WO2010137313A1 - 周波数割当装置およびプログラム - Google Patents
周波数割当装置およびプログラム Download PDFInfo
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- WO2010137313A1 WO2010137313A1 PCT/JP2010/003533 JP2010003533W WO2010137313A1 WO 2010137313 A1 WO2010137313 A1 WO 2010137313A1 JP 2010003533 W JP2010003533 W JP 2010003533W WO 2010137313 A1 WO2010137313 A1 WO 2010137313A1
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W72/00—Local resource management
- H04W72/50—Allocation or scheduling criteria for wireless resources
- H04W72/54—Allocation or scheduling criteria for wireless resources based on quality criteria
- H04W72/541—Allocation or scheduling criteria for wireless resources based on quality criteria using the level of interference
Definitions
- the present invention relates to a frequency allocation device and a program.
- This application claims priority based on Japanese Patent Application No. 2009-127644 filed in Japan on May 27, 2009, the contents of which are incorporated herein by reference.
- next generation cellular systems such as LTE (Long Term Evolution: official name is Evolved Universal Terrestrial Radio Access (E-UTRA)) and UMB (Ultra Mobile ⁇ ⁇ Broadband) are the successors of the third generation (3G) cellular system.
- 3rd Generation Generation Partnership Project is a study of standards related to IMT-Advanced system (also referred to as 4G cellular system), which is an evolution of 3.9G cellular system.
- 3GPP2 (3rd Generation Partnership Project 2) and IEEE 802.16 standardization organizations.
- OFDMA Orthogonal Frequency Division Multiple Multiple Access
- each subcarrier in a band can be allocated to a plurality of mobile stations (user terminals).
- the mobile station to which each subcarrier is allocated can be changed in the time axis direction. That is, in the OFDMA system, since radio resources are managed in two dimensions, the frequency axis and the time axis, radio resources can be flexibly allocated.
- the same frequency band is reused by a plurality of cells (hereinafter, “cell” includes “sector”) in order to increase frequency use efficiency.
- the technique of reusing all frequency bands available in the cellular system in all cells is called “one cell repetition”.
- CDMA Code Division Multiple Access
- communication channels can be separated by code even if the same frequency band is shared by adjacent cells.
- FDMA and OFDMA if the same frequency band is shared by adjacent cells, interference occurs and causes communication quality degradation.
- the signal power level is low and the interference power amount of an adjacent cell is high. It is easy to invite a decline.
- FFR Fractional Frequency Reuse
- a frequency band F4 different from the frequency bands F1, F2, and F3 allocated to the cell edge region is allocated to the cell center region. That is, in this example, the cell edge region is “3 cell repetition” and the cell center region is “1 cell repetition”.
- the frequency bands F1, F2, and F3 assigned to the cell edge region are reused (assigned) to the cell center region, but are assigned to the cell edge region of the own cell.
- a frequency band different from the determined frequency band is assigned to the cell center region. For example, frequency bands F2 and F3 different from the frequency band F1 are assigned to the cell center area of the sector to which the frequency band F1 is assigned to the cell edge area.
- Patent Document 1 proposes a technique of applying radio resources in an orthogonal relationship to a cell edge region and applying radio resources in a quasi-orthogonal state that is not completely in an orthogonal relationship to a cell center region.
- Non-Patent Documents 1 to 4 and Patent Document 1 allocate frequency channels other than the frequency channel allocated to the cell edge region in the adjacent cell to the cell edge region of the own cell. Yes. For this reason, the effect of reducing the amount of interference can be obtained.
- Non-Patent Document 5 defines control information that seems to be applicable to FFR. For example, the control information of the interface between base stations in the LTE system shown in (1) and (2) below is defined. In Patent Document 2, information called OI (to be described later) indicating the amount of interference is used in the control information defined in Non-Patent Document 5, and uplink (UL: Up-Link) is used. Has proposed a power control method for reference signals and control channels.
- Control information RNTP Relative Narrowband Tx Power related to downlink (DL): A binary variable indicating the size of usable transmission power. It is notified to neighboring cells. For example, the RNTP has a value “1” when the transmission power related to each RB exceeds a threshold, and a value “0” when the transmission power is less than the threshold (see Non-Patent Document 5).
- HII High Interference Indication
- OI Overload Indication
- FIG. 5 shows the concept of radio resources in the OFDMA system.
