The aim of project is to built, test and design a wireless feedback control system. Replace point to point connection with wireless has so many useful advantages like reduced weight, simpler installation, reliability, maintenance, improved flexibility [Irwin, W.G. and Scanlon, W. (2010)] . Wireless sensors reduces the cost and effort related with installing wide length of coaxial cables. In order to transmit real time data in control systems, coaxial cables are consider as safest way to exchange data. Although the wire fitting effort and charges related with each coaxial wire is $5,000 per transmission interface. As more actuators and sensor nodes are add in the system, the range of wires installed increases as well [Wang,Yang (1993).]. To work with low cost actuators installed in high density in single structure wireless communication is proposed to get rid of high cost coaxial wires. Wireless technologies in control system has many advantages like flexible installation, maintenance, mobile operation, monitoring and control of equipments in hazardous and difficult to access environments. Along with that they have adverse properties like path loss, multipath fading, adjacent channel interference. Wireless link have problems like jitter, delay and packet loss. The bit error rate of wireless channel is several time higher than wired channel which degrade the quality of control and system instability [Xia,Feng.et.al (2008)]. The challenges for wireless feed back control is existence of time delay within feed back loop and lost information due to an error [Phillips,L.C. feedback control systems]. Exploring the need working of different wireless technologies available in market is required for design of wireless feed back control systems.
1.2Research methodology:
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From different articles and journals, it is found that the wireless feedback system is cost effective, simple and easy to set up than wired connection. There are some issues in wireless communication like data loss or time delay which can potentially reduce the performance of control system. Actually it depends upon range and distance of communication system , if the distance or range is more then there are more chances of error. By comparing short range wireless technologies we can find an idea which technology and standard is suitable for system.
A wireless system is developed in which data has to transmit wirelessly in order to compare and control the feed back with reference voltage. The analog output of sensor is converted to digital by using smart sensor or ADC and then through transceiver data has to transmitted. Zigbee communication medium is preferred to transmit wireless data because it is a high level communication protocol. It is low cost, low power mesh networking technology. It has long distance range of 100 meter to transmit and receive data with security because of encryption and decryption algorithm used in modules. The transmitted data has to be received at other end and compare with given voltage.
1.3Literature review :
Prof. G.W. Irwin and Dr. W.Scanlon (2009) discussed the networked controlled system in which sensors, actuators, comparators are joined in a communication network. Replacing point to point connection has many advantages like reduced weight, maintenance, reliability, lower cost and simpler installation. The analysis lies on various factors like steady sample rate, actuation, synchronized control and non delay sensing. Latency and jitter are the problems which occur in control analysis and design due to addition of data in feedback. Wireless network controlled system using IEEE802.11 the most general wireless standard which offers caustic environmental traversal and intrinsic flexible prefrences over wire links. Infact wireless interface have some disadvantages of delay like high level of packet error rate and medium access contention. The main exception in NWS is to determine quality of service required for closed loop system. QoS is available to both wire or wireless link while certainly for multimedia and not for regular control. According to work done before the sample rate uses quality of service for permanent controller design. Closed loop strength measure the effect of channel fault and channel difference on wireless NCS. The new plan will base on maintain performance of closed loop of varying channel conditions in presence of changing control law. The other approaches can be unlike hard wired computer control, samples which are transmitted at each instant can be control and measure the availability of communication network. The most timely which can be used inside analytical control framework to handle time varying delays and packet losses introduced by wireless NCS.
Yang, Wang. et.al (2006) discussed wireless structural sensing and control system for response improvement in civil structure. A wire control structure and WiSSCon prototype is used to manage the arrangement when similar ground excitation are applied to the system. The wire control structure behave as baseline with which WiSSCon system performance is compared. In real time feedback the performance of wireless communication and embedded computing technologies is shown by response of WiSSCon structural control and wired control system. In WiSSCon system, wireless sensor act as control kernel for feedback of structural response data of wireless communication.Wireless sensing unit measures the active response of wireless sensor. For calculating control forces the control kernel uses its limited fixed computing resources to rapidly process sensor data, generate control signals and apply control commands to structural actuators inside the selected time step duration. A remote information and authority server with a wireless transceiver is fixed as an optional structure part reliable for organization of the flow of data. The command server during test first notice the wireless sensing and organize part then designate automatic operation. When wireless control unit received start command, It begins to broadcast beacon signals to the wireless sensing unit for fixed time period. As soon as they receive the beacon signal the wireless sensing unit provide a small time period to access the wireless bandwidth for transmitting its sensor data. The wireless control wait until it got data from every wireless sensing unit. Wireless control unit measures optimal control forces and issues consequent command signals to system actuator as soon as they receive the data. The data command server is utilize to initiate the control system . comparatively in real world applications the wireless control system could be automatically started when an earthquake or strong wind condition occurs.
