Uplink Coverage Enhancement via Repeated Access Preamble Transmissions
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Solution Overview
Problem
There is a need for solutions to enhance uplink coverage for wireless devices with reduced capabilities, such as wearables or industrial sensors, which often have limited antenna gain, reduced transmit power, and smaller operating bandwidth, leading to reduced coverage compared to legacy NR UEs.
Innovation Solution
The proposed solution involves a method where a UE acquires synchronization signals from a base station, synchronizes with it, and then transmits an access preamble in a first access channel resource. Based on meeting a repetition criteria, the UE transmits the access preamble again in a second access channel resource for enhanced coverage, specifically designed for conditions where the UE has unsatisfactory uplink coverage, such as at the cell edge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If UEs use reduced capabilities (fewer antennas, lower transmit power, smaller bandwidth) to reduce device complexity and energy consumption, then device complexity and energy consumption are reduced, but uplink coverage is degraded
Solution Approach 1:
The patent applies periodic action by implementing repeated preamble transmissions at regular intervals. The UE transmits the same access preamble multiple times in sequential access channel resources, allowing the base station to accumulate signal energy across multiple reception opportunities. This periodic repetition compensates for the lower transmit power and antenna gain of reduced-capability UEs, thereby maintaining reliable uplink coverage despite reduced device capabilities.
2Use of energy by moving object
If UEs transmit with lower power to conserve energy, then energy consumption is reduced, but the received signal strength at the base station is insufficient
Solution Approach 1:
The patent applies merging by combining multiple low-power transmissions into a single effective communication event. The base station receives and combines multiple preamble transmissions from the UE across different time instances, accumulating the signal energy. This allows the system to achieve the same effective signal strength as a single high-power transmission would provide, enabling energy-efficient operation while maintaining reception quality.
3Reliability
If sequential access channel resources with different timing are allocated, then coverage enhancement is achieved through repeated transmissions, but access latency increases
Solution Approach 1:
The patent applies partial action by implementing a configurable number of preamble repetitions based on coverage conditions. Rather than always transmitting the maximum number of repetitions, the system adapts the repetition count to the actual coverage needs of each UE. This allows the system to achieve sufficient coverage enhancement for cell-edge UEs while minimizing unnecessary repetitions for UEs with good coverage, thereby reducing average access latency.
Data Source
AI summary
Method for network access carried out in a User Equipment, UE, the method comprising: acquiring at least one of a plurality of synchronization signals transmitted from a base station, each synchronization signal identifying a synchronization resource usable for identifying an associated access channel resource of a sequence of access channel resources; synchronizing to the base station based on the at least one synchronization signal; obtaining, from the base station, information identifying a first access channel resource and a second access channel resource; transmitting an access preamble in the first access channel resource, and transmitting, based on meeting a repetition criteria, said access preamble in the second access channel resource for enhanced coverage operation.