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IEEE 802.15.3d: First Standardization Efforts for Sub-Terahertz Band Communications towards 6G

Vitaly Petrov, Thomas Kürner, and Iwao Hosako

arXiv:2011.01683v2cs.NI

TL;DR

The paper addresses how sub-THz wireless communications can be standardized for high-rate applications beyond current mmWave systems. It surveys IEEE 802.15.3d’s design, applications, PHY and MAC layers, and initial performance, finding that the standard satisfies essential rate and range requirements while retaining a fixed point-to-point scope.

  • Problem

    Future networks require ultra-high data rates, while mmWave backhaul and close-proximity wireless solutions have limited rates or involve costly and complex cabling.

  • Method

    The paper overviews IEEE 802.15.3d’s applications, channelization, PHY modes, MAC and PHY design, and initial performance assessment.

  • Results

    IEEE 802.15.3d supports 1.64–52.56 Gbit/s with THz-OOK and up to 315.39 Gbit/s with THz-SC, while preliminary assessment finds essential rate and range requirements satisfied across the described use cases.

  • Takeaways & Limitations

    The standard provides high-rate sub-THz point-to-point connectivity for applications including fronthaul, backhaul, data centers, kiosk downloading, and intra-device links.

  • Takeaways & Limitations

    IEEE 802.15.3d specifies fixed point-to-point links and does not yet address prospective THz WLAN requirements for antenna direction, interference, and shared access.

Abstract

from arXiv · show

With the ratification of the IEEE 802.15.3d amendment to the 802.15.3, a first step has been made to standardize consumer wireless communications in the sub-THz frequency band. The IEEE 802.15.3d offers switched point-to-point connectivity with the data rates of 100\,Gbit/s and higher at distances ranging from tens of centimeters up to a few hundred meters. In this article, we provide a detailed introduction to the IEEE 802.15.3d and the key design principles beyond the developed standard. We particularly describe the target applications and usage scenarios, as well as the specifics of the IEEE 802.15.3d physical and medium access layers. Later, we present the results of the initial performance evaluation of IEEE 802.15.3d wireless communications. The obtained first-order performance predictions show non-incremental benefits compared to the characteristics of the fifth-generation wireless systems, thus paving the way towards the six-generation (6G) THz networks. We conclude the article by outlining the further standardization and regulatory activities on wireless networking in the THz frequency band.

I. INTRODUCTION

The paper situates sub-THz communications as a prospective 6G technology for extreme data rates and introduces IEEE 802.15.3d as an initial standardized solution. It reviews the standard’s applications, protocol layers, performance, and future standardization needs.

  • 6G systems are expected to complement microwave and mmWave connectivity with THz communications to support ultra-high user data rates exceeding tens of gigabits per second.
  • The emerging 6G vision includes scenarios such as ubiquitous AR/VR, holographic telepresence, and collective driving by autonomous robots.
  • IEEE standardization of low-THz wireless communications began with an interest group in 2008 and produced IEEE Std. 802.15.3d–2017, approved in 2017.
  • IEEE 802.15.3d is the first IEEE-family standard for sub-THz wireless communications over channels up to 69 GHz wide between 253 GHz and 322 GHz.
  • The paper reviews target applications and usage scenarios, then details the MAC and PHY layers, evaluates initial performance, and outlines future THz standardization work.

II. IEEE 802.15.3D MOTIVATION AND USAGE SCENARIOS

IEEE 802.15.3d targets high-rate sub-THz connectivity for applications feasible with current electronics. Its static or quasi-static point-to-point scope reduces protocol complexity and signaling overhead compared with mobile multipoint systems.

  • IEEE 802.15.3d defines a 100 Gbit/s PHY with fallback to lower rates for low-complexity, high-rate connectivity in emerging applications.
  • The standard primarily targets static or quasi-static point-to-point links between devices, unlike IEEE 802.11-family systems targeting mobile point-to-multipoint communications.
  • Stationary point-to-point links relax multiple-access and interference-mitigation requirements, enabling simpler access and discovery procedures and lower signaling overhead.

