JP2008172658A - Wireless communication system and communication apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform communication end determination with higher determination accuracy than communication end determination using synchronization detection processing when a communication device on the receiving side cannot receive a signal related to communication end.
[Solution]
In a wireless communication system in which a plurality of communication devices perform wireless communication using a communication frame having an area for storing error-correctable information,
In the communication device on the reception side, the no-signal detection unit 18 performs error correction processing on the low-speed associated control channel SACCH unit in the communication frame wirelessly received by the reception RF unit 14 and demodulated by the demodulation unit 15. It is determined whether the number of error correction errors has exceeded a predetermined value, and when the number of error correction errors exceeds a predetermined value, a non-reception flag indicating “no signal state” is output to the control unit 20, and the control unit In response to the input of a non-reception flag 20 indicating “no signal state”, communication termination processing is performed.
[Selection] Figure 1

Description

  The present invention relates to a wireless communication system in which a plurality of communication devices perform wireless communication, and in particular, to a technology related to a communication end process in the communication device when the receiving communication device cannot receive a signal related to the communication end. .

FIG. 4 shows a control sequence in a communication phase of simplex communication performed by a plurality of mobile stations 1 and 2 via a base station in the standard “ARIB STD-T79” of a prefectural / municipal digital mobile communication system. .
The base station notifies each mobile station 1 and 2 of I (idle) by B / I (busy / idle bit) of the fast associated control channel FACCH (First Associated Control Channel). Access is permitted.

In this state, when the press talk becomes “ON” at the timing T1 in the mobile station 1, the mobile station 1 exchanges SB2 to 4 (SB: synchronization burst) between the base station and the traffic channel TCH from the base station. After B (busy) is notified to the mobile station 1 by B / I of (Traffic Channel), a voice signal is transmitted from the mobile station 1 to the mobile station 2 via the traffic channel TCH via the base station.
When the press talk is turned off at timing T2 in the mobile station 1, a transmission right release signal is transmitted from the mobile station 1 to the base station. When the base station receives the transmission right release signal at the timing of T3, I (idle) is notified to each mobile station 1 and 2 by B / I of the high-speed associated control channel FACCH, and each mobile station 1 and 2 again grants access. It becomes a state.

If the base station cannot receive a transmission right release signal from mobile station 1 at timing T3 due to fading or the like, other mobile stations will access even though press talk is turned off in mobile station 1. Cannot talk because it is not allowed.
In this case, a synchronization detection process is performed at the base station, and if the synchronization is lost for a predetermined period of time, it is determined that there is no signal (that is, the call ends), and the call is forcibly disconnected to Put the mobile station in an access-permitted state.

Conventionally, various inventions have been proposed for wireless communication systems.
For example, even if the base station calls and the call signal does not reach the desired mobile station for some reason, or the mobile station calls and the response signal to the base station for some reason Even if the calling station does not reach the calling mobile station, the base station and the mobile station, which are the calling stations, transmit a call termination signal when it is detected that a response signal is not returned from the called station. By canceling the state in which the mobile station transmission request is not issued before the fixed time elapses, the base station and the mobile station can issue an immediate communication request without waiting until the fixed time elapses after calling. An invention for increasing the effective utilization rate of a communication channel has been proposed (see Patent Document 1).

  For example, a bit error rate is detected from data sent from a mobile device, and when this value exceeds a certain threshold, a warning sound is output to both the mobile device and the telephone (or mobile device) that is the communication partner. There has been proposed an invention for notifying a user of a mobile device and a call partner that the call is likely to be disconnected by controlling (see Patent Document 2).

  For example, by detecting communication quality data in the SACCH frame based on the analysis result of the received frame by the receiving unit, the call quality reception level is measured, and counting is started when the reception level is lower than the set value. Counts up when the reception level is low even in the next SACCH frame, and when the count value reaches the set value, the speaker as an informing means is operated to generate a warning sound. An invention has been proposed that warns a person who is disconnected in advance of the possibility of a call disconnection (see Patent Document 3).

  For example, a communication device on the transmission side wirelessly transmits a communication channel signal including a traffic channel signal or an error detection encoded high-speed associated control channel signal, and the reception-side communication device transmits the received communication channel signal. A communication channel received on the receiving side by executing error detection processing on the signal and executing processing corresponding to the traffic channel or the high-speed associated control channel depending on whether the error level is equal to or higher than a predetermined threshold. An invention for effectively determining whether or not a high-speed associated control channel signal is included in the above-mentioned signal has been proposed (see Patent Document 4).

