New EU Regulation Mandates Operators To Inform Customers Of Roaming Costs Via SMS

Here’s an interesting additional piece of information on the EU decision to limit prices for European users roaming with their mobile phones to other EU countries: According to this Teltarif article, the EU roaming regulation coming into effect this summer not only limits prices but also requires operators to inform their customers via SMS of the prices they charge for incoming and outgoing calls when they detect that a user roams in a foreign EU network. Applause for this piece of legislation because I am sure 9 out of 10 people today have no idea who much they are charged when making or taking phone calls while abroad. Also, this is in my opinion the first positive usage for roaming detection devices that usually trigger useless SMS messages in the "Welcome in country XYZ, please use the network often for (undisclosed) roaming charges" fashion 🙂

Antenna Hide And Seek

Another reflection from my recent visit to the U.S.: While in Europe cellular towers and antennas can be spotted easily and everywhere be it both in cities and countryside, I was a bit astonished to only rarely notice them in the U.S!?

After a couple of days I figured out why: Many of the antennas are put directly on walls of taller buildings instead of on top of buildings and are sometimes even camouflaged. The sophistication ranges from using a similar color as the building up to painting the house’s brick structure on the antennas itself. Not sure if the trend continues as I saw quite a few examples of camouflaged antennas on buildings and the usual grey antennas on the top of the building, probably newer and by another operator. No longer a need for hiding them?

The Carnival Of The Mobilists #78

Cotmbutton
Ricky over at Symbian Guru hosts edition 78 of the Carnival of the Mobilist this week. The Carnival is definitely THE resource out there that captures the best articles written about wireless in the past 7 days in the blog sphere. Only quickly browsing over it before writing this reference, I’ve already discovered David Beer’s article analyzing Palm’s strategy for the Foleo. Can’t wait to go in depth on the rest as well. So head over and enjoy!

The Internet On The Go Is No Longer Slower Than At Home

Some reflection on my use of wireless Internet access over the last couple of years: Since I started using the Internet over wireless networks on the go back in 1998 it was always slower than at home. Back in 1998 I still used dial up, but my 64 kbit/s ISDN line at home was several times faster than the 14.4 kbit/s circuit switched dial up connection over the GSM network. Until recently the difference has pretty much remained the same just the speeds have changed.

For every step wireless made, be it GPRS, EDGE or UMTS, fixed line technologies had already made a similar step two or three years before. In most cases it was o.k. to live with the slower speed while not at home traveling the world but I always wished it would be as fast at home. Well, with HSDPA now deployed pretty much everywhere I go these days, access to the Internet on the go is now just as fast or even faster than my DSL line at home. I still catch myself thinking, "no can’t download this, have to wait until I am back home" just to smile at myself afterwards because it makes no difference anymore.

It’s not that DSL hasn’t made progress and is available in flavors of 16-20 MBit/s already in many places, but except for downloading very large files or for IPTV I have very little use for 20 MBit/s right now. I don’t have a doubt, however, that this void will be filled in the next couple of years. Of course by this time both wireless and wireline Internet access technologies will have progressed to even higher data rates.

Where’s the MAC Modem Driver For S60 Phones?

Tommi over at his S60 blog brings us the good news that Nokia has stepped up its activities to bring better support of N-Seires phones for Mac users. What I am still missing and constantly keep looking for is USB modem support for S60 phones. I am close to consider buying a Mac notebook when my current computing equipment needs replacement but this is one of the few things that still keep me from really doing it.

Some will say, pah, not needed, just use Bluetooth to connect to the phone. Good idea, but not fast enough anymore for HSDPA phones such as the N95. Anyone aware that USB modem drivers for the MAC exist for N-Series phones and I just did not find them so far?

Another theoretical approach might be to have a virtual machine running with Windows XP inside and install the drivers there!? Anyone tried this before? I haven’t the slightest clue if it’s possible. Even if it is would it be possible for Mac applications to use a dial up connection running in the virtual Windows XP? Any news and hints welcome!