CHAPTER 2 SYSTEM OVERVIEW
2.1 Introduction:
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A control system is an interconnection of components forming a system configuration that will provide a desired system response. The input-output relationship represents the cause and effect of the process, which in turn represents a processing of the input signal to provide an output signal variable [Dorf, C.Richard and Bishop, H.Robert (2008)].
2.1.1 Open closed loop system: An open closed loop control system uses a controller and an actuator to obtain desired response. It is a system without feed back. [Dorf, C.Richard and Bishop, H.Robert (2008)].
2.1.2 Closed loop system: A closed loop control system utilizes an advance measure of the actual output to compare the actual output with the required output response. The quantify of the output is called feedback signal. A feedback control system is a system that tends to keep an agreed relationship of one system variable to another by comparing functions of these variables and uses the difference as a mean of control. With an accurate sensor, the measured output is good approximation of actual output of system. A closed loop control system uses a measurement of the output and feedback of the signal to compare it with the desired output. [Dorf, C.Richard and Bishop, H.Robert (2008)].
A common example of an open loop control system is a microwave oven set to operate for a fixed time and closed loop control system is a person steering an automobile by looking at the auto's location on the road and making the appropriate adjustments.
The principle of the system is to transmit data wirelessly. This system helps to reduce the cost, labor, weight and time to install wires. At industrial level worker spend lot of time and cost to spread the wires. And in case if any point of wire is broken all the data will loss. In this system sensor will take data from system and convert it digital form and then through transceiver transfer it and then compare it with actual output.
2.2 System Architecture: For feedback control system, the physical variable architecture in all applications like industrial, military, environmental, medical, home appliance are sensors. Majority of sensor output signal are in electrical form. Depends on processing techniques used digital or analog components are used and methods are selected. Digital signal are easy to transmit, store, multiplex and immune to noise and encryption can be done easily. Digital transmission is much better than analog because of their flexibility in design instrument and programmability, communication purpose and easy to use. Some sensors produces analog signal they need to convert to digital form by using smart sensors or analog to digital converter. Analog to digital converter takes a long time to convert so if data has to transmit at high speed then timing can be problem. So in order to overcome this smart sensors can be used. The output of sensor is converted to digital form and transmit through transceiver. At receiving end, again data has to convert back to analog form and compare with actual output. To compare the actual output with the desired output response either embedded C or java language can be used.
2.2.1Sensor: A sensor is a device that measures a physical quantity and converts it into a signal which can be read by an observer or by an instrument. A large number of low power, inexpensive sensor devices are densely embedded in the physical environment, operating together in wireless network. There are so many applications of these wireless sensor networks like ecological habitat monitoring, structural health monitoring, environmental contaminant detection, industrial process control and military target tracking. Sensors are classified as active sensors and passive sensors. A passive sensor do not require any extra energy source and it can generates an electrical signal in respond to an outer stimulus that is input stimulus power is transformed by the sensor to output signal. Examples a photodiode and piezoelectric sensor. Active sensor require external power for their operation which is called an excitation signal. That signal is modified by sensor to produce output signal. Example thermistor. [Fradon, Jacob. (2004)]. There are different kind of sensors available:
2.2.2 RF Transceiver:
A RF transceiver consist of RF receiver and RF transmitter. RF receiver is defined as port connected receiver antenna to analog to digital convertor and RF transmitter is defined as digital to analog port connected to transmitter antenna. The ADC and DAC act as boundary between RF transceiver. The main building blocks of RF transceiver are frequency filter, frequency convertor amplifier modulator/demodulator, ADC/DAC signal coupler/divider/combiner/attenuator, switches, power voltage and so on. [Gu,Qizheng.(2005)]
2.2.3 Actuator: An actuator is interface component that converts hydraulic power component back into mechanical power. It can either be cylindrical giving linear motion or hydraulic giving rotating motion. [Schoolup.com] there are different kind of actuators like plasma actuator, electric actuator, linear actuator, motors, hydraulic cylinders. The efficiency of an actuator is an adimensional number less than 1 expressing the energy conversation factor.
2.2.4Microcontroller :it is kind of small computer which executes series of pre-programmed task and interact with other hardware devices. It is perfect controller for robots or machines because of its small integrated circuit whose weight and size is very less. Microcontroller contains memory to store the executed program and number of input and output lines can be used to interact with other devices. A single microcontroller can control security system, mobile robot or automatic washer machine. These days microcontrollers are very cheap and easily available, the most recent microcontrollers are ‘in system programmable' which means we can modify the program being executed without removing its place. [Kamal,Ibrahim (2008)]
2.2.5 Multiplexer:
it is a combinational circuit having certain number of data inputs but have only one output. It is used as digital semiconductor in CPU and graphical controller. Multiplexers are in expensive and effective way of transmission because output is compressed form of input. The medium through which signal transmits can be telephone wires. It is a digital circuit which gives single output for multiple analog and digital signals. There are different types of multiplexers for digital and analog circuits. In digital signal processing the multiplexer combines different streams of data in to single bit stream of higher data rate which can be sent from one place to another over physical link which saves cost [Data connect.com]. Time division multiplexer, frequency division multiplexer and code division multiplexer are the main kinds of multiplexer. In TDM, the time is shared between channels. In FDM, frequency is divided between channels. Each signal is assigned different frequency with a channel. These days CDM is used in communication technology. It uses spread spectrum technology and special coding scheme to allow multiple users to multiplexed over same physical channel [Thomas.net].