JP-A-2-272924 JP-A-8-19042 JP-A-8-37489 JP 2006-67262 A

FIG. 5 shows a communication frame format of a communication physical channel (hereinafter referred to as a communication channel) in the above standard.
The communication channel is a 6-bit burst transient response guard time R, a 2-bit preamble P, a 148-bit traffic channel TCH or a high-speed associated control channel FACCH, a 20-bit synchronization word SW, a 2-bit idle bit I, a 20-bit Low-speed associated control channel SACCH (Slow Associated Control Channel), 108-bit traffic channel TCH or high-speed associated control channel FACCH, and 8-bit guard time G.

In FIG. 4, when the base station cannot receive the transmission right release signal from the mobile station 1 at timing T3, the base station is in a standby state for a communication channel including the traffic channel TCH, and synchronization detection processing using the synchronization word SW It is carried out.
In the synchronization detection process, the number of error bits in the synchronization word SW is detected for each communication frame, and a communication frame whose error bit number exceeds a specified allowable number of bits (in this example, “2”) In the case of “10”), the communication frame with the number of error bits equal to or less than the specified allowable number of bits continues for the specified number of backward protection stages (“1” in this example). In this case (that is, when the number of error bits becomes 2 or less even once), “synchronization is established”.
Therefore, when the base station cannot receive the transmission right release signal from the mobile station 1 at the timing T3, in order to detect loss of synchronization for a specified period of time, the base station continues for at least the number of protection stages corresponding to the specified time. Therefore, the number of error bits of the synchronization word SW must exceed the allowable number of bits.

At this time, since the carrier is not transmitted from the mobile station 1, in the signal received at the base station, the signal corresponding to the synchronization word SW of the communication frame is a random signal with amplified noise. The probability that the random signal is erroneously recognized as a synchronization word (that is, the probability that the number of error bits is 2 bits or less) _Psw is calculated by the following equation.
Equation _{(1) P sw = (1 +} 20 C 1 + 20 C 2) / 2 20 = (1 + 20 + 190) / 2 20 = 2.01 × 10 -
^Four

Here, for example, the probability P that the number of error bits exceeds the allowable number of bits 250 times corresponding to about 10 seconds is calculated by the following equation.
(Equation 2) P = (1-P _sw ) ²⁵⁰ = 0.999799 ²⁵⁰ = 0.951 = 95.1%
That is, when it is determined that there is no signal (communication end) in response to detecting out-of-synchronization for 10 seconds continuously, a situation occurs in which 4.9% cannot end the call in 10 seconds. To do.

  The present invention has been made in view of the above-described conventional circumstances, and when the communication device on the receiving side cannot receive a signal related to communication termination, the determination accuracy is higher than that of communication termination determination using synchronization detection processing. The purpose is to propose a technology that can determine the end of communication.

  To achieve the above object, the present invention provides a wireless communication system in which a plurality of communication devices perform wireless communication using a communication frame having an area for storing error-correctable information. Error correction means for performing error correction processing on the region in the medium, and whether or not the number of consecutive error correction errors exceeds a predetermined value as a result of error correction processing by the error correction means for a plurality of communication frames. A determination unit for determining, and a control unit for performing communication termination processing in response to determination by the determination unit that the number of consecutive error correction errors exceeds a predetermined value, This is realized as a wireless communication system.

  The present invention also provides an error correction means for performing error correction processing on the area in a communication frame, and a plurality of communication in a communication apparatus that receives a communication frame having an area for storing error correctable information from another apparatus. A determination means for determining whether the number of consecutive error correction errors as a result of performing error correction processing on the frame by the error correction means exceeds a predetermined value; and a predetermined number of consecutive error correction errors. And a control unit that performs a communication termination process in response to the determination by the determination unit that the value has been exceeded.

In other words, if the demodulation result looks like a random bit string because the carrier from another device is not received, the probability that the error correction process erroneously determines “no error” is erroneously determined as “established synchronization” by the synchronization detection process. If the number of consecutive “error correction errors (with errors)” exceeds a predetermined value, it is determined that there is no signal (communication end), and communication end processing is performed. Do.
For example, when determining the end of communication using the result of the error correction process for the low-speed associated control channel SACCH part, as will be described later, it can be determined with higher accuracy than the case of using the result of the synchronization detection process. Can be completed.

