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Switzerland has had some pretty good tariffs for mobile Internet access via mobile networks for a while now but only for postpaid customers. Looks like times are slowly changing there, too. Sunrise and Aldi Switzerland (using the Sunrise network) now at least offer data tariffs with prices that should allow mobile eMail and web surfing via the mobile phone browser.

Sunrise and Aldi Switzerland ask for 0.10 Swiss Francs per 20 kb block which is 5 Swiss Francs per MB or about 2.90 Euros. Well, way to go, but it’s a start. But I definitely would not use it with a notebook.

When roaming the price per 20kb block is 0.30 Swiss Francs per 20 kb block for all roaming countries according to the price list of Sunrise. That’s 15 Swiss Francs per MB or about 8.90 Euros. Not really on the cheap side but still cheaper than many other roaming alternatives for countries for which you don’t have a SIM and don’t want to spend a full 15 Euros for a 24 hour Vodafone Germany Websession.

I had a look on the Aldi Switzerland homepage for the details. To get a SIM card a registration form has to be downloaded, filled out and taken to one of the Aldi supermarkets when buying a SIM card together with your passport. Activation of the SIM card then takes around 24 hours. I wonder if things work quicker when going to a Sunrise shop!?

One more note: Orangeclick also offers mobile Internet access but prices are not competitive unless you subscribe to a 5 Swiss Francs add on which is deducted from the prepaid account once a month. This gives you 2MB worth of data and a price of 2.5 euros per megabyte afterwards.

More information on prepaid wireless Internet access via cellular networks for many countries can be found here.

While driving back home from a weekend trip I listened to this very interesting BBC world service podcast on Nokia, Finland and the land of the mobile millionaires (of course on a Nokia mobile phone…). A very entertaining 22 minutes story about a BBC reporter’s trip to Finland to discover how Nokia has shaped the people, the country and how they have shaped Nokia. So if you are interested in Nokia, rubber boots, Finland, mobiles or a combination thereof, it’s worth to listen in.

Since the EU has stepped in prices for mobile phone calls to and from the home country of a subscriber while traveling have fallen to (almost) usable levels. A nice move for people like me who travel a lot. But prices for calling from one country to another are still very high, even with a local SIM card. The same is true when you want to call a friend in another country (who has a SIM card of that country) while you are mobile. This is where Rebtel comes in.

Rebtel’s idea is based on the fact that national mobile calls are usually a lot cheaper than international calls.  So instead of calling an international number you create a ‘national’ number in Rebtel which then forwards your call to the person in the other country. An example: You are in Germany, have a prepaid SIM card and want to call somebody in Austria. If you do it directly, this will cost you around 1.5-2 Euros a minute. The alternative is Rebtel. Once registered you can use their web page or their mobile site to create a local number for your friend abroad. Calling that number costs around 5-15 cents in countries where competition among mobile operators is healthy. Rebtel then charges around 2 cents to connect to a landline or around 14 cents (VAT included) to a mobile number.

The method also works the other way round. You can give your friend a local Austrian number he/she can call for little money which then connects to your mobile in the other country. Rebtel charges you for the incoming mobile call (again around 14 cents a minute, depending on the country of course).

And the best is that the local numbers follow you! Rebtel allows you to configure up to 5 different mobile phone numbers. When you go to another country, say Italy, and you have a local SIM card you can switch to that SIM card in Rebtel. All contacts you have created will then automatically get an Italian local number. In case you use the local SIM card for Internet access things are very easy since the contacts on the mobile web page which you can access from the mobile phone are automatically updated to the Italian numbers.

I’ve given it a try over the last couple of weeks and have to say that I am very happy with the service. It works most of the time (o.k. it’s still beta) and voice quality is usually excellent. The only negative thing I can really report is that a connection is established even if the other end is not available or does not pick up. Consequently you always have to pay the local mobile operator for the first minute. This aside, however, Rebtel has saved me tons of money already.

