Contention Resolution Mechanism Research Articles

A machine learning assisted optical multistage interconnection network: Performance analysis and hardware demonstration

AbstractIntegration of the machine learning (ML) technique in all‐optical networks can enhance the effectiveness of resource utilization, quality of service assurances, and scalability in optical networks. All‐optical multistage interconnection networks (MINs) are implicitly designed to withstand the increasing high‐volume traffic demands at data centers. However, the contention resolution mechanism in MINs becomes a bottleneck in handling such data traffic. In this paper, a select list of ML algorithms replaces the traditional electronic signal processing methods used to resolve contention in MIN. The suitability of these algorithms in improving the performance of the entire network is assessed in terms of injection rate, average latency, and latency distribution. Our findings showed that the ML module is recommended for improving the performance of the network. The improved performance and traffic grooming capabilities of the module are also validated by using a hardware testbed.

Performance Comparison of JIT and JET Protocols on the OBS Networks

Over the past few years, internet traffic has been explosive growth due to users' need for more applications and services. All these developments on the internet need more bandwidth. The Optical Burst Switching (OBS) mechanism along with Wavelength-Division-Multiplexing (WDM) technology is very useful in meeting the high bandwidth requirements. However, the OBS network uses a one-way resource reservation mechanism, as well as it is a buffer lack at the intermediate (core) node. Therefore, the OBS network depends on contention resolution mechanisms to achieve acceptable levels of performance. In this paper, the Deflection Routing (DR) mechanism is used to overcome contention. The performance of the OBS network has been estimated by executing Just-In-Time (JIT) and Just-Enough-Time (JET) signaling reservation protocols with the DR. NCTUns-6.0 simulator was employed to verify the performance of the OBS network based on two metrics: throughput and packets dropped in the network. The results show that the bandwidth resources utilization in the OBS network with JET and DR (OBS-JET-DR) is better than in the OBS network with JIT and DR (OBS-JIT-DR). However, the average number of packets dropped in OBS-JET-DR is less than OBS-JIT-DR by 21%. In addition, the throughput of OBS-JET-DR has increased by 4% compared with OBS-JIT-DR.

Packet blocking performance of optical networks under contention resolution mechanisms

Packet blocking performance of optical networks under contention resolution mechanisms

Packet Blocking Performance of Cloud Computing Based Optical Data Centers Networks under Contention Resolution Mechanisms

Abstract In data center networks use of optical communication has revolutionized the data transfer mechanism. Optical communication heavily relies on enormous bandwidth of optical fiber. Wavelength Division Multiplexing (WDM) technique can be used for utilization of huge bandwidth. To employ WDM which uses distinct set of wavelengths to carry data wavelength converters are required. However as the tunable range of wavelength converter increases both cost and technological design complexity rises exponentially. Therefore, both Limited Range Wavelength Converter (LRWC) and Full Range Wavelength Converter (FRWC) are considered. However, under higher loading conditions buffering is also required as using wavelength converter (WC) blocking can be reduced significantly. This paper presents comprehensive analysis of blocking performance under various types of wavelengths converters and buffering of contending packets.

Tone-Based Contention Resolution for Multi-hop Wireless Sensor Networks

Medium access control protocols with common active period (AP MACs) are frequently used in wireless sensor networks (WSNs) with medium-load traffic requirements. In this class of low duty-cycle contention-based protocols, sensor nodes synchronously alternate between active periods (used for data exchange) and sleep periods (used for energy conservation). The key component of AP MAC protocols is the contention resolution mechanism (CRM), which should provide channel access to as many nodes as possible, while eliminating, or at least minimizing the chance of date message collisions. Current AP MAC protocols commonly employ CRMs based on the traditional CSMA scheme, possibly extended with RTS–CTS handshake mechanism, which are known to be energy inefficient under heavy traffic conditions, especially in dense multi-hop WSNs. In this paper, we propose a collision-free and energy-efficient CRM, specially designed for application in AP MACs. The proposed CRM, referred to as AP/TONE protocol, replaces RTS-CTS control packets with short RF tones for exchanging elementary status information among neighbouring nodes. At the top of the tone-based signalling mechanism, AP/TONE implements a distributed two-phase multi-round contention resolution procedure. In the first phase, the network is partitioned into non-interfering clusters by selectively blocking sending/receiving status of contending nodes. In the second phase, the existing intra-cluster tone-based CRM is used to make the final selection. The performance of the proposed approach was evaluated by simulation of a multi-hop WSN with varying traffic parameters and node density. The obtained results show that AP/TONE achieves significantly higher throughput with reduced energy consumption with respect to CSMA-based approaches.

