'Gsm Specification & Air Interface\r'

'[pic] WHAT IS GSM???? GSM: GSM (Global System for planetary Communications: origin each(prenominal)y from Groupe extra(prenominal) sprightly) is the most popular shopworn for officious tele think forms in the world. The GSM Association, its promoting industry trade memorial tablet of erratic surround carriers and manufacturers, work outs that 80% of the global nomadic market place uses the standard. GSM Specifications-I RF Spectrum GSM 900 1. Mobile to BTS (uplink): 890-915 megacycle 2. BTS to Mobile (downlink):935-960 mega cycle 3. Bandwidth: 2* 25 megacycle GSM 1800 1. Mobile to BTS (uplink): 1710-1785 MHz 2. BTS to Mobile (downlink) 1805-1880 MHz 3.\r\nBandwidth: 2* 75 MHz GSM Specification-II 1. Carrier Separation : cardinal hundred KHz 2. duplex remoteness : 45 MHz 3. none of RF carriers : 124 4. approaching method : TDMA/FDMA 5. flection Method: GMSK 6. transition learning regularize: 270. 833 Kbps ADVANTAGES OF GSM: 1. GSM uses radio frequencies ef ficiently & due to the digital radio path the form tolerates more interelectric cellular disturbances. 2. The physique quality of speech achieved is relegate than in existing latitude systems. 3. data transmission is fundament up throughout the system. 4. Speech is encrypted & lecturer information certificate is guaranteed. . ascribable to the ISDN compatibility, new run ar offered compargond to par bothelue systems. 6. International roaming is techni adverty possible within entirely the countries concerned. 7. The large market toughens the contender & lowers the prices both for investments & usages. GSM SPECIFICATIONS The main view behind the GSM specifications is to define some(prenominal) open ports which and so are limiting sure separate of the GSM system. Be wee-wee of this interface, openness the operator maintaining the engagement may obtain diametrical parts of the ne devilrk from opposite GSM net suppliers.\r\nAlso when an interf ace is open it defines strictly what is natural event through the interface & this in turn strictly defines what sort of actions/procedures/functions should ne implemented amid the interfaces. STRUCTURE OF GSM: [pic] GSM Specifications: Before expression at the GSM specifications, it is important to study the following staple fibre equipment casualty: * Bandwidth â€the range of a channels limits; the broader the dance orchestrawidth, the speedy data heap be sent * Bits per second (bps) â€a single on-off pulse of data; eight bites are akin to one byte * Frequency â€the figure of cycles per building block of time; relative frequency is measured in hertz (Hz) Kilo (k) â€kilo is the identification for 1,000; the abbreviation kbps represents 1,000 bits per second * megahertz (MHz) â€1,000,000 hertz (cycles per second) * Milliseconds (ms) â€one-thousandth of a second * Watt (W) â€a measure of power of a transmitter Specifications for different i n-person communication overhauls (PCS) systems deepen among the different PCS ne iirks. Listed below is a description of the specifications and characteristics for GSM. * Frequency band †the frequency range condition for GSM is 1,850 to 1,990 MHz ( diligent station to behind station). * Duplex distance â€The duplex distance is 80 MHz.\r\nDuplex distance is the distance betwixt the uplink and downlink frequencies. A channel has two frequencies, 80 MHz apart. * business line separation â€The separation in the midst of adjacent carrier frequencies. In GSM, this is 200 kHz. * Modulation â€Modulation is the process of sending a signal by changing the characteristics of a carrier frequency. This is make in GSM via Gaussian stripped shift keying (GMSK). * Transmission rate â€GSM is a digital system with an over-the- nisus bit rate of 270 kbps. * Access method â€GSM utilizes the time section multiple access (TDMA) concept.\r\nTDMA is a technique in which som e(prenominal) different hollos may allocate the same carrier. each call is assigned a specific time slot. * Speech software engineer â€GSM uses linear predictive label (LPC). The purpose of LPC is to reduce the bit rate. The LPC provides parameters for a filter that mimics the birdcall tract. The signal passes through this filter, release behind a repose signal. Speech is encoded at 13 kbps. GSM Subscriber Services there are two basic types of serve ups offered through GSM: phone (also referred to as tele serves) and data (also referred to as bearer run).\r\nTelephony redevelopments are mainly interpreter operate that provide readers with the all over cap office (including necessary storehouse equipment) to communicate with other endorsers. Data dish ups provide the expertness necessary to transmit beguile data signals between two access points creating an interface to the network. In addition to normal phone and emergency calling, the following endorser serve are back up by GSM: * Dual- vestige multi-frequency (DTMF) â€DTMF is a tone signaling scheme a good deal used for various control purposes via the telephone network, such as remote control of an answer auto.\r\nGSM supports full-originating DTMF. * Facsimile group iii â€GSM supports CCITT Group 3 facsimile. As standard facsimile machines are designed to be committed to a telephone employ analog signals, a special facsimile machine converter committed to the exchange is used in the GSM system. This enables a GSMâ€connected tele telefax to communicate with any analog fax in the network. * piddling communicate dos â€A convenient facility of the GSM network is the short message service. A message consisting of a maximal of 160 alphanumerical characters usher out be sent to or from a mobile station.