2.2.6 Demultiplexer: it performs the opposite function of multiplexer. It is a data distributors which routes an incoming data to several outputs. It receives a transmission of multiple signals over a single line and then decode the single line signal to multiple signals. Demultiplexer is always at receiving end so it break the high rate data stream in to original low data rate. [Birds eye.net(2008)]
2.2.7Transmitter: An electronic device which can be used to generate and amplify a carrier wave, modulates it with a meaningful signal derived, as derived from speech or other sources and then radiate it through antenna. A device that converts mechanical movements in to coded electrical signals [free dictionary.com]
2.2.8 Receiver: A device which receives an incoming signal and converts it back to electrical signal. [free dictionary.com]
2.2.9Analog to Digital convertor: An Analog to Digital convertor is a device used to convert the value of some input signal compared to a regular information in to discrete states of signal generally with algebric values assigned to various combinations of discrete states of the signal. ADC are generally used to convert analog information like audio signals such as temperature, force in to digital form which can involve operations like processing by logic circuits, code conversion, storage until ready for proceed usage, display in numerical or graphical form and transmission. If a large amount of data can be transformed with adequate frequency, to a proper number of two bits , the digital representation of signal can be transmitted through a noisy medium without relative degradation of the fine structure of the original signal.
Conversion involve two steps quantization and encoding:
Quantizing means partitioning the analog signal range into a number of discrete quanta and determining to which quantum the input signal belongs.
Encoding means assigning a particular digital code to each quantum and determining the code that corresponds to the input signal. The most common system is binary system in which there are 2n quanta. [Answer.com]
2.2.10 Digital to Analog convertor: Digital to Analog convertor is a device use for converting information into form of discrete states in relation to standard. It's a device which have electrical input represent a parallel binary number and gives output in the form of voltage or current. It is used to represent the outcome of digital computation, transmission, storage, display of devices which operate with continuously varying quantities. [Answer.com]
2.2.11Security: Security is one of major issue in wireless transmission of data. In wireless LAN data is encrypted at low level before it is transmitted but it can be captured and analyzed at higher levels. One of the problem in wireless LAN that source and destination address are not encrypted. An intruder can notice the route and quantity of data traffic and then be capable to see the source and destination nodes. As data is only encrypted between source and destination, but not at end to end basis so intruder can easily interrupt network as well. The main three ways that WEP uses to secure data are by the Service Set Identifier (SSID) using Open System Authentication, using Shared Key Authentication which is used by all stations to connect to the access point, and last setting up your access point to accept only to accept the media access control (MAC) addresses of specific computers. [Esparza,C.R.(2005)]
2.2.12 Response time:
If the received output signal is differ from actual output signal then according to the difference of both outputs, the level of water tank will rise or low. As soon as this difference will occur the system will send signal to rectify the difference within few couple of seconds that time period is called response time.
CHAPTER 3 COMMUNICATION SYSTEM
3.1 INTRODUCTION:
communication means sending, receiving and processing of information by electronic means. Forms of communication include telegraphy, telephony, broadcasting, point to point mobile communication, radar and computer communication. The terms data and digital communication are the main part of communication which are used interchangeably and both transfer information electronically. Data communication means transfer of information between two points either via analog signal or via digital signal.
In point to point communication system each end of communication system consist of data terminal equipment (DTE) and data communication equipment (DCE). Data are carried between two ends of communication system by medium. The data terminal equipment is one where data originates. Early DTEs were teletype machines, but today they are more likely to be computers. DTE perform the function to send and receive data and error checking on received data. The data communication equipment (DCE) is the interface between DTE and medium. It accepts data transmitted from DTE and converts them back to format acceptable to the medium. Transmission channel or medium may be pair of wires, a coaxial cable or a radio waves.
DTE- Data terminal equipment DCE-Data communications equipment
3.2 WIRELESS COMMUNICATION:
Wireless communication is a term used for transmission of information from one place to another place without using wires. This may be one-way communication or two way communication as in broadcasting systems. The distance involve may be short (a few meters in television remote control) or long (thousand or million kilometer involve in radio communication). It encompasses different types of fixed, mobile and portable two-way radios, cellular telephones, wireless computer mice, keyboards, headsets, satellite televisions and cordless phones. Wireless permits operations such as long range communication which are practically not possible through wire connections. Wireless networking is used in many areas, infact the most common and popular use is to connect laptop users who travel from one location to another location or connect mobile networks via satellite. A wireless transmission technique is a reasonable choice to network a LAN segment that should oftenly change locations. The following situations validate the utilize of wireless technology.
to extent a distance a far from the capabilities of typical cabling.
to give a backup connection link in case of regular network failure
to overcome situations wherever usual cabling is not achievable or impractical
to distantly connect mobile users or networks.
