The Book to this Blog: A Solid Introduction to Wireless

I’ve dedicated well over 15 months of my quality time into my latest project and now it’s finally done and available in book stores around the world: Therefore, I am proud to announce general availability of the book to this blog "Communication Systems for the Mobile Information Society", published by John Wiley & Sons.

If you are looking for a solid introduction to GSM, GPRS including EDGE, UMTS with HDSPA and HSUPA, Wireless LAN, fixed and mobile WiMAX 802.16, as well as Bluetooth, this book is for you! My intention behind the book is to give a well balanced overview with a good level of detail for each technology rather than to go into the deepest details a book dedicated on a single technology would do. Here’s the link to the book on to find out more. If you have an account you can even browse through the book with their "look inside" functionality.

I felt it was time to write something like this as most students certainly do not read six individual books of 300 – 400 pages each for a college course on wireless. I’ve also seen that many wireless experts working in a particular field covered by the book would like to find out more about other technologies but simply do not have the time to read a 400 page book dedicated on a single wireless technology.

Each chapter contains a questionnaire at the end so you can test how
well you have understood the system explained in each chapter. The
answers to the questions are right here on this blog, take a look on
the left side.

If you come to this web site regularly you might have noticed that I do not only express my visions for the wireless future in my entries but usually also give them quite a technical spin. The book is similar in this regard as it contains my enthusiasm for wireless technologies, my knowledge on how they work, and explanations on why the systems were designed the way they are, their differences and their commonalities. The advantage of a book compared to a blog: You have more time and space to develop thoughts and explain.

Feedback and questions are always welcome! You can reach me at gsmumts (AT) Enjoy the book!

4G – The competitors

This blog entry is the fourth in a row about my thoughts on the current development of 4G wireless standards. You might want to take a look at the introduction before reading on. Previously, I’ve discussed why 4G networks are necessary and what to generally expect of 4G wireless networks. Three different standards are currently emerging and have already started to compete with each other for global dominance:

  • WiMAX aka IEEE 802.16e
  • UMTS Long Term Evolution (LTE)
  • CDMA EVDO Rev. C (also dubbed DORC)

All of the contenders are still paper ware only and widespread adoption of 4G technologies is still several years away. So how can they already compete with each other? From my point of view there are three axis of competition today:

Time to Market

As all three types of networks have similar properties, time to market will be an essential component of the overall competitiveness of a standard.

  • WiMAX is set to enter the market first as the air interface part of the standard, which is called IEEE 802.16e-2005, has already been approved by the members of the IEEE standards body back in February 2006. For those of you how like to read standards documents, you can find it here. Standards for the network infrastructure are specified by the WiMAX forum and you can download the latest drafts from this location. Here, work seems to be quite advanced but the standard has not been approved yet.
  • The 3GPP has also started its activities around 4G and the UMTS Long Term Evolution (LTE) standardization is well on track. First fruits of their work can be downloaded from The most interesting documents are 25.913 on requirements, the 25.912 feasibility study and 23.882, a report on different implementation options. To me, it looks like the work on the WiMAX standards is 12 to 24 months ahead of the LTE work.
  • The work on CDMA EVDO Rev. C seems to be even further behind WiMAX which might be because the CDMA Development Group is still working on EVDO Rev. B, the multi carrier extension for current EVDO Rev. A networks.

User Base of 3G Predecessor Technology

Having a predecessor technology already in place is a great help in introducing a new technology especially if new devices are backwards compatible to existing networks. Here, LTE has a big advantage as the standard will most likely be defined in such a way. Thus, handsets and other mobile devices will not only work in LTE networks but also in 3G UMTS networks and most likely also in 2G GSM/GPRS/EDGE networks. This is especially important in the first few years of network deployments when coverage is still limited to big cities. EVDO Rev C. is likely to follow a similar path.

WiMAX on the other hand is not backwards compatible to any previous wireless network standard. Thus, it remains to be seen if devices will also include a 3G UMTS or EVDO chip. This is not only a question of technology but also a question of strategy. If a company with a previously installed 2G/3G network deploys WiMAX then they will surely be keen on offering such handsets. New alternative operators without an already existing network on the other hand might be reluctant to offer such handsets as they would have to partner with an already existing network operator. They might not have much of a choice though if they want to reach a wider target audience.

Migration Path

At some point current 2G and 3G network operators will migrate to a 4G network technology. As 4G network technology is based on IP only and includes no backwards compatibility for circuit switched services, current operators do not necessarily have to select the evolution path of the standard they are currently using.

