Distributed ad hoc mesh network protocol for underground mine and hazardous area communications

A method for implementing a communications network protocol suitable for reliable voice and data communications in an underground, industrial, or hazardous area comprising:

• providing a wireless mesh network (WMN) comprising ad hoc mesh nodes that automatically form and re-form in clusters to provide wireless network communications to support voice, data, text and network service for personnel working in the hazardous area;
• wherein the wireless mesh network (WMN) comprises fixed mesh nodes (FMNs) and mobile nodes and each FMN provides creation and maintenance of the WMN by coordinating individual clusters within the WMN and routing data through the WMN between mobile nodes and a Gateway node for access to and/or from a remote Network Operations Center;
• establishing dedicated bandwidth transmission opportunities for each FMN in a given cluster to forward packets to a neighbor node in the cluster and to establish contention-based transmission opportunities for the FMNs and the mobile nodes to join the cluster;
• establishing contention-free transmission opportunities by providing a two-way medium for each node with a bonded frequency pair and associated contention-free time slot to provide a guaranteed time period during which an FMN transmits network packets to neighboring FMN(s) and to mobile units using the FMN as a parent to, wherein format for the contention-free time slot depends on voice or data dedication;
• establishing contention-based transmission opportunities to join the cluster by providing a two-way medium for each node with a bonded frequency pair and associated contention-based time slot, wherein format for the contention-based time slot depends on voice or data dedication;
• wherein distributing application layer packets is performed with high reliability and low latency to maintain reliable voice and data communications with mobile nodes carried by personnel and fixed or mobile sensors within the hazardous area and also with remote operation;
• providing an intelligent flood routing technique with dynamic packet routing to ensure that at least one mobile node can seamlessly roam within the ad hoc mesh network;
• wherein the intelligent flood routing technique immediately reacts to a mobile node roaming freely through the ad hoc mesh network and to removal of one or more FMNs with minimal or no loss of data since it does not establish static or semi-static routes for communication packets from a given source to a given destination;
• wherein the intelligent flood routing technique eliminates circular loops and duplicate voice packets by storing a history of data packet sequence numbers and voice packet timestamps to remove large amounts of redundant traffic associated with flood routing wherein each FMN and each mobile node contains a communications network protocol for automatically forming an association with one or more neighbor FMNs, and wherein the ad hoc mesh network is based on cooperative negotiation and a dynamic parent-child relationship between nodes for determination of network time synchronization without a pre-determined time master, discovery and merging of adjacent ad hoc mesh networks, and routing techniques for voice, data and network status packets which react to network topology changes, such that when a communications link in the ad hoc mesh network degrades or fails, another FMN is automatically designated;
• wherein when quality of a link between a mobile node and a parent FMN has degraded such that it is below a programmable threshold of acceptable operation, the mobile node seeks another parent which can provide a higher quality communication link;
• wherein each fixed node and mobile node is monitored and managed at the remote Network Operations Center for dispatch, remote supervision, and tracking of personnel, as well as, monitoring, asset control, and management of wireless sensors and equipment;
• wherein the ad hoc mesh network comprises at least one node cluster with (i) a plurality of peer-to-peer fixed mesh nodes (FMNs), one of which is a time master node, and (ii) at least one mobile mesh radio node;
• establishing a super-frame time interval for all nodes in a cluster, wherein the super-frame time interval is time synchronized with the time master node for the cluster based on node ID ranking, and wherein child nodes will synchronize to their respective parent nodes' slot timing thus inheriting the time master's timing with some offset due to propagation delay:
• wherein when a communications link in the ad hoc mesh network degrades or fails, another FMN is automatically designated as time master node based on node ID ranking;
• establishing at least two time slots in a primary channel and secondary channel within the super-frame time interval;
• assigning at least one of the time slots as a contention-based time slot for transmitting data to form parent-child associations to join the ad hoc mesh network by one or more of the plurality of FMNs and/or the at least one mobile mesh radio node;
• assigning at least one of the time slots as an FMN to FMN contention-free time slot for transmitting network packets from one or more of the FMNs to a neighboring FMN that will use a transceiver to tune to frequencies associated with a transmitting FMN and receive packets and/or to any mobile mesh radio node associated with an FMN that will use a transceiver to tune to frequencies associated with a transmitting FMN and receive packets;
• wherein for an FMN-to-FMN time slot not assigned to a neighbor, a node will use both transceivers to scan for other clusters to provide an improved time metric;
• and
• wherein each FMN will periodically puncture its own FMN-to-FMN time slot as well as a neighbors' assigned time slot(s) and contention access time slot to perform a scan operation for other clusters to provide an improved time metric.