06-10-2012, 12:22 PM
General Packet Radio Service
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INTRODUCTION
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.
The World Today
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 micro browser. 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.
EVOLUTION OF MOBILE NETWORKS
The evolution of the mobile networks is progressing from the existing second-generation mobile networks to the third generation of networks that are able to handle high-speed multimedia traffic. The migration path to the third generation (UMTS) is far fro there are several routes that may be taken as shown in the following picture m clear. There are several routes that may be taken as shown in the following picture.
TECHNOLOGY OF GPRS
How is the data transferred?
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.
USER FEATURES OF GPRS
The General Packet Radio Service (GPRS) is a new non voice value added service that allows information to be sent and received across a mobile telephone network. It supplements today's Circuit Switched Data and Short Message Service. GPRS is NOT related to GPS (the Global Positioning System), a similar acronym that is often used in mobile contexts. GPRS has several unique features which can be summarized as
SPEED
Theoretical maximum speeds of up to 171.2 kilobits per second (kbps) are achievable with GPRS using all eight timeslots at the same time. This is about three times as fast as the data transmission speeds possible over today's fixed telecommunications networks and ten times as fast as current Circuit Switched Data services on GSM networks. By allowing information to be transmitted more quickly, immediately and efficiently across the mobile network, GPRS may well be a relatively less costly mobile data service compared to SMS and Circuit Switched Data.
IMMEDIACY
GPRS facilitates instant connections whereby information can be sent or received immediately as the need arises, subject to radio coverage. No dial-up modem connection is necessary. This is why GPRS users are sometimes referred to be as being "always connected". Immediacy is one of the advantages of GPRS (and SMS) when compared to Circuit Switched Data. High immediacy is a very important feature for time critical applications such as remote credit card authorization where it would be unacceptable to keep the customer waiting for even thirty extra seconds.
NEW APPLICATIONS, BETTER APPLICATIONS
GPRS facilitates several new applications that have not previously been available over GSM networks ue to the limitations in speed of Circuit Switched Data (9.6 kbps) and message length of the short message service (160 characters). GPRS will fully enable the Internet applications from web browsing to chat over the mobile network. Other new applications for GPRS, profiled later, include file transfer and home automation- the ability to remotely access and control in-house appliances and machines.