JP3208643B2 - Receiver for spread spectrum communication - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a receiving apparatus for a radio station performing direct spread spectrum communication, and more particularly to a receiving apparatus having a plurality of despreading circuits for removing an interference signal.

[0002]

2. Description of the Related Art FIG. 4 shows an example of the prior art. In the figure, 4-1 is an antenna, 4-2 is a receiver, 4-3 is a despreading circuit, 4-4 is an interference removal circuit, and 4-5 is a demodulation circuit. Transmission signals from N radio stations (N is an integer of 2 or more) having the same information transmission rate are input to the 4-1 antenna, and the output of the 4-1 antenna is connected to the 4-2 receiver, The output of the 4-2 receiver is connected to N 4-3 despreading circuits, and despreading is performed with respective spreading codes corresponding to the N radio stations. The output is connected to a 4-4 interference removal circuit to remove an interference signal, and the output of the 4-4 interference removal circuit is connected to a 4-5 demodulation circuit, demodulated, and demodulated data is output.

[0003]

However, since interference is removed from signals between wireless stations having the same information transmission rate, the method cannot be applied to communication with wireless stations having a plurality of information transmission rates. Was.

An object of the present invention is to provide a receiving apparatus for spread spectrum communication which removes an interference signal when a plurality of information transmission rates are provided.

[0005]

According to the present invention, the above-mentioned object is solved by the means described in the claims. That is, the invention according to claim 1 is a receiving apparatus for spread spectrum communication that performs direct spread spectrum communication at a plurality of information transmission rates simultaneously with a plurality of wireless stations, wherein a plurality of despreading circuits corresponding to the respective wireless stations are provided. A plurality of switches connected to the despreading circuits corresponding to the wireless stations other than the wireless station having a low information transmission rate, and sequentially switching a switch to a plurality of outputs for each information symbol of the signal having the information transmission rate; A first changeover switch, an output signal of the despreading circuit corresponding to the radio station having the lowest information transmission rate, and one output of each of the first changeover switches as an input signal. Information transmission speed M
A plurality of interference canceling circuits each having a number corresponding to a value of a ratio M / N (M / N is an integer of 2 or more) of the information transmission rate N, which is the slowest, and connected to each of the interference canceling circuits; A second selector switch for switching the interference cancellation circuit to be input for each information symbol having a high information transmission rate; and a demodulator for demodulating an output signal of the second selector switch. An output signal of the changeover switch is sequentially input to the interference canceling circuit which is different for each of the information symbols.

According to a second aspect of the present invention, a plurality of information signals having a plurality of information transmission speeds are spread by respective spreading codes and transmitted, and the plurality of transmission signals are simultaneously received. , A plurality of despreading circuits corresponding to the respective spreading codes, and one of the signals having the respective information transmission rates connected to the respective despreading circuits other than the despreading circuit corresponding to the spreading code having the largest spreading factor. A plurality of first changeover switches for sequentially switching a switch to a plurality of outputs for each information symbol; an output signal of the despreading circuit corresponding to a spreading code having the largest spreading factor; and an output signal of each of the first changeover switches Is the input signal, and the value of the ratio M / N (where M / N is an integer of 2 or more) between the highest information transmission rate M and the lowest information transmission rate N A plurality of interference elimination circuits having a corresponding number, a second changeover switch connected to each of the interference elimination circuits and switching the interference elimination circuits to be input for each information symbol of the highest information transmission rate; A demodulator for demodulating an output signal of the second changeover switch, and an output signal of each of the first changeover switches is sequentially input to the interference canceling circuit which is different for each of the one information symbols. And a receiver for spread spectrum communication.

According to the present invention, as described above, the interference removal is performed in the interference removal circuit in which the output signal of the despreading circuit is different for each symbol of the fastest information transmission rate. It is possible to remove an interference signal with respect to a received signal from a wireless station having the same.

[0008]

FIG. 1 shows an embodiment of the present invention. A radio station of N _a1 station (N _a1 is an integer of 1 or more) whose information transmission rate is a1 (a1 is a real number);
(A2 is a real number that satisfies a2> a1) A radio station receiving station that performs direct spread spectrum spread radio communication simultaneously with a radio station of _Na2 station ( _Na2 is an integer of 1 or more) has a2 =
The case of 2 × a1 is shown. In the figure, 1-1 is an antenna, 1-2 is a receiver, 1-3 is a despreading circuit, 1-4 is a first switch a, 1-5 is an interference removal circuit,
6 is a second changeover switch b, and 1-7 are demodulation circuits. A transmission signal from a wireless station is input to an 1-1 antenna, an output of the antenna 1-1 is connected to a receiver 1-2, and an output of the receiver 1-2 is (N _a1 + N _a2 ) inverses. is connected to the diffusion circuit _{1-3, (N a1 + N a2} ) is despread with respective spreading codes corresponding to the radio station of the station performed, the output of the N _a2 amino despreading circuit 1-3 changeover switch a ( 1-
Is connected to 4), is switched for each information symbol of the information transmission rate a2, it is connected alternately to one of two interference removing circuit 1-5, wherein N _a1 single output of the despreading circuit 1-3 Is connected to all the interference elimination circuits 1-5, the interference signals are eliminated by the two interference elimination circuits 1-5, and the outputs of the two interference elimination circuits 1-5 are changed over by the changeover switch b (1-
6), switching is performed for each information symbol of the information transmission rate a2, connected to the demodulation circuit 1-7, demodulated, and demodulated data is output.

