Analytical and simulation performance modelling of indoor infrared wireless data communications protocols

The Infrared (IR) optical medium provides an alternative to radio frequencies (RF) for low cost, low power and short-range indoor wireless data communications. Low-cost optoelectronic components with an unregulated IR spectrum provide the potential for very high-speed wireless communication with good security. However IR links have a limited range and are susceptible to high noise levels from ambient light sources. The Infrared Data Association (IrDA) has produced a set of communication protocol standards (IrDA I. x) for directed point-to-point IR wireless links using a HDLC (High-level Data Link Control) based data link layer which have been widely adopted. To address the requirement for multi-point ad-hoc wireless connectivity, IrDA have produced a new standard (Advanced Infrared -AIr) to support multiple-device non-directed IR Wireless Local Area Networks (WLANs). AIr employs an enhanced physical layer and a CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance) based MAC (Media Access Control) layer employing RTS/CTS (Request To Send / Clear To Send) media reservation. This thesis is concerned with the design of IrDA based IR wireless links at the datalink layer, media access sub-layer, and physical layer and presents protocol performance models with the aim of highlighting the critical factors affecting performance and providing recommendations to system designers for parameter settings and protocol enhancements to optimise performance. An analytical model of the IrDA 1.x data link layer (IrLAP Infrared Link Access -Protocol) using Markov analysis of the transmission window width providing saturation condition throughput in relation to the link bit-error-rate (BER), datarate andprotocol parameter settings is presented. Results are presented for simultaneous optimisation of the data packetsize and transmission window size. A simulation model of the IrDA l. x protocol, developed with OPNETTM Modeler, is used for validation of analytical results and to produce non-saturation throughput and delay performance results. An analytical model of the AIr MAC protocol providing saturation condition utilisation and delay results in relation to the number of contending devices and MAC protocol parametersis presented.Results indicate contention window size values for optimum utilisation. The effectiveness of the AIr contention window linear back-off process is examined through Markov analysis. An OPNET simulation model of the Alf protocol is used for validation of the analytical model results and provides non-reservation throughput and delay results. An analytical model of the IR link physical layer is presented and derives expressions for signal-to-noise ratio (SNR) and BER in relation to link transmitter and receiver characteristics, link geometry, noise levels and line encoding schemes. The effect of third user interference on BER and resulting link asymmetry is also examined, indicating the minimum separation distance for adjacent links. Expressions for BER are linked to the data link layer analysis to provide optimum throughput results in relation to physical layer propertiesandlink distance

A review of communication-oriented optical wireless systems

This article presents an overview of optical wireless (OW) communication systems that operate both in the short- (personal and indoor systems) and the long-range (outdoor and hybrid) regimes. Each of these areas is discussed in terms of (a) key requirements, (b) their application framework, (c) major impairments and applicable mitigation techniques, and (d) current and/or future trends. Personal communication systems are discussed within the context of point-to-point ultra-high speed data transfer. The most relevant application framework and related standards are presented, including the next generation Giga-IR standard that extends personal communication speeds to over 1 Gb/s. As far as indoor systems are concerned, emphasis is given on modeling the dispersive nature of indoor OW channels, on the limitations that dispersion imposes on user mobility and dispersion mitigation techniques. Visible light communication systems, which provide both illumination and communication over visible or hybrid visible/ infrared LEDs, are presented as the most important representative of future indoor OW systems. The discussion on outdoor systems focuses on the impact of atmospheric effects on the optical channel and associated mitigation techniques that extend the realizable link lengths and transfer rates. Currently, outdoor OW is commercially available at 10 Gb/s Ethernet speeds for Metro networks and Local-Area-Network interconnections and speeds are expected to increase as faster and more reliable optical components become available. This article concludes with hybrid optical wireless/radio-frequency (OW/RF) systems that employ an additional RF link to improve the overall system reliability. Emphasis is given on cooperation techniques between the reliable RF subsystem and the broadband OW system

