Innovation #8: Interference Mitigation Techniques
8.1 Executive Summary
Better mechanisms are needed to reduce destructive interference on the communications signal, and thus improve the signal’s quality of service and/or communications range.
Interference can take the form of intentional jamming, as often occurs in military communications, or non-intentional interference often resulting from misused of equipment (wrong frequency settings, misplaced of towers) or power spillover in other bands. In either case, the interference decreases the signal to interference plus noise ratio at the receiving end of the communications path and, if of sufficient level, will substantially degrade or obliterate voice quality in a voice system and data throughput in a data system.
Innovations are sought that deal with how Software Defined Radio (SDR) and/or Cognitive Radio (CR) might alter the system design tradeoffs of primarily either to enable better rejection of interference without the exponential cost growth associated with more traditional solutions. Such innovations might include, but are certainly not limited to, the ones listed below. It is realized that many of these techniques are already used in some advanced communications systems, but not used in others because design tradeoffs or other factors may not have their deployment. It is recognized that cognitive radio techniques, whereby the frequency plans could be modified to operate in non-interfering bands, might be a solution, but the implementation cost of such techniques would be prohibitive for many applications. In the present cases, other techniques are sought. A few examples are given here:
- Power control throughout the communications system, using only enough power to maintain communications at the minimum acceptable level. In fact, for low priority communications paths, the power could even be set for degraded voice quality relative to the paths with the highest priority to reduce interference.
- Adaptive beamforming to maximize antenna gain in the direction of the communications path and minimize gain in the interference direction.
- Adaptable data rate to the minimum rate needed for the communication and/or according to priority of the operator.
- Adaptive frequency control to increase frequency separation of the interference sources from the desired radio path
- Adaptive receive filtering to provide better rejection of the interference balanced against possible sensitivity loss.
- Improved roaming algorithms (Change sites or systems to one that has a better Signal to Noise plus Interference ratio.
- Change channel coding algorithms to relax the required signal to interference plus noise ratio at the expense of more data overhead