Module4-WLAN_Bluetooth

nullELEC6099 Wireless Communication and Networking*ELEC6099 Wireless Communication and NetworkingModule 4: WLAN and BluetoothOutline*OutlineIEEE 802.11x WLAN Overview IEEE 802.11 MAC, Frame, Physical Layer Bluetooth Protocol Architecture Bluetooth Baseband Coexistence Issues IEEE 802.11 Wireless LAN*IEEE 802.11 Wireless LAN802.11b 2.4-5 GHz unlicensed spectrum up to 11 Mbps direct sequence spread spectrum (DSSS) in physical layer all hosts use same chipping code802.11a 5-6 GHz range up to 54 Mbps 802.11g 2.4-5 GHz range up to 54 Mbps 802.11n: multiple antennae 2.4-5 GHz range up to 200 Mbpsall use CSMA/CA for multiple access all have base-station and ad-hoc network versions802.11 LAN architecture*802.11 LAN architecturewireless host communicates with base station base station = access point (AP) Basic Service Set (BSS) (aka “cell”) in infrastructure mode contains: wireless hosts access point (AP): base station ad hoc mode: hosts onlyBSS 1BSS 2hub, switch or router802.11: Channels, association*802.11: Channels, association802.11b: 2.4GHz-2.485GHz spectrum divided into 11 channels at different frequencies AP admin chooses frequency for AP interference possible: channel can be same as that chosen by neighboring AP! host: must associate with an AP scans channels, listening for beacon frames containing AP’s name (SSID) and MAC address selects AP to associate with may perform authentication will typically run DHCP to get IP address in AP’s subnet 802.11: passive/active scanning*802.11: passive/active scanningAP 2AP 1H1BBS 2BBS 1Active Scanning: Probe Request frame broadcast from H1 Probes response frame sent from APs Association Request frame sent: H1 to selected AP Association Response frame sent: H1 to selected APAP 2AP 1H1BBS 2BBS 1Passive Scanning: beacon frames sent from APs association Request frame sent: H1 to selected AP association Response frame sent: H1 to selected APIEEE 802.11: multiple access*IEEE 802.11: multiple accessavoid collisions: 2+ nodes transmitting at same time 802.11: CSMA - sense before transmitting don’t collide with ongoing transmission by other node 802.11: no collision detection! difficult to receive (sense collisions) when transmitting due to weak received signals (fading) can’t sense all collisions in any case: hidden terminal, fading goal: avoid collisions: CSMA/C(ollision)A(voidance)IEEE 802.11 MAC Protocol: CSMA/CA*IEEE 802.11 MAC Protocol: CSMA/CA802.11 sender 1 if sense channel idle for DIFS then transmit entire frame (no CD) 2 if sense channel busy then start random backoff time timer counts down while channel idle transmit when timer expires if no ACK, increase random backoff interval, repeat 2 802.11 receiver - if frame received OK return ACK after SIFS (ACK needed due to hidden terminal problem) senderreceiverAvoiding collisions (more)*Avoiding collisions (more)idea: allow sender to “reserve” channel rather than random access of data frames: avoid collisions of long data frames sender first transmits small request-to-send (RTS) packets to BS using CSMA RTSs may still collide with each other (but they’re short) BS broadcasts clear-to-send CTS in response to RTS CTS heard by all nodes sender transmits data frame other stations defer transmissions avoid data frame collisions completely using small reservation packets!Collision Avoidance: RTS-CTS exchange*Collision Avoidance: RTS-CTS exchangeAPABtimedefer802.11 frame: addressing*802.11 frame: addressingAddress 2: MAC address of wireless host or AP transmitting this frameAddress 1: MAC address of wireless host or AP to receive this frameAddress 3: MAC address of router interface to which AP is attachedAddress 4: used only in ad hoc modenull*H1R1802.11 frame: addressingnull*802.11 frame: moreduration of reserved transmission time (RTS/CTS)frame seq # (for RDT)frame type (RTS, CTS, ACK, data)MAC Layer: Control Frames*MAC Layer: Control FramesPower Save Poll (PS-Poll): Sent by a station to the station (e.g., an AP) to request for a frame that has been buffered for the former while it was in power-saving mode Request to Send (RTS): The first frame in a 4-frame exchange Clear to Send (CTS): The second frame in a 4-frame exchange Acknowledgment (ACK): acknowledging receipt of data, management, or PS-Poll frame Contention-Free End (CF-End): Announces the end of a contention-free period used in PCF CF-End + CF-ACK: Acknowledges the CF-EndMAC Layer: Data Frames*MAC Layer: Data FramesData: the simplest data frame, used in both a contention period and a contention-free period Data + CF-ACK: May only be sent during a contention-free period. In addition to carrying data, this frame acknowledges previously received data Data + CF-Poll: Used by a point coordinator to deliver data to a mobile station and also to request that the mobile station send a data frame that it may have buffered Data + CF-ACK + CF-Poll: Combines the functions of the Data + CF-ACK and Data + CF-Poll into a single frameIEEE 802.11 Physical Layer: Overview*IEEE 802.11 Physical Layer: OverviewIssued in three stages: first part issued in 1997, the remaining two parts in 1999 The first part is simply called IEEE 802.11, which includes the MAC layer and three physical layer specifications (two in the 2.4-GHz ISM band and one in the infrared; all operating at 1 and 2 Mbps) IEEE 802.11a operates in the 5-GHz band at data rates up to 54 Mbps (with OFDM) IEEE 802.11b operates in the 2.4-GHz at 5.5 and 11 Mbps IEEE 802.11g (OFDM) with rates > 20 Mbps IEEE 802.11n (OFDM/MIMO) with rates > 100 MbpsIEEE 802.11 Physical Layer: Overview*IEEE 802.11 Physical Layer: OverviewIEEE 802.11 Physical Layer: Overview*IEEE 802.11 Physical Layer: Overviewnull*hub or switchAP 2AP 1H1BBS 2BBS 1802.11: mobility within same subnetH1 remains in same IP subnet: IP address can remain same switch: which AP is associated with H1? self-learning: switch will see frame from H1 and “remember” which switch port can be used to reach H1null*802.11: advanced capabilitiesRate Adaptation base station, mobile dynamically change transmission rate (physical layer modulation technique) as mobile moves, SNR varies QAM256 (8 Mbps)QAM16 (4 Mbps)BPSK (1 Mbps)10203040SNR(dB)BER10-110-210-310-510-610-710-4operating point1. SNR decreases, BER increase as node moves away from base station2. When BER becomes too high, switch to lower transmission rate but with lower BERnull*802.11: advanced capabilitiesPower Management node-to-AP: “I am going to sleep until next beacon frame” AP knows not to transmit frames to this node node wakes up before next beacon frame beacon frame: contains list of mobiles with AP-to-mobile frames waiting to be sent node will stay awake if AP-to-mobile frames to be sent; otherwise sleep again until next beacon frame null*radius of coverage802.15: personal area networkless than 10 m diameter replacement for cables (mouse, keyboard, headphones) ad hoc: no infrastructure master/slaves: slaves request permission to send (to master) master grants requests 802.15: evolved from Bluetooth specification 2.4-2.5 GHz radio band up to 721 kbps null*802.16: WiMAXlike 802.11 & cellular: base station model transmissions to/from base station by hosts with omnidirectional antenna base station-to-base station backhaul with point-to-point antenna unlike 802.11: range ~ 6 miles (“city rather than coffee shop”) ~14 Mbps point-to-multipointpoint-to-pointnull*802.16: WiMAX: downlink, uplink schedulingtransmission frame down-link subframe: base station to node uplink subframe: node to base stationbase station tells nodes who will get to receive (DL map) and who will get to send (UL map), and whenWiMAX standard provide mechanism for scheduling, but not scheduling algorithmWPAN Overview*WPAN OverviewWireless personal network (WPAN): Short range (typically < 10m) Support portable and mobile computing devices, e.g., PCs, PDAs, printers, cell phones, set-top boxes, etc. Technologies: Bluetooth (IEEE 802.15.1) Low cost solution for data rates up to 1 Mbps UWB (IEEE 802.15.3a) For streaming video signals at data rates up to 1 Gbps ZigBee (IEEE 802.15.4) Extremely low cost for command and controlIntroduction: IEEE 802.15 Committee*Introduction: IEEE 802.15 CommitteeIntroduction: IEEE 802.15 Groups*Introduction: IEEE 802.15 GroupsIEEE 802.15.1 and IEEE 802.15.4 focus on devices: Power management: low power consumption Range: 0-10m Rate: 19.2—100 kbps Size: 0.5 in3 without antenna Low cost relative to target host device Should be able to handle coexistence of multiple networks Networking support of a minimum of 16 devicesBluetooth: Overview*Bluetooth: OverviewBluetooth—named after the King Harald Blaatand of Denmark (tenth century A.D.) Initially developed by Ericsson in 1994 Using the 2.4-GHz ISM band, unlicensed low-power connections Range about 10 m and the peak data rate is 720 Kbps Example applications (limited only by your imagination): make calls from a wireless headset connected remotely to a cell phone eliminate cables linking computers to printers, keyboards, and the mouse hook up MP3 players wirelessly to other machines to download music set up home networks so that a couch potato can remotely monitor air conditioning, the oven, and children’s Internet surfing call home from a remote location to turn appliances on and off, set the alarm, and monitor activityBluetooth: Application Areas*Bluetooth: Application AreasData and Voice Access Points: Bluetooth facilitates real-time voice and data transmissions by providing effortless wireless connection of portable and stationary communication devices Cable Replacement: Bluetooth eliminates the need for numerous, often proprietary, cable attachments for connection of practically any kind of communication device. Connections are instant and are maintained even when devices are not within line of sight. The range of each radio is approximately 10 m, but can be extended to 100 m with an optional amplifier Ad Hoc Networking: A device equipped with a Bluetooth radio