Current IEEE Research Articles

Inaccuracies of a Plastic “Pinna” SAM for SAR Testing of Cellular Telephones Against IEEE and ICNIRP Safety Guidelines

A 2-mm-thick plastic shell with 5-10-mm-thick tapered plastic spacer in the shape of a pinna-specific anthropomorphic mannequin (SAM) head model is being used for determination of the specific absorption rate (SAR) of cellular telephones for compliance testing against IEEE and the International Commission on Non-Ionizing Radiation Protection (ICNIRP) Safety Guidelines used in the U.S. and Europe, respectively. We have used three-dimensional computer-aided design files of the SAM Model with 1-mm resolution to calculate peak 1- and 10-g SAR for cheek and 15/spl deg/-tilted positions of some typical telephones for comparison with those for three anatomic models of the head to show that the SAR obtained for SAM is up to two or more times smaller than for anatomic models. This is due to the shift of the high SAR locations to a low radiated fields region away from the antenna, particularly at 835 MHz, and a substantial physical separation from the absorptive phantom at 1900 MHz. Due to the use of lossless plastic for the pinna, another handicap of the SAM model is the total lack of knowledge of 1- or 10-g SAR in the pinna tissues required by all safety guidelines (current or proposed). To remedy this situation, we propose a modified SAM with a lossy pinna, for which 1- and 10-g SARs are relatively close to those for anatomic models, provided we use a fluid of higher conductivity than that currently used for compliance testing at 835 MHz. Lastly, we compare the implications of the current IEEE and ICNIRP guidelines and the newly proposed IEEE guidelines with a relaxed limit of 4.0 W/kg for any 10-g of tissue of the pinna for maximum allowable powers for cellular telephones at 835 and 1900 MHz to show that the newly proposed relaxed IEEE limits will allow radiated powers that may be 8-16 times those permitted by the current IEEE Standard and up to two times higher than those permitted under ICNIRP guidelines used in over 30 countries.

A New Collision Resolution Mechanism to Enhance the Performance of IEEE 802.11 DCF

The medium-access control (MAC) protocol is one of the key components in wireless local area networks (WLANs). The main features of a MAC protocol are high throughput, good fairness, energy efficiency, and support priority guarantees, especially under distributed contention-based environment. Based on the current standardized IEEE 802.11 distributed coordination function (DCF) protocol, this paper proposes a new efficient collision resolution mechanism, called GDCF. Our main motivation is based on the observation that 802.11 DCF decreases the contention window to the initial value after each success transmission, which essentially assumes that each successful transmission is an indication that the system is under low traffic loading. GDCF takes a more conservative measure by halving the contention window size after c consecutive successful transmissions. This "gentle" decrease can reduce the collision probability, especially when the number of competing nodes is large. We compute the optimal value for c and the numerical results from both analysis and simulation demonstrate that GDCF significantly improve the performance of 802.11 DCF, including throughput, fairness, and energy efficiency. In addition, GDCF is flexible for supporting priority access by selecting different values of c for different traffic types and is very easy to implement it, as it does not requires any changes in control message structure and access procedures in DCF.

Quality of service support in IEEE 802.11 wireless ad hoc networks

Supporting Quality of Service (QoS) in wireless networks is a challenging problem. The IEEE 802.11 LAN standard was developed primarily for elastic data applications. In order to support the transmission of real-time data, a polling-based scheme called the point coordination function (PCF) was introduced in IEEE 802.11. However, PCF was not able to meet the desired and practical service differentiation requirements to fulfill the need of real-time data. Therefore, Task Group E of the IEEE 802.11 working group released several IEEE 802.11e drafts, whose main task is to support QoS in IEEE 802.11 LANs. The polling scheme of PCF is extended in IEEE 802.11e into the more complex hybrid coordination function (HCF). We found that HCF has several performance issues that may affect its anticipated performance. In this paper, we address these issues and propose a QoS enhancement over PCF, called enhanced PCF (EPCF) that enables Wireless LAN to send a combination of voice, data and isochronous data packets using the current IEEE 802.11 PCF. First, we compare the performance of the proposed model (EPCF) with the HCF function of the IEEE 802.11e through simulation. Second, we extend the proposed model (EPCF) to work in a multihop wireless ad hoc mode and present the advantages and limitations in this case. Simulation results demonstrate an enhanced performance of our scheme over the legacy PCF and a comparable performance to the IEEE 802.11e HCF in terms of the average delay and system throughput. However, EPCF is much simpler than HCF, provides flow differentiation, and is easy to implement in the current IEEE 802.11 standard.

