JP2012222398A - Distributed antenna network system and channel allocation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a distributed antenna network system that can uniquely determine a channel to be selected in a distributed antenna system.SOLUTION: A central processing center 10 measures an average interference power of each distributed antenna for all channels (step S10), stores the average interference powers of all the channels after sorting them in ascending order of power in an interference table (step S11). A radio terminal 13 measures the average reception powers of beacons from distributed antennas located in the vicinity when a communication request occurs (step S12), and determines an antenna cluster and its cluster head based on the amplitude of the beacon average reception powers (step S13). The central processing center 10 allocates a channel which is unused and has the smallest interference power to communication (step S14) and starts communication.

Description

  The present invention relates to a distributed antenna network system in which a large number of antennas are distributed in a communication area, and a channel allocation method.

  In mobile radio communication, a limited number of channels are effectively used by arranging a large number of base stations in a service area and reusing the same channel at base stations sufficiently distant from each other. How to assign a channel to each base station is called channel assignment. Well-known is fixed channel allocation (FCA) (see Non-Patent Document 1, for example). In FCA, all available channels are divided into a plurality of groups, and each channel group is assigned to a different base station.

  FIGS. 10A to 10C are conceptual diagrams illustrating examples of FCAs with channel group numbers N = 3, 4, and 7, respectively. As shown in FIGS. 10A to 10C, as the number N of channel groups is increased, base stations using the same channel group are sufficiently separated. Therefore, co-channel interference becomes sufficiently weak and communication quality is improved. However, since the number of channels per channel group (that is, per base station) decreases, the channel utilization efficiency decreases.

  On the other hand, if the number of channel groups is reduced, the number of channels per base station increases. However, since the distance between the base stations using the same channel group becomes close, strong co-channel interference is received, so that the probability that the required communication quality is not satisfied increases. Therefore, it is necessary to allocate as many channels as possible to each base station while satisfying the required communication quality. However, the traffic varies from moment to moment, and the radio wave propagation environment depends on the location. Maximizing efficiency is extremely difficult.

  Therefore, many centralized control type dynamic channel assignment (DCA) has been proposed in which channels are dynamically allocated so as to satisfy required communication quality by adapting to traffic fluctuations and surrounding propagation environments. However, the calculation amount of the central control center is enormous and there is a problem that it is not practical. In order to solve this problem, an autonomous distributed control type DCA in which each base station autonomously assigns a channel has been studied. Among them, there is an autonomous distributed DCA that uses channel segregation (see, for example, Non-Patent Document 2).

  In channel segregation, a priority table representing past interference states of all channels is prepared for each base station. Each time a channel is assigned, the channel with the highest priority is selected, the interference of the channel is measured, and it is determined whether the amount of interference is less than the allowable value. If the amount of interference is less than the allowable value, the channel is assigned. Otherwise, the channel with the next highest priority is selected, and it is determined whether or not the interference amount is less than or equal to the allowable value. If the interference amount is less than or equal to the allowable value, the channel is assigned. Otherwise, this operation is repeated until a channel whose interference amount is less than or equal to the allowable value is found.

  Update the priority order of channels that have been successfully allocated (that is, the amount of interference is less than or equal to the allowable value) and channels that have been unsuccessful (that is, the amount of interference is greater than or equal to the allowable value) with a predetermined calculation formula. Reference 2). This channel segregation enables dynamic channel allocation while each base station is autonomously distributed.

  On the other hand, recently, development of ultrahigh-speed wireless communication technology exceeding 1 gigabit / second is required. In such ultra-high-speed wireless communication, if the transmission power is kept at a practical value, the communication distance becomes considerably short due to communication loss due to propagation loss, shadowing loss, and deterioration of communication quality due to multipath fading. Only high-speed wireless communication can be performed in the immediate vicinity of the station. Therefore, recently, as shown in FIG. 11, a central processing center 1 is used instead of a base station, and a large number of antennas 3, 3,. Distributed antenna networks (DAN: see non-patent document 3, for example) or a distributed antenna system in which the central processing center 1 and the wireless terminal 4 communicate with each other are actively researched.

