GPRS operation

This GPRS tutorial is split into several pages each of which address different aspects of the GPRS technology:

[1] GPRS technology tutorial
[2] GPRS network architecture
[3] GPRS mobiles and multislot classes
[4] GPRS radio air interface
[5] GPRS error coding
[6] GPRS operation

When looking at the way in which GPRS operates, it can be seen that there are three basic modes in which it operates. These are: initialisation / idle, standby, and ready.

Initialisation / idle

When the mobile is turned on it must register with the network and update the location register. This is very similar to that performed with a GSM mobile, but it is referred to as a location update. It first locates a suitable cell and transmits a radio burst on the RACH using a shortened burst because it does not know what timing advance is required. The data contained within this burst temporarily identifies the mobile, and indicates that the reason for the update is to perform a location update.

When the mobile performs its location update the network also performs an authentication to ensure that it is allowed to access the network. As for GSM it accesses the HLR and VLR as necessary for the location update and the AuC for authentication. It is at registration that the network detects that the mobile has a GPRS capability. The SGSN also maintains a record of the location of the mobile so that data can be sent there is required.

Standby

The mobile then enters a standby mode, periodically updating its position as required. It monitors the MNC of the base station to ensure that it has not changed base stations and also looks for stronger base station control channels.

The mobile will also monitor the PPCH in case of an incoming alert indicating that data is ready to be sent. As for GSM, most base stations set up a schedule for paging alerts based on the last figures of the mobile number. In this way it does not have to monitor all the available alert slots and can instead only monitor a reduced number where it knows alerts can be sent for it. In this way the receiver can be turned off for longer and battery life can be extended.

Ready

In the ready mode the mobile is attached to the system and a virtual connection is made with the SGSN and GGSN. By making this connection the network knows where to route the packets when they are sent and received. In addition to this the mobile is likely to use the PTCCH to ensure that its timing is correctly set so that it is ready for a data transfer should one be needed.

With the mobile attached to the network, it is prepared for a call or data transfer. To transmit data the mobile attempts a Packet Channel Request using the PRACH uplink channel. As this may be busy the mobile monitors the PCCCH which contains a status bit indicating the status of the base station receiver, whether it is busy or idle and capable of receiving data. When the mobile sees this status bit indicates the receiver is idle, it sends its packet channel request message. If accepted the base station will respond by sending an assignment message on the PAGCH on the downlink. This will indicate which channel the mobile is to use for its packet data transfer as well as other details required for the data transfer.

This only sets up the packet data transfers for the uplink. If data needs to be transferred in the downlink direction then a separate assignment is performed for the downlink channel.

When data is transferred this is controlled by the action of the MAC layer. In most instances it will operate in an acknowledge mode whereby the base station acknowledges each block of data. The acknowledgement may be contained within the data packets being sent in the downlink, or the base station may send data packets down purely to acknowledge the data.

When disconnecting the mobile will send a packet temporary block flow message, and this is acknowledged. Once this has taken place the USF assigned to the mobile becomes redundant and can be assigned to another mobile wanting access. With this the mobile effectively becomes disconnected and although still attached to the network no more data transfer takes place unless it is re-initiated. Separate messages are needed to detach the mobile from the network.

GPRS error coding

This GPRS tutorial is split into several pages each of which address different aspects of the GPRS technology:

[1] GPRS technology tutorial
[2] GPRS network architecture
[3] GPRS mobiles and multislot classes
[4] GPRS radio air interface
[5] GPRS error coding
[6] GPRS operation

In order to accommodate the packet data within GPRS it has been necessary to develop the coding schemes. Additionally the layers based on the OSI system has become more important than it was for some of the previous systems and descriptions what are contained within these layers are found below.

GPRS coding

GPRS offers a number of coding schemes with different levels of error detection and correction. These are used dependent upon the radio frequency signal conditions and the requirements for the data being sent. These are given labels CS-1 to CS-4:

1. CS-1: - This applies the highest level of error detection and correction. It is used in scenarios when interference levels are high or signal levels are low. By applying high levels of detection and correction, this prevents the data having to be re-sent too often. Although it is acceptable for many types of data to be delayed, for others there is a more critical time element. This level of detection and coding results in a half code rate, i.e. for every 12 bits that enter the coder, 24 bits result. It results in a throughput of 9.05 kbps actual throughput data rate.



2. CS-2: - This error detection and coding scheme is for better channels. It effectively uses a 2/3 encoder and results in a real data throughput of 13.4 kbps which includes the RLC/MAC header etc.



