JPH04368025A - Base station equipment of digital mobile communication system - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention enables efficient channel use without channel division loss in a TDMA mobile communication system, even when mobile devices with a plurality of voice coding rates coexist. The present invention relates to a base station device in a digital mobile communication system.

[0002] In this specification, a speech code decoding circuit (C
(ODEC) is used to refer to a device that encodes or decodes a digital audio signal into a low bit rate code.

0003

BACKGROUND OF THE INVENTION Conventionally, analog modulation methods have been mainly used in mobile communication systems, but with the recent increase in demand for digital transmission and ISDN communication methods,
In mobile communications as well, there are plans to introduce digital mobile communication systems that use digital modulation systems.

[0004] In the digital mobile communication system, from the viewpoint of effective use of frequencies, the 64
It is planned to use a high-efficiency speech code/decoder (CODEC) with a bit rate of about 10 kb/s, which is lower than a kb/s speech code/decoder (CODEC). However, technological development in the field of high-efficiency speech code/decoding technology has made remarkable progress, and it is predicted that a speech code/decoder circuit with a coding speed of about 5 kb/s, which is half the coding speed, will be realized in a few years. In other words, at the beginning of the service, mobile devices equipped with a 10kb/s voice code/decoder circuit were used, but a few years later, mobile devices equipped with a 5kb/s voice code/decoder circuit were introduced, and from then on, mobile devices equipped with a 10kb/s voice code/decoder circuit were introduced. Mobile devices equipped with different types of voice code/decoding circuits will be used together.

[0005] At this time, the voice code decoding circuit on the base station side that communicates with the mobile device equipped with a 10 kb/s voice code decoding circuit naturally needs to be of 10 kb/s, and
The voice code decoding circuit on the base station side that communicates with a mobile device equipped with a b/s voice code decoding circuit needs to be 5 kb/s. In the conventional base station configuration, 10kb/s and 5k
It was necessary to use separate radios and frequencies for b/s. In other words, the number of wireless devices compatible with 5 kb/s voice code decoding circuits is equal to the number of mobile devices equipped with 5 kb/s voice code decoding circuits, and the number of radio devices compatible with 5 kb/s voice code decoding circuits is equivalent to the number of mobile devices equipped with 10 kb/s voice code decoding circuits. It is necessary to prepare at each base station the number of radio devices compatible with a 10 kb/s voice code/decoder circuit.

FIG. 7 is a diagram illustrating an example of the configuration of a conventional base station apparatus, in which 1 is an antenna and 2 is a common amplifier. Modulation devices (MOD) 3 to 6 are connected to this common amplification device 2, and each modulation device 3 to 6 is connected to a multiplexing device (MUX).
)7 to 10. The multiplexers 7 and 8 are connected to 5 kb/s audio code/decoder circuits 11 and 12 for six channels, respectively. Three channels of 10 kb/s audio code/decoder circuits 13 and 14 are connected to the multiplexers 9 and 10, respectively. These voice code decoding circuits 11 to 14 are connected to a mobile communication exchange 15, and this exchange 15 has a 64k
b/s fixed network is connected.

Note that in FIG. 7, in order to simplify the explanation,
Although only the transmitting system of the base station is shown, the receiving system of the base station has a similar configuration. Further, the exchange 15 is connected to a fixed telephone or the like via a fixed network transmission line.

Next, the operation of this base station device will be explained. If the mobile device to be connected is equipped with a 5 kb/s voice code decoding circuit, the exchange 15 selects one of the voice code decoding circuits shown in 11 to 12 and connects to that voice code decoding circuit. The mobile device you are trying to connect to is 10kb/
s 13 to 14 if it is equipped with a voice code decoding circuit.
Select one of the voice code decoding circuits shown in and connect to that voice code decoding circuit. Audio code decoding circuits 11 to 14
encodes a 64 kb/s PCM audio signal into a 5 kb/s or 10 kb/s audio code, and multiplexes the signal into multiplexers 7 to 1.
0 to the corresponding multiplexer. Multiplexer 7
.about.10 rearrange the time slots so that the encoded audio can be transmitted by the TDMA modulation devices 3 to 6. Figure 8 is 5k
An example of the configuration of time slots of signals transmitted by the b/s compatible modulation devices 3 to 4 is shown. Further, FIG. 9 shows an example of the configuration of time slots of signals transmitted by modulation devices 5 to 6 compatible with 10 kb/s. As can be seen from FIGS. 8 and 9, TD
The case where the MA multiplexing number is 6 at 5 kb/s and 3 at 10 kb/s is explained. 16-1 and 17-1 are 5kb/s
Similarly, time slots 16-6 and 17-6 are used to communicate with the first mobile station equipped with a 5 kb/s voice code decoding circuit, and time slots 16-6 and 17-6 are used to communicate with the sixth mobile station equipped with a 5 kb/s voice code decoding circuit. Indicates the time slot for Also, 18-
1 and 19-1 indicate time slots for communicating with the seventh mobile station equipped with a 10 kb/s voice code decoding circuit, and the same applies to 18-2 and the like below. As described above, in the conventional technology, each modulation device 3 to 6 is 5 kb/s or 10 kb/s.
It was fixedly allocated for the kb/s voice code decoding circuit.

