Hidden Terminals Research Articles

Performance and Reliability Analysis of Prioritized Safety Messages Broadcasting in DSRC With Hidden Terminals

In this paper, we design a mathematical model for performance and reliability evaluation of the IEEE 802.11p Enhanced Distributed Channel Access (EDCA) broadcast scheme in Dedicated Short-Range Communication (DSRC) with the presence of hidden terminals. Specifically, we first introduce a more accurate semi-Markov process (SMP) model to portray the channel contention among multiple types of safety messages and their backoff behavior in DSRC based vehicular ad hoc networks (VANETs) with the influence of hidden terminals. Each type of safety message's generation and service in an individual vehicular node is modeled leveraging a unique M/G/1/K queue. For the channel contention, the SMP model interrelates with theM/G/1/K queue via fixed-point iteration. Additionally, grounded on the solution of fixed-point iteration, we acquire the performance indices such as packet delay (PD), packet delivery rate (PDR), and packet reception rate (PRR). The new SMP model considers the IEEE 802.11p EDCA backoff counter process, unsaturated packet arrivals, limited MAC queue length, hidden terminals, Nakagami-m fading channel with distance-related path loss, and distinct transmission, carrier sensing and interference ranges. Eventually, we validate the correctness of the model through the comparison between the numerical and simulation results under different network parameters and prove that the proposed model has an advantage over the existing models in analyzing the impact of hidden terminals on PDR and PRR.

Media Access Control in Large-Scale Internet of Things: A Review

The Media Access Control (MAC) serves as an imperative part of wireless communication networks which enables efficient provisioning of communication resources for device interconnectivity and ensures Quality of Service (QoS). The emergence of Large-Scale Internet of Things (LS-IoT) networks is characterised by a multi-domain distributed wireless communication network that provides end-to-end connectivity for a multitude of active heterogeneous Machine-to-Machine (M2M) devices. The nature of LS-IoT networks requires robust and scalable MAC protocols to manage concurrent, dynamic and massive media access and resource allocation. Several reviews have been conducted on MAC protocols with a handful of them focused on LS-IoT networks or massive M2M networks. In this paper, the characterisation of LS-IoT networks and the MAC component are extensively discussed delineating the impact of LS-IoT on the MAC. Emerging research issues on the MAC for LS-IoT networks including high collision probability, high control overheads, spectrum constraints, timing constraints, hardware constraints, energy consumption and hidden terminals are discussed. Some recently proposed solutions in literature for enhancing the MAC in LS-IoT networks are discussed under LS-IoT specific MAC protocol enhancement classifications. The contributions and drawbacks of the recent solutions in literature are discussed and summarised. The Future direction that is oriented towards the use of virtualisation within the framework of Network Function Virtualisation (NFV) and Software-Defined Networking (SDN) approaches is proposed. This is aimed at providing a dynamic distributed multidimensional MAC resource scaling approach for LS-IoT access network devices to ensure a robust and effective MAC for massive M2M devices in LS-IoT networks.

Analysis of hidden terminal\u2019s effect on the performance of vehicular ad-hoc networks

Vehicular ad-hoc networks (VANETs) based on the IEEE 802.11p standard are receiving increasing attention for road safety provisioning. Hidden terminals, however, demonstrate a serious challenge in the performance of VANETs. In this paper, we investigate the effect of hidden terminals on the performance of one hop broadcast communication. The paper formulates an analytical model to analyze the effect of hidden terminals on the performance metrics such as packet reception probability (PRP), packet reception delay (PRD), and packet reception interval (PRI) for the 2-dimensional (2-D) VANET. To verify the accuracy of the proposed model, the analytical model-based results are compared with NS3 simulation results using 2-D highway scenarios. We also compare the analytical results with those from real vehicular network implemented using the commercial vehicle-to-everything (V2X) devices. The analytical results show high correlation with the results of both simulation and real network.

Efficiency and Detectability of Random Reactive Jamming in Carrier Sense Wireless Networks

A natural basis for the detection of a wireless random reactive jammer (RRJ) is the perceived violation by the detector (typically located at the access point (AP)) of the carrier sensing protocol underpinning many wireless random access protocols (e.g., WiFi). Specifically, when the wireless medium is perceived by a station to be busy, a carrier sensing compliant station will avoid transmission while a RRJ station will often initiate transmission. However, hidden terminals (HTs), i.e., activity detected by the AP but not by the sensing station, complicate the use of carrier sensing as the basis for RRJ detection since they provide plausible deniability to a station suspected of being an RRJ. The RRJ has the dual objectives of avoiding detection and effectively disrupting communication, but there is an inherent performance tradeoff between these two objectives. In this paper we capture the behavior of both the RRJ and the compliant stations via a parsimonious Markov chain model, and pose the detection problem using the framework of Markov chain hypothesis testing. Our analysis yields the receiver operating characteristic of the detector, and the optimized behavior of the RRJ. While there has been extensive work in the literature on jamming detection, our innovation lies in leveraging carrier sensing as a natural and effective basis for detection.