3. CS-3: - This effectively uses a 3/4 coder and results in a data throughput of 15.6 kbps.



4. CS-4: - This scheme is used when the signal is high and interference levels are low. No correction is applied to the signal allowing for a maximum throughput of 21.4 kbps. If all eight slots were used then this would enable a data throughput of 171.2 kbps to be achieved.

Coding scheme		CS-1		CS-2		CS-3		CS-4
Date rate per slot (kbps)		9.05		13.4		15.6		21.4
Max data rate with 8 slots (kbps)		72.4		107.2		124.8		171.2

GPRS coding vs data rate summary

In addition to the error detection and coding schemes, GPRS also employs interleaving techniques to ensure the effects of interference and spurious noise are reduced to a minimum. It allows the error correction techniques to be more effective as interleaving helps reduce the total corruption if a section of data is lost.

As blocks of 20 ms data are carried over four bursts, with a total of 456 bits of information, a total of either 181, 268, 312, or 428 bits of payload data are carried dependent upon the error detection and coding scheme chosen, i.e. from CS-1 to CS-4, respectively.

Layers

Software plays a very large part in the current cellular communications systems. To enable it to be sectioned into areas that can be addressed separately, the concept of layers has been developed. It is used in GSM and other cellular systems but as they become more data-centric, the idea takes a greater prominence. Often these are referred to as layers, 1, 2, and 3.

Layer 1 concerns the physical link between the mobile and the base station. This is often subdivided into two sub-layers, namely the Physical RF layer that includes the modulation and demodulation, and the Physical link layer that manages the responses and controls required for the operation of the RF link. These include elements such as error correction, interleaving and the correct assembly of the data, power control, and the like.

Above this are the Radio Link Control (RLC) and the Medium Access Control (MAC) layers. These organise the logical links between the mobile and the base station. They control the radio link access and they organise the logical channels that route the data to and from the mobile.

There is also the Logical Link Layer (LLC) that formats the data frames and is used to link the elements of the core network to the mobile.

GPRS radio air interface

This GPRS tutorial is split into several pages each of which address different aspects of the GPRS technology:

[1] GPRS technology tutorial
[2] GPRS network architecture
[3] GPRS mobiles and multislot classes
[4] GPRS radio air interface
[5] GPRS error coding
[6] GPRS operation

In order to be able to carry the packet data and to increase the data rates that can be carried by the GPRS technology, it has been necessary to make some upgrades to the GPRS radio interface. In particular the GPRS slot or GPRS burst have been upgraded to accommodate the new scheme.

Despite the upgrades it was necessary to ensure that GPRS would operate alongside the existing GSM system, and this would require modifications to the air interface to accommodate both schemes.

GPRS modulation scheme

GPRS builds on the basic GSM structure. It uses the same signal format having 200 kHz channel bandwidths. It also has the same modulation scheme and using GMSK modulation. Retaining the same modulation scheme means that the level of upgrade required to be able to support GPRS in addition to GSM is minimised.

Note on GMSK: GMSK, Gaussian Minimum Shift Keying is a form of phase modulation that is used in a number of portable radio and wireless applications. It has advantages in terms of spectral efficiency as well as having an almost constant amplitude which allows for the use of more efficient transmitter power amplifiers, thereby saving on current consumption, a critical issue for battery power equipment. Click on the link for a GMSK tutorial

GMSK modulation was chosen for GSM originally because it offered a number of advantages including good spectral efficiency, resilience to interference, low levels of interference outside the wanted bandwidth, and the ability to use a non-linear RF power amplifier. This last point is of great importance because the use of a non-linear power amplifier brings greater levels of efficiency and this results in longer battery life - an important factor for mobile phones.

GPRS frame and slot structure

Again the GRPS air interface employs the same basic structure as that adopted for GSM. The overall slot structure for this channel is the same as that used within GSM, having the same power profile, and timing advance attributes to overcome the different signal travel times to the base station dependent upon the distance the mobile is from the base station. This enables the burst to fit in seamlessly with the existing GSM structure.

GSM slots showing offset between transmit and receive

GPRS burst structure

Each GPRS burst of information is 0.577 mS in length and is the same as that used in GSM. The GPRS burst carries two blocks of 57 bits of information in line with a GSM burst, giving a total of 114 bits per burst. It therefore requires four GPRS bursts to carry each 20 mS block of data, i.e. 456 bits of encoded data. Slots can be assigned dynamically by the BSC to GPRS dependent upon the demand, the remaining ones being used for GSM traffic.

