Bluetooth and BLE

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WIRELESS NETWORKING, 430.752B, 2020 SPRING

Bluetooth and BLE

Kyunghan Lee

Networked Computing Lab (NXC Lab)

Department of Electrical and Computer Engineering Seoul National University

https://nxc.snu.ac.kr kyunghanlee@snu.ac.kr

Adapted from Prof. Sunghyun Choi’s slides

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WIRELESS NETWORKING, 430.752B, 2020 SPRING SEOUL NATIONAL UNIVERSITY

Bluetooth 4.0 (2010)

□ AMP: Use Wi-Fi MAC/PHY

§ Data traffic is carried over a collocated Wi-Fi link

MWNLMultimedia & Wireless Networking Lab.

Bluetooth 4.0 (2010)

Bluetooth 4.0 (2010)

Basic Rate (BR) (2002)

Enhanced Data rate (EDR)

(2004)

Alternate MAC/PHY (AMP)

(2009) Low Energy (LE)

(2010)

Classic Bluetooth

Bluetooth High Speed Bluetooth Low Energy (BLE)

2

• AMP: Use Wi-Fi MAC/PHY

• Data traffic is carried over a collocated Wi-Fi link

(3)

Bluetooth Smart Marks (Smart/Smart Ready)

□ Why were the Bluetooth smart marks created?

§ To help consumers ensure compatibility among their Bluetooth enabled devices

□ Bluetooth Smart Ready device: dual mode

§ Classic Bluetooth connections + Bluetooth Low Energy connections

§ Backward compatible with all of the billions of Bluetooth devices

□ Bluetooth Smart device: single mode

§ Only Bluetooth Low Energy connections

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Bluetooth Core System

□ Consist of a single host and one or more controllers

□ Host and controller combinations

§ Dual mode devices are backward compatible with classic Bluetooth

Bluetooth Core System

• Consist of a single host and one or more controllers

• Host and controller combinations

• Dual mode devices are backward compatible with classic Bluetooth

Host

ControllerLE

Host

BR/EDR

Controller LE Controller

Bluetooth Smart Device

(Single Mode) Bluetooth Smart Ready Device (Dual Mode)

4

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Bluetooth Profiles

□ Bluetooth profiles

§ Define the required functions and features of each layer in Bluetooth system

□ Classic Bluetooth

□ Bluetooth Low Energy

Bluetooth Profiles

• Bluetooth profiles

• Define the required functions and features of each layer in Bluetooth system

• Classic Bluetooth

• Bluetooth Low Energy

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(File Transfer Profile)FTP A2DP

(Advanced Audio Distribution Profile) HFP

(Hands-Free Profile)

iBeacon/Eddystone (for location-based service

e.g., beacon) Glucose

(for healthcare application) Running speed and cadence (for sports/fitness applications)

Bluetooth Profiles

• Bluetooth profiles

• Define the required functions and features of each layer in Bluetooth system

• Bluetooth Low Energy

5

(File Transfer Profile)FTP A2DP

(Advanced Audio Distribution Profile) HFP

(Hands-Free Profile)

iBeacon/Eddystone (for location-based service

e.g., beacon) Glucose

(for healthcare application) Running speed and cadence (for sports/fitness applications)

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Classic Bluetooth – Protocol Stack

Protocol Stack

⁷

Radio Baseband Audio

Logical Link Control and Application Protocol (L2CAP)

RFCOMM

Host

Controller

TCS SDP

Applications/Profiles

*RFCOMM: Radio Frequency Communications

*TCS: Telephony Control Protocol

*SDP: Service Discovery Protocol

*HCI: Host Controller Interface Link manager

HCI

SCO or e-SCO Link ACL Link

* RFCOMM: Radio Frequency Communications

* TCS: Telephony Control Protocol

* SDP: Service Discovery Protocol

* HCI: Host Controller Interface Links

SCO: Synchronous Connection-Oriented

e-SCO: Extended Synchronous Connection-Oriented ACL: Asynchronous Connectionless

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Radio

□ Use 2.4 GHz ISM band

§ 79 channels with 1 MHz bandwidth

□ Transmit power levels

□ Range

§ Typical indoor scenario: 10 m with 1 mW power

MWNL

Radio

•

Use 2.4 GHz ISM band

• 79 channels with 1 MHz bandwidth

•

Transmit power levels

•

Range

• Typical indoor scenario: 10 m w/ 1 mW power

Power Class Maximum Power Nominal Power Minimum Power

1 100 mW (20 dBm) N/A 1 mW (0 dBm)

