Maintaining Connectivity in Sensor Networks Using Directional Antennae

Abstract

Connectivity in wireless sensor networks may be established using either omnidirectional or directional antennae. The former radiate power uniformly in all directions while the latter emit greater power in a specified direction thus achieving increased transmission range and encountering reduced interference from unwanted sources. Regardless of the type of antenna being used the transmission cost of each antenna is proportional to the coverage area of the antenna. It is of interest to design efficient algorithms that minimize the overall transmission cost while at the same time maintaining network connectivity. Consider a set S of n points in the plane modeling sensors of an ad hoc network. Each sensor is equipped with a fixed number of directional antennae modeled as a circular sector with a given spread (or angle) and range (or radius). Construct a network with the sensors as the nodes and with directed edges (u, v) connecting sensors u and v if v lies within u's sector. We survey recent algorithms and study trade-offs on the maximum angle, sum of angles, maximum range and the number of antennae per sensor for the problem of establishing strongly connected networks of sensors.

Connectivity and stretch factor trade-offs in wireless sensor networks with directional antennae

“…They also showed that when each sensor has k ≤ 5 directional antennas, the upper bound on the range is bounded by 2 sin(π /(k + 1)) times the optimal range, for every angle. A comprehensive survey of the antenna orientation problem is presented in [21]. In [20], the problem was studied in 3D where the authors consider the case when each sensor has one directional antenna.…”

“…A comprehensive survey of the antenna orientation problem is presented in [21]. In [20], the problem was studied in 3D where the authors consider the case when each sensor has one directional antenna.…”

“…When φ = 0 the antenna orientation problem is equivalent to the well-known Bottleneck Traveling Salesman Problem [15], where the an optimal approximation algorithm, given by Parker and Rardin [27], has an approximation ratio of 2. Several aspects of the Antenna Orientation Problem are addressed in the general survey [21]. An important generalization is studied in [11] when each sensor can be equipped with a given number of directional antennas which can be independently oriented.…”

The Sound of Communication in Underwater Acoustic Sensor Networks

“…In the symmetric model, communication is possible if the sender and receiver are within the range (determined by respective lobes) of each other, see [1,23]. In the asymmetric model, the sender can transmit directly a message to the receiver (provided the receiver is within the range of the sender) but the receiver may not be able to send directly a message to the sender, see [6,9,17,20]. In a way, the asymmetric model is less rigid than the symmetric one, but the receiver must seek a (alternate) path in the network if it also wants to talk to the sender.…”

“…Thus, to establish bidirectional communication between S, R in the asymmetric communication model not only a path must be found between source S and destination R; in addition, a path must be found in the reverse direction from destination R to source S. Despite this difficulty it is still possible to provide algorithms that can establish bidirectional communication [6,9,17,20] with constant stretch factor.…”