Automobile on-board and/or portable telephone system

Abstract

In an automobile on-board and/or portable telephone system capable of increasing the capacity of subscribers easily on the basis of changing of the information transmission bit rate, spread codes obtained by multiplying orthogonal spread codes (m in number) by a pseudo-random noise series are assigned to individual channels in the same cell in such a manner that the orthogonal spread codes are multiplied by some types of pseudo-random noise series having different phases, thereby making it possible to maintain the number of channels in the same cell at a value which is a multiple of the number of the orthogonal spread codes. Through this, in the case where the transmission bit rate is halved as compared to the presently existing rate in the future, assignment of spread codes which are increased in number to as large a value as necessary can be achieved and the subscriber's capacity can be increased within a range in which the necessary quality can be maintained even when link paths for m or more channels are set up in one cell from the viewpoint of Signal to Interference Ratio.

Description

the series channels and information input lines 26 to 28 and spread modulators 32 to 34 are in association with the channel numbers #(m+1) to #2m to constitute a second channel group of m series channels. Denoted by reference numeral 36 is a despreader adapted to perform, in the units at the receiver side 22, a despread processing in accordance with a spread code of a channel assigned to each user.

In the units at the transmitter side 21, the spread modulators 29, 30 and 31 of the first channel group are set so as to perform spread processings in accordance with the spread code codes corresponding to the individual channels by being supplied with parameters W1(t), W2(t) and Wm(t) representative of orthogonal spread codes (m is a the number of the codes), respectively, and a parameter PN(t) representative of a PN series. The spread modulators 32, 33 and 34 of the second channel group are set so as to perform spread processings in accordance with the spread codes corresponding to the individual channels by being supplied with the same parameters W1(t), W2(t) and Wm(t) representative of orthogonal spread codes as those for the spread modulators 29, 30 and 31 of the first channel group and a parameter PN(t−φ) representative of the PN series. The parameter PN(t−φ) representative of the PN series is of the same PN series as that represented by PN(t) but has a time phase which differs from that of PN(t) by a constant phase. Through this, in the automobile on-board and/or portable telephone system of the present embodiment, a maximum of m 2m channels can be set on the outbound link path of one cell.

In the units at the receiver side 22, each equipment has an a despreader 36 and when the channel number of the units at the receiver side 22 shown in FIG. 1 is #1, that despreader 36 is supplied with a parameter Wi(t) representative of an orthogonal spread code and a parameter PN(*) representative of the PN series, where PN(*) is

• PN(*)=PN(t) when i≦m, and
• PN(*)=PN(t−φ) when i≧m+1.

Then the orthogonal spread codes are multiplied by the PN series to produce spread codes and by performing a despread processing in accordance with a spread code corresponding to a channel of interest, a user signal destined for this apparatus can be reproduced. A channel structure for performing the above spread and despread processings is shown in FIG. 2.

The operation of the automobile on-board and/or portable telephone system will now be described. In the units at the transmitter side 21, when user information is inputted from one of the information input lines 23 to 28 at a predetermined transmission bit rate, for example, B/2 (bps) which is the half of the rate B, a spread processing is carried out by one of the spread modulators 29 to 34 in accordance with a spread code corresponding to a channel number assigned to the user of interest and then spread signals of a plurality of users are combined in the combiner 35 and transmitted. On the other hand, when a combined spread signal is received in the units at the receiver side, the combined spread signal is subjected to a despread processing by the despreader 36 in accordance with a spread code of the channel number assigned to that user to reproduce the information at the information transmission bit rate B (bps) and the reproduced information is delivered out through an information output line. When the signal indicative of the user information transmitted at the halved information transmission bit rate is subjected to the spread processing, transmitted and subjected to the despread processing, its waveform is changed. The operational condition of the waveform change has already been described with reference to FIGS. 8 to 10 and will not be described herein.

