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Enhanced Data GSM Environment
Justin Champion
Room C208 - Tel: 3273www.staffs.ac.uk/personel/engineering_and_technology/jjc1
Enhanced Data GSM Environment
Increased Data Use As discussed last week the
introduction of increased data rates technology will take place over time.
Each of these introductions will then allow development towards 3G.
Each of these technologies will be built upon to allow 3G
Last week we introduced GPRS This week we are looking at EDGE Both are referred to as 2.5G technology 2 G
GSM
2.5 GEDGEGPRS
3G UMTS
Enhanced Data GSM Environment
Edge Will allow another step towards the use of 3G This will allow the infrastructure to grow and improve
Consider what would happen if a network went from 9.6 Kbps data access to 2Mbps in a short time
It would not be able to cope as the companies would not be available to update the entire network infrastructure that quickly
The network infrastructure would not cope and upgrades will be required. This is already a consideration with EDGE level access 20 devices receiving a football stream at 200 (reasonable quality) Kbps in a
town centre Base station needs 20 * 200 = 4 Mbps
Now consider how many other base stations are also requesting the same data?
Enhanced Data GSM Environment
Edge Is now being considered as a replacement for 3G Vodafone are intending to allow EDGE services this
year Vodafone are pushing Edge now as a 3G technology
It will be available later this year via a data card attached to your laptops Intended for business data users only initially Manchester, Liverpool and London are the cities it will operate
within (www.computerweekly.com/Article127287.htm, 2004)
Enhanced Data GSM Environment
The amount of value added services is predicted to increase To allow a greater choice of these services a higher
throughput will be required for the devices Device will always have limited storage in comparison
to what is available for them A solution to this is to provide those services on-demand and
download them. After use these can be deleted with no impact on the actual
device Video on Demand is an example of this Location based services i.e. show me a web cam of the inside
of the “Peking Temple” restaurant now!
Enhanced Data GSM Environment
Video-on-Demand (VOD) Two choices for VOD
Stream the entire film across the network in real-time Sensitive to any delays in the network A powerful enough server would be needed to supply the demand Does not need a large amount of storage on the actual device
Download parts of the film in the background to the device and play it when the film is in the storage of the device
Device will need sufficient storage Some method would be needed to know what a person might be
interested in A pre-registration scheme for example with a football match
A scheme somewhere between the two would be ideal Part of the video would be downloaded to get the viewer watching
whilst the rest would be downloaded in real-time
Enhanced Data GSM Environment Multimedia Messaging Service (MMS)
With increased data rates and expectations we now have MMS as a replacement for SMS
MMS is designed to allow multimedia elements to be sent between compatible devices
Currently this consists mostly of photos The standards allow for
Video Pictures Audio Text Expansion for future use
Enhanced Data GSM Environment MMS continued
Based on a Open standard Allows for expansion and developments
(http://www.lebodic.net/mms_resources.htm, 2003)
MMS is not part of the GSM standard and can be implemented on any network infrastructure
High throughput networks are not necessarily required for MMS to operate
MMS messages will be trickled in the background to your device You will only receive notification once all of the message has been
processed Unlike SMS, MMS will need to be transported in multiple packets of
data MMS supports as base set of requirements
JPEG, GIF, PNG, SVG-Tiny (2D Vector Graphics) SP-MIDI (Synthetic sound) MPEG-4 ASCII Text
Enhanced Data GSM Environment MMS PDU
Specifications in details can be found at www.openmobilealliance.org/wapdocs/wap-209-mmsencapsulation-20020105-a.pdf
Enhanced Data GSM Environment MMS continued Charging for MMS
Issues around how to charge and who to charge At the moment the sender pays
Not a problem with the current relatively small amount of data sent Consideration needs to be given to who will pay for delivery
When larger video files are transferred Latest standard allows for the sender to pay for any reply to a
message This may be used by companies for advertising, equivalent of a free
phone number
Enhanced Data GSM Environment
EDGE Developed by Erricson for the benefit of the loser in the 3G spectrum bidding Operates at a theoretical 384 Kbps within the current GSM transmission bands
This means that a company who has not paid for out 3G can still provide fast data services
Companies that have bought 3G spectrum, will benefit from the infrastructure put in place for EDGE, as this will be used for UMTS
Current infrastructure The current Base stations will require a new transceiver and a software upgrade to
allow EDGE transmission This can take place as and when the normal BS are being serviced
This allows for a wider coverage than will be available at least initially with the UMTS network.