RELIABLE DETECTION OF SIGNAL TONES IN PRESENCE OF COLLISIONS

A reliable and energy-efficient contention resolution mechanism (CRM) is a crucial component of MAC protocols for wireless sensor networks (WSNs). Among a number of CRM proposals, CRMs based on exchanging short signal tones between competing nodes have recently drawn attention due to their promise of collision-freedom and energy-efficiency. However, the basic assumption of these protocols, i.e. the possibility to reliably detect the presence/absence of signal tone in case of simultaneous transmissions from multiple nodes, has not yet been confirmed. In this paper we present a technique for signal tone generation/detection, which uses only standard features of off-the-shelf RF transmitters. Furthermore, we present results of an experimental validation carried out in a real testbed which demonstrate a high accuracy of signal tone detection in presence of multiple simultaneous transmissions.

Hybrid MAC Protocol Design and Optimization for Full Duplex Wi-Fi Networks

Recently, owing to the advances in the self-interference cancellation technology, the in-band full-duplex (FD) capability has been demonstrated at Wi-Fi range. However, the simultaneous uplink (UL) and downlink (DL) transmission may lead to inter-user interference (IUI) and result in decoding failure. Spectrum efficiency should also be considered in the construction process of the FD transmission. In this paper, we propose a hybrid half-duplex/FD MAC protocol based on a two-fold RTS/CTS contention resolution mechanism, in order to fully exploit the channel access opportunities provided by the simultaneous UL and DL transmissions. The noteworthy features of the proposed protocol lie in the following two aspects. First, the protocol provides the flexibility for the AP to decide the probability of constructing FD transmission, and then it adopts a second-fold of RTS/CTS mechanism to prevent the constructed transmission from being affected by the IUI. The second-fold contention and the probability of constructing FD transmission are optimized separately to maximize the spectrum efficiency given different transmission demands. Simulation results show that the proposed MAC protocol achieves higher capacity compared with previous works, and the hybrid characteristic enables the FD Wi-Fi networks to meet with different system requirements.

Mathematical and simulation analysis of contention resolution mechanism for IEEE 802.11ah networks

IEEE 802.11ah Task Group has introduced group-based contention mechanism called Restricted Access Window (RAW) for accessing the shared medium. The RAW mechanism is an initial solution to control the collision that occurs due to the heavy contention in large networks. The Distributed Coordination Function (DCF) is a contention-based medium access method that uses Binary Exponential Backoff (BEB) to resolve contention among the stations inside the RAW group. As mentioned in several literatures, BEB suffers from high probability of collisions. This problem is mitigated through an efficient BO algorithm with appropriate integer sequences for calculating new Contention Window (CW) without any additional control overheads and complex computations. An analytical model is developed for computing saturated throughput, attained by the proposed algorithm. A comprehensive simulation is also carried out in NS3 network simulator with different packet sizes. It is observed from analytical and simulation results that, the proposed backoff algorithm outperforms BEB in terms of saturated throughput, packet delivery ratio, packet loss ratio and delay.

Contention Resolution Mechanisms for Multi-Channel Cognitive Radio Ad Hoc Networks

In this article, the channel hopping (CH) method for the rendezvous process of secondary users in multi-channel CRAHNs is overviewed. With the evolution of the Internet of Things, design criteria of CH sequences targeting these applications are discussed. While channel collision among CH sequences is inherent in realistic CRAHNs, most prior works focused on sequence designs without addressing the channel collision problem. Hence, the concept of contention resolution in CRAHNs is introduced in this article, and a "multi-round" contention resolution mechanism is studied. To quantify the performance, the RS rate of the mechanism is presented and validated with computer simulation. Finally, the rendezvous time savings, which, in turn, can enhance data throughput, of the multi-round mechanism over a single-round one are investigated.

