JP2013055446A - Cellular system and resource allocation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cellular system which can perform efficient resource allocation.SOLUTION: A cellular system of which first cell includes a plurality of types of cells having smaller coverage areas than the first cell and different sizes of coverage areas, comprises a resource allocation device which performs resource allocation of each cell on the basis of values indicating disposition relation between each cell with the other cells.

Description

  The present invention relates to a cellular system and its resource allocation apparatus.

  In a cellular system composed of a plurality of cells having different zone radii, when communication is performed using the same frequency band, inter-cell interference becomes a major issue. In a cellular system where a zone radius is large and a micro system covering a wide range includes a pico cell with a small zone radius or a femto cell with a zone radius smaller than that of a pico cell, a pico cell base station (PeNB: Pico eNodeB) When a femtocell base station (HeNB: Home eNodeB) communicates with terminals (picocell terminals, femtocell terminals) accommodated therein, signals transmitted from the macrocell base station (MeNB: Macro eNodeB) to the macrocell terminals are This is a very large interference source for pico cell terminals and femto cell terminals. When the pico cell or femto cell is located at a position close to the macro cell base station, the influence of interference is particularly large, and the reception characteristics of the pico cell terminal or femto cell terminal are significantly deteriorated due to the influence of these interference. On the other hand, for the macro cell terminal, a signal transmitted from the pico cell base station or the femto cell base station becomes interference. The transmission power in picocells and femtocells is very low compared to the transmission power in macrocells, but it is very large when macrocell terminals are located in the vicinity of those small zone cells or when there are many small zone cells in a macrocell. Interference will occur.

  In 3GPP (3rd Generation Partnership Project), as a method of reducing such inter-cell interference, a method of allocating different resources for each cell type has been proposed (Non-patent Document 1).

  Non-Patent Document 1 discloses a resource allocation method for transmitting using different frequencies for each cell type in a cellular system composed of a macro cell and a femto cell. That is, this is a method of reducing inter-cell interference between the macro cell and the femto cell by using different resources between the macro cell and the femto cell. Such a method can be similarly applied to a cellular system composed of a macro cell, a pico cell, and a femto cell as shown in FIG. 1, for example, resource allocation as shown in FIG. However, FIG. 2 shows resource allocation in the case where the base station of each cell shown in FIG. 1 performs transmission using resources that are temporally different depending on the cell type (macro cell, pico cell, or femto cell). Represents. Thus, the macro cell, the pico cell (P1, P2, P3, P4) and the femto cell (F1, F2a, F2b, F3) use different resources, respectively, so that the macro cell-pico cell, the macro cell-femto cell, the pico cell- It can control so that interference between femtocells may not occur.

3GPP TR 36.921 V9.0.0 (Release 9)

  In a cellular system in which cells having different coverage areas such as pico cells and femto cells are mixed in a macro cell, the environment in which those cells are actually arranged varies. For example, as shown in FIG. 1, there are picocells (picocells 1 and 2) in which femtocells exist in the cover range and picocells (picocell 4) in which no femtocell exists in the cover range. As for femtocells, if there are femtocells (femtocells 1, 2a, 2b) included in the picocell cover area, they are included in the macrocell cover area but are not included in the picocell cover area. There are also femtocells such as femtocell 3 (femtocells that exist directly in the macrocell). In this way, in an actual environment, the cells may be placed in different environments despite being the same type of cells (pico cells or femto cells). In such a case, the cells are placed. Depending on the environment, the influence of interference from surrounding cells or interference on surrounding cells is also different. Therefore, when resource allocation is performed based only on the type of cell as in the method of Non-Patent Document 1 in which different resources are used in the macro cell and the femto cell, resource allocation considering the actual environment cannot always be performed. Therefore, there is a problem that resource allocation becomes inefficient.

  The present invention has been made in view of such circumstances, and provides a cellular system and a resource allocation device capable of performing efficient resource allocation.

  The cellular system of the present invention is a cellular system in which a plurality of types of cells in which a cover area is narrower than the first cell and a width of a covered area is different in the first cell. The resource allocation apparatus which performs resource allocation based on the numerical value showing the arrangement | positioning relationship with another cell is provided.

  There are three or more types of arrangement relationships, and the numerical values representing the arrangement relationships may be three or more levels.

  The numerical value representing the arrangement relationship may be a value obtained by quantifying a relationship in which the first cell and a plurality of cells existing in the first cell overlap each other.

  The base station apparatus that controls each cell may acquire the numerical value representing the arrangement relationship.

  The number of resources that can be used in each cell may be calculated based on the numerical value representing the arrangement relationship, and resource allocation may be performed within a range that does not exceed the number of available resources.

  The first cell may be a macro cell, and the plurality of types of cells having a cover area narrower than that of the first cell and having different coverage areas may include a pico cell and a femto cell.

  The resource allocating device of the present invention is a resource allocating device for a cellular system in which a plurality of types of cells having a cover area narrower than the first cell and different areas of the cover area are present in the first cell. A means is provided for performing resource allocation in each cell based on a numerical value representing an arrangement relationship with another cell.

