Joint AP Synchronization via Relative Timing Offset
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Solution Overview
Problem
Current wireless communication systems face challenges in synchronizing joint transmissions from multiple access points (APs) to achieve beamforming gain and transmit power gain, as existing technologies struggle to maintain relative timing offsets between APs during channel sounding and data transmission, affecting the throughput and efficiency of data transmission to client stations.
Innovation Solution
The method involves a joint channel sounding procedure where a first AP receives a PHY data unit configured to initiate synchronization between itself and another AP, using training signals to calculate and adjust the relative timing offset, allowing for synchronous data transmissions to client stations, with the inclusion of additional fields in synchronization data units to provide sufficient processing time for slave APs to calculate and adjust their transmissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If joint transmissions are implemented by multiple access points, then throughput and data transmission efficiency are improved, but synchronization of transmissions between access points becomes complex and difficult to maintain
Solution Approach 1:
A master access point acts as an intermediary to coordinate and synchronize transmissions among multiple access points. The master AP generates trigger frames that slave APs use to align their transmissions, thereby managing synchronization complexity through a centralized coordinating entity rather than requiring complex peer-to-peer synchronization mechanisms.
Solution Approach 2:
The system implements feedback mechanisms where access points exchange timing information and transmission status through trigger frames and acknowledgments. Slave APs receive trigger frames from the master AP containing timing references, adjust their transmissions based on this feedback, and maintain synchronization through continuous exchange of timing information.
2Manufacturing precision
If relative timing offset calculation is performed between access points, then transmission synchronization is improved, but processing time and computational requirements increase
Solution Approach 1:
The master access point performs preliminary actions by generating and transmitting trigger frames that contain pre-calculated timing references and synchronization information. This allows slave APs to receive advance notice of timing requirements before actual data transmissions begin, enabling them to pre-adjust their timing without requiring complex real-time calculations during the transmission phase.
3Measurement precision
If training signals are included in PHY data units for timing offset calculation, then synchronization accuracy is improved, but overhead and data transmission efficiency are reduced
Solution Approach 1:
Training signals are strategically placed only in specific portions of the PHY data unit where they are most needed for timing offset calculation, rather than being uniformly distributed throughout the entire transmission. This localized approach ensures sufficient measurement precision at critical synchronization points while minimizing the overall overhead and preserving data transmission efficiency in the remaining portions of the transmission.
Data Source
AI summary
A first access point (AP) receives a first physical layer (PHY) data unit for initiating a joint channel sounding procedure between a group of APs and one or more client stations. The first AP receives a second PHY data unit for initiating a joint transmission by the group of APs. The first AP uses training signals in the first PHY data unit and the second PHY data unit to calculate a relative timing offset. The first AP uses the relative timing offset to adjust a transmit time of a third PHY data transmitted as part of the joint transmission.