Author: Martin

WiMAX II – 802.16m – Chasing the Ghost

Looking at presentations from a recent LTE meeting I found it quite interesting at how many of them mention WiMAX 802.16m. I haven’t heard much about 802.16m yet but since they all refer to it I thought it might be time to find out a bit more about it.

It seems to be a bit early for that search however. First announced in early 2007 the only facts so far known about 802.16m is that the IEEE would like to create a standard as much backwards compatible as possible to the current version of the WiMAX (802.16e or 820.16-2005) but with peak data rates of up to 1 GBit/s (that’s around 1.000 MBit/s).

Compared to current systems deployed in live networks today such as HSDPA with a theoretical top speed of 14 MBit/s and about 2 MBit/s with a Cat-6 HSDPA mobile today in live networks, these numbers are staggeringly impressive. So how can such data rates be achieved? As not much is known so far, let’s speculate a bit.

Between today and WiMAX II, there’s systems such as WiMAX and LTE which promise faster data rates than those available today by mainly doing the following:

  • Increase the channel bandwidth: HSDPA uses a 5 MHz channel today. WiMAX and LTE have flexible channel bandwidths from 1.25 to 20 MHz (Note: The fastest WiMAX profile currently only uses a 10 MHz channel today for the simple reason that 20 MHz of spectrum is hard to come by). So by using a channel that is four times as broad as today, data rates can be increased four times.
  • Multiple Input, Multiple Output (MIMO): Here, multiple antennas at both the transmitting and receiving end are used to send independent data streams over each antenna. This is possible as signals bounce of buildings, trees and other obstacles and thus form independent data paths. Both LTE and WiMAX currently foresee 2 transmitting and 2 receiving antennas (2×2 Mimo). In the best case this doubles data rates.
  • Higher Order Modulation: While HSDPA uses 16QAM modulation that packs 4 bits into a single transmission step, WiMAX and LTE will use 64QAM modulation under ideal transmission conditions which packs 6 bits into a single transmission step.

By using the techniques above, LTE and WIMAX will be able to increase today’s 2 MBit/s to about 20-25 MBit/s. That’s still far away from the envisaged 1.000 GBit/s. To see how to get there let’s take a look at what NTT DoCoMo is doing in their research labs, as they have already achieved 5 GBit/s on the air interface and have been a bit more open at what they are doing (see here and especially here):

  • Again increase of the channel bandwidth: They use a 100 MHz channel for their system. That’s 4 times wider than the biggest channel bandwidth foreseen for LTE and 20 times wider than used for today’s HSDPA. Note that in practice it might be quite difficult to find such large channels in the already congested radio bands.
  • 12×12 MIMO: Instead of 2 transmit and receive antennas, DoCoMo uses 12 for their experiments. Current designers of mobile devices already have a lot of trouble finding space for 2 antennas so a 12×12 system should be a bit tricky to put into small devices.
  • A new modulation scheme: VSF spread OFDM. This one’s a bit mind bogelling using CDMA and OFDM in combination. Wikipedia contains a description of something called VSF-OFCDM which might be a close brother.

A four times wider bandwidth with six times the number of antennas results in a speed increase factor of 24. So multiplying 25 MBit/s * 24 results in 600 MBit/s or 0.6 GBit/s. That’s still a factor of 8 away from what DoCoMo has said they have achieved, so I wonder where that discrepancy comes from!? I guess only time will tell.

Summary:

For the moment, the wireless world’s pretty much occupied with making LTE and WiMAX a reality. Pushing beyond that is not going to be an easy thing to do in the real world as bands that allow a single carrier of  100 MHz will be even harder to find than for the 20 MHz envisaged for LTE. Also, cramming more than 2 antennas into a small device will also be a formidable challenge.

More about 4G, LTE and WiMAX can be found here.

3G and 4G Wireless Is Private – DSL Is for Sharing

In countries such as Austria and Italy, mobile operators are heavily promoting the use of their HSDPA networks as an alternative to DSL access at home. Pushed by very interesting prices starting at €10.- a month for 250MB, €20.- for 3GB and €50 euros for 20GB in case of One in Austria, only the sky seems to be the limit.

I’ve recently been in Austria and talked to a number of people using these offers. Being mostly students, they like Internet access via 3G networks for two reasons: For many it’s cheaper (!) than DSL at home and they usually use it with a PC card and a notebook not only at home but also in other places.

For families, however, the equation might look differently. In many cases, several PCs or notebooks are available in the household and thus Internet access needs to be available to all family members. It can be done wirelessly for example by using a 3G/Wifi Access point but it of course immediately takes mobility out of the equation. On top, if you have kids then any kind of usage cap is just waiting to be stepped over as soon they start using file sharing applications, music downloads, YouTube and other bandwidth intensive applications.

Looking Ahead

So in the long run I expect mobile households to use DSL or cable coupled with Wifi to share a flat rate fat pipe with all members of the household, 3G/4G data cards in their notebooks for Internet connection while on the move and mobile phones which make good use of high speed wireless networks (3G, 4G and Wifi while at home) for anything from podcast downloads to video sharing. Wifi at home also has another advantage over using the 3G/4G network: It’s possible to communicate with your network enabled household appliances such as digital video recorder, music library, other PCs, mobile phones, etc. A good step towards the hyperconnectivity vision of Nortel’s CTO John Roese.

In such a scenario I it’s quite o.k. to have reasonable volume caps in place for 3G and 4G networks. This encourages the use of DSL/cable at home where I think most data traffic will occur due to the availability of big screens which require a much higher bandwidth for video applications than small screens on the mobile phone. Also, people have much more time available at home to communicate, to work and to play. After all, no matter how far 4G will push wireless capacity limits, DSL, cable and fiber will have infinitely more capacity available than wireless systems.

