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chanj0
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re: Real-world testing of Wi-Fi hotspots
chanj0   8/14/2012 4:24:39 PM
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The WAN throughput represents the utilization of the bandwidth, measuring the service quality that the ISP is providing. It varies according to the number of users and the content the users are pulling. On the contrary, the potential bandwidth of the wireless per user varies according to the relative location of the user to the connected AP. It affects the throughput the user is getting. How can we assure the user is getting the service quality he/ she is paying for? Maybe, the data rate relative to the RSSI will give us a clue. The article brings up a very good point. Service provider wants to know the information in different spot of the coverage. It isn't necessarily accurate. If we assume omnidirectional coverage, we will have an idea of signal strength vs distance from the AP. Smart antenna makes it complicated. Measuring quality in wide area deployment is one tough challenge. What's the best way to consistently monitor service level in a large scale deployment?

Skip_B
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re: Real-world testing of Wi-Fi hotspots
Skip_B   8/14/2012 8:53:42 PM
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The article is accurate in that the potential bandwidth of the wireless network will vary according to the number of users and the content. The location of the user (unless they are a Hidden Note) is irrelevant. If they are associated to the AP they are taking up available BW and a "slice" of the available Data Rate. What is relevant is the potential Data Rate available to the user. This is controlled by: 1) The available DR's as determined by the AP in the Beacon and/or Probe Response frame, set in the AP config. 2) The perceived RSSI at the client device which is provided to the Client NIC Driver and then used as part of the clients DRS(Data Rate Shift)decision process (Not covered in the 802.11 standard). This information is available my consistently monitoring the WLAN 'Airspace' and can be reported on as a whole and/or by device depending on the product used for monitoring. This is because 802.11 WLAN's are half duplex and the medium is shared utilizing DCF (Distributed Coordination Function) for medium Access, part of the medium contention and collision avoidance mechanism(s) of 802.11 CSMA/CA. With regard to Coverage Quality monitoring, your results will vary with the environment due to the irregular propagation characteristics of RF. We also cannot assume equal omni-directional coverage, because RF will not radiate equally in all directions and is also directly affected by the environmentals. The best way to monitor WLAN Quality for SLA is to use an independent overlay system such as Fluke Networks - Airmagnet Enterprise. This product can monitor multiple sites and multiple areas, providing performance alerting and statistical monitoring along with Active Health Checking of the HotSpot environment. This provides real-time, factual and trending over time data for SLA Performance analysis with the ancillary benefit of being able to remotely troubleshoot to Root Cause any wireless issues noted.



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As data rates begin to move beyond 25 Gbps channels, new problems arise. Getting to 50 Gbps channels might not be possible with the traditional NRZ (2-level) signaling. PAM4 lets data rates double with only a small increase in channel bandwidth by sending two bits per symbol. But, it brings new measurement and analysis problems. Signal integrity sage Ransom Stephens will explain how PAM4 differs from NRZ and what to expect in design, measurement, and signal analysis.

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