An Efficient Broadcast Scheme for Safety-Related Services in Distributed TDMA-Based VANETs

The medium access control (MAC) protocol should provide an efficient broadcast service to support the high-priority safety applications in vehicular ad hoc networks (VANETs). Basic safety messages (BSMs) transmitted through vehicle-to-vehicle and vehicle-to-infrastructure architectures are the most fundamental of these applications. The periodic transmission of BSMs results in a heavy burden on the load of the VANETs when traffic density is high, and the presence of hidden terminals degrade the performance of the network. This letter introduces a distributed time division multiple access (TDMA)-based scheme that controls the transmission range to improve the efficiency of BSM transmissions in VANETs. The transmission collisions can be reduced without lowering the awareness quality of the surrounding nodes at a close range. Meanwhile, merging collisions can be pre-detected and eliminated by cooperation among the nodes. Simulation results demonstrate that our strategies can provide an efficient and reliable BSM broadcast service.

A Simple and Practical Scheme Using Multiple Channels for Improving System Spectral Efficiency of Highly Dense Wireless LANs

As the density of wireless LANs increases, performance degradation caused by hidden terminals and exposed terminals becomes significant. These problems come from carrier sensing based medium access control used in current wireless LANs. Hidden terminals are created if carrier sense threshold is too high, whereas exposed terminals are created if carrier sense threshold is too low. A good threshold depends on how far nodes are placed from their destinations, but that cannot be controlled by the system. In this paper, we propose a simple scheme that makes use of multiple channels. Multiple channels could be utilized by equipping multiple radios or using advanced hardware such as SDR to divide a single channel into multiple channels. Nodes are assigned channels based on their estimated distance from the AP. Once the assignment is done, carrier sense threshold for the channel is selected so that as many concurrent transmissions take place as possible, while preventing hidden terminals. Simulation results show that the proposed mechanism achieves significantly higher throughput without causing starvation at the edge nodes.

Packet Rate Adaptation Protocol Based on Bloom Filter for Hidden Node Avoidance in Vehicular Ad-Hoc Networks

Most of the vehicular ad-hoc networks (VANETs) use the medium access control (MAC) layer of IEEE 802.11p, which is an extension of IEEE 802.11a standard. One of the critical issues with IEEE 802.11 networks is the hidden terminal problem. IEEE 802.11 networks use Request To Send (RTS) and Clear To Send (CTS) mechanism to alleviate the hidden terminal problem. The RTS/CTS mechanism, however, is inapplicable in broadcast communication. Since the safety data in VANET is transmitted over broadcast, the hidden terminal collision is still a critical problem. In this paper, we propose a hidden terminal collision mitigation protocol for broadcast communication of safety data, called Packet Rate Adaptation based on the Bloom filter (PRAB). The protocol derives the optimal packet generation rate as a function of the average number of hidden terminals. To estimate the number of hidden terminals, we introduce a notion of Bloom filter, which piggybacks the neighbor vehicles’ information at a low overhead of packet size. We implemented the proposed protocol and evaluated with various vehicular networks. The simulation results exhibit that the proposed protocol provides 90% or higher packet reception probability even for high vehicle density networks, which correspond to 15% ~24% improvement over the previous protocols considered.

Performance Evaluation of Joint Placement and Sleep Scheduling of Grid-Connected Solar Powered Road Side Units in Vehicular Networks

Ensuring ubiquitous connectivity in vehicular ad hoc networks (VANETs) has gained enormous importance in the research community. In this direction, placing a large number of road side units (RSUs) in the scenario has emerged as a solution. Although placing more RSUs leads to high coverage, it also leads to high deployment cost, operational cost, and total energy consumed. While optimal RSU placement helps to reduce cost, efficient sleep scheduling helps to reduce energy consumption at RSUs. In order to achieve both the benefits, for the first time, we propose joint placement and sleep scheduling of RSUs in a VANET environment. We perform a detailed analysis of the probability of successful packet delivery and expected vehicle-to-RSU delay for a packet by considering the presence of hidden terminals and retransmissions, and by modeling the buffer of a vehicle as an M/M/1 queue. We also formulate an optimization problem which captures the behavior of a realistic scenario and propose an energy efficient candidate location selection algorithm to jointly perform placement and sleep scheduling of grid-connected solar powered RSUs. Our simulation results show that the proposed approach performs better than the uniform placement strategy with and without sleep scheduling of RSUs and exhaustive search without sleep scheduling of RSUs. Also, the results obtained are close to the best case—exhaustive search with sleep scheduling of RSUs. Our analytical results are in good agreement with the simulation results.