  According to the present invention, efficient resource allocation can be performed.

It is a figure which shows an example of a structure of a cellular system. It is a table | surface which shows an example of the resource allocation in a cellular system. It is a block diagram which shows an example of a structure of the base station M which concerns on 1st Embodiment. (A) And (b) is a table | surface which shows an example of the interference source information which the base station M acquired. It is a flowchart which shows an example of the flow of a process of the upper layer 14 of the base station M which concerns on 1st Embodiment. It is a table | surface which shows an example of the resource allocation in 1st Embodiment. It is a block diagram which shows an example of a structure of the terminal m which concerns on 1st Embodiment. It is a flowchart which shows an example of the flow of the process of the upper layer of the base station M which concerns on 2nd Embodiment. (A), (b), and (c) are tables showing examples of resource allocation information in the second embodiment.

[First Embodiment]
The configuration of the cellular system according to the first embodiment of the present invention is the same as that shown in FIG. As shown in FIG. 1, the cellular system according to the present embodiment includes a macro cell that covers a wide area, a pico cell that covers a narrow area, and a femto cell that covers a narrower area than the pico cell. . The macro cell includes a base station M and one terminal m, and transmits a desired signal from the base station M to the terminal m. In addition, the pico cell 1 is composed of the base station P1 and the terminal f1, the pico cell 2 is composed of the base station P2 and the terminal p2, the femto cell 1 is the base station F1 and the terminal f1, the femto cell 2a is the base station F2a and the terminal f2a, and the femto The cell 2b is composed of a base station F2b and a terminal f2b, the femtocell 3 is composed of a base station F3 and a terminal f3, and the picocell 4 is composed of a base station P4 and a terminal p4, and each transmits and receives a desired signal within the cell. At this time, since each terminal receives a desired signal transmitted in another cell as an interference signal in addition to the desired signal of the own cell, inter-cell interference occurs.

  Here, as an example, a cellular system composed of three types of cells (macro cell, pico cell, and femto cell) is assumed. However, each covers a different area, and a desired signal in a certain cell or zone is different from that of another cell. Any combination of cells or zones that may interfere with the cell or zone may be used, and a cell or zone including a light emitting base station (RRE: Remote Radio Equipments), a hot spot, a relay station, or the like may be targeted.

  As shown in FIG. 1, in this cellular system, there is a femtocell 1 in a picocell 1, and a femtocell 2a and a femtocell 2b in a picocell 2. The femtocell 3 is not included in the picocell, and there is no femtocell in the picocell 4. All these cells are included in the macro cell. Here, the number of different types of cells (with a wider coverage area) including the target cell + 1 (for the own cell) is defined as the cell hierarchy (layer), and each cell is defined by the numerical value of this hierarchy. Represents the environment in which is placed. According to this definition, for example, a macro cell is not included in a cell having a wider coverage area than itself, and can be said to be the outermost cell, so that its hierarchy is 1, and pico cell 1 is included in the macro cell. The hierarchy is 2. Further, since the femtocell 1 can be said to be included in the picocell 1 and the macrocell, its hierarchy is 3. Similarly, the hierarchy of the pico cell 2 is 2, the hierarchy of the femto cells 2a and 2b is 3, the hierarchy of the femto cell 3 is 2, and the hierarchy of the pico cell 4 is 2.

  As described above, in the cellular system according to the present embodiment, for example, there are cells having different layers even in the same type of cells, such as femtocell 1 (hierarchy = 3) and femtocell 3 (hierarchy = 2). That is, it is assumed that there are cells having different environments even if the cells are of the same type. Therefore, the numerical value called a hierarchy in this embodiment can be paraphrased as a numerical value indicating the type of each cell. However, the cell type here is not the type of area covered by the cell, such as macro cell, pico cell, or femto cell, but the type of environment (placement relationship). Means. Then, by combining the cell type information such as macro cell, pico cell, and femto cell with the information (hierarchy) indicating the surrounding environment type, it is possible to grasp what cell is placed in what environment. be able to.

  Further, the base station M and other base stations are connected by a wired network (in the case of a relay, wireless), and information can be shared between the base station devices. However, a general femtocell base station exchanges information with a macrocell base station via the Internet, and an optical extension base station or picocell base station exchanges information with a macrocell base station via an optical fiber or a dedicated network. I do.

<About Macrocell>
FIG. 3 is a block diagram showing an example of the configuration of the base station M according to this embodiment. The receiving antenna 10 receives a signal transmitted from the terminal m and outputs it to the radio unit 11. The radio unit 11 down-converts the reception signal input from the reception antenna 10 to generate a baseband signal and outputs the baseband signal to an A / D (Analog to Digital) unit 12. The A / D unit 12 converts the input analog signal into a digital signal and outputs it to the receiving unit 13. The receiving unit 13 extracts information (interference source information) related to interference measured by the terminal from the input digital signal and outputs the information to the upper layer 14.

