JP3454663B2 - Received signal collision detection device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to collision detection between a signal received by a local station in a communication network and other signals.

[0002]

2. Description of the Related Art FIG. 8 shows the structure of a conventional collision detection device and the burst format of a received signal. 101 in the figure
Is a unique word detection unit, and 103 is a data error detection unit. 201 is a received bit string, 202 is a unique word detection signal, 204 is data, and 205 is a data error detection signal. 301 is a guard time, 302 is a unique word, 303 is a data word, and 304 is a data error check word.

Next, the operation will be described. The unique word detection unit 101 receives the received signal and receives the received bit string 2
While 01 is sequentially shifted by 1 bit, it is sequentially compared with a known unique word. If the correlation is equal to or more than a threshold value, it is determined that the unique word 302 has been detected, that is, normal reception, and the unique word detection signal 202 is activated. To do. Since the normal reception state is established, the data error control unit 10
3 uses the timing of the unique word detection signal 202 to extract the data word 303 from the received bit string 201. Also, a data error check word 3 such as a CRC code
04, the presence or absence of an error in the data word 303 is checked, and if there is an error, it is determined that the received data has an error, and the data error detection signal 205 is activated.

With the above-mentioned structure, the following occurs with respect to collision detection. (1) In collision detection, it is determined that a collision has occurred because the unique word cannot be detected and the input signal is input for a certain period or longer. In this case, as a system operation, a resend request is made in the response. However, even in that case, it cannot be distinguished from the fact that the unique word cannot be temporarily detected due to a simple data error and the occurrence of collision. In either case, the data can generally be recovered by retransmission. (2) Unlike the wired system, the wireless system has no limitation on the communication path length, and thus it is difficult to strictly manage the allocation time for each channel. In order to avoid burst communication data collision, the non-contention method allocates synchronization timing and the system is designed so that collision does not occur, but there is no collision at all due to timing fluctuations on each receiver side. Do not mean. Further, in a wired system, a simple collision detection can be performed by detecting an increase in DC component, but in a wireless system, the levels are too different, so this method cannot be adopted. There is a collision detection method by detecting the folding back of the bit pattern, but the device scale becomes too large.

[0005]

A conventional collision detection circuit for a received signal and another signal is constructed as described above,
Although the collision of the received data in the front can be detected, the collision occurring in the rear cannot be detected, which makes it difficult to restore the received signal. In addition, there is a problem that a simple collision detection by level detection cannot be performed unlike a wired system. Further, in the case of burst collision, it is necessary to change the synchronization timing, but there is also a problem that it is not possible to distinguish the data error from the burst collision and change the synchronization deviation for the burst collision.

The present invention has been made to solve the above problems, and an object thereof is to obtain an apparatus for detecting a collision with another signal during a predetermined length of received data which is not limited to the head portion. To do.

[0007]

A received signal collision detection apparatus according to the present invention includes a first unique word detection section for detecting a unique word set in advance in a received signal, and a rear side of the unique word in the received signal. A received signal and another signal by using the second unique word detection unit for detecting the word equivalent for error detection in FIG. 1, the detection output of the first unique word detection unit and the detection output of the second unique word detection unit. And a collision detection unit for detecting a reception collision of the.

Furthermore, the error detecting word is a code for detecting a data error in a predetermined area in the received signal.

Furthermore, in addition to the first unique word detecting section and the second unique word detecting section, another unique word detecting section for detecting the word equivalent for other error detection is provided, and the collision detecting section is Reception collision is detected by using the detection output of the unique word detection unit.

Furthermore, a level measuring unit for the received signal is provided, and when the level measured by the level measuring unit is low, the output of the collision detecting unit is suppressed so that no collision occurs.

Further, a collision information inserting section for inserting the information output of the collision detecting section into the received signal sequence is added.

