This paper investigated the throughput performance of a secondary user (SU) for a random primary user (PU) activity in a realistic experimental model. This paper proposed a sensing and frame duration of the SU to maximize the SU throughput under the collision probability constraint. The throughput of the SU and the probability of collisions depend on the pattern of PU activities. The pattern of PU activity was obtained and modelled from the experimental data that measure the wireless local area network (WLAN) environment. The WLAN signal has detected the transmission opportunity length (TOL) which was analyzed and clustered into large and small durations in the CTOL model. The performance of the SU is then analyzed and compared with static and dynamic PU models. The results showed that the SU throughput in the CTOL model was higher than the static and dynamic models by almost 45% and 12.2% respectively. Furthermore, the probability of collisions in the network and the SU throughput were influenced by the value of the minimum contention window and the maximum back-off stage. The simulation results revealed that the higher contention window had worsened the SU throughput even though the channel has a higher number of TOLs.

This paper presents the performance evaluation of Voice over Internet Protocol (VoIP) in Multi-hop Wireless Network (MWN) developed using Multi-radio Access Relay (MAR). The MWN is deployed using 3 MARs in Universiti Teknikal Malaysia campus. The performance of VoIP are investigated using Real Time Protocol (RTP) and Compress Real Time Protocol (CRTP) header techniques. RTP and CRTP are used to transport voice packets using G711.1, G723.1 and G729.2 codec. The performance of VoIP is analyzed based on three important elements which are delay, jitter and packet loss.

This paper investigates outage performance under overlay spectrum mode using relayassisted network model. Without harming the performance of the primary user (PU), secondary user (SU) makes use of a relay (R) for transmission as a supportive system besides the direct link transmission between secondary source (S) and secondary destination (D). Outage probability is used to represent the performance parameter for two different cases. In the first case, relay is able to forward the information from source to destination. In the second case, it is assumed the relay suffers an outage and could not decode the information from the source. We consider total probability law in two cases. The outage probability of SU is analyzed in term of different distance between the secondary nodes and model with relay and without relay. The analysis performances are verified by the simulation results.

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