- a radio resource defined by one subcarrier having a bandwidth of 180 kHz and one subframe having a time of 1 millisecond is referred to as a resource block (RB).
- RB resource block
- the number of subcarriers is 12.
- the base station of the cellular system determines a mobile station to which each RB is allocated (in terms of Non-Patent Document 6, this corresponds to UE (: User Equipment)).
- 3GPP TS 36.423 “Evolved Universal Terrestrial Radio Access Network (E-UTRAN), X2 application protocol (X2AP).
- E-UTRAN Evolved Universal Terrestrial Radio Access Network
- X2AP X2 application protocol
- 3GPP TS 36.211 “Evolved Universal Terrestrial Radio Access (E-UTRA); Physical Channels and Modulation (Release 8).”
- 3GPP TS 36.214 “Evolved Universal Terrestrial Radio Access (E-UTRA); Physical layer Measurements (Release 8).”
- a static FFR (FIGS. 4A and 4B shown in FIG. 4A and FIG. 4B) is premised on a static environment in which the traffic volume is uniform in all regions to be evaluated.
- FFR fixed (uniform) cell shape (cell structure), fixed (regular) cell arrangement, FFR such that the boundary between the cell center area and the cell edge area is constant and common to all cells Is assumed.
- the actual environment there is a variation in the traffic volume, and the actual cell shape, cell arrangement, and the like change dynamically.
- the cell shape fluctuates due to the influence of the antenna directivity pattern, antenna tilt angle, radio wave propagation environment, and the like, and the cell arrangement fluctuates due to the establishment or abolition of cells. Therefore, even if the conventional FFR technique that assumes a static FFR is applied to an actual environment, it is difficult to obtain the effect of reducing the amount of interference. Further, a specific method of using the control information of the inter-base station interface for realizing dynamic FFR in accordance with the actual environment is implementation-dependent and is not described in Non-Patent Document 5. In addition, no means for realizing dynamic FFR using control information of an interface between base stations has been proposed.
- the present invention has been made in view of the above-described problems, and an object thereof is to provide a technique for reducing the amount of interference in a dynamic FFR adapted to a real environment.
- a frequency allocation apparatus includes a frequency allocation apparatus that allocates a frequency channel used for communication to a mobile station located in a first cell region of a first cell.
- a cell that is a frequency channel other than the frequency channel assigned to the mobile station located in the second cell edge region of the second cell by the adjacent frequency assignment device provided in the second cell adjacent to the one cell A cell edge region unallocated channel estimation unit that estimates an edge region unallocated channel, and a channel allocation unit that allocates the cell edge region unallocated channel to a mobile station located in the first cell region.
- the channel allocation unit allocates a channel edge region unallocated channel to all mobile stations that need to be allocated and are located in the first cell region.
- the channel allocation unit prioritizes a cell edge region unallocated channel over a mobile station located in the first cell central region of the first cell, and the first cell of the first cell. You may make it allocate with respect to the mobile station located in an edge area
- the channel allocation unit when the channel allocation unit cannot allocate a cell edge area unallocated channel to all mobile stations that are located in the first cell area and require allocation, the channel edge area unallocated channel May be allocated to a mobile station that is located in the first cell edge region and requires allocation.
- the channel allocation unit allocates a cell edge area unallocated channel to a mobile station that needs to be allocated and is located in the first cell edge area, and assigns a frequency channel other than the cell edge area unallocated channel.
- the remaining assignable frequency channel may be assigned to the mobile station that requires remaining allocation.
- the cell edge region unassigned channel estimation unit determines whether each frequency channel is assigned to the mobile station located in the second cell edge region for each frequency channel from the adjacent frequency assignment device.
- a frequency channel having a cell edge region allocation likelihood less than a threshold may be estimated as a cell edge region unallocated channel.
- the frequency allocation apparatus further includes a cell edge region allocation presence / absence determination unit that determines whether or not each frequency channel is allocated to a mobile station located in the first cell edge region based on an allocation result by the channel allocation unit.
- the cell edge region allocation presence / absence determination unit may transmit the determination result to the adjacent frequency allocation device.
- a frequency allocation apparatus is a frequency allocation in which a frequency channel allocated to a mobile station stationary in the cell area of the first cell is changed over time.
