JP2762406B1 - Direct spreading code division communication system - Google Patents

Abstract

Abstract: PROBLEM TO BE SOLVED: To reduce interference caused by soft handoff when the number of code multiplexes is increased. A base station transmits a signal to a slave station existing in its own cell. A base station transmits a signal to a slave station outside its own cell during handoff. The base station transmitting apparatus 53 has a base station transmitting apparatus 53 which determines a signal spread with a PN code having the same timing as that of another adjacent base station by an integral multiple of the reciprocal of the synchronization T of the orthogonal code. Transmit at a frequency different from the frequency. At the time of handoff, the slave station receiver 46 separates and receives the signal from the main base station transmitter and the signal from the slave base station transmitter of the adjacent base station, and combines them.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a direct sequence code division communication system used in a wireless data communication system.

[0002]

2. Description of the Related Art In recent years, a direct spread code division communication system (DS-CDMA) has attracted attention as a wireless communication system capable of realizing a large transmission capacity. As one example, a direct spread code division standardized in North America has been attracting attention. A communication type cellular telephone system (TIA IS-95) is known. Generally, in wireless communication such as mobile communication, a transmission error peculiar to wireless transmission such as fading is likely to occur. In a system using the above-described DS-CDMA, a plurality of transmission errors are required to improve reliability and increase transmission capacity. In the case where a slave station exists at the boundary of the base station, the so-called soft handoff, in which the same data is transmitted from the plurality of base stations, is used.

[0003] In general, in the case of low transmission rate communication such as voice, communication can be performed with high quality and can be used by many users simultaneously. In the case of data such as moving images, a large amount of data and a need to transmit the data in real time require high transmission speed communication.
Even when the above-described direct spread code division communication system is used, when multimedia data is transmitted, high-speed operation of the entire system is required, and further code division is performed, that is, one user uses a plurality of channels. In this way, high transmission speed communication is realized.

[0004]

However, when the soft handoff is used as described above and the system is operated at high speed and code division is performed, signal degradation due to cross-correlation occurs and high quality data communication is performed. There was a problem that it could not be done. That is, in the case of low transmission rate communication such as voice, one user uses one code, and the amount of interference can be reduced by the effect of voice activation that reduces transmission power when there is no sound. However, as described above, code division is performed to achieve a high transmission rate, and when one user uses a plurality of channels, the voice activation effect cannot be expected, so that the amount of interference increases. There is a problem. Particularly, when performing soft handoff in the case of performing code decomposition, there is a problem that interference from signals from a plurality of base stations occurs even if there is no influence of a delayed wave, thereby deteriorating signal quality.

Hereinafter, this problem will be briefly described. FIG. 9 shows a model diagram of radio wave propagation in the DS-CDMA system. In this example, it is assumed that there are a base station 1 and a base station 2, and a mobile station 3 as a mobile terminal is receiving radio waves from the base station 1. At this time, the slave station 3 receives the direct wave and the delayed wave from the base station 1 as illustrated. At the time of soft handoff, the slave station 3 also receives the same signal transmitted from the base station 2.

First, the effect of a delayed wave will be considered. As shown in the figure, the slave station 3 receives a direct wave and a delayed wave,
The reception characteristics are degraded due to the interference by the delayed waves. FIG. 10 shows a simulation model for simulating the deterioration due to the delayed wave. In this model, input high-speed data is subjected to S / P conversion (serial / parallel conversion), and different orthogonal codes are applied to the input data, and code multiplexing is performed. Here, it is assumed that a Walsh code having a code length of 64 is employed as an orthogonal code for performing code multiplexing. Therefore, the total code multiplexing number is 64. The code-multiplexed data was spread by a PN code, and after passing through a root Nyquist filter, a part of the output was delayed to be delayed from the original signal (direct wave) which was not delayed. Signal (delayed wave).

[0007] The signals corresponding to the direct wave and the delayed wave generated in this way are added with thermal noise for evaluation and input to the root Nyquist filter. The signal that has passed through the root Nyquist filter is split into two, one of which is delayed. Then, a PN code is applied so as to synchronize with the direct wave and the delayed wave.
The signals corresponding to the despread direct wave and the delayed wave are combined, and the code-multiplexed data is detected. Finally, P / S conversion (parallel / serial conversion) is performed to obtain output data. . The bit error rate (BER) is measured by comparing the input and output data at this time. In addition,
In this model, the direct wave and the delayed wave have the same power.