Link layer protocol performance of indoor infrared wireless communications

The increasing deployment of portable computers and mobile devices leads to an increasing demand for wireless connections. Infrared presentsseveral advantagesover radio for indoor wireless connectivity but infrared link quality is affected by ambient infrared noise and by low power transmission levels due to eye safety limitations. The Infrared Data Association (IrDA) has developed the widely used IrDA 1.x protocol standard for short range, narrow beam, point to point connections.IrDA addressedthe requirement for indoor multipoint connectivity with the development of the Advanced Infrared (AIr) protocol stack. This work analyses infrared link layer design based on IrDA proposals for addressing link layer topics and suggests implementation issues and protocol modifications that improve the operation of short range infrared connections. The performance of optical wireless links is measuredby the utilization, which can be drawn at the data link layer. A new mathematical model is developed that reaches a simple equation that calculates IrDA 1.x utilization. The model is validated by comparing its outcome with simulation results obtained using the OPNET modeler. The mathematical model is employed to study the effectiveness on utilization of physical and link layer parameters.The simple equation gives insights for the optimum control of the infrared link for maximum utilization. By differentiating the utilization equation, simple formulas are derived for optimum values of the window and frame size parameters. Analytical results indicate that significant utilization increase is observed if the optimum values are implemented, especially for high error rate links. A protocolimprovement that utilizes special Supervisory frames (S-frames) to pass transmission control is proposed to deal with delays introduced by F-timer expiration. Results indicate that employing the special S-frame highly improves utilization when optimum window and frame size values are implemented. The achieved practical utilization increase for optimum parameter implementation is confirmed by meansof simulation. AIr protocol trades speedfor range by employing Repetition Rate (RR) coding to achieve the increased transmission range required for wireless LAN connectivity. AIr employs the RTS/CTS medium reservation scheme to cope with hidden stations and CSMA/CA techniques with linear contention window (CW) adjustment for medium access. A mathematical model is developed for the AIr collision avoidance (CA) procedures and validated by comparing analysis with simulation results. The model is employed to examine the effectiveness of the CA parameters on utilization. By differentiating the utilization equation, the optimum CW size that maximises utilization as a function of the number of the transmitting stations is derived. The proposed linear CW adjustment is very effective in implementing CW values close to optimum and thus minimizing CA delays. AIr implements a Go-Back-N retransmission scheme at high or low level to cope with transmission errors. AIr optionally implements a Stop-and-Wait retransmission scheme to efficiently implement RR coding. Analytical models for the AIr retransmission schemes are developed and employed to compare protocol utilization for different link parametervalues. Finally, the effectiveness of the proposedRR coding on utilization for different retransmission schemes is explored

Analytical and simulation performance modelling of indoor infrared wireless data communications protocols

The Infrared (IR) optical medium provides an alternative to radio frequencies (RF) for low cost, low power and short-range indoor wireless data communications. Low-cost optoelectronic components with an unregulated IR spectrum provide the potential for very high-speed wireless communication with good security. However IR links have a limited range and are susceptible to high noise levels from ambient light sources. The Infrared Data Association (IrDA) has produced a set of communication protocol standards (IrDA I. x) for directed point-to-point IR wireless links using a HDLC (High-level Data Link Control) based data link layer which have been widely adopted. To address the requirement for multi-point ad-hoc wireless connectivity, IrDA have produced a new standard (Advanced Infrared -AIr) to support multiple-device non-directed IR Wireless Local Area Networks (WLANs). AIr employs an enhanced physical layer and a CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance) based MAC (Media Access Control) layer employing RTS/CTS (Request To Send / Clear To Send) media reservation. This thesis is concerned with the design of IrDA based IR wireless links at the datalink layer, media access sub-layer, and physical layer and presents protocol performance models with the aim of highlighting the critical factors affecting performance and providing recommendations to system designers for parameter settings and protocol enhancements to optimise performance. An analytical model of the IrDA 1.x data link layer (IrLAP Infrared Link Access -Protocol) using Markov analysis of the transmission window width providing saturation condition throughput in relation to the link bit-error-rate (BER), datarate andprotocol parameter settings is presented. Results are presented for simultaneous optimisation of the data packetsize and transmission window size. A simulation model of the IrDA l. x protocol, developed with OPNETTM Modeler, is used for validation of analytical results and to produce non-saturation throughput and delay performance results. An analytical model of the AIr MAC protocol providing saturation condition utilisation and delay results in relation to the number of contending devices and MAC protocol parametersis presented.Results indicate contention window size values for optimum utilisation. The effectiveness of the AIr contention window linear back-off process is examined through Markov analysis. An OPNET simulation model of the Alf protocol is used for validation of the analytical model results and provides non-reservation throughput and delay results. An analytical model of the IR link physical layer is presented and derives expressions for signal-to-noise ratio (SNR) and BER in relation to link transmitter and receiver characteristics, link geometry, noise levels and line encoding schemes. The effect of third user interference on BER and resulting link asymmetry is also examined, indicating the minimum separation distance for adjacent links. Expressions for BER are linked to the data link layer analysis to provide optimum throughput results in relation to physical layer propertiesandlink distance.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Spread spectrum techniques for indoor wireless IR communications

Multipath dispersion and fluorescent light interference are two major problems in indoor wireless infrared communications systems. Multipath dispersion introduces intersymhol interference at data rates above 10 Mb/s, while fluorescent light induces severe narrowband interference to baseband modulation schemes commonly used such as OOK and PPM. This article reviews the research into the application of direct sequence spread spectrum techniques to ameliorate these key channel impairments without having to resort to complex signal processing techniques. The inherent properties of a spreading sequence are exploited in order to combat the ISI and narrowband interference. In addition, to reduce the impact of these impairments, the DSSS modulation schemes have strived to be bandwidth-efficient and simple to implement. Three main DSSS waveform techniques have been developed and investigated. These are sequence inverse keying, complementary sequence inverse keying, and M-ary biorthogonal keying (MBOK). The operations of the three systems are explained; their performances were evaluated through simulations and experiments for a number of system parameters, including spreading sequence type and length. By comparison with OOK, our results show that SIK, CSIK, and MBOK are effective against multipath dispersion and fluorescent light interference becausc the penalties incurred on the DSSS schemes are between 0-7 dB, while the penalty on OOK in the same environment is more than 17 dB. The DSSS solution for IR wireless transmission demonstrates that a transmission waveform can he designed to remove the key channel impairments in a wireless IR system

