Abstruct-We consider a wireless sensor network made of sensor nodes capable of sensing and communication, relay nodes capable of communication, and base stations responsible for collecting data generated by sensor nodes, to be deployed in sensor field, We address the problem of placing the sensor nodes, relay nodes and base stations in the sensor field such that (i) each point of interest in the sensor field is covered by a subset of sensors of desired cardinality (ii) the resulting sensor network is connected and (iii) the sensor network has sufficient bandwidth. We propose several deployment strategies to determine optimal placements of sensor nodes, relay nodes and base stations for guaranteed coverage, connectivity, bandwidth and robustness. We study several different objectives such as minimizing the number of sensor nodes deployed, minimizing the total cost, minimizing the energy consumption, maximizing the network lifetime and maximizing the network utilization. The placement problems for reliable as well as unreliable/probabilistic detection modeis are formulated as Integer Linear Programs (ILPs). The practicality, effectiveness and performance of the proposed strategies are illustrated through simulations. Distributed sensor networks, designed to monitor andfor control the surrounding environmental phenomena, have the potential to revolutionize many applications. A sensor network consists of sensor nodes and one or more base stations. Sensor nodes generate, process, and forward data (via intermediate sensor nodes) to base stations. Among the major design challenges in the design of sensor networks is the efficient utilization of resources available to sensor nodes such as scarce bandwidth and limited energy supply. In applications such as surveillance, target tracking and intrusion detection, the strategic placement of sensor nodes in the sensor field can greatly enhance the sensing quality, reduce the cost and minimize the energy consumption, thereby increasing lifetimes of sensor nodes. Depending on properties of sensing devices, terrain and application scenarios, the sensing capabilities of sensor nodes can be modeled as reliable (precise) or unreliable (imprecise). In the unreliable sensing model, a sensing/detection probability is assigned to each reading which characterizes the level of confidence in the reading. In the reliable detection model readings within the sensing range are assumed to be precise. The area in which a sensor can perform its sensing, monitoring, surveillance and detection tasks with a reasonable accuracy (i.e. the sensor readings have at least a threshold level 0-7803-8991-3/05/$20.00 0 2005 IEEE 58 1 of sensing/detection probabilities within that area) is known as the coverage area. The union of coverage areas of individual sensors is the coverage area of a sensor network. Coverage areas can be irregular and can be location dependent due to the obstructions in the terrain e.g. sensors deployed for indoor applications, in urban and hilly areas [I 3. The coverage area may also depend on the target, e.g. a sensor might be able to detect smaller targets from short distances and bigger targets from long distances. The degree of the sensing coverage required depends on the application [2]. Covering every location with multiple sensors can provide robustness. Some applications may require the preferential coverage of critical locations based on risk or tactical importance [I]. The coverage requirements can also change with time due to changes in environmental conditions, e.g. the visibility can vary due to fog or smoke. A low degree of coverage might be sufficient in normal circumstances but, when a critical event is sensed, a high degree of coverage may be desired in that area 121. It is desirable to achieve the required degree of coverage and robustness with the minimum number of active sensor nodes to minimize cost, interference and information redundancy [2], [3]. However, due to the limited range of the wireless communication and obstacles such as buildings, walls and trees, the minimum number of sensor nodes required for the coverage may not guarantee the connectivity of the resulting sensor network. Some technologies require the transmitter and the receiver to be in the line-of-sight, e.g. Infra-red, Ultrasound f41. Therefore, a sensor node placement strategy must take connectivity and wireless channel bandwidth limitation (communication bottlenecks) into consideration when deciding on where to place sensor nodes. Since the sensor nodes have limited energy supplies, a sensor node placement strategy, which minimizes the energy consumed in communication or maximizes the time till the required degree of coverage is maintained, is highly desirable. In this paper, we propose several deployment strategies which determine the optimal placements of sensor nodes, relay nodes and base stations for guaranteed coverage, connectivity, bandwidth and robustness. The placement problems for reliable as well as probabilistic detection models are formulated as ILPs. The proposed strategies are compared using simulations.
Another relay node placement is in REF .
Energy efficient sensor, relay and base station placements for coverage, connectivity and routing
PCCC 2005. 24th IEEE International Performance, Computing, and Communications Conference, 2005.
PCCC 2005. 24th IEEE International Performance, Computing, and Communications Conference, 2005.
Computer Science