FIG. 11 is a diagram showing a simulation result when the simulation model shown in FIG. 10 is used, and shows a relationship between BER and Eb / No. In the figure, "without combining" indicates a case based on data demodulated from only the direct wave signal, and "with combining" indicates a case where the direct wave and the delayed wave are combined and demodulated as described above. I have. M is the number of code multiplexes,
It shows the number of code channels used by the same user. That is, m = 1 when one user is using one code channel, m = 8 is when one user is using eight code channels simultaneously, and m
= 32 indicates a case where one user is simultaneously using 32 code channels.

As shown in FIG. 11, when the code multiplex number m is 1, the BER is rapidly improved as Eb / No is improved, but the BER is not improved as the code multiplex number m is increased. It can be seen that the characteristics have deteriorated. For example, when m = 32, BER does not decrease at all even if Eb / No increases. As described above, when high-speed data transmission is performed by increasing the number of code multiplexes, interference due to a delayed wave increases.

Next, the interference at the time of soft handoff will be discussed. FIG. 12 is a diagram showing the relationship between pilot signals transmitted from each base station. Here, a base station that communicates with a slave station located in the cell of the own station is a main base station, and a base station that communicates with a slave station located outside the cell range of the own station for soft handoff is a slave base station. Shall be called. In the example shown in this figure, the base station 1 serves as a main base station and communicates with the slave station 3, and the base station 2 communicates with the slave station 3 as a slave base station. Each base station transmits a pilot signal modulated with a common PN code with a predetermined offset time (phase difference) in order to identify a cell (range of stations). As shown in the drawing, the PN code from the main base station 1 and the PN code from the base station 2 have a predetermined offset time (phase difference), and the slave station 3 has received from each base station. The cell to which it belongs is identified by the electric field strength of the pilot signal and the offset time from the reference time of the PN code.

When performing a soft handoff, the slave station 3
Signals respectively transmitted from the base stations 1 and 2 are received and combined, but cross-correlation occurs because the two data are not orthogonal. From this, soft handoff is equivalent to combining the direct wave and the delayed wave in the simulation model of FIG. When the method based on code division is adopted in order to cope with high-speed data transmission as described above, even if there is no influence of a delayed wave, the same bit error rate degradation as shown in FIG. There is a problem that occurs.

Accordingly, the present invention provides a system using a direct spreading code division multiplexing system in which the data transmission speed is increased by code division even if soft handoff is performed, even if soft handoff is performed. It is an object of the present invention to provide a direct spreading code division communication system capable of preventing data transmission and performing stable data transmission.

[0013]

In order to achieve the above object, a direct spreading code division communication system according to the present invention comprises a plurality of base stations and slave stations, each of which is a pilot station for identifying each base station. A direct spreading code division communication system adapted to transmit a signal, wherein each base station transmits data to be transmitted and the pilot signal to a first signal.
A first code multiplexing means for code-multiplexing using an orthogonal code generated by the orthogonal code generator of the above, and an output of the first code multiplexing means is a PN generated by a first PN code generator.
A main base for transmitting a signal to a slave station existing within its own cell range, comprising: first spreading means for spreading with a code; and means for transmitting the output of the first spreading means at a reference carrier frequency. A second local code transmitting apparatus multiplexes the same data to be transmitted and a pilot signal as those of the main base station transmitting apparatus of another adjacent base station using an orthogonal code generated by a second orthogonal code generator. Code multiplexing means, a second spreading means for spreading an output of the second code multiplexing means with a PN code generated by a second PN code generator, and an orthogonal code in the second orthogonal code generator. Control means for controlling the generation timing of the second PN code generator and the generation timing of the PN code in the second PN code generator. The output of the second spreading means is output from the reference carrier frequency to the frequency n / T
(T is the period of the orthogonal code, n is an integer), and a slave base station transmitting apparatus for transmitting a signal to a slave station existing outside its own cell range. A first orthogonal detector for orthogonally detecting a received signal at the reference carrier frequency, and a first unit for despreading an output of the first orthogonal detector with an orthogonal code and a PN code. Despreading means, second orthogonal detection means for orthogonally detecting a received signal at a frequency n / T away from the reference carrier frequency, and orthogonal code and PN code for the output of the second orthogonal detection means. A second despreading unit for performing despreading, and a unit for combining outputs of the first and second despreading units, wherein a signal transmitted from a main base station transmitting apparatus in the base station and the adjacent other The slave base station in the base station The signals with different carrier frequencies transmitted from the transmission device synthesizes is obtained by such a receiving apparatus for demodulating.

