Random Access Coverage Enhancement for Reduced-Capability UEs
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Solution Overview
Problem
Complexity reduction techniques in REDCAP UEs, such as reduced number of antennas and bandwidth, result in coverage degradation due to loss of frequency diversity and spatial multiplexing, necessitating methods for coverage enhancement in wireless communication networks.
Innovation Solution
Implementing a coverage enhancement indicator prior to the UE achieving an RRC connected state, using techniques like repetition in the time domain, frequency hopping, or lower MCS tables, to enhance coverage during the random access procedure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If complexity reduction techniques are applied to REDCAP UEs (reduced number of antennas and bandwidth), then device complexity is reduced, but coverage is degraded due to loss of frequency diversity and spatial multiplexing
Solution Approach 1:
The patent applies preliminary action by configuring coverage enhancement parameters before the UE enters RRC connected state. The network sends coverage enhancement configuration in system information or RRC release message, enabling the UE to apply appropriate coverage enhancement techniques (like repetition or frequency hopping) during random access procedure, thereby compensating for the coverage loss from complexity reduction before actual data transmission begins
Solution Approach 2:
The patent implements parameter changes by dynamically adjusting coverage enhancement parameters based on UE capability and channel conditions. The network can configure different repetition factors, frequency hopping patterns, or MCS tables for REDCAP UEs versus legacy UEs, allowing the system to optimize coverage for reduced-complexity devices without impacting overall network performance
2Device complexity
If reduced bandwidth is used in REDCAP UEs, then device complexity is reduced, but frequency diversity is lost resulting in coverage degradation
Solution Approach 1:
The patent applies preliminary action by pre-configuring frequency hopping parameters and repetition factors for REDCAP UEs before they enter connected mode. This allows the UE to immediately apply frequency diversity techniques during random access, compensating for the reduced bandwidth limitation from the outset
Solution Approach 2:
The patent implements dimensionality change by introducing time-domain repetition and frequency-domain hopping as additional dimensions for achieving diversity. Since REDCAP UEs have reduced bandwidth (limiting frequency diversity), the patent compensates by repeating transmissions multiple times across different time instances and frequency locations, thereby recovering coverage through diversity in time and frequency dimensions
3Device complexity
If reduced number of receive antennas is used in REDCAP UEs, then device complexity is reduced, but spatial multiplexing and diversity are reduced resulting in coverage degradation
Solution Approach 1:
The patent applies preliminary action by configuring coverage enhancement parameters before the UE enters RRC connected state. The network sends coverage enhancement configuration in system information or RRC release message, enabling the UE to apply appropriate coverage enhancement techniques (like repetition or frequency hopping) during random access procedure, thereby compensating for the coverage loss from complexity reduction before actual data transmission begins
Solution Approach 2:
The patent implements periodic action through time-domain repetition of transmissions. By repeating the same transport block multiple times across different time slots with appropriate spacing, the system allows the UE to accumulate energy and perform combining, thereby compensating for the reduced antenna diversity and achieving reliable reception despite having fewer receive antennas
Data Source
AI summary
A method implemented by an access node includes sending, by the access node to a user equipment (UE), an indicator indicating use of coverage enhancement technique, the indicator being sent prior to the UE achieving a radio resource control (RRC) connected state with the access node; receiving, by the access node from the UE, an uplink transmission in accordance with the indicator; and sending, by the access node to the UE, a contention resolution message in accordance with the indicator.