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Wireless Communication and Mobile Technology Chapter 1: Introduction What is Wireless? Wireless refers to the method of transferring information between computing devices, such as a personal data assistant (PDA) and a data source such as an agency database server, without a physical connection or wires. The distances involved may be short (a few meters as in television remote control) or long (thousands or millions of kilometers for radio communications). Not all wireless communication technologies are mobile. What is Wireless? For example, lasers are used in wireless data transfer between buildings, but cannot be used in mobile communication at this time. Because in this technology transmitter and receiver will remain at fixed position and if is change the communication may loss. What is Mobile? Mobile simple describes a computing device that is not restricted to a desktop. Mobile device may be a PDA, a “smart” cell phone, a laptop computer, or any one of numerous other devices that allow the user to complete computing task without being connected to a any Network. What is Wireless communication? Wireless communication is simply data communication without the use of landlines. This may involve cellular telephone, two-way radio, fixed wireless (broadband wireless), laser (free space optics), or satellite communications. What is Mobile Computing? It is a technology that allows transmission of data via, a computer without having to be connected to a fixed physical link. Mobile computing environment as being made up of three main components: a computer (that moves), a N/W (that is either wired or wireless) & co-ordination S/W that ties them together. In mobile N/W computing activities are not disrupted when the user changes the computer’s points of attachment to the internet. What is Mobile Computing? Instead all the needed reconnection occurs automatically & no interactively. Truly mobile computing offers many advantages. Confident access to the internet any time, any where will help free us from the ties that bind us to our desktops. Why Wireless communication? People now a day are demanding instant communication at the same time they do not want to stick to their desk or office. What they want is communication at any where and any time, even though they are on move. The solution for complete mobility is only. Wireless computing can make significant difference in your productivity, responsiveness to the customer. You can also reduce or eliminate cabling cost and relocate devices without having to rewire your facilities. Advantages of Wireless Communication? Mobility: Wireless network systems can provide network users with access to real-time information anywhere in there organization. The mobility supports productivity and service opportunities not possible with wired networks. Advantages of Wireless Communication? Installation speed & simplicity: Installation a wireless network system can be fast and easy and can eliminate the need to pull cable through walls and ceilings. Installation Flexibility: Wireless technology allows the network to go where wire can not go. Advantages of Wireless Communication? Reduced cost of Ownership: While the initial investment required for wireless network hardware can be higher than the cost of wired. N/W hardware overall installation expenses and life-cycle costs can be significantly lower. Long term cost benefits are greatest in dynamic environments requiring frequent moves and changes. Advantages of Wireless Communication? Scalability: Wireless N/W systems can be configured in a variety to topologies to meet the need of specific application and installations. Configurations are easily changed and range from peer to peer N/W suitable for a small no of users to full infrastructure N/Ws of thousands of users that enable roaming over a broad area. Disadvantage of wireless communication Radio signal interference: Because wireless devices operate using radio signals, the potential for two type of signal interference exists. Signals from other devices can disrupt what a wireless device is trying to transmit, or a wireless device may itself be a source of interference for other devices. several common office devices transmit radio signals that may interfere with a WLAN. Disadvantage of wireless communication These devices include microwave ovens, elevator motors and other heavy electrical equipment. These may cause errors to occur in the transmission between a wireless device and an access point. In addition, Bluetooth and WLAN 802.11 devices both operate in the same radio frequency, potentially resulting in interference between such devices. Disadvantage of wireless communication The solution for wireless devices is the same as that for standard cabled network devices: locate the source of the interference and eliminate it. This usually is solved by moving a photocopier or microwave oven across the room or another room. In addition many wireless devices can identify that an error has occurred in the transmission and retransmit the data as necessary. Disadvantage of wireless communication Security: Because a wireless device transmits radio signals over a broad area, security becomes a major concern. It is possible for an intruder to be lurking outdoors with a note book computer and wireless NIC with the intent of intercepting the signals from a nearby wireless network. Because much of a business network traffic may contain sensitive information, this is a real concern for many users. Disadvantage of wireless communication However, some wireless technologies can provide added levels of security. A special coded number can be programmed into every authorized wireless device and the device must transmit the special number prior to gaining access to the network, otherwise it is denied access. Network managers can also limit access to a wireless network by programming it with a list of approved wireless devices.