JP2012156976A - Radio communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radio communication system avoiding interference between base station groups by controlling a use frequency and transmission power by a base station with coordination of groups of moving terminal stations or base stations.SOLUTION: In the radio communication system, a base station 21 makes synchronized terminal stations 11 as a base station group 1, receives information on a radio wave situation from the terminal stations 11, performs carrier sensing based on information of the radio wave situation, transmits/receives information on positions of the base stations and radio terminal stations in the respective groups, information on movement and information on communication as coordination information among the base stations of each group to share it when occurrence of the interference is detected with the other approaching base station group 2, performs an operation processing of interference avoidance based on the coordination information and controls the interference avoidance.

Description

  The present invention relates to a wireless communication system having a plurality of moving base stations and a plurality of terminal stations, and in particular, the base station controls the use frequency and transmission power while coordinating between the base stations. The present invention relates to a wireless communication system that avoids interference between stations.

[Conventional technology]
As a digital radio communication system in practical use, one that includes one or a plurality of radio base stations that secure a service area and a plurality of radio terminal stations that perform radio communication via the radio base stations is known. It has been.
In addition, in wireless communication systems, there are systems in which not only terminal stations but also base stations move.

[Related technologies]
Incidentally, as a related prior art, there is JP-A-2002-325281 “Communication Control Method” (Hitachi Kokusai Electric Co., Ltd.) [Patent Document 1].
In Patent Document 1, when a wireless terminal station performs direct communication in a digital wireless system, the output is reduced within the service area of the wireless base station, thereby preventing interference with the wireless base station due to the output of the wireless terminal station. It has been shown.

JP 2002-325281 A

However, in the conventional wireless communication system, since the terminal stations or base station groups that are moving are not linked, when a plurality of terminal stations and base station groups that use the same frequency band approach each other However, there is a problem that communication quality may deteriorate due to interference.
In particular, it is a problem how a radio or terminal station that does not have the ability to sense a radio wave environment solves the interference problem with surrounding radios.

  Patent Document 1 discloses a technique for preventing interference between base stations from base stations, and does not disclose a technique for avoiding interference between base stations.

  The present invention has been made in view of the above circumstances, and the base station controls the use frequency and the transmission power by cooperating between the moving terminal stations or groups of base stations, thereby preventing interference between base station groups. An object is to provide a wireless communication system that can be avoided.

  The present invention for solving the problems of the above-described conventional example is a wireless communication system having a movable wireless terminal station and a movable base station, and the base station defines the synchronized wireless terminal station as its own station. When receiving radio wave status information from a wireless terminal station as a group, performing carrier sense based on the radio wave status information, and detecting the occurrence of interference with a group of another base station that is approaching , Information on the location of base stations and wireless terminal stations in each group, information on movement, and information on communication are exchanged and shared among base stations of each group as information for cooperation, and interference avoidance is performed based on the information for cooperation. It is characterized by performing arithmetic processing and controlling interference avoidance.

  According to the present invention, the base station sets the wireless terminal station to be synchronized to its own group, receives information on the radio wave status from the radio terminal station, performs carrier sense based on the radio wave status information, and approaches. When the occurrence of interference is detected with another group of base stations, information on the positions of base stations and wireless terminal stations in each group, information on movement, and information on communication are used as linkage information. Since it is a wireless communication system that performs interference avoidance calculation processing based on cooperation information by transmitting and receiving and sharing between base stations, and controls interference avoidance, a group of mobile terminal stations and base stations By the cooperation, there is an effect that the base station can control the use frequency and the transmission power to avoid interference between the base station groups.

It is a figure which shows the TDD frame structure of a 1st base station and a terminal station. It is a figure which shows a base station group state (Embodiment 1-1). It is a figure which shows a base station group state (Embodiment 1-2). It is a figure which shows a base station group state (Embodiment 1-3, 4). It is a figure which shows a base station group state (Embodiment 1-5). It is a figure which shows a base station group state (Embodiment 1-6). 3 is a flowchart showing a first process 1; 10 is a flowchart showing a first process 2. It is a figure which shows the TDD frame structure of a 2nd base station and a terminal station. It is a figure which shows a base station group state (Embodiment 2-2). It is a figure which shows a base station group state (Embodiment 2-3). It is a figure which shows a base station group state (Embodiment 2-4). It is a flowchart which shows a 2nd process.

Embodiments of the present invention will be described with reference to the drawings.
[Outline of the embodiment]
In the wireless communication system (this system) according to the embodiment of the present invention, when a cognitive mobile radio (base station) group using the same frequency band approaches or leaves, a plurality of base stations cooperate with each other. By autonomously recognizing position / time information and moving direction / velocity by GPS (Global Positioning System), it is possible to effectively use the frequency by controlling the frequency band to be used and the transmission power of the base station. This is to avoid communication deterioration.

  In addition, when the cognitive mobile radio (base station) group using the same frequency band approaches or leaves the system, a plurality of base stations cooperate with each other through the terminal stations of each group. It is intended to avoid communication deterioration due to interference while effectively using frequencies by controlling the used frequency band to be used, the transmission power of the base station, and the time slot allocation.

