Rate-Adaptive Code Combining over Time and Space for Wireless Radio Frequency and Infrared Communication Systems

Open Access
Akhavan, Koorosh
Graduate Program:
Electrical Engineering
Doctor of Philosophy
Document Type:
Date of Defense:
May 26, 2000
Committee Members:
  • Kenneth Jenkins, Committee Member
  • Rajeev Sharma, Committee Member
  • Shizhuo Yin, Committee Member
  • Hao Che, Committee Member
  • Lynn A Carpenter, Committee Member
  • Mohsen Kavehrad, Committee Chair
  • ARQ
  • Wireless Infrared
  • Code Combining
This dissertation deals primarily with the design and analysis of various rate-adaptive packet transmission schemes intended for wireless radio and infrared channels. To make the communication reliable and robust, all the proposed schemes take advantage of some form of diversity combining. Diversity, in general, can be provided in many dimensions including time and space. Usual ways of creating time diversity is through retransmitting, coding and interleaving, whereas the most common way of achieving space diversity is by using antenna arrays at the transmitter and/or the receiver. Although increasing the diversity order in only one dimension is sufficient for increasing the system capacity, it does not always result in an ideal solution as there are many practical considerations such as system complexity, underlying channel fading characteristics, power consumption, delay, etc. that favor use of one diversity scheme over another. It seems therefore reasonable to combine diversity schemes of different dimensions with one another to arrive into a practical solution. This is the primary focus in this thesis. In addition, to further increase the capacity, we consider some practical rate-adaptive coding (modulation) schemes to be used along with the proposed space and time diversity schemes. The first part of this thesis is dedicated to applying the above concepts to some well-known radio channels, having the goal of providing a guaranteed Quality-of-Service (QoS) at all channel conditions. The second part of this work is dedicated to indoor wireless infrared channels. In these channels, it is possible to provide space diversity in a manner somewhat different from the way it is provided in radio systems, and for this reason, it is commonly referred to as direction (or angle) diversity. We first investigate the properties of our proposed infrared channel and look into some of its deterministic as well as statistical characteristics. Based on these characteristics we propose efficient modulation, coding and combining schemes to achieve the desired goal of QoS provisioning at all possible positions within the coverage area. Coding in time as well as in space in this case allows for having a low-power wireless local-area network that can operate at very high bit rates.