Method and system for providing corrected time dependent data across a wireless network

In a public transit vehicle arrival information system having a plurality of remotely located receiving and display modules at transit vehicle stations throughout a selected geographical area along transit vehicle routes, said system also having a base station computer for receiving transit vehicle location data and generating arrival prediction data for broadcast to said modules, said computer being connected to a data interface for transmission of said arrival prediction data to a broadcasting system, said data interface and broadcasting system causing an unpredictable delay;

• an apparatus comprising:
• a local receiving unit positioned in proximity to said base station computer and generating a signal received indication upon receiving said broadcast data, said signal received indication being input to said base computer for calculation of the elapsed time between said computer generation of data and said signal received indication, said elapsed time being substantially equal to said delay;
• and
• means in said computer for generating a correction signal for broadcast to said receiving units, said correction signal instructing said receiving units to compensate for said elapsed time.

In a network having a plurality of remotely located receiving units and a base station computer generating time-dependent data and having a data interface with a transmitter for broadcasting the time-dependent data to the receiving units, the data interface causing an unpredictable, variable delay between the generation of data by the computer and broadcasting of the data by the transmitter;

• the method comprising the steps of:
• providing a local receiving unit positioned in proximity to said base station computer;
• said local receiving unit generating a signal received indication upon receiving said broadcast data;
• inputting said signal received indication to said computer;
• calculating the elapsed time between said computer generation of data and said signal received indication;
• generating a correction signal for broadcast to said receiving units, said correction signal instructing said receiving units to compensate for said elapsed time.

In a public transit vehicle arrival information system having a plurality of remotely located receiving and display modules at transit vehicle stations throughout a selected geographical area along transit vehicle routes, said system also having a base station computer for receiving transit vehicle location data and generating arrival prediction data for broadcast to said modules, said computer being connected to a data interface for transmission of said arrival prediction data to a broadcasting system, said data interface and broadcasting system causing an unpredictable delay;

• the method comprising the steps of:
• providing a local receiving unit in direct communication with said base station computer;
• said local receiving unit generating a signal received indication upon receiving said broadcast data;
• inputting said signal received indication to said computer;
• calculating the elapsed time between said computer generation of data and said signal received indication;
• generating a correction signal for broadcast to said receiving units, said correction signal instructing said receiving units to compensate for said elapsed time.

An apparatus for synchronizing time on a plurality of nodes in a one-way broadcast network, comprising:

• a base station having a controller;
• a plurality of receivers located remotely from said base station controller;
• a special receiver located within direct communication distance of the base station controller and able to communicate to the base station;
• means for encoding the current time in a time stamp message, and means for queueing that message for transmission to said plurality of receivers and to said special receiver;
• means for recognizing the reception of the time stamp message at the special receiver, and calculating the latency between said queueing and said reception;
• means for encoding the measured latency in a correction message;
• means for queueing that message for transmission;
• and
• means for the remote receivers to determine the correct time based on the time stamp message, as adjusted by the correction message.