Wireless LAN Standards Research Articles

МОДЕЛИРОВАНИЕ БЕСПРОВОДНОЙ MESH-СЕТЬ НА ОСНОВЕ СПЕЦИФИКАЦИИ ZigBee

Currently, the most widespread wireless access technology, which is widely used to transmita large amount of traffic of various types, is the IEEE 802.11 wireless LAN standard. MESH networkshave become one of the most promising areas of technology development. MESH networksprovide the most interesting solutions integrating various wireless access technologies. The possibilityof organizing local (LAN) and metropolitan (MAN) networks using MESH topology, easilyintegrating into wide area networks (WAN), is a positive factor for use on a ship. In maritimepractice, networks based on digitalization and automation are increasingly used. This article discussesmodeling the interaction of devices in a MESH network based on the ZigBee specification,the principle of operation of the data link layer, which is used in this network, as well as a variant of the method for preventing increased consumption of energy used by the network. One of theadvantages of the ZigBee network is the ability to track network participants and the topologyitself in the mode of their frequent connections, disconnections and reconnections. In this case, itis necessary to analyze the network speed, reliability, bandwidth. For this purpose, we estimatedthe average waiting time for connecting a node, the probability of a successful connection of anode to the network, the probability of finding a channel busy during the first and second probingof the carrier, and a test of the throughput of the network under consideration. The obtained resultsof the analysis indicate the operability of the network in various situations: both under normalconditions and in a difficult jamming environment.

Performance Comparison of IEEE802.11a, IEEE802.11b, IEEE802.11g and IEEE802.11n in Multiple Routers

Nowadays, WLAN (Wireless Local Area Networks) has evolved into one of the most auspicious and lucrative technology. The most prominent use of the application of wireless network technology is 802.11 WLAN. IEEE 802.11(Institute of Electrical and Electronics Engineers) standard specified the frequencies of different WLAN standards. The aspiration of this research is to scrutinize and compare the performance of different wireless LAN standards for the increasing number of routers in a predefined area. For evaluating the performance Wireless LAN throughput, wireless LAN load delay, and wireless LAN media access delay metrics are used. For all combinations of the number of routers, IEEE802.11b shows the highest and IEEE802.11n shows the lowest WLAN media access delay and average wireless LAN delay for 64 nodes.

Design of Low Power Low Noise Amplifier using Gm-boosted Technique

This paper presents the development of low noise amplifier integrated circuit using 130nm RFCMOS technology. The low noise amplifier function is to amplify extremely low noise amplifier without adding noise and preserving required signal to a noise ratio. A detailed methodology and analysis that leads to a low power LNA are being discussed throughout this paper. Inductively degenerated and Gm-boosted topology are used to design the circuit. Design specifications are focused for 802.11b/g/n IEEE Wireless LAN Standards with center frequency of 2.4 GHz. The best low noise amplifier provides a power gain (S21) of 19.841 dB with noise figure (NF) of 1.497 dB using the gm-boosted topology while the best low power amplifier drawing 4.19mW power from a 1.2V voltage supply using the inductively degenerated.

A learning algorithm for rate selection in real-time wireless LANs

To achieve a real–time behavior in wireless communication systems, the multi–rate support (MRS) provided by the IEEE 802.11 Wireless LAN standard may reveal particularly advantageous. Unfortunately, the most widespread rate adaptation algorithms designed for general purpose applications proved to be unsuitable for the challenging real–time scenario. This has led to the definition of purposely designed algorithms such as RSIN, a rate adaptation technique based on the SNR measurement, which showed very good performance in terms of timeliness and reliability. The goal of this paper is to propose an improvement of RSIN that extends its applicability to a wider range of applications. To this aim, we introduce RSIN–E, an enhanced version of RSIN based on an estimation of the SNR obtained through a learning algorithm. In detail, this paper first provides an exhaustive description of both the proposed learning algorithm and the relevant estimation procedure. Then it presents an extensive performance assessment of RSIN–E carried out via both experimental sessions and simulations. The obtained results confirm the effectiveness of the proposed technique and highlight that its performance figures are comparable with those of RSIN, and significantly better than those of Minstrel, a widespread rate adaptation algorithm adopted by most general purpose applications.