Improving fairness in IEEE 802.11 using enhanced carrier sensing

Fair access of the shared wireless medium among different contending stations is a very important issue, especially when quality of service needs to be provided. In the CSMA/CA-based IEEE 802.11 protocol, carrier sensing (CS), collision avoidance (CA) and contention resolution (CR), the three main components, affect its fairness. While the influences of CA and CR on the fairness have already been documented, to the best of the authors knowledge there is no research work taking into account CS's influence. The authors focus on the CS part to improve the fairness. In the current IEEE 802.11 standards, whenever a node detects a sensing range (SR) frame on the medium, it defers the transmission by a fixed duration. It is shown that this duration is sometimes smaller and sometimes larger than the desired period by which the transmission should be deferred, and it is the main cause of the unfairness in some cases. The authors propose an enhanced carrier sensing (ECS) scheme, which distinguishes among the SR frames based on their lengths and defers the transmission accordingly. Simulation results show that ECS improves the fairness substantially.

An efficient multipolling mechanism for IEEE 802.11 wireless LANs

To expand support for applications with QoS requirements in wireless local area networks (WLANs), the 802.11 E Task Group was formed to enhance the current IEEE 802.11 Medium Access Control (MAC) protocol. The multipolling mechanism was discussed in the task group, but some problems remain unsolved. In this paper, we show a design of the multipolling mechanism with the advantages of high channel utilization and low implementation overhead. In our proposed mechanism, wireless stations use a priority-based contention scheme to coordinate in themselves the transmission order on the channel. Moreover, we propose a polling schedule mechanism for our proposed multipoll to serve real-time traffic with constant and variable bit rates. The bounded delay requirement of the real-time traffic can be satisfied in our scheduling model. We establish an admission test to estimate the system capacity and to determine whether a new connection can be accepted. We study the performance of our proposed mechanism analytically, as well as through simulated experiments. The results show that the proposed mechanism is more efficient than the one discussed in the IEEE 802.11 E task group.

Performance analysis and enhancement for the current and future IEEE 802.11 MAC protocols

The IEEE 802.11 specifications provide up to 54 Mbps data rates, respectively. The industry is seeking Higher Data Rates (HDR's) over 100Mbps for IEEE 802.11a extension. However, the medium access control (MAC), which they are based upon, is the same. In this paper, we explore the overhead of HDR's to find out whether the MAC is good enough for the increasing data rates and what to expect as the industry seeks higher data rates. We prove that a theoretical throughput upper limit and a theoretical delay lower limit exist for IEEE 802.11 protocols. The existence of such limits indicates that the overhead must be reduced to get good performance for HDR's. Otherwise, the enhanced performance of HDR's is limited and bounded even when the data rate becomes infinitely high. Both reducing overhead and pursuing HDR's are therefore necessary and important. In order to reduce overhead, we propose a burst transmission and acknowledgement (BTA) mechanism, in which, instead of acknowledging each frame, a burst of frames is received first, and then the whole burst is acknowledged one time. Our study shows that with the BTA mechanism, overhead has been greatly reduced and performance has been greatly improved.

Benefits of upgrading paper mill generator protection

There are a number of functional protection areas on paper mill generators 20 years or older that have significant shortcomings when compared to current IEEE recommended generator-protection practices. This article identifies these protection areas and the risks of not addressing the shortcomings. It also points out the advantages of using multifunction digital relaying to upgrade generator protection as a technology that offers many advantages over older electromechanical relays. The completed upgrade project at MeadWestvaco's Luke Mill in Maryland provided a number of examples of these benefits in uncovering mill problems that, if they had gone undetected, could have resulted in costly mill shutdowns or damage to mill generators.

