S42). The suppression of the assignment indicates either the assignment prohibition in step S22 or the conditional assignment prohibition in step S31. In this way, buffer area resource candidates are non-persistently excluded, and the excluded resources can be allocated, thereby efficiently and fairly using resources while reducing inter-cell interference when multiple cells are adjacent to each other. As a result, the upstream communication start delay can be shortened.

  Specifically, the buffer area resource candidates for any adjacent cell correspond to the RACH resource, and are usually arranged at a constant period in the time direction. Therefore, the buffer area resource can be generated by thinning out the buffer area resource candidates arranged in the time direction with a random pattern (or a predetermined pattern). Further, when there are buffer area resource candidates for adjacent cells also in the frequency direction, the buffer area resource can be generated by thinning out with a random pattern (or a predetermined pattern) in the frequency direction. Furthermore, when a plurality of cells are adjacent to each other, it is possible to generate a buffer area resource by selecting a cell corresponding to a buffer area resource candidate to be thinned out by a random pattern (or a predetermined pattern). . Although fairness can be ensured by selecting at random, the selection probability of the target neighboring cell may be changed in consideration of the RACH interference level of each cell.

2. First Embodiment FIG. 4 is a resource configuration diagram showing an allocation example of RACH resources and UL-SCH resources to which a resource allocation control method according to a first embodiment of the present invention is applied. Here, it is assumed that cell A and cell B are not completely synchronized in the time domain. That is, if the time resources t1, t2,... Of the cell A are used as a reference, the time resources t1, t2,. For this reason, one time resource in one cell spans two time resources in the other cell. For example, time resource t7 of cell A overlaps both time resources t6 and t7 of cell B.

  If cell A and cell B are controlled by the same wireless communication device and are fully synchronized, the time resource locations of both cells should coincide in time. When the cell A and the cell B are controlled by different wireless communication apparatuses, any synchronization means or a known synchronization mechanism may be provided. For example, the internal clocks can be synchronized with each other by exchanging time information (transmission frame number, etc.) between wireless communication apparatuses directly or via a mobile station. Alternatively, the wireless communication devices can be synchronized according to the synchronization protocol of the central office, and high-precision synchronization can be achieved using GPS. However, in general, in consideration of fluctuation factors such as signal propagation delay and clock generator variation, one time resource in one cell is equal to two consecutive time resources in the other cell or If necessary, it is desirable to associate three or more continuous time resources (hereinafter referred to as a set of time resources) as buffer area resources. If one time resource can be further time-divided, the time width of a set of buffer area resources can be set with a finer granularity.

  It is assumed that such cell A and cell B are adjacent to each other, and one UL-SCH transmission is in a positional relationship that can interfere with the other RACH transmission. Further, the RACH transmission of the cell A is periodically assigned to the time resources t2, t7, t12,... Of the frequency resource FB # 3, and the RACH resource of the cell B is assigned to the time resources t4, t9 by the frequency resource FB # 2. , T14... Periodically assigned. Since each RACH resource allocation position can be known by exchanging RACH resource information, one cell has a set of resources corresponding to the RACH resource allocation position of the other cell (here, two consecutive groups). Time resource) can be set as a buffer area resource.

  In FIG. 4, the resource position of each cell is displayed in time-frequency coordinates such as (frequency resource, time resource), and when a plurality of resources are allocated, it is assumed that “+” is displayed. For the RACH resource (FB # 3, t2) of the cell A, one set of buffer area resources (FB # 3, t1 + t2) is set in the cell B. Conversely, for the RACH resource of cell B (FB # 2, t4), one set of buffer area resources (FB # 2, t4 + t5) is set in cell A. Similarly, for each RACH resource in one cell, one set of buffer area resources is set in the other cell.