FIG. 2 shows an example of a transmission signal sequence according to the present invention. In the figure, 2-1 indicates a transmission signal sequence of a wireless station at an information transmission rate a1, and 2-2 indicates a transmission signal sequence of a wireless station at an information transmission rate a2. The time required for transmitting one information symbol from the wireless station having the information transmission rate a1 corresponds to the time required for transmitting two information symbols from the wireless station having the information transmission rate a2. When demodulating a received signal from a wireless station having an information transmission rate a2, the interference power from a1-1 with respect to a2-1 is the cross-correlation value of the hatched portion of a1-1 and a1-
1 and the interference power from a1-1 with respect to a2-2 is determined by the product of the cross-correlation value of a1-1 other than the hatched portion and the received signal power of a1-1. . In the present invention, the output signal of the despreading circuit corresponding to the spreading code of the wireless station having the information transmission rate a2 is input to a different interference canceling circuit for each information symbol, and the interference signal is canceled.

FIG. 3 shows an example of a specific configuration of the interference elimination circuit according to the present invention. In the figure, 3-1 is a tap coefficient generator, 3-2 is a multiplier, and 3-3 is an adder. The outputs of N _a1 despreading circuits 1-3 and the outputs of N _a2 changeover switches a (1-4) are input. The output of the tap coefficient generator 3-1 for generating tap coefficients in the multiplier 3-2 is multiplied by the outputs of the above-mentioned 1-3 and 1-4, and the output of the multiplier 3-2 is sent to the adder 3-3. The adder 3-3 outputs a signal obtained by adding the (N _a1 + N _a2 ) input signals and inputs the signal to the changeover switch b (1-6). As a method of determining the tap coefficient, for example, a training signal is transmitted, and the training signal and the adder 3-
(Kudo, "A Study on Interference Cancellation in DS / CDMA Wireless Communication"), IEICE Spring Conference, B-392
(1994)), there is a method of determining from cross-correlation values between spreading codes (R. Lupus & S. Verdu,
“Linear Multiuser Detecto
rs for Syschronous Code-D
ivision Multiple-Access C
hannels ”, IEEE Transaction
s on Information Theory, v
ol. 35, no. 1 pp. 123-136 (198
9)).

In this embodiment, the case of a2 = 2 × a1 is shown. However, also in the case of a2> 2 × a1, a changeover switch a is additionally provided to input signals for a large number of information symbols to the interference canceling circuit. By doing so, a similar effect can be obtained. Further, in this embodiment, the receiving apparatus of the wireless station having two kinds of information transmission rates has been described, but the same applies to the case of three or more kinds.

[0012]

As described above, according to the present invention,
Interference cancellation is performed in the interference cancellation circuit in which the output signal of the despreading circuit is different for each symbol of the highest information transmission rate, so that the interference signal for the reception signal from the wireless station having the highest information transmission rate is eliminated. be able to.

[Brief description of the drawings]

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

FIG. 2 is an example of a transmission signal sequence according to the present invention.

FIG. 3 is a diagram illustrating a specific configuration example of an interference cancellation circuit of the present invention.

FIG. 4 is a diagram showing an example of a conventional technique.

[Explanation of symbols]

 1-1 Antenna 1-2 Receiver 1-3 Despreading circuit 1-4 Changeover switch a 1-5 Interference elimination circuit 1-6 Changeover switch b 1-7 Demodulation circuit 2-1 Transmission from wireless station at information transmission rate a1 Signal sequence 2-2 Transmission signal sequence of radio station at information transmission rate a2 3-1 Tap coefficient generator 3-2 Multiplier 3-3 Adder 4-1 Antenna 4-2 Receiver 4-3 Despreading circuit 4- 4 Interference elimination circuit 4-5 Demodulation circuit

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) H04B 1/69-1/713 H04J 13/00-13/06 H04B 1/10

Claims (2)

(57) [Claims] 1. A spread spectrum communication receiver for directly performing spread spectrum communication at a plurality of information transmission rates simultaneously with a plurality of radio stations, comprising: a plurality of despreading circuits corresponding to the respective radio stations; A plurality of first switches connected to the despreading circuit corresponding to each of the wireless stations other than the wireless station having a speed, and sequentially switching a switch to a plurality of outputs for each information symbol of the signal having the information transmission speed; A changeover switch, an output signal of the despreading circuit corresponding to the radio station having the lowest information transmission rate, and one output of each of the first changeover switches as input signals, and a highest information transmission rate M And the ratio M / N of the lowest information transmission rate N
(M / N is an integer equal to or greater than 2) A plurality of interference canceling circuits each having a value corresponding to the value, and each of the interference canceling circuits is connected to each of the interference canceling circuits. A second switch for switching the interference canceling circuit; and a demodulator for demodulating an output signal of the second switch. An output signal of each first switch is different for each of the information symbols. A receiver for spread spectrum communication, which is sequentially input to the interference cancellation circuit. 2. A spread spectrum communication receiving apparatus for transmitting a plurality of information signals having a plurality of information transmission rates, each of which is spread by a corresponding spreading code and receiving the plurality of transmission signals simultaneously. And a plurality of despreading circuits corresponding to each of the spreading codes, and each of the despreading circuits other than the despreading circuit corresponding to the spreading code having the largest spreading factor, is switched for each information symbol of the signal having the information transmission rate. A plurality of first changeover switches for sequentially switching to a plurality of outputs, and an output signal of the despreading circuit corresponding to a spreading code having the largest spreading factor and an output signal of each of the first changeover switches as input signals, The ratio M / N of the highest information transmission rate M and the lowest information transmission rate N (where M / N
/ N is an integer equal to or greater than 2) and a plurality of interference canceling circuits, each of which is connected to each of the interference canceling circuits and which is input for each information symbol of the highest information transmission rate. A second switch for switching the interference canceling circuit; and a demodulator for demodulating an output signal of the second switch. The output signal of each of the first switches is different for each one information symbol. A receiver for spread spectrum communication, which is sequentially input to an interference canceling circuit.