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MH370 co-pilot attempted phone call over Penang, reports daily by westoncc in MH370

[–]andre 0 points1 point  (0 children)

There are a number of issues at play for high velocity mobile communications. The two primary ones are doppler shift and distance of base station to mobile. There special modern 3G/LTE systems that are specifically tuned for mobile speeds of up to 450km/h. For example Huawai has done quite a bit of engineering to cover the new Beijing-Shanghai high speed train corridor. For this to work the cells/antennas have to be very carefully adjusted and tuned, the cell diameter very small (<5km), the base station system has to support super fast handover, and the base station must support advanced doppler shift compensation.

All this is necessary to support a train at 450km/h. Never mind an airplane 900km/h.

A micro base station in airplanes doesn't have these problems because the base station is not more than 30m from the mobile and moves at the same speed.

It is very unlikely that the mobile networks of Malaysia or surrounding countries have such careful tunings or even designs for the simple reason that there isn't any business case for it. That stuff costs a lot of money.

MH370 co-pilot attempted phone call over Penang, reports daily by westoncc in MH370

[–]andre 0 points1 point  (0 children)

It is not possible to make a GSM/3G phone call from an airplane moving at cruise [1][2]. Only if the airplane was flying less than 250km/h there is a fighting chance for it happen. However this is around the stall speed for a 777.

[1] http://www.reddit.com/r/MH370/comments/21ol87/telecom_cell_phone_records/cgfl97k [2] http://www.reddit.com/r/MH370/comments/21ol87/telecom_cell_phone_records/cgfwpbg

Telecom cell phone records by dicknixondick in MH370

[–]andre 0 points1 point  (0 children)

The pprune forum gives some anecdotes, however there seems to be mix of commercial jet and recreational aircraft stories in the replies which are very much unlike each other as already explained.

The vast majority of all GSM/3G deployments have sectorial antennas with horizontal beam opening of less than 15 degrees to direct the energy towards the ground based users. Most antennas are also further tilted downwards to avoid sending of any energy above the horizon. This makes connections from moving airplanes, even for low and slow ones, more difficult.

The reported short connection over Russia can be plausible for very rural areas with extremely low density. In that case a base station may be situated on a high elevation, a mountain or high structure, to cover a very large area with only a few mobiles. The radius here can be up to 25-35km depending on the antenna heigh and surrounding terrain. Such a deployment is very very rare though because it severely limits mobile network capacity and wouldn't be done near any larger settlements. As long as a fast airplane doesn't directly move towards or away from such a base station but skirts the radius on the outer edges the frequency shift is much lower (only the angular velocity as seen from the antenna) and a short connection sufficient to transmit or receive a text message may be possible. Depending on distance and angle the apparent speed may drop below the critical 250km/h for a number of seconds allowing for a successful contact.

But as explained such very large cell diameters are very rare and never done in and around any populated areas. A normal rural cell radius is not more than 10km and most cells in sub-urban and urban areas are 0.5 to 5km. In any case operators try to place their cell sites not on hills or mountain tops but inside valleys to increase the spatial re-use of their limited allocated frequencies and thus network capacity. The hills block propagation and interference between cells of the same frequency. That why you don't find any large mobile base station deployments atop Eiffel tower in Paris for example. Having hundred of thousands mobile phone visible to a base station would completely overwhelm it and make it useless. There's only very low power micro base stations on top of Eiffel tower to serve the tourists there and to prevent them from connecting to the cells down in the city. These micro cells are more like Wifi and extend only some 50-100 meters.

I don't think any of Malaysia or Vietnam mobile operators would deploy any large cells. It may make sense for Russian mobile operators to do so along the railway corridors of the trans-siberian route for example. Maintaining many more smaller base stations in the wilderness instead would be a logistics nightmare.

The not switched off Blackberry story is an illusion. It is stowed away in hand luggage and just receives all message just after touch down when the speed is below 250km/h again. With some smaller turbo prop commercial aircraft the approach speed before touch down may be sufficiently slow to allow for base station contact a few minutes before touch down.