  Each of cell A and cell B is provided with a reference frequency oscillator, which enables frequency division of frequency resources FB # 1, FB # 2, FB # 3... Thus, it is also desirable to set a buffer area resource with a margin in the frequency direction. For example, the buffer area resource set (FB # 2, t4 + t5) of the cell A for the RACH resource (FB # 2, t4) of the cell B is expanded by a predetermined width α in the frequency direction, and is referred to as (FB # 2 ± α, t4 + t5). It can also be set as follows. The predetermined width α may be set to be equal to or less than the frequency resource width.

  Each of the radio communication apparatuses in the cell A and the cell B performs UL-SCH scheduling so that the buffer area resources set in this way are not allocated to UL-SCH transmission. Since UL-SCH transmission is allocated to resources other than the buffer area resource, it is possible to reliably avoid interference with the RACH resource of the other cell.

3. Second Embodiment FIG. 5 is a resource configuration diagram showing an allocation example of RACH resources and UL-SCH resources to which a resource allocation control method according to a second embodiment of the present invention is applied. Here, in order to maintain the consistency of the description, it is assumed that the RACH resource and the buffer region resource are arranged at the same frequency-time position as the cell A in FIG.

  Also in the second embodiment, UL-SCH transmission is not basically allocated to the buffer area resource as described above, but the interference level that UL-SCH transmission gives to other cells is within the allowable range, or is allowed. When it is considered that it is within the range, the allocation of the buffer area resource to the UL-SCH transmission is exceptionally permitted.

  In FIG. 5, the buffer area resource is set corresponding to the RACH resource position notified from the adjacent cell B. If there is a mobile station UE requesting voice packet transmission (VoIP) in the cell A, the radio communication apparatus of the cell A allocates UL-SCH resources for frequency hopping for each time resource for the voice packet transmission. . For example, voice packet transmissions can be randomly assigned across frequency resources such that frequency diversity gain is maximized.

  When assigning voice packet transmission, it is desirable to preferentially assign the voice packet transmission to the buffer area resource in the time resource (here, t4, t5, t9, t10...) Where the buffer area resource exists. This is because, in voice packet transmission, the required bandwidth is relatively narrow and the required transmission power is low, so that even if it is allocated to a buffer area resource, no significant interference occurs with other cells. As a result, there is room for resources to be allocated to high-speed UL-SCH transmission. In the example of FIG. 5, for example, low power request voice packet transmission is allocated to different frequency bands in the buffer area resources (FB # 2, t4) and (FB # 2, t4). However, since it should be avoided to continuously assign voice packet transmissions of a plurality of mobile stations UE to the buffer area resource, it is desirable to predetermine an allocation upper limit for one buffer area resource.

4). Third Embodiment FIG. 6 is a diagram showing an example of a cell configuration when there are a plurality of neighboring cells, and FIG. 7A is a buffer for explaining a resource allocation control method according to a third embodiment of the present invention. FIG. 7B is a resource configuration diagram schematically showing region resource candidates and persistent interference avoidance patterns, and FIG. 7B is a resource configuration diagram showing an example of buffer region resource allocation to which the resource allocation control method according to the present embodiment is applied. is there. Here, in order to maintain the consistency of the description, it is assumed that the RACH resource is arranged at the same frequency-time position as the cell A in FIG.

  First, as shown in FIG. 6, it is assumed that there are a plurality of cells around a certain cell A, and interference can occur between adjacent cells B, C, D, and E here. In this situation, RACH resource information is shared between adjacent cells, so that in the cell A, buffer area resources respectively corresponding to the cells B, C, D, and E are set as shown in FIG. Thus, when the number of adjacent cells is large, the buffer area resource occupies a large proportion of the resources available for the cell A, and the effective capacity of the cell A is reduced. In this example, each of neighboring cells B, C, D and E allocates one RACH resource for every five resources, so the total of the buffer area resources corresponding to these resources reaches 40% of the total available resources. . According to the second embodiment described above, such a buffer area resource can be allocated to a low-speed data transmission mobile station or the like, but is not allocated to a high-speed data transmission mobile station that causes interference with adjacent cells. . Since the effective capacity is reduced in each cell as described above, the capacity of the entire network is consequently reduced.