It is possible to transmit information where physical cable lying is not possible and cost of wired connection is very high. Also the wired connection have some draw back like connection time for dial up lines is too long for some applications, data rates are fixed and limited, limited ability to carry higher frequencies and propagation problem. Wireless communication can be connected via radio frequency communication, micro wave communication (long range), infrared communication (short range). Wireless communication can be point to point communication, point to multipoint communication, broadcasting, cellular network and other wireless network. Wireless network are difficult to set up, maintain, troubleshoot. Loss of privacy, problem with speed and security but it is easy to add temporary machines to the networks. [Goldsmith,Andrea.(2005)]
Wireless communication is basically of two types analog communication and digital communication. Analog communication is the transfer of continuously varying information signal and digital communication is the transfer of discrete message. These days all new system use digital communication rather than analog because digital technology is fast, cheaper and programmable.
Analog communication
Digital communication
3.2.1 ANALOG COMMUNICATION:
Analog communication is the transfer of continuously varying information signal. Analog system is used in analog modulation (AM) & Frequency modulation (FM) radio, television, telephone. An analog signal is one in which values taken can be continuous. For example if a signal varies between 0 and 5 volts it can take any value between 0 and 5. It is a data transmitting technique that uses constant signals to broadcast data including voice, video, image etc. An analog signal is a changeable signal constant in both time and amplitude which is usually carried by use of modulation. Analog circuits do not involve quantization of information unlike the digital circuits and therefore have a primary drawback of random deviation and signal degradation, mainly resulting in adding noise to the audio or video quality over a distance.[Akshay Bhatia(2005)]. Analog communication is economical and enables information to be transmitted from point to point or from one point to many. As soon as the data reached at the receiving end, it is transformed back into digital form so that it can be processed by receiving computer. Analog system are less tolerant to noise, make good use of bandwidth, and are easy to manipulate mathematically. Analog signal require hardware receiver and transmitter that are designed to perfectly fit the particular transmission.[Rappaport,t.(2008)]
3.2.2 DIGITAL COMMUNICATION:
It is the transfer of continually varying information signal or discrete messages. These messages are either represented by binary signals 1 or 0. It is the physical transfer of digital bit stream over point to point or point to multi point transmission medium. The medium can be wire, space, fibre optic cable, under water acoustic channel are used. The data is often represented as electro magnetic signal such as electrical voltage signal, microwave, radio wave or infrared signal. Digital signal are more liberal to sound but digital signals can be totally corrupted in the existence of so much noise. In digital signals, noise could cause 1 to be interrupted as 0 or vice versa which makes received data different than original data. Most modern communication system are digital these days any analog input are converted to digital called sampling and conversion back analog to digital is called reconstruction. Signal processing and coding techniques used in digital communication increase the bit rate that can be supported through physical channel. Optical fibre has reduced the cost of transmitting high bit rates over long distances. [Kennedy,George.(1998)]
In this section we are going to use digital communication because wirelessly only digital data can be transmitted. And digital data is fast, cheap and programmable as well.
CHAPTER 4 WIRELESS TECHNOLOGIES
4.1 Introduction:
wireless technology gives information anywhere in the world. It allows to connect with anyone even if there is no telephone line near by. Modern technology gives us easy methods to transfer information and communicate. Wireless technology includes mobile phones, wireless internet connections, handheld devices such as PDAs, medical devices like cardiac pacemakers, GPS system. Wireless technology includes sending and receiving information without using wires like car radios, baby monitors, remote control. Wireless technology means electronic devices that can send and receive large amount of information through radio waves. Any information can be transmitted wirelessly like text, images, sound, videos, the three basic parts are needed for this transmitter, receiver and a carrier wave.[Firestone,Mary(2009)]
wireless communication is the transfer of information over a distance without use of wires. The distance involve can be short or long. The beginning of wireless communication is not much later than beginning of wireline communication. In 1895 guglielmo macroni invented the wireless radio used to send and receive signal at a distance of almost 3 kilometers by using simple on and off signals but with the evolution of telegraphy there was need of analog rather than digital transmission through the air. During last few years wireless has emerged from being only a broadcast technology. Infact its use has explanded in to world of personal communication. Earlier broadcasting can be done by wires using analog method but these days it is possible to transmit data wirelessly using digital method. Wireless implementations can be short-range point-to-point communication like Wireless Microphones, Remote Controls, Wireless USB, RFID, Wireless Sensor Networks like Ultra Wideband, Bluetooth, Zigbee and Wireless Network like Wireless LAN, Wimax, WAN, WiFi. [Prabhu,C.S.R (2006)]
4.2 BLUETOOTH:
