GSM vs. UMTS… and the CDMA tipping point finally reached

Recently, we’ve noticed there is confusion regarding GSM cellular technology, and how it relates to CDMA. Not a big surprise given the wealth of jargon, buzzwords and semi-informed “analysts” in this area, but worth straightening out.

First generation: analog
In the beginning was analog cellular mobile radio. This was the first generation (1G) of cellular, an improvement on the previous Mobile Phone System (MPS) that provided better coverage, more capacity and allowed mobility: the possibility of the user moving, and being handed off from one base station [antenna] to another without dropping the call.

Various flavors were deployed by operators in different countries, including AMPS in North America, TACS in England and NMT in Scandanavian countries. These 1G systems are Frequency-Division Multiple Access (FDMA), meaning that the spectrum [radio band] allocated to the operator is divided into smaller bands called channels, and channels are allocated to users.

Second generation: digital and the warring factions
Problems with capacity and data communication led us to second generation (2G) cellular. Two warring factions emerged, with radically different views on sharing spectrum amongst users: the TDMA faction and the CDMA faction.

TDMA, Time-Division Multiple Access, means sharing one radio channel amongst a number of users by taking turns, one after another, in time. In North America, systems conforming to the IS-136 standard implement eight time slots on 30 kHz channels, allowing three users (one time slot for each direction for each user, plus time slots for control information). In the Rest Of The World, systems conforming to the Global System for Mobile Communications (GSM) standard implement sixteen time slots on 200 kHz channels, allowing seven users. Modems transmit 1s and 0s that are digitized speech (or digitized silence), or data (or idle patterns) at 9.6 kb/s between the phones and the base station over the radio channel.

CDMA, Code-Division Multiple Access, means not dividing spectrum into narrow channels, and not implementing time-sharing on those channels, but instead having all users transmit in the same carrier [wide frequency band], all at the same time. However, instead of transmitting 1s and 0s directly, the users transmit codes to represent 1s or 0s, and only transmit when they have something to say. Codes are binary numbers – strings of 1s and 0s – chosen so that if some users transmit and some do not, the base station can determine which transmitted. In North America and in limited places in the Rest of The World, a solution from Qualcomm Incorporated called CDMAOne and standardized as IS-95 was deployed. Qualcomm has patents on several functions necessary for cellular CDMA.

GSM/TDMA is the most popular today
GSM/TDMA became far more popular than IS-95, and so the market for selling phones and collecting money from GSM users is currently the largest. But, GSM/TDMA assigns 9.6 kb/s time slots to users, and even with band-aids and add-ons like GPRS and HSCSD, bandwidth like that is not useful for data communication (email, text messaging, Internet browsing, Google maps and location-based advertising, video) in any meaningful way. Further, GSM/TDMA reserves bandwidth for users whether they have anything to transmit or not – a very wasteful and inefficient use of scarce radio spectrum.

Third generation broadband: the factions continue to disagree
So we needed a third generation (3G). Because of the 2G schism, it was desired to have a global standard for 3G mobile radio. A group called International Mobile Telecommunications 2000 (IMT-2000) was formed to come up with a single world standard – and failed. They produced a document that had five incompatible variations. The two serious variations both were CDMA, since it is the most flexible and most efficient way of sharing the radio spectrum.

The warring factions did not make peace, they just changed what they were arguing about.

The 2G CDMA faction supported the variation called IMT-Multi Carrier, known as CDMA2000, basically a software upgrade from IS-95. A version called 1X using 1.25 MHz carriers was immediately deployed. 1X Evolution – Data Optimized (1XEV-DO) allows high-bitrate data communications.

The GSM/TDMA faction supported the variation called IMT-Direct Spread, known as Wideband CDMA and now marketed as Universal Mobile Telecommunications System (UMTS), which uses 5 MHz carriers and allows high-bitrate data communications using technologies like High-Speed Packet Access (HSPA).

The CDMA tipping point in the GSM/UMTS faction
After numerous false starts, the tipping point between 2G and 3G in the GSM/UMTS camp was finally reached in the summer of 2007, when more new activations on GSM/UMTS carriers’ networks were UMTS (3G CDMA) instead of GSM (2G TDMA).

What to take away from this discussion

  • The 2G TDMA technology GSM at present has far more users, but like 1G analog, GSM will eventually disappear.
  • Two incompatible competing 3G CDMA-based technologies: IMT-MC (CMDA2000 1X) and IMT-DS (UMTS) will go forward.
  • Qualcomm sells a chip or gets a patent license royalty for every handset and base station sold, for both 1X and UMTS.
  • Many users, salespeople and semi-informed analysts and reporters will erroneously refer to IMT-DS (UMTS) as “GSM”.
  • Want more ?
    There is, of course, more to the story than this brief tutorial. This topic is covered in more detail in Teracom instructor-led courses, DVD video Computer-Based Training courses, and textbooks:
    Course 101 Telecom, Datacom and Networking for Non-Engineers: Chapter 6
    Course 120 Understanding Wireless: Chapters 8, 9 and 10
    DVD 6 Understanding Wireless 1: Parts 2, 3 and 4
    Telecom 101 textbook, 3rd edition: Sections 8.2 – 8.7 (21 pages)

    What is "Web 2.0"?

