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ultra wide band tutorial


Due to environmental concerns and strict constraints on interference imposed on other networks, the radiated power of emerging pervasive wireless networks needs to be strictly limited, yet without sacrificing acceptable data rates. Pulsed Time-Hopping Ultra-Wideband (TH-UWB) is a radio technology that has the potential to satisfy this requirement. Although TH-UWB is a multi-user radio technology, non-zero cross-correlation between time-hopping sequences, time-asynchronicity between sources and a multipath channel environment make it sensitive to strong interferers and near-far scenarios. While most protocols manage interference and multiple-access through power control or mutual exclusion, we base our design on rate control, a relatively unexplored dimension for multiple-access and interference management. We further take advantage of the nature of pulsed TH-UWB to propose an interference mitigation scheme that alleviates the need for an exclusion scheme. A source is always allowed to send and continuously adapts its channel code (hence its rate) to the interference experienced at the destination. In contrast to power control or exclusion, our MAC layer is local to sender and receiver and does not need coordination among neighbors not involved in the transmission. We show by simulation that we achieve a significant increase in network throughput compared to alternative designs.

Emerging pervasive networks assume the deployment of large numbers of wireless nodes, embedded in everyday life objects. For environmental and health concerns as well as coexistence with other wireless technologies, it is important that the level of radiated energy per node be kept very small.1 At the same time, many applications require high data rates. Ultra-wideband (UWB) wireless networks have the potential to satisfy both requirements. The low emitted power of UWB limits very high data rates to sender-receiver distances of tens of meters. Longer distance networks can be achieved through appropriate coding and modulation schemes at the expense of the achievable data rate. UWB is characterized by an extremely broad use of the radio spectrum which makes it relatively robust against channel impairments such as multipath fading.

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