A. Wireless Fronthaul and Backhaul Links

IEEE 802.15.3d is positioned as a wireless alternative for fronthaul and backhaul links in dense mmWave deployments. It combines approximately 100 Gbit/s rates with reduced cabling compared with optical-fiber-based approaches.

  • Dense mmWave deployments require reliable, high-rate backhaul and fronthaul connections between small cells, remote radio heads, and baseband units.
  • ≈100 Gbit/s is supported by IEEE 802.15.3d, an order of magnitude higher than state-of-the-art mmWave technologies, while simplifying cabling.

B. Additional Wireless Links in Data Centers

The paper identifies data-center cabling as a barrier to reconfigurability and cooling and presents high-rate point-to-point wireless links as a complementary inter-rack option. It also describes close-proximity consumer applications, including kiosk downloads.

  • B. Additional Wireless Links in Data Centers: Many fiber-optic cable channels between server racks challenge data-center reconfigurability and complicate cooling by blocking air streams.
  • B. Additional Wireless Links in Data Centers: High-rate point-to-point wireless links can provide more flexible data-center designs and reduce cabling while complementing fiber optics in selected deployments.
  • C. Close-Proximity Communications: IEEE 802.15.3d targets close-proximity consumer communications through device-to-device links and kiosk downloads.
  • C. Kiosk Downloads: A 900 MB, two-hour movie download is reduced from around 10 s with IEEE 802.11ac to 0.1 s with IEEE 802.15.3d.
  • B. Additional Wireless Links in Data Centers: Internal computer links currently contribute to complex motherboard and processor designs, while IEEE 802.15.3d is presented as a possible alternative for connecting critical components.

III. IEEE 802.15.3D MAC LAYER

IEEE 802.15.3d uses switched point-to-point pairnets with a setup phase followed by an associated data-exchange phase. This design reduces interference and access contention while supporting connection establishment and termination procedures.

  • IEEE 802.15.3d supports point-to-point pairnets connecting no more than two devices, reducing interference and competition for access.
  • Pairnet setup period: Pairnet setup begins with coordinator beacons, followed by a device’s Association Request in an advertised access slot and an Association Response.Higher-layer protocol setup may also occur during this period.
  • Pairnet associated period: During the pairnet associated period, both devices exchange data frames and optional acknowledgments, beginning with the pairnet device and separating frames by SIFS.
  • Pairnet associated period: A Disassociation Request or coordinator timeout ends the associated period, after which the coordinator resumes beacon transmission and awaits new connections.A Probe Request can restart the coordinator’s timeout timer when the device has no data but wants to remain connected.

IV. IEEE 802.15.3D PHY LAYER

The IEEE 802.15.3d PHY layer provides two modes tailored to different device and application requirements. THz-SC targets the highest rates, while THz-OOK supports simpler, lower-cost devices and can still reach tens of Gbit/s with wide channels.

  • The PHY layer defines two modes: THz single carrier (THz-SC) and THz on-off keying (THz-OOK).
  • THz-SC PHY is designed for high data rates and targets bandwidth-oriented applications such as wireless fronthaul, backhaul, and data-center links.
  • THz-OOK PHY targets lower-cost devices unable to process complex signals, using amplitude information and solutions such as resonant tunneling diodes.
  • Tens of Gbit/s can be achieved with THz-OOK PHY when the widest channels are used.

B. Supported Channels

IEEE 802.15.3d supports flexible sub-THz channelization from narrow 2.16 GHz channels to a single 69.12 GHz channel. The plan provides multiple bandwidth choices while defining a default channel and regulatory conditions.

  • The standard operates from 252.72 GHz to 321.84 GHz using 69 overlapping channels and eight bandwidths from 2.16 GHz to 69 GHz.
  • A single 69.12 GHz-wide channel can occupy the full frequency range, or smaller channels can divide it using integer multiples of 2.16 GHz.
  • Channel 41, with 4.32 GHz bandwidth, is the default channel.
  • The depicted bands are globally available for THz communications under conditions protecting radio astronomy and earth exploration satellite services.The conditions primarily affect narrow areas surrounding ground radio astronomy stations and do not explicitly specify transmit power limits.

