Hidden Station Problem/ Hidden Terminal Problem in WLAN

• In WLAN, when two or more stations who are out of range with each other or unknown about the presence of each other send data at the same time, simultaneously to the common station and it leads to the collision at the common station side.
• Then this kind of problem arises most probable in decentralized WLAN faces this problem due to lack of centralized system server.
• This affects the performance capacity of WLAN. Hence, it is necessary to take some preventive measures to avoid this problem in WLAN.

The Solution to Avoid Hidden Station Problem

Various methods can be applied to avoid hidden station problems some of them are as follows:

Use Omni Directional Antennas

• Most of the time stations use directional antennas hence, only sense the stations only at one side which follows directional antenna, other stations remain hidden. This creates hidden station problems to a major extend.
• To avoid this it is helpful WLAN can use both directional, omnidirectional antennas to sense all other stations involved in the WLAN.

Move the Stations

• The movement of the station is necessary so that each station can detect other stations involved in the WLAN.
• Force station to move is to extend the WLAN to add proper coverage of the hidden station.
• This may be done by increasing access points, or increasing the sensing power of the stations involved in the WLAN.

Increase transmitting power of stations

• If stations can send a large range of transmitting power then other stations can easily sense the presence of each other in WLAN.
• If all the stations can sense the presence of other stations involved in the WLAN then the hidden station problem vanishes to a greater extent.

Use Protocol Enhanced Software

• If the network is based on the poll and select method then the problem of the hidden station may be solved very easily.
• In the poll and select method the stations are divided into two categories like primary and secondary stations.
• The primary station polls the secondary station to send data in a round-robin fashion.
• Then primary station selects the secondary station to receive data sent by the secondary station.
• Each time if the secondary station wants to communicate with other secondary stations it is done with the primary station as an intermediate station.
• The primary station is an access point and the secondary stations are the communicating stations in the network.