Power Line Communication Using Zero-Crossing Time Slots
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Solution Overview
Problem
Current communication systems over power lines face inefficiencies in handling non-stationary noise sources, which are common in environments with multiple disturbing devices, leading to suboptimal performance due to constant noise variations in time and frequency.
Innovation Solution
The method involves encoding data using a signal diversity scheme that includes time and frequency diversification techniques, specifically by modulating data signals around zero crossings of the power signal and using Frequency Shift Keying (FSK) with multiple frequencies and phases, allowing for differential energy detection to improve robustness against noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If continuous transmission is used for each message, then data can be transmitted without interruption, but the system becomes inefficient in handling non-stationary noise with quiet periods
Solution Approach 1:
The patent applies periodic action by dividing continuous transmission into discrete time slots and using periodic sampling at zero crossings. The system transmits data in periodic bursts synchronized with the power line frequency, using only the quiet periods (zero crossings) for transmission while remaining silent during noisy periods, thereby improving efficiency without sacrificing reliability
Solution Approach 2:
The system dynamically adapts to non-stationary noise by detecting quiet periods and adjusting transmission timing accordingly. The transmitter and receiver synchronize their time slots based on detected zero crossings, allowing the system to dynamically exploit temporal variations in noise characteristics rather than using fixed continuous transmission
2Reliability
If signal diversity scheme with multiple time slots and frequencies is used, then robustness against noise is improved, but system complexity increases
Solution Approach 1:
The patent segments the transmission process into multiple time slots, each carrying portions of the data signal. By dividing the message into segments transmitted at different times and frequencies, the system achieves diversity without requiring complex real-time processing, as each segment can be independently decoded and reassembled
Solution Approach 2:
The system merges multiple signal paths by combining transmissions across different time slots and frequencies. The receiver integrates information from multiple time slots to reconstruct the original data, achieving robustness through diversity while maintaining manageable complexity through systematic combining rules
3Reliability
If FSK modulation with multiple frequencies is used, then frequency diversity is achieved, but bandwidth requirements increase
Solution Approach 1:
The patent uses partial action by employing FSK modulation with multiple frequencies but only utilizing a subset of available frequency slots for each transmission. The system uses m modulating frequencies where an integral number of full cycles fit into each time slot, achieving frequency diversity without requiring the full bandwidth to be actively used at all times
Data Source
AI summary
A communication system for a power line is described. A transmission system of the communication system divides the time axis into a number of time slots synchronized such that one time slot can start about a zero crossing of the power line signal. These time slots may be referred to as channels. Data may initially be modulated into at least one of these time slots over a first transmission period according to a modulation scheme. The time slots and/or modulation scheme used in subsequent transmission periods may be adjusted depending on transmission feedback relating to prior modulated data.