Accordingly, for example, when a voice signal coded having a rate which is half the presently existing rate becomes applicable in the future, channels of a maximum of 2 m channels can be set simultaneously if the requisite communication quality can be maintained in spite of the fact that link paths in excess of m channels are set up in one cell from the viewpoint of the necessary SIR, thereby making it possible to increase the capacity of subscribers without drastically improving component units manufactured in correspondence to the existing automobile on-board and/or portable telephone system or exchanging all of the component unit units with new ones. In order to maintain the communication quality from the viewpoint of the necessary SIR, a the maximum value of the number of link paths allowed to be set up simultaneously in the cell can be decided on the basis of information transmission bit rates for individual users set on of link paths set up in the units at the transmitter side 21 or the base station and the setting of link paths for the users can be allowed within the maximum value.

In the foregoing embodiment, the PN series by which the orthogonal spreads are multiplied is exemplified to have two different phases, however, the number of phases can be determined desirably as desired. For example, in the case where service at a very low information transmission bit rate is given as a system and the user often receives the service, the requisite quality can be maintained from the viewpoint of the necessary SIR even when link paths are set up for very many users in one cell. In such a system, three or more types of phases of the PN series by which the orthogonal spread code are multiplied can be employed instead of two types and hence the number of spread codes to be assigned can be increased to a great extent to further increase the subscriber's capacity.

As described above, according to the present invention, different phases of the PN series by which the orthogonal spread codes are multiplied are given to provide some types of PN series so that the number of channels in the same cell may be maintained at a value which is a multiple of the number of series and therefore in the case where a voice signal coded is applied at a rate which is half the presently existing rate in the future, assignment of spread codes which are increased in number to as large a value as necessary can be achieved and the subscriber's capacity can be increased without drastically altering the components within a range in which the necessary quality can be maintained even when link paths for m or more channels are set up in one cell from the viewpoint of SIR.

Claims

1. A mobile telephone system comprising:

a transmitting side apparatus serving as a base station and including spread modulation means for spreading information data from a plurality of users by using a plurality of spread codes corresponding to channel numbers assigned to said plurality of users respectively and combining means for combining the spread information data and transmitting the combined information data; and

a receiving side apparatus including despread means for despreading the transmitted information data by using said plurality of spread codes corresponding to the channel numbers assigned to said plurality of users respectively;

wherein said plurality of spread codes are obtained by multiplying m orthogonal spread codes by pseudo-random noise codes and assigned to individual channels in the same cell in such a manner that the spread codes, which are obtained by multiplying said m orthogonal spread codes by a first pseudo-random noise code, are assigned to channel numbers #1 to #m and that the spread codes, which are obtained by multiplying said m orthogonal spread codes by a second pseudo-random noise code having the same code as the first pseudo-random noise code but having a different time phase from that of the first pseudo-random noise code by a predetermined time period, are assigned to channel numbers #(m+1) to #2m, thereby making a number of channels in the same cell larger than number of the orthogonal spread codes.

2. A mobile telephone system according to claim 1, wherein said m orthogonal spread codes are multiplied by n pseudo-random noise codes having different time phases from each other to obtain n×m spread codes where n is an integer larger than 2, thereby making the number of channels in the same cell to be n times as large as the number of the orthogonal spread codes.

3. A cdma (code division multiple access) transmitter, comprising:

first means for multiplying a plurality of orthogonal codes by a first pseudo-random noise code to obtain a plurality of first spreading codes and for employing the first spreading codes to spread information associated with a first plurality of channels to which the first spreading codes are assigned respectively;

second means for multiplying the orthogonal codes by a second pseudo-random noise code to obtain a plurality of second spreading codes and for employing the second spreading codes to spread further information associated with a second plurality of channels to which the second spreading codes are assigned respectively, the second pseudo-random noise code being substantially the same as the first pseudo-random noise code except for a phase difference; and

means for combining at least the information spread by the first and second means to obtain combined information for transmission.