GPRS burst structure

The BSC assigns PDCHs to particular time slots, and there will be times when the PDCH is inactive, allowing the mobile to check for other base stations and monitor their signal strengths to enable the network to judge when handover is required. The GPRS slot may also be used by the base station to judge the time delay using a logical channel known as the Packet Timing Advance Control Channel (PTCCT).

Summary

The GPRS radio interface is very similar to that used by GSM, enabling the two systems to operate together on the same carrier, bursts of GSM and GPRS occupying the same frame. In this way it is possible for a single base station to support both systems. As a result of the GPRS burst and GPRS slot fitting being compatible with operation on a GSM signal does place restrictions regarding what can be done, but it enables the systems to operate together which is one of the essential requirements.

GPRS mobiles and multislot classes

This GPRS tutorial is split into several pages each of which address different aspects of the GPRS technology:

[1] GPRS technology tutorial
[2] GPRS network architecture
[3] GPRS mobiles and multislot classes
[4] GPRS radio air interface
[5] GPRS error coding
[6] GPRS operation

GPRS mobiles are able to support data transmission as well as voice. GPRS mobiles are available with a variety of levels of operation. These are often defined by defining them as a particular GPRS class. These GPRS classes indicate the level of service they are able to provide.

In many respects many GPRS mobile phones may not look different to ordinary GSM phones, but they are able to offer a level of data service that cannot be provided by a standard GSM phone. Some GPRS phones may even offer a keyboard for emails, etc.

GPRS performance categories

Not all GPRS mobiles are designed to offer the same levels of service. As a result they are split into three basic categories according to their capabilities in terms of the ability to connect to GSM and GPRS facilities:

1. Class A: - This class describes mobile phones that can be connected to both GPRS and GSM services at the same time.



2. Class B: - These mobiles can be attached to both GPRS and GSM services but they can be used on only one service at a time. A Class B mobile can make or receive a voice call, or send and or receive a SMS message during a GPRS connection. During voice calls or texting the GPRS service is suspended but it is re-established when the voice call or SMS session is complete.



3. Class C: - This classification covers phones that can be attached to either GPRS or GSM services but user needs to switch manually between the two different types.

GPRS multislot classes

GPRS mobiles are also categorized by the data rates they can support. Within GSM there are eight time slots that can be used to provide TDMA, allowing multiple mobiles onto a single RF signal carrier. Within GPRS it is possible to use more than one slot to enable much higher data rates to be achieved when these are available. The different speed classes of the mobiles are dependent upon the number of slots that can be used in either direction.

There are a total of 29 speed classes. Class one mobiles are able to send and receive in one slot in either direction, i.e. uplink and downlink, and class 29 mobiles are able to send and receive in all eight slots. The classes within these two limits are able to support sending and receiving in different combinations of uplink and downlink slots.

GPRS class	Slots used	Max upload speed kbps	Max download speed kbps
2	3	8 - 12	16 - 24
4	4	8 - 12	24 - 36
6	4	24 - 36	24 - 36
8	5	8 - 12	/ 32 - 40
10	5	16 - 24	32 - 48
12	5	32 - 48	32 - 48

Common GPRS classes

Summary

GPRS mobile phones are available with a very wide range of different performance levels. These are defined by the different GPRS categories and GPRS classes. In particular the GPRS class will be seen mentioned in the literature and this defines the maximum data rates that can be achieved under ideal conditions.

GPRS network architecture

This GPRS tutorial is split into several pages each of which address different aspects of the GPRS technology:

[1] GPRS technology tutorial
[2] GPRS network architecture
[3] GPRS mobiles and multislot classes
[4] GPRS radio air interface
[5] GPRS error coding
[6] GPRS operation

With GPRS providing a move from circuit switched technology to packet switched technology, it was necessary to upgrade the network architecture to accommodate this. To accommodate this the GPRS network architecture added new elements including the GGSN and SGSN to the existing GSM network to be able to accommodate this.

However it was still necessary for the GPRS network elements and those from the existing GSM elements to work along side one another. Accordingly the introduction of GPRS technology saw the addition of some new entities within the over network architecture.

GPRS network architecture upgrades

With GPRS providing additional connectivity in terms of packet data, there are naturally a number of upgrades needed to the network architecture required. A number of new elements are needed for the network, but these can operate alongside the existing elements meaning that the GPRS capability is an upgrade to the network and not a completely new network structure.