Supplement to Surviving With Wifi In The U.S.

I am back from Boston reflecting on what’s happened over the week. One of the things I found quite interesting was to see how much Wifi Internet access is used at the two hotels I stayed during the week. In the DaysInn hotel which offered free Wifi, throughput was in the range of around 300-400 kbit/s in the evening and in the range of 1 MBit/s in the early morning hours. Looks like heavy use to me.

I detected the same behavior in the Westin hotel in Boston which charges 10 dollars a day for Internet access. During evening hours, I didn’t get speeds any higher than 300 kbit/s and the voice quality of my Skype sessions where at times a bit rough. I did a quick check with Wireshark which detected around 150 active computers in the network! It’s probably not surprising as there were around 300 telecoms people staying in the hotel 🙂 As in the previous hotel, speeds where much higher in morning hours (around 5 MBit/s).

And the moral of the story: Internet access in hotels is quickly becoming an expected basic service. For 300 bucks a night however, I wonder why the towels and soap are free while Internet has to be paid for separately!? One could argue if one stays at a hotel for 300 bucks a night 10 extra dollars will not hurt. Good point. But again, why don’t they then lower the room price and charge separately for towels, soap, water, light, air conditioning, room cleaning and TV inside the room? I just don’t see the difference…

P.S.: And of course, these findings also indicate that hotels should monitor usage and think about upgrading their DSL backhaul.

Amazed By The Wifi Mesh of MIT’s One Laptop Per Child Project

Last week I had the enormous pleasure to have been invited to MIT’s Media Lab in Cambridge, Massachusetts to take a look at their activities and in particular the One Laptop Per Child (OLPC) project. Walter Bender gave an intro and a hands on demo of the laptop and as you can see on the picture on the left he had all the eyes and ears of the audience.

Olpc_sm
It’s difficult if not impossible not be amazed by any part of the project and the green/white prototypes of the laptop and its software. As somebody who looses a word or two every now and then about communication and networks, I was especially interested in the Wifi Mesh network implementation and what kids can do with it. Communicating with each other, playing, painting pictures etc. etc. and of course get access to the Internet if a gateway is in reach of just one of the laptops forming a mesh network. Individual laptops act as a mesh node even when they are switched off. Great stuff! Details about the OLPC project in general and about the mesh implementation (complying to the current draft of 802.11s as much as possible) specifically can be found here.

The 3GSMWorldCongress Has Been Rebranded

Heike Scholz over at "Mobile Zeitgeist" is at the pulse of the time with her report that the 3GSMWorldCongress has been re-branded by the GSM Association into the "Mobile World Congress".

It’s an interesting move but I still haven’t figured out the real reasons for it… I think it’s more than just a new marketing strategy. Has there been a struggle about the rights to the name? Anyone?

Removing "3GSM" from the name of the conference opens up a number of interesting possibilities for the congress to develop in the future. The official statement for the re-branding is:

"The GSMA is rebranding the 3GSM World Congress and its sister event in
Asia to reflect their role encouraging the development of compelling
new mobile services for end-users."

I am not quite sure how the re-branding will help that goal!? Anyone? By removing "3GSM" from the name the congress might open up potentially for other technologies to be also present. We saw a bit of this already this year with a number of people showing WiMAX at their booths.

Another possibility for the name change could be that the GSM Association now considers GSM and UMTS to be the world’s dominant wireless standard implying that it’s obvious that a mobile world congress can only be about this technology!?

Whatever the reasons are I am sure it’s more than what they say in their official statement. Comments welcome.

WiMAX Waves

Lately, I’ve stumbled over statements like "Our WiMAX product supports 802.16e Wave 1 and 2 feature sets". It’s mentioned a lot but nobody goes into the details of what kind of features the different "waves", or versions, actually contain. So I’ve done some research on my own. I still don’t have all the details, but at least some clues.

From an article on "Mobilehandsetsdesignline":

"…The Wave 1 feature set focuses on single-input, single-output antenna systems and basic mobility.


