Moble Communication


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Moble Communication

  1. 1. Mobile Communication Solutions for Test 2 Prof. Suthikshn Kumar
  2. 2. Part A Q 1 <ul><li>What is the distance of the GEO satellites from earth’s surface? </li></ul><ul><li>What is footprint of a satellite? </li></ul><ul><li>Define elevation angle of a satellite. </li></ul><ul><li>Why satellites cannot be placed in Van-Allen radiation belts? </li></ul><ul><li>What is the altitude of LEO satellites? </li></ul><ul><li>Calculate the latency of signal for GEO satellite. </li></ul><ul><li>Name one advantage of LEO satellite systems. </li></ul><ul><li>Name one disadvantage of MEO satellite Systems. </li></ul><ul><li>What is Iridium? </li></ul><ul><li>What is ISL? </li></ul>
  3. 3. Part A Q1 Answers: <ul><li>GEO is 35,786KM </li></ul><ul><li>Each satellite can cover a certain area on earth with its beam called footprint. </li></ul><ul><li>Elevation angle is defined as the angle between the center of the satellite beam and the plane tangential to the earth’s surface. </li></ul><ul><li>Van Allen Radiation belts consists of ionized particles, at heights of about 2000-6000 km and about 15,000-30,000 Km make satellite communication very difficult in these orbits. </li></ul><ul><li>LEO satellites have altitudes in the range of 500-1500Km </li></ul><ul><li>35,786 / 3,00,000 = 120ms RTT = 240ms </li></ul><ul><li>Advantages of LEO: Low transmit power, higher bandwidth, low delay, smaller footprint, better reuse of frequency, better global coverage. </li></ul><ul><li>Disadvantage of MEO: Increased delay ( 70-80ms), high transmit power, require special antennas for smaller footprints. </li></ul><ul><li>Iridium system is a constellation of 77 satellites ( Iridium atom has 77 electrons) for Global satellite communication. </li></ul><ul><li>ISL is Intersatellite Links with which satellites can communicate directly with each other. </li></ul>
  4. 4. Part A Q2 <ul><ul><li>What is SUMR? </li></ul></ul><ul><ul><li>What is Gateway Handover? </li></ul></ul><ul><ul><li>Name one advantage of MEO Satellite System. </li></ul></ul><ul><ul><li>Name One Disadvantage of LEO satellite System. </li></ul></ul><ul><ul><li>Name one advantage of ISL. </li></ul></ul><ul><ul><li>Define Inclination angle of a satellite. </li></ul></ul><ul><ul><li>What is GPS? </li></ul></ul><ul><ul><li>Give an equation which can be used for calculating distance of the satellite from the earth using its frequency of rotation. </li></ul></ul><ul><ul><li>Name one advantage of GEO satellite system. </li></ul></ul><ul><ul><li>Name one disadvantage of GEO satellite system. </li></ul></ul>
  5. 5. Part A Q2: Answers <ul><ul><li>SUMR: Satellite User Mapping Register stores current position of satellites and mapping of each user to the current satellite through which communication with a user is possible. </li></ul></ul><ul><ul><li>Gateway Handover: While the mobile user and satellite might still have good contact, the satellite might mover away from the current gateway. The satellite has to connect to another gateway. </li></ul></ul><ul><ul><li>Advantage of MEO Satellite System: Requires less number of satellites ( around 12) to give global coverage, Simpler system design due to slow moving satellites, MEO can cover larger populations, requires fewer handovers. </li></ul></ul><ul><ul><li>Disadvantage of LEO satellite System: Requires large number of satellites ( 50-200) for global coverage, Short time of visibility requires more handover, High complexity, Short lifetime of satellites, Requires routing of data packets from satellite to satellite. </li></ul></ul><ul><ul><li>Advantage of ISL: Reduces delay, reduces the number of gateways needed on earth. </li></ul></ul>
  6. 6. Answer Part A Q2 <ul><ul><li>6. Define Inclination angle of a satellite: is defined as the angle between equatorial plane and the plane described by the satellite orbit. </li></ul></ul><ul><ul><li>7. GPS stands for Global Positioning System used for precise localization worldwide. </li></ul></ul><ul><ul><li>8. An equation which can be used for calculating distance of the satellite from the earth using its frequency of rotation. </li></ul></ul><ul><ul><li>9. Advantage of GEO satellite system: Three GEO satellites are enough for global coverage, Senders and receivers can use fixed antenna positions, Life time expectation of GEOs are high, GEOs don’t need any handover, GEOS don’t exhibit any Doppler shift. </li></ul></ul><ul><ul><li>10. Disadvantage of GEO satellite system: Northern or southern regions of the earth have more problems due to low elevation angle. Shading of signals in cities due to high buildings, Transmission power needed is high, High latency of .25 s. Large footprints mean frequencies cannot be reused. </li></ul></ul>
