Combined adaptive spatio-temporal processing and multi-user detection for CDMA wireless systems

• US 20050128985A1
• Filed: 01/31/2005
• Published: 06/16/2005
• Est. Priority Date: 03/21/2000
• Status: Active Grant

• Current Assignee: Nytell Software LLC (Intellectual Ventures LLC)
• Original Assignee: Telcordia Licensing Co LLC (Telefonaktiebolaget LM Ericsson)
• Inventors: Moshavi, Shimon, Liberti, Joseph Charles Jr., Zablocky, Paul Gerald
• Granted Patent: US 7,688,777 B2
• Time in Patent Office: Days
• US Class Current: 370/335
• CPC Class Codes: H04B 1/71055 using minimum mean squared error [MMSE] detector
• CPC Class Codes: H04B 1/71072 Successive interference cancellation
• CPC Class Codes: H04B 1/71075 Parallel interference cancellation

Abstract

Methods and systems in a wireless receiver for enabling the reception of input signals at varied power levels in the presence of co-channel interference utilizing combinations of space-time adaptive processing (STAP), interference cancellation multi-user detection (MUD), and combined STAP/MUD techniques. In MUD, code, timing, and possibly channel information of multiple users are jointly used to better detect each individual user. The novel combination of adaptive signal reconstruction techniques with interference cancellation MUD techniques provides accurate temporal cancellation of interference with minimal interference residuals. Additional methods and systems extend adaptive signal reconstruction techniques to take Doppler spread into account. STAP techniques permit a wireless receiver to exploit multiple antenna elements to form beams in the direction of the desired signal and nulls in the direction of the interfering signals. The combined STAP-MUD methods and systems increase the probability of successful user detection by taking advantage of the benefits of each reception method. An additional method and system utilizes STAP techniques in the case where no pilot signal is available. This method compares the outputs of various hypothesized STAP solutions.

Claims

1-46. -46. (canceled)

47. In a wireless receiver for a CDMA system, a combination for enabling the receiver to receive input signals at varied power levels in the presence of interference wherein an input signal to said receiver is a vector comprised of one signal from each antenna in an antenna array of the receiver, said combination comprising:

a space-time adaptive processing (STAP) processor;

means for hypothesizing a possible symbol transmitted during a symbol period;

a respread processor;

means for weight computation wherein the hypothesized symbol and the input signal vector are used to form a set of STAP weights which filter the input signal vector spatially and temporally;

a matched filter bank;

means for determining a metric to measure a quality of the matched filter bank; and

means for comparing generated metrics.

48. The combination of claim 47 wherein the STAP processor comprises a plurality of tapped delay lines, one per antenna element.

49. The combination of claim 47 wherein the possible symbols transmitted are 64 Walsh symbols for an IS-95 reverse link transmitter.

50. The combination of claim 49 wherein the matched filter bank is a bank of 64 matched filters corresponding to the 64 Walsh symbols.

51. The combination of claim 47 wherein the means for weight computation further comprises a means for using previously detected or known symbols.

52. A method in a combination system for enabling a receiver to receive input signals at varied power levels in the presence of interference wherein an input signal to said receiver is a vector comprised of one signal from each antenna in an antenna array of the receiver, the method comprising the steps of:

receiving the input signal vector;

determining a metric, said determining step comprising;

hypothesizing which symbol was transmitted;

respreading the hypothesized symbol;

determining STAP weights based on the respread hypothesized symbol and the input signal vector;

applying a tap delay line to each signal vector component;

applying the STAP weights to each signal vector component, one per antenna;

summing the weighted signal vector components in a mathematical summation circuit;

despreading an output of the summation circuit and inputting the despread signal to a matched filter bank; and

generating a metric associated with the hypothesized symbol;

repeating the metric determining step for each of possible 64 Walsh symbols;

comparing each of the 64 metrics; and

determining, based on the comparison, the transmitted symbol.

53. A method in a combination system for enabling a receiver to receive input signals at varied power levels in the presence of interference wherein an input signal to said receiver is a vector comprised of one signal from each antenna in an antenna array of the receiver;

the method comprising the steps of;

receiving the input signal vector;

determining a metric, said determining step comprising;

hypothesizing which symbol was transmitted;

respreading the hypothesized symbol;

determining STAP weights based on the respread hypothesized symbol and the input signal vector;

despreading delayed signal vector components, one per antenna;

applying the STAP weights to each of the despread signal vector components;

summing the weighted signal vector components in a mathematical summation circuit; and

generating a metric associated with the hypothesized symbol;

repeating the metric determining step for each of possible 64 Walsh symbols;

comparing each of the 64 metrics; and

determining, based on the comparison, the transmitted symbol.

54-75. -75. (canceled)