Bluetooth is a name given to new technology that replace cables connecting mobile device with their peripherals. The first Bluetooth consortium was formed in 1998 by Ericsson, INTEL, IBM, NOKIA and TOSHIBA. It is an open standard that enables communication among different devices with standard short range wireless radio connection. Its basically an cable replacement technology and it got innumerous applicable areas. The main key issues focused for Bluetooth technology are low complexity architecture, low price, low power consumption, robustness, secure support for voice as well as data transmission and accessibility of local network and intranet. It is a radio technology that operates in global unlicensed 2.4 GHz ISM band, it can communicate through pockets, walls, etc. its range varies from 10 m to 100 m depend on the power of transmitter at antenna. The power consumption is very low from 1mWatt to 100mWatt. Bluetooth supports communications such as omni directional communication, point-to-point communication, point-to-multi-point communication, data and voice communication, circuit switched data communication and packet switched data communication. [Prabhu,C.S.R (2006)]
4.2.1 BLUETOOTH PROTOCAL ARCHITECTURE:
4.2.1(a) Radio Layer:
The radio layer defines the sensitivity of the transceiver, which operates at 2.4 GHz band. It found the necessity used for spread spectrum rate hopping and distinguish Bluetooth devices in to three different classes:
4.2.1(b) Baseband Layer:
Baseband layer which is also called physical layer of Bluetooth. It is a link controller which install connection between link manager and other devices. It performs various functions like power saving operation, device addressing control, channel control through paging, flow control and synchronization among Bluetooth devices.
4.2.1(c) Link Manager Protocol:
A link manager protocol carries out link setup, link configuration, Authentication and other protocols. It find out other Link manager inside the area and communicates with them via the Link manager protocol.
4.2.1(d) Host Controller Interface:
Host controller interface is above the Link manager protocol which permit authority line contact to Baseband layer and Link manger protocol for manage and to obtain condition information. It consist of three parts
4.2.1(e) Logical link control and adaptation protocol (L2CAP): Logical Link Control and Adaptation Protocol is over the HCL level and accommodate data services to the upper level host protocols. It is located in the data link layer and plugs in to baseband layer relatively than drift straight over LMP. It gives connection loctae and connectionless data services to higher layer protocols. Information services are provided in logical link control and adaptation protocol using protocol multiplexing, segmentation, group abstraction and reassembly operation. It allows higher level protocols and applications to send and receive data packets upto 64 kilobytes.
4.2.1(f) RFCOMM:
The RFCOMM protocol is what actually makes upper layer protocols think they are communicating over a RS232 wired serial interface.
Service Discovery Protocol: Service Discovery Protocol provides a method for applications to identify which services are available and to determine the characteristics of those available services. [BlueTomorrow.com(2010)]
4.2.2 Topology: Bluetooth devices communicate with each other in a piconet. Devices within this piconet participate either as a master role or as a slave role. The master uses timer or hopping sequence to coordinate all other devices or slaves in piconet. The unit that carries the paging procedure and establishes a connection is because of default of the master of connection. The slaves are synchronized to master via its lock and hopping sequences within the piconet. Bluetooth has multiple-piconet structure. As Bluetooth supports both point to point and point-to-multipoint connections, number of piconets can be linked together in a topology called ‘scatternet' which is a group of independent and non synchronized piconets which divide at least one common Bluetooth device.[BellaOnline.com(2010)]
4.3 WiMAX:
WiMAX is a wireless internet access technology used like Wi-Fi. WiMAX is highly scaleable and can have long range that may cover as much as 30 miles. WiMAX or world wide interoperability for microwave access promises wireless broadband communication ubiquitously. The high speed wireless access delivered by WiMAX facilities fixed and mobile broadband services specifically to cover larger areas.
4.4 UWB: Ultra wideband technology is based on the WiMedia standard. It brings the ease and mobility of wireless connection to high speed interconnects in devices throughout the digital home and office. It is designed for low power, short range, wireless personal area networks. UWB allow wireless connection of multiple devices broadcast of video, audio and other high bandwidth data. It is mxture of broader spectrum and lesser power improves speed and reduces obstruction with other wireless spectra. [Lin,C.h.(2005)]. UWB can legally operate in the range from 3.1 GHz up to 10.6 GHz, at a limited transmit power of -41 dBm/MHz. It have many advantages like coexistence with current narrowband and wideband radio services, ability to work with low SNR offers high degree of security with low probability of detection and intercept, large channel capacity, good time domain resolution, simple transceiver architecture. There are some issues with UWB like low performance using classical matched filters receivers, very fast ADCs required, information can travel only short distances.[Bandyopadhyay,L.K.(2010)]
4.4.1 UWB Applications:
4.4.2 UWB TOPOLOGIES:
4.4.3 Standard used for UWB:
The most important activities in the field of standardization of UWB technologies
The IEEE 802.15.3 is a study group to characterize a new physical layer idea for short distances, high data-rate applications. The goals for this new standard are data rates of up to 110 Mb/s at 10m distance, 200 Mb/s at 4m distance, and higher data rates at smaller distances. [Molish,A.F.(2003)].With a least data rate of 110 Mbps at a distance of 10 m, it has intended to produce a standard to deal with applications such as video or multimedia links or cable replacement. The study group has been focus of two alternative technical solutions led to a deadlock. One side was taken by the multiband orthogonal frequency division multiple (OFDM) approach of the multiband OFDM Alliance (MBOA), which unified with the WiMedia Alliance (WMA) in 2005. The other side took a pulse-based approach and is mainly supported by the UWB forum around Free scale semiconductor. This approach is very similar to the Direct Sequence Spread Spectrum (DSSS).
