Access point planning 41A site survey is critical to designing and implementing a wireless LAN. Thesite survey is used to determine the number of APs needed to support thewireless handset users and to determine the best placement of the APs.Different AP vendors provide different tools to do this.Site surveyTo conduct a site survey, set up an AP at a particular location. Use acomputer equipped with a wireless LAN device and site survey softwareor a handset operating in Site Survey mode to measure the strength ofthe signal from the AP. Move the wireless device around and repeat themeasurements to determine the optimum number and best locations forthe APs. This method helps identify dead zones and areas where buildingmaterials or other factors affect the performance of the network.Site Survey modeThe handset Site Survey mode displays negative dBm levels. These levelsrepresent the strength of the received signal (Received Signal StrengthIndication or RSSI) from an AP. The RSSI information aids in determining ifWLAN coverage is adequate.For information about using the Site Survey mode, see WLAN HandsetsFundamentals (NN43001-505).Note: The handsets do not require connectivity to a 2245 IP TelephonyManager or the Call Server to enable the Site Survey mode to beused. The minimum configuration required is the Extended ServiceSet Identifier (ESSID) of the WLAN or test AP and the WEP keys, ifapplicable.Access point requirement considerations for b radioEach site is unique in its AP requirements. Consider the following pointswhen determining how many APs are needed and where to place them:• Minimum Radio Signal Strength—All APs in the coverage area mustreceive a signal strength better than -70dBm. Measurement is made innegative dBm, which measure the amount of signal loss due to distance.Therefore, stronger signals are those with smaller values. For example,-50 and -60 indicate stronger signals than -70; -80 is a weaker, poorersignal than -70.• Adjacent APs and channel interference—In order to avoid undesirableinterference from adjacent APs, ensure that adjacent APs do not usechannels that overlap on the same frequencies.For more information, see Figure 3 "Frequencies used by b radio" (page42). In the figure, channels on the same horizontal line do not overlap.In the coverage area of any given AP, signals from other APs usingoverlapping channels must be at least -15 to -20dBm weaker. BecauseNortel Communication Server 1000WLAN IP Telephony Installation and CommissioningNN43001-504 01.02 StandardRelease 5.0 15 June 2007Copyright © 2004-2007, Nortel Networks.
