H3c-technologies H3C WA3600 Series Access Points Manuel d'utilisateur télécharger pdf (Page 275)

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802.11n

As the next generation wireless LAN technology, 802.11n supports both 2.4GHz and 5GHz bands. It

provides higher throughput to customers by using the following methods:

1. Increasing bandwidth: 802.11n can bond two adjacent 20-MHz channels together to form a

40-MHz channel. During data forwarding, the two 20-MHz channels can work separately with

one acting as the primary channel and the other acting as the secondary channel or work together

as a 40-MHz channel. This provides a simple way of doubling the data rate.

2. Improving channel utilization through the following ways:

• A-MPDU frame—By aggregating multiple message protocol data units (MPDUs) and using only

one PHY header for the Aggregated MAC Protocol Data Units (A-MPDUs), the overhead in

transmission and the number of ACK frames to be used are reduced, and thus improves channel

utilization.

• A-MSDU—Multiple MAC service data units (MSDU) can be aggregated into a single A-MSDU. This

reduces the MAC header overhead and thus improves MAC layer forwarding efficiency and

channel utilization.

• Short GI function at the physical layer—This feature shortens the guard interval (GI) of 800 ns in

802.11a/g to 400 ns. This feature effectively reduces the channel idle time, and improves channel

utilization. The short GI feature can increase the performance by about 10 percent.

Introduction to WDS

WLAN distribution system (WDS) wireless bridging uses wireless links to connect two or more separate

wired LANs or WLANs to provide connectivity between them.

Advantages of WDS

802.11 based WLAN technologies are widely applied in the home, SOHO, and enterprise scenarios,

allowing users to easily access the Internet. To provide network access services for wireless users, APs

have to be connected to existing wired networks. In the traditional method, APs must be connected to

wired networks. As a result, the network deployment cost is high, and it requires a lot time to deploy a

large-scaled network.

WDS enables you to deploy a WLAN easily in some complex environments. It has the following

advantages:

• Providing wireless connectivity between two separate LAN segments.

• Low cost for high performance deployment options

• Expandable without the need for new wiring or more access points

• Easy to deploy in scenarios of company, office, large warehouses, manufacturing, ports and

waterfronts and so on

WDS network topologies

The WDS feature provides the following three topologies as required by actual applications. WDS is

implemented through configuration of a peer MAC address for each AP. For more information, see

"Configuring a neighbor MAC address."

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H3c-technologies H3C WA3600 Series Access Points Manuel d'utilisateur Page 275