2Outline Cellular Network Concept First Generation AMPS Second GenerationCellular Access TechnologiesFDMA, TDMA, CDMAGSMThird GenerationUMTS
3Cell Concept Cell phone is basically a radio Combination of telephone (Alexander Graham Bell) and wireless communications (Guglielmo Marconi)Originally used powerful radio telephonesProblemsNeeded to be very powerfulNot many distinct frequencies (50)Finally split cities into cells to allow cell reuse and reduce the required power – the cell conceptEach cell has a towerAbout 800 frequencies across a cellSize of cell is about 10 sq. milesOne of the most interesting things about a cell phone is that it is really a radio -- an extremely sophisticated radio, but a radio nonetheless. The telephone was invented by Alexander Graham Bell in 1876, and wireless communication can trace its roots to the invention of the radio in 1894 by a young Italian named Guglielmo Marconi. It was only natural that these two great technologies would eventually be combined!In the dark ages before cell phones, people who really needed mobile communications ability installed radio telephones in their cars. In the radio telephone system, there was one central antenna tower per city, and perhaps 25 channels available on that tower. This central antenna meant that the phone in your car needed a powerful transmitter -- big enough to transmit 40 or 50 miles. It also meant that not many people could use radio telephones -- there just were not enough channels.The genius of the cellular system is the division of a city into small cells. This allows extensive frequency reuse across a city, so that millions of people can use cell phones simultaneously. In a typical analog cell phone system in the United States, the cell phone carrier receives about 800 frequencies to use across the city. The carrier chops up the city into cells. Each cell is typically sized at about 10 square miles (26 square kilometers).
4BasicsMobile: Any radio terminal that could be moved during operation or a radioterminal that is attached to a high-speed mobile platform (e.g. a cellulartelephone in a fast moving vehicle) whereas the portable describes a radioterminal that can be hand-held and used by someone at walking speed.Subscriber: A mobile or portable user (user pay fee).Subscriber Unit or Mobile Station: Each user communication device.Mobiles or Users: Collective group of users in a wireless system. Many usersmay actually user portable terminals.Base Stations: A fixed stations in a mobile radio system used forcommunication with mobile stations. They are located at the center or on theedge of a coverage region and consist of radio channels and transmitter andreceiver antennas mounted on a tower.Mobile Switching Center: Switching center, which coordinates the routing ofcalls in large service area. In a cellular radio system, MSC connects cellularbase station and the mobiles to the PSTN. An MSC is also called a mobiletelephone switching office (MSTSO).
5BasicsControl Channel: Radio Channels used for transmission of call setup, callrequest, call initiation and other beacon or control purpose.Forward Channel: Transmission of information from the base to a mobilestation.Reverse Channel: Transmission of information from the mobile to a baseRoamer: A mobile station, which operates in a service area (market) otherthan that from which service has been subscribe.Handoff: The process of transferring a mobile station from one channel orbase station to another.Page: A brief message, which is broadcast over the entire service area.
6ClassificationSimplex: Communication is possible in only one direction (no acknowledge) e.g. Paging Systems.Half duplex: Communication is bi directional but use same channel for both receiving and transmission (push-to-talk and release-to-listen).Half duplex: Communication is bi directional but allows simultaneous transmission and reception b/w subscriber and base station. Implemented by FDD (frequency division duplex; separate channel) or TDD (time division duplex; adjacent time slots).