  The upper layer 14 determines resource allocation based on the interference source information notified from the base station of another cell via the wired network and the interference source information of the terminal m input from the receiving unit 13.

  Here, the interference source information acquired by the base station M will be described with reference to FIG. 4A and 4B are tables showing examples of interference source information acquired by the base station M. FIG. In FIG. 4, interference received by each cell from other cells is indicated by “◯” when receiving interference, and blank when not receiving interference. For example, in the second row (P1 row) of FIG. 4A, the columns of the interference stations M and F1 are ◯. This is because the pico cell 1 receives interference from the macro cell and the femto cell 1. Represents that.

  In the cellular system of FIG. 1, for example, assuming that pico cell 1 and pico cell 2 are located in the vicinity, pico cell 1 and pico cell 2 may interfere with each other, as shown in FIG. Interference source information. That is, in addition to FIG. 4A, the columns of interference given from P1 to P2 and from P2 to P1 are “◯”. As described above, the interference source information is not limited to the example of FIG. 4 as long as the relationship of interference in all the cells that can be grasped is known. Actually, it is considered that almost all cells interfere with each other. However, here, only interference with relatively large influence is observed, such as interference with an output exceeding a certain threshold is observed. . Therefore, it is assumed that the interference source information regarding the interference source having such a large influence is grasped and used for resource allocation.

  Here, the flow of processing of the upper layer 14 will be described with reference to FIG. FIG. 5 is a flowchart illustrating an example of the processing flow of the upper layer 14. In step S101, it is determined whether or not the interference source information has been updated. If the interference source information has been updated, the process proceeds to step S102 (YES), and if not, the process proceeds to step S111 (NO). That is, in the present embodiment, the resource allocation of each cell is determined based on the interference source information, but the timing for determining the resource allocation is when the interference source information is updated. For example, a new cell is added. Such as when the power on / off state of the femtocell changes, or when the interference state changes.

  In step S102, cells that interfere with each other are grouped based on the interference source information. In the interference source information in FIG. 4A, the macro cell and all other cells interfere with each other, and in addition, the pico cell 1 and the femto cell 1 interfere with each other, and the pico cell 2, the femto cell 2a, and the femto cell. Cells 2b interfere with each other. Therefore, the groups of cells that interfere with each other are group 1 (macro cell, pico cell 1, femto cell 1), group 2 (macro cell, pico cell 2, femto cell 2a, femto cell 2b), group 3 (macro cell, femto cell 3). , Group 4 (macro cell, pico cell 4). When the interference source information is in FIG. 4 (a), it matches the positional relationship to which each cell belongs. However, when the interference source information is in FIG. 4 (b), some cells (pico cell 1 and pico cell 2) are mutually connected. Interfering and difficult to group clearly. In such a case, grouping may be performed based on the positional relationship of cells in consideration of the hierarchy. At this time, the information on the hierarchy may be set in advance when the base station is installed, or is estimated from the number of different types of cells from the own cell among the cells that are the interference sources based on the interference source information. May be.

  In step S103, the condition is determined so that the processes in steps S104 and S105 are performed for 1 ≦ n ≦ number of groups (in this embodiment, the number of groups is 4).

  In step S104, a duplication number for each group is determined. Here, the overlap number in each group represents the number of cells having a cover range that overlaps the cover range of the cell having the largest number of layers in the group. If there is no base station that stops transmission as in this embodiment, the overlap number is the maximum value of the hierarchy in the cells in the group. This overlapping number can also be rephrased as a numerical value representing the type of each cell (the surrounding environment and the type of arrangement relationship), as in the hierarchy described above. Therefore, the present embodiment relates to a method of utilizing information indicating the cell type for resource allocation in each cell.

  When n = 1, for group 1, the cell with the highest hierarchy is femtocell 1 (hierarchy = 3), and femtocell 1 has overlapping coverage with picocell 1 and macrocell. 3 In step S105, 1 is added to n, so that n = 2, and the process proceeds to “YES” in step S103.

  When n = 2, for group 2, the cells with the highest hierarchy are femtocell 2a and femtocell 2b (each hierarchy = 3), and femtocell 2a and femtocell 2b have overlapping coverage with picocell 2 and macrocell. Therefore, the overlap number of group 2 is 3. In step S105, 1 is added to n, so that n = 3, and the process proceeds to “YES” in step S103.

  When n = 3, for group 3, the cell with the highest hierarchy is femtocell 3 (hierarchy = 2), and the femtocell has a macro cell and a coverage that overlaps, so the overlap number of group 3 is 2. In step S105, 1 is added to n, so that n = 4, and the process proceeds to “YES” in step S103.

  When n = 4, with respect to group 4, the cell with the highest hierarchy is pico cell 4 (hierarchy = 2). Since pico cell 4 has a macro cell and a cover range overlapping, the overlap number of group 4 is 2. In step S105, 1 is added to n, and n = 5. In step S103, the process proceeds to “NO”, and the process proceeds to step S106.

