Moslem Noori

Lifetime Analysis of Random Event-Driven Clustered Wireless Sensor Networks

Considering event-driven clustered wireless sensor networks, a probabilistic approach for analyzing the network lifetime is presented when events occur randomly over the network field. To this end, we first model the packet transmission rate of the sensors, using the theory of coverage processes and Voronoi tessellation. Then, the probability of achieving a given lifetime by individual sensors is found. This probability is then used to study the cluster lifetime. In fact, we find an accurate approximation for the probability of achieving a desired lifetime by a cluster. Our proposed analysis includes the effect of packet generation model, random deployment of sensors, dynamic cluster head assignment, data compression, and energy consumption model at the sensors. The analysis is presented for event-driven networks, but it comprises time-driven networks as a special case. Computer simulations are used to verify the results of our analysis.

Characterizing the traffic distribution in linear wireless sensor networks

In a multi-hop wireless sensor network (WSN), the traffic load is not evenly distributed over the nodes. For example, the sensors which are one hop away from the sink relay the whole network traffic. This imbalanced traffic distribution can degrade the network lifetime and functionality. Here, an analysis is proposed to characterize the traffic load distribution over a randomly deployed linear WSN. The effect of the number of nodes and their distribution over the network is taken into account and the results are verified through computer simulation.

Cost-efficient data aggregation point placement for advanced metering infrastructure

This paper investigates the problem of placement of data aggregation points (DAPs) in advanced metering infrastructures (AMIs). The specific constraints are that DAPs are to be located on utility poles and that communication is done over wireless links. While the resulting optimization problem is an integer program, we propose to adapt the K-means algorithm to obtain an efficient and less-complex method to solve the DAP placement problem. Simulations of the developed optimization method illustrate the effects of smart-meter density and communication range on the selection of DAP locations.

Optimal User Pairing for Asymmetric Multi-Way Relay Channels with Pairwise Relaying

We study an asymmetric multi-way relay channel where users have different channel conditions. To enable data exchange between the users, an existing practical approach, where users transmit their data to the relay in pairs, is considered. For pairwise transmission, we consider two different scenarios at the relay, called functional-decode-forward (FDF) and decode-and-forward (DF). For both FDF and DF, we first show that due to unequal channel conditions, the achievable common rate of the pairwise strategy depends on the order in which the users are paired. This motivates us to find the pairing strategy maximizing the achievable rate. This rate is then compared with the capacity upper bound and the achievable rate of a random user pairing.

A Probability Model for Lifetime of Event-Driven Wireless Sensor Networks

In event-driven wireless sensor networks, the network lifetime has a random nature due to the randomness of data reporting. The lifetime is even more nondeterministic when sensors are also deployed randomly. The lifetime of such a network is influenced by node deployment, initial energy of sensors, packet generation model and the number of sensors. This work quantifies the effect of these parameters on the lifetime of randomly deployed event-driven networks. First, the lifetime of individual sensors are studied. Then, an analytical expression is obtained for the complementary cumulative density function of the network lifetime. Such an analysis can be used for choosing the network parameter and efficiently optimizing the network lifetime. The results of this work are obtained for both multi- hop and single-hop wireless sensor networks and are verified with computer simulation. The approaches of this paper are shown to be applicable to more general cases.

Improving data rate in relay-aided power line communications using network coding

Power line communication (PLC) provides a reliable and inexpensive solution to enable high data rate services for indoor environments. In this work, we consider an indoor PLC network where several devices (or users) want to exchange data. To prevent severe signal attenuation and thus performance degradation over relatively long PLC links, we consider the use of a relay at a central location to assist the users in their data communication. For this scenario, we suggest the application of amplify-and-forward (AF) multi-way relaying (MWR) based on physical-layer network coding at the relay. To evaluate the performance of this scheme, its achievable data rate is studied with practical assumptions applicable to PLC systems. Our study shows that the employed AF MWR improves the system performance and increases the achievable common data rate at the users.

A Probabilistic Lifetime Analysis for Clustered Wireless Sensor Networks

Clustering sensors is considered as an efficient way for increasing the lifetime of a wireless sensor network. One of the main advantages of these networks, leading to a longer lifetime, is the ability of data aggregation by the cluster head (CH). Assuming a fixed-shape for the cluster, the probability of achieving a desired lifetime by the cluster has been derived when the nodes are randomly deployed within the cluster. Having the clusters lifetime, the network lifetime can be consequently determined. In addition, it is shown that clustered networks are not necessarily better than the non-clustered networks in terms of the energy consumption and consequently the network lifetime. To this end, a condition related to the data aggregation capability of CH is found indicating when the clustered networks outperform non-clustered ones.

Characterizing the path coverage of random wireless sensor networks

Wireless sensor networks are widely used in security monitoring applications to sense and report specific activities in a field. In path coverage, for example, the network is in charge of monitoring a path and discovering any intruder trying to cross it. In this paper, we investigate the path coverage properties of a randomly deployed wireless sensor network when the number of sensors and also the length of the path are finite. As a consequence, Boolean model, which has been widely used previously, is not applicable. Using results from geometric probability, we determine the probability of full path coverage, distribution of the number of uncovered gaps over the path, and the probability of having no uncovered gaps larger than a specific size. We also find the cumulative distribution function (cdf) of the covered part of the path. Based on our results on the probability of full path coverage, we derive a tight upper bound for the number of nodes guaranteeing the full path coverage with a desired reliability. Through computer simulations, it is verified that for networks with nonasymptotic size, our analysis is accurate where the Boolean model can be inaccurate.

On the achievable rates of symmetric Gaussian multi-way relay channels

Considering a symmetric Gaussian multi-way relay channel (MWRC) with K users, this work compares two transmission strategies, namely one-way relaying (OWR) and multi-way relaying (MWR), in terms of their achievable rates. While in OWR, only one user acts as data source at each time and transmits in the uplink channel access, users can make simultaneous transmissions in MWR. First, we prove that for MWR, lattice-based relaying ensures a gap less than12(K−1) bit from the capacity upper bound while MWR based on decode-and-forward (DF) or amplify-and-forward (AF) is unable to guarantees this rate gap. For DF and AF, we identify situations where they also have a rate gap less than12(K−1) bit. Later, we show that although MWR has higher relaying complexity, surprisingly, it can be outperformed by OWR depending on K and the system SNR. Summarily speaking, for large K and small users’ transmit power, OWR usually provides higher rates than MWR.

Optimal power allocation to improve secrecy performance of non-regenerative cooperative systems using an untrusted relay

To protect data communication from eavesdropper nodes, different techniques have been developed to improve the physical-layer security (PLS) of communications systems. Destination-based cooperative signalling (DBCS) is one of such techniques where the destination sends an intended artificial noise to the untrusted listeners helping to protect the source message from being captured reliably at eavesdroppers. In this study, the authors investigate the application of DBCS to improve the PLS, and as a consequence the secrecy performance of a two-hop amplify-and-forward cooperative system with an untrusted relay. To get the best performance out of DBCS, the transmit power of the sources signal as well as the artificial noise should be carefully adjusted. To address this, they have introduced the optimal power allocation to maximise the secrecy rate of the system under a sum-power constraint at the network nodes. For a system with large-scale antenna arrays at the base station, then then find the closed-form solution for the secrecy outage probability and the ergodic secrecy rate of the optimised system for both uplink and downlink. The presented simulation results validate the authors’ theoretical analysis and reveal that the proposed DBCS with optimal power allocation significantly improves the secrecy performance of the system.