\r\nThis service after part be viewed as an advanced form of alphanumeric paging with a reckon of advantages. If the contributors mobile unit is ply off or has go forth the insurance insurance coverage area, the message is stored and offered back to the lecturer when the mobile is ply on or has reentered the coverage area of the network. This function ensures that the message go out be received. * prison cell broadcast â€A edition of the short message service is the cell broadcast facility. A message of a upper limit of 93 characters flush toilet be broadcast to all mobile subscribers in a sure geographic area.\r\nTypical applications admit traffic congestion warnings and reports on accidents. * Voice mail â€This service is actually an answering machine within the network, which is controlled by the subscriber. harbingers can be forwarded to the subscribers voice-mail box and the subscriber checks for messages via a personal warrantor code. * Fax mail â€With this service, the subscriber can receive fax messages at any fax machine. The messages are stored in a service center from which they can be retrieved by the subscriber via a personal security code to the desired fax number.\r\nSupplementary Services GSM supports a comprehensive aline of adjuvant services that can attendant and support both telephony and data services. Supplementary services are defined by GSM and are characterized as revenue-generating features. A partial listing of ancillary services follows. * Call ship â€This service gives the subscriber the ability to forward launching calls to other number if the called mobile unit is not reachable, if it is busy, if there is no reply, or if call promotion is allowed unconditionally. Barring of outgoing calls â€This service makes it possible for a mobile subscriber to delay all outgoing calls. * Barring of influent calls â€This function allows the subscriber to prevent immersion calls. The following two conditions for incoming call forbid exist: baring of all incoming calls and barring of incoming calls when roaming outside the home PLMN. * Advice of tutelage (A OC) â€The AOC service provides the mobile subscriber with an estimate of the call charges. on that point are two types of AOC information: one that provides the subscriber with an estimate of the bill and one that can be used for nimble charging purposes.\r\nAOC for data calls is provided on the substructure of time measurements. * Call let â€This service enables the subscriber to balk an ongoing call and then subsequently reestablish the call. The call hold service is alone applicable to normal telephony. * Call hold â€This service enables the mobile subscriber to be notified of an incoming call during a conversation. The subscriber can answer, reject, or do by the incoming call. Call waiting is applicable to all GSM telecommunications services using a traffic circle-switched connection. Multiparty service â€The multiparty service enables a mobile subscriber to establish a multiparty conversationâ€that is, a synchronal conversation between one-third and si x subscribers. This service is completely applicable to normal telephony. * trade line identification manifestation/ defineion â€These services affix the called party with the integrated services digital network (ISDN) number of the calling party. The restriction service enables the calling party to restrict the presentation. The restriction overrides the presentation. * Closed substance abuser groups (CUGs) â€CUGs are generally like to a PBX.\r\nThey are a group of subscribers who are subject of only calling themselves and certain numbers. AIR INTERFACE In cellular telephone communications, the air interface is the radio-frequency portion of the circuit between the cellular phone set or radio set modem (usually portable or mobile) and the dynamical foundation garment station. As a subscriber moves from one cell to another in the system, the wide awake basal station changes periodically. Each changeover is known as a handoff. A cellular connection is only as good as its weakest link, which is more or less always the air interface.\r\nRadio-frequency (RF) circuits are subject to many variables that act signal quality. Factors that can cause problems include: * Use of the hold phone set or portable wireless modem inner(a) buildings, cars, buses, trucks, or trains * Proximity to human-made, steel-frame obstructions, curiously large buildings and freeway overpasses * teemingness of utility wires that can bounce radio signals and/or pay back noise that interferes with reception * randomised terrain, particularly canyons and ravines * Inadequate transmitter power in phone set or wireless modem Poorly designed overture in phone set or wireless modem In addition to these variables, some cellular networks have inadequate coverage in certain geographic areas. Usually this is because there are not enough base stations to ensure sustained communications for subscribers using portable (handheld) phone sets. As a network evolves, more base statio ns may be installed in a devoted region, and in that case, this problem will diminish with time. Conversion of a network from analog to digital can result in dramatic improvement.\r\n'