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76 | BROADBAND COMMUNITIES | www.broadbandcommunities.com | MAY/JUNE 2016 TECHNOLOGY Managed Wi-Fi in an MDU Trade-ofs among signal, coverage and interference make installing Wi-Fi in multifamily housing a challenge – but not an insurmountable one. By Andrew Peterson / Calix Consulting Services Te following is adapted from a report on the frst multiple-dwelling-unit installation of Calix GigaCenters – a combination ONT, residential gateway and 802.11ac Wi-Fi access point. Te GigaCenters were installed in the Deer Ridge Apartments in Jamestown, N.D., a deployment described in detail in the October 2015 issue of BroadBand Communities . Te report's fndings were discussed at the 2016 BroadBand Communities Summit. C alix Consulting Services assisted with the design and testing of the wireless network for a planned Dakota Central Telecom (DakTel) deployment of Calix 844G GigaCenters in a 163-unit apartment building in Jamestown, N.D. Te deployment included a dedicated GigaCenter in each apartment unit. Wireless connectivity is used for Internet access only; IPTV is handled via wired connections within each unit. Te density of deployment raised concerns regarding the performance of the wireless network. Specifcally, co-channel interference had to be kept to a minimum because of the close proximity of the GigaCenters in neighboring apartments. Te limited channel space available at 2.4 GHz presented a particular challenge. Te initial design used RF simulation tools to model the structure of the building and the placement of GigaCenters within it. Te design consisted of building material simulation, access point placement, channel width and assignments, and transmitted power levels. Te second foor of the three-foor building was chosen as a "worst case," as it included potential interference from above and below. All these factors were taken into account to produce detailed simulations of the following: • Signal strength as seen by a receiver (RSSI) • Signal-to-noise ratio • Channel overlap • Estimated throughput. Te objective of the design was to maximize throughput within individual units while minimizing impact to neighboring units. Each client needs to see only a single GigaCenter, though many are visible from any given location. At minimum, a client device within a given unit had to attain the following metrics when associated to its GigaCenter on either band: • Minimum -65 dBm RSSI • Minimum 20 dB SNR • Minimum 150 Mbps predicted PHY rate on 5 GHz • Minimum 80 Mbps predicted PHY rate on 2.4 GHz • No more than 1 GigaCenter visible on the unit's assigned 5 GHz channel. In dense housing, setting Wi-Fi access points to operate in narrow channels and at low power settings may help avoid interference.