LTE LAA Hidden Node Detection via eNB-UE Coordination
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Solution Overview
Problem
Current methods for hidden node detection in LTE Licensed-Assisted Access (LAA) are unreliable, particularly in unlicensed spectrum scenarios, as they do not adequately account for regulatory requirements and interference from nodes not visible to the serving eNodeB, complicating coexistence with other technologies like WiFi and affecting uplink operations.
Innovation Solution
A method and apparatus for improved hidden node detection in LTE LAA, involving determining specific resources for measurement, coordinating channel state information interference measurements between network elements, and reporting results to ensure accurate detection of interference from hidden nodes, thereby facilitating better spectrum sharing and regulatory compliance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If CSI measurements and reporting are used for hidden node detection, then some information about hidden nodes can be obtained, but the detection reliability is insufficient and does not account for regulatory requirements such as LBT
Solution Approach 1:
The patent segments the detection process into two distinct parts: (1) eNB performs LBT and determines channel occupancy status, (2) UE performs LBT and reports channel status to eNB. This segmentation allows each node to independently assess the channel according to regulatory requirements while combining their observations for reliable hidden node detection.
Solution Approach 2:
The patent implements a feedback mechanism where the UE performs LBT measurements and reports the channel status back to the eNB. This feedback loop enables the eNB to make informed scheduling decisions based on real-time channel conditions observed by both the eNB and UE, significantly improving detection reliability.
2Reliability
If eNB and UE both perform LBT at the same time for hidden node detection, then detection reliability improves, but the specification impact and system complexity increases
Solution Approach 1:
The patent leverages the existing LBT functionality already present in both eNB and UE for other purposes (channel access control) and applies it additionally to hidden node detection. This multi-functionality approach avoids creating separate dedicated detection mechanisms, thereby limiting the increase in system complexity while achieving improved reliability.
3Adaptability or versatility
If LBT is performed to ensure fair coexistence in unlicensed spectrum, then regulatory compliance is achieved, but hidden node detection capability is reduced due to simultaneous channel occupancy by multiple nodes
Solution Approach 1:
The patent performs LBT measurements at specific predetermined resources (downlink subframes for eNB, uplink subframes for UE) before making scheduling decisions. This preliminary action allows the system to assess channel conditions in advance, accounting for regulatory requirements while maintaining the ability to detect hidden nodes that may transmit during these measurement opportunities.
Data Source
AI summary
The application relates to improved hidden node detection for Long Term Evolution LTE Licensed-Assisted Access LAA. Channel State Information CSI measurements can be seen as one existing solution that could be used for obtaining information about the existence of a hidden node. However, relying on CSI reporting alone is rather unreliable. One of the reasons for this is that the CSI measurements and reporting do not take into account the regulatory requirements such as LBT. A further possible way to detect hidden nodes is to perform LBT (clear channel assessment CCA) at the transmitter (e.g. eNB) and receiver (e.g. UE) at the same time. However, there is still the need for an improved solution for how to detect hidden nodes preventing LTE LAA uplink operation and complicating coexistence. These problems are solved by ensuring that interference from non-hidden nodes (such as WLAN node 1 in FIG. 1) is not measured. Therefore the serving eNB detects a free channel during LBT procedure, i.e. that non-hidden nodes are not transmitting, and informs the UE which performs the hidden node detection measurements, by downlink scheduling, whether the serving eNB is active in the current subframe. The UE then performs the measurements only in subframes of the channel occupied by the serving eNB. Thereby, the UE only captures interference coming from hidden nodes.