[Outline of this system]
Next, an outline of the present system will be described.
Here, in this system, a cognitive mobile radio base station (hereinafter referred to as a base station) having the capability of recognizing the surrounding radio environment by spectrum sensing and making a decision on switching of radio specifications according to the result, Mobile radio terminal stations (hereinafter referred to as terminal stations) synchronized with the base station are configured as one group. This grouping of terminal stations and base stations is defined as a base station group.

  In the base station group, both communication from the base station to the terminal station (hereinafter referred to as downlink) and communication from the terminal station to the base station (hereinafter referred to as uplink) are usually both TDD (Time Division Duplex) having the same frequency fa. Communication), and when interference avoidance cannot be avoided, use a different free allocated frequency band.

The base station and the terminal station have recognition information, and the base station synchronized with the terminal station can grasp the recognition information of the synchronized terminal station.
Here, the recognition information is information on position / time information by GPS, moving direction / speed, allocation available frequency, transmission power, reception power, signal-to-interference wave ratio, belonging base station group, individual ID (identifier). It is.
Here, the position / time information is referred to as “position information”, the movement direction / speed information is referred to as “movement information”, the allocation available frequency, transmission power, reception power, signal to interference ratio, affiliation Information related to the base station group and individual ID may be referred to as “information related to communication”.

  In addition, the base station has a function of sensing the surrounding spectrum, operates a calculation program for the purpose of avoiding interference based on information obtained by sensing and recognition information, and determines a condition for avoiding interference, The synchronized terminal station is controlled as needed under the determined conditions.

  The inter-base station cooperation specific to the base station is to perform a unified operation based on a common judgment by the mutual controllers of the base stations. In order to perform inter-base station cooperation, a frame for inter-base station cooperation is provided in the base station frame at the same frequency fa, and the two base stations determine transmission / reception frames using their own random number algorithms, It is assumed that when the frame is in the same frame and the transmission / reception relationship is established between the two base stations and the response of the cooperation signal is completed, the base stations can cooperate with each other.

The partner base station linked between the base stations has the capability of recognizing and recognizing the recognition information grasped including the terminal station from which the base station has acquired the control right.
In particular, the base station analyzes the obtained information and selects the optimal communication parameters (transmission power, allocated available frequency) in consideration of communication interruption avoidance and frequency effective use, high-speed communication and delay time each time. Then, the selected parameter is exchanged as control information with the terminal stations in the base station group and other base stations linked with the base station.

When a terminal station moving autonomously approaches a base station or a base station group, synchronization is established.
Here, the synchronization establishment of the terminal station means that the terminal station receives the base station preamble signal, and accordingly, the terminal station returns a response signal to the base station and the terminal station synchronizes with the base station. After receiving the RSSI (Received Signal Strength Indictor) and CINR (Carrier-to-Interference and Noise Power Ratio) values from the terminal station to the base station (to the terminal station), A reception response is returned to the terminal station. The values of RSSI and CINR correspond to information on radio wave conditions.

The base station recognizes and recognizes the necessary surrounding radio wave environment, and exchanges information with other base stations and base station groups, including the recognition information of the terminal station having the control right.
A base station or group of base stations capable of communicating at a short distance that recognizes and recognizes the surrounding wireless status by changing the base station with sensing capability of the radio wave environment to a terminal station that does not have sensing capability. The terminal is controlled by controlling the output of the transmission power of the base station and the frequency that can be allocated so that the communication environment is analyzed and the interference condition is analyzed by a calculation program to avoid interference and the communication environment does not deteriorate. A communication environment is secured while considering effective use of frequency (a method of avoiding interference by transmission power control) when a station is a base station or a group of base stations approach each other.

For the terminal station, after synchronization with the base station, the base station receives the minimum necessary control (control of the use frequency and transmission power) related to the radio specifications so that the base station does not interfere with the terminal station.
When a plurality of base stations perform inter-base station cooperation, in order to confirm the presence of the base station when the downlink CINR value to the terminal station to which it belongs has decreased, At the time of reception, spectrum sensing is performed to confirm the spectrum of the counterpart base station, and then inter-base station cooperation is performed in that frame.

  After inter-base station cooperation, the base stations in the base station group exchange recognition information including the terminal stations they have, and perform analysis to avoid interference using a calculation program that includes other base station groups. By controlling elements (utilization frequency, transmission power) that can avoid radio wave interference including other base station groups, it is possible to operate by autonomous distribution in groups. In addition, when the communication between the base stations is long and the communication is interrupted, the cooperation between the base stations is canceled.

  When the terminal station has its own identification information and there is a base station nearby, the terminal station enters a synchronization operation with the base station, and becomes a terminal station (base station group) belonging to the base station group after the operation is completed. When communication with the base station is interrupted and synchronization is no longer possible, the synchronization with the base station to which it belongs is cancelled. In addition, even when the base station is synchronized with a certain base station, if there is a base station with a shorter distance, the synchronization with the distant base station is released, and the synchronization operation with the near base station by the above method is repeated.

