Multiuser detectors suffer from their relatively higher computational complexity that prevents widespread use of this technique. In addition, one of the main characteristics of multichannel communications that can severely degrade the performance is the inconsistent values of processing gain (PG) that result in high multiple access interference (MAI). However, if we could lower the complexity of multiuser detectors and produce better values of PG, most of the CDMA systems would likely take advantage of this technique in terms of increased system capacity and a better data rate .This paper presents a deterministic formalization of the PG for a wireless multi-channel DS-CDMA system The proposed deterministic formalization demonstrates that how the reduced BER could be used to achieve reasonable values of PG by which unwanted signals can be suppressed relative to the desired signal at the receiving end. The performance measure adopted in this paper is the achievable bit rate for a fixed probability of error (10-7).

Null message algorithm (NMA) is one of the efficient conservative time management algorithms that use null messages to provide synchronization between the logical processes (LPs) in a parallel discrete event simulation (PDES) system. However, the performance of a PDES system could be severely degraded if a large number of null messages need to be generated by LPs to avoid deadlock. In this paper, we present a mathematical model based on the quantitative criteria specified in (Rizvi et al., 2006) to optimize the performance of NMA by reducing the null message traffic. Moreover, the proposed mathematical model can be used to approximate the optimal values of some critical parameters such as frequency of transmission, Lookahead (L) values, and the variance of null message elimination. In addition, the performance analysis of the proposed mathematical model incorporates both uniform and non-uniform distribution of L values across multiple output lines of an LP. Our simulation and numerical analysis suggest that an optimal NMA offers better scalability in PDES system if it is used with the proper selection of critical parameters.

The capacity of mobile ad hoc network (MANET) is typically determined by the size of network, routing protocol, mobility and the interactions that occur between the nodes. Moreover, these critical parameters cause the loss rate that has severed impact on the performance of the MANET. This situation even becomes worst when these critical parameters are chosen inappropriately. This paper presents an analytical model that incorporates most of the critical parameters that can influence the capacity of MANET. Based on the analytical model, an efficient 3-phase algorithm is designed to optimize the performance of MANET in terms of an increased capacity and the reduced transmission delay. The proposed 3-phase algorithm considers both delay-tolerant and delay-sensitive network traffics. In addition, the 3-phase algorithm can be used to approximate both the best and worst case capacities of MANET with the relaying and non-relaying nodes.

This paper presents a Reputation-Trust (RT) system that can be used to stabilize the performance of the network for the working nodes even in the presence of malicious nodes which intentionally do not route and forward packets send by others correctly. The situation becomes even worst when nodes do not rely on any routing infrastructure but relay packets for each other. We introduce two extensions to the Dynamic Source Routing algorithm (DSR) [1] to mitigate the effects of routing misbehavior: the watchdog and the pathrater. Using these two approaches, the proposed RT system will update the RT table of each node with the ranked values of other nodes. The implementation of the proposed RT system is entirely based on the underlying proposed RT algorithm. Simulation results demonstrate that the RT system can be used to reduce the malicious behavior of mobile nodes and consequently improve the overall performance of MANET.