Various wireless communication systems according to the present invention may be used. For example, a prefectural / municipal digital mobile communication system may be used. Moreover, any communication system of simplex communication and duplex communication may be used.
Various devices may be used as the communication device on the receiving side according to the present invention. For example, a base station device, a portable wireless terminal device, an installed wireless terminal device, or the like may be used. In addition, the communication device may be a device having a transmission function as well as a reception function.

  According to the present invention, the communication end on the receiving side cannot receive the communication end signal because the end of communication is determined using the result of the error correction process with a lower probability of erroneous determination of the random signal than the synchronization detection process. In this case, it is possible to determine the end of communication with higher accuracy than when the synchronization detection process is used, and it is possible to perform the end process of communication more reliably.

The present invention will be specifically described based on an example.
FIG. 1 shows functional blocks of a receiving side communication apparatus (base station apparatus in this example) in a prefecture / municipal digital mobile communication system to which the present invention is applied.
The base station apparatus generates a transmission RF unit 11, a modulation unit 12, and an encoding unit 13 for realizing a transmission function, and a reception RF 14 unit, a demodulation unit 15, and a decoding unit 16 for realizing a reception function. It has a timing generator 19 and a controller 20 that controls the radio.

The base station device encodes (encodes) transmission data supplied from the control unit 20 with the encode 13, modulates it with the modulation unit 12, and wirelessly transmits the result as a transmission signal by the transmission RF unit 11.
Also, the base station apparatus demodulates the received signal received wirelessly by the reception RF unit 14 by the demodulation unit 15 and decodes the result by the decode processing unit 17 included in the decoding unit 16 to obtain received data. To the control unit 20.

In the communication system of this example, the low-speed associated control information exchanged via the low-speed associated control channel SACCH is encoded by channel coding processing of the scheme shown in FIG.
In this example, the information unit of the low-speed associated control information is 59 bits, and a 16-bit CRC (Cyclic Redundancy Code) and a 5-bit fixed bit are added to 80 bits, and 160 bits are obtained by convolutional coding. After that, interleaving processing is performed to change the order of arrangement of internal data.
The 160-bit low-speed associated control information encoded in this way is divided into 8 blocks of 20-bit units, and the second to ninth eighth frames out of 0 to 17 consecutive communication frames, or 10 to 17 It is stored in the low-speed associated control channel SACCH part in the 8th frame and transmitted.

  The decoding unit 16 of this example further includes a no-signal detection unit 18 that performs no-signal detection processing using the result of the error correction processing. The no-signal detection unit 18 is a 40 ms input from the timing generation unit 19. The no-signal detection process is performed according to the “interrupt signal” for each frame period and the “frame counter value” that is incremented for each frame period and circulates from 0 to 17.

The no-signal detection processing by the no-signal detection unit 18 according to the present invention will be described with reference to the flowchart shown in FIG.
The no-signal detection unit 18 reads the frame counter value at the timing of the interrupt signal (step S101).
Then, it is determined whether or not the read frame counter value is 2 to 9 (step S102). If the frame counter value is 2 to 9, the low-speed associated control channel SACCH portion in the demodulated communication frame is cut out, The second to ninth eighth frames are stored in the memory so that the demodulation results of the respective low-speed associated control channel SACCH sections are continuous (step S103). If the read frame counter value is not 2 to 9, it is further determined whether or not the frame counter value is 10 to 17 (step S104). If the frame counter value is 10 to 17, in the demodulated communication frame The low-speed associated control channel SACCH portion is cut out and stored in the memory so that the demodulation results of the low-speed associated control channel SACCH portions of the 10th to 17th eight frames are continuous (step S105).

Thereafter, it is determined whether or not the frame counter value is 9 or 17 (step S106). If the frame counter value is not 9 or 17, the process is terminated. If the frame counter value is 9 or 17, the following process is performed. I do.
First, decoding processing is performed on the information of the low-speed associated control channel SACCH portion for 8 frames stored in the memory in step S103 or step S105 (step S107). In the decoding process, a deinterleaving process for returning the data arrangement order, a Viterbi decoding process for correcting an error by Viterbi decoding, and a CRC code check process for checking the decoded CRC code are performed in order.

As a result of the decoding process, it is determined whether or not a CRC error (error correction error) has occurred (step S108). If it is not a CRC error, the counter Nerr is reset to “0” (step S109), and a non-reception flag is set. “0 (not a no-signal state)” is output to the control unit 20 (step S110). On the other hand, in the case of a CRC error, the counter Nerr is incremented (added by 1) (step S111).
Then, it is determined whether or not the counter Nerr is equal to or greater than the specified number of times (in this example, 28 times corresponding to about 10 seconds) (step S112). If the counter Nerr is equal to or greater than the specified number of times, the non-reception flag is set to “1 (no signal Status) ”to the control unit 20 (step S113).
When the non-reception flag of “1 (no signal state)” is input, the control unit 20 terminates the communication (in this example, I (idle) with the B / I of the high-speed associated control channel FACCH) for each mobile station. Notification).

