Global Positioning System Reference
In-Depth Information
may be used within a wireless transceiver and configured by software, so that the
common blocks can be assigned to tasks according to the demands of each type of
radio system. Instead of a computing platform of today with many separate
subsystems (with one for each standard), the future will consist of a set of more
general-purpose processing blocks that can be configured and reconfigured
depending on the mix of standards and protocols that are needed.
The requirements of positioning will be added to the list of radio processing
tasks that software defined radio will be performing. These include measuring
signal flight times (for lateration), processing antennae arrays to steer beams (for
angulation) and collecting multiband signal strengths (for proximity estimates).
Although there will be radio hardware in the digital transceiver of the future, it
will be more versatile so that when a new radio standard is needed or a new
processing function required (perhaps for a Whereness service), the platform will
not need to be modified physically since the changes will be all in the
configuration of the DSP elements performed by software drivers. It is unlikely
that true software radio will ever be common (i.e., all radio processing done in
software) but the software defined radio, with the DSP array approach, is both
economic and pragmatic and a very useful way to converge standards and
functions.
9.1.3
Cognitive Radio
Cognitive radio is a new paradigm for the self-organization of radio spectrum,
radio coverage, and radio systems. Whereness could have a profound effect on the
more advanced configurations.
Currently, radio coverage and spectrum allocation are organized centrally.
Regulatory bodies, who many years ago allocated single channels to individual
organizations, now tend to allocate blocks of spectrum to trunked operators who
then share out individual channels on demand. A centralized network management
system is used to control the trunking and radio channel allocation. Full cognitive
radio takes the approach that each radio itself should make the decisions about the
allocation of resources, based on local knowledge of the actual state of spectrum
occupancy. This is a decentralized approach and involves the radio nodes having
the capabilities to sense, scan, and operate (peer-to-peer) with other local nodes,
perhaps avoiding many of the centralized control functions present (e.g., in a
cellular radio system).
Supposing Whereness was widespread and by a variety of means, some of
which may not be wireless, mobile nodes know exactly their location and the
location of other nodes. Supposing also each node has a detailed map that includes
a terrain model. It would then be possible for any node to establish a wireless link
to any other viable node with optimal power, direction, band, and modulation. No
energy would be radiated that was unnecessary and overall co-channel
interference levels would be reduced, greatly improving frequency reuse and
spectral efficiency.