  According to the present embodiment, the buffer region resource candidates respectively corresponding to the cells B, C, D, and E shown in FIG. 7A are excluded non-persistently (a continuous interference is avoided) (in the drawing) And a buffer area resource for each cell is determined according to the persistent interference avoidance pattern as shown in FIG. 7B, for example. Which pattern is used may be determined autonomously by the wireless communication device of each cell, or may be determined by information exchange with other wireless communication devices.

  As the continuous interference avoidance pattern, a random pattern that excludes buffer region resource candidates with a certain probability is a desirable example. The resources excluded from the buffer region resource candidates are assigned high-speed data transmissions and are more likely to cause interference, but because they are excluded at random, they only interfere partially with RACH transmissions, either persistently or Continuous interference can be effectively avoided. Further, by using a random pattern, there is an advantage that the probability of occurrence of partial interference is fair among the cells B, C, D, and E.

  However, even a random pattern can be generated by setting a ratio of excluded resources, a period distribution, and a buffer area width distribution, and is appropriate depending on the situation of RACH interference of neighboring cells. A random pattern can also be selected.

  The continuous interference avoidance pattern may be a predetermined pattern instead of random. Next, the predetermined pattern will be described by taking the continuous interference avoidance pattern in FIG.

1) Pattern I:
As shown in the buffer area resource for cell B, every other pair of buffer area resource candidates based on the RACH resource information is left (or deleted). Specifically, the initial buffer area resource candidate sets are (FB # 4, t3 + t4), (FB # 4, t8 + t9), (FB # 4, t13 + t14), and so on. In accordance with the pattern to be excluded (or left), the resource pairs (FB # 4, t3 + t4), (FB # 4, t13 + t14),... In FIG. 7B are finally set as buffer area resources. In the pattern of this example, the period of the buffer area is 10 resources, the width is 2 resources, and the remaining ratio of the buffer area is 1/2.

2) Pattern II:
As shown in the buffer area resource for cell C, two pairs of buffer area resource candidates based on the RACH resource information are left (or excluded every other pair). Specifically, the initial sets of buffer area resources are (FB # 3, t5 + t6), (FB # 3, t10 + t11), (FB # 3, t15 + t16)..., But leave these every two. According to the pattern, the resource set (FB # 3, t5 + t6),... In FIG. 7B is finally set as a buffer area resource. In the pattern of this example, the period of the buffer area is 15 resources, the width is 2 resources, and the remaining ratio of the buffer area is 1/3.

3) Pattern III:
As shown in the buffer area resource for the cell D, a group that leaves (or excludes) the previous resource and a group that leaves (or deletes) the subsequent resource among the sets of buffer area resource candidates based on the RACH resource information. Switch alternately. Specifically, the initial set of buffer area resources is (FB # 2, t4 + t5), (FB # 2, t9 + t10), (FB # 2, t14 + t15)..., But these are left for each set. In accordance with the pattern for switching the resource position back and forth, the resources (FB # 2, t4), (FB # 2, t10), (FB # 2, t14),... In FIG. Set as a resource. In the pattern of this example, the period of the buffer area is 4 or 6 resources, the width is 1 resource, and the remaining ratio of the buffer area is 1/2.

4) Pattern IV:
As shown in the buffer area resource for cell E, a group that leaves (or excludes) the previous resource and a group that leaves (or deletes) the subsequent resource among the buffer area resource candidate sets based on the RACH resource information. Switch alternately every other two, and delete other buffer area resources. Specifically, the initial sets of buffer area resources are (FB # 1, t1 + t2), (FB # 1, t6 + t7), (FB # 1, t11 + t12), etc., but these are left in every three sets. The resources (FB # 1, t1), (FB # 1, t17),... In FIG. 7B are finally used as buffer area resources according to a pattern in which the resource positions are switched back and forth, and the others are deleted. Set. In the pattern of this example, the period of the buffer area is 14 or 16 resources, the width is 1 resource, and the remaining ratio of the buffer area is 1/4.

