VoWLAN basic Q & A 3 802.11e protocol analysis

Will 802.11e really become a VoWLAN savior as people claim?

The answer is either or not. 802.11e is a quality of service (QoS) standard. It has now ruled out some significant burdens and is praised by people as a panacea for wireless VoIP, in fact, it does not meet such requirements.

First, the seller has made little effort to require it to change the hardware interface to adapt to the 802.11e standard, which is why there is a pre-standard version, By the way: WMM certification from the Wi-Fi Alliance is a complete test of the ARE accreditation criteria ). Hardware replacement is not expected by everyone, which makes it difficult to use 802.11e.

Second, 802.11e basically has two items: one is the Enhanced Distributed Coordination function EDCF), which gives priority to transmission of important clients, and the other is the Hybrid Coordination function HCF ), it supports identified and probably mixed channel access in a marked way.

In a single access point AP), The 802.11e will be absolutely enhanced by 802.11. That is to say, the home, Home Office, and small office will greatly improve communication and multimedia applications. However, large configurations still have problems.

Large configuration means there are many Access Point APs that are very close to each other) and more clients. This makes the final 100 feet transmission problem more complicated. I usually divide it into wired or network problems, the last 100 feet problems, or air transmission problems for and away from access points ). If there are many clients, EDCF may have problems. This is because if there are many top clients, there will be a lot of conflicts in terms of statistics, because in the unordered time lottery, they will not truly become lucky, and they will continue to conflict with other clients. So what if we only use HCF? HCF is certainly helpful for a large number of client accesses, but there are many access points in large configurations, and each access point will effectively get its own "flag ". Because there are too many access points, the neighboring access points may show their signs at the same time, so that the client will interfere with each other. Therefore, this function is not very effective.

802.11e will be a good supplement for hot areas, home or small offices. For large enterprises, networks with coordinated transmission for channel control can provide real service quality. It is not uncommon to use the network control and coordinated transmission mode. The cellular telephone network has already integrated this technology. It is a large network with a large number of compound access points and millions of clients.

1. 802.11e enhanced Lan-free QoS service
2. 802.11 summary of the protocol family