Vehicular communications using a scalable ad hoc geographic routing protocol

Abstract

Vehicle-to-vehicle and vehicle-to-infrastructure communications are accomplished via a scalable ad hoc geographic routing protocol. As vehicles move along roadways, they can query other vehicles and entities for information. Responses to queries can be used to determine information such as traffic conditions, a retail store sale, that a restaurant has tables available, and/or that parking spaces are available, for example. Businesses, vehicles, and other entities along roadways can geocast pertinent information to vehicles passing by. Vehicles can cache information as it is received.

What is claimed: 
     
         1 . A method comprising:
 receiving, by a first communications device, a broadcasted message comprising an indication of a location of a second communications device and a description of a region of intended reception of the message; and   retransmitting, by the first communications device, the message based on a distance from the second communications device to a center point of the region of intended reception of the message.   
     
     
         2 . The method of  claim 1 , wherein retransmitting the message is further based on a distance from the first communications device to the center point of the region. 
     
     
         3 . The method of  claim 2 , wherein the distance from the second communications device to the center point of the region is greater than the distance from the first communications device to the center point of the region. 
     
     
         4 . The method of  claim 1 , wherein the description of the region of intended reception comprises a description of a circular physical area defined by the center point and a radius. 
     
     
         5 . The method of  claim 4 , wherein the radius is no more than 20 meters. 
     
     
         6 . The method of  claim 1 , wherein retransmitting the message is further based on a determination, by the first communications device, that the message has not been received a predetermined number of times. 
     
     
         7 . The method of  claim 1 , further comprising:
 queuing, by the first communications device, the message before retransmitting it.   
     
     
         8 . The method of  claim 1 , wherein the message is queued for a period of time comprising a backoff delay. 
     
     
         9 . The method of  claim 1 , wherein the backoff delay comprises a random amount of time. 
     
     
         10 . The method of  claim 1 , wherein the first communications device is located within a vehicle. 
     
     
         11 . A first communications device comprising:
 a processor; and   memory coupled to the processor, the memory comprising executable instructions that when executed by the processor cause the processor to effectuate operations comprising:
 receiving a broadcasted message comprising an indication of a location of a second communications device and a description of a region of intended reception of the message; and 
 retransmitting the message based on a distance from the second communications device to a center point of the region of intended reception of the message. 
   
     
     
         12 . The first communications device of  claim 11 , wherein retransmitting the message is further based on a distance from the first communications device to the center point of the region. 
     
     
         13 . The first communications device of  claim 12 , wherein the distance from the distance from the second communications device to the center point of the region is greater than the distance from the first communications device to the center point of the region. 
     
     
         14 . The first communications device of  claim 11 , the operations further comprising:
 queuing the received message before retransmitting it.   
     
     
         15 . The first communications device of  claim 14 , wherein the backoff delay comprises a pseudo-random amount of time. 
     
     
         16 . The first communications device of  claim 11 , wherein the description of the region of intended reception comprises a description of a circular physical area defined by the center point and a radius. 
     
     
         17 . The first communications device of  claim 11 , wherein retransmitting the message is further based on a determination that the message has not been received a predetermined number of times. 
     
     
         18 . A computer-readable storage medium comprising executable instructions that cause a processor executing the instructions to effectuate operations comprising:
 receiving a plurality of messages, wherein each message of the plurality of messages comprises an indication of a location of a sending device and a description of a description of a region of intended reception of the message; and   retransmitting a message of the plurality of messages based on a determination that a distance from the location of the first communications device to the a center point of the region of intended reception is greater than a distance from the location of the sending device of the message of the plurality of messages.   
     
     
         19 . The computer-readable storage medium of  claim 18 , wherein the received message is queued for a period of time comprising a backoff delay. 
     
     
         20 . The computer-readable storage medium of  claim 18 , wherein the first communications device is located within a vehicle.