MOBILE COMPUTING Unit 3.pptx
- 1. Unit – III TELECOMMUNICATION SYSTEM
- 2. TELECOMMUNICATION SYSTEM Unit – 3 • Cellular Mobile communication- Global System for Mobile Communication (GSM) - General Packet Radio Service (GPRS) - Generation of Mobile communication - SDR.
- 3. Introduction to Cellular Systems • Cellular network is an underlying technology for mobile phones, personal communication systems, wireless networking etc • The technology is developed for mobile radio telephone to replace high power transmitter/receiver systems. • Cellular networks use lower power, long range and more transmitters for data transmission.
- 4. Features of Cellular Systems • The features of cellular systems are as follows − • Offer very high capacity in a limited spectrum. • Reuse of radio channel in different cells. • Enable a fixed number of channels to serve an arbitrarily large number of users by reusing the channel throughout the coverage region. • Communication is always between mobile and base station (not directly between mobiles). • Each cellular base station is allocated a group of radio channels within a small geographic area called a cell. • Neighboring cells are assigned different channel groups.
- 5. • By limiting the coverage area to within the boundary of the cell, the channel groups may be reused to cover different cells. • Keep interference levels within tolerable limits. • Frequency reuse or frequency planning. • Organization of Wireless Cellular Network. • Cellular network is organized into multiple low power transmitters each 100w or less.
- 6. Shape of Cells • The coverage area of cellular networks are divided into cells, each cell having its own antenna for transmitting the signals. • Each cell has its own frequencies. Data communication in cellular networks is served by its base station transmitter, receiver and its control unit • The shape of cells can be hexagon
- 8. • Frequency Reuse • Frequency reusing is the concept of using the same radio frequencies within a given area, that are separated by considerable distance, with minimal interference, to establish communication. • Frequency reuse offers the following benefits − • Allows communications within cell on a given frequency • Limits escaping power to adjacent cells • Allows re-use of frequencies in nearby cells • Uses same frequency for multiple conversations • 10 to 50 frequencies per cell • For example, when N cells are using the same number of frequencies and K be the total number of frequencies used in systems. Then each cell frequency is calculated by using the formulae K/N. • In Advanced Mobile Phone Services (AMPS) when K = 395 and N = 7, then frequencies per cell on an average will be 395/7 = 56. Here, cell frequency is 56.
- 9. BASIC CELLULAR SYSTEMS The two basic cellular systems are • Circuit-switched system • Packet-switched system
- 10. FEATURES CIRCUIT SWITCHING PACKET SWITCHING Orientation Connection oriented Connectionless Purpose Initially designed for Voice communication Initially designed for Data Transmission Flexibility Inflexible, because once a path is set all parts of a transmission follows the same path Flexible, because a route is created for each packet to travel to the destination Order Message is received in the order, sent from the source Packets of a message are received out of order and assembled at the destination Technology/ Approach Circuit switching can be achieved using two technologies, either Space Division Switching or Time- Division Switching Packet Switching has two approaches Datagram Approach and Virtual Circuit Approach
- 11. Layers Circuit Switching is implemented at Physical Layer Packet Switching is implemented at Network Layer Resource Resource reservation is the feature of circuit switching because path is fixed for data transmission. There is no resource reservation because bandwidth is shared among users. Wastage Wastage of resources are more in Circuit Switching Less wastage of resources as compared to Circuit Switching Reliability More reliable Less reliable
- 12. GSM • GSM is a mobile communication modem • it is stands for global system for mobile communication (GSM). The idea of GSM was developed at Bell Laboratories in 1970. • Presently GSM supports more than one billion mobile subscribers in more than 210 countries throughout the world. • It is a digital cellular technology used for transmitting mobile voice and data services.
- 13. • GSM owns a market share of more than 70 percent of the world's digital cellular subscribers. • GSM makes use of narrowband Time Division Multiple Access (TDMA) technique for transmitting signals. • GSM was developed using digital technology. It has an ability to carry 64 kbps to 120 Mbps of data rates.
