Hidden Node Problem Research Articles

Energy and spectrum efficient retransmission scheme with RAW optimization for IEEE 802.11ah networks

Restricted Access Window (RAW) and group-based media access are new features that are exploited by IEEE 802.11ah standard to resolve massive access problem in Internet of Things (IoT) applications. Nevertheless, inefficient device grouping and inappropriate contention resolution in a RAW may still result in collisions and consequently lead to degradation of QoS, energy efficiency, and channel utilization. In existing works, contention resolution schemes schedule all failed devices to retransmit in the next slot of the RAW, which increases the probability of collisions. In this paper, we propose a new retransmission scheme that allows the collided devices of each RAW slot to have another transmission chance in one of the next µ upcoming slots, randomly. We represent the proposed retransmission method via a probabilistic model and formulate a problem based on it, to adjust the number of slots of each RAW with the aim of increasing overall energy efficiency and overall channel utilization regarding delay constraint of devices. Solving the formulated problem, a meta-heuristic algorithm is used to adjust the number of RAW slots and so the size of each RAW regarding the results of the device grouping algorithm. To better exploit the capabilities of the proposed idea, we suggest a load-aware and distance-based device grouping algorithm that not only considers the hidden node problem, but also attends to the load balance of the groups. Simulation results show that the proposed retransmission and RAW adjustment scheme alongside the proposed device grouping algorithm, improve energy efficiency and channel utilization by 25 % and 17 % respectively, and reduce the access delay by 31 % in average, compared to the previous retransmission method.

Performance Modeling of an NR-U and WiFi Coexistence System Using the NR-U Category-4 LBT Procedure and WiFi DCF Mechanism in the Presence of Hidden Nodes

The hidden-node problem is an important problem that should be considered in the design of a wireless communication system. This paper studies the performance modeling of an NR-U and WiFi coexistence system using the NR-U category-4 LBT procedure and WiFi DCF mechanism in the presence of hidden nodes. 2-D Markov models are first developed to describe the NR-U category-4 LBT procedure of an NR-U gNB and the WiFi DCF procedure of a WiFi AP, respectively, taking into account the effects of hidden nodes. Based on the two Markov models, theoretical models are further derived for analyzing the throughput of a gNB/AP and the delay of an NR-U/WiFi packet. Finally, the derived theoretical models are validated through simulation results and based on the theoretical models, the impacts of major system parameters on the system performance in terms of the throughput and packet delay are investigated, including the data packet arrival rate, the density, the sensing distance, and the channel transmission rate of a gNB.

Novel Emergency Message Dissemination in Vehicular Networks

The number of vehicles has increased proportionally over the last couple of times and this number is rising due to the increase in population extension and the number of vehicles that are manufactured every day. The high business viscosity leads to several problems, from which effectively propagating emergency messages is a major concern. VANETs (Vehicular Ad-hoc Networks), it is a vehicle networks of digital communication between cars, trucks, and also roadside units like antennas & buildings. In VANETs, significant challenges are faced, while disseminating the message across the network. The major challenges are the broadcast storm problem, hidden node problem, and packet collisions. We propose an Effective Emergency Message Dissemination Scheme (EEMDS) for urban VANETs. The scheme is grounded on our mobility metrics to escape communication outflow and to maintain the stability of the cluster structure. Every vehicle takes into account its direction and path loss factor for opting appropriate cluster head. Also, we introduce estimated link stability to choose a suitable dependent vehicle (an intermediary that communicates between multiple clusters) that reduces the number of retransmits and communication traffic in the network. Simulation results covey that NEMDS provides an acceptable end-to-end detention, information coverage, & packet delivery ratio compared to the eminent Emergency Messages dissemination schemes.

