Wireless LAN Technology Research Articles

A Power-Efficient Access Point Operation for Infrastructure Basic Service Set in IEEE 802.11 MAC Protocol

Infrastructure-based wireless LAN technology has been widely used in today's personal communication environment. Power efficiency and battery management have been the center of attention in the design of handheld devices with wireless LAN capability. In this paper, a hybrid protocol named improved PCF operation is proposed, which intelligently chooses the access point- (AP-) assisted DCF (distributed coordinator function) and enhanced PCF (point coordinator function) transmission mechanism of IEEE 802.11 protocol in an infrastructure-based wireless LAN environment. Received signal strength indicator (RSSI) is used to determine the tradeoff between direct mobile-to-mobile transmission and transmission routed by AP. Based on the estimation, mobile stations can efficiently communicate directly instead of being routed through AP if they are in the vicinity of each other. Furthermore, a smart AP protocol is proposed as extension to the improved PCF operation by utilizing the historical end-to-end delay information to decide the waking up time of mobile stations. Simulation results show that using the proposed protocol, energy consumption of mobile devices can be reduced at the cost of slightly longer end-to-end packet delay compared to traditional IEEE 802.11 PCF protocol. However, in a non-time-critical environment, this option can significantly prolong the operation time of mobile devices.

Achieving per‐flow fairness in wireless ad hoc networks

AbstractMobile ad hoc networks attract tremendous attention as one form of future network configuration. Among wireless LAN technologies, the IEEE 802.11MAC standard can be considered as the most prominent technology deployed in ad hoc networks. For realization of mobile ad hoc networks, providing QoS support in ad hoc networks is an important task. Among numerous parameters of QoS, per‐flow fairness is an important and problematic issue in ad hoc networks. In the traditional wireline networks, per‐flow unfairness occurs mainly due to the link layer. However, in mobile ad hoc networks, in addition to the link layer, the MAC layer has significant impact on per‐flow fairness problems. In particular, although IEEE 802.11MAC provides per‐node fair bandwidth allocation, in order to achieve per‐flow fairness, a method that provides per‐flow fair bandwidth allocation is required. In this paper, a new scheme is proposed that enables a fair bandwidth allocation to each flow. In addition to fairness, the proposed scheme provides a positive impact on the network in terms of total performance and medium utility. The performance of the proposed scheme is investigated with an ns‐2 network simulator. © 2006 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 89(8): 37–49, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.20250

Roaming in the USA

Wireless technologies have dramatically increased the accessibility of the Internet. Because it is fast, cheap, and easy to install and use, Wi-Fi wireless LAN technology has played a leading role in this expansion. Wi-Fi has revolutionized the way people use the Internet in their homes, offices, and increasingly, in public places. Wi-Fi access points can easily be secured by activating standard encryption technology. However, many home and office users choose not to activate this encryption, sometimes because they choose to provide Internet access to outsiders, sometimes because they are not willing to go to the trouble of securing their networks, and sometimes because they do not understand the risks of leaving a network open. As a result, open networks are ubiquitous. It is possible in almost any populated area (and many rural areas) to find an open Wi-Fi access point, and to use that access point as a means to get highspeed Internet access. In fact, the popular Windows XP operating system frequently alerts users that wireless networks are nearby, and prompts users as to whether they would like to connect, or may connect automatically, depending on the user's settings. Using a random open network is certainly convenient. Is this practice illegal? Maybe. Should the law allow this type of access? Definitely. This article explores the legality of accessing the Internet through open Wi-Fi connections in situations where the user has not obtained prior permission from the network operator. This article will first discuss the policy considerations behind permitting or prohibiting such roaming Wi-Fi access. The article will then summarize US law that applies to this type of behavior. Finally, the article will propose an approach that legislators and courts worldwide should take to conform the law to the policy considerations identified in the article.

QoS mechanisms for multimedia communications over TDMA/TDD WLANs

The design of high-performance wireless LAN technologies making use of TDMA/TDD MAC is a very active area of research and development. The control of the network resources of such networks is taken care by a central controller. The mobile terminals may place their resource requests by making use of a well-defined set of primitives. In turn, the central controller allocates the channel bandwidth among all the competing mobiles. In this work, we undertake the design and performance evaluation of a set of QoS-aware mechanisms built on top of the underlying signalling and bandwidth allocation mechanisms provided by most wireless LANs standards. On our design, we assess the amount of overhead introduced by the proposed mechanisms: an important feature when designing scalable mechanisms for wireless environments. Furthermore, we validate the effectiveness of our proposed schemes by quantitatively evaluating the video quality as perceived by the end user. Our results show that the proposed schemes are able to guarantee the QoS requirements of the various services: voice, video, best-effort, and background.