  Since several distributed antennas are found near the wireless terminal 4, the required quality can be ensured even with low transmission power. Moreover, the required transmission power required in order to ensure required communication quality can further be reduced by performing diversity transmission / reception using the plurality of distributed antennas 3, 3,. If the required transmission power is reduced, co-channel interference is reduced, so that the same channel can be reused closer.

W.C.Jakes, Jr., Microwave Mobile Communications, Wiley, 1974. Y. Furuya and Y. Akaiwa, “Channel Segregation, A Distributed Adaptive Channel Allocation Scheme for Mobile Communication Systems,” IEICE Trans., Vol.E 74, No.6, pp.1531-1537, June 1991. F. Adachi, K. Takeda, T. Obara, and T. Yamamoto, “Recent Advances in Single-carrier Frequency-domain Equalization and Distributed Antenna Network,” IEICE Trans. Fundamentals, Vol. E93-A, No. 11, pp .2201-2211, Nov. 2010. Ryusuke Matsukawa, Daiki Matsuda, Kazuki Takeda, Fumiyuki Adachi, “BER Distribution of Downlink Distributed Antenna Network Using Space-Time Coded Transmit / Receive Diversity,” IEICE General Conference, B-5-118, p.550, March 2010 . K. Takeda and F. Adachi, “Frequency-domain MMSE Channel Estimation for Frequency-domain Equalization of DS-CDMA Signals,” IEICE Trans. Commun., Vol.E90-B, No.7, pp.1746-1753, July 2007.

  By the way, until now, the channel allocation in DAN has not been studied. In DAN, since a plurality of distributed antennas (called antenna clusters) are selected for each wireless terminal, if the conventional channel segregation algorithm is used as it is, the contents of the priority table of each distributed antenna in the antenna cluster are different. Therefore, there is a problem that it is impossible to determine which channel is assigned to the antenna cluster.

  The present invention has been made in consideration of such circumstances, and the purpose of the present invention is to distribute the control load related to channel assignment to each central processing center in the distributed antenna system, and to change the traffic and the surroundings. Disclosed is a distributed antenna network system that can uniquely determine a channel to be selected and a channel allocation method that are suitable for a propagation environment.

  In order to solve the above-described problem, the present invention communicates with a wireless terminal, a distributed antenna composed of a plurality of antennas distributed in a wide geographical range, and the wireless terminal via the distributed antenna. A distributed antenna network system including a central processing center, wherein the wireless terminal selects an antenna cluster that is a set of antennas used for communication with the central processing center from the distributed antennas Antenna cluster selection means, and cluster head selection means for selecting one antenna as a cluster head from the antenna clusters selected by the antenna cluster selection means, and the central processing center constitutes the distributed antenna Measured for each of the multiple channels for each antenna When there is a communication request from the wireless terminal and an interference management unit that records an interference state, the interference state of the cluster head selected by the wireless terminal is acquired from the interference management unit, and the interference state of the cluster head A distributed antenna network system comprising channel selection means for selecting one of the channels.

  According to the present invention, in the above invention, the interference management means records the interference power measured in each of a plurality of channels for each antenna constituting the distributed antenna, and the channel selection means The interference power of the selected cluster head is acquired from the interference management means, and a channel that has the minimum interference power of the cluster head and is not used in the antenna cluster selected by the wireless terminal is selected. It is characterized by doing.

  The present invention is characterized in that, in the above invention, the antenna cluster selection means selects the antenna clusters in order from the distributed antennas in descending order of reception power.

  The present invention is characterized in that, in the above-mentioned invention, the cluster head selecting means selects, as the cluster head, one having the highest received power from the antenna cluster.

