Source: https://patents.google.com/patent/EP1096719A2/en
Timestamp: 2018-02-19 10:26:10
Document Index: 49938452

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EP1096719A2 - Relay data retransmission method and system - Google Patents
Relay data retransmission method and system
EP1096719A2
EP1096719A2 EP20000123380 EP00123380A EP1096719A2 EP 1096719 A2 EP1096719 A2 EP 1096719A2 EP 20000123380 EP20000123380 EP 20000123380 EP 00123380 A EP00123380 A EP 00123380A EP 1096719 A2 EP1096719 A2 EP 1096719A2
EP20000123380
EP1096719A3 (en )
In a relay transmission method and system, and a device used therefor, efficiently realizing relay transmission on a half-duplex transmission path while controlling retransmission, a transmitter on the transmission side (30) receives a polling from a transmitter on the reception side (20), and then transmits a frame-numbered data frame to a relay transmitter (10). The relay transmitter (10) stores the data frame, if normally received, in a retransmission frame buffer (105), and simultaneously, transfers the data frame to the next stage. If the data frame is not normally received, the transmitter on the reception side (20) generates a retransmission request asking for retransmission thereof, and outputs the request for the relay transmitter (10). If storing the requested data frame in its retransmission frame buffer (105), the relay transmitter (10) deletes the data frame's frame number from the retransmission request, and then transfer the request. Thereafter, the relay transmitter (10) adds, to the retransmitted data frame, the data frame whose frame number has been deleted during last transfer.
The present invention relates to methods and systems for relay transmission utilizing a relay transmitter located between data transmitters on the transmission and reception sides and, more specifically, to a method and a system for relay transmission in which data transmission is not done concurrent with data reception.
Here, in simultaneous data transmission and reception by radio, a radio wave emitted by a transmitter for radio transmission is generally intense but received is weak as came across the long distance. Consequently, the radio wave during transmission interferes with that during reception, rendering data reception difficult. This is an exemplary near-far problem. Moreover, if a transmission channel and a reception channel are close in frequency to each other in such case, interference therebetween is increased due to leakage of signal component from the transmission channel, rendering data reception more difficult. If those channels are equal in frequency, needless to say, the difficulty for data reception gets considerably high. Thus, transmitting the retransmission request in the conventional data transmission system may affect data transmission on other data links, resulting in transmission failure. In order to avoid such problem, required is a carefully designed circuit for assuredly receiving data, although leading to high cost and another effort to design and manufacture a device equipped with such circuit.
To reduce cost and size of the transmitters, equipping each transmitter with only one radio modem is effective. Generally, the radio modem, however, is functionally incapable of simultaneously perform data transmission and reception even in the different frequencies, and switching between the frequencies must be concurrently done. Consequently, if those transmitters share the same frequency of channel, the retransmission request transmitted in the conventional manner may collide with data being transmitted on other data links, resulting in transmission failure. Even if the transmitters do not share the same frequency of channel, the radio modems should be switched between frequencies with appropriate timing, otherwise failed in relay.
A first aspect of the present invention is directed to a relay transmission method for not-concurrently performing data transmission and reception, and sequentially transmitting a data frame from a transmitter on the transmission side to a transmitter on the reception side via one or more relay transmitters, the method comprising:
a data transmission step of plurally transmitting the data frame with a frame number added from the transmitter on the transmission side to the transmitter on the reception side;
a data transfer step of sequentially transferring the data frame by one or more relay transmitters;
a retransmission request transmission step of transmitting, to the transmitter on the transmission side, a retransmission request indicating any data frame, by frame number, which has not normally received by the transmitter on the reception side;
a retransmission request transfer step of sequentially transferring the retransmission request by one or more relay transmitters;
a data retransmission step of sequentially retransmitting the data frame requested by the retransmission request from the transmitter on the transmission side to the transmitter on the reception side; and
a retransmission data transfer step of sequentially receiving and transferring the data frame by one or more relay transmitters.
the data transfer step comprises the steps of:
storing, in a buffer each provided in one or more relay transmitters, any data frame normally received thereby; and
sequentially transferring the normally-received data frame,
the retransmission request transfer step comprises the steps of:
deleting, from the retransmission request received by one or more relay transmitters, any frame number corresponding to the data frame stored in the buffer therein; and
sequentially transferring the retransmission request after deletion of frame number, and
the retransmission data transfer step comprising the steps of:
adding, to the data frame received by one or more relay transmitters, any data frame stored in the buffer; and
sequentially transferring the data frame added with a newly-generated data frame.
the retransmission request transfer step further comprising the steps of:
determining whether the buffer stores every frame number included in the retransmission request received by one or more relay transmitters; and
retransmitting, if determined every frame number included, the data frame requested by the retransmission request to the transmitter on the reception side, and if determined not included, deleting the frame number found in the buffer from the retransmission request for sequential transfer.
one or more relay transmitters have a directional antenna which is initially adjusted in a predetermined direction, wherein
setting, at data reception, a retention time Ta for the directional antenna to be in the predetermined direction by one or more relay transmitters;
adjusting the directional antenna in a direction where an adjacent transmitter on transmission side is located by one or more relay transmitters; and
readjusting, with a lapse of the retention time Ta, the
directional antenna back in the initially predetermined direction by one or more relay transmitters.
the directional antenna is plurally provided; and
the directional antennas are switched thereamong for setting direction thereof.
setting, at data reception, a retention time Ta to be in the predetermined frequency channel by one or more relay transmitters;
selecting a frequency channel for communicating with the transmitter on the transmission side by one or more relay transmitters; and
selecting again, with a lapse of the retention time Ta, the predetermined initial frequency channel by one or more relay transmitters.
selection of the frequency channel is based on which frequency channel shows a maximum throughput with the transmitter on the transmission side.