Next, the configuration of the present system, the TDD frame configuration, and the processing in states 1 to 6 will be specifically described.
In this system, one base station and a plurality of terminal stations synchronized with the base station are used as one unit of the base station group. In other words, the terminal station is synchronized with the base station to form a base station group, and the area changes as the base station or the terminal station moves.

For example, when communication is possible between base stations in two base station groups, the system is based on cooperation.
Even when there are a plurality of terminal stations with respect to a single base station, it can be adapted by adopting the TDMA (Time Division Multiple Access) system. However, in the present embodiment, the case of a single terminal station is shown.

[System configuration]
As shown in FIGS. 2 to 6, in this system, specifically, the base station group 1 includes a base station 21 and a terminal station 11, and the base station group 2 includes a base station 22, a terminal station 12.
The base station and the terminal station communicate at the same frequency fa unless the terminal station receives control by synchronization with the base station or control such as frequency change after cooperation between base station groups.

  Since the base stations 21 and 22 and the terminal stations 11 and 12 are all synchronized with the GPS in frame synchronization, the base station 21 and the terminal station 11, the base station 22 and the terminal station 12, Assume that the base station 21 and the base station 22 also synchronize frames by GPS.

[Frame configuration: Fig. 1]
A first frame configuration used in the present system will be described with reference to FIG. FIG. 1 is a diagram illustrating a TDD frame configuration of a first base station and a terminal station.
As shown in FIG. 1, the configuration of the TDD frames of all the terminal stations 11 and 12 and the base stations 21 and 22 includes the frames of the terminal station 11 (to the base station 21) and the terminal station 12 (to the base station 22), The frame of the base station 21 (vs. base station 22), the frame of the base station 22 (vs. base station 21), the random number code sequence of the base station 21, and the random number code sequence of the base station 22 are shown.

[Description of frame]
The TDD frame configuration is selected by a random number algorithm having no correlation between the base stations 21 and 22.
Regarding the random number values (0 = reception, 1 = transmission) of 1 and 2 frames for inter-base station cooperation, when the base station 21 is 0 (reception) and the base station 22 is 1 (transmission), or the base station 21 When 1 (transmission) and the base station 22 is 0 (reception), it is determined that transmission / reception is possible, and when both are 0 (reception) or 1 (transmission), it is determined that transmission / reception is not possible.

In FIG. 1, in frame 2, the base station 22 (transmission) is changed to the base station 21 (reception) by a random number code sequence.
In the previous frame, the base station 21 (transmission) is changed to the base station 22 (reception).
In 1 and 2 frames for inter-base station cooperation, random number = 0 is reception, and random number = 1 is transmission.

As for the TDD frame configuration of the terminal stations 11 and 12, for the terminal station uplink frames up to 1 and 2 frames, the uplink from the terminal station (terminal station transmission) is prohibited to make an empty frame, and other 3 to n frames Up to the frame is an upstream frame.
With respect to the TDD frame configuration of the base stations 21 and 22, up to 1 and 2 frames are used for inter-base station cooperation, and the other 3 to n frames are uplink (terminal station transmission) frames from the terminal station 11. That is, the first few frames up to n frames are used for inter-base station cooperation.

  Transmission / reception is selected by random numbers in the 1st and 2nd frames of the base station 21, and when a cooperation signal is received in the inter-base station cooperation frame, a response signal is transmitted and returned.

  Transmission / reception is selected by random numbers in the 1st and 2nd frames of the base station 22, a cooperation signal is transmitted in the inter-base station cooperation frame, and a return of the response signal is awaited as reception. If a response signal cannot be received, the base station repeats the operation of waiting for a response signal by continuously transmitting a cooperation signal until a different timeout time. If the response signal does not return, it times out once and returns to spectrum sensing.

[First processing operation in this system]
When the base station 22 detects a decrease in the downlink CINR value of the synchronized terminal station 12 and then detects the base station 21 by spectrum sensing using the inter-base station cooperation frame (reception), the base station 22 21. Randomly transmit a signal for cooperation (such as a preamble signal for synchronization between base stations) to the base station using a random number algorithm having no correlation between base stations, and a response signal from the base station 21 (cooperation) Waiting for a predetermined time-out period until receiving a reception confirmation of the signal for use and a return of the cooperation signal).

In addition, when the cooperation signal can be received in the inter-base station cooperation frame without detecting the decrease in the terminal station downlink CINR value, the same operation is continued thereafter.
If the response signal can be received in the inter-base station cooperation frame before the timeout, the base station 22 continues to exchange information using the base station cooperation frame.

However, if the response signal cannot be obtained, the base station 22 repeats once again stopping spectrum signal transmission and performing spectrum sensing again.
The preamble signal for communication between the base station and the terminal station is inserted at the head of each frame and all frequencies are detected and controlled within the frame, so there is no problem even if the detection of several frames is delayed with respect to the speed of the moving body. Shall.

