JP2001231078A - Wireless packet relay station and wireless packet relay method - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To reduce the time required for relay processing of a data packet and to prevent the data packet from being stuck at the relay station and unable to be promptly transmitted to the destination station. SOLUTION: When a relay station completes reception of a data packet from a source relay station, the relay station transmits an RTS packet to the source relay station instead of an ACK, and the relay of the source receiving the RTC packet. The station recognizes that the relay station has received the data packet normally, and stops the data packet transmission preparation processing until the transmission of the data packet described in the RTS packet is completed. The relay station that has received the RTS packet transmits a CTS packet to the relay station after the SIFS, if the relay station itself can receive a data packet, and the relay station that has received the CTS packet, The next relay station recognizes that the next relay station is ready to receive the data packet, and transmits the data packet to the next relay station after the SIFS.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wireless packet relay station for wirelessly relaying a data packet and a wireless packet relay method in the wireless packet relay station. The present invention relates to a technique for quickly relaying a data packet to a destination station by preparing for transmitting a data packet transmitted from a previous relay station on a communication route to the next relay station when transmitting a packet. .

[0002]

2. Description of the Related Art As a prior art of a wireless packet relay method (wireless access method) in which stations without a master station share a line autonomously, for example, IEEE802.11, which is carrying out global standardization work, DCF of CSMA / CA specified in
(Distributed Coordination Function) “RTS-CTS
The "-DATA-ACK" procedure is known. This procedure is described in “IEEE P8
02.11, Draft Standard for Wireless LAN Medium Acces
s Control (MAC) and Physical Layer (PHY) Speci
fication, P802.11 D6.1, 9 May 1997 ". A conventional technique for applying this wireless access scheme to wireless relay will be described below.

FIG. 4 is an explanatory diagram showing a relay procedure of a conventional wireless relay station (wireless packet relay station). Relay station A
FIG. 3 is a diagram showing an example in which a received data packet is relayed to a relay station B, and the relay station B is relayed to a relay station C.

[0004] Relay station A receives the data packet, transmits an acknowledgment (ACK) packet indicating that the data packet has been received, and then enters a process of transferring the data packet to relay station B. Relay station A uses a DIFS (DCF Inter Frame Spac
While it is called e), it monitors whether another terminal is using the line (hereinafter referred to as carrier sense). During DIFS,
After performing carrier sense, when it is recognized that the line is not used, the next processing is started.

If a line is used between the DIFSs, the line is vacant thereafter, and after the carrier is sensed again for the DIFS time, a random number is generated, and the carrier is sensed for the duration specified by the value. Enter processing. When each station performs the back-off process, the probability of collision with another station can be reduced.

After performing back-off processing between DIFS or after DIFS, relay station A recognizes that the line is not used as a result of carrier sense during this time, and then relay station B transmits data packet. An RTS packet for determining whether the packet is in a receivable state is described to the relay station B, describing the time until the transmission of the data packet is completed.

[0007] The relay stations other than the relay station B that has received the RTS packet recognize that the relay station A is about to transmit a data packet and start carrier sense between DIFS after the time described therein. .

[0008] Upon receiving the RTS packet, the relay station B recognizes that the data packet can be received.
At intervals called SIFS (Short Inter Frame Space)
A CTS packet, which is a packet for confirming the transmission, is described to the relay station A until transmission of the data packet is completed, and is transmitted to the relay station A.

[0009] A relay station other than the relay station A that has received the CTS packet (for example, the relay station C) recognizes that the relay station B is about to receive the data packet, and waits for the time described therein. After that, the career sense between DIFS is started. The relay station A that has received the CTS packet can recognize that the relay station B is in a receivable state, and transmits a data packet after the SIFS.

When the relay station B that has received the data packet recognizes that the data packet has been normally received,
After a while, the AC informs that the data packet was received normally.
Send K packet. Each relay station repeats the same processing as described above, and relays the data packet to the destination station.

[0011]

As a problem to be solved by the present invention, in FIG. 4 which is a sequence diagram of the prior art, the relay station B completes the reception of the data packet,
It is assumed that when an ACK packet is transmitted to relay station A, relay station A has a data packet waiting to be transmitted. The relay stations A and B prepare to transmit the data packet,
Carrier sense between DIFS.

Here, after confirming that the carrier is free as a result of the carrier sense between the DIFSs, each station generates a random number and back-off continues carrier sense for a time designated by the value. Start processing. At this time, if the relay station A can transmit with a value smaller than that of the relay station B, the relay station B, upon receiving the RTS packet from the relay station A, transmits the data packet from the relay station A. Until completion, preparation for data packet transmission will be refrained.

