JP2017017618A - Communication control method and relay station device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a communication control method and a relay station device, capable of suppressing power consumption with the suppression of a throughput deterioration in a multi-hop network.SOLUTION: A communication control method for a relay station device includes the steps of: acquiring, from another upper level relay station device, a first control signal which includes the information of a first transmission permission period, which is a period when a signal can be transmitted to the other relay station device at an upper level than the self-device, and the information of a communication history of a relay station device group at the lower level; determining, based on the first transmission permission period information and the communication history information, a second transmission permission period which is a period when a signal can be transmitted to the self-device from the other lower level relay station device than the self-device; generating a second control signal which includes the information of the communication history of the other lower level relay station device group than the self-device and the information of the second transmission permission period; and transmitting the second control signal to the other lower level relay station device than the self-device.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a communication control method and a relay station device.

  When providing a communication environment in an environment where it is difficult to secure a communication line or a commercial power source, a multi-hop network using a wireless communication device such as a relay station device driven by energy harvesting or a storage battery is effective. Wireless communication devices forming a multi-hop network need to be driven with low power consumption so as not to cause instantaneous interruption of operation. As a technique for reducing power consumption of a wireless communication device, a sleep control method has been proposed (see Patent Document 1). Hereinafter, a state other than the sleep state is referred to as an “awake state”. A wireless communication device such as a base station device shifts to a long sleep state even when there is traffic in order to improve the effect of reducing power consumption by sleep control. Thereby, the wireless communication apparatus reduces the period of unnecessary awake state and improves the effect of low power consumption.

  In addition, a method of intermittently transmitting packets periodically in a wireless communication device that is a transmission source node of a multi-hop network has been proposed as another method for reducing power consumption (see Non-Patent Document 1). In the method for reducing power consumption disclosed in Non-Patent Document 1, frequency reuse on a relay path can be controlled by causing a wireless communication device to intermittently transmit packets periodically. In addition, the radio communication device can suppress packet collision in the middle of the relay path and achieve high throughput by appropriately determining a time interval for transmitting a signal. In addition, the wireless communication device can keep the throughput constant regardless of the number of hops of the wireless communication device.

  The beacon is a control signal for controlling communication. Hereinafter, the period from the beacon transmission time to the next beacon transmission time is referred to as a “beacon interval”. FIG. 19 is a diagram illustrating an example of a beacon of a lower link in a conventional wireless communication system. As disclosed in Patent Document 1, in a control state when there is no traffic (hereinafter referred to as “control (1)”), the wireless communication device transmits a beacon at the start time of the beacon interval. After transmitting the beacon, the wireless communication device goes to sleep in the remaining beacon interval.

  When there is traffic, the wireless communication device shifts the control state to a control state in which there is traffic (hereinafter referred to as “control (2)”). In the control (2), the wireless communication apparatus controls the control state when there is no traffic after processing related to a DIFS (DCF IFS: Distributed Coordination Function Inter Frame Space), a CW (contention window), and a CTS (Clear to Send) signal. Is transferred to control (1).

  However, when the control (1) and the control (2) are applied to a multi-hop network, the time required for transitioning the control state from the control (1) to the control (2) when traffic occurs is the wireless communication. The longer the number of hops of the device, the longer. That is, the communication environment becomes unfair according to the number of hops. Hereinafter, a link between a relay station device that is a wireless communication device and a terminal is referred to as a “terminal link”.

  FIG. 20 is a diagram illustrating an example of a terminal link beacon in a conventional wireless communication system. When traffic occurs, the time required for transitioning the control state from control (1) to control (2) (difference in time required for control switching) is, as shown in FIG. The more it is, the longer it is.

  In addition, there is a limit to the frequencies that can be used for wireless communication. For this reason, in a multi-hop network, a relay station apparatus that is a wireless communication apparatus may perform single-channel relay (hereinafter referred to as “single-channel relay”). In single channel relay, a relay station apparatus communicates using a single channel.

  There is a CTS signal as a signal for the wireless communication device to execute the control (2). The CTS signal is a signal for notifying a wireless communication device that has received the CTS signal of a transmission prohibition period (NAV: Network Allocation Vector). The CTS signal includes Duration information. When the CTS signal is used for single channel relay, for example, the wireless communication device P notifies the adjacent wireless communication device of the transmission prohibition period using the CTS signal. The wireless communication apparatus notified of the transmission prohibition period does not communicate with the wireless communication apparatus P in the transmission prohibition period notified from the wireless communication apparatus P. In addition, the wireless communication device notified of the transmission prohibition period does not communicate with a wireless communication device other than the wireless communication device P in the transmission prohibition period notified from the wireless communication device P. Therefore, the wireless communication device affects the communication of other adjacent wireless communication devices by executing the control (2).

  Further, in the single channel relay in the multi-hop network, the end-to-end throughput of the wireless communication device becomes unfair according to the number of hops. The more wireless communication devices (relay station devices) that relay signals, the more frame loss occurs due to signal interference and insufficient buffer capacity, the end-to-end throughput of the wireless communication device becomes smaller (non-patent) Reference 2).

  In the control method disclosed in Non-Patent Document 1, the wireless communication apparatus intermittently transmits packets at a predetermined time interval to suppress a decrease in throughput. When the wireless communication apparatus is in the sleep state from the transmission of the packet in the awake state to the next transmission of the packet, the state transition between the sleep state and the awake state is repeated in a short time. The short time is, for example, a time length corresponding to several packets.

Japanese Patent No. 5518807

"Proposal of packet transmission interval control method in wireless multi-hop network", IEICE Technical Report, TECHNICAL REPORT OF IEICE. A / P2003-225, RCS2003-231 (2003-11) "Analysis of throughput unfairness in IEEE802.11 compliant multi-hop wireless LAN", IEICE Technical Report, IEICE Technical Report NS2008-56 (2008-09)

  A predetermined time is required for the state transition between the sleep state and the awake state. When the relay station device goes into the sleep state by executing the method disclosed in Non-Patent Document 1, the conventional relay station device repeats the state transition between the sleep state and the awake state in a short time. The effect of reducing power cannot be improved. Further, the conventional relay station device needs to relay a signal immediately when a signal (packet) to be relayed arrives. Since the relay station apparatus on the signal receiving side needs to maintain the awake state in order to wait for the signal, the effect of reducing the power consumption cannot be improved.

  When conventional sleep control is applied to single channel relay in a multi-hop network, the relay station apparatus may interfere with communication of other relay station apparatuses. Also, in single channel relay in a multi-hop network, the opportunity for the relay station device to transmit a signal becomes unfair according to the number of hops of the relay station device. In addition, when a conventional technique that suppresses a decrease in throughput is applied to single channel relay in a multi-hop network, an improvement in the effect of reducing power consumption due to the sleep state cannot be expected. That is, the conventional relay station apparatus has a problem that power consumption cannot be reduced while suppressing a decrease in throughput in single channel relay in a multi-hop network.

  In view of the above circumstances, an object of the present invention is to provide a communication control method and a relay station apparatus capable of suppressing power consumption while suppressing a decrease in throughput in a multi-hop network.

  One aspect of the present invention is a communication control method in a relay station apparatus that relays a radio signal, wherein the first transmission permission is a period during which a signal can be transmitted to another relay station apparatus higher than the own apparatus. A step of obtaining a first control signal including period information and communication history information of a lower relay station apparatus group from the other upper relay station apparatus; and from another lower relay station apparatus lower than the own apparatus A step of determining a second transmission permission period, which is a period during which a signal can be transmitted to the own apparatus, based on the information of the first transmission permission period and the information of the communication history; Generating a second control signal including communication history information of the relay station apparatus group and information of the second transmission permission period, and sending the second control signal to another relay station apparatus lower than the own apparatus. And a communication control method comprising: A.

  According to an aspect of the present invention, in the communication control method, in the determining step, the transmission permission control unit is configured to prevent the second transmission permission period from overlapping with the first transmission permission period in a predetermined time interval. This is a communication control method for determining a transmission permission period.

  One aspect of the present invention is the communication control method according to the communication control method, further including a step of including, in the signal, data having a data amount that can be transmitted in the first transmission permission period based on a transmission speed of the signal.

  One aspect of the present invention is the communication control method, further comprising the step of switching a temporal arrangement between the first transmission permission period and the second transmission permission period for communicating the downlink signal and the uplink signal. A communication control method is provided.

