Wireless Network for Sensor Array

Abstract

A linear wireless sensor network includes network nodes having monotonically varying network node identifiers along each branch of the network. The network identifiers enable the nodes to forward network packets without use of routing tables. Low duty cycle wireless communication protocols enable network packets to be routed to all nodes of very large networks while consuming very little electrical power. Broadcast, rather than unicast, transmissions between nodes take advantage of favorable signal propagation conditions to forward messages using largest possible hops, skipping over nodes when possible. A group of network packets is broadcast and forwarded by a most distant receiving node that received all packets of the group. A receiving node's clock is automatically adjusted, based on which packet(s) of a group of packets was received. A sending node synchronizes near-by receiving nodes. Nodes are provisioned over-the-air, with built-in scheduling. Health and welfare information piggybacks on other network traffic.

What is claimed is: 
     
         1 . In a wireless linear network comprising a first node, a plurality of second nodes proximate the first node and a plurality of additional nodes, all arranged along a branch, wherein each node comprises a wireless transmitter and a wireless receiver and has a node identifier, the node identifiers monotonically varying along the branch, a method for the first node to automatically identify the plurality of second nodes, the method comprising:
 the first node wirelessly broadcasting a plurality of time spaced-apart synchronization messages, the plurality of synchronization messages containing information about a plurality of transmit time slots and, for each transmit time slot of the plurality of transmit time slots, information about a single respective potential second node to which the transmit time slot is assigned;   each second node of the plurality of second nodes receiving at least one of the plurality of synchronization messages directly from the first node;   each second node identifying which one of the plurality of transmit time slots is assigned to the second node;   each second node, in response to receiving the at least one of the plurality of synchronization messages, wirelessly transmitting, during its assigned transmit time slot, an acknowledgement message that includes the second node's identifier, the plurality of second nodes thereby collectively transmitting a plurality of transmitted acknowledgement messages;   the first node receiving at least one acknowledgement message of the plurality of transmitted acknowledgement messages; and   the first node prioritizing a set of the plurality of second nodes whose acknowledgement messages were received by the first node, the prioritization being based at least in part on the identifiers of the second nodes whose acknowledgement messages were received by the first node.   
     
     
         2 . A method according to  claim 1 , wherein each second node comprises a clock, the method further comprising each second node:
 adjusting the second node's clock, based on timing of receipt by the second node of the at least one of the plurality of synchronization messages; and   using the clock to control when to turn on the second node's wireless receiver and when to turn off the wireless receiver.   
     
     
         3 . A method according to  claim 1 , wherein each second node comprises a clock, the method further comprising each second node:
 adjusting the second node's clock, based on timing of receipt by the second node of the at least one of the plurality of synchronization messages; and   using the clock to control when the second node enters a sleep state and when the second node wakes from the sleep state.   
     
     
         4 . A method according to  claim 1 , wherein prioritizing the set of second nodes comprises, for each second node of the set of second nodes, assigning a priority to the second node based on a difference between the second node's identifier and the first node's identifier, such that a second node with a larger difference is assigned a higher priority than a second node with a smaller difference. 
     
     
         5 . A method according to  claim 4 , further comprising, for each second node in the set of second nodes, the first node wirelessly transmitting a prioritization message, the prioritization message containing the priority assigned to the second node. 
     
     
         6 . A method according to  claim 5 , further comprising:
 after transmitting the prioritization message, the first node transmitting a synchronization confirmation request message; and   in response to receiving the synchronization confirmation request message, each second node in the set of second nodes transmitting a synchronization acknowledgement message during a respective time slot associated with the priority assigned to the second node.   
     
     
         7 . A method according to  claim 1 , further comprising the first node storing, in a memory, information about each second node in the set of second nodes, the information comprising the node identifier of the second node and the priority assigned to the second node.