According to an eighth aspect, in the first aspect.
the data frame and the retransmission request are each additionally provided with transfer valid period information indicating a predetermined time left for transfer, and
the data transmission step comprising the steps of:
calculating, by sequentially deducting a time taken for transmitting one data frame from the predetermined time, a time left for transfer; and
the data transfer step, the retransmission request transmission step, the retransmission request transfer step, the data retransmission step, and the retransmission data transfer step comprise the steps of:
calculating, by sequentially deducting a time taken between data reception and transmission from the transfer valid period information included in the data frame or the retransmission request, the time left for transfer;
the transfer valid period information is a natural number N when the time taken for transmitting one frame is presumed to be 1.
According to a tenth aspect, in the eighth aspect,
one or more relay transmitters each have a directional antenna which is initially adjusted in a predetermined direction, wherein
setting a retention time Ta for the directional antenna to be in the predetermined direction by one or more relay transmitters using the transfer valid period information;
adjusting the directional antenna in a direction where the transmitter on transmission side is located by one or more relay transmitters; and
readjusting, with a lapse of the retention time Ta, the directional antenna back in the initially predetermined direction by one or more relay transmitters.
As described above, in the tenth aspect, in a case where a transmission path is a radio transmission path, a directional antenna is used and changed its direction depending on from which data comes. In this manner, a relay transmitter by radio can be directionally set for transmission/reception so that multipath fading can be prevented. Further, the antenna can be adjusted to be ready for next transmission frame without waiting, i.e., no longer than required, for transmission frames which have not transmitted due to some error. Therefore, data transfer can be assuredly achieved.
According to an eleventh aspect, in the eighth aspect, in one or more relay transmitters, a predetermined frequency channel is initially selected among plural, and
setting, at data reception, a retention time Ta to be in the predetermined channel by one or more relay transmitters;
As described above, in the eleventh aspect, when a transmission path is a radio transmission path, each different frequency channel is available for transmitters. Therefore, even if any disturbance wave source is observed in the vicinity of the transmitters, and even if such source has each different frequency characteristics, the transmitters can be in each appropriate frequency channel. Accordingly, a throughput can be increased. Further, the frequency channel can be set to be ready for next transmission frame without waiting, i.e., no longer than required, for transmission frames which have not transmitted due to some error. Therefore, data transfer can be assuredly achieved.
the retransmission request transmission step comprising the steps of:
not transmitting the retransmission request when the predetermined time is smaller in value, and when the predetermined time is equal or larger, transmitting a retransmission request indicating any data frame, by frame number, which has not normally received by the transmitter on the reception side to the transmitter on the transmission side.
the maximum length of time taken to retransmit data responding to the retransmission request is obtained by adding 1 to the number of to-be-retransmitted frames, multiplying the value by the number of transfers and a time taken to transmit one frame, and adding the value with α (a predetermined value determined by processing capability).
A fourteenth aspect of the present invention is directed to a relay transmission system for non-concurrently performing data transmission and reception, and sequentially transmitting a data frame from a transmitter on the transmission side to a transmitter on the reception side via one or more relay transmitters,
the transmitter on the transmission side comprising:
a reception part for receiving a retransmission request indicating any data frame, by frame number, which has not normally received by the transmitter on the reception side;
a frame header analysis part for extracting a frame number from the retransmission request received by the reception part;
a data frame generation part for generating a retransmission data frame by adding transmission data with the frame number; and
a transmission part for transmitting the transmission data frame,
the transmitter on the reception side comprising:
a reception part for receiving the data frame;
a frame header analysis part for extracting the frame number from the data frame received by the reception part;
a retransmission request frame generation part for generating a retransmission request including the frame number of the data frame not normally received by the transmitter on the reception side; and
a transmission part for transmitting the retransmission request, and
one or more relay transmitters each comprising:
a reception part for receiving the data frame or the retransmission request; and
a transmission part for transmitting the data frame or the retransmission request received by the reception part, wherein
when the transmitter on the reception side failed to receive every data frame transmitted by the transmitter on the transmission side, the transmitter on the reception side transmits the retransmission request, and responding thereto, the transmitter on the transmission side sequentially retransmits the data frame to the transmitter on the reception side.
one or more relay transmitters each further comprising:
a retransmission frame buffer for storing any normally-received data frame, and generating a transmission data frame, in response to retransmission of data frame by the transmitter on the transmission side, a transmission data frame by adding the stored data frame to the data frame; and
a retransmission request frame reconstruction part for deleting, from the retransmission request, any frame number corresponding to the data frame stored in the retransmission frame buffer.
one or more relay transmitters further comprise:
a directional antenna for transmitting/receiving a signal; and
an antenna control part for controlling the directional antenna to direct in a direction where the signal goes/comes, and readjusting the directional antenna in a predetermined initial direction with a lapse of a predetermined retention time Ta.
According to a seventeenth aspect, in the fourteenth aspect,
one or more relay transmitters each further comprise:
a directional antenna for transmitting/receiving a signal;
an antenna switching part for selectively switching among plurally-provided the directional antennas; and
one or more relay transmitters each further comprise a frequency channel control part for selecting a frequency channel among plural, and with a lapse of a predetermined retention time Ta set to be in the selected frequency channel, reselecting the same frequency channel, and
the transmission part and the reception part transmit/receive a signal in the frequency channel selected by the frequency channel control part.
According to a nineteenth aspect, in the fourteenth aspect, the transmitter on the transmission side further comprises:
a transfer valid period control part for calculating a time left for transfer, as another transfer valid period information, by sequentially deducting a time taken for transmitting one data frame from transfer valid period information indicating a predetermined time allowed for the transfer, and stopping transmission when the transfer valid period information becomes negative, and
a transfer valid period addition part for adding the transfer valid period information to the data frame,
a transfer valid period addition part for adding the transfer valid period information to the retransmission request, and
a transfer valid period control part for calculating a time left for transfer, as another transfer valid period information, by sequentially deducting a time taken between data reception and transmission from the transfer valid period information included in the data frame or the retransmission request, and stopping transmission when the transfer valid period information becomes negative, and
a transfer valid period addition part for adding the transfer valid period information to the data frame or the retransmission request.
