INSTITUTE OF AERONAUTICAL ENGINEERING (Autonomous) Dundigal, Hyderabad

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1 INSTITUTE OF AERONAUTICAL ENGINEERING (Autonomous) Dundigal, Hyderabad ELECTRONICS AND COMMUNICATION ENGINEERING TUTORIAL QUESTION BANK Course Name : SATELLITE COMMUNICATION Course Code : AEC Class : B.Tech VI Semester Branch : ECE Academic Year : 01-1 Course Coordinator : Dr. V. Sivanagaraju, Professor, ECE Course Faculty : Dr. V. Sivanagaraju, Professor, ECE COURSE OBJECTIVES: The course should enable the students to: S. NO DESCRIPTION I Be Proficient in the concept of Satellite communication and understand placement of communication satellite in GEO II Analyze the Satellite link budget and explain the satellite subsystems like telemetry, tracking and command system III Discuss the different types of multiple access techniques in communication satellites. IV the concept of VSAT systems and packet switching in satellites. COURSE LEARNING OUTCOMES: Students, who complete the course, will have demonstrated the ability to do the following: CAEC.01 CAEC.0 CAEC.0 CAEC.0 CAEC.0 CAEC.06 CAEC.0 CAEC.0 CAEC.0 CAEC.10 CAEC.11 Discuss the different satellite systems like Low earth orbit (LEO), Medium earth orbit (MEO) and Geo synchronous earth orbit (GEO). how the satellite is locating with respect to earth and orbital perturbations due to earth s oblateness, moon and sun. the satellite sub systems like Telemetry, tracking and command system, power system, satellite antenna equipment, communications subsystem and transponders Analyze the design of satellite links for a specified C/N with and without frequency Re-use and link budget. Discuss the propagation effects like atmospheric absorption, cloud attenuation, troposphere and ionospeheric scintillation and low angle fading. Discuss the effects of rain, rain induced attenuation, rain induced cross polarization and interference. Analyze the various multiple access techniques used in communication satellites like FDMA, TDMA and CDMA. Analyze the concept of demand assignment multiple access (DAMA), types of demand assignment and characteristics. the significance of Spread Spectrum Multiple Access (SSMA), Direct sequence CDMA (DS-CDMA) or DS spread spectrum transmission and reception. and analyze the Earth Station technology transmitters, receivers, antennas, tracking systems, terrestrial interface, power test methods and lower orbit considerations Analyze the Very Small Aperture Terminal (VSAT) network architecture, access control and multiple access selection. 1 P a g e

2 CAEC.1 CAEC.1 CAEC.1 CAEC.1 CAEC.16 CAEC.1 Analyze the constellation design of Non Geostationary Orbit (NGSO) coverage, frequency bands, delay and throughput. the message transmission by FDMA using M/G/1 queue and message transmission by TDMA using pure aloha. Apply the error control coding for digital satellite links like block codes and convolution codes. Evaluate the future satellite communication systems and introduction to satellite laser communication. Apply the concept of satellite communication to understand and analyze real time applications. Acquire the knowledge and develop capability to succeed national and international level competitive examinations. TUTORIAL QUESTION BANK S. No QUESTION Blooms Taxonomy Level Course Learning Outcome UNIT-I COMMUNICATIONS SPACECRAFT AND ORBITS PART-A (SHORT ANSWER QUESTIONS) 1 Explain how a satellite is located with respect to earth? CAEC.01 Discuss the present trends of satellite communications? CAEC.01 Define sun transit outage? CAEC.01 Describe the effect of solar eclipse? CAEC.01 Define Doppler shift? CAEC.01 6 Define Kepler s law for planetary motion? CAEC.01 Describe the meant by first point of Aries? CAEC.0 Define coverage angle? CAEC.01 Define an orbit? CAEC Describe the meant by slant range? CAEC Describe the types of orbits? CAEC.01 1 Describe the steps involved in launching a satellite? CAEC.0 1 Describe the difference between a geosynchronous and a CAEC.01 geostationary satellite? 