Inertial navigation as a CellID sanity check
Last week-end I ventured outside of the big city, in the land where cells are measured in kilometres and where signal is not taken for granted. So what surprised me was not to have to deal with only the faint echo of the network’s signal. Cell of origin location on the other hand was quite a surprising feature in that environment : sometimes it works with an error consistent with the cellular environment, but often the next moment it estimated my position to be way further from where I actually was – 34 kilometres west in this case.
The explanation is obvious : my terminal chose to attach to the cell it received best. Being physically located on a coastal escarpment, it had line of sight to a cell on the opposite side of the bay – 34 kilometres away.
But being on the edge of a very well covered area, it was regularly handed over to a nearby cell. In spite of the handover damping algorithms, this resulted in a continuous flip-flop nicely illustrated by this extract of my Brightkite account’s checkin log :
Isn’t that ugly ? Of course I won’t comment on this network’s radio planning and cell neighbourhood settings – I promised my employer I will not mention him anymore. But there has to be a better way and my device can definitely do something about it : it is already equipped with the necessary hardware.
Instant matter displacement being highly unlikely for the time being, we can posit that sudden movement of kilometre-scale distances will result in the corresponding acceleration. And the HTC Magic sports a three axis accelerometer. At that point, inertial navigation immediately springs to mind. Others have thought about it before, and it could be very useful right now for indoor navigation. But limitations seem to put that goal slightly out of reach for now.
But for our purposes the hardware at hand would be entirely sufficient : we just need rough dead reckoning to check that the cell ID change is congruent with recent acceleration. With low quality of the acceleration measurement, using it as a positioning source is out of question, but it would be suitable for dampening the flip flopping as the terminal suffers the vagaries of handover to distant cells.
So who will be the first to refine cell of origin positioning using inertial navigation as a sanity check ?
Economy and Networking & telecommunications
19 Oct 2009 at 11:41 by Jean-Marc Liotier
ADSL at cost with your mobile telecommunications subscription
Let’s go out on a limb and make a prediction. In five years, in dense urban areas, you will get your ADSL at cost, provided you subscribe to your telecommunications operator’s mobile offering.
Three major trends are at play :
- Cells are getting smaller
- Radio throughput is increasing
- ADSL throughput is not going anywhere
Once cell throughput approaches ADSL throughput, the value of ADSL drops to zero. Why bother with ADSL when you have unlimited traffic at decent speeds with no geographical limitations ? In Paris, I seldom bother to even switch on my Android G2’s Wi-Fi networking – now it is all UMTS, all the time.
Why not ADSL for free ? As I can even get full motion video on demand on my mobile communicator, the availability of video services on the ADSL remains an incentive only if I’m interested in high definition. But to some people, high definition is important so ADSL retains some perceived value. In addition, giving away free ADSL access bundled with a mobile subscription would be gross abuse of a dominant position by operators protected behind the barrier to entry that their license affords them – so the worse they can do is selling ADSL at cost. But it is nevertheless tempting to squeeze out the perceived value of ADSL from the consumer’s point of view in order to cut the fixed access pure player’s oxygen supply. Isn’t life so much more comfortable among oligopolistic old pals ? Marginalization of ADSL pure players will be even worse if they are not playing along in the fiber optics arms race.
So the incentives combine :
- Users want the convenience of permanent unlimited cell access
- Operators are happy to squeeze out ADSL pure players
As a result, cell traffic increases and leads us to the next step of this self-reinforcing process : femtocells. Spectral efficiency nearing the Shannon limit, antenna diversity, spectral multiplexing and other 3G MIMO techniques can combine to provide the peak throughput that all the shiny marketing pie in the sky presentations promise. But in operations in the field those speeds are not achieved unless you camp under the antenna. For example, LTE 2×2 MIMO is advertised at a peak throughput of 173 Mb/s but actual rates are somewhere between 4 and 24 Mb/s in 2×20 MHz. They drop sharply as distance increases and it gets worse as the cell gets crowded. So there will be strong user demand for small cells – demand theoretically exists until there is one cell per user.
Approximately 60% of mobile usage already takes place indoors, yet providing in-building coverage is a technical problem at the gigahertz frequencies used for Wimax and LTE. This is only set to get worse as the mobile continues to replace the home phone. Research indicates that, as “all you can eat” data packages become commonplace, this number is likely to reach 75% by 2011.
