Gugrajah_Yuvaan_ Ramesh_2003.pdf

Introduction Chapter 1
devices can communicate wirelessly over short ranges with up to seven other devices
in a small network referred to as a piconet. One device in the piconet becomes a
master while the others are considered slaves. Two or more piconets can be
interconnected to form a scattemet. However solutions for forming multi-hop ad hoc
networks over Bluetooth scattemets still need to be introduced.
Bluetooth neither addresses routing, nor specifies which of the unicast and multicast
routing protocols to use and the Bluetooth medium access control protocol does not
specify how to cope with mobility. Initially, Bluetooth is being used as a replacement
for point to point and point to multipoint cables. However, the small size of
Bluetooth solutions (a chip is approximately 2 cm 2 centimetres in area), low cost
(approximately $10 per chip) and low power requirements (lmW to 100mW for
ranges of O.lm to lOOm), together with the involvement of many of the major
wireless communication device manufacturers (such as Ericsson, Nokia, Toshiba,
IBM, Lucent, Microsoft, 3Com and Intel) proves advantageous for the future of
Bluetooth.
IEEE 802.11 specifies a wireless interface between a client and a base station or
access point, as well as between clients, operating at between 1 and 2 Mbps. Two
physical layer characteristics are defined: direct-sequence spread spectrum (DSSS),
and frequency-hopping spread spectrum (FHSS), both o.f which operate in the 2.4
GHz range. The 802.11b "High Rate" amendment to the standard added two higher
speeds at 5.5 Mbps and 11 Mbps to 802.11 and selected DSSS as the sole physical
layer technique. The point coordination function (PCF) uses a centralized approach
to allow an access point to control all traffic, while the distributed coordination
function (DCF) allows direct communication between wireless clients. However, the
IEEE 802.11 standard also does not specify a method for multihop ad hoc
networking.
Other protocols that have potential for ad hoc networking include the HomeRF
working group's Shared Wireless Access Protocol (SWAP) [CSDMagOO] and the
infrared communication protocols [IrDA] of the Infrared Data Association (IrDA).
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