  In order to solve the above-described problems, the present invention communicates with a wireless terminal, a distributed antenna including a plurality of antennas distributed in a wide geographical area, and the wireless terminal via the distributed antenna. A channel allocation method in a distributed antenna network system configured by a central processing center that performs communication, wherein the wireless terminal uses a set of antennas used for communication with the central processing center from among the distributed antennas An antenna cluster selection step of selecting an antenna cluster, and a cluster head selection step in which the wireless terminal selects one antenna as a cluster head from the antenna clusters selected in the antenna cluster selection step, The central processing center has each antenna constituting the distributed antenna. An interference management step for recording an interference situation measured in each of a plurality of channels, and when the central processing center receives a communication request from the wireless terminal, the interference situation of the cluster head selected by the wireless terminal Is obtained from the information recorded in the interference management step, and includes a channel selection step of selecting one of the channels according to the interference status of the cluster head.

  According to the present invention, in the above invention, the interference management step records the interference power measured in each of a plurality of channels for each antenna constituting the distributed antenna, and the channel selection step is performed by the wireless terminal. The interference power of the selected cluster head is obtained from the recorded in the interference management step, and the interference power of the cluster head is the channel with the minimum interference and is used in the antenna cluster selected by the wireless terminal. It is characterized by selecting no channel.

  The present invention is characterized in that, in the above invention, the antenna cluster selection step selects the antenna clusters in order from the distributed antennas in descending order of reception power.

  The present invention is characterized in that, in the above-mentioned invention, the cluster head selecting step selects the cluster head having the highest received power from the antenna clusters as the cluster head.

  According to the present invention, each distributed antenna creates an interference table based on the past history of interference power, selects a channel with low interference, and performs allocation, thereby assigning a control load related to channel allocation to each central processing center. It is possible to allocate a low-interference channel that adapts to traffic fluctuations and the surrounding propagation environment.

It is a conceptual diagram which shows an example of the model of embodiment using DAN by this invention. It is a flowchart for demonstrating interference table preparation and channel allocation operation | movement by this embodiment. It is a flowchart for demonstrating the channel allocation operation | movement of DAN in step S14 mentioned above. It is a block diagram which shows the structure of the transmitter of the central processing center 10 for downlink transmission by this embodiment. It is a block diagram which shows the structure of the receiver of the radio | wireless terminal 13 for downlink transmission by this embodiment. It is a block diagram which shows the structure of the transmitter of the radio | wireless terminal 13 for uplink transmission by this embodiment. It is a block diagram which shows the structure of the receiver 110 of the central processing center 10 by this embodiment. It is a figure which shows the numerical calculation specification used by this computer simulation. It is a figure which shows the average channel capacity plotted as a function of packet generation probability _Ptrans which is a computer simulation result mentioned above. It is a conceptual diagram which shows the example of fixed channel allocation (FCA). It is a conceptual diagram which shows the structure of the conventional distributed antenna network (DAN).

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
The present invention is a channel assignment technique related to a distributed antenna system in which a central processing server and wireless terminals perform wireless communication via a plurality of antennas that are geographically distributed.
Conventionally, in Autonomous DCA (Dynamic Channel Assignment), an antenna measures a surrounding interference state for each channel, and a channel with low interference power is selected from among them. When this method is applied to a distributed antenna system, each antenna is geographically separated, so that there is a problem in that an interference situation differs for each antenna and a channel to be selected cannot be uniquely determined.

  In the present invention, an antenna cluster is generated by selecting an antenna used by a wireless terminal for communication with the central processing server in descending order of reception power. Among them, the one with the highest received power is selected as the cluster head. The central processing server manages the interference state of all antennas including the cluster head, and selects and assigns a channel that has the lowest interference power in the cluster head and is not used in the antenna cluster. With this configuration, even in a distributed antenna system, the control load related to the channel assignment of autonomous DCA is distributed to each central processing center, while adapting to traffic fluctuations and the surrounding propagation environment, It has the effect that a small channel can be allocated and communicated.

