JPH06237214A - Mobile communication system - Google Patents

Abstract

PURPOSE:To attain a mobile communication which has a large capacity and strong against a narrow band disturbance, and also, can change a data rate. CONSTITUTION:A spread spectrum system is used for a radio communication system, and in the case plural data trains are sent out by the same carrier wave by varying a pattern of a spreading code by spreading circuits 301-305, the data train of the same spreading code pattern is subjected to time division multiplex by a burst generating circuit 100 and a parallel/serial converting circuit 200, and a communication channel is allocated to each slot. In this case, by providing in advance a stand-by time slot in the data train in order to avoid a disturbance, both of a point that the spread spectrum system is strong against a narrow band disturbance, and a point that a data rate of a time division multiplex system is variable can be made the most of, many communication channels can be secured by the number of spreading code patterns being smaller than conventional, and deterioration of a desired wave receiving level by other spreading code in the same carrier wave can be suppressed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mobile communication system in which a radio base station forming a radio area of a certain range and a plurality of terminals or mobile units within the radio area perform radio communication.

[0002]

2. Description of the Related Art In recent years, a method of performing wireless communication between a wireless base station forming a wireless area of a certain range and a plurality of terminals within this wireless area by using a digital modulation method has been studied. The department is about to be put to practical use.

For example, in a Japanese car telephone using a digital radio communication system, the digital modulation system is π /
A plurality of carriers are used using 4-shift-QPSK, and 3ch time division multiplexing (3ch,
TDM) is performed for wireless communication.

In addition to this, in Europe, a method called GSM using a digital wireless communication method is being researched and put into practical use. This is a digital modulation system with GM
Using SK, a plurality of carriers are used to perform time-division multiplexing (8ch, TDM) of 8ch for each carrier to perform wireless communication.

In Europe, a system called DECT is under study as a system for wireless data transmission and wireless voice transmission for small-zone systems. In this system, GMSK is used as a digital modulation system, and a plurality of carriers are used to allocate an uplink of about 10 channels and a downlink of the same number of channels to each carrier. Time division multiplexing / time division transmission / reception distribution (TDM / TDD) is used.

[0006] In addition, various methods of time division multiplexing have been studied as methods for wirelessly communicating voice, data, etc. with a plurality of terminals in each service area using each wireless base station as one service area. There is.

This is because time division multiplexing has an advantage over frequency division multiplexing in that the rate of data to be communicated (data rate) can be changed, that is, flexibility of the communication channel is possible to some extent, and This is because wireless communication between each terminal and the wireless base station is bursty in time, and it is possible to set a time that does not require operation.

On the other hand, the disadvantages of time division multiplexing are that if the number of time division multiplexing is increased, the transmission band required for wireless communication increases, the equivalent noise bandwidth of the receiving system increases, and reception at the same reception level increases. The quality deteriorates, the service area becomes smaller for the same transmission output, and it is strongly affected by interference from multiple other terminals in the wireless service area formed by multiple adjacent wireless base stations. It will be.

In order to maintain the reception quality of each time-division communication channel, another communication channel of the same carrier wave at the same time modulated by the same method or
It has the drawback of being vulnerable to interference from other narrowband systems.
In order to maintain the reception quality of at least the desired communication channel, the reception level of the desired wave must be about 10 dB or more with respect to the reception level of the interfering wave.

On the other hand, a method called code division multiplexing (CDMA) is also under study. This is to spread the information bits to be communicated by a spread code pattern consisting of several tens to several thousands bits and multiplex them in the same carrier wave, and the number of spread codes can be accommodated.

The advantages of code division multiplexing are that it is resistant to narrow band interference and that multiple communication channels can be accommodated in the same carrier.

[0012]

However, the conventional configuration has flexibility of a communication channel capable of communicating data having different data rates, is resistant to narrow band interference, and is within the same frequency carrier. It was not possible to satisfy at the same time to accommodate a large number of users.

Further, in the case of the spread spectrum method in which the code is spread, the reception level of the desired communication channel spread by one spread code is different by another code and the received level of a plurality of spread spectrum signals of the same frequency. When the level is extremely lower than the signal level, there is a problem that the reception quality of the desired communication channel deteriorates.

In view of the above problems, the present invention can increase the number of communication channels, and can change the data rate of the communication channels by changing the number of timeslots used for the mobile device, and the same number of channels. Therefore, the number of spreading code patterns is smaller than that of the conventional method, and it is an object of the present invention to prevent deterioration of the reception level of a desired wave due to other spreading code patterns in the same carrier.

[0015]

In order to solve the above problems, the present invention provides a time slot burst generation circuit for generating burst data from data information and burst data sent from the time slot burst generation circuit. A parallel / serial conversion circuit that performs parallel / serial conversion as a time slot for each spread code pattern, a spread circuit that spreads the output of the parallel / serial conversion circuit using different spreading codes, and a local signal is used. In addition, a mixer that makes the data sequences spectrum-spread by the spreader circuit have the same carrier band frequency and an adder that synthesizes the respective carrier waves from the mixer are provided.

