Evolved EDGE – The New Kid On the Block

I couple of years ago I thought EDGE (Enhanced Data Rate for GSM evolution) would not have a big chance on the market with new technologies like 3G and later on HSDPA entering the market. An yet, EDGE has made it into many networks around the world. In some countries, 3G hasn’t made it beyond big cities yet and I have come to value EDGE quite a lot in my frequent travels which often bring me to smaller towns or even the countryside. Interesting to see that work is underway in 3GPP to push EDGE forward once again.

Evolved EDGE

Today, EDGE for GPRS mainly increases user data rates by using new modulation and coding schemes which go far beyond the original GPRS specification. Effectively, EDGE increases GPRS speeds about four times. In practice, speeds of about 220 kbit/s can be reached under good radio conditions. Evolved EDGE sets out to increase the user data rate once again to a level around 1 MBit/s with the following enhancements:

Multiple Receiver Chains: Today, GSM mobile phones use once receiver chain. By adding a second one which analyzes the incoming signal (with a different polarization or different phase I am not sure) independently, chances to decode the data stream correctly increases. This means that higher modulation and coding schemes can be used in the same conditions as if the mobile phone only had one receiver chain. Note that this is a receive diversity scheme and not a MIMO (multiple input, multiple output) which will be used in 4G systems like LTE, WiMAX and also in the next generation of Wifi (802.11n).

Higher Order Modulation: EDGE uses 8PSK modulation which encodes 3 bits per transmission step. Evolved EDGE introduces 16QAM modulation which can encode 4 bits per transmission step and 32QAM modulation which encodes 5 bits per step. In practice, however, 32QAM is difficult to use for average transmission conditions on the air interface.

Two Simultaneous Radio Channels: Since 1992 the principle of GSM has been to use only a single carrier frequency to receive data. With E-EDGE, mobiles can now receive data on two frequencies. This could in effect double the data rate available to a single user.

Independent Transmission and Reception Chains: Another principle that E-EDGE is about to lift is the use of only a single transmission and reception chain which so far restricts mobiles to only sending or receiving at a time. By introducing independent transmission and reception chains, data rates are increased as the mobile phone does not have to switch between transmission and reception. This doesn’t only free up the timeslots used for the reverse direction but also frees up adjacent timeslots which are not usable with a combined transmitter and receiver which needs some time to switch between transmission and reception mode. While most EDGE mobiles on the market today are still restricted to four timeslots per carrier due to this phenomenon, having independent transmission and reception chains could allow mobiles to use all eight timeslots of a carrier.

Speed Calculation

When putting it all together, speed can be increased as follow: Higher order modulation can increase transmission speed by 1/4, so 220 kbit/s become 293 kbit/s. Use of twice the number of timeslots per carrier increases the top speed to 2 * 293 kbit/s = 586 kbit/s. Using two carriers could again double the speed to about 1.173 kbit/s. Not bad for a 15 year old technology that was originally intended for a transmission speed of 12 kbit/s for voice communication.

While this all sounds quite fascinating, there will be a number of downsides in practice as well:


E-EDGE will not be around for quite some time. Taking past developments as a reference, I expect that it will take at least another two to three years before networks are upgraded and for mobiles to be available (if such a decision is made).

Spectrum Efficiency

E-EDGE, in contrast to EDGE, only modestly increases spectrum efficiency. Thus, the total available bandwidth per sector per cell will still be in the range of "only" 1.5 MBit/s for a typical base station which uses three carriers per sector. In addition, the base station is also used for voice communication which further limits transmission speeds. Compare this to a full blown UMTS 3.5G HSDPA base station which uses 2 carriers per sector to reach a total bandwidth beyond 20 MBit/s and the difference becomes quite obvious. Thus, to say that E-EDGE drives data rates up to HSDPA levels is true as far as per user speeds are concerned but certainly not as far as the overall base station capacity is concerned. In addition, data rates of HSDPA in two to three years from now will have certainly moved on to beyond 3.5 MBit/s per user. Therefore, statements saying that E-EDGE is en par with HSDPA is pure marketing nonsense… Additionally, the number of E-1 links (2 MBit/s each) which connects the base station to the network also has to be increased to support the new modulation and additional timeslots which will be usable for voice.

Terminal Support

Most of the enhancements of E-EDGE will have a strong impact on current GSM terminal design. Independent receiver and transmitter chains have been standardized already since the first days of GPRS (GPRS class A). However, up to this date there are no such mobiles on the market. This seems to be a hard nut to crack. I am not sure if this is for technology reasons or simply due to the price or increased packaging requirements.

Other radio systems

Today, one of the main issues that keeps many operators from deploying 3G in rural areas is the use of the 2100 MHz spectrum which requires a higher number of base stations due to the smaller range compared to what can be achieved in the 900/850 MHz band used currently used by many GSM operators. At least in North America it looks, though, as if UMTS 3G will also be used in the 850 MHz band in the near future thus leveling this advantage of GSM/EDGE today. Furthermore, UMTS has now also been standardized for the 900 MHz band but it remains to be seen if regulators in Europe will allow deployments in that band in the near future. Also, other technologies such as WiMAX should also not be underestimated as a competition in the rural area in three or four years from now. With data rates over ten times higher per base station site then what an E-EDGE cell could deliver it seems doubtful to me that the technology would compete very well.


