| Carrierless communication using extremely narrow pulses is becoming popular due to its inherent capacity for short range applications. Such a system is often referred to as an impulse radio (IR) system. The research reported in this dissertation can be summarized as design and development of tools and techniques targeted towards designing realistic, high performance, low cost, low power, nearly all-digital IR systems. These systems are extremely power limited with wide bandwidth to spare. Therefore, application of very low rate error control coding schemes to such systems result in added coding gain with no additional penalty. The additional coding gain can translate into added capacity in multi-user environment. In this work, novel low rate error control codes that are iteratively decodable, namely, turbo-like codes, are designed to be used in IR systems. Theoretically best as well as pragmatic codes are designed for this purpose. Since IR uses extremely narrow pulses for communication, it is vulnerable to oscillator instabilities, namely the long term drift and the short term jitter. An iterative algorithm is proposed to estimate drift. The drift estimator exchanges information with the channel estimator to refine its estimate. The drift estimation algorithm is shown to achieve the required accuracy for reliable data detection. In addition, a novel technique is proposed to estimate jitter in a coded IR system. By jointly tracking the jitter and decoding the code, using adaptive iterative detection, it is shown that the specification on the oscillators can be relaxed by orders of magnitude without significantly degrading the performance. Finally, the effect of front end quantization on UWB signals in the presence of narrow band interference is addressed. |