[0012]

DETAILED DESCRIPTION OF THE INVENTION

Embodiment 1. In the present embodiment, an apparatus for detecting a collision not only at the head portion but also at an arbitrary portion, for example, all portions of the valid data area will be described. For that purpose, the system sets unique words at the beginning and the end in the burst format of the communication data string. In response to this, the receiving device detects the unique words at the beginning and at the end, so that if there is an error in the received burst, it can be detected that there is a collision between the received signal and the burst of another signal. FIG. 1 shows the configuration and burst format of the receiving apparatus according to this embodiment. In FIG. 1A, 101 is a first unique word detecting unit, 102 is a second unique word detecting unit, 103 is a data error detecting unit, and 104 is a collision detecting unit. 201
Is a received bit string, 202 is a first unique word detection signal, 203 is a second unique word detection signal, 204 is data, 205 is a data error detection signal, 206 is a transmission timing signal, 207 is a reception collision detection signal, and 208 is transmission / reception collision. It is a detection signal. In FIG. 1B, 301 is a guard time, 302 is a first unique word, 303 is a data word, 304 is a data error check word, and 305 is a second unique word.

Next, the operation of the above apparatus will be described. Receiving the received signal, the first unique word detecting unit 101
Sequentially compares the received bit string 201 with the known first unique word 302 while shifting the received bit string 201 by 1 bit, and if the correlation is equal to or more than the threshold value, it is determined that the first unique word 302 is detected, that is, the normal reception is performed. Judge, first
The unique word detection signal 202 is activated. The second unique word detection unit 102 also operates similarly to the first unique word detection unit 101. However, different words are set for the first unique word 302 and the second unique word 305. With the above operation, the operation of only the first unique word detector is the same as the conventional one. That is, whether or not the leading portion has collided is determined by detecting the unique word and the reception level / period. In the present embodiment, further, after the normal reception, whether the second unique word can be detected or not can detect whether or not a collision has occurred during that time. Also, depending on the network, different unique words may be assigned to the respective stations, and in that case, the transmitting station can be specified when the unique word is detected. The data error detection unit 103 extracts the data word 303 from the received bit string 201 using the timing of the first unique word detection signal 202. Also,
Using a data error check word 304 such as a CRC code,
The presence or absence of an error in the data word 303 is checked, and if there is an error, the received data error detection signal 205 is activated.

The collision detector 104 monitors the first unique word detection signal 202 and the second unique word detection signal 203 to detect a collision between received bursts. Less than,
The details will be described. The collision detection unit 104 constantly monitors the first unique word detection signal 202 in the idle state. When the first unique word detection signal 202 becomes active, the idle state changes to the normal state,
After that, a state is detected in which a collision is received during data reception. Here, if the second unique word detection signal 203 does not become active after the scheduled time (here, accuracy does not matter so much), it is determined that a collision between the reception bursts has occurred, and the reception collision detection signal is detected. 207 is activated. There is also a method in which the reception collision detection signal 207 is not made active at this time, but is made active when the second unique word 305 of the collision partner behind is detected. When the transmission station of the burst can be identified, it is possible to activate the reception collision detection signal 207 and simultaneously output the information of the station.

Further, the collision detecting section 104 detects the collision between our transmission burst and the reception burst by using the transmission timing signal 206 from its own transmission device.
The details will be described below. The collision detection unit 104 also constantly monitors the transmission timing signal 206 in the above-mentioned idle state. When the transmission timing signal 206 becomes active, the transmission state is changed from the idle state, and at the same time, the transmission / reception collision detecting state is set. When the second unique word cannot be detected within the time range of the known burst length in this detecting state, it is determined that the collision between our transmission burst and the reception burst has occurred, and the transmission / reception collision detection signal 208 is transmitted. Activate. As in the case of the reception collision detection described above, when the transmission station of the burst can be identified, the transmission / reception collision detection signal 207 is activated and the information of the collision partner station is also output. As described above, it is possible to detect collisions between reception bursts and collisions between our transmission bursts and reception bursts separately from the detection of data error, and in some cases,
It is possible to detect the information of the transmitting station of the collision burst together.

