Multi-Carrier Channel Desynchronization for Crest Factor Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing multi-carrier communication systems face challenges in reducing the crest factor, leading to inefficient use of disjoint bands and signal degradation, particularly in HF communications, where peak-to-average power ratio (PAPR) variations cause issues with power amplification and spectral efficiency.
Innovation Solution
Introducing desynchronization symbols between channels of a multi-carrier waveform to prevent channels from being in phase, thereby reducing the crest factor without degrading the signal, by adding a number of desynchronization symbols at the start of each frame, chosen based on the number of transmission channels, and realigning channels at reception.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multi-carrier waveform is used to increase bandwidth and throughput, then spectral efficiency and data rate are improved, but the peak factor (PAPR) increases causing signal degradation and inefficient power amplifier operation
Solution Approach 1:
The multi-carrier waveform is segmented into multiple channels, each assigned a specific subset of subcarriers. By dividing the overall signal into separate channel components that can be independently managed and desynchronized, the peak factor of the composite signal is reduced while maintaining the total bandwidth and data rate capability.
Solution Approach 2:
Desynchronization symbols are inserted at the beginning of each channel's frame structure before the actual data transmission. This preliminary action introduces controlled time offsets between channels, preventing them from arriving in phase at the receiver, thereby reducing the peak factor before the main data transmission occurs.
2Object-generated harmful factors
If clipping techniques are applied to reduce peak factor, then PAPR is reduced, but signal quality is degraded requiring additional error correction coding
Solution Approach 1:
Desynchronization symbols act as intermediary elements inserted between the channel data and the composite multi-carrier signal. These symbols introduce time offsets that reduce the peak factor without directly modifying or clipping the actual data-carrying signal, thereby maintaining signal quality while achieving PAPR reduction.
3Productivity
If channels are synchronized for efficient resource utilization, then bandwidth usage is optimized, but the crest factor increases due to constructive interference
Solution Approach 1:
Symmetric time alignment of channels is replaced with asymmetric time offsets introduced by desynchronization symbols. Each channel is deliberately desynchronized by a different amount, breaking the symmetry that would otherwise cause constructive interference and high crest factor, while still allowing efficient bandwidth utilization through controlled overlapping.
Data Source
Figure 1
Figure 2
Figure 3
AI summary
The method involves transmitting data in a form of a frame comprising an initial synchronization preamble (12). A number of desynchronization symbols (11) are introduced at start of the frame, where the number is chosen as a function of a transmission channel number. The desynchronization symbols are adapted to introduce an offset between different channels of a multi-carrier wave form. The introduced desynchronization symbols are different for the channels. The number of desynchronization symbols equal to zero is introduced before initial synchronization preamble of the frame. An independent claim is also included for a system for reducing a peak factor in a multi-carrier high frequency (HF) communication system.