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telephone The mobile telephone revolution is well under way in Australia. Here's a rundown on the technology that's changing the way we talk to each other. for Telecom's mobile telephone service), it has attracted over 350,000 subscribers and that figure is growing by about 18,000 per month. The basic concept Motorola's "Business Classic" is one of the smallest & lightest mobile phones on the market. NCE considered the exclusive tool of high-powered executives, cellular telephones are now commonplace. Falling costs coupled with the rapid growth of the cellular network has made mobile telephones popular with anyone who needs instant communications. Mobile telephones are no longer the 0 6 SILICON CHIP preserve of the rich, nor are they any longer a status symbol. Indeed, in terms of per capita demand and usage, Australia has outstripped other countries in a boom which started with the introduction of cellular mobile telephone services in Sydney in February, 1987. In the five years since the launch of MobileNet (the name In simple terms , a cellular telephone is basically a low-power, 2-way radio which transmits and receives FM signals in the UHF (ultra-high frequency) band. These FM signals are picked up by (and broadcast by) nearby base stations which are connected to the normal public telephone network via a computer-controlled switching system. This system allows mobile telephone users to call anyone anywhere in Australia or in the world - as long as the user is within range of one of By GARRY CRATT & GREG SWAIN e revo n the MobileNet base stations. The concept behind MobileNet is quite different to earlier mobile radio communications systems. Those systems employed conventional 2-way radios to establish a link to a centrally-located base station running a powerful transmitter. However, these systems had only limited range, even if a relatively powerful transmitter was used in the car. Once you moved beyond the maximum range or into a no-signal area, the call would be terminated. This technique also limited the number of subscribers (due to the restricted number of frequencies available) and was subject to interference from adjacent areas. The cellular concept The cellular concept overcomes this limitation in an ingenious way: instead of using a single high-power transmitter to cover a wide service area, the area is divided into lots of smaller regions called "cells". Fig. l shows the cellular concept. Each cell is equipped with a lowpower transmitter and receiver, while the transmitter in the mobile phone also operates at much lower power (typically 0.6 to 3 watts). This low power operation limits the range of each cell to only a few kilometres (typically 2-16km) but as the car travels from one cell to the next, the computer network automatically switches communications to the new base station. This process happens so quickly that the user is generally unaware that Base stations like this one in bushland at Terry Hills, NSW, are now dotted throughout Australian cities & along many major highways. FEBRUARY1992 7 to provide billing and to switch mobile users from one cell to the next. Performance limitations BASE STATION Fig.I: each base station in the mobile telephone system is at the centre of a cell which defines its area of coverage & together these cells form an interlocking network. As the vehicle travels from one cell to the next, the system automatically switches communications to the new base station. SIGNAL - BASE STATION ' ---0 = 'II I • !H CELLULAR TELEPHONE Cl Fig.2: signal drop-outs can be caused by large buildings in the signal path (ie, between the caller & the base station) or by geographical features such as hills. anything ha~ happened. In fact, using a mobile telephone is no more complicated than picking up and using a conventional "wired" phone. There are many advantages to the cellular approach when compared to the old system. First, because only low power transmitters are used, the mobile phones can be made much smaller and lighter. Low transmitter powers also mean that interference between adjacent areas is virtually eliminated and means that the same frequencies can be used simultaneously in other non-adjacent cells, thus greatly increasing the system's capacity. Another important benefit of the 8 SILICO N CHIP cellular approach is the ability to reduce the radius of each cell to half and establish new cells to increase system capacity as required. Small cell areas also guarantee a good signal at all times, since the conversation can be handed off to an adjacent cell well before any serious signal degradation occurs. So the MobileNet telephone system relies on a number of different technologies. First, it uses FM radio techniques to transfer signals between the base station and the user. Second, it uses on the conventional telephone system to transmit signals back and forth. And finally, it uses computer switching