- a frequency channel other than a frequency channel assigned to a mobile station located in a cell edge region of the second cell by another frequency assignment device provided in a second cell adjacent to the first cell The frequency channel estimated to be is assigned to the mobile station located in the end area of the first cell with priority over the mobile station located in the center area of the first cell.
- a program provides a computer of a frequency allocation device that allocates a frequency channel used for communication to a mobile station located in a first cell region of a first cell.
- the frequency channel other than the frequency channel allocated to the mobile station located in the second cell edge region of the second cell by the adjacent frequency allocation device provided in the second cell adjacent to the first cell.
- a cell edge region unassigned channel estimation step for estimating a cell edge region unassigned channel and a channel assignment step for assigning the cell edge region unassigned channel to a mobile station located in the first cell region are executed.
- frequency channels other than the frequency channel assigned to the cell edge region in the adjacent cell are assigned to the cell edge region of the own cell. Can be reduced.
- the base station apparatus 1 and the base station apparatus 1 'adjacent thereto constitute a cellular system as shown in FIG.
- the base station apparatus 1 performs communication in the cell j, and the base station apparatus 1 'performs communication in the cell j'.
- Each cell j and j ' is composed of a cell center region and a cell edge (cell edge) region located in the periphery thereof.
- the base station apparatus 1 is demonstrated as a base station apparatus which comprises a LTE system.
- the base station devices 1 and 1 ′ have the presence / absence of assignment of control information (RNTP, HII, etc.
- Non-Patent Document 5 to the mobile station in the cell edge region of each frequency channel in the LTE system. It is used as information indicating. Since the exchange period of the control information between base stations is not defined in Non-Patent Document 5, it is set at the time of system design or system operation in view of the load on the network between base stations. As an example, the exchange period may be about several tens of milliseconds, for example.
- Base station apparatuses 1 and 1 'employ dynamic FFR technology. That is, the base station apparatuses 1 and 1 ′ allocate frequency channels to be used for communication to mobile stations located in the cells j and j ′, respectively, but also allocate frequency channels to be allocated to stationary mobile stations. Can change from moment to moment.
- a stationary mobile station is a mobile station whose position does not change within a certain period of time, that is, a mobile station that has not moved. In other words, in the mobile station located in the cell j, the base station apparatus 1 can change the allocation of the frequency channel of the mobile station over time even during stationary communication. it can.
- the base station apparatus 1 includes a frequency allocation unit 10 (wireless packet scheduler), an information acquisition unit 11 and a wireless access control unit 12.
- the frequency allocation unit 10 further includes an allocatable channel identification unit 100, a cell edge region unallocated channel estimation unit 110, a channel allocation unit 130, a cell edge region determination unit 120, and a cell edge region allocation presence / absence determination unit 140.
- the adjacent base station apparatus 1 ′ has the same configuration as the base station apparatus 1 and includes a frequency allocation unit 10 ′.
- the information acquisition unit 11 acquires information necessary for frequency channel allocation (for example, system specifications, various parameter values, and radio channel quality information). The information acquisition unit 11 supplies the acquired information to the allocatable channel identification unit 100, the cell edge region determination unit 120, and the channel allocation unit 130.
- information necessary for frequency channel allocation for example, system specifications, various parameter values, and radio channel quality information.
- the assignable channel specifying unit 100 specifies an assignable frequency channel (RB) based on the information acquired by the information acquiring unit 11. Specifically, the assignable channel specifying unit 100 obtains a set of assignable frequency channels and supplies the set to the channel assigning unit 130.
- RB assignable frequency channel
- the frequency allocation unit 10 ′ in the base station apparatus 1 ′ disposed in the adjacent cell j ′ allocates a frequency channel used for communication to a mobile station located in the cell edge region of the cell j ′.
- the cell edge region unassigned channel estimation unit 110 estimates a cell edge region unassigned channel which is a frequency channel other than the frequency channel assigned to the mobile station in the cell edge region by the frequency assignment unit 10 ′. Specifically, the cell edge region unassigned channel estimation unit 110 determines whether or not each frequency channel is assigned to the mobile station in the cell edge region of the cell j ′ from the frequency assignment unit 10 ′. Get the judgment result.