The main new network architecture entities that are needed are:

• SGSN: GPRS Support Node - this forms a gateway to the services within the network.



• GGSN: Gateway GPRS Support Node which forms the gateway to the outside world.



• PCU: Packet Control Unit which differentiates whether data is to be routed to the packet switched or circuit switched networks.

A simplified view of the GPRS network architecture can be seen in the diagram below. From this it can be seen that it is very similar to the more basic GSM network architecture, but with additional elements.

GPRS network architecture

SGSN

The SGSN or Serving GPRS Support Node element of the GPRS network provides a number of takes focussed on the IP elements of the overall system. It provides a variety of services to the mobiles:

• Packet routing and transfer



• Mobility management



• Attach/detach



• Logical link management



• Authentication



• Charging data

There is a location register within the SGSN and this stores location information (e.g., current cell, current VLR). It also stores the user profiles (e.g., IMSI, packet addresses used) for all the GPRS users registered with the particular SGSN.

GGSN

The GGSN, Gateway GPRS Support Node is one of the most important entities within the GPRS network architecture.

The GGSN organises the interworking between the GPRS network and external packet switched networks to which the mobiles may be connected. These may include both Internet and X.25 networks.

The GGSN can be considered to be a combination of a gateway, router and firewall as it hides the internal network to the outside. In operation, when the GGSN receives data addressed to a specific user, it checks if the user is active, then forwarding the data. In the opposite direction, packet data from the mobile is routed to the right destination network by the GGSN.

PCU

The PCU or Packet Control Unit is a hardware router that is added to the BSC. It differentiates data destined for the standard GSM network (circuit switched data) and data destined for the GPRS network (Packet Switched Data). The PCU itself may be a separate physical entity, or more often these days it is incorporated into the base station controller, BSC, thereby saving additional hardware costs.

GPRS network upgrading

One of the key elements for any network operator is the cost of capital expenditure (capex) to buy and establish a network. Capex costs are normally very high for a new network, and operators endeavour to avoid this and use any existing networks they may have to make the optimum use of any capital. In addition to the capex, there are the operational costs, (opex). These costs are for general maintenance and other operational costs that may be incurred. Increasing efficiency and reliability will reduce the opex costs.

Any upgrade such as that from GSM to GPRS will require new investment and operators are keen to keep this to the minimum. The upgrades for the GPRS network are not as large as starting from scratch and rolling out a new network.

The GPRS network adds to the existing GSM network. The main new entities required within the network are the SGSN and GGSN, and these are required as the starting point.

The base station subsystems require some updates. The main one is the addition of the PCU described above. Some modifications may be required to the BTS, but often only a software upgrade is required, and this may often be achieved remotely. In this way costs are kept to a minimum.

Summary

The GPRS network architecture can be viewed as an evolution of the GSM network carrying both circuit switched and packet data. The GPRS network architecture was also used as the basis for the 3G UMTS network. In this way network operators could evolve their networks through GPRS and possibly EDGE to the full 3G networks without having to replace and install more new equipment than was absolutely necessary.

GPRS technology tutorial

This GPRS tutorial is split into several pages each of which address different aspects of the GPRS technology:

[1] GPRS technology tutorial
[2] GPRS network architecture
[3] GPRS mobiles and multislot classes
[4] GPRS radio air interface
[5] GPRS error coding
[6] GPRS operation

GSM was the most successful second generation cellular technology, but the need for higher data rates spawned new developments to enable data to be transferred at much higher rates. The first system to make an impact on the market was GPRS. The letters GPRS stand for General Packet Radio System, GPRS technology enabled much higher data rates to be conveyed over a cellular network when compared to GSM that was voice centric.

GPRS became the first stepping-stone on the path between the second-generation GSM cellular technology and the 3G W-CDMA / UMTS system. With GPRS technology offering data services with data rates up to a maximum of 172 kbps, facilities such as web browsing and other services requiring data transfer became possible. Although some data could be transferred using GSM, the rate was too slow for real data applications.

GPRS benefits

GPRS technology brings a number of benefits for users and network operators alike. It was widely deployed to provide a realistic data capability via cellular telecommunications technology.

GPRS technology offered some significant benefits:

• Speed: One of the headline benefits of GPRS technology is that it offers a much higher data rate than was possible with GSM. Rates up to 172 kbps are possible, although the maximum data rates realistically achievable under most conditions will be in the range 15 - 40 kbps.



