Table 1: Key Features of GPRS (1)
Example: A GPRS mobile phone.
Figure 1: Motorola Timeport T260 GPRS Mobile Phone
3. Key Network Features of GPRS
3.1 PACKET SWITCHING
GPRS involves overlaying a packet based air interface on the existing circuit switched GSM network. An option is given to the user to use a packet-based data service. Circuit switched network architecture is used to supplement with packet switching which is, quite major. Packet switching is similar to a jigsaw puzzle- the image that the puzzle represents is divided into pieces at the manufacturing factory and put into a plastic bag jumbled up. When the recipient empties the bag with all the pieces, they are reassembled to form the original image. The Internet itself is another example of a packet data network, the most famous of many such network types.
3.2 SPECTRUM EFFICIENCY
Packet switching means that GPRS radio resources are used only when users are actually sending or receiving data. Rather than dedicating a radio channel to a mobile data user for a fixed period of time, the available radio resource can be concurrently shared between several users.
GPRS should improve the peak time capacity of a GSM network since it simultaneously: allocates scarce radio resources more efficiently by supporting virtual connectivity immigrates traffic that was previously sent using Circuit Switched Data to GPRS instead, and reduces SMS Center and signalling channel loading by migrating some traffic that previously was sent using SMS to GPRS instead using the GPRS/ SMS interconnect that is supported by the GPRS standards. (5)
3.3 INTERNET AWARENESS
For the first time, GPRS fully enables Mobile Internet functionality by allowing inter-working between the internet and the new GPRS network. Because of GPRS, Any service that is used over the fixed Internet today like for example; File Transfer Protocol (FTP), web browsing, chat, email, and telnet, will be as available over the mobile network because of GPRS.
The World Wide Web is becoming the primary communications interface; people access the Internet for entertainment and information collection, the intranet however is for accessing company information and connecting with colleagues and the extranet is for accessing customers and suppliers. Because it uses the same protocols, the GPRS network can be viewed as a sub-network of the Internet with GPRS capable mobile phones being viewed as mobile hosts.
3.4 SUPPORTS TDMA AND GSM
It should be noted right that the General Packet Radio Service is not only a service designed to be deployed on mobile networks that are based on the GSM digital mobile phone standard. The IS-136 Time Division Multiple Access (TDMA) standard, popular in North and South America, will also support GPRS. This follows an agreement to follow the same evolution path towards third generation mobile phone networks concluded in early 1999 by the industry associations that support these two network types.
4. The Evolution of mobile networks
Now, let’s take a look at the evolution of the mobile networks which has been progressing over the years. The mobile networks are 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 from clear. There are several routes that may be taken as shown in the following diagram.
Diagram 1. GSM migration paths.
The GPRS services reflects the GSM services with an exception that 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 travelling.
In this 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.
5. GPRS Architecture
From a high level, GPRS can be thought of as an overlay network onto a second-generation GSM network. This data overlay network provides packet data transport at rates from 9.6 to 171 kbps. Additionally, multiple users can share the same air-interface resources.
GPRS attempts to reuse the existing GSM network elements as much as possible, but in order to effectively build a packet-based mobile cellular network, some new network elements, interfaces, and protocols that handle packet traffic are required. Therefore, GPRS requires modifications to numerous network elements, as summarized in Table 1 and illustrated in Diagram 2.
Table 1: Modifications Required for GPRS
5.1 GPRS Reference Architecture
(Diagram2 : Generic GPRS Network)
5.2 GPRS Subscriber Terminals
New terminals (TE’s) are required because existing GSM phones do not handle the enhanced air interface, nor do they have the ability to packetize traffic directly. A variety of terminals will exist, as described in a previous section, including a high-speed version of current phones to support high-speed data access, a new kind of PDA device with an embedded GSM phone, and PC Cards for laptop computers. All these TE’s will be backward compatible with GSM for making voice calls using GSM.
6. Technology Of GPRS
6.1 How is 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.
6.2 Technology used by GPRS
The technology which is used by the GPRS are indeed advanced and is used almost globally. The main objectives to be reached by implementing GPRS are as follows.
• give support for bursty traffic
• use efficiently network and radio resources
• provide flexible services at relatively low costs
•possibility for connectivity to the Internet
• provide fast access time
• to have and support flexible co-existence with GSM voice
GPRS uses a packet-mode technique to transfer data and signaling in a cost-efficient manner over GSM radio networks and also optimizes the use of radio and network resources. New GPRS radio channels are also defined.
This allows GPRS to handle bit-rates from 9 to even up to 150 kbit/s per user. With these bit rates all types of transmissions can be handled: from slow-speed short messages to the higher speeds needed e.g. when browsing Web pages. GPRS will also permit the user to receive voice calls simultaneously when sending or receiving data calls. When the user switches on their phone, the message will be downloaded automatically.
7. Benefits of GPRS
• 3 TO 10 TIMES THE 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. (2)
• User benefits from shorter access times and higher data rates.
• User can be online for long; leave your phone connected all day, but only pay for the packets of information you use. Also, it only takes about 10 seconds to log on; unlike a circuit-switched GSM WAP connection, which typically takes 30 seconds to get online.