Doug Puley – “The macrocell is dead, long live the network”, 2008
With the user spending more than 60% of his time indoors, there will be a fixed line access nearby. Extension of the access network on top of ADSL and FTTH links is already underway to increase capacity and compress costs by getting the data off the mobile network as close to the user as possible. Femtocells work well on ADSL too. So ADSL will remain useful as a way for mobile operator to shed load from the rest of the access network. And on top of that, ADSL lets the operator reach subscribers in areas not covered by the radio network.
So to mobile operators who offer fixed line access, ADSL could soon be considered as a mere adjunct to their core offering : mobile access. That could add yet more pressure on the game of musical chairs of mobile access frequencies license allocation. Why not attempt to exclude the competition that does not own a mobile network ? That leads us to ADSL access at cost – or slightly below that if the operator is willing to be naughty and deal with the market regulator. It will happen sooner than you think.
By the way, for a wealth of data about 3GPP evolution from UMTS-HSPA to LTE & 4G, you can take a look at this September 2009 report by Rysavy Research. It provides about all you need to know about it and it is nearly as good as what I get internally from SFR.
Five months with Android on the HTC Magic – I’m barely convinced
Five months have elapsed since that first week-end when my encounter with Android was a severe case of culture shock. With significant daily experience of the device, I can now form a more mature judgement of its capabilities and its potential – of course from my own highly subjective point of view.
I still hate having to use Google Calendar and Google Contacts for synchronization. I hope that SyncML synchronization will appear in the future, make Android a better desktop citizen and provide more choice of end points. Meanwhile I use Google. With that out of the way, let’s move on to my impressions of Android itself.
I am grateful for features such as a decent web browser on a mobile device, for a working albeit half baked packaging and distribution system, and for Google Maps which I consider both a superlative application in its own right and the current killer albeit proprietary infrastructure for location enabled applications. But the rigidly simple interface that forces behaviours upon its user feels like a straitjacket : the overbearing feeling when using Android is that its designers have decided that simplicity is to be preserved at all costs regardless of what the user prefers.
Why can’t I select a smaller font for my list items ? Would a parameter somewhere in a customization menu add too much complication ? Why won’t you show me the raw configuration data ? Is it absolutely necessary to arbitrarily limit the number of virtual desktops to three ? From the point of a user who is just getting acquainted with such a powerful platform, those are puzzling questions.
I still don’t like the Android ‘s logic, and moreover I still don’t quite understand it. Of course I manage to use that system, but after five month of daily use it still does not feel natural. Maybe it is just a skin-deep issue or maybe I am just not the target audience – but some features are definitely backwards – package management for example. For starters, the “My Downloads” list is not ordered alphabetically nor in any apparently meaningful order. Then for each upgradeable package, one must first browse to the package, then manually trigger the upgrade package, then acknowledge system privileges the upgraded package and finally clear the download notification and the update notification. Is this a joke ? This almost matches the tediousness of upgrading Windows software – an impressive feat considering that the foundations of Android package management seem serious enough. Where is my APT ?
Like any new user on a prosperous enough system, I am lost in choices – but that is an embarrassment of riches. Nevertheless, I wonder why basics such as a task manager are not installed by default. In classic Unix spirit, even the most basic system utilities are independent applications. But what is bearable and even satisfying on a system with a decent shell and package management with dependencies becomes torture when installing a package is so clumsy and upgrading it so tedious.
Tediousness in package management in particular and user interaction in general makes taming the beast an experience in frustration. When installing a bunch of competing applications and testing them takes time and effort. Experimenting is not the pleasure it normally is on a Linux system. The lack of decent text entry compounds the feeling. Clumsy text selection makes cut and paste a significant effort – something Palm did make quick, easy and painless more than ten years ago. Not implementing pointer-driven selection – what were the developers thinking ?
PIM integration has not progressed much. For a given contact, there is no way to look at a communications log that spans mail, SMS and telephony: each of them is its own separate universe. There is no way to have a list of meetings with a given contact or at given location.
But there basic functionality has been omitted too. For example when adding a phone number to an existing contact, search is disabled – you have to scroll all the way to the contact. There is no way to search the SMS archive and SMS to multiple recipients is an exercise left to applications.
