Here is an interesting blog entry on the Nokia Beta Labs Blog: Tommi reports about the recent coverage of Nokia SportsTracker (which I like very much by the way) in Newsweek and about a YouTube advertising video that came out of the blue. Looks like it was not being done by Nokia!? Is the web 2.0 community now also coming up with the advertising for products they like? Incredible!
Sniffing Wifi Packets and Exploring Retransmission Behavoir
Since I figured out how to configure my eeePC for Wifi tracing with Wireshark, I’ve gained a number of interesting insights which go far beyond what you can read in literature on the topic. Standards are one thing, how they are implemented in devices are quite another sometimes. Here are some results I thought I’d share with you:
As a wireless medium is prone to transmission errors, each frame has to be acknowledged by the receiver. If the frame is not received it is automatically retransmitted. So how do devices do this in practice and how often does it happen? I’ve been able to do some pretty interesting traces with a Siemens Access point and a Nokia N95. The two devices are quite different in their radio characteristics as the antenna in the mobile device is far from ideal, especially if there is a wall separating the two devices as was the case in my test. Also, the behavior on the air interface is quite different, which has nothing to do with the antenna configuration.
The Siemens Access point is quite conservative concerning the use of modulation and coding schemes for a packet. The majority of packets are never sent with the maximum speed of 54 MBit/s, but instead with 36 MBit/s or even less. As a consequence, most packets are received correctly and are immediately acknowledged. In case there is no acknowledgement, the access point immediately reduces the modulation and coding by a step for the retransmission. As a result I haven’t seen many cases in which a frame has not been acknowledged after the second try.
The N95 on the other hand is pretty aggressive concerning modulation and coding scheme. It usually always starts with 54 MBit/s and even uses this setting for the first retry. If the first transmission has failed, the second usually does as well. Only for the third transmission is the modulation and coding scheme lowered to 48 MBit/s, then to 36 MBit/s and finally to 24 MBit/s. For subsequent frames, 36 MBit/s seems to be used for about 500 ms before the N95 Wifi chipset tries to go back to 54 MBit/s.
Also interesting is the repetition time in case no acknowledgment is received. On average, a packet is resent after around 0.5 ms. In case a packet is retransmitted 3 times, the resulting delay is about 2 ms. As a single frame usually carries 20 ms voice data, this time is negligible on the application layer and is far less than the jitter introduced on the way through the public Internet.
If you think three repetitions is a lot, you are right. However, I’ve seen cases in which the frame was transmitted 7 times before it was finally acknowledged. In this case, the backoff algorithm even allowed other stations to send their frame before the device could try all retransmissions. Pretty impressive.
The figure on the left shows how such a trace looks like in practice. Frame 6420 is sent but no acknowledgment is received. It is then resent as frame 6421 and then as 6422, after which an ack. is finally received. 6426, 6427 and 6430 are all the same frame, only acknowledged after the second retry. In between is 6428, a frame from another device together with its acknowledgment, 6429.
So that’s how it works in practice 🙂
S60, the Motion Sensor and an RC Truck
I first heard of a project at the University of Hagenberg to control an RC truck via an N95 over Bluetooth by using the N95’s built in motion sensor in a recent S60 podcast. At the Web 2.0 conference in San Francisco last week, the S60 marketing team gave a demo how it works in practice. Here’s a YouTube video showing how Oren Levine controls the truck. Very impressive!
Are We Going to See a Shootout between DVB-H and DVB-T?
Once the Nokia N96 hits the shelf it will probably be one of the first DVB-H (Digital Video Broadcast – Handheld) devices being shipped in large numbers. Not that DVB-H capable handsets haven’t sold for about two years now. However, DVB-H is only available in a few European countries such as Italy, and reception is not free. Maybe it is this fact coupled with licensing issues and access to the required spectrum that prevents mobile TV from taking off?
T-Mobile and Vodafone might think just that and have decided to launch DVB-T (Digital Video Broadcast – Terrestrial) capable handsets before the European football championship this year. The advantage: The DVB-T receiver in the mobile receives the non encrypted standard digital television signal for TVs. No subscription is required and there are no doubts concerning the programming, since users know it from their TV set at home.
Note that opening up the mobile platform to receive standard terrestrial programming is nothing new. In Japan, mobile TV seems to be quite popular, maybe just because among other things, there is also no subscription required to receive the program via the 1seq, the technology used there.