FIG. 1 is a conceptual diagram showing an example of a model of an embodiment using DAN according to the present invention. As shown in FIG. 1, the network assumed in the present embodiment includes N _total (≧ 1) distributed antennas 11 arranged for each cell with respect to U radio terminals 13 existing in the cell. of central processing center 10 comprising of _{N total,} select Nt (≦ _{N total)} antennas, is to simultaneous transmission and reception using it. However, it is assumed that the distributed antenna 11 and the central processing center 10 are connected by wire such as an optical fiber 12 or a metal fiber.

In the following description, it is assumed that N _t distributed antennas (referred to as antenna cluster 15) of the N _total distributed antennas and U radio terminals 13 transmit and receive simultaneously.

  FIG. 2 is a flowchart for explaining interference table creation and channel allocation operations according to this embodiment. When there is a communication request from the wireless terminal 13, the antenna cluster selection and the cluster head are determined, and channel assignment is performed. An interference table is used for channel assignment. Update the interference table periodically as follows.

  Each distributed antenna always measures the average interference power for all available channels (step S10). The calculation method of the average interference power by the primary filter will be described. The primary filter multiplies the interference power measured in the previous time slot by a forgetting factor β (0 ≦ β ≦ 1). Also, the filter output (average interference power) calculated in the previous time slot is multiplied by (1-β). Then, the sum is output as a filter output. The larger β is, the shorter the averaging time is, and the smaller β is, the longer the averaging time is. Then, the average interference power of all the channels is rearranged in order of increasing power and stored in the interference table (step S11). This operation is repeated for each time slot to update the interference table.

Next, when a transmission packet is generated in a certain wireless terminal 13 and a communication request is generated, first, an antenna cluster 15 (N _t distributed antennas) that communicates with the wireless terminal 13 is selected from a number of distributed antennas. The cluster head that is the center is selected. For this antenna selection, a method of periodically transmitting beacons from all the distributed antennas 11 can be used.

  Each terminal 13 receives the average received power of the beacons from the distributed antennas 11 present in the vicinity of the terminal 13 (long-term average received power (which is selected based on the distance from the wireless terminal 13), short-time average received power, or (Instant received power) is measured (step S12).

Next, each terminal has an antenna cluster 15 (N _t distributed antennas) that communicates with itself, and a cluster head (one of N _t distributed antennas) based on the magnitude of the average beacon received power. And the result is notified to the central processing center 10 for channel allocation (this information may be stored in the head of the communication request packet) (step S13).

Here, as a method for determining the antenna cluster 15, in the following example, it is considered that N _t antennas are selected from the N _total distributed antennas 11 in descending order of received signal power. However, it is possible to select all antennas that exceed the threshold value of the received signal power determined in advance by the central processing center 10 as antenna clusters, or both of them can be used together.

Also, the cluster head in the present embodiment, it is assumed to select the antenna was the largest received power in the N _t antennas selected, one antenna from among the N _t antennas optionally May be selected. In addition, instead of the received power, the signal power-to-noise power ratio (SNR), or the signal power-to-interference plus noise power ratio (SINR) May be used. That is, in the present application, “reception power” includes a signal power to noise power ratio and a signal power to interference / noise power ratio.

  Next, the central processing center 10 performs channel allocation. In channel allocation, referring to an interference table held by the cluster head, a channel with the smallest interference power is selected from unused channels, and the channel is communicated. (Step S14), and then communication is started.

  FIG. 3 is a flowchart for explaining the DAN channel assignment operation in step S14 described above. The cluster head first selects a channel with the smallest interference power from the interference table (step S141). Next, it is determined whether or not the channel is in use in the antenna cluster (step S142). If not, the channel is assigned (step S143).

  On the other hand, if the channel is in use, it is determined whether there is an unselected channel in the interference table held by the cluster head (step S144), and if there is no unselected channel, it waits for a certain period. After (step S145), the process returns to step S141 to resume channel selection.

  On the other hand, if there is an unselected channel in the interference table, the channel with the next smallest interference power is selected from the interference table (step S146), and the flow from step S142 is performed again.

