Wireless Communication | Set 2

• Last Updated : 29 May, 2020

Prerequisite – Wireless Communication | Set 1

Basic Service Set :
We know that wireless communication takes place over the Air. To regulate connection to devices, we need to make every wireless service area a closed group of mobile devices that form around a fixed device. Before mobile devices start data communication, they must advertise their capabilities, and then permission to join should be granted. There is a term defined to such arrangement, IEEE calls this standard a Basic service set (BSS).

At the center of every BSS, there is an access point (AP), it provides services that are necessary to form the infrastructure of Wireless communication. The AP operates in an infrastructure mode and uses a single wireless channel. All devices that want to connect to AP must use that same channel.

Because the operation of BSS depends on AP, BSS is bounded to the area covered by the AP i.e, the area up to which AP’s signal is reachable. This area is called the Basic Service Area (BSA) or cell. The cell is usually a circular shape with the center as AP. The AP serves as a single point of contact for the BSS. The AP uses a unique BSS identifier (BSSID) based on its own MAC address to advertise it’s existence to all devices in the cell.

The AP also advertises a human-readable text string called Service Set identifier (SSID) to uniquely identify the AP. You can say BSSID as a machine-readable unique tag to identify a wireless service and SSID a human-readable service tag.

Membership of mobile devices with BSS is called Association. Once associated, the device becomes a BSS client or an 802.11 station (STA). As long as devices are connected to AP, all data communication passes through AP using BSSID as a source and destination address. You can think why all traffic must pass through AP? They can simply communicate with other devices directly without AP as a middleman. If we don’t do so then the whole point of wireless service will go in vain. Sending data through AP make it stable and controllable

Repeater :
An AP in wireless infrastructure usually connected back to the switched networks. BSS has a limited signal coverage area, (BSA). To extend the signal coverage, we can add additional AP but in some scenarios, it is not possible to add additional AP. The solution in such a situation is a Repeater. The repeater is just an AP configured in Repeater mode. A wireless repeater takes a signal as an input and retransmits signals in a new cell around Repeater. The repeater uses two transmitters and receiver to keep the original and repeated signals isolated on a different channel.