Iterative multi-stage detection technique for a diversity receiver having multiple antenna elements
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. An apparatus for receiving a signal, comprising:
K antenna elements, wherein the K antenna elements are arranged to receive one of a corresponding K replicas of the signal and thereby generate K received signal replicas;
a signal processing chain;
a first multiplexer configured to receive N of the K received signal replicas and generate a first set of N channel signals, wherein each of the N channel signals is spread according to a corresponding one of N orthogonal sequences and corresponds to one of the N received signal replicas;
a second multiplexer configured to receive M of the K received signal replicas and generate a second set of M channel signals, wherein each of the M channel signals is spread according to one of the N orthogonal sequences and corresponds to one of the M received signal replicas;
a summing portion coupled between the signal processing chain and the first and second multiplexers, wherein the summing portion is configured to combine the first set of N channel signals and the second set of M channel signals into a multiplexed signal and provide the multiplexed signal to the signal processing chain;
a downconversion module configured to downconvert, within the signal processing chain, the multiplexed signal to a baseband multiplexed signal; and
a signal recovery module coupled to the signal processing chain, wherein the signal recovery module is configured to receive the baseband multiplexed signal and provide K separate signals from the baseband multiplexed signal, wherein each of the K separate signals corresponds to one of the K replicas of the signal.
2. The apparatus of claim 1 , wherein the first multiplexer comprises:
a first spreading module coupled to N of the K antenna elements, wherein the first spreading module is configured to receive N of the K received signal replicas and orthogonally spread each of the N received signal replicas with a corresponding one of the N orthogonal sequences so as to generate a set of N spread signals
a first summing module coupled to the first spreading module wherein the first summing module is configured to combine the set of N spread signals so as to generate a first composite signal; and
a first scrambling portion coupled to the first summing module, wherein the first scrambling portion is configured to generate the first set of N channel signals by scrambling the first composite signal.
3. The apparatus of claim 2 , wherein the second multiplexer comprises:
a second spreading module coupled to M of the K antenna elements, wherein the second spreading module is configured to receive M of the K received signal replicas and orthogonally spread each of the M received signal replicas with at least one of the N orthogonal sequences so as to be capable of generating a set of M spread signals;
a second summing module coupled to the second spreading module wherein the second summing module is configured to combine the set of M spread signals so as to be capable of generating a second composite signal; and
a second scrambling portion coupled to the second summing module, wherein the second scrambling portion is configured to generate the second set of M channel signals by scrambling the second composite signal.
4. The apparatus of claim 1 , wherein the signal recovery module comprises:
an N channel recovery portion configured to provide N separate signals from the baseband multiplexed signal, each of the N separate signals corresponding to one of the N received signal replicas; and
an M channel recovery portion coupled to the N channel recovery portion, wherein the M channel recovery portion is configured to provide M separate signals from the baseband multiplexed signal, each of the M separate signals corresponding to one of the M received signal replicas,
wherein the K separate signals include the N separate signals and the M separate signals.
5. The apparatus of claim 4 , wherein the N channel recovery portion is configured to provide an interference signal to the M channel recovery portion, wherein the interference signal is an estimate of interference the first set of N channel signals impart upon the second set of M channel signals, and wherein the M channel recovery portion is configured to subtract the interference signal from the baseband multiplexed signal before providing the M separate signals.
6. The apparatus of claim 4 , wherein the M channel recovery portion is configured to provide an interference signal to the N channel recovery portion, wherein the interference signal is an estimate of interference the second set of M channel signals impart upon the first set of N channel signals, and wherein the N channel recovery portion is configured to generate N despread baseband signals from the baseband multiplexed signal and subtract the interference signal from at least one of the N despread baseband signals before providing the N separate signals.
7. The apparatus of claim 4 , wherein the N channel recovery portion comprises:
a first despreading module configured to despread the first set of N channel signals so as to be capable of generating N despread baseband signals; and
a set of N threshold detectors, wherein each of the N threshold detectors is coupled to the first despreading module so as to receive a corresponding one of the N despread baseband signals, wherein each of the N threshold detectors provides a symbol estimate for a corresponding one of the N separate signals so as to generate N symbol estimates.
8. The apparatus of claim 7 , wherein the N channel recovery portion comprises:
a first respreading portion coupled to the set of N threshold detectors, wherein the first respreading portion is configured to receive the N symbol estimates and spread each of the N symbol estimates according to a corresponding one of the N orthogonal sequences so as to generate a first set of N spread symbol estimates;
a first baseband summing portion coupled to the first respreading portion, wherein the first baseband summing portion is configured to combine the N spread symbol estimates so as to be capable of generating a first baseband composite signal; and
a first baseband scrambling portion coupled to the first baseband summing portion, wherein the first baseband scrambling portion is configured to receive the first baseband composite signal and scramble the first baseband composite signal so as to be capable of generating an interference signal,
wherein the interference signal is an estimate of the interference from the first set of N channel signals imparted upon the second set of M channel signals.