[0009]

[Problem to be solved by the invention] As explained above,
A radio assigned for a 5 kb/s voice code decoding circuit cannot be used for a 10 kb/s voice code decoding circuit, and conversely, a radio assigned for a 10 kb/s voice code decoding circuit cannot be used. It cannot be used for a 5 kb/s speech code/decoder circuit. When radio equipment is fixedly divided into multiple groups and used, a division loss occurs as per traffic theory, and the total number of radio equipment for both groups is 5 kb/s voice code decoding circuit. The number of wireless devices is larger than that required when controlling a mobile device equipped with a 10 kb/s voice code/decoder circuit and a mobile device equipped with a 10 kb/s voice code/decoder circuit as a group, which is disadvantageous in terms of cost and effective frequency utilization. Ta.

For example, if there are 500 mobile devices equipped with a 10kb/s voice code/decoder circuit and 1000 mobile devices equipped with a 5kb/s voice code/decoder circuit, the average traffic during the busy hour for each mobile device is 0.01 erlang. and the call loss rate is 0.
03, then 10kb according to traffic theory.
10 channels are required as radio channels for the /s voice code/decoder circuit (in the case of TDMA, channels correspond to time slots), and 16 channels are required as the radio channels for the 5 kb/s voice code/decoder circuit. Since the wireless channel for the 5kb/s voice code/decoder circuit requires only 1/2 the time slots compared to the wireless channel for the 10kb/s voice code/decoder circuit, when converted to the time slot of the 10kb/s voice code/decoder circuit, , overall 10+16/2
=18 channels (time slots) are required. On the other hand, if 5kb/s and 10kb/s mobile devices are not divided into groups and use a communication channel as one group, the total traffic is converted to a 10kb/s channel, which is 500 x 0.01 + 1000 x 0.01/2=
This means that the number of channels required for this is 16. In other words, as a result of the split loss, (18-1
6)/16=12.5% of the wireless channels, in other words, an additional number of wireless devices and frequencies are required, which has the disadvantage of lowering the economic efficiency and frequency utilization efficiency of the system.

An object of the present invention is to divide a radio into a 5kb/s voice code/decoder circuit and a 10kb/s voice code/decoder circuit depending on the traffic situation. By making it possible to use the same for 10 kb/s, the above-mentioned division loss is eliminated and a digital mobile communication system excellent in terms of economy and frequency utilization efficiency is provided.

0012

[Means for Solving the Problems] The present invention provides a base station device for a digital mobile communication system that communicates with a plurality of groups of mobile stations equipped with voice code/decoder circuits having different voice encoding rates. , comprising a plurality of code/decoder circuits with different audio coding rates, a multiplexer, and a wireless device, the plurality of audio code/decoders are connected to the exchange and the multiplexer, and the multiplexer is connected to the multiplexer. The multiplexing device is connected to the wireless device via an exchange, the exchange includes means for selectively connecting an encoding/decoding circuit having the same rate as a voice encoding/decoding circuit installed in the mobile device of the communicating party, and the multiplexing device includes: The audio signal code rate obtained by removing the synchronization code or control code from the output signal of the audio code/decoding circuit is a common multiple of multiple types of audio encoding rates, and the overall code rate including the synchronization code or control code is It is characterized by comprising means for multiplexing so that the code rate is equal to the code rate handled by the exchange.

Conversely, it is also possible to demultiplex the multiplexed signals as described above using a demultiplexer instead of the multiplexer.