Network operators with both fixed line and wireless assets will surely figure out how to make interesting dual offers and can thus insure that the DSL/cable backhaul and not their wireless network deals with most of the data traffic. The high speed cellular network will then only be used as an overlay network by most people when leaving their Wifi cloud.

Surely there will also be people that use the 3G/4G wireless network as their sole access to the Internet. I expect, however, that their number is small compared to "converged" users which increases the chances that enough capacity is available to transfer their data traffic alongside the data traffic from people using it as an overlay network at a comfortable speed.

As always, comments are welcome!

GeoTagging the Next Step: ContextWatcher

While exploring the Yahoo Maps Flicker plugin in my recent geotagging experiments, I figured out that it can also show pictures other people have
uploaded in the neighborhood. Amazing how many pictures have already been taken even in small villages. I wonder if there is a
spot on earth left that has not yet been photographed with a digital camera or
camera phone and uploaded to the web?

When looking at photos taken by others close to a picture I had taken by I stumbled over a picture taken by Thomas Wagner who works for DoCoMo Labs Europe. Looks like they are working on an S60 Python program called ContextWatcher
for quite some time now and which they offer for downloading. The
program integrates information such as GPS, cell ID, body data, activities, visual data (e.g. 1D bar codes of books). Here’s the
description form their website:


The ContextWatcher is a mobile application developed in Python, and running on Nokia Series 60 phones.
Its aim is to make it easy for an end-user to automatically record, store, and use context information,
e.g. for personalization purposes, as input parameter to information services, or to share with family,
friends, colleagues or other relations, or just to log them for future use or to perform statistics on
your own life. E.g., it can be used to create automatic context bits for your own blog, so that your friends
can easily see what you have been doing the last days, including a summary of the pictures you have made.

Pretty powerful stuff and I think a lot of these things will become mainstream once tightly integrated into phones.

The Cell Hunters

I’ve recently discovered the blog of James Pole who’s writing about wireless networks in New Zealand. Looks like he is a ‘cell hunter’ and has good background information about how GSM, UMTS and cellular networks look like in practice. That reminds me of Nobbi, a German enthusiast who’s also got an interesting site about GSM cells and network monitoring. If you speak German and are interested in the topic his site contains a lot of gems.

If you know about other people who write about the topic, please leave a comment.

GeoTagging Revisited

I’ve found a lot of uses for my Bluetooth GPS receiver in the past. Beginning with a Python project to track network coverage and display it in Google Earth, GeoTagging became the next logical thing to look at and it’s clearly going to be a cool camera phone application once the GPS receivers are built in and geotagging is tightly integrated into the camera experience.

While I often use GPS these days together with Nokia Maps (see here and here) I haven’t used GeoTagging a lot when taking pictures for the simple reason that it wasn’t tightly integrated into my N70 and N93 and I found it not practicable to do an extra manual step after taking a picture to geotag it. Revisiting the topic a year later it looks like this important issue has now been fixed as well.

Shozu’s GPS GeoTagging

Encouraged by one of the comments left in a previous post I updated Shozu (a program to upload pictures from a camera phone to Flickr and other sites) as the latest version for my N93 supports external GPS receivers for automatic geotagging of pictures. A guide to get started from scratch can be found at AvecMobile.

After activating the GPS option in Shozu, it now automatically contacts my Bluetooth GPS receiver after taking a picture. While doing this, Shozu runs transparently in the background. It also works when having the Shozu query option disabled which asks if the picture just taken should be uploaded to Flickr.

Geoloc
Once the GPS receiver has a fix, the current position is saved in three tags together with the picture. When uploading such a geotagged picture to Flickr, the coordinates are detected and can then be used on the Flickr page to automatically show the location the picture was taken at in Yahoo Maps. If you prefer Google Earth for visualization, copy the coordinates from the lower right part of the Yahoo Maps splash screen and paste them into the "Location Box" of Google Earth. Works perfectly! Here’s a link to the one of my pictures that have been automatically geotagged by the phone. The link to the map can be found among the "additional information" on the right side of the Flickr page.

To see what happens when I don’t have my GPS receiver with me when taking a picture I switched it off and took another picture. Shozu then tries to contact the receiver via Bluetooth twice over a time of maybe 60 seconds before giving up. That’s good in case you forget to switch on the receiver before taking the picture.

Room for improvements

Still there are two areas of improvement: First, Shozu gives up too quickly when the GPS receiver can’t get an immediate fix. If it takes longer than about 45 seconds to get a fix, which happens especially after the GPS receiver was switched off for some time, Shozu disconnects from the GPS device and doesn’t save geotaggs. Also, Shozu adds the GPS co-ordinates in it’s own database, which works for Flickr, but it does not seem to include them in the EXIF information of the images. I checked by using Windows XP’s file explorer, Exifer, Exif Pilot and Nokia’s Lifeblog, but non of them shows any GPS information.

Sony’s GPS Stick

A lot of people still prefer to take digital camera with them which surely still has it’s advantages. For geotagging such pictures as well Sony’s GPS stick might come in handy. Completely autonomous it records the user’s location during the day and a software for the PC then combines the location information with the pictures once downloaded to the PC. I like the idea but I have to admit it wouldn’t work for me as I’ve so become used to uploading pictures to Flickr directly from the camera phone. For me it has the advantage that I can do it right away when I take the picture or shortly afterwards and not when I come back home in the evening and am already tired.

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.