According to the present invention, the signals received by the slave station during soft handoff are signals from the main base station transmitter of the base station in the cell and the slave base station transmitter of the base station outside the cell. Since the slave base station transmitting device transmits a signal at a timing predicted by the timing control means, the slave station encodes the signal with the PN code having the same timing, and uses the frequency f and f ′ (= f + n / T). Since the modulated data can be received in an orthogonal state, the two can be separated and combined to reduce the effect of cross-correlation.

In another direct spread code division communication system according to the present invention, the timing control means in the slave base station transmission device adjusts the generation timing based on a control signal input from the outside. It is. Thus, the timing control means can be controlled by an external control signal. Therefore, it is possible to perform fine adjustment for making the timings of signals received from both base stations in the slave station the same, and to increase the effect of reducing the influence of cross-correlation.

According to still another direct spreading code division communication system of the present invention, the slave station is detected from a synchronization timing detected from an output of the first despreading means and an output of the second despreading means. Timing means for calculating a time difference from the synchronization timing, and the synchronization time difference output from the timing means is output to the outside as a timing control signal. Thereby, the timing time difference calculated by the slave station is output to the outside, so that the base station receiving this signal can know the timing time difference, and can know the location of the slave station from this information. Become like

In still another direct spreading code division system of the present invention, a timing control signal output from the slave station is input to the timing control means in the slave base station transmitting apparatus of the other adjacent base station. , The generation timing is controlled so that the synchronization time difference becomes zero. Thereby, since it is possible to input the timing time difference output from the slave station and adjust the timing so that the time difference becomes zero, the main base station unit transmitting device and the slave base station unit received by the slave station Since the timings of the received signals from the transmitting device can be accurately matched, the effect of interference reduction is increased.

In still another direct spreading code division communication system according to the present invention, the main base station transmitter and the slave base station transmitter have directivity control means for controlling the directivity of a transmission antenna. is there. As a result, the base station transmission apparatus can optimally control the directivity of the transmission antenna for the slave station, and reduce interference with other slave stations in the own cell. As a result, the signal strength transmitted to the other slave stations decreases, and the effect of interference reduction increases.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a direct spreading code division communication system according to the present invention will be described in detail. In the direct spreading code division communication system of the present invention, a slave base station (a base station that transmits a signal to a slave station existing outside the cell range of the own station at the time of soft handoff) belongs to a main base station (to which the slave station belongs). Base station), a transmission signal having the same content as the transmission signal of the main base station encoded with the PN code of the same timing as the reference frequency used by the main base station and the period of the orthogonal code is T, Transmit at different frequencies by (1 / T) × n (n is an integer) so that the slave station can receive the signal from the master base station and the signal from the slave base station in an orthogonal state. Thus, interference due to transmission signals from both base stations at the time of soft handoff is prevented.

FIG. 1A is a block diagram showing a configuration of a transmitting device in each base station in the first embodiment of the direct spreading code division communication system of the present invention, and FIG.
FIG. 3 is a block diagram showing a configuration of a receiving device in the slave station. In FIG. 1A, the base station transmitting apparatus 28 includes code multiplexing means 12 and 21, direct spreading means 13 and 22, mixers 14 and 23, adder 15, antenna 16, first orthogonal code generator 17, and first orthogonal code generator 17. Code generator 18, reference frequency generating means 19 of frequency f, switch 20, second orthogonal code generator 24, second PN code generator 26, timing control means 25, frequency of frequency (f + n / T) And generating means 27. Where n is an integer,
T is the period of the orthogonal code.

