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“Performance Comparison of the Radio Link Protocols of IEEE 802.11a and HIPERLAN/2” – Hui Li, et al.

“Performance Comparison of the Radio Link Protocols of IEEE 802.11a and HIPERLAN/2” – Hui Li, et al. Presentation byTom Bruns. Outline. IEEE 802.11 standard Physical Layers MAC features HIPERLAN/2 standard MAC features Comparison. What is IEEE 802.11?.

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“Performance Comparison of the Radio Link Protocols of IEEE 802.11a and HIPERLAN/2” – Hui Li, et al.

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  1. “Performance Comparison of the Radio Link Protocols of IEEE 802.11a and HIPERLAN/2” – Hui Li, et al. Presentation byTom Bruns

  2. Outline • IEEE 802.11 standard • Physical Layers • MAC features • HIPERLAN/2 standard • MAC features • Comparison

  3. What is IEEE 802.11? • Standard for wireless local area networks (wireless LANs) developed in 1990 by IEEE • Intended for home or office use (primarily indoor) • 802.11 standard describes the MAC layer, while other substandards (802.11a, 802.11b) describe the physical layer • Wireless version of the Ethernet (802.3) standard

  4. Network Setup • Basic Network Setup is Cellular • Mobile Terminals (MT) connect with Access Points (AP) • Standard also supports ad-hoc networking where MT’s talk directly to MT’s

  5. IEEE 802.11 Physical Layers

  6. Media Access Control- Ethernet • CSMA/CD (Carrier Sense Multiple Access with Collision Detection) • If media is sensed idle, transmit • If media is sensed busy, wait until idle and then transmit immediately • Collisions can occur if more than one user transmits at the same time • If a collision is detected, stop transmitting. • Reschedule transmission according to exponential backoff

  7. Media Access Control (802.11) • Would like to use CSMA • Nice for bursty traffic • Make for seamless replacement of wired LANs with wireless LANS • Use CSMA, but can’t use CD • PT/PR ratio is too high • Don’t want to waste energy on mobiles • Use Collision Avoidance instead • Don’t always start transmitting immediately after someone else

  8. CSMA/CA Details • SIFS (Short Interframe Space) • DIFS (Distributed Interframe Space) • Scenario: • B and C want to transmit, but A currently has control of medium • B randomly selects 7 slots of backoff, C selects 4 slots • C transmits first, then B

  9. What is HIPERLAN/2? • European standard developed by ETSI/BRAN (European Telecommunications Standards Institute/Broadband Radio Access Networks) • Physical Layer is very similar to 802.11a (OFDM operating in the 5 GHz spectrum) • Standard based on wireless ATM (Asynchronous Transfer Mode)

  10. HIPERLAN/2 MAC BCH – Miscellaneous header FCH – Details how the DL and UL phases will be allocated ACH – Feedback on which resource requests were received RCH – Random access resource request

  11. Performance Comparison

  12. Conclusions • IEEE 802.11 is a widely accepted standard in the United States for wireless LANs • Primarily a “cellular” random access scheme with provisions for ad hoc networking and contention free access • 802.11b products are available now, but better to wait for 802.11a products later this year • HIPERLAN/2 is being pushed in Europe • Wireless ATM solution for real-time traffic • Standard reflects the network topology • There is an effort to agree on one world-wide standard, keep your fingers crossed

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