D. THz-OOK PHY Layer Mode

The THz-OOK PHY mode is designed for simpler devices and short-range applications. It uses OOK, a reduced PHY header, and the same target minimum receiver sensitivity as THz-SC under the specified configuration.

  • THz-OOK targets simpler devices for kiosk downloading and intra-device communications, with a transmission range of no more than a few meters.
  • THz-OOK supports one low-complexity modulation scheme, on-off keying, where data are represented by signal presence or absence.
  • The THz-OOK PHY header uses two MCS bits instead of four because it has one modulation and three FEC options.
  • Both THz-OOK and THz-SC have a target minimum receiver sensitivity of −67 dBm with 11/15 LDPC and 2.16 GHz bandwidth.

V. INITIAL PERFORMANCE EVALUATION

The initial evaluation examines IEEE 802.15.3d data rates and communication ranges across target use cases. Results indicate that the standard’s essential rate and range requirements are met, with a clear range–performance trade-off.

  • Data rates: 315.39 Gbit/s is the maximum theoretical THz-SC PHY rate, while THz-OOK ranges from 1.64 to 52.56 Gbit/s across supported channel bandwidths.The THz-SC figure assumes 64-QAM modulation and a 14/15 LDPC code.
  • Evaluation approach: The evaluation uses a link-level simulator with application-specific parameters and sub-THz channel models for each use case.The study uses 64-QAM for long-range setups and evaluates maximum reliable distance as a function of channel bandwidth.
  • Communication range: ≈100 m, 17 m, 0.61 m, and 0.03 m are the maximum ranges maintaining 100+ Gbit/s for fronthaul/backhaul, data center, kiosk downloading, and intra-device links, respectively.The broader range spans centimeters for intra-device connectivity to several hundred meters for fronthaul/backhaul.
  • Communication range: Highly directional antennas with gains of ≥30 dB are required for long-range fronthaul and backhaul to mitigate spatial loss and absorption.This requirement applies on both the PRC and PRDEV sides.
  • Overall assessment: The results highlight a trade-off between range and link-level performance that operators may adjust for each application and deployment.The reported values are several times lower than those achievable with a 2.16 GHz channel.
  • Overall assessment: The preliminary assessment finds that essential rate- and range-related requirements are satisfied across all described use cases.Further evaluations are still in progress for realistic backhauling environments and complex data-center topologies.

VI. THE ROAD AHEAD IN STANDARDIZING THZ BAND COMMUNICATIONS

The road ahead combines expanded regulatory access to THz spectrum with ongoing hardware prototyping. Further regional rules and practical demonstrators will shape deployment of IEEE 802.15.3d systems.

  • Regulatory aspects: 160 GHz of spectrum was opened for THz communications after WRC-2019, including conditions for using the 275–450 GHz band.Certain portions still require sharing with passive services, while other listed sub-bands need no EESS protection conditions and have manageable RAS conditions.
  • Regulatory aspects: WRC allocations provide a global baseline, but additional regional and national regulations are expected to specify transmit-power limits and sub-band allocations.The passage states that no specific transmit-power limits were specified to date.
  • Prototyping activities: End-to-end IEEE 802.15.3d implementations remain active work in progress, including demonstrators using THz-SC-compatible MCSs and RTD-based solutions.These demonstrators are primarily developed within large-scale research and infrastructure projects.
  • Prototyping activities: Final standard approval and WRC-19 frequency allocations have accelerated prototyping, with a transceiver chip supporting channels 49–51 and 66.Further prototypes are expected as hardware becomes available for sub-THz radio links.

C. Towards Prospective THz Band WLANs

IEEE 802.15.3d currently supports fixed point-to-point THz links under controlled directional and access conditions. Prospective THz WLANs require new solutions for mobility, interference, and multiple access.

  • Current scope: IEEE 802.15.3d assumes known antenna directions, interference mitigation through link planning, and no contention for access.These assumptions define the current fixed point-to-point operating scope.
  • Future WLANs: Prospective THz WLANs do not satisfy the standard’s current assumptions, so solutions for mobility, interference, and access coordination must be developed.Potential standardization paths include amendments to IEEE 802.15.3d, incorporation into future IEEE 802.11 releases, or entirely new standards.
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