  The predetermined patterns I-IV are an example, but can be used as characteristic patterns since the periods, widths, and remaining ratios are different. Therefore, one of the plurality of characteristic patterns may be selected and applied to all adjacent cells, or different patterns may be applied to each cell as in the example shown in FIG. Is possible. Furthermore, these predetermined patterns I-IV can be selected at random and applied to each cell.

  Further, the continuous interference avoidance pattern is not only applied to the time domain as shown in FIG. 7, but can also be applied to the frequency domain and the cell domain. When a random pattern is used, the buffer area resource corresponding to one adjacent cell is set to avoid continuous interference in the time domain by randomization in the time domain as described above. In addition, for a cell in which a plurality of buffer region resources exist in one time resource, a buffer region resource corresponding to one adjacent cell is obtained by a combination of randomization in the frequency domain or randomization in the time domain. It is set to avoid persistent interference in the frequency domain. In addition, when there are multiple neighboring cells, the buffer area resource corresponding to each neighboring cell is set to avoid persistent interference by randomizing in the cell area where the cell is selected with a random pattern. Is done. It is also possible to combine randomization in the cell domain with randomization in the frequency domain and / or randomization in the time domain.

  For example, in the GSM (Global System for Mobile Communications) method, randomization in the time domain and / or cell domain can be performed, and in WCDMA and LTE, random combinations in the cell domain, frequency domain, and time domain can be arbitrarily combined. it can.

  Although the continuous interference avoidance pattern cannot completely eliminate interference, it improves the interference by making the time and frequency arrangement of RACH resources in each cell the same by communication between wireless communication devices in neighboring cells. It is also possible to do. In this case, it is possible to avoid the RACH from interfering with the UL-SCH, and since the RACH has a low transmission probability, collision within the cell or interference between cells is relatively difficult to occur.

5. System Configuration FIG. 8 is a block diagram showing a schematic configuration of a radio communication system including a radio communication apparatus in which the present invention is implemented. Here, it is assumed that a plurality of wireless communication devices including the wireless communication devices 10 and 11 are communicably connected via the network 12. The wireless communication devices 10 and 11 control the cell A and the cell B, respectively, and the cells A and B have the resource configuration shown in FIG. Each wireless communication apparatus executes UL-SCH scheduling by applying any of the channel assignment control according to the first to third embodiments described above.

  A plurality of wireless communication devices connected by the network 12 may be included in one base station eNB, or each wireless communication device may be one base station eNB. In any case, the interference between adjacent cells when a plurality of mobile stations UE perform RACH transmission or UL-SCH transmission in the cell A or the cell B is reduced by this embodiment. Hereinafter, configurations and operations of the wireless communication apparatus and the mobile station will be described.

5.1) Radio Communication Device FIG. 9 is a block diagram showing the configuration of a radio communication device that implements the resource allocation control device according to the present invention. The wireless communication apparatus includes a wireless transmission / reception unit 101 as a physical layer device that wirelessly communicates with a plurality of mobile stations. The radio transmission / reception unit 101 broadcasts the RACH resource information designated by the RACH resource control unit 102 through the broadcast channel BCH, thereby enabling RACH transmission of each mobile station.

  RACH related information measurement section 103 detects at least one of the number of RACH accesses from a plurality of mobile stations, access delay, received power, etc., and measures the RACH interference level and RACH access load status in the cell.

  The inter-cell resource management unit 104 receives the RACH resource information from each radio communication device in the adjacent cell, and transmits the local station RACH resource information specified by the RACH resource control unit 102 to each radio communication device in the adjacent cell. The received RACH resource information of the neighboring cell is output to the buffer area resource setting unit 105. The buffer region resource setting unit 105 receives the RACH interference information from the RACH related information measurement unit 103 as necessary, determines the buffer region resource for each neighboring cell as described in the above-described embodiment, and determines the UL-SCH scheduler. To 106.

