JP2013005339A - Device and method for switching between heterogeneous systems - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique capable of relaying inter-system communication by making coexistent two cognitive radio systems having greatly different transmission power by the common use of frequency.SOLUTION: A relay device between heterogeneous systems, for connecting a first and a second system of cognitive radio of mutually different systems, includes: switching equipment 102, functioning at least as a client in the first system, for radio communication with a base station in the first system; and an AP unit 103, functioning as an access point (AP) in the second system, for radio communication with a subscriber station in the second system. The switching equipment 102 supplies to the AP unit 103 information related to a frequency or a time range, acquired to be usable in the first system, with a format understandable by the AP unit 103. The AP unit 103 performs radio communication with a mobile station 3 only within the supplied frequency or the time range. The switching equipment 102 relays communication between the AP 103 and the subscriber station to the base station.

Description

  In the white space wireless communication system that uses radio waves flexibly while sufficiently avoiding the influence on the existing system (primary system), the present invention provides a plurality of available frequency channels. It is related with the technology which enables utilization of the same frequency with the radio system using different white space.

  The progress of the information society in recent years is quite remarkable, and wireless communication is used for many information communication devices and services. Along with this, the demand for radio frequency, which is a finite resource, is constantly increasing, and the depletion of allocatable frequencies has become a major problem in countries around the world. Generally, licenses are managed by licenses depending on the country, etc., and only those who are assigned licenses can use the frequencies under strict management at specific locations and times. In order to respond, there is a need for a new frequency utilization method that is not confined to conventional frequency utilization methods.

  As a new frequency usage method to solve the frequency depletion problem, the frequency band (white space) that can be used spatially and temporally even if it has already been allocated has been sufficiently affected in the past. Research and development of wireless systems using white space, such as cognitive radio, that avoids the problem and uses radio waves flexibly.

For example, standardization in IEEE802.22 and IEEE802.11af is progressing as a wireless system using white space. In order to avoid impact on existing business (such as TV broadcasting) in these standards,
1) Each wireless station accesses a database (Incumbent DB) that manages white space on the IP network and a network manager to obtain an available frequency list and maximum transmittable power based on its own location information,
2) Use the spectrum sensing function (signal detection function) to confirm that there are no existing stations that use the frequency to be used, and perform communication.
Is stipulated. In order to perform these efficiently, it is considered that the bandwidth and the channel arrangement are the same as those of the television broadcast.

  By the way, each standard has a different target service. IEEE802.22 aims to construct a WRAN (Wireless Regional Area Network) that covers a wide area by long-distance wireless transmission. The goal is to build a wireless metropolitan area network (WMAN) that covers the mid-range by wireless transmission over a distance and a wireless local area network (WLAN) that covers a small area. Considering the diversification of information communication forms in recent years, a system configuration that is scalable and flexible due to the cooperative operation for coexistence between wireless systems conforming to different standards for such purposes, and cooperation between standards It is clear that there is a need to make this possible.

  For example, there is a case where IEEE802.11af WLAN / WMAN is receiving interference from IEEE802.22 WRAN when there is only one frequency that can be used as a white space as an example in which cooperative operation between systems is required. . In such a case, it is not easy to coexist because there is no means for notifying due to the difference in communicable distance between systems, but even in such a situation, cooperative operation is indispensable.

  In addition, an example in which cooperative operation between systems is required is to provide a wireless network instead of laying a wired network such as FTTH (Fiber To The Home) when providing broadband lines to homes in suburbs and remote areas. The method provided by can be considered. In such a case, a long-distance transmission facility as a backhaul line and a medium / short-distance transmission facility used by each home or the like cooperate, and a method based on interconnection with different wireless systems or multi-hop transmission is considered as a solution.

Non-Patent Document 1 describes a method in which IEEE802.22 WRANs coexist by autonomous distributed means called Self-Coexistence function provided in a base station (BS) of IEEE802.22. ing.
FIG. 1 is a flowchart showing the flow of Self-Coexistence in Non-Patent Document 1.

