Hierarchical Modulation for LTE MBMS Throughput
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Solution Overview
Problem
In LTE systems, the use of low-order modulation and coding schemes for MBMS data transmission to ensure robustness for cell-edge UEs results in reduced system throughput and spectrum utilization efficiency, as higher-order schemes cannot be used for cell-center UEs due to channel quality differences.
Innovation Solution
Implementing hierarchical modulation, where service data is modulated into base-layer and additional-layer components with different priorities, allowing cell-center UEs to receive high-priority data using higher-order modulation and cell-edge UEs to receive low-priority data using lower-order modulation, while using modulation configuration information to demodulate the hierarchical signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If low-order modulation and coding scheme is used for MBMS data transmission to ensure robustness for cell-edge UEs, then service transmission robustness is improved, but system throughput and spectrum utilization efficiency are reduced
Solution Approach 1:
The service data is segmented into two layers: base-layer data and additional-layer data. The base-layer data is transmitted using low-order modulation to ensure robustness for cell-edge UEs, while the additional-layer data is transmitted using high-order modulation to improve throughput for cell-center UEs. This segmentation allows different portions of the data to be transmitted with different reliability requirements.
Solution Approach 2:
Different modulation schemes are applied to different layers of data based on their priority and reliability requirements. The base-layer data receives high-quality transmission with low-order modulation for maximum robustness, while the additional-layer data uses lower-quality high-order modulation for higher throughput. This local quality differentiation resolves the contradiction between reliability and productivity.
2Reliability
If low-order modulation and coding scheme is used to ensure cell-edge UE can receive MBMS data, then coverage is improved, but system spectrum utilization efficiency is reduced
Solution Approach 1:
The data stream is segmented into base-layer and additional-layer, where base-layer data is transmitted with robust low-order modulation to ensure wide coverage for all UEs including cell-edge devices. The additional-layer data is transmitted with efficient high-order modulation to maximize spectrum utilization for UEs with better channel conditions.
Solution Approach 2:
The modulation order parameter is changed based on the data layer: low-order modulation (e.g., QPSK) is used for base-layer data to ensure coverage, while high-order modulation (e.g., 16QAM, 64QAM) is used for additional-layer data to improve spectrum utilization. This parameter differentiation simultaneously achieves both coverage and efficiency goals.
Data Source
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AI summary
The present invention relates to the field of communications technologies, and in particular, to a signal transmission method and apparatus, so as to resolve a problem that system spectrum utilization efficiency and a system throughput are relatively low due to a signal transmission manner in an LTE system. The signal transmission method provided in embodiments of the present invention includes: determining a modulation type of service data that needs to be transmitted, where the modulation type includes hierarchical modulation and non-hierarchical modulation; modulating, by means of the hierarchical modulation when it is determined that the modulation type is the hierarchical modulation, the service data that needs to be transmitted, and sending a modulated hierarchical modulation signal to UE; and sending modulation configuration information to the UE, where the modulation configuration information includes information used to indicate the modulation type. By using the embodiments of the present invention, the system spectrum utilization efficiency and the system throughput can be greatly improved.