On the heels of
Wave 1 will be Wave 2 certification testing. In addition to Wave 1
backward compatibility, Wave 2 focuses on advanced antenna array
features such as multiple-input, multiple output (MIMO) arrays and
using space-division multiple access (SDMA)-based beam forming. Wave 2
will most likely begin testing in late 2007 or early 2008. …"

And from "Informatm":

Wave 1 mobile WiMAX certification will embrace products in the 2.3GHz and 3.5GHz profiles. Wave 2 certification will then feature 2.5GHz products, and products with smart antenna capabilities like MIMO and beamforming.

In 2.3GHz the Plugfest tested channelization in the 8.75MHz range
for the Korean WiBro profile and 5MHz and 10MHz for the rest of the
world.

In 2.5GHz and 3.5GHz frequencies the channelization was 5MHz and 10MHz and in 3.5GHz the 7MHz profile was also utilised.

And finally, here’s a link to an Intel presentation where physical layer (only) functionality of wave 1 and wave 2 devices are described on the final two pages.

Is anyone aware of an official and published full list of wave 1 and wave 2 functionalities on all layers? If so, please let me know.

Impact Of 3G Traffic On HSDPA

Most HSDPA tests in live networks presented on this blog so far were always performed in lightly loaded cells. In this blog entry I take a closer look at HSDPA performance in a cell that servers other non-HSDPA 3G users simultaneously.

For this test I’ve used one HSDPA terminal (a Sierra Wireless 850 PCMCIA card) to download a file and a second 3G only terminal (a Nokia 6680) to create "interference" by also downloading a file. The 3G only terminal can not use the HSDPA channels and is thus assigned a dedicated channel (DCH) by the network. In the test, the network assigns a 64 kbit/s DCH first, quickly followed by 128 kbit/s and 384 kbit/s bearer upgrades. From a CDMA code point of view, a 384 kbit/s bearer with a spreading factor of 8 takes similar resources than 16 simultaneous circuit switched voice calls (spreading factor of 128). Thus, the test not only shows how fast DCH and HSDPA bearers work together in practice but also what kind of impact a fair number of voice calls have on HSDPA throughput in the cell.

Vodafone_d_simultaneous_384_dch_2_t
The first figure on the left shows the throughput of a file download via HSDPA. At the beginning no other users are in the cell. At about 20 seconds into the file transfer I started another file transfer via the 3G only terminal. The network then seems to modify resources in the cell between 25s and 45s. There are a number of characteristic downward spikes during that time which I was able to reproduce during each re-run of the test. As I can’t look into the network, I have no explanation for them. Finally at about 45s the throughput stabilizes at a slightly lower level than at the beginning where no interference was present.

Vodafone_d_simultaneous_384_dch_2_p
The second figure on the left shows an inter-packet spacing graph (for an intro on this kind of graph see here) of the same download. For about half the download there is only a significant line at 10ms inter-packet spacing. Then, when the file transfer of the 3G mobile sets in the lines at 20 and 30ms get more dots. Lines at 20 and 30ms can have the following reasons:

  • Retransmission because of faulty packets
  • The network has started to use a different coding scheme for the packets due to interference, so packets take longer to be transmitted
  • Other HSDPA users in the network with whom a terminal has to share the capacity.

In this test, the third reason can be discounted as there as no other HSDPA capable terminal in the cell at the time. So either the interference caused by the 3G mobile forced the network to increase the coding scheme or to accept more retransmissions. Both results in slower throughput for the HSDPA terminal. Whether it is one or the other for this test or a combination of both is difficult to say from a terminal perspective.

In total, this test shows that even a fair number of voice calls by other users in parallel to HSDPA has only little impact on throughput as long as reception conditions for the voice calls and HSDPA is good. In such conditions the noise generated by other users is still low enough for the HSDPA terminal to cope with. 

When I have time and opportunity I will run the same test again in an area with weaker coverage. Also, impact of DCH users on HSDPA networks supporting 16QAM modulation, which requires a higher signal to noise ratio than QPSK modulation used by the network for this test should be fun testing.