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Note for Mobile Computing - MC By Ramyaa Shenbagaraman

  • Mobile Computing - MC
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13. What is digital sense multiple access? The scheme which is used for the packet data transmission service Cellular Digital Packet Domain the AMPS mobile phone system is also known as digital sense multiple access (DSMA). 14. What is OVSF? Using orthogonal codes separates the different data streams of a sender UMT Successor called Orthogonal Variable Spreading factor codes (OVSF). 15. Specify the steps perform during the search for a cell after power on? Primary synchronization Secondary synchronization Identification of the scrambling code 16. Why baseband signals cannot be directly transmitted in a wireless system? Antennas must be the order of magnitude of the signal’s wavelength. Medium Characteristics. 17. Define beacon? Beacon frame is used to convey timing information within a BSS. It contains a time stamp and other management information used for power management and roaming. The timestamp is used by the node to adjust its local clock. 18. What are the handovers in hiperLAN? The handovers in hiperLAN are Sector handover Radio handover Network handover 19. Distinguish infrastructure and adhocnet works? Infrastructure networks Adhoc networks Communication takes place only between a wireless node and an access point Communication takes place only between two wireless nodes The wireless node is simple as The wireless node is complex Functionality is based on the access point Can forward messages across Networks Can forward messages only with in the specified range 20. Why is physical layer in IEEE802.11 subdivided? What are its sub layers? The physical layer in IEEE802.11 is subdivided because a sub layer has to be dependent on the upper layers (architecture dependent) and the other has to be medium dependent. The two sublayers are namely, Physical layer convergence protocol Physical medium dependent sub layer 21. Define MSDU lifetime? MSDU lifetime is used to provide time bounded service which specifies the maximum time that can elapse between sending and receiving a MSDU. It has arrange of 0-16000 ms. 22. What are the elements in core protocols in Bluetooth? The elements in core protocols in Bluetooth are, Radio Baseband Link Manager Protocol

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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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