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Luigi Paura » 1.Presentation of the course

Presentation of the course

Book: Communication System Engineering, J G. Proakis, M. Salehi, II edition
Goals of the course

The course introduces the main aspects and topics related to digital transmission systems. More specifically digital modulation and demodulation techniques are introduced and discussed and mail coding and channel models are analyzed as well. The approach is methological, but, applicative problems are also considered. The main tradeoffs between the fundamental parameters ( bandwidth, available power at the transmission side, hardware complexity and performances) of a digital communication system are studied.

Characteristics of the course

Propedeuticities: Signal Theory and Electrical Communications
It is mandatory for the curriculum Transmission and it is optional for the curriculum Telematics in the degree in Engineering of Telecommunications
It is mandatory for the degree in a Specialistic Engineering of Telecommunications
The course deals mainly with foundational and methodological topics

The objective of the course is to provide an introduction to the basic principles of analysis and design of digital communication
systems

Topics of the course

Characterization of the Information Source (I Shannon theorem)
Characterization of the Transmission Channel (II Shannon theorem)
Memoryless Modulation and optimum reception in AWGN (Comparison among the different techniques)
Transmission over bandlimited channel: ISI
Fundamentals of the Channel Coding: linear block codes
Fundamentals of the fading channel

Canonical scheme of a trasmission digital system for a point-to-point link

Canonical scheme of a trasmission digital system for a point-to-point link (next)

Canonical scheme of a transmission digital system for a point-to-point link (next)

The souce coder produces an efficient representation of the Information produced by the source dropping the existing redundancy of the sequence X_i → Data Compression

Less memory occupancy.
Less communication resources.

Canonical scheme of a transmission digital system for a point-to-point link (next)

The imput symbols ε Source coding alphabet.
The output symbols ε Channel coding alphabet.
The channel coder introduces “ad hoc” redundancy (e.g, parity bits, repetition codes, etc.) to make the information more tollerant against channel impairments such as additive noise, interferences and fadings.

Canonical scheme of a trasmission digital system for a point-to-point link (next)

The data modulator is the interface between the digital section of the transmission system and the transmission medium (twisted pair, coaxial cable, radio spectrum etc.).

It synthesizes the continuous-time signal (waveform) starting from the symbol sequence (digital signal) produced by the channel coder Es. Bock memoriless modulator : Y_i↔s_i(t).

Canonical scheme of a transmission digital system for a point-to-point link (next)

Canonical scheme of a trasmission digital system for a point-to-point link (next)

Canonical scheme of a transmission digital system for a point-to-point link (next)

The symbol block at the channel decoder input is transformed in a block of symbols ∈ Source Coding Alphabet

Canonical scheme of a trasmission digital system for a point-to-point link (next)

The blocks of source-coding symbols are converted in blocks of source-symbols to be delivered to the final user.

Canonical scheme of a trasmission digital system for a point-to-point link (next)

The final user imposes the reliability level to be guaranteed associated with the delivered information.

Accuracy degree → amount of data compression.
Reliability level → bit error probability (BER).

Canonical scheme of a transmission digital system for a point-to-point link (next)

The channel coding and the modulation can be performed by a single operation.
In a real system one or more blocks of the canonical scheme can be omitted.
Example:
The channel is good enough (or the required BER is sufficiently high) so that source coding can be avoided.

The source information is enough compressed so that the source coding can be avoided.