JPH11298420A - Signal transmission system in wll system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the signal transmission system in a WLL system where an optimum transmission rate is selected in accordance with a kind of a signal of a channel and the channel with a high efficiency and high quality is set up without giving any effect on a conventional communication protocol. SOLUTION: Transmission sections 102, 202 distinguish and discriminate a FAX signal and a MODEM signal or the like from a voice signal by monitoring a signal on a communication channel after the communication channel is reserved, decide whether or not ADPCM voice CODECs 101, 201 are set 'through' based on the discrimination result, and MODEM sections 103, 203 send the other signals than the voice signal by applying multi-value processing to the modulation. In order to avoid deterioration in the reception sensitivity by multi-value processing, multi-value processing is applied only to required part of the signals and the result is transmitted to minimize the deterioration in the reception sensitivity.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a signal transmission system in a WLL system for realizing a wired telephone network with a semi-fixed wireless network, and more particularly, to whether an analog subscriber line signal is a communication signal such as a FAX signal or a modem, or It is determined whether the signal is a voice signal, and if the signal is a fax signal or a communication signal of a modem or the like, high-quality fax transmission or modem communication is made possible by minimizing signal deterioration due to voice coding.

[0002]

2. Description of the Related Art FIG. 2 shows a conventional configuration example. WL
In order to efficiently assign a communication channel, the L system converts digital data A / D-converted by a 64 KBPS voice codec specified by general ITU-T Recommendation G711 as a voice codec based on G721 or G726. Generally, information is compressed to 32 KBPS (hereinafter abbreviated as ADPCM) and transmitted. In order to make the system more efficient, a codec having a higher information compression rate than the ADPCM method may be used, and a transmission rate of 8 KBPS or less may be realized.

Since the ADPCM system has a relatively low information compression rate, a speech quality equivalent to that of a 64 KBPS codec can be obtained from a speech signal in terms of audibility. In addition, even if the ADPCM is vulnerable to bit errors, the WLL system designed to be used in a semi-fixed network has relatively few errors in the wireless section, and provides an efficient communication system with high call quality for voice calls only. did it.

The base station equipment 300 performs conversion between 64K and 32K in the ADPCM unit, and converts the digitized audio signal into a desired transmission format such as adding a frame synchronization signal in order to wirelessly transmit the digitized audio signal. And the modem 107
Is converted into a baseband signal to be transmitted by the radio unit. In the radio section 104, the obtained baseband signal is modulated by the radio section 104, frequency-converted and amplified as a radio signal, and transmitted as radio waves to the terminal equipment 400. This system is a two-way system, and the operation of demodulating a radio signal coming from the terminal equipment 400, extracting only the audio data portion in the transmission unit 106, and returning the signal compressed by ADPCM to a 64 KBPS signal is also performed at the same time. .

The terminal equipment 400 is, like the base station equipment, an interface with the radio section 204, the modulation / demodulation section 207, the transmission section 206, the ADPCM section 201, and the telephone subscriber, that is, recommendation G71.
It comprises a 1 / D / D / A conversion unit, a ringer circuit, a DC voltage supply unit, a subscriber I / F unit 205 having a hybrid circuit, etc. The I / F unit 205 has a 2-wire telephone or F
AX can be connected.

FIG. 3 shows an example of a transmission format in a wireless section between base station equipment and terminal equipment when transmitting data in the TDMA system. For details, refer to PHS (Personal Handy p.
honeSystem) RCR STD-28.

The meanings of the abbreviations of the signal format of the slot in FIG. 3 will be described with reference to Table 1 below. This is an example of the traffic channel (Tch), and the control channel has another signal format.

[0008]

[Table 1]

In RCR STD-28, transmission in a radio section uses 4-phase phase modulation called π / 4 shift DQPSK, and two bits of a data sequence are assigned to four phase changes as one symbol and transmitted. FIG. 4 shows the phase assignment.

[0010]

However, in the above-mentioned conventional WLL system, the speech quality is comparable to that of voice communication, but if the available speech path bandwidth such as facsimile is to be used as wide as possible, the quantization must be reduced. The noise may affect the transmission path, and the transmission rate may decrease, or the transmission signal may cause erroneous image data to be disturbed. Particularly, in the WLL system, communication between terminal equipments always requires two links of the ADPCM, and is more susceptible to quantization noise.

When a radio section is transmitted by the TDMA method, there is a method of increasing the transmission rate by using a plurality of slots at the time of facsimile transmission. However, it is determined whether or not a signal to be transmitted is a facsimile signal. Only after a communication channel has been assigned can it be known. Therefore, it is extremely difficult in protocol to additionally secure a plurality of slots after a communication channel is allocated. It also involves significant changes to conventional protocols. In particular, when the interface with the public network is analog in the WLL system, the FA is set before the communication path is assigned.
It is impossible to know whether it is X or voice.