Comparing Wireless LAN Standards and a Model Proposal for University Wireless Network Security with 802.1x

Comparing Wireless LAN Standards and a Model Proposal for University Wireless Network Security with 802.1x

A Compact Dual-Band MIMO Antenna for WLAN Applications

This paper presents a compact dual-band MIMO antenna that is compatible to the IEEE 802.11n wireless LAN standards. The MIMO antenna contains two tree-type elements placed back to back with distance of one-sixth wavelength of 2.4GHz; the element in the MIMO antenna is structured with a two-branch tree-type planar inverted-L monopoles, the lengths in both branches are set to the electrical quarter-wavelength of the frequency bands of 5.2GHz and 2.4GHz respectively. The MIMO antenna characterized by small size, low mutual coupling effect and nearly omni-directional coverage in radiation pattern make it entirely applicable to the mobile wireless network applications. The measurement results of the fabricated MIMO antenna demonstrate the success of the suggested design topologies.

A Performance Evaluation for Rate Adaptation Algorithms in IEEE 802. 11 Wireless Networks

The wireless LAN standards IEEE 802.11 (a/b/g) provides multi-rates capabilities. To achieve high network performance, devices need to adapt their transmission rate dynamically under varying conditions. Rate adaption algorithm is a critical component of their performance, only very a few algorithms have been published and the differences between their mechanisms have been publicly discussed. In this paper rate adaption algorithms categorized according to the metric that sender and/or receiver used to calculate the best bit rate uses to transmission date. In addition, a comparative study conducted in IEEE 802.11-based ad-hoc networks of most existing rate adaptation algorithms. General Terms Performance, Algorithms, Simulation, Wireless Network

Design and Development of HiperLAN/2 Physical Layer Model Based Wavelet Signals

HiperLAN (High Performance Radio LAN) is a Wireless LAN standard. It is defined by the European Telecommunications Standards Institute (ETSI). In ETSI the standards are defined by the BRAN project (Broadband Radio Access Networks). In this paper, we improve HIPERLAN/2 based Orthogonal Frequency-Division Multiplexing OFDM, based wavelet signals execution via a MATLAB/ Simulink simulation .These systems provide channel adaptive data rates up to 54 Mb/s (in a 20 MHz channel spacing) in the 5 GHz radio band. For dissimilar channels. MATLAB/ Simulink modeling proved that the performance of wavelet OFDM has a significant degradation in the packet (PDU or PSDU) error rate (PER) compared to based OFDM on Fast Fourier transform (FFT) due to the considerable channel models. With HiperLAN/2 based DWT-OFDM, Carrier-to-Noise Ratio (C/N) development compared to conventional HiperLAN/2 based FFT-OFDM is accomplished. Keywords: HiperLAN/2, OFDM, DWT, IDWT.

TDMA based Approach on MAC Layer for IEEE Wireless LAN Standards

layer is key of wireless network. TDMA approach is based on Maximum utilization of frequency spectrum. Packet error is also depending on frequency spectrum. The demands of WLAN Devices day by day increases exponentially and it operates in the specific narrow spectrum of frequency bands and also increase communication parameters programmed and control over Most modern wireless devices. In this paper, simulate and analyze the performance of existing MAC layer protocol and hybrid MAC with TDMA protocol in wireless local Area Network is presented. In this simulation, we present a MAC protocol based on IEEE 802.11g standard in the DCF mode and DCF with TDMA mode which is useful to improve packet collision in traditional wireless networks. In this analysis, improved performance with TDMA base MAC layer is compared without TDMA. We used simulation through using NS-2 Simulator.

Frame Aggregation Mechanism for High-Throughput 802.11n Wlans

IEEE 802.11n Draft is next-generation wireless LAN standard. This article gives detailed description and comparative study of A-MPDU and Two level frame aggregation mechanisms proposed in the latest 802.11n draft standard, which improve extensively the channel efficiency and data throughput. Ns 2 simulator is used for simulation of 802.11n WLAN frame aggregation. Simulation results confirm that AMPDU, and Two level frame aggregation methods improve extensively data throughput. It analyse the performance of each frame aggregation scheme in distinct scenarios, and it conclude that overall, the two-level aggregation can improve throughput performance of 802.11n. Two level aggregation can more effectively deliver data from multiple sources, PDR rate is much higher with much lower delay and Two level aggregation consumed less energy as compared with A-MPDU approach..

Extending Service Area of IEEE 802.11 Ad Hoc Networks

AbstractAccording to the current IEEE 802.11 wireless LAN standards, IEEE 802.11 ad hoc networks have the limitation that all STAs (Stations) are in the one-hop transmission range of each other. In this paper, to alleviate the limitation of IEEE 802.11 ad hoc networks we propose the efficient method for selecting the most appropriate pseudo AP (Access Point) from among the set of ad hoc STAs and extending the service area of IEEE 802.11 ad hoc networks by the pseudo AP’s relaying the internal traffic of IEEE 802.11 ad hoc networks. Numerical examples show that the proposed method significantly extends the service area of IEEE 802.11 ad hoc networks.

