Vallabhajosyula S. Somayazulu

Detect and Avoid (DAA) Mechanisms for UWB Interference Mitigation

Worldwide ultra-wideband (UWB) radio regulations are slowly taking shape, and are reaching the final stages of work. The main reasons for the continued debate has of course been the potential interference that can be caused by UWB radios to other radios with which they would share the spectrum. Specifically for the case of broadband wireless access (BWA) systems serving indoor subscriber stations (SS), it has been proposed to impose a requirement that UWB systems should detect and avoid interference to the downlinks of such BWA SS. In this paper we discuss some of the aspects of such solutions, and present some results and description of the ongoing work in this area

A multibanded system architecture for ultra-wideband communications

The FCC ruling in 2002 allowing for the unlicensed deployment of ultra-wideband (UWB) devices for communications purposes in the 3.1-10.6 GHz band has sparked great interest in the industry. In particular, the IEEE 802.15.3a task group is currently developing a standard for high-rate, short-range wireless communication systems that is expected to use UWB technology. One of the main challenges for UWB system design is minimizing the possible interference to other narrowband systems, while, at the same time, dealing with the large interference that may be coming from these narrowband systems into the UWB receiver. Traditional UWB systems have used very short time impulses that occupy several giga-hertz of bandwidth. This approach makes it difficult to efficiently avoid other system that may be sharing the same band. This paper will describe a channel model that has been adopted by the industry to evaluate the merits of different UWB physical layer approaches and introduce an alternate approach to a high-rate UWB system that is based upon the concatenation of multiple narrower band UWB waveforms.

Context-adaptive cross-layer TCP optimization for Internet video streaming

The tremendous growth of video content over the Internet and evolution towards more personalized video applications has led to a need for a network and service infrastructure better suited to todays content and mobility needs. Quality of Experience (QoE) management is one of the major challenges for video delivery given the limited bandwidth for wireless access network causing video packet drops and the core network congestion impacting video service delay. In this context, the current TCP-based model used for HTTP streaming presents challenges due to throughput variation and high latency. We present a context-adaptive cross-layer optimization approach to enhance video streaming over TCP that introduces network and content awareness in TCP operation to provide adaptive reliability and smoother throughput. Our proposed solution requires implementation changes only on the receiver side without impacting the TCP sender implementation. We validated the proposed solution through OPNET simulations and the results show some significant performance gains in both TCP throughput and video QoE metrics.