On the other hand, in FIG. 1B, the slave station receiver 46 comprises an antenna 29, mixers 30 and 41, first and second code separation means 31 and 42, synchronization circuits 32 and 44,
Despreading means 33, 45, combining means 34, detecting means 35,
The reference frequency generating means 36 for the frequency f, the frequency (f + n /
T) frequency generating means 40, orthogonal code generator 37, PN
It comprises a code generator 38, a switch 39, and a timing means 47. The first PN code generator 18, the second PN code generator 26 in the base station transmitter 28, and the PN code generator 38 in the slave station receiver 46 all generate the same PN code. is there.

The base station transmitting apparatus 28 thus configured
When a certain mobile station functions as a main base station, a block 52 indicated by a chain line functions, and when it functions as a slave base station, a block 53 indicated by a dotted line functions. Accordingly, when all the slave stations existing within the cell range of the own station operate as the main base station and do not communicate with the slave stations existing outside the cell range of the own station, the switch 20 is turned off. When a slave station existing within the cell range of the own station operates as the main base station and a slave station located outside the cell area of the own station operates as the slave base station, the switch 20 is used. Is turned on, the signals for the main base station unit and the slave base station unit are added to the adder 15 and the antenna 1
6 to the corresponding slave stations.

Next, an operation when the base station transmitting apparatus configured as above functions as a main base station will be described. First, the pilot signal for the main base station and the transmission data are input to the code multiplexing means 12 and code-multiplexed using the orthogonal code generated by the first orthogonal code generator 17. Then, the PN code generated by the first PN code generator 18 and the output of the code multiplexing means 12 are directly spread using the direct spreading means 13. The output of the direct spreading means 13 is supplied to the mixer 14 by the reference frequency generating means 1.
The signal is modulated by the signal of the frequency f supplied from the antenna 9 and transmitted from the antenna 16.

Next, the operation when base station transmitting apparatus 28 functions as a slave base station will be described. First, the pilot signal for the slave base station and the transmission data are input to the code multiplexing means 21 and code-multiplexed using the orthogonal code generated by the second orthogonal code generator 24. And PN
The PN code generated by the code generator 26 and the output of the code multiplexing means 21 are directly spread by the direct spreading means 22. After that, the direct spread signal is modulated by the mixer 23 by the signal of the frequency (f + n / T) supplied from the frequency generating means 27, and the switch 20 and the adder 15 are modulated.
Via the antenna 16. The timing control means 25 is for adjusting the timing of the PN code and data signal for the slave base station transmitted from the slave base station transmitter 53 to the timing of the PN code and data signal of the master base station.

That is, when the base station transmitting device 28 is the main base station 1 in the example shown in FIG.
A signal spread with a PN code synchronized with the start timing a shown in FIG. 12 is transmitted from the main base station transmitter 52. If there is no slave station in which the main base station 1 operates as a slave base station, the switch 20 is turned off, and no signal is transmitted from the slave base station transmitter 53 of the base station 1. It will be.

Assuming that the base station transmitter 28 shown in FIG. 1A is a facility of the slave base station 2 in FIG. 12, the master base station transmitter 52 sends a PN code synchronized with the start timing b. Is transmitted. In addition, the slave base station transmitter 53 transmits a signal spread with a PN code synchronized with the start timing a.

As described above, the slave base station transmitter 53 in the base station transmitter 28 outputs the same signal as the transmission signal of the master base station spread by the PN code having the same start timing as the PN code of the master base station. Is transmitted at a frequency shifted from the reference frequency f by the frequency n / T.

The signal transmitted from each base station in this manner is received by the slave station receiver 46 shown in FIG. 1 (b). In the slave station receiver 46, the signal of frequency f (the signal from the main base station transmitter 52 of the base station transmitter 28) among the signals received by the antenna 29 is converted by the mixer 30 into reference frequency generating means. The code signal to be received by the slave station is code-separated by code separation means 31 by quadrature detection based on the signal of frequency f from 36 and taken out. A despreading process is performed on the code-separated signal using the PN code supplied from the PN code generator 38. This despread signal is supplied to the synchronization circuit 32, and the synchronization timing is detected.