Time flies… another week another carnival! This week the carnival is hosted by Andreas Constantinou over at the VisionMobile forum. So for all the latest on the mobile web 2.0, applications and devices head over and enjoy!

It’s a strange situation: Most mobile operators today would like to retain control over the application layer and rollout new services themselves instead of letting Internet economics do the job. In practice however, they do not spend a lot of effort to making even the few advanced services they have universally usable. MMS is a prime example as I had to discover recently.

Situation 1: I am in France, I have a French SIM card and wanted to send an MMS to a prepaid subscriber of another French operator, Bouygues. Instead of receiving the MMS, only a text message arrives at the other end with a web link. The reason is that the other end did not have a GPRS subscription. 5 years after the introduction of MMS!? It leaves me puzzled.

Situation 2: O.k. so I can’t send my French friend an MMS but maybe I can send one to a friend in Germany. Message sent, I’ve been charged for it but the MMS never arrived. How nice.

Situation 3: Some days later I was in Spain and repeated the international MMS scenario with a Spanish SIM card. Again, the MMS to a German SIM card was not delivered.

To me it looks like even 5 years after the introduction of MMS, there are still no international agreements in place to forward MMS between operators. Could you imagine eMail not being delivered because the recipient lives in another country? No, probably not. That’s because no international agreements for applications have to be in place to forward eMail. And if there had to be, just imagine how the Internet would look like today and how many people would use it.

Some might say, the difficutlies stem from the fact that telephone numbers are used instead of eMail addresses for MMS messages. True, but international SMS messages which also use telephone numbers work just fine these days. But maybe 5 years is too short a time to make it work? One should not think so.

In case you haven’t heard of Nokia’s Mobile Web Server yet, go check out my blog entry on it. In short the mobile web server is a port of the Apache web server to the S60 platform with a front end to access your mobile phone via the Internet or via a local Wifi network. Not a main stream application yet but with a lot of potential for the future. For those who want to stay informed what’s going on with the project check out the mobile web server blog which has just been created over at S60.

While doing some research on how capacity will grow in fixed line and wireless networks in the future I stumbled over the following thing right in my neighborhood: Future bandwidth increases on the last
mile to the subscriber come with an additional cost in comparison with today’s
standard ADSL or ADSL2+ deployments because of extra hardware that has to be installed close the the subscriber.

For ADSL2+ the DSLAM is usually installed
in the telephone exchange and the cable length to the subscriber can be up to 8
km for a 1 MBit/s service. For VDSL, which offers data rates of 50 MBit/s
in downlink, the cable length must not exceed 500m. Thus, DSLAMs can no longer
be only installed in central telephone exchanges but equipment has to be
installed in cabinets on the street. The cabinets themselves are quite large (about half the size of a GSM or UMTS base station),
require power, active cooling, and create noise. For the installation
of the cabinets earthworks are necessary to lay the additional fiber
and power
cables required to backhaul the data traffic. The picture on the left shows a VDSL DSLAM cabinet that
has been installed alongside a ‘legacy’ small telecom cabinet as part of the current VDSL build out in my region.

To connect a
new subscriber a technician is required to manually rewire the customer’s line
to one of the ports. Different sources currently
specify the maximum capacity of such cabinets from about 50 to 120 VDSL
ports. To support 500 VDSL connections per km², several cabinets are thus
required. I wonder what happens when 5 different companies put such DSL ‘base stations’ in place!?

I often wondered in the past what ‘Secondary PDP Contexts’ are good for in UMTS networks. I had a vague idea but never had the time to look up the details. These days I had and here’s a short explanation:

‘Secondary PDP contexts’ can be used to separate the real time data traffic from background or signaling traffic into different streams on the air interface while keeping a single IP address on the mobile device. This is done by an application providing the network with a list of IP addresses in a Traffic Flow Template. The mobile device and gateway router (GGSN) in the network will then screen all incoming packets and handle packets with the specified IP addresses differently, like not repeating them on the RLC layer after an air interface transmission error. This is transparent to the IP stack and the applications on both ends of the connection.

