JPH0856229A - Radio communication method - Google Patents

Radio communication method

Info

Publication number
JPH0856229A
JPH0856229A JP6190689A JP19068994A JPH0856229A JP H0856229 A JPH0856229 A JP H0856229A JP 6190689 A JP6190689 A JP 6190689A JP 19068994 A JP19068994 A JP 19068994A JP H0856229 A JPH0856229 A JP H0856229A
Authority
JP
Japan
Prior art keywords
time
master station
command
radio terminal
information
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
JP6190689A
Other languages
Japanese (ja)
Inventor
Hisafumi Hara
尚史 原
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Oki Electric Industry Co Ltd
Original Assignee
Oki Electric Industry Co Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Oki Electric Industry Co Ltd filed Critical Oki Electric Industry Co Ltd
Priority to JP6190689A priority Critical patent/JPH0856229A/en
Publication of JPH0856229A publication Critical patent/JPH0856229A/en
Pending legal-status Critical Current

Links

Landscapes

  • Detection And Prevention Of Errors In Transmission (AREA)
  • Small-Scale Networks (AREA)
  • Mobile Radio Communication Systems (AREA)

Abstract

PURPOSE:To reduce the communication traffic and to shorten the reply time of a slave station on the occurrence of an error by allowing the slave station to make a reply to a master station when a transmission request is not received by the slave station within a prescribed time. CONSTITUTION:A radio terminal equipment #1 sends periodically a command to radio terminal equipments #2 to #n at an interval within a time t1. After the receipt of the command from the radio terminal equipment #1, the radio terminal equipments #2 to #n return a reply after the lapse of a random time and use a timer to count a time after the reception of the command. When the count exceeds the time t1, it is discriminates that the command is sent from the radio terminal equipment #1 at least within this time and when the radio terminal equipments #2 to #n are terminal equipments making status monitor for example, the status information for that case is sent to the radio terminal equipment #1 as its reply even when the command from the radio terminal equipment #1 is not received. Thus, it is not required for the master station to send a re-transmission command in the case of no reply from slave stations.

Description

【発明の詳細な説明】Detailed Description of the Invention

【0001】[0001]

【産業上の利用分野】本発明は無線通信システムにおけ
る無線通信方法に関するものである。
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wireless communication method in a wireless communication system.

【0002】[0002]

【従来の技術】従来、複数の端末間で通信を行なう無線
通信システムの無線通信方法は、例えば、無線端末#1
が無線端末#2〜#nに対してコマンドを送信し、コマ
ンドを受信した無線端末#2〜#nはランダムな時間経
過後に無線端末#1に応答を返すようになっている。し
かし、回線品質の劣化等により無線端末#1と無線端末
#2〜無線端末#n間の通信が正常に終了しなかった場
合には、その通信が正常に終了しなかった無線端末に対
して無線端末#1はコマンドを再送して応答を得ること
になる。また、送信するデータ形式は、無線端末#2〜
#nが、例えば状態監視を行なう監視端末の場合には、
状態監視を行う監視対象の状態情報に識別情報やCRC
(Cyclic Redundancy Check)
などを付加した形式が用いられることが多い。
2. Description of the Related Art Conventionally, a wireless communication method of a wireless communication system for communicating between a plurality of terminals is, for example, wireless terminal # 1.
Transmits a command to the wireless terminals # 2 to #n, and the wireless terminals # 2 to #n that receive the command return a response to the wireless terminal # 1 after a lapse of random time. However, if the communication between the wireless terminal # 1 and the wireless terminals # 2 to #n is not normally terminated due to the deterioration of the line quality or the like, the wireless terminals for which the communication is not normally terminated are The wireless terminal # 1 will retransmit the command and obtain a response. The data format to be transmitted is wireless terminal # 2.
If #n is, for example, a monitoring terminal that monitors status,
The status information of the monitoring target for status monitoring includes identification information and CRC.
(Cyclic Redundancy Check)
The format with the addition of such as is often used.