- the estimation unit 110 calculates a cell edge region allocation likelihood indicating the probability that each frequency channel is allocated to a mobile station in the cell edge region of the cell j ′ based on the obtained determination result, A frequency channel having a cell edge region allocation likelihood less than a threshold is estimated as a cell edge region unallocated channel.
- the cell edge region unallocated channel estimation unit 110 supplies information indicating the estimated cell edge region unallocated channel to the channel allocation unit 130.
- the cell edge region unassigned channel estimation unit 110 estimates a frequency channel that is not assigned to a mobile station in the cell center region in addition to the cell edge region unassigned channel. Also good.
- the cell edge area determination unit 120 determines whether the location of each mobile station in the cell j is a cell edge area based on the radio channel quality information acquired by the information acquisition unit 11.
- the cell edge region determination unit 120 supplies the determination result as to whether or not each mobile station is located in the cell edge region to the channel allocation unit 130 and the cell edge region allocation presence / absence determination unit 140.
- the channel allocation unit 130 allocates the cell edge region unallocated channel estimated by the cell edge region unallocated channel estimation unit 110 to all mobile stations that require allocation in the cell j region. Specifically, channel assignment section 130 assigns a cell edge region unassigned channel to a mobile station in the cell edge region with priority over a mobile station in the cell center region in cell j.
- channel allocator 130 cannot allocate a cell edge region unallocated channel to all mobile stations that require allocation in the cell region, that is, there is a cell terminal allocated channel that only transmits all packets of all mobile stations. There may be no case.
- the channel allocation unit 130 allocates a cell edge region unassigned channel to a mobile station that requires assignment in the cell edge region and assigns a frequency channel other than the cell edge region unassigned channel in the cell center region.
- the traffic load is low (when the number of frequency channels that can be used is larger than the traffic volume), it is highly possible that the cell edge area unallocated channel can be allocated to all mobile stations, and the traffic load is high. If it is high, the possibility is low.
- the channel allocation unit 130 allocates a cell edge area unallocated channel to a mobile station that requires allocation in the cell edge area and moves a frequency channel other than the cell edge area unallocated channel that requires allocation in the cell center area.
- the remaining assignable frequency channels are assigned to mobile stations that need the remaining assignment.
- the frequency allocation algorithm is not particularly limited, for example, a proportional fairness algorithm is used.
- the channel allocation unit 130 supplies the allocation result to the radio access control unit 12 and the cell edge region allocation presence / absence determination unit 140.
- the radio access control unit 12 performs access control and packet transmission / reception processing in the radio physical layer based on the allocation result by the channel allocation unit 130.
- the cell edge region allocation presence / absence determination unit 140 detects which frequency channel is allocated to each mobile station in the cell edge region based on the allocation result by the channel allocation unit 130 and allocates each frequency channel. The presence or absence of is determined. Cell edge region allocation presence / absence determination section 140 transmits the determination result to the adjacent frequency allocation apparatus.
- a resource block of the LTE system (hereinafter referred to as “RB”) is used as a specific example of the frequency channel.
- ) k ID of RB (or ID of a resource block group (RBG) composed of a plurality of RBs).
- A A set of RBs that can be allocated within the system band. However, when “Persistent allocation” suitable for initial transmission of a VoIP (Voice over IP) call or “Retransmission packet allocation” in Hybrid ARQ is given priority, RBs allocated by these are excluded from the set A.
- p (j, k) Bitmap information indicating the determination result of whether or not RBk is allocated to the mobile station in the cell edge area of own cell j. It is notified to neighboring cells using RNTP or HII.
- e (j, k) Variable indicating whether or not RBk is assigned to the mobile station in the cell edge area in the neighboring cell of own cell j
- E (j) Cell edge in the neighboring cell adjacent to own cell j A set of RBs (cell edge region unallocated RBs) having a high probability (likelihood) assigned to mobile stations in the region.
- Cell edge area unallocated channel group (cell edge area unallocated RB group).
- r (i, j, t) instantaneous value of RSRP value (or RSRQ value) of cell j in radio frame t at mobile station i
- R (i, j, t) cell in radio frame t at mobile station i
- R (i, j, t) E ⁇ r (i, j, t) ⁇ (1)
- E ⁇ is a function which calculates
- Prob (k) number of times RBk is assigned to the mobile station in the cell edge area during ⁇ T / total number of RBs assigned during ⁇ T ... (2)
- the cell edge region allocation presence / absence determining unit 140 may calculate Prob (k) by applying an exponential smoothing filter using the past Prob (k). Further, the cell edge region allocation presence / absence determination unit 140 may calculate Prob (k) according to the following equation (3) when the number of times allocated to RBk is sufficiently large.