According to a twenty-first aspect, in the nineteenth aspect,
an antenna control part for controlling the directional antenna to direct in a direction where the signal goes/comes, and readjusting the directional antenna in a predetermined initial direction with a lapse of a predetermined retention time Ta determined by using the transfer valid period information.
According to a twenty-second aspect, in the nineteenth aspect,
one or more relay transmitters each further comprise a frequency channel control part for selecting a frequency channel among plural to receive/transmit a signal, and with a lapse of a predetermined retention time Ta determined using the transfer valid period information, reselecting the same frequency channel, and
As described above, in the twenty-second aspect, when a transmission path is a radio transmission path, each different frequency channel is available for transmitters. Therefore, even if any disturbance wave source is observed in the vicinity of the transmitters, and even if such source has each different frequency characteristics, the transmitters can be in each appropriate frequency channel. Accordingly, a throughput can be increased. Further, the frequency channel can be set to be ready for next transmission frame without waiting, i.e., no longer than required, for transmission frames which have not transmitted due to some error. Therefore, data transfer can be assuredly achieved.
A twenty-third aspect of the present invention is directed to a transmitter on the transmission side for non-concurrently performing data transmission and reception, and sequentially transmitting a data frame to a transmitter on the reception side via one or more relay transmitters, comprising:
a transmission part for transmitting the transmission data frame, wherein
when the transmitter on the reception side failed to receive every data frame transmitted, the transmitter on the reception side transmits the retransmission request, and responding thereto, the transmitter on the transmission side sequentially retransmits the data frame to the transmitter on the reception side.
According to a twenty-fourth aspect, in the twenty-third aspect,
the transmitter on the transmission side further comprises:
a transfer valid period addition part for adding the transfer valid period information to the data frame.
A twenty-fifth aspect of the present invention is directed to a transmitter on the reception side for non-concurrently performing data transmission and reception, and sequentially transmitting a data frame to a transmitter on the transmission side via one or more relay transmitters, comprising:
a transmission part for transmitting the retransmission request, wherein
when failed to receive every data frame transmitted from the transmitter on the transmission side, transmits the retransmission request, and responding thereto, the transmitter on the transmission side sequentially retransmits the data frame.
According to a twenty-sixth aspect, in the twenty-fifth aspect,
the transmitter on the reception side further comprises:
a transfer valid period addition part for adding the transfer valid period information to the retransmission request.
A twenty-seventh aspect of the present invention is directed to one or more relay transmitters for non-concurrently performing data transmission and reception, and sequentially transmitting a data frame from a transmitter on the transmission side to a transmitter on the reception side, each comprising:
one or more relay transmitters further comprises:
FIG. 6 is a block diagram showing the structure of a receiver applying the relay transmission method of the second embodiment:
FIG. 10 is a block diagram showing the structure of a receiver applying the relay transmission method of the third embodiment:
In FIG. 1, the relay transmitter 10 is provided with a data reception part 101 for demodulating a transmission wave on the transmission path 40 so as to generate a transmission frame including polling frame, retransmission request frame, data frame, and the like, an error detection part 102 for detecting any error in the transmission frame using an error detection code added to the transmission frame, a frame header analysis part 103 for analyzing the transmission frame for its frame type and destination address, a relay controller 104 for controlling other parts, a retransmission frame buffer 105 for accumulating a to-be-retransmitted transmission frame, a relay buffer 106 for accumulating the transmission frame at relay, a destination address change part 107 for rewriting the destination address in the transmission frame, an error detection code addition part 108 for calculating and rewriting the error detection code in the transmission frame, a data transmission part 109 for modulating the transmission frame for send-out onto the transmission path as another transmission wave, and a retransmission request frame reconstruction part 110 for changing a frame number in a retransmission request frame requested for retransmission.
The data reception and transmission parts 101 and 109 are typically in a single modem 100, resulting in no simultaneous data transmission and reception. Here, there no need to put those in the same modem as long as simultaneous data transmission and reception is prevented. This is for avoiding the above-described near-far problem and interference between adjoining channels, for example.
Described next is the operation of the relay transmitter 10. In the relay transmitter 10, the data reception part 101 receives a transmission frame. The received transmission frame is determined as being normal or not by the error detection part 102. If any error is detected in the frame, the error detection part 102 discards the frame. Otherwise, the frame is analyzed for information by the frame header analysis part 103.
If determined the analyzed frame as being a polling frame addressed to its own terminal, the frame header analysis part 103 informs the relay control part 104. The relay control part 104 clears the retransmission frame buffer 105 and the relay buffer 106. The frame header analysis part 103 also outputs the analyzed frame to the destination address change part 107. In response thereto, the destination address change part 107 rewrites the frame to address to the transmitter on the transmission side, and then outputs the frame to the error detection code addition part 108. Therein, the frame is provided with an error detection code, and outputted out of the data transmission part 109.
If determined the analyzed frame as being a data frame addressed to its own terminal, the frame header analysis part 103 informs the relay control part 104. The frame header analysis part 103 also outputs the analyzed frame to the destination address change part 107. In response thereto, the destination address change part 107 rewrites the frame to address to the transmitter on the reception side, and then outputs the frame to the error detection code addition part 108. Therein, the frame is provided with an error detection code, and accumulated in the retransmission frame buffer 105. The frame is also stored in the relay buffer 106. The relay control part 104 controls, if detected reception of a series of data frames having been completed, data stored in the relay buffer 106 to be transmitted out of the data transmission part 109, and then clears the relay buffer 106.
