JPH07297753A - Control method for frame transmission timing - Google Patents

Abstract

PURPOSE:To reduce the probability of collision of control data in the non-voice state by providing an offset to a frame transmission timing to each station so as to deviate transmission timing of control data. CONSTITUTION:Voice data are given to a voice-sound discrimination section 103-1 to discriminate voiced sound 7 non-voice and the result is given to a frame generating section 104-1 and a transmission power control section 107-1. The generating section 104-1 generates a frame in the timing of a frame timing generating section 101. When an output of the discrimination section 103-1 indicates voiced sound, voice and control data are processed into a frame and modulated by a spread modulation section 106-1. Each channel signal to be modulated is decided for the transmission at a control section 107-1 based on the presence of a voice signal. That is, in the case of the voiced signal, control and voice data are sent and in the case of non-voice signal, control data are sent. A signal synthesizer section 108 adds signals of all channels and the added signal is sent. Then a voice data transmission traffic channel, a call signal paging channel and a frame synchronization synchronizing signal are subject to spread spectrum processing and modulated by the same frequency and the resulting signal is sent to each mobile station.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to code division multiple access (C
DMA) communication, especially personal communication system (PCS)
Is used for synchronous CDMA communication in mobile communication as described above, and the transmission power is variable depending on the presence / absence of voice when transmitting voice-encoded data at the timing of a frame to be transmitted to each mobile station. Therefore, the interference between control data that need to be transmitted even when there is no sound is reduced, and the number of users who can transmit at the same time is increased.

[0002]

2. Description of the Related Art A configuration in which transmission power is variable depending on the presence / absence of voice is disclosed in, for example, the following document. Reference: "Mobile Station-Base Station Compatibility
Standard for Dual-Mode Wideband Spread Spectrum C
ellular System ", IS-95. pp. 6-7 to 6-28. In CDMA modulation, all transmission stations communicate using the same frequency, so the transmission signal of one station is transmitted to another station. Since it becomes an interference signal, if the number of transmitting stations exceeds a certain number, an error occurs during decoding and communication becomes impossible. It distinguishes between voiced / non-voiced, and when there is no voice, the coding rate is lowered,
By reducing the amount of transmission data, it is possible to reduce the number of stations transmitting at the same time and reduce the amount of interference. In the above-mentioned document, the number of users who can use the same frequency is increased by varying the average transmission power in the asynchronous CDMA depending on the presence or absence of voice and reducing the apparent average interference amount. This is realized by reducing the probability that the transmission signals of the stations collide by utilizing the fact that the transmission timings of the transmitting stations are random.

[0003]

However, in order to perform communication, it is necessary to send control data in addition to the data in which voice is encoded, and it is necessary to send this control data even when the voice is silent. Asynchronous CDM such as reverse link of PCS (uplink: transmission from mobile station to base station)
In A, the transmission timing differs for each station, and the radio propagation delay time differs depending on the position of the mobile station. Therefore, the control data of each station arrives at a random time at the time of reception, which has the effect of reducing the amount of interference. In synchronous CDMA such as the forward link (downlink: transmission from a base station to a mobile station), the transmission timings to each mobile station are equal, so the control data and voice data timings to each station match. Therefore, control data is always transmitted by all mobile stations at the same time, and the effect of reducing interference with control data cannot be expected.

[0004]

According to the present invention, when transmitting from a base station, the transmission timing of control data is shifted for each station by providing an offset in the frame transmission timing for each station, and when the voice is silent. The probability that control data collide with each other is reduced, and the amount of interference with control data is reduced.

[0005]

According to the present invention, the control data transmitted from each station regardless of the presence or absence of voice is realized by shifting the frame transmission timing for each transmission station. In a PCS downlink using CDMA modulation, a synchronization signal is used to synchronize a base station and a mobile station. Conventionally, transmission is performed in perfect synchronization with this synchronization signal, but in the present invention, an offset is provided in the frame of each traffic channel. Since the amount of this offset is determined by the transmitting side, that is, the base station, it is necessary for the base station to notify the mobile station at the start of communication. In the PCS system, there is a common channel used for calling a mobile station and the like, which is called a paging channel. Although the mobile station is instructed to start communication by this channel, in the present invention, the mobile station is instructed of the channel number and the offset amount of the channel using the paging channel. Since communication can be performed with different offsets depending on the channel, the control data timing varies from station to station, and when the transmission power is controlled depending on the presence or absence of voice, it is possible to reduce the amount of control data interference.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a code division multiple access (CDMA) modulation system will be described. FIG. 1 shows the configuration of the transmission side (base station) that implements the present invention. Reference numeral 101 is a frame timing generation unit, 102-1 and 102-2 are voice encoding units, 103-1 and 103-2 are voice determination units, and 104-
1, 104-2, 104-3 are frame generation units, 105
Is a fixed data generator for synchronization signals, 106-1 and 106-
2, 106-3 and 106-4 are spread modulators, 107-
1, 107-2 are transmission power control units, and 108 is a signal combining unit. The input voice data is processed by the voice encoding unit 102.
It is encoded by −1 and input to the frame generation unit 104-1. The voice data is also input to the sound presence determination unit 103-1 and determines whether there is sound or silence. The determination result is input to the frame generation unit 104-1 and the transmission power control unit 107-1. In the frame generator, the frame timing generator 1
A frame is generated according to the frame timing from 01. If the output from the voice determination unit 103-1 is voice, the voice data and the control data are framed and spread-modulated by the spread modulator 106-1. The spread-modulated signal of each channel has a transmission power control unit 107 depending on the presence or absence of voice.
-1 determines whether to transmit. That is, when there is sound, control data and voice data are transmitted, and when there is no sound, only control data is transmitted. The presence / absence of voice is determined by the voice determination unit 103-1. Signal synthesizer 108
Then, all channels are added and transmitted.