(e.g:cyber roam) Disadvantage of wireless communication Only those devices on the list will be allowed access. As a further protection, data transmitted between the access point and the wireless device can also be encrypted or encoded in such a way that only the recipient can decode the message. If an unauthorized user were to intercept the radio signals being transmitted, he or she could not read the messages being sent. Disadvantage of wireless communication Health risks: Wireless devices contain radio transmitters and receivers that emit radio frequency (RF) energy. Typically, these wireless devices emit low levels of RF while being used. Scientists know that high levels of RF can produce biological damage through heating effects. (This is how a microwave oven is able to cook food.) Disadvantage of wireless communication In the United States, the Food and Drug Administration (FDA) and the Federal Communications commission (FCC) set policies and procedures for some wireless devices, such as cellular telephones. The latest FDA update stated that “ the available science does not allow us to conclude the that (wireless devices) are absolutely safe, or that they are unsafe.” Disadvantage of wireless communication Thus the available science does not permit a conclusion either way about the safety of wireless mobile devices. There is no evidence regarding any health risks associated with using any wireless device, it is always wise to be aware of the concern and to monitor ongoing scientific research. Different between Mobile and Wireless Two aspects of mobility: user mobility: users communicate (wireless) “anytime, anywhere, with anyone” device portability: devices can be connected anytime, anywhere to the network Wireless vs. mobile Examples stationary computer notebook in a hotel wireless LANs in historic buildings Personal Digital Assistant (PDA) Mobile and Wireless Devices Pager • receive only • tiny displays • simple text messages PDA • graphical displays • character recognition • simplified WWW Mobile phones • voice, data • simple graphical displays Laptop/Notebook • fully functional • standard applications Smart phone • tiny keyboard • simple versions of standard applications performance Application of Mobile and Wireless Communications Education: Wireless technology is an ideal application of colleges and schools. An instructor can create a classroom presentation on the notebook computer in his home or school office and this presentation can access in classroom using wireless devices. Teachers can also distribute handouts directly to students who have brought their own wireless devices to class. Application of Mobile and Wireless Communications The wireless connection also frees students from having to go to a specific computer lab or the library to get on the college campus network. They can access the campus network “wirelessly” from almost any location on campus. Application of Mobile and Wireless Communications Home Entertainment: Several large computer manufacturers are introducing specialized media PCs that enable movie and audio enthusiasts to download, distribute and control all forms of digital entertainment from anywhere in the house. Some of the systems also have the ability to control lights, air conditioners and other household devices. Application of Mobile and Wireless Communications You can send music, movies, or pictures to a stereo receiver, portable device or PC located anywhere in the house. You can also download the files to your digital media portable devices, such as MP3 and video players that can be used while roaming throughout the house. Application of Mobile and Wireless Communications Vehicles : Transmission of news, road condition, weather, music via DAB(Digital Audio Broadcasting ) Personal communication using GSM(Global System for Mobile Communications)/UMTS(Universal Mobile Telecommunications System ) Position via GPS(Global Positioning System ) local ad-hoc network with vehicles close-by to prevent accidents, guidance system vehicle data (e.g., from busses, high-speed trains) can be transmitted in advance for maintenance Typical application: road traffic UMTS, WLAN, DAB, DVB, GSM, cdma2000, TETRA, ... Prof. Dr.