• Packet switched operation: Unlike GSM which was used circuit switched techniques, GPRS technology uses packet switching in line with the Internet. This makes far more efficient use of the available capacity, and it allows greater commonality with Internet techniques.



• Always on connectivity: A further advantage of GPRS is that it offers an "Always On" capability. When using circuit switched techniques, charges are based on the time a circuit is used, i.e. how long the call is. For packet switched technology charges are for the amount of data carried as this is what uses the services provider's capacity. Accordingly, always on connectivity is possible.



• More applications: The packet switched technology including the always on connectivity combined with the higher data rates opens up many more possibilities for new applications. One of the chief growth areas that arose from GPRS was the Blackberry form of mobile or PDA. This provided for remote email applications along with web browsing, etc.



• Capex and opex: The Capital expenditure (capex) and operational expenditure (opex) are two major concerns for operators. As GPRS was an upgrade to existing GSM networks (often implemented as a software upgrade achieved remotely), the capital expenditure for introducing GPRS technology was not as high as deploying a complete new network. Additionally opex was not greatly affected as the basic basestation infrastructure remained basically the same. It was mainly new core network elements that were required.

The GSM and GPRS elements of the system operate separately. The GSM technology still carries the voice calls, while GPRS technology is sued for the data. As a result voice and data can be sent and received simultaneously.

GPRS and packet switching

The key element of GPRS technology is that it uses packet switched data rather than circuit switched data, and this technique makes much more efficient use of the available capacity. This is because most data transfer occurs in what is often termed a "bursty" fashion. The transfer occurs in short peaks, followed by breaks when there is little or no activity.

Using a traditional approach a circuit is switched permanently to a particular user. This is known as a circuit switched mode. In view of the bursty nature of data transfer it means that there are periods when it will not be carrying data.

To improve the situation the overall capacity can be shared between several users. To achieve this, the data is split into packets and tags inserted into the packet to provide the destination address. Packets from several sources can then be transmitted over the link. As it is unlikely that the data burst for different users will occur all at the same time, by sharing the overall resource in this fashion, the channel, or combined channels can be used far more efficiently. This approach is known as packet switching, and it is at the core of many cellular data systems, and in this case GPRS.

GPRS network

GPRS and GSM are able to operate alongside one another on the same network, and using the same base stations. However upgrades are needed. The network upgrades reflect many of those needed for 3G, and in this way the investment in converting a network for GPRS prepares the core infrastructure for later evolution to a 3G W-CDMA / UMTS.

The upgraded network, as described in later pages of this tutorial, has both the elements used for GSM as well as new entities that are used for the GPRS packet data service.

The upgrades that were required for GPRS also formed the basis of the network required for the 3G deployments (UMTS Rel 99). In this way the investment required for GPRS would not be a one off investment used only on GPRS, it also formed the basis of the network for further developments. In this way GPRS became a stepping stone used for the migration from 2G to 3G.

GPRS mobiles

Not only does the network need to be upgraded for GPRS, but new GPRS mobiles were also required. It is not possible to upgrade an existing GSM mobile for use as a GPRS mobile, although GSM mobiles can be used for GSM speech on a network that also carries GPRS. To utilise GPRS new modes are required to enable it to transmit the data in the required format.

With the incorporation of packet data into the network, this allowed far greater levels of functionality to be accessed by mobiles. As a result a new bread of started to appear. These PDAs were able to provide email and Internet browsing, and they were widely used especially by businesses as they allowed their key people to remain in touch with the office at all times.

Key GPRS parameters

The key parameters for the GPRS, General Packet Radio System, are tabulated below:

Parameter	Specification
Channel Bandwidth	200 kHz
Modulation type	GMSK
Data handling	Packet data
Max data rate	172 kbps

GPRS summary

GPRS technology offered a significant improvement in the data transfer capacity over existing cellular systems. It enabled many of the first email and web browsing phones such as PDAs, Blackberrys, etc to be launched. Accordingly GPRS technology heralded the beginning of a new era in cellular communications where the mobile phone capabilities allowed significantly more than voice calls and simple texts. GPRS enabled real data applications to be used and the new phones to become mobile computers on the move allowing businessmen to be always in touch with the office and domestic users to be able to use many more data applications.

Mobile phone GPRS Technology

THE 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. It is a step ahead to provide a massive boost to mobile data usage and usefulness. Payments are made as per data volume, instead of per minute pulse rate. You need to pay a fixed rent around Rs. 750 per month, after which you can surf for unlimited hours. Except for one thing, as a developing technology, the net connection is a slow process.

