FIELD OF INVENTION
The present invention is in the field of pervasive tracking and monitoring of enterprise objects / assets
leading to better management and better return on investments to organizations. The tracking and
monitoring of objects are made through the deployment of a wireless mesh network. In particular, this
invention allows an easy deployment method where the end user can effortlessly deploy the wireless
mesh network. The system of the invention will have various types of end uses and applications
involving tracking and managing of mobile assets and people, such as tracking of the movement of
persons in sensitive and high risk zones, such as in mines to improve the safety of miners and mine
equipment. This improves the surveillance ol the miners and the mine equipment and is of particular
importance in the event of an emergency anc helps in mine rescue. The tracking applications are also
present in the management of a fleet of trucks in a campus thus enabling the detection of unauthorized
entry into the campus or the movement of a i ruck in an unauthorized area of the campus. The system
also has applications in the hospital sector where the movement of doctors, nurses and patients will
allow better knowledge of their whereabout;. More critically, the system can track the location of
hospital equipment like oxygen cylinders, defibrillator trays, first aid trays, mobile ECG machines etc.
The system has applications in other sectors like retail, where the location of items in a warehouse are
tracked, in logistics, where we can track the movement of inventory from one warehouse to another, to
have an accurate picture of the amount of inventory/ left. Thus the system of the invention has
numerous industrial applications where it fas the potential to provide accurate and real time
information of the location of the assets of the organization thus leading to better management and
improved return on investment.
BACKGROUND ART
It is well known in the art that from time to lime tracking and monitoring systems have been made
available. Some of the well known and presently available systems of such remote tracking and
monitoring are discussed hereunder.
Standard Wi-Fi (IEEE 802.11) networks have been used to provide location tracking using customer
deployed Wi-Fi hotspots. Aeroscout is a commercial provider of such a system and offers indoor and
outdoor real-time asset location, long range active RFID, choke point visibility and telemetry. A similar
offering is provided by Ekahau where the core of the tracking solution is based on commercially
available Wi-Fi networks. In both systems, active tags are essentially small IEEE 802.11 compliant
wireless devices. These tags are attached to equipment or carried by people for real time tracking. The
location of a tag is based on location of the Wi-F hotspots.
The above related works are based on the IEEE standard of 802.11 (Wi-Fi). Further, the solutions expect
a customer deployed Wi-Fi mesh network is already in place. Using the Wi-Fi standard has severe
restrictions as elaborated subsequently. In hazardous areas like the mines, safety precautions are
mandatory, such as, the output power of the devices should be restricted to within 1 watt and the
devices must be intrinsically safe. Restricting the output power restricts the effective range of the Wi-Fi

devices. Further, the Wi-Fi devices consume high power and it is therefore impractical and infeasible to
run such devices on small batteries like that of size AA.
Another restriction on the solution provided by already deployed Wi-Fi hotspots is that the multi hop
communication is not possible. Therefore, such systems expect the hotspots to be the last mile of a
traditional wired connection where data from the hotspot can then exploit the wired connection to
reach the intended destination. This aspect is severely restrictive in new deployments where there have
been no prior communication networks. For example, in deployments in mines, it is infeasible to deploy
an additional wired network to support the Wi-Fi hotspots. Not only is this prohibitive in terms of cost, it
also puts a burden on the power requirements.
A further restriction of the competing solutions is that they provide no support for the deployment of
Wi-Fi Hotspots. In all these solutions it is assumed that the customer has already placed the hotspots.
This is impractical, as the efficient placement of the hotspots will determine the efficacy of the tracking
and the wireless coverage of the solution.
The current state of the art systems in tracking of mobile objects generally use either of the following
two methods. The first involves building up of ii table (AODV), which tells where an object is and what is
the path to reach it. This is done by sending control packets to all the nodes of the network. However,
this system is extremely slow and hugely wasteful on network resources. The other method is to have
the address of the mobile tag change as it moves. This system has a very low overhead but cannot track
highly mobile nodes as the changing of the address takes time and the tag loses its identity when the
address changes.
OBJECTS OF THE INVENTION
It is thus the basic object of the present invention to make an easy and effortless deployment of tracking
devices that are manufactured by Pen/Com Consulting. The devices offer cost effective tracking, has low
power requirements and has a large wireless range. The devices are based on the newly ratified
standard, IEEE 802.15.4.
Yet another object of invention is the unique way in which the routing of messages between devices is
preserved where it is taken care that the message loops (also known as count to infinity problem) does
not occur.
Another object of invention is the integration of the fault tolerance into the routing method. Thus, in
spite of device failures, the network is maintained and messages are routed correctly.
Finally, we also present the object of invention where routing for tags that are mobile is made possible.
This allows for simplistic design and operation of the devices, thus making the deployment as easy as
simply placing them in the area to be tracked.

