Uplink Load Estimation via Interference Whitening in WCDMA
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Solution Overview
Problem
Existing load estimation algorithms in WCDMA cellular communication systems overestimate air-interface load, leading to under-scheduling and reduced throughput, capacity, and blocking in admission control due to their inability to accurately account for interference suppression and interference cancellation gains.
Innovation Solution
The method involves computing a noise floor measure and estimating neighbor cell interference power after interference whitening, using frequency domain equalization or pre-equalization techniques, to derive a noise rise measure that accurately reflects uplink cell stability, enabling more effective load scheduling and resource utilization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If existing load estimation algorithms are used, then cell stability is maintained, but air-interface load is overestimated leading to under-scheduling and reduced throughput
Solution Approach 1:
The patent applies preliminary action by performing interference whitening processing before load estimation. The received uplink radio signals are first processed through frequency domain equalization or pre-equalization to whiten the interference, and only then is the load estimation performed. This preliminary processing step removes the distorting effect of colored interference on the load measurement, enabling accurate load estimation that reflects the true post-interference-suppression state of the system.
2Object-affected harmful factors
If interference suppression and cancellation are applied, then interference reduction is achieved, but accurate load measurement becomes difficult
Solution Approach 1:
The patent introduces an intermediary approach by using frequency domain equalization or pre-equalization as a intermediate processing step. This intermediary technique transforms the colored interference into white noise, creating an intermediate state where the interference is suppressed but the measurement remains valid. The frequency domain processing acts as a mediator that reconciles the conflict between interference suppression and accurate load measurement.
3Reliability
If conservative margins are used in scheduling, then cell stability is ensured, but system capacity and coverage are reduced
Solution Approach 1:
The patent implements feedback by using the accurate load estimation result to dynamically adjust scheduling decisions. The scheduler receives precise feedback about the actual uplink load condition after interference suppression, and uses this feedback to make optimal scheduling decisions. This feedback mechanism eliminates the need for conservative margins because the system has accurate real-time information about the true load state, enabling it to operate at the true stability boundary rather than using overly cautious estimates.
Data Source
AI summary
A method for assisting load scheduling in a wireless communication system comprises computing of an estimate of a noise floor measure for received uplink radio signals and a neighbor cell interference power is estimated. An interference whitening of the received uplink radio signals is performed based on frequency domain equalizing or frequency domain pre-equalizing. A useful signal power after interference whitening is determined and a first user noise floor compensation factor is derived. A noise rise measure is calculated based at least on the useful signal power after interference whitening, the noise floor compensation factor, the noise floor measure and the estimated neighbor cell interference power.