  According to the first embodiment, when there is a UL-SCH transmission schedule request from a mobile station in its own cell, the UL-SCH scheduler 106 determines available resources excluding the RACH resource and buffer area resource in its own cell. Allocating and responding to the mobile station with a schedule grant (GRANT). However, according to the second embodiment, if the type of service requested by the mobile station is a low transmission power service such as VoIP or a high path loss for a neighboring cell, the UL-SCH scheduler 106 determines that UL-SCH. Buffer area resources can be allocated for SCH transmission.

  When the UL-SCH resource thus allocated is notified to the mobile station, the mobile station starts data transmission or L2 / L3 control packet transmission using the UL-SCH resource. The L2 processing unit 107 and the L3 processing unit 108 of the wireless communication apparatus process the received uplink data according to each layer protocol.

  Note that the RACH resource control unit 102, the RACH related information measurement unit 103, the inter-cell resource management unit 104, the buffer region resource setting unit 105, and the UL-SCH scheduler 106 are similar by executing a program on a program control processor or computer. It is also possible to realize the function.

5.2) Mobile Station FIG. 10 is a block diagram showing a configuration of the mobile station shown in FIG. The mobile station UE includes a radio transmission / reception unit 201 as a physical layer device that performs radio communication with a base station eNB or a radio communication apparatus. The radio transmission / reception unit 201 receives the RACH resource information broadcast from the radio communication device and outputs it to the RACH control unit 202. The RACH control unit 202 performs RACH transmission by the radio transmission / reception unit 201 when out of synchronization or when transmission data is generated according to the received RACH resource information. The RACH control unit 202 establishes uplink synchronization by receiving a response to the RACH transmission from the wireless communication apparatus.

  The UL-SCH control unit 203 generates a schedule request when data is generated, and transmits the schedule request by the wireless transmission / reception unit 201. When the schedule permission is received from the wireless communication apparatus as a response to the schedule request, the UL-SCH control unit 203 outputs the transmission format to the L2 processing unit 204, and the L2 processing unit 204 allocates the transmission data input from the L3 processing unit 205. It transmits through the radio | wireless transmission / reception part 201 using the transmitted UL-SCH resource.

  The mobile station may be provided with a path loss measurement unit 206. The path loss measuring unit 206 can estimate the path loss with the adjacent cell by measuring the reception quality of the downlink pilot from the adjacent cell. The information on the path loss to the adjacent cell is reported to the wireless communication apparatus under the control of the control unit 207, and is used for determining the buffer area resource allocation permission in the second embodiment described above. Note that the control unit 207 controls the operation of the entire mobile station including the RACH control unit 202 and the UL-SCH control unit 203.

6). Operation FIG. 11 is a sequence diagram showing a resource rearrangement operation in the radio communication system shown in FIGS. First, when the RACH resource control unit 102 of the radio communication device 10 in the cell A performs the rearrangement of the RACH resources (step S40), the inter-cell resource management unit 104 sends new RACH resource information to the radio communication device 11 in the adjacent cell B. Notification is made (step S41), and further, the radio transceiver unit 101 notifies the mobile station UE1 located in the cell A (step S42).

  When the inter-cell resource management unit 104 of the wireless communication device 11 of the adjacent cell B knows that the RACH resource of the adjacent cell A has been changed, it outputs new RACH resource information of the adjacent cell A to the buffer region resource setting unit 105. Then, the buffer area resource is determined according to each embodiment described above. Then, the UL-SCH scheduler 106 performs rearrangement (scheduling) of UL-SCH resources based on the RACH resource of the own station cell B and the buffer area resource for the adjacent cell A (step S43), and is located in the own station cell B. And it notifies to the mobile station UE2 which performs UL-SCH transmission (step S44).