[0016]

According to the above-mentioned structure of the present invention, the same spread code pattern is used by the spread spectrum, and the spread spectrum data string includes several time-division multiplexed communication channels. Is the product of the number of code patterns (M) of the spread code pattern and the number of time division multiplexing (N) (that is, M ×).
N). Further, by including several time-division multiplexed communication channels in each spreading code pattern, the data rate of the communication channel can be changed by using one or more time-division multiplexed time slots. It is also possible to deal with the case.

[0017]

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

FIG. 1 is a block diagram of a main part (transmission side) of a mobile communication system according to an embodiment of the present invention. In this embodiment, there are five types of spreading code patterns for one carrier, and the time division multiplexing number is 5 including one spare time division multiplexing slot.

In FIG. 1, a time slot burst generation circuit 100 generates burst data. 20
Reference numeral 0 is a parallel / serial conversion circuit that converts burst data into time slots T1, ..., T4 for each spreading code pattern.
As parallel / serial (P / S) conversion. Thirty
1, ..., 305 are spreading circuits for spreading codes C1 ,. 401, ..., 405 are up-mixers,
Using the local signal from the local signal source 600, the data string spread by each spreading code is raised to the same carrier band frequency. Reference numeral 500 is an adder for synthesizing respective carriers, 700 is a reception status monitoring circuit for monitoring the reception status of each slot, and 800 is a time slot control unit for controlling which spreading code pattern time slot to allocate burst data to. is there.

In the above structure, first, the time slot control section 800 determines allocation of burst data and time slots for each spreading code pattern based on information such as the number of input data and respective data rates, and time slot burst. Generation circuit 100, P / S conversion circuit 20
Send control information to 0.

Then, the burst generation circuit 100 generates arbitrary burst data corresponding to the time slot in the system from each of the plurality of transmission data strings D1 ... Dk, and outputs the burst data as P /
It is sent to the S conversion circuit 200. At this time, the number of bursts to be generated can be arbitrarily changed according to the data rate based on the information from the time slot control unit 800. In this embodiment, a maximum of 20 burst data can be generated at the same time.

Next, in the P / S conversion circuit 200, the burst data is similarly spread based on the information from the time slot control section 800 to the time slot T1 for each spreading code pattern.
... Stored in T4, converted to P / S, and spread circuit 30 respectively
1, ..., Send to 305. Then, the diffusion circuits 301, ...
In 05, each spreading code C1, ..., C5 spreads,
After being raised to the carrier wave band by the up mixers 401, ..., 405, the adder 500 outputs all signals together.

The reception status monitor circuit 700 monitors the level and error rate of the received signal and sends the information to the time slot controller 800. Time slot control unit 8
In 00, the reception status information is monitored, and when the reception status of any slot is deteriorated, the P / S conversion circuit 200 is controlled so as to shift to the spare slot T5.

FIG. 2 is a diagram showing allocation of communication channels. , C5 indicate different spreading code patterns, and T1, ..., T5 indicate time-division multiplexed time slot numbers. # 1, # 2 in the figure,
... # 20 indicates a communication channel, for example, each communication channel of a plurality of mobile devices within a certain range and a wireless base station within the range.

In FIG. 2, the communication channel of # 1 is
The spreading circuit 301 is assigned to the time slot number T1 of the time-division multiplexed data string including # 2, # 3, # 3, and # 4.
, The spectrum is spread by the spread code pattern C1.

Similarly, # 5, # 6, # 7, and # 8 are assigned to time-division-multiplexed time slot numbers T1, T2, T3, and T4, and the spreading circuit 302 spreads the spectrum with the spreading code pattern C2. Diffused.

In FIG. 2, time slot number T5 is a time slot for avoiding interference, and in the communication channel allocation example of the present embodiment, communication channel # 3 is also allocated to time slot number T5 in order to avoid interference. ing.

FIG. 3 is a diagram for explaining in more detail an example of communication channel allocation. FIG. 3A shows, for example, time-division-multiplexed transmission communication channels from a wireless base station to a plurality of mobile devices, which are # 1, # 2, ... # 7.
Are communication channel data for mobile units 1, 2, ... 7 respectively.

FIG. 3 (b) shows a state of time division multiplexing in the radio lines for the spreading code patterns C1 and C2 based on FIG. 3 (a). 1, # 2, # 3, and # 4 are time-division multiplexed time slot numbers T1, T2, T3, and 5, 6, 7, and 8, respectively.
Assigned to T4. After that, 10, 11, 12
Communication channels # 1, # 2, and # 3 are assigned to the time slot numbers T1, T2, and T3 indicated by. Similarly, the communication channels # 5, # 6, # 7, # 8 are assigned to the time slot numbers T1, T2, T3, T4 indicated by 5, 6, 7, and 8.
In the figure, the time slot number T5 indicated by 9 is the interference avoiding time slot described above, and normally does not emit radio waves.

