osewalrus (osewalrus) wrote,
osewalrus
osewalrus

Trying out an idea for subsequent blogging. Software Defined Radios

I posted this to a list where the nth iteration of "the FCC's rules are holding back the development of software defined radios (SDRs)." For those not familiar, SDRS (also referred to as "smart" radios or "cognitive" radios) are radios that sense their spectrum environment, including having an ability to sense or receive instructions with regard to the desired receiver, and will transmit and receive on multiple frequencies without causing interference to other devices (which may or may not have similar capacities). In theory, the use of SDRs would allow elimination of the existing wireless technology dependent on licensed exclusive use of wireless frequencies (spectrum). Your cell phone is an example of a device that operates on multiple licensed frequencies on the assumption that only licensee can give permission for a device to function on that frequency, and then only in accordance with the terms of the license.


There is a problem we never talk about in the unlicensed advocacy community. How do we make the transition from the current wireless structure, which depends heavily on exclusive licensing, to a system that relies heavily on SDRs and unlicensed access? Most folks in our movement argue, in essence, for a "hot cut." Lets just authorize SDRs and that technology will naturally win. There is an associated argument that the failure of regulatory authorities (the one I'm most familiar with is the U.S. Federal Communications Commission) resist expanding the rules for SDRs not from genuine engineering concern, but because of the political influence of incumbents licensees, the mobile bullies, the dinosaurs, who will fight to the death to protect their business models and their irrational and baseless fear of interference.

Granted the later is true. But even leaving aside the economic problems, the mobile bullies, etc., there is a very real engineering problem of compatibility with embedded technologies. Bluntly put, I have come to doubt the idea that we could suddenly make a "hot cut" from the existing world of predominantly licensed to a new world of predominantly unlicensed spectrum use. Indeed, I have come to view the problem here as remarkably similar to the problem of IPv6 adoption. Those favoring an upgrade are completely ignoring how human beings actually act and what is important to those who view wireless merely as an input for doing cool stuff.

Before folks get the wrong idea, I continue to believe that the technology will, ultimately, work just fine and in the predicted way. That we can develop smart devices that remove the need for exclusive licensing and that would therefore allow us to radically alter the way in which we construct wireless networks and what we can expect them to do, and at what price. But I do not believe it is enough simply to get the FCC to change its rules. Worse, I have come to believe that the FCC should phase in these technologies gradually. Not because I fear the licensed lobby, but because there are 300 million people dependent on devices operating under assumptions developed in the existing regime and the vast majority of these devices are crappy pieces of hardware that could not survive a sudden, radical shift in rule changes as they are likely to be implemented in the real world.

What shook my faith was the current relatively minor incidences of interference in FAA Doppler radar from unlicensed operation in the neighboring 5.3 GHz band. Operation of unlicensed in 5.3, shared with the U.S. military radar, is a triumph of engineering technology and proof of the sensing concept. The military would not reveal any information about the nature of its radar systems -- the wave form, the energy, or positions of transmitters. It was necessary to build devices that could nevertheless avoid interference with military radar yet still prove useful and economical to build. After several years, this was achieved, and we have seen the recent opening of the 5.3 GHz band for commercial use.

The problem is that, as the equipment manufacture got ramped up and economies of scale kicked in, production got just a smidge cheaper and shoddier. Chips complied with sensing and avoidance in band, but became just a bit noisier out of band. Shielding was reduced to make devices just that half cent cheaper which can mean a difference between a profitable run and an unprofitable run. All of which resulted in a device just a little bit noisier than actually allowed.

This might not have been a problem had the neighboring service not been FAA Doppler radar with _extremely_ sensitive double-array receivers. As it was, however, the increase in the number of devices, combined with their increased noisiness, began to cause interference problems. Happily, the situation appears to be resolved.

But the process is entirely too reminiscent to me of how the 800 MHz band got screwed up by Nextel. Any individual conversion of a system to a digital two-way system was not problematic. But when you ramped up to several million users, operating at about a zillion times greater frequency of use that the previous set of users, it started to cause problems.

Lesson 1: Reality always plays out funny. Not because the underlying science or engineering is wrong. Often it is from extraneous factors. It is _predictable_ that manufacturers will develop cheap devices. It is known that the current universe of devices are built as cheaply and inefficiently as possible given the current set of rules assumptions. Change the underlying rules and unanticipated things happen as the interplay of these facts on the ground start manifesting themselves at hyper speed from dramatic ramp up. Because if we are right about how much better these technologies are in terms of cost savings, ramp up will be incredibly dramatic.

Lesson 2: Any serious plan to alter the current wireless paradigm must take into account the embedded technology and figure out how to change it, gradually. _This_ requires considerable subtlety and a willingness to consider taking the scenic route to the ultimate goal. This route must detour through lots of apparently unrelated places such as overall improvements to receiver standards to enhance robustness on the receiver/embedded tech end, creating incentives for licensed services to want better spectrum sharing and spectrum reuse technologies that do not directly undermine their business models. It includes a couple of stops designed to introduce new considerations in business model and encourage people to want to own/deploy their own networks without worrying whether they also "own"/hold the license to the spectrum.

In short, it is no longer merely a complicated technical problem. Like conversion to IPv6, it is a complicated technical problem made worse by the irrational and unrelated (and often contradictory) needs and desires of the human beings actually using the legacy technology who do not respond well to the argument of "look, just trust us and switch, you stupid non-technical monkey boy." Unlike conversion to IPv6, however, there is no near term looming crisis to drive people to the preferred engineering solution.

For those serious about engendering a social revolution based on technological change, this requires a radical rethinking of tactics and strategy. It also requires gaining a new perspective on FCC regulations. Absolutely they are manipulated by incumbents. But after nearly 10 years working with the Office of Engineering and Technology (OET) on spectrum issues, I have developed a respect for their inherent conservatism, even as I chafe under it and try to move them along a more aggressive path. They _must_ consider what happens if we are wrong and the ramp up unexpectedly screws up vital services in the embedded technology. It is not enough to know that a solution is possible. It is not enough to blame others for making cheap receivers for licensed services. Because if this stuff screws up, real people are impacted. That's enough to give anyone charged with the responsibility of making the decision a serious case of cautious conservatism _without_ insulting them by claiming they are simply tools of the existing licensed incumbents. At them same time, however, anyone who thinks that the economic incentives of incumbents and the political power they wield is not a significant factor weighting against change would be a naive waif doomed to failure.

So how do we move forward? Excellent question! I am only now starting to struggle with this. But the first stage is to recognize the enormous complexity of the problem and the pressing weight not merely of economically invested incumbents, but of the embedded technology base predicated on more than 75 years of technological assumptions. My gut feeling tells me that countries outside the U.S. willing to free themselves of the "Washington consensus" that got everybody to auction spectrum should have an advantage here, simply because the weight of embedded tech should bear less heavily on them. But this may not prove correct, at least in the short term.
Subscribe
  • Post a new comment

    Error

    Anonymous comments are disabled in this journal

    default userpic

    Your IP address will be recorded 

  • 2 comments