  The mobile station UE1 that has received the new RACH resource information performs RACH access using the new RACH resource (step S45), and the mobile station UE2 that has received the new UL-SCH resource information uses the new UL-SCH resource. UL-SCH transmission is executed (step S46). As already described, the UL-SCH transmission of the mobile station UE2 is in a frequency band or timing different from the RACH resource of the mobile station UE1, or to the extent that interference with the RACH transmission of the mobile station UE1 can be tolerated. Therefore, the possibility that a large delay occurs in the establishment of uplink synchronization of the mobile station UE1 is reduced.

  Here, although the case where RACH resource information is notified from the wireless communication apparatus 10 to the wireless communication apparatus 11 is shown, the RACH resource information is also notified from the wireless communication apparatus 11 to the wireless communication apparatus 10, and in this case Since the basic operation is as described above, the description thereof is omitted. Hereinafter, an embodiment of the present invention will be described by taking as an example the case where one radio communication apparatus is one base station eNB.

7). First Embodiment FIG. 12 is a flowchart showing a resource allocation control method according to a first embodiment of the present invention. The base station eNB controlling each adjacent cell shares the RACH resource information between the cells by reporting the RACH scheduling information and the currently occupied RACH resource to the other base station eNB by the RACH resource control unit 102. (Step S301). Subsequently, the buffer area resource setting unit 105 of each base station eNB determines whether or not the RACH interference level from the RACH related information measuring unit 103 is greater than a predetermined threshold (step S302). If the RACH interference is large (YES in step S302), the buffer area resource setting unit 105 sets a buffer area resource for the adjacent cell from the RACH resource information of the adjacent cell (step S303). The UL-SCH scheduler 106 performs scheduling so as not to allocate buffer area resources to UL-SCH transmission, that is, to allocate UL-SCH transmission to resources other than its own RACH resource and buffer area resource (step S304). . If the RACH interference is small (NO in step S302), scheduling is performed so that UL-SCH transmission is allocated to resources other than the RACH resource of the own station without setting a buffer area resource (step S304).

8). Second Embodiment According to the second embodiment of the present invention, the base station eNB operates as follows.
The base station eNB reports the currently used RACH scheduling information to neighboring cells.
-The base station eNB retains the RACH resource of an adjacent cell and its neighboring resources as uplink buffer area resources. This uplink buffer area resource can be used by the VoIP mobile station UE or the mobile station UE that is located in the center of the cell and has a large path loss to an adjacent cell.

  More specifically, the inter-cell allocation control of RACH and UL-SCH is performed as follows.

  FIG. 13 is a flowchart showing a resource allocation control method according to the second embodiment of the present invention. The base station eNB controlling each adjacent cell shares the RACH resource information between the cells by reporting the RACH scheduling information and the currently occupied RACH resource to the other base station eNB by the RACH resource control unit 102. (Step S401). Subsequently, the buffer area resource setting unit 105 of each base station eNB determines whether or not the RACH interference level from the RACH related information measurement unit 103 is greater than a predetermined threshold (step S402). If the RACH interference is large (YES in step S402), the buffer area resource setting unit 105 sets the buffer area resource from the RACH resource information of the adjacent cell and outputs it to the UL-SCH scheduler 106 (step S403).

  Subsequently, the UL-SCH scheduler 106 determines whether or not the mobile station UE requests low transmission power from the schedule request (here, a mobile station that performs VoIP packet transmission) (Step S404), and VoIP. If it is a mobile station UE (YES in step S404), UL-SCH resources that are frequency-hopped for each time resource are allocated to the VoIP packet transmission. In step S405, priority allocation of the buffer area resource is permitted. Desirably, VoIP packet transmissions are randomly allocated over the entire frequency resource so as to maximize the frequency diversity gain. If it is not a VoIP mobile station UE or a mobile station UE that is located in the center of the cell and has a large path loss to an adjacent cell (NO in step S404), step S405 is skipped.