Welcome to IEEE Xplore

IEEE Xplore is a new online information delivery system. IEEE Xplore contains abstract/citation records and PDF full text for all IEEE and IEE journals, transactions, magazines, and conference proceedings published since 1988 and current IEEE standards. This article briefly discusses features and functionality, and access rights for members and subscribers.

A finite plate technique for the determination of piezoelectric material constants

An improved resonator method is presented for the determination of piezoelectric material constants. The improved method addresses a fundamental limitation of the measurement methods recommended in the current IEEE Standard on Piezoelectricity: the relations between vibrator response and material constants presented in this Standard are based upon the 1-D approximation of an essentially infinite flat plate with a uniform distribution of vibratory motion. The calculation or measurement of the effects due to the nonuniform vibrational amplitude distribution in a laterally bounded plate is a nontrivial task. The practical result is that the current IEEE 176-1987 resonator method recommendations are of limited usefulness in the determination of intrinsic piezoelectric material constants. This limitation can, however, readily be overcome using an improved measurement technique based on measurands unaffected by the vibrational amplitude distribution. In the improved technique, the measurands of choice are the zero-mass-loading, fundamental mode, thickness-field excitation (TE) antiresonance, or lateral-field excitation (LE) resonance frequencies. A recommended experimental procedure, using the preferred measurands, is presented.

Efficiency testing of medium induction motors-a comment on IEEE Std 112-1991

The energy crisis of 1973 focused attention on the efficiency of polyphase induction motors, and the need to have a test procedure that was repeatable and accurate. Medium power induction motors, especially those in the size range 1 through 125 horsepower, were important because of the large number in service and the fact that a significant efficiency improvement through redesign was economically feasible. In response to this the ANSI/IEEE Std. 112, Standard Test procedure for Polyphase Induction Motors and Generators Method B was chosen for testing medium power AC motors for efficiency. The current version IEEE Std. 112-1991 Method B contains several requirements for accuracy improvement which have been found to be effective. Even though the Method B procedure with the additional accuracy requirement has been in use since 1984 no rational has been published to support these extra requirements. The paper discusses the purpose of these improvements, and also points out some weakness in procedure.

Delay analysis of DQDB networks with slot preuse and reuse

The current IEEE 802.6 standard has defined the distributed queue dual bus (DQDB) as the subnetwork for metropolitan area networks (MAN). However, this standard leaves some latitude in the possibility of slot multiuse. This paper addresses the issue of DQDB network delay performance when special devices called erasure nodes are employed with or without the so-called slot preuse technique, which has been proposed recently. It is shown that introducing this technique into DQDB networks dramatically improves system performance in terms of average segment delay and maximum throughput, especially when there is some locality in traffic patterns or the network consists of a small number of nodes.

Underexcitation limiter models for power system stability studies

Underexcitation limiter models suitable for use in large scale power system stability studies are presented. These models are compatible with current IEEE recommended excitation system models. Using these models, it is expected that most underexcitation limiters in use on large system-connected synchronous machines can be represented.

Predicting liquid filled transformer loading capability

The IEEE Transformer Loading Guide equations use the top oil temperature rise over ambient to determine the winding hottest spot temperature during an overload. Recent investigations by the author and others have shown that during overloads there is a time lag between the top oil temperature rise and the oil temperature rise in the winding cooling ducts. This phenomena results in winding hottest spot temperatures greater than predicted by the current (1981) IEEE Loading Guide equations. Accurate predictions of the winding hottest spot temperature requires the use of the temperature of the oil entering and exiting the winding cooling ducts. Low flammability liquids such as silicone or high temperature hydrocarbons are not covered in the present Loading Guide. Resistance change with temperature and liquid viscosity are not considered in current Loading Guide equations. Loading Guide equations also assume a constant ambient air temperature during a load cycle. Improved loading equations based on analysis and testing are presented in this paper. The improved equations consider type of liquid, cooling mode, winding duct oil temperature rise, resistance and viscosity changes, and ambient temperature and load changes during a load cycle. A PC BASIC computer program to perform the calculations was developed and will be included in the next edition of the IEEE Loading Guide for Mineral Oil Immersed Transformers.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

A General Bandwidth Allocation Scheme for Multi-Priority Traffic on DQDB Networks