A Graph Convolution Network Based Adaptive Cooperative Spectrum Sensing in Cognitive Radio Network

The hidden node problem is one of the most challenging issue in Cooperative Spectrum Sensing (CSS). The system models adopted by the existing Deep Learning-based spectrum sensing methods have not focused on modeling the hidden node scenario in cognitive radio networks. Further, these methods are unable to adapt to the dynamic channel conditions in the wireless environment since they have not considered the effect of fading environment. Motivated from these limitations, we propose GCN-CSS, a novel Graph Convolution Network (GCN) based cooperative spectrum sensing methodology which adapts to the dynamic changes in the Cognitive Radio Network. To the best of the author's knowledge, this is the first work to apply GCN for solving CSS problem. We have considered a practical system model which handles the dynamic channel condition i.e. SUs with multiple antennas experiencing different fading models with different fading severity. We have also catered the scenario of imperfect reporting channel between the SUs and the fusion centre along with the imperfect sensing channel to prove the robustness of the proposed model. With sufficient simulations, the superiority of the proposed methodology is proven in different dynamic scenarios of the wireless environment.

Single decision reporting for cooperative spectrum sensing under erroneous feedback channels with Byzantine attack

Spectrum sensing based on a single user suffers from low detection performance due to fading, shadowing, and hidden node problems. Cooperative spectrum sensing (CSS) is thought to be a potential method to overcome these issues and improve detection performance in determining the available spectrum in cognitive radio (CR). However, CSS suffers in case of erroneous reporting channels, and it is also susceptible to Byzantine attacks by malicious users (MUs). In this paper, we first analyze the traditional CSS under erroneous feedback channels. And then, we extend the analysis to include erroneous reporting channels in the presence of the Byzantine attack. We propose a single decision reporting (SD-R) algorithm immune to erroneous reporting channels. The proposed algorithm also improves the performance under the Byzantine attack. With the proposed algorithm, MUs can attempt only false alarm attacks, whereas the miss detection attack is not possible. An extensive analysis is carried out, and the plots are shown to prove the superiority of the proposed algorithm.

Implementation of Hidden Node Detection Scheme for Self-Organization of Data Packet

The mobile nodes are infrequent movement in nature; therefore, its packet transmission is also infrequent. Packet overload occurred for routing process, and data are lossed by receiver node, since hackers hide the normal routing node. Basically, the hidden node problem is created based on the malicious nodes that are planned to hide the vital relay node in the specific routing path. The packet transmission loss occurred for routing; so, it minimizes the packet delivery ratio and network lifetime. Then, proposed enhanced self-organization of data packet (EAOD) mechanism is planned to aggregate the data packet sequencially from network structure. The hacker node present in routing path is easy to separate from network with trusty nodes. In order to secure the regular characteristics of organizer node from being confirmed as misbehaving node, the hidden node detection technique is designed for abnormal routing node identification. This algorithm checks the neighboring nodes that are hacker node, which hide the trust node in the routing path. And that trust nodes are initially found based on strength value of every node and assign path immediately. It increases network lifetime and minimizes the packet loss rate.

Evolved Wireless ad Hoc Network: Design and Operating Principle for Wireless Resource Management of Mobile Terminals

This paper proposes an evolved wireless ad hoc network (WANET) in which user equipment (UE) can manage radio resources by itself without the control by infrastructure. There are two independent channels in the proposed WANET, one is a data channel, the other is a tone channel for resource management. UEs allocate, occupy, and return resources by using tones in the tone channel. Although UEs do not exchange channel information with each other, they are able to occupy a clear one-hop area without a hidden node problem by setting the data communication area and the tone communication area differently. A UE occupying a resource performs a real time collision check on the occupied resource, and if a collision is detected, it is able to re-occupy a resource without collision. In this paper, we present the operating principle of the proposed WANET, and design its communication area, and analyze the average resource occupation time. Since the proposed WANET operates in a general communication environment that is not limited to special assumptions, it supports periodic and aperiodic communication and broadcast links and unicast links without hidden node problem, and could be utilized to various communication fields such as drones, vehicles, ships, and smartphones.

