Simulation Research On VoIP QoS In Wireless Infrastructured Networks

Based on global standards for wireless LANs, VoIP simplifies network infrastructure by enabling the convergence of voice and data traffic over a common wireless network. These WLANs are generally compliant with the 802.11 standard; so long as callers are within range of a WLAN access point and using a VoIP enabled handset, they can make and receive calls over the wireless network. The wireless LAN infrastructure lacks the capacity to deliver scalability, Quality of service (QoS) and user-friendliness. In a WLAN solution, radio frequency (RF) resource is the scarcest resource because it is a shared medium in which many devices will play for same bandwidth; the objective of the IEEE 802.11e working group is to prioritize packet traffic on the air and 802.11e EDCF has been designed to be compatible to 802.11 DCF.The main purpose of my work was to provide good end-to-end delay and delay variation or jitter. The combination of RSVP (Resource Reservation Protocol) support for LLQ (Low Latency Queue) QoS mechanism have been used to provide admission control and transmit voice flows within the lowest possible end-to-end delay and delay variation or jitter in order to improve the current standards with additions that take into account the different requirements of regular data traffic such as FTP, HTTP, Email and Video conferencing traffics. Using OPNET, the comparison of scenarios for different QoS mechanisms (RSVP support for LLQ, FIFO, PQ, and WFQ (Class Based)) using the metrics; Data Dropped, Throughput, Media Access Delay and Retransmission attempts in case of WLAN, End to End Delay and Jitter in case of real-time multimedia traffic like VoIP and Video conferencing, Download Response Time, and Page Response Time in case of Email, FTP and HTTP type applications were analyzed and the simulation experiments results have shown that RSVP support for LLQ significantly improves End-to-End delay and delay variation (jitter) of transmission of voice traffic over WLAN.This paper is structured into six chapters as follows: First chapter introduces the VOIP communication systems, defining the problem, motivation and the contribution. Second chapter discusses related works. Third chapter present the research methodology. Chapter four describes the implementation using OPNET simulator. Chapter five analyses the simulation results. Last chapter draws conclusions, summarizes the main contributions of this research and suggests future research directions.