Palm OS may have been unstable, incapable of contemporary operating system features, offering only basic functionality and generally way past its shelf date. But in the mind of users, it remains the benchmark against which all PIM systems are judged. And to this day I still don’t see anything beating Palm OS on its home turf of PIM core features and basic usability.
Palm OS was a poster child for responsiveness, but on the Android everything takes time – even after I have identified and killed the various errant applications that make it even slower. Actually, the system is very fast and capable of feats such as full-motion video that were far beyond the reach of the Palm OS. But the interaction is spoilt by gratuitous use of animations for everything. Animations are useful for graphically hinting the novice user about what is going on – but then hey are only a drag. But please let me disable animations as I do on every desktop I use !
The choice of a virtual keyboard is my own mistake and I am now aware that I need a physical keyboard. After five months, I can now use the virtual keyboard with enough speed and precision for comfortable entry of a couple of sentences. But beyond that it is tiring and feels too clumsy for any meaningful work. This is a major problem for me – text entry is my daily bread and butter. I long for the Treo‘s keyboard or even the one on the Nokia E71 – they offered a great compromise of typing speed and compacity. And no multitouch on the soft keyboard means no keyboard shortcuts which renders many console applications unusable – sorry Emacs users.
The applications offering is still young and I cannot blame it for needing time to expand and mature. I also still need to familiarize myself with Android culture an develop the right habits to find my way instinctively and be more productive. After five months, we are getting there – one handed navigation has been done right. But I still believe that a large part of the user interface conventions used on the Android does not match the expectations for general computing.
It seems like everything has been meticulously designed to bury under a thick layer of Dalvik and Google plaster anything that could remind anyone of Unix. It is very frustrating to know that there is a Linux kernel under all that, and yet to suffer wading knee-deep in the marshes of toyland. The more I use Android an study it, the more I feel that Linux is a mere hardware abstraction layer and the POSIX world a distant memory. This is not the droid I’m looking for.
Books and Military
18 Oct 2009 at 11:58 by Jean-Marc Liotier
Book review : Danger Close – Commanding 3 PARA in Afghanistan Danger Close: commanding 3 Para in Afghanistan
Danger Close is a candid commander’s point of view of 3 Para’s deployment in Afghanistan in the early phases of the British commitment. This is an entirely subjective account, so don’t expect insight into the great game – but do expect a rare insight into the relationship between a commander and his men, in the dirt among the sangars under rocket and mortar fire. The loneliness at the top comes through very clearly.
I was stunned to discover how little means were available and how rapidly those means have been stretched almost to breaking point. As a result, during most of its time in Afghanistan, 3 Para was reduced to holding hastily fortified besieged positions in politically important towns – which is not how might expect this sort of unit to be employed.
This books is a quick read but it provides a valuable vignette of the Afghanistan conflict. It is also a story of the fortitude of the British troops in the face of highly challenging odds. 479 000 rounds fired in six months is a level of sustained combat not seen by the British Army since the end of the Korean war.
Consumption and Cycling and Roller skating
12 Oct 2009 at 0:22 by Jean-Marc Liotier
[review] Princeton Tec Switchback 3 – great light with great service
As a preamble, let me declare that I am in no way affiliated with Princeton Tec and that I stand to gain or lose nothing by expressing my opinions about their products.
A year ago, I needed a light for both cycling and skating, powerful enough for seeing and being seen in urban traffic, and with the capability to rapidly switch between the two modes, which means helmet mounting. So I went searching the web. Among the most interesting finds was Bike Magazine’s December 2007’s test of eight LED trail lights – the Princeton Tec Switchback are HID not LED, but the tests were otherwise informative. I ended up with a shortlist of two candidates : the Niterider TriNewt and the Princeton Tec Switchback 3.
As MTBR’s light shootout illustrates, the Switchback 3 is far from being as powerful as the Nite Rider Trinewt, but it has twice the autonomy (six hours at full power) which is important because on a skating raid I want reliable lighting that can last the whole night. Its list price is 40% lower price and it features a blinking mode which I find useful for surviving the daily commute among zombie drivers with mobile phones. Considering the startled looks on people’s face when I ride across town, I’m guessing that the Switchback 3 is plenty powerful enough for that purpose – it even gets me well noticed in daytime, especially on blink mode.