On the transmitting side, a traffic channel for transmitting voice data to each mobile station, a paging channel for transmitting a calling signal, etc., and a synchronization signal for frame synchronization are spread spectrum using a spreading code unique to each channel. Then, the signals of all channels are modulated at the same frequency and transmitted. Since voice data is not included in the paging channel, constant information is always transmitted. Therefore, the frame offset according to the present invention is not applied, and the frame is transmitted in synchronization with the synchronization signal without an offset. Since the traffic channel transmits voice-encoded data, the frame offset is determined for each channel. The frame timing generation unit 101 determines the frame transmission timing of each traffic channel. The frame transmission timing is generated for each channel based on the synchronization signal. FIG. 2 shows an example of the timing of the synchronization signal and the traffic channel. 201 and 202 are synchronization signals, 203-1, 203-2, 203-3, and 203.
-4, 205-1, 205-2, 205-3, 205-
4, 207-1, 207-2, 207-3, 207-4
Is transmission of control data, 204-1, 204-2, 204
-3, 204-4, 206-1, 206-2, 208-
4, 210-2 is transmission of voice data, 206-3, 2
06-4, 208-1, 208-2, 208-3, 21
0-1 and 210-2 indicate a state in which no sound is transmitted because there is no sound. In this example, the frame transmission timing is controlled in units of 1/8 of the synchronization signal. The frame offset of the traffic channel notifies the frame offset together with the channel number from the transmitting side to the receiving side when allocating the traffic channel to the mobile station. A paging channel is used for this. After notifying the receiving side of the traffic channel and frame offset, the transmitting station transmits voice data using the traffic channel. When there is sound, control data and voice data are transmitted on the traffic channel, and when there is no sound, only control data is transmitted. Whether the voice is present or the voice is not present is notified to the receiving side using the control data.

The operation on the receiving side will be described. The receiving side first captures the synchronization signal. Since the synchronization signal is a signal that is always transmitted while the base station is operating, the mobile station first captures the synchronization signal after turning on the power. After capturing the synchronization signal, the mobile station demodulates the paging channel. Since the paging channel has the same cycle as the sync signal and is transmitted at the same timing as the start time of the sync signal, the mobile station performs demodulation at the frame timing synchronized with the sync signal. Since the mobile station that should receive the paging channel is determined for each frame, only the information addressed to itself is taken out. When the call signal addressed to the own station is detected, the channel number and frame offset to be moved are extracted and the channel is moved to the corresponding channel. The presence or absence of voice is detected from the control data in the traffic channel, and if voice is present, the voice signal is also demodulated and output.

[0009]

As described above in detail, by using the present invention, it is possible to reduce the interference by changing the transmission power depending on the presence / absence of voice in the synchronous CDMA, and control to transmit regardless of the presence / absence of voice. Prevents control data from interfering with each other even if data are mixed,
Interference with control data can also be reduced. 1
By reducing the average amount of interference that one station gives to another station, the number of users that can be used in the same frequency band can be increased, and the frequency can be effectively used.

[Brief description of drawings]

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

FIG. 2 is a diagram showing an example of frame transmission timing in an embodiment of the present invention.

[Explanation of symbols]

101 Frame Timing Generation Units 102-1, 102-2 Speech Encoding Units 103-1, 103-2 Voice Determination Units 104-1 to 104-3 Frame Generation Unit 105 Sync Data Fixed Data Generation Units 106-1 to 106 -4 Spreading modulator 107-1, 107-2 Transmission power controller 108 A signal combiner.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI Technical display location H04B 7/26 109 N (72) Inventor Takuro Sato 1-7-12 Toranomon, Minato-ku, Tokyo Oki Electric Industry Co., Ltd.

Claims (1)

[Claims] 1. A means for transmitting intermittently generated data and continuously generated data as one frame by one channel, a means for determining a transmission timing of the frame, and a means for spread-modulating the frame. A means for generating a periodic synchronizing signal; a means for spreading and modulating a paging channel; a means for synthesizing and transmitting the spreading-modulated frame, the synchronization signal, and the spreading-modulated paging channel signal; And a means for determining the timing, wherein the transmission timing is variable for each channel, and the relative time with respect to the synchronization signal is determined.