JPH07131400A - Transmission method for digital mobile communication - Google Patents

Abstract

PURPOSE:To improve the multiplicity of the TDMA(time division multiplex system) between a base station and an exchange station by not adopting a part of correction and detection for transmission line encoding in the transmission section between the base station and the exchange station. CONSTITUTION:In a transmission line 15 between a base station 14 and an exchange station 26, a part of or whole error correction and detection is not used for transmission line encoding. In short, a part of or whole error correction/detection code is decoded on the information sent from a mobile station 11 to the exchange station 26 by the mobile station 11. The remaining error correction and detection codes are decoded by the exchange station 26. On the information to be sent from the exchange station 26 to the mobile station 11, a part of or whole error correction/detection encoding is not performed and the remaining error correction/detection encoding is performed by the base station 14 and the redundant addition information is given. As the result, the transmission speed on the transmission line 15 between the base station 14 and the exchange station 26 is reduced and the TDMA multiplicity in the transmission section between both stations 14 and 26 can be increased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a TDM (time division) multiplex transmission method for a wireless transmission section between a mobile station and a base station and a transmission section between a base station and a switching station in a digital mobile communication system. is there.

[0002]

2. Description of the Related Art FIG. 5A shows a configuration of a voice transmission system between a base station and a switching center in a digital mobile communication system. The transmission path coding method in the Japanese standard (Radio System Development Center "Digital Car Telephone System Standard") is described below. The voice input by the mobile station 11 is voice-encoded by the voice encoder 12 in the mobile station 11, is subsequently transmission line-encoded, and is transmitted to the base station 14 through the wireless transmission line 13, and further transmitted from the base station 14. It is transmitted to the voice decoder 16 in the exchange through the inter-station transmission line 15, is subjected to the transmission line decoding in the voice decoder 16, is subsequently voice-decoded, and is transmitted to the public network 17.

On the contrary, the voice input from the public network 17 to the exchange station is voice-encoded by the voice encoder 18 in the exchange station, and is subsequently channel-coded to form the inter-station transmission line 1.
5 to the base station 14 and further from the base station 14 to the mobile station 11 via the wireless transmission path 13 and transmission channel decoding is performed in the voice decoder 19 in the mobile station 11,
Then, the sound is decoded and output.

Three techniques are used for channel coding,
First, the most important bit for hearing is set to CRC (cyclic red).
undancy check: Protect using a cyclic redundancy check. After error correction is performed on the receiving side, these CRC bits are used to check whether the most significant bits have been correctly received. Second, convolutional coding is performed in order to protect bits that are vulnerable to errors in the speech coded data sequence. Third
First, the transmitted data of each voice coded frame is interleaved over two time slots to reduce the influence of Rayleigh fading.

FIG. 5B shows an error correction process of the speech coder. The first step in the error correction processing is to divide, for example, 134-bit information of a speech coded frame into, for example, 75-bit class 1 and 54-bit class 2. The 75 bits of class 1 represent the part on the audio data stream to which convolutional coding is applied. The operation result for CRC is performed on the most acoustically important, for example, 44 bits in the class 1 bit in each frame, and 7 CRC bits are added. 54 bits of class 2 are transmitted without error protection. CRC
The purpose of is to detect when the error correction fails to correct the transmission path error that occurs during the transmission of the auditory most important bit. If the error cannot be corrected and an error is detected,
The received data of this frame is replaced with the previous frame data.

As a second step, forward error correction (FE
C), and the forward error correction is performed with a memory length of 5 for 9
/ 17 rate convolutional coding. This convolutional code is 7 of class 1 out of the output 134 bits of speech coding.
Applies to 5 bits, CRC 7 bits, and overhead 5 bits required by the decoder. These 87
The bits are encoded into 165 bits by this convolution process. This redundant addition increases the transmission speed from 6.7 Kbps (134 bits / 20 ms) to 11.2 Kbps (224 bits / 20 m).
s) will increase the information transmission rate of the voice coded frame.

As a third step, one frame (20 ms) of data is multiplexed into two adjacent time slots by interleaving. That is, half of the 224 bits of one frame are sent in the first time slot and the remaining frame bits are sent in the following time slot. Therefore, mobile station 11
-The wireless transmission line 13 between the base stations 14 and the inter-station transmission line 15 between the base station 14 and the exchange 26 are both 11.2 Kbps (224
The bit rate is 20 ms). The above numerical examples are for the case of the full-rate transmission coding method in the Japanese standard.

As shown in FIG. 6, conventional voice coding / decoding and transmission line coding / decoding are processed in the respective voice encoders in the mobile station and the switching center. That is, in the mobile station 11, the voice encoding / decoding process 22 and C
RC operation / check 23 and convolutional encoding / decoding 2
4 and slot interleave / deinterleave 25 are performed, and similarly, the exchange 26 also performs slot interleave / deinterleave 27, convolutional encoding / decoding 28,
CRC calculation / check 29 and voice encoding / decoding 31
Has been done.

[0009]

DISCLOSURE OF THE INVENTION In the prior art,
In each of the speech coder 12 in the mobile station 11 and the speech coder 16 in the exchange 26, a plurality of error correction / detection schemes are applied to the encoded speech information to add redundant additional information. Therefore, the transmission information rates per channel are the same between the mobile station 11 and the exchange 26.
Therefore, the wireless transmission path 13 between the mobile station 11 and the base station 14
Compared with the above, the amount of information on the inter-station transmission line 15 between the base station 14 and the switching center 26 where the transmission error is sufficiently low is lengthened redundantly, and the number of multiplexes in the transmission line is limited more than necessary. A flaw has arisen. An object of the present invention is to provide a transmission line multiplexing method for digital mobile communication, which solves this drawback in the intra-transmission line multiplexing between a base station and a switching center.

