SATELLITE COMMUNICATION (NEN-044)
According to the uploaded question paper
The Satellite Communication examination is structured into three sections: A, B, and C. The paper begins with fundamental definitions and gradually advances toward system design, link budget analysis, modulation techniques, coding methods, and orbital mechanics.
Below is a detailed explanation of each section in a clear and descriptive format.
Section A – Basic Concepts and Terminology (20 Marks)
Section A consists of ten compulsory short-answer questions, each carrying two marks. This section tests your understanding of fundamental satellite communication concepts and definitions.
The questions include apogee and perigee, disadvantages of satellite communication, noise temperature, uplink and downlink frequencies in C-band, pre-emphasis and de-emphasis, comparison between FDMA and TDMA, channel capacity, rain and cloud effects, differences between GEO and LEO satellites, and basic explanation of GPS.
Although the answers are short, they require conceptual clarity. For example, noise temperature should be explained as a measure of system noise power expressed in temperature units. Similarly, rain attenuation must be described as signal weakening due to absorption and scattering by rain droplets, especially at higher frequencies.
This section evaluates your foundational understanding of orbital parameters, multiple access techniques, propagation effects, and system noise.
Section B – Orbital Mechanics and System Design (30 Marks)
Section B requires you to attempt any three questions, each carrying ten marks. This section focuses on orbital calculations, uplink and downlink design considerations, multiple access systems, propagation impairments, and DBS receivers.
One question includes a Molniya orbit problem where you must calculate orbital period and velocities at apogee and perigee. This requires application of Kepler’s laws and orbital mechanics formulas.
Another important topic is uplink and downlink design. You are expected to explain factors such as transmit power, antenna gain, path loss, atmospheric attenuation, system noise temperature, and carrier-to-noise ratio. You must also explain how uplink design differs from downlink design, particularly in terms of power requirements and noise considerations.
CDMA systems and spread spectrum techniques are also included. You must explain how multiple users share the same frequency band using unique spreading codes, and how throughput efficiency is calculated.
This section tests your analytical ability and understanding of satellite link design and multiple access techniques.
Section C – Advanced Topics and Numerical Analysis (50 Marks)
Section C carries the highest weightage and requires you to attempt one part from each question. This section evaluates advanced knowledge in satellite launch systems, antenna design, link budget analysis, modulation techniques, error control coding, and satellite navigation systems.
Topics include Kepler’s laws and orbital nodes, satellite launch vehicles and launch sequence, satellite communication antennas and their requirements, derivation of C/N ratio, FM threshold effect and improvement, DAMA systems, convolutional coding, cyclic codes, LEO and non-geostationary systems, DBS television, and satellite navigation.
For example, one question requires derivation of the C/N ratio and calculation of G/T (antenna gain to noise temperature ratio) using link budget parameters such as GRP, path length, frequency, and losses. This involves understanding free space path loss and Boltzmann’s constant.
Another question requires generating a systematic cyclic code using a given generator polynomial. This involves polynomial division in modulo-2 arithmetic.
Similarly, convolutional coding must be explained in terms of shift registers, encoder structure, and improved error correction capability compared to block codes.
This section tests deep understanding of satellite link analysis, digital communication techniques, coding theory, and advanced satellite systems.
Overall Paper Structure and Preparation Strategy
The paper is logically structured:
Section A checks fundamental definitions and concepts.
Section B evaluates orbital calculations and system design principles.
Section C tests advanced theoretical derivations, numerical problems, and communication techniques.
To score well:
Strengthen your understanding of orbital mechanics and Kepler’s laws.
Practice link budget calculations and C/N derivations.
Study multiple access techniques (FDMA, TDMA, CDMA).
Understand error control coding methods such as cyclic and convolutional codes.
Learn block diagrams of DBS receivers and satellite communication systems.
