JPS63178700A - Relay exchange system - Google Patents

Abstract

PURPOSE:To attain multi-link connection without deterioration in information quality by using a digital exchange to apply relay exchange to a low bit rate coding signal and a code making remaining bits idle in place of a PCM signal without applying coding/decoding between the low bit rate coding signal and a PCM signal. CONSTITUTION:M bits of N bits per one time slot are brought to a low bit rate coding signal by a multiplex separator 13 and the remaining (N-M) bits are kept idle in the digital signal and them are sent to a relay exchange 15. The multiplex separator 13 separates only the M bit low bit rate coding signal from the digital signal and sends it to a high-speed digital line 16-2 or 16-1. Thus, the low bit rate coding signal is not coded not decoded and the idle (N-M) bits are added and separated and the result is subjected to relay exchange as it is. Thus, even with multi-link connection, the information quality is the entirely same high quality as that of one link connection and the quality deterioration is prevented.

Description

[Detailed Description of the Invention] [Summary] The present invention encodes a PCM signal (pulse code modulation signal) to a low bit rate, and uses it in a relay switching system when connecting multiple high-speed digital lines using a digital switch. , without performing encoding and decoding between the low bit rate encoded signal and the PCM signal, and instead of the PCM signal, the low bit rate encoded signal and the code with the remaining bits vacant are relay exchanged by a digital exchange. This allows multiple link connections to be made without degrading information quality.

[Industrial application field]

The present invention relates to a relay switching system, and more particularly to a system in which a low bit rate coded signal is relayed and exchanged by a digital switch instead of a PCM signal.

In corporate networks that connect long-distance head offices, branch offices, and business operators using high-speed digital lines, encoding equipment that transmits low-bit-rate encoded signals has been introduced in order to make more economical use of high-speed digital lines. There is a tendency to Therefore, even when such a low bit rate encoding device is used, there is a need for a relay switching system that allows multi-link connections with good information quality using a digital switch.

[Conventional technology]

FIG. 6 shows the concept of a general multi-link connection.

In the figure, 1-1 to 1-5 are high-speed digital lines, 2-1
~2-4 is a multiplexing and demultiplexing device (MUX), and 3-1 to 3-4 are private branch exchanges (PBs) equipped with relay exchange functions and terminal exchange functions.
X), 4, A and B are each subscribers (telephone II).

In the case of multi-link connections, high-speed digital lines 1-1 to 1-
A PCM signal inputted to one of the demultiplexing devices 2-1 to 2-4 from one of the PCM signals of 64 kbps, for example,
CM audio data always enters one of the private branch exchanges 3-1 to 3-4, and then goes back to the corresponding demultiplexer 2-
High-speed digital line 1-1 to 1-5 through 1 to 2-4
Which of the following will be sent to.

For example, when subscriber A calls subscriber B, A
→3-1→2-1→1-2→2-2→3-2→2-2→
1-3→2-3→3-3→2-3→1-4→2-4→3
Follow the route -4→B.

Demultiplexing device 2-1 in such multi-link connection
The connection form between 2-4 and private branch exchange (PBX) 3-1 to 3-4 is as shown in Figure 7 if the private branch exchange is an analog exchange, and as shown in Figure 8 if it is a digital exchange. become. In FIG. 7, an A/D-D/A converter 5 for mutually converting an analog audio signal and a 64 kbt+sP CM signal is provided in the demultiplexer 2a, and the demultiplexer 2a and the analog exchange 3a
Audio signals are exchanged between the two as analog signals. Note that 6 indicates a data terminal.

On the other hand, in the connection form shown in FIG. 8, an A/D-D/A converter 7 is provided in the digital exchange 3b, and the audio signal between the demultiplexer 2b and the digital exchange 113b is converted into a digital signal. It is exchanged in

When making a multi-link connection in the connection form shown in Fig. 7, the A/D-D/A converter 5kTA performs A/D conversion and D/A conversion every time there is a relay exchange. The more the number of links increases, the more the voice quality deteriorates due to the generation of mother-child noise caused by this, the mixing of noise in the analog section, etc.