But power is not everything. In addition to the power, the Switchback 3 has a well designed beam pattern with enough reach for moderately high speeds in the dark, and enough width close up for seeing what you are sticking your wheels into. The two outer beams provide the reach, and the diffused center beam provides the breadth. The regulated power supply ensures stable lighting power whatever the state of the lithium-ion battery (which charges in two hours). With battery, the Switchback 3 is 300 grams heavier than the Nite Rider Trinewt, but if I need to lose weight I’ll start with some body fat. In addition, the weight of the light itself is very low and the hefty remote battery can be stuck near the center of gravity, where its weight is not a concern.
The whole system is watertight – even the connectors are very well designed. During the year it endured heavy rains with no problem although one handed connection and disconnection is a bit difficult with wet gloves.
The lamp not only looks solid – it most definitely is very solid. Skating in a traffic jam, as I passed a stationary dump truck I ducked under its rear and forgot about the light topping my helmet, thus underestimating my height. The light smashed hard into the dump. While my head strapped to the helmet stopped my upper body, the rest continued and I fell down on my ass. The light took the full brunt of the shock of my skating 93 kilograms – backpack not included. That was enough to make it pop out of its otherwise sturdy quick-release tool-less helmet mount, but I was able to slide it back in right away and it is still as secure as before. There is now a dent in the frame, but the frame played its role right as the slightly recessed optics did not suffer the slightest. The system has been performing nominally ever since.
I love this light and I think that my security on the road has markedly improved since I have been wearing it. Here is another review from Crankfire and one from Metro Sucks – both go along the same lines.
My only gripe was that the extension cord was too short. For applications such as roller skating raids and even for exploring the catacombs of Paris (hint – mount it on the side of the helmet to avoid bumping into the low ceiling all the time) really for anytime a backpack is worn, the original extension cord is perfect for having the accumulator pack in the backpack and the lamp on the helmet. But for strapping the battery on my bicycle frame while using the light on the helmet mount, it is far too short. Of course, mounting the lamp on the handlebars would not require an additional extension, but on top of the additional flexibility, helmet mounting allows me to point the beam towards the direction from which I want to attract attention – for cycling and skating, that provides appreciable extra security in dense urban traffic. So I went looking for an extension cord that is longer than the one supplied with the package, but did not find anything like that.
I asked Princeton Tec support for help and the extremly helpful Rob confirmed that instead of a longer cord I could chain two of the original ones. But I only had the one shipped with the lamp and searching for Princeton Tec Switchback extension cord only yielded pages of shops displaying the description of the accessories kit sold with the lamp. None of those seems to sell the cord itself.
I asked Rob again and his reaction utterly surprised me – he simply offered to ship me an additional extension cord… Free of any cost ! That is support above and beyond the call of duty. The Switchback’s price led me to expect good support, but I have often been disapointed by other companies pretending to care. That was not the case with Princeton Tec : those guys plainly turned a slight gripe into complete satisfaction – with a cord now long enough I have nothing left to complain about. Considering the cost of an extension cord, one could see their reaction as just good commercial sense – a happy and probably returning customer for a few dollars, but it is not everyday that I stumble upon a supplier with that sort of intelligence. It looks like I am not the only one to have had that sort of experience with them. Thank you Princeton Tec – next time I need a lamp for anything, you can be sure you’ll end up shortlisted at least !
Africa and Travels
11 Oct 2009 at 20:51 by Jean-Marc Liotier
Dispatches from Ghana 9/13 – Wandering around Prince’s Town
Up at quarter past five and off twenty minutes later to the lagoon behind the beach to watch the sea monkeys. I’m amazed that Pauline was unusually easy to rouse from her sleep – we had a delicious night in the wind and maybe the lure of a few biscuits helped her make up her mind and exit her sleeping bag.
One of the boys is leading us to the lagoon. He rented a dugout from a fisherman for five Cedis and asked for five more for his services. The lagoon is surrounded by mangrove. A corridor among the roots opens on the lake and the rising sun.
I find mangrove fascinating, especially with the dugout gliding silently on the still mirror-smooth water.
It does not take a hundred meters before we spot a first group of monkeys. At first I can’t distinguish them from the mangrove mesh of branches and roots – and I don’t even know what a seamonkey is supposed to look like.
