JP2001053745A - Radio packet communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid interference from a peripheral zone using the same frequency by permitting an access point(AP) and a station(STA) to reserve a necessary frequency resource in accordance with a request and permitting a radio station to which the frequency resource is allocated to confirm the use situation of a channel to transmit preferential data only when the channel is not used. SOLUTION: A radio stations STA111 to which a frequency resource is allocated judges whether a channel is used at present or not from a physical carrier sense, namely, from a reception signal level before data are transmitted at designated transmission timing N1. Then, preferential data 501 and 502 are transmitted after confirming that the channel is not used at present, namely, the other radio station STA112 is not in the middle of transmission. NAV721 and 722 are set while preferential data 501 and 502 are transmitted, the other radio station STA112 inhibits the transmission of the self-station and gives priority to data 501 and 502 that the radio station STA111 transmits.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radio packet communication system provided with a frequency resource reservation method in a data link layer.

[0002]

2. Description of the Related Art When transmitting real-time data such as voice and moving images using packet communication, a part of a frequency band which is a resource of the system on a path between a transmitting station and a receiving station. It is pointed out that it is necessary to make a reservation.
A method of transmitting a data packet having real-time properties by using the reserved bandwidth is generally used.

[0003] As a method of reserving frequency resources in conventional packet communication, an RSVP (Resource Reservation Prism) is used.
otocol) exists ("Resource Reservation Protocol (R
(SVP)-Version 1 Functional Specification, RFC 220
5, IETF). RSVP is intermediate between a transport layer protocol such as TCP and a network layer protocol such as IP, and is a protocol for reserving frequency resources for an end-to-end IP data flow from a sending application to a receiving application. RSVP instructs lower layer protocols to reserve frequency resources required for data transmission.

In the method of reserving frequency resources by RSVP, information called PATH is transmitted from the transmitting side at a fixed period, and after receiving the PATH, the receiving side transmits the RESV signal upstream to reserve frequency resources. In addition, the receiving side can continuously reserve frequency resources by continuously sending the RESV signal. The actual securing of frequency resources plays the role of the IP layer or data link layer instructed by RSVP.

[0005] A network layer or data link layer protocol instructed to reserve frequency resources by a protocol such as RSVP needs to actually reserve resources. For example, in a network using an ATM (Asynchronous Transfer Mode) exchange, end-to-end QoS (Quo
quality of service), and a procedure for resource reservation is performed when a connection for data transfer is established.

As a method for performing priority control in the data link layer, there is a method defined by IEEE 802.1D Annex H. IEEE 802.1D Annex H is Switche
d Defines the data queuing method in a LAN environment. The data link layer has seven types of transmission queues having different priorities, and a data flow sent from an upper layer is buffered in a transmission queue having a priority corresponding to a service class. Although the method of transmitting queued data is not specified in IEEE 802.1D Annex H, it is similar to assigning priority to each data flow by transmitting data in the order according to the priority of the queue. The effect of is obtained.

As an example of a priority control method in a conventional wireless packet communication system, there is a method using a CFP (Contension Free Period) of an IEEE 802.11 wireless LAN system. This is taken as an example of a priority control method in a conventional wireless packet communication system, and the outline is shown in FIG. CFP
Is an optional procedure for IEEE 802.11 systems,
Manages access to the channel, and performs non-contention type data transfer. The channel of the IEEE 802.11 system is CFP and the CP (Contention P
eriod) are set alternately, and CFP appears at a constant cycle. Downlink data transfer in the CFP is performed by the AP transmitting data and the destination STA of the data returning an ACK. On the other hand, the STA prohibits voluntary data transmission by setting the NAV by the virtual carrier sense function during the CFP, and transmits data only when polled by the AP. For this reason, data transmission from the STA is always performed immediately after receiving the polling frame P. At this time, by defining a procedure for priority control for data transfer in the CFP in the AP, priority control for a specific data flow can be performed.

