Alamouti Coding in Filterbank Multi-Carrier Systems
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Solution Overview
Problem
Filter bank multi-carrier transmission schemes face difficulties in applying Alamouti codes due to inherent inter-carrier interference, which is not effectively addressed by existing technologies.
Innovation Solution
An Alamouti coding method that maps real-valued data symbols to subcarriers using a frequency reversal scheme, adjusting phases based on subcarrier indices and time intervals, and dividing subcarriers into blocks based on frequency selective fading characteristics to eliminate inter-carrier interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Alamouti code is applied to filter bank multi-carrier transmission, then diversity gain and reliability are improved, but inter-carrier interference occurs due to inherent system characteristics
Solution Approach 1:
The patent applies frequency reversal to the Alamouti coded symbols, mapping them to subcarriers in reverse order. This inversion technique transforms the harmful inter-carrier interference into constructive interference that can be cancelled at the receiver, thereby maintaining reliability while eliminating the interference problem
Solution Approach 2:
The patent modifies the mapping parameters by introducing phase rotation factors and frequency reversal indexing. By changing how symbols are mapped to subcarriers (using equations like x'(k) = x(k) * exp(j*θ_k)), the system maintains diversity gain while transforming the interference characteristics to be cancelable
2Object-generated harmful factors
If frequency reversal Alamouti coding is applied, then inter-carrier interference is eliminated, but device complexity increases due to additional mapping and phase adjustment operations
Solution Approach 1:
The patent divides the N subcarriers into two segments: first half (0 to N/2-1) and second half (N/2 to N-1). Alamouti coded symbols are mapped to one segment while their frequency-reversed counterparts are mapped to the other segment. This segmentation organizes the complex mapping process into manageable parts while maintaining interference cancellation
Solution Approach 2:
The patent performs frequency reversal and phase adjustment operations during the encoding stage at the transmitter. By preliminarily transforming the symbols before transmission, the complex operations are completed upfront, simplifying the receiver processing and distributing the complexity burden to the encoding side where it can be more efficiently managed
3Measurement precision
If complex phase adjustment and frequency reversal mapping are implemented, then bit error rate performance is improved under multipath fading, but computational complexity increases
Solution Approach 1:
The patent employs phase rotation parameters (θ_k) that are predetermined and systematically applied. By changing the mapping parameters in a structured way rather than performing complex adaptive adjustments, the system achieves improved bit error rate performance under multipath fading while keeping computational complexity manageable through parameter-based solutions
Data Source
AI summary
An Alamouti coding method includes mapping real number data symbols to a first subcarrier to an (N/2−1)th subcarrier, based on indices of the subcarriers, mapping the mapped real number data symbols and real number data symbols constituting an Alamouti coded symbol pair to an (N/2+1)th subcarrier to an (N−1)th subcarrier, in a frequency inversion scheme with reference to an (N/2)th subcarrier, adjusting a phase of each real number data symbol mapped to the first subcarrier to the (N/2−1)th subcarrier, by using a first phase adjustment value, based on indices of the mapped subcarriers and an index of a time interval, and adjusting a phase of each real number data symbol mapped to the (N/2+1)th subcarrier to the (N−1)th subcarrier, by using a conjugate value of a first phase adjustment value for a corresponding real number data symbol and the real data symbols constituting the Alamouti coded symbol pair.