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O.k., the winter chaos in Europe has gotten to me as well and I was stuck in various places waiting for planes and trains like many others. So while the situation was far from comfortable I noticed that being connected and being able to get information from online sources not only proved to be entertaining and useful, as I could get some work done while waiting but also helped to keep my mood up. Here are some things I noticed:

Congestion: In airport lounges, free Wi-Fi is sometimes provided, but it is usually quite congested and slow due to many people using it at once. Good when one has a 3G dongle and can make oneself independent from the rest.

Flight Status: Flight status reports are not accurate at all, neither online nor at the airport. It's interesting to observe that a flight status on airport information displays and also online is marked as "on schedule" until just one hour before departure when it then suddenly changes to indicate a two hour delay. I wonder why this is done that way as airlines do know better!?

In my case for example, the plane that would take me to Frankfurt was coming from Frankfurt in the first place. Online, the delay for that plane was visible while for the outgoing leg the flight status remained "on schedule". Most people have better things to do than to spend time at the airport when a delay of several hours that is clearly predictable would allow them to do something else in the city. So perhaps the airlines want you at the airport so they can judge who shows up for a flight and who doesn't!? In the age of email, twitter, instant messengers and other methods to stay connected, even automatically, it's an archaic way of organization.

Abnormal situations also reveal how flight status displays at airports are working. The system used at Istanbul airport, for example, is not updated in real-time at all. For my flight, which was 3 hours late, somebody forgot to update the system so at the "theoretically correct time" the display showed "boarding" and then "final call". Very nice, except there was no plane at the gate to board and no ground personnel to inform people of what was going on. Quite a confusion. Once the theoretical time for "final call" was over the display went blank, still no plane and still no ground crew at the gate. You can imagine the confusion. Unless, of course, the online information on your mobile device from your airline tells you the real story.

Getting a Hotel at Midnight: And the best use of mobile Internet connectivity is when you are stuck at the airport, figure out from the online schedule of the train company that the last train home has just left despite a massive delay and you start wondering how and where you'll spend the night. Hundreds of people are around you with the same problem and the picture of camp beds in a big hall springs to mind. But your online hotel reservation system tells you that there are many hotel rooms close to the airport still available. It could be just as fake as the online schedule displays but a call to one of the hotels quickly revealed that rooms were indeed still available. Interestingly enough, the hotels shown did not take advantage of the situation but offered the standard rates per room. Much better than spending the night at the airport.

Stay in bed longer: And finally, the next morning your mobile is your best friend when it tells you that the train you want to take home is either on time or delayed, so you know it's worth getting out of bed or if there is no real rush to get up.

Entertainment and connectivity: And all the while it also plays your favourite music, keeps you informed about what's going on in the rest of the world and you can call people back home and wished your travels were as quick and easy as that of those electrons and waves that carry your voice through the maze we call a telecommunication network.

Are you already back from vacation? If so, you might want to have a look at the program of the Mobilware 2011 conference being held in London this year from the 22nd to the 24th of June. As you'll see in the scope and topics overview below it's about advances in communication middleware, mobile operating systems, networking protocols and applications. So just my thing 🙂

The call for paper ends February the 1st, so if you have an interesting paper to propose, you have a couple of weeks from now to send your proposal. It would be great to see you there!

Conference Scope

The advances in wireless communication technologies and the proliferation of mobile devices have enabled the realization of intelligent environments for people to communicate with each other, interact with information-processing devices, and receive a wide range of mobile wireless services through various types of networks and systems everywhere, anytime. A key enabler of these pervasive and ubiquitous connectivity environments is the advancement of software technology in various communication sectors, ranging from communication middleware and operating systems to networking protocols and applications.