[Status of this system 1-1 to 1-6]
Next, states 1-1 to 1-6 in the first process in the present system will be specifically described as Embodiments 1-1 to 1-6 with reference to FIGS. 2 is a diagram showing a base station group state (Embodiment 1-1), FIG. 3 is a diagram showing a base station group state (Embodiment 1-2), and FIG. 4 is a diagram showing a base station group state. FIG. 5 is a diagram illustrating a group state (Embodiments 1-3 and 4), FIG. 5 is a diagram illustrating a base station group state (Embodiment 1-5), and FIG. 6 is a diagram illustrating a base station group state (Implementation). It is a figure which shows the form 1-6).

[State 1-1: FIG. 2]
In the state 1-1 (embodiment 1-1), as shown in FIG. 2, the base stations 21 and 22 are in close proximity and perform a synchronization operation with a recognizable terminal station.
The synchronization operation is performed by returning a signal indicating establishment of synchronization from the terminal station to the base station when the terminal station receives the preamble signal of the base station from the terminal station.

  A terminal station 11 corresponding to the area of the base station 21 is referred to as a base station group 1, and a terminal station 12 corresponding to the base station 22 is referred to as a base station group 2. And it moves as base station groups 1 and 2. Thereafter, base station group 1 and base station group 2 approach.

  In FIG. 2, the terminal station 11 is synchronized with the base station 21, the terminal station 12 is synchronized with the base station 22, the base station and the terminal station are synchronized, and the base station is grouped and all communicate at the same frequency fa. Indicates approaching.

[State 1-2: FIG. 3]
In the state 1-2 (embodiment 1-2), as shown in FIG. 3, the terminal station 11 transmits all the recognition information including the RSSI and CINR values to the base station 21 and the terminal station 12 to the base station 22, respectively. The base stations 21 and 22 perform spectrum sensing by FFT (Fast Fourier Transform), determine interference, and detect other base station groups. When there is no interference, the process returns to the state 1, and when there is interference, the process proceeds to the state 1-3.

  Here, for example, it is determined that there is interference by comparing the RSSI value and CINR value with a specific threshold value, and another base station group is detected by comparing the RSSI value and CINR value with another threshold value. It is determined that

[State 1-3: FIG. 4]
In state 1-3 (embodiment 1-3), as shown in FIG. 4, the distance between the base station groups approaches each other, and after determining that there is interference in state 1-2, When the other base station can receive the preamble signal transmitted in the inter-base station cooperation frame, the base station transmits a response signal in the inter-base station cooperation frame and the other base station receives it. Interact with base stations.

  Exchange the recognition information (including the RSSI and CINR values of the terminal stations) including the base stations that are known to each other and the terminal stations that belong to the group, and perform unified operations to avoid interference In order to do this, the control which takes "inter-base station cooperation" is performed.

Inter-base station cooperation is a control unit in a plurality of cognitive radio mobile base stations for a calculation program that collects all the recognition information held by each other and finds an optimal solution for the transmission power of the base station group. This is an operation of exchanging information by communicating with each other through a wireless line and sharing and processing an analysis program for avoiding interference according to the ability of each control unit.
In the calculation program processing, the distance between the terminal station and the base station is obtained from the position of the terminal station and the position of the base station, and the transmission power is optimized. Also, the sharing process is to distribute the program process in half because there are two base stations.

  The base station 21 and the base station 22 between the base station groups 1 and 2 transmit the base station 21 to the base station 22 with respect to each other's recognition information including the RSSI and CINR values of the terminal stations that have acquired the control right. The data is transmitted from the station 22 to the base station 21 to exchange information as needed.

[State 1-4: FIG. 4]
In state 1-4 (Embodiment 1-4), as shown in FIG. 4, in order to examine whether the influence of interference of the same frequency occurs from the positional relationship of all radios or the moving direction from the viewpoint of effective use of frequency. In addition, information received and monitored by the terminal station for the received RSSI value and CINR value of each of the terminal station 11 and the terminal station 12 is shared via the base station.

  Position by grasping the position information (latitude, longitude) of the base station / terminal station in GPS, calculating the relative position / distance by calculation, and recognizing the relative position between the base station and terminal station radio groups as needed Since the information is known, distance information regarding mutual interference is used as supplementary information, and interference avoidance conditions are calculated by a calculation program.

  When interference can be avoided, the transmission power of the base station is controlled. That is, by suppressing the transmission power of one or both of the base stations, it is possible to prevent interference with terminal stations of other base station groups.

When interference avoidance is impossible even with transmission power control, the frequency is changed to a spare allocation available frequency fb (a frequency different from the frequency fa), or usage is allocated by determining the priority.
The allocation of usage based on priority is that one of the base stations is determined to be prioritized in advance, and time allocation is preferentially allocated to the priority base station.

[State 1-5: FIG. 5]
In state 1-5 (Embodiment 1-5), as shown in FIG. 5, when the distance between base station groups is far away, the RSSI value between base stations decreases, and communication is interrupted, Leave base station cooperation.
Further, when approaching another radio group, the operation by the cooperation between base stations in the state 3 is repeated.

[State 1-6: FIG. 6]
In the state 1-6 (Embodiment 1-6), as shown in FIG. 6, the distance between the base station and the terminal station is far away in the base station group, and the RSSI value between the base station and the terminal station is When the signal drops and reception becomes impossible, the synchronization operation between the base station and the terminal station in the base station group is canceled.

