| For ≥10-Gbit/s bit rates that are transmitted over ≥100 km, it is essential that chromatic The traditional method of sending a training signal to identify a channel, followed by data, may be viewed as a simple code for the unknown channel. Results in blind sequence detection suggest that performance similar to this traditional approach can be obtained without training. However, for short packets and/or time-recursive algorithms, significant error floors exist due to the existence of sequences that are indistinguishable without knowledge of the channel. In this work, we first reconsider training signal design in light of recent results in blind sequence detection. We design {lcub}em training codes{rcub} which combine modulation and training. In order to design these codes, we find an expression for the pairwise error probability of the joint maximum likelihood (JML) channel and sequence estimator. This expression motivates a pairwise distance for the JML receiver based on principal angles between the range spaces of data matrices. The general code design problem (generalized sphere packing) is formulated as the clique problem associated with an unweighted, undirected graph. We provide optimal and heuristic algorithms for this clique problem. For short packets, we demonstrate that significant improvements are possible by jointly considering the design of the training, modulation, and receiver processing.; As a practical blind data detection example, data reception in a fiber optical channel is investigated. To get the most out of the data detection methods, auxiliary algorithms such as sampling phase adjustment, decision threshold estimation algorithms are suggested. For the parallel implementation of detectors, semiring structure is introduced both for decision feedback equalizer (DFE) and maximum likelihood sequence detection (MLSD). Timing jitter is another parameter that affects the BER performance of the system. A data-aided clock recovery algorithm reduces the jitter of the clock with the help of decisions from the data detection module. Performance of such an data-aided clock recovery scheme is analyzed and simulated. The algorithms suggested in this thesis cover some of the basic algorithms to optimize the performance of an receiver both in complexity and BER. |