External providers of speech services such as Skype, however, do not have access to this functionality. A big advantage for operator controlled IMS services when things get wild on the air interface!?

Resources:

• Secondary PDP Context Activation: 3GPP TS 23.060, Chapter 9.2.2.1.1 (Rel 6)
• Traffic Flow Template Description: 3GPP TS 24.008, Chapter 10.5.6.12 (Rel 6)

For those interested in getting a feeling of how Wifi works on the physical layer, Metageek’s Wi-Spy is the ideal tool. I’ve already reported about my first experiences here and here. Wifi has become very popular in Paris due to DSL being quite cheap. So it should thus probably not be surprising that I can see 13 access points in my Paris apartment. As there are only three non-overlapping Wifi channels on the 2.4 GHz ISM band the question is what kind of impact such a high number of access points has on throughput.

Matters are made worse by the fact that some of the networks I can see are used for TV and video streaming. This is quite popular in Paris as this is offered by most DSL ISP’s and one even offers video streaming over Wifi to a remote set top box. The picture on the left shows a trace taken with Wi-Spy under these conditions. The lower graph in the figure shows the frequency range of the ISM band between 2400 and 2480 MHz. Instead of showing the frequency in MHz the x-axis labs show the 13 available Wifi channels. On the y-axis the amplitude of the signal received over the band is shown. The color of the peak depends on the intensity of the signal received during 60 minutes. Bright color indicates high activity. The graph shows five partially overlapping networks with their center frequency on channel 1 (only little traffic so the arch is not very well visible), channel 3, 5,6 and 11.The most activity can be observed in the wireless network that is centered around channel 11.

The upper graph shows a time graph over the frequency range. On the y-axis I’ve chosen a resolution of 60 minutes to show the activity in the ISM band in the course of one hour. The Wifi networks on channel 5 and 11 were most likely used from streaming as there is uninterrupted activity throughout the test period. The Wifi networks on 3 and 6 were also used for streaming. Streaming was stopped on the Wifi network on channel 6 after about 12 minutes while streaming was started on the Wifi network on channel 3 about 40 minutes into the trace.

To see what the impact of that streaming has on throughput in my network I used two notebooks, one connected via Ethernet, the other via Wifi and Iperf, a UDP and TCP throughput measurement tool. With a fully overlapping Wifi network which is used for TV streaming, capacity of the Wifi network under test was reduced to 72%. Partial overlapping entails an even bigger speed penalty and performance was reduced to 59%.

Here are the absolute values:

• No interference: 22.5 MBit/s
• Full Overlapping: 16.3 MBit/s
• Partial Overlapping: 13.4 MBit/s

Looks like it is time equipment manufacturers are taking the 5 GHz band a bit more seriously…

For more traces take a look at my previous traces or head over to Metageek where you can download the software and check out some sample traces yourself.

Back in mid September I reported on using my Linksys WRT54 Access Point in "Access Point Client Mode" to create a wireless link to another access point for a number of notebooks which are connected via Ethernet to the Linksys. The traces which I took on the Linksys and on the notebooks indicated that the Linksys replaces the MAC addresses of the notebooks with its own before it sends the packets over the wireless link. Equally it replaced its own MAC address in incoming packets with the MAC address of the real recipient. This is neither layer 2 bridging nor layer 3 IP switching but something in between. I couldn’t quite believe it.

In the meantime thanks to the suggestions I received I made some further tests and I can now confirm that the Linksys really does replace the MAC addresses. Take a look on the picture on the left which shows the ARP table of a PC connected wirelessly to the real access point. The notebooks connected to the Linksys Client AP both have the same MAC address. The MAC address is that of the access point! Quite sophisticated! (Note: All devices in the network are in the same IP subnet)

I am not sure how this feature should be called. It’s not really ‘Layer 3 switching’ which is already a highly overloaded term anyway. I’d prefer the term ‘MAC masquerading’ although the term is also already used for something else as well.

Thanks to all who sent their comments and suggestions!