Performance Analysis of License Assisted Access LTE with Asymmetric Hidden Terminals

License Assisted Access (LAA) LTE (LTE-LAA) is a new type of LTE that aggregates the licensed LTE bands with the unlicensed bands via carrier aggregation. To operate in unlicensed bands, LTE-LAA adopts the listen-before-talk policy and designs its channel access mechanism similar to WLAN's DCF. In this paper, we consider an LAA network consisting of an LTE-LAA eNB coexisting with a Wi-Fi STA, and capture the {\em asymmetric hidden terminal problem} where the eNB recognizes the STA while the opposite is not true, which is caused by the asymmetric CCA thresholds between them. We model the network as a joint Markov chain (MC) consisting of two individual MCs, and derive its steady-state probabilities, throughput, and channel access delay along with other key metrics like transmit, busy, collision, and doubling probabilities. Through extensive evaluation, we confirm that the proposed model well predicts the dynamics of the LAA network, and identify important design guidelines for fair coexistence between LTE-LAA and WLAN as follows. First, LTE-LAA should design its contention window (CW) doubling policy by considering Wi-Fi's packet duration and subframe-dependent collision probabilities. Second, there exists a tradeoff between throughput and channel access delay, according to which the CW doubling policy should be adapted.

Hidden Terminal Aware Clustering for Large-scale D2D Networks

In device-to-device (D2D) environments where a number of wireless nodes are connected in ad hoc mode, the most popular mechanism for multiple access control is CSMA/CA as in IEEE 802.11 networks. Consequently, a considerable number of hidden terminals can be found in large-scale and dense D2D networks, and usually they may cause severe performance problems. Previous studies to improve the hidden terminal problem in dense wireless networks have suggested various solutions: e.g., channel assignment, transmit power control, and grouping schemes. In this paper, we adopt a different approach—a hidden terminal aware clustering mechanism, which detects the hidden terminals and enables the nodes to form clusters based on the detected information. A simple polling-based channel access scheme is also proposed such that all nodes belonging to a same cluster can access channel through their neighbors’ polling, which eliminates the hidden terminal problem. Mathematical analysis and simulations show that our proposed scheme significantly improves the performance of large-scale D2D networks.

Cooperative Spectrum Sensing: A Blind and Soft Fusion Detector

Cooperative spectrum sensing has been studied to combat the hidden terminal problem by exploiting the spatial diversity in cognitive radio (CR) networks. This paper concerns blind cooperative spectrum sensing with soft fusion, where the a priori knowledge of channels and primary signals is unavailable, and soft information is transmitted from each secondary user (SU) to a fusion center for detection. We first introduce the Quade test to design a blind detector. Then, a new detector with both lower computational complexity and lower overhead is derived, where only the estimated power and the variance of the instantaneous power at each SU are required at the fusion center. The analytical expressions for the detection performance, in terms of false-alarm probability and detection probability, are derived for the proposed detector. Simulation results are provided to validate the theoretical analyses and demonstrate the superior performance of proposed detector compared to the state-of-the-art detectors. It is also shown that, with the increase of the number of hidden terminals in the CR, the proposed detector can maintain high detection performance while the conventional detectors exhibit rapid performance degradation.

Packet relay‐assisted V2V communication with sectorised relay station employing payload combining scheme

A reliable vehicle-to-vehicle communication (V2VC) is essential to enable safe and highly automated driving system. Addition of a relay station (RS) can improve packet delivery rate (PDR) of CSMA/CA-based V2VC. However, the improvement is limited by packet collision at RS due to a hidden terminal (HT). This HT problem can be alleviated by employing sectorised receive antenna at RS, i.e. sectorised relay-assisted (SR-) V2VC. However, SR-V2VC still faces another problem, i.e. packet congestion at RS under high traffic conditions due to the improved packet reception rate. This leads to packet drop at RS and hence limits the improvement brought by SR-V2VC. Consequently, it is crucial to introduce a kind of traffic congestion avoidance methods to RS. In this article, the authors propose SR-V2VC with a payload combining forwarding (PCF) method (SR-V2VC/PCF) and theoretically evaluate the system performance using a CSMA/CA collision model. Large-scale computer simulations are also conducted to confirm the performance improvement brought by SR-V2VC/PCF. It is shown that the lowest broadcast PDR of 62% for the non-relay system is improved to higher than 81% by SR-V2VC/PCF and the directivity of the sector antenna has impact on the benefit of the proposed scheme.