Each BS first checks the frequency used by the existing station in the neighborhood and the frequency used in the neighboring cell in Step 101 (S101), and the frequency that can be used by itself (free frequency). Judge whether there is any.
If there is a frequency that can be used independently as step 102 (S102), the frequency is selected and communication is performed. If there is no free frequency, one arbitrary frequency is selected to coexist with other IEEE802.22 WRAN.
In step 103 (S103), when it is determined in S101 that there is no free frequency, it is determined whether or not the interference when the frequency is used is only from the BS of the adjacent cell.

In step 104 (S104), when it is determined in S103 that the interference is only from the BS, the other BS transmits while the other BS is receiving by synchronizing the downlink and uplink timing between cells. To avoid interference.
In step 105 (S105), when the interference is not only from the BS in S103, that is, when there is interference from a customer facility equipment (CPE: Customer Premises Equipment) belonging to an adjacent cell, the frame is released to the BS of the adjacent cell. A request is made and a frame is released or not released by a random algorithm called frame contention.
In step 106 (S106), when an available frame is acquired by the frame contention of S105, communication is performed by time-sharing a common frequency between cells.
The BS communicates with the CPE in a manner corresponding to S102, S104, or S106. During this time, as step 107 (S107), every time there is a frame request from another cell or an increase in its traffic volume, Processing is re-executed.

Special Table 2010-522448

IEEEE 802.22 / P802.22 / D3.0, March 2011, Draft Standard for Wireless Regional Area Networks Part 22: Cognitive Wireless RAN Medium Access Control (MAC) and Physical Layer (PHY) specifications: Policies and procedure for operation in the TV Bands .

  In this way, different IEEE802.22 WRAN systems can coexist with different systems. However, cooperative operation between white space-based wireless systems compliant with different standards, and systems with different standards due to linkage operations. In addition, little consideration has been given to multihop transmission.

  Therefore, between wireless systems of different standards, each wireless system operates only for optimizing its own wireless system, and does not consider cooperative operation with other systems. As a solution to this problem, it is conceivable to introduce a protocol for cooperation or coexistence in advance, but not only does it require major changes to the related standards, but every time the coexistence method is changed. Because the standard must be changed, it is not always a realistic solution.

  Therefore, the present invention provides a multi-hop transmission across systems such as IEEE802.11af WLAN / WMAN using the IEEE802.22 WRAN as a backhaul line to access the Internet, and a cooperative operation between systems. By providing a simple exchange between systems, the purpose is to provide a technology that enables simple interconnection between systems using white space and simple expansion of the system without changing each other's standards. And

The relay device between different systems according to the present invention uses a common frequency band and connects the first and second cognitive radio systems having different schemes.
An exchange unit that operates as at least a client in the first cognitive radio system and wirelessly communicates with a base station of the first cognitive radio system;
An access point unit that operates as an access point in the second cognitive radio system and wirelessly communicates with a subscriber station of the second cognitive radio system,
The switch unit provides the access point unit with information regarding the frequency or time range acquired as available in the first cognitive radio system, the access point unit providing the given frequency or time range. Wireless communication with the subscriber station.

The relay device between different systems of the present invention further includes
The first cognitive radio system has a longer communication distance than the second cognitive radio system;
The exchange unit checks an available frequency based on access to a database related to an existing station and spectrum sensing, and if there is an available frequency, gives information on the available frequency to the access point unit, and if there is no available frequency, the exchange unit The base station is requested to be released within a predetermined time range, and information on the frequency used by the base station and the available time notified from the base station is given to the access point unit. .

The relay device between different systems of the present invention further includes
The exchange unit uses the in-system coexistence function defined by the first cognitive radio system to request an opening within the predetermined time range for use in the first cognitive radio system, and The time range is determined by assigning a predetermined frame from a plurality of frames constituting a super frame transmitted by the base station.

