Broadcast Modulation for Persistent Interference
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Solution Overview
Problem
In cellular communication systems, downlink broadcasting from multiple transmitters can result in patterns of constructive and destructive interference, particularly in strong LOS environments, leading to weak signal spots where users experience poor channel conditions due to persistent destructive interference, especially for stationary users.
Innovation Solution
Modulating each block of broadcast transmission with a random time-varying phase rotation pattern, independent between sectors, and employing outer codes like Reed-Solomon codes, along with inner error correction techniques, to create time-varying self-interference diversity, preventing persistent destructive interference and improving signal quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If multiple transmitters broadcast the same signal simultaneously, then coverage area and system capacity are increased, but patterns of constructive and destructive interference are created leading to weak signal spots
Solution Approach 1:
The patent applies dynamics by making the phase rotation pattern time-varying rather than static. Each transmitter applies a different time-varying phase rotation pattern to the broadcast signal, which causes the interference patterns to change over time. This temporal variation prevents stationary users from experiencing persistent destructive interference, thereby improving signal quality while maintaining expanded coverage area from multiple transmitters.
Solution Approach 2:
The patent changes the phase parameter of the broadcast signal by applying different phase rotation patterns at each transmitter. By varying the phase parameter dynamically over time and differently across transmitters, the interference characteristics are modified to prevent persistent weak signal spots, thus resolving the contradiction between coverage expansion and signal quality maintenance.
2Productivity
If multiple transmitters are used to increase capacity, then more users can be served, but stationary users experience persistent destructive interference in certain areas
Solution Approach 1:
The patent employs dynamic phase rotation patterns that vary with time at each transmitter. This temporal dynamics ensures that the relative phase relationships between signals from multiple transmitters change continuously, preventing stationary users from being trapped in persistent destructive interference zones. This maintains reliable channel conditions while allowing the system to serve more users through multiple transmitters.
Solution Approach 2:
The patent implements periodic phase rotation patterns where each transmitter applies phase rotations that vary periodically over time. This periodic action ensures that the interference pattern cycles through different configurations, preventing any single destructive interference pattern from persisting for extended periods, thereby improving channel conditions for stationary users while maintaining high system capacity.
3Area of stationary object
If the same signal is broadcast from multiple sectors, then broadcast coverage is extended, but self-interference patterns are created that degrade signal quality
Solution Approach 1:
The patent transforms the static self-interference problem into a dynamic one by applying time-varying phase rotation patterns. This makes the self-interference patterns change over time rather than remaining fixed, preventing the formation of persistent harmful interference zones that would degrade signal quality in specific geographic locations while maintaining extended broadcast coverage.
Solution Approach 2:
The patent changes the phase parameter of the broadcast signal dynamically at each transmitter to alter the self-interference characteristics. By varying this parameter over time and differently across transmitters, the harmful self-interference patterns are transformed into time-varying patterns that do not persist in any single location, thus extending coverage without proportionally increasing harmful interference.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach increases coverage and quality of broadcast signals, reducing packet errors and ensuring more users receive high-quality broadcasts by making self-interference time-varying, thus improving overall system performance and user throughput.
Implementation Method 1
modulating each block of broadcast transmission with a random time-varying phase rotation pattern
Implementation Method 2
patterns of constructive and destructive interference
Data Source
AI summary
In a cellular network, randomness is introduced into a transmitted signal at each transmitter, and the resulting received signal, which is the sum of all received signals, fluctuates more in time than a signal transmitted without the introduced randomness. While the introduction of randomness can diminish reception of some parts of the signal at the receiver, the transmitted signal can be encoded using forward error correction coding techniques, which allows the receiver to recover all of the signal information despite some diminished reception. Such randomization provides time diversity so that receivers can have more consistent performance. For broadcasted data, where users with the worst channel condition dictates the overall performance, having consistent performance across users can improve the overall network performance.