Topics

The conference solicits original technical papers, not previously published and not currently under review for publication elsewhere. Topics of interest include but are not limited to:

• New middleware concepts for mobile devices
• Cross platform application development
• Open terminal and network APIs
• End-to-end architectures for seamless service provisioning and deployment
• Integration of heterogeneous wired and wireless networks and frequency bands
• Interworking of mobile applications in mobile cloud environments
• QoS awareness, adaptation, and fault-tolerance of mobile services
• Opportunistic and delay-tolerant mobile and wireless networking
• Location-aware and context-aware networking and computing
• Energy-efficient applications and services and OS air interface management
• Mobility and handoff management
• Location and tracking supports and services
• Human-computer interface and portable 3D graphics for mobile devices
• Novel applications and communication protocols for wireless sensor networks, vehicular networks, and home networks
• Modeling, simulation, and performance evaluation of mobile wireless systems and services
• Trustworthiness, security, and privacy of mobile and wireless systems

An interesting but probably not well known functionality of the SMS system are delivery reports. By default, requesting delivery reports is usually deactivated in the mobile device, so few people know about it. On Symbian phones, delivery reports can be activated in the SMS settings. Once active, the SMS Service Center sends a report back to the originator as soon as an SMS has been delivered, which is then displayed for a couple of seconds on the screen and also put into the "Delivery Reports" folder in the SMS application. So while this feature works well for SMS messages to other subscribers of the home network, I was wondering if it also worked when sending messages to other networks, both national and international?

The quick answer is yes. I tested this by sending an SMS to a SIM card of another national network operator and to SIM cards from network operators in Italy, Spain, and for the ultimate test, Thailand. To ensure the delivery report is not only sent in some cases once the SMS is received at the service center I only switched on the phone with the respective SIM a couple of minutes after the SMS was sent. In all cases the delivery report came in right after the SMS was delivered, i.e. right after the phone was switched-on and the SMS was delivered.

So in other words, SMS delivery notifications work even for international SMS transfers.

Back in 2006, I published my first book in English (Communication Systems for the Mobile Information Society) on the different network technologies available at the time (GSM, GPRS, UMTS, WiMAX, Wi-Fi and Bluetooth). I've been more than pleased with the success and the feedback I got over the years. But things have certainly moved on since then so it was about time to release a second edition.

And things have progressed well, the second edition, now titled "From GSM to LTE – An Introduction to Mobile Networks and Mobile Broadband" is almost ready for shipping. I'm enormously happy I've finally managed to do it because a lot of things have changed in the past 5 years. Consequently a lot of additional material made it into the new edition:

In the chapter on GSM, I've included up-to-date information on the MSC R4 Bearer Independent Core Network architecture to which many network operators have migrated their circuit switched voice and SMS infrastructure over the last few years or are in the process of doing so. Little has changed in the GPRS/EDGE chapter but the UMTS chapter has been almost a complete rewrite. 5 years ago, 3GPP Release 99 with its dedicated channels was state of the art and HSDPA was just on the horizon (but already described in the book). In the second edition, I rewrote the chapter to put HSDPA and HSUPA in the focus instead of R99 dedicated channels, which are nowadays only used for voice and video calls.

And then of course, LTE is a must, so I've added a full new chapter that gives a solid intro to the new radio access technology and the new core network architecture and its interfaces to various other network technologies (GSM, UMTS, CDMA). The book then goes on and has a look at WiMAX, where not a lot has changed since the last edition. Some significant additions can be found in the Wi-Fi chapter, with new material on 802.11n, Wireless Multi Media (WMM), significant additions to the security section, etc. etc. And finally in the Chapter on Bluetooth I brought the text up to date with enhancements such as the new pairing variants.

As you can see, the updates are plentiful and it has kept me quite busy in the last couple of months. So if you are looking for one single resource that gives you a solid introduction to all these technologies, then this is the book for you! At the moment it's listed on Amazon for pre-order and it should become available in the next two weeks. And should you attend the Mobile World Congress in Barcelona in February and can wait a bit longer, you can certainly pick up a copy from the Wiley booth there as well. I'll be there on one of the days as well so make sure you'll come by in any case! More details on that later.

A friend recently commented that Apple doesn't seem to be active in 3GPP (but they are a member), the standardization body responsible for the development and evolution of GSM, UMTS and LTE. That is an interesting observation as not participating at 3GPP meetings means they don't have much of a say in future advances of the cellular radio interface and so perhaps see cellular connectivity pretty much as a commodity for their business in a similar way as Wi-Fi and Bluetooth. What about HTC, how active are they in 3GPP? Any others, that could potentially be in the same category? And yet another question on this subject, which standards bodies is Apple active in?

