doc.: IEEE 802.15-15-13-0119-00-0thz Project ... · Project: IEEE P802.15 ... Slide 1 Sebastian...

doc.: IEEE 802.15-15-13-0119-00-0thz

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<March 2013>

Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) Submission Title: MAC Layer Concepts for THz Communications Date Submitted: 17 March, 2013 Source: Sebastian Priebe, Technische Universität Braunschweig Address: Schleinitzstraße 22, D-38106 Braunschweig, Germany Voice: +49-531-391-2417, FAX: +49-531-391-5192, E-Mail: [email protected] Abstract: Wireless THz radio networks will, alike any other digital data transmission system, need an appropriate Medium Access Control protocol definition, which has not been subject to any discussions in the Interest Group THz yet. Hence, this document identifies the basic requirements for a THz MAC layer to be fulfilled. Those requirements differ significantly from conventional wireless data communications systems and depend highly on the use cases of THz radio, as is illustrated. Moreover, the document addresses the potential reuse of established MAC protocol definitions forTHz communications and names required amendments, where applicable.

Purpose: Basis for discussion of appropriate MAC layer concepts for THz communications

Notice: This document has been prepared to assist the IEEE P802.15. It is offered as a basis for discussion and is not binding on the contributing individual(s) or organization(s). The material in this document is subject to change in form and content after further study. The contributor(s) reserve(s) the right to add, amend or withdraw material contained herein. Release: The contributor acknowledges and accepts that this contribution becomes the property of IEEE and may be made publicly available by P802.15.

Slide 1 Sebastian Priebe, TU Braunschweig

doc.: IEEE 802.15-15-13-0119-00-0thz

Submission

<March 2013>

Sebastian Priebe, TU Braunschweig Slide 2

MAC Layer Concepts for THz Communications

Sebastian Priebe1

1 Institut für Nachrichtentechnik, Technische Universität Braunschweig, Germany

doc.: IEEE 802.15-15-13-0119-00-0thz

Submission

<March 2013>


Outline

1.  Introduction 2.  General MAC Layer Requirements 3.  Use-Case-Specific MAC Requirements 4.  Suitability of Existing IEEE MAC Protocols 5.  Conclusion

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Introduction (1) <March 2013>


Steps so far: 1.  Identification of use cases (amongst others):

(1) THz WLANs (2) THz WPANs

(3) Chip-to-chip links (4) Fixed links

100 Gbit/s

10…100 Gbit/s

100 Gbit/s

10 Gbit/s

10…50 Gbit/s

(5) Data center links

100 Gbit/s

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2.  Characterization and modeling of the THz radio channel:

TX

RX

à  Analytical propagation models à  Validated ray tracing propagation simulator

a) Propagation investigations:

b)  Indoor channel measurements:

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3.  Studies on the interference of THz communications with passive Earth exploration services:

à  Interference mitigation schemes can help avoiding interference completely

1.) Outdoor-operated TX 2.) Fixed links 3.) Airborne-operated TX

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•  Up to now: good understanding of the physical layer requirements •  Next: consideration of the Medium Access Control layer

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Definition of a complete THz radio system standard:

7. Applicaton 6. Presentation 5. Session 4. Transport 3. Network 2. Data link 1. Physical

Not subject to IEEE standardization

Routing by other protocols, e.g. •  Proprietary •  IPv4/IPv6

OSI model layers:

Open point: Medium Access Control (MAC) Layer • Which requirements does a MAC protocol for

THz communication systems have to fulfill ? •  Can existing IEEE MAC definitions meet these?

doc.: IEEE 802.15-15-13-0119-00-0thz

Submission

<March 2013>


Outline

1.  Introduction 2.  General MAC Layer Requirements

•  MAC Functions •  Out-of-Band Signaling

3.  Use-Case-Specific MAC Requirements 4.  Suitability of Existing IEEE MAC Protocols 5.  Conclusion

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The MAC layer must support: •  Access/association •  Data transmission