[Processing flow of this system: FIGS. 7 and 8]
Processing related to the states 1-1 to 1-6 will be described with reference to FIGS. FIG. 7 is a flowchart showing the process 1, and FIG. 8 is a flowchart showing the process 2. FIG. 7 and FIG. 8 are continuous in the parts (A) and (B).
First, the base station and the terminal station are each in a standby state (S1).

[Process of Embodiment 1-1]
Then, the base station 21 approaches the terminal station 11 and the base station 22 respectively approach the terminal station 12 to complete the synchronization operation, move as the base station groups 1 and 2 and approach each other (S2). This is state 1-1 (processing of the embodiment 1-1).

[Processing in Embodiment 1-2]
Then, between the base station 21 to the terminal station 12 and between the base station 22 to the terminal station 11, the recognition information is transmitted to the base station to which the terminal station belongs, including the RSSI and CINR values. Determine the presence or absence of interference. Specifically, the base station 21 and the base station 22 perform spectrum analysis (S3). This is state 1-2 (the process of the embodiment 1-2).

[Processing in Embodiment 1-3]
When there is interference, the transmission / reception of the inter-base station cooperation frame of the TDD system is switched at the frequency fa, and the preamble signal is received in that frame to synchronize with each other, and the inter-base station cooperation is performed. (S4). If there is no interference, the process returns to step S2.

  Then, the RSSI and CINR values from the terminal stations to which the base stations 21 and 22 have acquired the control right are updated as needed. The recognition information of the terminal station and the base station is transmitted from the synchronized base station 21 to the base station 22 and from the base station 22 to the base station 21 (S5). This is state 1-3 (processing of Embodiment 1-3).

[Process of Embodiment 1-4]
Furthermore, in order for the control units of the base stations 21 and 22 to cooperate to avoid interference, the RSSI and CINR values are improved by the time synchronization with the GPS including the terminal stations to which it belongs and the adjustment of the transmission power. Thus, the calculation by the program is performed, and it is analyzed and examined by calculation whether the base station groups 1 and 2 have the condition that interference can be avoided by output control at the same frequency (S6).

  When interference avoidance is not possible (A), the change from the allocation available frequency to the backup frequency is selected (S7). However, when there is no backup frequency, it is assigned to each base station group (base station G) according to the priority and the amount of communication in cooperation between base stations (S8).

If interference avoidance is possible (B), output power output control is selected (S9). In this case, the position information and the moving direction of the base stations are grasped, and interference due to the output control of the base station groups 1 and 2 is avoided (S10). This is state 1-4 (processing of Embodiment 1-4).
In addition, when the cooperation in the base station group is lost in the processes S5, S6, S9, and S10, the process returns to the process S4 for re-cooperation between the base stations.

[Process of Embodiment 1-5]
Then, when the distance between the base stations 21 and 22 increases and the RSSI decreases and communication is interrupted, the cooperation with the outside of the base station group is canceled (S11). This is state 1-5 (processing of embodiment 5-1).

[Process of Embodiment 1-6]
In addition, when the distance between the base station and the terminal station in the base station group increases and RSSI decreases and communication is interrupted, the synchronization in the base station group is canceled. At the time of cooperation outside the group (outside G), the other base station is notified of the withdrawal of the terminal station (S12). This is state 1-6 (processing of the sixth embodiment).

If it is determined in step S11 that the synchronization is within the base station group, the process proceeds to step S12. If the cooperation is canceled outside the base station group in step S12, the process proceeds to step S11.
If the synchronization within the base station group is continued in step S11, or if the cooperation outside the base station group is continued in step S12, the process proceeds to step S1 if the synchronization of the terminal station is released. If synchronization continues, the process proceeds to step S2.

[Second processing operation of this system]
The second processing operation in this system will be described below.
A base station that has sensing capability of radio wave environment recognizes and recognizes the surrounding wireless status on behalf of a terminal station that does not have the ability to sense a certain bandwidth when switching frequencies, and the information is short-range A terminal station or a base station that avoids interference by sharing interference information including base station groups or base station groups that affect communication, analyzing interference conditions using a calculation program, and preventing degradation of the communication environment. The communication environment is ensured while considering the effective use of frequency (interference avoidance method by transmission power control) when the terminal station is close to the base station or the base station group by controlling the time slot, output, and allocated available frequency.

  The calculation program for avoiding interference changes, for example, the time slot of the transmitting station at the interference target from the position and output power of the wireless station obtained from the recognition information, the output power, and the RSSI and CINR values, and performs power control. Thus, an analytical solution for improving the CINR value of the receiving station and maintaining the communication state is derived.

Here, the recognition information includes GPS position / time information, moving direction / speed, allocation available frequency, transmission power, reception power, signal-to-interference wave ratio, belonging base station group, individual ID, and time slot. Will be.
For the terminal station, the base station receives necessary minimum control information (use frequency, transmission power, time slot information) related to radio specifications for preventing the base station from interfering with the terminal station after synchronization with the base station.

