关于进一步加强预应力混凝土管桩

Bluetooth: The Universal Radio Interface for Ad hoc, Short-Range Connectivity,CIS 642Maria Adamou,1/5/2018,2,Overview,IntroductionBluetooth Air InterfaceArchitectureConnection EstablishmentPiconets and ScatternetsPower ManagementSecurityCompeting technologiesIssues facing Bluetooth,1/5/2018,3,Introduction,In February 1998 five major telecom and PC companies Ericsson, Nokia, IBM, Toshiba, and Intel- formed a Special Interest Group (SIG) to create a standard radio interface for short-range connectivity between electronic devicesThe radio interface was named Bluetooth after a Danish Viking king Harald Bluetooth who united Denmark and Norway during 10th centuryThis group was further expanded in December 1999 with 3Com, Lucent, Microsoft and Motorola Today more than 2000 companies have joined as adopters of the Bluetooth technology,1/5/2018,4,What is Bluetooth,Bluetooth is a universal standard radio interface for short-distance, point-to-multipoint voice and data transfer between portable devicesIts nominal link range is from 10 cm to 10 meters but can be extended to 100 meters by increasing the transmission powerPrinters, desktops, fax machines, cellular phones and virtually any other digital device can be part of the Bluetooth system and form ad hoc groupings that replace cables,1/5/2018,5,Goals,The system must operate globallyThe system must support peer connectivity, connections are made on an ad hoc basisThe connection must support voice and data Ability to withstand interference from other sourcesThe radio transceiver must be small and operate at low power, to fit into small, portable devices, such as mobile phones, headsets, PDAs etcLow cost, short-range,1/5/2018,6,User Scenarios,3-in-1 phone: At home, portable phone (fixed line charge), when on the move, mobile phone (cellular charge), and when your phone comes within range of another mobile phone a walkie-talkie (no telephony charge)Ultimate Headset: Connect your wireless headset to your mobile phone, mobile computer or any wired connectionInteractive Conference in meetings and conferences Automatic Synchronizer: Automatic synchronization of your desktop, PDA, notebook and your mobile phone. Internet Bridge: use of a mobile telephone or cordless modem device that provides modem services to a PC, to enable cordless access for dial-up networking services. LAN access: use of a device that acts as a LAN access point (LAP) providing Bluetooth access services to one or more data terminals. many others.,1/5/2018,7,Definitions,Piconet: a collection of (up to eight) devices connected via Bluetooth technology in an ad hoc fashion. Each piconet is identified by a different frequency hopping sequence and all hosts on the same piconet are synchronizedScatternet: two or more independent and non-synchronized piconets that communicate with each otherMaster unit: the device in a piconet whose clock and hopping sequence are used to synchronize all other devices in the piconetSlave units: all devices in a piconet that are not the master (up to 7 active units for each master),1/5/2018,8,Bluetooth Air Interface,License-free, globally available frequency band: Industrial-Scientific-Medical (ISM) band, at 2.45 GHz in most countries in the worldFrequency-hopping (FH) spread spectrum to better support low-cost, low-power radio implementations with maximum immunity to interferenceChannels use a Frequency-Hopping/ Time Division Duplex (TDD) scheme: the channel is divided into slots of 625ms giving 1600hops/sec and subsequent slots are alternately used for transmitting and receiving (TDD)One packet can be transmitted per slotThe channel makes use of 79 equally spaced 1-MHz channels (from 2,402 MHz to 2,480 MHz), frequency shift keying (FSK) modulation1 Mb/s transmission/reception rate2 power levels: 0dBm for 10 meters or 20dBm (100 meters),1/5/2018,9,Packet Definition,72-bit access code unique for the channel, used for packet identification and synchronization, derived from the masterHeader: 3-bit slave address, packet type, flow control bits, ARQ bit, sequence number, Header-Error-Check fieldsPayload: 0-2745 bitsMultislot packets have been defined: a packet may cover one, three or five slots, sent on a single hop channel,Access code,PacketHeader,Payload,0 - 2745 bits,54 bits,72 bits,ARQN,TYPE,FLOW,SEQN,HEC,M_ADDR,3,4,1,1,1,8,1/5/2018,10,Links supported,Two types of links to support multimedia applications:Synchronous Connection-Oriented (SCO) linkAsynchronous Connectionless Link (ACL)SCO links support symmetrical, circuit-switched point-to-point connections typically used for voiceReservation is carried out by the master and the slaveACL links support packet-switched point-to-multipoint connection typically used for bursty data transmissionMaster units use a polling scheme to control ACL connections: a master-to-slave packet or a POLL packet poll the slave. Collisions are avoided.All SCO and ACL traffic is scheduled by the master,1/5/2018,11,Architecture,1/5/2018,12,RF and Baseband,Controls the units synchronization and transmission frequency hopping sequence, compresses and puts data into packets, assigning