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Mobile Computing
Being able to stay in touch whilst away from the office is vital these days. The growth of the cellular phone is testimony to this fact, with busy executives keen to maintain contact with colleagues and customers whilst in the car, on the train or even in the back garden. But there is more to staying in touch than just being able to take voice calls, and there is a gradual shift away from using cellular phones as voice-only communications devices. For many mobile users, however, the idea of remote access to the corporate network is a new one, and one that is often shied away from as being too complicated, too slow and too error prone for everyday use. What is needed is the ability to provide the same level of plug’n'play network connectivity whilst on the road in order to provide constant access to the various corporate databases and applications wherever you may be. That is where GSM comes in, since most GSM operators now offer mobile data services – including straight data transfer, fax and SMS – as well as voice. PCMCIA cellular data cards have been available for a while now allowing road warriors to connect their laptops direct to their mobile phones for data calls. Many of the companies specialising in mobile comms devices such as TDK (ex Grey Cell) and Compaq (recently) have begun to combine this functionality with other options. For instance, you can now get a single PCMCIA card that incorporates 10/100 Ethernet LAN access, 56K modem, ISDN and GSM functionality. This covers just about every communications option you are ever likely to need. A number of GSM phone manufacturers now provide what are known as "soft modems" that allow you to connect your mobile phone directly to the serial port on your laptop, where they then behave like a standard modem as far as your applications are concerned. This solution is not completely wireless, however, in that you still need a cable to connect your laptop to the phone. One way around this is to use the Nokia Communicator 9000i which has an infra-red capability. This means that all you have to do is point it at your laptop in order to use it as an external fax or data modem. Taking things a step further, however, we have the "cardphone". Produced by the likes of Ericsson, Nokia and Compaq, these are complete cellular phones in a PCMCIA card format. These simply slot straight into the PCMCIA or Cardbus slots of your laptop whereupon they once again behave like a standard modem. For those of you who want to make voice calls, they can do this too, with on-screen diallers and miniature ear piece and microphone or hands-free calls via the laptop’s microphone and speakers. The biggest obstacle to the widespread adoption of GSM as the standard means of remote access to the corporate network is the perceived lack of speed and reliability. The current data rate across GSM connections is 9600 bits per second, seemingly paltry against the latest 56000bps modems. And who has not been frustrated by GSM phones losing the connection constantly during a call? This is fatal in a data call, where you have to start the data transfer again from the beginning each time the connection is re-established. What is needed is some clever software to manage the GSM connection, and this is exactly what is provided by Apollo Emulator, from Brand Communications. Unlike other remote access solutions, the Emulator provides a true bi-directional network connection, allowing all the same software to be used when on the road, and making it appear to the user as if he or she is attached directly to the network back at head office. This connection can be made over a high-speed ISDN link, a standard PSTN line using any modem, or a GSM phone. Full line management capability ensures that the call is dropped when there has been no activity for a period of time, thus keeping on-line costs to a minimum. When this happens, the connection is "spoofed", making it appear to both ends as though the line is still up. The next time data is transmitted, the call is re-established automatically and things carry on from where they left off. You can see, therefore, that the same mechanism will work when the line is dropped as a result of bad reception, improving reliability to the point where it is every bit as good as a wired connection. Advanced data compression helps to reduce costs further, whilst giving the impression of data transfer speeds far in excess of the basic 9600bps. Given that cellular data is still something of a mystery to many, the alternatives could be considered even more esoteric – but alternatives there are. Possibly the most esoteric of all at the moment is the satellite phone. Costs are coming down all the time and there are approximately 250,000 VSAT (Very Small Aperture Terminal) installations world-wide at the moment. For some locations, satellite is the only means of communication, and companies such as California-based SatCom Media offer a portable satellite access package for data, fax and voice. The SatPC product provides end users with a transceiver, portable satellite dish and PC Cards to support data compression, encoding/decoding, videoconferencing and an ISDN interface. Yet another alternative is wireless communications using various forms of radio technology. In this country, the common-or-garden wireless LAN products are restricted to fairly local operations, making them useless for anything other than campus LANs. However, there is the option of Public Access Mobile Radio (PAMR) offering mixed voice and data capability, and a very-short (23 character) messaging facility. There are also the Packet Radio services from the likes of RAM, which are aimed at short message applications in areas such as field service, distribution, etc. In the short term, however, GSM remains the best bet for the mobile user, and both the laptop and cellular phone have come a long way in the last year or so. It has finally reached the point where you can have exactly the same computing experience on the train, in a hotel room or in your car (stationary, of course!) as you can seated at your desk. Summary
Glossary Smart Phone – combination of low-powered computing functionality with cellular phone – both data and voice communications in a single device. GSM – the standard for digital cellular communications SMS (Short Message Service) – A means to send short text messages between GSM phones Cardbus – Next generation of PCMCIA cards offering a 32bit data path as opposed to 16bit ISDN (Integrated Services Digital Network) – digital telephone line offering two 64Kbps data channels (can be used for voice calls too) Contact: Compaq UK Contact: Brand Communication |
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