[0014]

[Operation] The digital exchange for mobile communications at the base station allows mobile equipment to connect calls from fixed networks or other communication parties to either be equipped with a 5 kb/s voice code decoding circuit or to be connected to a 10 kb
Select a 5kb/s audio code/decoder or a 10kb/s audio code/decoder depending on whether the /s audio code/decoder is installed and connect it to this audio code/decoder. Encode audio by rate. The multiple output signals of the audio code/decoding circuit are processed by a multiplexer so that the code rate excluding the synchronization or control code is a common multiple of the multiple audio encoding rates, and the code rate including the synchronization or control code is a common multiple of the multiple audio encoding rates. The signals are combined and multiplexed so that the code rate matches the code rate handled by the exchange. The combined and multiplexed signals are again connected to the line to the wireless device by the switch.

The signal format finally transmitted from the radio is the same regardless of whether the transmission signal is 5 kb/s audio or 10 kb/s audio. In other words, in the case of 5kb/s audio, every other time slot is used compared to the case of 10kb/s audio, but this time slot allocation is done by the multiplexer mentioned above, and the radio The rearranged signals are then transmitted by the converter.

In this way, each radio is not fixedly used for the type of voice code/decoder circuit, but can be used as a radio for a 5 kb/s voice code/decoder circuit or a 10 kb/s voice code/decoder depending on the traffic situation. It can be used as a radio for a voice code/decoding circuit, or as a radio for mixed use of 5 kb/s and 10 kb/s. Therefore, there is no division loss of radio equipment and frequencies, and efficient use is possible.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing the configuration of a base station transmission system in a digital mobile communication system according to an embodiment of the present invention. In FIG. 1, 1 is an antenna, 2 is a common amplifier, and 20 to 23 are modulators. In addition, 15 is a digital exchange for mobile communication, 24 is a transmission line to the fixed network,
25 is a 5kb/s audio code/decoder circuit, 26 is a 5kb/s audio code/decoder circuit
Multiplexing device for audio code/decoding circuit, 27 is 10 kb/s
28 represents a multiplexing device for a 10 kb/a audio code/decoder circuit. In addition, in FIG. 1, the receiving system is also the same, and is omitted to simplify the explanation.

Here, the feature of this embodiment is that the voice code/decoder circuits 25, 27 and the multiplexers 26, 28 are connected to the exchange 15 in a so-called headband shape, and two types of voice code/decoders can be used. The 5 kb/s and 10 kb/s signals encoded by the circuit at their respective code rates are removed by a multiplexing device, and the code rate is a common multiple of the two audio coding rates. , and codes for synchronization or control are combined and multiplexed so that the code rate matches the code rate handled by the exchange (64 kb/s).

The operation of this embodiment will be explained below with reference to FIGS. 2 to 6.

[0021] When a call is received from a fixed telephone to a mobile unit via the transmission path 24, the exchange 15 transmits a 5 kb/s voice code/decoder circuit if the voice code/decoding circuit installed in the mobile unit to which the call is to be made is 5 kb/s.
One of the kb/s voice code decoding circuits 25 is selected and connected, and if the voice code decoding circuit installed in the mobile device is 10 kb/s, one of the 10 kb/s voice code decoding circuits 27 is connected. Select and explain.

FIG. 2 is a format diagram illustrating a 64 kb/s signal structure. The signal handled by switch 15 is 64k.
It has a speed of b/s, and as shown in FIG. 2, it consists of signals in 8-bit units as shown in 29 to 36, each consisting of 8-bit units. This 8-bit signal 29~
The transmission time for each of the 36 is 8 bits/64kb/s =
It is 125 μs.

The 10 kb/s audio code/decoder circuit 27 compresses this 64 kb/s audio signal to a bit rate of 10 kb/s. The three channels of this 10kb/s audio signal are transmitted to the multiplexer 28 for the 10kb/s audio code/decoder circuit.
is input. The multiplexer 28 multiplexes three channels of audio signals into a 64 kb/s signal as shown in FIG. FIG. 3 shows a multiplexing device 28 for a 10kb/s voice code/decoder circuit.
FIG. 2 is a diagram illustrating a signal structure multiplexed with
indicates an audio signal encoded at 10 kb/s. In FIG. 3, #1 to #8 represent the respective bit positions of the 8 bits in the 64 kb/s signal. The first signal 29 in units of 8 bits is used as a synchronization code 37 for frame synchronization. The next unit, signal 30, is the first 3
The bits are wasted code 40 and the remaining 5 bits are the 10 kb/s encoded voice signal 49 for the first mobile station. Similarly, the first 3 bits of the signal 31 are a waste code 41, and the remaining 5 bits are a 10 kb/s encoded voice signal 50 for the second mobile station. Similarly, signal 32 is the first 3
The bits are a wasted code 42, and the remaining 5 bits are a 10 kb/s encoded voice signal 51 for the third mobile station. Although not shown in FIG. 3, signals 33, 34, 35...
are the same as the signals 29, 30, 31, . . . one cycle before. The encoded audio signals 49, 50, 51 are each 125μ
Since 5 bits are transmitted in a time of s x 4, the transmission speed is 5 bits x / (125 x 4 μs) = 10 kb/s, and an audio signal encoded with a 10 kb/s audio code/decoder circuit can be transmitted. It is.

