LTE Carrier Sensing in Shared Spectrum for Interference Management
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Solution Overview
Problem
The 3GPP Long Term Evolution (LTE) communications standard faces challenges in deploying radio resource management in shared access spectrum due to the lack of protocols and procedures for UEs to respond to primary users, leading to potential interference from hidden stations and inefficiencies in dynamic frequency selection and carrier sense multiple access with collision avoidance schemes.
Innovation Solution
Implementing a method where UEs and eNodeBs monitor shared frequency spectra, with UEs reporting busy conditions and eNodeBs directing them to vacate or adjust frequency bands, using proprietary DFS and CSMA/CA functions to manage radio resource allocation and prevent interference, and introducing new measurement reports and procedures to enhance protection of primary users.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If LTE communications operate in shared spectrum without carrier sensing, then spectrum utilization is improved, but interference to primary users increases and reliability deteriorates
Solution Approach 1:
The system performs carrier sensing before transmission to detect primary user activity. The eNodeB and UEs sense the spectrum in advance and adjust their transmission behavior accordingly, preventing interference before it occurs rather than reacting after interference happens
Solution Approach 2:
The LTE system dynamically adapts its transmission behavior based on real-time spectrum conditions. When primary users are detected, the system dynamically adjusts resource allocation, transmission power, and scheduling to avoid interference while maintaining efficient spectrum utilization when the spectrum is clear
2Reliability
If carrier sensing is implemented in LTE shared spectrum, then interference protection is improved, but system complexity increases due to new protocols and procedures
Solution Approach 1:
The carrier sensing mechanism is integrated into the existing LTE protocol stack, allowing the same sensing infrastructure to serve multiple purposes: detecting primary users for interference avoidance, identifying spectrum opportunities for efficient utilization, and coordinating between eNodeB and UEs. This multi-functional approach reduces the need for separate dedicated sensing protocols
Solution Approach 2:
The eNodeB and UEs autonomously perform carrier sensing and make transmission decisions based on detected spectrum conditions. The system self-regulates its behavior without requiring complex external coordination or centralized control, reducing overall system complexity while maintaining reliable interference protection
3Speed
If UEs autonomously perform carrier sensing and frequency selection, then response time is improved, but coordination with eNodeB becomes more complex
Solution Approach 1:
The carrier sensing function is segmented between eNodeB and UE, with each performing sensing in their respective contexts. The eNodeB performs downlink carrier sensing and makes scheduling decisions, while UEs perform uplink carrier sensing and report conditions to the eNodeB. This segmentation allows autonomous rapid response at the UE level while maintaining centralized coordination through standardized reporting and scheduling mechanisms
Data Source
AI summary
A method of operating a long term evolution (LTE) communication system on a shared frequency spectrum is disclosed. A user equipment (UE) is initialized on an LTE frequency band. A base station (eNB) monitors the shared frequency spectrum to determine if it is BUSY. The eNB transmits to the UE on the shared frequency spectrum if it is not BUSY. The eNB waits for a first time if it is BUSY and directs the UE to vacate the shared frequency spectrum after the first time.