Flexible Synchronization Signals for 5G Random Access
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Solution Overview
Problem
Current wireless communication systems face challenges in providing sufficient synchronization accuracy for multiple configured numerologies without increasing receiver complexity or wasting radio resources, particularly in 5G and NR networks, where UEs with limited bandwidth struggle to detect synchronization signals across different subcarrier spacings.
Innovation Solution
The method involves designing downlink synchronization signals with flexible subcarrier spacing and bandwidth, using a baseline PSS sequence and an extended sequence for finer timing accuracy, and configuring PRACH resources to support various numerologies, allowing UEs to select appropriate subcarrier spacings based on their capabilities and service requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a common synchronization signal is used for multiple configured numerology sets with a predefined subcarrier spacing and bandwidth, then UE cell search receiver complexity and synchronization signal overhead are reduced, but the ability to provide sufficient relative timing accuracy for all configured numerologies deteriorates
Solution Approach 1:
The synchronization signal is segmented into two parts: a common synchronization signal (e.g., PSS) with predefined parameters that all UEs can use for initial cell search, and an extended synchronization signal with configurable bandwidth that provides enhanced timing accuracy for specific numerologies. This segmentation allows different UEs to use only the portion they need, reducing overall complexity while maintaining accuracy where required.
Solution Approach 2:
The system dynamically selects whether to transmit the extended synchronization signal based on the configured numerologies. When multiple numerology sets are configured, the network can activate the extended signal with appropriate bandwidth to meet the timing accuracy requirements of higher subcarrier spacings, while keeping the basic common signal always available for universal use.
2Measurement precision
If the synchronization signal bandwidth is increased to provide sufficient timing accuracy for larger subcarrier spacings, then relative timing accuracy for all numerologies is improved, but radio resource overhead increases
Solution Approach 1:
Instead of always transmitting a wide-bandwidth synchronization signal, the system segments the signal transmission into a mandatory narrow common signal and an optional extended signal. The extended signal with larger bandwidth is transmitted only when needed for specific numerology configurations, thereby providing high timing accuracy only when required and reducing overall resource overhead.
Solution Approach 2:
The bandwidth parameter of the synchronization signal is changed dynamically based on the configured numerologies. For larger subcarrier spacings requiring finer timing accuracy, the extended signal uses a larger bandwidth. For smaller subcarrier spacings or when accuracy requirements are met by the common signal alone, the extended signal can be omitted or use a smaller bandwidth, optimizing resource usage.
3Measurement precision
If multiple PRACH configurations are configured for different subcarrier spacings, then uplink synchronization accuracy for all numerologies is improved, but configuration complexity and resource allocation overhead increase
Solution Approach 1:
The PRACH configuration is designed to be universal across multiple numerologies. A single PRACH configuration can serve multiple subcarrier spacings by allowing the UE to select the appropriate configuration based on the active numerology. This multi-functionality reduces the number of separate configurations needed while maintaining synchronization accuracy for all numerologies.
Solution Approach 2:
The network pre-configures PRACH resources with parameters that are suitable for multiple numerologies. The UE performs preliminary selection of the appropriate PRACH configuration based on the configured numerology before initiating random access, avoiding the need for complex real-time configuration changes and reducing overall system complexity.
Data Source
AI summary
A method and apparatus provide synchronization signals and random access for flexible radio communication. Information can be received from a base station. The information can include a plurality of subcarrier spacings and at least one random access configuration for a cell. Each of the at least one random access configuration can be associated with at least one subcarrier spacing of the plurality of subcarrier spacings. The at least one subcarrier spacing can be used for communication. A random access configuration can be selected from the at least one random access configuration. A random access preamble can be transmitted according to the selected random access configuration.