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In many dynamic spectrum access networks, it is necessary for secondary users to monitor the frequency band in which they are communicating so that they can determine if the primary user has begun transmission. Traditional sensing methods require the transmitters of the secondary users to be silent while spectrum monitoring is performed. Statistics that are derived easily in a communications receiver...
Effective adaptation of error-control coding in a packet radio network requires certain statistics to be developed in the demodulator and decoder of the receiving radio during the reception of each packet. The statistics from one packet are employed to select the code for the next packet. The design and evaluation of cross-layer protocols that use such statistics typically require numerous simulations...
Demodulation of M-ary quadrature amplitude modulation (M-QAM) requires the receiver to estimate the phase and amplitude of the received signal. The demodulator performance is sensitive to errors in these estimates, and the sensitivity increases as M increases. We examine the effects of phase and amplitude errors on the performance of QAM communication systems with error-control coding and soft-decision...
Alternative protocols are presented for adapting the code from packet to packet in a mobile, wireless, ad hoc network that employs frequency hopping, coherent or noncoherent demodulation, and soft-decision decoding on channels with time-varying propagation loss and time-varying partial-band interference. The protocols can be employed with a wide range of codes and decoding algorithms. No channel measurements...
Communication devices that employ adaptive transmission protocols can exploit good channel conditions to increase throughput and compensate for poor channels to enhance survivability. We examine the performance of a protocol for the combined adaptation of the modulation, error-control-code, and transmitter power in high-rate direct-sequence spread-spectrum systems. The protocol requires only simple...
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