【0003】[0003]

【発明が解決しようとする課題】上記のような従来の無
線通信方法では、有線通信に比べて無線通信の回線品質
が悪い為、通信エラーが度々発生してしまい、その都度
コマンドを再送し、応答を得ているので、無線回線の通
信トラフィックは増大し、電波のぶつかりあるいは回線
ビジーによる情報伝達までの時間が長くなり、また、デ
ータ誤りによる通信エラーが発生する確率は、伝送する
データが長くなるほど高くなるので、長いデータを送信
するとさらに情報伝達までの時間が長くなってしまうと
いう問題点があった。
In the conventional wireless communication method as described above, since the line quality of the wireless communication is worse than that of the wired communication, a communication error frequently occurs, and the command is retransmitted each time. Since the response is received, the communication traffic of the wireless line increases, the time until information transmission due to collision of radio waves or line busy becomes long, and the probability of communication error due to data error is that the transmitted data is long. Since it becomes higher, the longer it takes to transmit information, the longer it takes to transmit information.

【0004】[0004]

【課題を解決するための手段】本発明に係る無線通信方
法は、少なくとも1つの親局から一定の周期で送信要求
を送信し、複数の子局で親局からの送信要求を受信し、
その受信した送信要求に基づいて親局に応答する無線通
信方法において、あらかじめ設定された一定時間内で送
信要求が子局で受信できなかったとき、親局に応答する
ものであり、また、親局に応答する情報があらかじめ設
定された一定時間内で同一のときには、親局への応答を
行わないものである。
A wireless communication method according to the present invention transmits a transmission request from at least one master station at a constant cycle, and receives a transmission request from the master station at a plurality of slave stations,
In the wireless communication method that responds to the master station based on the received transmission request, when the slave station cannot receive the transmission request within a preset fixed time, it responds to the master station. When the information responding to the station is the same within a predetermined time set in advance, it does not respond to the master station.

【0005】[0005]

【作用】本発明においては、あらかじめ設定された一定
時間内において、送信要求が子局で受信できなかったと
きには、子局は親局に応答し、また、親局に応答する情
報があらかじめ設定された一定時間内で同一のときに
は、親局への応答を行わないようにする。
In the present invention, when the transmission request cannot be received by the slave station within a preset time, the slave station responds to the master station, and information for responding to the master station is preset. Also, if the same within a certain period of time, do not respond to the master station.

【0006】[0006]

【実施例】【Example】

実施例1.図1は本発明の一実施例に係る無線通信方法
を示すシーケンス図、図2はこの実施例の無線通信方法
を適用した無線通信システムの構成を示す概略図であ
る。この実施例では、図2に示すように、無線端末#1
と無線端末#2〜#nの複数の無線端末との間で通信を
行うものであり、あらかじめ設定された一定時間t1
に1回は、無線端末#1から無線端末#2〜#nに対し
てコマンドが送信されることがわかっている場合で、そ
の一定時間t1 内に無線端末#2〜#nの中でコマンド
が正常に受信できなかった無線端末があったとき、その
無線端末はその間に無線端末#1からコマンドが送信さ
れたが回線の劣化によりデータが届かなかったというこ
とを判断し、無線端末#1からの再送コマンドの送信が
なくてもその無線端末は無線端末#1に応答を返すよう
にしたものである。
Example 1. FIG. 1 is a sequence diagram showing a wireless communication method according to an embodiment of the present invention, and FIG. 2 is a schematic diagram showing the configuration of a wireless communication system to which the wireless communication method of this embodiment is applied. In this embodiment, as shown in FIG. 2, wireless terminal # 1
And wireless terminals # 2 to #n communicate with each other, and the wireless terminals # 1 to # 2 to #n once within a preset fixed time t 1 . When it is known that a command will be transmitted to the wireless terminal, and if there is a wireless terminal among the wireless terminals # 2 to #n that cannot receive the command normally within the fixed time t 1 , the wireless terminal The terminal determines that the command was transmitted from the wireless terminal # 1 in the meantime but the data did not arrive due to the deterioration of the line, and the wireless terminal # 1 determines that the wireless terminal has not transmitted the retransmission command. The response is returned to # 1.