1 Describe the difference between active and passive satellites? CAEC.01 1 Describe the meaning of apogee and perigee? CAEC.01 PART-B (LONG ANSWER QUESTIONS) 1 Explain the historical background of satellite communication? CAEC.01 6 Describe different frequency bands which are allocated for satellite Communication and explain the uses of these frequencies? Demonstrate the orbital aspects, which are of importance in synchronous satellite communications. Explain these aspects in brief? State the various steps involved in placing the satellite in geostationary orbit and explain it with diagram? Examine the term first point of ARIES and what is its importance in the determination of position of satellite in space? Give the mathematical formulation of Kepler s third law of planetary motion. What do the terms perigee and apogee mean when used to describe the orbit of a satellite orbiting the earth. Explain the importance of inclined orbits in satellite communication. CAEC.01 CAEC.0 CAEC.0 CAEC.0 CAEC.01 CAEC.01 P a g e

3 Give a overview of present and future trends of satellite communications. CAEC.0 Explain the following terms: CAEC.01 (i) LEO (ii) MEO (iii) GEO Discuss the steps involved locating the satellite with respect to the CAEC.0 earth. PART-C (PROBLEM SOLVING AND CRITICAL THINKING QUESTIONS) The earth rotates once per sidereal day of h 6min s, show that CAEC.01 the radius of the GEO is,16.1 km. A low earth orbit satellite orbits at an altitude of 0km above the CAEC.01 earth s surface, the mean earth s radius is approximately 6.1km, calculate the period of the satellite orbit when the altitude is 0km and the orbit is circular. Find the velocity of the satellite along its orbit. A satellite is in an elliptical with a perigee of 1000km and an CAEC.0 apogee of 000km. using a mean earth radius of 6.1km; find the period and the eccentricity of the orbit. A quasi-geo satellite is in a circular orbit close to geosynchronous CAEC.0 altitude; its orbital period is exactly h. Calculate the radius of the orbit and the rate of drift. A low earth orbit satellite is in a circular polar orbit with an altitude CAEC.01 of 1000 km. a transmitter on the satellite has a frequency of.6 GHz. Find the velocity of the satellite and Doppler shift of the received signal. Derive the coverage angle and slant range to the CAEC.01 geostationary satellite in detail. What are the maximum values of the two parameters. A satellite is moving in an elliptical orbit with the semi major axis CAEC.01 equals to 1 Km. If the perigee distance is 6 Km, find the apogee height and orbit eccentricity Calculate the slant range of a geostationary satellite orbiting at CAEC km from an earth station making an elevation angle of. Also find the viewing of the satellite. A satellite is in -km high circular orbit Estimate. CAEC.0 i. Orbital angular velocity. ii. Orbital period & Orbital linear velocity. Apogee and perigee of a elliptical satellite orbit are 000km and 00km, Determine the eccentricity semi major axis and the semi minor axis UNIT-II CAEC.0 SPACE SEGMENT PART-A(SHORT ANSWER QUESTIONS) 1 List out the types of satellite subsystems. CAEC.0 Describe the importance of Telemetry and monitoring CAEC.06 Describe the attitude and orbit control system (AOCS) CAEC.0 List the types of antennas are used on satellites CAEC.0 Describe the term of housekeeping in satellite communication CAEC.06 6 Describe the link outage CAEC.0 Discuss about low angle fading CAEC.0 P a g e

4 Describe different frequency bands which are allocated for satellite communication CAEC.06 Describe the EIRP? CAEC.0 10 Describe the tracking, command? CAEC.0 11 Describe the propagation effects CAEC.0 1 Discuss the affect of C/N and G/T ratios CAEC.0 1 Define path loss CAEC.0 1 Describe the rain effects at Ku band CAEC.0 1 Classify the types of transponder used in satellite CAEC.0 PART-B (LONG ANSWER QUESTIONS) 1 Formulate general link equation using basic transmission theory. CAEC.06 Explain telemetry, tracking and command (TT&C) subsystem of a satellite With the help of block diagram? CAEC.06 Analyze the travelling wave tube amplifier operation. CAEC.0 Explain the working operation of transponder with the help of block diagram for both single and double conversion CAEC.06 State how does the system noise temperature affect the performance? Derive the expression for overall system noise CAEC.06 temperature at the receiving earth station. 