Moreover, if determined the analyzed frame as being a retransmission request frame addressed to its own terminal, the frame header analysis part 103 informs the relay control part 104. The retransmission request frame also goes to the retransmission request frame reconstruction part 110. The relay control part 104 clears the relay buffer 106, and then determines whether the retransmission frame buffer part 105 has every data frame requested for retransmission. If every data frame is found therein, the data frame(s) is stored in the relay buffer 106. The relay control part 104 also informs the retransmission request frame reconstruction part 110 of the data frame(s) by frame number not found In the retransmission frame buffer 105.
The retransmission request frame reconstruction part 110 removes, out of the retransmission request frame, any frame number(s) already stored in the retransmission frame buffer 105, and forwards the retransmission request frame to the destination address change part 107. The destination address change part 107 rewrites the retransmission request frame to address to the transmitter on the transmission side, and then outputs the frame to the error detection code addition part 108. Therein, the retransmission request frame is provided with an error detection code, and transmitted out of the data transmission part 109.
The data reception and transmission parts 205 and 204 are typically in a single modem 200. Here, as described in the foregoing, there no need to put those in the same modem as long as simultaneous data transmission and reception is prevented.
The transmission frame received by the data reception part 205 is determined if being normal or not by the error detection part 206. If any error is detected in the frame, the error detection part 206 discards the frame. Otherwise, the frame is analyzed for information by the frame header analysis part 207. If determined the analyzed frame as being a data frame addressed to its own terminal, the frame is accumulated in the frame order reconstruction part 208. The retransmission control part 209 then detects, after receiving a series of data, whether every data has been accumulated in the frame order reconstruction part 208. If every data frame is found therein, the retransmission control part 209 brings the frame order reconstruction part 208 to output the accumulated data frames in order of frame number. Here, the output is reception data.
If any data frame has not yet reached the frame order reconstruction part 208, the retransmission control part 209 calculates, based on the timing when the last command of polling transmission was inputted from the polling period count part 201, a length of time until the next polling transmission. The calculated time is compared with a value calculated by an equation of (the number of to-be-retransmitted frames + 1) × (the number of transfers among the transmitters) × (a time taken to transmit one frame) + α (a constant determined by the processing capability). If the length of time exceeds the value, the retransmission control part 209 controls the retransmission request frame generation part 210 to generate a retransmission request frame, which includes the frame number(s) of the not-yet-reached data frame(s). Thus generated retransmission request frame is herein addressed to the adjacent relay transmitter. The generated retransmission request frame is added with an error detection code by the error detection code addition part 203, and is transmitted out of the data transmission part 204. On the other hand, when the calculated length of time until the next polling transmission is smaller than the value obtained by the above equation, the retransmission control part 209 stops transmission of the retransmission request frame.
The data reception and transmission parts 301 and 309 are typically in a single modem 300. Here, as described in the foregoing, there no need to put those in the same modem as long as simultaneous data transmission and reception is prevented.
Described next is the operation of the transmitter on the transmission side 30. In the transmitter on the transmission side 30, the data reception part 301 receives a transmission frame. The received transmission frame is determined if being normal or not by the error detection part 302. If any error is detected in the frame, the error detection part 302 discards the frame. Otherwise, the frame is analyzed for information by the frame header analysis part 303.
If determined the analyzed frame as being a polling frame addressed to its own terminal, the frame header analysis part 303 informs the transmission control part 304 and the retransmission control part 310. In response thereto, the retransmission control part 310 clears the retransmission frame buffer 305. Thereafter, the transmission control part 304 controls data in the transmission data buffer 306 to be outputted by the predetermined number for the data frame generation part 307. Therein, the data is then sequentially provided with a frame number. Thus, the data is framed, and addressed to the adjacent relay transmitter. The framed data is provided with an error detection code by the error detection code addition part 308. Then, the data is accumulated in the retransmission frame buffer 305, and transmitted out of the data transmission part 309.
If determined the analyzed frame as being a retransmission request frame addressed to its own terminal, the frame header analysis part 303 informs the retransmission control part 310, and also forwards the retransmission request frame to the retransmission control part 310. The retransmission control part 310 extracts the frame number(s) in the received retransmission request frame, and then outputs the data frame(s) corresponding to the frame number(s) from the retransmission frame buffer 305 to the data transmission part 309. The outputted data is then transmitted out of the data transmission part 309.
In FIG. 4, once received the polling, the transmitter on the transmission side transmits 1st to 7th data frames to the first relay transmitter. Herein, a cross in the drawing shows that any error occurs in the data frame. The crossed data frame is discarded by the transmitter on the reception side, the first relay transmitter, or the second relay transmitter.
The first relay transmitter stores the normally-received 1st, 2nd, 5th, 6th, and 7th data frames into its retransmission frame buffer as already described, and simultaneously, transmits those to the second relay transmitter. The second relay transmitter then stores the normally-received 1st, 2nd, 5th, and 7th data frames into its retransmission frame buffer, and simultaneously, transmits those to the transmitter on the reception side.
The transmitter on the reception side stores the 1st, 2nd, 5th, and 7th data frames as already described into the frame order reconstruction part 208. Then, the retransmission control part 209 determines that the 3rd, 4th, and 6th data frames are missing.
Assumed herein are a time taken to transmit one transmission frame being T, a polling transmission period being 40T, and a constant α of processing capability being 0. As is known from the above, the total number of already-transmitted frames is 19. Therefore, a length of time until the next polling is known as being 21T. Accordingly, the equation of (the number of to- be-retransmitted frames + 1) × (the number of transfers among the transmitters) × (a time taken to transmit one transmission frame) + α will be (3 + 1) × 3 × T + 0 = 12T. Since the length of time until the next polling is larger in value, instructed here is generation of a retransmission request frame asking for retransmission of the 3rd, 4th, and 6th data frames. The retransmission request frame thus generated is transmitted to the second relay transmitter.
The first relay transmitter has the 6th data frame stored in its retransmission frame buffer. Therefore, as described above, the 6th data frame is stored in the relay buffer. The frame number of the 6th data frame is then deleted from the retransmission request frame, and another retransmission request frame is generated to request retransmission of the 3rd and 4th data frames. Such generated retransmission request frame is transmitted to the transmitter on the transmission side.