    Teaching a class, a student asked me, “What is ‘Web 2.0′”? 

    Having briefly scanned some online articles about it, I answered “It doesn’t mean anything. Just hot air”. 

    Later, I did a bit more digging on “Web 2.0” and confirmed my initial take: hot air. 

    In fact, I re-defined “Web 2.0” it in my mental storage system as: “Been there, done that.”

    The term “Web 2.0” appears to have been coined during a “brainstorming session” between Tim O’Reilly of O’Reilly Media and MediaLive International. Presumably, the purpose of this brainstorming session was to create themes for a new commercial tradeshow. 

    According to O’Reilly, they formulated a definition of Web 2.0 by example:

    Web 1.0
      Web 2.0
    DoubleClick
    –>
    Google AdSense
    Ofoto
    –>
    Flickr
    Akamai
    –>
    BitTorrent
    mp3.com
    –>
    Napster
    Britannica Online
    –>
    Wikipedia
    personal websites
    –>
    blogging
    evite
    –>
    upcoming.org and EVDB
    domain name speculation
    –>
    search engine optimization
    page views
    –>
    cost per click
    screen scraping
    –>
    web services
    publishing
    –>
    participation
    content management systems
    –>
    wikis
    directories (taxonomy)
    –>
    tagging (“folksonomy”)
    stickiness
    –>
    syndication

    The main theme: the web as a platform for applications. Second theme: collaborative efforts.

    So Web 1.0 was the development and adoption of the browser, HTTP and HTML. Web 2.0 was the development of applications like Wikipedia that use it. 

    Been there, done that, or what?

    Let’s talk about Web 3.0 and 4.0!

    At Teracom, we’re interested in getting you up to speed on the technology underlying today’s and tomorrow’s telecom products and services. 

    Taking our acclaimed training, you’ll understand the concepts and ideas, mainstream solutions and how it all fits together.

    For example: we’ll cover the idea of virtual circuits, how they are implemented in the IP world with MPLS, and how MPLS can be used to implement Quality of Service guarantees and Service Level Agreements in the IP world. 

    … this is knowledge you can’t get from pundits or trade shows. Career-enhancing knowledge you can leverage going forward.

    So let’s talk about the next two technology steps: 
    call them Web 3.0 and 4.0 – or VoIP and IPTV. 

    Web 3.0: The IP-PSTN 

    Web 3.0 will have happened when the Public Switched Telephone Network and the Internet become the same thing.

    You will know we have reached that point when you read that a telephone company has applied to its regulator to stop being required to provide analog POTS for new service orders. 

    Broadband IP Dial Tone will be the new Plain Ordinary Telephone Service.

    In this future, you won’t have analog telephone service. You’ll only pay for high-speed internet access – from the cable company, the telephone company or maybe some metro wireless or metro fiber outfit.

    They’ll give you a drop wire / entry cable / wireless access plus an adapter which does the functions of Modem / UPS / Gateway / Edge router / Ethernet switch / NAT (a MUGEEN). 

    You can plug this box into an existing phone jack and it will implement POTS on your inside wiring – dial tone, ringing, off-hook detection… 

    The MUGEEN also has Gigabit Ethernet ports. You can plug it onto your LAN and it provides Gigabit Ethernet LAN switching in your house and access to the Internet for anything on the LAN. 

    You can also plug in an Ethernet IP phone to do VoIP over the Internet. If you can set up a phone call by right-clicking on someone’s email address on your computer screen and choosing “Call” or “Talk”, then pick up the phone to use its microphone and speaker, you’ll know you have arrived at Web 3.0. Some people are already there!

    Web 3.0 is covered in: 

    Course 130, Understanding Voice over IP (2 days, for managers) and 

    Course 110, IP Telecom: VoIP and the All-IP Network (3 days, for the more technically-oriented). 

    Web 4.0: IPTV 

    So if VoIP and broadband IP dial tone is Web 3.0, what is Web 4.0? 

    Well, as a picture is worth a thousand words… 
    video is next

    HD video streaming from a video server to your video display over your 20+ Mb/s Internet connection. 

    Subscribe to a package of “channels” or customize your own feeds via a web page. 

    On the web page, search for, then download or stream and initiate the playing of any television show episode, movie, sporting event or other video that has been catalogued. 

    Access this web page on-screen via a wireless keyboard, on your desktop or maybe see it on your wireless palmtop. Or just use a clicker. 

    Much of the existing video will be archived somewhere on the Web. Content that is out of copyright or public license will be free. You’ll have to pay for new episodes of Lost. 

    One milestone will be good-quality streaming of Standard Definition video (DVD quality, 480×720 pixels). You’ll know we are truly there when you can stream HD (1080×1920). 

    You’ll get a good understanding of the network that will support Web 4.0 in Course 110, IP Telecom: VoIP and the All-IP Network. We’ll beef up the IPTV content in that course as the story progresses.