Recently, I've been to Istanbul and as I've never been in Turkey before I was quite interested to see how well the mobile networks would perform there. After all, 3G only started in Turkey in late 2008 so they haven't had much time to play catch-up.

To my delight, the networks performed flawlessly and 3G coverage was good in all except one place I was throughout Istanbul. The hotel I was staying in the Maslak district even had dedicated 3G indoor coverage from one network operator so Internet access even on the 17th floor was quick. Quite interesting to see that towards the windows, 3G interference quickly grew and speeds slowed down. However, just a meter or two into the room and around a corner, the interference from outside cells was gone.

The one coverage exception mentioned above is metro line 2 from Taksim square to Maslak. There is 2G coverage in the underground stations and in some parts of the tunnels but no timeslots have been configured for GPRS or EDGE!? I tried all three operators and they all had their GSM networks configured for voice only (+SMS) in the metro system. I have to admit I don't quite understand that!? I don't think its for security reasons and I also can't imagine that the Istanbul underground authority has never heard of mobile Internet on phones. So why? Anyone? Capacity perhaps but if so, they are just doing it on the cheap as other cities are very well capable of having sufficient voice and data capacity in the metro, with 3G no longer only an "over ground" technology.

Initially, I wanted to buy a local SIM for Internet access as I usually do but this time I decided to use my Vodafone Germany prepaid SIM and daily Websessions. That worked very well but was a bit more expensive than a local SIM card. Next time perhaps.

Over Christmas, I was staying at a place away from home that had predictably little network coverage. Right at the place where I was staying the network operator's coverage map had a peculiar hole. So I took a UMTS power amplifier with me that is available, for example at these places, for a less than 200 Euros.

And indeed, at that place I had no 2100 MHz UMTS coverage at all that could be detected by my devices and even 900 MHz GSM coverage was very weak. The power amplifier I brought along has a directional antenna with an opening angle of 60 degrees and a total gain of 7 dbi. Pointed towards the next city with a UMTS base station, my coverage jumped from nothing to -89 dbm and an EcNo of -4. Throughput reached was beyond 6 MBit/s in the downlink direction and 2 MBit/s in the downlink direction. Incredible!

The picture on the left shows the setup. For local distribution I used my Huawei D100 I bought a couple of years ago, basically a 3G to Wi-Fi bridge that uses a 3G dongle for UMTS connectivity. The dongle itself is in the cradle of the power amplifier that induces the signal it picks up via the antenna (not shown) into the antenna of the stick and vice versa. The roll of cable on the right of the picture is the extension cable to the antenna, which I put on the cabinet above. No need to even put it outside the house, just directing it to the nearest UMTS base station was enough.

Over the days I've been at the place, the setup has proven its worth as the Wi-Fi signal of the D100 just perfectly received everywhere. Next time, I should bring a femto along as well so voice telephony also benefits from the setup 🙂

A quick self observation today: For the second time in so many weeks, I've sent an MMS message to someone just to get a call later-on in which the other person tells me that they've received an SMS message that I sent them a picture and that they can take a look at a web address. With all the spam these days, both callers were a bit worried if it was actually a scam.

Three things are not right here:

First, the MMS should have been delivered but wasn't because both persons lately changed their phones and it seems the network was not quite sure the multimedia messaging configuration in the phone was correct.

Which brings me to the second point: In many networks, MMS messages still cost significantly more than SMS messages. And while SMS messages are perceived as practically free by many people because an unlimited amount is part of their contract, MMS is still the expensive and disregarded sibling. While this goes on, MMS will never become popular.

And finally, I wonder how many of those MMS messages that were not delivered would have gone through anyway if the system had tried!? The system could even be sure that the configuration is correct by sending an MMS message once an initial auto-configuration SMS has been delivered to the phone (that the user has to confirm). When this MMS is delivered correctly, one can assume that the configuration succeeded.

So quite a number of fronts to work on to bring MMS to the masses. It's not a technology question anymore…

Since the start several years ago, Nokia Maps, called Ovi Maps these days had offline navigation capabilities, i.e. maps data can be stored on the mobile so there's no data cost for navigation except for the few kilobytes of data required to get the A-GPS ephemeris almanac when the program is started to give the GPS chip a hint where the satellites can be found. This is not only beneficial to keep the delay down when scrolling through a map but is a bare essential requirement for me due to the high roaming charges for data as I often use navigation abroad. I guess I am not the only person with the problem which is why I find it even more surprising that Google still doesn't have an offline mode for Google maps. But perhaps its not so surprising because Google is a company that has its services in the cloud. So an offline mapping application doesn't make much sense for their product portfolio. So maybe that's the explanation!?