Further, the inter-system relay method according to the present invention uses a common frequency band and connects the first and second cognitive radio systems having different schemes.
An exchange unit entering the network as a client of the first cognitive radio system;
An exchange unit or an access point unit accesses a database for managing a frequency usage state provided outside, and obtains information on available frequencies; and
An exchange unit and an access point unit receiving radio signals and detecting available frequencies in respective ways in the first and second cognitive radio systems;
Initiating communication with a subscriber station using the first frequency when a first frequency available in the first and second cognitive radio systems is detected;
Communicating with the base station of the first cognitive radio system to which the switch unit belongs when the available first frequency is not detected and performing frame contention;
The exchange unit receives a notification of the release of the frame as a result of the frame contention and notifies the access point unit as an available time for the access point unit;
The access point unit communicating with the subscriber station within the available time;
Relaying user data between the exchange unit and the access point unit.

  The present invention enables interconnection and coexistence between systems of different standards without hindering the independent development of multiple standards.

Self-Coexistence operation flowchart (prior art) Configuration of wireless communication system (embodiment) Configuration diagram of relay station 2 Configuration diagram of switch 102 IEEE802.11af access point configuration diagram IEEE802.22 frame configuration diagram Self-Coexistence operation flowchart (embodiment) Time sequence indicating communication between BS1, RS2, and MS3 after frame contention

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 2 shows a configuration example of the entire wireless communication system. In the present embodiment, the white space utilization system includes a BS 1, a relay station (RS: Relay Station) 2, and a mobile station (MS: Mobile Station) 3.
BS1 is a base station compliant with IEEE802.22.
RS2 communicates with BS1 through IEEE802.22, and communicates with MS3 through IEEE802.11af, while relaying communications performed between BS1 and MS3, and in the communicable area (cell) of BS1. It is installed inside and becomes a IEEE802.11af access point (AP) at that location, forming a relatively small communicable area. In general, an access point may be referred to as a base station, a master station, or the like, and a mobile station may be referred to as a client, a subscriber (station), a slave station, a terminal, or a user.

  FIG. 3 is a configuration diagram of RS2. RS2 includes an antenna 101, an exchange 102, an AP unit 103, and terminals 104, 105, 106, and 107. The exchange 102 is a part that performs wireless communication with BS1 and IEEE802.22, the AP unit 103 is a part that performs wireless communication with MS3 and IEEE802.11af, and the antenna 101 is shared.

  FIG. 4 is a configuration diagram of the exchange 102. The switch 102 includes a terminal 104 connected to an antenna, an RF unit 201 that performs frequency conversion from a baseband (BB) to a radio frequency (RF) band, frequency conversion from a radio frequency band to a baseband, signal amplification, and the like. BB signal processing unit 202 that performs error correction coding / decoding processing and modulation / demodulation processing, frequency channel to be used, transmission / reception timing control, addition of ID for identifying radio to packet, recognition of transmission source radio, etc. A MAC (Medium Access Control) processing unit 203 that performs, a main control unit 204 that controls the entire radio, a self-coexistence function control unit 205 that performs protocol processing for coexistence with BS1, An interface unit 206 serving as an interface with the AP unit 103 and a connection terminal 105 of the interface unit 206 are provided.

The main control unit 204 can be configured by, for example, a processor, a data storage area defined on the memory, and software. The BB signal processing unit 202, the MAC processing unit 203, and the self-coexistence function control unit 205 It can be replaced with a program executed by the main control unit 204.
With these configurations, the exchange 102 functions as a CPE, and also exhibits functions normally possessed only by the BS, such as functions necessary for participating in frame contention (described later).