Embodiment 2. In the previous embodiment, the second
Although the code determined by the system is used as the unique word, any unique code in the received data string may be used. The case where a data error check word is used as this unique error detection word will be described below. The configuration of the receiving apparatus according to the second embodiment and the burst of received signals
The format is shown in FIG. In FIG. 2B, 30
6 is a first data word string, 307 is a first data error checking word, 308 is a second data word string, and 309 is a second data error checking word. This burst format has two data word strings and a data error check word associated with the two data word strings, and the receiving device performs error detection of each data word string. This allows the location of the error in the received burst to be identified, and consequently the location of the collision between the bursts to be detected.

Next, the operation will be described. The unique word detection unit 101 performs the same operation as the first unique word detection unit 101 of the first embodiment. The data error detection unit 103 extracts the first data word sequence 306 and the second data word sequence 308 from the received bit sequence 201 using the timing of the unique word detection signal 202. Also, the first data error check word 307 and the second data error check word 309 such as a CRC code are used to check the presence or absence of an error in the data word, and if there is an error, the received data error detection signal 205 is made active. To do. The collision detection unit 104 can detect in which data stream the collision between the reception bursts has occurred by monitoring the data error detection signal 205.

When the unique word detection signal 202 becomes active, the collision detection unit 104 determines that normal reception has started, and enters the reception collision monitoring state. Here, when the data error detection signal 205 is inactive (normal) and active (error detection) at the time positions corresponding to the data error check words 307 and 309, respectively, the collision between received bursts is the latter half. It is determined that this may have occurred during the reception of the second data word sequence of, and the reception collision detection signal 207 is activated. However, since the frequency of occurrence of a data error is relatively high, in order to distinguish it from a normal data error, the operation of activating the reception collision detection signal 207 only when the above-mentioned event occurs repeatedly is adopted. When the transmission station of the burst can be identified, it is possible to activate the reception collision detection signal 207 and simultaneously output the information of the station. According to the above-mentioned configuration, there is an advantage that the number of dedicated unique word detection units can be reduced.

If the positions corresponding to the unique words for collision detection in the above embodiment are increased and distributed,
It is possible to know in which part the collision has occurred, retransmit only that part, and select the retransmission timing appropriately. A collision detection device that meets such a demand will be described.
FIG. 3 shows the configuration of the receiving apparatus having the above-mentioned function and the burst format of the received signal. In FIG. 3A, 1
Reference numeral 05 is a distributed unique word detection unit, and reference numeral 209 is a distributed unique word detection signal. Further, 310 in FIG. 3B is a distributed unique word. As shown in FIG. 3B, the unique words are divided and distributed, and detection is performed for each of the distributed unique words in the receiving device, whereby a collision between the burst signal received at any part and another signal is prevented. You can know what was there.

Next, the operation of the part different from the previous embodiment will be described. The distributed unique word 310
Changes the character code depending on where it is embedded in the burst format. In this way, it is possible to obtain the distribution position information indicating in which part the error has occurred, that is, the collision has occurred. The collision detection unit 104 instantaneously obtains an error position in the reception burst based on the distribution position information included in the distributed unique word detection signal 209. When the position is biased forward or backward, the collision between the reception bursts is detected. It is determined that the reception collision detection signal 207 may have occurred.
To be activated. In addition, the collision detection unit 104 uses the transmission timing signal 206 from the transmission device,
In the same way, it is possible to detect the collision between our transmission burst and reception burst. In this case, the transmission / reception collision detection signal 20
8 is activated. As described above, in addition to the detection of the data error, it is possible to separately detect the collision between the reception bursts and the collision between the transmission burst and the reception burst of the present invention by using the transmission timing signal 206. As in the other embodiments, it is possible to detect the information of the transmitting station of the collision burst together.

Embodiment 3. In the present embodiment, a case will be described where a collision detection signal is corrected using a reception level signal such as an AGC signal for the purpose of improving the reliability of collision detection. FIG. 4 shows a burst format of a received signal in the configuration of the receiving apparatus according to the present embodiment. Figure 4
In the figure, 106 is a collision detection correction unit, and 107 is a level measurement unit. Reference numeral 210 is a reception level signal, 211 is a corrected reception collision detection signal, and 212 is a corrected transmission / reception collision detection signal. The collision detection / correction unit 106 outputs the result of measuring the reception level signal as a control signal for the AGC if it exists, and the reception signal measured by the level measurement unit 107 if it does not. When the value of the reception level signal 210 in the burst period is less than or equal to the threshold (small level), the reception collision detection signal 20
7 and the transmission / reception collision detection signal 208 may have been erroneously detected, and the reception / transmission / reception detection signal 21 after each correction
The outputs of 1 and 212 are masked, that is, burst collision detection is not performed, and the reliability of collision detection is improved.

