Pulse or digital communications – Spread spectrum – Direct sequence
Reexamination Certificate
2000-08-14
2004-12-28
Le, Amanda T. (Department: 2634)
Pulse or digital communications
Spread spectrum
Direct sequence
C375S152000
Reexamination Certificate
active
06836507
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to communications systems, and more particularly to an architecture for transforming a software defined radio having independently operated channels into a fully shared multi-channel software defined radio.
2. Description of Related Art
A coherent digital communications system typically requires that signal phase, symbol and frame synchronization be performed at the system receiver, as the phase of the transmitted carrier signal must be accurately reproduced at the receiver. In addition, the receiver must have the capability of determining the timing boundaries of the transmitted symbols. This capability is referred to as symbol synchronization.
In wireless digital radios having multi-element antenna arrays, multi-path fading often significantly degrades communications system performance. The effects of fading can be countered through spatial diversity techniques in which antenna elements are separated as a function of signal wavelength so that associated Rayleigh fading is independent at each antenna. Consequently, when a deep Rayleigh fade occurs at one of the antennas, other antennas in the array will likely have corresponding stronger signal reception.
Current spatial diversity techniques attempt to overcome the effects of signal fading by estimating frequency offset and carrier phases and attempt to determine symbol timing. However, these techniques typically add a significant amount of complexity to the radios. In addition, in a radio such as a software defined radio in which digital signals are communicated over wireless channels, a symbol synchronization technique must be robust enough so that the bit error rate (BER) performance of the received data is not degraded. The robustness of the synchronization technique is important, as such systems are often utilized in hostile environments in which interferers and jammers weaken the capability of the radio to synchronize with the desired signal, and in which frequency-hopped signals require the radio to resynchronize after each hop. Because current spatial diversity techniques assume signal synchronization, the techniques therefore often do not provide a symbol synchronization technique that is robust enough for problematic channel operating conditions such as those described above.
REFERENCES:
patent: 6282229 (2001-08-01), Aoyama
patent: 6377613 (2002-04-01), Kawabe et al.
patent: 2001/0036223 (2001-11-01), Webster et al.
“Blind Algorithms for Joint Clock Recovery and Baseband Combining in Digital Radio”, F. Guglielmi et al., Radio Relay Systems Conference, Publication No. 386, Oct. 1993, pp. 279-286.
“Combined Equalization, Decoding, and Antenna Diversity Combining for Mobile/Personal Digital Radio Transmission Using Feedforward Synchronization”, S. A. Fachtel et al., Proceedings of Vehicular Technology Conference, 43rdIEEE, 1993, pp. 633-636.
“Performance of Nonlinear Receivers in Mobile Communications”, A.R.S. Bahai, Proceedings of ICC, vol. 2, 1993, pp. 1209-1212.
Digital Communications,B. Sklar, Fundamentals and Applications, Prentice Hall, 1988. (not included).
Digital Communications,J.G. Proakis, 3rdEd. McGraw-Hill, 1995. (not included).
“Blind Adaptation Using Maximin Algorithm”, D. Torrieri et al., Asilomar Conference on Signals, Systems and Computers, Nov. 1993, pp. 638-642.
Digital Communication Receivers,H. Meyr et al., John Wiley & Sons, 1998. (not included).
“Joint Blind Equalization, Carrier Recovery, and Timing Recovery for 64-QAM and 128-QAM Signal Constellations”, N.K. Jablon, Proceedings of ICC, vol. 2, 1989, pp. 1043-1049.
“Digital Communications in Fading Channels”, Mission Research Corporation, Final Report PL-TR-92-1024, Mar. 1993. (not included).
“Real-time Implementation of a Reconfigurable IMT-2000 Base Station Channel Modem”, D. Murotake et al., Software and DPS in Radio, IEEE Communications Magazine, Feb. 2000, pp. 148-152.
“An ADEPT Performance Model of the Mercury RACEway Crossbar Interconnection Network”, G. Han et al., Proceedings of 6THAnnual Conference on Parallel Interconnects (PI'99), pp. 83-90.
Bergstrom Chad S.
Chuprun Jeffery Scott
Gifford Carl Steven
Kleider John Eric
General Dynamics Decision Systems, Inc.
Jenner & Block LLP
Le Amanda T.
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