Optical Transport Network Electronic Cross-Connect for RAN
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Solution Overview
Problem
Current radio transport networks face challenges in extending the reach of CPRI connections beyond a few hundred meters, requiring new fibers and inefficient use of infrastructure, especially when distances between remote radio units (RRUs) and digital units (DUs) exceed a few kilometers, and there is a need for dynamic load balancing and failure recovery without disrupting traffic.
Innovation Solution
A transport network with an electronic cross-connect switch that connects multiple RRUs and DUs, allowing for dynamic reconfiguration of connections and data flow management over optical links, enabling efficient switching and multicasting of data flows between DUs and RRUs, and utilizing a control unit to optimize resource allocation and synchronization across different granularities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If dedicated point-to-point optical connections are used between DU and RRU, then connection reliability is improved, but infrastructure cost and complexity increase when extending reach beyond a few kilometers
Solution Approach 1:
An optical add-drop multiplexer (OADM) is introduced as an intermediary device in the optical network. The OADM enables dynamic connection establishment between DUs and RRUs without requiring dedicated point-to-point fibers for each connection. It acts as a mediator that can selectively add or drop optical signals at different network nodes, providing reliable connectivity while reducing infrastructure complexity through shared optical paths.
Solution Approach 2:
The optical add-drop multiplexer serves multiple functions: it establishes dynamic connections, drops signals for specific DUs, adds signals from multiple DUs, and enables flexible reconfiguration of the optical network. This multi-functional device replaces the need for multiple dedicated point-to-point connections, reducing overall infrastructure complexity while maintaining connection reliability.
2Measurement precision
If CPRI protocol is used for connecting DUs and RRUs, then synchronization accuracy is improved, but latency control requirements become more stringent over extended distances
Solution Approach 1:
The system performs preliminary synchronization and timing alignment at the optical network level before data transmission begins. The OADM and associated control mechanisms pre-establish synchronized connections and align timing references, ensuring that when data flows are established over extended distances, the synchronization accuracy is maintained and latency is minimized through pre-configured optimal paths.
3Productivity
If a pool of DUs serves multiple RRUs, then resource optimization is improved, but dynamic reconfiguration capability is required to maintain load balancing and failure recovery
Solution Approach 1:
The optical network implements dynamic reconfiguration capability through the OADM, which can adaptively change connection configurations in real-time. When load balancing is needed or failures occur, the system dynamically reroutes optical signals to different DUs or RRUs, maintaining resource optimization while providing the necessary adaptability for failure recovery and load distribution across the DU pool.
Data Source
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AI summary
A transport network (10) is configured to connect a plurality of remote radio units (3) with a plurality of digital units (5) in a radio access network. The transport network comprises an electronic cross-connect (31) common to the plurality of remote radio units and digital units, and a control unit (32) configured to control the electronic cross-connect. The transport network further comprises an optical link (40) between the electronic cross- connect and remote radio units. The electronic cross-connect is a multi-layer switch. The electronic cross-connect is configured to switch data flows between one or more of said plurality of digital units (5) and one or more of said plurality of remote radio units (3).