Here, the 16-bit CRC code is uniquely determined for the 59-bit low-speed associated control information information unit. In the decoding process, the remaining 85 bits are not a CRC error even if they have an arbitrary bit pattern. Therefore, when the low-speed associated control channel SACCH portion of the signal received by the base station apparatus is a random signal due to noise, the probability P _SACCH that does not cause a CRC error (error correction error) is calculated by the following equation.
( _Equation 3) P _SACCH = 2 ^{59 +} _85/2 ¹⁶⁰ = 2 ^-16 = 1.53 × 10 ^-5
Then, the probability P of determining that there is no signal state in about 10 seconds, that is, 28 units in succession, is calculated by the following formula.
(Equation 4) P = (1-P _SACCH ) ²⁸ = 0.9999847 ²⁸ = 0.99957 = 99.957%

Therefore, the probability that the communication end processing cannot be performed without detecting the no signal state (communication end) in 10 seconds is 0.043%, and the case of detecting the no signal state using the result of the synchronization detection processing (4 .9%) is 1/100 or less.
As described above, when the base station apparatus cannot receive a signal indicating the end of communication (for example, a transmission right release signal), if the result of the error correction process for the low-speed associated control channel SACCH part is used, the result of the synchronization detection process The communication end can be determined with higher accuracy than in the case of using and communication end processing can be performed more reliably.

In addition, this invention is not limited to the communication system shown to the said Example, It can apply to a various radio | wireless communications system.
In this example, the result of the error correction process for the low-speed associated control channel SACCH part is used, but the result of the error correction process for another channel storing error correctable information may be used.
In this example, each of the decoding processing unit 17 and the no-signal detection unit 18 performs decoding processing (error correction processing) for the low-speed associated control channel SACCH unit. The error correction processing may be performed on the SACCH unit, and the result may be notified to the no-signal detection unit 18 to determine the no-signal state (communication end).

The present invention is implemented as a wireless communication system and a communication device (base station device, portable wireless terminal device, installed wireless terminal device, etc.), for example, a method for executing the processing according to the present invention, The present invention can also be implemented as a program for causing a computer to realize processing functions.
Further, in the base station apparatus of this example, the no-signal detection unit 18 that is the correction unit and the determination unit according to the present invention and the control unit 20 that is the control unit according to the present invention are realized by a dedicated hardware circuit. However, for example, a program for causing a computer to realize each processing function is held in a storage device such as an HDD (Hard Disk Drive) or ROM (Read Only Memory), and the program is stored in a CPU (Central Processing Unit) or the like. You may comprise by performing by an arithmetic processing part.

It is a block diagram of the base station apparatus which concerns on one Example of this invention. It is a figure which shows the flowchart of the no signal detection process which concerns on one Example of this invention. It is a figure explaining a channel coding process. It is a figure which shows the control sequence in the communication phase of simplex communication. It is a figure which shows the signal format of the physical channel for uplink communications.

Explanation of symbols

11: Transmission RF unit,
12: Modulator
13: Encoding part,
14: Reception RF section,
15: Demodulator
16: Decoding part
17: Decoding processing unit,
18: No signal detector,
19: Timing generator,
20: Control unit

Claims (2)

In a wireless communication system in which a plurality of communication devices perform wireless communication using a communication frame having an area for storing error-correctable information,
The communication device on the receiving side
Error correction means for performing error correction processing on the region in the communication frame;
As a result of performing error correction processing by the error correction unit for a plurality of communication frames, a determination unit that determines whether the number of consecutive error correction errors exceeds a predetermined value;
Control means for performing communication termination processing in response to the determination by the determination means that the number of consecutive error correction errors exceeds a predetermined value;
A wireless communication system comprising: In a communication device that receives a communication frame having an area for storing error-correctable information from another device,
Error correction means for performing error correction processing on the region in the communication frame;
As a result of performing error correction processing by the error correction unit for a plurality of communication frames, a determination unit that determines whether the number of consecutive error correction errors exceeds a predetermined value;
Control means for performing communication termination processing in response to the determination by the determination means that the number of consecutive error correction errors exceeds a predetermined value;
A communication apparatus comprising:

Images