2 (most common) 2.5 mW (4 dBm) 1 mW (0 dBm) 0.25 mW (-6 dBm)

3 1 mW (0 dBm) N/A N/A

9

Regulatory Range RF Channels

2.400-2.4835 GHz f_c=2402+k MHz, 0, ,78

21 3 4 5 6 87 9 10 11 12 1413 15 16 17 18 2019 21 22 23 24 25 26 2827 29 30 31 32 3433 35 36 37 38 39

0Index 2403 2404 2405 2406 2407 2408 2409 2410 2411 2412 2413 2414 2415 2416 2417 2418 2419 2420 2421 2422 2424 2425 2426 2427 2428 2429 2430 2431 2432 2433 2434 2435 2436 2437 2438 2439 2440 2441

2402 2423

Center Frequency (MHz) 4241 43 44 45 46 4847 49 50 51 52 5453 55 56 57 58 6059 61 62 63 64 65 66 6867 69 70 71 72 7473 75 76 77 7840 2443 2444 2445 2446 2447 2448 2449 2450 2451 2452 2453 2454 2455 2456 2457 2458 2459 2460 2461 2462 2464 2465 2466 2467 2468 2469 2470 2471 2472 2473 2474 2475 2476 2477 2478 2479 2480

2442 2463

Radio

• Use 2.4 GHz ISM band

• Transmit power levels

• Range

1 100 mW (20 dBm) N/A 1 mW (0 dBm)

3 1 mW (0 dBm) N/A N/A

9

2.400-2.4835 GHz f_c=2402+k MHz, 0, ,78

21 3 4 5 6 87 9 10 11 12 1413 15 16 17 18 2019 21 22 23 24 25 26 2827 29 30 31 32 3433 35 36 37 38 39

0Index 2403 2404 2405 2406 2407 2408 2409 2410 2411 2412 2413 2414 2415 2416 2417 2418 2419 2420 2421 2422 2424 2425 2426 2427 2428 2429 2430 2431 2432 2433 2434 2435 2436 2437 2438 2439 2440 2441

2402 2423

2442 2463

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Radio

•

Use 2.4 GHz ISM band

•

Transmit power levels

•

Range

1 100 mW (20 dBm) N/A 1 mW (0 dBm)

3 1 mW (0 dBm) N/A N/A

9

2.400-2.4835 GHz f_c=2402+k MHz, 0, ,78

21 3 4 5 6 87 9 10 11 12 1413 15 16 17 18 2019 21 22 23 24 25 26 2827 29 30 31 32 3433 35 36 37 38 39

0Index 2403 2404 2405 2406 2407 2408 2409 2410 2411 2412 2413 2414 2415 2416 2417 2418 2419 2420 2421 2422 2424 2425 2426 2427 2428 2429 2430 2431 2432 2433 2434 2435 2436 2437 2438 2439 2440 2441

2402 2423

2442 2463

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PHY

□ Basic Rate (BR)

§ 1 Mb/s (Gaussian Frequency Shift Keying (GFSK)) modulation

□ Enhanced Data Rate (EDR)

§ 2 Mb/s (π/4-DQPSK), 3 Mb/s (8DPSK)

□ Time Division Duplex (TDD) & Frequency Hopping (FH)

§ Master and slave alternately transmit

§ 1600 hops/s FH (in connection state)

• f(k): channel index used in slot k

•

Basic Rate (BR)

• 1 Mb/s (Gaussian Frequency Shift Keying (GFSK)) modulation

•

Enhanced Data Rate (EDR)

• 2 Mb/s ( /4-DQPSK), 3 Mb/s (8DPSK)

•

Time Division Duplex (TDD) & Frequency Hopping (FH)

• Master and slave alternately transmit

• 1600 hops/s FH (in connection state)