-Ing. Jochen H. Schiller www.jochenschiller .de MC - 2009 Personal Travel Assistant, PDA, Laptop, GSM, UMTS, WLAN, Bluetooth, ... Application of Mobile and Wireless Communications In Companies: In companies mangers can use mobile computer in, say critical presentations to major customers. They can access the latest market share information. At a small recess, they can revise the presentation take advantages of this information. They can communicate with the office about possible new offers and call meetings for discussing responds to the new proposals. Therefore, mobile computers can leverage competitive advantages. Application of Mobile and Wireless Communications Government: Government applications center around assessments, inspections and work orders. Most of these applications involve auditing some sort of facility or process For e.g.: food service, restaurant, child care, schools, and residential buildings. Application of Mobile and Wireless Communications Emergency Services: Emergency services ability to receive information on the move is vital where the emergency services are involved. Information regarding the address, type and other details of an incident can be dispatched quickly, via CDPD(Cellular Digital Packet Data) system using mobile computers. Here, the reliability and security implemented in the CDPD system would be of great advantage. Application of Mobile and Wireless Communications Healthcare: The focus in the industry has been on automting patient records, medication dispersion and sample collection. A common goal is to leverage mobile computing in the implementation of positive patient identification. Application of Mobile and Wireless Communications Market Research: Automating the survey process has enable these companies to get their data more accurately and quickly while being able to customize their queries at will. Application of Mobile and Wireless Communications Credit Card Verification: At Point of Sale (POS) terminals in shops and supermarkets, when customers use credit cards for transactions, the intercommunication required between the bank central computer and the POS terminal, in order to effect verification of the card usage, can take place quickly and securely over cellular channels using a mobile computer unit. This can speed up the transaction process and relieve congestion at the POS terminals. Application of Mobile and Wireless Communications Electronic Mail/Paging: Usage of mobile unit to send and read emails is a very useful asset for any business individual, as it allow him/her to keep in touch with any colleagues as well as any urgent developments that may affect their work. Access to the internet, using mobile computing technology, allows the individual to have vast array of knowledge at his/her fingertips. Application of Mobile and Wireless Communications Paging is also achievable here, giving even more intercommunication capability between individuals, using a single mobile computer device. Application of Mobile and Wireless Communications Taxi/Truck Dispatch: Using the idea of a centrally controlled dispatcher with several mobile units(taxis), mobile computing allows the taxis to be given full details of the dispatched job as well as allowing the taxis to communicate information about their whereabouts back to the central dispatch office. This system is also extremely useful in secure deliveries i.e.: securicor. Application of Mobile and Wireless Communications This allows a central computer to be able to track and receive status information from all of its mobile secure delivery vans. Again, the security and reliability properties of the CDPD system shine through. Wireless Operating Systems and Languages Major Operating System Palm OS EPOC (Symbian) Windows CE JAVA Micro Edition Wireless Languages HDML WML cHTML Types of Wireless Systems AMPS and European Analog cellular (Advanced Mobile Phone System) TDMA (Time Division Multiple Access) CDMA (Code-Division Multiple Access) GSM (Global System for Mobile Communication) GPRS (General Packet Radio Service) EDGE (Enhanced Data Rates for Global Evolution) Types of Wireless Technologies Radio Waves Microwave Wi-Fi Wi-Max ZIGBEE Location Dependent Services Many research efforts in mobile computing and wireless networks try to hide the fact that the network access has been changed or that a wireless link is more error prone than a wired one. Examples: Mobile IP tries to hide that fact of changing access points by redirecting packets but keeping the same IP address, and many protocols try to improve link quality using encoding mechanisms or retransmission so that applications made for fixed networks still work. Location Dependent Services In many cases, however, it is important for an application to ‘known’ something about the location or it might be that the user needs location information for further activities. Several services that might depend on the actual location can be distinguished: Follow-on Services: Location aware Services: Privacy: Information Services: Support Services: Location Dependent Services Follow-on Services: The function of forwarding calls to the current user location is well-known from the good old telephone system. Wherever you are just transmit your temporary phone number to your phone and it redirects incoming calls using mobile computer a followon service could for instance. This offer the same desktop environment wherever you are around the world. Location Dependent Services All e-mail would automatically be forwarded, all changes to your desktop and documents stored, at a central location at your company. If someone wanted to reach you using a multimedia conferencing system, this call would then also be forwarded to your current location. Location Dependent Services Location aware Services: Imagine you wanted to print a document sitting in the lobby of a hotel using your laptop. If your drop the document over the printer icon, where would you expect the document to be printed? Certainly not by the printer in your office! But without additional information about your environment, this might be the only thing you can do. Location Dependent Services Therefore services are needed that provide information about the capabilities of your environment. For instance, there could be a service in the hotel announcing that a