The received signal of the frequency (f + n / T) transmitted from the slave base station transmitting device 53 is supplied to the mixer 41 by the frequency (f + n / T)
(n / T) signal, and is taken out by quadrature detection and separated by the code separation means 42. Then, a despreading process is performed using the PN code supplied from the PN code generator 38, and the despread signal is supplied to a synchronization circuit 44 to detect a synchronization timing. The timing means 47 outputs a signal for controlling the processing timing of the code separation means 42 and the despreading means 45 so that the synchronization timing detected from the synchronization circuit 32 and the synchronization timing detected from the synchronization circuit 44 match. Generate.

According to the example of FIG. 12, the slave base station 2
The PN code having the same timing as the PN code of the main base station 1 and data having the same contents are transmitted from the slave base station unit 53. Therefore, the despreading means 33
And 45 should output the despread signal at the same timing. However, there may be a slight timing deviation depending on the distance from the base station and the like. Is provided.

The output signal output from the despreading means 45 is supplied to the synthesizing means 34 via the switch 39, and the signal demodulated by the reference frequency generating means 36 having the frequency f is despread. The signal is combined with the processed signal and detected by the detection means 35 to become demodulated data.

It is to be noted that whether or not a signal obtained by despreading a signal demodulated using an output of the frequency (f + n / T) frequency generating means 40 is synthesized by the synthesizing circuit 34 is determined by a soft handoff of the slave station. Switching can be performed by controlling whether the switch 39 is on or off by detecting whether or not the data exists in the area where the function is used, that is, whether or not data is transmitted from a plurality of stations.

As described above, from the viewpoint of the slave station in the soft handoff state, the data transmitted from the main base station is modulated at the frequency f, while the data transmitted from the slave base station is modulated at the frequency f + n / T. Modulated. Since the frequency difference between the signals encoded by the PN code and the orthogonal code having the same timing is set to an integral multiple of 1 / T, both signals are received orthogonally. Therefore, on the receiving side, the two signals can be completely separated, and by demodulating them, it is possible to reduce the influence of the cross-correlation.

As described above, in order to completely prevent interference due to cross-correlation, it is necessary to completely match the timings of the PN codes of data transmitted from the base station. It is necessary to consider the amount of delay due to the difference in distance. Therefore, another embodiment of the present invention in which the timing can be adjusted in more detail on the base station transmitting apparatus side will be described.

(Second Embodiment) FIG. 2 is a diagram showing a configuration of a base station transmitting apparatus according to a second embodiment. In this figure, the same components as those in FIG. 1A are denoted by the same reference numerals to avoid duplication of description. In this embodiment, the control signal input terminal is provided in the timing control means 48 of the slave base station transmitting apparatus, and the timing control means 48 is finely adjusted by a control signal supplied from the outside so that the delay error can be adjusted. It was done. This enables fine adjustment for making the timing of the received signal in the slave station the same.

(Third Embodiment) FIG. 3 is a diagram showing a configuration of a slave station receiving apparatus according to a third embodiment of the present invention. In this figure, FIG.
The same components as those in (b) are denoted by the same reference numerals, and the description will not be repeated. In the slave station receiver 46 shown in FIG. 3, the time difference between the synchronization timing of the reception signal from the main base station transmitter of the master base station and the synchronization timing of the reception signal from the slave base station transmitter of the slave base station. Is provided with an output terminal for outputting a timing control signal corresponding to the delay time difference to the outside. Thus, the timing difference can be known on the base station side, and the position of the slave station can be known.

(Fourth Embodiment) In this embodiment, a timing control signal corresponding to the delay time difference outputted from the timing means 47 of the slave station receiver in the third embodiment shown in FIG. The (error signal) is used as an external control signal, and the control signal is transmitted to the base station via an uplink from the slave station to the base station. Then, the base station inputs the control signal transmitted from the slave station in this way to the timing control of the timing control means 48 in the second embodiment shown in FIG. 2 to adjust the delay error. Things. This makes it possible to eliminate a minute delay error caused by a distance difference between the base station and the slave station. As a result, as described above, it is possible to completely eliminate the interference between the transmission signal from the main base station and the transmission signal from the slave base station.

