Broadcast vary with respect to whether time is continuous

Broadcast
signals are used to link networks. This paper deals with the MAC protocol of
the broadcast links.

         In any wireless network, the main problem is how to verify
who gets to use the channel when there is conflict for it. When only one
channel is accessible, it is much choasful to determine who should send the
next bit. Many protocols for solving the problem are known.

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                                                      In the
literature, relay channels are occationally referred to as multiaccess channels
or random access channels.

The MAC sublayer is mainly
important in LANs, especially wireless ones because wireless is by default a
broadcast channel.

 

MULTIPLE ACCESS PROTOCOLS

The Medium Access
Control (MAC) sublayer, also called the media
access control sublayer allocates the
flow switch and multiplexing for the transmission medium (physical layer).

The channel access control anatomy alloted
by the MAC layer are also known as a multiple access protocol. This makes
it viable for various stations tethered to the same physical
medium to divide it. The multiple access protocol may identify or evade
data packet collisions if a packet mode variance   based channel access method is
used. The channel access control mechanism rely on a physical layer multiplex plot.

                        Many algorithms for
allocating a multiple access channel are known. Some of the protocols are,

 

ALOHA:

                              ALOHA
uses short-ranged radios, with each user terminal sharing the same upstream
frequency to send frames to the central computer. It includes a simple and
elegant method to solve the channel allocation problem.

                                                            There
are two genres of ALOHA: pure and slotted. They vary with respect to whether
time is continuous as in the pure version or divided into discontinuous time
slots into which all frames must fit as in the slotted kind.

 

CSMA/CD:

With ALOHA, the maximum channel employment that can be
achieved is 1/e. Protocols in which stations tune in for a transmission and act
correspondingly are called Carrier Sense Protocols(CSP).

CSMA/CD is the basic of the classic Ethernet LAN.
CSMA/CD is used to enhance CSMA performance by winding up transmission as soon
as a collision is identified, thus trimming the time needed before a reattempt
can be carried out.

 

RTS/CTS:

 RTS stands for Request to
Send whereas CTS is the acronym for Clear to Send is a mechanism used by the wireless
networking protocol to lessen frame collisions initiated by the hidden node trouble
and was used by the 802.11 networking protocol as an elective mechanism.

 

I.     INTRODUCTION
TO WIRELESS SENSOR NETWORKS

A Wireless Sensor Network is a kind of wireless network that
includes a large number of circulating,
self-directed, minute, low powered devices. There are sensor nodes and
are called as motes.

A wireless sensor network
collects data and send the same to the sink node by using the wireless link to
base station. This Network is used in calamity management, biomedical,
military, and so on. The sensor node consists of batteries, microcontrollers, memory
devices, the sensor nodes is like low cost, power consumption, small size, ease
of deployment and self-organization.

These networks clearly traverse a huge number of spatially distributed, little, battery-operated,
embedded devices that are networked to cautiously accumulate, process, and transfer data to the operators, and it has
control over the forte of computing & processing.