14 1 IEEE 802 11 IEEE has defined

14 -1 IEEE 802. 11 IEEE has defined the specifications for a wireless LAN, called IEEE 802. 11, which covers the physical and data link layers.

Basic Service Set: Note A BSS without an AP is called an ad hoc network; a BSS with an AP is called an infrastructure network.

Basic service sets (BSSs)

Extended service sets (ESSs)

CSMA/CA flowchart

CSMA/CA and NAV

Hidden station problem

Note The CTS frame in CSMA/CA handshake can prevent collision from a hidden station.

Use of handshaking to prevent hidden station problem

Exposed station problem

BLUETOOTH Bluetooth is a wireless LAN technology designed to connect devices of different functions such as telephones, notebooks, computers, cameras, printers, coffee makers, and so on. A Bluetooth LAN is an ad hoc network, which means that the network is formed spontaneously.

The Basic Idea • Bluetooth is a standard for a small , cheap radio chip to be plugged into computers, printers, mobile phones, etc • Bluetooth chip is designed to replace cables. Information normally carried by the cable, is transmitted at a special frequency to a receiver Bluetooth chip. • These devices can form a quick ad-hoc secure “piconet” and start communication. • Connections in the “piconets” can occur even when mobile.

“Piconet” – – – A collection of devices connected via Bluetooth technology in an ad hoc fashion. A piconet starts with two connected devices, and may grow to eight connected devices. However, when establishing a piconet, one unit will act as a Master and the other(s) as slave(s) for the duration of the piconet connection.

Requirements • Low cost as cables • Secure as cables – must support authentication and encryption • Must support both data and voice. • Must connect to a variety of devices. • Must be able to function in a noisy environment. • Must support many simultaneous and private “piconets”. • Must be low power, compact and global.

Piconet

Scatternet