Ch 7. Wireless Personal Area Networks Myungchul Kim mckim@icu.ac.kr

Wireless Personal Area Networks WPANs Bluetooth Home Networking UWB Overview Wireless Sensor Networks

WPANs Short range networks (< 10 meters) Used in homes, cars, small offices Can be interconnected to form large networks IEEE 802.15 is the main standards environment Many active areas of work: Bluetooth, UWB, Wireless sensor networks, Zigbees

Bluetooth Wireless LANs Overview Applications and Examples Piconets and Scatternets Standards Overview Core standards

Bluetooth Overview Supports open-ended list of applications Founders: Ericsson, IBM, Intel, Nokia, Toshiba; May 98 Currently: Over 1000 companies Low-cost, short range radio link between mobile PCs, phones and other portable devices 2.4 GHz ISM band (unlicensed): Short packets, fast-hopping, and FEC limits impacts of interference Software for service and device discovery Typical application: cellular phone to PDA or earphone Supports open-ended list of applications Data, audio, graphics, video Many products from Nokia, Motorola, Apple, etc. Bluetooth.com and palowireless.com/bluetooth have great deal of info

Bluetooth PSTN Access Point Wired LAN Bluetooth Piconet Cellular Network Wired LAN Bluetooth Piconet (1 Mbps, 10 meters)

Bluetooth Application Areas Cable replacement Eliminates need for numerous cable attachments for connection (e.g., RS232) Data and voice access points Real-time voice and data transmissions Ad hoc networking Device with Bluetooth radio can establish connection with another when in range

Piconets and Scatternets Basic unit of Bluetooth networking Master and one to seven slave devices Master determines channel and phase Scatternet Device in one piconet may exist as master or slave in another piconet Allows many devices to share same area Makes efficient use of bandwidth

Bluetooth Configurations Master A B Slave/Master E D C Slave Slave Slave F G H Slave Slave Slave 2.4 GHZ ISM band supports around 80 physical channels with 1 MHz. bandwidth These 80 channels are managed through piconets and scatternets All radios in a scatternet share the same frequency hopping (FHSS)

Bluetooth Piconets PC Slave Master PC Master Slave Piconet2 (Cubicle2) printer Ear Phone Slave /Master Cellular Phone PC Slave Slave Piconet1 (Cubicle 1) printer Slave Slave PC Piconet3 (Cubicle3)

Bluetooth versus Wi-Fi Table 7‑2: Bluetooth versus Wi-Fi Bluetooth versus Wi-Fi Factor Wi-Fi Bluetooth Data Rate 11 Mbps 1 Mbps Distance Covered (range) 100 meters 10 meters Application focus Cable replacement Connection to corporate networks Ease of use Piconets good for small networks Complex even for 2 devices Security Short distance, multiple levels (link level, app level) WEP Power Very low power (smaller devices such as consumer electronics) High power  

State Transitions in Bluetooth Standby Disconnected State Page Inquire Connecting State Active Active State Park, Sniff, Hold- Low-Power States Typical Scenario: Devices initially in standby mode Issue an inquire (I am available, does someone need me) Devices scan the inquire list and then page the ones they want to invite Devices go into an active transfer mode (Piconet) If too many in a piconet, go into park-sniff-hold mode After transfer go into standby mode

Bluetooth Standards Documents Standards specifications Details of various layers of Bluetooth protocol architecture (more than 1500 pages) Bluetooth is a layered protocol architecture Core protocols (5 layer) - required Cable replacement and telephony control protocols Adopted protocols (PPP, WAP,,) . Profile specifications Use of Bluetooth technology to support various applications

Protocol Architecture Core protocols Radio layer - Bluetooth transceiver operating in the 2.4 GHz Baseband layer -Bluetooth Link Controller (LC) low- level link routines (complex). Link Manager Protocol (LMP) is used by the Link Managers (on both side) for link Host Controller Interface (HCI) a command interface to access to hardware status and control registers. Logical Link Control and Adaptation Protocol (L2CAP) supports higher level protocol multiplexing Service Discovery Protocol (SDP) applications to discover which services are provided by a Bluetooth device

Bluetooth Stack Legend Core vCard/vCal WAE AT- Commands TCS Bin SDP Cable replacement OBEX WAP Telephony control TCP UDP IP Adopted PPP Audio RFCOMM Logical Link Control and Adaptation Protocol ( L2CAP) Host Controller Interface Link Management Protocol (LMP) Baseband Bluetooth Radio Shaded areas (see legend) represent different families of Bluetooth Protocols

Protocol Architecture (cont.) Cable replacement protocol: provides emulation of serial ports over the L2CAP protocol (e.g., emulates EIA RS232 communications over the Bluerooth baseband layer. Telephony control protocols: (TCS BIN) defines the signalling and control sequences needed for telephone conversations over Bluetooth. Adopted protocols: minimize new by Bluetooth: PPP: used to transport IP packets over point-to-point links such as dial-up lines. TCP/UDP/IP. foundation protocols for the Internet OBEX: The object-exchange protocol developed for the exchange of objects (similar to HTTP, vCard and vCalendar) WAE/WAP: The Wireless Application Protocol and Wireless Application environment are included in Bluetooth.

Usage Models File transfer: to transfer files over Bluetooth. protocols used can be SDP or OBEX. Internet bridge (Dial-Up networking): to wirelessly connect a PC with a cordless modem or a cellular phone uses PPP and AT protocols LAN access: connect a piconet device to access a LAN. uses SDP and PPP-IP protocols. Synchronization: synchronize device-to-device PIM (personal information management) information such as calendars and phone books. The model uses OBEX and IrMC (infrared mobile communications) Three-in-one phone: Telephone headsets and handsets can be used in this model as audio input and output devices. This model uses Audio, SDP, and AT commands.

