Ack transmission
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ACK Transmission. Authors:. Date: 2012-3-13. Abstract. This presentation addresses an ACK transmission issue in IEEE 802.11ah, where asymmetric transmissions will likely to prevail. Asymmetric Transmission. AP to STN (Downlink) vs STN to AP (Uplink)

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ACK Transmission

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Ack transmission

ACK Transmission

Authors:

Date: 2012-3-13

Zander Lei, I2R Singapore


Abstract

Abstract

This presentation addresses an ACK transmission issue in IEEE 802.11ah, where asymmetric transmissions will likely to prevail

Zander Lei, I2R Singapore


Asymmetric transmission

Asymmetric Transmission

  • AP to STN (Downlink) vsSTN to AP (Uplink)

  • STN has more constraints as opposed to AP

    • Transmission power (power amplifier etc)

    • Capability

      • Transmission capability (1 MHz vs AP with 2 MHz and beyond)

      • Functionalities (AP may serve different types STN)

  • Use Cases

    • Use Case 3 : Extended range Wi-Fi

    • Use Case 1 : Sensors and meters

Zander Lei, I2R Singapore


Problems

Problems

DIFS

AP

Data

SIFS

STN

ACK

  • STN cannot reach as far as AP

    • STN can receive Data

    • AP cannot receive ACK sent by STN

    • Given Data and ACK using the same modulation and coding rates

  • More likely where range is longer in 11ah

Zander Lei, I2R Singapore


Simple fix

Simple Fix

  • Allow transmitting ACK with a different modulation and coding rate

    • E.g. Data from AP using 16 QAM

    • ACK may use QPSK or BPSK

  • Allow transmitting ACK with 1MHz PHY (MCS0-rep2) after receiving 2 MHz (or above) PHY packets

    • All STN support both 1 MHz and 2 MHz PHY [Specification Framework]

    • 2 MHz is preferred whenever available (11-1535r0)

      • Throughput and energy efficiency

    • 1 MHz is necessary, especially when

      • Range is an issue

      • STN with 1MHz transmission capability

Zander Lei, I2R Singapore


Conclusions

Conclusions

  • In 11ah, ACK from STN may not reach AP

    • AP may transmit at higher power and better off in capability

    • STN can receive Data but its ACK can not reach AP

    • Given Data and ACK using the same modulation and coding or same channel bandwidth, e.g. 1 MHz, 2 MHz etc.

  • Propose to allow ACK using different modulation and coding, including MCS0-2rep

Zander Lei, I2R Singapore


Straw poll 1

Straw Poll 1

Zander Lei, I2R Singapore

Do you agree to allow STN transmit ACK with lower (or more robust) modulation and coding rates than that of received frames from AP?


Straw poll 2

Straw Poll 2

Zander Lei, I2R Singapore

Do you agree to allow STN transmitting ACK with 1MHz PHY after received 2 MHz frames from AP?


Straw poll 3

Straw Poll 3

Zander Lei, I2R Singapore

Do you agree to allow STN transmitting ACK with narrower bandwidth PHY after received frames from AP?


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