6 Explain in detail satellite communication link design procedure CAEC.06 Find out an expression for C/N and G/T ratios. Explain the importance of these ratios on satellite link design CAEC.0 Explain the functions and characteristics of satellites and various sub- systems of satellites CAEC.0 Explain what do understand by G/T ratio? Prove that the figure of merit shows the performance of the receiver circuitry CAEC.0 10 Discuss the propagation effects like atmospheric absorption, cloud attenuation and troposphere scintillation CAEC.06 PART-C (PROBLEM SOLVING AND CRITICAL THINKING QUESTIONS) A satellite at a distance of 0000 km from a point on the earth s surface radiates a power of 10W from an antenna with a gain of 1 CAEC.0 1 db in the direction of the observer. Find the flux density at the receiving point and the power received by an antenna at this point with an effective area of 10 meters square A satellite at a distance of 0000 km from a point on the earth s surface radiates a power of 10W from an antenna with a gain of 1 CAEC.06 db in the direction of the observer and operates at a frequency of 11GHz. The receiving antenna has a gain of. db, find the received power. Suppose we have a GHz receiver with the following gains and CAEC.0 noise temperatures,,,,,,, Calculate the system noise temperature assuming that the mixer has a gain. An earth station antenna has a diameter of 0m, has an overall efficiency of 6%, and is used to receive a signal at 10MHz. At this frequency, the system noise temperature is K when the CAEC.0 antenna points at the satellite at an elevation angle of degrees. What is the earth station G/T ratio under these conditions, if heavy rain causes the sky temperature to increase so that the system noise temperature rises to K, what is the new G/T ratio? An earth station transmits at.6 GHz from an antenna of 6m. The transmitter generates an output of KW. The satellite is 0 km CAEC.06 from the earth station. The efficiency of transmitting antenna being 0.. Calculate path loss, transmitting antenna gain, transmitter power in dbw, EIRP and received power at the satellite. P a g e

5 6 10 In a satellite receiving system, the input equivalent noise temperature to RF antenna is 0K. The receiving system has following characteristics,,,,,, Calculate the system noise temperature and noise power produced by this receiver, if receiver BW is 10MHz. A satellite orbiting at 000km transmits signal at 11. GHz. The output power of the satellite transmitter is 0 mw fed to an antenna of directive gain 1. db. The earth station antenna being m dish with efficiency 60%. Find the G/T ratio of the earth station of bandwidth 6MHz if C/N equal 0dB. A constellation of low earth orbit satellites has an altitude of 1000 km. each satellite has two multiple beam antennas that generate 16 beams. One antenna is used to transmit at. GHz and the other antenna receives at 1.6 GHz. Find the coverage angle of the satellite antenna when the lowest elevation angle for an earth station is 10 degrees. A satellite at geo stationary orbit from a point on the earth s surface operates at a frequency of 1GHz. The receiving antenna has a gain of db, find the received power. Thermal noise in an earth station receiver results in a (C/N) dn ratio of 0 db. A signal is received from a bent pipe transponder with a carrier to noise ratio (C/N) up is 0 db. What is the overall (C/N)o at the earth station? If the transponder introduces intermodulation products with (C/I) ratio is db, what is the overall (C/N) ratio at the receiving earth station? CAEC.06 CAEC.06 CAEC.06 CAEC.06 CAEC.0 UNIT-III COMMUNICATION SATTELLITE ACCESS SYSTEMS PART-A(SHORT ANSWER QUESTIONS) 1 Define multiple access. CAEC.0 Write the advantages of time division multiple access CAEC.0 Describe the pre assigned access CAEC.0 Describe frequency division multiple access CAEC.0 Describe the code division multiple access CAEC.0 6 Describe the demand access CAEC.0 Describe the categories of FDMA scheme. CAEC.0 Define preamble CAEC.0 State any two types of spread spectrum techniques CAEC.0 10 Explain the function of various controls in DAMA system CAEC.0 11 Discriminate multiplexing with multiple access CAEC.0 1 List the applications of spread spectrum techniques. CAEC.0 1 Describe CBTR in TDMA system CAEC.0 1 Recall the expression for calculation of C/N with intermodulation CAEC.0 1 Define burst? Explain the method of control burst plan CAEC.0 1 Describe the time division multiple access CAEC.0 Describe the disadvantages of FDMA CAEC.0 Describe the demand assignment multiple access CAEC.0 List out the limitations of frequency division multiple access CAEC.0 List Out the benefits of satellite diversity CAEC.0 6 Describe the disadvantages of time division multiple access CAEC.0 Write what is guard time? Mention its role in TDMA efficiency CAEC.0 Describe the single channel per carrier CAEC.0 Define SPADE CAEC.0 P a g e