I recently read somewhere that 3GPP stage 2 specifications for Local IP Access (LIPA) are in pretty good shape by now so I thought it was time to take a look to understand the basic principle that is taken forward. So here’s my summary:

First of all, the general idea of LIPA is to enable a UMTS or LTE device to access the local IP network that a femtocell is connected to. In other words, when a user has a femtocell at home or in the office, mobile devices can use LIPA to access devices that are connected to the local network such as connected TVs, video and picture libraries on computers, NAS servers, etc. over the femtocell.

A number of different approaches were studied in 3GPP and the different options can be found in 3GPP TR 23.829. The selected solution that now goes into Technical Specification (TS) documents can be found in 7.2.1, where it says that LIPA solution 1 variant 1 described in 5.2 has been selected. Note that TR 23.829 also treats SIPTO, which stands for Selective IP Traffic Offload, but that’s something different and a topic for another post.

The selected solution for LIPA works as follows: To get access to devices on a local network to which a femto is connected to, the mobile device can use a special APN. The APN tells the SGSN (UMTS) or the MME (LTE) that the mobile device wants to get a connection to the local network and not to the network operator’s core network. This way, the solution is backwards compatible to current devices, i.e. LIPA will work without any software modifications on devices. Optionally, a LIPA flag is defined that can be sent by the mobile device during the PDP context establishment (UMTS) or the Default Bearer activation (LTE) for the same purpose. This, however, requires some additional software in the mobile device.

For simultaneous access to the local network and the Internet, two solutions are given in the TR. First, the mobile could have two PDP contexts (UMTS) or two default bearers (LTE), one that terminates in the local network and one that goes through the core network to the GGSN/P-GW. Also the TR specifically says that the in case Internet connectivity is available through the local network, LIPA does allow the UE to reach the Internet this way. This might be desirable in many cases as it nicely offloads Internet traffic as well but has some consequences for IP based network operator services such as MMS as these can’t be reached that way.

Further, the TR specifies a (logical) Local Gateway (L-GW) in the femtocell that acts as a GGSN (UMTS) or P-GW (LTE). Once the LIPA PDP context / default bearer is established data flows directly to the L-GW and from there into the local network without traversing the radio access network or the core network of the network operator.

Control of the LIPA PDP context / default bearer, however, remains with the SGSN / MME in the core network. In other words, authentication, authorization and security procedures remain with the network operator. An interesting result of this architecture is how incoming packets from the local network are forwarded to a mobile device that is in UMTS Idle/Cell- or URA-PCH state or LTE Idle state respectively. In these states the mobile device needs to be paged first and has to re-establish an RRC (Radio Resource Control) connection before the data can be forwarded. The paging remains a responsibility of the SGSN/MME and hence, the femtocell needs to send a notification to the SGSN/MME which then pages the mobile device via the femtocell. Once the RRC connection is established again, the data packet is forwarded.

Mobility of the LIPA bearer between femtocells, e.g. when several femtocells are deployed in an office is discussed in the TR, but the conclusion is that this part will not be specified in 3GPP Release 10. In other words, in a first version of LIPA, the bearer is lost when the mobile looses contact to the femtocell.

And finally, here’s a list of some of the specs that will be expanded for LIPA in Release 10: TS 23.060, TS 23.203 and TS 23.401.

There we go, this should be enough to get you started once you want to find out more about LIPA. The question for me is if it will find traction!? Today, smartphones with  operating systems such as Symbian, Android, iOS, etc. already have a Wi-Fi chip build in and the OS is capable of switching between a known Wi-Fi network and 3G connectivity automatically. Many Symbian applications can even be configured to use a specific APN / Wi-Fi network, e.g. a podcast catcher application can always and exclusively use the Wi-Fi network at home if configured that way. In other words, local access that LIPA wants to give mobile devices is already done over Wi-Fi today. As always, any thought on the topic are greatly appreciated.