Wireless & Mobile Computing Submitted by : Manika Gandhi 115325 Company N1 LOGO
Company LOGO Contents1.Wireless communication 7.CDMA & DAMA2.Effects of device portability 8.Wireless networks3.Mobile computing platform 9.CSMA problems4.Wireless & fixed networks 10.Hidden terminal problem5.Wireless management 11.Applications6.Building blocks 12.Security concerns
CompanyLOGO Mobile/wireless communication Two aspects of mobility: user mobility: users communicate (wireless) “anytime, anywhere, with anyone” device portability: devices can be connected anytime, anywhere to the network
CompanyLOGO Effects of device portability Power consumption –limited computing power, low quality displays –loss of data with higher probability Limited user interfaces –compromise between size of fingers and portability –character/voice recognition, abstract symbols
CompanyLOGO MobileComputing Platforms Platforms Mobile Computing Server Mobile Device (Web Server, eMail server, (Cell Phone, PDA, Pocket PC) Mainframe) Application Application Middleware Middleware Services Mobile Services Computing Local Network Platform Local Network Platform Transport Platform Transport Services Services Services Services Physical Wireless Network (Antennas, Transceivers, Base Stations, Cellular Networks, 802.11 LANs, Satellites)
CompanyLOGO Wireless v/s fixed networks Higher loss rates due to interference Restrictive regulationsTEXTfrequencies TEXT of TEXT Low transmission rates Higher delays, higher jitter Lower security, simpler active attacking Always shared medium
CompanyLOGO Wireless Management & Business STRATEGIC PLANNING • Business Strategy Analysis •Analyzing Business Processes and Business Workflows •Mobile Application Identification and Selection. CAPABILITY EVALUATIONORGANIZING/STAFFING •Wireless Infrastructure Planning. Mobile Virtual Teams •Capacity Planning & Traffic Engineering. Mobile Real-time Enterprises •Resource and Cost EstimationMONITORING AND CONTROL DEVELOPMENT AND DEPLOYMENT•Wireless fault and • Mobile application development performance management • Wireless infrastructure development•Wireless Security and Outsourcing the Wireless Infrastructure configuration management
Company LOGO The Building Blocks of Mobile ComputingDrivers •Wireless Business, Mobile Business, Government, and Life Regulations, and Standards Mobile Computing Applications •Architectures and Integration Mobile Computing Platforms (Wireless Middleware, Mobile IP) •Wireless Security Wireless Networks •Management and (Wireless LANs, Cellular Networks, Support Satellites, Wireless Local Loops) Enablers
CompanyLOGO Demand Assignment Multiple Access In a DAMA protocol, nodes first reserve slots which they intend to use for broadcasting. Each round of broadcast is preceded by a reservation round. DAMA protocols are widely used in satellite communication and increasingly being used in wireless networking.
CompanyLOGO Code Division Multiplexing CDMA has been adopted for the 3G mobile phone technology. CDMA is not very suitable for ad hoc networking as we cannot expect specialized hardware/software support at the nodes. TDMA and its variations are most suitable for ad hoc networking.
Company LOGO Wireless Networks Wireless Networks Wireless LANs Wireless MANs Wireless WANs Wireless Cellular Satellite PagingPersonal Business Local Loops Networks Systems NetworksArea LANs (Fixed Wireless)NetworksExample1: Example1: Example1: Example1: Example1: Example1:Bluetooth 802.11b LMDS GSM, 9.6 Kbps, Motorola FLEX,1 Mbps, 11 Mbps, 37 Mbps, wide coverage Iridium10 Meters 100 Meters 1.2 Kbps 2-4 Km up to 64 Mbps Example2: globallyOther examples: Other Example2: 3G, 2 Mbps, Example2:wireless sensor examples: FSO wide coverage Example 2: ReFLEX,networks, UWB 802.11g, 1.25 Gbps Deep space 6.4Kbps HiperLAN2 1-2 KM communication
CompanyLOGO Physical layers in wireless networks Use a medium that has neither absolute nor readily observable boundaries outside which stations are unable to receive frames Are unprotected from outside signals Communicate over a medium significantly less reliable than wired PHYs Have dynamic topologies Lack full connectivity and therefore the assumption normally made that every station (STA) can hear every other STA in invalid (I.e., STAs may be “hidden” from each other) Have time varying and asymmetric propagation properties
CompanyLOGO CSMA Problems in Wireless Network Collision detection is easy in wired networks but difficult in wireless medium With only one antenna, nodes can only listen or send Full duplex radios are extremely expensive CSMA gives rise to hidden terminal and exposed terminal problems
CompanyLOGO Hidden Terminal Problem Wireless transmission is usually short range. Even if the medium is free near the transmitter, it may not be free near the intended receiver. A B C Collision at B
CompanyLOGO Message Loss due to Collision Using CSMA in wireless medium results in message loss and requires retransmission of lost messages. A node spends much more energy while receiving or transmitting messages. Hence, retransmission wastes a lot of energy. The other alternative is to use a reservation based TDM protocol.
CompanyLOGO Applications I Mobile, pervasive, ubiquitous, nomadic computing Computing anytime anywhere TEXT Distributed computing, CORBA TEXT Cellular and satellite networks Ad hoc networks: rescue, battlefield, conference Sensor networks: monitoring environment to detect object movement or presence of TEXT chemicals, fire, temperature reports Mesh networks;: rooftop networks for multi-hop wireless Internet access
CompanyLOGO Applications II Vehicles –transmission of news, road condition, weather, music –personal communication using GSM –position via GPS –local ad-hoc network with vehicles close-by to prevent accidents, guidance system, redundancy –vehicle data (e.g., from busses, high-speed trains) can be transmitted in advance for maintenance Emergencies – early transmission of patient data to the hospital – replacement of a fixed infrastructure in case of earthquakes, hurricanes, fire etc.
CompanyLOGO Security Concerns Authentication is critical » Normal network point of attachment is a wall tap » Wireless access makes network attachment too easy Exposure to over-the-air wiretapping » Any transmitter can also be a receiver » Some wireless networks provide secure air links » Made more difficult by spread spectrum technologies