Performance Analysis of Improved IEEE 802.11 Infrastructure Power Saving Under Time-Correlated Channel Errors

Orthogonal signaling-based queue status investigation method in IEEE 802.11

A research on approaches to energy saving through energy service contract (ESC) use has been conducted in this work. It is determined that the main requirement to the content and structure of the ESC is the existence of a list of measures aimed at energy saving and energy efficiency improvement. A procedure of efficiency estimation of energy saving measures implementation is given. The factors and parameters that affect the result of energy saving measures realization are outlined. It is defined that success of any ESC critically depends on the correct calculation of savings from energy efficiency measures implementation.The need for transition to an energy efficient variant of development through strengthening the requirements for compliance with European standards in terms of energy efficiency is substantiated. Otherwise economic growth will be restrained by high prices and reduced accessibility to energy resources.It is also inferred that providing of standardized and unified norms and approaches to the energy efficiency parameters determination requires the development of appropriate methodological framework of formal methods and documented rationale for projects effectiveness evaluation, as well as implementation of procedure for organization of measurements and verification of the energy savings achieved. The procedure for energy efficiency measurement and verification involves the inspection of facilities, energy usage measuring, independent variables monitoring, calculations, including computation of target indicators values in the field of energy saving and energy efficiency improvement in comparable conditions, as well as computation of energy consumption reduction in comparable conditions. Creation of a comprehensive methodological framework, without any doubts, will make possible energy servicing market development, increase investment in energy saving and energy efficiency improvement projects, contribute to the professional growth and realization of specialists in energy saving and energy efficiency.

Multiband simultaneous transmission (MST) system has been studied to enhance the spectral efficiency of wireless local area network (WLAN). In this system, information bits are divided into multiple bands and appropriately modulated taking account for the channel condition of each frequency band, and then a transmission frame consists of differently modulated symbols. To achieve higher spectrum efficiency, it is important to select an appropriate modulation and coding scheme satisfying an allowable frame error rate (FER). It means that FER prediction is a key technique to avoid low rate transmission and the frequent frame error. In this paper, we propose a FER prediction method for MST system. To predict the FER, we derive pairwise error probability (PEP) for this system. Moreover, we also consider the FER calculation based on the PEP for the WLAN system with a block interleaver. Furthermore, in order to improve prediction accuracy, we consider the impact of symbol error occurring beyond adjacent symbols on the PEP derivation. The simulation results show the accuracy of the proposed FER prediction method for both the additive white Gaussian noise channel and a multipath channel.

The central aim of this project is to provide knowledge and tools for increasing the energy efficiency and performance of new and existing laboratory-type facilities in California. We approach the task along three avenues: (1) identification of current energy use and savings potential, (2) development of a {ital Design guide for energy- Efficient Research Laboratories}, and (3) development of a research agenda for focused technology development and improving out understanding of the market. Laboratory-type facilities use a considerable amount of energy resources. They are also important to the local and state economy, and energy costs are a factor in the overall competitiveness of industries utilizing laboratory-type facilities. Although the potential for energy savings is considerable, improving energy efficiency in laboratory-type facilities is no easy task, and there are many formidable barriers to improving energy efficiency in these specialized facilities. Insufficient motivation for individual stake holders to invest in improving energy efficiency using existing technologies as well as conducting related R&D is indicative of the ``public goods`` nature of the opportunity to achieve energy savings in this sector. Due to demanding environmental control requirements and specialized processes, laboratory-type facilities epitomize the important intersection between energy demands in the buildings sector and the industrial sector. Moreover, given the high importance and value of the activities conducted in laboratory-type facilities, they represent one of the most powerful contexts in which energy efficiency improvements stand to yield abundant non-energy benefits if properly applied.

The DCF (Dcistributed Coordination Function) and PCF (Point Coordination Function) are the basic MAC (Medium Access Control) protocols of IEEE 802.11 wireless LANs. According to the DCF, each node performs the exponential backoff algorithm before the transmission of its data frame. Each node doubles the backoff waiting time before the transmission of its data frame whenever it detects the transmission collision with other nodes. Therefore, as the number of the active nodes having the data frames to transmit increases, the overall MAC performance of the DCF decreases. On the other hand, according to the PCF, each node is granted the transmission opportunity by which the PCF transmission is possible without the collision with other nodes. Therefore, as the number of the active nodes increases, the MAC performance of the PCF increases, In this paper, considering the tradeoff of MAC performance between the DCF and PCF, a hybrid MAC protocol is proposed to enhance the performance of IEEE 802.11 wireless LANs. †

This paper proposes a decentralized scheme to improve the energy efficiency (EE) in dense wireless local area networks (WLANs), based on inversely proportional setting (IPS) of carrier sense threshold (CST) and transmit power. Jointly adjusting the CST and transmit power in an inversely proportional manner, i.e., keeping their product to be a constant, is a promising technique to increase transmit opportunities in dense WLANs, without generating unfairness issue of asymmetric carrier sensing. The proposed scheme is formulated in the non-cooperative game framework. Two utility functions are designed, where the first utility function is an approximation of the EE. To guarantee the existence of the equilibrium, and to ensure the convergence of the proposed scheme, we further incorporate potential games, based on which the second utility function is de- signed. The second utility function can be considered as assigning a cost on the first utility function. Simulation results show that the proposed scheme provides considerable improvement in EE and average throughput under various node densities. The second utility function outperforms the first utility function, while the first one requires only local information to be calculated.

