IEEE 802.11 ax TECHNOLOGY INTRODUCTION

1 White paper | Version | Lisa WardIEEE TECHNOLOGY INTRODUCTION22 This white paper introduces the TECHNOLOGY used in the IEEE amendment to the IEEE standard and gives an overview of receiver and transmitter test requirements. IEEE , also known as high efficiency wireless (HEW), provides mechanisms to more efficiently utilize the unlicensed spectrum bands ( GHz, 5 GHz and 6 GHz) and improve user IEEE core documents ..33 IEEE goals and features ..44 IEEE (high efficiency PHY) .. PPDU formats .. From single user to multiple users (MU) .. Subcarrier types .. Unused subcarriers .. Data subcarriers .. Pilot subcarriers .. OFDMA downlink resource unit assignments .. OFDMA uplink resource unit assignments.

2 Contents of trigger frame common field .. Contents of trigger frame user field ..185 IEEE measurements .. IEEE transmitter specification .. Transmit spectrum mask .. Spectral flatness .. Transmitter modulation accuracy .. Transmitter local oscillator (LO) leakage .. Error vector magnitude .. HE receiver requirements .. Receiver minimum input sensitivity .. Adjacent and nonadjacent channel rejection .. Receiver maximum input level .. HE trigger based PPDU precorrection specifications .. Transmit power accuracy and RSSI .. Carrier frequency offset (CFO) error and timing drift ..336 Abbreviations/acronyms/initialisms ..35 Rohde & Schwarz | White paper IEEE TECHNOLOGY INTRODUCTION 31 INTRODUCTIONIEEE is the IEEE working group developing wireless local area network specifications.

3 The group began work in the late 1990s and since then has created several successful standards/amendments, including IEEE , b and is now ubiquitous, with one or more WLAN technologies included as standard capabilities on most laptops and many smartphones. The IEEE group has continued to build and improve on the earlier IEEE and g with the official approval of IEEE in 2009 and IEEE in 2013. There is a drawback to this success, however. Because WLAN is everywhere, it is common to find many access points and stations located in dense locations such as apartment buildings and stadiums. Since WLAN uses spectrum in the unlicensed ISM band, it is likely that several connections may interfere each other and cause some capacity crunch.

4 There is no common scheduler in WLAN, and the channel access uses a CSMA scheme that has some drawbacks in high occupancy scenarios. In addition, users utilize WLAN for many different applications such as video streaming and accommodate the challenging applications and the large number of WLAN users in dense locations, the IEEE working group formed the high efficiency wireless (HEW) study group in 2013 to find ways to improve the user experience for these applications and to more efficiently use the GHz and 5 GHz spectrum. In March 2014, the HEW study group became an official task group, Task Group IEEE , to develop the IEEE amendment to IEEE This white paper contains four parts: 1. Core documents for the IEEE amendment development 2.

5 IEEE goals and features 3. TECHNOLOGY overview that covers key parts of the IEEE draft 4. Test requirements for measuring key metrics such as EVM and adjacent channel rejection 2 IEEE CORE DOCUMENTSMuch of the information in this paper comes from two key IEEE core docu-ments. The IEEE draft and the IEEE specification framework document version 17. The IEEE amendment draft [1] contains the proposed changes to IEEE in order to meet the IEEE requirements and goals. These changes include a new clause for the PHY specifications and a new MAC clause for supporting the new PHY features. In addition, the IEEE amendment contains modifications to the current IEEE MAC layer in order to maintain compatibility with legacy devices.

6 The amendment is expected to be published end of 2020. The IEEE specification framework document contains the features and require-ments that were agreed to by the IEEE task group members and is used as the framework or outline of the IEEE amendment. The specification framework document can be obtained by all at this link: While all IEEE draft versions are only available to voting members of the IEEE working group, the IEEE draft is available for 4 purchase by non-members at this link: IEEE task groups provide public status updates of their work. The IEEE status can be found at: 3 IEEE GOALS AND FEATURESThe main goal of IEEE is to improve the user experience and network perfor-mance in dense deployments in the unlicensed bands.

7 Specific targets (as defined in the project authorization request [2]) are: At least four times improvement in the average throughput per station (measured at the MAC data service access point) in a dense deployment scenario, while maintaining or improving the power efficiency per station Backwards compatibility and coexistence with legacy IEEE devices operating in the same bandIEEE will use the spectrum efficiency, area throughput and performance improvements to target several usage models including (see [3]): Airports/train stations E-education Public transportation Dense apartment buildings Picocell street deploymentsA high-level overview of new IEEE features and their key benefits can be found in Table 1.

8 IEEE features and key benefitsFeatureKey benefitsUplink MU-MIMOH igher throughput upstreamDownlink OFDMAO verhead reductionUplink OFDMAH igher aggregate throughputUplink range extensionOverhead reduction4 symbol durationIncreased robustness for outdoor operation1024 QAMH igher maximum data rateExtended range preamble and MCS0 rep2 Range extension Rohde & Schwarz | White paper IEEE TECHNOLOGY INTRODUCTION 54 IEEE (HIGH EFFICIENCY PHY)A high efficiency (HE) device will have to comply with mandatory requirements of the legacy WLAN PHY layers. This means that an HE device operating in the GHz band will need to comply with the IEEE PHY requirements and an HE device operating in the 5 GHz band will be required to be in line with the IEEE and IEEE PHY this compliance requirement, there are significant changes in IEEE from previous IEEE generations.

9 One of the main differences is the addition of support for multi-user MIMO (MU-MIMO) in both the uplink and downlink and orthogonal fre-quency division multiple access (OFDMA). Another change in IEEE is the sym-bol time, which is s four times the legacy symbol time of main reasons for increasing the symbol time are [4]: Robustness in outdoor channels Greater tolerance to timing jitter across users in UL MU-MIMO/OFDMA Higher indoor efficiency (by lowering CP overhead)Along with the increased symbol time, IEEE mandates support for three cyclic prefix (CP) times: s: using this legacy CP time with the longer symbol time improves efficiency since there is less overhead from the CP s: targeting high efficiency in outdoor channels and indoor UL MU-MIMO/OFDMA s.

10 Targeting robustness in the more demanding case of outdoor UL MU-MIMO/OFDMAIn consequence of the higher symbol time, the subcarrier spacing decreases from kHz to kHz and the FFT size for a channel bandwidth of 20 MHz increases from 64 to 256. A narrow subcarrier spacing allows better equalization and thus higher channel robustness. Although a larger FFT size could have been used, the implementa-tion complexities increase as FFT increases. In addition, as the subcarrier spacing be-comes smaller, the carrier frequency offset (CFO) correction needs to be more precise. Table 2: Overview comparison between IEEE , 11ac and 11axIEEE bandwidth (MHz)20, 4020, 40, 80, 80+80, 16020, 40, 80, 80+80, 160 Subcarrier spacing (kHz) time ( s) prefix (us) , , , and downlinkModulationOFDMOFDMOFDM, OFDMAData subcarrier modulationBPSK, QPSK, 16 QAM, 64 QAMBPSK, QPSK, 16 QAM, 64 QAM, 256 QAMBPSK, QPSK, 16 QAM, 64 QAM, 256 QAM, 1024 QAMC odingBCC (mandatory), LDPC (optional)BCC (mandatory), LDPC (optional)BCC (mandatory), LDPC (mandatory) PPDU formatsIEEE distinguishes itself from the legacy frames at the PHY layer by introducing four new PPDU (packet protocol data unit) formats.