Similarly, when a plurality of slots are assigned, a channel switching protocol for avoiding interference becomes complicated.

[0013] A method in which the FAX modem itself is inserted into the terminal and the base station equipment and the ADPCM conversion is not performed in the case of FAX is conceivable. However, the addition of the FAX modem increases the cost.

Although there is a method of improving the algorithm of ADPCM and reducing the quantization noise, the S / N when a signal always exists at a constant level, such as a facsimile, is different from an audio signal having a silent section. It cannot be improved beyond the number of quantization bits. 8K for 32KBPS ADPCM
4 bits (S / N 24dB) with Hz sampling, 6.4K
5 bits at 30 Hz sampling (S / N 30dB), 5.33K
If the number of quantization bits is increased to 6 bits in Hz sampling, the transmission band is impaired.

As a method for improving the transmission rate in a wireless section, a QAM method or the like is conceivable, but linearity is required for the wireless section, which leads to an increase in cost.

The present invention solves such a problem, and performs modem communication such as facsimile with high quality without changing the conventionally used radio unit, air protocol, and voice codec. It is an object of the present invention to provide an excellent signal transmission method in a WLL system capable of performing the above.

[0017]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention distinguishes between a fax signal, a modem signal and the like and a voice signal by monitoring a signal on the communication path after the communication path is secured. , Determine whether to make the ADPCM audio codec through based on the determination result.
The modulation is multi-valued and transmitted. Also, in order to avoid the deterioration of the receiving sensitivity due to the multi-valued conversion, only the necessary parts are multi-valued and transmitted so that the deterioration of the receiving sensitivity is suppressed as much as possible.

Therefore, according to the present invention, an optimum transmission rate can be selected according to the kind of signal of a communication channel, and a communication channel of very high efficiency and high quality is not affected by a conventional communication protocol. This has the effect of providing a signal transmission method in a WLL system.

[0019]

FIG. 1 shows the configuration of a first embodiment of the present invention. In FIG. 1, base station equipment 100
Is a public network I / F unit 105, an ADPCM unit 101, and a transmission unit 102
, A modulation / demodulation unit 103 and a radio unit 104.

The public network I / F unit 105 is an I / F unit for connecting base station equipment to, for example, a public network or a private network, and the network side complies with the analog interface G711 recommendation.
It has a 4KBPS codec.

The transmission section 102 can determine whether or not the signal on the communication path is a voice signal, and determines whether or not to make the ADPCM section 101 through. In the case of a voice signal, a conventional transmission method is used, but in the case of non-voice communication, transmission and reception are performed as follows.

1) At the time of transmission In the case of non-voice communication, the code convention CI is changed to the non-voice signal code convention with the slot signals in FIG.
K transmission. Since all of the above are performed after the communication protocol establishes the communication channel, there is no change in the conventional communication protocol.

Immediately after the CI becomes a code rule for non-voice communication, the modulation / demodulation section 103 converts the baseband signal into a 4-bit, 1-symbol Tch digital data sequence, which was a 2-bit, 1-symbol, as shown in FIG. To generate a 16-phase signal. The phase assignment in FIG. 5 is an example, and there is no particular need to stick to the Gray code assignment.

FIG. 6 shows a state of signal transmission when the transmission rate is changed halfway. As shown in FIG. 6, only the transmission rate of the signal of Tch is changed. Since the modulation / demodulation unit 103 has a built-in Nyquist filter, even if the value is suddenly multi-valued, the symbol rate is unchanged, so that there is no intersymbol interference of the previous code.

The signal converted into a modulation baseband signal by the modulation / demodulation section 103 is transmitted as a radio signal via the radio section 104. Also in this case, the Nyquist filter band for band limiting the baseband signal is invariable,
The wireless band does not spread, and there is no effect on adjacent channels due to a sudden change in the transmission rate. It should be noted that the CRC code is assigned including the target Tch.

2) At the time of reception At the time of reception, the CI obtained from the data reproduced by the modulation / demodulation section 103 is constantly monitored. If the CI is determined to be non-voice data, the received data determination level is immediately increased to 16 levels. To the determination level of the phase modulation signal. It is to be noted that the determination change start time is accurately determined in symbol units with the UW as the starting point of the detection point. When the data of Tch is completed, the CRC unit needs to return to the original judgment criteria again.
Also in this determination, the determination change time is calculated for each symbol starting from UW.

