Multi-mode OFDM Transmitter with Partial-Response Shaping
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Solution Overview
Problem
Existing communications methods and systems are overly power hungry and spectrally inefficient, particularly in high-capacity wireless and wireline communication systems like WiFi, 3GPP-LTE, and G.hn, which rely on suboptimal detection algorithms and are inferior to maximum likelihood receivers.
Innovation Solution
The implementation of a multi-mode transmitter using orthogonal frequency division multiplexing (OFDM) with reduced state/complexity maximum likelihood decoders, partial response signaling, and transmitter shaping filtering to achieve high spectral efficiency, reduce bandwidth usage, and improve performance in AWGN environments without the need for pilot symbols.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional OFDM systems use suboptimal detection algorithms, then device complexity is reduced, but spectral efficiency and performance deteriorate
Solution Approach 1:
The system dynamically switches between full-response OFDM and partial-response OFDM modes based on channel conditions and performance requirements. The receiver adapts its detection algorithm complexity accordingly, using reduced-state sequence estimation (RSSE) for partial-response mode and conventional detection for full-response mode, thereby optimizing the trade-off between complexity and spectral efficiency
Solution Approach 2:
The invention changes the fundamental parameter of inter-symbol correlation by introducing controlled partial response signaling. This modifies the pulse shaping filter characteristics to create intentional inter-symbol correlation, which when combined with RSSE detection, achieves higher spectral efficiency without proportionally increasing complexity
2Productivity
If maximum likelihood detection is used to improve performance, then spectral efficiency improves, but device complexity increases significantly
Solution Approach 1:
The system applies partial-response signaling which introduces controlled excess inter-symbol correlation, but compensates by using reduced-state sequence estimation that processes only the necessary state information. This partial application of maximum likelihood principles achieves near-optimal performance with reduced complexity compared to full maximum likelihood detection
Solution Approach 2:
The detection process is segmented into manageable states by limiting the memory depth of the partial-response filter. The RSSE algorithm segments the state space into a finite number of states based on the filter order, making the detection problem tractable while maintaining high spectral efficiency
3Productivity
If bandwidth is increased to improve communication capacity, then productivity increases, but loss of energy increases due to power-hungry systems
Solution Approach 1:
The multi-mode transmitter can operate in both full-response OFDM mode and partial-response OFDM mode, providing universal compatibility with different system requirements. This allows the system to achieve high communication capacity through partial-response mode without the excessive power consumption of conventional high-capacity systems, as the controlled inter-symbol correlation enables more efficient signal transmission
Data Source
AI summary
A transmitter may comprise a symbol mapper circuit and operate in at least two modes. In a first mode, the number of symbols output by the mapper circuit per orthogonal frequency division multiplexing (OFDM) symbol transmitted by said transmitter may be greater than the number of data-carrying subcarriers used to transmit the OFDM symbol. In a second mode, the number of symbols output by said mapper circuit per orthogonal frequency division multiplexing (OFDM) symbol transmitted by said transmitter is less than or equal to the number of data-carrying subcarriers used to transmit said OFDM symbol. The symbols output by the symbol mapper circuit may be N-QAM symbols. While the circuitry operates in the first mode, the symbols output by the mapper may be converted to physical subcarrier values via filtering and decimation prior to being input to an IFFT circuit.