For current UMTS network operators the most likely evolution path will be to LTE. Devices will most likely be backwards compatible to their existing 3G and 3.5G networks. Also, connectivity of the new LTE radio network to their existing core network infrastructure, billing systems and services will be seamless. Also, current 3.5G networks offer enough capacity for a number of years to come. Thus, UMTS operators are currently in no hurry with 4G technologies. Nevertheless, I think that WiMAX might have a chance with some operators trying a different game to see if they can gain a competitive advantage. In my opinion, the availability of dual mode handsets will be crucial for such a decision. In theory, UMTS operators might also choose EVDO Rev. C. I don’t think this is likely though due to the standard being nowhere on the horizon yet and the fact that the current EVDO market share is on the decline.

For EVDO operators the picture is a bit different. For them, EVDO Rev. C is still far out. Some of them especially in Taiwan and Australia have decided to make a radical move even sooner and are in the process of migrating from the current 3.5G EVDO networks to 3.5G UMTS/HSDPA. Recently, Sprint in the U.S. has made another early decision and announced that they have chosen WiMAX as their 4G technology instead of Rev. C and will start with the rollout of the network in 2007.


In the end I am quite convinced that at least two technologies will gain global traction. If WiMAX is one of them, and I am quite convinced that it will be, there will be even more competition in the wireless domain than today. The disadvantage of WiMAX of not having a network legacy could in the end be a major advantage. It will allow new companies to enter the market more easily and thus increase competition, network coverage, services and hopefully decrease prices.

Podcast: Wireless Operator Landscape in Spain

It seems that creating podcasts has drawn me into its ban. After producing my first podcast back in July with Debi Jones on the US Wireless Carrier landscape, I’ve virtually ventured out to Spain this time and had a discussion with Rudy de Waele of In the podcast we chat about his thoughts on the wireless operator landscape in Spain and how things are changing. I hope operators see it as constructive criticism.

Topics of the podcast:

  • Wireless Internet prices in Spain and recent changes
  • Usage scenarios
  • On portal / off portal strategies
  • Block mobile Internet access for your kids?
  • Nokia’s new web browser in N-series phones
  • Topics for the next Mobile Mondays in Barcelona

Podcast with Rudy de Waele.mp3 – 33 mins.

GSM + WLAN VoIP phones now on the market

It might be CTIA time in the U.S. but here in Germany, the IFA (Internationale Funkausstellung) has also brought a couple of very interesting news. Previously, I thought that it would probably be high end phones such as the Nokia N80 and free VoIP (SIP) providers who would be the first to introduce fixed/mobile convergence cellular / WLAN phones. Instead, two carriers, the German Telecom (T-COM) and Arcor, the fixed line branch of Vodafone in Germany, have launched GSM/VoIP phones and services at the fair. Looks like fixed/mobile convergence is starting to happen.

Second surprise: Instead of using high end and expensive smart phones, the services were launched with low end, no-name GSM phones with only rudimentary functionality beyond GSM and WLAN. Here’s a link to an article on the topic (sorry, in German only).

While at home, the phones can use the Wireless LAN and DSL connection to the Internet. When roaming outside the reach of the WLAN hotspot the phones act as a standard GSM phone. I’d love to get my hands on them as the article above does not mention important technical details like for example if the phones can be reached via WLAN and GSM at the same time. Also, no information on standby and talk times are given.

Interesting possibilities will open up once alternative SIP providers see the opportunity: Only a single phone for home and away use and ‘free’ calls (let’s forget the fee for the DSL connection for a moment…) to friends who use the same SIP provider as long as I am close to a WLAN hotspot.

It looks like fixed/mobile convergence phones could become the playground for operators to develop their expertise for future VoIP services. This will make it easier for them to introduce wireless VoIP phones in the future which do not only use VoIP over WLAN access points but also over 3G and 4G wireless networks. For background information on this topic take a look here for SIP over wireless and here for IMS over wireless.

Finally, I think the UMA (Unlicensed Mobile Access) guys will probably not be very happy about this development. While the convergence phones presented here use WLAN for true VoIP over SIP, UMA phones use WLAN access points to emulate a cellular network base station. Why make it some complicated when pure SIP over WLAN also works fine? Surely worth a thought. For those of you not familiar with UMA technology, here’s a short overview.

