Belong to Science Subject

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Wireless and
Mobile
Communication
Upena Dalal
Manoj K. Shukla

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Chapter 1
Fundamentals and
Present Scenario

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Key Topics
• Fundamental terms of communication
• Wireless communication link model
• Bandwidth and Signal-to-Noise Ratio
• Types of signals
• Types of communication systems
• Wired vs Wireless Communication
• Types of wireless systems
• Existing technologies and requirements
• Evolution of wireless systems
• First-to-fourth generation wireless systems
• Licensed and unlicensed band communication
• Spectrum policies

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Interdisciplinary Learning Model for Wireless
Communication

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Fundamental Terms of Communication
• Information---It is analog/digital form messages or meaningful
data to be received
• Modulation---It is Process by which a signal is transformed into
waveforms that are compatible with the channel requirements
• Carrier---It is the frequency over which actual communication is
done
• Transmitter---It is system that prepares the signal to transmit
over the channel
• Channel---It is media through which signal propagates
• Receiver---It is system that receives the signal and interpret the
messages

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Types of Channel
 Simplex---one way communication
 Half duplex---bidirectional but on switching basis,
one way at a time
 Full duplex---bidirectional and simulteneous

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Noise Addition in the Signal over the
Channel

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Basic Model of Wireless Digital
Communication Link

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About the Blocks
• Source Encoder-Decoder---Encoder does the job of digitization
and compression as per the information theory. Decoder does
the reverse tasks
• Encryption and decryption are for secure presentation of the
message
• Channel Coder-Decoder---Coder adds structured redundancy to
mitigate channel errors. Decoder tries to remove the error
• Other peer stages are modulator-demodulator, IF to RF
frequency up converter at the transmitting end and RF to IF
down converter at receiving end

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Additional Tasks at Transmitter
• Sending training sequences for channel estimation and
equalization and also for synchronization
• Filtering for allowing certain frequencies, pulse shaping to
reduce the bandwidth and windowing to reduce out of band
components are few actions at the transmitter end.

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Additional Tasks at the Receiver
• The peer and reverse tasks of that of transmitter mentioned in
the previous slide are performed at the receiver.
• Apart from that estimation and equalization process for
channel corrections and phase corrections respectively.
• Following are the desirable receiver characteristics:
 Sensitivity
 Selectivity
 Fidelity
 Noise Figure

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Bandwidth
No universally satisfying definition of bandwidth
• Spectrum of a signal is the collective representation of all the
frequency contents along with their amplitude weights. It is used
to characterize a signal, which can be the input signal as well as
baseband or broadband to be transmitted. Correspondingly, this is
called the signal or transmission bandwidth.
• Channel allocated to the user or application is identified as channel
bandwidth.
• While designing the transceiver hardware, certain frequency
components are allowed, is called system bandwidth.
• Transmission or system bandwidths must be less than or equal to
channel bandwidth.

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Bit rate, Symbol rate and Baud rate
• Bit is the smallest unit representing a binary level of the digital
signal. Digital data transfer is normally measured in bits per
second unit. Group of bits in general is called symbols or words.
• When the number of bits are processed together at modulator
front end for amplitude and phase mapping, they are called
symbols and rate of transfer is measured into symbol rate and
measured in symbols per second unit.
Symbol rate =
• Each symbol represents M finite states. Each symbol represents k
bits of information, where, k = log2M
• Baud rate is the rate of change of signalling or electrical (or
voltage level) transitions per second.
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