When such a case exists repeatedly or when the number of relays increases, the time required for relay station B to relay the data packet to relay station C becomes slow, and the throughput of the data packet to the destination station is reduced. There is a problem that it becomes low.

Another problem to be solved by the present invention is:
For example, in the above case, even if the relay station B transmits the data packet first during the back-off process, the transmission of the data packet transmitted by the relay station A is started (the RTS is transmitted). ACK transmission time + SIFS time + DIFS time (+ back-off processing time). Therefore, there is a problem that the relay of the data packet is delayed and the throughput is reduced.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems, and it is possible to reduce the time required for data packet relay processing, and to quickly send data packets to a destination station without being stuck in a relay station. It is an object of the present invention to provide a wireless packet relay station and a wireless packet relay method capable of transmitting to a wireless network.

[0016]

In order to achieve the above object, a feature of the present invention is that a plurality of wireless stations use a common wireless carrier to autonomously and discretely relay wireless packet signals. A wireless packet relay station in a communication system that transmits a wireless packet signal to a desired wireless station. When a data signal to be transmitted is generated, carrier sense is performed for a certain time Td, and the wireless line is A transmission enable function for transmitting a signal for checking whether transmission is possible to the next relay station after confirming that it is free, and the next relay station can receive a data signal by the transmission enable function. A wireless packet transmitting function for transmitting the data signal as a wireless packet signal after a certain time Ts (Ts <Td) after the confirmation, When receiving a signal from the previous relay station to confirm whether the own relay station is capable of receiving the data signal, if the signal is receivable, transmitting a signal notifying the reception to the previous relay station Wireless packet receiving function for receiving a data signal transmitted as a wireless packet signal by confirming that the previous relay station is capable of receiving the previous relay station by the reception enable notification function,
In order to relay the data signal received by the wireless packet receiving function, a signal for confirming whether or not transmission is possible to the next relay station is transmitted a certain time Ts after the reception of the data signal. Relay confirmation function,
A wireless packet relay function of transmitting the data signal as a wireless packet signal after a certain period of time Ts after the confirmation that the next relay station can receive the data signal by the relay enable function; The own relay station monitors a signal transmitted by the next relay station to confirm whether transmission of the data signal to the next relay station of the next relay station is possible, and the reception of the signal was confirmed. Sometimes, a wireless packet signal relay confirmation function for confirming that a wireless packet signal including a data signal relayed by the own relay station has been normally received is provided.

A feature of the invention according to claim 2 is that a plurality of radio stations transmit radio packet signals to desired radio stations by relaying radio packet signals autonomously and distributedly using a common radio carrier. In a wireless packet relay method in a communication system, when a relay station has completed receiving a data packet from a source relay station, a data packet can be received instead of an ACK packet indicating that the data packet has been normally received. And transmitting an RTS packet to the transmission source relay station.

A feature of the invention according to claim 3 is that the transmission source relay station that has received the RTS packet recognizes that the relay station has received the data packet normally, and outputs the data described in the RTS packet. The object of the present invention is to stop the data packet transmission preparation processing until the packet transmission is completed.

The relay station that has received the RTS packet according to the fourth aspect of the present invention transmits a CTS packet for transmission confirmation to the relay station after the SIFS if the relay station itself can receive a data packet. The relay station that has transmitted and received this CTS packet recognizes that the other relay station is in a state where it can receive data packets, and after SIFS, transmits the data packet to the next relay station. .

According to the present invention, when the relay station completes the reception of the data packet from the source relay station, the RTS packet is transmitted to the source relay station instead of the ACK. In addition to reducing the time required for packet relay processing, it is also possible to prevent data packets from being stuck at the relay station and being unable to be quickly transmitted to the destination station.

[0021]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a configuration of an embodiment of a wireless packet relay station according to the present invention. The wireless packet relay station includes a wireless transceiver 1, a communication route control unit 2, a communication route information storage unit 3, a data packet relay unit 4, an ACK packet transmission unit 5, an ACK packet reception unit 6, an RTS
Packet transmitter 7, RTS packet receiver 8, CTS packet transmitter 9, CTS packet receiver 10, NAV processor 11, DI
An FS timer processor 12, a SIFS timer processor 13, a back-off processor 14, and a carrier sense processor 15 are provided.