On the other hand, when a multi-link connection is made in the connection form shown in FIG. 8, the digital signal is relayed and exchanged as it is, so the voice quality hardly deteriorates compared to the case of one link. Therefore, it can be seen that digital exchanges are superior to analog exchanges in the case of multi-link connections.

By the way, among the signals transmitted on high-speed digital lines in conventional multi-link connections, PCM audio signals have a sampling frequency of 8 kHz per channel, a quantization bit count of 8 bits, and a transmission bit rate of 64 kbps. And it is fast.

In addition, in recent years, in order to make more economical use of existing high-speed digital lines, the transmission bit rate per audio channel has been increased to 32kbps, 16kbos, or 8kbps.
Thus, audio encoding systems that compress the 54 kbps PCM audio signal to 1/2, 1/4, or 1/8 are being put into practical use.

Figure 9 shows a multiplex valve l! that uses this low bit rate audio encoding method. 1 is a block diagram of an example of a connection form between a 1ltvi device and an exchange. FIG. 9 shows the connection form for one channel, in which a codec (GO
DEC) 8 is provided.

The above C0DEC 8 converts (decodes) the low bit rate encoded audio signal from the high-speed digital line 1 into a 64 kb DsP CM audio signal and supplies it to the digital exchange 3b, and also supplies the 64 kb DsP CM audio signal from the digital exchange 1113b.
tlsP Converts (encodes) the CM audio signal into a low bit rate encoded audio signal and outputs it to the high-speed digital line 1.

Note that the private branch exchange (PBX) may be an analog switch, in which case an A/D is installed between the C0DEC and the demultiplexer.
- A D/A converter is provided.

[Problem that the invention seeks to solve]

When the above low bit rate audio encoding method is introduced and multi-link connections are made, private branch exchange (PBX)
for 64 kbpsP CM audio signal, or 64 kbps for
Since it is necessary to transmit the analog audio signal obtained by D/A converting the kbpsP CM audio signal, a C0DEC8 is required in the demultiplexing bag @2C, and it is necessary to convert the low bit rate encoded audio signal and 64kbpsPc
Even if digital exchange t1m3b is used, there is a problem in that the audio quality deteriorates because encoding and decoding are repeated with the M audio signal. This tendency of voice quality deterioration becomes more pronounced as the PIP1 rate becomes lower, such as from 16 kbps to 8 kbps.

For this reason, low bit rate audio encoding systems such as 16 kbps and 8 kbps have a limit on the number of links or can only be used with one link.

The present invention was created in view of the above points, and an object of the present invention is to provide a relay exchange system that can perform relay exchange with little deterioration in quality even when low bit rate encoded signals are connected in multiple links.

[Means for solving problems]

FIG. 1 does not show a block diagram of the principle of the present invention. In the same figure, 11
is a terminal exchange that converts analog signals from a plurality of terminals 12-1 to 12-n or pulse code modulation (
PCM) of N bits per time slot obtained by
Outputs a CM signal.

Replace the terminal of the multiple valve 1ift device 13! analog from fi11 (no. 3 or PCM signal per time slot)
An encoding/decoding unit (CODEC) that encodes into a low bit rate encoded signal (where M<N) and decodes it into the analog signal or PCM signal when the low bit rate encoded signal is input. It has 14. The relay exchange 15 is provided between the demultiplexer 13 and the terminal exchange 11.

The demultiplexer 13 is a high-speed digital line 16-1.16
-2, the low bit rate encoded signal is sent to A low bit rate encoded signal with the remaining (N-M) bits left blank is output to the relay exchange 15 as a digital signal.

[Effect]

When relay switching is performed between a plurality of high-speed digital lines 16-1 and 16-2 using a digital exchange consisting of a terminal exchange 11 and a relay exchange 15, the high-speed digital line 16
The low bit rate encoded signal input from -1 or 16-2 is demultiplexed! ``+3, of the N bits per time slot, M bits are the input low bit rate encoded signal, and the remaining (N-M) bits are made into empty digital signals and sent to the relay exchange 1!15, Further, the signal is supplied again to the demultiplexer 13 via the relay exchange 15.