  In step S106, the overlapping numbers for each group determined in step S104 are rearranged in the descending order of the super plurality. In the present embodiment, it is assumed that the processing after step S107 is performed in the order of group 1, group 2, group 3, and group 4. However, the group rearrangement in step S106 may be performed in the order of the overlapping number, for example, the order of group 2, group 1, group 4, and group 3.

  In step S107, conditions are determined so that the processing in steps S108 and S109 is performed for 1 ≦ j ≦ number of groups (in this embodiment, the number of groups is 4) in the order rearranged in step S106.

  In step S108, resource allocation of cells belonging to group j among the groups rearranged in step S106 is determined. Here, resource allocation in the present embodiment refers to cells that belong to the same group and have overlapping coverage, by limiting the number of resources that can be used by each cell belonging to each group according to the overlapping number in each group. This refers to a process of allocating resources used in each cell within the above-described restrictions so that interference between the cells can be suppressed. In other words, the number of resources that can be used is different in a group having different overlap numbers. Then, resources are shared so that cells belonging to the same group do not use the same resource within the limit of the number of resources that can be used.

  FIG. 6 is a table showing an example in which a plurality of time resources are allocated to each cell (base station of each cell) by the resource allocation method according to the present embodiment, and the time resource allocated to each cell is indicated by “◯”. Is shown. That is, each cell performs transmission only in a time resource with “◯”, and does not perform transmission with a time resource without “◯”.

  Specifically, when j = 1, resource allocation to the macro cell, pico cell 1 and femto cell 1 belonging to group 1 is performed. Here, since the overlap number of group 1 is 3, the number of resources that can be used by each cell belonging to group 1 is limited to 1/3 of all resources. Therefore, here, since the time resource is divided into six, each cell (macro cell, pico cell 1, femto cell 1) belonging to group 1 uses two time resources. After determining the number of resources that can be used in each cell in this way, resource allocation is performed for each cell. This resource allocation can be achieved by preventing cells belonging to the same group from interfering with each other. You may go to For example, resource allocation may be performed so that resources allocated to each cell are in order, such as M (macrocell), P1 (picocell 1), and F1 (femtocell 1) in FIG. After such an assignment, in step S109, 1 is added to j, j = 2, and the process proceeds to “YES” in step S107.

  When j = 2, resource allocation is performed for group 2. Here, since the overlap number of group 2 is 3 as in group 1, the number of resources that can be used by each cell belonging to group 2 is limited to 1/3 of all resources. That is, each cell (macro cell, pico cell 2, femto cell 2a, femto cell 2b) belonging to group 2 uses two time resources. However, since the assignment of the macro cell has already been determined when j = 1, the assignment is retained, and resource assignment to cells other than the macro cell is performed. As described above, this resource allocation is performed so that cells belonging to the same group do not interfere with each other, and resources other than the resource allocated to the macro cell when j = 1 are assigned to the remaining cells of the group 2. (Picocell 2, femtocell 2a, femtocell 2b) are allocated so as to be shared. However, the same resources are allocated to cells having the same hierarchy (femtocell 2a and femtocell 2b). If the hierarchy is the same, this is often the same type of cells such as macro cell-macro cell, pico cell-pico cell, femto cell-femto cell (even if the same type, the hierarchy is not always the same). However, allocating the same resource to such cells does not mean that the situation is such that a cell having a different hierarchy, particularly a cell having a lower hierarchy, receives a great deal of interference by allocating the same resource. This is because it is considered that transmission can be performed to a certain degree. By performing such allocation, resource allocation to these cells is, for example, P2 (picocell 2), F2a (femtocell 2a), and F2b (femtocell 2b) in FIG. In step S109, 1 is added to j, so that j = 3, and the process proceeds to “YES” in step S107.

  When j = 3, resource allocation is performed for group 3 in which the overlap number is 2. In this case, since the overlapping number is smaller than those of group 1 and group 2, each cell belonging to group 3 can use more resources than each cell belonging to groups 1 and 2. . For example, it is assumed that half of the resources can be used in each cell belonging to group 2. However, as described above, since the assignment of the macro cell has already been determined, assuming that the macro cell assignment is retained, resources other than the resource assigned to the macro cell are assigned to the remaining cells of the group 3 (femto cell 3 ). At this time, the resource allocation to the femtocell 3 is as shown in F3 of FIG. 6, and even if the same type of cells (in this case, femtocells), the femtocells 3 belonging to the group having a small overlap are overlapped. Compared to the femtocell 1 and the femtocells 2a and 2b belonging to a large group, twice as many resources can be used. However, for a cell belonging to a plurality of different groups such as a macro cell, use resources are allocated under the limitation of the group having the maximum number of overlaps, and the allocation result is assigned to the subsequent group. It shall be held at the time of. After such assignment, in step S109, 1 is added to j, j = 4, and the process proceeds to “YES” in step S107.