Similarly, 5 kb/s audio code decoding circuit 25
compresses a 64 kb/s audio signal to a bit rate of 5 kb/s. Six channels of this 5 kb/s audio signal are input to a multiplexer 26 for a 5 kb/s audio code/decoder circuit. The multiplexer 26 converts audio signals for six channels into FIG.
It is multiplexed into a 64kb/s signal like this. Figure 4 is 5kb
/s is a diagram illustrating the configuration of signals multiplexed by the multiplexer 26 for the audio code/decoding circuit, and 29 to 36 are 64 kb.
/s signal in 8-bit units, 38 and 39 are synchronization codes, 4
3 to 48 are useless codes, and 53 to 57 are coded audio signals.

The first signal 29 in units of 8 bits is used as a synchronization code 38 for frame synchronization. The first 3 bits of the signal 30, which is the next unit, are waste codes 43, and the remaining 5 bits are 5 kb/s for the fourth mobile station.
This is an encoded audio signal 52. Similarly, the signal 31 is from the wasted code 44 and the 5 kb/s encoded audio signal 53 for the fifth mobile, and the signal 32 is from the wasted code 45 and the 5 kb/s encoded audio signal 54 for the sixth mobile. is from the synchronization code 39, the signal 34 is the waste code 46 and the 5 kb/s encoded voice signal 56 for the seventh mobile station.
, the signal 36 is composed of a waste code 48 and a 5 kb/s encoded voice signal 57 for the ninth mobile station, respectively. Thereafter, 5 kb/s encoded audio signals are multiplexed at this cycle.

In this way, the audio signal encoded by the 5 kb/s audio code/decoder circuit 27 and the audio signal encoded by the 10 kb/s audio code/decode circuit 25 are multiplexed, so that the audio signal following the synchronous code is multiplexed. It has a unified format of 3 unit audio signals and can be handled by the exchange 15.64
It becomes a kb/s signal. The exchange 15 connects the multiplexed signal of 64 kb/s to the transmission line corresponding to an empty one of the modulators 20 to 23. The modulators 20 to 23 modulate the encoded voice signals and transmit them to the mobile device via the common amplifier 2 and antenna 2.

As mentioned above, the signals reaching the modulators 20 to 23 have a fixed format regardless of whether they are encoded with a 5 kb/s audio code/decoder circuit or a 10 kb/s audio code/decoder circuit. are arranged. Figure 5
6 is a diagram explaining time slots of a modulated signal when transmitting a 5 kb/s encoded audio signal, and FIG.
FIG. 2 is a diagram illustrating time slots of a modulated signal when transmitting a /s encoded audio signal. 5 and 6, 58 to 66 are codes for performing frame synchronization in the radio section, 67 to 72 are 5 kb/s encoded audio signals, and 7
3 to 75 are 10 kb/s encoded audio signals.

The modulators 20 to 23 rearrange the time slots of the signals transmitted in the format shown in FIG. 3 or 4 as shown in FIG. 6 or 5, which is suitable for transmission over a radio section, and transmit the signals. Signals 67 to 72 are signals for different mobile stations, which are TDMA multiplexed and repeated in units of 6 time slots to form transmission signals for the same mobile station. Similarly, 73 to 75 are TDMA multiplexed signals for different mobile stations, which are repeated in units of three time slots to form transmission signals for the same mobile station.

For example, if the TDMA burst length is 10/3ms
, when the code required for radio section frame synchronization etc. is 20 bits per burst, 58 in FIGS. 5 and 6
~66 is 20 bits, 67~72 is 10/3ms
x 6 slots x 5 kb/s = 100 bits, 73 to 75
is 10/3 ms x 3 slots x 10 kb/s = 100 bits. At this time, the wireless section signal transmission speed is (100+
20) bits/(10/3ms)=36kb/s.

[0030] In this way, the modulated signal also has the same format regardless of the type of audio code/decoding circuit.

