Now the price is no longer an issue, but WiFi performance is. Performanceīack then access points were expensive and they were placed far apart. Such a weak signal won’t penetrate walls, so you need more access points – see the next section Performance… 4. By setting the AP transmit power to 5mW (7dBm) for example, you can increase the battery life of the clients. The logic is that if the mobile device can receive the AP at that power level, the same applies in reverse as the symmetry was explained earlier. Mobile devices will adjust their transmit power level to match to save battery. The access point informs the clients what its transmit power is (802.11h TPC, 802.11k TPC or Cisco DTPC). The entrance AP is overloaded while other APs are idle.
When users arrive their devices will associate with the entrance AP and keep using it for the rest of the day. In the worst scenario the access point by the entrance covers the entire office just barely. This behaviour affects access point utilisation as well. By lowering the transmit power the connection will break sooner and the client will roam to a better access point. This results in clients using far away access points with poor connections. Only when the connection breaks will they associate with the next AP – and keep that connection to the end. They hold on to the first chosen one even when there is a much stronger AP next to the device. (This is contrary to the mobile telephone network, where access points decide which one will serve which client.) Many devices are very reluctant to roam to another AP. In WiFi the client devices decide which access point they want to associate with and when to switch to next. Unilateral transmit power increase will only work in one direction. So a good antenna and good location will improve the connection in both directions. The antenna gain and any attenuation factors work symmetrically in both directions. It doesn’t matter if the AP has a better antenna or is located higher up. The bidirectional connection is symmetrical. Have you ever been unable to connect – even though you appear to have good signal? This is the reason. It does no good if the client can receive the AP if the AP can’t receive the client. However, WiFi connection is always bidirectional. To minimize power consumption their radios typically max at 15mW (12dBm), while access points max at 100mW (20dBm) on 2.4GHz and 200mW (23dBm) on 5GHz. Mobile devices like phones and tablets have very limited batteries. All APs on the same channel will give other APs equal access to the spectrum. If your AP can receive other APs then it will share the air time with them by taking turns. In a congested environment it doesn’t matter if your access point is stronger than the neighbor’s. It even makes sense to start with minimum power and increase it until the necessary area is covered.
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