  When linking between base station groups, when the downlink or uplink CINR value with the terminal station to which the affiliated station belongs decreases, in order to confirm the presence of the terminal station or base station group, As shown in FIG. 9, after receiving the base station / terminal station cooperation frame, after confirming the existence of the base station group (configuration of the radio station group) and the recognition information of each radio station, Perform inter-group collaboration.

  After cooperation between base station groups, the base stations in the wireless group exchange the recognition information including the terminal stations that each other has, and perform analysis to avoid interference using a calculation program that includes other base station groups. By controlling elements (utilization frequency, transmission power, time slot) that can avoid radio wave interference including other base station groups, it is possible to operate by autonomous distribution in groups.

  Further, when the communication between the base station groups is long and the communication is interrupted, the cooperation between the base station groups is canceled. In the first process, the inter-terminal station cooperation operation is performed between the base station groups via the inter-base station communication, but the cooperation operation via the inter-terminal station communication is not easily performed. There is.

  In order to establish the above interference avoidance operation at the time of radio wave interference between radio stations, a normal data transmission slot (hereinafter referred to as “uplink frame” from the terminal station to the base station, and from the base station to the terminal station) This can be solved by providing special linkage frames for base stations and terminal stations to exchange transmission / reception information for base stations and terminal stations, instead of “downlink frames”). .

  In this special frame, in addition to the recognition information, it is transmitted including a synchronization signal for cooperation, and when a reception response (ACK) is received in the reception response frame, transmission / reception of the target base station / terminal station cooperation frame is performed. Temporarily fix and synchronize. After that, when the target communication partner is changed, the linkage frame is unfixed.

[System configuration for second processing]
In this system for realizing the second processing, one base station and a plurality of terminal stations synchronized with the base station are set as a unit of the base station group.
The terminal station is synchronized with the base station to form a base station group, and the area changes as the base station or the terminal station moves. When communication is possible between base station groups in two base station groups according to this definition, the system is based on cooperation.

  Even if there are a plurality of terminal stations for one base station, the TDMA method can be applied. However, in FIGS. 10 to 13, the case where there are three terminal stations is shown. About the specific configuration The configuration of the base station group 1 is (base station 21, terminal stations 11, 11A, 11B), and the configuration of the base station group 2 is (base station 22, terminal stations 12, 12A, 12B). It is.

  The base station / terminal station performs communication at the same frequency fa unless the terminal station is controlled by synchronization with the base station or control such as frequency change after cooperation between base station groups. Since the base stations 21 and 22 and the terminal stations 11 and 12 are all synchronized with the GPS in frame synchronization, the base station 21 and the terminal station 11, the base station 22 and the terminal station 12, It is assumed that GPS frames are synchronized between the terminal station 11 and the terminal station 12 as well.

[TDD frame configuration of second base station and terminal station: FIG. 9]
The TDD frame configuration of the base station and terminal station in the second process will be described with reference to FIG. FIG. 9 is a diagram illustrating a TDD frame configuration of the second base station and the terminal station.
It is assumed that the TDD frame configuration of all the terminal stations 11 and 12 and the base stations 21 and 22 is the TDD frame configuration shown in FIG.

As shown in FIG. 9, a frame is composed of a preamble, base station cooperation, terminal station cooperation, data transmission downlink (base station → terminal station), data transmission uplink (terminal station → base station), and reception response. Is done.
As for the downlink / uplink frame allocation of the terminal station, before interference avoidance (# 0: terminal stations 11 and 12, # 1: terminal stations 11A and 12A, # 2: terminal stations 11B and 12B), after interference avoidance (# 0: Terminal stations 11 and 12A, # 1: terminal stations 11A and 12, and # 2: terminal stations 11B and 12B).
The contents of the base station / terminal station cooperation frame are recognition information and a synchronization signal for cooperation (before cooperation).

[Random number algorithm operation]
Regarding the operation by the random number algorithm, the base stations 21 and 22 and the terminal stations 11 and 12 have an uncorrelated random number algorithm (random number = 0; frame reception for base station / terminal station cooperation, random number = 1; base station / terminal station) The transmission / reception of the base station / terminal station cooperation frame is selected by the (cooperation frame transmission).

  In particular, in FIG. 9, in the terminal station cooperation frame, the base station 21 (transmission) → the terminal station 11 (reception), the base station 22 (transmission) → the terminal station according to the code sequence of the random number algorithm having no correlation between the base station and the terminal station. 12 (reception), terminal station 12 (transmission) → terminal station 11 (reception) / base station 22 (reception) is successfully transmitted and received, and a reception response (ACK) is returned.

It is assumed that synchronization is established when a reception response (ACK) to transmission is completed between wireless stations, and thereafter, the transmission and reception frames of the base station / terminal station cooperation frame are temporarily fixed.
If the partner radio station is changed, the base station / terminal station cooperation frame is temporarily released. Thick arrows in FIG. 9 indicate when transmission and reception are successful in transmission / reception determined by a random number code sequence.

