Title :
Capacity of Gaussian channels with duty cycle and power constraints
Author :
Zhang, Lei ; Guo, Dongning
Author_Institution :
Dept. of Electr. Eng. & Comput. Sci., Northwestern Univ., Evanston, IL, USA
fDate :
July 31 2011-Aug. 5 2011
Abstract :
In many wireless communication systems, radios are subject to duty cycle constraint, that is, a radio only actively transmits signals over a fraction of the time. For example, it is desirable to have a small duty cycle in some low power systems; a half-duplex radio cannot keep transmitting if it wishes to receive useful signals; and a cognitive radio needs to listen and detect primary users frequently. This work studies the capacity of scalar discrete-time Gaussian channels subject to duty cycle constraint as well as average transmit power constraint. The duty cycle constraint can be regarded as a requirement on the minimum fraction of nontransmission or zero symbols in each codeword. A unique discrete input distribution is shown to achieve the channel capacity. In many situations, numerical results demonstrate that using the optimal input can improve the capacity by a large margin compared to using Gaussian signaling over a deterministic transmission schedule, which is capacity-achieving in the absence of the duty cycle constraint. This is in part because the positions of the nontransmission symbol in a codeword can convey information. The results suggest that, under the duty cycle constraint, departing from the usual paradigm of intermittent packet transmissions may yield substantial gain.
Keywords :
Gaussian channels; channel capacity; cognitive radio; Gaussian signaling; channel capacity; cognitive radio; convey information; deterministic transmission schedule; discrete input distribution; duty cycle constraint; half-duplex radio; intermittent packet transmissions; power constraints; scalar discrete-time Gaussian channels; wireless communication systems; zero symbols; AWGN channels; Channel capacity; Mutual information; Relays; Schedules; Signal to noise ratio; Wireless communication;
Conference_Titel :
Information Theory Proceedings (ISIT), 2011 IEEE International Symposium on
Conference_Location :
St. Petersburg
Print_ISBN :
978-1-4577-0596-0
Electronic_ISBN :
2157-8095
DOI :
10.1109/ISIT.2011.6034180