Performance of Voice over 802.11 Networks Date: January 18, 2005 Performance of Voice over 802.11 Networks Author: Fanny Mlinarsky, Azimuth Systems fanny_mlinarsky@azimuthsystems.com Fanny Mlinarsky, Azimuth Systems

Discussion Outline VoIP Cell WiFi VoIP and VoWiFi history Cell-WiFi convergence Voice network requirements Emerging voice standards Quality of Service Security Roaming VoWiFi performance and certification testing Future trends and opportunities Cell WiFi Fanny Mlinarsky, Azimuth Systems

VoIP-Data Convergence Traditional Enterprise connectivity VoIP converges telephony and data networks First VoIP products emerged in 1996 PSTN = Public Switched Telephone Network Fanny Mlinarsky, Azimuth Systems

VoWiFi - Legacy PBX Systems VoWiFi manufacturers Cisco, Symbol, Spectralink Spectralink WiFi phones available since 1999 802.11b only for now Most IP PBXs use proprietary protocols Cisco SCCP (skinny call control protocol) Alcatel UA NEC Protims Avaya CCMS Nortel UniStim Siemens CorNet IP Mitel MiNet Standard IP telephony protocols H.323 Media Gateway Control Protocol (MGCP) Session Initiation Protocol (SIP) Fanny Mlinarsky, Azimuth Systems

Voice over WiFi Use Cases SOHO WiFi or WiFi-Cell handset, soft phone Service providers: Vonage, ATT CallVantage, Net2Phone No handoff, low capacity, basic security Range Enterprise Handoff speed Call capacity Security Public access (WiFi hotspots) WiFi-Cell handset, soft phone Call Capacity Roaming issues Net2Phone WiFi handset Fanny Mlinarsky, Azimuth Systems

Cell-WiFi Convergence Standards UNC Server SCCAN - seamless converged communication across networks First converged system Proxim, Motorola, Avaya UMA - unlicensed mobile access An extension of GSM/GPRS to WiFi Alcatel, AT&T Wireless, British Telecom, Cingular, Ericsson, Kineto Wireless, Motorola, Nokia, Nortel Networks, O2, Rogers Wireless, Siemens, Sony Ericsson, T-Mobile US Internet UMA-enabled components: - UNC (UMA Network Controller) server - Handset DSL/Cable Modem Router AP Wi-Fi Fanny Mlinarsky, Azimuth Systems

Voice Network Requirements Client Range Power-save Fast roaming Infrastructure Call capacity Delay, jitter, packet loss Fanny Mlinarsky, Azimuth Systems

IEEE 802.11 Standards for VoWiFi Minimize bursty packet loss by controlling roaming time 802.11r Fast Roaming 802.11k Radio Resource Measurement (RRM) 802.11i Pre-authentication Manage power consumption 802.11e Power-save Maintain isochronous nature of voice packet streams by controlling delay, jitter and packet loss 802.11e Quality of Service (QoS) prioritization Fanny Mlinarsky, Azimuth Systems

QoS Protocols WMM (Wireless MultiMedia) AC (Admission Control) Subset of 802.11e Specifies 4 priorities: voice (highest), video, background, best effort (lowest) Wi-Fi certification has started in September 04 AC (Admission Control) Enables APs to reject calls when call capacity is reached WMM SA (WMM Scheduled Access) Specifies polling mechanism to optimize bandwidth utilization Wi-Fi certification expected in July 05 APSD (Automatic Power Save Delivery) Unscheduled APSD works with WMM Scheduled APSD works with WMM-SA SVP (Spectralink Voice Priority) Proprietary prioritization scheme that combines priority mechanism with tight synchronization to optimize bandwidth utilization Fanny Mlinarsky, Azimuth Systems

Security Protocols WPA WPA2 Subset of 802.11i TKIP, WEP EAP-TLS, PSK (pre-shared key) WPA Enterprise (TLS, PSK) WPA Personal (PSK) WPA2 Entire 802.11i Superset of WPA AES support Pre-Authentication to help with 802.11r fast roaming Fanny Mlinarsky, Azimuth Systems

