BL UE CE Level Management via PRACH Resource Selection
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Solution Overview
Problem
Current LTE systems face inefficiencies in managing Coverage Extension (CE) levels for Bandwidth reduced Low complexity User Equipment (BL UE), particularly in determining and indicating CE levels during idle states and mobility procedures, which affects paging message transmission and Random Access Channel (RACH) processes.
Innovation Solution
A method where BL UE determines the CE level based on Downlink measurements and configuration information, selecting appropriate PRACH resources for random access preamble transmission, and communicates this to the base station, allowing the network to adjust transmission repetitions accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If BL UE determines CE level autonomously based on downlink measurements, then the network can efficiently manage coverage extension, but the network cannot know the CE level in idle state for paging message transmission
Solution Approach 1:
The network pre-configures multiple PRACH resources corresponding to different CE levels before the UE needs to access. When the UE performs random access, it selects the appropriate pre-configured PRACH resource based on its determined CE level, allowing the network to infer the CE level from the selected resource without requiring explicit UE indication.
Solution Approach 2:
The PRACH resource selection acts as an intermediary mechanism that transfers CE level information from the UE to the network indirectly. Instead of direct communication, the UE's choice of PRACH resource serves as the mediator that conveys the CE level information to the network for paging message transmission.
2Reliability
If the network transmits paging messages with multiple repetitions for all UEs, then UEs in extended coverage can receive messages, but network resources are wasted for UEs in normal coverage
Solution Approach 1:
The network applies different transmission strategies to different UEs based on their CE levels. UEs in normal coverage receive paging messages with standard transmission parameters, while UEs in extended coverage receive messages with increased repetitions and power. This localized adaptation ensures reliable delivery to extended coverage UEs without wasting resources on normal coverage UEs.
Solution Approach 2:
The network dynamically changes transmission parameters (number of repetitions, power level) based on the CE level of the target UE. By adjusting these parameters according to the UE's coverage requirements, the system achieves reliable message delivery while optimizing network resource utilization.
3Ease of manufacture
If BL UE uses limited bandwidth of 1.4 MHz to reduce cost, then device cost decreases, but data rate and coverage are restricted
Solution Approach 1:
The system dynamically adapts the operational bandwidth of the BL UE based on its CE level and coverage requirements. While BL UEs are capable of operating in 1.4 MHz bandwidth for cost reduction, the network can configure and switch to wider bandwidths when higher data rates or extended coverage are required, providing flexible adaptation to different operational scenarios.
Solution Approach 2:
The network changes key operational parameters (bandwidth, power, repetition count) based on the UE's CE level and service requirements. This parameter adaptation allows BL UEs to operate in cost-effective 1.4 MHz mode when sufficient, while enabling higher performance modes when needed, thus resolving the contradiction between cost and performance.
4Area of stationary object
If BL UE performs repeated transmissions for coverage extension, then coverage is extended, but transmission time and power consumption increase
Solution Approach 1:
The system applies repeated transmissions selectively rather than universally. Repetitions are applied only when necessary based on the UE's CE level and channel conditions, not for all transmissions. This partial application of repetition reduces unnecessary transmission time and power consumption while still achieving the required coverage extension for UEs that need it.
Solution Approach 2:
The system uses feedback mechanisms where the UE reports its CE level and channel conditions to the network. Based on this feedback, the network determines the appropriate number of repetitions and transmission power, optimizing the balance between coverage extension and transmission time/power consumption.
Data Source
AI summary
Disclosed herein is a method of managing indication of Coverage Extension (CE) level, the method including determining the CE level from a Downlink (DL) measurement, indicating the CE level determined to a Base station (BS), determining a change in the CE level and indicates the change in the CE level to the BS, and attempting a RRC connection establishment using one of a CE specific Random Access Channel (RACH) preamble and CE specific Physical Random Access Channel (PRACH) resources.