6 10 Describe the multiple channels per carrier CAEC.0 11 Discuss the direct sequence spread spectrum CAEC.0 1 Write the formula for processing gain CAEC.0 1 Define frame efficiency CAEC.0 1 List out the types of handover in satellite communication CAEC.0 1 Compare any three multiple access techniques CAEC.0 PART-B(LONG ANSWER QUESTIONS) 1 With necessary diagrams explain the principle of TDMA CAEC.0 Draw the burst structure of TDMA frame and explain briefly. CAEC.0 Explain the concept of onboard processing in transponder. CAEC.0 Describe the DS spread spectrum transmission and reception in CAEC.0 code division multiple access. Describe the characteristics of demand access multiple access. CAEC.0 1 Describe the term satellite switched TDMA. CAEC.0 With a neat sketch explain the frame structure of a TDMA. CAEC.0 Mention the types of demand assignment and Explain the demand CAEC.0 assignment multiple access (DAMA). Explain the block diagram of typical FDMA satellite systems. CAEC.0 Explain the following terms: i) Handover ii) inter modulation iii) satellite diversity CAEC.0 PART-C (PROBLEM SOLVING AND CRITICAL THINKING QUESTIONS) Estimate the buffer requirement of a TDMA switch if the transmitter and receiver are operating at.mhz and. MHz CAEC.0 1 respectively. While 6,1 symbols are transmitted during a frame period of 1ms.thestability requirement is.* seconds and frame transmission rate MBps. A satellite has an EIRP of dbw and earth stations each with G/T of. db/k share equally the total transponder in FM/FDMA. These links are characterized as : uplink C/N = db, CAEC.0 inter modulation C/N =0dB, output back off = 6dB, downlink path loss = 1 db, RMS frequency deviation of carrier = 60 khz. Calculate the number of KHz voice channels that each earth station can transmit in order to meet an overall C/N of 16 db at receiver input. Assuming voice activity advantage of 10dB. A 1-GHz uplink operates with transmission losses and margins totaling 1 db and a satellite [G/T] 10 db/k. The required uplink [Eb/N0] is 1 db. (a) Assuming FDMA operation and an earth CAEC.0 station uplink antenna gain of 6 db, calculate the earth station transmitter power needed for transmission of a T1 baseband signal. (b) If the downlink transmission rate is fixed at dbb/s, calculate the uplink power increase required for TDMA operation. In a TDMA network the reference burst and the preamble each requires 60 bits, and the nominal guard interval between bursts is CAEC.0 equivalent to 10 bits. Given that there are eight traffic bursts and one reference burst per frame and the total frame length is equivalent to 0,00 bits, calculate the frame efficiency. FDMA is used for uplink access in a satellite digital network, with each earth station transmitting at the T1 bit rate of 1. Mb/s. CAEC.0 Calculate (a) the uplink [C/N0] ratio required to provide a [Eb/N0] 1 db ratio at the satellite and (b) the earth-station [EIRP] needed to realize the [C/N0] value. The satellite [G/T] value is db/k, and total uplink losses amount to 10 db. 6 P a g e

7 1 The IF bandwidth for a CDMA system is MHz, the roll off factor for the filter being 1. The information bit rate is. kb/s, and an [Eb/No] of 11 db is required for each channel accessing the CDMA system. Calculate the maximum number of accesses permitted. In an FDMA link the following data is available:,, CAEC.0 CAEC.0,,, Calculate the overall C/N of the link. A BPSK TDMA system is to transmit 1000 digital voice channels, each with bits per sample at a 6 kbps rate. The system must CAEC.0 accommodate 1000 data bits/slot at a frame efficiency of 0%.i) what is the number of slots in a frame. ii) what is the length of TDMA frame.iii) how many preamble bits can be used.iv) what is the required satellite bandwidth. Assume that the TDMA system uses a 1 μs frame time. Find the CAEC.0 number of channels that each earth station