QoS Support Polling Scheme for Multimedia Traffic in Wireless LAN MAC Protocol

Wireless LAN has become increasingly popular as a medium to connect portable devices to the network. Most of the existing wireless LAN protocols based on IEEE standard 802.11 assume that the wireless channel is time invariant and thus assign radio resources accordingly. In this paper, we devise a modified MAC level channel allocation method by carefully scheduling radio resource according to temporal channel characteristics, assuming the influence of channel fading. Based on this method we propose new protocols for the distributed coordination function (DCF) and the point coordination function (PCF), the two modes of communication defined in the IEEE standard for WLAN. The proposed protocols introduce minimum computational overhead. Our simulations show that the proposed PCF protocol improves the channel capacity up to 14% and the DCF protocol improves the channel capacity up to 90%, depending on the loss rate and temporal characteristics of the wireless channel. We also show that the proposed DCF protocol can lower SNR requirements thus potentially extending the battery life of portable devices that use WLAN.

As wireless local area networks (WLANs) are rapidly deployed to expand the field of wireless products in military settings, the provision of robust and efficient communication in the face of noisy environments will be mandatory. Such design needs to take into consideration the WLANs limited bandwidth and high error rates. We introduce the concept of super polling which can be implemented within the IEEE 802.11 Point Coordination Function (PCF) media access control scheme. We notice a dramatic throughput increase (up to 85%) when compared with the single poll mechanism used in IEEE 802.11 PCF. The throughput increase is measured as a function of the channel noise, the superpoll overhead per data packet and the packet size.

An effective adaptive scheme is proposed to improve the performance of IEEE 802.11 wireless local area networks (LANs) to support real-time traffic. In order to accurately estimate system status, the scheme employs a bi-dimensional Markovian model and a point coordination function (PCF) model to depict distributed coordination function (DCF) and PCF respectively. The scheme adaptively adjusts the ratio of DCF duration to PCF duration to satisfy the requirements of real-time traffic in a runtime manner. Simulation results show that the proposed scheme significantly improves quality of service (QoS) in terms of throughput and delay metrics

The Point Coordination Function (PCF) of the IEEE 802.11 standard represents a well-known Medium Access Control (MAC) protocol providing Quality-of Service guarantees in Wireless Local Area Networks (WLANs). However, with the currently employed polling mechanism WLANs consume a significant amount of the energy resources from battery-powered user devices. To provide energy saving, an improved MAC protocol is presented in this paper, where bidirectional transmissions of fixed duration are incorporated into PCF in order to enable dynamic scheduling of real-time traffic. Based on this new strategy, wireless access points (APs) can estimate the proper duration of the Contention Free Period (CFP), in order to allow mobile stations to acknowledge any received data packet with a data packet equal to the received packet in size. Having this information, a mobile station, following the data exchange with the AP, can determine its wake-up timer and activate the sleep mode for the rest of the CFP interval. Comprehensive computer-based simulations demonstrate the feasibility of the proposed MAC improvements to achieve energy efficiency with negligible impact on packet delivery delay.

More and more devices, such as Bluetooth and IEEE 802.15.4 devices forming Wireless Personal Area Networks (WPANs) and IEEE 802.11 devices constituting Wireless Local Area Networks (WLANs), share the 2.4 GHz Industrial, Scientific and Medical (ISM) band in the realm of the Internet of Things (IoT) and Smart Cities. However, the coexistence of these devices could pose a real challenge—co-channel interference that would severely compromise network performances. Although the coexistence issues has been partially discussed elsewhere in some articles, there is no single review that fully summarises and compares recent research outcomes and challenges of IEEE 802.15.4 networks, Bluetooth and WLANs together. In this work, we revisit and provide a comprehensive review on the coexistence and interference mitigation for those three types of networks. We summarize the strengths and weaknesses of the current methodologies, analysis and simulation models in terms of numerous important metrics such as the packet reception ratio, latency, scalability and energy efficiency. We discover that although Bluetooth and IEEE 802.15.4 networks are both WPANs, they show quite different performances in the presence of WLANs. IEEE 802.15.4 networks are adversely impacted by WLANs, whereas WLANs are interfered by Bluetooth. When IEEE 802.15.4 networks and Bluetooth co-locate, they are unlikely to harm each other. Finally, we also discuss the future research trends and challenges especially Deep-Learning and Reinforcement-Learning-based approaches to detecting and mitigating the co-channel interference caused by WPANs and WLANs.

