Mechanisms for Quick Bluetooth Device Discovery Jehn-Ruey Jiang, Bing-Rong Lin, and Yu-Chee Tseng Presented by Jehn-Ruey Jiang

Outline Overview of Bluetooth Bluetooth Device Discovery Problems and Existent Solutions Analysis of Frequency-Matching Delay Proposed Mechanisms and Their Analyses Conclusion

Outline Overview of Bluetooth Bluetooth Device Discovery Problems and Existent Solutions Analysis of Frequency-Matching Delay Proposed Mechanisms and Their Analyses Conclusion

General characteristics Low-cost

General characteristics Low-cost Low-power

General characteristics Low-cost Low-power Short-range

General characteristics Low-cost Low-power Short-range Small-size

General characteristics Low-cost Low-power Short-range Small-size Robust wireless technology RF Baseband Link Manager Audio L2CAP Control Data RFCOMM SDP IP Applications

Standard for Data and Voice

Cable Replacement

Automatic Synchronization In the Office At Home

Frequency Hop Spread-Spectrum Pseudo random hopping sequence through the entire 79 RF frequencies Nominal hop rate of 1600 hops per second Channel Spacing is 1 MHz 80 MHz in unlicenced ISM band at 2.4 GHz

time Freq. High Capacity and Robustness

Outline Overview of Bluetooth Bluetooth Device Discovery Problems and Existent Solutions Analysis of Frequency-Matching Delay Proposed Mechanisms and Their Analyses Conclusion

INQUIRYPAGECONNECTION Connection Establishment

A Purpose: Looking for Unknown Devices Responses include: Device Address Class of Device Inquiry

A D C B master A slave C slave D Paging Purpose: Establish Connection Done for each device independently Paging device becomes master slave B

Inquiry Timing … potential master (inquiry) T inquiry T w inquiry BA … ABABBAABAB 256 times ……… F(16)F(15 ) S(16)S(15) … F(2)F(1)S(2)S(1) 1 slot(625  s) T train (16 slots=10ms) S(i) stands for sending ID packet in inquiry hopping frequency channel i, i= F(i) stands for listening to FHS packet in inquiry hopping frequency channel i, i=1..32.

Inquiry Scan Timing potential slave (inquiry scan) T inquiryscan … T w inquiryscan (16 slots=10ms) R(1) T w inquiryscan (16 slots=10ms) R(2) R(i) stands for listening to ID packet in inquiry hopping frequency channel i, i=1..32.

Frequency-Matching ID packet S(i+1) 10ms AAA … BBB … AAA … BBB … T w inquiry (=2.56s) potential master (inquiry) ID packet S(i+1) R(i+1) R(i) potential slave (inquiry scan) T inquiry scan random backoff delay(0~1023 slots) FHS packet S(i+1) Frequency-Matching

Timing Parameters ParameterDescriptionAdopted value T inquiry inquiry interval60s T w inquiry inquiry window length10.24s T inquiryscan inquiry scan interval1.28s T w inquiryscan inquiry scan window length10ms T train length of a train10ms N inquiry train repetition number  256

Outline Overview of Bluetooth Bluetooth Device Discovery Problems and Existent Solutions Analysis of Frequency-Matching Delay Proposed Mechanisms and Their Analyses Conclusion

Device Discovery Dealy Time Delay is too long Inquiry delay: 10.24s or longer (frequency-matching delay is the major component) Paging delay: 7.68s or longer

Existent Solutions #1 To decrease or eliminate the random backoff To use one single 32-frequency train rather than two 16-frequency trains The combination of the two solutions

Existent Solutions #2 Devices are assumed to alternate between “ potential master ” and “ potential slave ”

Existent Solutions #3 Using auxiliary devices: IrDA FRID

Existent Solutions #4 Exchanging neighbor knowledge among cooperative devices

Existent Solutions #5 Bluetooth V1.2: Interlaced Inquiry scan hopping sequence f1, f2, f3, f4, …  f1, f18, f3, f20, …

Problems Except BT V1.2 Not Fully compatible Extra Overhead

Outline Overview of Bluetooth Bluetooth Device Discovery Problems and Existent Solutions Analysis of Frequency-Matching Delay Proposed Mechanisms and Their Analyses Conclusion