Here, the wireless transceiver 1 performs wireless communication between the wireless packet relay station and another wireless packet relay station. The communication route control unit 2 includes a communication route information storage unit 3
Based on the communication route information stored in (1), the address of the station when each packet is transmitted is managed. The data packet relay unit 4 holds the received data packet, refers to the address and the like obtained by the communication route control unit 2, and
Prepare to relay data packets. When confirming that the data packet has been successfully received, the ACK packet transmitting unit 5 creates an ACK packet for notifying the reception, and prepares for transmission.

After receiving the ACK packet, the ACK packet receiving section 6 recognizes that the transmission of the data packet to the station of the transmission partner has been normally completed. RTS packet transmitter 7
Creates an RTS packet when there is a data packet transmission request, and completes the data packet transmission (Dur
ation) to prepare for transmission. The RTS packet receiving unit 8 receives the RTS packet transmitted from the station,
Recognize the address of the transmission destination, and if the transmission destination is its own terminal, move to the CTS packet transmitting unit 9 and change the transmission destination to
If the terminal is not its own terminal, the processing shifts to the NAV processing unit 11.

When the RTS packet receiving unit 8 requests the CTS packet creation, the CTS packet transmitting unit 9
A packet is created, and the time for completing the transmission of the data packet (Duration) is described to prepare for transmission. After receiving the CTS packet, the CTS packet receiving unit 10 recognizes the address of the transmission destination, and if the transmission destination is its own terminal, the data packet relay unit 4 shifts to preparing for data packet transmission. If the transmission destination is not its own terminal, the process moves to the NAV processing unit 11.

The NAV processing unit 11 waits for RTS (DIFS timer + back-off processing), which is data packet transmission preparation processing, and CTS packet transmission processing until the Duration time described in the RTS or CTS. DIFS timer processing unit 12
Performs a carrier sense by the carrier sense processing unit 15 for a preset DIFS time when there is a data packet transmission request, and monitors whether there is a packet transmission from another station. . When recognizing the processing of the packet from another station, the DIFS timer is started again from the moment when the transmission of the packet is completed and the line becomes free, and after the timer expires, the process proceeds to the back-off processing unit 14. When a transmission request for a CTS packet, an ACK packet, and a data packet is issued, the SIFS timer processing unit 13 prepares for transmission for a preset SIFS time.

The back-off processing section 14 generates a random number when the DIFS timer expires in the back-off processing in the DIFS timer processing section 12 and performs carrier sense by the carrier sense processing section 15 for a designated time. And monitor whether there is any transmission from another packet. When the transmission of a packet from another station is recognized, the process proceeds to the DIFS timer processing unit 12.

FIG. 2 is an explanatory diagram showing an embodiment of the wireless packet relay method according to the present invention. The wireless packet relay station A having the configuration shown in FIG. The transmission / reception procedure when transmitting to the wireless packet relay station C is described.

FIG. 3 is a sequence diagram showing the operation of each station when transmitting a data packet from the wireless packet relay station A to the wireless packet relay station C via the wireless packet relay station B in the transmission / reception procedure shown in FIG. is there.

Next, the operation of this embodiment will be described with reference to FIGS. FIGS. 2 and 3 show a situation where data packets are relayed from the source station A to the relay stations B and C in this order. The source station A prepares an RTS packet when a request for data packet transmission is made (step 301a). When transmitting source station A transmits an RTS packet,
As in the prior art, carrier sensing is performed during a so-called DIFS (step 302a). After performing the carrier sense between DIFSs, when it is recognized that no packet is transmitted from another station and the line is free, the RTS packet is transmitted to the relay station B.
It is transmitted to the address (step 303a). The RTS packet describes the time required to complete the transmission of the data packet from the source station A to the relay station B.

If packet transmission from another station is confirmed during carrier sense between DIFSs, transmission of the packet from the other station is completed, and from the moment when it is recognized that the line is free, the packet is transmitted again. Start the DIFS timer. After the completion of the DIFS timer, a random number is generated, and the process enters a back-off process of performing carrier sense only for a period specified by the value. In the meantime, if the transmission of the packet from another station is not detected, the RTS packet is transmitted.

When the relay station B receives the RTS packet,
It is determined whether or not the data packet from the source station A can be received (step 301b). If it is not in a receivable state, no reply is made (step 302).
b). If it is in a receivable state, it waits for the elapse of a time called SIFS (step 303b), and transmits a CTS packet to the source station A (step 304b). Like the RTS packet, the CTS packet also describes the time required to complete the transmission of a data packet from the source station A to the relay station B.

