Impact of processing energy on the capacity of wireless channels

Power efficiency is a capital issue in the study of mobile wireless nodes owing to constraints on their battery size and weight. A careful examination of the power consumption in low-power nodes shows that, as the total power available to such nodes decreases, the ratio of power consumed for transmission purposes to the power consumed on other non-transmission processes also decreases. The latter power therefore constitutes a considerable fraction of the total power available to such devices. We perform our study in terms of power per unit of time, or energy. Traditional in- formation theoretic energy constraints consider only the energy used for transmission purposes. We study optimal transmission strategies by explicitly taking into account the energy expended by processes other than transmission, that run when the transmitter is in the 'on' state. We term this energy by 'processing energy'. We first derive the capacity of a single user Additive White Gaussian Noise (AWGN) channel in the presence of processing energy. We prove that, unlike the case where only transmission energy is taken into account, achieving capacity may require intermittent, or 'bursty', transmission. We show that in the low Signal to Noise Ratio (SNR) regime, burstiness becomes optimal when the processing energy is greater than half the square of the total energy available to the transmitter. This analysis is extended to the AWGN multiple access channel with M senders and a single receiver. We first show that, under a processing energy constraint, Time Division Multiple Access (TDMA) outperforms other known multiple access techniques in the maximization of the sum rate.

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Electrical Engineering and Computer Science.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2005

Author dc:creator

• Youssef-Massaad, Pamela, 1981-

Advisor dc:contributor.advisor

• Muriel Médard and Lizhong Zheng.

• Electrical Engineering and Computer Science.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/30178

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/30178