Performance Of Wireless Local Area Networks Research Articles

Performance analysis of WiFi networks based on sporadic traffic model using NS3

Wireless local area networks (WLANs) are widely used nowadays due to their high data rate and cheap cost. The unpredictable exponential demand of wireless devices such as phones, digital devices and internet of thing (IoT) sensors leads to a huge demand on Wi-Fi access. WLANs experience many challenges in the design and implementation due to their popularity and the large demand. One of these challenges is the effect of the interactive multimedia traffic on the performance of the WLANs. We investigated the impact of sporadic traffic on the behaviour of WLANs using NS3. The main WLANs performance metrics were analyzed using two different types of traffic distributions based on the N-burst analytical traffic model. The results show the negative impact of heavy-tailed applications on the performance WLANs. Also the results show that the effect of heavy-tailed application is less significant in high utilised networks.

Performance analysis of WiFi networks based on sporadic traffic model using NS3

Wireless local area networks (WLANs) are widely used nowadays due to their high data rate and cheap cost. The unpredictable exponential demand of wireless devices such as phones, digital devices and internet of thing (IoT) sensors leads to a huge demand on Wi-Fi access. WLANs experience many challenges in the design and implementation due to their popularity and the large demand. One of these challenges is the effect of the interactive multimedia traffic on the performance of the WLANs. We investigated the impact of sporadic traffic on the behaviour of WLANs using NS3. The main WLANs performance metrics were analyzed using two different types of traffic distributions based on the N-burst analytical traffic model. The results show the negative impact of heavy-tailed applications on the performance WLANs. Also the results show that the effect of heavy-tailed application is less significant in high utilised networks.

The Weakness Examination of Wireless Network Security at the Hospital Using QoS

Computer networks today are a much needed service. Computer networks enable the shared use of data, software and tools. So that the working group can be communicate more effectively and efficiently. This study aims to determine the existing QoS in Surya Asih Hospital and analyze the deficiencies. (Bahasa: Hospital is Rumah Sakit (RS)) In this research started from collecting data that exist in location either that support hardware or connection internet RS Surya Asih have used Wireless Local Area Network (WLAN) network service. WLAN is a network where can be exchanged data and resources between computers in one building. To know the performance of WLAN network (Wireless Local Area Network In RS Surya Asih, it should be done a measurement analysis of network performance parameters QoS (Quality of Services) is the ability to guarantee the delivery of important data flow Analysis of the performance of WLAN (Wireless Local Area Network) Surya Asih stressed the process of monitoring and measuring network parameters on the network infrastructure such as access speed and transmission capacity, from the point of delivery to the point of receiver that became the demands, the parameters used Bandwidth, Throughput, Delay and Packet Loss. Superior LAN on RS Surya Asih has reliability sufficient maintenance and good network availability Analysis of network performance is seen through Wireshark, Uptime and Downtime results are not bad, The availability of complete devices and fulfilled according to reliability and maintenance is not difficult. QoS parameter test results that bandwidth management shows the use of more bandwidth and evenly distributed to every user of RS Surya Asih Pringsewu network.

Q-learning-enabled channel access in next-generation dense wireless networks for IoT-based eHealth systems

One of the key applications for the Internet of Things (IoT) is the eHealth service that targets sustaining patient health information in digital environments, such as the Internet cloud with the help of advanced communication technologies. In eHealth systems, wireless networks, such as wireless local area networks (WLAN), wireless body sensor networks (WBSN), and wireless medical sensor networks (WMSNs), are prominent technologies for early diagnosis and effective cures. The next generation of these wireless networks for IoT-based eHealth services is expected to confront densely deployed sensor environments and radically new applications. To satisfy the diverse requirements of such dense IoT-based eHealth systems, WLANs will have to face the challenge of assisting medium access control (MAC) layer channel access in intelligent adaptive learning and decision-making. Machine learning (ML) offers services as a promising machine intelligence tool for wireless-enabled IoT devices. It is anticipated that upcoming IoT-based eHealth systems will independently access the most desired channel resources with the assistance of sophisticated wireless channel condition inference. Therefore, in this study, we briefly review the fundamental models of ML and discuss their employment in the persuasive applications of IoT-based systems. Furthermore, we propose Q-learning (QL) that is one of the reinforcement learning (RL) paradigms as the future ML paradigm for MAC layer channel access in next-generation dense WLANs for IoT-based eHealth systems. Our goal is to contribute to refining the motivation, problem formulation, and methodology of powerful ML algorithms for MAC layer channel access in the framework of future dense WLANs. This paper also presents a case study of next-generation WLAN IEEE 802.11ax that utilizes the QL algorithm for intelligent MAC layer channel access. The proposed QL-based algorithm optimizes the performance of WLAN, especially for densely deployed devices environment.

