Author: Martin

Mobile Web Megatrends Conference in Berkeley

Mobile Web Megatrends
Do you know Ajit Jaokar and Michael Mace? If not I suggest to head over and check out their blogs (here and here) for great insight into the mobile domain. Or, even better, use the opportunity to meet them in person on the 8th of September at the University of Berkeley, California at the Mobile Web Megatrends Conference on September 8th, 2008. Topics of the conference range from mobile browser evolution, browser offline capabilites, advertising models, the iPhone (of course…), mass market impact with Nokia's S40 6th edition, cloud computing, etc. etc.

Lots of other great speakers, I let the conference's web site speak for itself.

Definitely a conference not to miss if you can make it. Unfortunately my calender is already booked for that date so I won't be able to make it. But good for you since I have one free ticket to give away! First come first served.

1st Anniversary of the Prepaid Wireless Internet Wiki

A year ago, I decided to share my knowledge about how to stay connected to the Internet while on the move with prepaid SIM cards. A Wiki looked like the best solution for the info I had on about four or five different countries. Pages can easily be changed because offers are changing frequently and I was speculating that others might put there info in there as well. Now a year later, I have to say the result is stunning!

  • My initial 4 or 5 pages have expanded to 85, most supplied by others.
  • Entries now range from North and South America, Europe and Asia to Australia.
  • In July 2008, the Wiki had 12.000 page hits from 6.000 different visitors, that's about 200 visitors a day.

I am very happy because my willingness to share has actually brought me great new tips I was not aware about. Especially the following have been invaluable to me personally:


So thanks to all of you how have added your information to the Wiki and to those who that keep the pages up to date in this quickly changing market. Together we have created an invaluable source of information for travelers!

How To Extend SIP For Mobile Networks

In the fixed line world, the basic Session Initiation Protocol (SIP) has become quite popular for offering voice telephony service. Lots of companies such as Vonage, Siptel and DSL providers are making use of it today. So why are we not using SIP in 3.5G and 4G networks as well? I guess there are both policital and technical answers to this question. From a technical point of view there are a few features missing that are essential in wireless networks:

– Voice codecs: Current SIP implementations usually use G.711 voice encoding which produces a 64 kbit/s data stream. Transported over IP the total bandwith requirement per direction is 80 kbit/s. Compared to the effient codecs used in wireless networks today such as 12.2 kbit/s AMR with a similar voice quality this is quite a lot and significantly reduces the number of simultaneous voice calls per cell. The current voice architecture uses a transcoder between the radio network and the core network to restore G.711 compatability. So from a capacity point of view, using G.711 in the radio network is probably not a good idea and would meet the resentment of most operators. So from my point of view we need AMR capable mobile SIP clients and transcoders in the network to reach non AMR capabale (fixed) SIP clients and circuit switched networks. Note that such transcoders are already present in the SIP networks today, usually as media gateways between the SIP world and the classic circuit switched world to which most people are still connected to with their fixed line and mobile phones.

– We need to get rid of NAT and STUN: Most mobile operators use private IP addresses for their customers. This requires Network Address Translation (NAT) which in turn unfortunately requires frequent polling packets to the SIP and STUN (Simple Traversal of UDP through NAT) server. These packets keep the connection to the network open continuously but drain the battery of a mobile device very quickly. The solution to this issue is to use public IP addresses and to ensure that keep alive messages are removed from the SIP implementation as much as possible. With the lack of sufficient public IPv4 addresses this will require IPv6 at some point.

– End to End – Encryption: All SIP clients I use today do not encrypt signalling or the voice call itself. With freely available tools such as Wireshark, calls can easily be traced and recorded. While circuit switched networks are reasonably secured it is difficult to ensure there are no unwanted listeners in the route in public IP networks.

– The missing link: Handover to 2G circuit switched connections when running out of coverage. This one is very difficult to do. Sure there is VCC (Voice Call Countinuity) for IMS but the complexity both in the network and the mobile device is significant. I have to admit I have no easy solution for that.

Are there other essential SIP extensions that you, fellow readers, can think of to enable SIP for mobile networks without going to a full blown IMS implementation?

Linksys launches a simulatenous 2.4 and 5 GHz Wi-Fi Access Point

Good news on the Wi-Fi front: Linksys has launched the WRT610N access point, which simultaneously operates in the 2.4 GHz band for current 802.11b/g devices and in the 5 GHz band for new 802.11n devices that support the so far little used frequency band. Should make the transition to the new frequency band much easier, especially if more vendors do the same in the future and integrate it with DSL modems!

From a technical point of view it's interesting to note that the data sheet says each band has it's own set of three antennas (I guess to support MIMO).

Have You Heard of WIPI?

In a report I read today I learnt that WIPI (Wireless Internet Platform for Interoperability), a mobile device runtime environment for applications similar to BREW and JAVA, is mandated by the Korean government to be included on any mobile phone sold in Korea that allows Internet access.

An interesting way to prevent companies such as Nokia, SE, Apple and others to sell their devices in Korea. In the past there were only CDMA based 3G networks available in Korea so this technology dispute was mainly between Korea and the US (hello Qualcomm…). As some Korean operators have now transitioned from CDMA to UMTS the issue now gains a more global dimension.

