Time-Varying Precoding Matrix for OFDM Channel Randomization
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Solution Overview
Problem
Existing transmit diversity techniques for MIMO OFDM systems face challenges in minimizing the adverse effects of signal-to-noise ratio (SNR) degradation due to factors like multi-path fading and noise in wireless communication channels.
Innovation Solution
A physical layer module employing time-varying gains and permuted space-frequency coding, with cyclic delays applied to RF channels, maps data streams across multiple antennas to enhance diversity and mitigate channel impairments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If transmit diversity techniques are used to compensate for SNR degradation, then reliability is improved, but device complexity increases
Solution Approach 1:
The patent applies dynamics by making the precoding matrix time-varying through channel randomization. The precoding matrix is updated at each time slot based on the current channel state, allowing the system to adapt to changing channel conditions. This dynamic approach enables the system to maintain diversity benefits while managing complexity through adaptive rather than static configurations
Solution Approach 2:
The patent changes the parameters of the precoding matrix dynamically. By randomizing the channel matrix H and recomputing the precoding matrix W at each time slot, the system varies the transmission parameters adaptively. This parameter change strategy allows the system to optimize performance for current channel conditions while maintaining diversity advantages
2Reliability
If multiple transmit antennas are used to provide diversity, then reliability is improved, but loss of energy increases
Solution Approach 1:
The patent applies partial action by using precoding to focus energy transmission. Instead of transmitting equal power from all antennas without directionality, the precoding matrix W applies complex weights that concentrate the signal energy more effectively toward the intended receiver. This partial action approach maintains diversity benefits while reducing overall energy loss compared to uniform multi-antenna transmission
Data Source
AI summary
A physical layer (PHY) module includes NT radio frequency (RF) channels and a mapping module. The NT RF channels each include N subcarriers. The mapping module includes Ns inputs receiving corresponding ones of NS data streams. The mapping module further includes NT outputs communicating with corresponding ones of the NT RF channels. Each of the NT outputs includes N outputs. The mapping module further includes a mapping matrix that maps the NS data streams to the NT outputs. NT, NS, and N are integers greater than or equal to 2. The NT RF channels include NT gain modules that apply NT different complex gains to the NT outputs, respectively. One of the NT different complex gains is applied to each of the N outputs of a corresponding one of the NT outputs. The NT different complex gains correspond to NT transmit antennas of the NT RF channels, respectively.