The IEEE 802.15.4a study group is an extension to the IEEE 802.15.4 low-rate WPAN task group. It approach new applications which need just reasonable data throughput, but extended battery time such as low-rate wireless personal area networks, sensors and a small network.
4.4.3.(a) Physical layer: UWB systems is based on impulse radio concepts. Recently more and more attention was attributed to OFDM-based multiband approaches.
1.Impulse radio schemes: Impulse radio (IR) refers to the creation of chain of very short length pulses, of the array of hundreds of picoseconds. Every pulse has a very extensive spectrum, which should hold to the spectral mask needs. The given pulses have very low energy because of the very less power limits permit for transmission. Therefore, many pulses will naturally be joint to transmit the information for one bit. (Nekoogar, F, 2005).IR has the important advantage of being essentially a baseband technology, which potentially lead to very simple, homodyne transceiver design.
2.Multiband OFDM Schemes: Another method to widen the techniques, utilize for direct sequence spread spectrum (DSSS) or Code Division Multiple Access (CDMA) schemes is to generate a spread-spectrum multicarrier (SS-MC) transmission. In a multi-carrier CDMA system, the original abstract stream is extended over the different sub-carriers with single chip of pseudo-random chip. But in a multi-carrier (DSSS) system, the original data is extended in the time field later than serial-to-parallel conversion of the data Stream.
4.4.3(b) Data link layer: In reality the design of an efficient MAC often requires an accurate knowledge of the under laying physical layer. In case of UWB this is a crucial issue because of the distinct features of UWB systems such as low-power constraints versus rather precise ranging capability. These specific features enable the definition of novel MAC-functionality which requires different MAC implementations. Within the standardization it was specified that each device should have an individual MAC address called device address (DevAddr), which identifies a single MAC sublayer.
Each address is a 16-bit value which is generated locally. The standard provides mechanism for resolving ambiguous DevAddrs. The addressing scheme includes multicast and broadcast address values. A multicast address identifies a group of MAC entities, and the broadcast address identifies all MAC entities. .[Oppermann,Ian.(2005)]
4.5 ZIGBEE: There are multiple number of standards which address mid to high data rates for voice, PC LANs, video etc. but till now there is no wireless network standard which complete exceptional needs of sensors and control devices. Sensors and controls doesn't require high bandwidth rather they require low latency and very less energy utilization for long battery lives and for big device arrays. There are so many wireless systems in the market to resolve the issues which do not need high data rates rather low cost and very low current domain.
Zigbee is a specification for high level communication protocols, using small low power based on IEEE 802.15.4 2003 standard for WPAN. Zigbee alliance is a not a technology rather it's a standardized base set of solution for sensor and control system. It is balanced to become the global control/sensor network standard. This technology is simple less expensive than other WPANs. It is low cost , low power mesh technology. Zigbee can turn on in 15 msec or less, the latency can be very less and devices can be very approchable specifically compared to Bluetooth wake up delays which are typically around 3 seconds. Because Zigbee can sleep most of the time average power consumption can be very low, resulting in long battery life.
It has following features:
4.5.1 Applications of Zigbee:
4.5.2 Architecture of zigbee:
1. Star topology: it support a single zigbee coordinator with one or more Zigbee end devices.
2.Combined topology:
Cluster tree: network provides a beaconing multi hop network
Mesh topology: networking routing permits path formation from any source device to any destination device
3.Peer to peer topology:
CHAPTER 5 WIRELESS SENSOR NETWORK
5.1 Introduction: recently a smart device is found which could provide added value through its embedded computing capability. It needs to communicate and collaborate wirelessly through machine to machine communication, cooperating objects, internet or web of things, capture different aspects of this revolution brings a shift in individual devices in business processes, defence and homeland security applications. A key technology which satisfies these concepts is called wireless smart sensor networks (WSN). These are small embedded sensing platforms with computing and communication capabilities which combine low cost, flexible and fast deployment, resilient self management and embedded intelligence for cooperatively delivered value added services. Sensors integrated into structures, machinery and the environment, joined with the capable delivery of sensed information, could give incredible profits to society. Possible profits include conservative of natural resources, catastrophic failures, improved manufacturing productivity and enhanced homeland security. Bundle of lead wires and fibre optics are barriers subject to breakage and connector failures. Long wires need considerable installation, long time maintenance, cost and limit the number of sensors that may be deployed and therefore decrease the overall quality of the data reported. Wireless sensing networks can reduce these costs, they are easy to install, consume very less power, competent of fast data acquisition, consistent and correct over long term, cost little to purchase and required no real maintenance.[Lewis,F.L.(2004)] Wireless sensor networks are the most interesting research areas with effect on technological developments. Selecting optimum sensors and wireless communication link requires applications lie battery life, sensor update rates and size. Low data rate sensors include temperature, humidity and high data rates include acceleration, strain and acceleration. Recent advances are integrate sensors, radio communications and digital electronics into a common integrated circuit (IC) package. This potential enables network of very low cost sensors that are capable to transmit with each other using low power wireless data routing protocols. A wireless sensor network generally consists of a basestation which transmit with a number of wireless sensors through a radio link. Data is gathered at wireless sensor node, condensed and transmitted to the gateway or if required uses other wireless sensor nodes to forward data to gateway.[Townsend,chris.]
With expansion of Microelectromechanical Systems (MEMS) technology, sensors are becoming smaller. It is achievable to fit them into a lesser volume with more power and with less construction costs. Many sensors can be deployed in harsh environments to sense and regularly transmit data to the sink or base station. A wireless sensor node consists of sensing, computing, actuation, transmit and control components. These apparatus are included on a singe or multiple boards and filled in few cubic inches. Because of low power circuit and networking technologies a sensor node powered by 2 AA batteries can last upto 3 years. A wireless sensor network usually consists of ten to thousand number of nodes which communicate within wireless channels for information distribution and mutual processing. Wireless sensor network can use for environmental monitoring, and habitat study, over a battle field for military surveillance, health monitoring infrastructure in buildings, condition based maintenance in factories, in human bodies for patient monitoring. [Xu,Ning.]
After initial deployment sensor nodes are dependable for self planned network infrastructure with multi-hop links between sensor nodes. Sensors then start collecting acoustic, seismic, infrared or magnetic information about the environment using either contstant or event driven working modes.Location and position regarding knowledge can be gathered by using global positioning system. The information gathered across the networkcan be processed to construct a global view of monitoring objects. The basic criteria behind wireless sensor network is that, the capability of each individual sensor node is limited, but average power of network is sufficient for required mission. The user can gather information from wireless sensor network by injecting queries and get the results from base station which act as a interface between user and networks.
5.2 Types of wireless sensor network:
Terrestrial WSN
Underground WSN
Underwater WSN
Mobile WSN
Multimedia WSN
5.3 Applications of WSN: The concept of wireless network is based on
Sensing+CPU+Radio= Thousand of potential applications
Wireless sensor network gives a wide range of applications which can basically divided in to three categories:
Monitoring Space: It includes habitat monitoring, indoor climate control, environmental, intelligence alarms, surveillance, treaty verification, precision agriculture
Monitoring Things: It includes structural monitoring, ecophysiology, medical diagnostics, urban terrain mapping, condition based equipment maintenance.
Monitoring the interaction of things with each other and the encompassing space: It includes disaster management, wild life habitat, health care, emergency response, asset tracking, ubiquitous computing environments. [Culler,David.et.al(2004)]
5.3.1 Monitoring Energy Consumption In Office Buildings: A WSN can be used to monitor energy consumption in large office buildings. Its main aim to detect the devices and locations which consume a lot of energy to provide suggestion for prospective reduction in power consumption. Sensor nodes are connected t power grid to determine power consumption for their own power supply.[Aye,Lu.(2008)]
5.3.2 Environmental Data Collection: A canonical data collection application is based on to gather number of sensor readings from different set of points in an environment above a period of time. For data to be significant it should be collected at regular intervals of time and nodes would remain at known locations. At network level large number of nodes are continuously sensing and transmitting data back to set of base station which stores the data using traditional methods. These networks need very low data rates and extremely long lifetimes. After deployment, the nodes initially discover the topology of network and then estimate optimal routing strategies. It can then be used to route data to a central collection point. It is not compulsory that nodes buildup the optimal routing strategy at their own. It can calculate it outside the network and then communicate. Environmental data collection application mainly use tree based routing topology. Data is time to time transmitted from child node to parent node until it reaches the sink. Because of this type of data collection each node is responsible for forwarding the data of all its descendants. As soon as network is configured, each node time to time samples its sensors and transmits data up the routing tree and back to base station. The covering time period is generally between 1 and 15 minutes but it can be high as well. The typical environment parameters being monitored such as temperature, light intensity and humidity. These donot change quickly enough to need higher reporting rates. Data samples can be delayed inside the network for some duration of time but it didn't affect the application performance. The most important characteristics of environmental monitoring application are long life time, precise synchronization, low data rate and relatively static topologies.