While these UMTS networks now theoretically enable Nokia, Sony Ericsson, Apple and others to sell their devices in Korea, the WIPI ruling prevents that from happening. But it looks like some operators have become rather unhappy and are asking for lifting the WIPI ruling. Lots of questions poping up here:

  • I wonder if there is a black market in Korea for such phones today?
  • Not sure if such phones would even be desired at the moment due to the probably missing Korean language integration and also due to the sophistication of LG/Samsung phones.
  • Also, I wonder how widely WIPI is used at the moment, is it seen as an integral part by a large user base?
  • In case the application environment is very popular I wonder if lifting the WIPI ruling would have an immediate effect if people would not buy devices without it.

Fellow readers in Korea, what do you think?

Do you have a wireless BHAG?

Recently a friend made me aware that companies should have a BHAG, a Big Hairy Audacious Goal to be successful and to motivate employees! I found this a rather intriguing way of looking at things and this article on Wikipedia gives some details and also some good examples of BHAGs.

BHAGs in the wireless domain I can see today are for example:

  • David Wood’s vision of Symbian to become the most widely used operating system in the world.
  • Nokia’s mission to become an Internet company.

What about your company? Do you have a BHAG?

IMT-Advanced (4G) Submission and Evaluation Process

News from the ITU (International Telecommunication Union) on 4G, aka IMT-Advanced: In a recent meeting it was decided that technology has now moved sufficiently beyond enhanced 3G systems (such as UMTS HSPA, WiMAX, CDMA1xEvDo also called ‘enhanced IMT-2000 systems’ in ITU terms) that the selection process of suitable technologies for 4G can now begin. In a paper, the ITU describes the steps that will now follow and the time frame they see for the process:

  • 2008 – beginning of 2009: Companies can submit proposal for candidate technologies. I guess 3GPP’s LTE Advanced and IEEE’s WiMAX 802.16m are hot candidates. Let’s see who else will come up with something.
  • Up to 2010: Evaluation of the proposed technologies
  • Mid-2010: Decision will be made which systems will get the IMT-Advanced stamp

A further interesting note is that the new documents now published by the ITU do not specify any new technical details concerning the properties of future 4G systems. Instead, they just reference ITU-R M.1465, which has been around for some time now, which calls for data rates of 100 MBit/s while moving and 1 GBit/s while stationary.

Via LTE Watch

Wi-fi Hotspots Are Spreading But Network Management Is Not Keeping Up

It’s rare that I use public Wi-Fi hotspots since for me, mobile Internet access via a cellular 3G network is usually a cheaper and more flexible alternative. But every now and then I just log on to them to see how much users are charged for connectivity. These days, however, more often than not, the Wi-Fi hotspots I log on to are not working as they should. Either I don’t get an IP address (in one instance Wireshark showed that the DHCP server returns failure messages because the IP address pool is exhausted), the portal page fails loading which probably means the backhaul link is broken or the speed is so abysmally slow (for whatever reason) that any meaningful use of the service is not possible. Yes, I am complaining! Or is it just something specific of the countries I travel to? Not that the reliability of 3G wireless networks is beyond complaint but I can still count the instances a network didn’t work on a single hand (and I travel to many countries in Europe).

Why They Should Cover This Office Building?

There is this new office quarter in a Paris suburb to which I go every now and then. 2G and 3G coverage is o.k. while being on the street but as soon as I enter one of the office buildings, signal levels of all networks drop like a stone in the water and in many meeting rooms I have little or now network coverage. Which network I receive depends on the part of the building I am in.

Well, this quarter is not so new anymore, operators had more than two years now to improve the situation. I am really puzzled why they haven’t done so!? There are tens of thousands of people working there and many must feel disappointed by the wireless network coverage they have at their desk. I guess many have in the meantime made the decision for which operator to go on their private phones depending on which network they can receive at their desk. And always living in fear of having to move to a new desk…

A bizzare situation. So listen up, dear network carriers, a lot of potential new clients are just waiting for that new antenna that gives them better coverage in the building they spend the major part of their time. A strong argument you don’t have to work very hard for next time that contract runs out… And if that is not enough, think of all the additional SMS messages, eMails and phone calls these people will use their mobile phones for once they can do so.

Vikuiti: To Be Seen Or Not To Be Seen

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3G networks offering me mobile Internet access at most places I go has definitely changed the way I work and where I work. Yet, there is also one big disadvantage: In some places people next to me can look at the screen of my notebook and see what is sometimes is not really for their eyes. Privacy is definitely an issue sometimes. A couple of weeks go, I thus bought a Vikuiti display filter from 3M that restricts the viewing angle. Since then, nobody is looking anymore and I get questions like “is your notebook turned on”? Very nice 🙂 The picture on the left proves my point. More resources:

  • Here’s a video of how it works on YouTube. Thanks 3M, not cheap, but very usueful.
  • And here’s a link to a recent 3GPP meeting with an interesting picture on the right. You can see who’s using a filter and who is not 🙂