  7. 7. Part B Q3 <ul><li>What is Asymmetrical communication system? </li></ul><ul><li>What is symmetrical Communication system? </li></ul><ul><li>What is broadcast disk? </li></ul><ul><li>What is flat disk and skewed disk? </li></ul><ul><li>What is Single Freqency Networks (SFN)? </li></ul><ul><li>What is DAB ensemble? </li></ul><ul><li>What is Program Associated data? </li></ul><ul><li>Which modulation technique is used in DAB? </li></ul><ul><li>What are the advantages of DAB? </li></ul><ul><li>What is the function of Fast Information Channel ( FIC) in DAB? </li></ul>
  8. 8. Answers: Part B Q3 <ul><li>Asymmetrical communication system: Unidirectional distribution systems or broadcast systems where tycpically a high bandwidth data stream exists from one sender to many receivers. </li></ul><ul><li>Symmetrical Communication system offer the same transmission capabilities in both communication directions. </li></ul><ul><li>Broadcast disk refers to cyclical repetition of data blocks sent via broadcast. </li></ul><ul><li>Flat disk : is a broadcast disk with all blocks are repeated one after another, every block is transmitted for an equal amount of time, average waiting time is same for all the blocks. Skewed disk favor one or more data blocks by repeating them once or several times. </li></ul><ul><li>Single Freqency Networks (SFN): DAB uses SFN where all senders transmitting the same radio program operate at the same freqeuncy. </li></ul><ul><li>. </li></ul>
  9. 9. Answers: Part B Q3 <ul><li>6. DAB ensemble: With every frequency block of 1.5MHz, DAB can transmit up to six stereo audio programmes with a data rate of 192 kbits/s each. The DAB ensemble may consist of six radio programs and two data channels. </li></ul><ul><li>7. Program Associated data: PAD is the information accompanying an audio stream. It may contain program information, still pictures for display on a small LCD, title display etc. </li></ul><ul><li>8. Modulation technique used in DAB: DQPSK </li></ul><ul><li>9. Advantages of DAB: CD-like audio quality, immune to interference and multipath propagation effects. </li></ul><ul><li>10. Function of Fast Information Channel ( FIC) in DAB: FIC carries all control information required for interpreting the configuration and content of the MSC </li></ul>
  10. 10. Part B Q4 <ul><li>What is the problem addressed by Multimedia Object Transfer Protocol? </li></ul><ul><li>Name some of the formats supported by MOT. </li></ul><ul><li>What is Multiprotocol Encapsulation? </li></ul><ul><li>Draw the block diagram of DAB sender? </li></ul><ul><li>What is OFDM? </li></ul><ul><li>What is the advantage of OFDM? </li></ul><ul><li>How DVB can be used for High speed internet access? </li></ul><ul><li>What are interaction channels? </li></ul><ul><li>What is a data carousel? </li></ul><ul><li>What are the bandwidths and data rates of DAB and DVB? </li></ul>
  11. 11. Answers: Part B Q4 <ul><li>The problem addressed by Multimedia Object Transfer Protocol is the broad range of DAB receiver capabilities such as simple audio-only devices with single line text displays or more advanced radios with extra color graphics displays or multimedia PCs. All DAB receivers should atleast be able to recognize all program associated data and process some of it. </li></ul><ul><li>Some of the formats supported by MOT: MHEG, JPEG, ASCII, MPEG, HTML, HTTP, BMP, GIF </li></ul><ul><li>Multiprotocol Encapsulation: Transport of arbitrary data network protocols on top of the MPEG-2 transport stream; optimized for IP, support for 48 bit MAC addresses, unicast, multi-cast and broadcast. </li></ul><ul><li>Block diagram of DAB sender ( see next Slide) </li></ul><ul><li>OFDM: Orthogonal Frequency Division Multiplexing : Parallel data transmission on several orthogonal subcarriers with lower rate </li></ul>
  12. 12. Answers Part B Q4 <ul><li>6.The advantage of OFDM: no equalizer necessary, no expensive filters with sharp edges necessary, better spectral efficiency (compared to CDM) </li></ul><ul><li>7. DVB can be used for High speed internet access: See next slide </li></ul><ul><li>8. Interaction channels:Through GSM, UMTS, user interaction is added to DAB, DVB. </li></ul><ul><li>9. Data carousel: Also Broadcast disk, periodic transmission of data. </li></ul><ul><li>10. The bandwidths and data rates of DAB are 1.5MHz and 1.5Mbps. The DVB has bandwidth of 8MHz and data rate of 5-30Mbps </li></ul>