•  Disassociation •  Multiple clients •  Security •  Roaming

MAC Functions (1) <March 2013>


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Submission

•  Admission control

•  Channel estimation

•  Adaptive modulation

•  Control of beamswitching/-steering/-forming

•  Interference cancellation/coexistence



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5. Data transmission

Channel estimation updates Packet retransmission (ARQ) Link parameter updates Beam alignment updates

4. Connection establishment

Authentication Encryption

3. Link parameter negotiation Initial channel

estimation Modulation scheme Coding scheme Transmit power control

Bandwidth and frequency

2. Beam alignment procedure

Double-directional beam alignment at TX and RX

1. Access request

Parameters to be defined in PHY layer

How to submit an access request in case of not aligned antennas? à Main difference compared to conventional 802.11/802.15 A

ccess procedure

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•  Problem: Access request transmission in the THz band not possible in case that antennas are not aligned

•  How does IEEE 802.15.3c solve this issue? •  Iterative scanning procedure:

à  Unfeasible at THz frequencies because of very high

propagation losses and low output powers •  Idea: Access signaling for the THz link over an additional

conventional WLAN channel

Out-of-Band Signaling (1) <March 2013>


1.) Begin with a broad, quasi-omnidirectional beam

2.) Increase directivity and refine beam direction

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Procedure

1.  Access request via conventional 802.11a/b/g/n WLAN, UWB or any other radio system with omnidirectional antennas

2.  Initiation of beam scanning •  Coordinated scanning by TX and RX •  If possible initial rough direction estimation with UWB or 802.11n MIMO

à Optimum beam alignment possible despite high directivites



1.) Access and beam scanning request

802.11 a/b/g/n

2.) Iterative, coordinated scanning of the THz beams by TX and RX

à Control information exchange via conventional WLAN link

3.) Data transmission over THz link

THz link

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3.  Optional: Retransmission of corrupt packages via conventional WLAN Link

•  Advantages: +  THz link for ultra fast, non-disrupted data transmission +  ARQ manageable via simple data transmission over the conventional

WLAN +  No complex ARQ necessary in the THz MAC framework

•  Disadvantage: -  Very large buffers required due to potential latencies



THz data pipe

802.11 a/b/g/n

802.11 a/b/g/n

Continuous data transmission

Retransmission request (NACK)

Packet retransmission

doc.: IEEE 802.15-15-13-0119-00-0thz

Submission

<March 2013>


Outline

1.  Introduction 2.  General MAC Layer Requirements 3.  Use-Case-Specific MAC Requirements

•  Use Case Radio Channel Conditions •  Implications on the MAC Layer •  Special Requirements of the Use Cases

4.  Suitability of Exisiting IEEE MAC Protocols 5.  Conclusion

doc.: IEEE 802.15-15-13-0119-00-0thz

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Use Case Radio Channel Conditions <March 2013>


1.) Fixed links

2.) Data center links

3.) Intra device

4.) Kiosk 5.) WPAN 6.) WLAN

Multipath propagation

None High; sup-pressible

Low Medium-high

Dynamics None Low Medium

Control over environment and TX/RX placement

High Medium None

Beam alignment

Once during setup; manual Not necessary

Initial alignment and tracking; automatic

Multiple stations

No Yes, time multiplex

No No Yes

Access Possible in THz band Via conventional radio technology

Type (a): No dynamic beam alignment, THz access,

point-to-point

Type (c): Dynamic beam alignment, conventional

access, multi-user

Type (b): Type (a) + conventional

radio access

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Implications on the MAC Layer <March 2013>