Critics say the DVB-T receiver chip is likely to consume more energy than the mobile optimized DVB-H chip. That’s probably true but the big question will be if it really matters…
Small Screen Web Browsing and Other Definitions
In the mobile world, words like ‘free’, ‘open’ and ‘unlimited’ have pretty much lost their original intrinsic meaning. Instead, these words have become mere marketing shells which make it difficult to compare different offers. In many cases a free, open and unlimited mobile Internet access offer usually means that it is only intended for use on the mobile phone, most services are blocked and a cap is put into place if the user manages to consume more than the unlimited data in the offer. So how could one realistically call such offers? How about:
- Small screen web browsing within reasonable limits
or, in case eMail is included:
- Small screen web browsing and eMail access within reasonable limits
To many marketing departments the Internet and the web seem to be the same thing. But please take note: The (world wide) web is just one of many applications using the Internet as a bearer. Therefore only allowing web browsing and eMail is not an Internet offer, it’s a web browsing and eMail offer!
But then, we are all free to give any word unlimited meanings and should be open for other opinions 🙂 Long live the fine print!
Intercepting VoIP Calls with Wireshark
In case you have an Nokia N95 or similar SIP capable 3G / Wifi / VoIP phone and wondered why the little icon during a VoIP call shows an ‘open lock’, the answer is simple: The encoded voice data is not end-to-end encrypted. That means that anyone on the network between you and the other party who can intercept the data packets can listen to your conversation.
Sounds difficult to do in practice? Well, not really. I recently discovered that Wireshark, a free network monitoring tool, can decode G.711 PCM encoded speech data of SIP VoIP calls as shown in the picture on the left.
Just to be clear, this is not the fault of Nokia as I haven’t seen any other SIP client in practice yet that encrypts the voice data stream. In a public Wifi hotspot, intercepting the call and listening to the conversation is very simple, as the data packets are not encrypted between the device and the Wifi access point. In home networks, things get more difficult because most people nowadays have encryption between their devices and the Wifi access point enabled. But do you know what happens on the other side of your DSL connection…?
Orange France, the Small Screen Internet and Prepaid
Good news for mobile Internet use in France! Orange France has started to offer the same small screen Internet add-ons for prepaid and postpaid users. In addition to the ‘Découverte Multimédia’ option, which includes 5 MB worth of data for €3.-, Orange now also offers the ‘Internet Max’ add-on for €9.- a month to prepaid users.
What one can do with it: The offer includes mobile phone based web browsing and sending/receiving eMail from/to any POP/IMAP/SMTP server. Email transfers are limited to 10 MB a month.
What one can NOT do with it: The fine print states that Orange reserves the right to throttle transmission speeds if use exceeds 200 MB a month. The offer also excludes ‘peer-to-peer’, VoIP, and ‘newsgroups’ (whatever that is). Furthermore, the use of the mobile phone as a PC modem is not allowed. I am not sure if instant messaging is possible and whether only specific TCP ports are open for communication as the T&C’s don’t mention that specifically. To me, that looks like some sort of deep packet inspection is performed in the network. Should be fun play around with the option a bit to see what’s enforced in practice.
Despite the limitations I generally think this is good news since the price and availability with prepaid SIMs opens the mobile Internet to a wider audience. For the details, have a look on the Prepaid Wireless Internet Wiki.
3GPP Moves On: LTE-Advanced
LTE is not yet even deployed and the 3GPP Third Generation Partnership Project) is already thinking about how to further evolve the technology. A main driver is probably the ITU (International Telecommunication Union), who will in due time release their requirements for so called IMT-Advanced 4G wireless systems.
It is quite certain that in terms of bandwidth, LTE and all other beyond 3G wireless systems such as the current WiMAX 802.16-2005 (802.16e) specification will fall short of the ITU requirements, which will probably be in the range of 100 MBit/s to 1 GBit/s. A very ambitious goal. Earlier this month, 3GPP hosted an IMT-Advanced workshop in Shenzen to which 170 representatives of network vendors and network operators from all over the world attended.
Not much has been reported about it yet in the news or on blogs, so one could think they are working in the shadows. But far from that, the 3GPP website reported on it here and all papers presented during the workshop and a report can be downloaded from here. Tons of information! Compared to other standards bodies that keep their proceedings to themselves, it is great to see 3GPP is so openly distributing their information. They set a good example!
The following bullets list some of the first ideas for LTE-Advanced presented during the meeting to comply with the likely requirements of IMT-Advanced. During the meeting it was decided to officially gather and approve them in 3GPP TR 36.913 over the coming months:
- LTE advanced shall be backwards compatible to LTE (i.e. like HSPA is backwards compatible to UMTS)
- Primary focus should be on low mobility users in order to reach ITU-Advanced data rates.
- Use of channel bandwidths beyond 20 MHz currently standardized for LTE (e.g. 50 MHz, 100 MHz).
- Increase the number of antennas for MIMO beyond what is currently specified in LTE
- Combine MIMO with beamforming.
