Performance and design of optical CDMA communication systems with single-user and multiuser detection
by Tang Tai Kwan Jimmy
M.Phil. Electrical and Electronic Engineering
ix, 100 leaves : ill. ; 30 cm
Lightwave technology has played a key role in long-haul data communication because of its capacity for high data rate transmission over long distances. With the advent of fiber optics, an enormous amount of bandwidth can be transmitted in a single fiber. Thereby, allowing a host of applications to be employed in broadband communication systems such as high speed local area and wide area communication networks....[ Read more ]
Lightwave technology has played a key role in long-haul data communication because of its capacity for high data rate transmission over long distances. With the advent of fiber optics, an enormous amount of bandwidth can be transmitted in a single fiber. Thereby, allowing a host of applications to be employed in broadband communication systems such as high speed local area and wide area communication networks.
Avalanche photodiode detectors are often used in optical communications systems. The exact output statistics of an APD detector are determined by an intricate process and this complicates the bit error rate evaluation of such systems. There has been an attempt to simplify the statistics by using the Webb, McIntyre, Conradi (WMC) distribution. However, the statistical properties of the WMC distribution are not well developed. In this thesis, we develop new expressions of the generating functions of the WMC model. We will then use these expressions to derive very simple and accurate bit error rate evaluation methods for APD based optical communication systems.
Following the success of CDMA in wireless communication networks, the application of CDMA to optical systems have aroused much interest. One of the key objectives of this thesis is the study and design of CDMA fiber-optic systems. The study begins with the performance analysis of an optical direct sequence CDMA system with the conventional correlation receiver. To do so, we develop a method which allows a flexible, quick and simple way to estimate the performance of optical CDMA systems.
In a CDMA system, it will be desirable to combat multiuser interference which is the major cause of performance degradation. It turns out that multiuser detection, or joint detection, can offer significant performance gain. However, the optimal multiuser detection algorithm has an exponential complexity as the number of users increases and is not practical. Hence, we have studied the design of suboptimal detection schemes and propose a multiuser receiver known as the interference suppression receiver. The performance of the proposed receiver is analyzed and accords with what multiuser detection promises. It turns out that all the previous studies on multiuser detection are only limited to PIN diode based systems. Thus, in this thesis we extend multiuser detection to systems which employ APD detectors. Besides multiuser detection, blind detection can also serve to improve the system performance. Blind detection is advantageous since it does not require certain knowledge of other users. In this thesis, we also study the problem of blind detection and devise a blind detector. Performance of the blind detector along with that of multiuser receivers will be investigated.