The data strings 1 and 2 created as described above are spectrum-spread with spreading code patterns C1 and C2 as shown by 3 and 4 in FIG. 3 (c).

FIG. 4 shows a case where two mobile stations in the same area wirelessly communicate data to the base station using the same spreading code pattern C4.

In FIG. 4A, the data string 20 of the communication channel data # 1 of the mobile station MS1 and the data string 21 of the communication channel data # 2 of the mobile station MS2 are burst data # 11, # for time division multiplexing. 12, # 13 and # 21, # 22, # 23
Shows the configuration of each. In FIG. 4B, the data # 11, # 12, # 13 of MS1 divided into bursts are spread spectrum as shown by 22, 23, 24 using the spreading code C4 and transmitted to the base station. A data series 28 is shown. Similarly, 29 is M divided into bursts
The data # 21, # 22, and # 23 of S2 are a wireless data sequence transmitted to the base station which has been spread spectrum in burst using the same spreading code C4 as that of the mobile station MS1.

FIG. 4 (c) is a diagram showing the reception status of the modulated wave which is spread spectrum spread from each mobile station at the base station. In the reception time slots indicated by 30, 32, 34, Radio data from the device MS1 is 31, 33, 3
In the reception time slot indicated by 5, wireless data from the mobile device MS2 is received.

With the above configuration, it is possible to accommodate the maximum number of communication channels for the same spreading code pattern and the number of time-division multiplex, and to use each communication channel with time. Since division and multiplexing are used, it becomes possible to construct a communication channel having a higher data rate between a specific mobile station and a base station by using a plurality of time slots.

FIG. 5 shows a case where the number of spreading code patterns according to one embodiment of the present invention is two and the number of time division multiplexes is five including one time slot for avoiding interference. 2 schematically shows a reception level situation of a modulated wave which is spread spectrum spread in the base station.

In FIG. 5, a spread code pattern C4 designated by 40 is used to spread spectrum spread 4
The levels of the communication channels # 1, # 2, # 3, # 4 from one mobile unit are 42, 43, 44, 45, 47, 48, 49.
It is assumed that the situation is as shown in Fig. 4, and another spreading code pattern C5 is used to spread the other 4
The reception levels of the communication channels # 5, # 6, # 7 and # 8 from one mobile unit are 50, 51, 52, 53, 55, 56,
It is assumed to be 57. In this case, when receiving at the base stations of the communication channel # 3 and the communication channel # 7 in the same reception time slot having extremely different reception levels, the reception quality of the communication channel # 3 is spread even after the spread spectrum is spread. Due to the communication channel # 7 spread by the code C5, the reception quality is extremely deteriorated. In such a case, the base station detects the reception quality, and commands the mobile station corresponding to the communication channel # 3, which has poor quality, to transmit in the time slot 5 for avoiding interference, and then the time slot. In 5, the communication channel # 3 is transmitted from the mobile device.

As a result of the above, the level of the interfering signal spectrum-spread by another spread code pattern is increased with respect to the desired communication channel spread-spread by a spread code pattern having the same carrier, which is generally a problem. When the size is extremely large, it is possible to excellently solve the problem of deterioration of reception quality.

[0038]

As described above, according to the present invention, when a spread spectrum system is used as a communication system and a plurality of data strings are transmitted with the same carrier in different spread code patterns, the data strings having the same spread code pattern are transmitted. The number of communication channels can be increased by time division multiplexing, and the data rate of the communication channels can be made variable by changing the number of timeslots used for the mobile unit.

[Brief description of drawings]

FIG. 1 is a block diagram of a transmission side block of a main part of a mobile communication system according to an embodiment of the present invention.

FIG. 2 is a conceptual diagram showing communication channel allocation in the mobile communication system.

FIG. 3 is a conceptual diagram showing a configuration of a wireless communication channel from a wireless base station to a plurality of terminals in the mobile communication system.

FIG. 4 is a conceptual diagram showing a configuration of a wireless communication channel from a terminal to a wireless base station in the mobile communication system.

FIG. 5 is a conceptual diagram schematically showing reception levels of time slots of two types of spread code patterns on the base station side in the same mobile communication system.

[Explanation of symbols]

 100 Burst generation circuit for time slot 200 Parallel / serial conversion circuit 301 to 305 Spreading circuit 401 to 405 Up mixer 500 Adder 600 Local signal generation source 700 Reception status monitoring circuit 800 Time slot control section

Claims (1)

[Claims] 1. A time slot burst generation circuit for generating burst data from data information, and parallel processing for parallel / serial conversion of burst data sent from the time slot burst generation circuit as a time slot for each spreading code pattern. / Serial conversion circuit, a spreading circuit that spreads the output of the parallel / serial conversion circuit by using different spreading codes, and the same data string spread spectrum by the spreading circuit using a local signal. A mobile communication system comprising: a mixer having the carrier band frequency of 1. and an adder that combines the carrier waves from the mixer.