  Note that the priority order of the wireless terminals 13 in assigning channels as in step S14 is, for example, assigned in the order in which communication is requested, assigned in the order in which received signal power is larger, or in the order of higher QoS (Quality of service). Or may be assigned at random.

  In the case of a time division duplex system, the downlink (communication from the central processing center 10 to the wireless terminal 13) and the uplink (communication from the wireless terminal 13 to the central processing center 10) have the same channel. In the case of a frequency division duplex system using frequencies, the downlink and uplink channels have a one-to-one correspondence, and therefore it is sufficient to assign downlink channels.

  After the selection of the antenna cluster and the channel assignment are completed, in downlink transmission, a transmission signal to the wireless terminal 13 is generated in the central processing center 10, and diversity transmission is performed from all the distributed antennas 11 in the antenna cluster 15. Here, the channel gain between the antenna cluster 15 and the terminal 13 is estimated for transmission diversity (see Non-Patent Document 4).

  As the channel estimation method, channel estimation (see Non-Patent Document 5) based on a pilot signal that performs channel estimation by periodically transmitting a known signal (pilot) can be used. The wireless terminal 13 receives signals transmitted from all the distributed antennas 11 in the antenna cluster 15 and performs reception signal detection. On the other hand, in uplink transmission, a transmission signal is generated by the radio terminal 13 and received by all the distributed antennas 11 in the antenna cluster 15. The reception signal of the distributed antenna 11 is transmitted to the central processing center 10 using the optical fiber 12, and after diversity combining, the reception signal is detected.

In the present embodiment, it is assumed that signal transmission by orthogonal frequency division multiplexing (OFDM) using N _c subcarriers is performed as signal transmission. Each channel is composed of several orthogonal subcarrier groups among _Nc orthogonal subcarriers. Hereinafter, an uplink / downlink transmission / reception method will be described.

First, a downlink transmission / reception method will be described.
FIG. 4 is a block diagram illustrating a configuration of a transmission apparatus of the central processing center 10 for downlink transmission according to the present embodiment. The transmission apparatus 100 of the central processing center 10 has data modulation circuits 100-1,..., 100-U, transmission weight multiplication circuits 102-1,... 102-U, _Nc point IFFT 103- for the wireless terminals # 1 to #U. , 103-U and a frequency mapping circuit 101 are provided. The data modulation circuits 100-1,..., 100-U convert the binary transmission information block to be transmitted to the radio terminal #u (u = 1 to U) into M _u data modulation symbols.

Frequency mapping circuit 101, a M _u number of data modulation symbols, assigned to M _u orthogonal subcarriers position, the replicating the N _t created. The transmission weight multiplication circuits 102-1,... 102-U perform transmission equalization by multiplying each of the M _u orthogonal subcarriers by a complex weight. N _c point IFFT circuit 103-1, ..., 103-U is converted into a time domain signal and transmitted from _{N t} book distributed antenna #. 1 to # _{N t.}

FIG. 5 is a block diagram illustrating a configuration of a receiving device of the wireless terminal 13 for downlink transmission according to the present embodiment. Each of the wireless terminals 13 (#u: u = 1 to U) has an N _c point IFFT 131-u, a frequency demapping circuit 132-u, and a signal detector as the receiving device 130-u (u = 1 to U). A circuit 133-u is provided. The Nc point FFT circuit 131-u converts the received signal into a frequency domain signal. The frequency demapping circuit 131-u extracts only the component at the frequency position allocated to the radio terminal 13 (#u) from the _Nc subcarriers. The signal detection circuit 133-u obtains a binary information block.

Next, an uplink transmission / reception method will be described.
FIG. 6 is a block diagram illustrating a configuration of a transmission apparatus of the wireless terminal 13 for uplink transmission according to the present embodiment. Each of the wireless terminals 13 (#u: u = 1 to U) has a data modulation circuit 141-u, a frequency mapping circuit 142-u, and N _c points as its transmission device 140-u (u = 1 to U). An IFFT circuit 143-u is provided. Data modulation circuit 141-u converts the binary transmission information block to be transmitted to the central processing center 10 to M _u number of data modulation symbols. Frequency mapping circuit 142-u is a M _u number of data modulation symbols, assigned to M _u orthogonal subcarriers position, inserting zeros in the other position. The Nc point IFFT circuit 143-u converts to a time domain signal and transmits it.