can establish instant connection to another Bluetooth radio as soon as it comes into rangeBluetooth: Protocol Architecture*Bluetooth: Protocol ArchitectureBluetooth: Protocol Architecture*Bluetooth: Protocol ArchitectureRadio: Specifies details of the air interface, including frequency, the use of frequency hopping, modulation scheme, and transmit power Baseband: Concerned with connection establishment within a piconet, addressing, packet format, timing, and power control Link Manager Protocol (LMP): Responsible for link setup between Bluetooth devices and ongoing link management. This includes security aspects such as authentication and encryption, plus the control and negotiation of baseband packet sizes Logical Link Control and Adaptation Protocol (L2CAP): Adapts upper-layer protocols to the baseband layer. L2CAP provides both connectionless and connection-oriented services Service Discovery Protocol (SDP): Device information, services, and the characteristics of the services can be queried to enable the establishment of a connection between two or more Bluetooth devicesBluetooth: Protocol Architecture*Bluetooth: Protocol ArchitectureRFCOMM is the cable replacement protocol included in the Bluetooth specification. RFCOMM presents a virtual serial port that is designed to make replacement of cable technologies as transparent as possible. Serial ports are one of the most common types of communication interfaces used with computing and communication devices Thus, RFCOMM enables the replacement of serial port cables with the minimum of modification of existing devices. RFCOMM provides for binary data transport and emulates EIA-232 control signals over the Bluetooth baseband layer. EIA-232 (formerly known as RS-232) is a widely used serial port interface standardBluetooth: Protocol Architecture*Bluetooth: Protocol ArchitectureBluetooth specifies a telephony control protocol. TCS BIN (telephony control specification—binary) is a bit-oriented protocol that defines the call control signalling for the establishment of speech and data calls between Bluetooth devices. The adopted protocols that can make use of Bluetooth: PPP: the point-to-point protocol is an Internet standard protocol for transporting IP datagrams over a point-to-point link TCP/UDP/IP: These are the foundation protocols of the TCP/IP protocol suite OBEX: the object exchange protocol is a session-level protocol developed by the Infrared Data Association (IrDA) for the exchange of objects. OBEX provides functionality similar to that of HTTP, but in a simpler fashion. It also provides a model for representing objects and operations. Examples of content formats transferred by OBEX are vCard and vCalendar, which provide the format of an electronic business card and personal calendar entries and scheduling information, respectively WAE/WAP: Bluetooth incorporates the wireless application environment and the wireless application protocol into its architectureBluetooth: Service Profiles*Bluetooth: Service ProfilesBluetooth: Service Profiles*Bluetooth: Service ProfilesBluetooth: Service Profiles*Bluetooth: Service ProfilesBluetooth: Service Profiles*Bluetooth: Service ProfilesFile Transfer: The file transfer profile supports the transfer of directories, files, documents, images, and streaming media formats. This usage model also includes the capability to browse folders on a remote device Internet Bridge: With this profile, a PC is wirelessly connected to a mobile phone or cordless modem to provide dial-up networking and fax capabilities. For dial-up networking, AT commands are used to control the mobile phone or modem, and another protocol stack (e.g., PPP over RFCOMM) is used for data transfer. For fax transfer, the fax software operates directly over RFCOMM LAN Access: This profile enables devices on a piconet to access to a LAN. Once connected, a device functions as if it were directly connected (wired) to the LAN Synchronization: This profile provides a device-to-device synchronization of PIM (personal information management) information, such as phone book, calendar message, and note information. IrMC (Ir mobile communications) is an IrDA protocol that provides a client/server capability for transferring updated PIM information from one device to anotherBluetooth: Service Profiles*Bluetooth: Service ProfilesThree-in-one Phone: Telephone handsets that implement this profile may act as a cordless phone connecting to a voice base station, as an intercom device for connecting to other telephones, and as a cellular phone Headset: The headset can act as a remote device’s audio input and output interfaceBluetooth: Piconet and Scatternet*Bluetooth: Piconet and ScatternetBluetooth: Piconet and Scatternet*Bluetooth: Piconet and ScatternetBluetooth: Piconet and Scatternet*Bluetooth: Piconet and ScatternetPiconet: a master with up to a maximum of seven slaves Scatternet: piconets interconnected with each other via some bridge nodes, which can be a master/slave