DETAILS OF THE INVENTION
In this present invention we develop a simple approach to solving the two well known problems in the
routing of messages between nodes in a mesh network. The first problem is the prevention of loops in a
mesh network. This is also known as the count to infinity problem in similar works. This is a significant
problem in multi hop distributed mesh networks where data meant for a particular destination is
propagated by intermediate nodes between the source and the destination. Here every node that is part
of the route of the message from the source to the destination has to make a decision as to which of its
neighbors it must forward the message. This is pictorially depicted in figure 1.
A loop is said to occur if the message gets forwarded between the same set of nodes repeatedly without
reaching the intended destination. This occurs if one of the intermediate nodes makes wrong decision
on which of the nodes must be the next hop for the message and is usually the result of a change in the
topology of the network either due to a mobile node or due to the failure of a node. This is pictorially
shown in figure 2.
There are a few standard techniques for solving the looping problem. The most obvious one is to
maintain a list of the recent messages that have been forwarded by it. In case it is observed that the
same message has been received again by the device, a loop is detected. It is important to note that the
first node that detects the loop in the message would discard the message. In such a scenario the device
that has forwarded the message to the node that first detected the loop is the source of the problem.
This technique although simple, has overhead:, on the memory to maintain a history of the messages.
The length of the history determines the solution quality and this configurable parameter is a trade-off
between the amounts of memory needed veisus the solution quality. Further, the solution can only
identify the source of the problem and cannot correct it.
A more common technique employed is to include the maximum number of hops that a message can
make. This is employed in the routing on the Internet and is designated as TTY (time to live). This
solution has a per message overhead but is much less than the previous solution. However, the method
cannot identify the source of the problem or propose a solution to it.
The second problem in the routing of messages is to maintain an active route for tags that are mobile.
This is particularly true in the current tracking application where the objects to be tracked are mobile. A
mobile tag results in a dynamic topology where :he route for each tag has to be maintained.
The standard solutions for this include a dynamic address allocation strategy where the tags are
allocated an address every time it moves. This solution maintains the routing, however suffers from two
distinct problems. Firstly, allocating a new address every time it moves incurs a network overhead
where the mapping of the device name to the device address has to be maintained. The second and
often overlooked problem is that of loss of messages when a device moves. If for example, a message is
intended for address OA and when it propagates towards the tag, the last router finds that the tag has
moved away from it. It thus cannot deliver the message.

The other solution for the mobile tags is to proactively maintain a route every time a route changes. This
is done by a range of routing protocols like the distance vector routing solutions. Although this solution
ensures the messages reach the intended t*ig, it has a huge overhead on the network. Further, the
solution was designed for highly mobile nodes where overheads on network bandwidth and power
requirements are not considered to be a concism.
We now present our invention in detail. We IT ake certain assumptions. Every device is considered to be
IEEE 802.15.4 compliant and has a unique 16 bit address. This address becomes the identity of every
device. There is a single sink of the network, which is the root of the network. The sink has an address of
0. When a new node is switched on for the first time, it makes a scan of the channel it is operating in
and determines the devices in its vicinity. TMs is achieved by the 802.15.4 MAC primitive - MLME-
SCAN.request. The scan type is set to active with the macAutoRequest set to false. This particular
parameter of macAutoRequest is of extreme importance as it prevents the MAC from discarding beacon
responses from devices of the same PAN (Peisonal Area Network). This is exactly the case in a mesh
network, where every device is expected to have the same PAN. If the macAutoRequest is not set to
FALSE, there would be only one response from the channel scan primitive and we would lose data from
multiple devices.
Once the various responses to the channel scan have been received, we filter out those devices whose
addresses are greater than the current one. For example, if the device performing the scan has an
address of 10 and it gets a response from devices with addresses of 0, 5, 15, then, the filter would
remove the response from device 15. The nexi filter would choose the device that has the best signal
strength. For example, if the devices 0 and 5 have signal strengths of 67 and E4 respectively, then the
device 5 is chosen. This process of choosing I he device prevents a loop from being formed. This is
pictorially depicted in figure 3.
In case, no device is found, or the forwarding of a message fails, the channel scan procedure is repeated.
In this way, the same mechanism allows for faut tolerance. The fault tolerance provided is extremely
simple to implement and has no overheads. The simple procedure also makes the run time processing
very fast.
Once the device after the scan is chosen, it is designated as the current device's parent. Thus, when the
device needs to send a message to the sink (whose address is 0), it forwards the message to its parent.
Similarly, every parent keeps a record of all its children. When a message is to be sent to a tag (which is
the leaf of the network), a parent forwards the message to all its children. This is in effect a flooding
mechanism. The parent also retains the message with itself for a fixed amount of time. In this way, if the
tag moves and associates with the parent, it forwards the message meant for the tag. As the tag does
not change its address, its identity is not lost aid all messages meant for the tag are delivered. A tag
keeps the ID of the last message it has received so that it can discard duplicate messages.
Thus, through a simple mechanism as explained above, two prominent problems in mesh networks,
namely the looping problem and messaging for mobile tags are solved. This mechanism of routing
makes the deployment of devices extremely simple for the end customer. The network deployment is

started by first placing the sink (address of 0). In its vicinity the next device is placed (any device whose
address is greater than 0). The third device placed can be any device whose address is greater than that
of the second. In this way, the entire network can be deployed.

BRIEF DESCRIPTION OF ACCOMPANYING FIGURES
Figure 1: is a representative depiction of a wireless mesh network. It shows the multi-hop propagation
of messages from the source to the destination (sink).
Figure 2: shows how a loop is formed in a wireless mesh network.
Figure 3: shows the present invention where the formation of a loop is prevented.

WE CLAIM:
1. A real-time pervasive tracking, monitoring and management system based on IEEE 802.15.4 that
enables the tracking of highly mobile objects and performs even in the event of a device
malfunction.
2. A unique way for solving the looping problem in v/ireless mesh networks ad-hoc networks.

This present invention is in the field of real time pervasive tracking, monitoring and management system using IEEE 802.15.4 compliant wireless devices. Our invention enables the tracking on highly mobile objects in the area of deployment of the system. The tracking is made possible even in the event of a fault of a wireless device. The tracking involves concepts of network deployment, fault tolerance and
routing. In the process of our invention we solve well known problems in wireless mesh networks: mainly the looping problem, bypassing a fault and maintaining the identity of mobile tags. An application of our system is in the underground mines where the location of every mine worker and asset is important for safety and security purposes. Particularly, our technology allows for efficient mine rescue operations, provides enterprise visibility for better management and can help prevent
unauthorized entry in sensitive areas and improve surveillance.