RF network design typically involves determining the number of access points, their placement, channel assignment, and power settings to deliver the required coverage and throughput for a given physical environment. Traditionally, RF network design has evolved from a series of physical wireless site surveys, in some cases, to combining physical wireless site surveys with predictive planning tools.
The RSSI-based RF planning tools of the past are of little use in predicting and characterizing system performance for an 802.11n network. Planning tools must take into account the multipath characteristics of a wide variety of building construction material like concrete, glass, dry-wall, office cubicles, warehouse racks, etc. In addition accurately characterizing multipath is extremely important for optimal MIMO performance. Multipath characterization includes analyzing the geometrical structure of site drawings representing the actual physical dimensions of the intended radio coverage area.
Because 802.11n uses MIMO transmissions with multiple data streams of varying modulation, this analysis of the in-building multipath characteristics must be combined with knowledge of the predicted RSSI in order to arrive at an accurate prediction of the system performance. Thus, merely predicting RSSI at any given point is of little or no value.
802.11n requires a system capable of combining the effects of MIMO with multiple spatial streams and the underlying RSSI.
When supporting existing 802.11b/g clients and simultaneously deploying 802.11n in the 5 GHz band, there is no easy way to insert new 802.11n access points without causing harmful co-channel interference. Even with a rip and replace migration, a one-to-one replacement of legacy access points with an 802.11n AP (without transmit power
adjustment) is likely to cause interference issues given the improved receiver sensitivity of the new radio technology.
802.11n planning can be simplified by using planning tools designed specifically for 802.11n and that offer legacy deployment support. Businesses evaluating 802.11n should partner with companies like TPI utilizing tools that drive RF heat-map algorithms based on the detailed RF characterization of the specific access point radio deployed. Predictions and coverage maps generated for generic access point models can provide misleading results, delivering inconsistent coverage and poor performance when deployed.
Don’t make a classic design mistake…go with an expert.