Efficient Resource Sharing Architecture for Multistandard Communication System

The Fourth Generation (4G) network is expected to serve mobile subscribers under dynamic network conditions and offer any type service: anytime, anywhere, and anyhow. Two such technologies that can respond to the above said services are Wideband Code Division Multiple Access (WCDMA) and Orthogonal Frequency Division Multiplexing (OFDM). The main contribution of this paper is to propose a dedicated hardware module which can reconfigure itself either to the OFDM Wireless LAN or WCDMA standard. In this paper, Fast Fourier Transform (FFT) algorithm is implemented for OFDM standard, and rake receiver is implemented for WCDMA standard. Initially efficient implementations of these two algorithms are tested separately and identified the resources utilized by them. Then the new hardware architecture, which configures to any one of these two standards on demand, is proposed. This architecture efficiently shares the resources needed for these two standards. The proposed architecture is simulated using ModelSimSE v6.5 and mapped onto a virtex 5 FPGA device (xc5v1x30ff324) using the tool Xilinx ISE 9.2i, and the results are compared with the standard approach. These results show that the proposed hardware architecture utilizes less number of resources compared to the conventional Reconfigurable Receiver Architecture System.

Collision Localization for IEEE 802.11 Wireless LANs

In this paper, we examine an algorithm for estimating the location of packet collisions, in the presence of bandlimited multipath channels. We propose an improvement to the collision localization algorithm to further enhance its performance to compensate for the increased impairments of the multipath channel. We then examine the collision localization algorithm in conjunction with two common wireless LAN standards, 802.11b and 802.11a/g. We show that for the 802.11b standard, the collision localization algorithm performs well, even in the presence of a multi-path channel. We also show that the 802.11 a/g standards are compatible with collision localization. However, we will see that the IFFT/FFT operations required to perform OFDM transmission limit the effectiveness of collision localization. We therefore also investigate collision localization in conjunction with block-based single carrier transmission, a comparable technology to OFDM, and offers some advantages when used with collision localization. In addition, we also investigate two applications of collision localization. First, we will show that collision localization in conjunction with Viterbi decoding with erasures can, in many cases, allow for corrupted packets to be completely recovered at the receiver. Second, we will also demonstrate that collision localization can be used to combat narrow-band interference, such as Bluetooth, in 802.11 a/g networks.

Hub‐polling‐based IEEE 802.11 PCF with integrated QoS differentiation

AbstractIEEE 802.11 is one of the most influential wireless LAN (WLAN) standards. Point coordination function (PCF) is its medium access control (MAC) protocol with real‐time traffic (rt‐traffic) quality‐of‐service (QoS) guarantees. In PCF, it is very likely that non‐real‐time traffic (nrt‐traffic) will use the contention free period (CFP) that should be dedicated to traffic having higher priority such as rt‐traffic. Therefore, a modified PCF protocol called MPCF, which is based on hub polling and an integrated QoS differentiation, is presented in this paper. With the integrated QoS differentiation, MPCF can prioritize bandwidth requests according to service classes and QoS requirements. With hub polling, MPCF can reduce the bandwidth for control frames and improve the network throughput. A simple and accurate analytical model is derived and presented in this paper to calculate the system throughput of MPCF. Simulation results show that MPCF protocol is much better than PCF in terms of system capacity and rt‐traffic QoS guarantees. Copyright © 2008 John Wiley & Sons, Ltd.

A VCO with on chip tank for IEEE 802.11a

AbstractIn the last years, wireless LAN market has shown an incredible growth, exceeding expectations. This article presents a fully integrated LC voltage controlled oscillator in a low cost 0.35 μm BiCMOS process for the 5–6 GHz band, according to the IEEE 802.11a wireless LAN standard. The tank inductor has been designed by electromagnetic simulations. To test the VCO performance, a synthesizer for IEEE 802.11a has been designed. This work demonstrates the feasibility of a low cost silicon technology for the design of 5–6 GHz band circuits. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2632–2635, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23757

