Paper Presentation Wi-Fi (802.11b) and Bluetooth: Enabling Coexistence Jim Lansford, Ron Nevo, and Brett Monello CSC8900 Presented 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 b receiver senses both Bluetooth and b 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 b and Bluetooth signals at the same time. The inference occurs when the b 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!