Satellite Communication Systems - Design Principles

Multiple Access Techniques - Problems

1. With the help of diagrams discuss the principle of operation of the following multiple access schemes;
a) Frequency Division Multiple Access
b) Code division multiple scheme
c) Various Alloha Schemes
Mention the advantages and limitations of each.

2. Suggest possible satellite multiple accessing techniques for the following applications giving reasons for your choice.
a) An international FSS network.
b) A MSS network

3. Discuss the suitability of each multiple access scheme for the return link of a V-SAT network. Suggest a possible solution.

4. Describe the operation of a pre-assigned TDMA system. Illustrate a typical TDMA frame structure. Mention the advantage of TDMA over FDMA.

What do you understand by;
(i) bandwidth limited system
(ii) power limited system

b) Determine the TDMA transmission capacity of a transponder with the following characteristics: Transponder bandwidth (BT)= 72 MHz
Modulation = QPSK
Bt/Rb = 1.2 where Rb is the symbol rate.

c) Determine the TDMA capacity of a four GHz link with the following characteristics:
Satellite EIRP = 22.5 dBW
Path loss = 197 dB
G/T of earth station = 30 dB/K
Total link margin = 5dB
Required Eb/No = 8.5 dB

d) What is the voice channel capacity of a TDMA system with the following characteristics: Transmission bit rate = 60 Mbps
Voice channel bit rate = 64 Kb/s
Number of bursts/frame = 10
Number of bits in each preamble = 150
Frame time (micro seconds) = 750