A neighbor discovery algorithm for full duplex Ad Hoc networks with directional antennas

In this paper, we consider the neighbor discovery problem in Flying Ad Hoc Network using directional antennas. Based on realistic scenarios, the height of UAVs can be approximated to follow a Gaussian distribution. A novel 2-way neighbor discovery algorithm that adjusts the selection probability according to transmission space divided by pitch angle parameter is proposed. Then we derive analytical expressions of the probability of a successful discovery between two nodes and the expected value of time slots needed to complete the neighbor discovery. We also adopt a practical way to determine when to terminate the discovery procedure. Lastly, simulation results are presented to show the effectiveness of proposed algorithm.

In this paper, we consider the neighbor discovery problem in wireless ad hoc networks with directional antennas. One key performance measure is how long it takes to discover all the neighbors given that nodes do not have priori knowledge where their neighbors are. One common impression is that algorithms using directional transmission/receive take longer time than those algorithms using omni-antennas. In this paper, we prove that this is not the case. Furthermore, most of the proposed algorithms are 1-way only, which is not suitable for networks with directional antennas. We first propose three 2-way random neighbor discovery algorithms (based on the algorithms in [Vasuden et al., 2005]), two of which may still use omni-antennas in certain stages of the algorithms and a new scan based algorithm. Then we derive analytical expressions for the average number of slots required to discover all the neighbors for the three 2-way random algorithms and for two scan based algorithms. Analytic and simulation results are presented to compare 4 of the algorithms. From the numerical results, we conclude that scan-based all-directional algorithms give the best performance among all the algorithms considered. If designed properly, all-directional algorithms can discover neighbors in less time than those algorithms using omni-directional antennas.

Neighbor discovery is vital for initialing and maintaining self-organized ad hoc networks. In order to exchange advertise messages and learn about each other presence, nodes have to aim their antennas toward each other when they are only utilized by directional antennas. Since ad hoc networks nodes have no former information about each other, neighbor discovery in directional ad hoc networks becomes more challenging. An asynchronous pure directional quorum-based neighbor discovery technique is proposed for the first time in this paper. Using quorum system for realizing the pure directional asynchronous and deterministic neighbor discovery is the novelty of this approach. All nodes are able to find all their potential neighbors in a relatively small time interval using proposed and transmission scenario and neighbor discovery. The independency of quorum based neighbor discovery to omnidirectional antennas during discovery process divides this approach from former related solutions. The suggested approach, by means of quorum system guarantees at least a common active interval for any two reciprocal beams during neighbor discovery procedure. The correctness of quorum based neighbor discovery in directional ad hoc network is discussed besides evaluating by series of simulations. This approach can be classified as fully directional handshake-based deterministic neighbor discovery algorithm.

The unlicensed 60 GHz band brings the promise of multi-gigabit data rates to support new applications such as high definition video over wireless links. Signal propagation in the 60 GHz band significantly differs from that in the traditionally used 2.4 and 5 GHz bands. The propagation and penetration losses in the 60 GHz band are much higher. Furthermore, the signals are often reflected in indoor settings. Previous physical layer studies show that the use of directional antennas can significantly help in coping with these effects. In this paper, we address the problem of neighbor discovery in the 60 GHz band. We account for not only discovery via direct line-of-sight paths, but also via reflected beams. To the best of our knowledge, none of the previous efforts on higher layer protocols for use with directional antennas account for reflections. We consider two approaches for neighbor discovery (a) direct discovery where each node explicitly discovers its neighbors and, (b) gossip-based discovery where nodes exchange information with regards to their already discovered neighbors. We develop analytical models to capture the performance of the two approaches and validate the models via simulations in indoor settings with obstacles that reflect the transmitted signals. As one might expect, the gossip based discovery incurs a lower neighbor-discovery latency than direct discovery. We examine the impact of system parameters such as varying beamwidth and node density. Our study provides insights on the right choice of system parameters for efficient neighbor discovery in the 60 GHz regime.

The use of directional antennas in Ad Hoc networks can improve the performance of networks, but it will make neighbor discovery challenging. The neighbor discovery algorithms based on reinforcement learning improve the efficiency of neighbor discovery by learning the experience of the process according to the reward obtained by the nodes without the prior location information of neighbors. Four reinforcement learning algorithms, including Q-Learning, SARSA, Q(λ), and SARSA(λ), are used to simulate the time to discover all neighbors and the neighbor discovery ratio in different conditions. According to the simulation results, compared with the completely random algorithm, the neighbor discovery algorithm based on Q-Learning has the largest increase in efficiency with the 1-way handshake, especially in the network with high node density and low speed movement of nodes.

