Method and apparatus for using multi-dimensional trellis codes over multi-path channels
View Patent ↗An approach for using multi-dimensional trellis codes in a communication system over a multi-path channel, such as a wireless local area network, is provided. In this approach, the received signal is equalized and decoded by a joint decision feedback equalizer and multi-dimensional trellis decoder that is based on a multi-stage trellis diagram. The multi-stage trellis diagram used by the decoder comprises at least two stages of state transitions for each stage of state transitions in the encoder. The multi-stage trellis diagram makes the joint decision feedback equalizer and multi-dimensional trellis decoder possible, which in turn makes the use of multi-dimensional trellis codes in such a communication system advantageous.
1. A method of using an N-dimensional trellis code to communicate data over a multi-path channel, comprising the steps of:
(a) encoding said data into a sequence of N-dimensional signal points, each signal point being a concatenation of N/M M-dimensional symbols with N/M being an integer greater than one, each symbol being selected from an M-dimensional constellation;
(b) modulating and transmitting said N/M M-dimensional symbols of an N-dimensional signal point to said multi-path channel in at least two different signaling intervals;
(c) receiving channel-impaired N/M M-dimensional symbols; and
(d) removing interference on a current received M-dimensional symbol using a decision on a past received M-dimensional symbol.
2. The method of claim 1 , wherein said step (d) includes using at least one decision feedback equalizer to remove said interference.
3. The method of claim 1 , wherein said step (d) includes using a decoding process to recover said data.
4. The method of claim 3 , wherein said decision on a past received M-dimensional symbol in step (d) is provided by said decoding process.
5. The method of claim 4 , wherein said current and past M-dimensional symbols belong to a same N-dimensional signal point.
6. The method of claim 3 , wherein said encoding in step (a) includes using a finite state machine that goes from a current state to a next state while generating an N-dimensional signal point, and said decoding process is based on a multi-stage trellis diagram that goes from said current state to at least one intermediate state before reaching said next state.
7. The method of claim 1 , wherein N equals to 4 and M equals to 2.
8. The method of claim 1 , wherein said M-dimensional constellation in step (a) is a 2-dimensional 4-PSK.
9. The method of claim 1 , wherein said M-dimensional constellation in step (a) is a 2-dimensional 8-PSK.
10. The method of claim 1 , wherein said M-dimensional constellation in step (a) is a 2-dimensional multiple-amplitude QAM constellation.
11. The method of claim 1 , wherein N equals to 2 and M equals to 1.
12. A method for receiving signal and recovering data from a communication channel, comprising the steps of:
(a) receiving channel-impaired M-dimensional symbols of a sequence of N-dimensional signal points from said communication channel, each M-dimensional symbol being selected from an M-dimensional constellation, each N-dimensional signal point being a concatenation of N/M M-dimensional symbols with N/M being an integer greater than one, said N-dimensional signal point being generated by an N-dimensional trellis encoder while said encoder goes from a current state to a next state; and
(b) decoding said channel-impaired M-dimensional symbols to recover said data using a decoding process, wherein said decoding process is based on a multi-stage trellis diagram that goes from said current state to at least one intermediate state before reaching said next state.
13. The method of claim 12 , wherein said communication channel is a multi-path channel.
14. The method of claim 13 , wherein said step (b) further includes using at least one decision feedback equalizer that uses a decision on a past received M-dimensional symbol to remove interference on a current received M-dimensional symbol.
15. The method of claim 14 , wherein said decision is provided by said decoding process.
16. The method of claim 15 , wherein said current and past M-dimensional symbols belong to a same N-dimensional signal point.
17. A method for receiving signal and recovering data from a communication channel, comprising the steps of:
(a) receiving channel-impaired M-dimensional symbols of a sequence of N-dimensional signal points from said communication channel, each M-dimensional symbol being selected from an M-dimensional constellation, each N-dimensional signal point being a concatenation of N/M M-dimensional symbols with N/M being an integer greater than one, said N-dimensional signal point being generated by an N-dimensional trellis encoder; and
(b)decoding said channel-impaired M-dimensional symbols to recover said data using a decoding process, said decoding process maintaining a plurality of surviving paths, each path being a sequence of tentative decisions on a plurality of past received M-dimensional symbols, wherein said decoding process updates said surviving paths more than once upon the reception of N/M channel-impaired M-dimensional symbols of an N-dimensional signal point.
18. The method of claim 17 , wherein each updating of surviving paths is based on a stage of a multi-stage trellis diagram that corresponds to an M-dimensional symbol of an N-dimensional signal point.
19. The method of claim 17 , wherein said communication channel is a multi-path channel.
20. The method of claim 19 , wherein said step (b) further includes removing interference on a current received M-dimensional symbol by using a plurality of decisions on a past received M-dimensional symbol in a plurality of decision feedback equalizers, each surviving path providing a decision to an associated decision feedback equalizer.