Space Division Multiple Access for Cellular V2X Communications

Vehicular communication is the backbone of future Intelligent Transportation Systems (ITS). It offers a network-based solution for vehicle safety, cooperative awareness, and traffic management applications. For safety applications, Basic Safety Messages (BSM) containing mobility information is shared by the vehicles in their neighborhood to continuously monitor other nearby vehicles and prepare a local traffic map. BSMs are shared using mode 4 of Cellular V2X (C-V2X) communications in which resources are allocated in an ad hoc manner. However, the strict packet transmission requirements of BSM and hidden node problem causes packet collisions in a vehicular network, thus reducing the reliability of safety applications. Moreover, as vehicles choose the transmission resources in a distributed manner in mode 4 of C-V2X, the packet collision problem is further aggravated. This paper presents a novel solution in the form of a Space Division Multiple Access (SDMA) protocol that intelligently schedules BSM transmissions using vehicle position data to reduce concurrent transmissions from hidden node interferers. The proposed protocol works by dividing road segments into clusters and sub-clusters. Several sub-frames are allocated to a cluster and these sub-frames are reused after a certain distance. Within a cluster, sub-channels are allocated to sub-clusters. We implement the proposed SDMA protocol and evaluate its performance in a highway vehicular network. Simulation results show that the proposed SDMA protocol outperforms standard Sensing-Based Semi Persistent Scheduling (SB-SPS) in terms of safety range and packet delay.

Communication-Aware Consensus-Based Decentralized Task Allocation in Communication Constrained Environments

Most of the consensus-based task allocation algorithms assume reliable and unlimited communication between the agents. However, this assumption can be easily violated in real environment with limited bandwidth and message collisions. This paper presents a deep reinforcement learning framework in which agents learn how to schedule and censor themselves amongst the other agents competing for access to a limited communication medium. In particular, the process learns to schedule the communication between agents to improve the performance of task allocation in environments with constrained communication in terms of limited bandwidth and message collision. The proposed approach, called Communication-Aware Consensus-Based Bundle Algorithm (CA-CBBA), extends the previous CBBA that the learned communication policy enables efficient utilization of the shared medium by prioritizing agents with messages that are important for the mission. Furthermore, agents in denser parts of the network are censored appropriately to alleviate the message collision and hidden node problems. We evaluate our approach in various task assignment scenarios, and the results show that CA-CBBA outperforms CBBA in terms of convergence time, rate of conflict resolution, and task allocation reward. Moreover, we show that CA-CBBA yields a policy that generalizes beyond the training set to handle larger team sizes. Finally, the results on time-critical problems, such as a search-and-rescue mission, show that CA-CBBA also outperforms the baselines considered (e.g., CBBA, MCDGA, and ACBBA) in terms of number of unassigned and conflicted tasks in most of the scenarios.

Listen Before Receive (LBR) Assisted Network Access in LAA and WiFi Heterogeneous Networks

The Listen-Before-Talk (LBT) is the main procedure for Licensed Assisted Access (LAA) to accomplish fair and friendly coexistence with other operators or technologies operating over unlicensed spectrum. However, in LBT, the lack of coordination with other existing systems brings challenges in sustaining performance in the coexistence of LAA and WiFi networks. Specifically, the hidden node problem (HNP) and exposed node problem (ENP) cannot be effectively handled when both LAA and WiFi nodes attempt to access the unlicensed spectrum at the same time. Thus, transmission failure might occur and the network performance would be degraded. In order to mitigate the influences caused by HNP and ENP, based on LBT, we firstly analyze HNP and ENP by means of mathematical approach. The analytical results surprisingly reveal that the hidden node and exposed node probabilities are as high as 41% and 39.33%, respectively. Then, a Give And p-persistent Take (GAT) mechanism with the Listen-Before-Receive (LBR) procedure, namely LBR-GAT, is proposed to cope with LBT to reduce the collision caused by HNP as well as to retrieve the bandwidth sacrificed by the ENP. With LBR-GAT, the LAA sender conditionally gives up or takes back transmission opportunities, and thus the unlicensed spectrum could be efficiently shared between LAA and WiFi. Evaluation results show that the proposed LBR-GAT could conditionally obtain better network performance comparing to legacy LBT.