Saturation Throughput Analysis of an Asymmetric Full-Duplex MAC Protocol in WLANs With Hidden Terminals

The wireless in-band full-duplex technique enables wireless nodes to transmit and receive in the same channel simultaneously. To fully and effectively leverage this capability of the IBFD technique, new full-duplex medium access control (FD MAC) protocols that accommodate the features of the IBFD technique must be designed and analyzed. In this paper, we first propose an asymmetric FD MAC protocol, and then we develop an analytical model for the proposed protocol to evaluate the saturation throughput performance of wireless local area networks in the presence of hidden terminals. In the proposed protocol, asymmetric full-duplex transmissions can be established with the access point (AP) and two stations that hidden from each other. Thus, the well-known interstation interference problem in asymmetric full-duplex transmissions can be overcome. In the developed model, we adopt the stationary distribution of the backoff counter values at the beginning of a generic transmission to characterize the behavior of a node. The saturation throughput is then derived based on the stationary distribution. The accuracy of the proposed analytical model is verified through simulations. Using the proposed analytical model, the saturation throughput performance of the FD MAC protocols is studied with respect to different numbers of stations in each region and the minimum contention windows. In addition, the effects of hidden terminals on performance are thoroughly investigated, since the hidden terminals play an important role in the saturation throughput. Moreover, we compare the saturation throughput performance between symmetric and asymmetric FD MAC protocols to demonstrate the gains provided by asymmetric full-duplex transmissions.

The analysis of IEEE 802.11 PCF protocol based on LEO satellite Wi-Fi

In view of the problem of long propagation delay, hidden terminals and serious user conflicts in LEO satellite Wi-Fi scenario, this paper analysis the incompatibility of 802.11 DCF protocol briefly. A scheme of PCF polling mechanism based on priority is proposed and the frame format is adaptively modified. Through MATLAB simulation, the system throughput of the original scheme and the improvement scheme over the different transmission distance and nodes are analysed. The simulation results show that the improved PCF protocol can improve the throughput under the multi-user over long distances.

In-band full duplex wireless communications and networking for IoT devices: Progress, challenges and opportunities

The new era of IoT devices call for wireless communications with high spectral efficiency because of the congested spectral space in reality. Current wireless communication systems work at half duplex mode in an either time-division or frequency-division approach to transmit and receive wireless signals. Half duplex results in poor spectral efficiency because only unidirectional communications are allowed. Recent research has aimed at enabling In-band full duplex wireless communication that allows a wireless node for simultaneous transmission and reception of signals. The benefits of in-band full duplex includes the doubled spectra efficiency which is in great need in the rapidly growing IoT devices and the potentials to solve the hidden terminals, unfairness and the exposed problems presented in the current single channel half duplex wireless communications. This paper investigates the research background and progress of in-band full duplex wireless. It also presents the research problems as well as opportunities. In addition, this paper summarizes the performance of literature solutions with experiment results in achieving in-band full duplex wireless communications. It also compares the Throughput and Packet Reception Ratio performance of full duplex to that of half duplex from a Software Defined Radio platform.

On the Performance of IEEE 802.11p and LTE-V2V for the Cooperative Awareness of Connected Vehicles

To improve safety on the roads, next-generation vehicles will be equipped with short-range communication technologies. Many applications enabled by such communication will be based on a continuous broadcast of information about the own status from each vehicle to the neighborhood, often referred as cooperative awareness or beaconing. Although the only standardized technology allowing direct vehicle-to-vehicle (V2V) communication has been IEEE 802.11p until now, the latest release of long-term evolution (LTE) included advanced device-to-device features designed for the vehicular environment (LTE-V2V) making it a suitable alternative to IEEE 802.11p. Advantages and drawbacks are being considered for both technologies, and which one will be implemented is still under debate. The aim of this paper is thus to provide an insight into the performance of both technologies for cooperative awareness and to compare them. The investigation is performed analytically through the implementation of novel models for both IEEE 802.11p and LTE-V2V able to address the same scenario, with consistent settings and focusing on the same output metrics. The proposed models take into account several aspects that are often neglected by related works, such as hidden terminals and capture effect in IEEE 802.11p, the impact of imperfect knowledge of vehicles position on the resource allocation in LTE-V2V, and the various modulation and coding scheme combinations that are available in both technologies. Results show that LTE-V2V allows us to maintain the required quality of service at even double or more the distance than IEEE 802.11p in moderate traffic conditions. However, due to the half-duplex nature of devices and the structure of LTE frames, it shows lower capacity than IEEE 802.11p if short distances and very high vehicle density are targeted.