But their movments give away their position and we face them for a while until they decide they have had enough of watching the wild tourists in their natural environment.
Going round the lagoon takes more than an hour. We spot crocodiles from afar, a few couples of kingfishers, big fishes just under the surface and more monkeys albeit in more evasive appearances. Among the mangrove clutter, those monkeys move very fast.
Yesterday I bought a loaf of bread, and some more has been served to Pauline this morning. The Ghanaian bread is an horrible fluffy textureless tasteless piece of British heritage. It can be rendered edible by toasting, but eating it straight out of the bag is self-inflicted gastronomical torture. Lucky the countries colonized by the French and the Italians – we may not have been much better overall, but at least they have good bread.
We decide to spend a day in Prince’s Town – the place is really that nice and on top of that it is cheap. Time to go for a good long walk along the beach and the lagoon.
During the rainy season and high tides every year, local fishermen have a tradition of reconnecting the lagoon to the ocean. They pour libations and then begin to dig so that a channel is created between them. This reunion ritual is supposed to enhance their mutual fertility. The channel seals itself again after a few weeks. Digging must be a considerable community effort – I walked as far as Prusi Akatakyi, the harbour village four kilometers away at the other extremity of the lagoon, and at its narrowest the strip of earth between lagoon and sea is a good twenty meters wide.
I have had confirmation that the path between Axim and Prince’s Town is a bad idea, and also that the one between Dixcove and Prince’s Town is doable. About that last one I gained an additional bit of information : the road ends at Cape Three Points, and there is only a sandy path between from Cape Three Points and Prince’s Town. From Prince’s Town, the road is found somewhere east of Prusi Akatakyi. But Google Map imagery for that area is dreadful and I have therefore been unable to confirm that visually. Also, it looks like I did indeed reach the village of Achenim – the one after the footbridge – it is there that I missed my turn and followed the crowd’s advice against all reason.
More playing in the waves today, and Pauline plays with the local kids at the fort. We take is easy today. Tomorrow we’ll start early – I can’t wait to see our friends in Takoradi. Siesta on the beach under the shade – but with a strange tickling on my left leg… A violinist crab repeatedly checking if I’m a rotting carcass fit for crab consumption. He beats a hasty retreat to its burrow every time I sit up, and then starts nibbling anew a few minutes later.
The view from the fort dominating the bay on two sides never ceases to fascinate me. I always appreciate high viewpoints, but the comfort of living on the fort’s walls with the ocean’s wind certainly makes it the best accommodation I’ve encountered in Ghana so far – and at 20 Cedis a night including evening meal for Pauline and me it is the best value too.
One of the multipurpose artists introduces himself to me as a traditional musician. When I ask him which region or which people of Ghana his music is inspired from, he claims it is Ghanian’s – which contradicts any claim of tradition : Ghana is a synthetic identity whose tradition as a whole is still dwarfed by what its different people bring to the table.
Pauline likes the multipurpose artists . They are harmless to children, but I sense a teenage catastrophe looming.
The multipurpose artist tells me he usually stays in Krokrobite. I was wondering about that place, but now I know why I’ll avoid it : it sounds like a Ghanaian equivalent of other places I won’t name but whose hashish smoking population I have striven to avoid too. Not that I have any hate toward hashish smokers in general – but in Africa, a significant concentration of them is usually a bad sign, especially if they are equipped with djembe.
On the way back from the beach, we spot a colony of ants forming a living tunnel accross the single track path, covering the moving of the whole complement of larvaes from the colony. The stream of workers carrying larvaes was easily ten per second, and all traffic was one way. Soldiers were patrolling the whole thing, and the stream was using galleries under the humus on both sides of the path. This was impressive. I wonder what pushes ants to move their entire colony in a hurry like that.
Yesterday night we ate sauteed eel with fried rice – very nice. Today we are having calamar in a tomato sauce with white rice and way too much salt – not nice… Its only redeeming value is that the excess salt reminds me of Veronique, my current world record holder for excess salt in food. But generally, you can count on great seafood all along the Ghanaian coast.