- 14. Why GSM? • Listed below are the features of GSM that account for its popularity and wide acceptance. • Improved spectrum efficiency • International roaming • Low-cost mobile sets and base stations (BSs) • High-quality speech • Compatibility with Integrated Services Digital Network (ISDN) and other telephone company services • Support for new services
- 15. • MS Mobile Station = phone + SIM card • BTS Base Transceiver Station • BSC Base Station Controller • HLR Home Location Register • MSC Mobile services Switching Centre • VLR Visitor Location Register • AUC Authentication Centre • EIR Equipment Identity Register • SMSC Short Message Service ”Support” Centre
- 16. • VMS Voice Messaging System • IN Intelligent Network services • PSTN Public Switched Telephone Network • PABX Private Automatic Branch Exchange
- 17. GSM Call Setup
- 18. MSC SMSC EIR INTERNET BSC IN PrePaid VMS Voicemail HLR MSC BSC PABX PSTN International PSTN Fixed Network Reference Model
- 19. GSM Services • Bearer Services • Teleservices • Supplementary services
- 20. Teleservices GSM provides both the voice oriented teleservices and the non voice teleservices • Voice calls • Video Calls • Short Text Messages • Fax • Emergency number
- 21. Bearer Services • Send and receive data from mobile phone • This services supporting SMS, e-mail, and internet access • Data rates up to 9.6 kbps.
- 22. Supplementary services • Supplementary services are additional services that are provided in addition to teleservices and bearer services. • These services include caller identification, call forwarding, call waiting, multi-party conversations, and barring of outgoing (international) calls, among others
- 23. • Conferencing : It allows a mobile subscriber to establish a multiparty conversation, i.e., a simultaneous conversation between three or more subscribers to setup a conference call. This service is only applicable to normal telephony • Call Waiting : This service notifies a mobile subscriber of an incoming call during a conversation. The subscriber can answer, reject, or ignore the incoming call • Call Barring : Stop incoming calls from undesired numbers.
- 24. • Call Hold : This service allows a subscriber to put an incoming call on hold and resume after a while. The call hold service is applicable to normal telephony • Call Forwarding : Call Forwarding is used to divert calls from the original recipient to another number. It is normally set up by the subscriber himself. It can be used by the subscriber to divert calls from the Mobile Station when the subscriber is not available, and so to ensure that calls are not lost
- 25. GSM architecture is mainly divided into three Subsystems 1. Base Station Subsystem (BSS) 2. Network & Switching Subsystem (NSS) 3. Operations Subsystem (OSS) GSM SYSTEM ARCHITECTURE
- 27. • GSM - The Base Station Subsystem (BSS) • The BSS is composed of two parts − • The Base Transceiver Station (BTS) • The Base Station Controller (BSC) • The Base Transceiver Station (BTS) • The BTS houses the radio transceivers that define a cell and handles the radio link protocols with the MS. In a large urban area, a large number of BTSs may be deployed.
- 28. • The BTS corresponds to the transceivers and antennas used in each cell of the network. • A BTS is usually placed in the center of a cell. Its transmitting power defines the size of a cell. • Each BTS has between 1 and 16 transceivers, depending on the density of users in the cell. • Each BTS serves as a single cell. It also includes the following functions − • Encoding, encrypting, multiplexing, modulating, and feeding the RF signals to the antenna • Transcoding and rate adaptation • Time and frequency synchronizing • Voice through full- or half-rate services • Decoding, decrypting, and equalizing received signals • Random access detection • Timing advances • Uplink channel measurements
- 29. The Base Station Controller (BSC) • The BSC manages the radio resources for one or more BTSs. It handles radio channel setup, frequency hopping, and handovers. The BSC is the connection between the mobile and the MSC. • The BSC also translates the 13 Kbps voice channel used over the radio link to the standard 64 Kbps channel used by the Public Switched Telephone Network (PSDN) or ISDN.
- 30. • It assigns and releases frequencies and time slots for the MS. The BSC also handles intercell handover. It controls the power transmission of the BSS and MS in its area. • The function of the BSC is to allocate the necessary time slots between the BTS and the MSC. It is a switching device that handles the radio resources. • The additional functions include− • Control of frequency hopping • Performing traffic concentration to reduce the number of lines from the MSC • Providing an interface to the Operations and Maintenance Center for the BSS • Reallocation of frequencies among BTSs • Time and frequency synchronization
- 31. GSM - The Network Switching Subsystem (NSS) • The Network switching system (NSS), the main part of which is the Mobile Switching Center (MSC), performs the switching of calls between the mobile and other fixed or mobile network users, as well as the management of mobile services such as authentication
- 32. • Home Location Register (HLR) • The HLR is a database used for storage and management of subscriptions. • The HLR is considered the most important database, as it stores permanent data about subscribers, including a subscriber's service profile, location information, and activity status. • When an individual buys a subscription in the form of SIM, then all the information about this subscription is registered in the HLR of that operator. • Mobile Services Switching Center (MSC) • The central component of the Network Subsystem is the MSC. • The MSC performs the switching of calls between the mobile and other fixed or mobile network users, as well as the management of mobile services such as registration, authentication, location updating, handovers, and call routing to a roaming subscriber. • It also performs such functions as toll ticketing, network interfacing, common channel signaling, and others. • Every MSC is identified by a unique ID.