  Subsequently, the UL-SCH scheduler 106 determines whether or not the mobile station UE has a large path loss to the adjacent cell from the information on the path loss to the adjacent cell reported from the mobile station UE (step S406). The determination may be made not only based on whether or not the path loss to the adjacent cell is large, but also based on whether or not the ratio between the path loss in the current cell and the path loss to the adjacent cell is large. If the mobile station UE has a large path loss to an adjacent cell (YES in step S406), since interference to the adjacent cell is small, the UL-SCH scheduler 106 permits allocation of buffer area resources for transmission of the mobile station UE. (Step S407). If the path loss to the adjacent cell is small (NO in step S406), step S407 is skipped.

  In this way, the UL-SCH scheduler 106 performs UL-SCH scheduling so as not to allocate buffer area resources other than the UL-SCH transmission permitted in step S405 or S407 (step S408). If the RACH interference is small (NO in step S402), the UL-SCH scheduler 106 executes normal UL-SCH scheduling without executing steps S403 to S407.

  An example of the resource allocation control described above is shown below. First, the base station eNB shares the arrangement of RACH resources in the time and frequency domain with neighboring cells. The allocation to the buffer area resource corresponding to the RACH resource of the adjacent cell is performed as follows.

The base station eNB assigns the mobile station UE with a large path loss to the adjacent cell by being located in the center of the cell (however, the mobile station UE assigns the path loss to the adjacent cell to the current main cell) Need the ability to report). This corresponds to the processing flow of NO in step S404, YES in step S406, and steps S407 and S408.
-Alternatively, the base station eNB assigns to a mobile station UE (for example, a mobile station performing VoIP) with a low transmission power request. This corresponds to the processing flow of YES in step S404, NO in step S406, and step S408.
-Alternatively, the base station eNB leaves the resource area unused. This corresponds to the processing flow of NO in step S404, NO in step S406, and step S408.
Alternatively, the base station eNB allocates a mobile station UE for high-speed data transmission when an overload indicator such as a power control signal indicating that the interference is large is not received. This corresponds to the processing flow of NO in step S402 and step S408.

9. Third Embodiment According to the third embodiment of the present invention, based on the RACH resource information of another cell and the pattern for avoiding persistent interference to the other cell, the buffer area resource for the other cell is determined. decide.

  FIG. 14 is a block diagram showing a configuration of a wireless communication device in which the resource allocation control device according to the third example of the present invention is mounted. In addition, the same reference number is attached | subjected to the block of the function same as the structure shown in FIG. The configuration shown in FIG. 14 is different from that shown in FIG. 9 in that a buffer area resource candidate setting unit 105 and a thinning control unit 109 are provided, but the buffer area resource candidate setting unit 105 is the buffer area resource candidate setting unit shown in FIG. Since it has the same function as 105, the same reference number is attached. That is, the buffer area resource candidate is equal to the buffer area resource corresponding to the RACH resource of the adjacent cell.

  The thinning control unit 109 uses the persistent interference avoidance pattern that non-persistently excludes the buffer region resource candidates and, if necessary, the RACH interference information, the buffer region resource candidates set by the buffer region resource candidate setting unit 105. Exclude non-persistently. In this way, buffer area resources are generated by thinning out buffer area resource candidates and output to the UL-SCH scheduler 106. The persistent buffer avoidance pattern may be set in the wireless communication apparatus as a setting file, or may be acquired and stored through any network.

  FIG. 15 is a flowchart showing a resource allocation control method according to the third embodiment of the present invention. The base station eNB controlling each adjacent cell shares the RACH resource information between the cells by reporting the RACH scheduling information and the currently occupied RACH resource to the other base station eNB by the RACH resource control unit 102. (Step S501). Subsequently, the buffer area resource setting unit 105 of each base station eNB determines whether or not the RACH interference level from the RACH related information measuring unit 103 is greater than a predetermined threshold (step S502). If the RACH interference is large (YES in step S502), the buffer region resource candidate setting unit 105 sets the buffer region resource candidate from the RACH resource information of the adjacent cell and outputs the buffer region resource candidate to the thinning control unit 109 (step S503).