Obviously there are still the same issues as GPRS in respect that a channel that is used for EDGE takes one away from a voice call
Enhanced Data GSM Environment
EDGE continued The data transferred is transferred using 8 Phase
shifting Key (8 PSK) This can change and will be discussed further in a further
slide This allows the transfer of 3 bits in each modulation Three times GPRS and one of the reason why EDGE is 3x
faster EDGE is more sensitive to errors and as such needs to be
close to the transmitter to allow maximum throughput of data
Enhanced Data GSM Environment EDGE continued
Works the same as GPRS as in a single GSM frame is divided between the transmission
Voice7
FFAFFAFFABABBBBB8
BBBBABABAFFFFFFF6
AAAFAFAFFFAFFFFB5
AAABAABAAAFAAAA4
Voice3
AAAABBABBAAAAFA2
Voice1
Use of the ChannelChannelData Users
A = User 1B = User 2F = User 3
In this instance we have 3 voice calls and 3 users receiving data
Enhanced Data GSM Environment
EDGE As with GSM and GPRS will have separate downlink
and uplink channels A discussion is currently taking place regarding the use
of 8-PSK As the internet is a download intensive environment
8-psk may only be used in the downlink Uplink may well remain as the GSM GMSK
This will reduce the overhead of the 8-PSK
Enhanced Data GSM Environment
Quality EDGE uses packets which are physically closer together than the
GPRS system This increases the likelihood of error taking place
Coding Scheme As with GPRS, EDGE has a number of coding schemes to allow for
these errors They range from
MSC1 to MCS4 (using GMSK modulation) MSC5 to MSC9 (using the 8PSK modulation)
As with other wireless technologies The best transmission rate is used to start and then a lower one will be
selected until successful communications can take place
Enhanced Data GSM Environment Quality
The code rate indicates how much of the packet is data (including headers) and how much is error checking code
MCS3 indicates that 15% of the packet is error checking code
0.928PSK54.4 KbpsMSC8
18PSK59.2 KbpsMSC9
0.768PSK44.8 KbpsMSC7
0.498PSK29.6 KbpsMSC6
0.378PSK22.4 KbpsMSC5
1GMSK17.6 KbpsMSC4
0.85GMSK14.8 KbpsMSC3
0.66GMSK11.2 KbpsMSC2
0.53GMSK8.8 KbpsMSC1
Code RateModulation TechniqueData RateModulation
Enhanced Data GSM Environment
Packet Handling improvements over GPRS If a packet is sent which arrives corrupted
GPRS will send the packet again using the same modulation technique
EDGE will lower the modulation technique used and send the packet again.
The lowering of the modulation is a problem The available data in a new packet is reduced
EDGE allows for resegmentation and the packet being sent again This allows EDGE to send packets at a rate which would normally
corrupted and then resend them again when a error takes place
Enhanced Data GSM Environment
Error checking continued Receipts for frames
In GPRS a maximum addressing number is 128 The window for receipts is a maximum of 64 This means that after a sequence of packets are sent an acknowledgement
for the last (at most) 64 packets is sent If one of these packets were in error that packet must be resent based on the
addressing number This can be an issue with large amounts of data being sent in error as the
addressing window will restart again at 0 Indicating that an incorrect packet maybe resent In this event the entire frame sequence would need sending again to the
device EDGE
Has increased the addressing number to 2048 and the window is now 1024 Thereby reducing the chance of lost packets
Enhanced Data GSM Environment
Error checking continued Forward Error Checking (FEC)
As discussed previously it is better to send some redundant bits with each packet, which in the event of error can be used to mathematically recreate the original packet
Alternative is to send each packet again with an increased rate of FEC
EDGE Will send the packet again, but the new packet will be combined with
the original packet to recreate the corrupted part of the packet No increase in the amount of FEC bits are sent the same
number are sent again, but using different bits. Correctly received packets
The FEC bits are a waste of available bandwidth!
Enhanced Data GSM Environment
Working out the correct sending rate This is a particular issue for data communications, rather
than voice To carry this out the radio environment needs measuring
Measuring for Bit error rate, carrier strength, interference, etc.
Once measurements are made the correct coding scheme can be selected
Measurements can be taken on every burst of data sent These measurements are used to generate the Bit Error Probability
(BEP) Several of these taken can be used to give an accurate reading of
the quality of the signal and to calculate the velocity of the device
Enhanced Data GSM Environment
Rollout Stages Phase 1
Introduce single and multi-slot packet switched services Introduce single and Multi-slot circuit switched services
Phase 2 Web Use Email Real-time services
VOIP Video Conferencing
Enhanced Data GSM Environment
Interleaving of data The data is sent in bursts
These bursts refer to the amount of information sent If one of the bursts arrives corrupted the entire burst sequence
needs sending again A radio block
The sequence of the packets being sent is referred to as a radio block
GRPS The radio block are interleaved into 4
EDGE The radio block are interleaved into 2
Increased throughput The potential for interference in the EDGE system has now been
reduced by a half Assuming all other factors remain the same
Enhanced Data GSM Environment
Infrastructure will not need adding to from the GPRS environment
(www.ericsson.com/products/white_papers_pdf/edge_wp_technical.pdf, 2003)
Enhanced Data GSM Environment Infrastructure
Changes Base station System GRPS Protocol (BSSGP)
Different quality of services are required require minor changes to the GPRS standards
The other changes are obviously taking place in the layers 0 and 1 of the device and the base station
A EDGE Based device will be able to communicate with GPRS
If a EDGE based service is not available at the time
Enhanced Data GSM Environment QOS classes
The classes which are supported by EDGE are the same as UMTS
Conversational Real-Time communications highest priority
Two way communications Streaming
Video – audio files, time dependent One way communication
Interactive WWW usage, telnet etc
Reduced request response time Background
SMS, email, MMS Best effort delivery
Each of the communications will be issued with one of these classes.
This will depend ion the technology being used for EDGE
Enhanced Data GSM Environment
Problem with the installation of EDGE No Killer App YET !
There is no reason at this stage for user to want a EDGE based phone
Potential killer app maybe the downloading of music Apples i-pod (http://www.apple.com/ipod/, 2003) Allows the downloading of music onto the device, with 20Gb of
storage Consider if these songs were downloaded in the background of
your phone and you pay for them. You specify and pay for the album a few days in advance Albums available to you the second they are released Massive potential, with records that shops usually sell out of