  FIG. 5 is a configuration diagram of the AP unit 103. The AP unit 103 includes a terminal 106 connected to an antenna, an RF unit 301 that performs frequency conversion from a baseband to a radio frequency band, frequency conversion from a radio frequency band to a baseband, signal amplification, and the like, error correction coding / A BB signal processing unit 302 that performs decoding processing and modulation / demodulation processing, and a MAC processing unit 303 that performs frequency control to be used, timing control of transmission / reception, addition of an ID for identifying a radio to a packet, recognition of a transmission source radio, and the like A main control unit 304 that controls the entire radio, an available frequency storage unit 305 that stores information on frequencies that can be used by IEEE802.11af obtained by the database and the Self-Coexistence function of the exchange, and the exchange 102 And an interface unit 306 serving as an interface with the connection terminal 107.

Basically, the AP unit 103 only needs to faithfully implement the AP function defined by IEEE802.11af.
The interface between the exchange 102 and the AP unit 103 only needs to be able to transmit user data, usable frequency information, and the like. For example, IEEE802.3 can be used.
The exchange 102 converts the frequency and time information to be used by the AP unit 103 into a format that can be understood by the AP unit 103 and outputs it from the interface unit 206, so that the AP unit 103 transmits it through the interface unit 306. It is received and stored in the available frequency storage unit 205, and its own transmission operation is performed only at that frequency and time. Further, when the frame period of IEEE802.22 and IEEE802.11af can be made the same, the AP unit 103 may synchronize the frame period of IEEE802.11af transmitted by itself with the frame period of RS2 (BS1).
When there is a risk of a loop topology due to multi-hop between systems in this example, IEEE 802.1D (Spanning Tree Protocol) included in the MAC layer of the BS 1, the exchange 102, and the AP unit 103 is used.

  FIG. 6 is a diagram showing a frame structure of IEEE802.22. One super frame is configured as 16 consecutive frames having a period of 10 ms. The frame is configured in the order of a downlink subframe, an uplink subframe, and a self-coexistence window (not essential), and has a length corresponding to 24 to 41 OFDM symbols (depending on a bandwidth and a cyclic prefix). In the downlink subframe, a preamble is arranged at the head, followed by MAP information (information on arrangement of each downlink / uplink burst), a frame control header (FCH), and the like, and thereafter, a plurality of downlink bursts have frequencies. (To be precise, subchannels on the MAC) are arranged in order. In the case of the first frame of the superframe, a superframe preamble is provided before the preamble and a superframe control header (SCH) is provided after the preamble. The FCH includes information such as the length of the frame and the length of the MAP information.

In the uplink subframe, a ranging signal from the CPE, a bandwidth request, an emergency location notification (UCS message), and an uplink burst are arranged in time order in slot units.
In the Self-Coexistence window, a Coexistence Beacon Protocol (CBP) burst is arranged, and a BS or a CPE instructed by the BS transmits a beacon. The beacon contains information about the channel that the BS is currently using (Operating), scheduled to be used (Backup), and the candidate for change destination (Candidate). By exchanging this information, the frequency between adjacent BSs is changed over time. It is called Frame-based Spectrum contention. The SCH is used to transmit frame arrangement information indicating how each frame in the superframe is allocated by the BS (or an adjacent BS).

  FIG. 6 shows the flow of the coexistence operation of RS2 in this example. This example is characterized in that the RS 2 is provided with means for notifying the AP about the available frequency and time acquired by the Self-Coexistence function, like a DB for managing white space or a network manager. In addition, the self-coexistence function of this example is characterized in that the process of determining whether interference is only between BSs and the process of synchronizing the downlink and uplink between BSs in the prior art are also excluded. It is. This is because the IEEE802.22 WRAN service range is wide enough to cover the entire IEEE802.11af WLAN / WMAN service range. is there.