• f(k): channel index used in slot k

PHY

¹⁰

Master

Slave

HDR (ACK) HDR (NACK) Access code Payload

M1

S1

M2

M2 S2

M2

f(k) f(k+1) f(k+2) M2

Master

Slave

625 us

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PHY

□ Single and multi-slot packets

§ 1-slot, 3-slot, 5-slot packets

• Master starts at even numbered time slots

• Slave starts at odd numbered time slots

□ Max throughput

§ Asymmetric link: 2178 kb/s

• 5-slot data packet with 3 Mb/s + 1-slot ACK

§ Symmetric link: 2 x 864 kb/s

• Bidirectional 3-slot packets with 3 Mb/s

PHY

•

Single and multi-slot packets

• 1-slot, 3-slot, 5-slot packets

• Master starts at even numbered time slots

• Slave starts at odd numbered time slots

•

Max throughput

• Asymmetric link: 2178 kb/s

• 5-slot data packet with 3 Mb/s + 1-slot ACK

• Symmetric link: 2 x 864 kb/s

• Bidirectional 3-slot packets with 3 Mb/s

f(k) f(k+1) f(k+2) f(k+3) f(k+4)

f(k) f(k+3) f(k+4)

f(k)

f(k+5)

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Adaptive Frequency Hopping (AFH)

□ Adaptive Frequency Hopping

§ Channel classification

• Used channel set (good channels), unused channel set (bad channels)

§ Hopping within used channel set

• To avoid static channel interference, e.g., Wi-Fi signal

Adaptive Frequency Hopping (AFH)

• Adaptive Frequency Hopping

• Channel classification

• Used channel set (good channels), unused channel set (bad channels)

• Hopping within used channel set

• To avoid static channel interference, e.g., Wi-Fi signal

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ADDRESS CLOCK

Hop Selection System

Is fk in the set of used channels

f_k _YES

NO

Re-mapping Function

Use fk for next slot

fk'

Use f_k' for next slot

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Link Types

□ Synchronous Connection-Oriented (SCO) link

§ Circuit switched link (data communication in reserved slots)

§ For delay sensitive information, e.g., voice transmission

□ Asynchronous Connectionless (ACL) link

§ Packet switched link

§ For data traffic

□ Extended Synchronous Connection-Oriented (eSCO) link

§ Circuit switched + packet switched link for retransmission

§ For delay sensitive information, e.g., voice transmission

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Link Types

□ Master has full control over ACL link

§ In slots not reserved for SCO (& eSCO), master polls a slave on a per-slot basis

§ Slave only allowed to transmit in slave-to-master slot after polled by the master

□ Retransmission is enabled in ACL by ARQ

Link Types

• Master has full control over ACL link

• In slots not reserved for SCO (& eSCO), master polls a slave on a per-slot basis

• Slave only allowed to transmit in slave-to-master slot after polled by the master

• Retransmission is enabled in ACL by ARQ

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Master

Slave 1

Slave 2

Slave 3

SCO SCO ACL ACL ACL ACL SCO

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Automatic Repeat Request (ARQ)

□ Applied to ACL & eSCO

§ Transmitted until acknowledgement is returned (ACL) or timeout occurs (eSCO)

□ ACK (ARQN=1)

§ Both HEC (Header Error Check) & CRC succeed

□ NAK (ARQN=0)

§ Only HEC succeeds, data can be piggybacked

Automatic Repeat Request (ARQ)

•

Applied to ACL & eSCO

• Transmitted until acknowledgement is returned (ACL) or timeout occurs (eSCO)

•

ACK (ARQN=1)

• Both HEC (Header Error Check) & CRC succeed

•

NAK (ARQN=0)

• Only HEC succeeds, data can be piggybacked

Master

Slave

HDR (ACK) HDR (NACK) Access code Payload

M1

S1

M2

M2 S2

M2

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State Diagram

¹⁶

Standby

Page (master)

Page scan (slave) Inquiry

(master)

Inquiry scan (slave)

Park Active

Sniff Hold

Connection Device Discovery

Connection Establishment

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Device Discovery & Connection Setup

□ Inquiry (to discover other devices)

§ To discover devices in inquiry scan

§ Searching 32 inquiry channels

□ Inquiry scan (to be discoverable)