Improving energy efficiency (EE) is vital to ensure a sustainable, affordable, and secure energy system. The residential sector represents, on average, 18.6% of the total final energy consumption in the OECD countries in 2018, reaching 29.5% in the UK (IEA, 2020a). Using a staggered differences-in-differences approach with dynamic treatment effects, we analyse changes in residential gas consumption five years before and after the adoption of energy efficiency measures. The analysis includes energy efficiency interventions involving the installation of new heating-related insulation equipment—i.e., of loft insulation and cavity walls, supported by energy efficiency programmes in England and Wales between 2005 and 2017—using a panel of 55,154 households from the National Energy Efficiency Data-Framework (NEED). We control for, among other factors, energy prices and the extent to which gas consumption changes are dependent on household characteristics and variations in weather conditions. Our results indicate that the adoption of EE measures is associated with significant reductions in household residential gas consumption one year after their implementation. However, the effect does not last in the long run and energy savings disappear four years after the retrofitting of cavity wall insulation measures and after two years following the installation of loft insulation. The disappearance of energy savings in the longer run could be explained by the energy performance gap, the rebound effect and/or by concurrent residential construction projects and renovations associated with increases in energy consumption. Notably, for households in deprived areas, the installation of these efficiency measures does not deliver energy savings. These results confirm the existence of effects that reduce the energy savings from the adoption of these efficiency technologies over time and indicates that, for some groups, these net savings do not seem to materialize.

Algorithms for minimum-energy routing in wireless networks typically select minimum cost multihop paths. In scenarios where the transmission power is fixed, each link has the same cost and the minimum hop path is selected. In situations where the transmission power can be varied with the distance of the link, the link cost is higher for longer hops; the energy aware routing algorithms select a path with a large number of small distance hops. In this chapter, we argue that such a formulation based solely on the energy spent in a single transmission is not able to find minimum energy paths for end to end reliable packet transmissions. The proper metric should include the total energy (including that expended for any retransmissions necessary) spent in reliably delivering the packet to its final destination. We first examine how link error rates affect this retransmission aware metric, and how it leads to an efficient choice between a path with a large number of short distance hops and another with a smaller number of large distance hops. Such studies motivate the definition of a link cost that is a function of both the energy required for a single transmission attempt across the link and the link error rate. This cost function captures the cumulative energy expended in reliable data transfer, for both reliable and unreliable link layers. Through detailed simulations, we show that such schemes can lead to up to 30-70% energy savings over best known current schemes, under realistic environments. We next describe how these techniques can be applied to work with on demand routing protocols. In particular, we focus on one specific on demand routing protocol, namely Ad hoc On Demand routing protocol (AODV), and show how it should be adapted to compute energy efficient reliable paths. We perform a detailed study of the AODV protocol and our energy efficient vari ants, under various noise and node mobility conditions. Our results show that even in low noise environments there are specific scenarios where an unmodified on demand protocol will achieve significantly lower throughput in comparison to our modified variants. Our results show that our proposed variants of on demand routing protocols can achieve between 10% to orders of magnitude improvement in energy efficiency of reliable data paths.

Wireless communication provides users many benefits such as portability, flexibility, reduced hardware need and lower installation costs. Wireless local area networks (WLANs) for example allow users the ability to carry their laptops from place to place without any physical wires and without losing network connectivity.However, some amount of security risk is always associated with wireless networks. The most significant security risk for wireless technology is the potential outsiders have in gaining access to the communications medium, the communications medium being the air waves. Though WLANs provide the users with the option of roaming, this convenience is facilitated by broadcasting packets to anyone with compatible equipment within range of a transmitting device. This broadcasting of packets induces a compromise between convenience and security. Having an unsecured WLAN can result in a loss of service, or can be used as a staging area to launch attacks against other networks. The significant challenges faced today in securing wireless LANs are maintaining privacy, data confidentiality, and preventing unauthorized access using proper access control mechanisms.As wireless networking and security become more prevalent in the market, more and more computer science programs are incorporating courses in wireless networks or at the least, devoting a significant percentage of the advanced networking courses to wireless topics. As a result, in addition to industry practitioners, there is a growing interest among university researchers and faculty regarding tools used in monitoring and assessing security threats for wireless networks.This paper will demonstrate and evaluate a free and open source software tool, called Network Stumbler, used for monitoring and assessing security threats for wireless networks. Network Stumbler is a Windows-based tool that allows you to detect Wireless Local Area Networks (WLANs) using 802.11b, 802.11a and 802.11g. It has many uses:• Verifies that your network is set up the way you intended.• Find locations with poor coverage in your WLAN.• Detects other networks that may be causing interference on your network.• Detects unauthorized rogue access points in your workplace.• Helps aim directional antennas for long-haul WLAN links.• Can be used recreationally for WarDriving.