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Amendment Proposal for TV White Spaces Operation

Amendment Proposal for TV White Spaces Operation. Date: February 28, 20 10. Authors:. Introduction. The technical issues raised in this proposal Spectral Efficiency Issue based on IEEE 802.11n Bandwidth Adaptation Issue Scanning Issue. Slide 2. Technical Issues. Available Spectrum

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Amendment Proposal for TV White Spaces Operation

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  1. Amendment Proposal for TV White Spaces Operation Date:February 28, 2010 Authors:

  2. Introduction The technical issues raised in this proposal Spectral Efficiency Issue based on IEEE 802.11n Bandwidth Adaptation Issue Scanning Issue Slide 2

  3. Technical Issues Available Spectrum VHF (54~72, 76~88, 174~216 MHz), UHF (470~698Mhz) Advantages of TVWS Smaller propagation loss than 2.4GHz or 5GHz Robust against diffraction loss Lower Doppler  Extended Coverage, Low Power Consumption, Robust Link Quality Application Scene Home multimedia streaming Seamless WLAN Slide 3

  4. Technology Throughput enhancement Required for home multimedia streaming Spectral Efficiency Bandwidth Adaptation (e.g., 5MHz/10MHz/20MHz) Low power consumption Required for seamless WLAN Scanning Submission Slide 4

  5. Spectral Efficiency IEEE 802.11n-based standard In order to improve spectral efficiency Utilizing 802.11n features A-MPDU that leads to reduce MAC overhead should be applied, especially necessary for 5MHz channel bandwidth in TVWS FEC coding can be employed Number of utilizing tones should be 56 (52 data tones and 4 pilot tones) Submission Slide 5

  6. Bandwidth Adaptation 802.11af should support 5MHz/10MHz/20MHz Channelization Center frequency at the center of 6MHz TVWS channel Optimal for 5MHz channel bandwidth But, for 10MHz/20MHz, available number of channels should be 3/5, respectively * Reference: R. Chandra, R. Mahajan, T. Moscibroda, R. Raghavendra, and P. Bahl, “A Case for Adapting Channel Width in Wireless Networks” ACM SIGCOMM 2008. Submission Slide 6

  7. Bandwidth Adaptation • Channelization of TVWS spectrum • Center frequency at the boundary of 6MHz TVWS channel • Not appropriate for 5MHz channel bandwidth • However, 2/4 TVWS channels are enough for 10MHz/20MHz operation, respectively • Therefore, AP should choose the carrier frequency and the channel bandwidth according to the available spectrum • STA should scan AP with the frequency raster of 3 MHz Submission Slide 7

  8. Bandwidth Adaptation STA should dynamically change the channel bandwidth according to the service coverage and the supported channels STA should also protect incumbent user signal by bandwidth adaptation In order to support the bandwidth adaptation, the protection mechanism is required Submission Slide 8

  9. Scanning Number of scanning channels in TVWS The candidate channels are almost 30 (=180MHz/6MHz) when one channel bandwidth is 5 MHz Considering 10MHz/20MHz channel bandwidth, channels that STA should scan are tripled (around 90). With 3MHz frequency raster for channelization, scanning channel list is doubled (around 180). Massive initial access delay of Passive Scanning Scanning time might be around 18,000ms i.e., 3 (Number of candidate bandwidth) x 60 (Number of candidate channels with 3MHz frequency raster) x 100ms (Beacon Interval) Power consumption Power consumption depends on the number of scanning channels Submission Slide 9

  10. Scanning • White space map within Beacon Frame • White space map is provided by beacon frame • White Space Map specifies the channel list unoccupied by the primary users • Once STA listens to beacon frame, STA doesn’t need to scan channels occupied by incumbent users • By skipping the channels occupied by incumbent users , initial access delay and power consumption problem can be resolved a little. • However, enhanced scanning mechanism is still desired such as active scanning • White space map within Probe Response • AP provides White Space Map information to STA for reducing the scanning overhead • White Space Map is transmitted within Probe Response Frame • However, probe request transmission power is constrained to 50mW Submission Slide 10

  11. Scanning Limitation of active scanning Active scan does not support complete scanning because EIRP is constrained to 50mW before associating with AP Advanced scanning is required in TV Whitespace spectrum Submission Slide 11

  12. Scanning Relaying probe request frame Probe request frame can be relayed by other STAs in the vicinity of the STA transmitting probe request frame By the help of other STAs, probe requesting STA can discover AP However, data traffic could be possibly interrupted by the excessive probe request relaying frames, which are asked by STAs out of the service coverage of AP Submission Slide 12

  13. Scanning Enhanced Scanning Mechanism Power constraint information element should be transmitted with shorter interval than Beacon Interval AP transmits Probe Setup Frame frequently than BI, which contains power constraint information element STA can transmit probe request frame with max. allowable power according to power constraint information element within probe setup frame Submission Slide 13

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