can send within the TDMA frame when a μs preamble is added and μs guard band is used. A transponder has a bandwidth of 6 MHz and an available single carrier to noise density ratio of 6dBHz. It is intended for SCPC CAEC.0 service, with expected voice activity of 0%. Using a voice activated system, calculate the number of 6Kbps QPSK channels that can be sustained by this transponder. UNIT-IV EARTH STATION AND VSAT SYSTEMS TECHNOLOGY PART-A (SHORT ANSWER QUESTIONS) 1 Describe the effective isotropic radiated power CAEC.10 State the functions of low noise amplifier, where it is employed CAEC.10 List the applications of satellite communication CAEC.11 Describe the feed arrangement system in earth stations CAEC.11 Describe the drawbacks of parabolic reflector antenna CAEC.11 6 Define earth segment. CAEC.10 List the types of satellite services CAEC.1 Sketch the elements of satellite tracking system CAEC List the types of tracking techniques used for satellites. CAEC List the design considerations of lower orbit CAEC.10 1 Determine the frequency band for MEO system CAEC.10 1 List the types of VSAT network architectures CAEC.11 1 Describe the NGSO orbits CAEC.1 1 Describe the VSAT system CAEC.11 PART-B (LONG ANSWER QUESTIONS) 1 Analyze the reason why cassegrain antenna is popular for large CAEC.10 earth stations In detail, explain the block diagram representation of a typical CAEC.10 earth station. Explain the various feed systems employed in an earth station CAEC.10 antenna. Discuss in detail the effects of these feeds on the performance of the link. With a neat sketch explain the working of VSAT network. Why CAEC.11 such a system facilities the use of very small antenna terminals? P a g e

8 Briefly explain about the type of limitations is placed in the design CAEC.10 of the satellite link by high power amplifiers. 6 Describe the operation of typical VSAT user set-up giving detail of CAEC.11 the outdoor and indoor units. With the help of block diagram explain tracking system in earth CAEC.10 station of satellite communications. Discuss the various important characteristics of a low noise CAEC.10 amplifier. Explain what mesh and star architectures are in a VSAT network CAEC.11 state two advantages and disadvantages of each. 10 Explain the non geo stationary orbit ( NGSO ) constellation design CAEC.1 PART-C (PROBLEM SOLVING AND CRITICAL THINKING QUESTIONS) 1 A satellite downlink at 1 GHz operates with a transmit power of 6 CAEC.10 W and an antenna gain of. db. Calculate the EIRP in dbw. The range between a ground station and a satellite is 000 km. CAEC.10 Calculate the free space loss a frequency of 6 GHz. Analyze the A satellite in circular orbit with 1000 Km orbital CAEC.10 height transmits at.6 GHz. A station in the plane of the satellite orbit receives the signal from the satellite when it is rising from horizon. Find the Doppler shift of the received signal. Determine the visibility arc on earth equator from the satellite CAEC.10 located at E in the geostationary orbit. An artificial earth satellite is in an elliptical orbit which brings it to CAEC.10 an altitude of 0 km at perigee and out to an altitude of 00 km at apogee. Calculate the velocity of the satellite at both perigee and apogee A satellite in earth orbit passes through its perigee point at an CAEC.10 6 altitude of 00 km above the earth's surface and at a velocity of,0 m/s. Calculate the apogee altitude of the satellite. A satellite in earth orbit has a semi-major axis of 6,00 km and an CAEC.1 eccentricity of Calculate the satellite's altitude at both perigee and apogee. Calculate the escape velocity of a spacecraft launched from the CAEC.1 surface of the earth. Likewise, calculate the escape velocity from the surface of the moon where the mass of the moon is 0.01 times the mass of the earth and the moon's radius is,160 miles. A spacecraft weighing 0,000 lb (including fuel) is drifting in gravity-free space. Its engine is fired for minutes. During the CAEC.1 burn, mass is ejected at a rate of 0 lb/s with an exhaust velocity of 10,000 ft/s. Calculate the spacecraft's thrust and acceleration as a function of time during the burn. A satellite is in a circular equatorial orbit moving in the same CAEC.1 10 direction as of earth rotation with a period hours exactly. Determine the rate of drift of sub-satellite point around the equator in degrees per solar day. UNIT-V SATELLITE PACKET COMMUNICATION PART-A(SHORT ANSWER QUESTIONS) 1 Define throughput of a satellite. CAEC.1 Describe the types of mobile satellite services. CAEC.1 Describe the applications of satellites CAEC.1 Describe the architecture of DRSS satellite CAEC.1 Describe the function of the error control codec CAEC.1 P a g e

