Cellular Technologies of the World Analogue Cellular Networks AMPS Advanced Mobile Phone System.

Developed by Bell Labs in the 1970s and first used commercially in the United States in 1983. It operates in the 800 MHz band and is currently the world's largest cellular standard. C-450 Installed in South Africa during the 1980's. Now known as Motorphone and run by Vodacom. C-Nezt Cellular technology found mainly in Germany. It operates at 450 MHz. N-AMPS Narrowband Advanced Mobile Phone System. Developed by Motorola as an interim technology between analogue and digital. It has some three times greater capacity than AMPS and operates in the 800 MHz range. NMT450 Nordic Mobile Telephones/450. Developed specially by Ericsson and Nokia to service the rugged terrain that characterises the Nordic countries.Operates at 450 Mhz. NMT900 Nordic Mobile Telephones/900. The 900 Mhz upgrade to NMT 450 developed by the Nordic countries to accommodate higher capacities and handheld portables. NTT Nippon Telegraph and Telephone. The old Japanese analogue standard. A highcapacity version is called HICAP. TACS Total Access Communications System. Developed by Motorola. and is similar to AMPS. It was first used in the United Kingdom in 1985, although in Japan it is called JTAC. It operates in the 900 MHz frequency range. Digital Cellular Networks. CDMA Code Division Multiple Access. Developed by Qualcomm Inc. and is characterised by high capacity and small cell radius. It was adopted by the Telecommunications Industry Association (TIA) in 1993. The first CDMA-based networks are now operational. D-AMPS Digital AMPS. An upgrade to the analogue AMPs. A AMPS/D-AMPS infrastructure can support use of either analogue AMPS phone or digital D-AMPS phones. This was because the Federal Communications Commission mandated only that digital cellular in the U.S. must act in a dual-mode capacity with analogue. Both operate in the 800 MHz band. DCS 1800 Digital Cordless Standard. GSM operated in the 1800 MHz range. It is a different version of GSM, and (900 MHz) GSM phones cannot be used on DCS 1800 networks. GSM Global System for Mobile Communications. The first European digital standard, developed to establish cellular compatibility throughout Europe. It's success has spread to all parts of the world and over 80 GSM networks are now operational. It operates at 900 MHz. PCS Personal Communications Service. The American version of GSM, but GSM phones cannot be used on PCS networks. It operates in the 1,900 MHz range.

PHS Personal Handy System. A Japanese-centric system that offers high speed data services and superb voice clarity. TDMA Time Division Multiple Access. The first U.S. digital standard to be developed. It was adopted by the TIA in 1992. The first TDMA commercial system began in 1993.

Components Microphone - Captures your voice for conversion from analogue to digital mode Speaker - Allows monitoring of remote phone LCD Display - Shows Call, Phone, Signal & Network Info Keypad - Allows access to specific remote phones Battery + Meter - While battery housings on cellphones are standard input deigns, some cellphones also have some "battery processing" intelligence built in. For example, they will check the charge level to start or stop the charge when the phone is connected to a desktop, car or quick charger and even automatically discharge the battery for you when necessary. This is usually linked to the LCD display and to an audible beep to warn you of the battery charge status. LED Lights Status Information, usuallay Green, white & Red. Digital Signal Processor The DSP chipset is a critical component. It co-ordinates the voice, SMS and data/fax features of a cellphone. It processes speech, handles voice activity detection, as well as discontinuous GSM transmission and reception. Another section amplifies the input signal received from the microphone, while another converts this microphone voice signal from "analogue" to "digital". The digital conversion is necessary because the GSM cellular standard is a completely digital system. CODEC This DSP's voice processing is done in tandem with highly sophisticated compression technique mediated by the "CODEC" (compressor/decompressor) portion of the cellphone. T RF Unit The CODEC chipset instantly transfers this "compressed" information to the cellphones Radio Frequency (RF) unit. This RF unit, which is essentially the transmit and receive section of the cellphone, then sends out the voice or data information via the cellphone antenna, over the air and on to the nearest cellular base station - and ultimately to your call destination. The incoming voice also travels much the same route, although it is first uncompressed from its incoming digital form into an audible analogue form which is then piped out as sound through the cellphones speaker. This analogue-to-digital and digital-to-analogue