FIG. 7 is a block diagram showing the configuration of the receiving device 110 of the central processing center 10 according to this embodiment. The reception device 110 of the central processing center 10 includes an _Nc point FFT circuit 110-u (u = 1 to U), a reception weight multiplication circuit 111-u, a diversity combining circuit 112, a frequency demapping circuit 113-u, and a signal detection. A circuit 114-u is provided.

Nc-point FFT circuits 110-u converts the _{N t} received signal received by the antenna clusters of the _{N t} distributed antenna #. 1 to # _{N t} in the frequency-domain signal. Reception weight multiplying circuit 111-u, for each orthogonal subcarriers distributed antenna #. 1 to # N _t, performs reception equalization multiplying the complex weights.

Diversity combining circuit 112 combines the respective subcarrier components received by the _{N t} distributed antenna #. 1 to # _{N t.} The frequency demapping circuit 114-u extracts M _u orthogonal subcarrier components allocated to the radio terminal #u. The signal detection circuit 114-u obtains a binary information block.

Next, the effect of the method of the present invention evaluated by computer simulation will be described.
Assuming a distributed antenna network in which seven distributed antennas are arranged in each cell as shown in FIG. 1 (N _total = 7), the average channel capacity characteristic of the downlink is obtained by Monte Carlo numerical calculation. FIG. 8 is a diagram showing numerical calculation specifications used in the computer simulation. The total number of channels is 3, and in the above-described embodiment, the number of distributed antennas constituting an antenna cluster is N _t, and one of them is a cluster head, but here, N _t = 1. (In other words, there is no need to select a cluster head).

Further, it is assumed that the position of the wireless terminal 13 is random within the area of FIG. It is assumed that there are U radio terminals 13 in each radio cell, and packets are generated in each time slot with a probability of P _trans . In the above-described embodiment, it is assumed that OFDM transmission using _Nc subcarriers is performed, but here, a computer simulation focusing on only one subcarrier among them is performed.

  Therefore, the channel assumes a frequency non-selective block Rayleigh fading channel. The transmission weight is a zero forcing (ZF) weight. Channel estimation is ideal. It is assumed that the influence of an interference limited channel, that is, noise, is sufficiently small compared to interference and can be ignored.

FIG. 9 is a diagram showing the average channel capacity plotted as a function of the packet occurrence probability P _trans , which is the result of the computer simulation described above. It compares the average channel capacity when using fixed channel assignment (FCA) with autonomous distributed DCA using channel segregation. The number of channel groups when using FCA is N = 3. Since the total number of channels is three, only one channel is assigned to each radio cell, and the same channel is assigned to all distributed antennas included in the cell.

  Although FCA is designed to reduce interference between the same channels, the number of wireless terminals that request packet transmission frequently exceeds the number of channels because there are few channels allocated to each cell. . This limits the number of wireless terminals that can transmit in each time slot.

On the other hand, in the autonomous distributed DCA, channel allocation can be performed as long as the number of wireless terminals that request packet transmission in each cell does not exceed the total number of channels. As a result, the average channel capacity is improved as compared with FCA. The effect of improving the channel capacity increases as the packet traffic (U × P _trans ) increases. For example, when the number of users per radio cell is U = 3 and the packet generation probability is P _trans = 1.0, it can be seen that the channel capacity of the autonomous distributed DCA is increased by about 11 bps / Hz compared to the FCA.

  According to the above-described embodiment, each distributed antenna creates an interference table based on the history of past interference power, selects a channel with low interference, and performs allocation, thereby controlling the control load related to channel allocation at each center. It is possible to perform communication by allocating a channel with low interference adapted to traffic fluctuations and surrounding propagation environments while being distributed to processing centers.

