In this paper, the performance of short constraint length convolutional codes in imperfect phase tracking conditions is discussed. Convolutional codes are used to provide error protection to a particular user in an Asynchronous CDMA (A- CDMA) system undergoing slow Rician fading. Maximum likelihood decoding with a Viterbi algorithm recovers the information symbols. A Phase Locked Loop (PLL) depicting the variations in the phase error for abrupt phase changes in the input signal is considered. Analytical bounds, which are useful in predicting the performance of the A-CDMA system are derived and plotted for the cases of infinite and finite channel memory. The upper bounds on the unconditional Bit Error Rate (BER) with Viterbi decoding are derived and plotted for the various convolutional codes considered. The simulated BERs are found to agree well with their upper bounds.

We statistically characterize the spatial correlation of measured far-end crosstalk collected on 2 kft of 26 AWG twisted-pair copper cable. We then develop and verify a parameterized model of this spatial correlation and use it to investigate the behavior of the spatial correlation of far-end crosstalk in a twisted-pair environment.

Reservations based admission control, using Multi-protocol Label Switching (MPLS) is the leading method being considered by traditional carriers for maintaining Quality of Service (QoS) when deploying Voice over Internet Protocol (VoIP). In this research we explore an alternative to reservations based admission control called Delay Based Congestion Detection and Admission Control (DBCD/AC), a form of Endpoint Admission Control. DBCD/AC is a method for edge devices, such as media gateways, to detect impending congestion in the core based on delay measurements and analysis. When impending congestion is detected, the edge devices refuse new incoming connections to the media gateways to mitigate the congestion. This research examines the characteristics of DBCD/AC and finds that DBCD/AC is a promising alternative to a reservations based admission control approach for enterprise or carrier controlled IP Networks.

The paper presents a comparison of communication systems using different signal constellation sizes and Reed-Solomon or Bose-Chaudhuri-Hocquengem codes with different rates so that the overall required bandwidth is the same for each system. In these comparisons, the channel symbol size is smaller than the code symbol size, so that a code symbol contains parts of multiple channel symbols. Thus, the normal assumption of independent code symbols does not apply. Instead, consideration must be taken to obtain the best arrangement of channel symbols in each code symbol. Analytical expressions are developed to compare the bit error probability performance of comparable systems, based on individual codewords using errors-only decoding and errors and erasures decoding with transmission over a Rayleigh fading channel.