9 6 Calculate the response time of a queue CAEC.1 Describe the automatic repeat request (ARQ). CAEC.1 Define satellite packet switching CAEC.1 Describe which queuing system is used in FDMA CAEC.1 10 Describe the meant by forward error correction code. CAEC.1 11 Define burst code word CAEC.1 1 Explain the delay analysis of TDMA CAEC.1 1 Explain the slotted aloha CAEC.1 1 Explain packet reservation? CAEC.1 1 List the advantages of convolution codes over the other codes. CAEC.1 PART-B(LONG ANSWER QUESTIONS) 1 Differentiate pure ALOHA satellite packet switching with slotted CAEC.1 ALOHA packet switching? Discuss in brief the message transmission by FDMA by using CAEC.1 M/G/I Queue? Explain packet collision and how it is resolved in pure and slotted CAEC.1 ALOHA with the help of tree algorithm? Write short notes on tree algorithm. CAEC.1 Describe in detail about the message transmission by using TDMA CAEC.1 technique? 6 Discuss the preliminaries in packet communications CAEC.1 Explain the design network channel architecture and transmission CAEC.1 of ALOHA net? Explain the concept of Dynamic allocation of satellite capacity CAEC.1 through packet reservation Discuss in brief about packet reservation multiple access with the CAEC.1 help of traffic load? 10 Write short notes on applications of satellites CAEC.1 PART-C (PROBLEM SOLVING AND CRITICAL THINKING QUESTIONS) A (6, ) block code has a minimum distance of two. CAEC.1 1. a) How many errors can be detected in a codeword? b) How many errors can be corrected in a codeword? Consider a TDMA channel with a capacity of 0 Kbps serving an earth station population of 100. Assume that messages arriving at CAEC.1. the earth station are two types: single packet and 10 packets. A packet has a fixed length of 1000 bits. Find the average message delay when the traffic intensity is 0.. Assume 0% of the messages is the single packet type. Find the average packet delay for a 0 Kbps aloha satellite channel operating at a throughput of Kbps with bit packets. The CAEC.1. average satellite roundtrip delay is 1 packets, and the randomized retransmission interval is 10 packet lengths. If the average throughput over time is 1 packet/ min, estimate the number of users the channel could support.. Analyze the instability of aloha protocol can be resolved by using CAEC.1 tree algorithm Consider a (,) cyclic code with, i) let data CAEC.1. word d =(1010) find the corresponding code word.ii) let the code word c = ( ) find the corresponding data word. An aloha satellite channel serves a community of 000 users, each with an average throughput of bps. The channel capacity is 0 CAEC.1 6. Kbps, and the packet length is 1000 bits. Find the average packet delay if the randomized retransmission interval is 0 packet lengths. The average satellite roundtrip is 1. packets. P a g e

10 Consider a FDMA system of 00 users sharing a satellite channel with a capacity of R = 1. Mbps. Assume that each user generates a constant- length message of bits according to the Poisson process at the rate of three messages per second. A community of N earth stations shares a 6-kbps aloha satellite channel. Each earth station sends out a 1000-bit packet on an average of once every 100s.Caluculate what is the maximum value of N? Design the channel backlog in packets for a slotted ALOHA satellite channel with an infinite population and at equilibrium. The channel input rate is 0.6, the randomized retransmission interval is 60 packet lengths, and the satellite roundtrip propagation delay is taken to be 1 packet slots. What is the average packet delay in packet slots? Consider a slotted aloha system in which a guard time of 1 bits is used between slots to account for satellite movement. The channel bit rate is 6 Kbps and the packet length is ms. The channel has a bit error probability of p. Find the throughput of the channel. CAEC.1 CAEC.1 CAEC.1 CAEC.1 HOD, ECE 10 P a g e