  According to one aspect of the present invention, information on a first transmission permission period, which is a period during which a signal can be transmitted to another relay station apparatus higher than the own apparatus, and communication history information on a lower relay station apparatus group, And a higher link communication unit that acquires the first control signal from the other higher-order relay station device, and a period in which a signal can be transmitted to the own device from another lower-layer relay station device lower than the own device. A transmission permission control unit that determines a certain second transmission permission period based on the information on the first transmission permission period and the information on the communication history, and information on the communication history of another relay station apparatus group lower than the own apparatus A control signal generating unit that generates a second control signal including information on the second transmission permission period, and a lower link communication unit that transmits the second control signal to another relay station device lower than the own device And a relay station device.

  In one aspect of the present invention, in the relay station device, the transmission permission control unit sets the second transmission permission period so as not to overlap the first transmission permission period in a predetermined time interval. It is a relay station device to be determined.

  One aspect of the present invention is the relay station apparatus according to the above relay station apparatus, wherein the transmission permission control unit includes a data amount of data that can be transmitted in the first transmission permission period in a signal based on a transmission speed.

  According to an aspect of the present invention, in the relay station device, the transmission permission control unit is configured to perform a temporal comparison between a period during which a downlink signal is communicated and the first transmission permission period and the second transmission permission period during which an uplink signal is communicated. It is a relay station device that switches various arrangements.

  According to the present invention, the communication control method and the relay station device can suppress power consumption while suppressing a decrease in throughput in a multi-hop network.

It is a figure which shows the structural example of the radio | wireless communications system in embodiment of this invention. It is a figure which shows the transmission permission period of a low-order link in embodiment of this invention. It is a figure which shows the transmission permission period of a terminal link in embodiment of this invention. It is a figure which shows the transmission timing of a beacon in embodiment of this invention. It is a figure which shows the structural example of the relay station apparatus in embodiment of this invention. It is a figure which shows the example which makes basic arrangement | positioning the time arrangement | positioning of a transmission permission period and a transmission permission period in embodiment of this invention. It is a figure which shows the transfer period in the transmission permission space | interval of a lower link in embodiment of this invention. It is a figure which shows the transmission permission period and transfer period for downlink signals in embodiment of this invention. It is a figure which shows the transmission permission period and transfer period for uplink signals in embodiment of this invention. It is a figure which shows the example which makes temporal arrangement | positioning of a transmission permission period and a transmission permission period an evolution arrangement | positioning about the case where simultaneous transmission / reception of data is permitted in embodiment of this invention. It is a figure which shows the example of the start time of the transmission permission period of relay station apparatuses other than the lowest in the embodiment of this invention, and the end time of a transmission permission period. It is a figure which shows the example of the start time of the transmission permission period of the relay station apparatus lower than the switching relay station apparatus, and the end time of a transmission permission period in embodiment of this invention. It is a figure which shows the example of the start time of the transmission permission period of the lowest relay station apparatus 2, and the end time of the other transmission permission period after a transmission permission period in embodiment of this invention. It is a figure which shows the example of the start time of the transmission permission period of the switching relay station apparatus in the embodiment of this invention, and the end time of the other transmission permission period after a transmission permission period. It is a figure which shows the example of the start time of the transmission permission period of the lowest relay station apparatus 2, and the end time of the other transmission permission period after a transmission permission period in embodiment of this invention. It is a figure which shows the transmission permission period of a high-order link, and the transmission permission period of a low-order link at the time of permitting simultaneous data transmission / reception to the relay station apparatus higher than the switching relay station apparatus in embodiment of this invention. It is a figure which shows the transmission permission period of a high-order link, and the transmission permission period of a low-order link at the time of permitting simultaneous data transmission / reception to the relay station apparatus which is a switching relay station apparatus in embodiment of this invention. It is a figure which shows the transmission permission period of a high-order link, and the transmission permission period of a low-order link at the time of permitting simultaneous data transmission / reception to a relay station apparatus lower than a switching relay station apparatus in embodiment of this invention. It is a figure which shows the example of the beacon of a lower link in the conventional radio | wireless communications system. It is a figure which shows the example of the beacon of a terminal link in the conventional radio | wireless communications system.

A communication control method and a relay station apparatus according to an embodiment of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a diagram illustrating a configuration example of a wireless communication system 100. The wireless communication system 100 includes an external network 1 and relay station devices 2-0 to 2-N (N is an integer of 3 or more in FIG. 1). In FIG. 1, the wireless communication system 100 includes a relay station device 2-0 at a lower level of the external network 1 with respect to a signal (data) flow. The relay station device 2-0 is the highest relay station device among the relay station devices 2-0 to 2-N. The relay station device 2-0 includes the relay station device 2-1 at a lower level than the relay station device 2-0 with respect to the signal flow. The number of hops of the relay station device 2-1 is 1. The relay station apparatus 2-1 includes a relay station apparatus 2-2 at a lower level than the relay station apparatus 2-1. The relay station apparatus 2-2 includes a relay station apparatus 2-N at a lower level than the relay station apparatus 2-2 with respect to the signal flow. The relay station device 2-N is the lowest relay station device among the relay station devices 2-0 to 2-N.

  The relay station apparatus 2-n (n is any one of 0 to N) has a link for accommodating the terminal 3-n by communication for each relay station apparatus 2. Hereinafter, with respect to matters common to the relay station devices 2-0 to 2-N, the description of a part of the reference numerals is omitted and the relay station devices 2-0 to 2-N are referred to as “relay station device 2”. The relay station device 2 uses the same radio frequency for communication connection with another relay station device 2 higher than its own device and communication connection with another relay station device lower than its own device. The relay station device 2 uses a radio frequency different from the radio frequency used for communication connection with other relay station devices 2 for communication connection with the terminal 3.

  Therefore, when the relay station apparatus 2 and another relay station apparatus 2 transmit and receive signals simultaneously (when simultaneous transmission and reception of data is permitted), that is, the relay station apparatus 2 and the other relay station apparatus 2 operate in parallel. When the transmission / reception operation is executed, the signal may interfere or the signal may collide. On the other hand, when the relay station device 2 and the terminal 3 communicate with each other, there is no case where signals interfere or signals collide.

  Further, the relay station device 2 communicates with another relay station device 2 that has transmitted a beacon based on a beacon transmitted from another relay station device 2 that is higher than the own relay device. The beacon includes information (element) for notifying the transmission permission period or the transmission prohibition period. The information for notifying the transmission permission period or the transmission prohibition period includes communication history information of the relay station device 2. The transmission permission period is a period during which a signal is permitted to be transmitted, that is, a period during which a signal can be transmitted. The transmission prohibition period is a period during which transmission of signals is prohibited, that is, a period during which signals cannot be transmitted.

  In a wireless LAN (IEEE 802.11), a relay station device 2 as a station (STA) communicates with another relay station device 2 as an access point (AP) higher than the own device. Further, the relay station device 2 as an access point communicates with another relay station device 2 or a terminal 3 as a lower station than the own device. A protocol for communication between the relay station device 2 and the terminal 3 is, for example, a TCP (Transmission Control Protocol) protocol.

  In the wireless communication system 100, the relay station device 2 transmits a beacon to another relay station device 2 or the terminal 3. When the relay station device 2 receives a beacon from another upper relay station device 2 than the own device, the relay station device 2 is based on the information of the transmission prohibition period notified from the other higher relay station device 2 than the own device. A transmission prohibition period is set for the other lower relay station apparatus 2. The relay station device 2 notifies the determined transmission prohibition period to other relay station devices 2 lower than the own device. The lower relay station apparatus 2 sends a new beacon including information on the transmission prohibition period of the own apparatus to another lower relay station apparatus 2 lower than the own apparatus, and another lower relay station apparatus lower than the own apparatus. 2 is notified.

  Hereinafter, a communication link with another relay station apparatus 2 higher than the own apparatus is referred to as “upper link”. Hereinafter, a communication link with another relay station device 2 lower than the own device is referred to as a “lower link”. Hereinafter, a channel that uses one radio frequency for the upper link and the lower link is referred to as “relay ch”. Hereinafter, a channel using one radio frequency for the terminal link is referred to as “terminal ch”.

  FIG. 2 is a diagram illustrating a transmission permission period of a lower link. In the lower link, the beacon includes an element α, an element β, and an element γ as information for assigning a transmission permission period. In FIG. 2, the transmission prohibition period (1) (NAV) is from time t0 (beacon interval start time) to t1. The transmission prohibition period (2) (NAV) is from time t2 to time t3. The transmission prohibition period (3) (NAV) is from time t4 to “beacon interval end time”.

  The element α is information for designating the transmission prohibition period (1). The element β is information for designating the transmission prohibition period (2) and the start time offset. The element γ is information for designating the transmission prohibition period (3) and the start time offset.

