A communication system having a forward link and/or reverse link comprising: at least one base station which transmits multiple radio frequency (RF) signals; and a mobile station, the mobile station including: a receiver for receiving the RF signals; means for converting the RF signal to an intermediate frequency (IF) signal; means for sampling the IF signal to generate a digital signal, the digital signal having a data component and an interference component; means for canceling co-channel and or cross-channel interference in the digital signal by projecting the IF signal into a subspace orthogonal to a subspace of the interference component and multiplying this projection with the digital signal; and means for acquisition and tracking of the digital signal.
CROSS-REFERENCE TO RELATED APPLICATIONS
This application makes reference to U.S. Provisional Patent Application No. 60/326,199 entitled "Interference Cancellation in a Signal," filed Oct. 2, 2001; U.S. Provisional Patent Application No. 60/251,432, entitled "Architecture for Acquiring, Tracking and Demodulating Pseudorandom Coded Signals in the Presence of Interference," filed Dec. 4, 2000; U.S. patent application Ser. No. 09/612,602, filed Jul. 7, 2000; U.S. patent application Ser. No. 09/137,183, filed Aug. 20, 1998; U.S. Provisional Patent Application No. 60/325,215, entitled "An Apparatus for Implementing Projections in Signal Processing Applications," filed Sep. 28, 2001; U.S. Provisional Patent Application No. 60/325,215, entitled "Construction of an Interference Matrix for a Coded Signal Processing Engine," filed Nov. 16, 2001; and to U.S. patent application Ser. No. 09/988,219, entitled "A Method and Apparatus for Implementing Projections in Signal Processing Applications," filed Nov. 19, 2001. The entire disclosure and contents of these applications are hereby incorporated by reference.
Interference rejection in a wireless communication system involves determining a complement spatial-temporal signal subspace that is complement to a spatial-temporal signal subspace of an interference signal included in a received signal. The received signal is projected onto the complement spatial-temporal signal subspace, whereby the interference signal included in the received signal is reduced. Determining the complement spatial-temporal signal subspace can include estimating the interference signal; determining a Block Yule-Walker matrix for the estimated interference signal; and determining the complement spatial-temporal signal subspace from the Block Yule-Walker matrix.
An equalization method and apparatus for a downlink channel in a telecommunication system transmitting MC-CDMA symbols on a plurality of carrier frequencies, in which a plurality of links are established between a transmitter and a plurality of receivers in order to transmit a plurality of coded signals, each link using a distinct access code amongst N possible codes, there being P links for P users where P is less than N. The equalization including the formation and use of a matrix of reduced size based upon the number of links being P by eliminating matrix elements relating to the unused codes and effecting an estimation of the said transmitted symbols according to a mean square error minimization criterion.
The method of interference cancellation in a CDMA wireless communication system comprises receiving an incident digital signal containing a user signal transmitted on a CDMA user physical channel and an interfering signal, projecting said incident digital signal onto a projection space orthogonal to the space containing said interfering signal, filtering said projected signal with a filter matched to the CDMA user physical channel for detecting the data contained in said user signal.
Techniques for reducing search time using known scrambling code offsets are disclosed. In one embodiment, a plurality of search results is generated by correlating a received signal with a synchronization sequence. The plurality of search results is reduced by removing any results whose offset is within a threshold of a stored offset. In another embodiment, stored offsets correspond to previously identified cells. In yet another embodiment, a searcher further correlates the received signal with a scrambling code over a search window to produce a list search result. The scrambling code may be associated with one of the cells in a neighbor list. Various other embodiments are also presented. Benefits include efficient searching which allows for improved base station selection and therefore improved performance and system capacity.
The present invention concerns a multi-user detection method for a receiver in a MC-CDMA telecommunication system, each communication to or from a user of the system being coded with a signature, the signal received by said receiver being decomposed into a first plurality of frequency components, where the frequency components are subjected to a first filtering matched to the respective signatures of a second plurality of users and to the common or the respective responses of the transmission channels associated to the communications to or from said users; a first estimation of the symbols transmitted to or by the users is obtained from the output of the first filtering; a multi-user interference is derived from the first estimation and subtracted from the output of the first filtering to provide a cleared output; a second estimation of the symbols transmitted to or by the users is obtained from the cleared output.