- 33. • Visitor Location Register (VLR) • The VLR is a database that contains temporary information about subscribers that is needed by the MSC in order to service visiting subscribers. • The VLR is always integrated with the MSC. When a mobile station roams into a new MSC area, the VLR connected to that MSC will request data about the mobile station from the HLR. • Later, if the mobile station makes a call, the VLR will have the information needed for call setup without having to interrogate the HLR each time.
- 34. Authentication Center (AUC) • The Authentication Center is a protected database that stores a copy of the secret key stored in each subscriber's SIM card, which is used for authentication and ciphering of the radio channel. • The AUC protects network operators from different types of fraud found in today's cellular world.
- 35. Equipment Identity Register (EIR) • The Equipment Identity Register (EIR) is a database that contains a list of all valid mobile equipment on the network, where its International Mobile Equipment Identity (IMEI) identifies each MS. • An IMEI is marked as invalid if it has been reported stolen or is not type approved.
- 36. GSM - The Operation Support Subsystem (OSS) • The operations and maintenance center (OMC) is connected to all equipment in the switching system and to the BSC. The implementation of OMC is called the operation and support system (OSS). • Here are some of the OMC functions− • Administration and commercial operation (subscription, end terminals, charging, and statistics). • Security Management. • Network configuration, Operation, and Performance Management. • Maintenance Tasks.
- 37. • The OSS is the functional entity from which the network operator monitors and controls the system. • The purpose of OSS is to offer the customer cost-effective support for centralized, regional, and local operational and maintenance activities that are required for a GSM network. • An important function of OSS is to provide a network overview and support the maintenance activities of different operation and maintenance organizations.
- 38. Protocols of GSM • GSM Architecture is a layered model that is designed to allow communication between two different systems. • Lower layers and upper layers • Each layer suitable notifications to ensure the transmitted data has been formatted, transmitted and received accurately
- 40. GSM PROTOCOL LAYERS FOR SIGNALING • MS and BTS between Um interface • BTS and BSC between Abis interface • BSC and MSC between A interface
- 41. GSM protocol layers Mobility management (MM) • The MM layer is in-charge of maintain the location data, in addition to the authentication and ciphering procedures Communication Management (CM) • The CM layer consists of setting up call at the user request • Its functions are call control, which manages the supplementary services configuration, short message services which provides point- to-point short message services
- 42. • Radio Resource (RR) • The RR management layer is in-charge of establishing and maintaining a stable uninterrupted communication path between the MSC and MS over which signaling and user data can be covered • Handovers are part of the RR layer responsibility • Most of the functions are controlled by the BSC, BTS and MS though some are performed by the MSC
- 43. Base Transceiver Station Management (BTSM) • The BTSM is responsible for transferring the RR information to the BSC Link Access Protocol for the ISDN D-Channel (LAPD): • Provides error free transmission between the BSC and MSC LAPDm: • It is a modified version of the LADP protocol • The layer two protocols are provided for by LAPDm over the air-interface
- 44. Base Station System Application Part (BSSAP): • The BSSAP is split into two parts the Base station system management application part(BSSMAP) and the direct transfer application part (DTAP) SS7 • Signaling system no.7 is used for signaling between MSC and BSC • This protocol also transfer information between MSCs, HLR, VLR, Auc, EIR and MOC
- 45. GSM CONNECTION ESTABLISHMENT LOCALIZATION • The localization is a process by which a mobile station is identified, authenticated and provided service by a mobile switching center through the base station controller and base Tran receiver either at the home location of the MS or at a visiting location.
- 46. Frequency allocation • GSM has been allocated an operational frequency from 890 MHz • MS and BS use different frequency ranges • EX: MS (890 MHz to 915 MHz ) BS(935 MHz to 960 MHz ) GSM system uses a varity control channel to ensure uninterrupted communication between MS and BS
- 47. • Broad cast control channel (BCCH) Used for transmitting system parameters • Frequency correction channel (FCCH) • Synchronization channel(SCH) • Random access channel(RACH) • Paging channel (PCH) • Access grant channel (AGCH) BS to send information timing and synchronization.