- Prob (k) number of times RBk is assigned to the mobile station in the cell edge area during ⁇ T) / number of times RBk is assigned during ⁇ T ... (3)
- the cell edge region allocation presence / absence determination unit 140 generates p (j, k) according to the following formulas (4) and (5).
- Cell edge region unallocated channel estimation section 110 calculates e (j, k) according to the following equation (6).
- Cell edge region unallocated channel estimation section 110 calculates E (j) according to the following equation (7).
- RSRP Reference Signal Received Power
- RSRQ Reference Signal Received Quality
- RSRQ N ⁇ RSRP / (E-UTRA carrier RSSI)... (8)
- N is the number of RBs in the measurement band.
- E-UTRA carrier RSSI is an average value of the sum of received power (W) observed in a measurement band composed of N RBs only for OFDM symbols including a reference signal. The average value includes interference power and noise power.
- region determination part 120 determines with it being a cell edge area
- the cell edge region determination unit 120 may determine that the cell edge region is a cell edge region when the following equation (10) is satisfied instead of the following equation (9).
- the cell edge region determination unit 120 accumulates past r (i, j, t) for all mobile stations in the cell j, and accumulates the probability distribution P r (j, j, in the cell j in the radio frame t. If t) is calculated and the following equation (11) is satisfied, it may be determined that the region is a cell edge region.
- Cell edge area determination section 120 all mobile stations intended for R in the cell j (i, j, t) accumulated historical data, the cumulative probability distribution of cell j in the radio frame t P R (j, t ) And the following equation (12) is satisfied, the cell edge region may be determined. P R (j, t) ⁇ C 2 (12)
- the cell edge area determination unit 120 determines the cell center area and the cell edge area as shown in FIG.
- the allocatable channel specifying unit 100 calculates an allocatable RB group (set A) based on the information acquired by the information acquisition unit 11, and assigns the allocatable RB group (set A) to the channel allocation unit 130. Supply (step S100).
- the cell edge region unallocated channel estimation unit 110 is based on a determination result (p (j ′, k)) that determines whether or not there is an assignment to a mobile station in the cell edge region of each RB acquired from the adjacent base station apparatus 1. Then, the cell edge region unallocated RB group (set E (j)) is estimated (step S110). The cell edge region unallocated channel estimation unit 110 supplies the estimated cell edge region unallocated RB group (set E (j)) to the channel allocation unit 130.
- the channel allocation unit 130 allocates each RB of the cell end area unallocated RB group (set E (j)) to all mobile stations that require allocation in the cell area (in the cell edge area and in the cell center area) (Ste S120).
- Channel assignment section 130 determines whether or not an unassigned mobile station that requires RB assignment remains in the cell area (in the cell edge area and in the cell center area) (step S130). That is, the channel allocation unit 130 determines whether or not each RB has been allocated to all the mobile stations.
- channel assignment section 130 determines that there are no unassigned mobile stations that require RB assignment remaining in the cell area (in the cell edge area and in the cell center area) (step S130: No).
- this flowchart ends.
- the RB having a low probability of being used in the cell edge region of the adjacent cell is assigned to all the mobile stations in the cell, interference with the adjacent cell is less likely to occur.
- the traffic load is low, there is a high possibility that each RB of the cell edge region unallocated RB group (set E (j)) can be allocated to all mobile stations.
- channel assignment section 130 determines that an unassigned mobile station that requires RB assignment remains in the cell area (in the cell edge area and in the cell center area) (step S130: Yes), That is, if it is determined that the RBs cannot be assigned to all the mobile stations, the assignment in step S120 is reset (step S140). Subsequent to step S140, the channel allocation unit 130 allocates each RB of the cell end region unallocated RB group (set E (j)) to the mobile station that needs to be allocated in the cell end region, and Each RB of the RB group (set A-set E (j)) other than the cell edge region unassigned RB group is assigned to the mobile station that needs to be assigned (step S150).
