The Analysis of System Capacity of VoIP System Supporting CBR and VBR Traffic in IEEE 802.11b WLAN U

• 作 者: FENG Xi-ping LIU Yuan-an
• 机 构: Beijing University of Posts and Telecommunications
• 出 处: 中国邮电高校学报（英文版）
• 发表日期: 2004年期
• 关键词: IEEE 802.11 DCF VoIP voice suppression delay capacity

In this paper, the capability of IEEE 802.11b Distributed Coordination Function (DCF) mode supporting of Constant Bit Rate (CBR) and Variable Bit Rate (VBR) Voice over IP (VoIP) traffic is investigated. Then, the capacity of 802.11b Wireless Local Area Network (WLAN) system carrying voice calls in a wide range of scenarios, including varying delay and packet loss rate constraints is analyzed and evaluated. Both G.711 and G.729 voice encoding schemes and a range of voice inter-arrival time are considered. The analyses and simulation results show that capacity is highly sensitive to the delay budget allocated to the sum of packetization and wireless network delays. For a given packet loss rate constrained, G.729 is shown to have a capacity greater than that when G.711 is used. The simulation results show that by supporting VBR under DCF mode the network has the approximately twice much capacity as supporting CBR has, regardless of the encoding schemes and the inter-arrival time.