Paper Presentation

Wi-Fi (802.11b) and Bluetooth:

Enabling CoexistenceJim Lansford, Ron Nevo, and Brett Monello

CSC8900Presented by: Tu Tran

Presentation Outline

Introduction Overview of Wi-Fi Bluetooth Technologies Issues of coexistence Experimental Results Solutions to coexistence issues Questions or Comments

Introduction

Two prominent wireless technologies: WPAN: Wireless Personal Area Networking

supports a short range (10m), implemented in Bluetooth applications such as wireless headsets, PDAs, keyboards,

mice, etc.

WLAN: Wireless Local Area Networking supports wider range (100m), designed in Wi-Fi (802.11b) applications such as wireless routers, wireless cards,

wireless printers, etc.

Introduction (cont’d)

WPAN & WLAN are complementary Collocation of Wi-Fi and Bluetooth become

increasingly significant. Coexistence: “wireless systems can be

collocated without significantly impacting the performance of either”

Overview of Bluetooth and Wi-Fi Characteristics Bluetooth

a cable replacement radio frequency technology: low cost, modest transfer rate, and short range.

supports piconets of up to eight active devices with three synchronous connection-oriented links / asynchronous connectionless.

piconet: an ad-hoc computer network PHY uses frequency-hop-ping spread spectrum

(FHSS) at 1600hops/s data transfer rate 11Mb/s or higher

Overview of Bluetooth and Wi-Fi Characteristics (cont’d) Wi-Fi (802.11b)

supports multipoint networking data types as broadcast, multicast, unicast MAC address built-in, allowing unlimited

number of devices to be active PHY uses direct-sequence spread spectrum

Both Wi-Fi and Bluetooth share the same frequency band, 2.4Ghz

Issues of Coexistence

Both Wi-Fi & Bluetooth operate at the same time within the same frequency band, they will interfere with each other, creating in-band colored noise.

The inference is called noise Noise: in-band noise & out-of-band noise

in-band noise: the transmitter uses the undesired energy in frequencies to transmit the desired signal.

out-band noise: the transmitter does not use.

Issues of Coexistence (cont’d)

white noise: interference from multiple sources without their coordination.

colored noise: interference transmitted by two intentional radiators, behave in time & frequency

Occurrence of the interference: An 802.11b receiver senses both Bluetooth and

802.11b signals at the same time. The effect happens when Bluetooth signal is within the 22-MHz wide pass band of the receiver.

Issues of Coexistence (cont’d)

A Bluetooth receiver senses both 802.11b and Bluetooth signals at the same time. The inference occurs when the 802.11b signal is within the Bluetooth receiver.

The interference reduces the performance of data transfer rate and packet lost.

Experimental Results

Recommended Solutions

Usage and Practices: No coexistence

Technical Approaches: General System Approach: lowering the power levels in the

collocated Bluetooth node would lessen the interference impact on Wi-Fi.

Driver Layer: using software layers above the MAC to switch the two technologies

MAC layer: listen-before-talk functions Bluetooth is difficult to detect Wi-Fi operations.

Physical Layer: via design decisions Alternating Frequency bands: separating two different frequency.

Questions or Comments?

Thank you!