In this project we propose an Energy efficient transmission scheme for wireless sensor networks using Compression with Null Symbol (CNS). In this scheme we combine the power of data compression and communication through silent symbol. The average theoretical energy saving is more at the transmitter by CNS when calculated with an ideal channel and for equal likelihood of all possible binary strings of a given length. Next aim of our project is to propose a receiver design that uses a hybrid modulation scheme FSK and ASK so as to reduce a ratio of cost/complexity. In this method considering an additive white Gaussian noise (AWGN) channel and non-coherent detection based receiver, CNS shows saving in transmitter energy by 30%. There is a 50% saving at the receiver for all type of data modulation due to halving of the transmitted data duration, compared to binary encoding. The energy savings for transmission of text data is 42.6% and for JPEG image files is found to be 33% for CNS. We also compare the different parameters with CNS, results clearly establish that CNS can be a suitable candidate for communication in low power wireless sensor networks Keywords-Energy-efficient communication, Wireless sensor networks, Non-coherent detection, Communication through Silent symbol I. INTRODUCTION Inwireless sensor networks (WSNs) we face the problem in regular replacement or recharging of the batteries of the sensor devices as such networks are continuously in use for monitoring or surveillance purposes. Communication being a major consumer of energy, design of energy efficient communication schemes for WSNs is important. In order to reduce energy consumption we look into MAC layer designing for a survey of routing, power control and energy optimization. Communication through silence (cts) method uses the silent time period and another method for saving energy is variable-Base Tacit communication which uses variable radix-based coding. But for noisy channel both methods are not suitable as they are exponential in communication time. By using appropriate source coding method and digital modulation technique we can enhance the energy saving measures. We can convert the given binary data into 'm' possible symbols (m>2) which contains one symbol having higher probability of occurrence. By keeping transmitter silent for that dominant symbol one can save energy for transmission. In CNS different modulation scheme like OOK, ASK, FSK can be used but FSK is selected due to low bit error rate (BER) in a noisy channel. ASK demodulation is used to detect the null symbol at the receiver, with this instantaneous power levels of the (m-1) non-silent symbols have to be raised, due to the relatively inferior (higher) signal to noise ratio (SNR) requirements of ASK for the same BER value. II. BASIC IDEA
