US 9,312,977 B1Granted

System and method to provide channel access synchronization without time-stamp exchange in time division multiple access (TDMA) multi-hop networks

AssigneeBAE Systems Information and Electronic Systems Integration Inc.

InventorsPhong C. Khuu, Brian D. Loop, Qui M. Le, Kevin M. McNeill, Michael J. Weber, Tim McNevin

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Abstract

The present invention relates to a system and method for providing channel access synchronization in a time division multiple access (TDMA) multi-hop network employing a plurality of time slots defined within a frame structure which repeats. The system and method includes nodes which have local clock variables. The local clock variables generate an expected arrival time of signals from other nodes in the network. Each node then determines whether the local clock variable needs adjusting after receiving a transmission and comparing the expected arrival time with the actual arrival time. Thus, time synchronization across the network is distributed and updated locally at each node. Networks may be merged by casting out nodes in one network and joining those cast out nodes with the other network. Newly joined nodes are thereafter time synchronized into their new network by comparing actual and expected arrival times and updating their clock accordingly.

Claims9

Dependent claims

A method for providing channel access synchronization in a time division multiple access (TDMA) multi-hop network employing a plurality of time slots defined within a frame structure which repeats, the method comprising:

providing a first network of nodes, wherein each node includes a processor connected to a memory by logic circuitry, and a clock variable stored in the memory;
transmitting a first signal from a first node in the first network of nodes to a second node in the first network of nodes during a first time slot in the plurality of time slots, wherein the first time slot is assigned to the first node;
using the processor and the clock variable of the second node to calculate an expected arrival time of the first signal at the second node;
receiving the first signal at the second node at an actual arrival time;
comparing the expected arrival time to the actual arrival time;
adjusting the clock variable of the second node if the difference between the expected arrival time and the actual arrival time is greater than a threshold;
the first node monitoring an amount of collisions of data transmitted by the first node;
the first node determining whether the amount of collision is beyond a collision rate threshold stored in the memory of the first node;
the first node casting itself out of the first network of nodes if the amount of collisions is beyond the rate;
receiving at the first node a second signal from a third node, wherein the third node is in a second network of nodes;
and
joining the first node to the second network of nodes in response to the first node receiving the second signal from the third node.

9 more elements

A system to provide channel access synchronization without time-stamp exchange in a multi-hop network, said system comprising:

a channel access scheme employing a frame structure which repeats, with a plurality of time slots being defined within said frame structure;
a plurality of nodes communicating via the channel access scheme, each node comprising:
a processor connected to a memory by logic circuitry;
an adjustable clock variable stored in the memory;
a receiver element connected to the memory and processor by the logic circuitry, wherein the receiver element is adapted to receive a signal from a transmitting node and store an actual arrival time in the memory upon receipt of the signal, wherein the transmitting node is one of the other nodes in the network;
an expected arrival time associated with the signal and stored in the memory, wherein the expected arrival time is derived from the clock variable;
and
a threshold variable stored in the memory;
wherein the processor adjusts the clock variable if the difference between the expected arrival time and the actual arrival time is greater than the threshold variable;
and further including:
a collision rate threshold variable stored in the memory of a first node of the plurality of nodes;
a current rate of collisions variable stored in the memory of the first node and updated by the processor of the first node, wherein the current rate of collisions variable holds a current rate of collisions the first node is experiencing;
and
wherein the processor of the first node compares the current rate of collisions variable and the collision rate threshold variable and executes logic for casting the first node out of the network if the current rate of collisions the first node is experiencing is greater than the collision rate threshold variable.

11 more elements

Dependencies are inferred from the claim text.

Facts

Application: 14/012,421Filed 28 Aug 2013 · us provisional application
Priority: 28 Aug 2012
Granted: 12 Apr 2016
Term ends: Not estimatedThe source records don’t support an estimate.

Classification8 codes

H04J 3/1694
In which the time allocation to individual channels within a transmission cycle is variable, e.g. to accommodate varying complexity of signals,…
H04W 56/0075
Open loop measurement: based on arrival time vs. expected arrival time
H04W 8/005
Network data management: discovery of network devices, e.g. terminals
H04W 40/12
Communication route or path selection, e.g. power-based or shortest path routing: based on transmission quality or channel quality