Network management 49Both location-solution types use a form of triangulation to compute thelocation of the device. Depending on the power level of the AP, it cansometimes hear devices that it cannot transmit to. These factors combinedcreate the following two scenarios:• It is difficult to calibrate network-based solutions by using a laptoprunning the site survey, because APs can sometimes hear clientsthat cannot hear the AP. If AP transmission power levels are not ata maximum, they can hear clients over a greater distance than theirown transmissions can travel. This scenario can cause the site surveyapplication to underestimate the number of APs that can participatein triangulation.• Client-based solutions cannot triangulate APs that are not detectablebecause their power is lower. But the site survey application canaccurately reflect the number of APs that can be used for triangulation.Assessment using NetIQ Vivinet AssessorThe Network Health Check is probably the most critical step towardensuring a smooth rollout for any VoIP deployment. This statement applieseven more so to VoWLAN, because a WLAN is a more challenging QoSenvironment than modern wired networks.The NetIQ Vivinet Assessor 3.0 or later is the tool of choice for networkhealth checking. (Previously NetIQ Chariot, now an Ixia product, wasrecommended for network health checking.) This product uses a laptop(for WLAN testing for WLAN mobility) as a voice-traffic generation andanalysis tool. You can configure several nodes in various parts of thenetwork, to simulate calls to and from those areas. Each node simulatescall volumes through traffic generation so that you can stress-test accesslinks, backbones, and WAN links as necessary. You can also configurecodecs, packetization rates, and other factors to closely mimic the futureVoIP environment.Vivinet Assessor performs a comprehensive analysis of the simulatedtraffic, including reports on delay, jitter, and packet loss. The R values orMean Opinion Score (MOS) are reported for these simulated traffic loadsto provide a baseline for performance expectations. These analyses arealso used for capacity planning because they show the capacity at whichthe Quality of Experience (QoE) ratings start to fall. More importantly, theprocess of analyzing the network reveals many latent network problems thatcan otherwise remain undetected until deployment.For example, duplex mismatches can exist in various locations of thenetwork, and data applications, being very tolerant to packet loss, typicallydo not reveal the problem unless it is severe. The issue is immediatelyNortel Communication Server 1000WLAN IP Telephony Installation and CommissioningNN43001-504 01.02 StandardRelease 5.0 15 June 2007Copyright © 2004-2007, Nortel Networks.
