cmpe 257: wireless and mobile networking

CMPE 257 Spring 2003 1

CMPE 257: Wireless and Mobile Networking

Spring 2005Bluetooth

CMPE 257 Spring 2003 2

Announcements

CMPE 257 Spring 2003 3

Today Bluetooth.

CMPE 257 Spring 2003 4

Simulation Results

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Experimental Setup Qualnet simulator 802.11 MAC with 371m radio range. 50 nodes in a 1500x1500 area. Random node placement. Two different underlying multicast

routing protocols (MAODV and ODMRP).

Application data size 512 bytes. 5 sources and 10 group members.

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Reliable Delivery Ratio over MAODV

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Reliable Delivery Ratio over ODMRP

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Average Goodput - MAODV

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Average Goodput - ODMRP

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Bluetooth

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Cable Replacement

1 Mb/s. Range ~10 meters. PANs Single chip radio.

Low power & low cost.

Why not use Wireless LANs?- power- cost

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Applications: Synchronization

Automatic synchronization of calendars, address books, business cards.

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Applications: Cordless Headset

Multiple device access.

Hands-free operation.

Cordlessheadset

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More applications… Conference table. Cordless computer. Instant photo transmission. Cordless phone.

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Features Cost20 dBm (~100 m)

Point-to-multipoint

No Scatternet

ApplicationsFile Transfer,

Dial-Up Networking

LAN access, Fax, …

169 $

---

200 $

0 dBm (~10 m)

Point-to-multipoint

No Scatternet

File Transfer,

Dial-Up Networking

LAN access, Fax, …169 $

---

CompanyToshiba,

Motorola,

Digianswer

IBM, TDK

3COM

10 m user-user;

100 m user-Base Station

Point-to-multipoint

SW- & FW-upgradeable

File Transfer,

Dial-Up Networking

LAN access, Fax, E-mail

Unconscious connection

149 $

Nokia

10 m user-user;

Point-to-point

Connectivity Battery

for the cell phone

File Transfer,

Dial-Up Networking

LAN access, Fax, E-mail

Unconscious connection

149 $

Ericsson,

Sigma

10 m user-user;

Point-to-point;

ARM processor;

USB; RFCOMM ports

Basic BT Radio stack

Embedded or Host stack

Programmable

500 $

1500$

Bluetooth on the market:Bluetooth on the market:PC cards, Cell phones, Head sets, Chip sets,…

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Bluetooth WG History May 1998: Bluetooth SIG is formed.

Promoter company group: Ericsson, IBM, Intel, Nokia, Toshiba.

Goal: develop license-free technology for universal wireless connectivity.

Target: handheld market. Bluetooth spec: defines RF wireless

communication interface and protocols.

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Bluetooth WG History May 1998: Public announcement of

Bluetooth SIG. July 1999: 1.0A spec (>1,500 pages)

published. December 1999: version 1.0B released. December 1999: promoters increases to

9. 3Com, Lucent, Microsoft, Motorola

February 2000: 1,800+ adopters. February 2001: version 1.1 out.

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More History… Recently, IEEE 803.15.1 standard

for Wireless PANs (WPANs) Only MAC and PHY.

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Goals Low cost. Power efficiency. Single-chip implementation. (early implementations are double-

chip)These goals defined: Link speed. Communication range. Transmit power.

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Bluetooth Protocol Stack

RF

Baseband

Link Manager

L2CAP

RFCOMM/SDP

Single chip with RS-232,USB, or PC card interface

Applications

Link Controller

Host Controller Interface

Radio+partof baseband=Physical layer

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Radio Band Public, i.e., no need for licenses. Available worldwide. Industrial, Scientific, Medical (ISM)

band. Unlicensed, globally available. Centered around 2.4 GHz.

Frequency hopping. Range: 10cm to 10m.

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Unlicensed Radio Spectrum

902 Mhz

928 Mhz

26 Mhz 83.5 Mhz 125 Mhz

2.4 Ghz

2.4835 Ghz5.725 Ghz

5.785 Ghz

cordless phonesbaby monitorsWireless LANs

802.11BluetoothMicrowave oven

unused

33cm 12cm 5cm

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Bluetooth Radio Link

MA scheme: Frequency hopping spread spectrum. 2.402 GHz + k MHz, k=0, …, 78 1,600 hops per second. 1 Mb/s data rate.

Number of hopping sequences defined. Master node defines sequence to be used. Slave units use master id to pick sequence.

. . .

1Mhz

1 2 3 79

83.5 Mhz

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BT Radio Link (Cont’d) Time-division duplex (TDD)

Separation of Xmission and reception in time: one-chip implementation.

Units alternately transmits and receives. Gaussian Frequency Shift Keying (G-

FSK) modulation. ‘1’s as positive frequency deviations

from carrier frequency; ‘0’s as negative deviations.

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Multiple Access BT targets large number of independent

communications active in the same area at the same time.

Single FH channel: 1 Mb/s. Each 1Mb/s channel shared by limited number

of participants. In target user scenarios, it’s unlikely that all units in-

range will share data among all of them. 1 MB/s is reasonable. (is it?)

Theoretically, total bandwidth is 79 Mb/s. In practice, < 79 Mb/s since codes are non-

orthogonal.

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Baseband

Carries out MACfunctions.

