Cell Selection for MTC Devices Using Coverage Enhancement Offsets
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Solution Overview
Problem
Machine Type Communication (MTC) devices face challenges in selecting the optimal cell for network access due to limited measurement accuracy and the lack of coverage enhancement information in existing cell selection methods, leading to potential selection of suboptimal cells with lower signal strength but without coverage enhancements.
Innovation Solution
The method involves determining cell selection values based on measured signal parameters, such as RSRP and RSRQ, and applying offsets based on the measurement accuracy capability of the user equipment (UE), while also considering coverage enhancement levels and reducing measurement frequency once a connection is established, to ensure reliable network access.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional cell selection methods based solely on received signal strength are used, then devices can quickly select a cell, but MTC devices with poor coverage may select suboptimal cells that do not provide coverage enhancement
Solution Approach 1:
The patent changes the cell selection parameter from simple received signal strength to a composite metric that includes coverage enhancement capability. The network node determines whether a cell supports coverage enhancement and uses this information to adjust the selection criterion, allowing MTC devices to prioritize cells with coverage enhancement over those with slightly higher signal strength but no enhancement capability.
Solution Approach 2:
The patent introduces an intermediary evaluation step where the network node assesses coverage enhancement capability as a mediating factor between raw signal strength measurements and final cell selection. This intermediary assessment allows the system to account for the special needs of MTC devices without completely overriding traditional signal strength-based selection.
2Measurement precision
If MTC devices perform frequent measurements to ensure accurate cell selection, then selection accuracy improves, but device power consumption increases
Solution Approach 1:
The patent applies partial action by having MTC devices perform measurements at reduced frequency compared to traditional requirements. The network compensates for this reduced measurement activity by providing coverage enhancement, which ensures reliable communication even with less frequent updates. This allows the device to conserve power while maintaining adequate cell selection accuracy through the coverage enhancement mechanism.
3Loss of information
If cells transmit coverage enhancement information frequently, then MTC devices can make better cell selection decisions, but network signaling overhead increases
Solution Approach 1:
The patent implements periodic action by having the network transmit coverage enhancement information at specific intervals rather than continuously or on every cell update. This periodic transmission reduces signaling overhead while ensuring that MTC devices receive coverage enhancement information sufficiently often to make accurate cell selection decisions. The period is configured to balance information freshness with network resource conservation.
Data Source
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AI summary
Cell selection techniques are provided for network access to cells that may employ one or more coverage enhancement techniques. A user equipment (UE), which may be a machine type communication (MTC) device, upon initial acquisition or upon wakeup may measure a reference signal received power (RSRP), reference signal received quality (RSRQ), or both, and determine a cell selection value based at least in part on the RSRP, RSRQ, or a combination thereof. The cell selection value may be determined based on an offset, which may be selected based on a measurement accuracy capability of the UE. UE sequential access attempts, neighbor cell list information that may include coverage enhancement of neighboring cells transmissions, and cell re-selection measurement frequency adjustments are also described.