White Space Device Interference Compensation
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Solution Overview
Problem
White space devices (WSDs) face transmit power limitations due to strict adjacent channel protection requirements, limiting the availability of usable white space channels, especially for high power levels, without making changes to primary system receivers.
Innovation Solution
A method where a WSD determines and retrieves signal information from a primary wireless system to transmit a second signal on a further channel that would be interfered by the first signal, compensating for interference and allowing higher power transmission on the white space channel without altering primary system receivers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If WSDs transmit on white space channels, then spectrum utilization is improved, but transmit power is limited due to adjacent channel interference
Solution Approach 1:
The patent converts the harmful interference that WSDs cause to adjacent channels into a beneficial signal by having the base station transmit the same signal on both the white space channel and the adjacent channel. This allows the interference to be transformed into useful signal energy, enabling higher transmit power on white space channels while protecting adjacent channel receivers.
Solution Approach 2:
The patent segments the transmission into two parts: the original WSD signal on the white space channel and a compensated signal on the adjacent channel. The base station separately processes and transmits these signals, with the adjacent channel signal specifically designed to compensate for interference, allowing independent optimization of each channel's transmit power.
2Reliability
If strict adjacent channel protection is enforced, then primary system reliability is improved, but WSD channel availability deteriorates
Solution Approach 1:
The base station acts as an intermediary between WSDs and primary receivers. It receives signals from WSDs on white space channels and simultaneously transmits compensated signals on adjacent channels, mediating the interference issue and enabling both WSD operation and primary receiver protection without direct modification to either end device.
Solution Approach 2:
The base station performs preliminary compensation by transmitting the compensated signal on the adjacent channel before the interference becomes problematic for primary receivers. This proactive approach ensures that when primary receivers experience potential interference from WSD transmissions, the compensating signal is already present to mitigate the harm.
3Reliability
If WSD transmit power is increased, then communication quality is improved, but interference to primary receivers worsens
Solution Approach 1:
The patent applies counterweight by transmitting a compensated signal on the adjacent channel that has equal magnitude but opposite phase characteristics to the interference caused by the WSD signal. This counterbalancing approach cancels out the harmful interference while allowing the WSD to transmit at higher power levels for improved communication quality.
Data Source
AI summary
The disclosure relates to a white space device (WSD) of a secondary wireless network, and to a related method for transmitting a first signal on a channel available for secondary usage allocated to a primary wireless system. The method in the WSD comprises determining (410) a further channel used by the primary wireless system, that would be interfered by a transmission of the first signal on the channel available for secondary usage, retrieving (420) signal information associated with the determined further channel from the primary wireless system, transmitting (430) the first signal on the channel available for secondary usage, and transmitting (440) a second signal on the determined further channel based on the retrieved signal information, simultaneously with the first signal on the channel available for secondary usage* such that an interference generated in the primary wireless system by the first signal transmission is compensated for by the second signal transmission.