Comments on “Interference-Based Capacity Analysis of Vehicular Ad Hoc Networks”

A new effective interference-based capacity model was proposed for vehicular ad hoc network safety message broadcast scenario in M. Ni et al. ( Commun. Lett. , vol. 19, no. 4, pp. 621–624, Apr. 2015). This letter is a reconsideration and extension of the model in Ni et al. . First, we point out that the analysis in Ni et al. is incomplete and show a new derivation of the node transmission probability and the SIR distribution accounting for the impact of asynchronous timing of hidden terminals and all possible interference occurrence cases. Second, the analysis is extended to the derivation of other important quality of service metrics, such as packet reception probability, packet reception ratio, and transmission capacity. The proposed analysis is cross validated by MATLAB, PYTHON, and NS2 simulations.

Throughput optimization for dual collaborative spectrum sensing with dynamic scheduling

Cognitive radio technology is envisaged to alleviate both spectrum inefficiency and spectrum scarcity problems by exploiting the existing licensed spectrum opportunistically. However, cognitive radio ad hoc networks (CRAHNs) impose unique challenges due to the high dynamic scheduling in the available spectrum, diverse quality of service (QOS) requirements, as well as hidden terminals and shadow fading issues in a harsh radio environment. To solve these problems, this paper proposes a dynamic and variable time-division multiple-access scheduling mechanism (DV-TDMA) incorporated with dual collaborative spectrum sensing scheme for CRAHNs. This study involves the cross-layered cooperation between the Physical (PHY) layer and Medium Access Control (MAC) layer under the consideration of average sensing time, sensing accuracy and the average throughput of cognitive radio users (CRs). Moreover, multiple-objective optimization algorithm is proposed to maximize the average throughput of CRs while still meeting QOS requirements on sensing time and detection error. Finally, performance evaluation is conducted through simulations, and the simulation results reveal that this optimization algorithm can significantly improve throughput and sensing accuracy and reduce average sensing time.

Evaluation of a duty-cycled asynchronous X-MAC protocol for vehicular sensor networks

An asynchronous medium access control (MAC) duty-cycled protocols have higher energy efficiency and lower packet latency than synchronized ones due to reduced idle listening. Moreover, they provide efficient utilization of energy supplied to mobile sensors. They are considered very important in MAC protocols due to the adverse effects of hidden terminals which causes energy consumption in sensor networks. Therefore, in this paper, the impact of hidden terminals on the performance of an asynchronous duty-cycled MAC protocol X-MAC for vehicle-base sensor is investigated via analysis and simulations. We propose a Markov model to analyze the quality-of-service (QoS) parameters in terms of energy consumption, delay, and throughput. Our analytical model provides QoS parameter values that closely match the simulation results under various network conditions. Our model is more computationally efficient and provides accurate results quickly compared with simulations. More importantly, our model enables the designers to obtain a better understanding of the effects of different numbers of mobile sensor nodes and data arrival rates on the performance of an asynchronous MAC duty-cycled protocol.

Neighbors-Aware Proportional Fair scheduling for future wireless networks with mixed MAC protocols

In this paper, we consider a beyond-5G scenario, where two types of users, denoted as scheduled and uncoordinated nodes, coexist on the same set of radio resources for sending data to a base station. Scheduled nodes rely solely on a centralized scheduler within the base station for the assignment of resources, while uncoordinated nodes use an unslotted Carrier Sense Multiple Access (CSMA) protocol for channel access. We propose and evaluate through simulations: (a) a novel centralized resource scheduling algorithm, called Neighbors-Aware Proportional Fair (N-PF) and (b) a novel packet length adaptation algorithm, called Channel-Aware (CA) Packet Length Adaptation algorithm for the scheduled nodes. The N-PF algorithm considers the uplink channel state conditions and the number of uncoordinated nodes neighboring each scheduled node in the aggregate scheduling metric, in order to maximize packet transmission success probability. The CA algorithm provides an additional degree of freedom for improving the performance, thanks to the fact that scheduled nodes with lower number of hidden terminals, i.e., having higher packet capture probability, are assigned longer packet transmission opportunities. We consider two benchmark schemes: Proportional Fair (PF) algorithm, as a resource scheduling algorithm, and a discrete uniform distribution (DUD) scheme for packet lengths distribution. Simulation results show that the proposed schemes can result in significant gain in terms of network goodput, without compromising fairness, with respect to two benchmark solutions taken from the literature.