Here, a length of time until the next polling is 10T. Accordingly, the equation of (the number of to-be-retransmitted frames + 1) × (the number of transfers among the transmitters) × (a time taken to transmit one transmission frame) + α will be (1 + 1) × 3 × T + 0 = 6T. Since the length of time until the next polling is larger in value, instructed here is generation of a retransmission request frame asking for retransmission of the 3rd data frame. The retransmission request frame thus generated is transmitted to the second relay transmitter.
In FIG. 6, the transmitter on the reception side 60 is almost similar in structure to the transmitter on the reception side 20 in FIG. 2, but additionally provided with a transfer valid period control part 601 and a transfer valid period addition part 602. Here, the transfer valid period control part 601 stores a transfer valid period, and decreases the period by 1 whenever a time taken for transmitting one frame. As to the transfer valid period addition part 602, information on such transfer valid period is added on the transmission frame.
In FIG. 7, the transmitter on the transmission side 70 is almost similar in structure to the transmitter on the transmission side 30 in FIG. 3, but additionally provided with a transfer valid period control part 701 and a transfer valid period addition part 702. Here, the transfer valid period control part 701 stores a transfer valid period, and decreases the period by 1 whenever a time taken for transmitting one frame. As to the transfer valid period addition part 702, information on such transfer valid period is added on the transmission frame.
First, referring to FIG. 5, described next is the operation of the relay transmitter 50. In the relay transmitter 50, the data reception part 101 receives a transmission frame. The received transmission frame is determined as being normal or not by the error detection part 102. If any error is detected in the frame, the error detection part 102 discards the frame. Otherwise, the frame is analyzed for information by the frame header analysis part 103.
If analyzed the frame as being addressed to its own terminal, the frame header analysis part 103 decreases a transfer valid period in the frame by 1, and then stores information on the transfer valid period in the transfer valid period control part 501. The frame header analysis part 103 also informs the relay control part 104 of the frame type of the analyzed.
The relay control part 104 also informs the retransmission request frame reconstruction part 110 of a frame number(s) found in the retransmission frame buffer 105. The relay control part 104 controls the retransmission request frame reconstruction part 110 to remove, out of the retransmission request frame received from the frame header analysis part 103, any frame number(s) already stored in the retransmission frame buffer 105, and forwards the retransmission request frame to the destination address change part 107. The relay control part 104 brings the destination address change part 107 to rewrite the retransmission request frame to address to the transmitter on the transmission side, and then to output the frame to the transfer valid period addition part 502.
The data reception part 205 receives a transmission frame from the adjacent transmitter. The transmission frame is then determined as being normal or not by the error detection part 206. If any error is detected in the frame, the error detection part 206 discards the frame. Otherwise, the frame is analyzed for information by the frame header analysis part 207.
With reference to FIG. 7, described next is the operation of the transmitter on the transmission side 70. In the transmitter on the transmission side 70, the data reception part 301 receives a transmission frame. The error detection part 302 determines the transmission frame as being normal or not. If any error is detected in the frame, the error detection part 302 discards the frame. Otherwise, the frame is analyzed for information by the frame header analysis part 303.
If determined the analyzed frame as being a polling frame addressed to its own terminal, the frame header analysis part 303 decreases a transfer valid period in the frame by 1, and then stores information on the transfer valid period in the transfer valid period control part 701. The stored transfer valid period information is informed to the transfer valid period addition part 702. The frame header analysis part 303 also informs the transmission control part 304 of the polling frame having arrived.
The transmission control part 304 informed of the poling frame having arrived then clears the retransmission frame buffer 305, and reads data from the transmission data buffer 306 by the predetermined number of frames. The read data is then sequentially provided with a frame number by the data frame generation part 307, thus the data is framed, and addressed to the adjacent relay transmitter. The transmission control part 304 stores the framed data in the retransmission frame buffer 305, and simultaneously forwards the framed data to the transfer valid period addition part 702.
To the retransmission request frame, the transfer valid period addition part 702 adds the transfer valid period information received from the transfer valid period control part 702. The retransmission request frame then additionally provided with an error detection code by the error detection code addition part 308, and is transmitted out of the data transmission part 309.
FIG. 8 is a diagram showing a transfer sequence in the data transmission system of this embodiment. Therein, a first to a third data links are presumed to perform radio data transmission in the same frequency range. Also, presumably, a polling generated in the transmitter on the reception side in this system goes to a second relay transmitter and then a first before reaching the transmitter on the transmission side. Here, bracketed figures such as (1) in the drawing denote frame numbers, while those such as [1] denote a transfer valid period. The transfer valid period is decreased by 1 whenever a transmission frame is relayed or transmitted.
Referring to FIG. 11, unlike the transmitter on the transmission side 70 in FIG. 7, the transmitter on the transmission side 71 does not include the data reception and transmission parts 301 and 309. Alternatively provided therein are a radio reception part 1101 for demodulating a transmission wave on the transmission path 41 so as to generate a transmission frame including data frame, polling frame, retransmission request frame, and the like, and a radio transmission part 1102 for modulating a data frame for send-out onto the transmission path as another transmission wave.
Referring to FIG. 9, described next is the operation of the relay transmitter 51. In the relay transmitter 51, the radio reception part 901 receives a transmission frame. The received transmission frame is determined as being normal or not by the error detection part 102. If any error is detected in the frame, the error detection part 102 discards the frame. Otherwise, the frame is analyzed for information by the frame header analysis part 103.
If determined the frame as being addressed to its own terminal, the frame header analysis part 103 decreases a transfer valid period stored therein by 1, and stores information on the transfer valid period in the transfer valid period control part 501. The frame header analysis part 103 informs the frame type of the analyzed to the relay control part 104.
