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Note for Mobile Computing - MC By Ramyaa Shenbagaraman

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Logical Link control and adaptation protocol Service discovery protocol. 23. What are the advantages and disadvantages of FHSS? (Dec 2009) Advantages • frequency selective fading and interference limited to short period • simple implementation • uses only small portion of spectrum at any time Disadvantages  not as robust as DSSS   simpler to detect  24) What are the categories of Mobile services? • Bearer services • Tele services • Supplementary services 25) What are the services provided by supplementary services? • User identification • Call redirection • Call forwarding • Closed user groups • Multiparty Communication 26) What are the four types of handover available in GSM? 1. Intracell Handover 2. Intercell Intra BSC Handover 3. Inter BSC Intra MSC handover 4. Inter MSC Handover 27). What is meant by GPRS? The General Packet Radio Service provides packet mode transfer for applications that exhibit traffic patterns such as frequent transmission of small volumes. 28) What are subsystems in GSM system? • Radio subsystem(RSS) • Network & Switching subsystem(NSS) • Operation subsystem(OSS) 29) What are the information in SIM? • card type, serial no, list of subscribed services • Personal Identity Number(PIN) • Pin Unlocking Key(PUK) • An Authentication Key (KI) 30) Define Normal Burst? The frame used for normal data transmission with in a time slot is called Normal Burst. 31) What are the logical channels in GSM? • Traffic channel (TCH) • Control channel (CCH) 32) what is meant by beacon? A beacon contains a timestamp and other management information used for power management and roaming. e.g., identification of the base station subsystem(BSS) 33).What are the reasons for delays in GSM for packet data traffic. 1. Different data rates provided by traffic channels are low.

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2. Authentication and encryption also makes the packet data transmission low. 3. Various interferences and noises from the channel also causes delay. 34).List out disadvantages of cellular system. 1. Self–jamming 2. Near–far problem 3. Soft Handoff 35).How much of the original GSM network does GPRS need. Which elements of the network perform the data transfer. GPRS is an enhancement of SM. It uses same physical channel as GSM and only new logical GPRS radio channels are defined. Elements needed for data transfer: 1. GPRS support nodes(GSN) 2. Gateway GPRS Support Node(GGSN) 3. Servicing GPRS Support Node(SGSN) 4. GPRS Register(GR) 36).Explain the various entities available in radio subsystem 1. BSS: It performs all function necessary to maintain radio connections to a MS. 2. BTS: It comprises all radio equipments 3. BSC: It basically manages BTSs. 4. MS: It comprises all user equipment and software needed for communication with in a GSM network. 37). Explain the various entities available in NSS. NSS consist of following switches and databases. 1. MSC: They setup connection to other MSCs and to BSCs via A interface. 2. HLR: It is the most important database which stores all user relevant information. 3. VLR: It is a dynamic database which stores all important information needed for MS Users currently in the that is associated to MSC. 38). Explain the various systems available in Operation Subsystem. Operating sub system: It contains necessary functions for network operation and maintenance. 1. OMC: It manages traffic monitoring, accounting and billing 2. AuC : It is used to protect user identity and data transmission. 3. EIR : Its to res all device identifications registered for this network. 39). Explain the various control channels available in GSM. 1. BCCH: ABTS uses this channel to signal information to all MSs with in a cell. 2. CCCH: All information regarding connection setup between MS and BS are exchanged via CCCH. 3. DCCH: It is used to exchange large amounts of data in less time. 40). What is mobile routing? Even if the location of a term in alis known to the system, its till has to route the traffic through the network to the access point currently responsible for the wireless terminal. 41). What are the functions which support service and connection control? Access point control function Call control and connection Control function Network security agent Service control function Mobility management function