BENEFITS

Surfing the net; emailing; all through the mobile. Fast transmission of text documents, spreadsheets, photographs and illustrations; mobile chatting and on-line games. A round the clock net connection, even when you are on the move.

FEATURES

SPEED
A GPRS can achieve speeds up to 171.2 kilobits per second (kbps) using all eight timeslots at the same time. This is thrice as fast as current data transmission systems.
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.
NEW APPLICATIONS, BETTER APPLICATIONS
GPRS facilitates several new applications that have not previously been available over GSM networks due 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 you are used to on your desktop from web browsing to chat over the mobile network.

WHAT DO YOU NEED FOR A GPRS ?

To begin with, a mobile phone or terminal that supports GPRS. A subscription to a mobile telephone network that supports GPRS. § Knowledge of how to send and/ or receive GPRS information using their specific model of mobile phone, including software and hardware configuration. 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.

KEY NETWORK FEATURES OF GPRS

PACKET SWITCHING GPRS
involves overlaying a packet based air interface on the existing circuit switched GSM network. This gives the user an option to use a packet-based data service. With GPRS, the information is split into separate but related "packets" before being transmitted and reassembled at the receiving end.
SPECTRUM EFFICIENCY
Efficient use of scarce radio resources means that large numbers of GPRS users can potentially share the same bandwidth and be served from a single cell. The actual number of users supported depends on the application being used and how much data is being transferred. Because of the spectrum efficiency of GPRS, there is less need to build in idle capacity that is only used in peak hours. GPRS therefore lets network operators maximise the use of their network resources in a dynamic and flexible way, along with user access to resources and revenues.
INTERNET AWARE
GPRS fully enables Mobile Internet functionality by allowing inter-working between the existing Internet and the new GPRS network.

LIMITATIONS OF GPRS

LIMITED CELL CAPACITY FOR ALL USERS
There are only limited radio resources that can be deployed for different uses- use for one purpose precludes simultaneous use for another. For example, voice and GPRS calls both use the same network resources. The extent of the impact depends upon the number of timeslots, if any, that are reserved for exclusive use of GPRS.
SPEEDS MUCH LOWER IN REALITY
Achieving the theoretical maximum GPRS data transmission speed of 171.2 kbps would require a single user taking over all eight timeslots without any error protection. Additionally, the initial GPRS terminals are expected to be severely limited- supporting only one, two or three timeslots. The bandwidth available to a GPRS user will therefore be severely limited.

