BlueStar:EnablingEfficientIntegrationbetweenBluetoothWPANsandIEEE802 BlueStar:EnablingEfficientIntegrationbetweenBluetoothWPANsandIEEE802.11WLANs 學號：693430007 蘇彥文

Abstract 本論文提出一個架構- BlueStar，有效利用藍芽與無線網路，來提供藍芽裝置連結上網路 由於藍芽與WLAN同樣運作在 ISM band，同時使用會發生互相干擾的情形，本文亦在BlueStar架構下提出兩種解決的機制

Outline Introduction Bluetooth overview BlueStar architecture Simulation Conclusion 心得

01.Introduction Bluetooth vs. WLAN Why propose BlueStar Challenge of BlueStar

Bluetooth vs. WLAN operating in the 2.4 GHz ISM (industrial-scientific-medical) frequency band should be able to coexist as well as cooperate with each other access each other’s resources complementary to each other Bluetooth devices obtain information through the WLAN, and ultimately the Internet

Why propose BlueStar WPAN Device use Bluetooth (like cell phone ) WLAN infrastructure is readily available complementary to Bluetooth and WLAN BlueStar whereby Bluetooth wireless gateways (BWG) empowering low-cost, short-range devices to access the global Internet use of WLAN-based high-powered transmitters

Challenge of BlueStar (1/2) Both Bluetooth and WLAN employ the same 2.4 GHz ISM band

Challenge of BlueStar (2/2) To provide effective coexistence Adaptive frequency hopping (AFH) mitigate persistent interference by scanning the channels Bluetooth carrier sense (BCS) takes care of the intermittent interference by mandating that before any Bluetooth packet transmission Bluetooth and WLAN on a signal device

02.Bluetooth overview Base specification Network Topology Protocol Stack Two distinct types of links

Base specification (1/2) Operate at 2.402GHz~ 2.438GHz unlicensed ISM band Transmission range : 10~100 meters Addressing 48-bit Bluetooth Device Address 3-bit Active Member Address 8-bit Active Member Address

Base specification (2/2) 79 RF channels of 1 MHz width Data rate is 1 Mbit/s Time Division Multiplexing ：625 µs slot Maximum frequency hopping rate of 1600 hops/s

Network Topology (1/2) Piconet Scatternet Master can connect to 7 slaves per piconet 圖a、b Scatternet Interconnecting multiple piconets to form a large network 圖c

Network Topology (2/2)

Protocol Stack

Two distinct types of links ACL (asynchronous connectionless) support of data applications allows the use of 1-, 3-, and 5-slot data packets SCO (synchronous connection-oriented) support of voice applications

03.BlueStar architecture BlueStar proposed architecture Protocol stack Bluetooth carrier sense (BCS) Bluetooth adaptive frequency hopping (AFH)

BlueStar proposed architecture

Protocol stack (1/2)

Protocol stack (2/2) carry IP packets over Bluetooth to outside world is managed by the BWG BlueStar reuses existing protocols by Bluetooth network encapsulation protocol (BNEP) BWG look like a layer

Bluetooth carrier sense (BCS) Introduction of BCS Packet collision

Introduction of BCS (1/3) Bluetooth does not have any provision for carrier sensing ! Contrary to IEEE 802.11, Bluetooth carrier sensing would be much simpler by MAC protocol Should improvements in the Bluetooth chip design

Introduction of BCS (2/3) sense window of size WBCS If the next channel is busy or becomes busy during the sense window the sender will withholds any attempt for packet transmission skips the channel waits for the next chance

Introduction of BCS (3/3)

Packet collision (1/5) packet transmission in different piconets are transmitted with period Tp Tp = 2 · slotsize Bluetooth slotsize is equal to 625 µsec

Packet collision (2/5) probability of packet collision between piconets i and j , pc(i, j ) ： packet collision probability with a packet originated at the i th piconet： packet withdrawal probability of Bluetooth with BCS ：

Packet collision (3/5) the aggregate throughput of N piconets relative to a Bluetooth packet X ： acknowledgements do not carry payload information ACKinbits(X) equal to 126 bits the aggregate throughput for Bluetooth with BCS becomes ：

Packet collision (4/5) packet collision and withdrawal probabilities for all three Bluetooth slot length packets, and WBCS = 50 µs

Packet collision (5/5) Bluetooth with BCS practically doubles the available throughput for most packet types

Bluetooth adaptive frequency hopping (AFH) Why need AFH ? Implementation of AFH

Why need AFH ? some packet collisions are still not detected by BCS

Implementation of AFH Bluetooth devices scan every T SCAN seconds for each of the 79 channels used by Blue-tooth and collect PER statistics All devices within a piconet carry out this procedure and when the piconet master request this, the slaves send their measured “good” and “bad” channel marks Master collected and conducts a referendum process based on information of all device

04.Simulation How to simulation Bluetooth-only simulation Combined Bluetooth and WLAN simulation

How to simulation Use tools transmission range to be 10 m network simulator (ns-2) BlueHoc open-source Bluetooth simulator provided by IBM transmission range to be 10 m interfering range to be 22 m

Bluetooth-only simulation (1/4) Bluetooth-only network topology model

Bluetooth-only simulation (2/4) total area of 500 m × 500 m total of 200 piconets MTU of 512 bytes WBCS = 50 µs Result Only Bluetooth 8 Mbps when there are 60 piconets in the network Bluetooth with BCS 15.5 Mbps for a total of 90 piconets

Bluetooth-only simulation (3/4)

Bluetooth-only simulation (4/4)

Combined Bluetooth and WLAN simulation (1/3) Total area of 500 m × 500 m Increase the number of piconets in steps of 10 till 200 piconets

Combined Bluetooth and WLAN simulation (2/3) Scenario A: The flow of data packets is from the WLAN AP to the BWG, reflecting an application where Bluetooth devices downloading contents from the WAN Scenario B: This scenario is the opposite of the previous one with the Bluetooth devices uploading information to the WAN, i.e., the flow of data packets is from the BWG to the WLAN AP Scenario C: A BWG might find itself in a situation where it simultaneously receives data packets from both the WLAN AP and the Bluetooth devices in order to synchronize information in the BWG Scenario D: This scenario models the opposite situation as described in scenario C. In other words, it is the case where the BWG simultaneously transmits data packets to both the Bluetooth devices and the WLAN AP

Combined Bluetooth and WLAN simulation (3/3)

Construction of BWGs

05. Conclusion BlueStar Future work Solve the problem that Bluetooth-enabled devices can access to global networks employs a combination of AFH and BCS to efficiently provide advanced wide area services to Blue-tooth devices Future work define a more elaborate capacity allocation algorithm

06.心得 研究課題具備創意與實用 架構設計良好 論文闡述明確完整，值得學習 未來可用於家庭無線閘道器中 尚未解決的問題： Fair transmission

Q & A

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