  13. 13. DAB sender Trans- mitter Trans- mission Multi- plexer MSC Multi- plexer ODFM Packet Mux Channel Coder Audio Encoder Channel Coder DAB Signal Service Information FIC Multiplex Information Data Services Audio Services Radio Frequency FIC: Fast Information Channel MSC: Main Service Channel OFDM: Orthogonal Frequency Division Multiplexing 1.5 MHz f carriers
  14. 14. DVB for high-speed Internet access <ul><ul><li>downlink: DVB receiver, data rate per user 6-38 Mbit/s </li></ul></ul><ul><ul><li>return channel from user to service provider: e.g., modem with 33 kbit/s, ISDN with 64 kbit/s, DSL with several 100 kbit/s etc. </li></ul></ul>DVB-S adapter PC Internet TCP/IP leased line service provider information provider satellite provider satellite receiver DVB/MPEG2 multiplex simultaneous to digital TV
  15. 15. Part B Q5 <ul><li>What are the GSM tele services? </li></ul><ul><li>What are the GSM supplementary services? </li></ul><ul><li>What are the three subsystems of GSM system? </li></ul><ul><li>Draw the functional architecture diagram of GSM system? </li></ul><ul><li>What is the function of Base Transceiver station? </li></ul><ul><li>What is the function of Home Location Register(HLR)? </li></ul><ul><li>What is the function of Visitor Location Register (VLR)? </li></ul><ul><li>What is the use of Equipment Identity Register (EIR)? </li></ul><ul><li>What is comfort noise? </li></ul><ul><li>Draw the GSM protocol architecture diagram? </li></ul>
  16. 16. Answers: Part B Q5 <ul><li>The GSM tele services: encrypted voice transmission, message service and basic data communication. ( Telephony, Emergency Number, SMS, group3 fax) </li></ul><ul><li>GSM supplementary services: user identification, call redirection, forwarding of ongoing calls, closed user groups, multi-party communication. </li></ul><ul><li>The three subsystems of GSM system: Radio Subsystem (RSS), Network and Switching Subsystem (NSS), and Operation Subsystem (OSS). </li></ul><ul><li>Functional architecture diagram of GSM system( Next Slide) </li></ul><ul><li>The function of Base Transceiver station: A BTS comprises of all radio equipment( antenna, signal processing and amplifiers) necessary for radio transmission. A BTS can form a radio cell, or several cells using sectorized antennas. </li></ul>
  17. 17. Answers Part B Q5 <ul><li>6. The function of Home Location Register(HLR): HLR is the most important database in the GSM System, as it stores all user-relevant information. This consists of static information such as Mobile subscriber ISDN number, subscribed services, the IMSI. Dynamic information also such as Current location area of the MS, the Mobile Subscriber Roaming Number, and the current VLR and MSC. </li></ul><ul><li>7. The function of Visitor Location Register (VLR): VLR is associated with each MSC is a dynamic database which stores all important information needed for the MS users currently in the LA that is associated with MSC.( IMSI, MSISDN, HLR address). </li></ul><ul><li>8. The use of Equipment Identity Register (EIR): EIR is a databse for all IMEI;s ie., it stores all device identifications registered for this network. EIR has a blacklist of stolen ( or locked) devices. EIR also contains a list of valid IMEIs and list of malfunctioning devices ( white and gray lists). </li></ul><ul><li>9. Comfort noise: During periods of silence, the physical layer generates a comfort noise to fake a connection as complete silence can confuse a user, but no actual transmission takes place. The noise is even adapted to the current background noise at the communication partner’s location. </li></ul><ul><li>10GSM protocol architecture diagram ( see next slide) </li></ul>
  18. 18. GSM: elements and interfaces NSS MS MS BTS BSC GMSC IWF OMC BTS BSC MSC MSC A bis U m EIR HLR VLR VLR A BSS PDN ISDN, PSTN RSS radio cell radio cell MS AUC OSS signaling O
  19. 19. GSM protocol layers for signaling CM MM RR MM LAPD m radio LAPD m radio LAPD PCM RR’ BTSM CM LAPD PCM RR’ BTSM 16/64 kbit/s U m A bis A SS7 PCM SS7 PCM 64 kbit/s / 2.048 Mbit/s MS BTS BSC MSC BSSAP BSSAP