As shown in FIG. 6, the coexistence operation of this example is realized mainly by the Self-Coexistence function control unit 205 executing Step 201 (S201) to Step 209 (S209).
(S201)
First, the exchange 102 of the RS2 makes a network entry to the IEEE802.22 WRAN as a CPE in order to establish a line with the BS1.
(S202)
After communication between BS1 and RS2 is established, the DB managing the white space is accessed to obtain a list of frequency candidates that can be used by IEEE802.11af WLAN / WMAN. At that time, the RS 2 appropriately passes the geographical position information acquired by the GPS, the maximum transmission power of the AP unit 103, and the like to the DB.
(S203)
The main control unit 204 notifies the acquired information to the self-coexistence function unit 205 of the exchange 102 and the usable frequency management unit 305 of the AP unit 103 in respective formats compliant with IEEE802.22 and IEEE802.11af.

(S204)
Based on the notified information, the exchange 102 and the AP unit 103 determine whether there is a frequency that can be used solely by the IEEE802.11af WLAN / WMAN by receiving a beacon or spectrum sensing.
(S205)
If there is a frequency that can be used by the system itself, the AP unit 103 selects an arbitrary frequency from the frequencies and performs communication.
(S206)
If there is no frequency that can be used by the system itself and it must share the same frequency with IEEE802.22 WRAN, the exchange uses the Self-Coexistence function to secure the frequency by performing frame contention. Try. At this time, RS2 is recognized as another BS sharing the frequency from BS1.

The flow after frame contention is shown in FIG. Specifically, a frame release request is made to BS1 using frame content defined by IEEE802.22. In BS1, according to a random algorithm defined by IEEE802.22, frame release / non-release is determined, and the result is notified to RS2.
(S207)
When a frame can be used due to a frame release request, the available frequency and time are set to IEEE802.11af.
Is notified to the AP usable frequency management unit 305 in a format compliant with the above.
(S208)
The AP unit 103 notifies the available frequency and time to the MS 3 at the obtained available time. In other words, among the frame timings managed by BS1, the frame period communicated between BS1 and RS2 and the frame period exclusively used for communication between RS2 and MS3 are alternately repeated to obtain the uplink received from MS3. Data is carried to uplink data to BS1, downlink data from BS1 is carried to downlink data to MS3, and user data is brokered. This repetition can be done on demand or in superframe cycles. As a result, the IEEE802.11af WLAN / WMAN can communicate with the IEEE802.22 WRAN in a coexistent manner.
(S209)
Thereafter, the Self-Coexistence function unit 205 of the exchange 102 monitors the IEEE802.11af WLAN / WMAN traffic (and their QoS class) connected to the backhaul line using itself as a relay station, and the traffic amount of the IEEE802.11af is determined. When the number increases, the above means are re-executed in order to request the BS to use a further frequency. Conversely, when there is a request for use of a frequency from another system or BS, the above means are re-executed in order to accommodate the frequency according to the QoS.

  When a plurality of RSs belong to BS1, once one RS successfully releases a frame, the frame time is recognized as a time that can be used by other RSs and can be assigned to IEEE802.11af. For example, before the frame contention in S206, the SCH from the BS1 is received to check the empty frame. If there is no empty frame, the process proceeds to S206, and if there is an empty frame, the frequency and time are notified to the AP unit 103. Thereafter, the process may proceed to S207.

  In the above example, RS2 uses the frequency and time that can be used (transmitted) by itself by IEEE802.11af instead of IEEE802.22, which is acquired by IEEE802.22 frame contention.

In order for RS2 to participate in the frame contention of S204, it is necessary for BS1 to recognize that the CBP transmitted by RS2 is from a regular BS. Various operations of the control management plane are performed as necessary.
In addition, when RS2 is provided with a backhaul line such as another wireless system or FTTH other than IEEE802.22, the exchange 102 or the AP unit 103 may access the DB before S201. In this case, RS2 Rather than a repeater, it functions as a system for cooperative operation.