identifiers etcThe two link types SCO and ACL are also managed by this layerTakes care of retransmissions and transmission error detection and recovery,1/5/2018,13,HCI,Provides a uniform interface method for accessing the Bluetooth hardware capabilitiesIt contains a command interface to the Baseband controller and link manager and access to the hardware status,1/5/2018,14,Link Manager Protocol (LMP),Responsible for:Connection set-up Generation, exchange and control of link and encryption keys for Authentication and EncryptionLink mode negotiation and set-up, e.g. data or data/voice Sending and receiving of dataManagement of power modes, power consumption and state of a unit,1/5/2018,15,Logical Link Control and Adaptation Protocol (L2CAP),L2CAP is an interface between upper layer protocols and baseband and operates in parallel to LMPMultiplexing: L2CAP must support protocol multiplexing, since a number of protocols (e.g. SDP, RFCOMM and TCS Binary) can operate over L2CAP. Segmentation and Reassembly: Data packets exceeding the Maximum Transmission Unit, MTU, must be segmented before being transmitted. This and the reverse functionality, reassemble, is performed by L2CAP. Quality of Service: The establishment of an L2CAP connection allows the exchange of information regarding current Quality of Service for the connection between the two Bluetooth units,1/5/2018,16,Service Discovery Protocol (SDP),Defines how a Bluetooth clients application shall act to discover available Bluetooth servers services (like printing, file transfer, synchronization) and their Bluetooth characteristics. Defines how a client can search for a service based on specific attributes without the client knowing anything of the available services. Provides means for the discovery of new services becoming available when the client enters an area where a Bluetooth server is operating. Provides functionality for detecting when a service is no longer available,1/5/2018,17,Other protocols,RFCOMM - Cable replacement protocol: emulates serial port to cover applications that use serial ports of the kind used in PCs and provides transport capabilities for upper level servicesTelephony Control ProtocolsTCS BIN: defines the call control signaling for the establishment and release of calls between unitsTCS AT Commands: transmitting control signals for telephony control Adopted protocolsPPPTCP/UDP/IPThe TCP/UDP/IP standards are defined to operate in Bluetooth units allowing them to communicate with other units connected, for instance, to the Internet. WAP,1/5/2018,18,Connection Establishment,When units are not connected they are in STANDBY mode, where they listen to 32 unique (for each unit) wake-up channels, for page or inquiry messages, for about 10ms eachWake-up interval ranges between 0 to 3.84s (usually 1.28s)A unit enters the PAGE or INQUIRY state in which it broadcasts page or inquiry messagesIf the paging unit knows the identity of the unit to which it wants to connect, it knows the wake-up sequence and transmits the units access code every 1.25ms to 16 different hop frequencies defined for the slave unit (total 10ms period)If the pager does not know the identity of the unit, it broadcasts an inquiry message according to a common inquiry sequence, every 0 to 2.56s,1/5/2018,19,Connection Establishment,1/5/2018,20,Piconets and Scatternets,Two or more Bluetooth units that share a FH channel form a piconet. At most 1 master and 7 slaves can be in one piconetAny unit can become a master, but by definition the paging unit that establishes the piconet is the masterThe master identity and clock specify the channel parametersAll devices in a piconet are synchronized to the same FH sequenceUp to 10 piconets can co-exist with overlapping coverage areas and form a scatternetA unit can be a master in one piconet and a slave in another, or slave in several piconets,1/5/2018,21,Power Management,Frequency-hopping mechanism provides synchronization between master-slaves therefore no dummy packets have to be exchagedA receiver can quickly decide whether a packet is present or not, by the access code and the header and sleep for the rest of the slotPower-save modes:HOLD mode, where no communication is possible for a specified hold timeSNIFF mode, where the slave listens only to some slots (depends on the application)PARK mode, where the slave listens to the masters beacon at large intervals to re-synchronize, does not have a MAC address and does not participate in the traffic,1/5/2018,22,Modes of operation,1/5/2018,23,Security,As radio signals can be easily intercepted, Bluetooth devices have built-in security to prevent eavesdropping or falsifying the origin of messages (spoofing)The main security features are:a challenge-response routine for authenticationstream cipher for encryptionsession key generation session keys can be exchanged during a connection,1/5/2018,24,Competing Technologies,Infrared Data Association (IrDA) vs BluetoothIEEE 802.11b vs Bluetooth,1/5/2018,25,IrDA vs Bluetooth,Wireless StandardIrDA already proven standard (50 million units)Bluetooth still in development Data TransfersIrDA up to 4Mbps; 16Mbps