Iterative multi-stage detection technique for a diversity receiver having multiple antenna elements
View Patent ↗An iterative multistage detection system and method for orthogonally multiplexing K channels onto a signal processing chain using N orthogonal sequences of length N. The K channels include a first set of N channels and a second set of M channels (the M channels being separate and distinct from the N channels), where K=N+M. In a first iteration, interference from the first set of N channels imparted on the second set of M channels is removed from the multiplexed signal, thereby enabling the symbol values associated with the second set of M channels to be reliably estimated. In a second iteration, interference from the second set of M channels imparted on the first set of N channels is removed from the first set of N channels, thereby enabling the symbol values associated with the first set of N channels to be reliably estimated.
1. A method for separating K symbol streams, each of the K symbol streams being conveyed by K respective orthogonally spread channels in a receiver chain, the K channels including a first set of N channels and a second set of M channels, each of the N channels being spread according to a corresponding one of N orthogonal sequences and each of the M channels being spread according to one of the N orthogonal sequences, the method comprising:
despreading the first set of N channels so as to generate N separate channels;
detecting, from the N separate channels, a set of N symbols wherein each of the N symbols is conveyed by a corresponding one of the N channels;
generating a first interference signal due to the first set of N channels based upon the set of N symbols;
subtracting the interference signal from the second set of M channels;
despreading the second set of M channels so as to generate M separate channels;
detecting, from the M separate channels, a set of M symbols wherein each of the M symbols is conveyed by a corresponding one of the M channels; and
providing K separate symbols wherein the K separate symbols include the set of N symbols and the set of M symbols.
2. The method according to claim 1 , comprising canceling interference due to the first set of N channels from the second set of M channels.
3. The method according to claim 1 , comprising generating a set of N despread baseband signals from the first set of N channels.
4. The method according to claim 3 , comprising generating an interference signal which is a function of the generated N despread baseband signals.
5. The method according to claim 4 , comprising subtracting the generated interference signal from the generated N despread baseband signals.
6. The method according to claim 1 , comprising canceling interference due to the second set of M channels from the first set of N channels.
7. The method according to claim 6 , comprising generating a set of N despread baseband signals from the first set of N channels.
8. The method according to claim 7 , comprising generating a set of M despread baseband signals from the second set of M channels.
9. The method according to claim 8 , comprising generating an interference signal which is a function of the M despread baseband signals.
10. The method according to claim 9 , comprising subtracting the interference signal from each of the N despread baseband signals.
11. A system for separating K symbol streams, each of the K symbol streams being conveyed by K respective orthogonally spread channels in a receiver chain, the K channels including a first set of N channels and a second set of M channels, each of the N channels being spread according to a corresponding one of N orthogonal sequences and each of the M channels being spread according to one of the N orthogonal sequences, the system comprising:
one or more circuits that despreads the first set of N channels so as to generate N separate channels;
said one or more circuits detects, from the N separate channels, a set of N symbols wherein each of the N symbols is conveyed by a corresponding one of the N channels;
said one or more circuits generates a first interference signal due to the first set of N channels based upon the set of N symbols;
said one or more circuits subtracts the interference signal from the second set of M channels;
said one or more circuits despreads the second set of M channels so as to generate M separate channels;
said one or more circuits detects, from the M separate channels, a set of M symbols wherein each of the M symbols is conveyed by a corresponding one of the M channels; and
said one or more circuits provides K separate symbols wherein the K separate symbols include the set of N symbols and the set of M symbols.
12. The system according to claim 11 , wherein said one or more circuits cancels interference due to the first set of N channels from the second set of M channels.
13. The system according to claim 11 , wherein said one or more circuits generates a set of N despread baseband signals from the first set of N channels.
14. The system according to claim 13 , wherein said one or more circuits generates an interference signal which is a function of the generated N despread baseband signals.
15. The system according to claim 14 , wherein said one or more circuits subtracts the generated interference signal from the generated N despread baseband signals.
16. The system according to claim 11 , wherein said one or more circuits cancels interference due to the second set of M channels from the first set of N channels.
17. The system according to claim 16 , wherein said one or more circuits generates a set of N despread baseband signals from the first set of N channels.
18. The system according to claim 17 , wherein said one or more circuits generates a set of M despread baseband signals from the second set of M channels.
19. The system according to claim 18 , wherein said one or more circuits generates an interference signal which is a function of the M despread baseband signals.
20. The system according to claim 19 , wherein said one or more circuits subtracts the interference signal from each of the N despread baseband signals.
21. A system for separating K symbol streams, each of the K symbol streams being conveyed by K respective orthogonally spread channels in a receiver chain, the K channels including a first set of N channels and a second set of M channels, each of the N channels being spread according to a corresponding one of N orthogonal sequences and each of the M channels being spread according to one of the N orthogonal sequences, the system comprising:
at least one processor that despreads the first set of N channels so as to generate N separate channels;
said at least one processor detects, from the N separate channels, a set of N symbols wherein each of the N symbols is conveyed by a corresponding one of the N channels;
said at least one processor generates a first interference signal due to the first set of N channels based upon the set of N symbols;
said at least one processor subtracts the interference signal from the second set of M channels
said at least one processor despreads the second set of M channels so as to generate M separate channels;
said at least one processor detects, from the M separate channels, a set of M symbols wherein each of the M symbols is conveyed by a corresponding one of the M channels; and
said at least one processor provides K separate symbols wherein the K separate symbols include the set of N symbols and the set of M symbols.
22. The system according to claim 21 , wherein said at least one processor cancels interference due to the first set of N channels from the second set of M channels.
23. The system according to claim 21 , wherein said at least one processor generates a set of N despread baseband signals from the first set of N channels.
24. The system according to claim 23 , wherein said at least one processor generates an interference signal which is a function of the generated N despread baseband signals.
25. The system according to claim 24 , wherein said at least one processor subtracts the generated interference signal from the generated N despread baseband signals.
26. The system according to claim 21 , wherein said at least one processor cancels interference due to the second set of M channels from the first set of N channels.
27. The system according to claim 26 , wherein said at least one processor generates a set of N despread baseband signals from the first set of N channels.
28. The system according to claim 27 , wherein said at least one processor generates a set of M despread baseband signals from the second set of M channels.
29. The system according to claim 28 , wherein said at least one processor generates an interference signal which is a function of the M despread baseband signals.
30. The system according to claim 29 , wherein said at least one processor subtracts the interference signal from each of the N despread baseband signals.