Wireless VoIP Demystified – Part 3: IMS

Wireless VoIP is a hot topic at the moment and the name is used for quite a number of different technologies. In this mini series on my blog I’ve already taken a look at UMA in part one and SIP in part two. This entry takes a closer look at the IMS, the IP Multimedia Subsystem.

In very generic terms, SIP as described in part two is the core of the IMS. In addition, the IMS standardizes a number of additional functionalities:

  • SIP is the abbreviation for Session Initiation Protocol. As it is just a session (e.g. voice call) initiation protocol, it does not contain any mechanisms to ensure Quality of Service or a certain bandwidth of the connection. While fixed networks usually have enough bandwidth available to ensure the quality of a call, things are  different in mobile networks. Here, bandwidth to and from a subscriber is limited. In addition, the total bandwidth of a base station that has to be shared by all users of the base station is also limited and much scarcer than in the fixed line world. To ensure that a voice or video call established with an IMS capable device is maintained with a good quality of service (e.g. jitter, latency, etc.) and that a sufficient amount of bandwidth is ensured for the call while it is established, the IMS contains mechanisms to communicate with the radio network to ensure enough bandwidth is reserved during the call.
  • IMS standardizes authentication and encryption of SIP commands and responses in the network.
  • IMS standardizes how media gateways are controlled to enable SIP clients to establish connections with legacy circuit switched fixed line and wireless clients.
  • IMS standardizes the access to the Home Subscriber Server (HSS, aka HLR) in the GSM/UMTS/CDMA network.
  • IMS standardizes what kind of information is put on the SIM card of the subscriber and in which way.
  • IMS standardizes the codecs used for different services (e.g. voice codecs, video codecs)
  • And very important: IMS standardizes a service framework and a protocol between the IMS core and application servers that allows third parties to create new services based on IMS and SIP commands. Such services are for example instant messaging, presence, voice mail, video mail, location based services, short dialing numbers, private dialing plans, music and video streaming, push to talk, etc.
  • And last but not least: IMS standardizes how to get billing information because after all, operators want to make money with it.

By standardizing all of these aspects it is ensured that an operator can buy different parts of the overall IMS solution from different vendors. In turn, the architecture also ensures that application developers can design new applications for a standard platform and can then sell their products without customization to many different network operators. Furthermore, this approach ensures that IMS systems of different operators can interoperate with each other. This is a fundamental requirement to enable calls between different national and international operators without using media gateways.

Want to know more? Here’s a good book on the topic that I can recommend as it was great fun reading it: "The 3G IP Multimedia Subsystem" by Gonzalo Camarillo and Miguel A. Garcia-Martin. It’s in it’s second edition already after only a year so I guess I am not the only one who likes it.

My 5 cents on Google Mobile’s Content Transformation

The Blogsphere has been in turmoil lately discussing Google’s approach to transform web pages to make them better suited for viewing on small screens of mobile devices. The main problem most people (content providers) see is that adds get dropped which thus has a negative impact on their business model. So here’s what I think about this from my (the consumers) point of view.

For easy reference, here’s a link to Russell Buckley’s blog entry on the topic which has attracted a lot of attention. And here’s a link to a blog entry at WAP Review on how Google Mobile works.

From the consumers point of view, probably 99% of the web content today is not mobile optimized (including this blog, shame on me, shame on Typepad) when requested from a mobile device. Most of this content can not be displayed correctly on a small device today. Recently, some mobile browsers have appeared on the market that render a complete page correctly and show you a small portion on it. I have my doubts that this makes it really usable. Also, mobile phone rendering capabilities are very limited and I simply don’t have the time to wait for the download of a full page and don’t have the deep pockets required for the amount of data transferred.

I often read blogs on my mobile phone with a great program called Resco News. Often enough an interesting blog entry is not contained completely in the RSS feed or has some interesting links to follow. In this case I am stuck on my mobile phone without Google Mobile’s help. With Google Mobile, however, I can get the complete blog entry and can also follow the link no matter if the page is mobile optimized or not (and most are not).

Sure, if the web page is already delivered in a mobile optimized format then Google should just pass it through without modifications. Thus, graphics in general and adds in particular that behave in a mobile friendly way stay in. I guess this is not so difficult for Goggle to do. They could fetch the page from the original web server pretending to be a mobile phone. In case the server returns a gigantic page with heavy graphics, java script, etc. then kind of a "self justice" has to kick in and the page needs to be stripped down to something usable on a mobile device. Sorry if some content is lost on the way but it is still much better than not to get the page on the mobile at all.

