Energy efficient source coding and modulation for wireless applications

A simple and energy efficient source coded on/off keying modulation and near optimal error detection scheme for wireless applications is presented in this paper. Many low-power battery operated radio systems, especially for microsensor applications, has a need for saving power both at the system level and circuit level implementation. Our main objective in this paper is to come up with energy efficient coded modulation scheme that consumes comparatively less power both at system and circuit level. A simple on/off keying (OOK) digital modulation scheme is used for this purpose. The basic idea of minimum energy coding (ME-coding) for source with known statistics (probabilities of occurrence of symbols) is obtained from [A.C. Erin and H.H. Asada, Dec. 1999]. In ME-coding scheme, source bits are mapped to constant length codes (ME-codes) which has less number of high-bits in it. Since the OOK transmitter consumes energy only when transmitting a high bit, mapping to ME-codes reduces the total energy consumed in RF transmitter. In this paper, we have come up with ME-coding scheme for sources with unknown statistics and we further propose a new method of code-by-code detection that can detect and correct certain errors in the codeword received. The inferior performance of OOK when compared to other simple modulation schemes is overcome by ME-coding. A total of about 6 dB improvement in signal-to-noise ratio (SNR) per bit is observed when a 3-bit message symbol is mapped to a 7-bit ME-code. It also performs 3 dB better than a Hamming (7,4)-coded BPSK.