  20. 20. Part C Q6 <ul><li>What is Handover Margin? </li></ul><ul><li>What are the two basic reasons for Handover in GSM? </li></ul><ul><li>Draw a message flow diagram for Mobile Terminated Call (MTC). </li></ul><ul><li>What are the four possible Handover scenerios in GSM? </li></ul><ul><li>How is a GSM subscriber authenticated? </li></ul><ul><li>What are the data rates offered by GSM and GPRS? </li></ul><ul><li>What is QoS-Profile os a GPRS user? </li></ul><ul><li>What are new network elements introduced by GPRS? </li></ul><ul><li>What is the use of GPRS Register (GR)? </li></ul><ul><li>Why is RTTs in GPRS more than Fixed Networks? </li></ul>
  21. 21. Answers: Part C Q6 <ul><li>Handover Margin is a threshold used by BSC to decide on the handover. It includes some hysteresis to avoid ping pong effect. </li></ul><ul><li>The two basic reasons for Handover in GSM: The mobile moves out of the range of a BTS or a certain antenna of a BTS. The MSC may decide that the traffic in one cell is too high and shoft some MS to other cells for load balancing. </li></ul><ul><li>Draw a message flow diagram for Mobile Terminated Call (MTC).( See next Slide) </li></ul><ul><li>The four possible Handover scenerios in GSM: Intra-cell, Inter-cell intra-BSC, Inter-BSC intra-MSC, Inter MSC </li></ul>
  22. 22. Answer Part C Q6 <ul><li>5. GSM subscriber authenticated using SIM, which stores the individual authentication key Ki, the user Identification IMSI, and algorithm used for authentication A3. Authentication uses Challenge-response method. </li></ul><ul><li>6. The data rates offered by GSM is 9.6Kbps and GPRS is 171Kbps ( max) </li></ul><ul><li>7. QoS-Profile of a GPRS user determines the service precedence, reliability class and delay class of transmission and user data throughput. </li></ul><ul><li>8. The new network elements introduced by GPRS: GGSN, SGSN </li></ul><ul><li>9. The use of GPRS Register (GR) </li></ul><ul><li>10. RTTs in GPRS are more than Fixed Networks. The delay within GPRS network is incurred by channel access delay, coding for error correction, and transfer delays in the fixed and wireless part of the GPRS network. </li></ul>
  23. 23. MTC/MOC BTS MS paging request channel request immediate assignment paging response authentication request authentication response ciphering command ciphering complete setup call confirmed assignment command assignment complete alerting connect connect acknowledge data/speech exchange BTS MS channel request immediate assignment service request authentication request authentication response ciphering command ciphering complete setup call confirmed assignment command assignment complete alerting connect connect acknowledge data/speech exchange MTC MOC
  24. 24. Part C Q7 <ul><li>What are the data rates offered by UMTS? </li></ul><ul><li>Draw the UMTS system Architecture diagram. </li></ul><ul><li>What is Orthogonal Variable Spreading Factor (OVSF)? </li></ul><ul><li>What is the chipping rate used by UMTS? </li></ul><ul><li>Draw the basic architecture diagram of UTRA Network. </li></ul><ul><li>Why is power control required in UTRAN? </li></ul><ul><li>Draw the user plane protocol stacks diagram of UTRAN for circuit switched data. </li></ul><ul><li>What is Macro Diversity? </li></ul><ul><li>What is Soft Handover? </li></ul><ul><li>What are the different handover types in combined UMTS/GSM network? </li></ul>
  25. 25. Answers Part C Q7 <ul><li>The data rates offered by UMTS: Minimum 144Kbps for rural, for urban max 2 Mbps, for suburban outdoor 384Kbps. </li></ul><ul><li>The UMTS system Architecture diagram( Next Page) </li></ul><ul><li>Orthogonal Variable Spreading Factor (OVSF): UMTS uses OVSF for spreading the user data and separating the different data stream of the sender. </li></ul><ul><li>The chipping rate used by UMTS is 3.84Mchips/s. </li></ul><ul><li>The basic architecture diagram of UTRA Network( Next Page) </li></ul><ul><li>The power control required in UTRAN to minimize interference between the neighbouring cells or controls the size of the cell. </li></ul>
  26. 26. Answers Part C Q7 <ul><li>7. Draw the user plane protocol stacks diagram of UTRAN for circuit switched data( Next page) </li></ul><ul><li>8. Macro Diversity: a basic property of CDMA where an UE receives sinal from up to three different antennas which may belong to different node Bs. UE also sends the data which is received by several node Bs and RNC combines the data stream received from the Node Bs. ( see next slide for diagram ) </li></ul><ul><li>9. Soft Handover: The fact that a UE receives data from different antennas at the same time makes a handover soft. Moving from one cell to another is a smooth and not an abrupt process. </li></ul><ul><li>10 The different handover types in combined UMTS/GSM network: Intra-node B intra RNC, Inter node B Intra-RNC, Inter-RNC, Inter-MSC, Inter-System </li></ul>
