Optical Wireless Beam Alignment Using CDMA Beacon Front Ends
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Solution Overview
Problem
Existing optical wireless communication systems face challenges in achieving rapid and precise beam alignment between remote devices due to narrow beam angles and large separation distances, leading to long latency in alignment procedures.
Innovation Solution
Employing a transmitter with a main optical transmitter front end and multiple auxiliary optical transmitter front ends that send beacon signals using a synchronous CDMA method, with unique identifiers, to assist in beam alignment, and a receiver with a rotatable optical front end to detect and align with the transmitter using CDMA-based beacon signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If narrow beam angles are used to achieve high data rate communication over large separation distances, then data rate and communication distance are improved, but beam alignment precision and latency are worsened
Solution Approach 1:
The transmitter is divided into a main optical transmitter front end for data communication and multiple auxiliary optical transmitter front ends for beacon signal transmission. This segmentation allows the narrow beam main transmitter to maintain high data rate communication while the auxiliary front ends with wider coverage areas facilitate rapid beam alignment through beacon signals, thereby reducing alignment latency without compromising productivity
Solution Approach 2:
Beacon signals are introduced as intermediary elements to assist in beam alignment between the main optical transmitter and remote receiver. These beacon signals are transmitted by auxiliary front ends and detected by the receiver to determine relative positioning, enabling the system to achieve precise alignment quickly without sacrificing the high data rate capability of the narrow beam main transmitter
2Productivity
If narrow beam angles are used to achieve high data rate communication, then data rate is improved, but alignment precision is worsened
Solution Approach 1:
The system segments the transmission function into two parts: the main optical transmitter front end with narrow beam for high-speed data communication, and auxiliary optical transmitter front ends with wider coverage areas for beacon signal transmission. This segmentation enables the receiver to first acquire rough alignment information from auxiliary beacons and then achieve precise alignment with the main transmitter, thereby maintaining both high data rate and alignment precision
Solution Approach 2:
The auxiliary optical transmitter front ends perform preliminary beam alignment actions by transmitting beacon signals with wider coverage areas before the main narrow beam transmitter establishes precise communication link. This preliminary action allows the receiver to acquire rough positioning information and orient itself toward the transmitter, enabling subsequent precise alignment without compromising the narrow beam data transmission capability
3Loss of time
If multiple auxiliary optical transmitter front ends are added to improve beam alignment, then alignment speed is improved, but device complexity is worsened
Solution Approach 1:
The auxiliary optical transmitter front ends are designed to serve multiple functions: transmitting beacon signals for beam alignment, providing coverage area overlap for robust positioning information, and operating on the same frequency channel as the main transmitter. This multi-functionality reduces the need for separate alignment and communication systems, thereby reducing overall device complexity while maintaining fast alignment capability
Solution Approach 2:
The system merges the beacon signal transmission function with the existing optical transmitter structure by using auxiliary front ends that operate on the same frequency channel as the main data transmission front end. This merging approach allows beam alignment and data communication to share common hardware resources, reducing overall device complexity while achieving rapid alignment through multiple auxiliary beacons
Data Source
AI summary
A transmitter (100) for use in an optical wireless communication system, the transmitter (100) comprising a main optical transmitter front end (150) configured to send data on a first frequency band to a remote receiver (200) for data communication; and send a beacon signal on a first frequency channel to the remote receiver (200); a plurality of auxiliary optical transmitter front ends (160a, 160b, 160c) configured to send beacon signals on the first frequency channel to the remote receiver (200); wherein the beacon signals sent by the main (150) and the auxiliary optical transmitter front ends (160a, 160b, 160c) are used to assist a beam alignment procedure between the main optical transmitter front end (150) and the remote receiver (200) for data communication; and a first controller (109) configured to generate individual beacon signals for the main and the plurality of auxiliary optical transmitter front ends according to a synchronous CDMA method, with each beacon signal comprising a unique identifier corresponding to the main and the plurality of auxiliary optical transmitter front ends respectively.