standard laser printer is available in the lobby, a color printer in a hotel meeting room etc. In return your computer might then transmit your personal profile to your environment, so that the hotel can charge you with the printing costs. Location Dependent Services Privacy: The two service classes listed above immediately raise the question of privacy. You might not want video calls following you to dinner, but may be you would want important emails to be forwarded. So there might be locations and/or times when you want to exclude certain services form reaching you, thereby telling the caller that you do not want to be disturbed. Location Dependent Services Furthermore, although you want to utilize location dependent services, you might not want the environment to know exactly who you are? Imagine a hotel monitoring all guests and selling these profiles to companies for advertisements. Location Dependent Services Information Services: While walking around in a city you could always use your wireless travel guide to ‘pull’ information from a service, e.g., ‘where is the next Mexican restaurant to my current position?’ But a service could also actively ‘push’ information on your travel guide, e.g., that the Mexican restaurant just around the corner has a special offer. Location Dependent Services Support Services: Finally, many small additional mechanisms can be integrated to support a mobile device. Intermediate results of calculations, state information or cache contents could ‘follow’ the mobile node through the fixed network. As soon as the mobile node reconnects, all information is available again. Location Dependent Services This helps to reduce access delay and traffic within the fixed network. The alternative would be a central location for user information and a user accessing this information through the network all the time as it is typically done today. Early history of wireless communication Many people in history used light for communication heliographs, flags (“semaphore”), ... 150 BC smoke signals for communication; (Polybius, Greece) 1794, optical telegraph, Claude Chappe Here electromagnetic waves are of special importance: 1831 Faraday demonstrates electromagnetic induction J. Maxwell (1831-79): theory of electromagnetic Fields, wave equations (1864) H. Hertz (1857-94): demonstrates with an experiment the wave character of electrical transmission through space (1888, in Karlsruhe, Germany) History of wireless communication I 1896 Guglielmo Marconi 1907 Commercial transatlantic connections huge base stations (30 100m high antennas) 1915 Wireless voice transmission New York - San Francisco 1920 Discovery of short waves by Marconi first demonstration of wireless telegraphy (digital!) long wave transmission, high transmission power necessary (> 200kW) reflection at the ionosphere smaller sender and receiver, possible due to the invention of the vacuum tube (1906, Lee DeForest and Robert von Lieben) 1926 Train-phone on the line Hamburg - Berlin wires parallel to the railroad track History of wireless communication II 1928 many TV broadcast trials (across Atlantic, color TV, news) 1933 Frequency modulation (E. H. Armstrong) 1958 A-Netz in Germany 1972 B-Netz in Germany analog, 160MHz, connection setup from the fixed network too (but location of the mobile station has to be known) available also in A, NL and LUX, 1979 13000 customers in D 1979 NMT at 450MHz (Scandinavian countries) 1982 Start of GSM-specification analog, 160MHz, connection setup only from the mobile station, no handover, 80% coverage, 1971 11000 customers goal: pan-European digital mobile phone system with roaming 1983 Start of the American AMPS (Advanced Mobile Phone System, analog) 1984 CT-1 standard (Europe) for cordless telephones History of wireless communication III 1986 C-Netz in Germany 1991 Specification of DECT analog voice transmission, 450MHz, hand-over possible, digital signaling, automatic location of mobile device was in use until 2000, services: FAX, modem, X.25, e-mail, 98% coverage Digital European Cordless Telephone (today: Digital Enhanced Cordless Telecommunications) 1880-1900MHz, ~100-500m range, 120 duplex channels, 1.2Mbit/s data transmission, voice encryption, authentication, up to several 10000 user/km2, used in more than 50 countries 1992 Start of GSM in D as D1 and D2, fully digital, 900MHz, 124 channels automatic location, hand-over, cellular roaming in Europe - now worldwide in more than 200 countries services: data with 9.6kbit/s, FAX, voice, ... History of wireless communication IV 1994 E-Netz in Germany 1996 HiperLAN (High Performance Radio Local Area Network) ETSI, standardization of type 1: 5.15 - 5.30GHz, 23.5Mbit/s recommendations for type 2 and 3 (both 5GHz) and 4 (17GHz) as wireless ATMnetworks (up to 155Mbit/s) 1997 Wireless LAN - IEEE802.11 GSM with 1800MHz, smaller cells as Eplus in D (1997 98% coverage of the population) IEEE standard, 2.4 - 2.5GHz and infrared, 2Mbit/s already many (proprietary) products available in the beginning 1998 Specification of GSM successors for UMTS (Universal Mobile Telecommunications System) as European proposals for IMT-2000 Iridium 66 satellites (+6 spare), 1.6GHz to the mobile phone History of wireless communication V 1999 Standardization of additional wireless LANs IEEE standard 802.11b, 2.4-2.5GHz, 11Mbit/s Bluetooth for piconets, 2.4GHz, <1Mbit/s decision about IMT-2000 Start of WAP (Wireless Application Protocol) and i-mode first step towards a unified Internet/mobile communication system access to many services via the mobile phone 2000 GSM with higher data rates HSCSD offers up to 57,6kbit/s first GPRS trials with up to 50 kbit/s (packet oriented!) UMTS auctions/beauty contests several “members” of a “family”: UMTS, cdma2000, DECT, … Hype followed by disillusionment (50 B$ paid in Germany for 6 licenses!) Iridium goes bankrupt 2001 Start of 3G systems Cdma2000 in Korea, UMTS tests in Europe, Foma (almost UMTS) in Japan History of wireless communication VI 2002 2003 over 3.3 billion subscribers for mobile phones (NOT 3 bn people!) 