CDMA Data Channel Noise Estimation Using Pilot Symbol Differences
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current communication systems face challenges in accurately estimating noise levels for data channels in CDMA receivers, particularly in HSDPA mode, where pilot channel noise is often much lower than the signal, leading to distorted noise estimation due to pilot signal leakage.
Innovation Solution
The method involves computing differences between selected soft pilot symbols received on the pilot channel to estimate noise levels for data channels, using techniques such as subtracting complex numerical values, averaging, and applying adaptive time durations based on receiver velocity, and scaling noise estimates by spread factor ratios, while accounting for transmit diversity modes like STTD and CLTD.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If pilot channel noise is measured directly, then noise estimation is simplified, but the estimation becomes distorted due to pilot signal leakage
Solution Approach 1:
The patent extracts the pilot signal component from the received pilot channel by computing differences between selected soft pilot symbols. This removes the dominant pilot signal leakage that distorts direct noise measurement, allowing the remaining noise component to be estimated accurately without being overwhelmed by the strong pilot signal.
Solution Approach 2:
The patent introduces an intermediate processing step of computing differences between soft pilot symbols as a mediator. This intermediary operation transforms the contaminated pilot channel measurements into a form where noise can be extracted, bridging the gap between the strong pilot signal and the weak noise measurement requirement.
2Device complexity
If the maximal time duration between symbols is fixed, then the computation is simplified, but the noise estimation accuracy deteriorates in high mobility scenarios
Solution Approach 1:
The patent makes the maximal time duration parameter dynamic by adaptively setting it as a function of receiver velocity. In high mobility scenarios, a shorter duration is used to capture noise before channel conditions change significantly, while in low mobility scenarios, a longer duration can be used for better averaging. This dynamic adjustment maintains accuracy across varying conditions without excessive complexity.
Solution Approach 2:
The patent changes the parameter of maximal time duration based on receiver velocity conditions. By adjusting this temporal parameter according to mobility state, the system optimizes the trade-off between computation complexity and noise estimation accuracy for different operating scenarios.
3Measurement precision
If spread factor is increased to reduce pilot signal leakage, then noise estimation accuracy improves, but data channel capacity is reduced
Solution Approach 1:
The patent extracts noise information from the pilot channel before the spread factor issue affects data channel capacity. By computing differences between soft pilot symbols and removing the pilot signal component, the system obtains accurate noise estimates without needing to increase the spread factor, thereby preserving data channel capacity while achieving accurate noise estimation.
Data Source
AI summary
A method includes receiving a Code Division Multiple Access (CDMA) carrier carrying at least a pilot channel. Differences are computed between selected soft pilot symbols received on the pilot channel. Based on the computed differences between the selected soft pilot symbols received on the pilot channel, a level of noise is estimated for a data channel that is to be transmitted on the CDMA carrier.