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Data transmission method, transmitter, and receiver
| Details |
Inventors: Hottinen, Ari;
Assignee: Nokia Mobile Phones Ltd. (Salo, FI)
Primary Examiner: Pham; Chi H.
Assistant Examiner: Yao; Kwang B.
Attorney, Agent or Firm: Perman & Green, LLP
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. |
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DETAILED DESCRIPTION What is claimed is: 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
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Telecommunications 