In addition, only the bold line frame and the bold numbers are frames in which transmission / reception is determined by a variable of the random number algorithm.
In FIGS. 10 and 11 (Embodiments 2-2 to 2-3), there is interference between the base stations 21 and 22 and the terminal stations 11 and 12, respectively. The terminal station 11 can transmit to the terminal station 12 or the base station 21, and the terminal station 12 can transmit to the terminal station 11 when the random number value of the terminal station 12 is “0 (receive)”. Alternatively, it can be received from the base station 22.
In the terminal cooperation frame, when the random number value of the terminal station 11 is “0 (reception)” and the random value of the terminal station 12 is “1 (transmission)”, the terminal station 11 is the terminal station 12 or the base station. The terminal station 12 can transmit to the terminal station 11 or the base station 22.

In the base station cooperation frame, when the random number value of the base station 21 is “1 (transmission)” and the random number value of the base station 22 is “0 (reception)”, the base station 21 can transmit to the terminal station 11 and Station 22 can receive from terminal station 12.
In the base station cooperation frame, when the random number value of the base station 21 is “0 (reception)” and the random value of the base station 22 is “1 (transmission)”, the base station 21 can receive from the terminal station 11 and Station 22 can transmit to terminal station 12.

[Overview of states 2-1 to 2-4]
An outline of states 2-1 to 2-4 described later will be described.
In this system, the terminal station 11 (or the terminal) is detected after detecting a decrease in the downlink or uplink CINR value or the like with the terminal station 11 (or the terminal station 12) synchronized with the base station 21 (or the base station 22). The station 12) transmits the recognition information and the cooperation signal that each has in the terminal station cooperation frame, and the terminal station 12 (or the terminal station 11) and the base station 21 (or the base station 22) receive and receive them. A reception response (ACK) is returned in the response frame to synchronize.

The received terminal station 12 (or terminal station 11) transfers the recognition information received by the terminal station cooperation frame to the base station 22 (or base station 21) and returns a reception response (ACK) for synchronization.
The base station 21 (or the base station 21) that has detected the base station group 1 (or the base station group 2) uses the base station cooperation frame from the base station 22 (or the base station 21) in the opposite direction. Once the recognition information and the cooperation signal are sent to the terminal station 12 (or the terminal station 11), the signal for cooperation (in cooperation between the base station groups in the partner base station / terminal station cooperation frame via the terminal stations) , A preamble signal for synchronization, etc.) is transmitted to the partner base station.

In addition, when the link signal can be received in the link frame between the terminal stations without detecting a decrease in the terminal station downlink CINR value, the same operation as described above is continued thereafter.
If a response signal is received in the base station / terminal station cooperation frame before the time-out, information exchange using the base station / terminal station cooperation frame is continued. However, when the response signal is not obtained, the transmission of the cooperation signal is once stopped and transmitted again.

By repeating transmission and reception by an algorithm using a random number in the base station / terminal station cooperation frame, the base station groups can be linked even when the uplink and downlink are interfered and information exchange is impossible.
When the base station group cooperates, control information is exchanged using the respective cooperation frames via the base stations and terminal stations to which the control station belongs. The operation of avoiding interference is controlled by analysis by an interference avoidance program between base stations.

[Status of this system 2-1 to 2-4]
Next, states 2-1 to 2-4 in the present system will be specifically described as Embodiments 2-1 to 2-4 with reference to FIGS. FIG. 10 is a diagram illustrating a base station group state (Embodiment 2-2), FIG. 11 is a diagram illustrating a base station group state (Embodiment 2-3), and FIG. 12 is a diagram illustrating a base station group state. It is a figure which shows a group state (Embodiment 2-4).

[State 2-1]
In the state 2-1 (Embodiment 2-1), the base stations 21 and 22 perform a synchronization operation with a terminal station that can be recognized by being nearby. State 2-1 is the same state as state 1-1 in FIG.
Specifically, when the terminal station receives the synchronization signal for cooperation of the base station, a signal indicating establishment of synchronization from the terminal station to the base station is returned to the base station accordingly. There are a terminal station 11 corresponding to the area of the base station 21 (hereinafter referred to as base station group 1) and a terminal station 12 corresponding to the base station 22 (hereinafter referred to as base station group 2), which move as base station groups 1 and 2.

[State 2-2: FIG. 10]
In the state 2-2 (embodiment 2-2), as shown in FIG. 10, the base station group 1 and the base station group 2 approach each other, and in particular, the terminal station 11 and the terminal station 12 to which the same time slot is allocated. Therefore, interference occurs between the terminal stations 11 and 12 and the base stations 21 and 22, and the CINR values between the terminal station 11 and the base station 21 and between the terminal station 12 and the base station 22 Is in a lowered state.

[State 2-3: FIG. 11]
In the state 2-3 (embodiment 2-3), as shown in FIG. 11, the terminal stations 11 and 12 that have detected a decrease in the CINR value, etc. The terminal station recognition information is transmitted to terminals 12 and 11 in a terminal station cooperation frame using a random number algorithm having no correlation.
Then, after the terminal stations 11 and 12 synchronize with the reception response (ACK) for the transmission, the terminal stations 11 and 11 that have received the recognition information transfer to the base station to which they belong in the same terminal station cooperation frame. Transfer recognition information.