9. The apparatus of claim 8 , wherein the M channel recovery portion comprises:
a difference element coupled between the downconversion module and the first baseband scrambling portion, wherein the difference element is configured receive the interference signal from the first baseband scrambling portion and the baseband multiplexed signal from the downconversion module, wherein the difference element is configured to subtract the interference signal from the baseband multiplexed signal so as to be capable of removing interference that the first set of N channel signals imparts upon the second set of M channel signals.
10. The apparatus of claim 1 , wherein the signal complies with a communication protocol selected from the group consisting of: orthogonal frequency division multiplexing (OFDM), time division multiple access (TDMA), code division multiple access (CDMA), gaussian minimum shift keying (GMSK), complementary code keying (CCK), quadrature phase shift keying (QPSK), frequency shift keying (FSK), phase shift keying (PSK), and quadrature amplitude modulation (QAM).
11. A system for receiving a signal using K antenna elements, the system comprising:
at least one processor that receives, via the K antenna elements, one of a corresponding K replicas of the signal and thereby generating K received signal replicas;
said at least one processor receives N of the K received signal replicas and generating of a first set of N channel signals, wherein each of the N channel signals is spread according to a corresponding one of N orthogonal sequences and corresponds to one of the N received signal replicas;
said at least one processor receives M of the K received signal replicas and generates a second set of M channel signals, wherein each of the M channel signals is spread according to one of the N orthogonal sequences and corresponds to one of the M received signal replicas;
said at least one processor combines the first set of N channel signals and the second set of M channel signals into a multiplexed signal, and provides the multiplexed signal to the signal processing chain;
said at least one processor downconverts the multiplexed signal to a baseband multiplexed signal; and
said at least one processor receives the baseband multiplexed signal and providing of K separate signals from the baseband multiplexed signal, wherein each of the K separate signals corresponds to one of the K replicas of the signal.
12. The system of claim 11 , wherein said at least one processor:
receives N of the K received signal replicas and orthogonally spreading each of the N received signal replicas with a corresponding one of the N orthogonal sequences so as to generate a set of N spread signals;
combines the set of N spread signals so as to generate a first composite signal; and
generates the first set of N channel signals by scrambling the first composite signal.
13. The system of claim 12 , wherein said at least one processor:
receives M of the K received signal replicas and orthogonally spreading each of the M received signal replicas with at least one of the N orthogonal sequences so as to be capable of generating a set of M spread signals;
combines the set of M spread signals so as to be capable of generating a second composite signal; and
generates the second set of M channel signals by scrambling the second composite signal.
14. The system of claim 11 , wherein said at least one processor:
provides N separate signals from the baseband multiplexed signal, each of the N separate signals corresponding to one of the N received signal replicas; and
provides M separate signals from the baseband multiplexed signal, each of the M separate signals corresponding to one of the M received signal replicas,
wherein the K separate signals include the N separate signals and the M separate signals.
15. The system of claim 14 , wherein said at least one processor provides an interference signal with the M separate signals, wherein the interference signal is an estimate of interference the first set of N channel signals impart upon the second set of M channel signals, and wherein said at least one processor subtracts the interference signal from the baseband multiplexed signal before providing the M separate signals.
16. The system of claim 14 , wherein said at least one processor provides an interference signal with the N separate signals, wherein the interference signal is an estimate of interference the second set of M channel signals impart upon the first set of N channel signals, and wherein said at least one processor generates N despread baseband signals from the baseband multiplexed signal and subtracting the interference signal from at least one of the N despread baseband signals before providing the N separate signals.
17. The system of claim 14 , wherein said at least one processor:
despreads the first set of N channel signals so as to be capable of generating N despread baseband signals; and
receives a corresponding one of the N despread baseband signals, wherein each of the N threshold detectors provides a symbol estimate for a corresponding one of the N separate signals so as to generate N symbol estimates.
18. The system of claim 17 , wherein said at least one processor:
receives the N symbol estimates and spreading each of the N symbol estimates according to a corresponding one of the N orthogonal sequences so as to generate a first set of N spread symbol estimates;
combines the N spread symbol estimates so as to be capable of generating a first baseband composite signal; and
receives the first baseband composite signal and scrambling the first baseband composite signal so as to be capable of generating an interference signal,
wherein the interference signal is an estimate of the interference from the first set of N channel signals imparted upon the second set of M channel signals.
19. The system of claim 18 , wherein said at least one processor:
receives the interference signal and the baseband multiplexed signal, and subtracts the interference signal from the baseband multiplexed signal so as to be capable of removing interference that the first set of N channel signals imparts upon the second set of M channel signals.