Neighbor discovery in wireless networks with sectored antennas

Network connectivity and link quality information are the fundamental requirements of wireless sensor network protocols to perform their desired functionality. Most of the existing discovery protocols have only focused on the neighbor discovery problem, while a few number of them provide an integrated neighbor search and link estimation. As these protocols require a careful parameter adjustment before network deployment, they cannot provide scalable and accurate network initialization in large-scale dense wireless sensor networks with random topology. Furthermore, performance of these protocols has not entirely been evaluated yet. In this paper, we perform a comprehensive simulation study on the efficiency of employing adaptive protocols compared to the existing nonadaptive protocols for initializing sensor networks with random topology. In this regard, we propose adaptive network initialization protocols which integrate the initial neighbor discovery with link quality estimation process to initialize large-scale dense wireless sensor networks without requiring any parameter adjustment before network deployment. To the best of our knowledge, this work is the first attempt to provide a detailed simulation study on the performance of integrated neighbor discovery and link quality estimation protocols for initializing sensor networks. This study can help system designers to determine the most appropriate approach for different applications.

SummaryIn recent years, neighbor discovery techniques using directional antennas have attracted widespread attention. Most currently available directional neighbor discovery techniques are designed based on two‐dimensional (2D) space. Although these algorithms can accomplish the discovery between nodes, the algorithm portability is poor for three‐dimensional (3D) platforms, and the application scenarios are limited since new communication scenarios such as unmanned aerial vehicle (UAV) groups and maritime fleets emerge where information needs to be delivered in real time and nodes are located in 3D space. This paper proposes a new deterministic directional neighbor discovery algorithm in 3D space named 3D scan‐based algorithm (3D‐SBA) to meet the needs of the line‐of‐sight (LOS) scenes. Four existing neighbor discovery algorithms, namely, SBA‐based random mode selection (SBA‐R), quorum, complete random algorithm (CRA), and SBA‐based leader election algorithm (LE), have been extended to our proposed 3D algorithm model for simulation and comparative analysis with 3D‐SBA. The simulation results show that the 3D‐SBA algorithm consumes 51.15%, 180.20%, 9.48%, and 17.49% of the time slots compared with the four existing algorithms mentioned above. However, the quorum algorithm has a very high node collision rate, up to 92.11%. Ultimately, the 3D‐SBA algorithm has the best performance considering the conflicts and the density of network nodes.

One of the key element in performance measurement for a neighbor discovery algorithm with switched beam antennas is how long it takes to discover the neighbors given that nodes do not have any prior knowledge about their neighbors. An impression we may have in neighbor discovery is that algorithms based on directional antennas takes longer time for a node to discover all its neighbors than those entirely based on omnidirectional antennas. We propose two neighbor discovery schemes, one is based on time slotting and the other on the well known CSMA/CA unslotted version. We evaluate the time that the sink needs to discover its neighbors when it is equipped with a switched beam antenna, and when it uses an omnidirectional antenna. Through our simulation results, we show that when neighbor discovery algorithms based on directional antennas are correctly designed, they achieve the same order of performance in terms of time needed by the sink to discover all its neighbors as those based on omnidirectional antennas. Our simulation results also show that when using a switched beam antenna and CSMA/CA algorithm for medium access at the sink, the discovery delay is higher.

Many wireless applications urgently demand an efficient neighbor discovery protocol to build up bridges connecting user themselves or to some service providers. However, due to intrinsic constraints of wireless devices, e.g., limited energy and error of clock synchronization, there is still absence of effective and efficient neighbor discovery protocols in the literature. In this work, we propose neighbor discovery protocols for the following two problems. First, we study Asynchronous Symmetry Neighbor Discovery problem, in which potential neighbor devices with asynchronous time clocks but the same duty cycle aim to find each other. Second, we propose an efficient protocol (utilizing Bouncing strategy) named BlindDate with guaranteed worst-case performance ${ 9\over 10} (1+\delta)^2x^2$ where $\delta$ is a small fraction of the length of a time slot unit and ${ 1\over x}$ is the duty cycle. Third, we extend this strategy to address Asynchronous Asymmetry Neighbor Discovery problem, in which both the time clock and the duty cycles of potential neighbors are considered to be heterogeneous. We conduct extensive experiments and simulations to examine the feasibility and efficiency of the proposed protocols, and results show that BlindDate greatly outperforms existing approaches in average-case. Compared with known protocols, BlindDate also achieves a better worst-case discovery latency bound (e.g., $10$ percent performance gain comparing with Searchlight [1] ).

