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Introductory TGah Proposal

Introductory TGah Proposal. Authors:. Date: 2011-01-16. We propose re-banding and down clocking of TGac for the purpose of Tgah To achieve low data rates, we propose two simple methods: Repetition Preamble extension For the TGah MAC we propose optional HCCA mechanism. Summary.

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Introductory TGah Proposal

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  1. Introductory TGah Proposal Authors: Date: 2011-01-16 Ron Porat, Broadcom

  2. We propose re-banding and down clocking of TGac for the purpose of Tgah • To achieve low data rates, we propose two simple methods: • Repetition • Preamble extension • For the TGah MAC we propose optional HCCA mechanism Summary Ron Porat, Broadcom

  3. This amendment defines an Orthogonal Frequency Division Multiplexing (OFDM) Physical layer (PHY) operating in the license-exempt bands below 1 GHz, e.g., 868-868.6 MHz (Europe), 950 MHz -958 MHz (Japan),  314-316 MHz, 430-434 MHz, 470-510 MHz, and 779-787 MHz (China), 917 – 923.5 MHz (Korea) and 902-928 MHz (USA), and enhancements to the IEEE 802.11 Medium Access Control (MAC) to support this PHY, and provides mechanisms that enable coexistence with other systems in the bands including IEEE 802.15.4 and IEEE P802.15.4g. • The data rates defined in this amendment optimize the rate vs. range performance of the specific channelization in a given band. • This amendment also adds support for: • transmission range up to 1 km • data rates > 100 kbit/s while maintaining the 802.11 WLAN user experience for fixed, outdoor, point to multi point applications. TGah Scope Ron Porat, Broadcom

  4. We propose to use TGac features as a basis for TGah • Preliminary TGac Draft was presented during the November 2010 IEEE meeting • 11-10/1361r2 Proposed TGac Draft Amendment • Adoption by the Task Group is pending (to become Draft 0.1) • MU-MIMO – for low frequencies the antennas will be more correlated and reduce the ability to do spatial multiplexing hence making this feature much more important. • Beamforming • 802.11n has many options and there was no industry convergence • 802.11ac has only one beamforming option for SU and MU • LDPC • Enhanced MAC features agreed upon in TGac TGac Basis for TGah Proposal Ron Porat, Broadcom

  5. The requirements of TGah may get us closer to wide area networks, hence OFDM parameters may need to be adjusted accordingly • Need to create a system operating from low to high available bandwidth • 600KHz to 20MHz • Need to extend OFDM rates down to at least what currently is supported by 802.11b • Higher delay spread can exist not just in S1G frequencies but also in 2.4GHz for Metro-WiFi deployment. • TGah design provides an opportunity to define a system more suitable for such deployments Challenges and Issues Ron Porat, Broadcom

  6. PHY parameters are derived from the delay spread and Doppler that need to be supported • What is the right delay spread we need to support? • LTE uses 15KHz subcarrier BW and CP=4.7uS (there is an option for long CP=16uS) for all BW between 1.25MHz to 20MHz • WiMAX uses 11KHz subcarrier BW and CP=11uS (other options exist) for all BW between 1.25MHz to 20MHz • 802.15.4g uses 10.4KHz and CP=24uS for all BW between 160KHz to 1.2MHz • 802.11ac uses 312.5KHz and CP=400nS (or 800nS) for all BW between 20MHz to 160MHz • Reference [1] discusses delay spread measurements in 3G cellular systems and concludes that the typical RMS delay spread is 0.2uS • Reference [2] conducted delay spread measurements in the 900MHz frequency and reports 1-2uS maximum delay spread Basic PHY parameters for TGah Ron Porat, Broadcom

  7. Leverage three 802.11ac PHY definitions with lower PHY clocks to achieve larger delay spread tolerance which is also similar across different system BW • Specifically use FFT sizes: • 256 for 20MHz and 10MHz BW • 128 for 5MHz and 2.5MHz BW • 64 for 1.25MHz BW • 64 (or 32) for 0.625MHz BW Proposal Ron Porat, Broadcom

  8. Parameters Table * To be investigated Ron Porat, Broadcom

  9. Currently 2.4GHz deployments rely on 802.11b for the lowest rates (1-11Mbps) • The lowest rate of the OFDM waveform is 6Mbps • The lowest rate of OFDM is not reliable due to weak preamble (especially with BF) • Propose to add OFDM lower rates by using simple repetition. • 64 FFT can support repetitions 2,4,13,52 • 128 FFT can support repetitions that divide 4x27 • 256 FFT can support repetitions that divide 2x9x13 OFDM low rates Ron Porat, Broadcom

  10. The current 802.11ac/a/n preamble is not robust enough to support the lowest rates (even without Beamforming). • It is the limiting factor for using the OFDM lowest rates. • 802.11ah PAR does not include 802.11b modulations (CCK/DSSS) • Significantly reduces range as the CCK signal provides • Low PAPR • Low data rate thus lower SNR requirement • Simple option to improve OFDM preamble performance is to increase preamble length Improved Preamble/Control Channel Ron Porat, Broadcom

  11. Some of the applications envisioned for TGah may benefit from more centralized MAC: • Smart utility networks – high density of nodes with low link budget may cause CSMA/CA to fall apart • Usage of WiFi for providing broadband wireless access – QoS should be guaranteed in high density and CSMA/CA may fall apart • Metro-WiFi applications – for example deployments of WiFi hotzones by AT&T in NYC, SF and elsewhere • Enable centralized MAC using HCCA mechanism • The hybrid coordinator (HC) coordinates channel access by polling stations. Stations do not compete for access to the channel medium • Allows improved network coordination Usage of Centralized MAC Ron Porat, Broadcom

  12. [1] How typical is the "Typical Urban" channel model? Ericsson Research • [2] 15-09-0279-01-004g-channel-characterization-for-sun.ppt References Ron Porat, Broadcom

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