- channel allocation section 130 determines whether or not an unallocated mobile station requiring RB allocation remains in the cell area (in the cell edge area and in the cell center area) (step S160). ). That is, the channel allocation unit 130 allocates each RB of the cell end region unallocated RB group (set E (j)) to all mobile stations that need to be allocated in the cell end region, and allocates the allocation in the cell center region. It is determined whether or not each RB of the RB group (set A-set E (j)) other than the cell edge region unassigned RB group has been assigned to all the required mobile stations.
- step S160 determines that there is no unassigned mobile station that requires RB assignment in the cell area (in the cell edge area and in the cell center area) (step S160: No), that is, All RBs in the cell edge area unallocated RB group (set E (j)) are assigned to all mobile stations that require allocation in the cell edge area, and cells are assigned to all mobile stations that require assignment in the cell center area.
- the flowchart ends.
- an RB having a low probability of being used in the cell edge area of the adjacent cell is assigned to a mobile station in the cell edge area in the cell, and an RB having a high probability of being used in the cell edge area of the adjacent cell is assigned to the cell. Since it is assigned to the mobile station in the cell center area, interference with adjacent cells is hardly caused.
- step S160 when it is determined that an unallocated mobile station that requires RB allocation remains in the cell area (in the cell edge area and in the cell center area) (step S160: Yes), that is, in the cell edge area.
- RBs in the cell edge area unallocated RB group (set E (j)) could not be assigned to at least one of the mobile stations that need to be assigned, or at least of the mobile stations that need to be assigned in the cell center area
- the channel allocation unit 130 determines that the unallocated RB ( Whether or not each RB in the cell edge area unallocated RB group (set E (j)) or RB groups other than the cell edge area unallocated RB group (set A ⁇ set E (j)) remains) (Step S170) .
- step S170: No When the channel allocation unit 130 determines that the unallocated RB does not remain (step S170: No), the flowchart ends. On the other hand, when the channel allocation unit 130 determines that the unallocated RB remains (step S170: Yes), the channel allocation unit 130 requires the unallocated RB to be allocated to the unallocated mobile station (cell edge region). A mobile station that has not been assigned an RB of the cell edge region unassigned RB group (set E (j)) in step S150, and a mobile station that needs to be assigned in the cell center region in step S150 The RBs other than the cell edge region unallocated RB group (set A-set E (j)) RBs are assigned (step S180). That is, RBs are allocated to as many mobile stations as possible while reducing interference with adjacent cells. And this flowchart is complete
- the amount of interference can be reduced in the dynamic FFR adapted to the actual environment.
- the frequency allocation unit 10 is a component of the base station apparatus 1, but the frequency allocation unit 10 is not a component of a certain apparatus but may be an independent apparatus (frequency allocation apparatus 10). Good.
- frequency allocation apparatus 10 includes assignable channel specifying section 100, cell edge area unassigned channel estimation section 110, channel assignment section 130, cell edge area determination section 120, and presence / absence of cell edge area allocation.
- a determination unit 140 is provided.
- the frequency allocation unit 10 is recorded by recording a program for executing each process of the frequency allocation unit 10 on a computer-readable recording medium, causing the computer system to read and execute the program recorded on the recording medium. 10 may be performed.
- the “computer system” may include 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” means a flexible disk, a magneto-optical disk, a ROM, a writable nonvolatile memory such as a flash memory, a portable medium such as a CD-ROM, a hard disk built in a computer system, etc. This is a storage device.
- the “computer-readable recording medium” means a volatile memory (for example, DRAM (Dynamic DRAM) in a computer system that becomes a server or a client when a program is transmitted through a network such as the Internet or a communication line such as a telephone line. Random Access Memory)), etc., which hold programs for a certain period of time.
- the program may be transmitted from a computer system storing the program in a storage device or the like to another computer system via a transmission medium or by a transmission wave in the transmission medium.
- the “transmission medium” for transmitting the program refers to a medium having a function of transmitting information, such as a network (communication network) such as the Internet or a communication line (communication line) such as a telephone line.
- the program may be for realizing a part of the functions described above. Furthermore, what can implement
- the present invention can be applied to an OFDMA system in which a plurality of mobile stations (user terminals) can be changed in the time axis direction and each subcarrier in a band can be assigned. Since the frequency channel other than the frequency channel assigned to the cell edge region in the adjacent cell is assigned to the cell edge region of the own cell, the amount of interference can be reduced.