§ Periodically listen for inquiry packets at a single inquiry channel

□ Page (Master)

§ Establish a piconet with a device in page scan

§ Searching 32 page channels

□ Page scan (Slave)

§ Periodically listen for page packets at a single page channel

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Low Power Mode

□ Hold mode

§ ACL link in hold mode for a hold duration (i.e., one time)

• Free slave to

ü Attend another piconet

ü Perform inquiry scan, page scan, page, or inquiry operations ü Move into low-power sleep

□ Sniff mode

§ Only communicate during (periodically allocated) sniff time slots

• Reduce duty cycle of a slave’s activity

□ Park state

§ Does not need participate piconet but still needs synchronization

• Wake up at regular intervals

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Bluetooth Low Energy – Protocol Stack

Protocol Stack

Host

Controller

*GAP: Generic Access Profile

*SMP: Security Manager Protocol

*HCI: Host Controller Interface Physical Layer

Link Layer

Logical Link Control and Application Protocol (L2CAP)

SMP Attribute Protocol (ATT) Generic Attribute Profile

(GATT) Non-core profiles GAP

HCI

20

Controls connections and advertising in BLE

Protocol multiplexer

Fragmentation and recombination

Defines a basic data structure and procedures

* GAP: Generic Access Profile

* SMP: Security Manager Protocol

* HCI: Host Controller Interface

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BLE communications

□ BLE communicates in two ways

§ 1) Broadcasting

BLE communications

•

BLE communicates in two ways

• 1) Broadcasting

• Sends non-connectable

advertising packets periodically

• BLE beacons

• Repeatedly scans the channel

• Receive any non-connectable advertising packets

Broadcaster Observer

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• Sends non-connectable

advertising packets periodically

• BLE beacons

• Repeatedly scans the channel

• Receive any non-connectable advertising packets

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BLE communications

□ BLE communicates in two ways

§ 2) Connections

• Scans connectable advertising packets

• Initiates a connection

• Manages the timing and initiates the periodical data exchange

• Sends connectable advertising packets periodically

• Accepts incoming connections

• Follows the central’s timing and exchange data

MWNL

BLE communications

•

BLE communicates in two ways

• 2) Connections

• Scans connectable advertising packets

• Initiates a connection

• Manages the timing and initiates the periodical data exchange

• Sends connectable advertising packets periodically

• Accepts incoming connections

• F he ce a g a d exchange data

Central (master) Peripheral (slave)

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Connection topology

□ From 4.1 specification, any restrictions on role combinations have been removed

§ A device can act as a central and a peripheral at the same time

§ A central can be connected to multiple peripherals

§ A peripheral can be connected to multiple centrals

• Previous versions limited the peripheral to a single central connection

Connection topology

• From 4.1 specification, any restrictions on role combinations have been removed

• A device can act as a central and a peripheral at the same time

• A central can be connected to multiple peripherals

• A peripheral can be connected to multiple centrals

• Previous versions limited the peripheral to a single central connection

BLE PERIPHERAL

BLE PERIPHERAL BLE PERIPHERAL

BROADCASTERBLE

BLE OBSERVER

BR/EDR SLAVE BR/EDR/LE

CENTRAL+OBSERVER +BR/EDR MASTER

PERIPHERAL+CENTRALBLE

Advertising and Scanning BLE Connection BR/EDR Connection

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PHY

□ Use 2.4 GHz ISM band

§ 40 channels with 2 MHz bandwidth

§ 37 data channels for connection (ch. 0–36)

§ 3 advertising channels (ch. 37, 38, and 39)

• To set up connections and send broadcast data

PHY

• 37 data channels for connection (ch. 0 36)

• 3 advertising channels (ch. 37, 38, and 39)

• To set up connections and send broadcast data

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Regulatory Range RF Channels 2.400-2.4835 GHz f_c=2402+2k MHz,

0, ,39

MWNL

PHY

• 37 data channels for connection (ch. 0 36)

• 3 advertising channels (ch. 37, 38, and 39)

• To set up connections and send broadcast data

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2.400-2.4835 GHz f_c=2402+2k MHz, 0, ,39

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PHY

□ Data rate

§ 1 Mb/s (Gaussian Frequency Shift Keying (GFSK)) modulation

□ Transmit power levels

§ 0.01–10 mW (-20–10 dBm)