techniques to direct calls, A number of factors affect the performance of cellular mobile telephones. Unlike cable systems, radio communications are imperfect and international design rules set a socalled 90/90 standard. This means that the signals should achieve 90% coverage of an area for 90% of the time. Because radio signals can be affected in various ways, complete coverage cannot be guaranteed in all areas within the cellular network. That's because UHF signals are easily obstructed or scattered by objects in the signal path. In particular, tall buildings, tunnels , underground carparks and even the terrain can contribute to momentary loss ofreception or signal "drop-outs". Naturally, signal drop-outs are more likely to occur on the edges of the coverage area, although the system is designed to tolerate short drop-outs without disconnecting the call. If prolonged dropouts occur, however, the system may interpret the signal loss to mean that one party has hung up and disconnect the call. Fig.2 shows a typical situation w.p.ere communications can be lost. These sorts of problems are disappearing as cell areas are progressively made smaller, however. MobileNet is now available in all Australian capital cities and over 40 large regional centres, covering around 80% of the population. Thus far, Telecom has invested over $600 million in MobileNet and continues to invest about $50 million annually to upgrade the network. MobileNet features As well as providing reliable mobile telephone communications over a large are, MobileNet also boasts a number of other important features. These are as follows: • Roaming: with the MobileNet system, you're not confined to just using your phone in a particular area. The automatic "roaming" facility allows you to travel to any part of the service area (eg, from Sydney to Melbourne) and still make or receive calls on the same number. • Call Diversion: you can divert calls from your mobile phone to your office, home, pager or any other phone you choose. In addition, you can di- Designed for use in the car, this Audiovox cellular telephone features a large LCD screen, 96 telephone number memories, hands-free operation, an automatic answering facility, a last number re-dial memory & an auxiliary port for fax machines or modems (via an optional interface). It also has comprehensive call restriction & security capabilities, a microphone mute control & numerous other features. vert incoming calls if you are already engaged on a call, or if the phone goes unanswered when it rings. • 2-Way Communication: unlike a 2way radio system, MobileNet allows 2-way conversations in the same manner as a normal telephone (ie, both parties can speak simultaneously). This is made possible by the use of separate transmit and receive frequencies. No special radio procedure is required to use the system. The remaining features are those that you would expect to find on any modern office phone (and on some home telephones as well). These features include: volume control, last number re-dial, on-hook dialling, hands-free operation, memory dialling, and facilities to prevent access to STD and/or ISD services. Some mobile telephones even have a theft alert function. Types of mobile phones Although Telecom is the sole pro- vider of the MobileNet system, there are many different brands of mobile phones to choose from. That said, there are three basic types: car phones, transportable phones and handheld phones. Car phones have a 3-watt power rating and are probably the best choice if more than 50% of the average working day is spent on the road. They take their power directly from the car's electrical system and, because they have the highest power rating, their performance will generally be better than other types, especially when conditions are marginal. Transportable phones are generally rated from 1.6 to 3 watts but lack the convenience of the much more compact handheld phones that are now available. On the other hand, handheld phones are only rated at 0.6 watts and have a more limited "talk-time" between battery charges (typically 80120 minutes vs about 200 minutes for transportables). Their standby time is also more limited (typically 12-18 hours). But whatever the type, all mobile telephones contain a transmitter, a receiver and a control module. The MARK ONE COMMUNICATIONS Specialising in: Mitsubishi , Motorola & NEC mobile phones INSTALLATION & SERVICE 7DAYS Cellular telephones from Motorola Also available from Motorola are the 8800 Ultra Classic portable phone (right) & the Mobile KS2000 car phone (far right). Among other things, the 8800 Ultra Classic features 2.2 hours of talk time, five call timers, six levels of call restrictions & 101 memories. The KS2000 is a fully-featured car phone with an LCD screen & faci lities for hands-free operation, on-hook dialling, electronic locking & microphone muting. Mobile Phone (018) 29 5888 (018) 21 4555 ,-c - - -· • _, 275 Ryedale Rd, Eastwood, NSW 