1.) Fixed links


3.) Intra device

4.) Kiosk 5.) WPAN 6.) WLAN

Access

Data transmission

Disassociation

Security

Roaming

Admission control

Channel estimation

Adaptive modulation

Beam control

Coexistence

Necessary Not necessary

Very simple MAC scheme sufficient

Hardware encryption

More complex MAC layer functions necessary

Secondary access technology

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Submission

1.  Fixed links: bit transparent transmission for the wireless extension of wired 40 Gbit/s or 100 Gbit/s links

2.  Data center links: transmission on demand, flow control and switch between multiple, predefined RX stations

3.  Intra device: transparent connection, very low protocol processing overhead desirable

4.  Kiosk downloads: fast and reliable association/disassociation

5.  WPANs: ad-hoc network functionality 6.  WLANs: robust operation, IEEE 802.11a/b/g/n user experience

Special Requirements of the Use Cases <March 2013>


doc.: IEEE 802.15-15-13-0119-00-0thz

Submission

<March 2013>


Outline

1.  Introduction 2.  General MAC Layer Requirements 3.  Use-Case-Specific MAC Requirements 4.  Suitability of Existing IEEE MAC Protocols

•  IEEE 802.3 (Ethernet) •  IEEE 802.11 •  IEEE 802.15.3c •  Recommendations

5.  Conclusion

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•  Basic frame structure:

•  Access scheme: Carrier Sense Multiple Access with Collision

Detection (CSMA/CD) à TX listens for other frames and transmits only if medium is free

•  Packet corruption test utilizing checksum à Retransmission request in case of errors

IEEE 802.3 (Ethernet) <March 2013>


Preamble Start frame delimiter

Destina-tion address

Source address

Length Data Frame check sequence

7 bytes 1 byte 6 bytes 6 bytes 2 bytes 45-1500 bytes

4 bytes

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•  Basic structure of 802.11:

•  Physical Layer Convergence Procedure (PLCP): ensures the interoperability of different 802.11 PHY layers with one MAC

•  Access scheme: CSMA/Collision Avoidance (CA) with back-off time

à  Severely limits data rates (e.g. 500 Mbit/s PHY à ~50 Mbit/s net)

DIFS (fixed)

IEEE 802.11 (1) <March 2013>


802.2 Logical Link Control

802.3 MAC 802.11 MAC

802.3 PHY

802.11 FHSS

802.11 DSSS

802.11a 802.11b 802.11g 802.11n 802.11ad

TX

RX

Other station

ACK

Data

Data

Back-off (random)

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•  Frame structure of 802.11:

IEEE 802.11 (2) <March 2013>


Preamble PLCP Header MAC Packet Data Unit (MPDU)

Frame Control

Duration Addr 1 Addr 2 Addr 3 Sequence Control

Addr 4 Frame Body Frame Check Sequence

Protocol Version

Type Subtype To DS From DS

More Frag

Retry Pwr Mgt

More Data

WEP Rsvd

Flexible MAC structure for various kinds of control data à Could be extended/adapted for THz WLANs

Control Power Encryption Distribution System

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IEEE 802.11 (3) <March 2013>


à  Not possible for THz systems due to need for high gain

802.11n

•  Multi antenna operation in IEEE 802.11n: MIMO defined in PHY, not in MAC layer (Space-Time Block Codes)

•  MAC improvements introduced by IEEE 802.11n: •  Aggregation of MPDUs •  Block acknowledgement of several MAC frames •  …

à  Reduction of MAC-induced throughput impairments

802.11ad

•  Beamforming support: •  Sector Level Sweep (SLS) •  Beam Refinement Protocol (BRP)

•  Personal Independent Basic Service Set: •  Direct connection between two devices without CSMA/CA •  Third device as control point •  Access according to coordinated schedule

à  Can deal with directive antenna systems

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•  Networks organized as piconets (ad-hoc) •  One node as piconet controller (PNC)

•  Hybrid CSMA/CA

•  CSMA/CA for access procedure •  TDMA for transmission (slots administered by PNC)

•  Beamforming: codebook-based approach for antenna array weight vectors (different predefined beams selectable)

1.  Quasi-omnidirectioal patterns (low gain, low directivity) 2.  Sector patterns (mid gain, mid directivity) 3.  Beam patterns (high gain, high directivity)

à  Sequential beam refinement coordinated by PNC

IEEE 802.15.3c <March 2013>


1.)

