Martin – Page 275 – WirelessMoves

Vodafone WebSessions Tested With A Nokia N93

In the previous blog entry I’ve taken a look at how to use the Vodafone Germany WebSession offer for data roaming with a PC. As a ultra-mobile roamer, however, I use my mobile phone almost as much as my PC when traveling. So the natural question is, are WebSessions also usable with the N93 on-board applications?

The simple answer is yes, but with a slight quirck 😉 As described in the previous entry a web session starts and is restarted by pressing the accept button on the WebSession portal in the web browser. This enables an "almost" transparent tunnel for IP traffic between the terminal and the Internet. Activating a web session with Nokia’s built in browser is easy and works flawlessly. Afterwards, all other applications in the phone can also use the connection so sending and receiving eMails for example works well.

So here’s the catch: It’s also possible to connect to the network from the eMail program. However, no data can then be transferred because each time the web session is entered again the portal web page has to be touched first. In order to use any other application the browser thus has to be started first to touch the portal page. Afterwards all other applications work. While at least one application is running to keep the connection to the network open the browser can be closed. As soon as the last application that requires Internet access closes, however, the only way to restart the session later on is to start the browser again first. Not very convenient, but practicable.

Another good thing is that a Web Session initially opened on the N93 can be re-used on the PC later on. This is very important to me since I usually use both devices throughout the day.

The Mobile Internet In Spain With A Yoigo Prepaid SIM

Looks like new entrant Yoigo (TeliaSonera) in the Spanish wireless market wants to shake things up a bit by offering competitive prices for phone calls and GPRS/UMTS web browsing via their prepaid SIM card. Dennis over at Wap Review reports about his experiences while on vacation.

Price per megabyte is €1.20. Not the cheapest prepaid data offer I have seen so far except for the interesting twist described below. ~~but it will do for many purposes~~. Denis also lists the required settings to access the Internet with the SIM. Unfortunately he doesn’t mention if all traffic has to go via the WAP 2.0 Proxy or if other services such as POP3 and SMTP for eMail also work. As they cap their daily price at €1.20 for data and they refer in their offer to ‘navigating’ I kind of doubt it. If someone has more info, please let me know.

Vodafone WebSessions Tested At HSDPA Speeds

A couple of weeks ago, Vodafone Germany announced during the CeBit that they will launch/lower their data roaming prices for their WebSession offer. On both prepaid and post paid Vodafone Germany SIM cards, WebSessions can be bought for €14.95 for a 24 hour period while roaming in many countries (for a list see below). While unlimited for now, Vodafone’s fine print says that a web session will be limited to 50 MB of data traffic starting in Seprember 2007. Definitely not on the cheap side for private travelers, the price will work for many business travelers when abroad for a couple of days. As I am one of those it was time to get a Voda prepaid SIM and give it a try.

How To Get A SIM

Apart from being very flexible with a prepaid SIM and not having to pay a monthly fee or being bound for a certain period a prepaid SIM additionally offers assurance that I will not come home one day to find a €3000.- invoice because I mis-configured my kit. This is not unheard of… As Vodafone Germany wanted €20.- for a prepaid starter kit, I decided to give eBay a try and got one for €2.-. The SIM card included €10.- worth of calls and Internet access, enough for a first test. Important note: As far as I know only German Vodafone SIM cards support WebSessions.

How to Connect

The most important thing with the WebSession offer is to use the correct Access Point Name (APN) when connecting. For this offer it is "event.vodafone.de". If a different APN is used other fees will apply for the connection so be careful. After establishing the connection any web page access is redirected to the WebSessions portal page of Vodafone. Here, one can either select to begin a new session or browse the Vodafone.de page for free. Unlike advertised, the only payment option I had was to deduct the price for the WebSession from the prepaid account.

Once opening the web session is confirmed on the portal page the connection is put into transparent mode and full Internet access is possible. Before being forwarded to the initially selected page the portal tries to open a popup window to show the remaining online time. This fails in both Firefox and the Internet Explorer with standard pop-up blocker options enabled. No harm done, the Internet connection works anyway. However, it might be useful to have this information. To allow the pop-up window to open, the pop-up prevention can be manually deactivated in the browsers settings for the portal URL only.

Performance

For my tests I used the HSDPA notebook card I already used for my HSDPA tests in Italy. As in the Italien TIM network, HSDPA performance in the German Vodafone network were superb with maximum data rates of 180 kBytes/s, which is around 1.6 MBit/s. This is the maximum speed supported by the card. Round trip delay times were at around 100 ms and I had the same 2 seconds delay after some time of inactivity, just as in Italy. So it’s likely that TIM and Vodafone Germany use the same radio network manufacturer, who is most likely Ericsson. The maximum uplink speed was a remarkable 384 kbit/s.

