Wireless distribution system
The Wireless Distribution System ( WDS ) is a method for addressing data frames in wireless local area networks according to IEEE 802.11 , which enables sophisticated topologies , was defined briefly in 1999 and is often misunderstood. The definition leaves open how WDS should be used.
This addressing creates the basis for ad hoc networks , gateways to local area networks of other standards such as Ethernet , and, for example, for bridges using radio technology . For ad hoc networks and gateways, the data frames are assigned three addresses, for all other purposes with four addresses:
- addressee
- Transmitter
- target
- source
With this 4-address format , diverse applications are possible and are completely free from the WDS.
Wireless backbone
One possible application of WDS is a radio network made up of several WLAN base stations ( Wireless Access Point , AP). In this way, you can achieve greater network coverage than with a single access point without wiring all base stations. All that is required is the power supply to each individual base station. WDS can be integrated via a single WLAN interface on the AP as well as several.
technology
Single-Radio-WDS uses the WLAN interface both for the connection to a neighboring access point and for supplying the WLAN users ( clients ). The data transmission rate of the interface is halved because the packets have to be transmitted twice. Therefore, WDS can be better implemented with dual radio access points . One transmitter in the AP is used to connect the next access point, and a second for the clients.
As an alternative or in addition, more complex techniques such as directional radio , beamforming or multi-path propagation ( MIMO ) can be used to counteract or even prevent a reduction in bandwidth even when using a single radio channel. In practice, however, this rarely happens.
Ideally, transmitters with different standards are used (e.g. 802.11a , 802.11b / 802.11g and 802.11n ). The individual access points must know the WLAN MAC addresses of the other access points. In addition, everyone should use the same SSID (mandatory for WPA encryption), the same channel and the same network key ( WPA or the less secure WEP ), as otherwise roaming or handover , i.e. the "on the fly" change from one access point to another, is not possible.
WDS modes
A distinction is made between the bridging mode , in which two access points configured as WLAN bridges only communicate with each other (without further clients being able to connect), and the repeating mode , in which several access points are connected to each other via WDS and also each other WLAN clients are allowed to connect. In the latter mode, the WLAN can be "extended", but most devices only work with WEP encryption.
Connections in which an access point connects to a single other access point via WDS are called direct connections ( point-to-point ), while connections in which an access point connects to several access points are called point-to-multipoint Connections. However, these two connection types have no influence on the possibilities of using the bridge and repeater modes.
Comparison with alternative WLAN range extensions
WDS is often confused with the Universal Repeater Mode, which is supported by many access points.
| Wireless Distribution System (WDS) | Universal repeater mode | |
|---|---|---|
| function | Bridge between access points | Repeater acts as a client |
| configuration | Setting required on both access points | Setting only necessary on repeater (client) |
| Same WLAN channel required | Yes | Yes |
| Halving the WLAN bandwidth | Yes | Yes |
| Encryption | WEP only (WPA only possible in a proprietary manner from the same manufacturers) | WEP, WPA , WPA2 |
| Same SSID necessary | yes (with encryption) | No |
| Roaming between access points possible | Yes | No |
Web links
- WDS using the example of DD-WRT (English)
- WDS using the example of TP-LINK (English)
Individual evidence
- ↑ a b c “WDS” Clarifications (DOC; 224 KB) Institute of Electrical and Electronics Engineers . Retrieved April 28, 2012.