CFFD-MAC: A Hybrid MAC for Collision Free Full-Duplex Communication in Wireless Ad-Hoc Networks

Infrastructure-less (sometimes known as ad-hoc) networking paradigm is very appealing and potentially shaping its future into almost all emerging networks (i.e., IoT, wireless sensor networks, vehicular ad-hoc networks, emergency, and tactical radio networks, etc.). However, when conventional networking protocols are used, such networks often perform poorly, mainly because of interference within the network and limited network throughput. Recent advancements in wireless communications have enabled full-duplex (FD) operation by suppressing self-interference, which can theoretically double the network throughput. However, conventional medium access control (MAC) protocols like carrier-sense multiple access with collision avoidance (CSMA/CA) favor half-duplex (HD) operation and fail to benefit from FD transmission opportunities. This article proposes a novel hybrid MAC protocol for full-duplex ad-hoc networks. The proposed MAC combines time division multiple access (TDMA) and IEEE 802.11 distributed coordination function (DCF) strengths in chains of time-slotted contention-based control frames and collision-free data frames. The aim is to fully utilize FD transmission opportunities to increase network throughput. The proposed protocol modifies request-to-send (RTS) and clear-to-send (CTS) frames in IEEE 802.11 DCF MAC to form FD-RTS/CTS frames. These frames are used to enable collision-free FD communications among neighbors. The proposed scheme mitigates conventional MAC issues like hidden-node problem (HNP) and exposed-node problem (ENP). It also allows concurrent FD data transmissions in a collision-free manner. The model is generic and can be applied to any ad-hoc wireless network. In this article, the design is applied to a single channel ad-hoc network with FD transceivers. We compared the proposed design with IEEE 802.11 CSMA/CA protocol with both HD and FD transceivers. The simulation results show a 30% gain in throughput, reduced latency, and fairness among participating wireless nodes.

An Analytical Model for CBAP Allocations in IEEE 802.11ad

The IEEE 802.11ad standard extends WiFi operation to the millimeter wave frequencies, and introduces novel features concerning both the physical (PHY) and Medium Access Control (MAC) layers. The hybrid MAC layer provides for two different kinds of resource allocations: Contention Based Access Periods (CBAPs) and contention-free Service Periods (SPs). In this paper, we propose a Markov Chain model to represent CBAPs, taking into account operation interruptions due to scheduled SPs and the deafness and hidden node problems that directional communication exacerbates. We also propose a mathematical analysis to evaluate the interference among stations and derive analytical expressions to assess the impact of various system parameters on some key performance metrics such as throughput, delay, and packet drop rate. This information may be used to efficiently design a transmission scheduler that allocates contention-based and contention-free periods based on the application requirements.

Effects of Retransmission Limit on the Performance of Centralized Random Backoff

Previous studies showed that the packet collision probability in the 802.11 Distributed Coordination Function (DCF) can approach zero by adopting Centralized Random Backoff (CRB), which improves the total throughput performance. Moreover, it was reported that wireless networks using CRB maintain a high level of compatibility to legacy wireless local area networks (WLANs) when they coexist. However, little attention has been paid to relations between the performance of CRB and the retransmission limit, although the number of retransmission limit is an essential parameter that must be carefully chosen when implementing CRB for efficient WLANs. This article presents more realistic Markov chain models, and studies the impact of retransmission limit on the performance of CRB. These relations are also investigated by Monte Carlo simulation in more practical scenarios. Results show the trade-off that the total throughput increases with the retransmission limit when the number of nodes is larger than 15; whereas, the channel access opportunities in the mixed network scenario are more unevenly distributed between nodes as the retransmission limit increases. It is also shown in the simulation results that the throughput degradation caused by the hidden node problem is alleviated as the retransmission limit increases.

Performance Analysis of DCF- Two Way Handshake vs RTS/CTS During Train-Trackside Communication in CBTC based on WLAN802.11b