It happened faster than I thought. So, Nokia, were is that SIP client for WLAN N-series phones? (Note: There’s already a SIP client built into E-series phones such as the E61. Take a look here)

Further background information:

  • This link leads to a PDF document which explains (again in German) how to configure the WLAN and SIP settings for one of the phones.
  • A review of the T-Com phone (sorry, in German).

4G Overview: WiMAX, UMTS LTE and EVDO Rev. C

This blog entry is the third in a row about my thoughts on the current development of 4G wireless standards. You might want to take a look at the introduction before reading on.

There are two main goals of 4G wireless systems. First of all, more bandwidth will be required for the reasons explained in the previous blog entry on this topic. Secondly, 4G networks will no longer have a circuit switched subsystem as current 2G and 3G networks. Instead, the network is based purely on the Internet Protocol (IP). The main challenge of this design is how to support the stringent requirements of voice calls for constant bandwidth and delay. Having sufficient bandwidth is a good first step. Mobility and Quality of Service for a voice connection is clearly another and taking a look at these topics is better left to another article series. So let’s focus on the additional bandwidth 4G networks are to deliver. Before taking a closer look at individual technologies, here is what they will all have in common:

Currently, 3G networks are transforming into 3.5G networks as carriers add technologies such as High Speed Data Packet Access (HSDPA) and High Speed Uplink Packet Access (HSUPA) to UMTS. Similar activities can be observed in the EVDO world. Staying with the UMTS example, such 3.5G systems are realistically capable of delivering about 6-7 MBit/s in a 5 MHz band. Numbers which are twice as high are circulating as well. However, these speeds can only be reached under ideal conditions (very close to the antenna, no interference, etc) which are rarely found in the real world.

4G networks will go far beyond this by mainly improving three things:

  1. Air Interface Technology: 2G networks such as GSM use Time Division Multiple Access (TDMA) on the air interface. 3G networks made a radical change and use Code Division Multiple Access. 4G standards will make another radical change and will use Orthogonal Frequency Division Multiplexing (OFDM). The new modulation itself will not automatically bring an increase in speed but very much simplifies the following two enhancements:
  2. Channel Bandwidth: 2G systems such as GSM use a channel bandwidth of 0.2 MHz. UMTS made a great leap forward and uses 5 MHz. 4G systems will use a bandwidth of up to 20 MHz, i.e. the channel offers four times more bandwidth than channels of current systems. As 20 MHz channels might not be available everywhere, most 4G systems will be scalable, for example in steps of 1.25 MHz. It can therefore be expected that 4G channel sizes will range from 5 to 20 MHz.
  3. MiMo: The second method to increase throughput on the air interface is to use a technology called Multiple Input Multiple Output, or MiMo for short. The idea itself is simple, the maths behind is everything but. The idea of MiMo is to use the phenomena that radio waves bounce of objects like trees and buildings and thus create several wave paths from sender to receiver. While this behavior is often not desired, MiMo makes active use of it by using several antennas at the sender and receiver side, which allows the exchange of multiple data streams, each over a single individual wave front. Two or even four antennas are foreseen to be used in a device. How well this works is still to be determined in practice but it is likely that MiMo can increase throughput by a factor of two in urban environments.

Increasing channel size and using MiMo will increase throughput by about 8-10 times. Thus speeds of 40 MBit/s per sector of a cell are thus possible. Other articles will claim even more but again these numbers can only be reached under ideal conditions which are usually not found in a real environment. Sophisticated base stations use three or even four individual sectors which results in a total throughput of a single base station of up to 120 to 160 MBit/s. Not bad by today’s standards.

So much for the technical details for the moment. Let’s look at who’s going to put the nice numbers above into real products. Three different standards are being put together at the moment:

  • WiMAX, aka IEEE 802.16e: Air interface specs are already pretty well put together and the technology definitely has a technical lead over the competition as far as this is concerned. The WiMAX forum [LINK] however is still working on standards for the radio access network and the core network which narrows its lead over other technologies.
  • UMTS Long Term Evolution (LTE): This standard is developed by the Third Generation Partnership Project (3GPP), the same standards body already responsible for the GSM, GPRS, UMTS and HSDPA standards.
  • EVDO Rev C. (also dubbed DORC): This standard is developed by the Third Generation Partnership Project 2 (3GPP2), the body responsible for CDMA and EVDO.

So why are there three standards, wouldn’t a single standard be enough? The short answer is “Well of course not”. The long answer is somewhat more complicated so I’ll leave this to part four of this mini series.

Why is there a need for 4G?

This blog entry is the second in a row about my thoughts on the current development of 4G wireless standards. You might want to take a look at the introduction before reading on.