  Finally, when j = 4, resource allocation is performed for group 4. Since the group 4 is a group having a duplication number of 2 as in the group 3, and only two cells of the macro cell and the pico cell 4 to which allocation has already been determined belong, the resource allocation is the same as that of the group 3. Become. At this time, the resource allocation of the pico cell 4 is as indicated by P4 in FIG. In step S109, 1 is added to j, and j = 5. In S107, the process proceeds to “NO”, and the process proceeds to step S110.

  As described above, even if the resource allocation information in this embodiment is the same type of cells, for example, femtocells, the femtocell 3 has more resource allocation than the femtocells 1, 2a, and 2b. This is because the duplication number of the group to which the femtocell 3 belongs is smaller than the duplication number of the group to which the femtocells 1, 2a, and 2b belong respectively. Similarly, with respect to the pico cell, the number of resources that can be used differs between the pico cell 4 and the pico cells 1 and 2 because the overlapping number of groups to which these cells belong is different. As described above, the overlapping number in this embodiment is a numerical value of the overlapping state of a plurality of cells included in each group and having different coverage ranges, that is, the arrangement state of cells in the group. Based on this numerical value, the influence of interference between a plurality of cells having different coverage ranges is evaluated. If this value is large, it is determined that there are many cells that interfere with each other in the group, and resources that can be used in each cell are finely limited. On the other hand, when the overlap number is small, it is determined that the number of cells that influence each other in the group is small, and each cell can use more resources. Therefore, due to such resource use restrictions and allocation, even when there are a plurality of cells of the same type, it is possible to efficiently use the resources in consideration of the environment where the cells are actually placed.

  In step S110, information indicating the resource allocation determined as described above (resource allocation information) is notified to each base station via the wired network. Then, based on the notified resource allocation information, each cell performs the processing after step S111.

  In step S111, it is determined whether or not resources are allocated to the own cell at the current time. If allocated (YES in step S111), the process proceeds to step S112, and the transmission bit string is output to the encoding unit 15. The process after the encoding part 15 of FIG. 3 is performed. On the other hand, if it is not assigned (NO in step S111), the cell is not transmitted at the current time, so the next transmission opportunity is awaited.

  After the processing in the upper layer 14 as described above, the encoding unit 15 in FIG. 3 encodes the transmission bit string input from the upper layer 14 and outputs it to the modulation unit 16. The modulation unit 16 modulates the encoded transmission bit string using a modulation scheme such as QPSK (Quadrature Phase Shift Keying) or 16QAM (Quadrature Amplitude Modulation), and outputs the result to the S / P conversion unit 17. The S / P conversion unit 17 rearranges the input serial data into parallel data, and then outputs the parallel data to the subcarrier allocation unit 18. The subcarrier allocation unit 18 allocates the transmission bit string to subcarriers on the frequency axis, generates an OFDM (Orthogonal Frequency Division Multiplexing) signal, and outputs the signal to the reference signal multiplexing unit 19. The reference signal multiplexing unit 19 multiplexes a reference signal (a pilot signal for propagation path estimation) with the input signal and outputs the multiplexed signal to the IFFT unit 20. The IFFT unit 20 converts the input transmission signal on the frequency axis into a signal on the time axis by IFFT (Inverse Fast Fourier Transmission) and outputs the signal to the CP insertion unit 21. The CP insertion unit 21 inserts a CP (Cyclic Prefix) into the input signal on the time axis, and outputs the signal to a D / A (Digital to Analog) unit 22. The D / A unit 22 converts the input signal from a digital signal to an analog signal and outputs the analog signal to the radio unit 23. The radio unit 23 up-converts the input analog signal to a radio frequency and transmits it to the terminal device m via the transmission antenna 24.

FIG. 7 is a block diagram showing an example of the configuration of the terminal m according to this embodiment. The receiving antenna 30 receives a signal transmitted from the base station M and outputs it to the radio unit 31. The radio unit 31 down-converts the received signal input from the receiving antenna 30 to generate a baseband signal, and outputs the baseband signal to an A / D (Analog to Digital) unit 32. The A / D unit 32 converts the input analog signal into a digital signal and outputs the digital signal to the CP removal unit 33.
The CP removal unit 33 removes the CP from the input digital signal and outputs it to the FFT unit 34. The FFT unit 34 performs an FFT (Fast Fourier Transmission) on the input received data signal, converts it to a signal on the frequency axis, and outputs the signal to the reference signal separation unit 35. The reference signal separation unit 35 separates the reference signal from the input signal, and outputs the reference signal to the propagation path estimation unit 36 and the reception data signal to the subcarrier extraction unit 37. The subcarrier extraction unit 37 extracts the input signal for each subcarrier to obtain a parallel received data signal, and outputs it to the P / S conversion unit 38. The P / S converter 38 rearranges the input parallel received data signals in series and outputs them to the demodulator 39. The propagation path estimation unit 36 outputs the propagation path information estimated from the reference signal to the demodulation unit 39, and the demodulation unit 39 receives the propagation path information input from the propagation path estimation unit 36 and the P / S conversion unit 38. The received data signal is demodulated to obtain a received bit string and output to the decoding unit 40. The decoding unit 40 demodulates the reception bit string input from the demodulation unit 39 to obtain a decoded bit string.