Here, the relay station (for example, relay station C) other than the source station A that has received the CTS packet sets the NAV for the time described in the CTS packet and prepares for data packet transmission. To stop.

The source station A, which has received the CTS packet, can recognize that the relay station B is in a state capable of receiving the data packet, waits for the inter-SIFS period (step 304a), and sends it to the relay station B. The data packet is transmitted (305a). The relay station B that has normally received the data packet waits for a lapse of SIFS (step 305b),
An RTS packet is transmitted to the next relay station, relay station C, on the communication route (step 306b).

The source station A, which has received the RTS packet, receives the RTS packet at the time of receiving the ACK packet for notifying the normal completion of the transmission of the data packet.
It recognizes that the transmission of the data packet to the relay station B has been completed normally. Thereafter, the source station A keeps the NAV until the relay station B completes the transmission of the data packet addressed to the relay station C.
Is set, and the data packet transmission preparation processing is stopped.

The relay station C that has received the RTS packet determines whether or not it is in a state where it can receive a data packet (step 301c). If it is not in a receivable state, no reply is made (step 302c). If it is in a receivable state, it waits for the elapse of SIFS (step 303c), and transmits a CTS packet to relay station B (step 304c).

The relay station B having received the CTS packet can recognize that the relay station C is in a state capable of receiving the data packet, and waits for the passage of the SIFS (step 307b). (Step 308b). The relay station C that has normally received the data packet, after the elapse of the SIFS (step 305c),
The RTS packet is transmitted to the next relay station on the communication route (step 306c). The above processing is repeated at each relay station until the data packet is delivered to the destination station, so that the data packet is relayed.

According to the present embodiment, the relay station B is
When receiving the data packet from the
Since the TS packet is transmitted to the relay station A, at this time, even if the relay station A has a data packet waiting to be transmitted, only the relay station B sends the received data packet to the relay station C promptly after the SIFS. be able to. Thereby, it is possible to prevent the data packet from being stuck in the relay station B and making it difficult to perform the relay processing of the data packet.

In addition, the function of the ACK packet for notifying the completion of the normal reception of the data packet is held in the RTS packet for determining whether the data packet can be received, so that the ACK transmission time + DIFS time (+ backoff processing ), The time required for the data packet relay process can be shortened, and the throughput to the destination can be increased.

[0039]

As described in detail above, by using the wireless packet relay station and the wireless packet relay method of the present invention, when a data packet is relayed from a source station to a destination station using the relay station. By allowing the RTS packet that requests transmission confirmation to have the function of the ACK packet that notifies the completion of the normal reception of the data packet,
The time corresponding to the transmission time + DIFS time (+ back-off processing time) can be reduced, and the relay station can quickly relay the data packet. As a result, the data packet can be relayed with priority and the time required for the transmission source station to transmit the next data packet can be reduced, so that the data packet is delayed at the relay station. This has the effect of quickly relaying to the destination station.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment of a wireless packet relay station according to the present invention.

FIG. 2 is an explanatory diagram showing one embodiment of a wireless packet relay method of the present invention.

3 is a sequence diagram showing an operation of each station when transmitting a data packet from a wireless packet relay station A to a wireless packet relay station C via a wireless packet relay station B in the transmission / reception procedure shown in FIG. 2;

FIG. 4 is an explanatory diagram showing a relay procedure of a conventional wireless relay station (wireless packet relay station).

[Explanation of symbols]

 Reference Signs List 1 wireless transceiver 2 communication route control unit 3 communication route information storage unit 4 data packet relay unit 5 ACK packet transmission unit 6 ACK packet reception unit 7 RTS packet transmission unit 8 RTS packet reception unit 9 CTS packet transmission unit 10 CTS packet reception unit 11 NAV processing unit 12 DIFS timer processing unit 13 SIFS timer processing unit 14 Back-off processing unit 15 Carrier sense processing unit A, B, C Wireless packet relay station

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[Procedure amendment]

[Submission date] March 16, 2000 (200.3.1.1)
6)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claim 2

[Correction method] Change

[Correction contents]

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0017

[Correction method] Change

[Correction contents]

A feature of the invention according to claim 2 is that a plurality of radio stations transmit radio packet signals to desired radio stations by relaying radio packet signals autonomously and distributedly using a common radio carrier. In the wireless packet relay method in the communication system, when the relay station has completed receiving the data packet from the source relay station, instead of an ACK packet that informs the previous relay station that the data packet has been normally received, Transmits an RTS packet to the next relay station to determine whether the data packet can be received .
Lies in the fact, including that step.

