Re:Jamming? Wait a minute...
on
Cell-Phone Wars
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· Score: 1
You can jam almost anything with a white noise generator and sufficient power. Spread spectrum is jam resistant, it can still be jammed, it just takes more power than is needed to jam older modes of communication.
Re:Question for Wireless Geeks
on
Cell-Phone Wars
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· Score: 1
Get yourself a neon sign transformer. Plug it in to the nearest convenient AC outlet. To verify that the transformer is operating properly, wet your hands and firmly grab the output leads of the transformer. This will solve your problems with annoying wireless calls.
You obviously haven't met one of the many people who will loudly proclaim that their body is being poisoned if anyone within a 1000 meters lights up a cigarette.
Motorola has left the pager business. The conventional wisdom is that traditional pagers are going to disappear over the next few years and be replaced by pager-like devices that operate on existing cell phone networks.
The problem with jammers is that they can't discriminate between cell phones, pagers, walkie-talkies and other devices that use the affected frequency range. In many areas, the police and fire departments use radio systems that operate in the 800 MHz frequency range, along with many cell phone networks.
Phased array antenna systems are used for applications like air defense radar, where you need to track multiple inbound targets, and satellite communications where the satellite transmits to multiple stations on the ground. The difference between a phased array and a parabolic dish is that the parabolic dish is mechanically aimed and can only point at one target at a time, while a phased array is electronically steered and can simultaneously track multiple targets.
A phased array is composed of a large number of simple antennas in a regular pattern. Each of the simple antennas is connected to a phase controlling element, usually controlled by a computer. By adjusting the phase of each simple antenna, the array's radiation pattern can be manipulated to form one or more directional beams, without having to move any mechanical parts.
For NASA's application on TDRS, it allows them to simultaneously track and communicate with multiple satellites in low-Earth orbit, with a single electronically steered antenna system.
The trick NASA pulled with the phased array antenna on TDRS was to take the phase controllers off the spacecraft and put them at the TDRS ground station. The TDRS spacecraft takes the output of all the simple antenna elements and retransmits each one to the ground station. The ground station has a magic phasing/combiner box that takes the outputs of all the simple antennas and adjusts the phase of each signal and combines them under computer control. This splits the phased array into two parts, with part in space (simple antenna array) and part on the ground (phasing/combiner/control computer). This removes a big chunk of hardware and complexity from the spacecraft and relocates it to the ground station.
Looking at the TDRS web page, the latest series of TDRS spacecraft (TDRS-H, I, J) have the beam-forming hardware on board the spacecraft, instead of doing it on the ground.
If I go to the opera or to a musical, I expect live musicians and actors/singers. If I wanted canned music, I would save a bunch of money and buy a CD or DVD. I don't care how many whiz-bang gadgets are in the synthesizer, it isn't going to sound like real musicians playing real instruments.
The problem is that it is much easier to build a satellite tracking system on the Earth's surface. The antennas can be large, the environment is benign, the hardware is cheaper and can be tweaked, repaired and upgraded. Plus there is relatively unlimited power and space, and there are human beings to make decisions. You need a compelling reason to try to do that in space. On the Earth, if an antenna mechanism gets stuck, you can send out Joe to whack it with a hammer. In space, you lose the whole antenna, permanently.
NASA spent billions of dollars on the development and deployment of the Tracking Data Relay System (TDRS), which can track spacecraft in low-Earth orbit. Even there they had to cheat a bit, by doing the beam-forming for the phased array multiple access
antenna on the ground instead of on the TDRS spacecraft.
DEC made the source for VMS available on microfiche. This allowed the customer to look at the code without making it easy for someone to copy and distribute the source code to unauthorized people.
For many agencies, like NASA, there are national security concerns. Anything that might make it easier for a hostile country to design, test, build and use, military hardware, is going to be closely scrutinized before release to the public. Do you want NASA to give away its latest and greatest rocket guidance software to anyone that asks for it?
Because most of it is written by other entities under contract to NASA. If a civil service employee of NASA writes a program, it isn't copyrighted according to federal law. If a contractor employee writes a program, it is copyrighted. Normally the copyright would be assigned to NASA, who paid for the development of the software.
Reliability requirements can be written into the contracts and specifications for closed source software. They can also be part of legislation and regulations, for example the FDA and FAA.
When I took a course in software reliability engineering, the examples were all closed source projects, like AT&T's 5ESS switch software.
Open source may have its virtues, but it isn't a panacea or a replacement for real engineering.