As an example of a conventional resource reservation method in wireless packet communication, there is a method using a distributed control procedure called DCF (Distributed Cordination Function) of an IEEE 802.11 wireless LAN system (for example, Inoue, Iizuka, Takanashi, Morikura, “CSMA / in high-speed wireless LAN systems
Priority control method using CA, IEICE, B-5-23
0, '97 General Conference, March 1999). An outline of this method is shown in FIG. The AP and the STA each have a timer, and manage the time modulo while maintaining synchronization. In DCF, both APs and mobile stations are equal in terms of position, and CSMA / CA (Carrier Sense
Data transmission is performed according to an iple Access with Collision Avoidance (collision avoidance type carrier detection access) protocol. That is, it is essential to perform carrier sense before performing data transmission. In this method, the AP allocates a transmission timing, a packet length, and the like for each data flow according to a request from an application program or a higher-level protocol. In the figure, the AP performs allocation (ALC) according to a resource allocation request (REQ) from the STA, and transmits frame transmission timings (N1, N2) for transmitting each data flow.
And the frame length (s1, s2) at that time. In addition, when the AP allocates resources, the beacon (202 to 207) transmitted thereafter notifies the allocated information, that is, the timing and size, to prohibit transmission of other stations at the same timing. are doing. on the other hand,
In the STA, the NAV is set at the transmission timing of the other station notified by the beacon, and the data transmission of the own station is prohibited.
As a result, it is possible to guarantee that a specific data flow is preferentially transmitted at a certain timing.

[0009]

Conventionally, priority control for transmitting a specific data flow and reservation of frequency resources have been performed using the above-described method. Generally, when a service area is configured by a plurality of zones, a frequency channel used in a certain wireless zone may be used in surrounding zones.

[0010] Therefore, in the example of the priority control in the conventional wireless packet communication system and the example of the resource reservation method in the conventional wireless packet communication, the transmission of the preferential data in one zone changes the transmission of the data in another zone. If the transmission overlaps with the transmission in time, there is a problem that reception of the data at the receiving station fails due to co-channel interference.

An object of the present invention is to provide a wireless packet communication system having means for avoiding interference from a peripheral zone using the same frequency when transmitting priority data in a certain zone.

[0012]

SUMMARY OF THE INVENTION In order to achieve the above object, a feature of the present invention is that an access point AP is a wireless station having a data relay function and a station is a mobile wireless station.
STA, the AP and the STA are channel access means according to the CSMA / CA protocol, and a timer, a time counter for modulo management with a counter circulating time from 0 to M-1 (M is a natural number), Physical carrier sense means for judging use / non-use of a channel from received signal power; virtual carrier sense means for prohibiting access to the channel while the frame is being transmitted based on information in the header of the received frame The AP periodically transmits a beacon, which is a broadcast signal, by a beacon generation processing unit, and the STA receives a beacon transmitted by the AP, performs time synchronization, and grasps a channel configuration. A station is a wireless packet communication system that performs collision avoidance according to the CSMA / CA protocol when transmitting data. (A) The AP and the STA When reservation of frequency resources required for communication is requested from an upper layer protocol, reserves required frequency resources instructed by the upper layer protocol with respect to a resource management process in the AP, (b The AP requested to reserve the frequency resource, if the requested resource can be allocated, a time counter value indicating the timing at which the wireless station performs transmission;
Data length, and determines the transmission cycle and notifies the requesting radio station, and, if the allocation of frequency resources is not possible, to the radio station to reject the allocation When the AP has allocated frequency resources to the wireless station, the AP notifies the STA in the cell of information such as the transmission timing and frame length allocated to the wireless station by a broadcast signal, and (c) ) The wireless station notified of the transmission timing of the priority data of the other station by the broadcast signal, at that timing by the virtual carrier sense means
By setting a NAV (Network Allocation Vector), that is, by assuming that the channel is in use regardless of the actual channel usage status, the transmission of the own station at the timing concerned is prohibited, and (d) priority is given to the AP. A radio station to which a frequency resource for transmitting data is assigned immediately before transmitting the priority data, judges whether or not the channel is in use from the physical carrier sense, that is, the received signal power, and determines whether the channel is not used. In the wireless packet communication system, transmission of priority data is performed when it is determined to be used, and transmission of priority data is postponed when it is determined that the channel is in use. is there.