If the informed frame type is a polling frame, the relay control part 104 clears the retransmission frame buffer 105 and the relay buffer 106. The relay control part 104 also brings the destination address change part 107 to rewrite the polling frame to address to the adjacent transmitter, and to output to the transfer valid period addition part 502.
The relay control part 104 also informs the retransmission request frame reconstruction part 110 of the data frame(s) by frame number found in the retransmission frame buffer 105. The relay control part 104 controls the retransmission request frame reconstruction part 110 to remove, out of the retransmission request frame, any frame number(s) already stored in the retransmission frame buffer 105, and forwards the retransmission request frame to the destination address change part 107. The relay control part 104 controls the destination address change part 107 to rewrite the retransmission request frame to address to the transmitter on the transmission side, and then to output the frame to the transfer valid period addition part 502.
With reference to FIG. 11, described next is the operation of the transmitter on the transmission side 71. In the transmitter on the transmission side 71, the radio reception part 1101 receives a transmission frame. The error detection part 302 determines the transmission frame as being normal or not. If any error is detected in the frame, the error detection part 302 discards the frame. Otherwise, the frame is analyzed for information by the frame header analysis part 303.
If analyzed the frame as being a polling frame addressed to its own terminal, the frame header analysis part 303 decreases a transfer valid period in the frame by 1, and stores information on the transfer valid period in the transfer valid period control part 701. The frame header analysis part 303 then informs the transmission control part 304 of the polling frame having arrived.
In FIG. 12, a polling generated in the transmitter on the reception side goes to the second relay transmitter, and then the first, before reaching the transmitter on the transmission side. Once received the polling, the first and second relay transmitters activate
timers Ta1 and Ta2, respectively, based on transfer valid period information included in the polling. Those timers Ta1 and Ta2 are respectively provided in an antenna control part of the first and second relay transmitters, and timeout after the transfer valid period passed. After the reception is complete, the antenna control parts each switch the directional antenna so as to direct in a direction where the transmitter on the transmission side is located. The switching timing is indicated by A and C in the drawing. By switching and keeping the direction of the antennas in such manner, the first and second relay transmitters can be prepared for any data frame transmitted from the transmitter on the transmission side.
Referring to FIG. 13, unlike the relay transmitter 51 in FIG. 9, the relay transmitter 52 includes a radio reception part 1401 capable of switching among several frequency channels, and a radio transmission part 1402. The radio reception and transmission parts 1401 and 1402 are typically in the
single modem 1400. Here, as described in the foregoing, there no need to put those in the same modem as long as simultaneous data transmission and reception is prevented. The relay transmitter 52 further includes a frequency channel control part 1403 for controlling switching of frequency channels according to information provided by the radio transmission part 1402 and the transfer valid period addition part 502. Here, the transmitter on the reception side 61 is structurally identical to that in FIG. 10, and the transmitter on the transmission side 71 to that in FIG. 11.
Referring to FIG. 13, described next is the operation of the relay transmitter 52. In the relay transmitter 52, the data reception part 1401 receives a transmission frame. The received transmission frame is determined as being normal or not by the error detection part 102. If any error is detected in the frame, the error detection part 102 discards the frame. Otherwise, the frame is analyzed for information by the frame header analysis part 103.
If determined the frame as being addressed to its own terminal, the frame header analysis part 103 decreases a transfer valid period in the frame by 1, and then stores information on the transfer valid period in the transfer valid period control part 501. The frame header analysis part 103 also informs the relay control part 104 of the frame type of the analyzed.
The transfer valid period addition part 502 adds the transfer valid period decreased by 1 to each corresponding data frame. Then, the data frames are also added each with an error detection code by the error detection code addition part 108. The frequency channel control part 1403 sets the radio reception and transmission parts 1401 and 1402 so as to be in a frequency channel for communications with the transmitter on the transmission side, which transmits the frames. Then, the radio transmission part 1402 transmits the data frames.
Assumed herein is that a wave source emitting a disturbance wave in the same frequency range as the channel 3 is in the vicinity of the first relay transmitter. In such case, the first relay transmitter may have some difficulties to receive waves from the second relay transmitter or the transmitter on the transmission side with the channel 3. This is because, a disturbance wave emitted by a neighboring wave source generally intense but a wave coming from the transmitters being weak as came across the long distance. Therefore, such disturbance wave is quite likely to disturb data reception. Similarly, if a wave source emitting a disturbance wave in the same frequency range as the channel 1 is in the vicinity of the second relay transmitter, the second relay transmitter may have some difficulties to receive waves from the first relay transmitter or the transmitter on the reception side with the channel 1. If this is the case, setting the frequency channels for the data links as in FIG. 14 is a solution. With such setting, signal reception among transmitters can be satisfactorily done without being disturbed by the disturbance waves from the source.
The first relay transmitter stores the normally-received 3rd, 4th, 5th, 6th, and 7th data frames into its retransmission frame buffer, and simultaneously, transmits those to the second relay transmitter. At this time, in the frequency control part therein, the timer Ta1 is reset, and thus the channel is put back to channel 2. This timing is indicated by D in the drawing. Herein, the timer Ta1 may be structured not to be reset, and update the transfer valid period information whenever another comes.
A relay transmission method for not-concurrently performing data transmission and reception, and sequentially transmitting a data frame from a transmitter on the transmission side (30) to a transmitter on the reception side (20) via one or more relay transmitters (10), the method comprising:
a data transmission step of plurally transmitting said data frame with a frame number added from said transmitter on the transmission side (30) to said transmitter on the reception side (20);
a data transfer step of sequentially transferring said data frame by one or more said relay transmitters (10);
a retransmission request transmission step of transmitting, to said transmitter on the transmission side (30), a retransmission request indicating any data frame, by frame number, which has not normally received by said transmitter on the reception side (20);
a retransmission request transfer step of sequentially transferring said retransmission request by one or more said relay transmitters (10);
a data retransmission step of sequentially retransmitting, said data frame requested by said retransmission request from said transmitter on the transmission side (30) to said transmitter on the reception side (20); and
a retransmission data transfer step of sequentially receiving and transferring said data frame by one or more said relay transmitters (10).