7PSTN Generic WCS (Wireless Communication System) Switch BaseStationBaseStationSwitchPSTN(Public SwitchedTelephone Network)HandsetHandset
9Cellular Call Setup1. Phone scans for towers for strongest signal on control channel2.Transmit Mobile Identification Number (MIN), Electronic Serial Number (ESN), and telephone number3. MTSO sets up callAll cell phones have special codes associated with them. These codes are used to identify the phone, the phone's owner and the service provider.Let's say you have a cell phone, you turned it on, and someone tries to call you. Here is what happens to the call:When you first power up the phone, it listens for an SID on the control channel. The control channel is a special frequency that the phone and base station use to talk to one another about things like call set-up and channel-changing. If the phone cannot find any control channels to listen to, it knows it is out of range, and displays a "no service" message.When it receives the SID, the phone compares it to the SID programmed into the phone. If the SIDs match, the phone knows that the cell it is communicating with is part of its home system.Along with the SID, the phone also transmits a registration request, and the MTSO keeps track of your phone's location in a database -- this way, the MTSO knows which cell you are in when it wants to ring your phone.The MTSO gets the call, and it tries to find you. It looks in its database to see which cell you are in.The MTSO picks a frequency pair that your phone will use in that cell to take the call.The MTSO communicates with your phone over the control channel to tell it what frequencies to use, and once your phone and the tower switch on those frequencies, the call is connected. You are talking by two-way radio to a friend!As you move toward the edge of your cell, your cell's base station will note that your signal strength is diminishing. Meanwhile, the base station in the cell you are moving toward (which is listening and measuring signal strength on all frequencies, not just its own one-seventh) will be able to see your phone's signal strength increasing. The two base stations coordinate themselves through the MTSO, and at some point, your phone gets a signal on a control channel telling it to change frequencies. This hand off switches your phone to the new cell.PSTNCar Phone = 2WMobileCellular Service SubscriberTelephoneHand Phone = 0.7WSwitchingOfficeMTSO
10Wireless “Generations” First Generation (1989)Analog voice using FM channelsAlso called AMPS (Advanced Mobile Phone System)Solved the issue of “mobility”
11Multiple AccessThe basis for any mobile system is its air interface design, andparticularly the way the common transmission medium is sharedbetween users, that is, multiple access scheme.Multiple access scheme defines how the radio spectrum isdivided into channels, and how the channels separate thedifferent users of the system.FDMA, TDMA, CDMA
12AMPS AMPS – Advanced Mobile Phone System Analog cell phone standard deployed across North AmericaApproved by FCC in 1983 – first deployed in ChicagoUtilizes 824MHz-894MHz frequencies832 available frequencies790 Voice42 Data (signaling)30 KHz wide – voice qualityFDMANAMPS – Narrowband AMPS –3x AMPS capacityIn 1983, the analog cell phone standard called AMPS (Advanced Mobile Phone System) was approved by the FCC and first used in Chicago. AMPS uses a range of frequencies between 824 MHz and 894 MHz for analog cell phones. In order to encourage competition and keep prices low, the U. S. government required the presence of two carriers in every market, known as A and B carriers. One of the carriers was normally the local exchange carrier (LEC), a fancy way of saying the local phone company.Carriers A and B are each assigned 832 frequencies: 790 for voice and another 42 for data. A pair of frequencies (one for transmit and one for receive) is used to create one channel. The frequencies used in analog voice channels are typically 30 kHz wide. The reason that 30 kHz was chosen as the standard size is because it gives you voice quality comparable to a wired telephone.The transmit and receive frequencies of each voice channel are separated by 45 MHz to keep them from interfering with each other. Each carrier has 395 voice channels, as well as 21 data channels to use for housekeeping activities like registration, paging, etc.A version of AMPS known as Narrowband Advanced Mobile Phone Service (NAMPS) incorporates some digital technology to allow the system to carry about three times as many calls as the original version. Even though it uses digital technology, it is still considered analog. AMPS and NAMPS only operate in the 800 MHz band and do not offer many of the features common in digital cellular service such as and Web browsing.
13Wireless “Generations” 2G - Second Generation (1998)Digital modulation used for speech compressionStill a voice-only network, except for limited circuit switched data capabilitySeveral different system types:TDMA - time division multiple accessCDMA - code division multiple accessGSM - global mobile system (the original acronym is French) – Group Special Mobile.Solved the issue of “capacity”
14Cellular Access Technologies There are three common technologies used by cell phone networks for transmitting information:Frequency Division Multiple Access (FDMA)FDMA puts each call on a separate frequency.Time Division Multiple Access (TDMA)TDMA assigns each call a certain portion of time on a designated frequency.Code Division Multiple Access (CDMA)CDMA gives a unique code to each call and spreads it over the available frequencies.The last part of each name is multiple access. This simply means that more than one user (multiple) can use (access) each cell.There are three common technologies used by cell phone networks for transmitting information:Frequency Division Multiple Access (FDMA)Time Division Multiple Access (TDMA)Code Division Multiple Access (CDMA)Although these technologies sound very intimidating, you can get a good sense of how they work just by breaking down the title of each one. The first word tells you what the access method is and the second word, division, lets you know that it splits calls based on that access method.FDMA puts each call on a separate frequency.TDMA assigns each call a certain portion of time on a designated frequency.CDMA gives a unique code to each call and spreads it over the available frequencies.The last part of each name is multiple access. This simply means that more than one user (multiple) can use (access) each cell.
15FDMAIn a FDMA system, the total system bandwidth is divided into several frequency channels that are allocated to users.MHz45 MHz893.7 MHz
16TDMAIn a TDMA system, one frequency channel is divided into time slots that are allocated to users, and the users only transmit during their assigned timeslots. Examples of demand-assignment contention less protocols are token bus and token ring LANs described by the IEEE in the and standards.6.7MSMHzDigital decodingDigital encoding893.7 MHz
17CDMACDMA takes an entirely different approach from TDMA. CDMA, after digitizing data, spreads it out over the entire bandwidth it has available. Multiple calls are overlaid over each other on the channel, with each assigned a unique sequence code. CDMA is a form of spread spectrum, which simply means that data is sent in small pieces over a number of the discrete frequencies available for use at any time in the specified range.1850MHzDigital decodingDigital decoding1990MHzCDMA
18GSM GSM – Groupe Spécial Mobile GSM is an international digital cellular standard in Europe, Asia, Australia, and AfricaOriginally, the acronym GSM stood for Groupe Spécial Mobile, a group formed by the Conference of European Posts and Telegraphs (CEPT) in 1982 to research the merits of a European standard for mobile telecommunications.Commercial service using the GSM system did not actually start until 1991.GSM was developed as a digital system using TDMA technology.