4. A cdma (code division multiple access) transmission method, comprising the steps of:

(a) multiplying a plurality of orthogonal codes by a first pseudo-random noise code to obtain a plurality of first spreading codes;

(b) employing the first spreading codes to spread information associated with a first plurality of channels to which the first spreading codes are assigned respectively;

(c) multiplying the orthogonal codes by a second pseudo-random noise code, when further channels are needed by further information, to obtain a plurality of second spreading codes, the second pseudo-random noise code being substantially the same as the first pseudo-random noise code except for a phase difference;

(d) employing the second spreading codes to spread the further information associated with a second plurality of channels to which the second spreading codes are assigned respectively; and

(e) combining at least the information that was spread during steps (b) and (d) to obtain combined information for transmission.

5. A cdma (code division multiple access) communication system, comprising:

a transmitter which includes:

first means for multiplying a plurality of orthogonal codes by a first pseudo-random noise code to obtain a plurality of first spreading codes and for employing the first spreading codes to spread information associated with a first plurality of channels to which the first spreading codes are assigned respectively,

second means for multiplying the orthogonal codes by a second pseudo-random noise code to obtain a plurality of second spreading codes and for employing the second spreading codes to spread further information associated with a second plurality of channels to which the second spreading codes are assigned respectively, the second pseudo-random noise code being substantially the same as the first pseudo-random noise code except for a phase difference, and

means for combining at least the information spread by the first and second means to obtain combined information for transmission; and

a receiver which includes means for recovering the information associated with at least one of the first and second plurality of channels by despreading the combined information with at least one of the first and second spreading codes.

6. A method for us in a cdma (code division multiple access) communication system for recovering information that was transmitted over a first channel or a second channel, said method comprising the steps of:

(a) multiplying a code selected from a set of orthogonal codes by another code to obtain a spreading code;

(b) despreading a received signal using the spreading code obtained in step (a); and

(c) selecting the first channel or the second channel by using, as the another code in step (a), a predetermined pseudo-random noise code or the pseudo-random noise code shifted in phase.

7. A cdma (code division multiple access) receiver for recovering information that was transmitted over a first channel or a second channel, said receiver comprising:

despreading means for despreading a received signal to recover the information that was transmitted over the first channel or the second channel; and

multiplying means for multiplying a code selected from a set of orthogonal codes by a pseudo-random noise code or the pseudo-random noise code shifted in phase, the information transmitted over the first channel being recovered if the selected orthogonal code is multiplied by the pseudo-random noise code and the information transmitted over the second channel being recovered if the selected orthogonal code is multiplied by the pseudo-random noise code shifted in phase.

8. A cdma (code division multiple access) communication system, comprising:

first transmitter means for multiplying a plurality of orthogonal codes by a first pseudo-random noise code to obtain a plurality of first spreading codes and for employing the first spreading codes to spread information;

second transmitter means for multiplying the orthogonal codes by a second pseudo-random noise code to obtain a plurality of second spreading codes and for employing the second spreading codes to spread information, the second pseudo-random noise code being substantially the same as the first pseudo-random noise code except for a phase difference;

first receiver means which includes means for recovering the information by despreading the information with one of the first spreading codes; and

second receiver means which includes means for recovering information by despreading the information with one of the second spreading codes.

9. A cdma (code division multiple access) communication method, comprising the steps of:

(a) multiplying a plurality of orthogonal codes by a first pseudo-random noise code to obtain a plurality of first spreading codes;

(b) employing the first spreading codes to spread information prior to transmission thereof;

(c) multiplying the orthogonal codes by a second pseudo-random noise code to obtain a plurality of second spreading codes;

(d) employing the second spreading codes to spread information prior to transmission thereof;

(e) recovering received information by despreading it with one of the first spreading codes; and

(f) recovering received information by despreading it with one of the second spreading codes.

10. A method for use in a cdma (code division multiple access) communication system for transmitting information, said method comprising the steps of:

(a) multiplying a code selected from a set of orthogonal codes by another code to obtain a spreading code; and

(b) using, as the another code in step (a), a predetermined pseudo-random noise code or the pseudo-random noise code shifted in phase.

11. A cdma (code division multiple access) transmitter for transmitting information, said transmitter comprising:

(a) spreading means for spreading the information; and

(b) multiplying means for multiplying a code selected from a set of orthogonal codes by a pseudo-random noise code or the pseudo-random noise code shifted in phase.