This new fangled radio technology was beginning to get exciting. Spark gap transmitters had been used to wirelessly send signals to a receiver. In 1888 Hertz was able to show the transmitters were producing electromagnetic waves predicted by Maxwell a quarter of a century earlier - waves that travel through space at the speed of light. Waves that could carry a signal.
The rush was on to create practical communication systems and ship to shore radio looked to be the killer application. Signals were sent using morse code and the number of radio equipped boats began to grow - particularly in the North Atlantic. But there was this little problem...
Signals sent from one spark gap transmitter would be received by all of the receivers within range. Early on communications were very sparce and it was possible to manage a few dozen ships, but it didn't scale. The solution of sending signals that didn't step on each other would be a form of multiplexing, but it wasn't obvious how until Marconi invented syntonic multiplexing. His idea was a transmitter that would radiate at a fixed frequency and a receiver to be able to resonate with just that frequency. In retrospect it wasn't terribly different from the tone based multiplexing that appeared in telegraphy in the 1870s, but it was one of the those breathtalking intellectual leaps. The sort of discovery that seemed obvious in retrospect. By 1901 the Navy was talking about introducing it on warships and discontinuing the use of carrier pigeons for naval communications.
Twenty years passed and radio became practical for broadcast communications. Children made crystal sets, families bought receivers in fine wood cabinets that cost a month's wages or more and radio stations popped into existence. The growth was astonishing. It was all based on Marconi's syntonic multiplexing. Frequencies and channels were assigned. International groups were formed to make sure long range communications wouldn't interfere with each other and within countries policy was created. In the US AM stations were regulated in frequency and power - the allowed power changing at sunrise and sunset for most to limit their range.
Radio had become a major applied research and development effort and new modulation schemes like frequency modulation were created allowing better audio fidelity for music. It's downside was the channels needed to be wide to prevent interference. To deal with the problem the Federal Communications Commission encoded the notion of available spectrum into policy - a policy based on the performance of radio receivers of the 1920s. The idea of what radio was was solidified through policy.
Policy was working. Radio was a huge industry and vital to the many other industries. Entertainment was exploding and a growth area even during the depression. It was also vital to the military.
After WWII limits began to appear. Television was FM radio on steroids requiring large chunks of spectrum. There was a limit to high frequency communications as they were strictly point to point and attenuated by the presence water and even air. The solution in the 50s was a combination of economics and policy. Some of the spectrum would be made legal property. A company could own and trade it. If you couldn't get your signal over the air, it was possible to move it through coax by building a new physical wired network. It was just money and people were willing to pay. The invisible hand would fix everything.
Except it didn't
Nothing in physics says there is a limit on the amount of information that can be carried by a certain chunk of spectrum. Shannon came along in the middle of the century with brilliant work explaining how much information could be carried, but under very specific conditions that made a lot of sense at the time. It was a beautiful theory based on sensible engineering. Low energy photons - the stuff of radio waves - pass through each other. We have no trouble with the light patterns we get watching a sunset in the West interfering with the patterns of light someone looking across our vision at a tree to the South is receiving.
But for the present we have issues - look at my WiFi situation. An interesting listen before sending spreadspectrum technique that is useful mainly for very short ranges. but it doesn't scale well. Here's my house with 40 basestations within view.
The physics is simple, but the engineering isn't obvious and has only been developed in the past two decades. Other forms of multiplexing, computational radios, tricks with the environment - many tricks are being learned and experimentation is underway. It is extremely unlikely that any of this will be applied soon as there are many details to hammer out and it interferes with the business models of some very power entities.1 Rather than diving into this rather esoteric subject I'll just note a decade or two from now, depending on policy, technology and need, we should easily see a factor of 100 improvement and much more is not unthinkable. It will happen, but other vision and policy is more important.
My belief is this needs to be understood if you are thinking about the future of the Internet and the Internet of Things (IoT - such an ugly term). Two polar models of wireless computation exist - the dumb piece of glass tightly connected to the cloud and the smart piece of glass connected more weakly connected to the cloud. One might say the Apple model and the Google model, but neither company is at the pole. Both models have advantages and disadvantages. The Apple model may offer better security as the IoT grows. At this point it seems likely that end user computational power will grow much more rapidly than direct wireless connection to the cloud.2
There will be enormous growth and surprise, but exactly what, how and when is unknown. My bias is the IoT will be much more human centric than the machine to machine models that are currently popular. I'll also bet that security and communication costs are going to be important and available spectrum will be a cost driver. There needs to be more flexibility in how radios talk to and coordinate with each other - heavens, my iPhone has six radios that don't interoperate. Some form of smart radio has to happen, even if it isn't the dramatic spectrum saving radio of the future.
A large amount of work needs to be done and it is mostly blue sky territory at this point. I would vote for building something in the spirit of the Internet. I'll need another post just describing why the Internet is so special and unusual - why it has survived this long. Perhaps it is evolving to something else, but there are some misconceptions. Even the creation story - that the Defense Department wanted a network that would be robust in a nuclear attack - is incorrect folklore.
stay tuned to this channel
that is until we get past the notion of channels...
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1 Regulating scarcity is a nice business to be in even if what you regulate is expensive to acquire. The FCC does not allow this sort of work outside of certain experimental, military and amateur radio licenses. Good work is being done by amateurs and the military.
2 Cost is a factor in wireless cloud connection when you are talking about very inexpensive IoT devices. There is a need for a local cache/aggregator for operations that permit latency.
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Recipe Corner
Falafel is wonderful, but often dripping with oil. Here's a nice baked version. Be sure and go with the dried chickpeas. There is a lot of room for experimentation in seasoning and you can, of course, have great fun with tahini and other sauces.
Low Fat Falafel
Ingredients
° 3 tbl olive oil
° 1 cup dried chickpeas soaked for at least a few hours
° 1/4 of a medium red onion chopped
° 1/2 c parsely
° 1/2 c cilantro
° 3 garlic cloves, minced
° 1/8 tsp ground cinnamon
° 1/4 tsp ground cumin
° 1 tsp sea salt
° 1/2 tsp freshly ground black pepper
Technique
° Oven to 375°F, oven rack in the middle
° coat a large iron skillet with a tablespoon of olive oil
° combine the drained chickpeas, onion, cilantro, parsely, 2 tbl olive oil, garlic, and seasonings. Process until smooth
° scoop out a couple of tablespoons at a time nad form into patties about 2 inches wide and a half inch thick .. or so.
° place them in the pan and bake for about 15 minutes before flipping. Bake for another 10 minutes for so until browed on both sides
° use 'em for falafely things
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