□ Frequency hopping spread spectrum (FHSS)

§ Basic algorithm

§ Adaptive frequency hopping (hopping within used channel set)

PHY

• Data rate

• 1 Mb/s (Gaussian Frequency Shift Keying (GFSK)) modulation

• Transmit power levels

• 0.01 10 mW (-20 10 dBm)

• Frequency hopping spread spectrum (FHSS)

• Basic algorithm

• Adaptive frequency hopping (hopping within used channel set)

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Last channel (f_k-1)

Hop increment

Mod 37 ^{Is f}^k in the set of used channels

f_k _YES

NO

Re-mapping Function

Use f_k for next slot

f_k'

Use fk' for next slot

+

Basic algorithm fk

Used channel set

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WIRELESS NETWORKING, 430.752B, 2020 SPRING WIRELESS NETWORKING, 430.752B, 2020 SPRING

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Link Layer State Diagram

Scanner Beacon

Master Slave

Link Layer State Diagram

Standby Standby

Connection

Initiating Advertising

Scanning

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Advertising/Scanning State

□ Advertising channel selection

§ Advertising event uses three predefined advertising channels

□ Advertiser and scanner are not synchronized

* Scanning interval = 50 ms

* Scan window = 25 ms

Advertising/Scanning State

• Advertising channel selection

• Advertising event uses three predefined advertising channels

• Advertiser and scanner are not synchronized

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Advertiser Scanner

0 ms 20 ms 40 ms 60 ms 80 ms 100 ms 120 ms 140 ms

• Scanning interval = 50 ms

• Scan window = 25 ms

Scanning on channel 37

0 ms 25 ms

50 ms 75 ms

100 ms 125 ms

• Advertising on 37 ( ), 38 ( ), and 39 ( )

• Advertising interval = 20 ms

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Connection State

□ Connection interval: an interval between anchor points (i.e., starts of connection events)

§ Connection interval has a value of a multiple of 1.25 ms (min. 7.5 ms, max. 4 s)

□ Frequency channel changes every connection interval

§ A single data channel is used for all packets in a connection event

§ Cf. Classic Bluetooth with hopping interval of 625 us

Connection State

• Connection interval: an interval between anchor points (i.e., starts of connection events)

• Connection interval has a value of a multiple of 1.25 ms (min. 7.5 ms, max. 4 s)

• Frequency channel changes every connection interval

• A single data channel is used for all packets in a connection event Cf. Classic Bluetooth with hopping interval of 625 us

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TX R

Master X Radio idle

Connection interval

TX R

X T

X R

X T

X R

X Connection interval RX T

Slave X Radio idle _R

X T

X R

X T

X R

X T

X

Connection event Connection event

Inter frame space = 150 us

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Connection Establishment

Bluetooth Low Energy Classic Bluetooth

Connection Establishment

• Bluetooth Low Energy Classic Bluetooth

Inquiry Scan

PageScan

Connection

Slave

Inquiry

Page

Connection

Master

Inquiry Inquiry response

Page Page response Connection request

Advertising Advertising

Connection

Slave

Initiating

Connection

Master

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Connection Establishment

• Bluetooth Low Energy Classic Bluetooth

Inquiry Scan

PageScan

Connection

Slave

Inquiry

Page

Connection

Master

Inquiry Inquiry response

Page Page response Connection request

Advertising Advertising

Connection

Slave

Initiating

Connection

Master

29

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Classic Bluetooth vs. BLE

□ Latency: a minimum time for a packet transaction between master and slave

□ Low power consumption of BLE: low Tx power, simple RF module design due to allowance of large modulation index (i.e., wider RF spectrum)

MWNL

Classic Bluetooth vs. BLE

Classic Low Energy

Data Rate 1, 2, 3 Mbps 1 Mbps

Modulation GFSK, DQPSK, 8DPSK GFSK

# channels 79 40

Frequency hopping Fast Slow

Max output power 100 mW 10 mW

Latency 100 ms 3 ms

Range ~100 m ~50 m

Voice Capable Not capable

Power consumption 1 as the reference 0.01 to 0.5

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• Latency: a minimum time for a packet transaction between master and slave