The relay transmission method according to claim 1, wherein said data transfer step comprises the steps of:
storing, in a buffer (105) each provided in one or more said relay transmitters (10), any data frame normally received thereby; and
sequentially transferring said normally-received data frame,
said retransmission request transfer step comprising the steps of:
deleting, from said retransmission request received by one or more said relay transmitters (10), any frame number corresponding to the data frame stored in the buffer (105) therein; and
said retransmission data transfer step comprises the steps of:
adding, to the data frame received by one or more said relay transmitters (10), any data frame stored in the buffer (105); and
The relay transmission method according to claim 2, wherein said retransmission request transfer step further comprising the steps of:
determining whether the buffer (105) stores every frame number included in said retransmission request received by one or more said relay transmitters (10); and
retransmitting, if determined every frame number included, the data frame requested by the retransmission request to said transmitter on the reception side (20), and if determined not included, deleting the frame number found in the buffer (105) from said retransmission request for sequential transfer.
The relay transmission method according to claim 1, wherein one or more said relay transmitters (10) have a directional antenna (906, 907) which is initially adjusted in a predetermined direction, wherein
said data transfer step, said retransmission request transfer step, and said retransmission data transfer step comprise the steps of:
setting, at data reception, a retention time Ta for said directional antenna to be in the predetermined direction by one or more said relay transmitters (10);
adjusting said directional antenna in a direction where an adjacent transmitter on transmission side is located by one or more said relay transmitters (10); and
readjusting, with a lapse of said retention time Ta, said directional antenna back in the initially predetermined direction by one or more said relay transmitters (10).
The relay transmission method according to claim 4, wherein said directional antenna (906, 907) is plurally provided; and
said directional antennas (906, 907) are switched thereamong for setting direction thereof.
The relay transmission method according to claim 1, wherein, in one or more said relay transmitters (10), a predetermined frequency channel is initially selected among plural, and
setting, at data reception, a retention time Ta to be in the predetermined frequency channel by one or more said relay transmitters (10);
selecting a frequency channel for communicating with the transmitter on the transmission side by one or more said relay transmitters (10); and
selecting again, with a lapse of said retention time Ta, the predetermined initial frequency channel by one or more said relay transmitters (10).
The relay transmission method according to claim 6, wherein selection of said frequency channel is based on which frequency channel shows a maximum throughput with the transmitter on the transmission side.
The relay transmission method according to claim 1, wherein said data frame and said retransmission request are each additionally provided with transfer valid period information indicating a predetermined time left for transfer, and
said data transmission step comprising the steps of:
adding said calculated time left for transfer as another transfer valid period information, and
said data transfer step, said retransmission request transmission step, said retransmission request transfer step, said data retransmission step, and said retransmission data transfer step comprise the steps of:
calculating, by sequentially deducting a time taken between data reception and transmission from the transfer valid period information included in said data frame or said retransmission request, a time left for transfer;
adding said calculated time left for transfer as another transfer valid period information; and
stopping data transmission or transfer when said another transfer valid period information becomes negative.
The relay transmission method according to claim 8, wherein said transfer valid period information is a natural number N when the time taken for transmitting one frame is presumed to be 1.
The relay transmission method according to claim 8, wherein one or more said relay transmitters (10) each have a directional antenna (906, 907) which is initially adjusted in a predetermined direction, wherein
setting a retention time Ta for said directional antenna to be in the predetermined direction by one or more said relay transmitters (10) using said transfer valid period information;
adjusting said directional antenna in a direction where said transmitter on transmission side is located by one or more said relay transmitters (10); and
The relay transmission method according to claim 8, wherein, in one or more said relay transmitters (10), a predetermined frequency channel is initially selected among plural, and
setting, at data reception, a retention time Ta to be in the predetermined channel by one or more said relay transmitters (10);
The relay transmission method according to claim 1, wherein said retransmission request transmission step comprising the steps of:
comparing a predetermined time allowed for said transmitter on the transmission side (30) to start next transmission with a maximum length of time taken to retransmit data responding to said retransmission request, and
not transmitting said retransmission request when said predetermined time is smaller in value, and when said predetermined time is equal or larger, transmitting a retransmission request indicating any data frame, by frame number, which has not normally received by said transmitter on the reception side (20) to said transmitter on the transmission side (30).
The relay transmission method according to claim 12, wherein the maximum length of time taken to retransmit data responding to said retransmission request is obtained by adding 1 to the number of to-be-retransmitted frames, multiplying the value by the number of transfers and a time taken to transmit one frame, and adding the value with α (a predetermined value determined by processing capability).
A relay transmission system for non-concurrently performing data transmission and reception, and sequentially transmitting a data frame from a transmitter on the transmission side (30) to a transmitter on the reception side (20) via one or more relay transmitters (10),
said transmitter on the transmission side (30) comprising:
a reception part (301) for receiving a retransmission request indicating any data frame, by frame number, which has not normally received by said transmitter on the reception side (20);
a frame header analysis part (303) for extracting a frame number from the retransmission request received by said reception part (301);
a data frame generation part (307) for generating a retransmission data frame by adding transmission data with the frame number; and
a transmission part (309) for transmitting said transmission data frame,
said transmitter on the reception side (20) comprising:
a reception part (205) for receiving said data frame;
a frame header analysis part (207) for extracting the frame number from the data frame received by said reception part (205);
a retransmission request frame generation part (210) for generating a retransmission request including the frame number of the data frame not normally received by said transmitter on the reception side (20); and
a transmission part (204) for transmitting said retransmission request, and
one or more said relay transmitters (10) each comprising:
a reception part (101) for receiving said data frame or said retransmission request; and
a transmission part (109) for transmitting said data frame or said retransmission request received by said reception part (101), wherein
when said transmitter on the reception side (20) failed to receive every data frame transmitted by said transmitter on the transmission side (30), said transmitter on the reception side (20) transmits said retransmission request, and responding thereto, said transmitter on the transmission side (30) sequentially retransmits the data frame to said transmitter on the reception side (20).