2008 HSDPA starts in Germany as fast UMTS download version offering > 3 Mbit/s WLAN draft for 250 Mbit/s (802.11n) using MIMO WPA2 mandatory for Wi-Fi WLAN devices 2007 WiMax starts as DSL alternative (not mobile) first ZigBee products 2006 UMTS starts in Germany Start of DVB-T in Germany replacing analog TV 2005 WLAN hot-spots start to spread “real” Internet widely available on mobile phones (standard browsers, decent data rates) 7.2 Mbit/s HSDPA, 1.4 Mbit/s HSUPA available in Germany, more than 100 operators support HSPA worldwide, first LTE tests (>100 Mbit/s) 2009 – the story continues with netbooks, iphones, VoIPoWLAN… Wireless systems: Overview of the Development cellular phones 1981: NMT 450 satellites 1986: NMT 900 1992: GSM 1994: DCS 1800 analog digital 1984: CT1 1987: CT1+ 1988: InmarsatC 1991: CDMA 1991: D-AMPS 1993: PDC 2000: GPRS wireless LAN 1980: CT0 1982: InmarsatA 1983: AMPS cordless phones 1989: CT 2 1992: Inmarsat-B Inmarsat-M 1991: DECT 1998: Iridium 199x: proprietary 1997: IEEE 802.11 1999: 802.11b, Bluetooth 2000: IEEE 802.11a 2001: IMT-2000 200?: Fourth Generation (Internet based) Worldwide wireless subscribers (old prediction 1998) 700 600 500 Americas Europe Japan others total 400 300 200 100 0 1996 1997 1998 1999 2000 2001 Areas of research in mobile communication Wireless Communication transmission quality (bandwidth, error rate, delay) modulation, coding, interference media access, regulations ... Areas of research in mobile communication Mobility location dependent services location transparency quality of service support (delay, jitter, security) ... Areas of research in mobile communication Portability power consumption limited computing power, sizes of display, ... usability ... Simple Reference Model The basic reference model used to structure communication system. In next slide figure a personal digital assistant (PDA) which provides an example for a wireless and portable device. This PDA communicates with a base station in the middle of the picture. The base station consists of a radio transceiver (sender & receiver) and an inter working unit connecting the wireless link with the fixed link. Simple Reference Model The communication partner of the PDA, a conventional computer, is shown on the righthand side. Each N/W element (such as PDA, inter working unit, computer), the figure shows the protocol stack implemented in the system according to the reference model. Simple Reference Model used here Application Application Transport Transport Network Network Data Link Physical Radio Network Network Data Link Data Link Data Link Physical Physical Physical Medium Simple Reference Model End-System, such as the PDA and computer in the example need a full protocol stack comprising the application, transport, network, data link and physical layer. Applications on the end-systems communicate with each other using the lower layer services. Intermediate system, such as the inter working unit, do not necessarily need all of the layers. Next slide to explain the functions of each layer in more derail in a wireless and mobile environment. Simple Reference Model Physical layer: This is the lowest layer in a communication system and is responsible for the conversion of a stream of bits into signals that can be transmitted on the sender side. The physical layer of the receiver then transforms the signals back into a bit stream. For wireless communication the physical layer is responsible for frequency selection, generation of the carrier frequency, signal detection, modulation of data onto a carrier frequency and encryption. Simple Reference Model Data link layer: The main tasks of this layer include accessing the medium, multiplexing of different data streams, correction of transmission errors, and synchronization. The data link layer is responsible for a reliable point-to-point connection between two devices or a point-to-multipoint connection between one ender and several receivers. Simple Reference Model Network layer: This third layer is responsible for routing packets through network or establishing a connection between two entities over many other intermediate systems. Important topics are addressing, routing, device location and handover between different networks. Simple Reference Model Transport layer: This layer is used in the reference model to establish an end-to-end connection. The quality of service, flow and congestion control are relevant, especially if the transport protocols known from the internet, TCP and UDP are to be used over a wireless link. Simple Reference Model Application layer: Finally, the application are situated on top of all transmission-oriented layers. And support for multimedia applications, adaptive applications that can handle the large variations in transmission characteristics and wireless access to the world wide web using a portable device. Very demanding applications are video and interactive gaming.