Furthermore, the base stations 21 and 22 that have received the recognition information synchronize by receiving reception (ACK). The base stations 21 and 22 that have received the recognition information send the cooperation signal to the partner base station groups 2 and 1 via the affiliated terminal stations 11 and 12 in the base station cooperation frame on the reverse route. The terminal stations 11 and 12 transmit the data to the partner terminal stations 12 and 11 in a terminal station cooperation frame.
Thereafter, the data is transmitted from the partner terminal stations 12 and 11 to the partner base stations 22 and 21 in the base station cooperation frame, and the base station groups are linked.

[State 2-4: FIG. 12]
In the state 2-4 (Embodiment 2-4), as shown in FIG. 12, the base stations 11 and 12 linked based on the information received in the state 2-3 change time slots and avoid interference. Perform transmission power control.
For example, the time slot of the terminal station 12 is changed from “# 0” to “# 1”, and the time slot of the terminal station 12A is changed from “# 1” to “# 0”.
Further, when interference cannot be avoided even by changing the time slot, interference is avoided by changing the frequency.

[Second processing flow of this system: FIG. 13]
Processing related to the states 2-1 to 2-4 will be described with reference to FIG. FIG. 13 is a flowchart showing the second process.
[Processing of Embodiment 2-1]
First, it is assumed that base station groups A and B (base station: 1 station, terminal station: 1 station) are independently moving in the TDMA system (S21). This is state 2-1 (Embodiment 2-1).

[Process of Embodiment 2-2]
Next, the base station groups are different, and the terminal stations 11 and 12 in a certain slot (# 0) approach each other to cause interference, and the uplink (terminal stations 11 and 12 → base station 21 moves to the terminal stations 11 and 12). (→ base station 22) and down (base stations 21, 22 → to terminal station 11, base stations 21, 22 → to terminal station 12) are disconnected (S22). This is state 2-2 (Embodiment 2-2).

[Processing in Embodiment 2-3]
Then, the interfering terminal stations 11 and 12 send the recognition information to the interfering terminal station in the vicinity of the affiliated base station and the terminal station cooperation frame by random numbers (in FIG. 9, in the base stations 21 and 22, the terminal stations 11 and 12 When the code sequence is “1” in the TDD frame configuration), it is transmitted (S23). This is state 2-3 (Embodiment 2-3).

  Next, the base station to which it belongs and the terminal station of the interference partner receive the recognition information when the code sequence is “0” in the terminal station cooperation frame, and synchronize with the reception response frame (ACK) after reception. To do. The received recognition information is transferred to the base station to which the terminal station belongs in the same way using the terminal station cooperation frame, and the reception response frame is received (ACK) and synchronized (S24).

  Furthermore, the base stations that have received the recognition information transmit the synchronization signal for cooperation to the partner base station via the affiliated terminal station and the partner terminal station, and the base station groups cooperate by receiving a response (ACK). (S25).

[Process of Embodiment 2-4]
Then, in order to avoid interference, analysis is performed by the interference avoidance program led by the base station using the collected recognition information, and control information is transmitted to the terminal station belonging to the base station and terminal station cooperation frame based on the analysis result Is transmitted to change the communication method to avoid interference (S26).
The change of the communication method includes time slot assignment change, output control, frequency switching, and the like.
As described above, the second process is performed.

  In the second processing, the base station performs processing for changing the communication method for avoiding interference based on the recognition information on the CINR from the terminal station, and the base station itself performs sensing as in the first processing. Although not performed, the recognition information from the terminal station is received as in the first process, the base station itself senses, and the interference avoidance process including interference between base stations may be performed. Good.

[Effect of the embodiment]
According to this system, the radio equipment that uses the same frequency band that does not have sensing capability by the first processing also shares the surrounding radio wave environment information by coordinating with the cognitive radio equipment (base stations 21 and 22). However, there is an effect that communication can be continued while avoiding interference even when another radio unit or group approaches.

  In addition, according to the present system, the second processing enables the wireless device using the same frequency band that does not have the sensing capability to cooperate with the cognitive wireless devices (base stations 21 and 22) and other wireless devices. There is an effect that communication can be continued while avoiding interference even when another radio group approaches by sharing the surrounding radio wave environment information.

  INDUSTRIAL APPLICABILITY The present invention is suitable for a wireless communication system in which a base station controls a use frequency and transmission power and avoids interference between base station groups by cooperation between mobile terminal stations or groups of base stations.

  11 ... terminal station, 12 ... terminal station, 21 ... base station, 22 ... base station

Claims (1)

A wireless communication system having a movable wireless terminal station and a movable base station,
The base station has a group of radio terminal stations to be synchronized as a group of the own station, receives information on the radio wave status from the radio terminal station, performs carrier sense based on the information on the radio wave status, When the occurrence of interference with a group of base stations is detected, information on the positions of base stations and wireless terminal stations in each group, information on movement, and information on communication are used as linkage information between the base stations of each group A wireless communication system characterized by performing interference avoidance calculation processing based on the cooperation information, and performing interference avoidance control based on the cooperation information.

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