2.)

3.)

à  Not possible for THz systems due to need for high gain

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Comparison of the Standards <March 2013>


Capability IEEE 802.3

IEEE 802.11n

IEEE 802.11ad

IEEE 802.15.3c

Access

Data transmission

Disassociation

Security

Roaming

Power saving

Channel estimation

Adaptive modulation

Beam control

Coexistence Robustness −−− +++ +++ ++ Overhead +++ −−− −− o

Provided

Not provided

802.3 appropriate for fixed links with stable, predefined conditions only; very low overhead

802.15.3c preferable over 802.11ad due to lower overhead

Missing beam-forming support in 802.11n

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Recommendations – Type (a)

<March 2013>


Requirements

1.) Fixed links


3.) Intra device

Access

Data transmission

Disassociation

Security

Roaming

Admission control

Channel estimation

Adaptive modulation

Beam control

Coexistence

à  Access and trans-mission with a simple proprietary format

à  Hardware encryption without need for authentication

à  Beam selection for data center links (e.g. with meshed networks 802.11s)


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Recommendations – Type (b)

<March 2013>


à  Access trigger via convetional WLAN/Bluetooth/UWB/...

à  Transmission in a simple proprietary format or based on 802.3

à  User credential verification in higher OSI layers

Requirements 4.) Kiosk

Access

Data transmission

Disassociation

Security

Roaming

Admission control

Channel estimation

Adaptive modulation

Beam control

Coexistence


doc.: IEEE 802.15-15-13-0119-00-0thz

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Recommendations – Type (c)

<March 2013>


à  WPANs: adoption of 802.15.3c

à  WLANs: 802.11ad or amendment of roaming to 802.15.3c

à  Amendment of access and beam alignment procedure via conventional radio

Requirements 5.) WPAN 6.) WLAN

Access

Data transmission

Disassociation

Security

Roaming

Admission control

Channel estimation

Adaptive modulation

Beam control

Coexistence Necessary Not necessary

doc.: IEEE 802.15-15-13-0119-00-0thz

Submission

<March 2013>


Outline

1.  Introduction 2.  General MAC Layer Requirements 3.  Use-Case-Specific MAC Requirements 4.  Suitability of Existing IEEE MAC Protocols 5.  Conclusion

doc.: IEEE 802.15-15-13-0119-00-0thz

Submission

•  Main difference compared to conventional WPANs/WLANs is the high antenna directivity and required steerability

à  MAC layer must encompass beam control as the key component •  Access and beam alignment cannot be realized in THz band

à  Out-band-signaling has to be employed •  Requirements for the MAC layer are highly use-case-dependent

à  Use-case-specific MAC solutions must be chosen

•  Suggested MAC layer concepts: •  Fixed links, data center, chip-to-chip: proprietary solution with very low

overhead •  Kiosk downloads: link activation via conventional radio system, proprietary

format for transmission •  WPANs/WLANs: Access and beam alignment via conventional radio system,

adoption of 802.15.3c or 802.11ad for control and transmission

Conclusion <March 2013>


doc.: IEEE 802.15-15-13-0119-00-0thz

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•  IEEE 802.11-10/0432r0: “PHY/MAC Complete Proposal to TGad” •  K.-W. Chin, D. Lowe: “The IEEE 802.15.3 MAC: Enabling High-

Rate Multimedia Applications in Wireless Personal Area Networks”, UoW-WTL-TechReport-3-05, June, 2005.

References <March 2012>


doc.: IEEE 802.15-15-13-0119-00-0thz

Submission

All information contained in this presentation is meant to be included in the technical expectations document 15-11-0745-05-0thz-thz-ig-technical-expectations-document-ted.doc.

Technical Expectations Document (TED) <March 2012>


doc.: IEEE 802.15-15-13-0119-00-0thz

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Thank you for paying attention. Dipl.-Ing. Sebastian Priebe [email protected]

<March 2013>


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