Implementing a wireless base station for a sensor network

Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2004.Includes bibliographical references (leaves 68-69).Using wireless sensor networks for monitoring infrastructure is a new trend in civil engineering. Compared with traditional ways to monitor infrastructure, wireless sensor networks are cheap, safe, and compact. However, there are many available wireless communication techniques and hardware for a wireless sensor network. Therefore, it is an important step to choose the best communication method and hardware to construct a wireless sensor network for a particular infrastructure. The London Underground project, which is described in this thesis as a reference case study, demands real-time data transmission, low-power network, and wireless network communication, and also a hardware/software system to collect, archive and display data from the monitoring activity. We consider the trade-offs in choosing 802.1 lb as a communication method. A web service architecture for data visualization is then described. Finally we discuss the appropriate selection of a computer device to serve as the base station.by Heewon Song.M.Eng

Controlling a contactless planar actuator with manipulator

An existing magnetically levitated planar actuator with manipulator has been studied and improved from a control point of view. This prototype consists of a magnetically levitated six-degree-of-freedom (6-DOF) planar actuator with moving magnets, with a 2-DOF manipulator on top of it. This system contains three different contactless technologies: contactless bearing and propulsion of the planar actuator, wireless powering of the manipulator, and wireless communication and control of the manipulator. The planar actuator (PA) consists of a Halbach magnet array, which is levitated and controlled in all six DOF’s above a stationary coil array. The PA is propelled in two horizontal translational DOF’s while the other four DOF’s are stabilized to accomplish a stiff bearing. Each active coil contributes to the production of forces and torques acting on the magnet array. Since the number of active coils is much larger than the number of DOF’s, the desired force production can be distributed over many coils. Therefore, a commutation algorithm has to be used to invert the mapping of the forces and torques exerted by the set of active coils as a function of the coil currents and the position and orientation of the translator. One method for linearization and decoupling of the forces and torques was developed in the past. The method is called direct wrench decoupling and guaranties minimal dissipation of energy. However, no constraints on the maximum current can be given. This study proposes two novel, norm-based commutation methods: l8-norm and clipped l2-norm based commutation. Both methods can put bounds on the maximum currents in the coils to prevent saturation of the current amplifiers. The first method focuses on minimization of the maximum current whereas the second method limits the peak current while it minimizes the power losses. Consequently, a higher acceleration of the translator can be achieved and/or less powerful (cheaper) current amplifiers can be utilized and/or fewer commutation errors arise. Only a long-stroke translational movement of the moving magnet planar actuators has been considered in the past. The possibility of a completely propelled and controlled rotation about the vertical axis instead of just stabilizing it for bearing has been analyzed in this thesis from a control point of view. Enhancing the planar actuator with a long-range rotation will increase its utility value and opens new application areas. Based on this investigation, a novel coil array with a triangular grid of rounded coils has been proposed for better controllability in any orientation of the PA. In addition, other coil and magnet topologies have been studied from a control point of view for their suitability for full rotation. The influence of different kinds of error-causes on the commutation precision has been studied. From this investigation, it has been found that the offsets of the measurement system have the highest influence on the precision of the commutation. Investigation of the convergence of the procedure for estimation and elimination of these offsets has been performed. Although it was not proven that the procedure could be applied on the whole workspace of the PA, the convergence has been shown at least for all the investigated points. From this investigation, convergence for any position in the workspace of the PA is expected. It was found that it is possible to use the procedure also with different topologies and with different commutations. A novel wireless link has been developed for the real-time control of a fast motion system. The wireless link communicates via infrared-light transceivers and the link has a delay and a packet-loss ratio almost indistinguishable from the wired connection for the bandwidth of the system up to several kilohertz. The clipped l2-norm based commutation method has been successfully tested on the experimental setup after improving the measurement system, the contactless energy transfer and the wireless communication. With a new, interferometer sensor system, a well-controlled PA with two long-stroke DOF’s has become available. Improved contactless energy transfer does not cause increased electromagnetic interference during switching between the primary coils any more and the wireless connection using the infrared link provides a reliable communication channel between the manipulator and the fixed world. Several control approaches have been tested on the experimental setup. Both, the classical PID control, Sliding-mode control and Iterative learning control have been implemented. Each controller brought better performance than the previous one. Also, a fourth-order trajectory and enhanced feedforward control helped to improve performance. Finally, the tracking errors, in comparison to the initial situation, were reduced by a factor 10 (and even more than by a factor 50 with deactivated contactless energy transfer) while the velocity and acceleration of the system were a factor 4 and 14, respectively, higher

Koshinrai kokoritsu deta densoyo kinkyori hikari musen tsushin hoshiki ni kansuru kenkyu

制度:新 ; 報告番号:甲2917号 ; 学位の種類:博士(国際情報通信学) ; 授与年月日:2009/9/15 ; 早大学位記番号:新514