  27. 27. UMTS architecture <ul><li>UTRAN (UTRA Network) </li></ul><ul><ul><li>Cell level mobility </li></ul></ul><ul><ul><li>Radio Network Subsystem (RNS) </li></ul></ul><ul><ul><li>Encapsulation of all radio specific tasks </li></ul></ul><ul><li>UE (User Equipment) </li></ul><ul><li>CN (Core Network) </li></ul><ul><ul><li>Inter system handover </li></ul></ul><ul><ul><li>Location management if there is no dedicated connection between UE and UTRAN </li></ul></ul>UTRAN UE CN I u U u
  28. 28. UTRAN architecture <ul><li>UTRAN comprises several RNSs </li></ul><ul><li>Node B can support FDD or TDD or both </li></ul><ul><li>RNC is responsible for handover decisions requiring signalingto the UE </li></ul><ul><li>Cell offers FDD or TDD </li></ul>RNC: Radio Network Controller RNS: Radio Network Subsystem Node B Node B RNC I ub Node B UE 1 RNS CN Node B Node B RNC I ub Node B RNS I ur Node B UE 2 UE 3 I u
  29. 29. UMTS protocol stacks (user plane) apps. & protocols MAC radio MAC radio RLC SAR U u I u CS UE UTRAN 3G MSC RLC AAL2 ATM AAL2 ATM SAR Circuit switched SAR= Segmentation and Reassembly AAL2: ATM Adaptation layer 2 PDCP= Packet Data Convergence protocol
  30. 30. Support of mobility: macro diversity <ul><li>Multicasting of data via several physical channels </li></ul><ul><ul><li>Enables soft handover </li></ul></ul><ul><ul><li>FDD mode only </li></ul></ul><ul><li>Uplink </li></ul><ul><ul><li>simultaneous reception of UE data at several Node Bs </li></ul></ul><ul><ul><li>Reconstruction of data at Node B, SRNC or DRNC </li></ul></ul><ul><li>Downlink </li></ul><ul><ul><li>Simultaneous transmission of data via different cells </li></ul></ul><ul><ul><li>Different spreading codes in different cells </li></ul></ul>CN Node B RNC Node B UE
  31. 31. Part C Q8 <ul><li>What is the difference between DECT and GSM systems? </li></ul><ul><li>Draw the DECT system architecture diagram. </li></ul><ul><li>Name two functions of MAC layer in DECT system. </li></ul><ul><li>Name two functions of network layer of DECT system. </li></ul><ul><li>What is TETRA? </li></ul><ul><li>What are the applications of TETRA? </li></ul><ul><li>What is HSCSD? </li></ul><ul><li>What is the difference between Circuit Switched Data and Packet Switched Data Networks? </li></ul><ul><li>What is use of SIM card in Mobile Phones? </li></ul><ul><li>What is the maximum number of characters in an SMS message? </li></ul>
  32. 32. Answers Part C Q8 <ul><li>The difference between DECT and GSM systems: Interms of Cell diameter and cell capacity. DECT is inexpensive compared to GSM which is very expensive. </li></ul><ul><li>DECT system architecture diagram( next slide) </li></ul><ul><li>Two functions of MAC layer in DECT system: maintaining basic services, activating/deactivating physical channels, multiplexing of logical channels, Segmentation/Reassembly, Error correction </li></ul><ul><li>Two functions of network layer of DECT system: offers services to request, check, reserve, control, and release resources at the basestation and mobile terminal call control: setup, release, negotiation, control , call independent services: call forwarding, accounting, call redirecting, mobility management: identity management, authentication, management of the location register </li></ul><ul><li>TETRA: Terrestrial Trunked Radio Which use many different radio carriers but only assign a specific carrier to a certain user for a short period of time according to demand. </li></ul>
  33. 33. Answers: Part C Q8 <ul><li>6. The applications of TETRA: Taxi services, transport companies, rescue teams, </li></ul><ul><li>7. What is HSCSD? </li></ul><ul><li>8. The Circuit Switched Data estblishes a dedicated path before the data can be exchanged. Packet Switched Data Networks use packets which are forwarded by nodes in the network based on the addresses in packets. </li></ul><ul><li>9. The use of SIM card in Mobile Phones: for user authentication in the network. </li></ul><ul><li>10. The maximum number of characters in an SMS message is 160. </li></ul>
  34. 34. DECT system architecture reference model global network local network local network FT FT PT PA PT PA VDB HDB D 1 D 2 D 3 D 4