2122. Motorola Micro- T•A•C Cellular Telephone Phone (02) 489 777 Fax (02) 489 7774 FEBRUARY1992 9 Mobile telephones from Telecom Australia Telecom Australia sells a wide range of mobile telephones, including the Walkabout 50 transportable phone pictured at right and the Traveller K car phone at far right. The Walkabout 50 is both a small handheld phone and an "answering machine". In "absence mode", it can actually record the phone numbers of people trying to contact you when you are away from the phone or simply don't wish to be disturbed. Other features include an automatic re-dial facility, call diversion, a call timer & several locking facilities. The unit can store up to 200 phone numbers & has an alphabetic memory that lets you store & view 8-letter names or other information with every phone number. It also has an automatic memory storage feature & lets you scroll through memories in either alphabetical order or according to location number. An optional in-vehicle kit provides hands-free operation, auto-answering & a boost in output power from 0.6W to 3W. The Traveller K car phone has all the features that one would expect in a mobile telephone, including call diversion, hands-free operation, automatic answering & a comprehensive array of memory & security features. A number of optional extras are also available, including a fax/computer interface, a horn alert/music mute relay (beeps the horn if a call comes in while you are away from the vehicle or, alternatively, mutes the car stereo during a phone call), and a facility that stores up to 9 telephone numbers from calling parties for later recall or diversion to a pager. control module is really the brains behind a mobile telephone and includes a microprocessor which oversees all operations. Among other things, it encodes signals from the dialling keypad before they are sent to the transmitter, and decodes any command or status signals received from the base station. These signals are then shown on the alphanumeric display if appropriate. The microprocessor also adjusts the output power of the mobile telephone to optimise the signal that reaches the base station. This does not apply to handheld phones, however, since their output power is fixed at 0.6W. pled to and from the receiver via a coupling box on the other side of the glass. Transportable telephones, on the other hand, are usually equipped with flexible "rubber duck" antennas, although some feature a telescopic whip which is extended while the phone is in use. Because the system operates at UHF (825-890MHz), the antennas are typically only about 10cm in length. Security Antenna requirements A correctly installed antenna is a vital component of a mobile telephone system, especially for fixed in-car models. An antenna mounted in the middle of the roof will provide the best performance. Alternatively, a glass-mounted antenna can be used if you don't fancy drilling a hole in your car's roof, but this will come at the cost of slightly reduced performance. A glass mounted antenna is attached .by adhesive to the rear window and signals are capacitively cou10 SILICON CI-IIP The Delegate 2000 from Mitsubishi Electric can be used in the car or quickly converted for transportable use. It features selectable transmit power, hands-free operation, 99 memories & a host of other facilities. One aspect of obvious concern to mobile phone users is security, particularly when it comes to charging. After all, you don't want to be paying for someone else's call! This problem has been overcome by programming a unique identification number into each mobile phone (usually at the time of purchase) and this ID number is transmitted each time the phone is used. This "initialisation" data is also used by the system to determine whether the mobile is in its home service area or has roamed to a new service area. In addition, you can program a unique PIN number into your phone to prevent unauthorised use. Call privacy, however, cannot be Cellular Phone Batteries Phone Model NOVATEL PTR 800 Premier Code PB 800 Description 7.2V lOO0mAh VOXON 2002 PB 800 7.2V lOO0mAh NEC P-3 PBP3 · 700mAh NEC P -9100 PB9B 6.0V 7.2V Mitsubishi 900 series PB 07S 7.2V 700mAh Telecom Walkabout Mk II PB 07S 7.2V 700mAh Telecom Walkabout Mill PB 110053S 9.6V 1800mAh Dlamondtel 99X PB 99X 6.0V 800mAh Technophone 105 PB 105 7.2V 700mAh Technophone 905 Motorola 6000. 8000. 