Performance Evaluation of Multiple IEEE b WLAN Stations in the Presence of Bluetooth Radio

Overview Evaluation of the performance of IEEE b WLANs with Bluetooth devices. Evaluation of multiple WLANs and one Access Point in the presence of Bluetooth. Competition between Bluetooth and WLAN stations can cause degradation of performance.

Modeling of the IEEE b MAC Key factors that will impact system performance Presence of hidden stations. Use of carrier sensing. Decentralized nature of multiple access methods.

Modeling of the IEEE b MAC Assumptions Ignore effects of framer error due to bit errors from channel noise There is limited station mobility

Successful Transmissions No station in the Rx’s capture area that is not hidden from the Rx, transmits in the time interval (t - β, t + β)

Successful Transmission No station in the Tx’s capture area that is not hidden from the Tx, receives successfully a data frame whose transmission was initiated in the time interval (t - β, t + β)

Successful Transmission No station in Hij(d’ij) transmits during the interval (t, t +l)

Successful Transmission No station in Hji(d’ij) transmits in the interval (t + l + DIFS, t + l + max{DIFS, SIFS + lack}).

Renews Intervals [ T s ] The average time the channel is sensed busy because of successful transmission. Basic Access Method [bs] With RTS/CTS [rc]

Time During Collision [ T c ] The average time the channel is sensed busy by each station during collision. Basic Access Method [bs] With RTS/CTS [rc]

Throughput of

Interference Modeling Propagation Model 2 Parts  Line of Sight (LOS) for the first 8 meters  Path Loss > 8 meters

Higher Packet Reception w/ Time Coincidence By using multiple time slot packets in Bluetooth, you  Reduce the Bluetooth hop rate  Increase throughput. = Reduced transmission time and results in longer gaps in Bluetooth interference, which increases the successful reception of WLAN packets

Higher Packet Reception w/ Frequency Coincidence  can provide reliable service in the presence of narrow-band interferer such as Bluetooth transmitters.  This will work if the Signal-to-Interference (SIR) is 10 greater than 10 dB.

Collisions Probability of collision with “n” slot overlap The overall probability of collision Probability of interference of m Piconets

Important Points With a light and heavy Bluetooth user scenario, the throughput of multiple WLAN STAs systems will degrade no matter what the data rate. Hidden Stations, Carrier Sensing, & a Decentralized nature of multiple access methods impact a systems performance. As long as the IEEE (b) receiver gets a desired signal that is 10dB stronger than the in-channel interference tone, the activity of a BT device does not harm. For a Bluetooth transmission to disrupt an b packet, there must be an overlap in time and in frequency.

Appendix Ai(d): a set of stations in a circular area of radius d around station i. Xi: a location of station i Dij: a distance between station i and station j α: capture parameter, α ≥ 1 d’ij: αdij Hj(d): a set of stations that are hidden from station j and are in a circle of radius d around j Hij(d): a set of stations that are hidden from station i but not from station j in a circle of radius d around station j β: propagation delay including carrier sensing delay (in wireless networks the propagation delay is dominated by the carrier sensing delay given the small diameter of BSSs, i.e., less than 100m) l : the length of a pay load – this does not include PHY and MAC header. l “type” is the length of a “type” frame.