MIMO Channel Randomization via Time-Varying Complex Multipliers
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Solution Overview
Problem
Communication systems face performance degradation due to quasi-static fading channels, where channel coefficients remain constant, leading to high bit error rates and inability of channel coding schemes to recover errors effectively.
Innovation Solution
A method that artificially changes quasi-static fading channels to time-varying channels by multiplying transmitting signals with time-varying complex multipliers, providing time diversity and improving system performance through randomization of channel coefficients at the transmitter, applicable to MIMO, OFDM, and OFDMA systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If channel coefficients remain constant in quasi-static fading channels, then channel coding schemes can be applied, but bit error rates remain high and error recovery is ineffective
Solution Approach 1:
The patent applies dynamics by transforming the static channel coefficients into time-varying coefficients through multiplication with pseudo-random sequences. The channel coefficient becomes h(n) = h * q(n), where q(n) is a pseudo-random sequence that changes over time, creating artificial time-varying characteristics that enable effective error recovery while maintaining system reliability
Solution Approach 2:
The patent changes the parameter of channel coefficients from constant to time-varying by introducing pseudo-random sequences. This parameter transformation allows the channel to exhibit time-varying behavior without physical movement, enabling channel coding schemes to effectively recover errors by experiencing diverse channel conditions across different time instances
2Reliability
If multiple versions of signals are transmitted to cope with fading, then diversity is achieved, but system complexity increases
Solution Approach 1:
The patent introduces pseudo-random sequences as an intermediary element that modulates the transmitted signals. These sequences act as a mediator between the original signal and the channel, creating time-varying signal versions that provide diversity without requiring multiple physical antennas or complex signal processing at the receiver
Solution Approach 2:
The patent creates virtual copies of the transmitted signal by multiplying with pseudo-random sequences. Instead of transmitting multiple physical copies through different antennas, the system generates time-varying signal versions through mathematical operations, achieving diversity with reduced hardware complexity
Data Source
AI summary
A method is provided for creating an artificial a fast fading channel in a MIMO communication system. The method includes encoding a series of source data to generate a first plurality of encoded output signals and multiplying the first plurality of encoded output signals by a plurality of random complex numbers to generate a second plurality of encoded output signals, and transmitting the second plurality of encoded output signals via the corresponding plurality of antennas. The transmitted signals vary in time and frequency independent of the channel conditions.