Sometimes you have to hit someone with a two-by-four to get their attention. The FCC didn't have this problem in the old days. If you broke the rules, they would pull your station off the air while they investigated the incident. If it was serious, they would revoke the station's license. They didn't take shit from station owners or networks. They put the fear of God in station owners and their staff.
You can't have responsibility without authority. The building never gets built without the signature of the civil engineer on the plans. Few software engineers have that control.
Re:Would this be any better in an OSS environment?
on
Blackout Cause: Buggy Code
·
· Score: 3, Insightful
I don't care whether it is open source or closed source or divine inspiration, software reliability requires testing. Depending on the reliability requirements, proper testing can be very expensive. That's assuming anyone has even bothered to state reliability requirements.
There are also system reliability requirements to be considered. Hardware fails. Software fails. Is the system designed to detect and cope with component failures?
GE's software may suck. I don't know. I've never seen it. I am suspicious of people who attempt to hide their own negligence by blaming a third party.
As long as everyday consumers aren't aware where their meat comes from, they'll eat it. But if the harsh truth faced them every day, nobody would touch a big mac.
If you've ever lived on a farm, you get used to it very quickly. It isn't a petting zoo.
One solution might be to build power control into these devices. My CDMA cell phone constantly adjusts its transmit power level to the minimum needed to maintain the RF link at an acceptable BER (bit error rate). Besides prolonging battery life, it allows more cell phones to operate in a given area.
I've often thought it would be useful for digital cameras to provide an option of signing all images with a camera-specific private key stored in a tamper-resistant chip. That would allow third parties to verify that the image file had not been altered after the fact.
While a "true geek" may not care about the history of IBM management, there are many interesting things that have been produced by IBM's scientists and engineers. Many of the neat features in today's microprocessors can be seen in IBM 360/370 series mainframes from the 1960s and 1970s. Today's microprocessors have yet to catch up with the reliability, availability and maintenance features of IBM's large systems. Anyone who is interested in computer architecture can learn a lot from studying the technical history of IBM.
Instead of being limited to some fixed approximations of red, green, and blue, they can use a larger set of filters that are tailored for various science objectives.
The human eye's color vision is a poor scientific instrument. It can be easily fooled.
It's a joint operation of NASA and CalTech. It's simplistic and incorrect to say that it is just another part of NASA. There are NASA standards and there are JPL standards. They cooperate and interoperate but they are distinct in many ways.
Most NASA satellites are in low-Earth orbit. Some are in geosynchronous orbit, like TDRSS. Some, like satellites that study the solar wind, are in unusual orbits that take them far away from the Earth. JPL handles the satellites that leave the vicinity of the Earth and the Moon.
NASA's satellite tracking and communication systems are adequate for spacecraft in the vicinity of the Earth and the Moon. They are not good enough to handle spacecraft at larger distances. That is why JPL's DSN (Deep Space Network) has much larger antennas, super low-noise preamps, and higher performance receivers and transmitters. Their systems are designed and optimized to work with very weak signals.
The difference between near space and deep space is more a matter of operating conditions than of geography.
That's questionable. Many people have been accidentally shot because someone thought the safety was on when it wasn't. Handguns without safeties, such as revolvers and Glocks, eliminate that point of possible confusion. User training is the key to handgun safety, not mechanical widgets. The short version:
Keep your finger outside of the trigger guard.
Keep the weapon pointed in a safe direction.
Always assume the weapon is loaded.
Never rely on a mechanical safety. It may be broken.
If you shoot, shoot to kill. Warning shots and wounding shots are for Hollywood movies.
Don't point a weapon at someone unless you intend to shoot them and kill them.
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You can jam almost anything with a white noise generator and sufficient power. Spread spectrum is jam resistant, it can still be jammed, it just takes more power than is needed to jam older modes of communication.
Get yourself a neon sign transformer. Plug it in to the nearest convenient AC outlet. To verify that the transformer is operating properly, wet your hands and firmly grab the output leads of the transformer. This will solve your problems with annoying wireless calls.
You obviously haven't met one of the many people who will loudly proclaim that their body is being poisoned if anyone within a 1000 meters lights up a cigarette.
The problem with jammers is that they can't discriminate between cell phones, pagers, walkie-talkies and other devices that use the affected frequency range. In many areas, the police and fire departments use radio systems that operate in the 800 MHz frequency range, along with many cell phone networks.
A phased array is composed of a large number of simple antennas in a regular pattern. Each of the simple antennas is connected to a phase controlling element, usually controlled by a computer. By adjusting the phase of each simple antenna, the array's radiation pattern can be manipulated to form one or more directional beams, without having to move any mechanical parts.