5.3.3 Security Monitoring: Security monitoring networks are composed of nodes which are placed at fixed locations through the environment and continuously monitor one or more sensor to detect an anomaly. Security networks does not collect any data. Infact each node has to check the regular status of sensor and to transmit a data report where ever security violation is needed. The instant and reliable communication of alarm message is the first priority of the system. If a node is disable or fail it would represent a security violation. Security network has linear topology which forms Hamiltonian cycle of network. In this network each node has one child and power consumption is proportional to number of children. Maximum of energy is utilize with strict latency requirement when security violation occurs. Once security violation is occurred it should be inform to base station immediately within couple of seconds. The network nodes must request quickly to neighbour nodes to forward data quickly. In security networks reducing the latency of alarm transmission is more important than reducing the energy cost of transmission.
5.3.4 Node Tracking Scenarios: it is the tracking of a tagged object within a region of space monitored by sensor network. Objects can be tracked by recording the last checkpoint that an object passed through. But we cant track the exact location of object. In wireless networks objects can be tracked by attached them with sensor node. The sensor node will track the object as it moves from the field of sensor nodes. These nodes can be used to sense the RF messages of nodes as well. The nodes can be used a s active tags which shows the presence of device. A data base can be used to record the location of tracked objects so that it become possible to check the current location of object rather than previous location. The topologies of network change continuously as nodes move through the network. [Hill,J.L (2003)]
CHAPTER 6 DESIGN METHODS
6.1 Introduction: we have to design a wireless feedback control system. With advances in wireless technologies wireless systems are becoming popular in industry or in academia. In wireless control system nodes of comparators, actuators and sensors are joined through wireless links. The microcontroller is joined to converter which is further connected to pump and tank and it is joined to level sensor. Level sensor will send data to zigbee transmitter after converting it to suitable digital form for transmitting. At other end zigbee receiver will receive the signal and then convert it back to analog form. Then compare it with reference voltage. If there is some difference between desired output and given output then the level of water in tank circuit will increase or decrease depend upon the difference and it immediately send information to the system.
BLOCK DIAGRAM:
6.2 8051 MICROCONTROLLER:
6.2.1 Introduction:
it is kind of small computer which executes series of pre-programmed task and interact with other hardware devices. It is perfect controller for robots or machines because of its small integrated circuit whose weight and size is very less. Microcontroller contains memory to store the executed program and number of input and output lines can be used to interact with other devices. A single microcontroller can control security system, mobile robot or automatic washer machine. These days microcontrollers are very cheap and easily available, the most recent microcontrollers are ‘in system programmable' which means we can modify the program being executed without removing its place. [Kamal,Ibrahim (2008)]
6.2.2 Architecture:
The 8051 is big family of microcontroller. We are going to use AT89S52 which is 8051 microcontroller made by Atmel. The below diagram showing the architecture of 89S52.
The 89S52 has 4 different ports each have 8 input and 8 output lines giving a total of 32 input/output lines. To read the state of sensor and output data these ports can be used. The majority of ports have dual function means they can be used for two different functions the first one is to perform input/output operation and second one is to implement special feature like performing serial data transfer, counting external pulses, interrupting the execution of program according to external events and connecting the chip to a computer to update software. There are two different type of memories RAM and EEPROM. RAM is used to store variable during program execution while EEPROM is used to store the program itself. Because of this it is also called ‘program memory'. Timer, counter, interrupt, serial port, SFRs are important features of microcontroller. 89S52 incorporates hardware circuits that can be used to avoid the processor from executing different cyclic tasks and save processing power for more complex calculations. CPU is the heart of microcontroller. It read the program from flash memory and implement it by interacting with different peripherals. [Kamal,Ibrahim (2008)]
The above figure show the pin configuration of 89S52. Al the pin functions are describe next to it and double functions are describe in brackets. All the 32 microcontroller pins are configured as input/output pins. Pin 29 and 30 are used to control external memory and pin 31 is always connected to VCC (5 volts) to allow the microcontroller to use the internal chip memory rather than external one. If we connect pin 31 to ground then it will show to microcontroller that external memory is in use rather than internal.
6.2.3 Memory organization:
RAM stands for random access memory, it behaves the same as RAM in desktop computer which is used to store data during execution of different programs. EPROM is called flash memory as well which is read only memory used to store the program when it is being executed. As general point of view it can be compared with hard disk of desktop. It stands for electronically erasable and programmable read only memory. In microcontroller memory is organized in registers which is further collection of number of bits where data can be stored. Most registers are 8 bit register which can store values of range from 0 to 255. Different registers can be used together for bigger values. [Kamal,Ibrahim (2008)]