DESCRIPTION OF SYMBOLS 10 Central processing center 11 Distributed antenna 12 Optical fiber 13 Wireless terminal 100 Central processing center transmitter 100-1 to 100-U Data modulation circuit 101 Frequency mapping circuit 102-1 to 102-U Transmission weight multiplication circuit 103-1 to 103 -U N _c point IFFT
130-1 to 130-U Receiving devices 131-1 to 131-U N _c point IFFT of wireless terminals # 1 to #U
132-1 to 132-U frequency mapping circuit 133-1 to 133-U signal detection circuit 141-1 to 141-U data modulation circuit 141-2~142-U frequency mapping circuit 142-1 to 142-U _{N c} point IFFT
110 Central Processing Center Receiver 110-1 to 110-UN _C Point IFFT
111-1 to 111-U reception weight multiplication circuit 112 diversity combining circuit 113-1 to 113-U frequency demapping circuit 114-1 to 114-U signal detection circuit

Claims (8)

A distributed antenna network system comprising a wireless terminal, a distributed antenna comprising a plurality of antennas distributed geographically over a wide range, and a central processing center that communicates with the wireless terminal via the distributed antenna There,
The wireless terminal is
Antenna cluster selection means for selecting an antenna cluster that is a set of antennas used for performing communication with the central processing center from among the distributed antennas;
Cluster head selection means for selecting one antenna as a cluster head from the antenna clusters selected by the antenna cluster selection means;
The central processing center is
Interference management means for recording the interference state measured in each of a plurality of channels for each antenna constituting the distributed antenna;
Channel selection means for obtaining the interference status of the cluster head selected by the radio terminal from the interference management means and selecting one of the channels according to the interference status of the cluster head when there is a communication request from the radio terminal A distributed antenna network system. The interference management means includes
For each antenna constituting the distributed antenna, record the interference power measured in each of a plurality of channels,
The channel selection means includes
The interference power of the cluster head selected by the wireless terminal is acquired from the interference management means, and the interference power of the cluster head is the channel with the minimum interference and is used in the antenna cluster selected by the wireless terminal. 2. The distributed antenna network system according to claim 1, wherein a non-existing channel is selected. The antenna cluster selection means includes
The distributed antenna network system according to claim 1, wherein the antenna clusters are selected from the distributed antennas in descending order of reception power. The cluster head selecting means includes
The distributed antenna network system according to claim 1, wherein the antenna cluster having the highest received power is selected as the cluster head. In a distributed antenna network system including a wireless terminal, a distributed antenna including a plurality of antennas arranged in a geographically dispersed manner, and a central processing center that communicates with the wireless terminal via the distributed antenna A channel allocation method,
An antenna cluster selection step of selecting an antenna cluster that is a set of antennas used by the wireless terminal to perform communication with the central processing center from the distributed antennas;
The wireless terminal includes a cluster head selection step of selecting one antenna as a cluster head from the antenna clusters selected in the antenna cluster selection step;
An interference management step in which the central processing center records an interference situation measured in each of a plurality of channels for each antenna constituting the distributed antenna;
When there is a communication request from the wireless terminal, the central processing center acquires the interference status of the cluster head selected by the wireless terminal from the recorded in the interference management step, and depends on the interference status of the cluster head. And a channel selection step of selecting one of the channels. The interference management step includes
For each antenna constituting the distributed antenna, record the interference power measured in each of a plurality of channels,
The channel selection step includes:
The interference power of the cluster head selected by the wireless terminal is acquired from the recording in the interference management step, and the channel is the channel with the minimum interference power of the cluster head, and the antenna cluster is selected by the wireless terminal. The channel allocation method according to claim 5, wherein a channel that is not used in is selected. The antenna cluster selection step includes:
6. The channel assignment method according to claim 5, wherein the antenna clusters are selected from the distributed antennas in descending order of reception power. The cluster head selection step includes:
The channel allocation method according to claim 5, wherein the antenna cluster having the highest received power is selected as the cluster head.

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