To prolong the lifetime of nodes in wireless sensor networks, both transmission cost and processing power should be minimized. For this purpose, we propose a new direct source channel mapping method which utilizes large bandwidth. The system combines a closed-loop Differential Pulse Code Modulation (DPCM) source coder followed by pulse position modulation (PPM) transmission. To accommodate closed-loop prediction over a noisy channel an additional feedback channel is used. Two or more sequential samples are predicted at a time and combined before transmission, thus reducing transmission cost further. Simulations performed on both an auto regressive AR(1) source and a test image over additive white Gaussian noise (AWGN) channel show that our proposed system can achieve significant energy saving for both noiseless and noisy feedback channels without delay. We therefore propose a new framework for direct joint source channel mapping utilizing large bandwidth. Our system combines a closed-loop DPCM encoder followed by pulse position modulation (PPM) transmission. The source data redundancy is removed by DPCM. The closed loop prediction in DPCM is achieved by using a feedback channel from the receiver back to the transmitter. The major advantage of the system is its simple implementation on sensor nodes, while still achieves significant energy efficiency, robustness to error and performs without delay. The system provides an effective way for bandwidth expansion with high expansion factors which is complicated to achieve with the previous approaches (2-3). We investigate our system in both noiseless and noisy feedback channels. PPM transmission can be used in noisy feedback link which can achieve nearly same performance for both noiseless and noisy feedback channel.
['Minh-Long Pham', 'Tor A. Ramstad', 'Ilangko Balasingham']
Minimizing Power Using Large Bandwidth PPM Transmission and DPCM Source Coding