19GSM GSM uses TDMA 900 MHz – 1800 MHz (Europe and Asia) 1900 MHz (North America)Used for digital PCS servicesOne phone for all standard GSM worldwide except North AmericaTo switch providers – switch SIM (subscriber identification modules) cardsTDMA is also used as the access technology for Global System for Mobile communications (GSM). However, GSM implements TDMA in a somewhat different and incompatible way from IS-136. Think of GSM and IS-136 as two different operating systems that work on the same processor, like Windows and Linux both working on an Intel Pentium III. GSM systems use encryption to make phone calls more secure. GSM operates in the 900 MHz and 1800 MHz bands in Europe and Asia and in the 1900 MHz (sometimes referred to as 1.9 GHz) band in the United States. It is used in digital cellular and PCS-based systems. GSM is also the basis for Integrated Digital Enhanced Network (IDEN), a popular system introduced by Motorola and used by Nextel.GSM is the international standard in Europe, Australia and much of Asia and Africa. In covered areas, cell-phone-users can buy one phone that will work anywhere else the standard is supported. To connect to the specific service providers in these different countries, GSM-users simply switch subscriber identification module (SIM) cards. SIM cards are small removable disks that slip in and out of GSM cell phones. They store all the connection data and identification numbers you need to access a particular wireless service provider.Unfortunately, the 1900 MHz GSM phones used in the United States are not compatible with the international system. If you live in the United States and need to have a cell phone access when you're overseas, the easiest thing to do is buy a GSM 900MHz/1800MHz cell phone for traveling. You can get these phones from Planet Omni, an online electronics firm based in California. They offer a wide selection of Nokia, Motorola and Ericsson GSM phones. They don't sell international SIM cards, however. You can pick up prepaid SIM cards for a wide range of countries at Telestial.com.
20GSM Features Uses encryption to make phone calls more secure Data networkingShort Message Service (SMS) for text messages and pagingCall forwardingCaller IDCall waiting
21GSM Network Architecture BSSNSSUmBTSMSCBSCTRAUAbisAterAPSTNMSVLRMS – Mobile StationBSS – Base Station SubsystemBTS – Base Trans StationBSC – Base Station ControllerTRAU - Transcoder / Rate Adaptation UnitMSC – Mobile Switching CentreNSS – Network Switching SubsystemVLR – Visitor Location RegisterHLR – Home Location RegisterAuC – Authentication CentreCHLR/AuCDA GSM system is basically designed as a combination of two major subsystems: the radio subsystem called the Base Station Subsystem (BSS) and the Network and switching SubSystem (NSS).In order to ensure that network operators have several sources of cellular infrastructure equipment, GSM decided to specify not only the radio interface, but also the main interfaces that identify different parts. They are three different dominant interfaces, named:Um interface between the MS (Mobile Station) and BTS (Base Transceiver Station),Abis interface between BTS and BSC (Base Station Controller), andA interface between the BSC and NSS.The Base Station Subsystem includes the equipment and functions related to the management of the connection on the radio path, including the handover treatment. It mainly consists of a BTS, BSC, and its aside component part: the Transcoder / Rate Adaptation Unit (TRAU). TRAU is called TransCoder Unit (TCU) within Nortel Networks products range.The Network and switching SubSystem includes the equipment and functions related to end-to-end-calls, management of subscribers, mobility, and interfaces with the fixed network, called Public Switched Telephone Network (PSTN).In particular, the Network and switching SubSystem consist of Mobile services Switching Centers (MSC), Visitor Location Registers (VLR), Home Location Registers (HLR), Authentication Center (AuC).
