Relay technology is one of the key technologies for long-term evolution advanced (LTE-A) project. The introduction of relay will not only bring a wider coverage and higher capacity to the system but also lower the cost of network building. Multihop wireless relay technology plays an important role in next-generation mobile and wireless communication systems. Nowadays, we are witnessing the formation of a new technological marvel: Internet of Things (IoT). This formation is able to combine in a particular operational entity, all the bits and pieces of the world around us. In this paper, we perform queuing modeling of a two-hop wireless relay network and carry out performance analysis of end-to-end packet delay. In the two-hop wireless relay network, two groups of wireless nodes (WNs) and a single relay node (RN) are considered. A Poisson packet arrival process and IEEE 802.11 distributed coordination function are assumed in the network for the network traffic model and for regulating the nodes' access to the shared channel, respectively. We model a node as a single-server queuing system, whose service time of a packet is unknown and dependent on the probabilistic parameters of IEEE 802.11 DCF medium access control (MAC). A system of equations is then obtained for numerically computing the probabilistic parameters of IEEE 802.11 DCF MAC through discretization of the continuous-time network operations, based on which we construct semi-Markov processes and derive an analytic result for the expectation of the end-to-end packet delay. As a key performance indicator in evaluation of wireless networks, the packet delay result helps measure the efficiency of IEEE 802.11 MAC in two-hop wireless relay networks.

Abstract Wireless communications and multihop networking based on electromagnetic (EM) radios have been considered as an alternative to acoustic communications in seawater because in typical applications for networked underwater sensing, EM waves are much less susceptible to multipath distortion and environmental noise. In this paper, we discuss the characteristics of EM channels in seawater and derive a novel EM signal propagation model. Based on the propagation model, we implement in the QualNet network simulator an EM underwater surveillance network for studying the impact of these unique characteristics of underwater EM channels on the media access control (MAC) layer performance. Both a single‐hop network model and a multihop network model are simulated. Simulation results show that the carrier sense multiple access without or with acknowledgement (CSMAWithoutACK or CSMAWithACK, respectively) has advantages over ALOHA and multiple access with collision avoidance in terms of packet average delay, packet delivery ratio, and MAC scheme overhead. In the multihop network model, the use of CSMAWithoutACK significantly reduces the packet average delay and the MAC scheme overhead, and both CSMAWithoutACK and CSMAWithACK achieve more than 90%packet delivery ratio. Therefore, CSMAWithoutACK (with no handshaking via request‐to‐send and clear‐to‐send control packets) is the most appropriate MAC protocol to be used in multihop EM‐based underwater surveillance networks. © Her Majesty the Queen in Right of Canada 2014. Reproduced with the permission of the Minister of Industry Canada

Recently, the use of digital beamforming (DBF) antennas has been drawing lots of interest in airborne platforms for resolving the network partition problem in airborne mobile ad hoc networks (MANETs). In this paper, properties of the network capacity of an airborne MANET with DBF antennas are investigated. This paper considers an ad hoc network consisting of a number of uniformly distributed airborne platforms in a bounded area. These platforms are either directly or indirectly connected with each other through DBF antennas, and form an airborne MANET. We first formulate a digital beamforming antenna system model, referred to as the omni-direction plus sector (OPS) model, and then carry out an exact analysis for the network capacity. The OPS model characterizes the radiation pattern of a DBF antenna. Under the condition that a Hamiltonian path exists in the network, an explicit expression is derived for the network capacity. We show that, for fixed values of the OPS model, the network capacity increases as the network size increases until it reaches an optimal value. If the network size continues to increase, the network capacity will decrease until it reaches zero. Explicit expressions for the optimal network size and the maximum network capacity are also obtained. Finally, numerical results are presented. It is shown that both the optimal network size and the maximum network capacity increase as the antenna beamwidth decreases. They increase slowly when the beamwidth is large, but as the antenna beam becomes narrower, they increase faster.

Multilateration is a fundamental localization technique for wireless sensor network applications. Classical multilateration techniques typically assume that the anchor locations are known and error free, an assumption that is always not valid in practice. Although the popular total least squares (TLS) method is able to take into account such errors in general, it requires that the noise components in the formulated data matrices be identically, independently distributed. In multilateration localization, however, it can be shown that the noise components in the formulated equations are algebraically related. In this paper, we formulate multilateration for sensor localization based on the use of the constrained total least squares (CTLS) method. By assuming that distance measurement errors are relatively small and can be neglected, we show that the CTLS solution leads to a weighted least squares problem. Computer simulations are used to demonstrate the effectiveness and performance of the proposed technique.

