Papers by Keyword: Voice over IP (VoIP)

Abstract: Due to the further development in recent years, VoWLAN(VoIP over Wireless LAN) will achieve convergence with other service inevitably and has a higher requirement for network performance. Service focused on the whole converged network is different, so the measure of network status has different demands, we should set parameters reasonably and make it adaptive network in order to realize the optimization of network performance according to the current channel load level and distribution of service condition. Therefore, we can adjust the Contention Window(CW) dynamically, according to the slot utilization rate to estimate the channel load and the concept of backoff discontinuation rate. Simulation results prove that this scheme is simple and effective, largely improved QoS performance of the throughput and delay of each service.

Abstract: A low-complexity echo canceller integrated with vocoder is proposed in this paper to speed up the convergence process. By making full use of the linear prediction parameters retrieved from decoder and the voice active detection feature of the vocoder, the new echo canceller avoids the need to calculate decorrelation filter coefficients and prewhiten the received signal separately. Simulation results show performance improvement of the proposed algorithm in terms of convergence rate and echo return loss enhancement.

Abstract: For the current encountered difficulties in UE-to-UE one-way delay test of VoIP business, this paper introduces a test system to measure the one-way delay between two user equipments (UE). The paper shows that the key to implement this system is that we make different UE obtain time information from the same computer instead of the traditional time synchronization process. Thus, we need a server in the core network to realize the function of packet forwarding. Moreover, when VoIP business is running, the packets from UE should be captured in order to calculate the time difference between the sender and the receiver. The purpose of this system is to provide a test solution of VOIP UE-to-UE delay.

Abstract: In IEEE 802.16e network, voice over IP (VoIP) scheduling is critical to system performance but no special algorithm is defined in the IEEE 802.16e standard. Based on this thinking, a novel VoIP scheduling algorithm named compensated based VoIP scheduling (CBVS) is proposed. This algorithm compensates the bandwidth of service flow whose bandwidth is lost using the remained bandwidth. The simulation results show that the proposed algorithm improves the performance much and increases the number of VoIP users.