An Improved Multi-Hop-Enabled Energy Efficient MAC Protocol for Underwater Acoustic Sensor Networks

Packet collisions occurred by hidden and local nodes in multi-hop enabled underwater acoustic sensor networks (UWASNs) have effect on throughput, energy efficiency and end-to-end delay. Existing Multi-HopEnabled Energy Efficient MAC Protocol for Underwater Acoustic Sensor Networks (MHEE MAC) utilized a double-phase contention resolution mechanism, which causes visit multiple time slot and energy overhead. In this paper, we propose a MAC protocol that use contention resolution mechanism with unique priority to provide energy efficiency. First, local nodes are eliminated comparing their priority and later, hidden nodes are mitigated. A simulation of proposed protocol is also developed to analyze the performance. Results obtained through simulation show that the proposed protocol achieves significantly lower energy consumption, reserve more energy and more stable throughput compared to MHEE-MAC, T-Lohi and slotted floor acquisition multiple access (S-FAMA).

Performance Analysis of a Network of Event-Based Systems

We consider a scenario where multiple event-based systems use a contention resolution mechanism (CRM) to communicate with their respective controllers over a wireless network. We present a Markov model that captures the joint interactions of the event-triggering policy and the CRM. This model is obtained by decoupling interactions between the different systems in the network, drawing inspiration from Bianchi's analysis of IEEE 802.11. We present Monte-Carlo simulations that validate our model under various network configurations, and verify the accuracy of the performance analysis.

Intra-cluster tone-based contention resolution mechanism for wireless sensor networks

This paper presents an energy-efficient technique for resolving intra-cluster contentions in cluster-based wireless sensor networks. The proposed technique, bit map – binary countdown (BM–BCD), provides collision-free medium access by exchanging short signal tones between the head node and member nodes of the cluster. The BM–BCD improves existing tone-based contention resolution schemes in the following two aspects. Firstly, BM–BCD overcomes the hidden terminal problem by actively involving head node into the contention resolution process. Secondly, BM–BCD introduces a novel group-splitting algorithm which improves energy efficiency of member nodes by spreading the contention resolution over all available elimination rounds. The paper also introduces a simple intra-cluster MAC protocol, named STAR–TONE, which incorporates the proposed BM–BCD, and provides an analytical model for dimensioning main protocol parameters. Our analysis, verified by simulations, demonstrates that BM–BCD reduces the power consumption during contention for up to 44.5% compared to the baseline countdown protocol under bursty traffic conditions.

Contention-Based Geographic Forwarding Strategies for Wireless Sensors Networks

This paper investigates solutions that combine relay selection algorithms and opportunistic geographic routing strategies for autonomous wireless sensor networks, wherein transmissions often occur over multiple hops. In order to design and assess such contention-based geographic forwarding strategies, we establish an analytical framework that incorporates concepts from probability generating functions (through power series expansion), spatial point processes, and auction theory, as well as Monte Carlo simulations to corroborate analytical results. The investigated strategies are built upon three constituent parts: 1) relay selection algorithm; 2) contention resolution mechanism; and 3) geographic forwarding strategy. We then propose an auction-based algorithm for selecting the relay node that relies on the network topology as side-information. Our results show that geographic solutions that iteratively exploit the local knowledge of the topology to ponder the algorithm operation outperforms established random approaches. Although, there is an intrinsic tradeoff between the time needed to identify a suitable next hop relay and the respective progress that is achieved toward the final destination.

Estimation and Adaptation for Bursty LTE Random Access

With the potential to generate numerous connection requests, an explosive growth in the volume of data traffic and the number of mobile and machine-to-machine devices has drawn new attention to the radio access network. Surging random-access attempts cause not only severe preamble collisions but downlink resource shortage as well, thus degrading the performance of the random-access procedure. However, the effect of downlink resource shortage on system performance has yet to be comprehensively studied. In addition, most existing random-access contention resolution mechanisms sacrifice random-access channel (RACH) throughput for a high success probability, and thus, the price is that low-throughput mechanisms need a lot of time to deal with access attempts. In this paper, we evaluate the medium-access-control (MAC)-level performance for the four-step random-access procedure in Long-Term Evolution (LTE) systems, both with and without constrained downlink resources. Furthermore, we propose a novel RACH contention resolution scheme, i.e., the dynamic backoff (DB) scheme. DB can achieve high RACH throughput, yielding a high random-access success probability under various RACH overloaded scenarios.