For NASA's application on TDRS, it allows them to simultaneously track and communicate with multiple satellites in low-Earth orbit, with a single electronically steered antenna system.
The trick NASA pulled with the phased array antenna on TDRS was to take the phase controllers off the spacecraft and put them at the TDRS ground station. The TDRS spacecraft takes the output of all the simple antenna elements and retransmits each one to the ground station. The ground station has a magic phasing/combiner box that takes the outputs of all the simple antennas and adjusts the phase of each signal and combines them under computer control. This splits the phased array into two parts, with part in space (simple antenna array) and part on the ground (phasing/combiner/control computer). This removes a big chunk of hardware and complexity from the spacecraft and relocates it to the ground station.
Looking at the TDRS web page, the latest series of TDRS spacecraft (TDRS-H, I, J) have the beam-forming hardware on board the spacecraft, instead of doing it on the ground.
If I go to the opera or to a musical, I expect live musicians and actors/singers. If I wanted canned music, I would save a bunch of money and buy a CD or DVD. I don't care how many whiz-bang gadgets are in the synthesizer, it isn't going to sound like real musicians playing real instruments.
NASA spent billions of dollars on the development and deployment of the Tracking Data Relay System (TDRS), which can track spacecraft in low-Earth orbit. Even there they had to cheat a bit, by doing the beam-forming for the phased array multiple access antenna on the ground instead of on the TDRS spacecraft.
DEC made the source for VMS available on microfiche. This allowed the customer to look at the code without making it easy for someone to copy and distribute the source code to unauthorized people.
For many agencies, like NASA, there are national security concerns. Anything that might make it easier for a hostile country to design, test, build and use, military hardware, is going to be closely scrutinized before release to the public. Do you want NASA to give away its latest and greatest rocket guidance software to anyone that asks for it?
Because most of it is written by other entities under contract to NASA. If a civil service employee of NASA writes a program, it isn't copyrighted according to federal law. If a contractor employee writes a program, it is copyrighted. Normally the copyright would be assigned to NASA, who paid for the development of the software.
When I took a course in software reliability engineering, the examples were all closed source projects, like AT&T's 5ESS switch software.
Open source may have its virtues, but it isn't a panacea or a replacement for real engineering.
Sometimes you have to hit someone with a two-by-four to get their attention. The FCC didn't have this problem in the old days. If you broke the rules, they would pull your station off the air while they investigated the incident. If it was serious, they would revoke the station's license. They didn't take shit from station owners or networks. They put the fear of God in station owners and their staff.
You can't have responsibility without authority. The building never gets built without the signature of the civil engineer on the plans. Few software engineers have that control.
There are also system reliability requirements to be considered. Hardware fails. Software fails. Is the system designed to detect and cope with component failures?
GE's software may suck. I don't know. I've never seen it. I am suspicious of people who attempt to hide their own negligence by blaming a third party.
If you've ever lived on a farm, you get used to it very quickly. It isn't a petting zoo.
One solution might be to build power control into these devices. My CDMA cell phone constantly adjusts its transmit power level to the minimum needed to maintain the RF link at an acceptable BER (bit error rate). Besides prolonging battery life, it allows more cell phones to operate in a given area.
I've often thought it would be useful for digital cameras to provide an option of signing all images with a camera-specific private key stored in a tamper-resistant chip. That would allow third parties to verify that the image file had not been altered after the fact.
While a "true geek" may not care about the history of IBM management, there are many interesting things that have been produced by IBM's scientists and engineers. Many of the neat features in today's microprocessors can be seen in IBM 360/370 series mainframes from the 1960s and 1970s. Today's microprocessors have yet to catch up with the reliability, availability and maintenance features of IBM's large systems. Anyone who is interested in computer architecture can learn a lot from studying the technical history of IBM.
I can't understand how anyone with half a clue could have deployed such an obviously broken service.
The human eye's color vision is a poor scientific instrument. It can be easily fooled.
When I've bought white paint in an art store, it has always been titanium dioxide pigment mixed in an oil or acrylic base.
It's a joint operation of NASA and CalTech. It's simplistic and incorrect to say that it is just another part of NASA. There are NASA standards and there are JPL standards. They cooperate and interoperate but they are distinct in many ways.
NASA's satellite tracking and communication systems are adequate for spacecraft in the vicinity of the Earth and the Moon. They are not good enough to handle spacecraft at larger distances. That is why JPL's DSN (Deep Space Network) has much larger antennas, super low-noise preamps, and higher performance receivers and transmitters. Their systems are designed and optimized to work with very weak signals.
The difference between near space and deep space is more a matter of operating conditions than of geography.