One aspect of spectrum sharing that’s receiving less attention than it should is security — specifically, potential problems brought on by the very attributes that makes this technology work.
There’s a basic concept in computer network security: If you don’t want A to attack B, make it impossible for A and B to communicate. That’s why sensitive military communications systems do not have links to the internet. Experts realize that, even with the best firewalls and filtering, if a connection exists, the system is inherently less secure.
That’s exactly the security problem that arises with spectrum sharing: It creates connections that could be compromised.
In current dedicated (non-sharing) spectrum-allocation approaches, devices operating in spectrum band “A” cannot interfere with systems using band “B.” Sure, sometimes there’s a little interference due to poor radio design — for example, the proposed LightSquared network and existing GPS devices — but the attack path does not exist. Even if a smartphone were infected with the worst virus imaginable, the malware could not interrupt communications provided over different spectrum bands.
Sharing spectrum could mean sharing viruses too.
That could change with spectrum sharing, where devices labeled as “secondary users” share spectrum belonging to “primary users.” Sharing happens either in specific geographic locations where the primary is not operating on the spectrum in question, or during specific periods of time when the primary system is not using the spectrum.
In what is called “dynamic spectrum access,” the primary system posts to a database the availability of its spectrum. Then, the secondary user queries the database to learn when and where it can use that available spectrum. Alternatively, the secondary system may use cognitive radios to sense the spectrum environment and determine whether the secondary system can use the spectrum without interfering with the primary user. Combining databases and cognitive radios is another possible approach to enable spectrum sharing.
One area of particular concern, however, is that, in many cases, primary users will be sensitive government systems, especially if up to 1 GHz of spectrum is set aside for sharing, as proposed by the President’s Council of Advisors on Science and Technology (PCAST.) What happens if the secondary user device doesn’t follow the rules and transmits at times or in locations it’s not supposed to? Worse yet, what if hundreds of thousands of devices are systematically compromised and start misbehaving in unison to launch a coordinated denial-of-service attack on the government communications systems?
It’s hard to know for sure the possible ramifications of such a barrage, because our industry currently has little information about the primary government systems with which commercial operations would share spectrum; much of that data is classified. But the effects can’t be good.
The whole point of spectrum sharing is for secondary users not to use the spectrum when the primary system needs it. Doing so could result in denial-of-service for the primary government system, with potential consequences that include lower reliability, operation over reduced distances, or even complete failure.
The airwaves aren’t the only problem.
Could this device harbor malware that might hop the airwaves?
That’s true even though the spectrum-sharing logic may, theoretically, be isolated from the application-execution space in the smartphone. As long as both are present and some form of connection exists, the consumer’s mobile device could become an attack path in spectrum sharing situations.
It gets worse.
So far we’ve only considered user devices being compromised. But what if an attacker infiltrated the database itself in a dynamic-spectrum access system? It’s that database that determines how secondary systems access the band, and if the database is manipulated into giving out incorrect information, the secondary system could massively disrupt the primary system. And this could occur on a network-wide basis.
Don’t panic, just pause.
We can share. Security just needs to be thought out first.
As I’ve stated previously, spectrum sharing can theoretically be made to work. Sharing scenarios can also be made secure. However, ensuring that a networking system is secure is a time-consuming process, regardless of the type of network.
It is impossible to predict just how much overhead thinking through security issues will add to developing spectrum-sharing solutions. Rather, security has to be added as yet one more consideration, along with all the other concerns raised by spectrum sharing. These include identifying what types of systems will be shared and how, determining the market for shared systems, and developing specifications and standards to allow sharing.
Beyond very basic-use cases, spectrum sharing is going to be a complicated proposition. Ensuring that sharing is secure and does not endanger existing government systems only adds to the complexity. Therefore, I don’t see sharing as a short-term solution to our spectrum woes.
Peter Rysavy is president of Rysavy Research, a wireless network engineering firm.
Radio wave photo courtesy of Shutterstock user fotographic1980, and sharing photo by Flickr user Ben Grey used under the Creative Commons Attribution-ShareAlike 2.0 Generic license.
Thank you Brett Glass. Excellent due diligence. Amazing how many angles there are to look at problems…each perspective lends its own spin to the problem/solution.
Alas, GigaOm and Mr. Rysavy fail to disclose that his big client is Intel, whose corporate policy is to attempt to deprecate spectrum sharing. In this case, he conjures a fictitious bogeyman. Yes, it’s possible to jam radio signals, but if you do you’re much more likely to be caught than if you set up an explosive device to destroy a fiber cable. Why? Because you have to keep transmitting to keep jamming, and the signal can be traced to its source. As for an attack via malware: it’s no different from mounting an attack on wired infrastructure by infecting routers and switches. Mr. Rysavy’s vested interests and bias are apparent, and his arguments do not hold water.
P.S. — According to his Web page at http://www.rysavy.com/clienthistory.html, other consulting clients of Mr. Rysavy include CTIA, AT&T, and Verizon, all of which likewise have lobbied for exclusive licensing of all spectrum and against unlicensed spectrum or spectrum sharing. Again, a strong vested interest.
Intel is one of the biggest supporters of shared spectrum there is. They’re leaders in the White Spaces, Wi-Fi, and Wi-Max worlds, and were a huge supporter of UWB.
As usual, Brett Glass is pulling aspersions out of, um, thin air, to put it politely.
Not so, Richard. At every forum where I’ve seen a speaker from Intel talk about spectrum, he has always advocated exclusive licensing. Most likely because Intel believes that devices which use exclusively licensed spectrum are the real money makers. (It makes Wi-Fi chips, but halfheartedly.)
P.S. — Lobbyists like Richard hate it when their ulterior motives are revealed. It shows his entire, deceitful industry for what it is.
Peter says “security has to be added as yet one more consideration, along with all the other concerns raised by spectrum sharing,” and I agree. It’s not, however, like we’re starting from scratch as of the publication of the PCAST report. A Wireless Innovation Forum document published in 2010, “Securing Software Reconfigurable Communications Devices,” includes guidance, key considerations, and recommendations for software-defined radio (including cognitive radio) developers on security issues. That advice should be updated and expanded as appropriate.
The PCAST report contemplates that more work needs to be done. Indeed, the report describes a long-term process, not a short-term switchover. Starting with sharing 100 MHz, increasing that to 1000 MHz over time.