Abstract
In this paper, we present an innovative transmit power control scheme, based on optimization theory, for wireless sensor networks (WSNs) which use carrier sense multiple access (CSMA) with collision avoidance (CA) as medium access control (MAC) protocol. In particular, we focus on schemes where several remote nodes send data directly to a common access point (AP). Under the assumption of finite overall network transmit power and low traffic load, we derive the optimal transmit power allocation strategy that minimizes the packet error rate (PER) at the AP. This approach is based on modeling the CSMA/CA MAC protocol through a finite state machine and takes into account the network adjacency matrix, depending on the transmit power distribution and determining the network connectivity. It will be then shown that the transmit power allocation problem reduces to a convex constrained minimization problem. Our results show that, under the assumption of low traffic load, the power allocation strategy, which guarantees minimal delay, requires the maximization of network connectivity, which can be equivalently interpreted as the maximization of the number of non-zero entries of the adjacency matrix. The obtained theoretical results are confirmed by simulations for unslotted Zigbee WSNs.
Highlights
Wireless sensor networks (WSNs) are an interesting research topic, both in military [1,2,3] and civilian scenarios [4]
In the proposed adjacency matrix-based power allocation strategy, the power is different at each sensor and is set according to optimization strategy presented in Section 2., where the total amount of available transmit power is assigned to each sensor in order to minimize the packet error rate (PER) at the access point (AP)
We have presented an optimized transmit power allocation strategy which allows to minimize the PER at the AP of a WSN
Summary
Wireless sensor networks (WSNs) are an interesting research topic, both in military [1,2,3] and civilian scenarios [4]. In [10] the authors present an opportunistic power allocation strategy based on local and decentralized estimation of the links’ quality In this scenario, only the nodes that experience channel conditions above a specific quality threshold are allowed to transmit in order to avoid waste of energy. In [11], the authors introduce a dynamic power allocation scheme for WSNs which relates the received signal strength indicator (RSSI) to the received signal-to-interference plus noise ratio (SINR) They propose two possible approaches: (i) a first approach based on a Markov chain system characterization and (ii) a second approach based on the minimization of the average packet error rate (PER).
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