21. The method of claim 20 , wherein said current and past M-dimensional symbols belong to a same N-dimensional signal point.
22. An apparatus of using an N-dimensional trellis code to communicate data over a multi-path channel, comprising:
an N-dimensional trellis encoder for encoding said data into a sequence of N-dimensional signal points, each signal point being a concatenation of N/M M-dimensional symbols with N/M being an integer greater than one, each symbol being selected from an M-dimensional constellation;
a transmitting unit for modulating and transmitting said N/M M-dimensional symbols of an N-dimensional signal point to said multi-path channel in at least two different signaling intervals;
a receiving unit for receiving channel-impaired N/M M-dimensional symbols; and
an intersymbol interference remover for removing interference on a current received M-dimensional symbol using a decision on a past received M-dimensional symbol.
23. The apparatus of claim 22 , wherein said remover includes at least one decision feedback equalizer to remove said interference.
24. The apparatus of claim 22 , wherein said remover includes a decoder to recover said data.
25. The apparatus of claim 24 , wherein said decision on a past received M-dimensional symbol is provided by said decoder.
26. The apparatus of claim 25 , wherein said current and past M-dimensional symbols belong to a same N-dimensional signal point.
27. The apparatus of claim 24 , wherein said encoder includes a finite state machine that goes from a current state to a next state while generating an N-dimensional signal point, and said decoder is based on a multi-stage trellis diagram that goes from said current state to at least one intermediate state before reaching said next state.
28. The apparatus of claim 22 , wherein N equals to 4 and M equals to 2.
29. The apparatus of claim 22 , wherein said M-dimensional constellation is a 2-dimensional 4-PSK.
30. The apparatus of claim 22 , wherein said M-dimensional constellation is a 2-dimensional 8-PSK.
31. The apparatus of claim 22 , wherein said M-dimensional constellation is a 2-dimensional multiple-amplitude QAM constellation.
32. The apparatus of claim 22 , wherein N equals to 2 and M equals to 1.
33. An apparatus for receiving signal and recovering data from a communication channel, comprising:
a receiving unit for receiving channel-impaired M-dimensional symbols of a sequence of N-dimensional signal points from said communication channel, each M-dimensional symbol being selected from an M-dimensional constellation, each N-dimensional signal point being a concatenation of N/M M-dimensional symbols with N/M being an integer greater than one, said N-dimensional signal point being generated by an N-dimensional trellis encoder while said encoder goes from a current state to a next state; and
a decoder for decoding said channel-impaired M-dimensional symbols to recover said data, wherein said decoder is based on a multi-stage trellis diagram that goes from said current state to at least one intermediate state before reaching said next state.
34. The apparatus of claim 33 , wherein said communication channel is a multi-path channel.
35. The apparatus of claim 34 , wherein said decoder further includes at least one decision feedback equalizer that uses a decision on a past received M-dimensional symbol to remove interference on a current received M-dimensional symbol.
36. The apparatus of claim 35 , wherein said decision is obtained from said decoder.
37. The apparatus of claim 36 , wherein said current and past M-dimensional symbols belong to a same N-dimensional signal point.
38. An apparatus for using a mult-dimensional trellis code to transmit data in a wireless local area network, comprising an encoder that encodes said data into a sequence of mult-dimensional signal points, each signal point having at least three coordinates.
39. The apparatus of claim 38 , wherein said trellis code is four-dimensional.
40. The apparatus of claim 38 , wherein said transmitting includes a modulator for modulating a single carrier with said coordinates.
41. An apparatus for receiving signal and recovering data from a communication channel, comprising:
a receiving unit for receiving channel-impaired M-dimensional symbols of a sequence of N-dimensional signal points from said communication channel, each M-dimensional symbol being selected from an M-dimensional constellation, each N-dimensional signal point being a concatenation of N/M M-dimensional symbols with N/M being an integer greater than one, said N-dimensional signal point being generated by an N-dimensional trellis encoder; and
a decoder for decoding said channel-impaired M-dimensional symbols to recover said data, said decoder maintaining a plurality of surviving paths, each path being a sequence of tentative decisions on a plurality of past received M-dimensional symbols, wherein said decoder updates said surviving paths more than once upon the reception of N/M channel-impaired M-dimensional symbols of an N-dimensional signal point.
42. The apparatus of claim 41 , wherein each updating of surviving paths is based on a stage of a multi-stage trellis diagram that corresponds to an M-dimensional symbol of an N-dimensional signal point.
43. The apparatus of claim 41 , wherein said communication channel is a multi-path channel.
44. The apparatus of claim 43 , wherein said decoder further includes an intersymbol interference remover that removes interference on a current received M-dimensional symbol by using a plurality of decisions on a past received M-dimensional symbol in a plurality of decision feedback equalizers, each surviving path providing a decision to an associated decision feedback equalizer.
45. The apparatus of claim 44 , wherein said current and past M-dimensional symbols belong to a same N-dimensional signal point.