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Sequence design for parallel ACK

This paper introduces a contention-free Probe and Pull MAC protocol designed for large networks, emphasizing the importance of Parallel ACK in the system. The proposed mechanism allows multiple Stations (STAs) to transmit Acknowledgments (ACKs) concurrently to minimize delays. We explore methods for resolving interference caused by these parallel transmissions, utilizing code-domain and time-domain multiplexing techniques, particularly focusing on Zadoff-Chu sequences as signatures. Simulation results demonstrate the system's robust detection capability, paving the way for efficient communication in dense environments.

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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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