23Wireless “Generations” Packet switched data at rates up to 144 kbpsSeveral different types:GPRS - evolved from GSM1xRTT - evolved from CDMAWill require a Core IP NetworkSolves the issue of “mobility” with packet data
24GPRS GPRS – General Packet Radio Services An evolution of GSM Higher speed data servicesGPRS has seamless interface capabilities to TCP/IP
25From GSM to GSM/GPRS Network BTSBSCTRAUUmAbisAterAPCUAgprsFrameRelayBackboneGbMSCVLRPSTNSGSNPrivateIPGGSNGnExternalPacket NetworksIntranet, InternetGiHLR/AuCDCGrMSThe support of GPRS does not represent a major upgrade to the existing GSM infrastructure.The largest impact is the addition of two new network entities, the Serving GPRS Support Node (SGSN) and the Gateway GPRS Support Node (GGSN). There is no hardware impact to the BTSs and overall GPRS represents a software upgrade to the BSS, except for the introduction of PCUs to support the packet oriented nature of the Gb interface, logically between the PCU and the SGSN.The architecture of GPRS is designed so that signaling and high level data protocols are system independent. Only the low level protocols in the radio interface must be changed to be able of operating the same service.The main functions of SGSN are:to detect and record GPRS MS in its service area,to send/receive data packets to/from the MS.The main function of GGSN is to forward data packets between an external packet network and the GPRS network.In addition to routing and data transfer functions, the SGSNs and GGSNs collect charging statistics that are commonly used as a basis for billing.MS – Mobile StationBSS – Base Station SubsystemBTS – Base Trans StationBSC – Base Station ControllerTRAU - Transcoder / Rate Adaptation UnitMSC – Mobile Switching CentreNSS – Network Switching SubsystemVLR – Visitor Location RegisterHLR – Home Location RegisterAuC – Authentication Centre\SGSN – Serving GPRS Support NodeGGSN – Gateway GPRS Support Node
27Wireless “Generations” 3G -Third Generation (future)Packet switched data at rates up to 2.4 MbpsITU standard - standards still evolvingAdds the high data rate component and quality of service parametersIntroduces an Open Standard concept that will foster increased development of wireless applications, much like the Internet.
28UMTS Universal Mobile Telecommunications System Third Generation (3G) TechnologyUses W-CDMA, FDD, TDDPhase 1, called Release 1999 (R99) is an evolution of the GSM network architectureKey features:Open standards basedall IP in the coredecentralized networkservice basedIn plain English : a network that will allow IP devices to roam while providing 384 kbps to 2 Mbps access rates.If successful, may become the “World Standard”
29UMTS Will provide 2 Mbps in a local environment Will provide 384 kbps at highway velocitiesWill use IP over ATM to control different data types:controlling data latency and qualityWill use W-CDMA-FDD for macro mobility at 144 kbpsWill use W-CDMA-TDD for micro mobility at 2 MbpsTwo-way conversational video or audio requires 100 ms latency, and accepts rounding of dataStreaming video/audio requires 1-10 seconds latency, and accepts rounding of dataFTP 100 seconds latency, absolute precision of data
30RNC - Radio Network Controller UMTS ArchitectureUMTS Terrestrial Radio Access Network (UTRAN)Access NetworkCore NetworkRNC - Radio Network ControllerUuNode B(BTS)Iu(CS & PS)ATMBackboneIub (ATM)Circuit DomainUEIurATMBackboneNode BThis is a concept representing a logical node responsible for radio transmission and reception in one or more cells to/from the UE.BTS (Base Transceiver Station)The Node B concept can be associated to the functionality a BTS performs. The BTS supports the 5 MHz carrier and provides the WCDMA coding required to control one or more cells. The maximum capacity of the BTS is more likely restricted by the number of users’ data rates possible before the interference level becomes too high.RNC (Radio Network Controller)The RNC is the UMTS equivalent of the GSM BSC and GPRS PCU. It is responsible for Radio Resource management and control of the Node Bs. As adjacent RNCs have an interface between them, the Core Network is not involved in handover.RNS (Radio Network Subsystem)The RNS is composed of one RNC and its associated Node Bs.UuNode B(BTS)IurPacket DomainIu(CS & PS)Iub (ATM)UERNC
31UMTS Interfaces Access Network Core Network Uu MSC Node B (BTS) TRAU PSTNRNCIu CSIu(CS & PS)Iub (ATM)UECIurVLRDATMBackboneATMBackboneHLR/AuCGrUuNode B(BTS)GGSNIurPrivateIPBackboneSGSNAs UMTS is a new technology, new names for interfaces have been given.The particularity of these interfaces is that they are fully standardized, even the one between RNC and Node B.Uu interface (UMTS User interface): this interface is used between Node B and UE. It is dependent from the technology used on the radio (it can be WCDMA or TD/CDMA for example).Iub interface (Interface UMTS Node B): it is between RNC and Node B. It allows to connect RNC and Node B from different manufacturers because it is standardized (it is not like Abis in GSM).Iu interface (Interface UMTS): it is between Core Network and Access Network. The Core Network can be connected to different Access Networks using it (equivalent to A interface in GSM).Iur interface (Interface UMTS RNCs): this interface between two RNCs, has been defined to support specific functions such as handover without having the Core Network involved (no equivalent in GSM).Iu(CS & PS)Iu PSIub (ATM)GnGnUERNCGiExternalPacketNetworks