STUDY OF MOBILITY AND QoS OF 802.11 AND 802.11e WIRELESS LAN STANDARDS

Quality of service (QoS) is a key problem in wireless environments where bandwidth is scarce and channel conditions are time varying and sometimes implies highly packet losses. IEEE 802.11b/g/a wireless LAN (WLAN) are the most widely used WLAN standards today, and the IEEE 802.11e QoS enhancement standard exists and introduces QoS support for multimedia applications. This paper presents a class based admission control algorithm for 802.11e based wireless local area networks . The strengths of our admission control is dynamicity and flexibility of the algorithm, which adapts to the situation of the BSS, like global load, number of best effort AC, and position of QSTA by report of QAP. Thus it achieves higher throughput than other admission control for 802.11 e. A summary of many good solutions on admission control for 802.11e is be done, and the model of our admission control is presented. The 802.11e standard starves the low priority traffic in case of high load, and leads to higher collision rates, and did not make a good estimate of weight of queues, so there is an unbalance enters the flows with high priorities. A discussion is presented in detail using simulation-based evaluations, with an aim of comparing results of our admission control algorithm, with the 802.11e standard and the FHCF algorithm. Results reveal an improvement of the network load and a decrease of the number of collisions.

A Coarse-Grained Array Accelerator for Software-Defined Radio Baseband Processing

A shrinking energy budget for mobile devices and increasingly complex communication standards make architecture development for software-defined radio very challenging. Coarse-grained array accelerators are strong candidates for achieving both high performance and low power. The C-programmable hybrid CGA-SIMD accelerator presented here targets emerging broadband cellular and wireless LAN standards, achieving up to 100-Mbps throughput with an average power consumption of 220 mW.

IEEE 802.11n MAC frame aggregation mechanisms for next-generation high-throughput WLANs

IEEE 802.11n is an ongoing next-generation wireless LAN standard that supports a very highspeed connection with more than 100 Mb/s data throughput measured at the medium access control layer. This article investigates the key MAC enhancements that help 802.11n achieve high throughput and high efficiency. A detailed description is given for various frame aggregation mechanisms proposed in the latest 802.11n draft standard. Our simulation results confirm that A-MSDU, A-MPDU, and a combination of these methods improve extensively the channel efficiency and data throughput. We analyze the performance of each frame aggregation scheme in distinct scenarios, and we conclude that overall, the two-level aggregation is the most efficacious.

Achieving optimal performance in IEEE 802.11 wireless LANs with the combination of link adaptation and adaptive backoff

IEEE 802.11 is one of the most popular wireless LAN standards [Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) specifications, IEEE Standard 802.11, August 1999]. In the paper, we propose a simple analytical model, which helps one obtain deep insight into the mechanism of achieving optimal performance by using IEEE 802.11 DCF (Distributed Coordination Function) protocol. The first contribution of this paper is the analysis of the optimal operation point where maximum goodput can be achieved. Through the analysis, we answer some fundamental questions about the existence and the uniqueness of the optimal operation point; about the maximum system goodput can be achieved; about the existence of a simple rule to check out if the system operates under the optimal state or not; and how do the data transmission rates, which is dependent on the selected physical transmission mode, and packet transmission errors, caused by channel fading and (or) interference, affect the final system performance. Another contribution is the proposal of a simple distributed adaptive scheme ''LABS'' (i.e., Link adaptation and Adaptive Backoff Scheme), which makes the system operate under the optimal operation point and, at the same time, achieves some pre-defined target service differentiation ratio between different traffic flows. In the LABS, two adaptive schemes are combined: one is the so called ''Link Adaptation'' scheme, which dynamically selects an optimal modulation mode at a given time so as to improve the achieved system goodput; the other one is the so called ''Adaptive Backoff'' scheme, which adaptively adjusts the minimum contention window size of each sending node to guarantee that the system operates under (or near) the optimal operation point. Results obtained in the paper are relevant to both theoretical research and implementation of real systems.

Multichannel mesh networks: challenges and protocols

Supporting high throughput is an important challenge in multihop mesh networks. Popular wireless LAN standards, such as IEEE 802.11, provision for multiple channels. In this article, we consider the use of multiple wireless channels to improve network throughput. Commercially available wireless network interfaces can typically operate over only one channel at a time. Due to cost and complexity constraints, the total number of interfaces at each host is expected to be smaller than the total channels available in the network. Under this scenario, several challenges need to be addressed before all the available channels can be fully utilized. In this article, we highlight the main challenges, and present two link-layer protocols for utilizing multiple channels. We also present a new abstraction layer that simplifies the implementation of new multichannel protocols in existing operating systems. This article demonstrates the feasibility of utilizing multiple channels, even if each host has fewer interfaces than the number of available channels.