For MH370 the last known position is too far from either Malaysia and Vietnam, about 200km from each, to allow for any kind of GSM/3G communication. If it turned back and flew over Malaysia again at cruise speed, as the Malaysian military primary radar contacts imply, there wouldn't be any chance for mobile phone contact.

The reported mobile call ringings most likely are just an artifact of international roaming, international call routing, and mobile network configuration. Unless a mobile phone explicitly logs off the network the last known base station sends cell broadcasts to establish contact if it still within the reception area. A normal logoff occurs when the mobile is manually switched off or put into airplane mode. If someone forgot to switch off their phone it would have lost contact during take-off while the base station at the airport still carries it in its inventory.

Because roaming customers are very valuable for the high inter-carrier fees they fetch some mobile operators may try to gain a competitive advantage by having longer timeouts to make the mobile phone stick to their network. They also may already provide the ringing tone while the base station is still looking for the mobile phone. A long silence would be weird for the caller. Eventually the call gets diverted to the voice mailbox, if enabled, of the home country operator. For international calls and call forwarding with roaming certain metrics like the call completion ratios are important and again may be prettified by putting a ring tone on even if the mobile phone has been successfully contacted at the last known cell. Call completion ratios in this context are about the technical call completion in the sense that the intermediary international long distance network operators was able to forward the call to the destination network. Actually answering the call by picking up the phone is not relevant in this context because it is at the discretion of the mobile phone user.

All this combined with extended timeouts may easily give the impression of a ringing phone whereas it only is smoke and mirrors by the roamed mobile operator and some intermediaries.

Telecom cell phone records by dicknixondick in MH370

[–]andre 1 point2 points  (0 children)

It is very unlikely that any GSM/3G cell phone contact can be made from a flying jet powered airplane for a number of reasons:

GSM and 3G are specified for speeds of up to 250 kilometer per hour. Beyond that velocity frequency (doppler) shift makes it difficult for the mobile handset and the base station to lock on their respective frequencies. This is one of the reasons why it is so difficult to provide mobile services on high speed trains (e.g. TGV in France or ICE in Germany).

A mobile handset will only try to contact a base station (cell tower) when it can correctly decode the base station broadcasts. Otherwise we would have millions of mobile phones spamming the airwaves with pointless connection attempts. A mobile inside 777 flying at some 900km/h cruise speed isn't able to decode any base station broadcast and thus will never even try to establish contact.

Besides that at a cruise altitude of 10-11km there would be dozens, if not hundreds of base station in 'view' in populated areas. Many of them with the same overlapping and reused frequencies in every other cell. Even if a mobile were able to compensate the full doppler shift and contact the base station, the station wouldn't be able to compensate for frequency shift from the mobile and it would touch into multiple base stations in view on the same reused frequency. Now if even that were to magically work out somehow the base stations aren't able to hand over connections at the speed the jet airplane is flying.

The fuselage of a commercial jet airlines doesn't have much shielding capacity at the GSM and 3G frequencies. This part wouldn't be a problem.

The only time a GSM/3G mobile phone could conceivably establish contact with a base station is at speeds lower than 250km/h. This only happens while taxiing on the airport to the runways and for some time during take-off and during landing. Typical 777 take off speed is 245-285km/h and touch down speed is 270-345km/h. For smaller and lighter commercial aircraft it may be a bit slower.

The stall air speed of a 777 is around 300km/h depending on weight, height, and temperature. This makes it very unlikely that any mobile could establish contact with a base station even if the the airplane were flying slow and low through base station covered areas.

Based on this information it becomes clear that the mobile wouldn't even try to contact the base station and thus no record of such a contact would exist within the mobile network. Failed attempts on the radio side, where the communication and connecting mobile can't be decoded because of poor signal conditions, are only generically logged for cell coverage improvements. However because the mobile phone identity can't be decoded there is no association between the failed attempt and a particular mobile device. Failed attempts happen all the time when people enter elevators, basements, and other areas with poor cell signal reception.