In this digital signal, when the N bits are 8 bits and the M pits are 2 bits, the signal format of one time slot is as shown in FIG. In Figure 2, b+, b2 are low bit rate PCM signals, 6
Each bit has a value of "○" and is considered empty. Therefore, the above-mentioned low-pitched to rate encoded signal has 8 bits per time slot l-, and is apparently transmitted between the demultiplexer 13 and the relay exchange 115 using the same bits as the PCM signal.

The demultiplexer 13 separates only the M-bit low bit rate encoded signal from this digital signal and sends it to the high speed digital circuit $116-2 or $16-1.

In this way, the low bit rate encoded signal is not encoded or decoded by the encoder/decoder 14 (N
-M) By adding and separating empty bits, the bits are relayed and exchanged as they are.

〔Example〕

FIG. 3 shows a block diagram of one embodiment of the invention.

In the figure, the same components as in FIG. 1 are given the same reference numerals. In FIG. 3, reference numeral 18 denotes a switch (TLS) that has both the functions of the terminal switch 11 and the relay switch 8115. In addition, in this embodiment, the encoding/decoding unit 14 in the demultiplexing device 13 converts the 64kbpsP CM audio signal and the 15kbps
Mutual conversion with a bps encoded audio signal is performed.

Further, the demultiplexer 13 sets routes for not only audio data but also various data and multiplexes them.

A line control unit 19 that performs separation and a 64 kbps P C
M data and 16 kbps encoded audio signal in 64 kb
A demultiplexing section 20 that multiplexes data on the psx30 channel and demultiplexes it, and an interface section (I
NF) 21 and general data terminal 2.
2 is externally connected.

Furthermore, the demultiplexer 13 exchanges t! via the line 23. 11
8 (connected to the interface section (INF>24).In addition to the above interface section 24, the exchange 18 also has 64 kbpsP CM data and 64ttbpsx
A demultiplexer 25 that multiplexes data into 30 channels of data and demultiplexes it, an exchanger 26 that performs exchange processing in units of 64 kbps, and an A/D/D/A converter 27-
1 to 27-n are provided.

2 Mbps between the demultiplexer 13 and the exchange 18
It is connected by the main line 23, but the logical bus is the first
It is exactly the same as the figure. An example of the frame format of this line 23 is shown in FIG. One time slot consists of 8 bits, and 32 time slots constitute one frame. Since one frame consists of 8kHz, line 2
The transmission speed of 3 is 8 bits x 32 x 8 kHz2 = 2048
(kbps).

In FIG. 4, the first time slot TSI is used for synchronization bits, signaling, etc., and the 17th time slot TS17 is not used. Also time slot TS
2 to TS16 and TS18 to TS32 are used as audio channels cH1 to CH30, and each channel has 64 channels.
The transmission bit rate is kbps (=8 bits x 8 kHz).

The above audio channels are for internal use, for between A and B stations, and for Aj
There are 60 inter-office channels, and 6 intra-office channels.
It is divided into one for 4 kbps P CM audio signal and one for 15 kbps encoded audio signal. Here, as an example, 64 kbps P C within eight genera as shown in FIG.
Channels for M audio signals are assigned to CH2-CH2, and five channels CH6 to CH10 are assigned as channels for 16 kbps encoded audio signals in the eight groups, as shown in FIG. 2(B).

In addition, the audio channels for A8B inter-offices are 10 channels CH21 to CH30 as shown in Figure 5(C), and the audio channels for A8C inter-offices are CH21 to CH30 as shown in Figure 5(D).
~CH30 each assigned to 10 Bouyanels. The data format of each audio channel shown in FIGS.
is 16 kbpsP CM audio signal data, and the remaining 6
The bit is empty and the value is always "0".

Next, the operation of the embodiment shown in FIG. 3 will be explained. First, to explain a call from A8 shown in FIG. 3 to a B station (not shown) (the B station and 0 station, which will be described later, have the same configuration as in FIG. 3), the terminal (telephone gl in this case) 12- 1-1
Analog voice signals from any terminal among 2-n are sent to A/D-D/A converters 27-1 to 27- in the exchange 18.
Analog-to-digital conversion is performed by the corresponding A/D-D/A converter of 64 kbllSP C
After being converted into an M audio signal, the exchange unit 26 converts CHI to CH.
5 audio channels (here,
- As an example, assume that it is connected to CHl).