In the conventional radio packet communication system, a radio station to which frequency resources have been allocated performs carrier sense before transmitting priority data, checks the use status of a channel, and determines that the channel is unused. The difference is that priority data is transmitted only in the case.

Another feature of the present invention is that at the transmission timing specified by the AP, priority data of a specified frame length is transmitted, and the radio station transmitting the priority data records the transmission result of the priority data, The AP is a wireless packet communication system that reassigns the transmission timing of the priority data by the radio station when the transmission of the priority data fails at a rate exceeding a predetermined rate.

[0015] In the above description, a radio station indicates either an address point (AP) or a station (STA).

The difference from the conventional wireless packet communication system is that when priority data transmitted using the allocated frequency resources fails continuously, the AP reallocates resources.

[0017]

FIG. 1 shows the configuration of an address point AP. The AP includes a physical layer, a data link layer, and an upper layer. The physical layer has modulation / demodulation processing means for transmitting and receiving signals, and the data link layer has channel access means based on CSMA / CA. The transmission / reception processing of the frame in the data link layer is performed via the channel access unit. Also, the AP has a timer and a time counter for modulo management of time, a beacon generation processing means for transmitting a beacon signal at regular intervals, a resource management means for executing management and reservation of frequency resources, A virtual carrier sense means for setting the NAV (Network A11ocation Vector) based on the information to consider that the channel is in use, and to refrain from transmitting its own station while other wireless stations are using the channel, Also, it has a physical carrier sense means for judging whether or not the channel is in use based on the signal level input to the receiver.

FIG. 2 shows the configuration of the station STA. STA
Is composed of a physical layer, a data link layer, and an upper layer. The physical layer has modulation / demodulation processing means for transmitting / receiving signals, and the data link layer has channel access means based on CSMA / CA. The transmission / reception processing of the frame in the data link layer is performed via the channel access unit. The STA also has a timer and a time counter for modulo management of time, a beacon analysis processing means for receiving a beacon transmitted by the AP, performing time synchronization and grasping a channel configuration, and a resource for requesting reservation of frequency resources. Request processing means, based on the information in the received frame, NAV (Network A11ocation
Vector), the channel is considered to be in use, and virtual carrier sense means for refraining from transmitting the own station while other radio stations are using the channel, as well as input to the receiver. There is a physical carrier sense means for determining whether or not the channel is in use based on the signal level.

[First Embodiment] FIG. 5 is a diagram for explaining a first embodiment of the present invention. An example is shown in which preferential data transfer is performed in zones 001 and 002 which may interfere with each other using the same frequency. At this time, in the zones 001 and 002, the time is synchronized by the beacon transmitted by each AP inside each zone, but the time between the zones is not synchronized.

In the zone 001, the AP 101 returns ALC401 and ALC402 as responses to REQ301 and REQ302 as resource allocation requests from the STA111 and STA112, respectively.
Is allocated a frequency resource defined by the transmission timing N1 and the frame length s1, and a STA 112 is allocated a frequency resource defined by the timing N2 and the frame length s2. In the zone 002, AP102 returns a response ALC411 to REQ311 which is a resource allocation request from the STA 113,
Frequency resources defined by the transmission timing N3 and the frame length s3 are allocated.

A radio station to which frequency resources have been assigned performs carrier sense before transmitting data at a designated transmission timing. Then, after confirming that another wireless station is not transmitting, transmission is performed. In addition, radio stations other than the radio station to which the frequency resource has been allocated set the NAV while the priority data is being transmitted, and prohibit transmission of the own station. In FIG. 5, STA111 is data 501,
During transmission of the data 502, the STA 112 sets NAV721 and NAV722, respectively, to give priority to the data transmitted by the STA111.