• Low power consumption of BLE: low Tx power, simple RF module design due to allowance of large modulation index (i.e., wider RF spectrum)

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iBeacon

□ Apple’s implementation of BLE wireless technology

§ Providing location-based information and services

□ iBeacon devices

§ iBeacon is a broadcast-only device that uses BLE advertising

§ iBeacon app compares the measure RSSI to the expected value of the RSSI in the beacon

□ iBeacon products

§ Estimote: A development kit

§ LassoTag: Alert system (valuables out of range)

§ Hanabee: check-in beacon for retail stores

iBeacon

• A e e e a BLE e e ec

• Providing location-based information and services

• iBeacon devices

• iBeacon is a broadcast-only device that uses BLE advertising

• iBeacon app compares the measure RSSI to the expected value of the RSSI in the beacon

• iBeacon products

• Estimote: A development kit

• LassoTag: Alert system (valuables out of range)

• Hanabee: check-in beacon for retail stores

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Using Beacons

□ An example retail implementation

§ Using iBeacon devices created by Estimote

§ Customers with store’s mobile application

• Mobile app receives beacon signals

MWNL

Using Beacons

•

An example retail implementation

• Using iBeacon devices created by Estimote

• C e e b e a ca

• Mobile app receives beacon signals

We e g a special offer for you today Shoes are on sale today !

Thank you for your purchase !

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Using Beacons

• An example retail implementation

• Using iBeacon devices created by Estimote

• C e e b e a ca

• Mobile app receives beacon signals

We e g a special offer for you today Shoes are on sale today !

Thank you for your purchase !

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Coexistence with Wi-Fi

□ IEEE 802.15.2 (2003)

§ Recommended practice for coexistence between classic

Bluetooth (IEEE 802.15.1-2002) and Wi-Fi (IEEE 802.11b-1999)

□ Collaborative coexistence solutions (collocated)

§ Packet traffic arbitration (PTA)

§ Alternating wireless medium access

□ Non-collaborative coexistence solutions (non-collocated)

§ Adaptive frequency-hopping

§ Adaptive packet selection

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Packet Traffic Arbitration (PTA)

□ PTA control entity approves Wi-Fi & BT transmission per packet

§ Predict collision based on Wi-Fi frame duration & BT time slot

§ Resolve collision by prioritized transmissions

• E.g., SCO > Wi-Fi > ACL

Packet Traffic Arbitration (PTA)

•

PTA control entity approves Wi-Fi & BT transmission per packet

• Predict collision based on Wi-Fi frame duration & BT time slot

• Resolve collision by prioritized transmissions

• E.g., SCO > Wi-Fi > ACL

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Broadcom BT & Wi-Fi Coexistence

□ BCM4325 solution

§ Shared low noise amp, power amp, and

antenna

§ PTA

§ Preemptive coexistence

• CTS-to-Self medium reservation

• Wi-Fi Power Save Mode with PTA

Broadcom BT & Wi-Fi Coexistence

• BCM4325 solution

• Shared low noise amp, power amp, and

antenna

• PTA

• Preemptive coexistence

• CTS-to-Self medium reservation

• Wi-Fi Power Save Mode with PTA

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Summary

□ Classic Bluetooth

§ Low rate short range connection

□ BLE

§ Extremely low rate with extremely low power connection

Summary

• Low rate short range connection

• BLE

• Extremely low rate with extremely low power connection

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Source: K. Torvmark, T Flavers B : W O C , Ma 2014, W Pa .

Source: K. Torvmark, “Three Flavers of Bluetooth: Which One to Choose,” March 2014, White Paper.

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References

□ Bluetooth specification version 4.2, Bluetooth SIG, 2014

□ IEEE 802.15.2-2003, Part 15.2: Coexistence of Wireless Personal Area

Networks with Other Wireless Devices Operating in Unlicensed Frequency Bands, IEEE std., June 2011

□ Broadcom, "BCM4325 Bluetooth and WLAN Coexistence," 2008, White Paper

□ http://chapters.comsoc.org/vancouver/BTLER3.pdf

□ https://developer.bluetooth.org/TechnologyOverview/Pages/BLE.aspx

□ http://estimote.com/