dual mode node, or a slave/slave dual mode node Scatternet formation is limited by collisions—different piconets using the same frequency for communications, even though the hopping sequences used may be different Scatternet traffic management is undefined yetBluetooth: Radio Specification*Bluetooth: Radio SpecificationBluetooth: Radio Specification*Bluetooth: Radio SpecificationThree classes of transmitters based on output power: Class 1: Outputs 100 mW (+20 dBm) for maximum range, with a minimum of 1 mW (0 dBm). In this class, power control is mandatory, ranging from 4 to 20 dBm. This mode provides the greatest transmission range Class 2: Outputs 2.4 mW (+4 dBm) at maximum, with a minimum of 0.25 mW (-6 dBm). Power control is optional Class 3: Lowest power. Nominal output is 1 mW. Bluetooth makes use of the 2.4-GHz band within the ISM (Industrial, Scientific, and Medical) band. In most countries, the bandwidth is sufficient to define 79 1-MHz physical channelsBluetooth: Radio Specification*Bluetooth: Radio SpecificationBluetooth: Baseband Specification*Bluetooth: Baseband SpecificationFrequency hopping (FH) in Bluetooth serves two purposes: It provides a resistance to interference and multipath effects It provides a form of multiple access among co-located devices in different piconets The total bandwidth is divided into 79 physical channels (in almost all countries), each of bandwidth 1 MHz FH occurs by jumping from one physical channel to another in a pseudorandom sequence The same hopping sequence is shared by all of the devices on a single piconet (this is referred to as FH Channel) The hop rate is 1600 hops per second, so that each physical channel is occupied for a duration of 0.625 msec Each 0.625 msec time period is referred to as a slotBluetooth: Baseband Specification*Bluetooth: Baseband SpecificationBluetooth radios communicate using a time division duplex (TDD) discipline Data are transmitted in one direction at a time, with transmission alternating between the two directions The piconet access is thus characterized as FH-TDD-TDMA Bluetooth: Baseband Specification*Bluetooth: Baseband SpecificationTransmission of a packet starts at the beginning of a slot. Packet lengths requiring 1, 3, or 5 slots are allowed. For multislot packets, the radio remains at the same frequency until the entire packet has been sent. In the next slot after the multislot packet, the radio returns to the frequency required for its hopping sequence, so that during transmission, two or four hop frequencies have been skipped Bluetooth Baseband: Physical Links*Bluetooth Baseband: Physical LinksSynchronous Connection Oriented (SCO): Allocates a fixed bandwidth between a point-to-point connection involving the master and a single slave. The master maintains the SCO link by using reserved slots at regular intervals. The basic unit of reservation is two consecutive slots (one in each transmission direction). The master can support up to three simultaneous SCO links while a slave can support two or three SCO links. SCO packets are never retransmitted. Asynchronous Connectionless (ACL): A point-to-multipoint link between the master and all the slaves in the piconet. In slot not reserved for SCO links, the master can exchange packets with any slave on a per-slot basis, including a slave already engaged in an SCO link. Only a single ACL link can exist. For most ACL packets, packet retransmission is applied.Bluetooth Baseband: Physical Links*Bluetooth Baseband: Physical LinksSCO links are used primarily to exchange time-bounded data requiring guaranteed data rate but without guaranteed delivery, e.g., audio data ACL links provide a packet-switched style of connection. No bandwidth reservation is possible and delivery may be guaranteed through error detection and retransmission A slave is permitted to return an ACL packet in the slave-to-master slot if and only if it has been addressed in the preceding master-to-slave slot For ACL links, 1-slot, 3-slot, and 5-slot packets have been defined. Data can be sent either unprotected (although ARQ can be used at a higher layer) or protected with a 2/3 forward error correction code The maximum data rate that can be achieved is with a 5-slot unprotected packet with asymmetric capacity allocation, resulting in 721 Kbps in the forward direction and 57.6 Kbps in the reverse directionBluetooth Baseband: Physical Links*Bluetooth Baseband: Physical LinksBluetooth Baseband: Physical Links*Bluetooth Baseband: Physical LinksBluetooth Baseband: Packet Format*Bluetooth Baseband: Packet FormatAccess code: Used for timing synchronization, offset compensation, paging, and inquiry Channel access code (CAC): Identifies a piconet (unique for a piconet) Device access code (DAC): Used for paging and its subsequent responses Inquiry access code (IAC): Used for inquiry purposes Header: Used to identify packet type and to carry protocol control information Payload: If present, contains user voice or data and, in mo