Low complexity maximum likelihood detection of concatenated space codes for wireless applications

• US 8,351,545 B2
• Filed: 12/30/2009
• Issued: 01/08/2013
• Est. Priority Date: 10/31/1997
• Status: Expired due to Fees

• Current Assignee: AT&T Mobility II LLC (AT&T, Inc.)
• Original Assignee: AT&T Mobility II LLC (AT&T, Inc.)
• Inventors: Alamouti, Siavash, Poon, Patrick, Tarokh, Vahid
• Primary Examiner(s): DEPPE, BETSY LEE
• Application Number:
  US12/650,007
• Publication Number:
  US 20100119006A1
• Time in Patent Office: 1,105 Days
• Field of Search: 375/265, 375/267, 375/299, 375/341, 375/347, 714/792, 714/795
• US Class Current: 375/299
• CPC Class Codes: H03M 13/256 with trellis coding, e.g. with convolutional codes and TCM
• CPC Class Codes: H04B 1/0475 with means for limiting noise, interference or distortion H04B1/0483 takes precedence
• CPC Class Codes: H04B 7/0669 using different channel coding between antennas space-time coding H04L1/0618
• CPC Class Codes: H04B 7/0697 using spatial multiplexing
• CPC Class Codes: H04L 1/0054 Maximum-likelihood or sequential decoding, e.g. Viterbi, Fano, ZJ algorithms
• CPC Class Codes: H04L 1/0057 Block codes H04L1/0061, H04L1/0064 take precedence
• CPC Class Codes: H04L 1/0059 Convolutional codes
• CPC Class Codes: H04L 1/006 Trellis-coded modulation
• CPC Class Codes: H04L 1/0065 Serial concatenated codes
• CPC Class Codes: H04L 1/0618 Space-time coding
• CPC Class Codes: H04L 1/0625 Transmitter arrangements
• CPC Class Codes: H04L 1/0631 Receiver arrangements
• CPC Class Codes: H04L 25/03178 Arrangements involving sequence estimation techniques
• CPC Class Codes: H04L 25/03331 Arrangements for the joint estimation of multiple sequences

Abstract

Good transmission characteristics are achieved in the presence of fading with a transmitter that employs a trellis coder followed by a block coder. Correspondingly, the receiver comprises a Viterbi decoder followed by a block decoder. Advantageously, the block coder and decoder employ time-space diversity coding which, illustratively, employs two transmitter antennas and one receiver antenna.

Claims

1. An apparatus comprising:

a trellis encoder, wherein the trellis encoder generates a first symbol and a second symbol; and

a block encoder responsive to the trellis encoder and adapted to feed a plurality of antennas, wherein the block encoder generates a block including the first symbol, the second symbol, a third symbol generated using a negative complex conjugation of the second symbol, and a fourth symbol generated using a complex conjugation of the first symbol.

2. The apparatus as recited in claim 1 further comprising the plurality of antennas.

3. In a transmitter, a method for linking trellis codes with block codes, the method comprising:

trellis encoding received data to generate a first symbol and a second symbol;

block encoding the first and second symbols to generate a block of symbols that includes the first and second symbols, the block encoding including generating a third symbol for the block of symbols using a negative complex conjugation of the second symbol, and generating a fourth symbol for the block of symbols using a complex conjugation of the first symbol; and

supplying the block of symbols for transmission over a plurality of antennas.

4. The method as recited in claim 3 wherein the plurality of antennas comprises a first and a second antenna.

5. The method as recited in claim 3 further comprising transmitting the block of symbols over the first and the second antenna by transmitting the first and second symbols over the first and second antennas, respectively, during a first time period, and transmitting the third and fourth symbols over the first and second antennas, respectively, during a second time period.

6. A receiver comprising:

a receive antenna;

a space block combiner configured to combine signals transmitted from at least a first and a second transmit antenna and received at the receive antenna at a first and second time interval, the received signals including a first signal received at the first time interval, the first signal including a first symbol and a second symbol transmitted from the first and second transmit antennas, respectively, and the received signals including a second signal received at the second time interval, the second signal including a negative complex conjugate of the second symbol and a complex conjugate of the first symbol, transmitted from the first and second transmit antennas, respectively; and

a Viterbi decoder responsive to output signals of the space block combiner to output estimates of transmitted symbols.

7. The receiver as recited in claim 6 wherein the space block combiner combines a frame of received symbols, wherein the frame comprises m symbols received over each of the first and second time intervals.

8. The receiver as recited in claim 7 wherein m=2.

9. The receiver as recited in claim 6 wherein received signals r₀ and r₁ received over the first and second time intervals by the receive antenna, respectively, are r₀(t)=h₀s₀+h₁s₁+n₀ and r₁(t)=h₁s₀*−

h₀s₁*+n₁, where h₀ represents characteristics of a first channel from a first transmit antenna to the receive antenna, h₁ represents characteristics of a second channel from a second transmit antenna to the receive antenna, n₀ is the received noise at the first time interval, and n₁ is the received noise at the second time interval, s₀ and s₁ are the first and second symbols respectively transmitted from the first and second transmit antennas and −

s₁* and s_o* are the negative complex conjugate and the complex conjugate respectively transmitted from the first and second transmit antennas.

10. The receiver as recited in claim 9 wherein the combiner generates signals {tilde over (s)}₀={tilde over (h)}₀*r₀+{tilde over (h)}₁r₁* and {tilde over (s)}₁={tilde over (h)}₁* r₀−

{tilde over (h)}₀r₁*, where {tilde over (h)}₀ and {tilde over (h)}₁ are estimates of h₀ and h₁, respectively.

11. The receiver as recited in claim 9 wherein the Viterbi decoder develops a metric M(s₀,s_i)=d²[{tilde over (s)}₀,(|{tilde over (h)}₀|²+|{tilde over (h)}₁|²)s_i] for the hypothesized branch symbol s_i corresponding to the symbol s₀, where {tilde over (h)}₀ {tilde over (h)}₁ are estimates of h₀ and h₁, respectively and d² represents the squared Euclidean distance.

12. The receiver as recited in claim 6 wherein the Viterbi decoder builds a metric M[(s₀,s₁),(s_i,s_j)]=d²(r₀, {tilde over (h)}₀s_i+{tilde over (h)}₁s_j)+d²(r₁{tilde over (h)}₁s_i*−

{tilde over (h)}₀s_j*), wherein s_i is a hypothesized signal at the first time interval, S_j is a hypothesized signal at the second time interval, s₀ is a transmitted symbol at the first time interval, s_j is a transmitted symbol at the second time interval, where {tilde over (h)}₀ is an estimate of channel characteristics between the first transmit antenna that transmits symbol s₀ and the receive antenna, and {tilde over (h)}₁ is an estimate of channel characteristics between the second transmit antenna that transmits symbol s₁ and the receive antenna, where d² represents the squared Euclidean distance, r₀ is the signal received at the first time interval and r₁ is the signal received at the second time interval.