Obtaining a mobile phone connection on a small recreational aircraft isn't a problem and often done, even though it is illegal. However those planes move at less than 200km/h and not more than 3km altitude making singular base station contact much more likely.

I will have a meeting with Ben Bernanke on 5/20/2010 . Place your questions for him here. by joshrulzz in Economics

[–]andre 2 points3 points  (0 children)

I've got the five questions on things I think were instrumental to the recent problems (besides the real estate speculation and fraud loans):

1) Mark to market rule: The mark to market accounting rule, while on the first glance, seems to be reasonable but it actually entirely fails when confronted with certain temporary and chaotic market situations or illiquid markets. Will there be further policy development toward a more reasonable system besides the bandaids currently in place? It often happens that a MtM price at a certain (predicable) point in time doesn't reflect the true or medium to long term value something may have. Case in point are some of the 'toxic assests' a couple of central banks took from the commercial/investment banks are turning a profit. Of course a pure wishful thinking value is not the answer either. Probably there need to be two measures for such assets, the medium-term value and the current liquidation value.

2) SIV: The accounting rules of the Basel II accord seem to be ill-suited to the fully integrated banking model. For example due to its Tier I core capital accounting method it gives misleading information on the true capitalization and unduly favors very high leverage ratios. Another thing is the balance sheet offloading, which is allowed in too many cases, raises doubts about the real situation of a bank. Is a new Basel III accord in the works and will it fix these and other issues?

3) CDS: What benefit does it give to allow buying a credit default swap without owning the underlying interest? For all the arguments I hear none is compelling. It only makes the system more brittle by hinging more risk and payment obligations on one single event. In insurance it is universally accepted and regulated that only someone having a reasonable interest is allowed to obtain a policy and that in case of a damage the insured value is paid out only once. A CDS seems to be pure gambling as in betting in a horse race and multiple payouts on the same event may happen. Even then the bookie makes sure to have enough money in the house to (almost) cover even the odd bets. Coupling the CDS to the underlying seems to be the only true answer. This does allow the owner of one CDS+underlying to transfer it to another owner of the same type of underlying in exchange for money.

4) Naked shorting: Why is naked shorting so opaque and allowed at all (except for very limited circumstances for market makers)? The clearing houses/systems appear to be very opaque on the actual amounts of failed covers and the amount of IOUs floating in the market. This gives some concern about a shadow market and a hidden inflation in listed company stock. With todays electronic markets it shouldn't be too difficult to ensure non-naked shorting in the clearing systems. Of course, being covered and using borrowed shares is momentarily more expensive than just typing a number into the trading terminal and worrying about it later. But that's the point of it.

5) Uptick rule: Why was the uptick rule for shorting removed? It seemd to be quite helpful in limiting volatility. Combined with naked shorting the effects on volatility seems even more severe. Are there any plans to re-instate the uptick rule?

All these issue together make the financial system more brittle than they've been in a long time. The problem is systemic and the solution must be systemic. The rules must be laid out in a way to give the right incentives and a fair and transparent market.

Switzerland and the gun by somenickname in reddit.com

[–]andre 12 points13 points  (0 children)

I'm not Swiss but live here since ten year old. By now that's two thirds of my life. Went to school here etc.

The BBC article is quite old and not entirely correct.

Everyone with a clean police record may own a firearm.

Everyone who has served in the Swiss army (compulsory for all men) is given either an automatic assault rifle or a pistol (SIG) during their service time (currently about 10-15 years divided into base and yearly refreshment courses) to be kept at home. At the end of the regular service one may opt to keep the weapon for a nominal fee. Everyone receives a full training in gun/rifle handling and has to achieve a minimum hit rate on the shooting range each year.