The fourth embodiment will be described in more detail with reference to FIG. First, in the initial state, as shown in (a), the main base station unit of the base station 1 transmits the signal 1 to the slave station 3 within the cell range of the base station using the main base station transmitting apparatus. It is also assumed that base station 2 transmits signal 2 to a not-shown slave station within its own cell range using its main base station transmitter. At this time, the handoff has not been performed yet.

Next, as shown in FIG.
Has moved near the boundary between the cell of base station 1 and the cell of base station 2. At this time, soft handoff is started, and the slave base station transmitter of the base station 2 sends the same signal 1 as the transmission signal from the main base station 1 to the slave station 3 using the frequency (f + T / n). Is sent. As described above, in the slave station 3, the signal 1 transmitted at the frequency f from the main base station transmitter of the base station 1 and the base station 2
And the signal 1 transmitted at the frequency (f + n / T) from the slave base station transmitting apparatus, and the timing means 47 calculates a delay time difference between the signals 1 received from both base stations.

Subsequently, as shown in FIG.
Transmits the delay time difference signal calculated by the timing means 47 to the base station 2. The base station 2 having received the delay time difference signal from the slave station 3 transmits the received delay time difference signal to the timing control means 4 of the slave base station transmitting apparatus.
8 as a control signal, and finely adjusts the generation timing of each code in the second orthogonal code generator 24 and the second PN code generator. As a result, as shown in FIG. 4D, the signal 1 is transmitted at the corrected timing. As a result, the slave station 3 can receive the signal 1 from the base station 1 and the signal 1 from the base station 2 at perfectly synchronized timing.

(Fifth Embodiment) FIG. 5 shows a constitutional instruction according to a fifth embodiment of the present invention. In this figure, the same components as those in FIG. 1A are denoted by the same reference numerals, and the description will not be repeated. Reference numeral 49 denotes the mixer 14 and the antenna 16 in the main base station transmitting apparatus.
A directivity control unit 50 is provided between the mixer 23 and the antenna 51 in the slave base station transmitting apparatus. As described above, in this modified example, the transmission signal from the main base station transmission device is transmitted with directivity control in the direction of the corresponding slave station using the directivity control unit 49 and the antenna 16 and transmitted by the slave base station transmission unit. A transmission signal from the device is transmitted to a transmission antenna 51 using a directivity control unit 50.
Is controlled so that the directivity of the mobile station is directed to the slave station.

FIG. 6 is a diagram for explaining the operation in the fifth embodiment. As shown in FIG. 6, a signal 1 transmitted from the main base station of the main base station 1 and
The signal 1 transmitted from the slave base station unit of the slave base station 2 is transmitted with the directivity controlled in the direction of the slave station 3.
As a result, it is possible to prevent the main base station transmission signal and the slave base station transmission signal from interfering with other slave stations.

FIG. 7 shows a simulation model for evaluating the direct spreading code division communication system of the present invention thus configured. In this model, a Walsh code having a code length of 64 is used as the orthogonal code, as in the simulation model of FIG. 10 described above. Further, a part of the output of the root Nyquist filter on the transmitting side is modulated at the frequency Δf (= n / T), and is added to the original output. On the receiving side, a part of the received signal is subjected to quadrature detection at a frequency Δf and input to a root Nyquist filter.

FIG. 8 shows a simulation result when the code multiplexing number m is 32. The conventional characteristic shown in this figure is a case where a delayed wave is synthesized at m = 32 shown in FIG. As is clear from this figure, in the case of the system of the present invention, the same characteristics as those in the case of the code multiplexing number m = 1 in FIG. 11 are obtained, and almost coincide with the theoretical values of QPSK modulation. You can see that.

[0045]

As described above, according to the present invention,
When realizing a high transmission rate by code division, it is possible to provide a direct spreading code division communication system capable of preventing interference due to cross correlation generated by soft handoff.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment of a base station transmitting device and a slave station receiving device in a direct sequence code division communication system of the present invention.

FIG. 2 is a block diagram showing a configuration of another embodiment of a base station transmitting apparatus according to the present invention.

FIG. 3 is a block diagram showing a configuration of still another embodiment of the slave station receiving device according to the present invention.

FIG. 4 is a diagram for explaining the operation of the direct sequence code division communication system of the present invention.

FIG. 5 is a block diagram showing a configuration of still another embodiment of the base station transmitting apparatus according to the present invention.