Multi-Hop-Enabled Energy-Efficient MAC Protocol for Underwater Acoustic Sensor Networks

In multi-hop underwater acoustic sensor networks (UWASNs), packet collisions due to hidden and local nodes adversely affect throughput, energy efficiency and end-to-end delay. Existing medium access control (MAC) protocols try to solve the problem by utilizing a single-phase contention resolution mechanism, which causes a large number of control packet exchanges and energy overhead. In this paper, we introduce a MAC protocol that splits this single-phase contention resolution mechanism into two phases to provide efficient multi-hop networking. In the first phase, local nodes are eliminated from the contention, and in the later phase, the adverse effects of hidden nodes are mitigated. This two-phased contention resolution provides higher energy efficiency, better throughput and shorter end-to-end delay, and it also enables adaptability for different network architectures. A probabilistic model of the proposed protocol is also developed to analyse the performance. The proposed protocol has been evaluated through quantitative analysis and simulation. Results obtained through quantitative analysis and simulation reveal that the proposed protocol achieves significantly better energy efficiency, higher and more stable throughput and lower end-to-end delay compared to existing protocols, namely T-Lohi and slotted floor acquisition multiple access (S-FAMA).

光突发交换网络中基于突发包分段的联合冲突解决方法研究

光突发交换网络中基于突发包分段的联合冲突解决方法研究

A Fixed Backoff-Time Switching Method for CSMA/CA Protocol in Wireless Mesh Networks

SUMMARY As a flexible and cost-efficient scalable Internet access network, we studied architectures, protocols, and design optimizations of the Wireless Internet-access Mesh NETwork (WIMNET) .W IMNET is composed of multiple access points (APs) connected through multihop wireless communications on IEEE 802.11 standards. The increasing popularity of real-time applications such as IP-phones and IP-TV means that they should be supported in WIMNET. However, the contention resolution mechanism using a random backoff-time in the CSMA/CA protocol of 802.11 standards is not sufficient for handling real-time traffic in multihop wireless communications. In this paper, we propose a Fixed Backoff-time Switching (FBS) method for the CSMA/CA protocol to improve the real-time traffi cp erformance in WIMNET by giving the necessary activation chances to each link. We implement our proposal on the QualNet simulator, and verify its effectiveness through simulations on three network topologies with four scenarios.

Reduced‐frame TDMA protocols for wireless sensor networks

SUMMARYTime‐division multiple‐access (TDMA) is a common medium access control paradigm in wireless sensor networks. However, in its traditional form, the TDMA‐based protocols suffer from low channel utilization and high message delay because of a long frame length needed to provide collision‐free transmissions, which is particularly damaging in dense wireless sensor networks. In this paper, we investigate the performance and the energy efficiency of a class of TDMA‐based protocols, called reduced‐frame TDMA, where every TDMA slot is augmented with a short time period dedicated for carrier sense multiple access‐based contention resolution mechanism. Because of their ability to dynamically resolve collisions caused by conflicting slot assignments, the reduced‐frame TDMA protocols can be configured with any frame length, independently of node density. In addition, we present a distributed heuristic slot assignment algorithm that minimizes interslot interference in the presence of limited number of slots per frame. The simulation results indicate that the reduced‐frame TDMA protocols significantly reduce the message delay and increase the maximum throughput without incurring significant penalty in energy efficiency compared with the traditional TDMA scheme. Copyright © 2012 John Wiley & Sons, Ltd.