- 48. GPRS(General Packet Radio Services) - Architecture • GPRS architecture works on the same procedure like GSM network, but, has additional entities that allow packet data transmission. • This data network overlaps a second-generation GSM network providing packet data transport at the rates from 9.6 to 171 kbps. • Along with the packet data transport the GSM network accommodates multiple users to share the same air interface resources concurrently. • The GPRS architecture introduces two new network elements – gateway GPRS support node (GGSN) – serving GPRS support node (SGSN)
- 50. • GPRS Mobile Stations • New Mobile Stations (MS) are required to use GPRS services because existing GSM phones do not handle the enhanced air interface or packet data. • A variety of MS can exist, including a high- speed version of current phones to support high-speed data access, a new PDA device with an embedded GSM phone, and PC cards for laptop computers. • These mobile stations are backward compatible for making voice calls using GSM.
- 51. GPRS Base Station Subsystem • Each BSC requires the installation of one or more Packet Control Units (PCUs) and a software upgrade. The PCU provides a physical and logical data interface to the Base Station Subsystem (BSS) for packet data traffic. • The BTS can also require a software upgrade but typically does not require hardware enhancements. • When either voice or data traffic is originated at the subscriber mobile, it is transported over the air interface to the BTS, and from the BTS to the BSC in the same way as a standard GSM call. • However, at the output of the BSC, the traffic is separated; voice is sent to the Mobile Switching Center (MSC) per standard GSM, and data is sent to a new device called the SGSN via the PCU over a Frame Relay interface.
- 52. • GPRS Support Nodes • Following two new components, called Gateway GPRS Support Nodes (GSNs) and, Serving GPRS Support Node (SGSN) are added:
- 53. • Gateway GPRS Support Node (GGSN) • The Gateway GPRS Support Node acts as an interface and a router to external networks. • It contains routing information for GPRS mobiles, which is used to tunnel packets through the IP based internal backbone to the correct Serving GPRS Support Node. • The GGSN also collects charging information connected to the use of the external data networks and can act as a packet filter for incoming traffic.
- 54. • Serving GPRS Support Node (SGSN) • The Serving GPRS Support Node is responsible for authentication of GPRS mobiles, registration of mobiles in the network, mobility management, and collecting information on charging for the use of the air interface. • Internal Backbone • The internal backbone is an IP based network used to carry packets between different GSNs. Tunnelling is used between SGSNs and GGSNs, so the internal backbone does not need any information about domains outside the GPRS network. Signalling from a GSN to a MSC, HLR or EIR is done using SS7.
- 55. • Routing Area • GPRS introduces the concept of a Routing Area. This concept is similar to Location Area in GSM, except that it generally contains fewer cells. Because routing areas are smaller than location areas, less radio resources are used While broadcasting a page message.
- 56. GPRS APPLICATION • Communications • E-commerce • Value-added services • Location-based applications
- 57. GPRS - Protocol Stack • The flow of GPRS protocol stack and end-to- end message from MS to the GGSN is displayed in the below diagram. GTP is the protocol used between the SGSN and GGSN using the Gn interface. This is a Layer 3 tunneling protocol.
- 59. • The process that takes place in the application looks like a normal IP sub-network for the users both inside and outside the network. • The vital thing that needs attention is, the application communicates via standard IP, that is carried through the GPRS network and out through the gateway GPRS. • The packets that are mobile between the GGSN and the SGSN use the GPRS tunneling protocol, this way the IP addresses located on the external side of the GPRS network do not have deal with the internal backbone. UDP and IP are run by GTP.
- 60. • SubNetwork Dependent Convergence Protocol (SNDCP) and Logical Link Control (LLC) combination used in between the SGSN and the MS. The SNDCP flattens data to reduce the load on the radio channel. A safe logical link by encrypting packets is provided by LLC and the same LLC link is used as long as a mobile is under a single SGSN. • In case, the mobile moves to a new routing area that lies under a different SGSN; then, the old LLC link is removed and a new link is established with the new Serving GSN X.25. Services are provided by running X.25 on top of TCP/IP in the internal backbone.