FIG. 6 is a diagram for describing control of antenna directivity of the base station transmitting apparatus in the embodiment shown in FIG.

FIG. 7 is a diagram for explaining a simulation model for evaluating the system of the present invention.

FIG. 8 is a diagram showing simulation results for evaluating the system of the present invention.

FIG. 9 is a diagram for explaining interference that occurs in a direct spreading code division system.

FIG. 10 illustrates a simulation model for evaluating a conventional method.

FIG. 11 is a diagram showing simulation results for evaluating a conventional method.

FIG. 12 is a diagram for describing a configuration of a pilot signal for cell identification.

[Explanation of symbols]

 1, 2 base station 3 slave station 12, 21 code multiplexing means 13, 22 direct spreading means 14, 23, 30, 41 mixer 15 adder 16, 29, 51 antenna 17, 24, 37 orthogonal code generator 18, 26, 38 PN code generator 19, 27, 36, 40 Frequency generation means 20, 39 Switch 25, 48 Timing control means 28 Base station transmitter 31, 42 Code separation means 32, 44 Synchronization circuit 33, 45 Despreading means 34 Synthesis means 35 detection means 46 slave station receiver 47 timing means 49, 50 directivity control means 52 main base station transmitter 53 slave base station transmitter

Continuation of the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H04J 13/04 H04B 7/26

Claims (5)

(57) [Claims] 1. A direct spreading code division communication system comprising a plurality of base stations and slave stations, wherein each of the base stations transmits a pilot signal to identify each of the base stations. The station comprises: first code multiplexing means for code-multiplexing data to be transmitted and the pilot signal using an orthogonal code generated by a first orthogonal code generator; and an output of the first code multiplexing means. A first spreading means for spreading with a PN code generated by a first PN code generator, and a means for transmitting an output of the first spreading means at a reference carrier frequency; A second orthogonal code generator generates a main base station transmitting apparatus for transmitting a signal to a slave station to be transmitted and the same data and pilot signal to be transmitted as the main base station transmitting apparatus of another adjacent base station. Orthogonal signs Code multiplexing using symbols
Code multiplexing means and the output of the second code multiplexing means
A second spreading means for spreading with a PN code generated by the PN code generator, an orthogonal code generation timing in the second orthogonal code generator, and a PN code generation timing in the second PN code generator And a means for transmitting the output of the second spreading means at a frequency separated from the reference carrier frequency by a frequency n / T (T is the period of the orthogonal code and n is an integer). And a slave base station transmitting apparatus for transmitting a signal to a slave station existing outside its own cell range. The slave station performs a first orthogonal orthogonal detection on a received signal at the reference carrier frequency. Detection means, first despreading means for despreading the output of the first quadrature detection means with an orthogonal code and a PN code, and converting a received signal from the reference carrier frequency to a frequency n / T
A second quadrature detection means for performing quadrature detection at a frequency separated from the second quadrature detection means;
A second despreading means for performing despreading using an N code; and a means for combining outputs of the first and second despreading means, wherein a signal transmitted from a main base station transmission device in the base station and A direct spread code division communication system, comprising: a receiving device for combining and demodulating signals with different carrier frequencies transmitted from the slave base station transmitting device in another adjacent base station. 2. The direct spreading code according to claim 1, wherein the timing control means in the slave base station transmitting apparatus adjusts the generation timing based on a control signal input from the outside. Split communication system. 3. The slave station includes timing means for calculating a time difference between a synchronization timing detected from an output of the first despreading means and a synchronization timing detected from an output of the second despreading means. 3. The direct-spread code division communication system according to claim 2, wherein a synchronization time difference output from the timing means is output to the outside as a timing control signal. 4. The timing control signal output from the slave station is input to the timing control means in the slave base station transmitting device of the other adjacent base station, and the timing control signal is adjusted so that the synchronization time difference becomes zero. 4. The direct spreading code division communication system according to claim 3, wherein the generation timing is controlled. 5. The transmission apparatus according to claim 1, wherein the main base station transmission device and the slave base station transmission device include directivity control means for controlling directivity of a transmission antenna. 2. The direct sequence code division communication system according to claim 1.