Enhanced Data GSM Environment

Enhanced Data GSM Environment

Justin ChampionRoom C208 - Tel: 3273

www.staffs.ac.uk/personel/engineering_and_technology/jjc1

http://www.staffs.ac.uk/personel/engineering_and_technology/jjc1


ContentsWhy do we need it?

Video-on-DemandMMSEDGEBenefits over GPRS

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)

http://www.computerweekly.com/Article127287.htm

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!


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

http://www.lebodic.net/mms_resources.htm

Enhanced Data GSM Environment MMS PDU

Specifications in details can be found at www.openmobilealliance.org/wapdocs/wap-209-mmsencapsulation-20020105-a.pdf

http://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


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


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

Channel Use of the Channel

1 Voice

2 AAAABBABBAAAAFA

3 Voice

4 AAABAABAAAFAAAA

5 AAAFAFAFFFAFFFFB

6 BBBBABABAFFFFFFF

7 Voice

8 FFAFFAFFABABBBBB

Data UsersA = User 1B = User 2F = User 3

In this instance we have 3 voice calls and 3 users receiving data


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


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

Modulation Data Rate Modulation Technique Code RateMSC1 8.8 Kbps GMSK 0.53

MSC2 11.2 Kbps GMSK 0.66

MSC3 14.8 Kbps GMSK 0.85

MSC4 17.6 Kbps GMSK 1

MSC5 22.4 Kbps 8PSK 0.37




MSC9 59.2 Kbps 8PSK 1


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


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


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!


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


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


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


Infrastructure will not need adding to from the GPRS environment

(www.ericsson.com/products/white_papers_pdf/edge_wp_technical.pdf, 2003)

http://www.ericsson.com/products/white_papers_pdf/edge_wp_technical.pdf

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


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

http://www.apple.com/ipod/


Summary Why do we need it?

Video-on-Demand MMS EDGE Benefits over GPRS

Documents

Enhanced Data GSM Environment