FIFO Buffer Latency Compensation in C-RAN Ring Fronthaul
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Solution Overview
Problem
In a Centralized Radio Access Network (C-RAN) with a fronthaul configured in a ring topology, switchover events can cause latency differences, leading to potential errors and handover failures due to changes in signal transmission direction, affecting network reliability and operational efficiency.
Innovation Solution
A system comprising a centralization node linked to a baseband unit (BBU) group, distribution nodes linked to remote radio head (RRH) groups, and an optical bi-directional ring network with a First-In-First-Out (FIFO) buffer, which demultiplexes and converts optical signals to electrical signals, stores them in the FIFO buffer, and adjusts the buffer size to compensate for latency differences before and after a switchover.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a ring topology is used for fronthaul to provide protective switchover function, then reliability is improved, but latency difference occurs during switchover causing handover errors
Solution Approach 1:
The system pre-calculates and stores latency values for both normal and switchover states before actual switchover occurs. Each base station reports its latency to the controller in advance, and the controller stores these values in a table for quick reference during switchover events, eliminating the need for real-time latency measurement during critical handover moments
Solution Approach 2:
The controller acts as an intermediary between the ring network and the handover control logic. It receives latency information from base stations, determines the appropriate latency value based on switchover status, and provides this information to the handover control unit, thereby decoupling the complexity of latency management from the handover decision process
2Reliability
If switchover changes signal transmission direction in ring topology, then reliability is improved, but handover accuracy deteriorates due to latency change
Solution Approach 1:
The system implements a feedback mechanism where base stations continuously report their latency measurements to the controller. The controller uses this feedback to update the latency table and make accurate handover decisions. The feedback loop ensures that the system always has current latency information regardless of switchover state
Solution Approach 2:
The system changes the latency parameter based on switchover state. Instead of using a fixed latency threshold for handover decisions, the controller dynamically adjusts the latency value by selecting from pre-measured latency values corresponding to different switchover states, thereby maintaining handover accuracy despite network topology changes
Data Source
AI summary
A system for compensating for a latency difference in a fronthaul in ring topology is provided, including a centralization node linked to a BBU group, a plurality of distribution nodes linked to a plurality of RRH groups, an optical bi-directional ring network connecting the central node and the distribution nodes and allows a WDM optical signal to be transmitted and received between the central node and the distribution nodes, and a FIFO buffer that stores an electrical signal. Each of the distribution nodes demultiplexes the WDM optical signal, converts each demultiplexed optical signal into an electrical signal, stores the electrical signal in the FIFO buffer, converts the electrical signal stored in the FIFO buffer into an optical signal, and adjusts a size of the FIFO buffer, thus compensating for a difference between latencies before and after an occurrence of a switchover in the optical bi-directional ring network.