Home and away
Mobile computing can be a bit of a palaver once you need to connnect to a network. Roger Gann looks at how GSM can ease the pain.
No person is an island and so if their notebook can't connect to act to a network. Roger Gann looks at how GSM can ease the pain. network it is little more than an expensive and underused corporate toy. Most mobile users will need to exchange data with the network back at the office on a fairly regular basis, sending and receiving emails, updating the Notes database or getting the latest stock figures and price lists.
When in the office, getting connected to the network is perfectly straightforward - you insert a PC card network interface card and plug in to the system.
But mobile users don't always have to connect physically to the network with a cable, whether in the office or off-site. Most mobile users will have a cellular phone and it's relatively easy and cheap to use this to make a connection through the global standard for mobile communications (GSM), from almost anywhere in the UK.
So far the penetration of cellular datacoms has been relatively modest - only one in 50 European GSM phone users has an adaptor for connecting a mobile computing device to their phone, and data transmissions made up only 0.5 per cent of GSM traffic in 1995, according to Dataquest.
Growth has initially been slow partly because of the grip exerted by Nokia on the digital cell-phone market. Until earlier this year, the company refused to license its GSM data interface to third-party manufacturers.
It has also charged as much as #600 for its own, recently discontinued, data card.
Psion Dacom broke the mould in February with the release of the Psion Dacom Gold multi-function PC card modem, which combined a data/fax modem, 10Mbps network card and a Nokia-licensed GSM interface into a single card.
REMOTE CHANCE
But the future is bright for GSM. By 2000, Dataquest predicts vast growth in the number of GSM subscribers - 70 per cent growth in Europe, 95 per cent in the US and 60 per cent in Japan.
GSM provides an attractive remote access solution, allowing a mobile user to connect to the network without having to rely on easy access to a PSTN (public service telephone network) phone socket.
Early adopters of cellular datacoms didn't have a particularly rewarding experience - the kit was expensive, unreliable, and, using the analogue cellular network at 2,400bps, was painfully slow. GSM offers a very different experience - hardware costs are far lower and the network delivers a much better service - it is capable of delivering data up to four times faster, at 9,600bps.
WELL CONNECTED
The GSM service is also digital, which results in a far more robust connection.
Although connection times are still relatively slow, they can be dramatically shortened if an ISDN connection is made.
Although GSM was designed from the outset to handle data, its transmission capabilities are modest. At present, network operators limit GSM throughput to a mere 9,600bps.
CODER PRACTICE
This slow throughput, compared with conventional modems running on the PSTN, is compounded by the absence of data compression, which is a standard feature on conventional modems and can improve throughput by between two and four times.
The good news is that by the end of the year the basic transmission speed will probably be increased to 14.4Kbps, thanks to new encoding techniques.
All four UK GSM network operators - Cellnet, One2One, Orange and Vodafone - have indicated they are ready to upgrade the GSM data service but as yet none has announced a precise date.
It will most likely happen with Orange first, simply because it has a more modern, more consistent network infrastructure (the so-called Internetworking Function) than its rivals. Orange, however, was reluctant to provide details of any planned network upgrades when asked for them.
It has to be said the network operators are in no particular rush to provide this extra bandwidth - at present the data service forms a tiny proportion of network traffic and the operators have their work cut out keeping up with demand for voice services.
However, there will come a point where GSM market penetration becomes so high, as it has in Scandinavia, that voice sales will eventually taper off, forcing network operators to address the needs of the data user to maintain growth.
THAT'S YOUR SLOT
When the new faster service, known as GSM 2+, is implemented, you'll probably need a new handset to take advantage of it. Faster throughputs will then follow. Eventually a technique akin to ISDN channel aggregation or bonding will become available for GSM. Known as high speed circuit switched data (HSCSD), it will let users combine between two and eight GSM 'time slots' or channels to provide up to 64Kbps of bandwidth on an as needed basis.
At present, GSM uses time division multiple access (TDMA), dividing each 200KHz carrier into eight slots. One voice channel consumes a slot, as does a 9,600bps data transmission, but under HSCSD up to eight slots can be used simultaneously. In practice, we're more likely to see two channels available for bonding rather than all eight. HSCSD will be relatively easy to implement using the existing GSM infrastructure. It was ratified in July.
Another proposed fast data standard for GSM is general packet radio services (GPRS). As it is packet based, call setup times will be brief.
It will provide a seamless connection to existing data services via interfaces to TCP/IP and X.25 services. GPRS will handle 14.4Kbps from a single TDMA slot and 115Kbps or better with all eight. Actual available bandwidth, however, will vary from moment to moment. Luckily, payment won't be time-based as it is at present, but will be based on the amount of data transferred.
GPRS probably won't be available before 1999 at the earliest.
In the long term, unified mobile telephony services (UMTS) promises a data transfer rate of 2Mbps when stationary, dropping to 140Kbps when mobile.
Things are also moving on the data compression front. By next year, non-transparent mode transmissions will be available - this means that V.42bis data compression is automatically applied by the data network, on the segment between the mobile and the remote modem.
An alternative mode, transparent mode, establishes a direct, uncompressed synchronous connection, which will offer better throughput.