So here’s the essence of my opinion in other words: If the content provider does not adapt content for mobile viewing, then somebody else has to do it to make it usable on small devices. If on the other hand the content provider is willing to include mobile devices in his design then the page should be handed down to the small device unaltered.

P.S.: Some people argue that it is "evil" to modify content without permission. Well, then I guess most desktop web browsers with popup blockers and mobile browsers without Java script and full HTML capabilities are just as "evil" as Google Mobile as they alter the page as well.

Carnival of the Mobilists 19 is out!

How quick the week has passed again, quite unbelievable… This weeks Carnival of the Mobilists, the best ressource of blog entries written by the mobile community, is now online at the blog of C. Enrique Ortiz. Great job, Enrique, thanks a lot!

If you have a blog entry of your own you would like to be included in the Carnival next week, send an eMail to mobilists at gmail.com no later then next Wednesday and have a look at Mobhappy, founder of the CoM. See you next week!

3G in the Eurostar

The Eurostar in Paris
The Eurostar in Paris
3G has made it into the digital world
3G has made it into the digital world

Eurostar track in Britain
Eurostar track in Britain
University in Stoke on Trent
University in Stoke on Trent

I am on the move again, this time on my way to Britain with the Eurostar from Paris to London. On the French side, EDGE coverage was quite good (I have no UMTS subscription in France, I can only use the EDGE) and I managed to get most of my work done and eMails out before we even got to the channel tunnel. No coverage in the tunnel, so 20 minutes of rest 🙂 On the other side of the tunnel, UMTS coverage by Orange was quite fantastic. I didn’t see a single network loss. Looks like they must have installed dedicated UMTS coverage for the Eurostar Railway track. Well done Orange!

The coverage from London to Stoke on Trent on the Virgin train was somewhat more patchy, so certainly no dedicated coverage on that track. However, there was 3G coverage in many places during the trip so looks like the UMTS coverage in the U.K. is quite advanced compared to France. Also good UMTS coverage in Stoke by several network operators.

Work Goes Mobile – An Interesting Book

It has sort of become a tradition for me to bring back a book on wireless from the 3GSMWorldCongress. This year, I’ve picked a somewhat unusual book for me as it is not about a particular technology but about how technology can enable work to go mobile. The book is called “Work Goes Mobile” and the three authors discuss the ongoing process at Nokia to mobilize their workforce. This blog entry is not intended as a full book review but rather for me to write done some thoughts about topics in the book that were of particular interest to me. Having said that I can recommend the book very much and further information about it can be found here.

Topics and statements in the book I found useful and some comments from my side:

Mobility is more than a technology: Mobilizing a business means to embed mobility into the fabric of a business.

Mobilizing a business has three dimensions
which need to be addressed: People, process and technology.

Zero latency: The aim of mobilizing a business is to come as close to a ‘zero latency’ process as possible. In other words, a process is optimized to contain as few disruptions as possible due to inefficient communication. E.g. writing down a failure report on a piece of paper that is manually put into a CRM system a couple of days later.

Good and bad sides of mobility
: The book discusses pros and cons of mobility and addresses prejudices and perceptions of workers on introducing new processes generally and mobility specifically.

Freedom of choice: One statement I particularly liked: “Mobility is about freedom of choice – it’s not a forced directive to work 24/7 but an individual decision to work when and where it is most appropriate”. Sometimes this is easier said and done and involves a learning process for both the mobile worker and the management that needs to understand how to manage mobile workers. Both mobile work and managing mobile workers are fundamentally different from working on a desk and managing desk bound workers.

The book is technology neutral: Even though written by Nokia employees and copyrighted by Nokia the book does not try to push any kind of Nokia devices or services. I like this approach very much as I find books, brochures, or articles written companies which only aim at pushing their products rather tiring.

Mobility is not an end state but an evolving process.

Workload management: Mobility is not intended to increase workloads. It helps workers to be as efficient as possible in the time they dedicate to their work. In general this is true but requires a management that understands this one the one hand and a good amount of self control to balance private and work time.

Challenges to Mobility: There are plenty and I like the discussion of how to overcome/deal/change/improve reluctance to change, management competency to deal with a mobile workforce, mobile workplace challenges, operation support, self management, family, processes.