In this paper, we present simulation results of an all directional transmission and reception algorithm, proposed in Z. Zhang (2005), (named as LiSL/d for a link scheduler) in mobile wireless ad hoc networks with directional antennas. The all-directional algorithms are designed mainly for military applications and exploit the beamforming capabilities of smart antennas to tailor resource access according to the services desired for individual traffic flows while limiting interference, probability of detection and jamming in the network. Specifically, the newly proposed protocol offers four significant advantages: (1) it assumes only directional transmission/reception (no omni-directional or omni-capability is assumed at all), (2) it is distributed, that is, it relies on local information only, (3) it allocates slots to different links dynamically based on demand, (4) power control is easily carried out during neighbor discovery, reservation as well as data transmission period with very little overhead. To evaluate the performance of the proposed algorithms against with IEEE 802.11 omni protocol and the directional virtual carrier sensing (DVCS) protocol, extensive simulations have been conducted in QualNet for the Lakehurst scenario and some random network topologies. Simulation results show that without jamming, both LiSL/d and DVCS improve the network performance by about 3 times and LiSL/d also outperforms DVCS. When there is jamming, depending on the power level of jamming nodes, the percentage of packet received under LiSL/d can be 7 times higher than that of DVCS and IEEE 802.11 with omni-directional antennas

Homes, offices and vehicles are getting networked. This will enable context aware, autonomous operation of many support systems that could be controlled remotely. To achieve this there would be a large number of tiny devices - sensors and actuators - which are networked and they are termed generally as Internet of Things (IoT) devices. In future, they will be powered through harvested energy from the ambience to enable perennial lifetime and minimal manual maintenance. Some examples of energy sources are photovoltaic panels and piezoelectric crystals. Several challenges arise due to the nature of sources of energy. One of these challenges is that the devices (nodes) leave and re-enter networks due to fluctuating availability of harvested energy. As a result, the neighbor table maintained at each node changes quite often leading to complications in forming and maintaining routes. In fact initial neighbor discovery (ND) itself is a difficult task. Further, usage of directional antennas would increase the time taken to complete ND. We study such a network through exhaustive simulation study considering various parameters. We demonstrate the benefits and challenges of using directional antennas for ND. We present a scheme that nodes could use to discover their neighbor during initial deployment and another scheme that could be used for subsequent discovery on re-entry into the network. We show that a dedicated ND protocol is necessary for energy harvesting networks and that directional ND is beneficial in these networks under some circumstances.

In cognitive radio ad hoc networks each node scans and finds its own available frequency channel set for transmitting or receiving signals. Since nodes may be tuned on different frequencies and the nodes available channel sets are not the same, neighbor discovery becomes more challenging in self-organized mobile ad hoc networks with cognitive radios. This paper proposes a quorum-based neighbor discovery algorithm for asynchronous networks by taking advantage of quorum systems. The novelty of this approach is using quorum systems for neighbor discovery in neighbor discovery procedure. The proposed algorithm presents outstanding performance in both synchronous and asynchronous networks. In this approach due to the random back off time before each transmission and by using quorum-based algorithm the discovery performance is almost independent of the number of nodes in the network. The quorum system as the key idea in this approach, guarantees at least a common active interval for any two frequency channels. This approach can be classified as handshake-based deterministic neighbor discovery algorithm for cognitive radio networks. In this paper, the correctness of quorum-based cognitive discovery technique has been proved and its performance is evaluated with a number of simulations for various synchronous and asynchronous networks.

The millimetre wave (mmWave) band offers the potential for multi-gigabit indoor wireless personal area networks (WPANs). However, it has problems such as a short wavelength. To compensate, utilisation of directional antennas at the physical layer is recommended. For communications using this band, neighbour discovery using directional antennas (D-ND) is one of the crucial steps. In this study, the D-ND process is analysed mathematically for mmWave WPANs based on the concept of an exclusive region, and the values that are derived from the effect of using directional antennas. Maximising the neighbour discovery probability for a given amount of time is considered as an objective function. Performance measures are derived in closed forms, such as the probability of discovering a device for one self-advertising packet and the power-efficient sojourn time of a device in one direction. Numerical results are obtained using parameters based on the IEEE 802.15.3c standard. The results show that the efficiency of the D-ND depends not only on how often devices transmit a self-advertising packet, but also on antenna properties such as beamwidth. The mathematical analysis provides a theoretical basis for the D-ND process, and the obtained results illustrate the physical layer impact on neighbour discovery.

Deterministic estimator learning automata-based neighbor discovery schemes for D2D networks with directional antennas