MIMO-OFDM Space-Frequency Coding for WLAN Power Distribution
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Solution Overview
Problem
Current MIMO wireless systems face challenges in efficiently transmitting data over multiple antennas with varying channel conditions, requiring innovative encoding techniques to maintain equal power distribution and adapt to changing link qualities.
Innovation Solution
A MIMO/OFDM system employing space-frequency code matrices with constant Frobenius norm for equal tone power and row norms for equal antenna power, along with permuted space-frequency coding and generalized cyclic delay diversity, to optimize data transmission across multiple antennas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If spatial multiplexing is used to increase data rate by transmitting multiple independent data streams on different antennas, then data rate is improved, but link quality deteriorates under varying channel conditions
Solution Approach 1:
The system dynamically adapts the spatial multiplexing rate based on channel conditions. The receiver feeds back channel quality information, and the transmitter adjusts the number of independent data streams (spatial multiplexing rate) accordingly, allowing the system to optimize between data rate and link quality in real-time varying channel conditions
Solution Approach 2:
The invention changes the parameter of spatial multiplexing rate (rs) from a fixed value to a variable parameter that can be adjusted between 1 and min(MR, MT). This parameter change allows the system to flexibly trade off between data rate (higher rs) and link quality (lower rs) based on channel conditions
2Productivity
If different power levels are used for different tones or antennas to optimize performance, then data transmission efficiency is improved, but power amplifier cost and complexity increase
Solution Approach 1:
The space-frequency code matrix applies different weighting factors to different tones and antennas through its structure. The matrix elements are designed such that the Frobenius norm is constant for equal tone power and row norms are equal for equal antenna power, achieving local power optimization without requiring complex power amplifiers
Solution Approach 2:
The invention uses parameter changes in the code matrix structure (Frobenius norm constraint and row norm constraint) to achieve power distribution optimization. By designing the code matrix with specific norm properties, the system achieves equal power distribution across tones and antennas, avoiding the need for complex power control mechanisms
Data Source
AI summary
A MIMO-OFDM system may use different types of space-frequency code matrices for encoding data on multiple substreams for transmission on multiple antennas. The system may utilize a MIMO-OFDM frame format that includes additional long training OFDM symbols for training additional antennas and for link adaptation and a header with an additional SIGNAL symbol to indicate MIMO-OFDM-specific information.