While talking about performance I’d also like to note that my desk is about 300 meters and two concrete walls away from the 3G base station. Therefore my reception conditions were excellent and unlike in Italy with slightly less favorable reception conditions, changes in antenna orientation had no big impact on throughput speed.

I also used the WebSession with an N93 connected to the PC and also quickly connected to the Swiss UMTS network which is available when I am on my penthouse veranda. All worked as it should, I am very satisfied!

Logging In and Out, eMail, VoIP and IPSec

A WebSession can be left and entered again as often as one likes while the clock is ticking. I connected and disconnected several times to check this feature one out and it works flawlessly as well. After every login, the portal page is shortly visited for the pop-up box to open up to show the remaining online time. Afterwards, the browser is immediately redirected to the requested page. EMail SMTP and POP3 works as well over the connection and my IPSec connection establishment to my company was working. Even Skype calls worked without a glitch despite Vodafone stating in their fine print that VoIP calls are blocked.

Automatic Web Page and Picture Compression

The only thing that I don’t like is the automatic picture compression on web pages Vodafone performs. While it helps to reduce the total transfer volume it’s not required to improve page download times over HSDPA. After all, the HSDPA connection is much faster than my ADSL line. I heard that it’s possible to deactivate the automatic picture compression with the Vodafone software that comes with their branded HSDPA cards. As I don’t use any Vodafone software or hardware I can’t change the setting. However, I can deactivate split tunneling in my IPSec client. Afterwards all data traffic is sent through the encrypted tunnel to the corporate network. This prevents the transparent web proxy in the Vodafone core network to touch the pages and pictures and things look as they should. Not a perfect solution to the problem but it works for me.

Supported Roaming Countries

Belgium (Proximus), Denmark (TDK), Finland (Elisa), France (SFR), Greece (Vodafone), U.K. (Vodafone), Ireland (Vodafone), Italy (Vodafone), Lichtenstein (Mobilkom), The Netherlands (Vodafone), Austria (Mobilkom), Portugal (Vodafone), Switzerland (Swisscom), Spain (Vodafone) and Germany (Vodafone).

Summary

For me, WebSessions are a great way to stay connected while traveling in other countries especially now that another program I previously used abroad has expired. It would be nice if the price comes down a bit more to also make it attractive for non-business travelers and if there was an easier way to deactivate picture compression. However, I can live with both drawbacks for the moment. I also used a WebSession with the built in applications of my Nokia N93. You can read about this in the next blog entry.

Insight Into Who Backs WiMAX And Who Opposes It

Ericsson recently announced that they will stop their WiMAX development and that they will instead accelerate their LTE development. The Register has taken up on this and has published a very interesting article by Wireless Watch on which companies are pushing WiMAX and which companies are rather opposed. So if you are interested in the technical and political quarrels between 3G, 3.5G, 3.9G, 4G, UMTS, HSPA, WiMAX, LTE and UMB this one is a must read.

The Big Supporters:

Motorola
Nortel
Samsung
Huawei
ZTE

The Big Reluctant Followers:

Alcatel-Lucent
Nokia Siemens Networks

The Big Opposers:

Ericsson
Qualcom

My personal opinion: I think it’s good to have different technologies out there in the market that compete with each other. It speeds up development and it offers new starters in the wireless operator world possibilites which have not existed so far. As I discussed in more detail here, I think the consumer will benefit from this no matter in which direction the market will go.

HSDPA Performance in Operational Networks Part 4

My recent trip to Italy produced quite a large amount of measurement data while I was using Telecom Italia Mobile’s (TIM) HSDPA network for everyday work and pleasure. In part 1, I’ve been giving a general overview of the performance of HSDPA in an operational network. Part 2 then focused on analyzing IP packet inter-spacing and revealed a number of interesting details of the HSDPA MAC layer. In part 3 I showed how antenna position and placement can have a tremendous impact on performance. This part now picks up the thread and shows how the HSDPA MAC layer adapts to the antenna position changes tested in part 3.

The picture on the left shows the packet inter-spacing diagram generated from the same data as the throughput graph presented in part 3. If you haven’t read part 2 which gives an introduction of how to read this type of diagram I strongly recommend you to do so before reading on. The throughput graph in part 3 starts off with a speed of around 500 kbit/s. In the packet inter-spacing graph the reason for this slow speed becomes apparent. Instead of most packets being transmitted with a inter-spacing of 10 ms or less, most packets are rather on the 20 ms and 30 ms lines. This either means that the Node-B has sent the packets with a more robust coding scheme or that most packets were retransmitted at least once. No exact telling without a L1 tracer but I guess it’s a more robust coding scheme.