  The relay station device 2 can specify the transmission permission period A_s after the transmission prohibition period (1) and the transmission permission period B_s after the transmission prohibition period (2) using elements included in the beacon. . The relay station device 2 can specify a transmission permission interval that is a period from the end time t2 of the transmission permission period A_s to the end time t3 of the transmission permission period B_s using an element included in the beacon.

  FIG. 3 is a diagram illustrating a terminal link transmission permission period. In the terminal link, the beacon includes an element α and an element β as information for assigning a transmission permission period. In FIG. 3, the transmission prohibition period (1) (NAV) is from time t0 (beacon interval start time) to t1. The transmission prohibition period (2) (NAV) is from time t2 to “beacon interval end time”.

  The element α is information for designating the transmission prohibition period (1). The element β is information for designating the transmission prohibition period (2) and the start time offset.

  The relay station device 2 can specify the transmission permission period after the transmission prohibition period (1) using the elements included in the beacon. The relay station device 2 can specify a transmission prohibition period (2), which is a period from the end time t2 of the transmission permission period to the end time of the beacon interval, using an element included in the beacon. The element α included in the beacon in the terminal link is, for example, a CFP (Contention Free Period) element defined in the wireless LAN (IEEE802.11). The element β included in the beacon in the terminal link is, for example, a Quiet element defined in the wireless LAN (IEEE 802.11).

  Note that the terminal 3 does not need to transmit the transmission permission period to the lower level of its own terminal after grasping the transmission permission period. For example, the relay station device 2 may notify the terminal 3 of the transmission prohibition period by a method other than the beacon based on the convenience of the relay station device 2 that communicates with the terminal 3 during the transmission permission period determined by itself. . That is, the relay station device 2 may notify the transmission prohibition period using a device other than a beacon. For example, the relay station device 2 may set the transmission prohibition period in the terminal 3 with the transmission prohibition period from the time when the CTS signal is transmitted to the end time of the period determined by the CTS signal. In the terminal link, relay station apparatus 2 may determine the transmission permission period of the own apparatus by determining a period other than the transmission permission period of the own apparatus.

  FIG. 4 is a diagram illustrating beacon transmission timing. The relay station device 2 receives a beacon from another relay station device 2 higher than the own device through the higher link of the relay channel communication unit 21 (described later). The relay station device 2 transmits a beacon by a lower link to another relay station device 2 lower than the own device at a time when a predetermined transmission shift time has elapsed from the time when the own device received the beacon.

  The relay station device 2 transmits a beacon via a terminal link to the terminal 3 accommodated by the own device at the time when the transmission shift time has elapsed from the time when the own device received the beacon. The transmission shift time is determined by the relay station device 2 receiving a beacon through the upper link, the relay station device 2 calculating the transmission permission period based on the information included in the received beacon, The predetermined time is determined in advance so that the relay station apparatus 2 can sufficiently transmit a beacon or the like. The transmission shift time is set to a time common to all the relay station devices 2.

  In addition, since the beacon is transmitted by the terminal link and the lower link at the time when the transmission shift time has elapsed from the time when the beacon is received by the upper link, if the beacon interval in the upper link is P time, the beacon in the terminal link and the lower link The interval is also set to P hours. Further, when the beacon interval in the upper link is changed to Q time, the beacon interval in the terminal link and the lower link is also changed to Q time.

  That is, when the information for notifying the beacon interval is defined in the element (element) included in the beacon as in the wireless LAN (IEEE 802.11), the beacon interval in the terminal link and the lower link is The time length is the same as the beacon interval in the upper link.

  FIG. 5 is a diagram illustrating a configuration example of the relay station device 2. The relay station device 2 includes an antenna 20, a relay channel communication unit 21, a communication control unit 22, a sleep control unit 23, an upper link beacon information processing unit 24, a transmission permission control unit 25, and a lower link beacon creation unit. 26, terminal information management unit 27, communication history storage unit 28, data amount setting history storage unit 29, parameter storage unit 30, link speed storage unit 31, shift time storage unit 32, and allocated data amount storage Unit 33, correspondence storage unit 34, interference hop count storage unit 35, terminal link beacon creation unit 36, terminal ch communication unit 37, sleep control unit 38, and antenna 39.

  Relay channel communication unit 21, communication control unit 22, sleep control unit 23, upper link beacon information processing unit 24, transmission permission control unit 25, lower link beacon creation unit 26, terminal information management unit 27, Part or all of the terminal link beacon creation unit 36, the terminal ch communication unit 37, and the sleep control unit 38, for example, a processor such as a CPU (Central Processing Unit) executes a program stored in the memory. This is a software function unit that functions according to the above. Some or all of these functional units may be hardware functional units such as LSI (Large Scale Integration) and ASIC (Application Specific Integrated Circuit).

  A communication history storage unit 28, a data amount setting history storage unit 29, a parameter storage unit 30, a link speed storage unit 31, a shift time storage unit 32, an allocated data amount storage unit 33, a correspondence storage unit 34, The storage unit such as the interfering hop number storage unit 35 includes a non-volatile storage medium (non-temporary recording medium) such as a ROM (Read Only Memory), a flash memory, and an HDD (Hard Disk Drive). Each storage unit may include, for example, a volatile storage medium such as a RAM (Random Access Memory) or a register. Each storage unit may store a program for causing the software function unit to function, for example.

The antenna 20 transmits and receives a radio signal between the other upper relay station apparatus 2 and the own apparatus. The antenna 20 also transmits and receives radio signals to and from its own device with other lower relay station devices 2.
The relay channel communication unit 21 includes both a station function (STA function) and an access point function (AP function) in a wireless LAN (IEEE802.11). The relay channel communication unit 21 transmits a beacon at a predetermined time interval through the upper link and the lower link.

  The communication control unit 22 controls communication of the upper link and the lower link by the relay channel communication unit 21. The communication control unit 22 controls terminal link communication by the terminal ch communication unit 37. The communication control unit 22 outputs information about the terminal (hereinafter referred to as “terminal information”) to the terminal management information unit. The communication control unit 22 stores the communication history information of the relay station device 2 in the communication history storage unit 28. The communication history information may be the communication history information of the own device or the communication history information of another relay station device 2. The communication history information includes, for example, information indicating the data amount of transmitted / received signals.

  The sleep control unit 23 shifts a circuit used for communication from the sleep state to the awake state so that the beacon can be reliably received or transmitted in a period other than the transmission prohibition period. The sleep control unit 23 stops a circuit used for communication in the sleep state. For example, the sleep control unit 23 transmits the transmission prohibition period (NAV) notified from the other upper relay station apparatus 2 by the upper link and the transmission prohibition notified from the lower apparatus to the other lower relay station apparatus 2 by the lower link. In a period in which the period overlaps in time, a circuit or the like used for communication is set in a sleep state.

  The highest relay station apparatus 2-0 enters a sleep state during a transmission prohibition period notified from the lower apparatus to the lower relay station apparatus 2-1. Further, the lowest relay station apparatus 2-N enters the sleep state during the transmission prohibition period notified from the higher relay station apparatus 2- (N-1) by the upper link.

  Thereby, the relay station apparatus 2 can reduce power consumption according to the sleep rate. The sleep rate is a ratio of a period in a sleep state with respect to a predetermined period. For example, when the sleep state is only 2 seconds out of 10 seconds, the sleep rate is 20%. In addition, since overhead occurs when the state transition from the sleep state to the awake state, the number of state transitions from the sleep state to the awake state is the same as the number of state transitions from the awake state to the sleep state even at the same sleep rate. The effect of reducing power consumption is higher when the number is smaller than that.

The upper link beacon information processing unit 24 processes information included in the beacon in the upper link.
The transmission permission control unit 25 includes information such as elements included in the beacon to notify the transmission prohibition period of the higher relay station apparatus 2 of its own apparatus, terminal information, communication history information, and communication data. Information on the amount setting history, parameters for setting the amount of data, signal transmission rate information on each link, information indicating transmission shift time, amount of data allocated when there is no communication, relay station apparatus 2 Based on at least one of information associating the number of hops and information indicating the number of interfering hops, the transmission permission period or transmission prohibition period of the own apparatus is determined.

  The lower link beacon creating unit 26 creates a signal corresponding to the beacon in the lower link. The lower link beacon creating unit 26 transmits a signal corresponding to the created beacon to the relay channel communication unit 21.

  The terminal information management unit 27 manages terminal information. The communication history storage unit 28 stores a communication history. The data amount setting history storage unit 29 stores a history of setting of the communicated data amount. The parameter storage unit 30 stores parameters for setting the data amount. The link speed storage unit 31 stores signal transmission speed information in each link. The shift time storage unit 32 stores transmission shift time information. The allocation data amount storage unit 33 stores data amount information allocated when there is no communication. The correspondence storage unit 34 stores information that associates the relay station device 2 with the number of hops. The interfering hop number storage unit 35 stores information indicating the number of interfering hops.

