Data transmission method, transmitter, and receiver

• US 5,943,330 A
• Filed: 10/23/1996
• Issued: 08/24/1999
• Est. Priority Date: 10/26/1995
• Status: Expired due to Fees

• Current Assignee: Nokia Mobile Phones UK Limited (Nokia Corporation)
• Original Assignee: Nokia Mobile Phones UK Limited (Nokia Corporation)
• Inventors: Hottinen, Ari
• Primary Examiner(s): Pham, Chi H.
• Assistant Examiner(s): YAO, KWANG BIN
• Application Number:
  US08/736,067
• Time in Patent Office: 1,035 Days
• Field of Search: 370/320, 370/328, 370/335, 370/342, 370/465, 370/468, 370/441, 375/200, 375/206, 375/207, 375/208, 375/209, 375/210
• US Class Current: 370/335
• CPC Class Codes: H04B 7/264 for data rate control
• CPC Class Codes: H04J 13/004 Orthogonal
• CPC Class Codes: H04J 13/18 Allocation of orthogonal codes

Abstract

The invention relates to a transmitter, a receiver and a data transmission method in a CDMA cellular radio system comprising in each cell at least one base station (100) and a number of subscriber terminals (102-108), and in which method the base stations communicate with terminal equipments situated within their area by using an at least partly overlapping frequency band, and wherein the signal of each user is modulated with one or several pseudo-random sequences the bit rates of which are substantially higher than the symbol rates of the users. In order to simplify multirate transmission, the pseudo-random sequence set (202-206) to be allocated to each user is selected on the basis of the symbol information contained in the user signal and the information rate required, and the subset to be modulated is selected from said set on the basis of the symbols to be transmitted.

Claims

1. A data transmission method in a CDMA cellular radio system comprising in each cell at least one base station and a number of subscriber terminals, wherein the method comprises steps of:

providing communication among the base stations with terminal equipments situated within their area by using an at least partly overlapping frequency band;

modulating a signal of each user with one or several pseudo-random sequences having bit rates which are substantially higher than symbol rates of users of the radio system;

allocating a pseudo-random sequence set to each of said users selected on a basis of symbol information contained in the user signal and required information rate; and

with respect to a subset of said pseudo-random sequence set to be modulated, selecting the subset from said set on the basis of symbols to be transmitted, wherein waveforms are allocated according to how many symbols are contained in the information to be transmitted per time unit, and the size of a code set is increased with higher data rate;

wherein said allocating step includes a further step of assigning different sets of pseudo-random sequences to respective ones of the user signals.

2. A method according to claim 1, wherein, in said allocating step, at least one sequence set allocated to a user is not orthogonal with another sequence allocated to the user.

3. A method according to claim 1, wherein, in said allocating step, the pseudo-random sequences allocated to each user are selected according to how many symbols per unit of time the signal to be transmitted contains.

4. A method according to claim 1, wherein, in said allocating step, two or more pseudo-random sequences are reserved for each user, and then when the user signal is transmitted, the pseudo-random sequences to be used at each instant are selected from the set of reserved sequences on the basis of the current symbol information of the signal.

5. A method according to claim 1, wherein, in said modulating step, the symbols to be modulated with the pseudo-random sequence are frame-structured bits, and that some of the frame bits determine the sequence set to be used and some determine the actual sequences from the selected sequence set.

6. A method according to claim 1, wherein, in said modulating step, the symbols to be modulated with the pseudo-random sequences are coded symbols.

7. A method according to claim 1, further comprising a step of connecting a base station to a mobile station within said radio system by employing connections comprising different data rates, and wherein the connections of different data rates of a user are realized user-specifically with different numbers of pseudo-random sequences.

8. A method according to claim 1, wherein, a common pseudo-random sequence can be simultaneously used by more than one user signal within the same coverage area.

9. A method according to claim 1, wherein, in said allocating step, one of the sequences allocated to a user may differ by a cyclic shift from another one of said sequences.

10. A method according to claim 1, wherein, in said allocating step, there are one or more codes selected to be transmitted, which codes are multiplied with a sequence that is selected on the basis of information to be transmitted.

11. A transmitter in a CDMA cellular radio system comprising:

in each cell of said radio system, at least one base station and a plurality of subscriber terminals, wherein the base stations of said at least one base station communicate with subscriber terminal equipments situated within the area of said base stations by using an at least partly overlapping frequency band;

wherein the transmitter comprises means for modulating a user signal to be transmitted with one or several pseudo-random sequences of a set of pseudo-random sequences having bit rates which are substantially higher than a symbol rate of the user signal;

wherein the transmitter further comprises means for selecting pseudo-random sequences modulating the user signal on the basis of symbol information comprised of the user signal and required information rate, wherein waveforms are allocated according to how many symbols are contained in the information to be transmitted per time unit, and the size of a code set is increased with higher data rate;

means for selecting from said set a subset to be modulated on a basis of symbols to be transmitted; and

means for providing plural sets of the pseudo-random sequences with assignment of different sets of the pseudo-random sequences to respective ones of the user signals.

12. A transmitter according to claim 11, further comprising means for selecting the pseudo-random sequences modulating the user signal in such a way that at least one sequence allocated to the user signal is not orthogonal with another sequence allocated to the user signal.

13. A transmitter according to claim 11, further comprising means for allocating two or more pseudo-random sequences for use over a connection, and means for selecting the pseudo-random sequences to be used at each instant from the set of allocated sequences on the basis of the current symbol information of the signal.

14. A transmitter according to claim 11, wherein the symbols to be modulated with the pseudo-random sequence comprise a series of bits arranged in a frame, and the transmitter comprises means for selecting the type of the sequence set to be used on the basis of some bits in the frame, and means for selecting sequences from the selected sequence type on the basis of some other bits of the frame.

15. A transmitter according to claim 11, further comprising means for encoding bits to be transmitted before they are multiplied with the selected pseudo-random sequence.

16. A receiver in a CDMA cellular radio system comprising:

in each cell, at least one base station and a plurality of subscriber terminals, wherein the base stations of said at least one base station communicate with terminal equipments situated within the area of the base stations by using an at least partly overlapping frequency band;

wherein a signal of each user is modulated with one or several pseudo-random sequences having bit rates which are substantially higher than symbol rates of the user signals;

the receiver comprises means for identifying from a received signal, on the basis of signal correlations, a modulating pseudo-random sequence set used when transmitting the signal; and

different sets of pseudo-random sequences have been assigned to respective ones of the user signals, wherein waveforms are allocated according to how many symbols are contained in the information to be transmitted per time unit, and the size of a code set is increased with higher data rate, and said receiver further comprises correlating means for identifying the different sets of the pseudo-random sequences of respective ones of the user signals.

17. A receiver according to claim 16, wherein the receiver comprises a demodulator which demodulates and detects simultaneously several different user signals.

18. A receiver according to claim 16, wherein the receiver comprises means for performing interference calculation on the received signal.

19. A receiver according to claim 16, further comprising a feedback from a demodulator to an identification means for pseudo-random sequences.