- Further increase in Voice over IP capacity
- Further improved cell edge data rates
- Improved self configuration of the network
Very ambitious goals, given that vendors are still working on the challenges of LTE. But then, what would the world be without ambitious goals?
Thanks to Zahid Ghadialy and his post on his ‘3G and 4G Wireless Blog’ for the pointer!
Geocaching with my Nokia N95
Geocaching has become almost a mainstream hobby these days. So on a previous weekend, I gave it a try to find out what this is all about. As I don’t have a dedicated GPS device, I wanted to use my Nokia N95 with the built in GPS receiver for the purpose. With a quick search I found exactly what I needed for the purpose: "Geocache Navigator" by Trimble. The software is free if you can live which an occasional advertisement, of which I haven’t seen one yet, though.
Strangely enough, the Geocache Navigator is a Java based program but seems to have been specifically developed for Nokia Nseries phones with a built in GPS API. I tried the program both with the built in GPS receiver and my external GPS Bluetooth mouse and it just works fine.
A "cache" can be hunted in several ways with the program. Either you use the program to find starting points for caches around you including instructions what to do at each waypoint, or you use the PC to visit a geocaching web site such as www.geocaching.com, locate a cache and print out the instructions. I preferred printing out the instructions to downloading them to the program.
Despite the program requesting access to the network, it’s not required if the instructions are printed out beforehand. In this case, however, the GPS co-ordinates have to be typed in manually. As you can see in the second picture on the left, I managed to find my first cache 🙂
For a visual explanation of how the program works, have a look at Trimble’s video that shows how the program works. Very nice, it won’t be the last cache I’ve hunted 🙂
Oxford Tech Conference Roundup
Last week it was a great pleasure to attend Oxford University’s Future Technology Conference. Hosted by Peter Holand, Ajit Jaokar and Tomi Ahonen, the event brought together over 70 people from all over the world, coming from as far as the U.S. and South Africa.
Unlike other conferences that mostly focus on presentations from new startups in the mobile domain, this conference had a much broader spectrum, which was reflected by the many refreshingly different topics presented during the day. Below are a couple of notes I took for contemplation. In addition, I’ve uploaded some pictures to Flickr.
Mark Selby, Vice President Industry Collaborations, Nokia:
- Mobile is about creating, consuming, interacting and connecting
- Berthold Brecht about the radio: It is nice that it is talking to me, but I would like to talk back.
TV = unhealthy fixation with furniture - DRM is a waste of time, people will always find a way around it. Social acceptance of ownership is necessary in the same way that it is accepted by most today that breaking into someone else’s house is not acceptable.
- Augmented Reality: I’ve reported about this before and Mark had a remarkably new application: What if you could point the camera of your phone towards a building and a server back on the Internet then recognizes the building and tells you about restaurants inside, apartments for rent, etc. In my opinion, still some years away, but I see a great potential here.
Jonathan MacDonald, Blyk:
- The ‘community’ doesn’t see themselves as the ‘community’. Everybody sees himself as an individual!
- The advocacy dial: ignore, review, engage, recommend
- Personal recommendation: The best form of advertising
- Offers solutions, not services
Niklas Blum, Fraunhofer R&D Institude FOKUS
- Reported on how to integrate web services with IMS. Interesting slides, my question, however, who integrates with whom, telco with web 2.0 company or vice versa remains.
William Volk, CEO NyNuMo
- Reported about service uptake of his games on the iPhone.
- Discovery is crucial and Apple did a superb job with application discovery for the iPhone.
- Since his games are browser based, they could be easily adapted to Nokia Nseries browsers.
- However, Nokia has no content discovery in place that comes even close to that of Apple.
Tomi Ahonen vs. Dean Bubley
- The great mobile debate: Will the future of the Internet be shaped by mobile, or is the PC still in control? Hilarious debate, no clear winner
Simon Cavill of mi-pay
- Gave a great presentation about using mobile phones to send money between countries, mostly from immigration countries such as the U.K. back to Africa.
- I’ve reported about M-Pesa before, which is something similar but only on a national basis. This one works for sending money home, bypassing expensive services such as Western Union. Hopefully, his slides are put online by Forum Oxford.
Antonio Vince Stabyl – CEO of itsmy.com (Gofresh)
- Great presentation of his mobile social networking service.
- During the presentation, he mentioned that the service first became successful when it was discovered by users in the U.S. markets with reasonably priced flat rate mobile data.
- Virality kicked in when people having data flat rates recommended the service to friends.
Christian Lindholm, Fjord
- As always a thought provoking presentation around user interfaces.
- “Users only exist in mobile & the drug industry”
And that’s it for the roundup. Once the link to the presentations is available, I’ll put it into the comments section below. Thanks to Peter, Ajit and Tomi for the great event. Looking forward to an ‘encore’ in 2009!