Simulation Study on 3G and WLAN Inter-Working

Seamless interconnection with wireless LAN and 3G technologies is essential for the future wireless environment. The Wireless Local Area Network (WLAN) integrated mobile device is designed to extend the reach of enterprise applications and to create new collaboration environments. Also rapid new service development has started to change traffic mixes in the cellular networks towards IP dominating carriers like GPRS (General Packet Radio Service) and WLAN. These drastic changes require new research in the network as well as system inter-working areas for both the cellular and WLAN technology areas. This is the main challenge our research is trying to solve giving answers to rising inter-working and interoperability questions.

Temporal fairness guarantee in multi-rate wireless LANs for per-flow protection

Wireless LAN technologies such as IEEE 802.11a and 802.11b support high bandwidth and multi-rate data transmission to match the channel condition (i.e., signal to noise ratio). While some wireless packet fair queuing algorithms to achieve the per-flow throughput fairness have been proposed, they are not appropriate for guaranteeing QoS in multi-rate wireless LAN environments. We propose a wireless packet scheduling algorithm that uses the multistate (multi-rate) wireless channel model and performs packet scheduling by taking into account the channel usage time of each flow. The proposed algorithm aims at per-flow protection by providing equal channel usage time for each flow. To achieve the per-flow protection, we propose a temporally fair scheduling algorithm called Contention-Aware Temporally fair Scheduling (CATS) which provides equal channel usage time for each flow. Channel usage time is defined as the sum of the packet transmission time and the contention overhead time due to the CSMA/CA mechanism. The CATS algorithm provides per-flow protection in wireless LAN environments where the channel qualities of mobile stations are dynamic over time, and where the packet sizes are application-dependent. We also extend CATS to Decentralized-CATS (D-CATS) to provide per-flow protection in the uplink transmission. Using an NS-2 simulation, we evaluate the fairness property of both CATS and D-CATS in various scenarios. Simulation results show that the throughput of mobile stations with stable link conditions is not degraded by the mobility (or link instability) of other stations or by packet size variations. D-CATS also shows less delay and less delay jitter than FIFO. In addition, since D-CATS can coordinate the number of contending mobile stations, the overall throughput is not degraded as the number of mobile stations increases.

Focus on Axis Communications' 206W wireless network camera

AbstractThere is an old adage that ‘good things come in small packages’. In this issue's Hardware Spotlight column we will turn our attention to what is billed as the world's smallest wireless network camera whose use validates the previously mentioned adage.The Axis 206W wireless network camera represents a unique merging of flash memory, a CMOS image sensor and IEEE 802.11b wireless LAN technology. The camera is packaged with a power adapter, fastened camera stand, USB cable, CD and manual. Because flash memory is used to store the camera's software, connecting the camera to a computer results in the Axis 206W appearing as a new drive. Clicking on that drive designator results in the display of the files contained in the camera's memory to include a setup program, making its setup a literal breeze.