  In addition, the interference state estimation unit 41 measures the reception level from the synchronization signal or the like, identifies the cell that causes interference to the own cell, outputs the cell ID of the cell that is the interference source as interference source information, and outputs the interference source information to the transmission unit 42. . The transmission unit 42 converts the estimated interference source information into a transmittable format and outputs it to the D / A unit 43. The D / A unit 43 converts the digital signal into an analog signal and outputs the analog signal to the radio unit 44. The radio unit 44 transmits the input analog signal toward the base station M via the transmission antenna unit 45. The interference source information may be transmitted only when the interference source information is updated.

<About cells other than macro cells>
As described above, the configurations of the base station and terminal in the macro cell are the configurations shown in FIGS. 3 and 7, respectively, but the same applies to the configurations of other types of cells (pico cells and femto cells). However, in this embodiment, since the base station M is configured to collectively determine resource allocation of all cells, base stations other than the macro cell do not perform resource allocation processing. That is, the base station other than the macro cell differs in the processing of the upper layer 14 in FIG. 3 and performs only the processing after S111 in FIG.

  The interference source information in this embodiment is generated based on the result of each cell receiving a radio signal such as a synchronization signal coming from a neighboring cell, but is not limited thereto, and is exchanged between base stations. You may produce | generate based on information. For example, in the LTE (Long Term Evolution) system standardized in 3GPP, a mechanism called an OI (Overload Information), which indicates information indicating an interference level for each resource block, is adopted between neighboring base stations. Yes. Based on this information, the resource allocation status of each base station and the approximate positional relationship, it is possible to grasp the rough interference source for each resource block, and it is possible to generate interference source information for each resource block Become. In this case, each base station notifies the base station M of OI.

  Further, since the macro cell and the pico cell are systematically installed by the communication operator, the interference source information may be set at the time of installation according to the positional relationship to install. For example, when a communication operator installs pico cells in a macro cell, information indicating that the cells interfere with each other can be registered in the cells as interference source information. Also, a femtocell is usually installed by a user, not an operator, but if the approximate location information is registered with the operator when the femtocell is installed, the femtocell is based on the registered location information. The operator can also create cell interference source information. Then, the hierarchy and duplication number shown in the present embodiment may be obtained based on the interference source information based on the positional relationship registered in advance, and processing for limiting the number of resources used by each cell may be performed. In this case, each terminal does not need to generate interference source information, and the processing on the terminal side can be simplified and control information (interference source information) to be notified can be reduced.

  In addition, control information such as RNTP (relative narrowband Tx Power) exchanged between base stations may be used. Since RNTP is information indicating the transmission power for each resource block of each cell, the transmission power of each cell can be grasped by referring to this information at each base station. A cell having a small transmission power can be determined as a cell that does not interfere with an adjacent cell, and a cell having a large value as a cell that interferes with an adjacent cell. Also, when the positional relationship of each cell is known in advance, it is possible to generate interference source information for each resource block by considering the positional relationship and RNTP.

  In the present embodiment, information necessary for determining resource allocation is collected in the base station M and cells to be transmitted at the same time are determined. However, the base station that performs such control is not limited to the base station M, and is newly concentrated. A control station may be installed, the central control station only determines resource allocation, and the base station M may perform transmission control based on the resource allocation information determined by the central control station in the same manner as other base stations.

[Second Embodiment]
In the first embodiment, the interference source information is notified from each base station to the base station M (centralized control station), and the base station M gives a limit to the number of resources that can be used in each cell. A configuration is shown in which allocation information is determined and transmission is controlled in the base station of each cell according to the resource allocation information determined by the base station M. On the other hand, in this embodiment, the base station of each cell acquires information (resource allocation information) for limiting the number of available resources, and the base station of each cell is autonomous based on the information. Shows the configuration for determining the resources used. Furthermore, it is assumed that the base station M changes the resource allocation only when the resource allocation needs to be adjusted with another cell.

  The configurations of the base station and the terminal according to this embodiment are the same as those shown in FIGS. However, upper layer processing in each base station is different.

  First, an example in which the base station M of the macro cell collectively generates resource allocation information in each cell will be described. FIG. 8 is a flowchart showing the flow of processing of the upper layer of the base station M in this case. The difference from the upper layer processing (FIG. 5) in the first embodiment is that step S108 and step S110 in FIG. 5 are added to step S203 and step S202 in FIG. 8, respectively. Is Rukoto. Note that the processing indicated by the same reference numerals in FIG. 5 and FIG. 8 as in step S101 is the same processing as in FIG.

  In step S201, resource allocation in each cell is determined in the order of the groups rearranged in step S106. Here, the resource allocation information represents the ratio of resource allocation in each cell. For example, if the resource allocation information is 1, all resources can be used, and if the resource allocation information is 2/3, all resources can be used. This means that 2/3 of the resources can be used.