Usage Models SDP SDP L2CAP L2CAP a) File Transfer File Transfer Application Modem Emulation or Driver Application OBEX AT Commands PPP SDP SDP RFCOMM RFCOMM L2CAP L2CAP a) File Transfer b) Dial-Up Networking LAN Access Application Synchronization Application IP IrMC PPP SDP OBEX SDP RFCOMM RFCOMM L2CAP L2CAP c) LAN Access c) LAN Access

Radio Specification Several classes of transmitters 2.4 GHZ ISM band that can support around 80 physical channels with 1 MHz. bandwidth These 80 channels are managed through piconets and scatternets. Several classes of transmitters Class 1: Outputs 100 mW for maximum range Power control mandatory Provides greatest distance Class 2: Outputs 2.4 mW at maximum Power control optional Class 3: Nominal output is 1 mW Lowest power Much less powerful than cellular phones (GSM operates at 1 to 3 Watts)

Baseband Specification Very complicated Specifies Frequency hopping Physical Links Bluetooth Packet Fields Error correction Logical Channels Bluetooth Audio Bluetooth Security

Baseband Specification Frequency Hopping in Bluetooth. FH occurs by jumping from one channel to another (80). (all devices on a piconet share same). Physical Links between Master and Slave. Synchronous connection oriented (SCO). point-to-point connection of master and slave. Mainly for voice Asynchronous connectionless (ACL). Point-to-multipoint link between master and all slaves is also supported. Bluetooth Packet Fields. Single slot & multiple slot consist of three fields: Access code – used for timing synchronization, offset compensation, paging, and inquiry Header – used to identify packet type and carry protocol control information Payload – contains user voice or data and payload header, if present

Baseband Specification (cont.) Error Correction Schemes:. different types of error correction codes that includes ARQ. Logical Channels and Channel Control: Bluetooth defines five types of channels for different types of payload such as Link control (LC), Link manager (LM), User asynchronous (UA), User isochronous (UI), and User synchronous (US). Bluetooth Audio. choice of two pulse code modulation (PCM) continuously variable slope delta (CVSD) modulation.(variable step) The choice is made by link manager Bluetooth Link Security. includes Authentication, Encryption (privacy) and Key management.

Link Management Protocol (LMP) LMP manages the radio links between Bluetooth masters and slaves. LMP specifies exchange of LMP PDUs PDUs supported by the LMP: General response Security Service Authentication Pairing: establish a key between authenticated pairs Change link key Change current link key Encryption

L2CAP Provides a link-layer protocol between entities with a number of services Similar to LLC Relies on lower layer for flow and error control Makes use of ACL links, does not support SCO links Provides two alternative services to upper-layer protocols Connection service Connection-mode service

Cordless Systems and Wireless Local Loop Cordless networks Wireless MANs (Wireless Local Loops)

Cordless Phone Public Switched Telephone Network (PSTN) Handset Base Unit Basically a cellular phone with no location services Typical coverage is 100-300 meters User owns handset and base unit -- no initial need for standards

Cordless System Operating Environments Residential – a single base station can provide in-house voice and data support Office A single base station can support a small office Multiple base stations in a cellular configuration can support a larger office Telepoint – a base station set up in a public place, such as an airport

Time Division Duplex (TDD) Also known as time-compression multiplexing Data transmitted in one direction at a time, with transmission between the two directions Simple TDD: Bit stream is divided into equal segments, compressed in time to a higher transmission rate, and transmitted in bursts Wireless TDD typically used with TDMA A number of users receive forward channel signals in turn and then transmit reverse channel signals in turn, all on same carrier frequency TDMA/TDD used more often : Improved ability to cope with fast fading (base station can detect strongest signals and send at the same) Improved capacity allocation (can assign more slots to forward channel for improved forward traffic)

TDD

Cordless Standards DECT (Digital Enhanced Cordless Telecommunications) developed in Europe PWT (Personal Wireless telecomm) developed in US DECT is most commonly used standard (mainly DECT Architecture (suited for voice) Physical layer – data transmitted in TDMA-TDD frames over one of 10 RF carriers Medium access control (MAC) layer – selects establishes/releases connections on physical channels; supports three services: Broadcast Connection oriented Connectionless Data link control layer – provides for the reliable transmission of messages using traditional data link control procedures

Home R/F

Home R/F Specification 150 feet, 10 Mbps www.homerf.org

How SWAP (Shared Wireless Application Protocol) Supports Voice and Data

UWB -- Overview Ultra Wideband (UWB) is emerging as a new wireless personal area network technology. Originally developed in the 1960s for the military. FCC approved the commercial implementation of UWB in February 2002, within limits. UWB provides high data rates (around 50 Mbps) in very short distances (10 meters). UWB is a radio system that uses narrow pulses (millions of pulses per second) for communication and sensing by using short-range radar. UWB radio sends data in millions of pulses across a wide frequency band Legal in the US as long as it uses less power than normal radio frequency leakage.

Wireless Sensor Networks (Overview) WSNs typically consist of small, low-powered devices (sensors) Sensors can be developed to measure temperature, humidity, motion, color changes in a painting, or any other measurable thing. Most WSNs consist of millions of tiny processors communicating over slow wireless networks, WSNs may consist of devices with a wide range of computation, communication, and sensing capabilities. The WSNs may use Bluetooth or IEEE 802.11 networks ZigBee IEEE 802.15.4

Sensor Node (Mote)

WSN Hierarchy

WSN Design

WSN Protocol Stack

Summary WPANs Bluetooth Home Networking UWB Overview Wireless Sensor Networks