• Network based on IP and X.25 is supported.
• Higher capacity Internet access - Up to 171.2 kbps transfer rate (in theory), 40 kbps in practice
• Quicker access to internet - No set up time, Internet access all the time available.
• Lower cost -Flat rate or volume based billing; No charge for the idle time of the “connection”.
• Instant Connections ;Immediate transfer of data - GPRS facilitates instant connections whereby information can be sent or received immediately as the need arises. Immediacy is one of the advantages of GPRS (and ) when compared to Circuit Switched Data. (5)
8. Limitations
8.1
9. Applications of GPRS
GPRS will enable a variety of new and unique services to the mobile wireless subscriber. These mobile applications contain several unique characteristics that enhance the value to the customers. Finally, localization allows subscribers to obtain information relevant to their current location. The core network components offered by Cisco enable seamless access to these applications, whether they reside in the service provider's network or the public Internet. A wide range of corporate and consumer applications are enabled by non-voice mobile services such as SMS and GPRS. This section will introduce those that are particularly suited to GPRS.
9.1 SERVICE ACCESS
To use GPRS, the user will need:
- a mobile phone or terminal that supports GPRS (existing GSM phones do not support GPRS)
- a subscription to a mobile telephone network that supports GPRS · use of GPRS must be enabled for that user. Automatic access to the GPRS may be allowed by some mobile network operators, others will require a specific opt-in
- knowledge of how to send and/ or receive GPRS information using their specific model of mobile phone, including software and hardware configuration (this creates a customer service requirement)
a destination to send or receive information through GPRS. (Whereas with SMS this was often another mobile phone, in the case of GPRS, it is likely to be an Internet address, since GPRS is designed to make the Internet fully available to mobile users for the first time).
Conclusion
From the research which I did on General Packet Radio Switching (GPRS), what I found was that GPRS is an important step in the evolution towards 3G mobile networks. Many customers and consumers will one day rely on GPRS to be connected all over the world without worrying about the cost as it is not charge for the idle time of connection but the information which you download so users could access and get connected the whole day. Eventhough there are transits delays, the access to the internet is available at all time thus making it so efficient.
What I predict in the near future is GPRS would play a major role in the future of cellular communications and hence, it is imperative to be aware of its importance. Even now, SMS is such a hit around the world because of the conveniences and hassle-free. Getting connected is what the technology and information age is about. It is much more cost effective when the billing of data transfer is done so and not the time spent online. Its packet switched transmission technology is optimized for bursty traffic Internet/Intranet services.
When it comes to mobile communication technology, there is usually more than one way to do it. Two years ago, buying drinks from a vending machine with a mobile phone was envisioned as a Bluetooth application. These days, SMS is used to achieve the same effect. A similar argument applies for the issue of CSD and GPRS. Although GPRS is starting to edge ahead in the argument of benefits, CSD is still good for certain uses. But as we move towards 3G (Third Generation), it is a matter of time before good old GSM data connections are finally phased out.
Well for the record, the GPRS takes only about 10 seconds to log on, unlike a circuit-switched GSM WAP connection, which typically takes 30 seconds to get online. Download speeds will not be the main issue, at least in the early days. At the moment, you can download at about 12Kbit/s per GPRS channel, or timeslot (the maximum number of channels is eight, including downloads and uploads). The first available GPRS phone, Motorola's Timeport 260(shown on page 5) , had three channels for downloading data and one for sending data back to the server, giving a maximum download speed of 36Kbit/s. Newer GPRS handsets have four down channels, and can reach speeds of 48Kbit/s. With improved compression technologies in future, data rates per channel could go considerably higher. (2, 3)
There is much debate today in the marketplace on the potential use of WLAN technology, especially in relation to other wireless access technologies such as GPRS and 3G. WLAN is clearly a complement to these access technologies, and together it provides greater flexibility, choice and convenience for end users.
From an operator’s point of view, WLAN provides additional sources of revenue and a mechanism for promoting overall growth and uptake of wireless data access for the mobile Internet. Ericsson is leading the way in standardizing and developing WLAN solutions for GPRS and 3G networks. Today the company provides solutions for operators that integrate WLAN as part of their current GPRS and 3G services. This enables operators to provide seamless mobile Internet access service for their customers.
The market for packet-based cellular services is largely untested and uncertain. Major questions in the introduction of the packet networks are the level of customer acceptance and the degree of integration of service components for cellular data services. To succeed, cellular packet data will need to deliver more effective solutions than existing substitutes, or new applications where no effective substitute exists.
GPRS will provide a massive boost to mobile data usage and usefulness. That much seems assured from its flexible feature set, its latency and efficiency and speed. The only question is how soon it takes off in earnest and how to ensure that the technical and commercial features do not hinder its widespread use of technology.
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References:
1.William Stallings, Data & Computer Communications (Sixth Edition), 2000, 1996 by Prentice-Hall, Inc.
2. Catherine Coombs and Sophia Chung Fegan, Data Communication and Networking, Behrouz A.Forouzan DeAnza College, International Edition 2000.
3. Andy Dornan, Prentice Hall PTR, The Essential Guide to Wireless Communication Applications, 2001, 132.
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