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Distributed transmission involving multiple uncoordinated transmitters has become a popular subject in wireless communications, such as cooperative transmissions, relaying, distributed MIMO, network coding, multi-access and multiuser detection. One of the major challenges for implementing distributed transmissions is the difficulty of synchronizing carrier frequency and timing of the distributed transmitters...
One of the major challenges to cognitive radios is the synchronization of distributed radios onto the same spectrum white spaces which vary in time and space. In this paper, we propose a frequency-hopping spread spectrum transmission scheme which works reliably without any a priori handshaking assumption. Each cognitive radio independently detects white spaces, and then selects one of them to transmit...
Cognitive radio is a desirable technique for secondary users to utilize the spectrum gray space. In order to avoid intolerable interference to primary users, the transmission power of cognitive radios must be carefully managed. In this paper, we analyze the sum transmission power of a group of randomly distributed but fully cooperated secondary transmitters in a network consisting of one primary transmitter...
In ultra-wide bandwidth (UWB) communication systems, dense multipath and severe multiuser interference (MUI) make the receiver high in hardware complexity and power consumption. It is desirable to shift the computation-demanding work to users with plentiful power and computational resources. We propose two prefiltering schemes which combat the MUI and multipath effects in the transmitter, so that...
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