By changing the antenna position the data rate suddenly increases to over 1.500 kbit/s. In the packet inter-spacing graph this is reflected by most packets being transmitted with the least robust coding scheme on the 10 ms. A certain percentage of the packets are retransmitted and show up on the 20 ms line but they are not many, around 20% I would say.

This interval with good signal conditions and the resulting good transmission speed is then followed by vary bad signal conditions. Here, the data rate drops to around 350 kbit/s. In the packet inter-space graph there are almost no frames transmitted on the 10 ms and 20 ms line. The first major line is at 30 ms. Surprisingly there is not only major additional line at 40 ms but also at 50 ms. Some packets even have an inter-space time of 70 ms. I was quite surprised by this at first. I did some reading in the meantime, however, and saw that Harri Homa and Antti Toskala in their book "HSDPA/HSUPA for UMTS" describe in figure 7.32 that during bad signal conditions their test system did not select only a single but more robust coding like in good signal conditions but diverged between 700 and 1700 bits of user data per 2 ms frame.

There remain those packets during good signal conditions to be explained which are between 2 ms and 10 ms. An interesting point here is that there is not a single IP packet between 0 and 2 ms. A clear indication of the 2 ms MAC layer frame duration. My best guess concerning these packet inter-space times is that they follow a packet which had a transmission error and were transmitted before the faulty MAC layer frame could be retransmitted. This is one of the strengths of the HARQ (Hybrid Automatic Retransmission Requests) used by HSDPA on the MAC layer which continues sending higher layer packets even if a previous one has not yet been transmitted successfully.

And this thought concludes today’s HSDPA entry. Should my German Vodafone prepaid SIM for data roaming have arrived when I come back home more entries will follow soon on HSDPA performance in other countries. So stay tuned…

Outdated Wifi WEP Encryption Can Now Be Broken In Less Than 1 Minute

Wifi networks have been around for a number of years now. At first the WEP (wired equivalent privacy) encryption algorithm was used to protect network owners from eavesdropping and misuse of their networks by others. Due to a number of security flaws, however, WEP was superseded by WPA (Wireless Protected Access) and WPA2. Nevertheless, most Wifi networks deployed today in my experience still use the old WEP encryption. Over the years, ever more clever schemes have been devised to crack the WEP encryption. The latest combination of attacks can now break the encryption scheme in less than a minute.

WEP started to fall apart in 2001 when Scott Fluhrer, Itsik Mantin, and Adi Shamir published an attack which allowed to break the cipher by analyzing about 6.000.000 intercepted frames. The number sounds quite large at first. However, users in a highly loaded network can generate the required number of frames in a number of hours. In 2004 a hacker named KoReK devised a new attack which only required 500.000 to 2.000.000 frames.

Waiting for packets can be tiresome. Unfortunately, WEP is not secured against replay attacks. This can be exploited by inserting intercepted packets back into the network to trigger response frames with unique ciphering keys from computers attached to the network. Thus, an attacker no longer has to wait for clients to generate traffic but he can trick the attached computers to automatically create the frames for him. This additionally greatly reduces the time required for an attack.

Now, researches at the Technical University Darmstadt, Germany have refined an attack strategy by Andreas Klein, which is based on the original Fluhrer, Mantin and Shamir attack. This new attack now only requires 85.000 frames to calculate the cipher key with a success probability of 95%. Together with the key replay attack WEP can now be broken in less than a minute.

All these attacks are not only theoretical in nature. Tools are available for all of them to automate the process. As a proof of concept, the TU Darmstadt researches have extended one of these tools. More information about their work can be found here.

All of this is quite scary. So if you still operate a Wifi with WEP encryption it’s time to change to WPA. If you access point does not support it yet, it’s time to throw it away and buy a new one.

Via: Heise Online

3G Connections Over 15km

Some time ago I reported how Telstra and Ericsson have implemented UMTS cell ranges of 200km. This is mainly designed for very rural areas and I am not quite sure what kind of terminal is required at this distance to communicate with the cell tower. I very much doubt a normal cell phone will do. While I was trying out a new Vodafone data roaming offer, however, I tested a UMTS connection while being in Germany with a cell tower of Swisscom in Switzerland.

The place I live in Germany is close to the Lake of Constance and obviously the cell tower of Swisscom has to be on the other side of the lake. I am not sure of the exact distance to the UMTS base station but on a map the shortest direct line of sight from my veranda to the other side is 15 km. My veranda is also slightly elevated and I can see the other side of the lake from there. Thus, I have a direct line of sight connection over that distance and there are no blocking obstacles such as buildings or hills in between. Usually, the antennas of 3G cells are directed a bit downwards to only cover a range of 1 or 2 km. In this case, however, the antenna is adjusted differently to cover as much of the lake as possible. This has the interesting effect that I can still receive the network 5 km inland on German territory.

