Multi-hop wireless networks can provide data access for large and unconventional hard-to-wire areas, but they have long faced significant limits on the amount of data they can transmit due to routing complexity, suboptimal path management, and delays caused by multi-hop relaying.
Now researchers from North Carolina State University have developed a more efficient data transmission approach called centrality-based power control that can dramatically boost the amount of data the networks can transmit.
"Our approach increases the average amount of data that can be transmitted within the network by at least 20 percent for networks with randomly placed nodes – and up to 80 percent if the nodes are positioned in clusters within the network," said Dr. Rudra Dutta, an associate professor of computer science at NC State.
The approach also makes the network more energy efficient, which can extend the lifetime of the network if the nodes are battery-powered.
Multi-hop wireless networks use nodes spread through a space that not only capture and disseminate data, but also serve as a relay for other nodes. But these networks have "hot spots" – places in the network where multiple wireless transmissions can interfere with each other, which puts a cap on how quickly the network can transfer data. The nodes have to take turns transmitting data at these congested points causing delays.
Traditionally, there are two ways to deal with the problem. Data can be transmitted at low power over short distances, which limits the degree of interference with other nodes. But in this case the data may have to be transmitted through many nodes before reaching its final destination. The alternative approach transmits data at high power, which means the data can be sent further and more quickly. The drawback is that the powerful transmission may interfere with transmissions from many other nodes.
NC State researchers Dutta and Ph.D. student Parth Pathak created what they call centrality-based power control to address the problem. It uses an algorithm that instructs each node in the network on how much power to use for each transmission depending on its final destination. The algorithm decides when a powerful transmission is worth the added signal disruption, and when less powerful transmissions are needed. The result is an overall jump in system efficiency.
A paper, "Centrality-based power control for hot-spot mitigation in multi-hop wireless networks," published online by the journal Computer Communications, details how hot spots can be better mitigated in wireless sensor networks:
Using a heuristic based on the concept of centrality, we show that if we increase the power levels of only the nodes which are expected to relay more packets, significant relay load balancing can be achieved even with shortest path routing. Different from divergent routing schemes, such load balancing strategy is applicable to any arbitrary topology and traffic pattern. With extensive simulations, we show that centrality-based power control can drastically increase the network lifetime of sensor networks. We compare its performance with other divergent routing schemes and multiple battery level assignment strategy. Also, it is shown that centrality-based power control results into better throughput capacity in many different topologies.
The research was supported in part by the U.S. Army Research Office.