【0007】次のこの実施例の動作について説明する。
まず、無線端末#1は時間t1 以内の間隔で定期的に無
線端末#2〜#nに対してコマンドを送信するようにな
っており、このコマンドは、無線端末#2〜#nのすべ
てを指定しているコマンドである。そして、無線端末#
2〜#nは無線端末#1からのコマンドを受信後、ラン
ダムな時間経過後に応答を返すと共に、タイマによりコ
マンド受信してからの時間をカウントする。このカウン
トが時間t1 を越えた場合には少なくともこの時間内に
無線端末#1からコマンドが送信されていると判断し
て、例えば無線端末#2〜#nが状態監視を行なってい
る端末であれば、その時の状態情報を無線端末#1から
のコマンドの受信がなくても無線端末#1に応答として
送信する。
The operation of this embodiment will be described below.
First, the radio terminal # 1 is arranged to transmit a command to the regular radio terminal #. 2 to # n within an interval of time t 1, the command, all the wireless terminals #. 2 to # n Is a command that specifies. And wireless terminal #
2 to #n return a response after a random time has elapsed after receiving the command from the wireless terminal # 1, and count the time after receiving the command by the timer. When this count exceeds the time t 1 , it is determined that the command is transmitted from the wireless terminal # 1 at least within this time, and, for example, the wireless terminals # 2 to #n are terminals monitoring the state. If so, the state information at that time is transmitted as a response to the wireless terminal # 1 even if the command is not received from the wireless terminal # 1.

【0008】この実施例では、無線通信が正常に行なわ
れなかった場合でも、送信側の無線端末#1からの再送
コマンドの送信がなくても、受信側の無線端末#2〜#
nが応答を返すようにしたので、再送コマンド送信する
必要がなくなり、通信トラフィックを低域でき、また、
エラー時の応答時間を短縮することが可能となる。
In this embodiment, even if the wireless communication is not normally performed, even if the resending command is not sent from the sending wireless terminal # 1, the receiving wireless terminals # 2 to # are received.
Since n returns the response, there is no need to send a resend command, and the communication traffic can be made low range.
It is possible to shorten the response time at the time of error.

【0009】実施例2.図3は本発明の他の実施例に係
る無線通信方法を示すシーケンス図であり、この実施例
の無線通信システムの構成は実施例1と同様である。こ
の実施例は、例えば、無線端末#2〜#nが状態監視を
行なっている端末であり、状態の変化が発生してから最
低でも時間t2 の間はその状態が継続することがわかっ
ている場合に、状態変化のない同じ状態情報を応答とし
て時間t2 以内には2回以上送信しないようにしたもの
である。
Example 2. FIG. 3 is a sequence diagram showing a wireless communication method according to another embodiment of the present invention, and the configuration of the wireless communication system of this embodiment is the same as that of the first embodiment. In this embodiment, for example, the wireless terminals # 2 to #n are terminals that monitor the state, and it has been found that the state continues for at least the time t 2 after the state change occurs. In this case, the same state information having no state change is not transmitted as a response more than twice within the time t 2 .

【0010】次に、この実施例の動作について説明す
る。まず、無線端末#nはある状態の変化が発生してか
ら最低でも時間t2 の間はその状態が継続する無線端末
である。そして、無線端末#nは状態変化が発生すると
タイマをスタートさせ時間をカウントし、タイマスター
ト後、無線端末#1からの1回目のコマンドに対しては
応答を返すが、時間t2 経過前に無線端末#1からの2
回目のコマンドを受信した場合は応答を返さない。ま
た、無線端末#1では、時間を計測するための時計を備
えており、無線端末#1側において、無線端末#nから
の状態変化のあった状態情報を受信した後、その状態情
報と共に時間情報を記憶しておき、時間t2 以内の無線
端末#nの不応答に対してはエラーとせず無視し、無線
端末#nに対して再送コマンドを送信しない。
Next, the operation of this embodiment will be described. First, the wireless terminal #n is a wireless terminal that remains in that state for at least the time t 2 after a certain state change occurs. Then, the wireless terminal #n starts the timer when the state change occurs, counts the time, and returns a response to the first command from the wireless terminal # 1 after the timer starts, but before the time t 2 elapses. 2 from wireless terminal # 1
No response is returned when the second command is received. In addition, the wireless terminal # 1 is provided with a clock for measuring time, and after the wireless terminal # 1 receives the status information indicating the status change from the wireless terminal #n, the wireless terminal # 1 and the time information together with the time information are received. The information is stored, and the non-response of the wireless terminal #n within the time t 2 is ignored without being regarded as an error, and the retransmission command is not transmitted to the wireless terminal #n.

