Method and apparatus for joint detection of data in a direct sequence spread spectrum communications system

• US 6,339,612 B1
• Filed: 02/09/1998
• Issued: 01/15/2002
• Est. Priority Date: 02/09/1998
• Status: Expired due to Term

• Current Assignee: Google Technology Holdings LLC (Alphabet Inc.)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Stewart, Kenneth A., Qiao, Yi
• Primary Examiner(s): Chin, Stephen
• Assistant Examiner(s): Liu, Shuwang
• Application Number:
  US09/020,970
• Time in Patent Office: 1,436 Days
• Field of Search: 375/343, 375/346, 375/368, 375/295, 375/233, 375/140, 375/150, 375/149, 370/330, 370/323, 370/342
• US Class Current: 375/140
• CPC Class Codes: H04B 1/7105 Joint detection techniques, e.g. linear detectors
• CPC Class Codes: H04B 7/0854 using error minimizing algorithms, e.g. minimum mean squared error [MMSE], "cross-correlation" or matrix inversion

Abstract

Joint detection of data signals occurs in a code division, multiple access (CDMA) communication system as follows: A digital signal processor (315) first extracts a midamble portion of transmitted signal vectors and generates an estimate of the channel response corresponding to each user-antenna pair using a channel estimator (401). In the preferred embodiment, each user'"'"'s transmission within the communication system comprises either the type-1 or type-2 burst with varying midamble and guard period durations. Next, a convolution processor (402) forms the convolution of the user signature sequence with the channel impulse response estimate associated with each user and each of the antennas (308)-(310). A detector (403) utilizes the set of vectors and creates a set of sub-system matrices and solves the sub-system matrices to extract symbol information from an individual remote unit'"'"'s transmission. Finally, the detector (403) outputs symbol information for subsequent infrastructure processing.

Claims

1. An apparatus for detection of data signals from a transmitted signal in a Time-Division, Code-Division Multiple Access (TD-CDMA) communication system, the transmitted signal comprising a plurality of time overlapping coded signals transmitted from individual remote units, each coded signal transmitted within the same timeslot and distinguishable only by a specific encoding, the apparatus comprising:

a channel estimator having the transmitted signal as an input and outputting a midamble portion of the transmitted signal;

a convolutional coder having the midamble portion of the transmitted signal as an input and outputting a set of vectors representative of the transmitted signal; and

a decoder having the set of vectors as an input and outputting symbol information for an individual remote unit'"'"'s transmission, the symbol information being a solution to a set of sub-system matrices derived from a system matrix via a recursive procedure, wherein the recursive procedure propagates estimated data symbols in only the forward or both the forward and backward directions as a means of refining the symbol information;

wherein the system matrix is represented by the equation $u_n=\{\begin{array}{cc}{A}_1<br><br>d_n^{+}<br><br>w_n,& n=1,\mathrm{\cdots <br><br>}<br><br>\text{\hspace{1em}<br><br>},N-1\\ A_{B,1}<br><br>d_n^{+}<br><br>w_n,& n=N\end{array}$

 

wherein u_n is a vector comprising the received signals and some prior estimated data symbols A₁ and A_B,1 is are subsystem matrices, w_n is noise, and d_n are data symbols to be estimated.

2. In a communication system utilizing Direct-Sequence, Spread-Spectrum (DS-SS) techniques for the transmission of signals, a method for determining an individual user'"'"'s transmitted data from a received signal, the method comprising the steps of:

representing the received signal as a system matrix, wherein the system matrix is represented by the equation $u_n=\{\begin{array}{cc}{A}_1<br><br>d_n+w_n,& n=1,\mathrm{\dots <br><br>}<br><br>\text{\hspace{1em}<br><br>},N-1\\ A_{B,1}<br><br>d_n+w_n,& n=N\end{array}$

 

wherein u_n is a vector comprising the received signals and some prior estimated data symbols A₁ and A_B,1 is are subsystem matrices, w_n is noise, and d_n are data symbols to be estimated;

partitioning the system matrix into sub-matrices to form a plurality of sub-system matrices;

solving the plurality of sub-system matrices via a recursive forward or forward-backward procedure to determine the individual user'"'"'s data from the transmitted signal; and

transmitting the individual user'"'"'s data to infrastructure equipment for further processing of the user'"'"'s data.

3. In a Time-Division, Code-Division Multiple Access (TD-CDMA) communication system, where a transmitted signal comprises a plurality of time overlapping coded signals transmitted from individual remote units, each coded signal transmitted within a same timeslot and distinguishable only by a specific encoding, a method for determining an individual user'"'"'s transmitted data from a received signal, the method comprising the steps of:

extracting a midamble portion of the transmitted signal;

convolutionally encoding the midamble portion of the transmitted signal to produce a set of vectors representative of the transmitted signal;

representing the convolutionally encoded midamble portion of the transmitted signal as a system matrix wherein the system matrix is represented by the equation $u_n=\{\begin{array}{cc}{A}_1<br><br>d_n+w_n,& n=1,\mathrm{\dots <br><br>}<br><br>\text{\hspace{1em}<br><br>},N-1\\ A_{B,1}<br><br>d_n+w_n,& n=N\end{array}$

 

wherein u_n is a vector comprising the received signals and some prior estimated data symbols A₁ and A_B,1 is are subsystem matrices, w_n is noise, and d_n are data symbols to be estimated;

partitioning the system matrix into sub-matrices forming a plurality of sub-system matrices;

solving the plurality of sub-system matrices via a recursive forward or forward-backward procedure to determine the individual user'"'"'s data from the transmitted signal; and

transmitting the individual user'"'"'s data to infrastructure equipment for further processing of the user'"'"'s data.