  The terminal link beacon creating unit 36 creates a signal corresponding to the beacon in the terminal link. The terminal link beacon creation unit 36 transmits a signal corresponding to the beacon to the terminal ch communication unit 37.

  The terminal ch communication unit 37 has an access point function in a wireless LAN (IEEE802.11). The terminal ch communication unit 37 transmits a beacon at a predetermined time interval through the terminal link. The terminal ch communication unit 37 notifies the other relay station apparatus 2 or the terminal 3 of the transmission permission period or the transmission prohibition period of the own apparatus. For example, the terminal ch communication unit 37 notifies the transmission permission period or the transmission prohibition period of its own device using a beacon based on the signal created by the terminal link beacon creation unit 36.

The sleep control unit 38 puts the terminal ch communication unit 37 in the sleep state during the transmission prohibition period set in the terminal 3 accommodated by the own device through the terminal link. The sleep control unit 38 causes the terminal ch communication unit 37 to transition from the sleep state to the awake state so that the beacon can be reliably received or transmitted.
The antenna 39 transmits and receives a radio signal to and from the terminal 3 accommodated by the own device.

  FIG. 6 is a diagram illustrating an example (basic example) in which the temporal arrangement of the transmission permission period and the transmission permission period is a basic arrangement. The arrangement of periods shown in FIG. 6 is a basic arrangement compared to the arrangement shown in FIG. In FIG. 6, the periods T1, T2, T3, T4, T5, and T6 for transmitting or receiving signals are determined so as not to overlap with each other in the relay channels of the relay station apparatus 2.

  The relay station apparatus 2-1 is the highest in the transmission permission period A_s (period T1) and the transmission permission period B_s (period T6) notified from the lower link of the highest relay station apparatus 2-0 to the upper link of the own apparatus. It communicates with the upper relay station apparatus 2-0. The relay station apparatus 2-2 does not communicate in the transmission permission period A_s (period T1) and the transmission permission period B_s (period T6). In addition, the relay station apparatus 2-N does not communicate in the transmission permission period A_s (period T1) and the transmission permission period B_s (period T6).

  The relay station device 2-1 sets the transmission permission period A_s (period T2), the transmission permission period B_s (period T5), and the transmission permission interval (from the end time of the period T2 to the start time of the period T5) In the transmission permission interval of relay station apparatus 2-0 (before the start time of period T1), the beacon in the lower link of the own apparatus is used to notify the upper link of relay station apparatus 2-2.

  The transmission permission period A_s (period T2) notified to the relay station apparatus 2-2 starts immediately after the start time (end time of the period T1) of the transmission permission interval of the lower link of the highest relay station apparatus 2-0. To do. The transmission permission period B_s (period T5) notified to the relay station apparatus 2-2 ends immediately before the end time (start time of the period T5) of the transmission permission interval of the lower link of the highest relay station apparatus 2.

  By applying the temporal arrangement of the transmission permission period and the transmission prohibition period for each relay station apparatus 2 to the relay station apparatuses 2-0 to 2-N, the relay station apparatuses 2-0 to 2-N receive signals (data The transmission permission period or the transmission prohibition period can be determined so as to prevent interference or collision in transmission / reception of packets).

  The relay station device 2 transfers the downlink signal (downlink traffic) received from the highest relay station device 2 in the transmission permission period A_s to the other relay station devices 2 lower than the own device in the transmission permission period A_s. Further, the relay station apparatus 2 transmits an upstream signal (upstream traffic) to be transmitted to the highest relay station apparatus 2 in the transmission permission period B_s, and another relay station apparatus 2 higher than the own apparatus in the transmission permission period B_s. Forward to.

  As a result, the uplink signal transmitted from the lowest relay station apparatus 2-N reaches the highest relay station apparatus 2-0 within one beacon interval (one beacon interval). Further, the downlink signal transmitted from the highest relay station apparatus 2-0 reaches the lowest relay station apparatus 2-N within one beacon interval.

  Therefore, the traffic of the same data amount is recorded in the communication history for all the relay station devices 2 of the wireless communication system 100. Accordingly, when the relay station device 2 determines at least one of the transmission permission period and the transmission permission interval of the own device based on the information of the communication history, the relay station device 2 is in the sleep state and the awake state even if the hop number of the own device is large. Transitions can be made in a short time.

  FIG. 7 is a diagram illustrating a transfer period in the transmission permission interval of the lower link. The transmission permission interval includes a transfer period A_t and a transfer period B_t. The transmission permission interval is longer than the result of adding the transfer period A_t and the transfer period B_t. A margin time may be set between the transfer period A_t and the transfer period B_t.

  The transfer period A_t is a period necessary for delivering the downlink signal transmitted from the external network 1 to the destination relay station apparatus 2 in the transmission permission period A_s. That is, the transfer period A_t is a period necessary for delivering the downlink signal transferred from the higher-order relay station apparatus 2 to the destination relay station apparatus 2 in the transmission permission period A_s. The transfer period B_t is a period for delivering the uplink signal transferred by the lower relay station apparatus 2 in the transmission permission period B_s to the external network 1.

  FIG. 8 is a diagram illustrating a transmission permission period d_s and a transfer period d_t for downlink signals. The relay station device 2-r is a relay station device at a position where the number of hops is r with respect to the highest relay station device 2-0. The transmission permission period d_s corresponds to the transmission permission period A_s illustrated in FIG. That is, the transmission permission period d_s is a period for delivering the downlink signal transmitted from the external network 1 from the relay station apparatus 2-r to the relay station apparatus 2- (r + 1). The transfer period d_t corresponds to the transfer period A_t illustrated in FIG. That is, the transfer period d_t is a period for delivering the downlink signal from the relay station apparatus 2- (r + 1) to the destination relay station apparatus 2-k (k is a number of hops larger than r).

  The transfer period d_t is a period for delivering the downlink signal transmitted from the external network 1 to the destination relay station device 2 in the transmission permission period d_s. The relay station device 2-r is the relay station device 2 at a position where the number of hops is r from the highest relay station device 2-0. In FIG. 8, the downlink signal transmitted by the relay station apparatus 2-r is relayed from the relay station apparatus 2- (r + 1) to the relay station apparatus 2-k, and is a destination terminal accommodated in the relay station apparatus 2-N. Delivered to 3-N.

  In FIG. 8, a period Td (r + 1) indicates a transmission permission period d_s determined by the relay station apparatus 2-r as the relay station apparatus 2- (r + 1). The period Td (r + 1) is expressed by Expression (1).

  Dd (x) represents the data amount of the downlink signal transmitted to the terminal 3-x accommodated in the relay station device 2-x. Sd (r + 1) indicates a transmission rate (downlink transmission rate) of a signal transmitted from the relay station device 2-r to the relay station device 2- (r + 1).

  The relay station apparatus 2- (r + 1) receives the downlink signal by the higher-order link of the own apparatus in the period Td (r + 1). Relay station apparatus 2- (r + 1) extracts a signal destined for terminal 3- (r + 1) accommodated by itself from the received downlink signal. The relay station apparatus 2- (r + 1) transfers the downlink signal including the remaining data without being extracted to the relay station apparatus 2- (r + 2). The same applies to relay station apparatuses 2- (r + 3) to 2-k. The transfer period A_t in the transmission permission period A_s is expressed by Expression (2).

  FIG. 9 is a diagram illustrating an uplink signal transmission permission period u_s and a transfer period u_t. The relay station device 2-r is a relay station device at a position where the number of hops is r with respect to the highest relay station device 2-0. The transmission permission period u_s corresponds to the transmission permission period B_s shown in FIG. That is, the transfer period u_t is a period for delivering the uplink signal from the relay station device 2-k to the relay station device 2- (r + 1). The transfer period u_t corresponds to the transfer period B_t illustrated in FIG. That is, the transmission permission period u_s is a period for delivering the uplink signal from the relay station device 2-r to the external network 1.

  In FIG. 9, the relay station apparatus 2-k transmits an uplink signal transmitted from the terminal 3- (k + 1) accommodated in the relay station apparatus 2- (k + 1) to the storage unit (buffer) of the relay station apparatus 2-k. ) In advance. Similarly, for relay station apparatuses 2- (k + 2) to 2-N, relay station apparatus 2-k stores the transmitted uplink signal in advance in the storage unit (buffer) of relay station apparatus 2-k. The relay station apparatus 2-r transmits the uplink signal transmitted from each terminal 3 accommodated in the relay station apparatus 2-N from the relay station apparatus 2- (r + 1) during the transmission permission period u_s. r + 1).