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0020

[Correction method] Change

[Correction contents]

According to the present invention, when the relay station completes receiving a data packet from the source relay station, the data packet is
Instead of an ACK to inform the previous relay station of the
Whether data packets can be received by the relay station
By transmitting the RTS packet for determining whether or not the data packet is relayed, the time required for the data packet relay processing is reduced, and the data packet is prevented from being stuck at the relay station and cannot be quickly transmitted to the destination station.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0034

[Correction method] Change

[Correction contents]

The source station A, which has received the RTS packet, before
Since the RTS packet addressed to the relay station C from the relay station B can be received at the time when the ACK packet notifying that the normal transmission of the data packet has been normally received is received, the RTS packet is received.
By receiving the packet, it is recognized that the transmission of the data packet to the relay station B has been completed normally. afterwards,
The source station A sets the NAV and stops the data packet transmission preparation processing until the relay station B completes the transmission of the data packet addressed to the relay station C.

[Procedure amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0037

[Correction method] Change

[Correction contents]

According to the present embodiment, the relay station B is
ACK packet when data packet from
Relay station A receives RTS packet to relay station C instead of
That transmission to relay station B has been completed normally
It can be recognized, at this time, even if there is a data packet waiting for transmission to the relay station A, only the relay station B can send post between SIFS, quickly the data packet received to the relay station C . Thereby, it is possible to prevent the data packet from being stuck in the relay station B and making it difficult to perform the relay processing of the data packet.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H04L 29/08 H04L 13/00 307Z (72) Inventor Masahiro Morikura 2-3-3 Otemachi, Chiyoda-ku, Tokyo No. 1 F-term in Nippon Telegraph and Telephone Corporation (reference) FF03 FF04 FF12 FF27 GG11 GG14

Claims (4)

[Claims] 1. A wireless packet relay station in a communication system in which a plurality of wireless stations relay a wireless packet signal autonomously in a distributed manner using a common wireless carrier to transmit a wireless packet signal to a desired wireless station. When a data signal to be transmitted is generated, a certain time T
A transmission permission confirmation function of transmitting a signal for confirming whether transmission to the next relay station is possible after performing carrier sense during d and confirming that the wireless line is free, and the transmission permission confirmation function A wireless packet transmission function of transmitting the data signal as a wireless packet signal after a certain period of time Ts (Ts <Td) when it is confirmed that the next relay station can receive the data signal; When a signal for confirming whether or not the own relay station can receive a data signal is received from a relay station in front of the own relay station, a signal notifying the reception is sent to the previous relay station if the signal can be received. And a reception enable notification function for transmitting the data signal transmitted as a wireless packet signal by confirming that the previous relay station is capable of receiving by the reception enable notification function. A wireless packet receiving function, and a signal for confirming whether or not transmission to the next relay station is possible in order to relay the data signal received by the wireless packet receiving function, after receiving the data signal. A relay confirming function to be transmitted after a fixed time Ts; and when the relay confirming function confirms that the next relay station can receive the data signal, the data signal is transmitted after a certain time Ts after the confirmation. A radio packet relay function of transmitting the data signal as a radio packet signal, and a signal transmitted by the next relay station, the signal for confirming whether the data signal can be transmitted to the next relay station of the next relay station. Monitoring, when the reception of the signal is confirmed, a radio packet for confirming that the radio packet signal including the data signal relayed by the own relay station has been normally received; Wireless packet relay station, characterized by comprising a preparative signal relay confirmation function. 2. A wireless packet relay method in a communication system for transmitting a wireless packet signal to a desired wireless station by autonomously distributing and processing a wireless packet signal by using a common wireless carrier by a plurality of wireless stations. When the relay station has completed receiving the data packet from the source relay station, it determines whether or not the data packet can be received instead of the ACK packet indicating that the data packet has been normally received. Transmitting a RTS packet to the source relay station. 3. The transmission source relay station receiving the RTS packet recognizes that the relay station has received the data packet normally, and waits until the transmission of the data packet described in the RTS packet is completed. 3. The data packet transmission preparation process is stopped during the time of.
The wireless packet relay method according to the above. 4. The next relay station receiving the RTS packet, if it can receive the data packet,
After the FS, a CTS packet for transmission confirmation is transmitted to the relay station, and the relay station receiving the CTS packet recognizes that the other relay station is in a state capable of receiving data packets, and The wireless packet relay method according to claim 2, wherein the data packet is transmitted to the next relay station after a while.