The above structure can be applied to each of the second embodiments. The device configurations applied to each are shown in FIGS.

Fourth Embodiment In the above embodiment, the detection operation has been described, but the final purpose is to notify this to a necessary part and cause the control operation. Here, the notification that does not use another line such as the detection information line will be described. FIG. 7 shows the device configuration of the present embodiment and the burst format of data output to the next stage. In FIG. 7A, 1
Reference numeral 08 is a data insertion unit. Further, in FIG. 7B, 311 is collision detection information inserted by the data insertion unit 108. The collision detection unit 104 of this configuration outputs a reception collision detection signal or a transmission / reception collision detection signal to the data insertion unit 108. Upon detecting the activity of these signals, the data insertion unit 108 inserts the corresponding collision detection information 311 into the received signal. According to the above configuration, the line for informing the collision detection is unnecessary.

Although not shown in the block diagram, the above-mentioned collision detection information or collision detection signal is used to change the transmission timing by the transmission means, response means, etc., shift the reception timing, or change the burst length. Request to change.

[0025]

As described above, according to the present invention, since the unique word in the different portion of the received signal is detected, there is an effect that the collision can be detected regardless of which portion the collision occurs. Furthermore, there is an effect that a data error and a collision can be identified and a clear collision notification can be made.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a received signal collision detection apparatus and a received signal burst format according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a configuration of a received signal collision detection device and a received signal burst format according to a second embodiment of the present invention.

FIG. 3 is a diagram showing a configuration of another received signal collision detection apparatus and a burst format of a received signal according to the second embodiment.

FIG. 4 is a diagram showing a configuration of a received signal collision detection device and a received signal burst format according to a third embodiment of the present invention.

FIG. 5 is a diagram showing a configuration of another received signal collision detection apparatus and a burst format of a received signal according to the third embodiment.

FIG. 6 is a diagram showing a configuration of another received signal collision detection apparatus according to the third embodiment and a burst format of a received signal.

FIG. 7 is a diagram showing a configuration of a received signal collision detection device and a received signal burst format according to a fourth embodiment of the present invention.

FIG. 8 is a diagram showing a conventional signal collision detection device and a burst format of a received signal.

[Explanation of symbols]

101 first unique word detection unit, 102 second unique word detection unit, 103 data error detection unit, 104
Collision detection unit, 105 distributed unique word detection unit, 1
06 collision detection / correction unit, 107 level measurement unit, 108
Data insertion part.

Claims (5)

(57) [Claims] 1. A first unique word detecting section for detecting a preset unique word from a received signal, and a second unique word detecting section corresponding to an error detection word behind the unique word in the received signal. A unique word detecting section; a detection output of the first unique word detecting section;
A received signal collision detection device comprising: a collision detection unit that detects a reception collision between the received signal and another signal by using the detection output of the unique word detection unit. 2. The received signal collision detection apparatus according to claim 1, wherein the error detection word is a code for data error detection in a predetermined area in the received signal. 3. In addition to the first unique word detecting section and the second unique word detecting section, another unique word detecting section for detecting a word equivalent for other error detection is provided, and the collision detecting section is different from the above. 2. The received signal collision detection device according to claim 1, wherein a reception collision is detected also by using the detection output of the unique word detection unit. 4. A received signal level measuring unit is provided, and when the level measured by the level measuring unit is low, the output of the collision detecting unit is suppressed so that no collision occurs. The received signal collision detection device according to claim 3. 5. The received signal collision detection apparatus according to claim 1, further comprising a collision information insertion section for inserting the information output of the collision detection section into a sequence of received signals.