  The period Tu (r + 1) indicates a transmission permission period u_s that the relay station apparatus 2-r notifies the relay station apparatus 2- (r + 1). The period Tu (r + 1) is expressed by Expression (3).

  Du (x) indicates the data amount of the uplink signal transmitted from the terminal 3-x accommodated in the relay station device 2-x. Su (r + 1) indicates a transmission rate (uplink transmission rate) of a signal transmitted from the relay station device 2- (r + 1) to the relay station device 2-r.

  The relay station apparatus 2- (k-1) transmits an uplink signal transmitted from the terminal 3 accommodated in the relay station apparatus 2 lower than the own apparatus from the relay station apparatus 2-k in the period Tu (k). get. Relay station apparatuses 2- (r + 1) to 2- (k-1) acquire uplink signals in the same manner. For example, the relay station device 2- (r + 1) transmits an uplink signal transmitted from the terminal 3 accommodated in the relay station device 2 lower than the own device in the period Tu (r + 2). ) Relay station apparatus 2- (r + 1) transmits an uplink signal to relay station apparatus 2-r higher than the own apparatus in period Tu (r + 1).

  The relationship between the transfer period u_t and the transmission permission period u_s, that is, the relationship between the transfer period B_t and the period Tu (x) is expressed by Expression (4).

  FIG. 10 is a diagram illustrating an example (development example) in which the temporal arrangement of the transmission permission period and the transmission permission period is an advanced arrangement when simultaneous data transmission / reception is permitted. The arrangement of the periods shown in FIG. 10 is a more advanced arrangement than the arrangement shown in FIG. In FIG. 10, a transmission permission period and a transmission prohibition period (NAV) are determined so that signal interference or collision does not occur when it is permitted to simultaneously transmit and receive signals between the relay station apparatuses 2. Yes.

  In the transmission permission period, the relatively higher relay station apparatus 2 among the relay station apparatuses 2 executes the access point function. Further, in the transmission permission period, the lower relay station apparatus 2 among the relay station apparatuses 2 executes the station function. Hereinafter, the maximum number of hops Cx of the relay station apparatus 2 that may interfere with the signal by the relay station apparatus 2-x is referred to as “interfering hop number”.

  The relay station apparatus 2- (C + 2) is a relay station apparatus (hereinafter referred to as “switching relay station apparatus”) that switches the temporal arrangement of the transmission permission period A_s and the transmission permission period B_s. The transmission permission control unit 25 of the switching relay station apparatus switches the temporal arrangement between the period for communicating the uplink signal and the period for communicating the downlink signal. That is, the transmission permission control unit 25 swaps the temporal relationship between the period for communicating the uplink signal and the period for communicating the downlink signal. A code C (C is an integer of 1 or more) indicates the number of interfering hops. In FIG. 10, as an example, the number C of interfering hops is 1. The switching relay station device may be, for example, relay station device 2- (C + 3). In FIG. 10, as an example, the relay station device 2-3 is a switching relay station device.

  The relay station devices 2-0 to 2-2 communicate downlink signals in the transmission permission period A_s illustrated in FIG. 7 as in the case illustrated in FIG. Similarly to the case illustrated in FIG. 6, the relay station devices 2-0 to 2-2 communicate uplink signals in the transmission permission period B_s illustrated in FIG. 7.

  The relay station apparatus 2-3 switches the temporal arrangement of the transmission permission period A_s and the transmission permission period B_s in the relay station apparatus 2-3. As a result, the temporal arrangement of the transmission permission period A_s and the transmission permission period B_s in the relay station devices 2-4 to 2-N is switched. That is, the relay station devices 2-3 to 2-N communicate uplink signals instead of downlink signals in the transmission permission period A_s illustrated in FIG. The relay station devices 2-3 to 2-N communicate downlink signals instead of uplink signals in the transmission permission period B_s illustrated in FIG. Therefore, the relay station devices 2-3 to 2-N transmit the downlink signal transmitted by the relay station devices 2-0 to 2-2 in the transmission permission period A_s in the transmission permission period B_s of the own device.

  Thus, the uplink signal transmitted from the lowest relay station apparatus 2-N reaches the highest relay station apparatus 2-0 within one beacon interval (one beacon interval). Further, the downlink signal transmitted from the highest relay station apparatus 2-0 reaches the lowest relay station apparatus 2-N within one beacon interval.

  Therefore, the traffic of the same data amount is recorded in the communication history for all the relay station devices 2 of the wireless communication system 100. Accordingly, when the relay station device 2 determines at least one of the transmission permission period and the transmission permission interval of the own device based on the information of the communication history, the relay station device 2 is in the sleep state and the awake state even if the hop number of the own device is large. Transitions can be made in a short time.

  The transmission permission period A_s and the transmission permission period B_s in the relay station apparatus 2-4 that is lower than the relay station apparatus 2-3 that is the switching relay station apparatus will be described.

  The transmission permission period A_s (period T7) notified to the relay station apparatus 2-4 ends immediately before the start time of the transmission permission period A_s (period T8) of the relay station apparatus 2-3. The transmission permission period B_s (period T10) notified to the relay station apparatus 2-4 starts immediately after the end time of the transmission permission period B_s (period T9) of the relay station apparatus 2-3.

  Therefore, the transmission permission interval of relay station apparatus 2-4 is from the start time of transmission permission period A_s (period T8) of relay station apparatus 2-3 to the end time of transmission permission period B_s (period T9). The transmission permission period of the relay station apparatus 2 lower than the relay station apparatus 2-4 is determined in the same manner. Thereby, the relay station apparatuses 2-0 to 2-N can determine the transmission permission period or the transmission prohibition period of the own apparatus so that signal interference or collision does not occur.

  The relay station device 2-3 that is the switching relay station device determines in advance whether or not to communicate with the relay station device 2 that is higher than the own device during a period of communication with the relay station device 2 that is lower than the own device. I can't. This is because the relay station device 2-3 does not acquire the communication history of the relay station device 2 higher than the own relay device. Therefore, there is a possibility that the relay station device 2-3 that is the switching relay station device communicates with the relay station device 2 that is higher than the own device during a period of communication with the relay station device 2 that is lower than the own device.

  Therefore, the start time of the transfer period A_t of the relay station apparatus 2-3 that is the switching relay station apparatus is determined to be the earliest time among the times when the signal to be transmitted does not interfere with or collide with the beacon in the beacon interval. The end time of the transfer period B_t of the relay station apparatus 2-3 that is the switching relay station apparatus is determined as the latest time among the times when the signal to be transmitted does not interfere or collide with the beacon in the beacon interval.

  In addition, the time length of the transmission permission period, the start time or end time of the transmission permission period, and the time length of the transmission permission interval in the relay station apparatus 2 higher than the relay station apparatus 2-3 that is the switching relay station apparatus The start time or end time of the transmission permission interval is determined based on the transfer period A_t and the transfer period B_t of the relay station apparatus 2-3 that is a switching relay station apparatus.

  The transmission permission period A_s, the transfer period A_t, the transmission permission period B_s, and the transfer period B_t are determined for each relay station device 2. The relay station apparatus 2 transmits based on the start time and end time of the transmission permission period for each relay station apparatus 2 and the beacon transmission time for each relay station apparatus 2 so that the beacon and the signal do not interfere or collide with each other. A permission period A_s, a transfer period A_t, a transmission permission period B_s, and a transfer period B_t are determined. The beacon transmission time is determined based on the transmission shift time.

  Hereinafter, matters common to both the case where the wireless communication system 100 includes the switching relay station device and the case where the wireless communication system 100 does not include the switching relay station device will be described.

  In the terminal link, one transmission permission period is defined for each beacon interval (beacon interval). As described above, the relay station apparatus 2 can reduce the energy required to transition from the sleep state to the awake state by minimizing the number of times of transition from the sleep state to the awake state.

  The transmission permission control unit 25 determines the transmission permission period based on the following viewpoints (1) and (2).

  Viewpoint (1): The relay station device 2 excluding the switching relay station device and the lowest relay station device 2 allows the transmission permission period A_s of the relay station device 2 higher than the switching relay station device to transmit the downlink signal. It is determined as a period d_s. The relay station device 2 excluding the switching relay station device and the lowest relay station device 2 defines the transmission permission period B_s of the relay station device 2 lower than the switching relay station device as the transmission permission period d_s of the downlink signal.

