Equal BER Power Control for MMSE-SIC Uplink MC-CDMA

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

The performance of uplink MC-CDMA systems is limited by multiple access interference (MAI), and existing interference cancellation techniques, such as SIC, are sensitive to received power allocation and degrade quickly with increasing system load, limiting their effectiveness.

Innovation Solution

Integration of a power control algorithm under an equal BER criterion with a nonlinear MMSE-SIC receiver to optimize power allocation among users, ensuring all users achieve the same signal-to-interference ratio, thereby suppressing MAI effectively in frequency-selective Rayleigh fading channels.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If successive interference cancellation (SIC) is used to suppress multiple access interference, then interference suppression capability is improved, but the system performance degrades quickly with increasing system load

Engineering Contradiction:

Improvemultiple access interferenceVSAvoidsystem performance

Core Design Contradiction:

Object-affected harmful factorsVSReliability

Solution Approach 1:

The patent changes the power allocation parameters among users to optimize SIC performance. By adjusting transmit power levels according to channel conditions and user priorities, the system maintains effective interference suppression even as system load increases. This parameter optimization prevents the performance degradation that normally occurs with higher user densities.

Inventive Principle:

Principle #35Parameter changes

2Productivity

If power control is integrated with SIC to improve system capacity, then system capacity is increased, but the complexity of power allocation increases

Engineering Contradiction:

Improvesystem capacityVSAvoidpower allocation complexity

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The patent implements a feedback-based power control mechanism where the receiver measures channel state information and sends power allocation commands back to transmitters. This closed-loop feedback system automatically adjusts power levels to maintain equal BER across users, increasing system capacity while managing complexity through standardized feedback protocols and algorithms.

Inventive Principle:

Principle #23Feedback

3Reliability

If equal BER power control is used to improve SIC reliability, then detection reliability is improved, but the complexity of power control algorithm increases

Engineering Contradiction:

Improvedetection reliabilityVSAvoidpower control algorithm complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent employs parameter changes in the power control algorithm to achieve equal BER performance. By dynamically adjusting transmit power based on calculated BER targets and channel conditions, the system improves detection reliability. The algorithm manages complexity by using iterative optimization methods that converge to optimal power allocations without requiring excessively complex computations.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS7620096B2Equal BER power control for uplink MC-CDMA with MMSE successive interference cancellation

Publication Date: 2009.11.17 NEW JERSEY INSTITUTE OF TECHNOLOGY

AI summary

For a given decision order, MMSE successive interference cancellation (MMSE-SIC) can simultaneously maximize SIRs of all users. To further increase its efficiency, a power control (PC) algorithm, under equal BER criterion, is disclosed for uplink MC-CDMA. In frequency-selective Rayleigh fading channels, the MMSE-SIC integrated with the equal BER PC suppresses multiple access interference (MAI) effectively, resulting in a performance very close to the single user bound (SUB).