Benefits: Mobility brings quantitive and qualitative benefits and one should be aware of both. A quantitive benefit can be measured in monetary terms, e.g. reduced time to spend on paperwork increases the number of cases a mobile field worker can deal with a day. Qualitative benefits are things one can not measure in such a way. Examples are increased employee satisfaction because of increased flexibility, freedom, etc., or increased customer satisfaction due to faster response times and quicker problem solutions.

This book is quite an eye opener for me as I mainly deal with the technical domain on a day to day basis. The book shows, however, that this is just one of many dimensions that need to be addressed to mobilize businesses in particular and people general.

P.S.: Daniel, this book could potentially be very interesting for you, too!

Carnival of the Mobilists – 18

I feel greatly honored to host this week’s edition of the Carnival of
the Mobilists, featuring the most interesting posts of mobilists submitted this
week. In the best tradition of a mobilist, I exchanged eMails with Russel
Buckley leading to this on my notebook and smartphone in various airports and
taxies while traveling to Portugal. As you can see in this week’s Carnival
once again, there are great ideas out there on the future of the mobile Internet:

  • Mobile Application Development: Kelly Goto
    has written an interesting post this week on mobile application
    development in which she goes into the details of why " […] How,
    when, why and most importantly – where interaction takes place […]"
    are major things to consider during the development process.
  • MVNO Strategies: Two entries this week on MVNOs (Mobile Virtual Network Operators): Carlo Longino gives us his thoughts on the business case of content MVNOs in his post called "Selling Dollars for a Dime". In another post, C. Enrique Ortiz takes a look at strategies of different MVNOs and gives us his thoughts on adoption curves for new services and service uptake.

  • The Phone is the Key: Jim Downing over at Smartmobs reports on a new system in Japan that lets people use their RFID enabled mobile phones as virtual house keys. RFID is a hotly discussed topic for a while now and this is one of the positive applications of the technology.
  • New Lifeblog version: It’s CeBIT time and lot’s of companies show their new products. Nokia is no exception, launching their latest version of Lifeblog. Stuart Mudie has taken a look and gives us his thoughts.
  • Mobile Internet and Politics: Justin Oberman has sent me a link to his recent blog entry where he reports about what some people do not get about the political mobile buzz
    during the recent "Politics Online" conference. He was invited
    as a speaker to talk about the mobile Internet in politics.
  • Mobile Gadgets on the Run: John Sun reviews the Garmin Forerunner 2005 runner’s watch and it’s cool functionality when combined with Google Maps. Still needs the PC to connect to the net but other products with that capability are not far away.
  • LBS Overview: Denis of Wap Review has written a great article on the how location based services work and how the U.S.’s E911 requirements have helped to bring the infrastructure in place not only for emergency services but also for great public LBS services. He does not stop there though and goes on to describe LBS in other parts of the world as well.
  • Women in Mobile: My favourite post of the week: Rudy De Waele continues his great series on interviewing women in mobile with an interview of Keren Flavell. His post contains interesting thoughts from ‘down-under’ in Australia! I very much liked the interview and Keren’s mobile technology podcasts on her website.
  • Service Discovery: Troy Norcross says that operators are not doing a good job in promoting their services because they only push their platform and not individual services.  In his recent post he shares some interesting thoughts on this topic .

And finally, my own post for this week is part two in my mini-series on different mobile VoIP systems, their applications, and their pros and cons. This week’s blog entry is on SIP and its use in the wireless word.

Next week, the Carnival
will be hosted by C. Enrique Ortiz. Make sure you’ve submitted your entry to “mobilists
(at) googlemail.com”
by next Wednesday.

I hope you’ve enjoyed this week’s selection and I wish you a happy weekend,


Moblog: 3G prices in Portugal

Never seen as many 6630 in one place as in Lisbon
Never seen as many 6630 in one place as in Lisbon

After having noticed that UMTS networks are quite used for data in Lisbon, I went to a mobile shop today to ask for prices for UMTS Internet access. The person in the TMN shop told me that they sell UMTS notebook PCMCIA cards for 99 euros which can be used with different service options:

1) The card can be bought with with a service contract that can be canceled on a month´s notice with no minimal contract duration. It includes 2 GB of data traffic for 29.90 Euros a month.

2) Same conditions with a one year contract and the 2 GB are only billed between 5 p.m. and 7 a.m. During the day you surf without limitations. Not quite sure how that makes sense but that´s what he said even when I asked him to confirm.