Normal modems make an asynchronous connection and require each 8-bit packet of data to be topped and tailed with a start and stop bit. But with synchronous comms, the need for start and stop bits disappears, delivering 20 per cent more throughput in the process. Data compression is left to the user.
Motorola has jumped the gun and implemented its own, proprietary form of data compression called Digital Data Fast, based on the ITU V.42bis standard. This promises maximum data transfer rates of almost 56Kbps, which is on a par with the kind of throughput that can be achieved with a 14.4Kbps modem using V.42bis. Motorola hardware, however, is needed at both ends of a connection for this to work.
The market is relatively well served with GSM data cards. Single-function cards are history and most now reside in multi-function combo cards that offer modem, GSM, fax and Lan connectivity in various permutations.
ALL ON THE CARDS
Psion Dacom dominates the European market for PC cards - its Gold Card range, which supports a range of GSM handsets, is a particularly popular choice. Psion Dacom was also the first to obtain a licence from Nokia, the most popular brand of digital cellphone, for its range of handsets.
It subsequently reported an upsurge in demand for GSM upgrades once the licensing deal had been done.
A number of rivals, notably Grey Cell and Xircom, have reverse engineered GSM handset interfaces. There is some question, however, over this process because the network operators are moving to award network accreditation only to licensed hardware - and this doesn't include reverse-engineered cards.
Motorola encrypts its data bus and the next generation of Nokia phones will employ similar protection, so reverse engineering may only be a transient process.
A relatively new development is the PC card phone - in essence a GSM data card and transmitter that provides GSM voice and data communications.
This is an attractive combination for specific vertical markets. A number of these cards are available in Europe, but only Ericsson has announced them in the UK.
Rebadged by Compaq, the GSM PC card combines the functions of a mobile phone and data modem, offering throughputs of up to 38.4Kbps. The card itself is a 'Type II and a half' and requires a pair of stacked Type II or one Type III PC card slot. Announced at the recent Mobile Data Comms show, the GSM PC card will be available in the first quarter of next year.
The pricing has yet to be set.
SERIAL KILLER PLAYS ITS CARDS
Although multi-function PC cards are perhaps the best option for the mobile professional, because they combine a choice of connectivity options in a single card, software-only GSM solutions have recently been announced by Psion Dacom and Grey Cell, which was recently acquired by TDK.
In theory, a simple serial cable is all you will need to connect a GSM phone to a notebook. This is good news if you don't need Lan or PSTN connectivity.
It will also sound attractive to PDA users. Although several Windows CE HPCs are equipped with PC card slots, plugging in a PC card modem is not a good idea - unless the machine is near to a mains socket, that is.
Most PC card modems draw so much power that they empty a Windows CE HPC's batteries in a matter of minutes. Even the latest low-current (<50mA) PC cards draw too much power. In contrast the serial port on a PDA draws perhaps as little as 5mA, making a software-based GSM solution very attractive, and remote access with a PDA a real possibility.
With the processor doing additional work, handling the GSM data stacks, there will still be a small processor 'hit'. This appears to be less noticeable with the ARM-driven Series 5 than the SH-3 powered Windows CE handhelds.
A number of software GSM products are in the offing. Nokia has its Cellular Mobile Suite, but this is restricted to its own handsets and Windows 95, and therefore to notebook PCs. Psion Dacom has Easy GSM in the works, which will support both Psion Series 5/ EPOC32 and Windows CE PDAs plus Windows 95 and a variety of handsets. It should appear at the turn of the year, carrying a projected price tag of about #100 - roughly the same price as a GSM upgrade for one its Gold Cards.
Grey Cell has announced the development of a 32-bit Windows utility, Softmobile, that allows a PC to be plugged into almost any digital phone, including US PCS 1900 variants, by a simple cable linking to the computer's serial port.
The software supports transparent and non-transparent GSM data to 9,600bps as well as transparent fax and short message service text messages.
Softmobile is host-based but even on a lowly 100 MHz Pentium, the software will use about one per cent of system resources, according to Grey Cell.
ROAM WASN'T BUILT IN A DAY
GSM is now 10 years old. It was originally based on a 900MHz digital multicellular telephone network and was a pan-European standard. In the UK, Orange also uses the 1,800MHz frequency.
But its gradual spread across the world to Australia, Hong Kong, Singapore, South Africa and the United Arab Emirates, does not include the US, where a multiplicity of network standards prevail. A GSM network using the 1,900MHz frequency, however, is being touted as a US standard.
Thanks to 'roaming' agreements, GSM is ideal for international travellers who can take and use their UK handset in up to 70 countries.
GSM provides not only voice traffic but also integral support for short message, fax and data services.
At the GSM World Conference in Cannes, the industry was urged to market a truly global GSM mobile phone, capable of use in Europe, America and Asia. It called for a triple-mode, triple-frequency, triple-codec digital handset as one of the targets for development this year. Such a handset would be compatible with GSM900 system at 900MHz and PCN1800 system at 1,800MHz, used outside the United States, and with the US PCS1900 system, which operates at 1,900MHz.
With the right roaming agreements in place, a single handset could be used on a journey from the US, through Europe and on to such Asian territories as India, Hong Kong and China.