I didn’t only see the Swisscom 3G network in the network search screen but I could also connect to it, establish an Internet connection and surf on some web pages. The speed was not great but it worked o.k. So while it was certainly not 200km, it’s interesting to see that a "non turbo charged" UMTS network works over such distances.

At this distance, network coverage is not very strong. When I moved between the antenna of the HSDPA card and the lake, the connection was immediately lost. A clear sign that the only thing that keeps this connection going is the line of sight environment.

Mobile Roaming Strategies Conference in Barcelona, Spain

Next week, Barcelona will see a small but maybe quite influential conference on Mobile Roaming Strategies. From the 16th to the 19th of April, operators from around the world will discuss everything about GSM and UMTS voice and data roaming. Topics from the home page of the event:

"Develop innovative strategies to recoup lost roaming revenues due to regulatory pressures". My comment: Gee, there is a lot of explosive potential in that one…

"Build attractive voice and data pricing models which encourage roaming mobile usage". My comment: Hello, I can see the word ‘data’ in that sentence! Good!

"Focus on your VAS strategy to reduce roaming revenue leakage and increase usage". My comment: I wonder what ‘roaming revenue leakage‘ is. Anyone?

"Examining techniques to Increase take-up of roaming data services". My comment: Tip: Affordable prices would help tremendously. No need for discussion, just do it! Vodafone Germany has gone ahead and done a positive step with their WebSessions roaming offer. Let’s have some competition here!

It’s not only operators giving presentations, however. It looks like Stephen Banable, working for the Information Society and Media DG of the EU Comission will hold a presentation as well. Into the lion’s den Stepehen…

I’d really like to see the presentation material distributed at this event, especially for the first and second bullet points above. Anybody reporting from this event?

HSDPA Antenna Fine Tuning

In previous blog entries on HSDPA (for links see below), I’ve been looking at HSDPA performance in operational networks from several different angles. Todays entry focuses on how sensitive an HSDPA card reacts to changes in antenna orientation.

For my tests, I’ve been using a Sierra Wireless 850 PCMCIA notebook HSDPA adapter. The card has a maximum throughput of 1.8 MBit/s and has an external antenna which can be swiveled back and forth at the side of the notebook and also tilted 180 degrees to and from the notebook. This design is not new and all Sierra Wireless cards I’ve seen so far use this kind of antenna.

While antenna adjustments seem to have no big impact on GPRS performance, a huge difference can be observed with HSDPA during medium reception conditions (3 out of 5 bars on the RX meter). As shown in the graph produced with Wireshark on the left, throughput during a file download varied dramatically between 50 kbyte/s and 150 kbyte/s depending just on the antenna position and orientation. I have to admit that I was quite surprised by this result. I tried again a couple of days later just to ensure that this was not a freak occurrence but I could easily reproduce the behavior again.

Users will probably not spend a lot of time experimenting with antenna position and orientation whenever they log on to the Internet. Thus, I think HSDPA card manufacturers have to work hard on antenna and receiver design in order to reduce such effects in the future. 3GPP standards already give some guidance for the work ahead as the standard describes optional HSDPA terminal features such as multiple antenna designs and advanced receiver algorithms for more throughput and to counter these effects. For people using the HSDPA network in a stationary or semi-stationary setup, for example with a 3.5G to Wifi bridge, I highly recommend using an external antenna or at least to place the bridge close to a window.

Designing notebooks with built in HSDPA chips might also help to reduce this effect. In such a setup the antenna can use space inside the notebook which means antennas can be bigger and thus more sensitive and less susceptible to radio interference effects.

In the next part of this article series on HSDPA, I will discuss the packet inter-spacing graph for the scenario presented here and what can be deducted from it about layer 1 air interface MAC behavior and performance.

Bearer Awareness Required for Fixed Mobile Convergence

Dean Bubley over at Disruptive Wireless has written an interesting article describing why applications running on multi bearer mobile handsets (read GSM, UMTS, HSDPA, Wifi, UMA, Femtocells) must be aware of which networks are available and react accordingly:

Some bearers are not terminated in the operator network: Think local network, phones interact with local equipment such as PCs, VCRs and home appliances in general.

Different bearer characteristics. Some bearers are fast, some are slow, some are cheap others are expensive. Applications should adapt to this.

To access web pages and services outside the operator’s domain it’s not necessary to tunnel the IP traffic through its backbone in case several bearers are available and one gives direct access to the Internet.

A well researched article, I fully recommend to read the full piece. And a quote from it to finish:

"A lot of people don’t understand all this [the points above], particularly if they work at a mobile operator and still fervently believe that anything you do on a handset is "a service", rather than understanding that sometimes you want to do non-service activities as well."