voice conversion via the CODEC is done at very high speeds, so that you never really experience any delay between talking and the other person hearing you (and visa versa). SIM Card Reader When you switch on your phone with a "live" SIM card inside, the subscriber information on the chip inside the SIM card is read by the SIM card reader and then transmitted digitally to the network via the RF unit. The same route is followed when you hit the Call button (and its variants) on the cellphone: the number youve inputted is instantly and digitally transferred to the network for processing. External Connectors At the bottom of most cellphones there is an external connector system. You can usually plug in a data/fax adapter, or a battery charger, or a personal hands free device, or a car-kit with external antenna connections. Youll also find many with separate "speaker" and LED lights that are activated when the phone rings and/or when the battery is low. Many phones also have tiny LED lights under the keypad that light up when you press a key and/or when the phone rings. On-Board Memory Many cellphones also have a certain amount of on-board memory chip capacity available for storing outgoing telephone numbers, your own telephone number, as well as incoming and outgoing SMS messages. Some allow copying between the (limited) memory on the SIM card and the phones own internal memory. Antenna System Cellphone manufacturers are implementing many weird and wonderful permutations of antenna system designs. While some are stubby, fixed types, the most predominant designs though are those with thin, pull-out steel rods all of whom usually fit snugly into a special antenna shaft. These antenna designs, be they the stubby or pull-out types, all conform to the same circa 900 MHz frequency transmit and receive range required by the GSM specification.

How They Work: GSM Networks GSM 900/DCS 1800 networks use a sophisticated array of digital equipment to provide you with a seamless, hiss-free connection.

Below are some of the critical components & procedures that allow them to do so: Component/ Purpose Procedure Base Station GSM (Global System for Mobile Communications) uses a series of radio transmitters called Base Stations (BS) to connect you and your cellphone to your cellular network. Each BS is also termed a cell, so named because it covers a certain range within a

discrete area (cell). Base Stations are all interconnected, which is why you can move from one cell to another - a process called "hand-over" - without (hopefully) losing your connection. Base Station Controller A set of Base Stations is connected to a particular Base Station Controller MSC The combination of a cellphone and the SIM card creates a special digital "signature" - that includes your subscriber number - which is sent from your cellphone to the nearest BS asking that you as a subscriber of a particular network be allowed to use the network. The request is passed on along the network of BSs to the multifaceted heart of a cellular network - the Mobile Switching Center (MSC). The MSC also routes all your incoming and outgoing calls to and from the fixed-line networks or other cellular networks. HLR The MSC also contains a critical component called the Home Location Register (HLR) which provides the administrative information required to authenticate, register and locate you as a that network's subscriber. Once its received your log-on request, the HLR immediately checks the special "signature" contained in the request against its special subscriber database. If your subscription is current, the MSC sends a message back to the phone via the network of BSs that indicates that youre allowed to access the network. The name or code of that network will appear on the LCD screen of the cellphone. Once this network "name" message appears on your phones LCD screen, it means youre connected to the network and able to make and receive calls. The entire log-on process usually takes only a couple of seconds. Polling At the same time, the HLR also registers which BS your cellphone is currently connected to, so that when the networks MSC needs to route an incoming call to your cellphone number, it will first check the HLR to see where you are. Every now and gain, the cellphone will send a message to the network indicating where it is, a process called Polling. Multiplexing Each BS uses digital techniques to enable a number of phones to be simultaneously connected to it, as well as simultaneously allowing a number of subscribers to make and receive calls. This sophisticated digital call-juggling ability is called Multiplexing. However, the combination of the tracking function and your unique digital signature allows the MSC to route that call to the precise BS your cellphone happens to be connected to, and then exclusively to your cellphone - even if a number of other subscribers are simultaneously connected to that BS. Hand Over When you "hand-over" to another cell whilst driving, the HLR is automatically updated, and continues to monitor where exactly it should route your calls should you then move within range of to another Vodacom BS. This sophisticated

routing procedure means that out of hundreds of thousands of subscribers, only the correct cellphone will ring when necessary. VLR When you want to make an outgoing call, another section of the MSC called the Visitor Location Register (VLR) checks whether you are actually allowed to make that call. For example, if you are barred for international dialing, a message to that effect will be generated by the VLR, sent along the network, and almost instantly back to your cellphone. MailBox If youre unavailable for some reason and your Mailbox has been activated, any incoming voice calls will be transferred to the Mail system. SMSC Some VoiceMail systems are linked to a network's SMS Center (SMSC), a special facility that handles Short Messages. The SMSC generates the special SMS message that notifies you that you have mail waiting in your Mailbox. SMS messages can be received on your SMS-capable cellphone even while youre on a voice call. Thats because they are sent on a different radio frequency - the GSM data channel - than voice calls, so that the two never interfere. These sophisticated digital facilities are the reason why GSM is now considered the de facto global cellular standard.