Tonight is much quieter than yesterday : no beer swilling Germans and no hanger-on girls… What a coincidence ! We have announced our departure for early next morning, so no one is trying to sell us services anymore. Even the multipurpose artists are absent – only the caretaker and his skeleton staff are with us. There is also a couple of Schwaben farmers camping in the courtyard, a German-Nigerian couple who lives in Ghana on a plantation, and Olly – a citizen of Switzerland. I have a good chat with an Italian girl who is writing a thesis about the divergences between African cultures and how African Americans perceive them.
Ghana Telecom is building a twenty eight meters high cell tower in the high point nearest to an electricity source in the area : right in front of the fort. Considering the value of tourism for the local economy, I have my doubts about how wise that choice of location is. But the unbeatable unobstructed view to the sea which drew the German founders of the fort to this location four hundred years ago may also be the reason for planting a BTS there. Correlation with the announced offshore oil boom may not be fortuitous either. But then, wouldn’t cell sites aboard drilling rigs3 0 km out at sea be a viable option ? The cell tower emplacement is a 18k USD rent every year and it is part of the money flowing directly or indirectly from the oil extraction, feeding the insatiable demand from the local chiefs.
France abolished chieftaincy as an administrative level, replacing it with the Fench direct rule. But the British indirect rule system used it as a leverage. As a result, village chiefs are still important in Ghana. Olly tells me that two chiefs compete in Prince’s Town. Last year, it came to combat and dynamite sticks – and some people fled to the bush.
Former fort caretaker had to abandon his commission under pressure from the chief’s war. Olly says he used to run a tight ship whereas things went downhill with the new one. Not only maintainance, but lack of discipline in the guests behavior, such as the beach rastas patronizing underage girls. Over ten years, Olly was the initiator of the fort’s improvement : repainting, refurbishment, more beds.
Olly claims that the dynamite was obtained through NGOs. NGOs are full of young overenthusiastic people with strange ideas about Africa and a crying lack of management. They often don’t understand local politics and become the unwilling tools of the political forces.
Prince’s Town has changed a lot in the last years. TV antennas have sprung on top of bamboo poles, now the cell towers. The next years are probably going to accelerate : with oil offshore, the town earns back its former strategic importance as Ghana’s southernmost tip. The navy has plans for a patrol base at Prusi Akatakyi. Some day the unsuspecting investors who are getting suckered by the chiefs, thinking they are the first to think about building an hotel will eventually succeed. Some day the dirt road may be tarred. The money, the beach rastas and everything else will come to Prince’s Town too.
The beach rastas are suborning minors and generally behaving like colonials toward the villagers. They piss in the communal showers at night when the toilets are ten meters away. They are so bad that Olly cut his own rastas for fear of being associated with those guys who they lack respect for people in spite of their tourist friendly message.
Meanwhile mosquito repellent does what is says on the tin, but I learn to my dismay that it does not repel blood sucking flies… Time to retreat under the mosquito net !
Networking & telecommunications and Politics and The media
08 Oct 2009 at 11:18 by Jean-Marc Liotier
Pirates ! French presidency makes 400 unauthorized copies of DVD
The French satirical investigative journalism weekly “Le Canard Enchaîné” reveals that our holier-than-thou presidency is in fact a pirate’s lair. In a stunning display of hypocrisy, the presidential audiovisual services produced 400 unauthorized copies of the 52 minutes documentary “A visage découvert : Nicolas Sarkozy“.
The editor, Galaxie Press had only shipped 50 copies, but the propaganda plan required more so the Elysee went to work, going as far as modifying the cover and replacing the Galaxie Presse name and logos with “Service audiovisuel de la présidence de la République”.
Isn’t is deliciously ironic that the same executive power is the main force behind the latest disgusting bungled piece of French legislation regulating and controlling the usage of the Internet in order to enforce the compliance to the copyright law ?
It is even more appalling that we are dealing with repeat offenders : last spring, while the Hadopi law was discussed, U.S. music duo MGMT received €30,000 as a settlement for a copyright infringement by French President Nicolas Sarkozy’s party who used one of its songs at a political rally without permission. Those who led the charge against Internet users are not the most respectful of copyright.
Hadopi is also known as the “three strikes” law because it after a certain number of warnings a copyright infringer’s Internet access would be cut off. Hadopi has just been adopted. Nicolas – one more of those antics and your Internet access is toast !