APPLICATIONS OF GPRS

A wide range of corporate and consumer applications are enabled by nonvoice mobile services such as SMS and GPRS.
CHAT
Because of its synergy with the Internet, GPRS would allow mobile users to participate fully in existing Internet chat groups rather than needing to set up their own groups that are dedicated to mobile users. Since the number of participants is an important factor determining the value of participation in the newsgroup, the use of GPRS here would be advantageous.
TEXTUAL AND VISUAL INFORMATION
You can receive information, which is in the form of not only text, but maps, graphs or other visuals.
STILL IMAGES
Still images such as photographs, pictures, postcards, greeting cards and presentations, static web pages can be sent and received over the mobile network as they are across fixed telephone networks. It will be possible with GPRS to post images from a digital camera connected to a GPRS radio device directly to an Internet site, allowing near real-time desktop publishing.
MOVING IMAGES
You will also be able to receive moving images and receive transmission from anywhere.
WEB BROWSING
You will also be able to use the GPRS for browsing the net. DOCUMENT SHARING/ COLLABORATIVE WORKING Mobile data facilitates document sharing and remote collaborative working. This lets different people in different places work on the same document at the same time.
AUDIO
Dictating to a mobile phone, would simply not give sufficient voice quality to allow transmission to be broadcast or analyzed for the purposes of background noise analysis or voice printing. Since even short voice clips occupy large file sizes, GPRS or other high speed mobile data services are needed.
JOB DISPATCH
Non-voice mobile services can be used to assign and communicate new jobs from office-based staff to mobile field staff. Customers typically telephone a call center whose staff take the call and categorize it. Those calls requiring a visit by field sales or service representative can then be escalated to those mobile workers.
CORPORATE EMAIL
With up to half of employees typically away from their desks at any one time, it is important for them to keep in touch with the office by extending the use of corporate email systems beyond an employee's office PC. Since GPRS capable devices will be more widespread in corporations than amongst the general mobile phone user community, there are likely to be more corporate email applications using GPRS than Internet email ones whose target market is more general.
INTERNET EMAIL
Internet email services come in the form of a gateway service where the messages are not stored, or mailbox services in which messages are stored. In the case of gateway services, the wireless email platform simply translates the message from SMTP, the Internet email protocol, into SMS and sends to the SMS Center. In the case of mailbox email services, the emails are actually stored and the user gets a notification on their mobile phone and can then retrieve the full email by dialing in to collect it, forward it and so on.
By linking Internet email with an alert mechanism such as SMS or GPRS, users can be notified when a new email is received.
REMOTE LAN ACCESS
Remote LAN applications encompasses access to any applications that an employee would use when sitting at their desk, such as access to the intranet, their corporate email services such as Microsoft Exchange or Lotus Notes and to database applications running on Oracle or Sybase or whatever. The mobile terminal such as handheld or laptop computer has the same software programs as the desktop on it, or cut down client versions of the applications accessible through the corporate LAN. This application area is therefore likely to be a conglomeration of remote access to several different information types- email, intranet, databases. This information may all be accessible through web browsing tools, or require proprietary software applications on the mobile device. The ideal bearer for Remote LAN Access depends on the amount of data being transmitted, but the speed and latency of GPRS make it ideal.
FILE TRANSFER
You may download sizeable data across the mobile network. This data could be a presentation document for a traveling salesperson, an appliance manual for a service engineer or a software application such as Adobe Acrobat Reader to read documents. The source of this information could be one of the Internet communication methods such as FTP (File Transfer Protocol), telnet, http or Java- or from a proprietary database or legacy platform. Irrespective of source and type of file being transferred, this kind of application tends to be bandwidth intensive. It therefore requires a high-speed mobile data service such as GPRS, EDGE or 3GSM to run satisfactorily across a mobile network.
HOME AUTOMATION
Home automation applications combine remote security with remote control. Basically, you can monitor your home from wherever you are- on the road, on holiday, or at the office. If your burglar alarm goes off, not only do you get alerted, but you get to go live and see who are perpetrators are and perhaps even lock them in. You can program your video, switch your oven on so that the preheating is complete by the time you arrive home and so on. Your GPRS capable mobile phone really does become like the remote control devices we use today for our television, video, hi-fi and so on. As the Internet Protocol (IP) will soon be everywhere- not just in mobile phones because of GPRS but all manner of household appliances and in every machine- these devices can be addressed and instructed. A key enabler for home automation applications will be Bluetooth, which allows disparate devices to inter work.

WHAT IS BLUETOOTH TECHNOLOGY ?

Bluetooth, named after the renowned Danish King, Harold Bluetooth, is a short-range wireless connectivity standard.
Bluetooth is capturing the minds of the present day technologists, as a technology enabler for the wireless unification of a wide variety of portable devices like mobile PCs, mobile phones and the like. It does away with the cables and enables voice and data transfer between the devices through wireless networks called piconets.
The primary segments identified for Bluetooth application are: Cellular & PCS Mobile Phones, Digital Cordless Phones, Data Access Points, PC Cards and Adapters , Notebook & Desktop PCs, Handheld PCs & Palm Companions / PDA s, Digital Still Cameras, Output Equipment, Automotive and Industrial & Medical applications.
The technology behind it:
Bluetooth is a Radio Frequency (RF) specification for short-range, point-to-multi-point voice and data transfer. An advantage of Bluetooth is it's similarity to many other specifications already deployed and it's borrowing of many a feature from these specifications. The 2.4GHz band is used by IEEE 802.11 to enable wireless LAN connectivity. Bluetooth borrows specifications to enable file sharing and data transfers between devices from IrDA (a wireless specification that uses InfraRed light to connect devices). HomeRF SWAP, a specification aimed at small network of devices for the home environment, is another source for Bluetooth.
It is omni-directional and has a present nominal link range of 10cm to 10m, which can be extended to 100m, with increased transmitting power. Bluetooth operates in the 2.4GHz Industrial-Scientific-Medical (ISM) Band and uses a Frequency Hop (FH) spread spectrum technology in which packets are transmitted in defined time slots on defined frequencies. A full duplex information interchange rate of upto 1Mbps may be achieved in which a Time-Division Duplex (TDD) scheme is used.
A Bluetooth System:

A Radio Unit - consisting of a radio transceiver, which provides the radio, link between the Bluetooth devices. A Baseband Unit - a hardware consisting of flash memory and a CPU. This interfaces with the radio unit and the host device electronics. Link Management Software - a driver software or firmware which enables the application software to interface with the baseband unit. An Application Software - this implements the user interface and is the application that can run on wireless.