- 62. GENERATIONS OF MOBILE COMMUNICATION TECHNOLOGIES • First Generation • Second Generation • Third Generation • Fourth Generation • Fifth Generation
- 63. GENERATIONS OF MOBILE COMMUNICATION TECHNOLOGIES • First Generation • Second Generation • Third Generation • Fourth Generation • Fifth Generation
- 64. First Generation • It uses analog technology that were introduced in the 1980s and continued until being replaced by 2G digital telecommunications It introduces the following mobile technologies • Mobile Telephone System (MTS) • Advanced Mobile Telephone System (AMTS) • Improved Mobile Telephone Service (IMTS) • Push to Talk (PTT)
- 65. Features • Maximum speed of 1G is 2.4 Kbps • Allows voice calls in 1 country • Use analog signal • Channel bandwidth 30khz Disadvantage • Poor Voice Quality • Poor Battery Life • Large Phone Size • No Security • Limited Capacity
- 66. Second Generation • Second Generation based on GSM. • It was launched in Finland in the year 1991. • It uses digital signals for voice transmission. • It make use of either CDMA or TDMA.
- 67. Features • Lower power emissions • Data speed was upto 64kbps • Use digital signals • Enables services such as text messages, picture messages and MMS(Multimedia message) Provides better quality and capacity Limitations • Requires powerful digital signals to work the mobile phones • Unable to handle complex data such as videos
- 68. Third Generation • It make use of TDMA and CDMA. • It provides value added services like mobile television, GPS (global positioning system), live streaming and video conferencing. • It is designed for multimedia communication
- 69. Features • Fast data transfer rates • Speed 2 Mbps • Send/receive large email messages • Provide seamless global roaming Limitations • Requires higher bandwidth • Cost is high
- 70. Fourth Generation • It is an all IP-based integrated system will be capable to provide 100 Mbps for high mobility and 1 Gbps. • The user services include IP telephony, ultra- broadband Internet access, gaming services and High Definition Television (HDTV) streamed multimedia.
- 71. Feature • Capable of provide 10Mbps-1Gbps speed • High quality streaming video • Combination of Wi-Fi and Wi-Max • High security • Low cost per-bit Limitations • Battery uses is more • Hard to implement • Need complicated hardware • Expensive equipment required to implement next generation network
- 72. Fifth Generation • Its not yet have been deployed and are still at a research and development phase • Increased data transmission capability 1 Gbps • Connectivity to a large number of devices due to the IoT. • Period of establishment 2016 to 2020.
- 73. Software Defined Radio Receiver • The basic concept of the SDR software radio is that the radio can be totally configured or defined by the software. • In an ideal world the incoming signal is immediately converted to a digital format, and the signal is then processed totally digitally. • Conversely for transmit, the signal is generated digitally, and converted to the final analogue signal at the antenna. • This approach has the advantages that the radio can be totally reconfigured for a new application, simply by changing the software. Updates can be made to keep up with new modulation formats, new applications, etc, simply by updating the software.
- 74. • It also means that a common hardware platform can be used across a variety of different products and applications, thereby reducing costs, whilst maintaining or improving the performance.
- 77. Software defined radio applications • The SDR software radio concept is applicable to many areas of use: • Mobile communications: Software defined radios are very useful in areas such as mobile communications. By upgrading the software it is possible to apply changes to any standards and even add new waveforms purely by upgrading the software and without the need for changes to the hardware. This can even be done remotely, thereby providing considerable savings in cost. • Research & development: The software defined radio, SDR is very useful in many research projects. The radios can be configured to provide the exact receiver and transmitter requirements for any application without the need for a total hardware design from scratch.
- 78. • Military: The military have made much use of software defined radio technology enabling them to re-use hardware and update signal waveforms as needed. • Amateur radio: Radio hams have very successfully employed software defined radio technology, using it to provide improved performance and flexibility. • Other: There are very many other applications that can make use of SDR technology, enabling the radio to be exactly tailored to the requirements using software adjustments.
- 79. Software defined radio definition • Many definitions have appeared that might cover a definition for a software defined radio, SDR. The SDR Forum themselves have defined the two main types of radio containing software in the following fashion: • Software Controlled Radio: Radio in which some or all of the physical layer functions are Software Controlled. In other words this type of radio only uses software to provide control of the various functions that are fixed within the radio. • Software Defined Radio: Radio in which some or all of the physical layer functions are Software Defined. In other words, the software is used to determine the specification of the radio and what it does. If the software within the radio is changed, its performance and function may change.
- 80. • Advantages of SDR technology • It is possible to achieve very high levels of performance. • Performance can be changed by updating the software (it will not be possible to update hardware dependent attributes though). • It is possible to reconfigure radios by updating software • The same hardware platform can be used for several different radios
- 81. • Disadvantages of SDR technology • Analogue to digital converters limit top frequencies that can be used by the digital section. • For very simple radios the basic platform may be too expensive. • Development of a software defined radio requires both hardware and software skills.