The carrier sense performed immediately before the transmission of the priority data is a physical carrier sense. If a signal having a power equal to or higher than a predetermined level is detected in the receiver during the carrier sense, The transmission of the priority data scheduled at that time is postponed. This situation is compared with the frequency resources allocated to STA 111 in zone 001 and zone O02.
The case where the frequency resources allocated to the STAs 113 in the STA 113 overlap in terms of timing will be described as an example. At this time, the transmission timing assigned to the STA 111 in the zone 001 is
If the transmission timing is earlier than the transmission timing assigned to the STA 113 in 2, the signal transmitted by the STA 111 is detected while the STA 113 performs carrier sense as shown in FIG. In this case, the STA 113 forgoes transmission of the priority data at the assigned timing.

[Second Embodiment] FIG. 6 is a diagram for explaining a second embodiment of the present invention. In the situation described in the first embodiment, it is possible to detect that the AP 102 in the zone 002 did not transmit data at the timing assigned by the STAl 13.

According to the second embodiment, the situation where the radio station to which the frequency resource is allocated by the AP does not send data at the transmission timing specified by the AP exceeds a predetermined ratio (N / L times). AP), the AP reassigns frequency resources to the radio station. zone
The AP 102 of 002 responds to the resource allocation request 311 from the STA 113 at the timing N3 specified by the ALC 411 at the timing N3.
It is assumed that the frame transmitted from 13 is not received. This is because STAl13 performed carrier sense immediately before transmission, and as a result, detected a signal from a peripheral zone (zone 001 in the figure), and thus postponed its own transmission.

When the above situation occurs N times out of L times at the transmission timing N 3 assigned to the STA 113, the AP 102 allocates frequency resources again. In FIG. 6, L = 1,
An example when N = 1 is shown. AP102 is STA1 by ALC412
13, a new transmission timing N3 ′ and a frame length s3
To avoid interference with other zones.

As a modification of the second embodiment, it is also possible to make the AP re-allocate the frequency resources when the transmission of the radio station has failed successively a predetermined number of times.

[0027]

As described above, according to the first embodiment, a radio station that wants to transmit priority data is assigned a frequency resource for it. At this time, the wireless station is assigned a frame length and a modulo counter value indicating the timing for transmitting the priority data. When transmitting data of a designated length at a designated timing from the AP, the wireless station performs carrier sense immediately before the transmission, and transmits priority data only when the channel is idle.

This solves the problem that in the conventional method, when the transmission timing of the priority data overlaps with that of the neighboring cell using the same channel, the problem of failure due to interference or collision is solved, and the packet error rate is improved. It becomes possible.

Further, the improvement of the packet error rate improves the throughput of the entire system.

The second embodiment is different from the first embodiment in that the wireless station transmitting the priority data determines that the channel is in use at the time of the immediately preceding carrier sense and forgos the transmission of the priority data. When transmission occurs, another transmission timing for transmitting the priority data to the wireless station to which the AP has forgotten the transmission, that is, one that can allocate a frequency resource different in time from the previous allocation It is.

Thus, it is possible to prevent a wireless station that has forgotten the transmission from forgoing the transmission as a result of the carrier sense even at the next transmission timing and continuously losing the opportunity to transmit the priority data.

[0032] This also enables dynamic allocation of frequency resources to STAs under the control of each AP while sharing bands with neighboring cells using the same frequency.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an access point AP.

FIG. 2 is a configuration diagram of a station STA.

FIG. 3 is a diagram illustrating an example of a priority control method in a conventional wireless packet communication system.

FIG. 4 is a diagram illustrating a resource reservation method in a conventional wireless packet communication system.

FIG. 5 is a diagram illustrating a first embodiment of the present invention.

FIG. 6 is a diagram illustrating a second embodiment of the present invention.

