Radio Spectrum

The US really needs to figure out a way to assign more spectrum for general public use. There really is a lot of spectrum out there and most of it seems to have been gobbled up by various groups with only tiny scraps left for the public in the form of ISM and UNII bandwidth. 

A full map showing exactly how tiny the ISM bandwidth is can be found here.

Below the various bands are little text saying “ISM blah +/- blah” showing what us in the public have to work with. It doesn’t amount to much, but with the tiny swaths of bandwidth we’ve been allocated we’ve done some pretty impressive stuff with it. That little 100mhz we’re allocated from 2400-2500mhz block can support around 150megabits of transfer with no collisions at all. That’s enough for broadband to about 3 neighbourhoods at cable modem speeds. We could run tons of radio stations digitally in that space. We could run around 30 480i digital TV channels with low (5000kbits per second) compression in that space. Going by channels 2-4 on that chart, this is about twice as efficient as the fuzzy, almost unwatchable analog TV channels. What really needs to happen is bringing all of these licensed channels up to modern technology. Many of them are just wasting the majority of their bandwidth. The techniques pioneered for sharing of bandwidth and reducing usage of bandwidth in the tiny blocks of ISM we have could be applied to all of the other spectrums probably freeing up far more bandwidth than is currently assigned to ISM. 

Take, for example, some of the current licensed industrial control systems that have been around since the dark ages. One that I recently heard of operated in the VHF band and over a voice channel. Instead of trying to transmit the signals digitally to turn on and off pumps and look at the status of switches, they used various frequency tones over the voice channel to indicate what the devices should do. If they instead used digital transmission they could share that bandwidth with many other similar applications and free up several mhz of bandwidth for other applications.

The government yanking the STV frequencies from the tv networks in 2009 is a step towards this. It’s giving them more bandwidth and a more efficient way of utilizing it, while phasing out the obsolete and inefficient use of other bandwidth. If these bands were handed back to the public or to internet companies we could have wide coverage non-line of site broadband (in the ISDN to 256kbit range per user, higher than 3G and CDMA) in much the same areas you can currently get TV signals. It’s not going to happen. The government has long since stopped caring about what we want, as evidenced by the fact that the HDTV specs they’re replacing the STV with are covered by very anti-public anti-consumer DRM.