- Base station apparatus Frequency allocation unit (frequency allocation apparatus) DESCRIPTION OF SYMBOLS 11 Information acquisition part 12 Radio
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Abstract
Description
本願は、2009年5月27日に、日本に出願された特願2009-127644号に基づき優先権を主張し、その内容をここに援用する。
(2)-1. HII(High Interference Indication):干渉の発生有無を示す2値変数。隣接セルに通知される。例えば、HIIは、各RBに大きな干渉が発生するときは値「1」、発生しないときは値「0」となる(非特許文献5)。
(2)-2. OI(Overload Indication):RB毎に、「high interference, medium interference, low interference」という情報を隣接セルに通知する。
チャネル割当部130は、割当結果を無線アクセス制御部12およびセル端領域割当有無判定部140に供給する。
i:移動局ID
j:自セル(Serving cell)のID
j’:自セルjに隣接する隣接セルのID(j’≠j)
J’:隣接セルj’の集合
N(j):自セルjの隣接セル数(=|J’|)
k:RBのID(または、複数のRBから構成されるリソースブロックグループ(RBG)のID)。
A:システム帯域内において割当可能なRBの集合。但し、VoIP(Voice over IP)呼の初送に適する“Persistent割当”やHybrid ARQでの“再送パケット用割当”が優先される場合は、集合Aからこれらによって割り当てられたRBを除外する。
p(j,k):自セルjのセル端領域内の移動局に対するRBkの割当の有無の判定結果を示すビットマップ情報。RNTP又はHIIを用いて隣接セルに通知される。
e(j,k):自セルjの隣接セルにおいてRBkがセル端領域内の移動局に割り当られているか否かを示す変数
E(j):自セルjに隣接する隣接セルにおいてセル端領域内の移動局に割り当られている確率(尤度)が高いRB(セル端領域未割当RB)の集合。セル端領域未割当チャネル群(セル端領域未割当RB群)。
r(i,j,t):移動局iにおける無線フレームtでのセルjのRSRP値(又はRSRQ値)の瞬時値
R(i,j,t):移動局iにおける無線フレームtでのセルjのRSRP値(又はRSRQ値)の長区間平均値。下記式(1)に従って算出される。
R(i,j,t)=E{r(i,j,t)}…(1)
但し、E{}は単純平均や指数平滑平均などの期待値を求める関数である。
ΔT:RNTP又はHIIの通知時間間隔
X1、X2、C1、C2:パラメータ
セル端領域割当有無判定部140によるビットマップ情報p(j,k)の生成手順を説明する。セル端領域割当有無判定部140は、Prob(k)≧X1を満たすとき、p(j,k)に割当有を示す値「1」をセットする。まず、セル端領域割当有無判定部140は、ΔT>サブフレーム長の場合、下記式(2)によってProb(k)を算出する。
p(j,k)=0,otherwise …(5)
セル端領域未割当チャネル推定部110は、下記式(6)に従ってe(j,k)を算出する。
セル端領域未割当チャネル推定部110は、下記式(7)に従ってE(j)を算出する。
セル端領域判定部120によるセル端領域の判定手順を説明する。なお、セル端領域の判定には、3GPPに規定されているRSRP(Reference Signal Received Power)とRSRQ(Reference Signal Received Quality)を用いる(非特許文献7参照)。RSRPとは、セル固有のリファレンス信号が配置されたOFDMシンボルとOFDMサブキャリアの組み合わせからなる無線リソースであるリソースエレメント(Resource Elements)におけるセル固有リファレンス信号の信号成分の受信電力(W)の総和を、セル固有リファレンス信号が送信されるリソースエレメントにより除算して得られる、平均のセル固有リファレンス信号受信電力値である。また、RSRQとは、下記式(8)から算出される値である
PR(j,t)≦C2 …(12)
10 周波数割当部(周波数割当装置)
11 情報取得部
12 無線アクセス制御部
100 割当可能チャネル特定部
110 セル端領域未割当チャネル推定部
120 セル端領域判定部
130 チャネル割当部