9000 Motorola Flip (Micro Tac) PB 905 12.0V PB M2 7.2V 1800mAh 1700mAh PB M7FB 6.0V 1200mAh Oki 700/750 PB 750 6.0V 1200mAh Shimatsu PB 842 7.2V 1200mAh Panasonlc/Unlden/ Okl Phillps Fm 9030 PB 1223 12.0V 2300mAh PB 124 12.0V 4500mAh Telecom Traveller PB 124 12.0V 4500mAh ECONOMIC ELECTRONICS, 24 Campbell Street, Bowen Hills, Old 4006. PO Box 481, Fortitude Valley, 4006 Telephone (07) 252 3762. lOO0mAh These Cellular Mobile Phone batteries are direct replacements for original manufacturers products. The batteries are manufactured using high performance cells to provide maximum life and reliability. SOUTHPORT ELECTRONIC SHOP, Shop 1/10 Welch St, Southport, Old 4215. Telephone (075) 32 3632 Fax (075) 51 0543 guaranteed, due in part to the ready availability of low-cost scanning receivers. On the plus side, the restricted range of mobile telephone signals should limit the number of potential eavesdroppers on any call to a relatively small area. In addition, the signal frequency will change if a mobile user moves from one cell to next, thus further frustrating attempts at eavesdropping. What does it cost? The prices for mobile telephones vary considerably but expect to pay $750 to $1500 for an in-car phone and $1200 to $2500 dollars for a portable phone. These are "ballpark" figures only - the price you pay will depend very much on the model and the facilities offered. Once you've purchased the phone, there is a once-only "commissioning fee" of $45 plus a monthly access rental fee of $40. After that, you're charged for calls on a toll basis. For distances up to 745km, the peak daytime rate is 39 cents per minute, reducing to 26 cents per minute for the off peak night-time rate (6-1 0pm MonFri) and 15 cents per minute for the off peak economy rate. According to Telecom Australia, the average monthly bill in Australia is around $136 and charges are generally comparable to or cheaper than in other countries. And unlike some countries, it is the originator of the call who pays the charge. So if someone calls you on your mobile telephone, they pay the toll. The future As the cellular network expands and improves, the demand for mobile telephones will grow tremendously during the next 10 years. This demand will also be fuelled by falling prices and by smaller and more reliable phones. Indeed, Telecom Australia predicts that by the year 2000, 60% of all calls will have a mobile component - that is, either one or both of the calling parties will be using a mobile phone. But for many people, the benefits of a mobile telephone already far outweigh its higher costs when compared to a standard telephone. The mobile telephone has now become an indispensable tool in business, particularly for trades people and sales executives. In the future, prices may fall to the 12 SILI CON CHIP Versatile handheld telephone from Uniden Continuing its successful line of cellular phones, Uniden Australia is about to enter the "micro" handheld market with a unit that's claimed to be the smallest cellular phone in the world; the Uniden CP5500. Due for release in mid-February 1992, this phone weighs only 300 grams (including the battery) and measures just 156 x 52 x 31 mm, making it small enough to fit into your pocket, briefcase or purse. The phone has many features which make calling quick and easy. For starters, you can store your most often used numbers in up to 30 memories for quick recall. You can also store call diversion codes in memory so that you don't have to remember what they are. In addition, there are various timers which record how long the last call took, call progress time, and the total on-air time. Separate volume controls let you adjust the ringing volume, the earpiece volume and the dialling volume, while a missed call indicator lets you know that a call has been diverted to a pager or to your office. Unlike many mobile phones, you don't have to press a specific key to answer a call. Instead, any numeric or function key can be pressed. Last number re-dial is easy-you just press the SEND button again. The CP5500 comes with three locking features. For example, you can lock the phone so that it will only dial numbers stored in the memory or so that it is only able to receive calls. Alternatively, you can disable the phone completely. A battery charge indicator is included so that you can monitor battery condition. Built into the CP5500 is a telescopic antenna which is extended only when placing or receiving a call. In standby mode, the antenna can be left retracted to eliminate the possibility of damage. The CP5500 is supplied with a slide on/off battery, which gives up to 11 hours on standby and 75 minutes of transmit time. Optional accessories include a leather case and a fast extent where just about anyone can afford to own a mobile telephone. They may even become a standard fitting in new cars, in much the same charger that will charge the battery in just one hour. Another option is the "In-Car Kit". This allows the unit to be mounted inside a car as a fully-functional hands-free unit. During in-car operation, you can recharge the internal battery while using the car's own battery to power the phone. In addition to this portable unit, Uniden also has a wide range of other telephones including the fully-featured CP 1500 car phone. For further information on this unit & other Uniden products: contact your local dealer or ring the Uniden office in your state. way as the now mandatory AM/FM radio-cassette player. The future for mobile communications is indeed an exciting one. SC