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Comment: Re:There is another way (Score 1) 244

by joebob2000 (#35216534) Attached to: Two-way Radio Breakthrough To Double Wi-Fi Speeds

TDMA (time domain multiple access) is how digital cellular worked before CDMA (code domain multiple access) took over. TDMA is an inferior system because it is possible in practice to get much higher utilization of bandwidth using CDMA.

The article is talking about SDMA (spatial domain multiple access) which is a way of allowing two transceivers to share the same frequency (and code in the case of a CDMA, or timeslot if TDMA) with reduced interference by shaping and processing the signals using arrays of antennas. The cheap-ass technique mentioned is not new and sounds like masters thesis or even senior project material, so the fact that this is a news article would be quite mystifying if i did not know that the society that i grew up in is devolving more rapidly that I could have ever imagined even 5 years ago.

P.S. This talk of full-duplex, chopping, etc. that everyone seems to be bringing up are pretty antiquated terms of art. Sort of like mentioning how your car has rack and pinion steering or a rear differential.

Comment: Re:Intelligent, elegant, simple idea ... (Score 1) 244

by joebob2000 (#35216374) Attached to: Two-way Radio Breakthrough To Double Wi-Fi Speeds

Why did it take more than 100 years for someone to think of it? If this is the first discovery of this idea, then that makes me despair for the intelligence of the human race ...

It didn't. People have been doing stuff like this for decades, and in much more sophisticated ways than what is described here. Despairing for the intelligence of journalists is appropriate, but probably a waste of time. I did not read too many Slashdot posts that indicated that anyone really understands much at all about telecom past downloading iPhone apps. Maybe you can despair about that.

Comment: Re:Impossible (Score 1) 244

by joebob2000 (#35214044) Attached to: Two-way Radio Breakthrough To Double Wi-Fi Speeds

That's not what they're doing here though, they're taking regular modulated signals and running filters to pick out each signal. So they grab the true received signal by filtering out the one they are transmitting. They operating around a similar center frequency but it's not the exact same frequency.

No, you miss the point. The signals could be close enough to interfere or right on top of each other in the frequency domain, the interference is mitigated by using the extra information gleaned from having multiple copies of the input signal sampled from different locations and from using an array of antennas to shape the transmit signal.

Having active array transmitters and receivers opens up a lot of options for processing the signal, but means you cannot use the basic point-source tx/rx model to analyze the problem. Using the term "filter" in this situation is a linguistic trap.

Comment: This is not new, it is at least 15 years old. (Score 1) 244

by joebob2000 (#35213820) Attached to: Two-way Radio Breakthrough To Double Wi-Fi Speeds

I do not understand how this article got written this way. This article describes a form of SDMA, spatial domain multiple access. Back in the late 90's there was a startup called ArrayComm that created a working cellular station with a 12 antenna SDMA system. Their demo had two callers on the same channel and timeslot (it was a TDMA cell system) walking right next to each other and even sticking their phones into the opposing cells antenna array without dropping the call.

The reason it never went anywhere was not because it did not work, but because CDMA got there first, works well enough, and does not cost as much to deploy. As wireless density increases, we keep seeing antenna diversity schemes pop up (MIMO), but usually they are two antenna systems. Maybe someday we will need to deploy SDMA systems that use large numbers of antennas, but it will be at least 20 years after it was done the first time.

Comment: Re:CMDA (Score 1) 244

by joebob2000 (#35213582) Attached to: Two-way Radio Breakthrough To Double Wi-Fi Speeds

CDMA stands for code division multiple access. One method of CDMA, the one currently used in phones is called spread spectrum where the digitized signal is "spread" (XORed) with a particular pseudo random sequence from a set of such sequences that are designed not to correlate with each other. the receiver knows the sequence and is time synchronized with the transmitter so can de-spread the signal on the other end. The point of the spreading is that each pseudo noise (PN) code in the set does not correlate with the other ones, so mulitiple spread signals can operate in the same band without interfering with each other. You tune into a particular CDMA channel by using that channel's PN code.

SDMA or spatial domain multiple access uses multiple antennas to process incoming and outgoing signals. the use of multiple antennas gives the ability to shape/sense the signals direction and strength. By arranging the signals properly, the SDMA system can allow two channels on the same frequency to coexist very near each other without interfering. You tune to a particular SDMA channel by analyzing and processing the n-dimensional manifold corresponding to the antenna architecture of the system.

this idea is not new and has been around in a more sophisticated way than described in this article for many many years. It was built, it works, and the only reason it is not used is because CDMA is good enough. for now.