The relay transmission system according to claim 14, wherein one or more said relay transmitters (10) each further comprising:
a retransmission frame buffer (105) for storing any normally-received data frame, and generating a transmission data frame, in response to retransmission of data frame by said transmitter on the transmission side (30), a transmission data frame by adding the stored data frame to the data frame; and
a retransmission request frame reconstruction part (110) for deleting, from said retransmission request, any frame number corresponding to the data frame stored in said retransmission frame buffer (105).
The relay transmission system according to claim 14, wherein one or more said relay transmitters (10) further comprise:
a directional antenna (906, 907) for transmitting/receiving a signal; and
an antenna control part (903) for controlling said directional antenna (906, 907) to direct in a direction where the signal goes/comes, and readjusting the directional antenna in a predetermined initial direction with a lapse of a predetermined retention time Ta.
The relay transmission system according to claim 14, wherein one or more said relay transmitters (10) each further comprise:
a directional antenna (906, 907) for transmitting/receiving a signal;
an antenna switching part (904) for selectively switching among plurally-provided said directional antennas (906, 907); and
an antenna control part (903) for controlling said antenna switching part (904) to direct the directional antennas in a direction where the signal goes/comes, and with a lapse of a predetermined retention time Ta, readjusting the directional antennas in the predetermined initial direction.
The relay transmission system according to claim 14, wherein one or more said relay transmitters (10) each further comprise a frequency channel control part (1403) for selecting a frequency channel among plural, and with a lapse of a predetermined retention time Ta set to be in the selected frequency channel, reselecting the same frequency channel, and
said transmission part (1402) and said reception part (1401) transmit/receive a signal in the frequency channel selected by said frequency channel control part (1403).
The relay transmission system according to claim 14, wherein said transmitter on the transmission side (30) further comprises:
a transfer valid period control part (701) for calculating a time left for transfer, as another transfer valid period information, by sequentially deducting a time taken for transmitting one data frame from transfer valid period information indicating a predetermined time allowed for the transfer, and stopping transmission when the transfer valid period information becomes negative, and
a transfer valid period addition part (702) for adding said transfer valid period information to said data frame,
a transfer valid period control part (601) for calculating a time left for transfer, as another transfer valid period information, by sequentially deducting a time taken for transmitting one data frame from transfer valid period information indicating a predetermined time allowed for the transfer, and stopping transmission when the transfer valid period information becomes negative, and
a transfer valid period addition part (602) for adding said transfer valid period information to said retransmission request, and
one or more said relay transmitters (10) each further comprise:
a transfer valid period control part (501) for calculating a time left for transfer, as another transfer valid period information, by sequentially deducting a time taken between data reception and transmission from the transfer valid period information included in said data frame or said retransmission request, and stopping transmission when the transfer valid period information becomes negative, and
a transfer valid period addition part (502) for adding said transfer valid period information to said data frame or said retransmission request.
The relay transmission system according to claim 19, wherein said transfer valid period information is a natural number N when the time taken for transmitting one frame is presumed to be 1.
The relay transmission system according to claim 19, wherein one or more said relay transmitters (10) each further comprise:
an antenna control part (903) for controlling said directional antenna (906, 907) to direct in a direction where the signal goes/comes, and readjusting the directional antenna in a predetermined initial direction with a lapse of a predetermined retention time Ta determined by using said transfer valid period information.
The relay transmission system according to claim 19, wherein one or more said relay transmitters (10) each further comprise a frequency channel control part (1403) for selecting a frequency channel among plural to receive/transmit a signal, and with a lapse of a predetermined retention time Ta determined using said transfer valid period information, reselecting the same frequency channel, and
A transmitter on the transmission side (30) for non-concurrently performing data transmission and reception, and sequentially transmitting a data frame to a transmitter on the reception side (20) via one or more relay transmitters (10), comprising:
a transmission part (309) for transmitting said transmission data frame, wherein
when said transmitter on the reception side (20) failed to receive every data frame transmitted, said transmitter on the reception side (20) transmits said retransmission request, and responding thereto, the transmitter on the transmission side (30) sequentially retransmits the data frame to said transmitter on the reception side (20).
The transmitter on the transmission side (30) according to claim 23, further comprising:
a transfer valid period addition part (602) for adding said transfer valid period information to said data frame.
A transmitter on the reception side (20) for non-concurrently performing data transmission and reception, and sequentially transmitting a data frame to a transmitter on the transmission side (30) via one or more relay transmitters (10), comprising:
a transmission part (204) for transmitting said retransmission request, wherein
when failed to receive every data frame transmitted from said transmitter on the transmission side (30), transmits said retransmission request, and responding thereto, said transmitter on the transmission side (30) sequentially retransmits the data frame.
The transmitter on the reception side (20) according to claim 25, further comprising:
a transfer valid period addition part (602) for adding said transfer valid period information to said retransmission request.
A relay transmitter (10) for non-concurrently performing data transmission and reception, and sequentially transmitting a data frame from a transmitter on the transmission side (30) to a transmitter on the reception side (20), each comprising:
The relay transmitter (10) according to claim 27, further comprising:
EP20000123380 1999-11-01 2000-10-31 Relay data retransmission method and system Withdrawn EP1096719A3 (en)
EP1096719A2 true true EP1096719A2 (en) 2001-05-02
EP1096719A3 true EP1096719A3 (en) 2007-12-05
EP20000123380 Withdrawn EP1096719A3 (en) 1999-11-01 2000-10-31 Relay data retransmission method and system
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US6728918B1 (en) 2004-04-27 grant
EP1096719A3 (en) 2007-12-05 application