The 64 klo+sP CM audio signal of CHl is multiplexed by the demultiplexer 25, sent to the line 23 via the interface 24, received by the interface 21, and further supplied to the demultiplexer 20, where it is demultiplexed. The 64 kbps PCM audio signal of audio channel CH1 is separated. The separated 64 kbps PcM audio signal is converted into a 15 kbps encoded audio signal (16 kbps code) by the encoding/decoding unit 14, and then converted into an audio channel C.
H6 is multiplexed by the demultiplexer 20, and further sent to the line 23 via the interface 21, and the exchange mis
reach.

Here, since one channel of the 2 Mbps line 23 is 8 bits, the demultiplexer 20 converts 2 bits of the 16 kbps encoded audio signal into bits 1 and 2 of the 16 kbps encoded audio signal. It is inserted into bit 2, and the remaining bits 3 to 8 are multiplexed as blanks (0's) to obtain an 8-bit digital signal of CH6 in the format shown in FIG. 5(B). This C)-16 digital signal is demultiplexed by the demultiplexing section 25 and supplied to the switching section 26, where it is demultiplexed by the demultiplexing section 25 and supplied to the switching section 26, where the audio channels CH11 to CH2O for the 8 stations of A station in the format shown in FIG. The signal is connected to one of the channels (temporarily assumed to be CHll), is returned to the demultiplexing section 25, is multiplexed this time, and is again sent out to the 2 M bps line 23 via the interface section 24.

The PCM audio signal of CH11 received by the interface unit 21 is demultiplexed by the demultiplexing unit 2o, in which only the necessary two bits, bit 1 and bit 2, are separated and extracted in the signal format shown in FIG. 5(C), and encoded at 16 kbps. After being made into an audio signal, it is multiplexed with other data etc. by the line control unit 19 and sent to the high-speed digital line 16-1, reaching the B station.

To summarize the signal path during a call from station A to station B, analog voice 64 kbpsP CM12
．． 27--------- Dimension H1 26--→25" Presentation 24" 1 fall 5 16" and σ→21" 1 field"> 20 20""Komi Soyo 19→16-1→B station C becomes 111.

During a call from station B to station A, the signal path is in the opposite direction of the arrows above. In addition, B station also connects A station and B via the same route.
Both station power packers are connected.

Next, a case will be described in which a relay exchange is performed at A station for a call from B station to 0 station. 1 generated by station B in the same manner as described above during the call between stations A and B.
The PCM audio signal encoded in 6kbDS is transferred to a high-speed digital circuit along with other data! The signal enters the demultiplexer 13 of station A via 16-1. Station A demultiplexer 1
3, the line control unit 19 separates and extracts the 16kbps encoded audio signal from the B station from the Haku data;
The bps encoded audio signal enters one of the audio channels CH11 to CH2O (here, it is assumed to be CH12).

The 16 kbps encoded audio signal of CH12 from the line control section 19 is demultiplexed by the demultiplexing section 20, and 6 blank bits are further added to the 2 bits of data, resulting in a total of 8 bits as shown in FIG. 5(C). After being formatted and multiplexed, the 2M
It is sent to the bps line 23 and reaches the exchange 118.

The PCM audio signal of CH12 is sent to the interface section 2.
4 to the demultiplexing section 25, where it is separated and extracted, and then sent to the exchange section 26 as the Aj4C interoffice audio channel C.
Any channel from H21 to CH30 (temporarily CH2
1), then returned to the demultiplexer 25 and multiplexed this time. The PCM audio signal of the audio channel CH21 which has been multiplexed by the demultiplexer 25 and has the signal format shown in FIG. Through the interface 21, the demultiplexer 20 separates and extracts only the necessary two bits, bit 1 and bit 2, of the signal format of the audio channel CH21 between stations A and C shown in FIG. 5(D), resulting in a 16 kbp signal.
s encoded audio signal.