【0011】この実施例では、状態に変化のない場合に
は、状態情報の送信をせず、不要な通信を省略したの
で、通信トラフィックが低域でき、電波のぶつかり等に
よるエラーを低減することが可能となる。
In this embodiment, when there is no change in the state, the state information is not transmitted and unnecessary communication is omitted. Therefore, communication traffic can be made low, and errors due to collision of radio waves can be reduced. Is possible.

【0012】実施例3.図4は状態情報を送信するとき
のデータ形式を説明するための説明図、図5はこの実施
例の状態情報の圧縮を説明するための説明図であり、こ
の実施例の無線通信システムの構成は実施例1と同様で
ある。
Embodiment 3. FIG. 4 is an explanatory diagram for explaining the data format when transmitting the state information, and FIG. 5 is an explanatory diagram for explaining the compression of the state information of this embodiment. The configuration of the wireless communication system of this embodiment Is the same as in the first embodiment.

【0013】この実施例は、状態情報を送信する際、一
般に、子局(無線端末#2〜#n)が親局(無線端末#
1)にデータ送信する間隔に比べて監視状態が変化する
間隔は長い為、この場合は同一のデータを何回も送信す
ることになり、また、状態変化が監視対象の一部に発生
しても、送信するデータは前回送信したデータと内容が
著しく異なることがないことを利用し、図4に示すよう
な無線端末#2〜#nから状態情報を送信するときの、
状態情報に識別情報やCRCなどが付加された伝送フレ
ームにおいて、図5に示すように状態情報を前回分と今
回分とを比較し、その差を状態情報の圧縮情報として、
その圧縮情報に識別情報やCRCなどを付加して伝送フ
レームを形成し送信するようにしたものである。
In this embodiment, when transmitting the status information, the slave stations (wireless terminals # 2 to #n) are generally connected to the master station (wireless terminal #).
Since the interval at which the monitoring status changes is longer than the interval at which data is sent to 1), the same data will be sent many times in this case, and the status change will occur in a part of the monitoring target. Also, utilizing the fact that the content of the data to be transmitted does not differ significantly from the previously transmitted data, when transmitting the status information from the wireless terminals # 2 to #n as shown in FIG.
In the transmission frame in which the identification information, CRC, etc. are added to the status information, the status information is compared with the previous one and the current one as shown in FIG. 5, and the difference is used as the compression information of the status information.
Identification information and CRC are added to the compressed information to form a transmission frame for transmission.

【0014】次に、この実施例の動作について説明す
る。まず、状態情報の圧縮は、前回送信した状態情報と
今回送信しようとする状態情報を比較して、MR(Mo
dified READ)符号を用いて今回送信しよう
とする状態情報を圧縮しするものである。子局(無線端
末#2〜#n)は親局(無線端末#1)からのコマンド
を受信した時、又は子局(無線端末#2〜#n)から定
期的に親局(無線端末#1)に送信する場合にそのタイ
ミングとなった時、その時の監視対象の状態情報を収集
し、メモリに蓄えておいた前回収集した状態情報とを比
較して圧縮処理を行なう。
Next, the operation of this embodiment will be described. First, the compression of the state information is performed by comparing the state information transmitted last time with the state information to be transmitted this time, and comparing the MR (Mo
The state information to be transmitted this time is compressed by using a differentiated READ) code. The slave stations (wireless terminals # 2 to #n) receive commands from the master station (wireless terminal # 1) or periodically from the slave stations (wireless terminals # 2 to #n) to the master station (wireless terminal # 1). When the timing is reached in the case of sending to 1), the status information of the monitoring target at that time is collected and compared with the previously collected status information stored in the memory to perform compression processing.