Comment: Sing for your supper like everyone else. (Score 2) 160

by joebob2000 (#35207898) Attached to: CRIA Files Massive Canadian Suit Against IsoHunt

Want money? go play gigs. Why is it a god given right to get rich off a few songs or get money for the rest of your life for performances over a short period of time. Same with software, etc. Someone still has to work to make the food that artists living off IP eat. Sounds like a great situation to be in, but getting on a moral high horse about your god-given right to hit the jackpot and be supported in luxury by society for the rest of your life is a stretch.

One day's work for one day's pay. No need for labels, copyrights, etc. Most people work under that system (jobs) and it does not require locking up college kids for downloading something that has an average economic shelf life of a couple weeks.

Comment: Congratulations! (Score 1) 59

by joebob2000 (#35169492) Attached to: Open Source Hardware Hits 1.0

I have a coil of wire that I would like to donate to the project. I call it an "inductor" because I wrapped it on the INside of a roll of DUCT tape OR similar. I also have a pencil broken in half with a wire glued on one end and another wire that you can "wipe" up and down the black graphite center... I call it a "variable resistor" for some reason...but in any case... I hereby release it to be OPEN HARDWARE! yay!

The quality of your work has earned you the title "Maker".

Comment: Re:This is not wrong! (Score 2) 181

by joebob2000 (#35071292) Attached to: US Authorities GPS Tagging Duped Indian Students

I'm an Indian [...] if an Indian abroad takes a job from somebody else he does so based on his talents and this is why the company picks him/her over a native. Sorry, today the world works on these terms.... So don't crib about Indians taking your jobs all the time.....there is a reason we get picked over natives.

Um, no. The reason that an Indian gets a job over an American is that the Indian is not a citizen, is here on a work visa, and must leave the country if he does not have a job. His employer usually promises to help him gain a green card through a process that takes years. If the Indian were to lose his job, this process could be screwed up or even reset and he would have to start all over again. All these things make him a compliant employee who is motivated to work hard, take less pay, and is less likely to leave a company.

Foreigners on work visas are model employees because they are working under a modern day version of indentured servitude. The carrot is the promise of help with a green card application. The stick is the promise of getting kicked out of the country if you lose your job.

Comment: Re:it's either ... (Score 2) 118

by joebob2000 (#34883352) Attached to: Low Quality Alloy Cause of Shuttle Main Tank Issue
Uhh, it's not a ferry boat. Its a fucking space shuttle. The goal is to get into space, not to meet some vague undergrad textbook factor of safety rule of thumb you read as a nooblet. Also, they are not buying bar stock from McMaster-Carr, they're whipping up batches of engineered materials for a specific application. This application is about as performance demanding as things get, the runs are small, the costs are high, and there is not a lot of room for error. Yet man is still not god, so errors happen despite the best efforts of a lot of dedicated people. If you are a real engineer, and you have never made a mistake, then count your blessings instead of acting like a cock. If you're not a real engineer then STFU.

Comment: Re: EEs not needing to know basics of programming (Score 1) 663

by joebob2000 (#32198090) Attached to: Exam Board Deletes C and PHP From CompSci A-Levels

Furthermore, non-CS majors (like mechanical and electrical engineers) don't have to understand the very basics of programming, they don't have much relevance to their field. For CS majors, start off with languages like C because their job is to understand the very very basics.

Perhaps I misunderstood what the basics of programming mean to you, or maybe times have changed in the 15 years since I got my BS in electrical engineering and became a HW engineer. In school, among other things, I was first taught how to make computers from scratch, then we learned some different computer architectures, then how to program them in assembly. At work, even though I do not get to design computers and program them in assembly, I do get to wire up ram, nvram, adc, dac, control lines to analog circuits, etc., pick their address in the programmers model, and then write c code to test that it's working right before handing it off to a team of embedded SW engineers. The programmers I'm working with are using c, so I will be using c as well. BTW, half of the programmers I work with have an EE degree too.

But I digress. As far as I could glean from your post, you're saying the basics of programming are knowing what is actually going on in the hardware. It used to be that HW engineers were EEs. Maybe something has changed in the curriculum since then, but in my job, you need to know how to bias an op-amp plus much other analog stuff, AND how to setup the programmers model of the HW the way the SW guys want it and much other digital stuff. Seems like EE is still the place where people like that are going to come from.

P.S. I know a few mechanical engineers who program traction control, active suspension, etc. Those guys need to know programming basics too.

"And do you think (fop that I am) that I could be the Scarlet Pumpernickel?" -- Looney Tunes, The Scarlet Pumpernickel (1950, Chuck Jones)

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