Sum Rate Optimization of Multi-Standard IEEE 802.11 WLANs

Aimed at providing high data rate in wireless local area networks (WLANs), the IEEE 802.11ac standard has been developed with key enhancements, including increasing the transmission rate and enlarging the packet payload length. The improvement in the sum rate performance, nevertheless, could become marginal or even disappear when nodes of legacy 802.11a/n standards coexist. It is, therefore, of paramount importance to study how to optimize the network sum rate of a multi-standard WLAN. In this paper, a multi-group model is proposed to analyze the data rate performance of a multi-standard WLAN where nodes with different standards have distinct transmission rates and packet payload lengths. It is shown that the packet payload length is a key system parameter that has a crucial impact on both the network sum rate and the ratio of node data rates. The enhancement proposed in the latest 802.11ac standard on enlarging the packet payload length can improve the data rate performance of its own nodes, but it may lead to the starvation of the legacy 802.11a/n nodes, and even impair the sum rate performance. To maximize the network sum rate with given target ratios of node data rates, the optimal packet payload lengths with or without joint tuning of the initial backoff window sizes are further obtained, which shed important light on the optimal network design of WLANs.

2.4 GHz Real-Time Prototyping Tool for OFDM Channel Estimation using USRP2 and LabVIEW

Wireless local area networks (WLANs) are currently playing an important role in serving the indoor traffic demand. Therefore, there is a need for software-defined radio platforms (SDRs) that can enable the solutions used in these systems to be tested in real environments as well as simulated results. In this paper, we present the SDR-based wireless receiver platform for determining the real-time WLANs performance and provide the comparison of the different channel estimation methods for IEEE 802.11g based on orthogonal frequency division multiplexing (OFDM) operations. The implementation of the receiver comprises the universal software radio peripheral and National Instruments LabVIEW. To determine the real-time receiver tool performance, we emphasized necessary signal processing techniques and different channel estimation methods with varying experimental parameters in real wireless environments. Experimental results report that the SDR-based receiver tool with the LabVIEW in real-time provides the throughput of the OFDM wireless network. The captured throughput performance concerning frame error rate by the receiver is also scrutinized with different channel estimation methods.

Enhancements of minimax access-point setup optimisation approach for IEEE 802.11 WLAN

As a flexible and cost-efficient internet access network, the IEEE 802.11 wireless local-area network (WLAN) has been broadly deployed around the world. Previously, to improve the IEEE 802.11n WLAN performance, we proposed the four-step minimax access-point (AP) setup optimisation approach: 1) link throughputs between the AP and hosts in the network field are measured manually; 2) the throughput estimation model is tuned using the measurement results; 3) the bottleneck host suffering the least throughput is estimated using this model; 4) the AP setup is optimised to maximise the throughput of the bottleneck host. Unfortunately, this approach has drawbacks: 1) a lot of manual throughput measurements are necessary to tune the model; 2) the shift of the AP location is not considered; 3) IEEE 802.11ac devices at 5 GHz are not evaluated, although they can offer faster transmissions. In this paper, we present the three enhancements: 1) the number of measurement points is reduced while keeping the model accuracy; 2) the coordinate of the AP setup is newly adopted as the optimisation parameter; 3) the AP device with IEEE 802.11ac at 5 GHz is considered with slight modifications. The effectiveness is confirmed by extensive experiments in three network fields.

Joint Optimization of Channel Selection and Frame Scheduling for Coexistence of LTE and WLAN

Recently, the interest in operating long term evolution (LTE) in unlicensed bands (i.e., LTE-U) has increased. However, since LTE does not sense for channel vacancy prior to transmissions, whereas a wireless local area network (WLAN) is based on carrier sensing multiple access, LTE interference severely degrades the performance of WLAN. To maximize the LTE throughput while maintaining fairness between LTE and WLAN, we formulate a joint optimization problem of channel selection and frame scheduling in LTE. As a practical solution of this problem, we propose a low-complexity heuristic algorithm called the sequential operation algorithm (SOA). Evaluation results demonstrate that SOA can achieve an LTE throughput comparable to that of the optimal solution, while maintaining fairness between LTE and WLAN by selecting appropriate channels and conducting effective frame scheduling.

