Filters are required in wireless communication systems for multiple reasons: 1) At the transmitting end, filters are needed to limit the bandwidth of the transmitted signal and prevent interference with other frequency bands. Without filters, a wide range of frequencies would be transmitted. 2) At the receiving end, filters are required to select the desired incoming signal and reject signals from other transmitters using nearby frequencies. Without filters, the receiver would not be able to distinguish different signals. 3) If no filters are used at all, the system would be unable to isolate different frequency bands and signals would interfere with each other, degrading performance and preventing reliable communication from taking place. Filters are necessary to allow multiple access techniques like FDMA

1. ASSIGNMENT
OF
WIRELESS COMMUNICATION
SUBMITTED BY :-
VISHAL KANATHIA
14 MBA 1347
SECTION – 3(D)

2. o WHY MULTIPLE ACCESS IS REQUIRED ? IDENTIFY THE
APPLICATION OF DIFFERENT MULTIPLE ACCESS
TECHNIQUES IN PRACTICALCOMMUNICATION SYSTEM
??
In telecommunications and computer networks, a channel access
method or multiple access method allows several terminals connected to
the same multi-point transmission medium to transmit over it and to share its
capacity.
A channel-access scheme is based on a multiplexing method, that allows
several data streams or signals to share the same communication
channel or physical medium. Multiplexing is in this context provided by
the physical layer.
A channel-access scheme is also based on a multiple access protocol and
control mechanism, also known as media access control (MAC). This protocol
deals with issues such as addressing, assigning multiplex channels to
different users, and avoiding collisions.
APPLICATION OF DIFFERENT MULTIPLE ACCESS
TECHNIQUES
Frequency Division Multiple Access (FDMA)
The frequency-division multiple access (FDMA) channel-access scheme is based on
the frequency-division multiplexing (FDM) scheme, which provides different
frequency bands to different data-streams. In the FDMA case, the data streams are
allocated to different nodes or devices.
A related technique is wavelength division multiple access (WDMA), based
on wavelength-division multiplexing (WDM), where different datastreams get
different colors in fiber-optical communications. In the WDMA case, different
network nodes in a bus or hub network get a different color.
Time division multiple access (TDMA)
The time division multiple access (TDMA) channel access scheme is based on the time-
division multiplexing (TDM) scheme, which provides different time-slots to different data-
streams (in the TDMA case to different transmitters) in a cyclically repetitive frame
structure. For example, node 1 may use time slot 1, node 2 time slot 2, etc. until the last
transmitter. Then it starts all over again, in a repetitive pattern, until a connection is
ended and that slot becomes free or assigned to another node. An advanced form is

3. Dynamic TDMA (DTDMA), where a scheduling may give different time sometimes but
some times node 1 may use time slot 1 in first frame and use another time slot in next
frame.
As an example, 2G cellular systems are based on a combination of TDMA and FDMA.
Each frequency channel is divided into eight timeslots, of which seven are used for
seven phone calls, and one for signalling data.
Code division multiple access (CDMA)
The code division multiple access (CDMA) scheme is based on spread spectrum,
meaning that a wider radio spectrum in Hertz is used than the data rate of each of the
transferred bit streams, and several message signals are transferred simultaneously
over the same carrier frequency, utilizing different spreading codes. The wide bandwidth
makes it possible to send with a very poor signal-to-noise ratio of much less than 1
Space division multiple access (SDMA)
Space division multiple access (SDMA) transmits different information in different
physical areas. Examples include simple cellular radio systems and more advanced
cellular systems which use directional antennas and power modulation to refine spacial
transmission patterns.
(2) why filters are required ? whatwould happen iffilters are not
used
(A) at the transmitting end.
(b) at the receivingend .
(c) no filters are used at all.
Filter design is the process of designing a signal processing filter that satisfies a set
of requirements, some of which are contradictory. The purpose is to find a realization
of the filter that meets each of the requirements to a sufficient degree to make it
useful.
Filters are requird because each filter increases line loss users should not
use more than 5 microfilters on their inside wiring. There are active

4. microfilters specifically designed for homes that require more than 5 filters
or you should create a homerun with a single dedicated splitter.
Typical requirements which are considered in the design process are:
 The filter should have a specific frequency response
 The filter should have a specific phase shift or group delay
 The filter should have a specific impulse response
 The filter should be causal
 The filter should be stable
 The filter should be localized
 The computational complexity of the filter should be low
 The filter should be implemented in particular hardware or software.
(A) IF FILTERS ARE NOT USED AT THE TRANSMITTING END ?