140 セル端領域割当有無判定部
Claims (8)
- 第1のセルの第1セル領域内に位置する移動局に通信に用いる周波数チャネルを割当てる周波数割当装置において、
前記第1のセルに隣接する第2のセルに設けられた隣接周波数割当装置が前記第2のセルの第2セル端領域内に位置する移動局に対して割り当てた周波数チャネル以外の周波数チャネルであるセル端領域未割当チャネルを推定するセル端領域未割当チャネル推定部と、
前記セル端領域未割当チャネルを前記第1セル領域内に位置する移動局に対して割り当てるチャネル割当部と
を備える周波数割当装置。 - 前記チャネル割当部は、前記セル端領域未割当チャネルを前記第1のセルの第1セル中心領域内に位置する移動局よりも優先させて前記第1のセルの第1セル端領域内に位置する移動局に対して割り当てる請求項1に記載の周波数割当装置。
- 前記チャネル割当部は、前記セル端領域未割当チャネルを前記第1セル領域内に位置し割当を要する全移動局に対して割り当てることができないときは、前記セル端領域未割当チャネルを前記第1セル端領域内に位置し割当を要する移動局に対して割り当てる請求項1に記載の周波数割当装置。
- 前記チャネル割当部は、前記セル端領域未割当チャネルを前記第1セル端領域内に位置し割当を要する移動局に対して割り当てるとともに前記セル端領域未割当チャネル以外の周波数チャネルを前記第1セル中心領域内に位置し割当を要する移動局に割り当てた場合において、残存する割当可能な周波数チャネルを、残存する割当を要する移動局に割り当てる請求項3に記載の周波数割当装置。
- 前記セル端領域未割当チャネル推定部は、前記隣接周波数割当装置から前記周波数チャネル毎に各周波数チャネルが前記第2セル端領域内に位置する移動局に対して割り当てられているかどうかを判定した判定結果を取得し、前記判定結果に基づいて前記各周波数チャネルが前記第1セル端領域内に位置する移動局に対して割り当てられる確からしさを示すセル端領域割当尤度を算出し、前記セル端領域割当尤度が閾値未満である周波数チャネルを前記セル端領域未割当チャネルとして推定する請求項1から請求項4の何れか1項に記載の周波数割当装置。
- 前記チャネル割当部による割当結果に基づいて、前記第1セル端領域内に位置する移動局に対する各周波数チャネルの割当の有無を判定するセル端領域割当有無判定部を更に備え、
前記セル端領域割当有無判定部は、前記判定結果を前記隣接周波数割当装置に送信する請求項5に記載の周波数割当装置。 - 第1のセルのセル領域内に静止している移動局に対して割り当てる周波数チャネルを経過的に変化させる周波数割当装置であって、
前記第1のセルに隣接する第2のセルに設けられた他の周波数割当装置が前記第2のセルのセル端領域内に位置する移動局に対して割り当てた周波数チャネル以外であると推定される周波数チャネルを前記第1のセルの中心領域内に位置する移動局よりも優先させて前記第1のセルの端領域内に位置する移動局に対して割り当てる周波数割当装置。 - 第1のセルの第1セル領域内に位置する移動局に通信に用いる周波数チャネルを割当てる周波数割当装置のコンピュータに、
前記第1のセルに隣接する第2のセルに設けられた隣接周波数割当装置が前記第2のセルの第2セル端領域内に位置する移動局に対して割り当てた周波数チャネル以外の周波数チャネルであるセル端領域未割当チャネルを推定するセル端領域未割当チャネル推定ステップと、
前記セル端領域未割当チャネルを前記第1セル領域内に位置する移動局に対して割り当てるチャネル割当ステップと
を実行させるプログラム。
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JP2013529443A (ja) * | 2011-04-27 | 2013-07-18 | 株式会社エヌ・ティ・ティ・ドコモ | セルラマルチユーザネットワークの部分的再使用による干渉調整を用いる負荷認識型動的セル選択 |
WO2014034679A1 (ja) * | 2012-08-27 | 2014-03-06 | 富士通株式会社 | 無線通信システム及び基地局 |
JP2014517598A (ja) * | 2011-05-17 | 2014-07-17 | 華為技術有限公司 | リソース配分のための方法、装置、及び基地局 |
WO2022138392A1 (ja) * | 2020-12-25 | 2022-06-30 | Hapsモバイル株式会社 | 基地局装置、プログラム、システム及び制御方法 |
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