Patent ID: 6442145
Filing Date: 2002-08-27
Classification: H04B,H04L,Y02D

Abstract:
A method of enabling wireless optical communication between a transmitting station and a first receiving station capable of receiving data which are modulated using a first modulation method and a second receiving station capable of receiving data which are modulated using a second modulation method, the method comprising:optically transmitting a preamble comprising frames forming a periodic sequence of pulses with defined period, the number of slots (L) per frame and the frame content being known to said receiving stations, performing carrier detection based on said sequence of pulses received, where each of said receiving stations determines said period of the sequence of pulses to obtain relative synchronization, and each of said receiving stations adjusts its clock to the phase of slots of the received sequence of pulses, and clocks said incoming sequence of pulses through a shift register, transmitting a unique synchronization word aligned to said period, said unique synchronization word being known to said receiving stations, correlating said sequence of pulses in said shift register with said unique synchronization word known to it in order to achieve absolute synchronization with said transmitting station upon recognition of said synchronization word, by each receiving station indicating in a control field of predefined length and structure, whether the first or second modulation method will be used for transmission of the data in a data/subsystem field, such that all receiving stations which are able to support the respective modulation method wait for said data.