  The relay channel communication unit 21 starts the transmission permission period d_s in the lower link of the own device immediately after the transmission permission period d_s notified from the higher-order relay station device 2 to the own device by the upper link of the own device ends. The transmission permission period d_s is a period for the relay station device 2 to transmit a downlink signal to the other lower relay station device 2. Therefore, when the relay station device 2 transmits an uplink signal from its own device to another upper relay station device 2 in the transmission permission period d_s, it inhibits transmission of the downlink signal.

  Viewpoint (2): When the terminal 3 transmits a response to the downlink signal received by the terminal 3 through the external link of the terminal 3 to the relay station device 2 by the uplink signal, communication RTT (round trip time) can be performed. It is desirable to be as short as possible. Accordingly, the terminal 3 transmits a response to the downlink signal received in the transmission permission period d_s as an uplink signal in the transmission permission period u_s after the latest transmission permission period d_s.

  FIG. 11 is a diagram illustrating an example of the start time (timing X) of the transmission permission period d_s and the end time (timing Y) of the transmission permission period u_s of the relay station apparatus 2 other than the lowest-order relay station apparatus 2 illustrated in FIG. FIG. 11 shows an example of the start time (timing X) of the transmission permission period d_s and the end time (timing Y) of the transmission permission period u_s of the relay station apparatus 2 higher than the switching relay station apparatus shown in FIG. It is also a figure which shows.

  FIG. 12 shows an example of the start time (timing X) of the transmission permission period d_s and the end time (timing Y) of the transmission permission period u_s of the relay station apparatus 2 lower than the switching relay station apparatus shown in FIG. FIG.

  The transmission permission period is determined for the following cases (i) and (ii) based on the above viewpoints (1) and (2).

(I) When the relay station device 2 copes with the setting of the transmission permission period without restricting the transmission of the signal (data) The relay station device 2 excluding the switching relay station device and the lowest relay station device 2 Immediately after the transmission permission period d_s notified from the higher-order relay station apparatus 2 to the own apparatus through the higher-order link ends, the transmission permission period d_s of the own apparatus notified to the other lower-order relay station apparatus 2 by the lower-layer link After the start time (timing X), the transmission permission period of the terminal link of the own apparatus is started. Further, the relay station apparatus 2 excluding the switching relay station apparatus and the lowest-order relay station apparatus 2 has a transmission permission period u_s after the transmission permission period d_s, and the other upper-layer link is transmitted by the upper link of the own apparatus. The transmission permission period of the terminal link of the own apparatus ends at a predetermined time earlier than the end time (timing Y) of the transmission permission period u_s notified from the relay station apparatus 2 to the own apparatus.

  However, when considering the transmission delay in the terminal link and the processing delay in the relay station device 2, the transmission permission period of the terminal link may start at a time earlier than the start time of the transmission permission period d_s. Further, when considering transmission delay in the terminal link and processing delay in the relay station apparatus 2, the transmission permission period of the terminal link ends at a time earlier than a predetermined time earlier than the end time of the transmission permission period u_s. May be.

  FIG. 13 shows the start time (timing Z) of the transmission permission period d_s of the lowest relay station apparatus 2 shown in FIG. 6 and the end time (timing Y) of the transmission permission period u_s after the transmission permission period d_s. It is a figure which shows an example.

  FIG. 14 shows an example of the start time (timing Z) of the transmission permission period d_s of the switching relay station apparatus shown in FIG. 10 and the end time (timing Y) of the transmission permission period u_s after the transmission permission period d_s. FIG.

  FIG. 15 shows the start time (timing Z) of the transmission permission period d_s of the lowest relay station apparatus 2 shown in FIG. 10 and the end time (timing Y) of the transmission permission period u_s after the transmission permission period d_s. It is a figure which shows an example.

  The switching relay station device and the lowest relay station device 2 are connected to each other by the lower link immediately after the transmission permission period d_s notified from the higher relay station device 2 to the own device by the upper link of the own device ends. The transmission permission period of the terminal link of the own apparatus starts after the start time (timing Z) of the transmission permission period d_s notified to the other relay station apparatus 2. Further, the switching relay station device and the lowest relay station device 2 have a transmission permission period u_s that is later than the transmission permission period d_s, and are transferred from the upper relay station device 2 to the own device by the upper link of the own device. The transmission permission period of the terminal link of the own apparatus is ended at a predetermined time earlier than the end time (timing Y) of the notified transmission permission period u_s.

  However, when the transmission delay in the terminal link and the processing delay in the relay station apparatus 2 are taken into consideration, the transmission permission period of the terminal link ends at an earlier time than the predetermined time earlier than the end time of the transmission permission period u_s. May be.

(Ii) When the relay station device 2 restricts transmission of signals (data) The relay station device 2 transmits a downlink signal in the transmission permission period d_s notified from the higher-order relay station device 2 by the higher-order link. Therefore, the uplink signal is not transmitted to the higher-order relay station apparatus 2 in the transmission permission period d_s notified for this purpose. The relay station apparatus 2 accumulates the uplink signal in its own buffer during the transmission permission period d_s notified to transmit the downlink signal. The relay station apparatus 2 transmits the transmission permission period of the terminal link of the own apparatus at the time when the transmission permission period u_s notified from the higher-order relay station apparatus 2 to the own apparatus ends by the upper link in a restriction that the uplink signal is not transmitted. Exit. The transmission permission period u_s is “timing Y” illustrated in FIG. 11, 12, 13, 14, or 15.

  However, when the transmission delay in the terminal link and the processing delay in the relay station apparatus 2 are taken into consideration, the transmission permission period of the terminal link ends at an earlier time than the predetermined time earlier than the end time of the transmission permission period u_s. May be.

  The relay station device 2 multiplies the result of adding the data amounts Du (x) and Dd (x) allocated to the own device and the transmission rate of the terminal link to the length of the terminal link transmission permission period. It may be good.

  The transmission permission control unit 25 shown in FIG. 5 predetermines the data amounts Dd (x) and Du (x) to be transmitted in the next beacon interval before transmitting the beacon. The transmission permission control unit 25 calculates a transmission permission period and a transmission permission interval based on the data amounts Dd (x) and Du (x). The transmission permission control unit 25 records the actual value Dd ′ (x) of the downlink signal data amount recorded in the communication history information as a result of the previous data amount setting value Dd (x) and the previous data amount. The set value Dd (x) is compared.

  The transmission permission control unit 25 determines a set value Dd (x) for the next data amount based on the comparison result. The transmission permission control unit 25 records the actual value Du of the data amount of the upstream signal recorded in the communication history as a result of the setting value Du (x) of the previous data amount and the setting value Du (x) of the previous data amount. A set value Du (x) for the next data amount is determined based on the result of comparing '(x).

  The transmission permission control unit 25 refers to the parameter storage unit 30 and acquires a parameter for setting the data amount. The transmission permission control unit 25 determines whether or not the radio resource becomes excessive or insufficient based on the result of comparing the data amount when the previous set value of the data amount is used. If the transmission permission control unit 25 determines that the radio resource does not become excessive or insufficient (the setting value is appropriate) when the setting value of the previous data amount is used, the previous setting value is set to the next setting value. And If the transmission permission control unit 25 determines that the radio resource becomes surplus when the setting value of the previous data amount is used based on the comparison result of the data amount, the transmission permission control unit 25 sets a value smaller than the previous setting value next time. Set value. If the transmission permission control unit 25 determines that the radio resource is insufficient when the setting value of the previous data amount is used based on the result of comparing the data amount, the transmission permission control unit 25 sets a value larger than the previous setting value next time. Set value.

  Note that the transmission permission control unit 25 sets the data amount Dd (x) and Du to be set so that the specific relay station device 2 consumes a large amount of bandwidth and the bandwidth allocation for each relay station device 2 is not unfair. An upper limit may be set for (x).

  All the relay station devices 2 of the radio communication system 100 assign information indicating the allocated data amount Dd_min when there is no downlink communication, and when there is no uplink communication, in order to allocate a transmission permission period to the relay station device 2 that does not communicate via the terminal link. The information indicating the allocated data amount Du_min in is shared in advance. Note that the relay station device 2 may share the allocated data amount Dd_min and the allocated data amount Du_min without using a predetermined packet, or may share using the predetermined packet.

  The relay station apparatus 2 allocates the allocated data amount Dd_min when there is no downlink communication for the downlink (relay link) to the relay station apparatus 2 having the maximum number of hops among the relay station apparatuses 2 that do not have downlink communication through the terminal link. . In addition, the relay station device 2 assumes that there is no transmission permission period in the relay station device 2 having a non-maximum hop number among the relay station devices 2 that do not have downlink communication through the terminal link. The allocated data amount Dd_min when there is no downlink communication is not allocated. Further, the relay station apparatus 2 allocates the allocated data amount Du_min when there is no uplink communication to the relay station apparatus 2 without uplink communication for the uplink (relay link).