Code division multiple access mobile ad hoc networks (CDMA-MANETs) are envisioned to be the next-generation networking architecture for networking military platforms in a battlefield. In this paper we consider a CDMA ad hoc network consisting of multiple unmanned aerial vehicles (UAVs). We propose a token-based connectivity update scheme to solve the code collision problem in assigning code channels as well as the network link update problem for the CDMA UAV ad hoc network. Our proposed scheme uses a token message, which continuously circulates around the network in a non-predetermined order, to conduct assignment of code channels for each UAV. By using the broadcast properties of the wireless communication media, our proposed scheme is able to discover new or lost neighbors almost in real time. Moreover, the proposed token-based connectivity update scheme implements spatial reuse of code channels, which is mandatory in large-scale ad hoc networks due to the limited size of the CDMA code set. We then derive a theoretical result for approximating the connectivity update latency, which is further verified through computer simulations.

Recent advances in interference cancellation and signal processing techniques can enable full-duplex radios and multi-packet reception (MPR) capability, which will have significant impacts on the medium access control (MAC) design. In this paper, we study the MAC design in UAV ad-hoc networks with full-duplex radios and MPR. To efficiently handle the highly mobile environment of a UAV ad-hoc network, a token-based technique is used for updating information in the network. The MAC scheme in the presence of perfect and imperfect channel state information are formulated as a combinatorial optimization problem and a discrete stochastic optimization problem, respectively. Simulation results are presented to show the effectiveness of the proposed MAC.

As a result of high mobility of Unmanned Aerial Vehicles (UAVs), designing a good routing protocol is challenging for Unmanned Aeronautical Ad-hoc Networks (UAANETs). Geographic-based routing mechanisms are seen to be an interesting option for routing in UAANETs due to the fact that location information of UAVs is readily available. In this paper, a combined routing protocol, called the Reactive-Greedy-Reactive (RGR), is presented for UAANET applications, which combines the mechanisms of the Greedy Geographic Forwarding (GGF) and reactive routing. The proposed RGR employs location information of UAVs as well as reactive end-to-end paths in the routing process. Simulation results show that RGR outperforms existing protocols such as Ad-hoc On-demand Distance Vector (AODV) in search UAANET missions in terms of delay and packet delivery ratio, yet its overhead is similar to traditional mechanisms.

Due to the availability of location information in unmanned aerial vehicles (UAVs), we propose to use geographic routing mechanisms as a core forwarding protocol in unmanned aeronautical ad-hoc networks (UAANETs) for the purpose of reducing routing overhead. As a result, this paper investigates the performance of the core forwarding mechanism i.e. the greedy geographic part. Since the forwarding mechanism for dynamic UAANETs with many statistical inter-dependencies is complex, a closed-form model does not exist. Therefore, a quadratic polynomial estimation is proposed for computing the success probability of greedy geographic forwarding based on the results of a set of realistic Monte Carlo simulations. This mathematical model can later be used to predict and evaluate the performance of other greedy-based geographic routing protocols for UAV applications.

Cognitive radio ad hoc networks (CRAHNs) have become a popular network architecture for connecting mobile nodes thanks to the flexibility and adaptability of such type of network. In this paper, we propose a novel scheme for efficient routing design in CRAHNs. The proposed routing scheme firstly forms a simple directed graph for the given physical network. Using the simple directed graph, multiple optimal routing paths can be computed for a pair of cognitive radio users. An optimal routing path minimizes both the hop count and the adjacent hop interference. Examples are used to demonstrate the performance and efficiency of the proposed CRAHN routing technique. Results are also compared with other existing routing techniques for CRAHNs.

In multipath packet data networks, packets may reach the receiver out-of-sequence, i.e., packets arrive at the receiver in a sequence different from their egressing order at the transmitter. In practice, however, many applications require an in-sequence packet delivery, meaning that packets need to be delivered to an application on the receiver in their original order at the transmitter. The in-sequence packet delivery is usually implemented through the approach of packet resequencing. In this paper, a multipath data network with packet resequencing is modeled and the asymptotic properties of the steady-state probability distribution of the resequencing queue length are studied. The assumptions used are that the packets sent from the transmitter according to a Poisson process, and the transmission period of a packet along a route follows an exponential distribution. An asymptotic distribution function of the resequencing queue length is derived for a large queue length in the steady state of the network. Numerical and simulation examples are presented to validate the derived result. Through comparisons of large deviation and asymptotic values of the resequencing queue length distribution, we show that the asymptotic result provides a better approximation to the distribution function of the resequencing queue length than the large deviation result reported in the literature.

In a mobile ad-hoc network (MANET), node mobility has a significant impact on the performance of routing protocols. Most of the previous research has been focused on entity mobility models, i.e., movements of the mobile nodes are independent of each other. In this paper, we investigate the impact of swarming behavior of mobile nodes, as observed in many mobile networks, on the performance of MANET routing protocols. The effects of coordinated movements of mobile nodes are characterized by using a Markov chain, through which a quantized collaboration degree is defined. Based on the swarm mobility model, we analyze the probabilistic properties of hop count as a complement to those analytical studies on packet delay performance. With a medium access control model, we derive an upper and a lower bound of routing overhead for MANET proactive routing protocols. Simulations are used to demonstrate the validity of the derived analytical expressions. Numerical and simulation results show that more coordinated movements of the nodes reduce the number of control packets required to be disseminated over the network, and in turn the routing overhead.