Despreading technique for CDMA systems
AssigneeAT&T Bell Laboratories
InventorQi Bi
Life of this patent
Estimating the term…
Abstract
Despreading of the received signal in a CDMA system is provided using code coefficient sequences which are derived from those utilized by the system users to encode their respective symbols. Each derived code coefficient sequence is a function of the correlation between a different user's code coefficient sequence and the code coefficient sequences of all other users. Advantageously, this technique substantially reduces interference effects and is suitable for use in the despreader of differentially or nondifferentially coded CDMA systems.
Claims16
Apparatus for use in a CDMA system which transmits a coded user signal for each of a plurality of users, each transmitted user signal being formed by processing that user's symbol with an associated sequence of code coefficients, and wherein a received signal includes a composite of all coded user signals, said apparatus comprising
- means for receiving samples of said received signal in a predetermined time interval;
- and
- means responsive to said received signal samples for forming an estimate of a user symbol in said time interval, said forming means including means for multiplying said received signal samples and a derived sequence of code coefficients, said derived sequence being a function of a correlation of the code coefficient sequence associated with said user and those code coefficient sequences associated with the other users.
A method for use in a CDMA system which transmits a coded user signal for each of a plurality of users, each transmitted user signal being formed by processing that user's symbol with an associated sequence of code coefficients, and wherein a received signal includes a composite of all coded user signals, said method comprising the steps of
- receiving samples of said received signal in a predetermined time interval;
- and
- estimating a symbol of a user in said predetermined time interval in response to said received signal samples, and a derived sequence of code coefficients, said estimating step including a multiplication of said received signal samples and a derived sequence of code coefficients said derived sequence being a function of a correlation of the code coefficient sequence associated with said user and those code coefficient sequences associated with the other users.
Dependencies are inferred from the claim text.