802.11 무선랜에서 1 비트를 이용한 패킷 인증 방안

IEEE 802.11 Wireless LAN은 무선 인터넷, 차세대 유무선 통합망, 홈네트워크망을 위한 필수적인 무선 액세스 기술이다. 그러나, IEEE 802.11 무선랜을 더 넓은 영역으로 확장하기 위해서는 사용자의 프라이버시를 제공하여야 한다. 현재 WEP이나 802.11i등의 보안 메커니즘이 MAC 계층에서 제안되어 있지만 이러한 보안 메커니즘이 VPN과 같이 사용될 경우. 보안 메커니즘의 중복적용이라는 결과가 나오게 되어 이를 해결하기 위해 1 비트를 인증비트로 사용하는 방식이 제안되었다. 본 논문에서는 기존의 1 비트를 인증 비트로 사용하는 방안에서 생길 수 있는 비트 동기화 실패와 그에 따른 패킷 낭비 문제를 제시하고, 동일 패킷의 수신 개수에 대한 카운터를 이용해 동기화를 한번에 맞춤으로써 이런 문제점들을 해결한 알고리즘을 제안한다. 또한, 성능 평가를 통해 제안하는 알고리즘이 패킷인증 성공률을 <TEX>$98\%$</TEX>까지 증가시킬 수 있으며 패킷 인증 비트 스트림의 효율성에서도 <TEX>$97\%$</TEX>까지의 개선된 성능을 나타냄을 검증하였다. IEEE 802.11 wireless LAN technology is essential for wireless internet, next generation converged network and home network. But, it is certain that user's privacy must be provided to expand the applicable area in IEEE 802.11 WLAN. Recently, WEP and 802.11i security scheme can be used in MAC Layer. But with VPN technology which is applied to WLAN user, it means that suity mechanism is used redundantly. One bit authentication mechanism was already proposed to solve this redundancy. In this paper, we analyze problems of 1-bit Authentication mechanism which are failure of synchronization and waste of packet. And we propose new algorithm which synchronizes sender with receiver, at once, using duplicated-packet-count information. We show that our algorithm improves success probability of packet authentication up to <TEX>$98\%$</TEX> and efficiency of authentication bit stream up to <TEX>$97\%$</TEX>.

Unlicensed cognitive sharing of TV spectrum: the controversy at the Federal Communications Commission

As societies become increasingly mobile and more dependent on information technologies, their radio spectrum also needs change. The basic spectrum management structure in all countries was developed over a long period, and much of the basic framework has remained stable for decades. The FCC is interested in making more spectrum available to unlicensed devices because of the explosive growth of IEEE 802.11/Wi-Fi unlicensed wireless LAN technology, and because the FCC recognizes that there is a great deal of white space that could be exploited by unlicensed devices. The FCC proposal selected the TV bands as an initial home for cognitive radio based on several factors. First, the frequencies used for TV can give greater range in rural areas than the microwave frequencies used for Wi-Fi, and can also give better building penetration than Wi-Fi in all areas. Second, TV broadcast systems usually use high antennas, and the intended receivers need greater than 10 dB signal-to-noise ratio (SNR) to function. A variety of controversial issues have emerged from public comments. One concern is that the confusion resulting from the proposal might discourage purchase of new digital televisions and hence delay the transition from analog to digital televisions. This would also delay the transfer of some current TV spectrum to new mobile uses, including public safety.

IEEE 802.11e와 802.11b 표준이 혼재하는 이종환경에서의 불공평 문제 성능 분석

The IEEE 802.11 based wireless local area networks are candidates to lead the broadband connectivity in the home and office scenarios. Recently IEEE proposed the 802.11e as a new standard to provide appropriate Quality of Services to a plethora of emerging real-time multimedia and high demanding applications such as high definition movie and audio distribution, video-conference and voice over IP. This paper studies the IEEE 802.11e/IEEE 802.11b interactions focusing on potential unfairness problems that might appear in networks with heterogeneous wireless LAN technologies as well as in the IEEE 802.11e deployment phase.

From battlefields to urban grids: New research challenges in ad hoc wireless networks

There has been much talk over the past two decades about commercialization of the mobile ad hoc network (MANET) technology. Potential ad hoc network applications with some commercial appeal are now finally emerging, “drafted” by the enormously successful wireless LAN technology. Closely coupled to commercial applications and critically dependent on commercial ad hoc networks will be the “pervasive computing” applications. Since military and civilian emergency MANETs have been around for over three decades, and since the Government has continuously supported MANET research for as many years, it may seem natural to assume that all the research has already been done and that commercial MANETs can be deployed by simply leveraging the military and civilian research results. Unfortunately, there is a catch. Commercial MANETs (and therefore pervasive computing applications) will evolve in a way totally different from their military counterparts. Most importantly, they will start small, and will initially be tethered to the Internet. They will be extremely cost-aware. They will also need to cater to a variety of different applications. This is in sharp contrast with the large scale, autonomous, special purpose and cost insensitive military networks. In this paper we review a typical “battlefield” MANET application and contrast it to two emerging commercial MANET scenarios—the urban vehicle grid and the Campus network. We compare characteristics and design goals and make the case for new research to help kick off commercial MANETs. In particular we argue that P2P technology will be critical in the early evolution of commercial MANETs and identify research directions for P2P MANETs.