A Self-Scrutinized Backoff Mechanism for IEEE 802.11ax in 5G Unlicensed Networks

The IEEE 802.11ax high-efficiency wireless local area network (HEW) is promising as a foundation for evolving the fifth-generation (5G) radio access network on unlicensed bands (5G-U). 5G-U is a continued effort toward rich ubiquitous communication infrastructures, promising faster and reliable services for the end user. HEW is likely to provide four times higher network efficiency even in highly dense network deployments. However, the current wireless local area network (WLAN) itself faces huge challenge of efficient radio access due to its contention-based nature. WLAN uses a carrier sense multiple access with collision avoidance (CSMA/CA) procedure in medium access control (MAC) protocols, which is based on a binary exponential backoff (BEB) mechanism. Blind increase and decrease of the contention window in BEB limits the performance of WLAN to a limited number of contenders, thus affecting end-user quality of experience. In this paper, we identify future use cases of HEW proposed for 5G-U networks. We use a self-scrutinized channel observation-based scaled backoff (COSB) mechanism to handle the high-density contention challenges. Furthermore, a recursive discrete-time Markov chain model (R-DTMC) is formulated to analyze the performance efficiency of the proposed solution. The analytical and simulation results show that the proposed mechanism can improve user experience in 5G-U networks.

Fuzzy logic-based performance improvement on MAC layer in wireless local area networks

There are many studies that have been done to improve the quality of service of wireless local area networks (WLANs). Institute of Electrical and Electronic Engineers (IEEE) WLAN are based on IEEE 802.11 protocol. The 802.11e medium access control (MAC) protocol is generally recommended for efficient quality of service in WLANs. There are many parameters in the MAC protocol that affect quality of services. Among these parameters, request to send threshold value (RSTV), fragmentation threshold value (FTV) and buffer size (BS) directly affect network performance. RSTV is used in the request to send/clear to send (RTS/CTS) mechanism in the carrier sense multiple access with collision avoidance (CSMA/CA) protocol for collision prevention. This parameter specifies the threshold used to activate the CSMA/CA protocol. FTV is another parameter that is used to send large-sized packets by dividing them into appropriate fragments during CSMA/CA transmission and reduces packet loss in WLAN. BS is another parameter that has a significant cost in the CSMA/CA model and also directly affects the performance. In this article, to improve the performance of WLANs, OPNET Modeler was used and ideal values were obtained for RSTV, FTV and BS by using fuzzy logic-based method. The values obtained by fuzzy logic were re-tested in OPNET Modeler, and the achieved improvement was as follows: for delay 36–38%, for load 2–10% and for throughput 25–44%, respectively. Thus, in WLANs, performance was improved by using fuzzy logic-based method.

Performance Improvement of Sub 1 GHz WLANs for Future IoT Environments

IEEE 802.11ah task group has developed a new wireless local area network (WLAN) technology, sub 1GHz (S1G) WLAN, for future Internet of Things (IoT) environments. Because of the superior propagation feature of S1G frequency band, S1G WLAN can provide very long transmission range, wild coverage, and support more than 8000 devices. In order to alleviate the high collision probability raised in the dense network environment, S1G WLAN adopts an restricted access window (RAW) mechanism. However, as the time slots of RAW are allocated without any consideration of traffic load of devices, the medium resource might be inefficiently used. In addition, devices belonging to a same group have to contend for channel, and thus severe collisions may occur in a large size group. In this paper, we propose a sequential transmission scheme, which provides an efficient way of source management in the S1G WLANs by considering the traffic loads and allocating channel access times of the devices. Through conducting mathematical analysis and performing simulations, we prove that our proposed protocol can enhance the performance of the S1G WLANs for the IoT environments.

