In previous issues of RCR Wireless News, we discussed Near-Far and its effect on in-building DAS performance, which included details on uplink and downlink Near-Far. For more details, check out our recent editorial posts: “Effect on In-Building DAS Performance,” “Uplink Near-Far: Causing Degraded DAS Performance,” and “Downlink Near-Far and the Impact on Non-users in DAS Coverage Zones.”
There are several environmental and DAS equipment parameters that affect Near-Far performance. For today’s reading, we will discuss those parameters and how they affect Near-Far. We will also introduce Westell’s DAS Near-Far evaluation tool.
Environmental Parameters Affecting Near-Far
Near-Far affects the performance for people on the DAS (participants) as well as those in the DAS coverage area who are not on the DAS (non-participants). In a conventional DAS, some of the basic design criteria can affect where a non-participant begins to cause Near-Far issues. These include environmental parameters such as frequency, bandwidth, path loss, in-building margin loss, desired SINR, antenna gain and cable loss. Along with the DAS design details, the transmit power of the non-participant will also determine the distance where a non-participant will cause Near-Far impact. Although all these parameters can influence the distance from a DAS antenna, the non-participant will cause Near-Far degradation. These are basic parameters of the design and coverage area that generally cannot be changed.
DAS Parameters Affecting Near-Far
There are a few parameters in the DAS equipment that can affect the Near-Far performance of a DAS system. In the uplink, these include AGC set point, AGC compensation range, and filtering. In the downlink, these include remote noise power output and filtering. These parameters can differ between DAS equipment manufacturers and should be considered when selecting DAS equipment.
For instance, on the uplink, if the AGC set point of one manufacturer’s equipment is higher than another without allowing the uplink performance to degrade prior to triggering AGC, their system would be less susceptible to strong signals from a non-participant and the area of Near-Far impact is reduced. On the downlink, remote noise power output is an important factor to consider. If one manufacturer’s remote transmits higher broadband noise than another’s, that manufacturer will have a greater area of Near-Far impact on a non-participant in the DAS coverage zone.
For a quick informational overview on Near-Far, please check out the Westell video.
DAS Near-Far Evaluation Tool
Westell has a new web-based tool, which compares Near-Far performance under defined conditions. Users can vary environmental parameters as well as DAS parameters and see the effect they have on Near-Far performance. This tool is available to our customers. You can register to access this tool via Westell’s customer support portal.