The Distributed Queue Dual Bus (DQDB) Media Access Control (MAC) protocol, the current IEEE 802.6 standard for Metropolitan Area Networks, functions well only for one priority level even when three priority levels are designed to support multi-priority traffic. In this paper, a general and flexible bandwidth allocation scheme for handling the multi-priority traffic is proposed. In this scheme, the entire bandwidth can be shared by different priority levels according to a pre-specified ratio. For any absent priority level, the corresponding pre-allocated bandwidth will be automatically reallocated to other priority levels. This scheme is also rather suitable for solving the bandwidth domination problem, the priority domination problem, the priority capturing problem, and the bandwidth allocation problem of the DQDB networks which are unable be effectively solved by the standard DQDB protocol with the bandwidth balancing mechanism.

The IEEE Systems. Man, and Cybernetics Society: past, present, and future

Four current and former IEEE Systems, Man, and Cybernetics (SMC) Society presidents consider the past, present, and future of the IEEE SMC Society to commemorate the society's 20th anniversary. The authors address its auspicious beginning, its transition from an incubatee to an incubator society, the breadth of its transactions, the international character of its membership, the appropriateness of the name, the move toward a systems-oriented umbrella organization, the evolving array of research areas, and the challenges and opportunities the society faces in the future.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Electromagnetic field analysis in remote field beddy current testing systems IEEE transactions on magnetics, Vol 25, No. 4, pp. 3010–3012 (Jul. 1989)

Electromagnetic field analysis in remote field beddy current testing systems IEEE transactions on magnetics, Vol 25, No. 4, pp. 3010–3012 (Jul. 1989)

The universal impedance diagram of the ferrite pot core eddy current transducer IEEE transactions on magnetics, Vol. 25, No. 3, pp. 2639–2645 (May 1989)

The universal impedance diagram of the ferrite pot core eddy current transducer IEEE transactions on magnetics, Vol. 25, No. 3, pp. 2639–2645 (May 1989)

Page associative caches on Futurebus

A cache scheme which uses page associative cache descriptors can offer advantages in terms of its impact on cache coherence in the presence of paged transactions, and on the use of local memory to minimize bus loading. It can also be used to preserve cache coherence when processor accesses are cached, i.e. a logical cache, in the presence of an external memory management unit. This paper proposes a mechanism for page associative cache operation for use with Futurebus systems, and analyses how such a cache would overcome the problems common to cache memory designs. Cache protocols are not included in the current Futurebus specification IEEE 896.1, recently standardized, but will be added after further development. Performance of page associative caches is compared with directly mapped caches and fully associative caches.

A class of compatible cache consistency protocols and their support by the IEEE futurebus

Standardization of a high performance blackplane bus, so that it can accommodate boards developed by different vendors, implies the need for a standardized cache consistency protocol. In this paper we define a class of compatible consistency protocols supported by the current IEEE Futurebus design. We refer to this class as the MOESI class of protocols; the term “MOESI” is derived from the names of the states. This class of protocols has the property that any system component can select (dynamically) any action permitted by any protocol in the class, and be assured that consistency is maintained throughout the system. Included in this class are actions suitable for copyback caches, write through caches and non-caching processors. We show that the Berkeley protocol and the Dragon protocol fall within this class, and can be extended to be compatible with other members of the class. The Illinois, Firefly and Write-Once protocols can be adapted to be compatible with this class; the facilities of he Futurebus currently do not support those protocols without adaptation. We discuss very briefly performance choices among protocols, and also other issues relating to a standard bus consistency protocol.

Applying IEEE Quality Assurance StandardsTo Computer Based Laser Jet And ServiceEquipment

Software Quality Assurance is an umbrella activity which covers all aspects of the software lifecycle. This paper discusses the development of a Software Quality Assurance Plan, appropriate to the development of an automated laser test system. This plan is derived from the IEEE standards for software Quality Assurance. The need to coherently integrate quality functions into the product lifecycle is discussed, along with the merits of an unorthodox hybrid systems analysis technique designed to encourage customer involvement. The current Ivel of implementation is discussed. Conclusions are drawn concerning the current IEEE software standards for this application, and the effectiveness of involving the customer in the product lifecycle.