Although the above embodiment has been explained with reference to only the base station transmitting system, the receiving system can be established based on the same principle by simply reversing the order. Also, although we have explained the case where there is only one base station, if there are multiple base stations, antenna 1
, it may be considered that there are a plurality of sets of amplifying device 2 and modulating devices 20 to 23. In addition, it is necessary to install the voice code decoding circuits 25, 27 and the multiplexers 26, 28 in the required number based on the number of mobile devices equipped with each voice code decoding circuit, but this is necessary for each base station. Instead, it is sufficient to prepare them according to the number of mobile devices in the entire system, so even if they are allocated fixedly, there is little loss. Therefore, the number of channels (
This is because the division loss becomes smaller when the number of subscribers is large.

[0032]

[Effects of the Invention] As explained above, when a plurality of mobile devices equipped with voice code/decoder circuits with different encoding rates coexist, it is necessary to divide the radio devices and channels for each group of mobile devices. Since it can be used in common, there is no division loss of radio equipment or channels. Therefore, it is possible to realize an excellent digital mobile communication system that can improve economical efficiency and effective frequency utilization efficiency.

[Brief explanation of the drawing]

FIG. 1 is a diagram illustrating the configuration of a base station transmission system according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating a 64 kb/s signal configuration.

FIG. 3 is a diagram illustrating a signal configuration multiplexed by a multiplexing device for a 10 kb/s audio code/decoder circuit.

FIG. 4 is a diagram illustrating a signal configuration multiplexed by a multiplexing device for a 5 kb/s audio code/decoder circuit.

FIG. 5 is a diagram illustrating time slots of a modulated signal when transmitting a 5 kb/s encoded audio signal.

FIG. 6 is a diagram illustrating time slots of a modulated signal when transmitting a 10 kb/s encoded audio signal.

FIG. 7 is a diagram illustrating an example of a conventional base station configuration.

FIG. 8 is a diagram illustrating a transmission time slot configuration of a 5 kb/s transmitter.

FIG. 9 is a diagram illustrating a transmission time slot configuration of a 10 kb/s transmitter.

[Explanation of symbols]

1 Antenna 2 Common amplification devices 3 to 6 Modulation devices 7 to 10, 26, 28 Multiplexing devices 11 to 14, 25, 27 Audio code decoding circuit 15
Exchange 16, 17 Time slot 1 of 5kb/s audio signal
8, 19 Time slot 2 of 10kb/s audio signal
0 to 23 Modulation device 24 Transmission line to fixed network 29 to 36 8-bit unit of 64 kb/s signal 37
~39 Synchronization codes 40-48 Useless codes 49-58, 67-75 Encoded audio signals 58-66
Code for radio frame synchronization and control signal transmission

Claims (2)

[Claims] Claim 1. A base station device for a digital mobile communication system that communicates with a plurality of groups of mobile stations equipped with voice code/decoder circuits with different voice encoding rates, including an exchange and a plurality of voice code/decoder circuits with different voice encoding rates. a code/decoder, a multiplexer, and a wireless device, the plurality of voice code/decode circuits are connected to the exchange and the multiplexer, and the multiplexer connects to the wireless device via the exchange. The exchange is equipped with means for selectively connecting an encoding/decoding circuit having the same rate as the voice encoding/decoding circuit installed in the mobile device of the communicating party, and the multiplexing device is configured to connect the output signal of the voice encoding/decoding circuit to The audio signal code rate excluding the synchronization code or control code is a common multiple of multiple types of audio encoding rates, and the overall code rate including the synchronization code or control code is the code handled by the above exchange. 1. A base station device for a digital mobile communication system, characterized by comprising means for multiplexing so that the speeds are equal. Claim 2: In a base station device of a digital mobile communication system that communicates with a plurality of groups of mobile stations equipped with voice code/decoder circuits having different voice encoding rates, a coding/decoding circuit, a multiplexing device, and a wireless device, the plurality of voice coding/decoding circuits are connected to the switching equipment and the multiplexing device,
The multiplexing device is connected to the wireless device via the exchange, and the exchange includes means for selectively connecting a code/decoder circuit having the same rate as a voice code/decoder circuit installed in a mobile device as a communicating party; The multiplexing device has a code rate for the audio signal excluding the synchronization code or the control code that is a common multiple of the audio encoding rate of the plurality of types of the audio code/decoding circuit, and the entire code rate including the synchronization code or the control code. A base station apparatus for a digital mobile communication system, comprising means for demultiplexing multiplexed signals such that the code rate of the signal is equal to the code rate handled by the exchange.