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Sequence design for parallel ACK

Sequence design for parallel ACK. Authors:. Date: 2012-01-09. Abstract. Proposed Contention-Free Probe and Pull MAC for large network [1] Parallel ACK is crucial to the proposed Probe and Pull MAC High level idea of physical layer support for parallel ACKs for Probe and Pull MAC.

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Sequence design for parallel ACK

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  1. Sequence design for parallel ACK Authors: • Date:2012-01-09 Taejoon Kim, Nokia

  2. Abstract • Proposed Contention-Free Probe and Pull MAC for large network [1] • Parallel ACK is crucial to the proposed Probe and Pull MAC • High level idea of physical layer support for parallel ACKs for Probe and Pull MAC Taejoon Kim, Nokia

  3. Parallel ACK Mechanism [1] • STAs with data to send transmit ACKs concurrently (in time-aligned manner) • Parallel ACKs imply inevitable interference Need method for resolving parallel ACKs SIFS SIFS Pull Probe AP ACK STA 1 has data to send ACK STA 2 has data to send ACK STA K has data to send Taejoon Kim, Nokia

  4. Sequences to Resolve Parallel ACKs • Separate STAs in code-domain • Consider combination of code- and time-domain Code-domain Sequence ID is used to identify STA ID Time-domain Use sequence ID & time slot instance to identify STA ID Code-domain Time slot 1 Time slot 2 Time slot 3 Taejoon Kim, Nokia

  5. Zadoff-Chu (ZC) Sequence as a Signature • Zadoff-Chu (ZC) sequence , • Zero cyclic autocorrelation • Minimum cyclic cross-correlation • If is relative prime with , • Amount of cyclic shifts and/or root values indicate sequence ID root of sequence length of sequence Cyclic shift by k • If is prime, the condition is guaranteed Taejoon Kim, Nokia

  6. Physical Parallel ACKs • Each STA maps ZC sequence (pre-assigned to STA) to OFDM subcarriers, perform IFFT, add cyclic prefix, and transmits it • Sum of ACKs arrives at AP with delays One OFDM symbol per time slot One time slot TRTT: max round-trip time, e.g., AP ACK_STA1+ACK_STA2 STA in 1km range TFFT TMD TMD: max multipath delay, e.g., ACK_STA1 for urban micro (RMS DS = 0.25us for SCM Umi [2]) TRTT ACK_STA2 TCP: CP duration, e.g., 8us =+ TCP TGI TRTT • : guard interval, e.g, FFT window FFT window FFT output Detect multiple STAs Taejoon Kim, Nokia

  7. Parallel ACK Detection at AP • Non-coherent detection • De-correlation(matched filter)-based threshold detection • Use of cyclic shifted ZC sequences enables efficient frequency domain implementation Taejoon Kim, Nokia

  8. Simulation Setup Taejoon Kim, Nokia

  9. Simulation Results Taejoon Kim, Nokia

  10. Conclusions • High level framework for Physical Parallel ACK: Combination of code- and time-domain multiplexing, use of Zadoff-Chu sequence, time slot structure • Simulation results demonstrate robust detection capability for Parallel ACK Taejoon Kim, Nokia

  11. References • [1] 11-11-1512-00-00ahr4-mac-consideration-for-802.11ah • [2] J. Salo et al., “3GPP Spatial Channel Model,” [Online] Available: http://www.tkk.fi/Units/Radio/scm/ Taejoon Kim, Nokia

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