RF

Baseband

Link Manager

L2CAP

RFCOMM/SDP

Applications

Link Controller

Host Controller Interface

Control end of baseband+link controller=Data link layer

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Piconets BT communication takes place over

piconets. Piconet formation initiated by master. All other participants are slaves. Number of participants limited to 8 (1

master and 7 slaves). Channel capacity and addressing overhead. Each slave assigned a locally unique ID.

Master/slave role last for the duration of the piconet.

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Piconets: considerations Most target applications involve

local communication among small group of devices.

Piconets with up to 8 nods match well.

If many groups of devices active simultaneously, each group as separate piconet.

Overlapping piconets can coexist.

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Contention-Free MA Master and slaves. Master performs medium access control.

Schedules traffic through polling. Time slots alternate between master and

slave transmission. Master-slave: master includes slave address. Slave-master: only slave chosen by master in

previous master-slave slot allowed to transmit. If master has data to send to a slave, slave

polled implicitly; otherwise, explicit poll.

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BT StatesStandby

Inquiry Page

Transmit Connected

Park Hold Sniff

Unconnected

Connecting

Active

Low power

. Initially, all nodes in standby.. Node (master) can begininquiry to find nearbydevices.. Piconet is then formed.. Devices join by paging.

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Inquiry

Device discovery Listeners respond with their address.

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Paging Master

Active Slave

Parked Slave

Standby

Device enters paging to invite others to join its piconet.

Establishes links with nodes in proximity. Paging message unicast to selected

receiver. Receiver sends ACK. Sender becomes master, receiver slave.

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Piconet New Node Admission Master can actively try to discover

new nodes or wait (in scan/listen mode) to be discovered.

Communication in the current piconet suspended.

Admission latency versus piconet capacity tradeoff.

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Bluetooth Link Formation

Point-to-point link: Master-slave relationship.

m s

ss

m

s

Piconet: 8 units: channel capacity. Master (establishes piconet) can connect to up to 7 slaves. Master/slave relationship lasts while link/piconet lasts. No slave-to-slave communication.

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Link Types 2 types of links:

Synchronous (SCO) links: Point-to-point between master and slave. Link established by reserving slots in either

direction periodically. Used to carry real-time traffic (voice).

Asynchronous (ACL) links: Point-to-multipoint between master and slaves. Use remaining slots on channel. Traffic scheduled by master.

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Error Control Supports both FEC and retransmission. FEC for SCO packets. ARQ for ACL traffic.

If no ACKs, retransmit. Stop-and-wait ARQ.

Fast-ARQ: ACK included in RX slot immediately following the TX slot in which packet was sent.

CRC to check for errors.

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Packet Format72 bits 54 bits 0 - 2744 bitsAccess code

Header Payload

DataVoice CRCNo CRCNo retries

625 µs

master

slave

header

ARQFEC (optional)

FEC (optional)

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Access Code

Address of piconet master.

Access code

Header Payload

72 bits

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Packet Header

Addressing (3) Packet type (4) Flow control (1) 1-bit ARQ (1) Sequencing (1) HEC (8)

Access code

Header Payload

54 bits

Purpose

Broadcast packets are not ACKed

For filtering retransmitted packets

18 bitstotal

ss

m

s

16 packet types (some unused)

Max 7 active slaves

Verify header integrity

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Multiple Piconets Piconets may overlap in space and

time. They can work independently.

Each with its own hopping sequence. Packets with different access codes.

Or they can overlap, i.e., nodes can participate in more than 1 piconet. “Time sharing”.

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Scatternets Interconnection of multiple

piconets.

Master

Slave

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Scatternets (cont’d…) Interconnection by bridge nodes.

Bridge nodes are members of piconets they interconnect.

Bridge node “stay” in a piconet for some time, then switch to another piconet by changing hop sequence.

Do this for all member piconets. Send and receive in each piconet. Forward from one piconet to another.

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Link Manager Protocol

. Main functions: powermanagement and security.

RF

Baseband

Link Manager

L2CAP

RFCOMM/SDP

Applications

Link Controller

Host Controller Interface

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Power Management Low-power modes: prolong battery

life. Devices can be turned-off when idle. Devices wake up periodically to

send/receive data.

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Low-Power Operation 3 modes:

Hold: node sleeps for specified interval. Master can put slaves in hold while searching for new

members, attending another piconet, etc. No ACL packets.

Sniff: slave low-duty cycle mode. Slave wakes up periodically to talk to master. Fixed “sniff” intervals.

Park: Very low power state. Used to admit more than 7 slaves in piconet.

Slave gives up its active member address. Receives “parked” member address.

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Security Authentication and encryption.. Authentication using challenge-

response mechanism based on shared secret key

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Host Controller Interface

RF

Baseband

Link Manager

L2CAP

RFCOMM/SDP

Applications

Link Controller

Host Controller Interface

Optional interface layerbetween higher and lower layers of the BT stack.

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L2CAP

Logical Link Control andAdaptation Protocol=

Session Layer.

L2CAP provides• Protocol multiplexing• Quality of service negotiationRF

Baseband

Link Manager

L2CAP

RFCOMM/SDP

Applications

Link Controller

Host Controller Interface

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RFCOMM/SDP

RF

Baseband

Link Manager

L2CAP

RFCOMM/SDP

Applications

Link Controller

Host Controller InterfaceService discovery, interoperability with IR applications, serial port interface.

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References: Bluetooth papers in reading list. Johansson and Gerla’s Bluetooth

Tutorial at Mobicom 2001. Bluetooth 1.1: Connect Without

Cables, Bray and Sturman.