NR Coverage Enhancement for Random Access Msg3 Uplink
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Solution Overview
Problem
Existing NR systems face challenges in extending coverage, particularly for rural deployments where wireless devices are far from serving base stations, and fail to support coverage extension of PUSCH carrying Msg3 during random access due to the absence of RRC signaling.
Innovation Solution
A serving base station configures coverage-limited UEs with parameters for a coverage enhancement mode using RRC signaling, enabling time and frequency diversity to enhance PDSCH, PUSCH, and PUCCH channels, including time domain repetitions and frequency hopping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If time domain repetitions are used to extend coverage, then coverage performance for downlink channels is improved, but coverage performance for uplink channels including PUSCH carrying Msg3 during random access cannot be supported
Solution Approach 1:
The base station configures coverage enhancement parameters in advance through RRC signaling before the random access procedure. This preliminary configuration enables the UE to perform coverage-enhanced PUSCH Msg3 transmissions without requiring RRC connection establishment first, resolving the contradiction between downlink coverage improvement and uplink Msg3 coverage support.
Solution Approach 2:
The system dynamically adapts the coverage enhancement mode based on the random access state. When the UE is in random access state, the base station activates coverage enhancement parameters specifically for PUSCH Msg3 transmissions. This dynamic activation allows the system to support both downlink coverage improvement and uplink Msg3 coverage extension simultaneously.
2Ease of manufacture
If RRC signaling connection is established before coverage enhancement configuration, then coverage parameters can be configured, but the base station cannot configure coverage enhancement parameters when UE is in random access state
Solution Approach 1:
The base station performs preliminary configuration of coverage enhancement parameters through RRC signaling before the random access procedure begins. This allows the UE to have coverage parameters pre-configured, enabling it to perform coverage-enhanced PUSCH Msg3 transmissions during random access without waiting for RRC connection establishment.
Solution Approach 2:
The system introduces an intermediary mechanism where the base station can activate coverage enhancement parameters specifically for random access state through RAR grant. This intermediary approach allows coverage configuration to occur independently of full RRC connection establishment, resolving the contradiction between parameter configurability and random access operation.
3Reliability
If coverage enhancement mode is activated, then time and frequency diversity gains are achieved, but device complexity increases due to additional configuration parameters
Solution Approach 1:
The coverage enhancement parameters are designed to serve multiple functions: they enable time domain repetitions for downlink coverage enhancement, support frequency hopping for diversity, and activate specifically for PUSCH Msg3 during random access. This multi-functionality reduces the need for separate mechanisms, thereby limiting the increase in device complexity while achieving comprehensive coverage extension.
Data Source
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AI summary
Methods to enhance the coverage of NR systems for coverage-limited wireless devices are disclosed. A serving base station may configure a coverage-limited UE with parameters for the UE to operate in a coverage enhancement mode through RRC signaling, DCI, or RAR grant. The UE may use the configuration parameters to determine whether to enter into the coverage enhancement mode when connecting and communicating with the serving base station. The configuration parameters may configure the UE to exploit both time diversity and frequency diversity to extend and enhance coverage when receiving the PDSCH and PDCCH channels, when transmitting the PUSCH and PUCCH channel, and when transmitting PUSCH Msg3 during random access. Advantageously, the base station may flexibly and dynamically configure the UE with coverage enhancement parameters to extend the coverage of the UE using time diversity and frequency diversity gains as the UE moves around.