【0015】そして、圧縮された状態情報をデータとす
る伝送フレームを形成して親局(無線端末#1)に伝送
する。また、親局(無線端末#1)では、受信した伝送
フレームのデータを伸長して監視対象の状態情報を得る
ことになる。
Then, a transmission frame having the compressed state information as data is formed and transmitted to the master station (wireless terminal # 1). In addition, the master station (wireless terminal # 1) expands the data of the received transmission frame to obtain the status information of the monitoring target.

【0016】この実施例では、状態情報を圧縮して伝送
データ量を少なくしたので、無線通信時のデータ誤り発
生確率を低くすることが可能となる。なお、この実施例
では、前回通信データと比較してMR符号を用いてデー
タ圧縮する例を示したが、前回データと比較しなくても
他の符号を用いて毎回その時のデータを圧縮して送信す
るようにしてもよい。また、実施例1,2及び3では、
1対nの通信について説明したがn対nの通信の場合に
おいても適用可能である。
In this embodiment, since the state information is compressed to reduce the amount of data to be transmitted, the probability of data error occurrence during wireless communication can be reduced. In this embodiment, an example in which the data is compressed by using the MR code in comparison with the previous communication data is shown, but the data at that time is compressed by using another code every time without comparing with the previous data. You may make it transmit. Moreover, in Examples 1, 2, and 3,
Although the one-to-n communication has been described, the present invention is also applicable to the n-to-n communication.

【0017】[0017]

【発明の効果】以上のように本発明によれは、あらかじ
め設定された一定時間内において、送信要求が子局で受
信できなかったときには、子局は親局に応答をするよう
にし、また、親局に応答する情報があらかじめ設定され
た一定時間内で同一のときには、親局への応答を行わな
いようにしたので、親局では、子局からの応答がなかっ
たときの再送コマンド送信する必要がなくなり、通信ト
ラフィックを低域でき、エラー時の応答時間を短縮する
ことができ、また、不要な通信を省略されることによ
り、通信トラフィックが低域でき、電波のぶつかり等に
よるエラーを低減することができるという効果を有す
る。
As described above, according to the present invention, when a transmission request cannot be received by a slave station within a preset time, the slave station responds to the master station, and When the information responding to the master station is the same within a preset time, the master station does not respond, so the master station sends a resend command when there is no response from the slave station. There is no need, communication traffic can be in the low range, response time at the time of error can be shortened, and communication traffic can be in the low range by omitting unnecessary communication, and errors due to radio wave collision etc. are reduced. It has the effect of being able to.

【図面の簡単な説明】[Brief description of drawings]

【図1】本発明の一実施例に係る無線通信方法を示すシ
ーケンス図である。
FIG. 1 is a sequence diagram showing a wireless communication method according to an embodiment of the present invention.

【図2】実施例1の無線通信方法を適用した無線通信シ
ステムの構成を示す概略図である。
FIG. 2 is a schematic diagram showing a configuration of a wireless communication system to which the wireless communication method according to the first embodiment is applied.

【図3】本発明の他の実施例に係る無線通信方法を示す
シーケンス図である。
FIG. 3 is a sequence diagram showing a wireless communication method according to another embodiment of the present invention.

【図4】状態情報を送信するときのデータ形式を説明す
るための説明図である。
FIG. 4 is an explanatory diagram for explaining a data format when transmitting status information.

【図5】実施例3の状態情報の圧縮を説明するための説
明図である。
FIG. 5 is an explanatory diagram illustrating compression of state information according to the third embodiment.

【符号の説明】[Explanation of symbols]

#1 無線端末(親局) #2〜#n 無線端末(子局) # 1 wireless terminal (master station) # 2 to #n wireless terminal (slave station)

Claims (3)