ARA MAC - A Qualifying Approach for improving Attack Resiliency and Adaptivity for Medium Access Control Protocol in WLAN 802. 11

The exponential growth of wireless network in recent years has brought some major research issues that include a fair share of the available bandwidth, quality of service (QoS) and control of misbehaving traffic nodes/sources. However, in wireless networks, including cellular, Ad Hoc, and sensor networks, that are based on a shared medium and often contention-oriented protocols, these issues have not been fully addressed. Most wireless networks are based on IEEE 802.11x standards which provide public wireless access to the Internet. The medium access control (MAC) in IEEE 802.11 uses a distributed contention resolution mechanism for sharing the channel. If the MAC protocol is manipulated or misused, then the consequences can be overwhelming, such as the disruption of the whole network. A selfish/cheater node [10] can manipulate the MAC protocol in different ways to gain access to the channel resulting in some cases of starvation of other nodes in the same network. The manipulation of the MAC layer protocol is hidden from the upper layers, and can be further enhanced if combined with more violations from these upper layers of the ISO/OSI Model. In wireless networks i.e. IEEE 802.11, all nodes contending to access the medium made-up to follow the rules of the Medium Access Control (MAC) sub layer. As the number of nodes increases; the probability of collisions obviously increases which causes longer back-off values of the collided nodes. A suspicious node may be either selfish node (or misbehaving node) which attempts to manipulate its back-off parameters of the CSMA / CA protocol to gain more and more access to the channel, hence get higher performance than their fair share. Suspicious nodes (Misbehavior Node). Which may be an attacker and can increase collisions to decrease the performance of MAC protocols by disobeying CSMA/CA or back-off rules. In this work, we discussed, analyzed and used selfish behavior by attackers to create an opportunist node. We also identified, declared and finally discard/disassociate the attacker nodes in IEEE 802.11 MAC layer environment. The Access point (AP) Allow most of the nodes offers more bandwidth (in terms of the extra number of slots to almost each node) while maintaining fairness if channel utilization is poor and this mode is called opportunist mode. The Proposed Protocol is called as the ARA-MAC. The performance of our method is evaluated through a simulation model to test efficiency. Various parameters are the basis for comparison between the implemented method and CSMA/CA. Key Performance Parameters i.e. Packet Delivery Ratio, RTS/Data Frames, Mean no. Of retry per frame have been used for comparison and performance evaluation. The results show that our proposed algorithm ARA-MAC outperforms basic CSMA/CA in terms of Attack Resiliency and Adaptability. ARA-MAC is able to detect and discard attacker nodes after identification of its maliciousness and also it provides adaptability in existing CSMA/CA. The time period for monitoring of node behavior varies according to the Fibonacci series to identify random timing attackers and also it reduces unnecessary execution of ARA-MAC algorithm at AP (Access Point). This is predominantly important in a distributed system where power consumption is a big concern especially in the case of Wireless Sensor Network. It is also important in a centralized system where constant monitoring of a large number of sources from the Access Point (AP) alone may become promptly a big burden on it. The main purpose of this work is to increase the channel utilization by offering opportunities to a node, and detect such node that is using this concept to degrade the network performance in terms of degraded channel utilization. General Terms Protocol Modification and System Development for Attack Resiliency at MAC Layer.

A backoff differentiation scheme for contention resolution in wireless converge‐cast networks

SUMMARYWireless converge‐cast networks (WCNs), such as data collection‐based wireless sensor networks, exhibit certain phenomena called funneling effect, where the region close to the sink node is heavily overloaded. In this paper, we identify that the funneling effect occurs not only close to the sink but also within the network region where nodes have collision and induce heavy traffic to relay; we name it hot‐spot funneling effect. This paper aims to improve the throughput and fairness of WCNs by mitigating the micro funneling effect. We propose a new mechanism, the backoff differentiation for contention resolution (BDCR), which is targeted to a system‐wide high throughput on the basis of the contention resolution mechanism. To achieve high spatial reuses, BDCR divides the network into several regions and does backoff differentiation within each region. Within each backoff differentiation region, the backoff window range is adjusted according to the traffic rate, and at the same time, the backoff values are set with the awareness of the traffic intensity level. All regions share the same algorithm, which uses Kelly's rate control theory and method to allow each sensor to locally adjust its backoff value. One of the key advantages of BDCR is that it is extremely easy to implement. With extensive simulations and testbed experiments, BDCR is proved to achieve much higher throughput over the traditional carrier sense multiple access and some recent media access control protocols in literature, particularly when the network suffers intensive congestions. Copyright © 2012 John Wiley & Sons, Ltd.