Throughput Performance Optimization of Super Dense Wireless Networks With the Renewal Access Protocol

As a promising solution for handling super dense wireless networks, wireless local area networks (WLANs) have been intensively considered due to their wide availability. However, the contention-based MAC protocol in WLANs should be modified because of its inefficiency. To this end, we consider a recently proposed novel MAC protocol called the renewal access protocol (RAP). With the RAP, we analyze two strategies for resolving collisions efficiently and achieving optimal throughput performance in super dense WLANs: strategies without and with grouping. First, we analyze the asymptotic behavior of the RAP itself (i.e., without grouping) as the number of terminals goes to infinity. We show that the RAP can achieve optimal throughput even in super dense WLANs and the relevant optimal access probability can be derived in a closed form. Second, we propose a grouping strategy in the RAP called the grouped RAP (G-RAP). While a grouping strategy in the IEEE 802.11ah standard is based on time division, our G-RAP is based on transmission attempts. So the G-RAP does not waste channel resources. We show that the G-RAP achieves the optimal network throughput for any group structure if terminals use the optimal access probability that we derive. Our analytical results are validated by simulation.

Fairness-aware radio resource management for medical interoperability between WBAN and WLAN

Wireless body area networks (WBANs) in the industrial, scientific, and medical (ISM) bands have been increasingly adopted for various medical applications. Due to the shared nature of the ISM bands, when a WBAN coexists with a wireless local area network (WLAN), performance of WBAN may significantly degrade because of asymmetric attributes between WBAN and WLAN such as transmit power and response time. In this paper, we propose a novel channel access protocol for achieving effective channel sharing in the aspect of efficiency and fairness, which adaptively controls the contention window size of WLAN based on the delay information of WBAN. Our extensive simulation results for real-time electrocardiogram (ECG) monitoring show that the proposed scheme can guarantee the required quality of service of WBAN while insignificant degradation of WLAN performance.

Semi-Distributed Backoff: Collision-Aware Migration from Random to Deterministic Backoff

Collision is imminent in wireless networks (WNs) capacitated with randomized distributed channel access. In such networks, the probability of frame drop (Pdrop) is greater than zero due to successive collisions with a finite retry limit m. The IEEE 802.11 DCF is one such widely accepted protocol used in wireless local area networks (WLANs). The objective of the work reported in this paper is to provide guaranteed channel access to colliding frames for avoiding successive collisions for any loss-sensitive application, and thus, increase network throughput under finite m. We propose the semi-distributed backoff (SDB) algorithm, which operates in two modes: S-mode and R-mode. The key idea of the SDB scheme is to perform receiver-side backoff, if a mobile station encounters collision even after performing the existing sender-side backoff procedures. Using the SDB scheme, we design Semi-DCF, a MAC protocol for WLANs, which performs opportunistic migration from random to deterministic backoff. Semi-DCF functions independent of m. This protocol exploits the collision detection capability of receivers for disseminating information on optimal backoffs to the contenders using signature vectors. An analysis of Semi-DCF using the 2D Markov chain, coupled with results of network simulation establishes its superior performance in WLANs.

Transmission priority scheme with adaptive backoff technique in fiber-wireless networks

This paper considers the realization of fiber-wireless (Fi-Wi) networks using the gigabits passive optical network (GPON) and the infrastructure-based wireless local area network (WLAN). The bottleneck of such hybrid system is the WLAN where interference limits the performance. As such, we focus on enhancing the WLAN performance by analytically deriving the optimum contention window (CW) sizes of access points (APs) and wireless users (WUs), respectively. An adjustable transmission priority factor is introduced to allow uplink-downlink transmission fairness. Further, an adaptive backoff technique using information from monitoring the GPON and WLAN networks is proposed. Simulations show the CW sizes of all WUs are maintained within a standard deviation of 1.5% at a cost of a 3% loss in throughput due to the effect of convergence and other estimates.

Performance enhancement of overlapping BSSs via dynamic transmit power control

In densely deployed wireless local area networks (WLANs), overlapping basic service sets (BSSs) may suffer from severe performance degradations. Mobile stations in a BSS may compete for channel access with stations that belong to another BSS in such environment, and it reduces overall throughput due to the increased collision probability. In this paper, we propose a new scheme for transmit power control, which enables mobile stations to dynamically adjust their transmit powers. Using our mechanism, those stations in different BSSs will have more chances of simultaneous transmissions and thus improve their performances by enhancing spatial reuse. We develop a Markov chain model to analyze the performance of the proposed scheme and also perform extensive simulations. Both the analytical and simulation results show that our mechanism effectively improves the network performance of WLANs.