20. The system of claim 11 , wherein the signal complies with a communication protocol selected from the group consisting of: orthogonal frequency division multiplexing (OFDM), time division multiple access (TDMA), code division multiple access (CDMA), gaussian minimum shift keying (GMSK), complementary code keying (CCK), quadrature phase shift keying (QPSK), frequency shift keying (FSK), phase shift keying (PSK), and quadrature amplitude modulation (QAM).
21. A system for receiving a signal using K antenna elements, the system comprising:
one or more circuits that receives, via the K antenna elements, one of a corresponding K replicas of the signal and thereby generating K received signal replicas;
said one or more circuits receives N of the K received signal replicas and generates a first set of N channel signals, wherein each of the N channel signals is spread according to a corresponding one of N orthogonal sequences and corresponds to one of the N received signal replicas;
said one or more circuits receives M of the K received signal replicas and generating of a second set of M channel signals, wherein each of the M channel signals is spread according to one of the N orthogonal sequences and corresponds to one of the M received signal replicas;
said one or more circuits combines the first set of N channel signals and the second set of M channel signals into a multiplexed signal, and provides the multiplexed signal to the signal processing chain;
said one or more circuits downconverts the multiplexed signal to a baseband multiplexed signal; and
said one or more circuits receives the baseband multiplexed signal and provides K separate signals from the baseband multiplexed signal, wherein each of the K separate signals corresponds to one of the K replicas of the signal.
22. The system of claim 21 , wherein said one or more circuits:
receives N of the K received signal replicas and orthogonally spreading each of the N received signal replicas with a corresponding one of the N orthogonal sequences so as to generate a set of N spread signals;
combines the set of N spread signals so as to generate a first composite signal; and
generates the first set of N channel signals by scrambling the first composite signal.
23. The system of claim 22 , wherein said one or more circuits:
receives M of the K received signal replicas and orthogonally spreading each of the M received signal replicas with at least one of the N orthogonal sequences so as to be capable of generating a set of M spread signals;
combines the set of M spread signals so as to be capable of generating a second composite signal; and
generates the second set of M channel signals by scrambling the second composite signal.
24. The system of claim 21 , wherein said one or more circuits:
provides N separate signals from the baseband multiplexed signal, each of the N separate signals corresponding to one of the N received signal replicas; and
provides M separate signals from the baseband multiplexed signal, each of the M separate signals corresponding to one of the M received signal replicas,
wherein the K separate signals include the N separate signals and the M separate signals.
25. The system of claim 24 , wherein said one or more circuits provides an interference signal with the M separate signals, wherein the interference signal is an estimate of interference the first set of N channel signals impart upon the second set of M channel signals, and wherein said one or more circuits subtracts the interference signal from the baseband multiplexed signal before providing the M separate signals.
26. The system of claim 24 , wherein said one or more circuits provides an interference signal with the N separate signals, wherein the interference signal is an estimate of interference the second set of M channel signals impart upon the first set of N channel signals, and wherein said one or more circuits generates N despread baseband signals from the baseband multiplexed signal and subtracting the interference signal from at least one of the N despread baseband signals before providing the N separate signals.
27. The system of claim 24 , wherein said one or more circuits:
despreads the first set of N channel signals so as to be capable of generating N despread baseband signals; and
receives a corresponding one of the N despread baseband signals, wherein each of the N threshold detectors provides a symbol estimate for a corresponding one of the N separate signals so as to generate N symbol estimates.
28. The system of claim 27 , wherein said one or more circuits:
receives the N symbol estimates and spreading each of the N symbol estimates according to a corresponding one of the N orthogonal sequences so as to generate a first set of N spread symbol estimates;
combines the N spread symbol estimates so as to be capable of generating a first baseband composite signal; and
receives the first baseband composite signal and scrambling the first baseband composite signal so as to be capable of generating an interference signal,
wherein the interference signal is an estimate of the interference from the first set of N channel signals imparted upon the second set of M channel signals.
29. The system of claim 28 , wherein said one or more circuits:
receives the interference signal and the baseband multiplexed signal, and subtracts the interference signal from the baseband multiplexed signal so as to be capable of removing interference that the first set of N channel signals imparts upon the second set of M channel signals.
30. The system of claim 21 , wherein the signal complies with a communication protocol selected from the group consisting of: orthogonal frequency division multiplexing (OFDM), time division multiple access (TDMA), code division multiple access (CDMA), gaussian minimum shift keying (GMSK), complementary code keying (CCK), quadrature phase shift keying (QPSK), frequency shift keying (FSK), phase shift keying (PSK), and quadrature amplitude modulation (QAM).