The primary question when looking at future 4G systems is why there is or will be a need for them. Looking back only a couple of years, voice telephony was the first application that was mobilized. The short message service (SMS) was the first data application that was mobilized as a mass market application. By todays standards comparably simple mobile phones were required. Also, bandwidth requirements were very small. In a way, the SMS service was a forerunner for other data services like mobile eMail, mobile web browsing, mobile blogging, push to talk, mobile instant messaging and many others. These were enabled by the introduction of packet based wireless networks that could carry IP data on the one hand and more and more powerful mobile terminals that could cope with the requirements of these applications on the other. Today, current 3G and 3.5G networks are able to cope quite well with these applications as they offer a sufficient bandwidth per user. Also, network capacity is still not an issue as only few people use these services today. Having said that, there are a number of trends which are already visible today which will increase bandwidth requirements in the future:

  • Rising use: As prices get more attractive, more and more people will use wireless networks for data applications. Consequently, bandwidth demand will rise.
  • Multimedia content: While first attempts at mobilizing the web resulted in mostly text based web pages only, embedded images are now the norm rather than the exception. A picture says more than a thousand words but it also increases capacity requirements. Video and music downloads are also starting to become popular which again increase bandwidth requirements.
  • Mobile Social Networks: Similar to the fixed line Internet, a different breed of applications is changing the way people are using the net. Before, users were mainly consuming content. Blogs as well as podcasts, picture- and video sharing sharing sites are reshaping the internet as users suddenly do not only simply consume content anymore but also create their own content which they want to share with others. Applications like Shozu and Lifeblog, for example, allow to create content on the mobile phone and upload them to the web in an easy fashion. Especially picture-, podcast- and video up- and downloading is multiplying the amount of data users send and receive.
  • Voice over IP: The fixed line world is rapidly moving towards Voice over IP these days. I expect that in 5 years from now traditional fixed line circuit switched voice networks will be on a massive retreat and a fair percentage of users will use VoIP, e.g. over DSL or cable, as their primary fixed line voice service. The circuit switched market is already pretty much dead as operators are no longer investing in this technology. The same is happening in wireless, although there is one major issue: VoIP requires much more air interface bandwidth than the super slim voice codecs which are currently used for circuit switched voice calls over wireless networks. The air interface has been optimized on all layers of the protocol stack for circuit switched voice. The same is not possible for VoIP as the IP stack is a general data transmission stack and thus it can not be optimized for voice. The only solution is to increase the available bandwidth.
  • Fixed line Internet replacement: Voice revenue in both the fixed line and the wireless market are on the decline. In many countries, operators are trying to compensate by offering Internet access for PCs, notebooks, etc. over their UMTS/HSDPA or CDMA networks. Thus, they have started to compete directly with DSL and cable operators. Again, this requires an order of magnitude of additional bandwidth on the air interface.
  • Competition from alternative wireless Internet providers: In some countries, alternative operators are already offering wireless broadband Internet access with WiFi or (pre-)WiMAX 802.16d networks. Here’s an example of a small operator which offers wireless broadband access for a rural region in Austria. As such they directly compete with traditional UMTS and CDMA carriers who are also active in this market.

When combining these trends, it becomes quite clear why operators and standards bodies are pushing for ever faster wireless data networks.

In my next blog entry on this topic, I’ll take a look which technologies are competing for dominance in the 4G space. The most likely candidates to me are UMTS LTE, CDMA Rev-C and WiMAX.

The Race For 4G Wireless

While most wireless operators are still struggling to understand how to properly monetize their third generation wireless networks, the race for fourth generation network technologies has already begun. This is not a contradiction as current 3G networks will be operated and enhanced for many years to come. Furthermore, specification, development, rollout and mass production of 4G devices all take their time. Thus, most 4G systems are at least five years or more away from the mass market. So why will there be a need for 4G networks and which standards are competing on a global scale? Also, which of those are the most promising candidates for different kinds of operators? I’ve been thinking about these questions for a while now and will put my thoughts into a number of blog entries which I will add over the course of the next couple of weeks:

Steve’s doing the Carnival Of the Mobilists this week

Steve Litchfield, also known for his great S60 reviews over at All About Symbian and of course from his web site is hosting the Carnival of the Mobilists this week. For those of you who don’t already know, the CoM is THE ressource which covers the best blog entries on mobile of the past week. I feel especially honored this week as Steve’s chosen my submission for the Carnival as best entry of the week. Thanks very much!