  The relay station device 2 allocates the allocated data amount Dd_min when there is no downlink communication to all the relay station devices 2 that do not have downlink communication through the terminal link. As a result, all relay station apparatuses 2 that do not have downlink communication through the terminal link share the allocated data amount Dd_min when there is no downlink communication for the relay channel.

  Thereby, the relay station device 2 can make a state transition from a state without communication to a state with communication. The relay station device 2 can improve the sleep rate by reducing the amount of data allocated to the relay station device 2 that has not communicated in the terminal link. The relay station device 2 can improve the bandwidth by reducing the amount of data allocated to the relay station device 2 that has not communicated in the terminal link.

  The relay station apparatus 2 may set an upper limit on the maximum number of relay station apparatuses 2 that share the allocated data amount when there is no communication for the relay channel. The relay station device 2 may increase the allocated data amount when there is no communication when the maximum number of relay station devices 2 sharing the allocated data amount when there is no communication exceeds the upper limit. The relay station apparatus 2 without communication shares the allocated data amount when there is no communication when the allocated data amount when there is no communication is increased. The relay station device 2 that has not communicated preferentially shares the allocated data amount when there is no communication, as the relay station device 2 with a larger hop count.

  The relay station device 2 allocates the allocated data amount when there is no communication to the relay station device 2 having the maximum number of hops among the relay station devices 2 exceeding the upper limit. The relay station apparatus 2 does not allocate the allocated data amount when there is no communication to the relay station apparatus 2 having a non-maximum hop number among the relay station apparatuses 2 exceeding the upper limit, assuming that there is no transmission permission period.

  The highest-order relay station apparatus 2-0 considers interference and collision between a signal and a beacon transmitted during a transmission permission period based on the communication history information and the transmission shift time information, and the highest-order relay station apparatus A transmission permission period and a transmission permission interval are determined for all the relay station apparatuses 2 from 2-0 to the lowest relay station apparatus 2-N. Based on the determined transmission permission period and transmission permission interval, uppermost relay station apparatus 2-0 transmits transmission permission period A_s, transmission permission period B_s, transmission permission interval start time, and transmission permission interval end time. Are determined for each subordinate relay station apparatus 2.

  The relay station device 2-3 that is a switching relay station device determines the start time of the transmission permission period A_s, the end time of the transmission permission period A_s, the start time of the transmission permission period B_s, and the end time of the transmission permission period B_s. It is determined based on the following viewpoints (I) and (II).

  Viewpoint (I): The relay station device 2-3, which is a switching relay station device, is connected to the lower link of the relay station device 2- (N-1) that is higher by one hop than the lowest relay station device 2-N. The transmission permission period A_s of the own device is determined so that the start time of the transmission permission period A_s is immediately after the beacon is transmitted.

  Viewpoint (II): The uplink signal transmitted in the transmission permission period B_s by the relay station apparatus 2 lower than the switching relay station apparatus may interfere or collide with the beacon transmitted by the higher relay station apparatus 2. For this reason, the relay station apparatus 2-3, which is the switching relay station apparatus, receives the uplink signal transmitted by the relay station apparatus 2 lower than the own apparatus by the time limit that does not cause interference or collision to the beacon. Next, the transmission permission period B_s of the own apparatus is determined based on the hop count C of the relay station apparatus 2 that may interfere with the beacon.

  The signal transmitted by the lower relay station apparatus 2 than the switching relay station apparatus in the transmission permission period A_s may cause interference or collision to the beacon transmitted by the higher relay station apparatus 2. For this reason, the relay station apparatus 2-3, which is the switching relay station apparatus, transmits the transmission permission period A_s of the own apparatus so that the signal transmitted from the lower relay station apparatus 2 does not interfere or collide with the beacon. Determine.

  The highest relay station apparatus 2 determines the start time of the transmission permission period A_s in consideration of interference and collision between the beacon transmitted by the lower relay station apparatus 2 and the signal in the beacon interval. The highest relay station apparatus 2 determines the time immediately before the beacon is transmitted as the end time of the transmission permission period B_s.

  The highest relay station apparatus 2 may set the start time of the transmission permission period A_s to a later time in order to satisfy the conditions shown in the viewpoints (I) and (II) of the switching relay station apparatus. In order to satisfy the conditions shown in the viewpoints (I) and (II) of the switching relay station device, the highest relay station device 2 sets the end time of the transmission permission period B_s to a predetermined time immediately before the time when the beacon is transmitted. It may be earlier.

  FIG. 16 is a diagram illustrating a transmission permission period for the upper link and a transmission permission period for the lower link when simultaneous data transmission / reception is permitted to the relay station apparatus 2 higher than the switching relay station apparatus.

  FIG. 17 is a diagram illustrating a transmission permission period for an upper link and a transmission permission period for a lower link when simultaneous transmission / reception of data is permitted to the relay station apparatus 2-3 serving as a switching relay station apparatus.

  FIG. 18 is a diagram illustrating an upper link transmission permission period and a lower link transmission permission period when simultaneous data transmission / reception is permitted to the lower relay station apparatus 2 than the switching relay station apparatus.

  The uppermost relay station device 2 may set upper limits on the data amounts Dd (x) and Du (x) determined for each relay station device 2 when the communication band is insufficient. For example, the highest relay station device 2 determines the maximum data amount as a temporary upper limit among the data amounts Dd (x) and Du (x) allocated to the relay station device 2. When the communication band is sufficient by decreasing the temporary upper limit, the uppermost relay station apparatus 2 sets the temporary upper limit when the communication band is sufficient as the data amount Dd (x) and Du (x ). The highest relay station device 2 may determine the upper limit of the data amount Dd (x) and Du (x) for each relay station device 2.

  The relay station devices 2 other than the highest level acquire information indicating the transmission permission period from other relay station devices 2 higher than the own device. The information indicating the transmission permission period includes the communication history information of another relay station apparatus 2 lower than the relay station apparatus 2 that has transmitted the information indicating the transmission permission period, and the data amount Dd ( x) and information indicating the upper limit of Du (x). The amount of data when the communication band is insufficient is determined based on the communication history information.

  The relay station devices 2 other than the highest one determine the data amount Du (x) based on the transmission permission period notified from the other relay station devices 2 higher than the own device. Similarly for the downlink signal, the relay station device 2 other than the highest level may determine the data amount Dd (x) based on the transmission permission interval notified from the other relay station device 2 higher than the own device. Good. The transmission permission control unit 25 of the relay station apparatus 2 other than the highest-order relay station apparatus 2 sets the amount of data that can be transmitted so that the amount of data transmitted in the transmission permission period falls within the data amounts Dd (x) and Du (x) The amount of data actually transmitted is determined based on the information indicating the transmission permission period (as included in the signal).

  The transmission permission control unit 25 includes a transmission permission period calculated based on communication history information of the relay station device 2 lower than the own device and information of communication history held by the own device, and higher than the own device. A transmission permission period determined by another relay station device 2 is compared.

  When the transmission permission period calculated by the transmission permission control unit 25 is longer than the transmission permission period determined by the other relay station device 2, the transmission permission control unit 25 determines that the communication band is insufficient. When the transmission permission control unit 25 determines that the communication band is insufficient, the data amount is the same as the method in which the uppermost relay station device 2 determines the upper limit of the data amount Dd (x) and Du (x). Determine the upper limits of Dd (x) and Du (x). The relay station apparatus 2 notifies the other lower relay station apparatus 2 of the determined transmission permission period by transmitting a beacon.

  The relay station apparatus 2 may assign a transmission permission period (time) instead of the data amount Du (x) and Dd (x) to the upper link, the lower link, and the terminal link. For example, the relay station apparatus 2 sets the transmission speeds Su (x) and Sd (x) to “1”, thereby setting the transmission permission period instead of the data amount Du (x) to the upper link and the lower link. Assign to terminal link. Further, for example, the relay station device 2 assigns a data amount to the upper link and the lower link, and assigns a transmission permission period to the terminal link.

  When the relay station apparatus 2 determines the time length of the transmission permission period, the time length of the transmission permission period, the start time of the transmission permission period, and the end time of the transmission permission period, the relay station apparatus 2 For example, beacons including the transmission prohibition periods (1), (2), and (3) shown in FIG.

  When the beacon can include the transmission prohibition periods (1), (2), and (3) determined for all the relay station apparatuses 2, only the highest-order relay station apparatus 2 has the time length of the transmission permission period and the transmission permission period. , The start time of the transmission permission period, and the end time of the transmission permission period may be determined. The relay station device 2 other than the highest level transfers the beacon received from the other upper relay station device 2 to the other lower relay station device 2, thereby allowing the terminal 3 accommodated in the own device by the terminal link. A transmission permission period may be set.