The reception sensitivity is degraded due to the multi-valued modulation. However, the sensitivity degradation when the 16-phase modulation is changed from the 4-phase modulation is
It becomes about 9 dB. However, since the WLL system is a semi-fixed network and receives signals at a relatively high reception electric field strength, the effect of sensitivity degradation can be reduced. The effect of fading is that only the transmission rate is changed in Tch. Therefore, demodulation of other parts can be performed by the method before the change of the transmission rate, and correction can be made to reduce the influence.

When the CI is non-voice, the transmission unit 102
The reproduced signal is passed to the network I / F unit 105 by passing through 101. Note that the transmission rate may be different since the uplink and the downlink operate independently.

Since the base station equipment generally needs to process a plurality of terminal equipment at a time, these controls need to be performed independently for each communication path, but the radio section 104 shares the baseband signal. The same one can be used because it can be converted.

The operation of the terminal equipment 200 is almost the same as that of the base station equipment. The processing corresponding to the public network I / F unit 105 is performed by the subscriber I / F unit 205 in the base station equipment. Subscriber I /
The F unit 205 also includes a Ringer circuit for ringing the telephone, a power supply circuit for the subscriber line, a Hybrid circuit for converting 2Wire to 4Wire, a circuit for monitoring OFF HOOK of the telephone,
It comprises a dial or a PB signal detection circuit.

[0031]

The present invention has the following effects, as apparent from the description of the above embodiment.

1. An optimum transmission rate can be selected according to the type of communication without changing the conventional communication protocol, and an efficient communication path can be provided.

2. When the transmission rate is increased, the transmission rate is increased by multi-leveling, so that the baseband bandwidth is not widened, and the conventional radio unit can be used as it is. Also, there is no interference with adjacent channels.

3. Since the transmission rate is changed only in the Tch portion, the deterioration of the receiving sensitivity due to the multi-level transmission and the deterioration of the anti-fading characteristic can be reduced by demodulating the portions other than the Tch.

4. The transmission rate is switched in synchronization with the frame according to the code convention CI, and the audio signal is
Since the encoding is performed according to the 711 recommendation, the audio signal is not interrupted when the transmission rate is switched. Therefore, seamless switching can be realized.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration according to an embodiment of the present invention;

FIG. 2 is a diagram showing a conventional configuration;

FIG. 3 is a diagram showing a transmission format in a wireless section;

FIG. 4 is a diagram showing a conventional phase assignment;

FIG. 5 is a diagram showing phase assignment in the present invention;

FIG. 6 is a diagram illustrating a state of transmission after a transmission rate is changed.

[Explanation of symbols]

 100, 300 Base station equipment 101, 201 ADPCM section 102, 106 Base station equipment transmission section 103, 107 Base station equipment modulation / demodulation section 104 Base station equipment radio section 105 Public network I / F section 200, 400 Terminal equipment 202, 206 Terminal equipment Transmission unit 203, 207 Terminal equipment modulation / demodulation unit 204 Radio unit 205 Subscriber I / F unit

Claims (5)

[Claims] 1. A facsimile signal, a modem signal or the like and a voice signal are discriminated and determined by monitoring a signal on the communication path after a communication path is secured, and whether or not the ADPCM voice codec is to be through based on the determination result is determined. Is determined, and when it is other than an audio signal, the modulation is multi-valued and transmitted.
Signal transmission method in L system. 2. The method according to claim 1, wherein, when the modulation is multi-valued and transmitted, only a necessary part is multi-valued and transmitted, so that the deterioration of the receiving sensitivity due to the multi-value is minimized. Signal transmission method in WLL system. 3. When a code other than a voice signal is used, the code protocol CI is changed to a non-voice signal code protocol, and as soon as the code CI becomes a non-voice communication code protocol, the number of bits per symbol for the digital data string of Tch is determined. 2. A signal transmission system in a WLL system according to claim 1, wherein the phase modulation is performed at twice that of the previous one, and the transmission rate of Tch is doubled. 4. A public network I / F unit, an ADPCM unit, a transmission unit, a modulation / demodulation unit, and a radio unit, wherein the transmission unit transmits and receives a fax signal, a modem signal, and the like and a voice signal. Means for discriminating by monitoring the signal of the communication path after being secured, and means for determining whether or not to make the ADPCM unit through based on the result of the determination. A base station apparatus comprising: means for converting a modulation into a multi-valued signal when transmitting. 5. A subscriber I / F unit, an ADPCM unit, a transmission unit, a modulation / demodulation unit, and a radio unit. The transmission unit transmits and receives a fax signal, a modem signal, and the like and a voice signal. Means for discriminating by monitoring the signal of the communication path after being secured, and means for determining whether or not to make the ADPCM unit through based on the result of the determination. A terminal device comprising a unit for converting a modulation into a multi-valued signal when transmitting.