Radio Resource Management 802.11k Mechanism for stations and APs to discover neighboring APs and to learn about their traffic load and signal conditions Helps 802.11r fast roaming Fanny Mlinarsky, Azimuth Systems

IEEE 802.11 Standards Study groups Current work Published MAC PHY 802.11 (’99) MAC + 2Mbps PHY 802.11s Mesh 802.11p WAVE 802.11r Fast Roam 802.11u WIEN SG 802.11h DFS & TPC 802.11e QoS 802.11v WNM 802.11i Security ADS SG 802.11k RRM 802.11n High Throughput (>100 Mbps) 802.11f Inter AP APF SG MAC 802.11m Maint 802.11T Test Methods PHY 802.11a (’99) 54 Mbps 5GHz PHY Study groups 802.11b (’99) 11 Mbps 2.4GHz PHY 802.11g 54 Mbps 2.4GHz PHY Current work Published Fanny Mlinarsky, Azimuth Systems

WiFi Alliance Roadmap Fanny Mlinarsky, Azimuth Systems

Voice Quality ITU-T Voice Quality Standards MOS (mean opinion score) uses a wide range of human subjects to provide a subjective quality score (ITU-T P.800) PESQ (perceptual speech quality measure) sends a voice pattern across a network and then compares received pattern to the original pattern and computes the quality rating (ITU-T P.862) E-Model computes Rating Factor or R-Factor as a function of delay and packet loss; R-Factor directly translates into MOS (ITU-T G.107) Fanny Mlinarsky, Azimuth Systems

ITU-T PESQ Model Fanny Mlinarsky, Azimuth Systems

ITU-T E-Model E-Model based on ITU-T G.107 Packet-loss Latency Fanny Mlinarsky, Azimuth Systems

E-Model Parameters Latency 500 ms max Packet loss 20% max Fanny Mlinarsky, Azimuth Systems

Phone Range vs. MOS Vary attenuation between the phone and the AP Measure packet loss, delay and jitter of a phone-AP link as a function of path loss Use ITU-T E-Model to compute R-Factor and MOS vs. range Fanny Mlinarsky, Azimuth Systems

MOS vs. Path Loss Fanny Mlinarsky, Azimuth Systems

Measuring Call Capacity Emulate voice traffic from multiple phones Emulate background data traffic Measure delay, jitter and packet loss* vs. number of calls and background traffic * Per IETF RFCs 2544, 2889 Fanny Mlinarsky, Azimuth Systems

AP Call Capacity Test Results % Frame Loss # calls Fanny Mlinarsky, Azimuth Systems

AP Call Capacity Test Results Delay (usec) # calls Fanny Mlinarsky, Azimuth Systems

AP Call Capacity Test Results Jitter (usec) # calls Fanny Mlinarsky, Azimuth Systems

AP Call Capacity Test Results MOS # calls Fanny Mlinarsky, Azimuth Systems

Measuring Roaming Time Emulate motion of the phone using programmable attenuators Monitor source and destination WiFi channels and Ethernet Derive roaming time from data captures Fanny Mlinarsky, Azimuth Systems

Roaming Process AP1 AP2 AP1 max Path to AP1 Atten Path to AP2 min Test cycle Data rate transition t ASSOCIATE t DATA t TRANSITION t SCAN t ROAM Last data packet before roam First data packet after roam Fanny Mlinarsky, Azimuth Systems

Sample Roaming Test Results Fanny Mlinarsky, Azimuth Systems

Sample Roaming Test Results Multi Mode Clients (ABG) Single Mode Clients (B only) Fanny Mlinarsky, Azimuth Systems

Future Technology Environments Applications SOHO Enterprise Public access Outdoor campus MAN/WAN Transportation Military Applications Data Voice Video Fanny Mlinarsky, Azimuth Systems