  As described above, the relay station apparatus 2-3 according to the embodiment includes the relay channel communication unit 21 including the upper link communication unit and the lower link communication unit, the transmission permission control unit 25, and the lower link beacon creation unit 26 (control). A signal generation unit). The relay channel communication unit 21 (upper link communication unit) and information of the first transmission permission period that is a period during which an uplink signal or the like can be transmitted to the relay station apparatus 2-2 (for example, the period T3) and the lower relay The beacon (first control signal) including the communication history information of the station device 2 group is acquired from the relay station device 2-2. The transmission permission control unit 25 sets a second transmission permission period, which is a period during which an uplink signal or the like can be transmitted to the own device (for example, a period T8), as information on the first transmission permission period and information on the communication history. Determine based on. The lower link beacon creating unit 26 creates a beacon (second control signal) including communication history information of other relay station devices 2 group lower than the own device and information of the second transmission permission period. The relay channel communication unit 21 (lower link communication unit) transmits a beacon (second control signal) to the relay station device 2-4. The same applies to relay station apparatuses 2 other than the relay station apparatus 2-3.

  Thereby, the relay station apparatus 2 of the embodiment can suppress power consumption while suppressing a decrease in throughput in a multi-hop network.

  That is, the relay station apparatus 2 of the embodiment calculates the transmission permission period and the transmission prohibition period for each communication based on the communication history. The relay station apparatus 2 transmits the beacon including information on the transmission permission period and information on the transmission prohibition period. The other lower relay station apparatus 2 and terminal 3 determine their own transmission permission period and transmission prohibition period based on the transmission permission period information and the transmission prohibition period information included in the beacon. The relay station device 2 acquires in advance information on signal interference or communication history between the relay station devices 2. Also, the relay station device 2 acquires in advance information on signal interference or communication history between the relay station device 2 and the terminal 3. The relay station apparatus 2 transmits / receives a signal in the same transmission permission period between the relay station apparatuses 2 in which no signal interference or collision occurs based on information on signal interference or communication history.

  As a result, the relay station apparatus 2 according to the embodiment can reduce the number of times of operation switching and can efficiently arrange the transmission permission period. The relay station apparatus 2 can appropriately execute state control such as a sleep state by efficiently arranging the transmission permission period. The relay station device 2 can keep power consumption low.

  Since the relay station device 2 of the embodiment controls transmission prohibition and transmission permission only by a beacon, sleep control can be executed without affecting communication between other relay station devices 2. That is, the relay station device 2 of the embodiment can execute sleep control without affecting the communication of other adjacent relay station devices 2.

  The relay station device 2 according to the embodiment transmits the uplink signal transmitted from all the relay station devices 2 of the wireless communication system 100 to the highest relay station device 2- of the wireless communication system 100 within one beacon interval. Can be delivered to zero. As a result, the relay station device 2 of the embodiment can return all the relay station devices 2 of the wireless communication system 100 from the sleep state fairly.

  The relay station device 2 according to the embodiment transmits a downlink signal transmitted from all the relay station devices 2 of the wireless communication system 100 to the lowest relay station device 2- of the wireless communication system 100 within one beacon interval. N can be delivered. As a result, the relay station device 2 of the embodiment can return all the relay station devices 2 of the wireless communication system 100 from the sleep state fairly.

  The relay station device 2 according to the embodiment is communication history information held by the communication history storage unit 28 of the own device, and is based on the communication history information of the relay station device 2 lower than the own device. Determine. Thereby, the relay station apparatus 2 of the embodiment can make the opportunity to transmit a signal fair. That is, the relay station device 2 according to the embodiment can prevent the communication environment from becoming unfair due to the switching time of sleep control being different depending on the number of hops.

  The relay station apparatus 2 of the embodiment determines the transmission permission period and the transmission prohibition period in consideration of signal interference for the relay channel. Thereby, the relay station device 2 of the embodiment can improve the throughput. That is, the relay station apparatus 2 of the embodiment can prevent the throughput from becoming unfair according to the number of hops in single channel relay.

  The relay station device 2 of the embodiment may be able to transition to the sleep state up to three times per beacon interval. That is, the relay station device 2 of the embodiment does not frequently change between the sleep state and the awake state. As a result, the relay station device 2 of the embodiment can reduce power consumption.

  You may make it implement | achieve at least one part of the relay station apparatus and radio | wireless communications system in embodiment mentioned above with a computer. In that case, a program for realizing this function may be recorded on a computer-readable recording medium, and the program recorded on this recording medium may be read into a computer system and executed. Here, the “computer system” includes an OS and hardware such as peripheral devices. The “computer-readable recording medium” refers to a storage device such as a flexible medium, a magneto-optical disk, a portable medium such as a ROM and a CD-ROM, and a hard disk incorporated in a computer system. Furthermore, the “computer-readable recording medium” dynamically holds a program for a short time like a communication line when transmitting a program via a network such as the Internet or a communication line such as a telephone line. In this case, a volatile memory inside a computer system serving as a server or a client in that case may be included and a program held for a certain period of time. Further, the program may be a program for realizing a part of the above-described functions, and may be a program capable of realizing the functions described above in combination with a program already recorded in a computer system. You may implement | achieve using programmable logic devices, such as FPGA (Field Programmable Gate Array).

  The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and includes designs and the like that do not depart from the gist of the present invention.

DESCRIPTION OF SYMBOLS 1 ... External network, 2 ... Relay station apparatus, 3 ... Terminal, 20 ... Antenna, 21 ... Relay channel communication part, 22 ... Communication control part, 23 ... Sleep control part, 24 ... Upper link beacon information processing part, 25 ... Transmission Permit control unit, 26 ... Lower link beacon creation unit, 27 ... Terminal information management unit, 28 ... Communication history storage unit, 29 ... Data amount setting history storage unit, 30 ... Parameter storage unit, 31 ... Link speed storage unit, 32 ... Shift time storage unit, 33 ... Allocation data amount storage unit, 34 ... Corresponding storage unit, 35 ... Interfering hop count storage unit, 36 ... Terminal link beacon creation unit, 37 ... Terminal channel communication unit, 38 ... Sleep control unit, 39 ... Antenna, 100 ... Wireless communication system

Claims (8)

A communication control method in a relay station device that relays a radio signal,
A first control signal including information on a first transmission permission period, which is a period during which a signal can be transmitted to another relay station apparatus higher than the own apparatus, and communication history information of a lower relay station apparatus group; Obtaining from other upper relay station devices;
Based on the information on the first transmission permission period and the information on the communication history, the second transmission permission period, which is a period during which a signal can be transmitted to the own apparatus from another relay station apparatus lower than the own apparatus. Steps determined by
Creating a second control signal including communication history information of another relay station device group lower than the own device and information of the second transmission permission period;
Transmitting the second control signal to another relay station apparatus lower than the own apparatus;
A communication control method.   The communication control according to claim 1, wherein in the determining step, the transmission permission control unit determines the second transmission permission period so as not to overlap with the first transmission permission period in a predetermined time interval. Method. The communication control method according to claim 1, further comprising a step of including data of a data amount that can be transmitted in the first transmission permission period in a signal based on a transmission speed of the signal. 4. The method according to claim 1, further comprising a step of switching a temporal arrangement between the period for communicating a downlink signal and the first transmission permission period and the second transmission permission period for communicating an uplink signal. The communication control method described in 1. A first control signal including information on a first transmission permission period, which is a period during which a signal can be transmitted to another relay station apparatus higher than the own apparatus, and communication history information of a lower relay station apparatus group; , An upper link communication unit obtained from the other upper relay station device,
Based on the information on the first transmission permission period and the information on the communication history, the second transmission permission period, which is a period during which a signal can be transmitted to the own apparatus from another relay station apparatus lower than the own apparatus. A transmission permission control unit determined by
A control signal generating unit that generates a second control signal including information of communication history of another relay station device group lower than the own device and information of the second transmission permission period;
A lower link communication unit that transmits the second control signal to another relay station device lower than the own device;
A relay station apparatus comprising:   The relay station apparatus according to claim 5, wherein the transmission permission control unit determines the second transmission permission period so as not to overlap with the first transmission permission period in a predetermined time interval.   The relay station apparatus according to claim 5 or 6, wherein the transmission permission control unit includes data of a data amount that can be transmitted in the first transmission permission period in a signal based on a transmission speed.   The transmission permission control unit switches a temporal arrangement between the first transmission permission period and the second transmission permission period in which a downlink signal is communicated and an uplink signal is communicated. The relay station device according to any one of the above.

Images