Analysis for Bluetooth V1.1 Suppose there is already a device turned on to be a master performing inquirying. And a device is turned on at a later time (t) to be a slave performing inquiry scanning Frequency-matching delay D is measured by the elapsing time from t to the time when the slave receives the ID packet from the master

Analysis for Bluetooth V1.1 Time axis is divided into inquiry window and non-inquiry window … potential master (inquiry) T inquiry T w inquiry inquiry window non-inquiry window X Y

Analysis for Bluetooth V1.1 There are 8 cases for the slave to start its inquiry scan in the inquiry window         1 st 2 nd 3 rd 4 th 5 th 6 th 7 th 8 th A… …AA… …AB… …BB… …BA… …AA… …AB… …BB… …B

Delay for the 1 st case Possibility 1: B A (with prob. u) Possibility 2: B B A A A (with prob. v) Possibility 3: B B B (with prob. w) 1/16 14/16 *The 3 rd case is the same as the 1 st case.

Delay for the 2 nd case 1/16 15/16 Possibility 1: B A A A (with prob. p) Possibility 2: B B (with prob. q) *The 4 th case is the same as the 2 nd case.

Delay for the 4 th case Possibility 1: B A (with prob. u) Possibility 2: B B A A A (with prob. v) Possibility 3: B B B (with prob. w) 1/16 14/16 *wait for the next inquiry window

Delays for the 5 th, the 6 th and the 7 th cases

Calculation of X and Y To sum up the products of probabilities and expected delays for all the 8 cases to get the value of X. We can calculate Y by the equation for the 1 st case. D=22.98 when T inquiry =60 D=1.075 when T inquiry =10.24

Analysis for Bluetooth V1.2 Similar to that of Bluetooth V1.1 D=21.95 when T inquiry =60 D=0.919 when T inquiry =10.24

Outline Overview of Bluetooth Bluetooth Device Discovery Problems and Existent Solutions Analysis of Frequency-Matching Delay Proposed Mechanisms and Their Analyses Conclusion

Goals Fully compatible with Bluetooth V1.1 and Bluetooth V1.2 Keep the same ratio of performing inquiry and inquiry scan

Proposed Mechanisms Half Inquiry (HI) Dual Inquiry Scan (DIS) Coupling Mechanism

Half Inquiry (HI) … original inquiry T inquiry T w inquiry BA … ABABBAABAB 256 times ……… … half inquiry T inquiry T w inquiry A … ABABB 256 times …

Dual Inquiry Scan (DIS) original inquiry scan T inquiryscan … T w inquiryscan (16 slots=10ms) R(1) T w inquiryscan (16 slots=10ms) R(2) dual inquiry scan T w inquiryscan (16 slots=10ms) R(1) T w inquiryscan (16 slots=10ms) R(2) T inquiryscan …

Analyses for Half Inquiry The equation of D is the same as that of Bluetooth V1.1. There are only four cases to calculate X, which are similar to the 5 th, the 6 th, the 7 th, and the 8 th cases for Bluetooth V1.1. D=13.89 when T inquiry =30 D=1.14 when T inquiry =5.12

Analyses for Dual Inquiry Scan The equation of D is the same as that of Bluetooth V1.1 except that Y is replaced with X. X  because there is T train (=0.01) delay of prob. ½. D=21.71 when T inquiry =60 D=0.005 when T inquiry =10.24

Analyses for the Coupling Method The equation of D is the same as that of Bluetooth V1.1 except that Y is replaced with X. X  because there is T train (=0.01) delay of prob. ½. D=11.38 when T inquiry =30 D=0.005 when T inquiry =5.12

Comparison

Outline Overview of Bluetooth Bluetooth Device Discovery Problems and Existent Solutions Analysis of Frequency-Matching Delay Proposed Mechanisms and Their Analyses Conclusion

Propose a model for analyzing BT V1.1 and V1.2 device discovery delay Propose mechanisms to speed up Bluetooth Device Discovery: Half Inquiry Dual Inquiry Scan Coupling Method The mechanisms are fully compatible with BT V1.1 and BT V1.2 The mechanisms keep the same ratio of performing inquiry and inquiry scan

Thanks