Hi Frank,
>>elaborate on your view of 'senseless sensing'. Are you suggesting that all frequency selection be table driven?<<
Not table driven, because it implies the table could be self-contained, but under control of an online geo-location database, based on the radio location and radio characteristics of the protected services and the cognitive device.
The traditional definition of a cognitive radio is it knows its location and the rules for its location (what radio services are to be protected), and it knows the radio environment at its location. The traditional cognitive radio does not know how to operate in bands where the protected services are mobile or portable unless it can sense their radio transmissions and avoid them.
In Europe, SE43 has been examining alternatives on how to share broadcast TV spectrum
ero.dk;
They have two task groups examining geo-database control (led by UK OFCOM William Webb) and sensing (Led by France ANFR Bruno Espinosa). The current view is sensing would have to be at -127 dBm (about 47 dB under the allowed energy threshold) to reliably detect wireless microphones. In the USA, only one percent of wireless microphones are used by Part 73 and Part 74 license holders, and 99 percent do not enjoy protection.
As IEEE 802 stated in 23) in the Petition for Reconsideration (see below), it is impossible for a sensing device to determine whether the radio signals it detects come from a transmitter that enjoys protection. Note that unlicensed devices are not prohibited from transmitting modulations that are similar to DTV or wireless microphones or any other devices that are used by the license holders.
This fact makes sensing senseless, just a waste of energy and time (senseless work, measured in Joules).
Note that Listen Before Talk has Energy Detect modes, which defer to other energy in a radio channel, independent of the energy's source. LBT is not sensing.
petere
23.
It is difficult, if not impossible, for a sensing approach to differentiate between a legal Part 74 device and any other narrowband signals sources such as spurious signals as allowed by Part 15.209(a) since the specified sensing threshold proposed by the FCC is 33.5 dB below the permitted level from such a source at a 10 m distance. |