So will this technology get deployed and will it be successful? With this one, my crystal ball remains clouded. E-EDGE has many good ideas and will certainly increase data rates somewhat but it will not compete very well with other 3.5G and 4G technologies, which are also evolving to higher data rates. The best I therefore expect is that todays gap between 2.5G on the one hand and 3.5G and 4G networks on the other hand does not further increase.

Recently, Peter Rysavy has also written a good column about this subject. Take a look here, his articles on wireless network technologies are among the best to be found on the web!

For the details take a look at the 500 pages of the 3GPP Technical Report TR 45.912.

7 thoughts on “Evolved EDGE – The New Kid On the Block”

  1. “E-EDGE, in contrast to EDGE, only modestly increases spectrum efficiency. ”

    This is different from the story I’ve heard… According to the recent research brief from ABI research, the expected spectral efficiency of EEDGE is 0.4 (Bps/Hz/Sector) where EDGE is only 0.08 – 0.10…

  2. I wonder where this huge increase in spectrum efficiency should come from. Form a spectrum efficiency perspective, the difference between 8PSK of EDGE and 16QAM (or whatever they want use in E-EDGE)is marginal. Also, the coders can’t make a big difference as the lowest EDGE coder almost has no redundancy. And finally as far as speed is concerned the 1 MBit/s they quote fits nicely into two carriers. Therefore, I think the “story” you heard should be treated with care.

  3. Hmmm. How about the MSRD and Type 2. Of course transmitting and receiving simultaneously will demand more processing power, which will drain the bettary faster. From that point of view i’d think that they might be doing the same thing as what they’ve done to exaggerate the performance of UMTS (which has been proved to be disppointing!)

  4. Hello Red,

    again a good comment! To MSRD (Mobile Station Receive Diversity): It’s certainly an interesting way to be able. It will take some time, however, before such chipsets are available. Even for HSDPA I haven’t seen a MSRD chipset yet.

    Type 2 (send/receive simultaneously) will be necessary to use all 8 timeslots of a carrier for a mobile simultaneously. Again, additional hardware in the mobile is necessary which is not available today.

    Here’s an interesting presentation from Blackberry (surprisingly!) which gives some further details on the different things to be done for Evolved EDGE: http://www.rabc.ottawa.on.ca/e/Files/ACFB7A8.ppt . Note: The presentation mentions 64QAM modulation which was not discussed in depth in the 3GPP Technical Report mentioned above as for example 32QAM did (I wasn’t aware that they were looking at 32QAM so I corrected the text above as well). I would be cautious even with 32QAM as HSDPA for example didn’t use it because designers said that in real life it would be very unlikely that 32QAM could be used often.

    The TR quoted above says: “Also, increasing the modulation order to
    32QAM, or maybe even to 64QAM, will probably result in such an increase of receiver complexity that new hardware is needed in both base stations and mobile stations.” -> We are definitely not talking about a software upgrade only solution for the network here!

    So my main criticism remains that theoretical E-EDGE performance (tomorrow) is compared to theoretical HSDPA performance (today). Even here, top speeds are much different. But to be fair, E-EDGE should be compared to UMTS LTE (Long Term Evolution) as timelines are identical and mobile station complexity with multiple antennas, receiver chains, etc. will be similar. Here, E-EDGE doesn’t compare very well at all.

    Again, thanks for your post!


  5. Hi Martin,

    In my opinion the main arguement for E-EDGE is business (again). It’s not about the technology. UMTS turns out to be too expensive to be deployed everywhere (and Qualcomm!). The return is not significant. Operators need something to fill in the blank and bridge the gap. I wouldn’t be surprised if operators take the approach of E-EDGE in suburbs and HSDPA in big cities only. They shouldn’t kill each other. LTE is too far out in the future.

    You’ve sort of convinced me that E-EDGE doesn’t have obviouse technical advantage. I know the author of the presentation you quoted quite well. He’s a true beliver of EDGE. 🙂

    guess i’m being a little bit disorganized here.

  6. Check out Telstra as a case study in Australia. They built the worlds largest HSDPA network covering 98% of Australia’s population and 25% of the land mass in just 10 months from concept to completion. (Australia is the size of the USA) A base station was commissioned on average ever 25 minutes, 24 hours a day throughout the project. It operates on the 850MHz band, to enable the wide coverage.

  7. Hello David,

    thanks for your comment. Very interesting! I wasn’t aware that the 850 MHz band is used in Australia. That unfortunately also quite limits the number of devices available for UMTS/HSDPA that can be used in the network as most mobiles today only support the 2100 MHz band. Do you know which devices Telstra offers and what prices they have for Internet access?


    TITLE: Evolved EDGE
    URL: http://www.cenriqueortiz.com/weblog/3G/?permalink=Evolved-EDGE.html
    BLOG NAME: C. Enrique Ortiz Mobility Weblog
    DATE: 11/15/2006 07:31:53 AM

    Evolved EDGE has surfaced as an alternative to 3G – when the technology delivers 3G data rates
    using existing GSM spectrum licenses, it all sounds good.
    Maybe. Read Martin Sauter informative piece Evolved EDGE – The New Kid On the Block.
    I would li…

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