In place of frame contention (S206) involving inter-base station communication, several methods for releasing part or all of the frame from the CPE to the BS can be used.
For example, in IEEE802.22, when a CPE receives a CBP burst or SCH from the same neighboring system, the information is reported to the BS to which it belongs, and the frame arrangement is scheduled so that the BS avoids interference. There is a function to do. Using it, RS2 reports to BS1 as if it had received interference for any frame time, received the SCH from BS1, and that frame time has not been assigned to any BS (ie freed) After confirming that, the frame time may be given to the AP unit 102 as being usable in IEEE802.11af.
Alternatively, if the BS response to the UCS message is sufficiently agile, the UCS message may be used to report to BS 1 as if it received interference.
These interference reports are meaningful predictions of the occurrence of interference in advance and are not fraudulent.

  In these BS-CPE communication methods, since fair frame allocation considering QoS such as frame contention is difficult, if it is determined from SCH that the number of frames used by BS1 is extremely small, it is truly Interference reporting should be suppressed unless it is subject to interference.

  As described above, according to the present embodiment, IEEE802.22 and IEEE802.11af can coexist without changing the conventional AP and without changing the standard.

  INDUSTRIAL APPLICABILITY The present invention is suitable for connecting two cognitive radio systems using a common frequency band and having different systems (especially cell sizes), and as a cognitive radio system having a smaller cell size (short communication distance). In addition to IEEE802.11af, many wireless systems that use TV white space such as ECMA-392 can be used.

1 ... Base Station, 2 ... Relay Station (Relay
Station), 3 ... Mobile Station,
101 ... antenna, 102 ... switch (Gateway), 103 ... access point (AP),
104 ... terminal, 105 ... terminal, 106 ... terminal, 107 ... terminal,
201 ... RF unit, 202 ... BB signal processing unit, 203 ... MAC processing unit,
204 ... main control unit, 205 ... self-coexistence function control unit,
206 ... interface part,
301 ... RF unit 302 ... BB signal processing unit 303 ... MAC processing unit
304 ... main control unit, 305 ... usable frequency storage unit, 306 ... interface unit

Claims (4)

In the inter-system relay device for connecting the first and second cognitive radio systems using a common frequency band and having different methods,
An exchange unit that operates as at least a client in the first cognitive radio system and wirelessly communicates with a base station of the first cognitive radio system;
An access point unit that operates as an access point in the second cognitive radio system and wirelessly communicates with a subscriber station of the second cognitive radio system,
The switch unit provides the access point unit with information regarding the frequency or time range acquired as available in the first cognitive radio system, the access point unit providing the given frequency or time range. A relay device between heterogeneous systems, which performs radio communication with the subscriber station only within the network. The relay device between different systems according to claim 1,
The first cognitive radio system has a longer communication distance than the second cognitive radio system;
The exchange unit checks the free frequency based on the access to the database related to the existing station and the result of spectrum sensing, and if there is a free frequency, gives information on the free frequency to the access point unit. Requesting the base station to release within a predetermined time range, and providing the access point unit with information on the frequency used by the base station and the available time notified from the base station. A relay device between different systems. The relay device between different systems according to claim 2,
The exchange unit uses the in-system coexistence function defined by the first cognitive radio system to request an opening within the predetermined time range for use in the first cognitive radio system, and A time range is determined by assigning a predetermined frame from a plurality of frames constituting a super frame transmitted by the base station. In a relay method between different systems for connecting the first and second cognitive radio systems using a common frequency band and having different methods,
An exchange unit entering the network as a client of the first cognitive radio system;
An exchange unit or an access point unit accesses a database for managing a frequency usage state provided outside, and obtains information on available frequencies; and
An exchange unit and an access point unit receiving radio signals and detecting available frequencies in respective ways in the first and second cognitive radio systems;
Initiating communication with a subscriber station using the first frequency when a first frequency available in the first and second cognitive radio systems is detected;
When the available first frequency is not detected, the exchange unit communicates with the base station of the first cognitive radio system to which the exchange unit belongs to perform frame contention;
The exchange unit receives a notification of the release of the frame as a result of the frame contention and notifies the access point unit as an available time for the access point unit;
The access point unit communicating with the subscriber station within the available time;
Relaying user data between an exchange unit and an access point unit.

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