BLUE TOOTH USAGE MODELS

The usage model being presented below are those which have been identified by the Bluetooth SIG's marketing group and helps us to get a peep into the vast areas of application of this wonderful standard.

The three-in-one phone: It can work as cordless phones connecting to the public switched telephone network at home and office and thus incurring the fixed line charge. It could function as a walkie-talkie with other telephones in the same office or building, without incurring any charge. This telephone can also connect to the cellular infrastructure and function as a cellular phone, incurring cellular charges. At home, your phone functions as a portable phone (fixed line charge). When you're on the move, it functions as a mobile phone (cellular charge). And when your phone comes within range of another mobile phone with built-in Bluetooth wireless technology, it functions as a walkie-talkie (no telephony charge). The Internet Bridge: In this usage model, mobile phone or cordless modem functions as a modem to the PC, providing dial-up networking and fax capabilities without a need for physical connection to the PC. Use your mobile computer to surf the Internet wherever you are, and regardless of whether you're cordlessly connected through a mobile phone (cellular) or through a wire-bound connection (e.g. PSTN, ISDN, LAN, xDSL). The Interactive Conference: Here, multiple data terminals, use a Local Access Network (LAN) access point as a wireless connection to a LAN. Once connected, the data terminals operate as if they were connected to the LAN via dialup networking. The terminals can access all of the services provided by the LAN. In meetings and conferences you can transfer selected documents instantly with selected participants, and exchange electronic business cards automatically, without any wired connections. The file transfer usage model offers the ability to transfer data objects from one device to another. Object types include, among others, ***.xls,***.ppt,***.wav,***.jpg,***.doc files or entire folders, directories or streaming data formats. Also, this offers a possibility to browse the contents of the folders on a remote device. The Ultimate Headset: The Headset, can be wirelessly connected for the purpose of acting as a remote device's audio input and output interface .The headset increases the freedom of movement while maintaining privacy. The headset can be typically used with a cellular headset, cordless handset or personal computer for audio input and output. This headset will also have the ability to answer incoming calls and then terminate them without physically manipulating the telephone handset. Connect your wireless headset to your mobile phone, mobile computer or any wired connection to keep your hands free for more important tasks when you're at the office or in your car. The Automatic Synchronizer: This provides a device-to-device synchronization of the personal information management (PIM) information. Synchronization requires business card, calendar and task information to be transferred and processed by computers, cellular phones and PDA s, utilizing a common protocol and format. This involves, automatic synchronization of your desktop, mobile computer, notebook (PC-PDA and PC-HPC) and your mobile phone. For instance, as soon as you enter your office, the address list and calendar in your notebook will automatically be updated to agree with the one in your desktop, or vice versa.

IrDA AND BLUETOOTH

IrDA-Data (IrDA -> Infra-red Data Association) is another short-range wireless connectivity standard with an installed base of 50 million units, by now. IrDA is a point-to-point, narrow angle (30 degree cone), ad-hoc transmission standard designed to operate over a distance of 0 to 1 meter and at speeds of 9.6kbps to 4Mbps, which is expected to increase to 16Mbps.
While the application areas of Bluetooth and IrDA overlap, they are not competitive standards, necessarily. The short range, narrow angle of IrDA allows the user to aim, in point-and-shoot style at a targeted recipient, for example in a conference hall. Close proximity to the other person is natural in a business card exchange situation and the short range is an advantage of IrDA for such applications.
The directional nature of IR enables a low level security because of direct line-of-sight nature; but it provides for, no security at the link level. There are security loopholes as it is possible to eavesdrop on a conversation by detecting reflected light and filtering out the surrounding ambient noise.
In contrast, Bluetooth addresses the security concerns by providing authentication and encryption in its baseband protocol. Authentication relies on a challenge-response protocol utilizing a secret key, personal identification number or PIN. Bluetooth devices talking to one another should have the same PIN. The protocol allows each device to authenticate the other. After the devices are authenticated it is possible to encrypt the transmission for added security.
Thus, it is expected that while in some devices both IR and Bluetooth may co-exist, for the other applications, the choice of Bluetooth and IR will be based on the applications and required usage models.
Mind-boggling technology like the Bluetooth and GPRS, is on its way to make communications in the future, a completely different ball game. A ball game with a win-win situation. Pave way for the future with these technologies then. Curtsy www compareindia com