[0010]

The main feature of the present invention is that the error correction / detection of at least a part of the above-mentioned channel coding is not applied in the transmission section between the base station and the exchange.

[0011]

In the transmission section between the base station and the switching station, the error correction / detection of at least a part of the above-mentioned channel coding is not applied, so that redundant additional information due to the coding is reduced, and the base station-switching station. The TDMA multiplicity of the transmission section between
It can be increased from the multiplicity of the transmission section between the mobile station and the base station.

[0012]

1 and 2, an embodiment of the present invention is shown in FIG.
The same reference numerals are given to the portions corresponding to A and 6. In the present invention, the transmission line 15 between the base station 14 and the switching center 26 does not apply some or all of the error correction / detection of the conventional transmission line coding. That is, for information transmitted from the mobile station 11 to the exchange 26, some or all of the error correction / detection codes are decoded by the base station 11 and the remaining error correction / detection codes are decoded by the exchange 26. . Further, regarding the information transmitted from the exchange 26 to the mobile station 11,
The voice signal is not partially or completely error-corrected / detected and encoded in the exchange 26, but the remaining error-correction / detection-encoding is performed in the base station 14 to add redundant additional information.

FIG. 1 shows an example in which the base station 14 performs the slot (de) interleaving 27 and the convolutional encoding / decoding 28 performed by the conventional exchange 26. In FIG. 2, the slot (de) interleave 27, the convolutional encoding / decoding 28, and the CRC calculation / check 29 are implemented in the base station 14. FIG. 3A shows an example of a decoding process for upstream voice (voice signal to the exchange 24) in the base station 14 of the embodiment shown in FIG.

As a first step, data from the mobile station 11 in which 20 ms frame data is multiplexed into two adjacent time slots by deinterleaving is deinterleaved. As a second step, 1
The class 1 information encoded in 65 bits is decoded. Therefore, the amount of signal to be transmitted to the inter-station transmission line 15 is a total of 141 bits including 75 bits of class 1 speech coded signal, 7 bits of CRC and 59 bits of class 2 speech coded signal. That is, 83 bits of the redundant additional information in the convolutional code are removed, and the transmission speed of the inter-station transmission line 15 is 7.05 Kbps from the conventional 11.2 Kbps (224 bits / 20 ms).
(141 bits / 20ms).

FIG. 3B shows the base station 1 of the embodiment shown in FIG.
4 shows an example of a decoding process for upstream voice in FIG. As a first step, the data from the mobile station 11 in which the data of 20 ms frame is multiplexed into two adjacent time slots by deinterleaving is deinterleaved.

As a second step, the deinterleaved data, that is, the class 1 information encoded to 165 bits by the convolution process is convolutionally decoded,
Get 75 bits of class 1 and 7 bits of CRC. Third
As a step, CRC check is performed. Therefore, the amount of signal sent to the inter-station transmission line 15 is 7
There are a total of 134 bits of 5 bits and 59 bits of class 2 speech coded signal. In other words, CRC is more than in the case of FIG.
7 bits are removed and the transmission speed is 11.2Kbp
It is further reduced from s (224 bits / 20 ms) to 6.70 Kbps (134 bits / 20 ms).

Inter-station transmission line 1 between the base station 14 and the exchange 26
FIG. 4 shows a comparison of the transmission rates of the method of the present invention in FIG. According to the present invention, the transmission speed can be reduced as compared with the conventional method, and the base station-
The TDMA multiplicity in the inter-station transmission line 15 between the exchanges is
For example, at 64 Kbps, the conventional 5 channels can be increased to 8 channels by the method of FIG. 1 and 9 channels by the method of FIG.

[0018]

As described above, according to the present invention, a part or all of the error correction / detection conventionally performed by the exchange station is performed by the base station, so that the transmission line transmission between the base station and the exchange station is performed. The speed is reduced, and thus the TDMA multiplicity in the transmission section between the base station and the switching center can be increased. Although the error protection between the base station and the switching center is weaker than in the wireless section, there is no problem because the transmission path error is sufficiently lower than in the wireless section.

Although the present invention is applied to the full rate in the above description, the rate in the wireless section is not limited.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a block diagram showing another embodiment of the present invention.

3A is a block diagram showing a decoding process for upstream voice in the base station in FIG. 1, and FIG. 3B is a block diagram showing a decoding process for upstream voice in the base station in FIG.

FIG. 4 is a diagram showing an example of a transmission rate multiplicity between a base station and a switching center in the conventional method and the method of the present invention.

FIG. 5 is a block diagram showing an error correction process of the voice encoder in the mobile station 11.

FIG. 6 is a block diagram showing speech encoding and error correction processing in the conventional method.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yutaka Oto 2-10-1 Toranomon, Minato-ku, Tokyo NTT Mobile Communication Network Co., Ltd.

Claims (1)

[Claims] 1. A mobile station having a voice encoding / decoding function, a base station forming a wireless communication path with the mobile station, and a voice encoding / decoding connected to the base station via an inter-station transmission line. Of digital mobile communication, which is composed of an exchange station having a digitalization function and performs time-division multiplexing of encoded voice information in a radio transmission section between the mobile station and the base station and a transmission section between the base station and the exchange station. In the transmission method, in the wireless transmission section between the mobile station and the base station, a plurality of error correction / detection methods are applied to the encoded voice information to add redundant additional information, and the transmission section between the base station and the switching station is added. Then, a transmission method of digital mobile communication, wherein at least part of the error correction / detection methods is not applied.