Background:Wireless Local Area Network (WLAN) is used primarily in CBTC because of easy availability of commercial WLAN equipment. In present scenario, WLAN Medium Access Control (MAC) protocol is a well-known protocol which is used to satisfy real-time traffic and delay- sensitive applications. The bidirectional train-trackside communication is the fundamental key of train control in CBTC.Methods:DCF describes two basic techniques used for packet transmission: First technique is a Two Way Handshake (TWH) mechanism and another is Four Way Handshake (FWH) mechanisms. RTS/CTS FWH protocol specified by IEEE802.11b is introduced to rectify the Hidden Node Problem (HNP) encounters in TWH protocol. That is why the TWH mechanism of DCF technique suffers from higher average packet delay time when this protocol is applied to CBTC. DCF- Four Way Handshake (FWH), Request To Send (RTS) and Clear To Send (CTS) delay model is proposed to develop Communication Based Train Control (CBTC) system.Results:FWH is applied in CBTC to overcome the packet delay and throughput limitations of Two Way Handshake (TWH) mechanism of distributed coordination function (DCF) based technique. An experiment is designed to simulate and compare the performance of RTS/CTS delay model against TWH mechanism of DCF.Conclusion:It was found that the Average packet delay is slightly higher and throughput is lesser in RTS/CTS in comparison to TWH method. By comparing the performance of these two medium access mechanism in CBTC it was found that for multiple retransmissions with various data rates the RTS/CTS model had better packet delay time than TWH.

Modeling and simulation of the IEEE 802.11e wireless protocol with hidden nodes using Colored Petri Nets

Wireless technologies are continuously evolving, including features such as the extension to mid- and long-range communications and the support of an increasing number of devices. However, longer ranges increase the probability of suffering from hidden terminal issues. In the particular case of Wireless Local Area Networks (WLANs), the use of Quality of Service (QoS) mechanisms introduced in IEEE 802.11e compromises scalability, exacerbates the hidden node problem, and creates congestion as the number of users and the variety of services in the network grow. In this context, this paper presents a configurable Colored Petri Net (CPN) model for the IEEE 802.11e protocol with the aim of analyzing the QoS support in mid- and long-range WLANs The CPN model covers the behavior of the protocol in the presence of hidden nodes to examine the performance of the RTS/CTS exchange in scenarios where the QoS differentiation may involve massive collision chains and high delays. Our CPN model sets the basis for further exploring the performance of the various mechanisms defined by the IEEE 802.11 standard. We then use this CPN model to provide a comprehensive study of the effectiveness of this protocol by using the simulation and monitoring capabilities of CPN Tools.

Hidden-Node Problem in Full-Duplex Enabled CSMA Networks

The in-band full-duplexing is a promising technique to boost wireless network throughput by allowing a node to transmit and receive simultaneously. This paper provides a comprehensive investigation on the hidden-node problem that arises in the full-duplex (FD) enabled carrier-sensing multiple-access (CSMA) networks. In particular, we first provide the fundamental conditions that guarantee successful receptions for all the FD transmission cases, and propose an ellipse interference model and an ellipse carrier-sensing model to capture the interference relations and the carrier-sensing mechanism in FD CSMA networks, respectively. We further establish the hidden-node-free design in FD CSMA networks. Specifically, we show the sufficient conditions on the carrier-sensing power threshold that can eliminate hidden-node collisions. We show that compared with half-duplex CSMA networks, the FD CSMA network needs a much smaller carrier-sensing power threshold to prevent hidden-node collisions, which leads to poor network spatial reuse. This motivates us to further propose a new medium access control (MAC) protocol with Full-duplex Enhanced Carrier-Sensing (FECS) mechanism. The FECS-MAC enables the secondary carrier-sensing before starting the secondary transmission. We show that with the secondary carrier-sensing design, the required carrier-sensing power threshold can be increased while keeping the network hidden-node free. Therefore, the network spatial reuse and throughput can be significantly improved. Simulation results demonstrate that the FECS-MAC can improve the throughput of dense three-node FD networks by more than 30 percent, compared with relay full-duplex (RFD) MAC protocol proposed in [1] .

RTS Threshold Variation Study on Contention-based IEEE 802.11n EDCA for Real-time Services

As a “wide-deployed” wireless local area networks (WLANs) standard, the IEEE 802.11n was designed to support a high data transmission rate (up to 600 Mbps) and maintain a compatibility with the previous versions. Due to a substantial demand of real-time data services, such as VoIP and video conference, an enhanced quality of service (QoS) mechanism become crucially important. The IEEE 802.11n standard inherits the enhanced distributed channel access (EDCA) mechanism from the IEEE 802.11e, as the MAC layer improvement. It classifies the traffic into four different classes of data, called access categories (ACs). However, EDCA still suffers from a data packet collision, caused by hidden nodes problems. The packet loss ratio and end-to-end delay increase along with the escalation of real-time traffic. To address the issue, we conduct a simulation in Riverbed Modeler 17.5 environment with a 128, 256, 512, and 1,024 Bytes of request to send (RTS) threshold variation value to overcome a collision caused by hidden nodes problem. The result shows that the 512 Bytes of RTS threshold value gives the best QoS output among them all.

