1. General Packet Radio Service Justin Champion Room C208 - Tel: 3273 www.staffs.ac.uk/personel/engineering_and_technology/jjc1

2. General Packet Radio Service Contents  Why do we need it  Details of GPRS  Sending of Packets

3. General Packet Radio Service Value Added Services  Operators have seen the use of data as a new source of revenue  The potential for data use is To sell the users the data applications To charge them for data needed to use them To charge other developers to allow the applications on to the network

4. General Packet Radio Service 3G data use  Although the UK operators have bought licensees to use 3G the infrastructure is not ready  The operators paid a lot for the radio spectrum licenses This left little available for infrastructure upgrades Also devices were not ready to be used with 2 Mbps CompanyPrice PaidCompanyPrice Paid Hutchison 3GUS$ 6.9 billionT-MobileUS$ 6.3 billion OrangeUS$ 6.44 billionO2US$ 6.35 billion VodafoneUS$ 9.4 billion

5. General Packet Radio Service General Packet Radio Service (GPRS)  This standard was agreed by ETSI March 1998  It is designed to allow data communication to take place within the existing GSM infrastructure.  A few additional servers are added to the network to allow this and these will be discussed later  This is described as being a 2.5G technology  To use GPRS you will need a GPRS enabled device Existing GSM devices will not be able to make use of the additional features

6. General Packet Radio Service General Packet Radio Service (GPRS)  Features Higher connections speeds  Theoretical Maximum of 171 Kbps  Interference  Distance from transmitter  All GSM channels would have to be dedicated to GPRS communications  This speed also does not take into account any error-correction  Does not consider a device uploading data  Actually speeds with conditions taken into account is theoretically a maximum of 53.6 Kbps  Studies have show the average is usually about 30 – 40 Kbps Always on Data communications  No delay in setting up a data communication

7. General Packet Radio Service GPRS Devices  In the standard there are three types of GPRS devices A  Capable of Simultaneous data transfer and voice communications B  Automatic switching between voice and data calls. This will need to be configured on the device itself C  Switching between data and voice operated by the device user manually.  All of these standards are backwards compatible with the GSM networks for voice communications

8. General Packet Radio Service GPRS  Relies on the fact that Internet communications are bursty in nature A large amount of data will be received and the user will process it before requesting more i.e. a web page A single voice circuit will from GSM will be broken into smaller parts and the GPRS data is sent on this circuit.  All data is sent in packets Data must be broken into small packets These packets are re-assembled at the destination These packets add an overhead in the form of the packet header

9. General Packet Radio Service GPRS Channel Breakdown ChannelUse of the Channel 0Voice 1AAAABBABBAAAAFA 2Voice 3AAABAABAAAFAAAA 4AAAFAFAFFFAFFFFB 5BBBBABABAFFFFFFF 6Voice 7FFAFFAFFABABBBBB Data Users A = User 1 B = User 2 F = User 3 In this instance we have 3 voice calls and 5 users receiving data

10. General Packet Radio Service GPRS Channel Breakdown Continued  A channel which is being used for GPRS data Can only be shared between other GPRS users It can not be allocated in that time slot for GSM voice calls  Even if part of the time slot is available The use of GPRS will reduce the amount of voice calls that can be made on that cell With enough data calls a cell will become useless for voice callers, which require exclusive access to the time slots

11. General Packet Radio Service GPRS Multi slot classes ClassDownlinkUplinkMaximum Active 1112 2213 3223 4314 5224 6324 7334 8415 9325 10425 11435 12445

12. General Packet Radio Service GPRS coding schemes  Depending on environment one of the following coding schemes are used SchemeMax Throughput per 1 Time SlotError Checking CS-18 KbpsGood CS-212 KbpsGood CS-314.4 KbpsModerate CS-420 KbpsPoor Schemes CS-1 and CS-2 are usually used

13. General Packet Radio Service GPRS network layers

14. General Packet Radio Service GPRS network layers  SNDCP Provides services to the higher layers  Compression  Connectionless, connection orientated services  Multiplexing  Segmentation  BSSGP Allows  Maps a SGSN to a BSS  Control information between a BSS and a SGSN  BSS Refers to a base station and an associated Base station controller

15. General Packet Radio Service GPRS Infrastructure  As discussed earlier GPRS build upon the GSM networks.  Network elements need changing Base stations  Requires a software upgrade Base station controller  Requires a software upgrade  New parts need adding Serving GPRS Support Node (SGSN)  Has VLR functionality  Authorise attached users  Details recorded of data packets to be charged for  Session Management  Router for packets which may be lost during a handover during a data call

16. General Packet Radio Service GPRS Infrastructure continued  Gateway GPRS Support Node (GGSN) Is the connection into the GPRS network It carries out all translations that area required Firewall for the network Collates data regarding the amount of packets received  Potentially in the future this will allow for competing GGSN’s in a network! Free market choosing either the cheapest or most reliable GGSN! There are 3 types of GGSN  A – Near Future/Now  The GGSN becomes part of its own ISP and provides Internet services. The devices will be assigned IP address using DHCP.  B – Now  The SSGN always selects the same GGSN to do the Internet work. The configuration will be done dynamically and on a temporary basis  C – Future  This allows a private company to have its own GGSN, with an encryption key so that only authorised devices can gain access. i.e. a VPN into a network, constant email access etc

17. General Packet Radio Service

18. Packet Control Unit (PCU)  Logically part of the Base station controller  Responsible for the radio interface of GPRS GPRS and SMS  SMS messages are sent in GPRS as a part of the normal data channels In GSM they are usually sent via the control channels  Why This changes has taken place ready for the Multimedia Messaging service  Due to the size of the messages

19. General Packet Radio Service Current Supported Protocols  IP Internet Protocol  Connectionless protocol, which delivers based on best effort  Widely used in most networks  X.25 Connection orientated communications Reliability built in with error checking the header Uses Virtual circuits  Intended for terminal services  Still used but is being replaced by other technologies

20. General Packet Radio Service General Packet Radio Service Problems  Initial problems existed in respect to the GPRS device When launched there was only a few compatible devices These had poor features and terrible battery life There was nothing to use the increased data rate Limited advertising of the features of GPRS  Potentially this was an issue around how much the advertising of the WAP services cost operators  This is now changing O2 have seen a 25% growth in usage of GPRS data from Jan to June 2003 (http://www.ovum.com/go/content/c,36230, 2003)http://www.ovum.com/go/content/c,36230

21. General Packet Radio Service Summary  Why we need the technology  What it is  Infrastructure changes