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42). If 8 speech channels are supported on a single radio channel, and it no guard band is assumed, what is the number of simultaneous users can be accommodated in GSM? A time slot is GSM can only be used by one user to transmit it or receive during one of the transmission (radio) channel. That is, we can accommodate1 user in one time slot. Therefore, for 8 speech channels we can accommodate 8 simultaneous users in GSM. 43) Define Base Station Subsystem GPRS protocol (BSSGP). The Base Station Subsystem GPRS protocol (BSSGP) is used to convey routing and QoS- related information between the BSS and SGSN. BSSGP not perform error correction and works on top of a Frame Relay(FR) network. UNIT II 1. What are the basic elements of telecommunication systems? Transmitter–it takes the information and converts into signal Transmission medium–it carries the signal Receiver–receives the signal and converts it back into usable information. 2. What are the major subsystems in GSM? GSM consists of three major components Base station subsystem Network and switching subsystem Operation support subsystem 3. List the databases of NSS in GSM? Home location register Visitor location register Authentication center 4. What are the functions of OSS in GSM? Manage all charging and billing procedures Manage all mobile equipment in the system 5. Write the interfaces used in GSM There are three interfaces used in GS, they are GSM radio airinterface Abis interface A interface 6. What are the services offered by the GSM? There are three user services offered by GSM, they are Bearer or data service Telephone service Supplementary ISDN service 7. List the security services offered by GSM? Access Control and Authentication Confidentiality Anonymity 8. Define the protocol architecture of DECT. The protocol architecture of DECT consists of three layers. They are: Physical Layer. Medium Access Layer. DataLink Control Layer. Network Layer. The first three layers are common for both Control Plane(C-Plane) and User Plane(UPlane). The network layer has been specified only for U-Plane, so that user data from layer two is directly forwarded to the U-Plane.

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9. What is meant by GGSN? GGSN is Gateway GPRS Support Node. It is the inter-working unit between the GPRS network and external packet data networks. The GGSN is connected to external networks via the Gi interface and transfers packets to the SGS Nviaan IP-based GPRS backbone net work. 10. What is meant by BSSGP? BSSGP is Base Station Subsystem GPRS Protocol. It is used to convey routing And QoS-related information between the BSS and SGSN.BSSGP does not perform error correction and works on top of a frame relay network. 11. What are the four possible handover scenarios in GSM? The four possible hand over scenarios in GSM are: Intra-cell handover. Inter-cell, intra-BSC handover. Inter-BSC, intra-MSC handover. Inter MSC handover. 12. List out the numbers needed to locate an MS and to address the MS. The numbers needed to locate an MS and to address the MS are: Mobile station international ISDN number(MSISDN). International mobile subscriber identity(IMSI). Temporary mobile subscriber identity(TMSI). Mobile station roaming number(MSRN). 13. Write the application of satellite network? Weather forecasting Radio and TV broadcast satellite Military satellite Satellites for navigation 14. Define elevation angle? The Elevation angle is the angle from the horizontal to the point on the center of the main beam of the antenna when the antenna is pointed directly at the satellite. 15. What are the advantages GEO? Three GEO satellites are enough for a complete coverage of almost any spot on earth. Senders and receivers can use fixed antenna positions, no adjusting is needed. Therefore GEO are ideal for TV and radio broadcasting 16. List the advantages of MEO? Using orbits around10,000km, the system only requires a dozen satellites which is more than a GEO system, but much less than a LEO system. Furthermore these satellites move slower relative to the earth’s rotation allowing simpler system design. 17. What are the types of transport mechanism used in DAB? The two basic transport mechanisms used by DAB are: Main Service Channel(MSC). Fast Information Channel (FIC). 18. What are the factors limited the number of sub channels provided with in the satellite channel? There are three factors limited the number of sub channels provided with in the satellite channel. They are:Thermal Noise. Inter modulation Noise. Crosstalk. 19. What is the frequency range of uplink and downlink in GSM network? The frequency range of uplink in GSM network is 890-960 MHz. The frequency range of downlink in GSM network is 935-960 MHz.

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