Emergency Message Dissemination in Vehicular Networks: A Review

The number of vehicles on the roads has increased proportionally over the last couple of years and this number is likely to rise due to the increase in population growth and the number of vehicles that are manufacturing every day. This high traffic density leads to several problems, from which effectively disseminating the emergency messages is a major concern. Keeping in view the dynamic characteristics of VANETs, significant challenges are faced in disseminating the message across the network. The major challenges are the broadcast storm problem, hidden node problem and the packet collision. Many studies have been performed to devise an effective and reliable mechanism for disseminating emergency messages in a Vehicular ad-Hoc Network (VANET). Researchers have proposed different models to tackle various types of scenarios for emergency message dissemination. This paper not only reviews some recent contributions to emergency message dissemination in vehicular networks but also discusses various proposed methods based on Intelligent Transportation System (ITS), Internet of Things (IoT), Priority messaging, Clustering approach, Software Defined Network (SDN) and Fog Computing. We have also tried to explore the latest developments in emergency message dissemination using 5G networks.

AN ENERGY EFFICIENT SPECTRUM AWARE ROUTING FOR COGNITIVE RADIO NETWORKS

Background: Now a days Due to rapid increase in the internet the Spectrum available is been overcrowded and thus the spectrum Sensing can be achieved by using the predominant technology i.e., Cognitive Radio as the spectrum is been under-utilized by the wireless communication technologies. Objective: The prime objective of the research work carried out is to achieve the energy efficiency and to use the spectrum effectively by using the spectrum management concept and achieve better throughput, end to end delay etc., Methods: The detection of the spectrum hole plays a vital role in the routing of the cognitive radio networks. As the hidden node problems and the multipath fading and the shadowing are considered to be impacting the sensing of the spectrum to overcome these issues Cooperative spectrum Sensing Mechanism is been adopted to sense the spectrum in an optimal manner and over cum the issues. Along with these issues the spectrum resources changes time to time in the routing. Result: An Energy Efficient Spectrum aware Routing (ESR) is been proposed which involves the timeslot and the routing schemes were been discussed. The simulation parameters have been proposed and the improvement in the performance of network through and a decrease in the end-to end delay have been observed and analyzed. Conclusion: An Energy Efficient spectrum management and the routing is successfully established to communication in the network and further traffic load is observed to be balanced in the protocol based on the residual energy in a node and further it prologs the Network Lifetime of the Overall Network and the Individual CR user. Further the end-to-end Delay has been observed to be lower which ensure higher throughput in the network and improves the network life time.

A New Planning-Based Collision-Prevention Mechanism in Long-Range IoT Networks

Wireless communication is prone to collisions, resulting from multiple devices transmitting at the same time. It implies subsequent retransmissions, which increase energy consumption of communicating devices and reduce throughput of the network. This is especially critical in Internet of Things (IoT) networks, in which the number of connected devices grows rapidly and the available energy of IoT end devices is rather limited (e.g., energy harvesting and battery powered). The number of retransmissions must be reduced in order the networks to be sustainable. However, in long-range wireless IoT networks, the most effective collision-resolution techniques using a transmission-channel listening to detect collisions cannot be reliably used due to various problems, such as a hidden-node problem or environment interference. In this article, a new solution of this problem is proposed, which consists of a new communication-planning mechanism for low-speed long-range IoT networks with a huge number of communicating energy-constrained devices. The access points (APs) (or IoT gateways) are used to plan the periodically repeated communication into a transmission schedule, allowing only a single IoT device to communicate at a time. This approach results in reduction of collisions, which leads to the increased network throughput, smaller delays, and lower power requirements of energy-constrained devices. The experiments indicate that the proposed approach provides better communication efficiency than the LoRaWAN and Sigfox collision-resolution techniques, when more than 15, respectively 125, end devices communicate with a single AP.