  The thinning control unit 109 excludes buffer area resource candidates according to the continuous interference avoidance pattern in the time domain, frequency domain, and / or cell area, and determines a buffer area resource for each adjacent cell (step S504). The set buffer area resource is output to the UL-SCH scheduler 106. What pattern is used may be determined autonomously by the base station eNB of each cell, or may be determined by information exchange with other base stations eNB. As already described, a random pattern is a desirable example of the continuous interference avoidance pattern.

  The UL-SCH scheduler 106 performs scheduling so as not to allocate buffer area resources to UL-SCH transmission, that is, to allocate UL-SCH transmission to resources other than its own RACH resource and buffer area resource (step S505). . If the RACH interference is small (NO in step S502), scheduling is performed so that UL-SCH transmission is allocated to resources other than the own RACH resource without setting a buffer area resource (step S505).

An example in which a random pattern is used as the persistent interference avoidance pattern of the resource allocation control described above will be described below. First, the base station eNB shares the arrangement of RACH resources in the time and frequency domain with neighboring cells. The allocation to the buffer area resource corresponding to the RACH resource of the adjacent cell is performed as follows.
Avoiding persistent interference to other cells according to a random pattern in the time domain;
Avoiding persistent interference to other cells according to a random pattern in the frequency domain;
Avoiding persistent interference to other cells according to a random pattern in the cell area;
Avoid persistent interference to other cells according to a random pattern in any combination of time domain, frequency domain and cell domain.

  The present invention is applicable to a radio communication system in which inter-cell interference may occur, and particularly to a mobile communication system using an access scheme (FTDMA) with a frequency division and time division resource configuration.

DESCRIPTION OF SYMBOLS 10, 11 Wireless communication apparatus 12 Network 101 Wireless transmission / reception part 102 RACH resource control part 103 RACH related information measurement part 104 Inter-cell resource management part 105 Buffer area resource setting part 106 UL-SCH scheduler 107 L2 processing part 108 L3 processing part 109 Decimation Control unit 201 Wireless transmission / reception unit 202 RACH control unit 203 UL-SCH control unit 204 L2 processing unit 205 L3 processing unit 206 Path loss measurement unit RACH Random access channel UL-SCH uplink shared channel

Claims (4)

A wireless communication system including a first base station, a second base station, and a mobile station,
The first base station transmits information on resource allocation of a random access channel (RACH) in the first base station to the second base station,
The second base station determines a resource for uplink communication with a resource arrangement different from the RACH resource arrangement in the first base station,
The mobile station communicates with the second base station using the uplink communication resource.
A wireless communication system. A communication method of a wireless communication system including a first base station, a second base station, and a mobile station,
The first base station transmits information about a resource arrangement of a random access channel (RACH) in the first base station to the second base station;
The second base station determines a resource for uplink communication with a resource arrangement different from the RACH resource arrangement in the first base station;
The mobile station communicates with the second base station using the uplink communication resource;
A communication method characterized by the above. A base station in a wireless communication system including a mobile station,
A receiving unit for receiving information on a resource arrangement of a random access channel (RACH) in another base station;
A resource determining unit that determines resources for uplink communication with a resource arrangement different from the RACH resource arrangement in the other base station;
A communication unit that communicates with the mobile station using the resource for uplink communication;
A base station comprising: A mobile station in a wireless communication system including a first base station and a second base station,
Means for receiving information related to resources for uplink communication determined by the second base station so as to have a resource arrangement different from a resource arrangement of a random access channel (RACH) in the first base station;
Means for communicating with the second base station by the resource for uplink communication;
A mobile station comprising:

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