This 16 kbps encoded audio signal is multiplexed with other data in the line control unit 19, and then transferred to the high-speed digital line 16.
-2 and reaches station 0.

If we summarize the signal route for relay exchange at station A during the above call from station 8 to station 0, it is as follows: 2 M bps -1-→24'' 252 Mb DS 242 Mbp8〉2319→16-2
→ Becomes station C. Further, when a call is made from station 0 to station 8, the relay exchange at station A is simply reversed in the direction of the above arrow.

In this way, during relay exchange, mutual conversion between the 16 kbps encoded audio signal and the 64 kbps P CM audio signal is not performed, and the relay exchange is performed as the 16 kbps encoded audio signal.

Therefore, when a multi-link connection is made, encoding and decoding for mutual conversion between a 16 kbps encoded audio signal and a 64 kbps P CM audio signal is performed by the encoding and decoding of the desired destination station.
The decoding unit 14 performs the decoding process only once, and the audio quality is as high as that of a one-link connection.

It should be noted that the present invention is not limited to the above-described embodiments, and the transmission bit rate may have other values, and the present invention can be similarly applied to other information signals such as image signals in addition to audio signals. Of course.

〔Effect of the invention〕

As described above, according to the present invention, low bit rate encoded signals are relayed and exchanged as they are without being encoded and decoded for mutual conversion with PCM signals, so multi-link connections are possible. However, the information quality is exactly the same as that of a one-link connection, and the quality deterioration caused by a multi-link connection can be eliminated.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of the principle of the present invention, Fig. 2 is a diagram showing an example of a signal format relayed and exchanged in the present invention, Fig. 3 is a block diagram showing an embodiment of the present invention, and Fig. 4 is a frame diagram. Figure 5 is a diagram showing an example of the format. Figure 5 is a data format diagram of each part of Figure 4. Figure 6 is a conceptual diagram of multi-link connection. Figure 7 is an example of the connection form between an exchange and a multiplex valve+m device. FIG. 8 is a diagram showing an example of a connection form between an exchange and a demultiplexer, and FIG. 9 is a diagram showing an example of a low bit rate speech encoding system. In the figure, 11 is a terminal exchange, 12-1 to 12-n are terminals, 13 is a demultiplexer, 14 is an encoding/decoding (fJ5 (CODEC)), 15 is a relay exchange, 16-1.16-2 is a High-speed digital line, 20.25
26 is a demultiplexing section and a switching section. Figure 4 (A) of 7 rays ^ 7'
CH5 (B) A No (8-drunk) F Ro I ■ Ro ■ Shoulder Ro CH
6~CH10 (C) AJt-+[3,4 (shadow to 16) times bz OOOOOOOCHll-CH20 (D) A station arc station (bps to 16, f?r) mouth xtxooooo
[Big mouth.] H2: I ~0430n≠Data for each year in the figure - Ma, So) Q;

Claims (1)

[Claims] A terminal exchange (12-1 to 12-n) that outputs analog signals from a plurality of terminals (12-1 to 12-n) or a PCM signal of N bits per time slot by pulse code modulating the analog signals.
11) and the analog signal or PCM signal from the terminal exchange (11) at M bits per time slot (however, M<N).
It has an encoding/decoding unit (14) that performs low bit rate encoding of the low bit rate encoded signal and decodes it into the analog signal or PCM signal and outputs it to the terminal exchange (11) when the low bit rate encoded signal is input. , a demultiplexer (13) that sends the low bit rate encoded signal to the high-speed digital line (16-1, 16-2), and a demultiplexer (13) and the terminal exchange (11). A relay exchange (15) and a demultiplexer (13) are provided for the high-speed digital lines (16-1, 16).
-2) as a digital signal in which M bits out of N bits per time slot are the low bit rate encoded signal and the remaining (N-M) bits are empty. Send to relay exchange (15),
The M-bit low bit rate encoded signal is separated from the digital signal passed through the relay exchange (15) and sent to the high-speed digital line (16-1, 16-2) for relay exchange. Features relay exchange method.