Dynamic FEC and MCS Adjustment for LTE Multicast Overhead
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Solution Overview
Problem
Mobile broadcast and multicast systems face inefficiencies due to the additional overhead introduced by forward error correction (FEC) schemes, which affect the performance of multicast/broadcast services, especially at the radio cell edge in LTE networks.
Innovation Solution
Implementing a feedback loop that adjusts FEC and modulation and coding scheme (MCS) values based on real-time quality of service metrics from user equipment, optimizing error protection and reducing overhead through dynamic FEC and MCS adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fixed FEC scheme is applied to provide error protection, then data reliability is improved, but transmission overhead increases
Solution Approach 1:
The patent implements dynamic FEC scheme selection that adapts to varying channel conditions. The system monitors quality of service metrics and dynamically adjusts the FEC overhead applied to multicast/broadcast data, transitioning between different FEC schemes (e.g., different redundancy ratios or coding rates) based on real-time network conditions. This resolves the contradiction by making the overhead variable rather than fixed, applying higher protection only when channel conditions warrant it.
Solution Approach 2:
The system changes the FEC parameters (such as redundancy ratio, coding rate, or error correction strength) based on observed quality of service metrics. By adjusting these parameters dynamically, the system optimizes the balance between error protection and transmission efficiency, reducing overhead when channel conditions are good while maintaining high reliability when conditions deteriorate.
2Device complexity
If a fixed MCS scheme is used for unified decoding, then system complexity is reduced, but performance at radio cell edge deteriorates
Solution Approach 1:
The patent implements dynamic MCS selection that adapts to spatial variations in signal quality across the cell. Different MCS schemes are assigned to different geographic regions or user groups based on their received signal quality, with more robust schemes applied to cell-edge users and higher-rate schemes to cell-center users. This resolves the contradiction by making the system adaptable to varying conditions without requiring every device to support all possible MCS configurations simultaneously.
Solution Approach 2:
The system applies different MCS schemes to different spatial locations or user groups within the cell coverage area. Cell-edge users receive transmissions with more robust modulation and coding, while cell-center users receive transmissions optimized for higher data rates. This local optimization resolves the contradiction by tailoring the transmission scheme to the specific conditions of each region rather than using a single uniform scheme.
3Reliability
If higher FEC overhead is applied to improve error protection, then packet loss is reduced, but transmission efficiency decreases
Solution Approach 1:
The system implements a feedback mechanism that monitors quality of service metrics (such as packet loss rate, bit error rate, or throughput) and uses this information to dynamically adjust the FEC overhead applied to subsequent transmissions. When packet loss is observed, the system increases FEC protection; when transmission is successful, it reduces overhead. This feedback-driven adaptation resolves the contradiction by optimizing the trade-off between error protection and efficiency based on actual performance.
Solution Approach 2:
The system dynamically changes the FEC parameters (redundancy ratio, coding rate, or error correction strength) based on observed transmission performance and channel conditions. By adjusting these parameters in response to measured quality metrics, the system achieves high reliability when needed while maintaining transmission efficiency under good conditions, resolving the fixed trade-off between packet loss and efficiency.
Data Source
AI summary
A method includes receiving an indication of current quality of service for a transmission received by user equipment from a base station. The method includes identifying target quality of service values for the transmission. A current FEC value and a current MCS value is identified for the transmission. An adjusted FEC value and an adjusted MCS value is determined based on the current FEC value and the current MCS value, the indication of current quality of service, and the target quality of service values. The method includes outputting the adjusted FEC value to a broadcast multicast service center for the transmission. The method also includes outputting the adjusted MCS value to the base station.