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| In My Opinion.......
The Future's Bright...... Why is it we are not all using cellular networks for data transmission? Most of us have notebook PC’s now, or CE devices or other PDA’s which we use to collect our e-mail, access corporate data, or even do some Web surfing while we are out of the office. And most of us have mobile phones too. Yet even though those phones often have data capabilities built in – or can acquire them by connecting to a PC Card – we still prefer to struggle with modems, cables and incompatible phone sockets. The biggest obstacle to the widespread adoption of GSM as the standard means of remote access to the corporate network or the Internet is the perceived lack of speed and reliability. Although wireless data promises to be the solution for connecting ‘anybody, anywhere, to any information - instantly’, at present, it is essentially a matter of moving small amounts of data slowly across a network that was designed entirely for voice traffic 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? Whilst this is merely frustrating in a voice call – you can always pick up where you left off once the reception improves, for instance – it 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. You may even have to contend with file corruption after a dodgy data transfer GSM may have been the technology that put digital mobile telephony on the world map, but it is new wireless data technologies such as High Speed Circuit Switched Data (HSCSD) and General Packet Radio Services (GPRS) will enable GSM network operators to offer mobile users effective email, remote LAN access, Internet access and more. HSCSD employs a new channel-coding scheme that increases the transmission rate of each time slot from the current 9600 bps to 14400 bps. More importantly, it also allows for multiple time slots to be combined into a single channel, providing multiples of the basic 9600 and 14400 bit rates. This will allow operators to provide a range of bit rates ranging from the current 9600 up to a near ISDN rate of 57600 bps. Add compression to the equation, and you could be looking at data transfer rates of up to 200 Kbit/s One nice feature of HSCSD for the service providers is that it is achieved via a software upgrade and does not entail new network elements. This means the GSM operator not only avoids having to redesign the network, but can also have fast implementation. The end user, unfortunately, is not quite so lucky – he or she requires a new data device.� As its name suggests, HSCSD is still a circuit-switched technology, similar to that which is already available, just running at higher bit rates. GPRS, on the other hand, is a packet switched technology that is designed to extend the Internet connection across the GSM network to the PC. It will also increase data transmission speeds from the current 9.6 Kbps to over 100 Kbps, though the investment in the network infrastructure required from the operators is much greater. GPRS will provide the type of data capabilities planned for "third generation" cellular networks (such as UMTS), but years ahead of them. The major difference between HSCSD and GPRS comes in the way the time slots are allocated. With GPRS, all the packets from the different users are interleaved so that transmission capacity is shared, with no pre-set time-slots being used. Instead, network capacity is allocated when needed and released when not needed. Using links in this way conserves network and air interface capacity and it also allows operators to offer cheaper services, since charging can be based on the amount of data sent or received.� The downside to this, of course, is that where networks have a limited number of time slots available for data, users will end up fighting for the bandwidth – similar to the shared Ethernet situation – and may actually end up being worse off than they are now. Ironically, although HSCSD is seen more as a “stepping stone” technology and inferior to GPRS, at least it guarantees bandwidth to the user. If a time slot is available, the user gets it for the duration of the session – analogous to the switched Ethernet scenario which is so popular today. This would seem to offer more potential for business applications. Of course, all this is way off in the future, so why worry about it now, right? Wrong. Anyone attending this year’s Networks show in Birmingham will be able to talk to Orange about its proposed HSCSD service. Orange is the only network operator to announce plans for HSCSD so far which is bizarre given that it should be the easier of the two technologies to implement in the short term. Or perhaps it is not so bizarre when you look at the Orange network.� Operating at a much higher frequency than its competitors requires Orange to install twice as many base stations to cover the same area. Twice as many base stations means twice as many time slots – so perhaps Orange is the only operator which will be capable of offering a decent HSCSD service? Vodafone and Cellnet would much rather use the slot-sharing capabilities of GPRS, simply because they do not have the spare network capacity at present. So Orange has announced plans for a 28800 bps service (2 x 14400 time slots), but this has thrown a spanner in the works as far as the equipment manufacturers are concerned. Wherever a digital network is used V.110 rate adaption is involved in getting two devices communicating (it handles speed negotiations between them). Unfortunately, most hardware vendors have made some fairly heavy assumptions when it comes to V.110. One of the major ones is that there will always be a clock available at each end of the line. This is not the case with GSM, which may lose sync for a while in poor reception conditions, requiring both clocks to be stopped and re-started. This is all in the standard, but is generally not implemented because it simply never happens in a normal digital network – GSM is a special case.� Another problem is caused by Orange opting for the maximum possible speed available from two time slots - 28.8 Kbps is not a standard V.110 rate. So have we got a proposed service that no one will be able to use? Actually, no. Also at Networks is Cambridgeshire-based Brand Communications, a leading supplier of remote LAN access and Internet access via GSM. Brand has a unique offering in the Brand Access Server, a remote access router that can scale to millions of users and can handle a mix of ISDN, GSM and LAN connections, making it an ideal choice for GSM service operators implementing the next generation of data-over-cellular technologies. It will also work with both HSCSD and GPRS, as well as today’s GSM networks, and it is currently the only router on the market that supports the non-standard 28,800 bps rate adaption, and the only one that can handle V.100 rate adaption correctly over GSM. As if that is not enough, it also includes advanced error correction, security, data compression and spoofing technology that will provide many of the benefits touted for GPRS in the future from a HSCSD service today. For instance, the idea that you share a time slot and only pay when you are sending data on GPRS can be achieved using Brand’s spoofing on HSCSD. This ensures that the connection is dropped when not being used – thus saving money – but maintains a logical connection between client and server so the application keeps on running, thinking it is connected to the network. When data needs to be transmitted, the connection is brought up again for the duration of the transmission - true LAN connectivity in a mobile environment. The key point here is that whenever the connection is up, the user receives guaranteed 28.8 Kbps bandwidth, something that cannot be said for GPRS. Brand’s Access Server also provides the means to offer volume-based billing, so that users only pay for the amount of data they send, not for the amount of time they spend on line. The final piece of the jigsaw is the data device used to connect to the new service. Even this is now available – from Nokia – and the Orange service has been proven to work with Nokia switching centres and the new Nokia data device. So the stage is set for Brand to be the first to launch high speed data services to existing and new customers later this year in partnership with Orange. According to Martin Kendrick, MD of Brand Communications, HSCSD is a superior technology to GPRS and will be preferred by many corporate users. “GPRS is being driven by the manufacturers because it conserves time slots for the network” he says. “It thus offers a more efficient use of scarce network resources and is more cost effective from the network operator’s point of view”.� However, he goes on to say that “I think HSCSD is substantially better than GPRS simply because of the guaranteed bandwidth and Quality of Service aspects. GPRS also relies on a lot of things that will be totally unacceptable to corporate users such as the shared bandwidth, and the potential security problems arising from having to re-authenticate remote users as they roam from cell to cell, changing IP addresses”. So it sounds like HSCSD could be a big hit with the end users – particularly corporates – if not the network operators, who seem to be favouring GPRS for reasons of their own (except for Orange, of course). How do YOU fancy surfing the Web, accessing your corporate data and managing your e-mail all at speeds exceeding 28.8 Kbps (eventually up to ISDN speeds and beyond) and with not a cable or phone socket in sight?� The next big question is how much will all this cost? I don’t know about you, but I have been intrigued by the Orange ads on TV recently offering two pence per minute voice calls. Now if they can offer a data service for the same price, then who in their right minds will ever bother with PSTN lines again?� To paraphrase Orange’s own ads: “The future is bright – the future is data over cellular”.
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