  When j = 1, the resource allocation information of each cell of the macro cell, the pico cell 1 and the femto cell 1 is set to 1/3 for the group 1 whose overlap number is 3.

  When j = 2, the resource allocation information is determined for group 2, but when j = 1, the macro cell resource allocation information is determined to be 1/3, so the remaining cells (picocell 2, femtocell 2a The remaining resources are allocated in the femtocell 2b). However, the same resources are allocated to cells having the same hierarchy (femtocell 2a and femtocell 2b). Therefore, in the group 2, resources other than the macro cell (1-1 / 3) may be allocated to the pico cell and the femto cell, and the resource allocation information of the cells other than the macro cell is (1-1 / 3) / 2 = 1. / 3.

  When j = 3, the resource allocation information for the group 3 is determined. Since the overlap number of the group 3 is 2, and the overlap number is smaller than the groups 1 and 2, the cells belonging to the group 3 have more cells. Resources can be used. Specifically, since the femtocell 3 allocates resources other than resources already allocated to the macrocell to the femtocell, the resource allocation information of the femtocell 3 is (1-1 / 3) / 1 = 2/3. Become.

  When j = 4, the resource allocation of the pico cell 4 is (1-1 / 3) / 1 = 2/3 for the group 4 as well as the group 3.

  In step S202, the resource allocation information determined in step S201 is notified to each base station via a wired network.

  The processes after step S203 are processes common to the respective base stations, and the number of resources that can be used in the own cell is grasped based on the resource allocation information notified from the base station M in each base station. Then, a resource to be used in the own cell is determined within a range not exceeding the number of usable resources, and transmission processing is performed based on resource allocation information indicating the determined resource allocation.

  Here, resource allocation after grasping the number of available resources may be performed by each cell autonomously, and any method may be used, but in this embodiment, the number of available resources is determined. A method of selecting resources at random within a range not exceeding is used. Thus, in S203, resource allocation information is determined using random numbers or the like based on the resource allocation information notified from the base station M. Specifically, the resources to be used can be determined by processing such as generating positive integers as many as the number of available resources and using the resources corresponding to the numbers.

  FIG. 9 is a table showing an example of resource allocation information. FIG. 9A shows a case where each base station independently determines resource allocation based on the resource allocation allocation determined in the upper layer of the base station M. As shown in FIG. 9 (a), the number of resources that each cell can use is limited according to the overlap number in each group, and by providing such a limitation, each cell autonomously allocates resources. Even when selected and used, it is possible to reduce probabilistically the situation in which cells that interfere with each other use the same resource. Thereby, efficient transmission can be realized.

  Furthermore, when there are a plurality of cells of the same layer in the same group (in this embodiment, femtocell 2a and femtocell 2b), it is also possible to control so that cells of the same layer have the same resource allocation. is there. In this case, it can be realized by notifying those corresponding cells of a common initial value for generating a random number in step S201 so that the same random number is generated in the process of step S205 in each base station. Here, the common initial value may use, for example, any one cell ID of the corresponding cells, and is not limited to this and may be any value as long as it is common.

  FIG. 9B shows a case where each base station independently determines resource allocation based on the resource allocation information notified from the base station M and the initial value, and the base station of each cell uniquely allocates the resource. In spite of the determination, it is possible to specify the same resource allocation for cells in the same hierarchy as in the base station F2a and the base station F2b. FIG. 9C shows a case where the base station F1, the base station F2a, and the base station F2b are allocated so as to have the same resource. In this case, the base station M This can be realized by giving the same initial values as those of the base station F2a and the base station F2b.

  In addition, here, an example is shown in which the base station M of the macro cell collectively determines the resource allocation information. However, each cell can calculate the resource allocation information if it can recognize the overlapping number of the group to which the cell belongs. Therefore, it is not always necessary for the base station M to collectively determine the resource allocation information. Therefore, each base station may acquire information indicating a duplication number or a hierarchy, calculate resource allocation information based on the information, and grasp the limitation on the number of resources that can be used by itself.

  In the above embodiment, time resources are allocated based on the overlapping number, but may be applied to frequency (subchannel) resource allocation. In LTE or the like using a plurality of subchannels, the terminal selects several subchannels that can obtain good reception quality, and feeds back the channel quality (CQI; Channel Quality Information) to the base station. Based on the quality of each channel and the overlapping number, the subchannels with good quality may be selected within the range of the number of usable subchannels. In addition, when the resource allocation method according to the present embodiment is applied to such a system, for example, CQIs of four subchannels are fed back in a duplicate cell, and two subchannels are fed in a duplicate cell. The number of subchannels that feed back CQI, such as feeding back the CQI of the channel, may be set according to the overlap number. In other words, the number of subchannels to which CQI is fed back is set according to a value of duplication (information indicating the type of cell) obtained by quantifying the situation where each cell is placed. Thus, the number of subchannels to be fed back is determined and feedback is performed. The duplication number is a value that limits the number of resources that each cell can use, and the CQI is a value that serves as an index for selecting a resource. Therefore, by setting the number of CQIs to be fed back according to the duplication number, Efficient feedback can be realized. Furthermore, the number of CQIs to be fed back is changed depending on whether the cell itself is a macro cell, a pico cell, or a femto cell, and the number of CQIs to be fed back is set considering only the overlapping number. You may enable it to make a finer setting than the case where it does. For example, the number of feedback is 3 for the macro cell of overlap 3, the number of feedback of 3 is the pico cell of overlap 3, the number of feedback is 2 for the femto cell, the number of feedback is 5 for the macro cell of overlap 2, and the number of feedback is the pico cell of overlap 2. It can also be set to four.

