General Packet Radio Service
computer science crazy|
Joined: Dec 2008
21-09-2008, 11:15 AM
Wireless phone use is taking off around the world. Many of us would no longer know how to cope without our cell phones. Always being connected offers us flexibility in our lifestyles, makes us more productive in our jobs, and makes us feel more secure. So far, voice has been the primary wireless application. But with the Internet continuing to influence an increasing proportion of our daily lives, and more of our work being away from the office, it is inevitable that the demand for wireless data is going to ignite. Already, in those countries that have cellular-data services readily available, the number of cellular subscribers taking advantage of data has reached significant proportions.
But to move forward, the question is whether current cellular-data services are sufficient, or whether the networks need to deliver greater capabilities. The fact is that with proper application configuration, use of middleware, and new wireless-optimized protocols, today's cellular-data can offer tremendous productivity enhancements. But for those potential users who have stood on the sidelines, subsequent generations of cellular data should overcome all of their objections. These new services will roll out both as enhancements to existing second-generation cellular networks, and an entirely new third generation of cellular technology.
In 1999, the primary cellular based data services were Cellular Digital Packet Data (CDPD), circuit-switched data services for GSM networks, and circuit-switched data service for CDMA networks. All of these services offer speeds in the 9.6 Kbps to 14.4 Kbps range. The basic reason for such low speeds is that in today's cellular systems, data is allocated to the same radio bandwidth as a voice call.
Since voice encoders (vocoders) in current cellular networks digitize voice in the range of 8 to 13 Kbps,
that's about the amount available for data. Back then, 9.6 Kbps was considered more than adequate. Today, it can seem slow with graphical or multimedia content, though it is more than adequate for text-based applications and carefully configured applications.
There are two basic ways that the cellular industry is currently delivering data services. One approach is
with smart phones, which are cellular phones that include a microbrowser. With these, you can view
specially formatted Internet information. The other approach is through wireless modems, supplied either in
PC Card format or by using a cell phone with a cable connection to a computer.
The GPRS services will reflect the GSM services with an exception that the GPRS will have a tremendous transmission rate which will make a good impact in the most of the existing services and a possibility of introduction of new services as operators and users (business/private) appreciate the newly introduced technology.
Services such as the Internet, videoconferencing and on-line shopping will be as smooth as talking on the phone, moreover we'll be able to access these services whether we are at work, at home or traveling. In the new information age, the mobile phone will deliver much than just voice calls. It will become a multi-media communications device, capable of sending and receiving graphic images and video.
The most common methods used for data transfer are circuit-switching and packet-switching. With circuit-switched transmission the dedicated circuit is first established across a sequence of links and then the whole channel is allocated to a single user for the whole duration of the call. With packet switched transmission, the data is first cut in to small parts called packages which are then sent in sequence to the receiver, which again builds the packages back together. This ensures that the same link resources can be shared at the same time buy many different users. The link is used only when the user has something to send. When there is no data to be sent the link is free to be used by another call. Packet switching is ideal for bursty traffic, e.g. voice.
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