Focus on Firetide HotPoint Wireless Mesh Routers

International Journal of Network ManagementVolume 15, Issue 1 p. 67-71 Hardware SpotlightFree Access Focus on Firetide HotPoint Wireless Mesh Routers Gilbert Held, Corresponding Author gil_held@yahoo.com 4-Degree Consulting, 4736 Oxford Road, Macon, GA 31210, USA.4-Degree Consulting, 4736 Oxford Road, Macon, GA 31210, USA.Search for more papers by this author Gilbert Held, Corresponding Author gil_held@yahoo.com 4-Degree Consulting, 4736 Oxford Road, Macon, GA 31210, USA.4-Degree Consulting, 4736 Oxford Road, Macon, GA 31210, USA.Search for more papers by this author First published: 24 December 2004 https://doi.org/10.1002/nem.552Citations: 1AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onEmailFacebookTwitterLinked InRedditWechat Citing Literature Volume15, Issue1January/February 2005Pages 67-71 RelatedInformation

Experimental Study of Radiation Efficiency from an Ingested Source inside a Human Body Model*.

The attenuation of human body trunk at frequency range of 100MHz to 6GHz from an internal source was estimated using a simplified experimental model. Antennas were placed in the model which was filled with distilled water, 0.9% NaCl saline solution, and porcine body tissue alternately to determine the attenuation of the system. Saline has greater attenuation than water due to its higher conductivity, while porcine body tissue has attenuation bounded by saline solution and water. Estimated attenuation at the four ISM bands, 434MHz, 915MHz, 2.45GHz and 5.8GHz were given and all of these bands satisfied the safety and sensitivity requirements of a biomedical telemetry system. 915MHz and 2.45GHz are good choices for the wireless link because of their relatively larger electrical size of RF components such as antenna. In addition, with the growth in wireless LAN and Bluetooth technology, miniaturized antennas, camera modules, and other RF devices have been developed which can be employed in biomedical ingested or implanted devices. This paper gives a reference of attenuation values of a human body trunk of average size. It should be noted that the attenuation values can be different for different body size and different body composition, and therefore the values in this paper serves as a reference only.

RECENT WIRELESS LAN MANAGEMENT TECHNOLOGIES: TRENDS AND OUTSTANDING ISSUES

This paper describes how outstanding issues and trends in Wireless LAN (WLAN) management technologies affect the IT world. The research results show that the usage of Wireless LAN technology is growing exponentially and the industry is striving to continuously to cope with the outstanding issues and trends.

Software testing for wireless mobile computing

4G wireless networks make it increasingly difficult to develop and test application software for mobile terminals in comparison with 3G or earlier generations. These 4G networks incorporate wireless LAN technologies, and mobile terminals can access the services provided by LANs as well as global network services. Therefore, software running on mobile terminals may depend on not only its application logic but also on services within the LANs to which the terminals are connected. To construct correct software to run in mobile terminals for 4G wireless networks and wireless LANs, it must be tested in all the networks to which the terminal could be moved and be connected. This article presents a new approach, called flying emulator, to testing software designed to run on mobile terminals. Like existing approaches, the approach provides software-based emulators of its mobile terminals for software designed to run the terminals. It is unique because it constructs emulators as mobile agents that can travel between computers. These emulators can carry the target software to the networks to which the terminals are connected and allow it to access services provided by the networks in the same way as if it was moved with and executed on the terminals connected to the networks. This article describes the idea of the approach, its implementation, and our experience with a typical application.

Improving TCP performance in integrated wireless communications networks

Many analytical and simulation-based studies of TCP performance in wireless environments assume an error-free and congestion-free reverse channel that has the same capacity as the forward channel. Such an assumption does not hold in many real-world scenarios, particularly in the hybrid networks consisting of various wireless LAN (WLAN) and cellular technologies. In this paper, we first study, through extensive simulations, the performance characteristics of four representative TCP schemes, namely TCP New Reno, SACK, Veno, and Westwood, under the network conditions of asymmetric end-to-end link capacities, correlated wireless errors, and link congestion in both forward and reverse directions. We then propose a new TCP scheme, called TCP New Jersey, which is capable of distinguishing wireless packet losses from congestion packet losses, and reacting accordingly. TCP New Jersey consists of two key components, the timestamp-based available bandwidth estimation (TABE) algorithm and the congestion warning (CW) router configuration. TABE is a TCP-sender-side algorithm that continuously estimates the bandwidth available to the connection and guides the sender to adjust its transmission rate when the network becomes congested. TABE is immune to the ACK drops as well as ACK compression. CW is a configuration of network routers such that routers alert end stations by marking all packets when there is a sign of an incipient congestion. The marking of packets by the CW-configured routers helps the sender of the TCP connection to effectively differentiate packet losses caused by network congestion from those caused by wireless link errors. Our simulation results show that TCP New Jersey is able to accurately estimate the available bandwidth of the bottleneck link of an end-to-end path; and the TABE estimator is immune to link asymmetry, bi-directional congestion, and the relative position of the bottleneck link in the multi-hop end-to-end path. The proactive congestion avoidance control mechanism proposed in our scheme minimizes the network congestion, reduces the network volatility, and stabilizes the queue lengths while achieving more throughput than other TCP schemes.