  Moreover, in said embodiment, about the structure etc. which are illustrated in drawing, it is not limited to these, In the range which exhibits the effect of this invention, it can change suitably. In the above-described embodiment, the transmission is performed from the base station to the terminal (downlink), but may be applied to the uplink. In addition, various modifications can be made without departing from the scope of the object of the present invention.

  In addition, a program for realizing the functions described in the present embodiment is recorded on a computer-readable recording medium, and the program recorded on the recording medium is read into a computer system and executed to execute processing of each unit. May be performed. The “computer system” here includes an OS and hardware such as peripheral devices.

  Further, the “computer system” includes a homepage providing environment (or display environment) if a WWW system is used.

  The “computer-readable recording medium” refers to a storage device such as a flexible medium, a magneto-optical disk, a portable medium such as a ROM and a CD-ROM, and a hard disk incorporated in a computer system. Furthermore, the “computer-readable recording medium” dynamically holds a program for a short time like a communication line when transmitting a program via a network such as the Internet or a communication line such as a telephone line. In this case, a volatile memory in a computer system serving as a server or a client in that case, and a program that holds a program for a certain period of time are also included. The program may be a program for realizing a part of the above-described functions, or may be a program that can realize the above-described functions in combination with a program already recorded in a computer system.

  As described above, according to the present invention, a microcell having a large zone radius and covering a wide range includes a picocell having a small zone radius and a femtocell having a smaller zone radius than a picocell in various situations. In existing cellular systems with complex environments, resource allocation is performed in consideration of the situation of each cell and the surrounding conditions, thereby reducing the effects of inter-cell interference and improving efficiency. Resource allocation can be performed.

  The present invention is applicable to a cellular system.

DESCRIPTION OF SYMBOLS 10 Reception antenna 11 Radio | wireless part 12 A / D part 13 Reception part 14 High-order part 15 Encoding part 16 Modulation part 17 S / P conversion part 18 Subcarrier allocation part 19 Reference signal multiplexing part 20 IFFT part 21 CP insertion part 22 D / A Unit 23 radio unit 24 transmission antenna 30 reception antenna 31 radio unit 32 A / D unit 33 CP removal unit 34 FFT unit 35 reference signal separation unit 36 propagation path estimation unit 37 subcarrier extraction unit 38 P / S conversion unit 39 demodulation unit 40 Decoding unit 41 Interference state estimation unit 42 Transmitting unit 43 D / A unit 44 Radio unit 45 Transmitting antenna

Claims (9)

  A cellular system in which a plurality of types of cells having a covering area narrower than the first cell and having different covering area widths exist in the first cell, wherein resource allocation in each cell A cellular system comprising a resource allocating device that performs based on a numerical value representing an arrangement relationship with a cell.   2. The cellular system according to claim 1, wherein there are three or more types of the arrangement relationship, and the numerical value representing the arrangement relationship is a numerical value of three or more stages.   3. The numerical value representing the arrangement relationship is a value obtained by quantifying a relationship in which the first cell and a plurality of cells existing in the first cell overlap each other. Cellular system.   The cellular system according to any one of claims 1 to 3, wherein a base station device that controls each cell acquires a numerical value representing the arrangement relationship.   5. The number of resources that can be used in each cell is calculated based on a numerical value that represents the arrangement relationship, and resource allocation is performed within a range that does not exceed the number of available resources. 2. A cellular system according to item 1.   The first cell is a macro cell, and the plurality of types of cells having a cover area narrower than that of the first cell and having different cover area sizes include a pico cell and a femto cell. The cellular system according to any one of 1 to 5.   A resource allocation apparatus for a cellular system in which a plurality of types of cells in which a cover area is narrower than the first cell and a coverage area is different exist in the first cell, and the resource allocation in each cell A resource allocating device comprising means for performing the processing based on a numerical value representing an arrangement relationship with another cell. A resource allocation method in a cellular system in which a plurality of types of cells in which a covering area is narrower than the first cell and a covering area is different in a first cell exist,
A resource allocation device obtaining interference source information, which is information about interference with other cells in each cell;
A resource allocating device grouping cells that interfere with each other based on the interference source information;
A step in which the resource allocation device determines a numerical value representing an arrangement relationship with other cells for each group;
A resource allocating apparatus that allocates resources to each cell in each group according to a numerical value representing the arrangement relationship.   A program for causing a computer to execute the resource allocation method according to claim 8.

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