BBU-RRU Delay Compensation via Segmented Timing Adjustment
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Solution Overview
Problem
Current methods for synchronization and delay compensation in GSM/EDGE systems are limited by their inability to accurately adapt to different transmission protocols, resulting in low accuracy of delay compensation, especially in scenarios with multiple carriers over the same links.
Innovation Solution
A method using a unified reference point clock for synchronization between the baseband unit and remote radio unit, which calculates and adjusts delays through downstream synchronization labels and upper layer signaling, allowing for precise delay compensation across different transmission protocols.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If data transmission is implemented through high-speed TDM link with frame format or packet construction, then data synchronization between BBU and RRU can be achieved, but delay compensation accuracy is limited by minimal granularity requirements of the transmission protocol
Solution Approach 1:
The patent segments the delay compensation process into two distinct parts: a first delay value determined by the BBU based on transmission protocol requirements, and a second delay value determined by the RRU based on actual reception timing. This segmentation allows each component to optimize its delay compensation independently, achieving higher overall accuracy without increasing protocol complexity.
Solution Approach 2:
The BBU performs preliminary delay compensation by determining a first delay value before data transmission based on the transmission protocol's minimal granularity requirements. This preliminary action prepares the data for accurate timing, allowing the RRU to perform final adjustment with higher precision after reception.
2Measurement precision
If synchronization is implemented strictly by means of link clock, then link delay measurement and synchronization can be achieved, but accurate delay compensation cannot be realized especially for GSM/EDGE system
Solution Approach 1:
The system performs preliminary synchronization using the link clock to establish basic timing alignment between BBU and RRU. This preliminary synchronization enables the measurement of link delay, which is then used to calculate precise delay compensation values without requiring continuous strict synchronization, thus reducing time loss while maintaining accuracy.
Solution Approach 2:
The patent introduces an intermediary mechanism where the BBU determines a first delay value based on transmission protocol requirements, and the RRU determines a second delay value based on actual reception timing. This intermediary approach allows the system to achieve accurate delay compensation without relying solely on strict link clock synchronization, reducing the time required for synchronization while maintaining precision.
3Productivity
If multiple carriers are multiplexed over the same links, then link utilization is improved, but delay compensation accuracy deteriorates due to protocol granularity limitations
Solution Approach 1:
The patent segments delay compensation into two independent components: a first delay value determined by the BBU for each carrier based on transmission protocol requirements, and a second delay value determined by the RRU for each carrier based on actual reception timing. This segmentation allows precise delay compensation for each multiplexed carrier independently, maintaining high accuracy even when multiple carriers share the same link.
Solution Approach 2:
The system applies local quality optimization by allowing the RRU to determine delay values based on actual reception timing for each specific carrier. This localized approach ensures that each carrier receives the precise delay compensation it needs, rather than applying a uniform compensation value, thereby maintaining high accuracy across multiple multiplexed carriers.
4Adaptability or versatility
If different transmission protocols are used between BBU and RRU, then system flexibility is improved, but synchronization and delay compensation accuracy deteriorates
Solution Approach 1:
The patent implements a universal delay compensation mechanism that works across different transmission protocols. The BBU determines a first delay value based on the specific protocol being used (CPRI, OBSAI, or other protocols), and the RRU determines a second delay value based on actual reception timing. This universal approach maintains high delay compensation accuracy regardless of which protocol is used, providing both protocol flexibility and measurement precision.
Solution Approach 2:
The BBU performs preliminary delay compensation by determining a first delay value based on the transmission protocol's requirements before data transmission. This preliminary action accounts for protocol-specific timing characteristics, allowing the system to adapt to different protocols while maintaining accurate delay compensation. The RRU then performs final adjustment based on actual reception timing.
Data Source
Figure 1~2
AI summary
The present invention discloses a method for synchronization and delay compensation between a baseband system and a radio frequency system. The method implements synchronization between a baseband unit (BBU) and a remote radio unit (RRU) through upstream and downstream time labels based on a high-speed link between the BBU and RRU. In a downstream direction, link delay compensation is realized by two-level delay adjustment between the BBU and RRU. The method realizes synchronization and accurate delay compensation between the baseband system and radio frequency system. Such method may allow signals between the baseband unit and the remote radio unit of GSM/EDGE to adapt to different transmission protocols. The method also applies to data transmission in a fixed frame format.