Seamless SIP-based VoIP in disparate wireless systems and networks

In the emerging data networks, session initiation protocol (SIP)-based voice over IP (VoIP) is gaining wide-scale acceptance as a means of transporting voice over the packet data networks. With the emergence of interoperability between various third-generation (3G) cellular technologies such as 1xEV, 1xEV-DO, 1xEV-DV, and the Universal Mobile Telecommunications System (UMTS) on one hand and wireless LAN (WLAN) technologies such as 802.11a/b/g, HiperLAN/2, and Bluetooth∗ on the other, multimedia applications would have to interoperate seamlessly among several air interfaces. Mobile IP, a layer 3 protocol, maintains the data session across heterogeneous air interfaces but does not guarantee minimal or no packet loss when handing over a mobile node from one air interface to another. This paper first discusses a network architecture that supports seamless interoperability between 3G and WLAN and proposes autonomous layer 2 enhancements at the client side to support SIP-based multimedia applications in general and voice applications in particular. Finally, it discusses some other network issues that pose a challenge to providing VoIP in commercial networks in general, such as using SIP with network address translation (NAT) over mobile IP, and it specifically addresses the problem of performing VoIP in CDMA2000∗ 1XRTT.

Human Pacman: a mobile, wide-area entertainment system based on physical, social, and ubiquitous computing

Human Pacman is a novel interactive entertainment system that ventures to embed the natural physical world seamlessly with a fantasy virtual playground by capitalizing on mobile computing, wireless LAN, ubiquitous computing, and motion-tracking technologies. Our human Pacman research is a physical role-playing augmented-reality computer fantasy together with real human–social and mobile gaming. It emphasizes collaboration and competition between players in a wide outdoor physical area which allows natural wide-area human–physical movements. Pacmen and Ghosts are now real human players in the real world, experiencing mixed computer graphics fantasy–reality provided by using the wearable computers. Virtual cookies and actual tangible physical objects are incorporated into the game play to provide novel experiences of seamless transitions between real and virtual worlds. We believe human Pacman is pioneering a new form of gaming that anchors on physicality, mobility, social interaction, and ubiquitous computing.

Internet telephony jumps off the wires

After years of unfulfilled hype, a growing number of service providers have begun offering Internet telephony, in which voice data from phone calls is broken up into packets and sent across the Internet. In response, more individuals and companies have begun using the technology. The providers are offering wireless Internet telephony, which adds convenience by letting users make Internet calls from their mobile phones via IEEE 802.11 (Wi-Fi) wireless LAN and third-generation (3G) cellular technologies. Wireless Internet telephony is less expensive than regular mobile telephony because carriers can use the existing Internet, rather than build a new infrastructure, to route calls. Using the Internet enables wireless telephony to offer good reception indoors, which is not always the case with traditional cellular service. However, despite rosy marketplace-growth projections, Internet telephony faces several important concerns, particularly power usage, security, and quality of service (QoS).

QoS-enabled residential gateway architecture

As networking technologies penetrate wide varieties of devices for daily usage, home networks are becoming a reality. The bandwidth and always-on connectivity provided by the rapidly growing broadband technologies, such as cable and digital subscriber line (DSL), render home networking even more attractive. A residential gateway is a device that interconnects various home devices to one another as well as to the Internet. The home networks being deployed today are simple and inexpensive with the residential gateway providing only connectivity. As home networks evolve and become more widespread, emerging applications on home networks will demand additional features that require quality of service. We present an architecture of a next-generation QoS-enabled residential gateway. Such a residential gateway, in conjunction with the developments in QoS-enabled wireless LAN technologies, will usher in a new generation of home networks that are capable of supporting a wide range of applications.