160 Software Networks
6.13. Software radio and radio virtual machine
Undoubtedly cognitive radio represents one of the greatest
revolutions of this new millennium. It facilitates much better use of
the spectrum of radio frequencies, which is generally very poorly
exploited. However, optimal use of the spectrum would be impossible
without a certain number of other, parallel developments, which we
shall now go on to discuss. We have already encountered this
technology in TVWS (TV White Space) Wi-Fi in the IEEE 802.11af
standard, pertaining to the use of unoccupied television bands.
Software radio, or SDR (Software-Defined Radio), defines a radio
transmitter or receiver which is in software, rather than hardware,
form. The implications of such technology are evident, because the
characteristics of the radio interface can be modified infinitely without
any technical problems at all; users will have the interface they need at
a given time t, and a completely different interface at time t + 1.
Obviously, a certain amount of hardware is needed to perform the
computations of encoding, modulation and filtering, and for the
transmission itself.
The computational power may be hosted on the device itself, or –
as we have seen – in the mobile Cloud, in a local Cloudlet, a regional
Cloud or even a central Cloud.
At present, progress in the area of this technology is being made
very rapidly, because it is possible to condense all the computations
for a large number of access points to a single machine. Nowadays,
we are seeing the emergence of a particularly interesting, attractive
solution: using a single antenna for all radio communications. The
signal is sent to the appropriate virtual machine for processing. In
other words, at certain times the antenna may receive Wi-Fi signals,
and then at other times signals from a 3G communication, then 4G,
then a TV signal, then Zigbee, and all of it is handled by virtual
signal-processing machines.
The Cloud, once again, is important in these technological
advances, and we can clearly see the amount of power and memory
that are needed to support the necessary software machines. However,
www.it-ebooks.info
6.13. Software radio and radio virtual machine
Undoubtedly cognitive radio represents one of the greatest
revolutions of this new millennium. It facilitates much better use of
the spectrum of radio frequencies, which is generally very poorly
exploited. However, optimal use of the spectrum would be impossible
without a certain number of other, parallel developments, which we
shall now go on to discuss. We have already encountered this
technology in TVWS (TV White Space) Wi-Fi in the IEEE 802.11af
standard, pertaining to the use of unoccupied television bands.
Software radio, or SDR (Software-Defined Radio), defines a radio
transmitter or receiver which is in software, rather than hardware,
form. The implications of such technology are evident, because the
characteristics of the radio interface can be modified infinitely without
any technical problems at all; users will have the interface they need at
a given time t, and a completely different interface at time t + 1.
Obviously, a certain amount of hardware is needed to perform the
computations of encoding, modulation and filtering, and for the
transmission itself.
The computational power may be hosted on the device itself, or –
as we have seen – in the mobile Cloud, in a local Cloudlet, a regional
Cloud or even a central Cloud.
At present, progress in the area of this technology is being made
very rapidly, because it is possible to condense all the computations
for a large number of access points to a single machine. Nowadays,
we are seeing the emergence of a particularly interesting, attractive
solution: using a single antenna for all radio communications. The
signal is sent to the appropriate virtual machine for processing. In
other words, at certain times the antenna may receive Wi-Fi signals,
and then at other times signals from a 3G communication, then 4G,
then a TV signal, then Zigbee, and all of it is handled by virtual
signal-processing machines.
The Cloud, once again, is important in these technological
advances, and we can clearly see the amount of power and memory
that are needed to support the necessary software machines. However,
www.it-ebooks.info