[Explanation of symbols]

 001,002 Wireless zone (cell) 010 Modulation / demodulation processing means 020 Channel access means 021 Virtual carrier sense means 022 Physical carrier sense means 023 Resource management means 024 Resource request processing means 025 Beacon generation processing means 026 Beacon analysis processing means 027 Time counter 028 Timer 030 Upper layer protocol processing means 101,102 Access point AP 111-114 Station STA 201-217 Beacon signal 301,302,311 Resource allocation request (REQ) 401,402,411 Resource allocation response (ALC) 501-503 Data 601-603 Response (ACK) 711,721,722,741 NAV (Network Allocation) Vector)

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Masahiro Morikura 3-19-2 Nishi-Shinjuku, Shinjuku-ku, Tokyo F-term within Nippon Telegraph and Telephone Corporation (reference) 5K033 AA07 CA08 CB01 CB06 CB17 CC01 DA01 DA19 DB09 DB16 EA02

Claims (3)

[Claims] 1. An access point (AP) which is a wireless station having a data relay function and a station (S) which is a mobile wireless station.
TA), and the access point (AP) and the station (STA) have a channel access means according to the CSMA / CA protocol, a timer, and a time from 0 to M-1 (M
Is a natural number), a time counter for modulo management by a counter circulating, a physical carrier sense means for judging use / non-use of a channel from received signal power, and a frame transmitted from information in a header of a received frame. The access point (AP) periodically transmits a beacon, which is a broadcast signal by beacon generation processing means, and the station (STA) transmits the access point to the access point. By receiving the beacon transmitted by (AP),
Time synchronization, and, to understand the channel configuration, each wireless station in a wireless packet communication system that performs collision avoidance according to the CSMA / CA protocol at the time of data transmission, (a) the access point (AP) and the station
(STA) is the access point (A) when requested to secure frequency resources necessary for communication from an upper layer protocol.
For the resource management process in P), it has means for reserving required frequency resources instructed by the upper layer protocol, (b) The access point (AP) requested to reserve frequency resources, If the requested resource can be allocated, the time counter value indicating the timing at which the wireless station performs transmission, the data length, and the transmission cycle are determined and notified to the requesting wireless station. Performing, and, if the allocation of the frequency resources is impossible, has means for notifying the radio station that the allocation is rejected, the access point (AP) to the radio station When frequency resources are allocated, the system has means for notifying a station (STA) in a cell of information such as a transmission timing and a frame length allocated to the wireless station by a broadcast signal, and (c) other information by the broadcast signal. The radio station is notified of the transmission timing of the priority data of NAV by the virtual carrier sense means in the timing (Network Allocation V
ector), that is, regardless of the actual state of use of the channel, by assuming that the channel is in use, has means for prohibiting transmission of its own station at the timing, (d) the access point The radio station to which the frequency resource for transmitting the priority data is transmitted by the (AP) determines whether or not the channel is being used based on the physical carrier sense, that is, the received signal power immediately before the transmission of the priority data. And, when it is determined that the channel is unused, transmission of the priority data is performed, and when it is determined that the channel is being used, a means for delaying the transmission of the priority data is provided. A wireless packet communication system, characterized by: 2. A transmission station according to claim 1, wherein said transmission unit transmits priority data having a designated frame length at a transmission timing designated by an access point, and a radio station transmitting said priority data records a transmission result of said priority data. The wireless access point according to claim 1, wherein the access point (AP) has means for reassigning the transmission timing of the priority data by the wireless station when the transmission of the wireless station fails beyond a predetermined rate. Packet communication system. 3. The transmission station transmits priority data of a specified frame length at a transmission timing specified by an access point (AP), and a wireless station transmitting the priority data records the transmission result of the priority data, The wireless packet communication according to claim 1, wherein the access point (AP) has means for re-assigning the transmission timing of the priority data by the wireless station when the transmission of the wireless station fails a predetermined number of times continuously. system.