Rateless Packets


How sensors talk to each other?

Information packets randomly walk around the sensor network, recombine with other packets and settle down at random locations. Original information is recovered by collecting any slightly larger number of Rateless Packets then the original information packets in the sensor network.

Wireless sensor networks (WSN) are a class of wireless ad-hoc networks established among a number of sensor nodes deployed over a monitored area such as agricultural field or enviromental protection area. Each sensor node is a lowcost, energy-constrained device capable of sensing its environment such as temperature, air or soil humidity, air pressure, concentration of various chemicals, etc., performing simple processing tasks and transmitting sensed data over the wireless medium towards neighboring sensor nodes. To perform more complex data processing, data gathering mechanisms are designed and deployed for efficient data collection at one or a small number of reliably powered sink nodes inside the WSN. At sink nodes, the data is either processed or forwarded to an external network for processing at a remote location.


In many scenarios of interest, it is desirable to design data gathering mechanisms able to recover all the data generated by sensor nodes by visiting only an arbitrary subset of sensor nodes. For example, WSNs may be deployed at inaccessible locations where it is not feasible to set up the reliable sink and/or to reliably access the external network.


In such cases, a convenient approach is to use mobile collectors such as unmanned ground or aerial vehicles, required to connect only to a subset of nodes due to topology constraints arising in critical applications. For example, mobile collectors could just fly over a sensor field and attempt to reconstruct all data by connecting only to a small set of sensor nodes. Other scenario might be the case where sensor field can be only accessed from perimeter due to e.g. concentration of dangerous chemicals inside the sensing area. Also, in applications where it is important to ensure the data persistence in case of massive sensor failures, data recovery should be possible only from a small subset of surviving nodes.


Our distributed coding scheme called Rateless Packets is based on revolutionary concept of Rateless Codes. In Rateless Packets scheme, information packets sensed at the sensor nodes are let to randomly walk around the sensor network and participate in distributed encoding process where they are combined with information packets of carefully selected set of other sensor nodes. The whole process of encoding Rateless Packets is distributed and simultaneous such that huge number of them travel around the network in a very short period, recombine with other packets and finally settle down at random locations. The number of created Rateless Packets is typically much larger then the original number of information packets in the sensor network. What makes the Rateless Packet approach appealing is that collecting any slightly larger number of Rateless Packets then there was original information packets in the sensor network is sufficient to recover all original information packets.

Wireless Sensor Networks are one of the key enabling technologies for monitoring in agriculture