【特許請求の範囲】[Claims] 【請求項1】 少なくとも1つの親局から一定の周期で
送信要求を送信し、複数の子局で前記親局からの送信要
求を受信し、その受信した送信要求に基づいて前記親局
に応答する無線通信方法において、 あらかじめ設定された一定時間内で前記送信要求が前記
子局で受信できなかったとき、前記親局に応答すること
を特徴とする無線通信方法。
1. A transmission request is transmitted from at least one master station at a constant cycle, a plurality of slave stations receives the transmission request from the master station, and a response is sent to the master station based on the received transmission request. The wireless communication method according to claim 2, wherein when the transmission request cannot be received by the slave station within a preset fixed time, the slave station responds to the master station.
【請求項2】 少なくとも1つの親局から一定の周期で
送信要求を送信し、複数の子局で前記親局からの送信要
求を受信し、その受信した送信要求に基づいて前記親局
に応答する無線通信方法において、 前記親局に応答する情報があらかじめ設定された一定時
間内で同一のときには、前記親局への応答を行わないこ
とを特徴とする無線通信方法。
2. A transmission request is transmitted from at least one master station at a constant cycle, a plurality of slave stations receive the transmission request from the master station, and a response is sent to the master station based on the received transmission request. In the wireless communication method, when the information for replying to the master station is the same within a preset fixed time, no reply is made to the master station.
【請求項3】 前記親局に応答する際、応答する情報と
前回応答したときの情報とを比較し、その比較結果に基
づいて前記応答する情報を圧縮し、その圧縮された情報
を前記親局に応答することを特徴とする請求項1又は2
記載の無線通信方法。
3. When responding to the master station, the responding information is compared with the previously responding information, the responding information is compressed based on the comparison result, and the compressed information is transmitted to the master station. Responding to the station 3.
The wireless communication method described.
JP6190689A 1994-08-12 1994-08-12 Radio communication method Pending JPH0856229A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
JP6190689A JPH0856229A (en) 1994-08-12 1994-08-12 Radio communication method

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP6190689A JPH0856229A (en) 1994-08-12 1994-08-12 Radio communication method

Publications (1)

Publication Number Publication Date
JPH0856229A true JPH0856229A (en) 1996-02-27

Family

ID=16262235

Family Applications (1)

Application Number Title Priority Date Filing Date
JP6190689A Pending JPH0856229A (en) 1994-08-12 1994-08-12 Radio communication method

Country Status (1)

Country Link
JP (1) JPH0856229A (en)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE19613489C2 (en) * 1996-04-04 2001-09-27 Esw Extel Systems Wedel Ges Fu Procedure for the transmission of bidirectional data between the headquarters and the participants of a combat training center
JP2010193243A (en) * 2009-02-19 2010-09-02 Panasonic Corp Wireless apparatus, wireless system, wireless communication method and program

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE19613489C2 (en) * 1996-04-04 2001-09-27 Esw Extel Systems Wedel Ges Fu Procedure for the transmission of bidirectional data between the headquarters and the participants of a combat training center
JP2010193243A (en) * 2009-02-19 2010-09-02 Panasonic Corp Wireless apparatus, wireless system, wireless communication method and program

Similar Documents

Publication Publication Date Title
CN1702993B (en) Wireless communication apparatus
US9923672B2 (en) Radio transmission apparatus and radio transmission method
US7542719B2 (en) Wireless communication system, wireless relay unit and wireless terminal constituting the wireless communication system, and wireless communication method
US7436854B2 (en) Transmitter device for controlling data transmission
US7151746B2 (en) Wireless data communication system
CA2051212C (en) Packet data communication system
JPH08307330A (en) Radio communication equipment
US5875292A (en) Packet transmission method without sending serial numbers
CN101827439B (en) Time alignment timer adjustment method, and related device and system
JP2000115051A (en) Radio multicast data transfer method and radio communication system using same method
CN102138295B (en) Communication system, dependent station thereof and dependent-station relay transmission method
JP2016174211A (en) Communication system
EP0866579A1 (en) Packet transmission method without sending serial numbers
JPH0856229A (en) Radio communication method
JP2001094574A (en) Radio lan system
JP2746220B2 (en) Wireless communication system
JP3950081B2 (en) Wireless relay method and apparatus
EP0726685A2 (en) Packet transmission method without sending serial numbers
US20060034200A1 (en) Wireless communication system, control station, and terminal station
JPH0530115A (en) Polling system
JPS6230439A (en) Radio communication system
JP3377935B2 (en) Polling method
JPH0787091A (en) Centralized radio communication system
JPH10190635A (en) Communication system that perform error resending, and its communication controller and error resending method
JPH0851414A (en) Radio communication arq method