Interference Effects of Blue tooth on WLAN Performance

In this paper, Network stumbler version 0.4.0 was used to estimate the impact of impulsive interference on Wireless Local Area Network (WLAN) when Bluetooth coexist by measuring radiation from a WiFi Access Point (AP) in a homogeneous and heterogeneous scenarios. The parameters measured include Received Signal Strength (RSS) and Signal-to-Noise ratio (SNR) while Bit Error Rate (BER) performance was theoretically deduced from the measured data. Results obtained from the measurements of both scenarios were compared and used in describing the interference problem. The study revealed that Bluetooth impact on performance was minimally significant with mean degradation of 4.74% in RSS and 0.77% in SNR despite the fact that its signal are weak and are designed to accommodate WiFi devices by AFH technology. http://dx.doi.org/10.4314/njt.v34i1.22

Enhancing Voice over WLAN via Rate Adaptation and Retry Scheduling

Today, voice over IP (VoIP) service is emerging as a popular and important application in wireless local area networks (WLANs). While rate adaptation (or link adaptation) has been identified as a key factor determining the performance of WLANs, we have observed that most (if not all) rate adaptation algorithms have been developed to improve the throughput of data traffic, not the quality of service (QoS) of VoIP traffic. Accordingly, in this paper, we investigate the characteristics of VoIP traffic and the limitations of state-of-the-art rate adaptation algorithms, and then enhance the QoS of voice over WLAN (VoWLAN) by ameliorating the existing rate adaptation algorithms. Specifically, we design fast decrease to control the transmission rate of retransmissions, and retry scheduling to avoid the deep fading of the wireless channel as well as hidden terminal interference. We comparatively evaluate the QoS of the revised rate adaptation algorithms via ns-3 simulations and MadWiFi implementations in various communication environments, and demonstrate that the proposed schemes improve the R-score performance by up to 80 percent depending on the network scenarios.

MU-MIMO MAC Protocols for Wireless Local Area Networks: A Survey

As wireless devices boom and bandwidth-hungry applications (e.g., video and cloud uploading) get popular, today's wireless local area networks (WLANs) become not only crowded but also stressed at throughput. Multiuser multiple-input-multiple-output (MU-MIMO), an advanced form of MIMO, has gained attention due to its huge potential in improving the performance of WLANs. This paper surveys random access-based medium access control (MAC) protocols for MU-MIMO-enabled WLANs. It first provides background information about the evolution and the fundamental MAC schemes of IEEE 802.11 Standards and Amendments, and then identifies the key requirements of designing MU-MIMO MAC protocols for WLANs. After this, the most representative MU-MIMO MAC proposals in the literature are overviewed by benchmarking their MAC procedures and examining the key components, such as the channel state information acquisition, decoding/precoding, and scheduling schemes. Classifications and discussions on important findings of the surveyed MAC protocols are provided, based on which, the research challenges for designing effective MU-MIMO MAC protocols, as well as the envisaged MAC's role in the future heterogeneous networks, are highlighted.

Dynamic Multiuser Sub-Channels Allocation and Real-Time Aggregation Model for IEEE 802.11 WLANs

Wireless local area networks (WLANs) are becoming increasingly popular due to the recent availability of affordable devices providing multiple and high rate capabilities. New PHY and MAC layer enhancements have been introduced in different IEEE 802.11 WLAN standards. These improvements have given birth to a wide range of bandwidth channels (up to 160 MHz) and very high transmission data rates (> 1 Gbps) to keep up with current and up-coming multimedia applications. The MAC layer in current WLANs randomly allocates the entire channel to only one user as a single resource, which, unfortunately, reduces the efficiency of WLANs. One way to significantly improve WLAN performance is to reduce the channel width and create many sub-channels. Based on the user's channel conditions and QoS requirements, the PHY layer resources can be dynamically allocated to several users at the same time. In this paper, we shall present a novel sub-channels access approach, titled MU-Access, with new features suitable for the forth-coming high-speed MIMO-based WLAN products. We will evaluate its performance compared to state-of-the-art systems, using NS-3 under a variety of network conditions. Our experiments will then demonstrate that our proposed scheme enhances the performance of IEEE 802.11 devices with a much higher throughput.