OFDM System Using Non-Linear Phase Transformation
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Solution Overview
Problem
Existing OFDM systems face inefficiency due to excess capacity when transmitting packets of varying sizes, as they typically use a single OFDM symbol size that compromises between minimizing cyclic prefix overhead and maximizing packing efficiency, leading to wasted bandwidth and poor packing efficiency for smaller information units.
Innovation Solution
The proposed solution involves modifying complex baseband symbols through non-linear transformations, specifically by applying phase modifications to complex number pairs based on associated values, and employing fast unitary transformations built in layers using block-U(m) matrices and permutations to enhance security and efficiency without amplifying noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single OFDM symbol size is used to compromise between minimizing cyclic prefix overhead and maximizing packing efficiency, then system complexity is reduced, but bandwidth efficiency deteriorates for packets of varying sizes
Solution Approach 1:
The system dynamically selects OFDM symbol sizes based on packet size characteristics. For small packets, a smaller OFDM symbol size is selected to improve packing efficiency and reduce cyclic prefix overhead. For large packets, a larger OFDM symbol size is selected to maximize bandwidth utilization. This dynamic adaptation resolves the contradiction by allowing the system to optimize for the appropriate metric depending on traffic conditions.
Solution Approach 2:
The invention changes the parameter of OFDM symbol size (Ns and Ncp values) based on packet size requirements. Different configurations of Ns (IFFT size) and Ncp (cyclic prefix length) are selected to match different packet sizes, thereby optimizing bandwidth efficiency without requiring a fixed compromise configuration.
2Loss of energy
If a large value of Ns is used to decrease cyclic prefix overhead proportion, then cyclic prefix efficiency improves, but packing efficiency deteriorates for small information units
Solution Approach 1:
The system dynamically adjusts the Ns parameter based on packet size. For small packets, a smaller Ns is selected to improve packing efficiency and reduce waste. For large packets, a larger Ns is selected to decrease the proportional overhead of the cyclic prefix. This dynamic parameter adjustment resolves the contradiction between cyclic prefix efficiency and packing efficiency.
Solution Approach 2:
The invention explicitly changes the Ns parameter (IFFT size) based on the size of the information unit being transmitted. This parameter change allows the system to optimize the balance between cyclic prefix overhead and packing efficiency for different traffic conditions, rather than being constrained to a fixed Ns value.
3Reliability
If non-linear transformation is applied to complex baseband symbols for security enhancement, then security is improved, but noise amplification occurs
Solution Approach 1:
The non-linear transformation is applied locally to pairs of complex baseband symbols rather than to the entire signal. By operating on localized pairs of symbols and using unitary transformations that preserve signal power, the system enhances security while minimizing noise amplification. The local application allows for controlled transformation that maintains signal integrity.
Solution Approach 2:
The invention uses unitary transformations that preserve the norm (signal power) of the complex baseband symbols. By changing the parameters of the transformation to be unitary rather than arbitrary non-linear transformations, the system achieves security enhancement without noise amplification, as unitary transformations maintain signal energy and do not amplify noise.
4Loss of energy
If multiple OFDM symbol sizes are supported for varying packet sizes, then bandwidth efficiency is improved, but system complexity increases
Solution Approach 1:
The system performs preliminary selection of the appropriate OFDM symbol size based on packet size classification before actual transmission. By pre-determining the optimal symbol size configuration based on simple packet size thresholds, the system avoids complex real-time optimization while still achieving good bandwidth efficiency. This preliminary action simplifies the management complexity.
Solution Approach 2:
The invention segments the packet size space into different ranges, each associated with a specific OFDM symbol size configuration. This segmentation allows the system to manage multiple symbol sizes in a structured way, where each segment has a predetermined optimal configuration, reducing the complexity of managing multiple configurations compared to continuous optimization.
Data Source
AI summary
A method of encoding data includes identifying multiple complex number pairs of a data vector and generating a transformed data vector by applying a non-linear transformation to each complex number pair from the multiple complex number pairs. The non-linear transformation includes modifying a phase of a first complex number from each complex number pair. The phase modification is based on a value associated with a second complex number from each complex number pair. A signal representing the transformed data vector is sent to multiple transmitters for transmission to multiple receivers. A signal representing the non-linear transformation is sent to a compute device for transmission of the non-linear transformation to the multiple receivers prior to transmission of the signal representing the transformed data vector from the multiple transmitters to the multiple receivers, for recovery of the data vector at the multiple receivers.