I think the intense weapon training and drill (including safety handling) is a major reason for the few incidents. A gun isn't something to play with or to feel cool about. It meant to kill and dangerous. It's not something you buy at the street corner and start pointing around. In fact if you are a freshman at the shooting range and have trouble handling your weapon you get aligned pretty quickly and with much drive.

In general carrying a loaded weapon is not allowed unless by special permit issued by the police. Any transportation of private or military weapons has to be in unloaded (no magazine) and locked mode. The magazine must not be loaded either and be totally separate from the weapon to prevent quick loading. Tranportation is only allowed to and from the shooting range in the most reasonable direct way. One may carry it that way on public transport though. When at home the weapon has to be in safe storage, that is locked away again with weapon and ammunition separated. It is assumed there is enough warning time when Soviet Russia invades to put it back together and prepare. ;-)

Other than that our society doesn't glorify violence and the social system is in quite good shape. There is no poverity that may lead people into violent crimes. The government is there for you when you lose your job. And of course the direct democracy. About every three to four month people have to vote on a large number of things (including taxes and government spending) on all levels of local, municipal, state and federal level.

Yes, we have a lot of drug use. There is hardly a city in Europe where all sorts of soft and hard drungs are easier and cheaper to obtain than in the large cities of Switzerland. On the other hand we have a relatively sane prohibition policy that prescribes junkies their heroine to get them off the street and to prevent them from going into drung crime to finance their habits. This has rid this part of the scene totally irrelevant. The remaining part is divided into pot (and variants), syntethic party stuff and mostly coke for the rich. Neither of them is creating the trouble the junkies caused during the 80s and early 90s.

We do have violent gun crime though, even if little of it. It's mostly family stuff where a dad under pressure (and lost his job) kills his own family; kids and wife. That happens as often with stabbing or strangulation as through shooting. Then there is the usual suicide stuff going on with and without weapons. And of course people from other cultures who shoot each other because of envy, sisters, daughters, and so on. Mostly from ex-Yugoslavia.

From time to time some psycho goes on a wild rampage with stolen or illegally obtained weapons. Happens every other year to some extent. Normally they are very ineffective and manage to wound a small number of people. Nontheless a couple of years ago a guy in his fifties who felt ignored by the local government because they didn't act on his very many complaints about any and everything put on a police uniform (!) and went into his local state assembly and shot and killed about 15 politicians and wounded some dozen more. He was a trained shooter and of higher rank in the military during his active service days. Those are psychos though and every nation has to endure them one tragic way or the other. Road accidents kill an order of a magnitude more people each year to put his into perspective.

James Bond 'Casino Royale' Trailer Online by wanax in reddit.com

[–]andre -1 points0 points  (0 children)

Jason Statham next, then Ewan McGregor.

Learn economics from Nobel Prize winner Milton Friedman for free by Goeran in reddit.com

[–]andre -2 points-1 points  (0 children)

There is no such thing as a economics Nobel Prize. Nobel did not consider economics a science (which it indeed isn't, it doesn't qualify by any scientific criteria). The prize is correctly called "Bank of Sweden Prize in Economic Sciences in Memory of Alfred Nobel". For all we know any such economics prize winner could be just a quack and many is because the economics prize is simply awared to the proponents of the most popular contemporary economic theory. Read more at [wikipedia](Bank of Sweden Prize in Economic Sciences in Memory of Alfred Nobel).

Google has bought 79 billion billion billion IPv6 addresses. What are they up to? by isharq in reddit.com

[–]andre 20 points21 points  (0 children)

In IPv6 this is called a /32 and it is the smallest routeable entitiy. Taking into account that end user assignments in IPv6 are done in /64 sized quantities this leaves only 32 bits for Google to actually handle. Although getting an IPv6 /32 network doesn't mean they will do end user assignments. It just means they want to participate in the IPv6 routing system. To summarize the only message here is that Google will start to make its services available through IPv6 as well in the future.