LC-MTC Coverage Enhancement Through ePBCH and ePRACH Selection
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Solution Overview
Problem
Low-cost machine-type-communication (LC-MTC) devices face challenges in achieving adequate service coverage, with relaxed requirements for throughput and latency, which preclude support for certain services like voice communication.
Innovation Solution
Enhancements to the physical broadcast channel (PBCH) and physical random access channel (PRACH) are implemented, including the use of an enhanced PBCH (ePBCH) and ePRACH resources, allowing devices to select resources based on coverage capability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If standard LTE cell coverage is used for low-cost MTC devices, then service coverage is insufficient, but enhancing coverage by up to 20 dB would require relaxed throughput and latency requirements
Solution Approach 1:
The patent applies local quality by providing different coverage enhancement techniques tailored to specific channels and device types. Enhanced PBCH is implemented only for MTC devices requiring coverage enhancement, while other devices use standard PBCH. The system selectively applies coverage enhancement to downlink and uplink channels based on device capabilities and coverage needs, rather than uniformly enhancing all communications.
Solution Approach 2:
The patent segments the coverage enhancement into separate techniques for different channels: enhanced PBCH for system information broadcast, enhanced PDCCH for control information, and TTI bundling for data transmissions. Each segmentation targets specific performance requirements, allowing coverage enhancement without uniformly impacting all throughput and latency characteristics.
2Reliability
If coverage enhancement is implemented for all devices, then service coverage improves, but device complexity increases
Solution Approach 1:
The patent implements dynamics by allowing devices to autonomously determine whether to use coverage enhancement techniques based on their coverage capability. Devices with poor coverage can activate enhanced PBCH and ePRACH, while devices with adequate coverage use standard procedures. The system dynamically adapts the enhancement level based on real-time coverage conditions rather than forcing enhancement on all devices.
Solution Approach 2:
The patent uses copying by introducing an enhanced PRACH (ePRACH) that mirrors the standard PRACH structure but with additional coverage enhancement features. The ePRACH copies the basic random access functionality while adding repetition and enhanced signal processing capabilities, allowing devices to select the appropriate version based on coverage needs without implementing entirely new mechanisms.
3Reliability
If enhanced PBCH is transmitted in all radio frames, then coverage is maximized, but network resources are wasted
Solution Approach 1:
The patent applies periodic action by transmitting enhanced PBCH only in specific radio frames rather than continuously. The enhanced PBCH is transmitted in a subset of radio frames determined by system configuration, allowing MTC devices to receive coverage-enhanced system information at periodic intervals. This reduces network resource consumption compared to continuous transmission while maintaining adequate coverage for MTC devices.
Data Source
AI summary
A method and apparatus are described for a low cost machine-type-communication (LC-MTC) wireless transmit/receive unit (WTRU) to enhance coverage. An example method for physical broadcast channel (PBCH) enhancement includes receiving system information on an enhanced PBCH (ePBCH). The ePBCH is located in a set of radio frames which is a subset of available radio frames, where the subset includes fewer than all the available radio frames. The ePBCH is received in at least one radio frame of the set of radio frames. An example method for physical random access channel (PRACH) enhancement includes receiving configuration of legacy PRACH resources and enhanced PRACH (ePRACH) resources. The WTRU selects one of legacy PRACH resources or ePRACH resources based on a coverage capability. Another example method for PRACH enhancement includes receiving configuration of ePRACH resources. The ePRACH resources include multiple ePRACH resource types, each ePRACH resource type being associated with a coverage capability.