Good prices, no wonder UMTS is used in this country.

Trip to Portugal and usage of 3G networks in Lisbon

Postal Service in Portugal?
Postal Service in Portugal?
Famous trams in Lisbon
Famous trams in Lisbon

A theater in Lisbon
A theater in Lisbon
Eifel elevator in Lisbon
Eifel elevator in Lisbon

Here are some pictures I took during my current trip to Lisbon in Portugal. My network analyzer shows quite some 3G packet data activities in the UMTS cells my phone uses from the hotel room. Also, I see lots of people in the streets using 3G phones for making phonecalls. The Nokia 6630 seems to be very popular here. As you can see in the pictures though, Lisbon has much more to offer than well functioning and used 3G networks…

Wireless VoIP Demystified – Part 2: SIP

In the first part of this mini-series on Mobile VoIP, I’ve taken a look at UMA as one of the many flavours of Mobile Voice over IP (VoIP). This part is dedicated to the Session Initiation Protocol (SIP) architecture and how it can be used in mobile devices.

SIP Architecture

SIP is a true end to end VoIP system and has been initially conceived without mobile networks in mind. Today, it is already widely adopted in the ‘classic’ Internet as one of the main protocols for VoIP. The basic architecture of SIP is simple: A SIP server in the network forms the central element of a VoIP network. VoIP clients are either software clients on PCs or notebooks or standalone devices like phones with an Ethernet port. When connected to an IP network their first task is to register their IP address with the SIP server. To call another device, a SIP client then sends a request to the SIP server. The SIP server then retrieves the IP address of the destination device from its database and contacts the destination device. If the destination device is willing to accept the call, the server informs the originator of the IP address of the destination device and a direct IP connection is established between the two parties. For VoIP, the connection is used to carry a voice data stream. Note, that the SIP server is only required for signalling as the voice stream is directly exchanged between the two parties. This is a big difference to circuit switched voice calls which are always routed through a switching center of a fixed or mobile operator. To call non VoIP destinations, gateways are used to convert the IP voice data stream into a 64 kbit/s circuit switched voice data stream.

SIP is more than just Voice Telephony

As the name Session Initiation Protocol (SIP) already implies, it is not limited to setting up voice sessions. More sophisticated clients also use the protocol for video telephony or the exchange of other multimedia data such as Instant Messaging, pictures and file transfers in general. These functionalities, however, are only available if both clients support them.

Comparison to UMA

While UMA (see part one of this series) only replaces the GSM air interface with Wireless LAN and IP, SIP is a true end to end voice over IP system offering a wide range of applications from voice, to video, and to rich multimedia applications like instant messaging and file exchange. Also unlike in UMA, the user is not bound to the mobile operator but can select from an abundant number of SIP server operators on the Internet.

SIP in the Wireless World

In the wireless world, SIP has not been very popular so far due to a number of wireless network limitations. GPRS and other first generation wireless IP packet networks are too slow and the latency of the connection was too high. In addition, speech algorithms used by current SIP implementations use inefficient codecs which require a substantial amount of bandwidth. 3G networks such as UMTS offer higher bandwidths compared to earlier networks and are thus able to carry SIP voice calls over the air interface. A SIP call, however, uses around five times more bandwidth then a traditional circuit switched mobile voice call for which very bandwidth efficient codecs are used in the radio network. This fact together with the openness of SIP for the user to choose the operator of the SIP server himself explains the reluctance of wireless operators to support the application of SIP services in their 3G networks.

The Future of SIP in the Wireless World

In the near future, SIP clients will mostly be adopted on GSM/UMTS/Wifi smart phones such as the Nokia N80, where they can be used to make phone calls over a Wireless LAN access point connected to DSL or a company network. In effect, a SIP client in the mobile phone can replace the fixed line phone at home and I am actually waiting for the day when I can use a single phone at home and when underway.

When leaving the office or home, a SIP client can still be used for voice calls but many operators (carriers) try to restrict SIP for the reasons discussed above. Very near term evolutions of 3G networks to technologies like HSDPA (High Speed Data Packet Access) might change these policies in the mid term.

SIP also forms the core of the IMS (IP Multimedia Subsystem), a standard designed by the mobile industry for mobile operators to offer their own VoIP and multimedia applications. IMS will be the focus of part 3 of this mini-series, so stay tuned…