Performance comparison of ultra-wideband time-hopping, DSSS and OFDM multiple access schemes for wireless sensor networks

Abstract

Ultra-wideband (UWB) radio communication sys- tems operate using extremely short duration base-band pulses. This paper compares the performance of three competing multi- ple access modulation schemes that have been proposed for appli- cation to UWB based wireless sensor networks. These multiple access schemes are ultra-wideband Time-Hopping (TH-UWB), Direct Sequence Spread Spectrum (DSSS-UWB) and Orthogonal Frequency Division Multiplexing (OFDM-UWB). Each system was investigated under four operating conditions of different bandwidths and bit rates for three different transmission ranges. The attributes measured to compare the performance of the multiple access schemes under consideration were packet link error rate, throughput and energy efficiency. TH-UWB outper- forms DSSS-UWB and OFDM-UWB for high bandwidth condi- tions. Whereas, DSSS-UWB performs better in low bandwidth conditions compared to the other two systems. Decreasing the transmission range significantly degrades the overall performance of the systems. I. INTRODUCTION Wireless sensor networks are special networks composing of a large number of inexpensive, low-power communication sensing devices (sensor nodes), which are densely deployed throughout a physical space and have the capability of col- laborating with each other to monitor a wide variety of ambient conditions. Realisation of sensor network applications requires wireless ad hoc networking techniques (1), therefore the sensor nodes are deployed in an ad hoc fashion and are required to organize themselves to form a multi-hop wireless communication network. Efficient and reliable communication between multiple sen- sor network entities is a big challenge. The increased collision probability resulting from multiple sensor nodes transmitting data simultaneously over the same transmission medium is a common problem facing communication in wireless networks. This problem can be overcome by using reliable multiple access techniques. An ideal wireless sensor communication network would require a multiple access scheme that allows the accommodation of multiple users and provides effective communication. It must also offer some measure of security and should have low probability of intercept. It should also be resistant to jamming and must be energy efficient. Ultra-wideband (UWB) radio is an emerging technology that operates using extremely short duration base-band pulses and has a number of advantages that makes it an attractive choice for sensor networks. In particular, UWB systems have low power and low complexity. They have a noise like signal and are therefore resistant to severe multipath and jamming. They also provide greater bandwidth and are more cost ef- fective for providing increased throughput without increasing power. The three approaches to multiple access in UWB are: