1. Generic MAC for Coordinated Topology
May 2015
doc.: IEEE /0496r1
November 2017
Generic MAC for Coordinated Topology
Date:
Authors:
Volker Jungnickel (Fraunhofer HHI)
Edward Au (Marvell Semiconductor)

2. May 2015
doc.: IEEE /0496r1
Abstract
This presentation proposes a generic MAC for the coordinated topology in featuring macro-diversity with mobility support between coordinators supervised by a master coordinator. The proposed MAC is suitable for industrial applications which require high link availability and very low latency.
Volker Jungnickel (Fraunhofer HHI)
Edward Au (Marvell Semiconductor)

3. Content Introduction: OWC for Industrial Wireless Coordinated topology
May 2015
doc.: IEEE /0496r1
Content
Introduction: OWC for Industrial Wireless
Coordinated topology
Generic MAC for coordinated topology
MAC procedures
How to build MAC frames
Implementation
Removal of DME
What functional split?
Summary
Volker Jungnickel (Fraunhofer HHI)
Edward Au (Marvell Semiconductor)

4. Introduction Li-Fi: Every light bulb becomes a mobile access point
May 2015
doc.: IEEE /0496r1
Introduction
Li-Fi: Every light bulb becomes a mobile access point
Li-Fi has challenging cost, energy, form factor
High volumes make it difficult to introduce Li-Fi in general
Introduce intermediate steps
Start with use cases that relax some of these requirements
Promising use cases for Li-Fi
Leverage unique selling points of light compared radio
Mobile backhauling of small radio cells  simple P2P
OWC for Industrial Wireless
Secure wireless access in conference rooms, class rooms etc.
Volker Jungnickel (Fraunhofer HHI)
Edward Au (Marvell Semiconductor)

5. OWC for Industrial Wireless
May 2015
doc.: IEEE /0496r1
OWC for Industrial Wireless
Industrial OWC: high availability, low latency  use MIMO!
Use omni-directional Tx at robot and distributed Rxs
Build first Li-Fi channel sounder (200 MHz BW, 8x8 MIMO)
Take 6x8 MIMO measurements in real robotics environment
Volker Jungnickel (Fraunhofer HHI)
Edward Au (Marvell Semiconductor)

6. Distributed MIMO Setup
May 2015
doc.: IEEE /0496r1
Distributed MIMO Setup
6 Tx at robots arm pointing to all directions
8 Rx at the fence of manufacturing cell
48 channels between all Tx and all Rx measured along mobile robots trajectory
Observations
SNR is low in wide-beam setups
Design may differ from high SNR scenario typical for Li-Fi
Few MHz bandwidth, SC modulation
Diversity-oriented MIMO
Volker Jungnickel (Fraunhofer HHI)
Edward Au (Marvell Semiconductor)

7. Results High availability reached with macro-diversity concepts
May 2015
doc.: IEEE /0496r1
Results
MIMO measured along robots trajectory
Fast time variance due to blocked LOS
Spatial diversity creates robust OWC link
High availability reached with macro-diversity concepts
Fit well to ow SNR and moderate data rate rate requirements
Volker Jungnickel (Fraunhofer HHI)
Edward Au (Marvell Semiconductor)

8. Requirements for Industrial Wireless
May 2015
doc.: IEEE /0496r1
Requirements for Industrial Wireless
High reliability (almost 100% link availability)
spatially distributed OWC frontends
mobile devices with omni-directional beam characteristics
Low latency (< 5 ms)
Conventional handover is too slow for industrial wireless
Move mobility support from network layer into the MAC layer!
Proposal: Use the new coordinated MAC topology in
distributed OWC frontends are considered as coordinators (CO)
Macro-diversity realized with centralized master coordinator (MC)
protocols for distributed multi-user MIMO
suitable functional split between MC and CO inside MAC or PHY
Volker Jungnickel (Fraunhofer HHI)
Edward Au (Marvell Semiconductor)

9. Coordinated Topology Central control unit: master coordinator (MC)
May 2015
doc.: IEEE /0496r1
Coordinated Topology
Central control unit: master coordinator (MC)
Distributed access points at fixed locations: coordinators (COs)
Mobile devices with omni-directional characteristics = devices (DEVs)
Volker Jungnickel (Fraunhofer HHI)
Edward Au (Marvell Semiconductor)

10. Generic MAC for coordinated topology
May 2015
doc.: IEEE /0496r1
Generic MAC for coordinated topology
CAPs are only used for network access / joining
High reliability requires contention-free medium access : GTSs in CFP
Connectivity matrix in wavelength-division (WDD) and time-division duplex (TDD) modes
WDD: downlink WDD: uplink TDD:
WDD: VLC is not always reciprocal
TDD: Additional direct links between COs and DEVs TX RX
CO 1
CO 2
CO 3
DEV 1
DEV 2
DEV 3 X TX RX
CO 1
CO 2
CO 3
DEV 1 X
DEV 2
DEV 3 TX RX
DEV 1
DEV 2
DEV 3
CO 1 X
CO 2
CO 3
Volker Jungnickel (Fraunhofer HHI)
Edward Au (Marvell Semiconductor)

11. Generic MAC functions Network joining
May 2015
doc.: IEEE /0496r1
Generic MAC functions
Network joining
At any location where the mobile device is situated
TDD with fixed, network-wide split between down- and uplink
CAP for admission / join-request / connectivity estimation
Beacon frame  multicell channel estimation  feedback in CAP  superframe specification
Macro diversity
Multiple COs act as one cluster i.e. transmit or receive jointly
All COs are synchronized e.g. using PTP + SynchE
Flexible clusters depending on UL/DL connectivity matrix
Data forwarded from/to MC to/from cluster over infrastructure network
Volker Jungnickel (Fraunhofer HHI)
Edward Au (Marvell Semiconductor)

12. Generic MAC frames: Overview
May 2015
doc.: IEEE /0496r1
Generic MAC frames: Overview
Classical frame structure
Applicable to
Global transmissions e.g. for network access
synchronously transmitted by all COs
Regional transmissions e.g. for macro-diversity
transmitted by individual CO or clusters of COs synchronously
same time slot is reused by distant clusters (disjoint connectivity)
different time slots are used in case of overlaping clusters
Local transmissions e.g. for identification and connectivity estimation
transmitted by individual COs in parallel  interference-limited
an appropriate frequency reuse scheme may be implemented here
Volker Jungnickel (Fraunhofer HHI)
Edward Au (Marvell Semiconductor)

13. Global and local frames
May 2015
doc.: IEEE /0496r1
Global and local frames
Global frames
All COs send the same signal
Needs full synchronization
Local frames
Frames are orthogonal
Use orthogonal resources for adjacent COs
Use non-orthogonal resources for distant COs
Operated in interference- limited scenario
Volker Jungnickel (Fraunhofer HHI)
Edward Au (Marvell Semiconductor)

14. Regional frames Used for macro-diversity
May 2015
doc.: IEEE /0496r1
Regional frames
Used for macro-diversity
All COs in a cluster jointly transmit or receive the same signal on the same resource
Distant clusters (with no connectivity) transmit or receive different signals on the same resources
Overlapping clusters do the same but use different time slots or frequencies to avoid interference
Volker Jungnickel (Fraunhofer HHI)
Edward Au (Marvell Semiconductor)

15. What frame is local/regional/global?
May 2015
doc.: IEEE /0496r1
What frame is local/regional/global?
Beacon frame is global
Allow DEVs to synchronize to the whole network
Contains e.g. macOWPANId, MAC address of MC, feedback mode field, reduced superframe spec to advertise CAPs for network access
Medium access frame is typically regional
Transmitted as part of the data in a scheduled cluster
Spatial reuse is supervised by the MC based on connectivity
Multicell channel estimation frame is local
Contains orthogonal sequences to identify adjacent COs
Local information about the specific CO such as MAC address, reuse factor and optional sequence index
Sequences are reused by distant Cos
Volker Jungnickel (Fraunhofer HHI)
Edward Au (Marvell Semiconductor)

16. What frame is local/regional/global? (2)
May 2015
doc.: IEEE /0496r1
What frame is local/regional/global? (2)
Feedback frame is global or regional
As a global frame, FB is used for joining the network
Then it contains connectivity information and is transmitted in CAP
More complex feedback can be provided for scheduling/joint processing (applicable feedback mode is signaled in the beacon frame)
As a regional frame, it is used in a cluster to limit feedback overhead
Simultaneous transmissions take place in distant clusters
In overlapping clusters, transmissions take different time slots
Volker Jungnickel (Fraunhofer HHI)
Edward Au (Marvell Semiconductor)

17. Generic MAC procedures
May 2015
doc.: IEEE /0496r1
Generic MAC procedures
Beacon transmission
Beacon allows mobile devices to synchronize to the network
Moreover, it informs the device where CAPs are availabe for network access
Information is extracted from global superframe specification
Volker Jungnickel (Fraunhofer HHI)
Edward Au (Marvell Semiconductor)

18. Generic MAC procedures (2)
May 2015
doc.: IEEE /0496r1
Generic MAC procedures (2)
Multicell channel estimation
Enables measuring all channels from all COs
Done by all COs in dedicated resources
Overhead is reduced by spatial reuse
Pulsed Modulation PHY
Code-division multiplex (energy efficincy): different orthogonal code at each CO
Code length, codes+reuse assigned by MC
OFDM PHYs
Frequency-division multiplex: Comb of subcarriers, another comb shift for each CO
Carrier spacing, shift+reuse assigned by MC
Volker Jungnickel (Fraunhofer HHI)
Edward Au (Marvell Semiconductor)

19. Generic MAC procedures (3)
May 2015
doc.: IEEE /0496r1
Generic MAC procedures (3)
Feedback delivery
Mobile DEVs
Connectivity varies over time
Detected by the device by observing
i) the regular beacon frame
ii) the multi-cell channel estimation frame
In idle mode, the DEV sends a feedback frame during next CAP.
Before a DEV can start uplink transmission, it has to send a feedback frame, even if downlink connectivity was unchanged.
For continuous transmissions, feedback delivery happens in a CFP.
The feedback packet is fed forward by the CO(s) to the MC.
Volker Jungnickel (Fraunhofer HHI)
Edward Au (Marvell Semiconductor)

20. Generic MAC procedures (4)
May 2015
doc.: IEEE /0496r1
Generic MAC procedures (4)
Superframe Specification in parallel clusters
MC knows global connectivity and broadcasts global Superframe Spec
Regional Superframe Spec for the cluster is filtered out at the CO
Only the regional SF Specification is forwarded to the DEVs
This allows spatial reuse for both, control information and data
Volker Jungnickel (Fraunhofer HHI)
Edward Au (Marvell Semiconductor)

21. Generic MAC procedures (5)
May 2015
doc.: IEEE /0496r1
Generic MAC procedures (5)
Superframe Specification in parallel clusters
MC knows global connectivity and broadcasts global Superframe Spec
Regional Superframe Spec for the cluster is filtered out at the CO
Only the regional SF Specification is forwarded to the DEVs
This allows spatial reuse for both, control information and data
Volker Jungnickel (Fraunhofer HHI)
Edward Au (Marvell Semiconductor)

22. Available mechanisms in G.hn/TG13 D1
May 2015
doc.: IEEE /0496r1
Available mechanisms in G.hn/TG13 D1
Many mechanisms can be reused or mobile OWC operation, some t.b.d.
Selected examples
G.hn D1
Centralized scheduling
G , 8.3.1, coarse time slots only
T.b.d.
Synchronization
Time and frequency; yes, using MAPs, G
Time: yes, beacon periods, 5.1.7,
Frequency: T.b.d.
Random access
Yes, CBTXOPs in G.9961, ,
Yes, in CAP
QoS and traffic flows
Yes: G.9961, 8.6.2
Yes, in CFP
Channel Feedback
Yes: per user
Yes: per user, T.b.d.: per cell
Volker Jungnickel (Fraunhofer HHI)
Edward Au (Marvell Semiconductor)

23. How to build generic frames
May 2015
doc.: IEEE /0496r1
How to build generic frames
Beacon frame
Global transmission for synch, advertisement of the whole network
Bitwise equal for all COs at a specific time
Contains the assignment of CAPs for network access
Use very robust modulation and coding
Multicell channel estimation frame
Local transmission using orthogonal ressources
HCM can be used as orthogonal codes in Pulsed Modulation PHY
Subcarrier masks can be used in HB OFDM PHY to define comb
Channel between subcarriers in the comb is obtained by interpolation
Channel information can be used for precise localization by triangulation (additional protocol like ranging a.k.a. timing advance)
Volker Jungnickel (Fraunhofer HHI)
Edward Au (Marvell Semiconductor)

24. How to build generic frames (2)
May 2015
doc.: IEEE /0496r1
How to build generic frames (2)
Feedback frame
Transmitted by OWC DEVs in uplink direction
Using a „general purpose“ MLME frame with new primitive in a reserved GTS which contains management message
Uplink channel estimation can be part of the feedback frame, by adding orthogonal channel estimation sequence
Medium access frame / superframe specification frame
Informs devices about CAPs and GTSs
Contains regional information only, not the global superframe spec.
Transmitted on orthogonal ressource, to avoid interference with other clusters
Volker Jungnickel (Fraunhofer HHI)
Edward Au (Marvell Semiconductor)

25. How to build generic frames (3)
May 2015
doc.: IEEE /0496r1
How to build generic frames (3)
Macro diversity data frame
Macro diversity = signals transmitted/received by multiple COs („cluster“)
Clusters are preconfigured e.g. by using dedicated VLAN IDs for each cluster and dynamically selected using an appropriate control message protocol
MAC layer has the same data available at all COs: Data is classified and queued at MC and then broadcast to all COs in the cluster via the infrastructure network
Acknowledgements and retransmissions are also processed at the MC
This approach avoids/repairs packet losses during MAC-internal „handover“  high robustness, low latency for industrial wireless
Volker Jungnickel (Fraunhofer HHI)
Edward Au (Marvell Semiconductor)

26. DME in 802.15.7-2011 DME in 802.15.7-2011 is used for dimming control
May 2015
doc.: IEEE /0496r1
DME in
DME in is used for dimming control
Should be removed in
Volker Jungnickel (Fraunhofer HHI)
Edward Au (Marvell Semiconductor)

27. What functional split in 802.15.13?
May 2015
doc.: IEEE /0496r1
What functional split in ?
Optical SAP/PHY switch
Not defined as digital or analog?
Switch is part of PHY and so far controlled by PLME
Should become part of the MAC and (remotely?) controlled by MC
Concept should be revised in , needs more detailled substructure of MAC and PHY
Leverage previous work from
IEEE Radio over Ethernet (RoE)
IEEE 1914 on Next Generation Fronthaul Interface (NGFI)
Coordinator
Master
Coordinator
Analog
or digital
Fronthaul?
Volker Jungnickel (Fraunhofer HHI)
Edward Au (Marvell Semiconductor)

28. Summary A generic MAC layer is proposed for the coordinated topology.
May 2015
doc.: IEEE /0496r1
Summary
A generic MAC layer is proposed for the coordinated topology.
It is designed for the use of OWC in industrial wireless applications where high availability and low latency are required.
A distributed multiuser MIMO featuring macrodiversity and mobility support inside the MAC has been proposed.
MAC functions have been classified into global, regional and local ones, together with the associated frame structures.
Generic MAC procedures have been highlighted and explained how to build the corresponding frames.
TG13 needs a clearer view what MAC functions shall be centralized and what distributed, i.e. find a good functional split btw. MC and COs.
Volker Jungnickel (Fraunhofer HHI)
Edward Au (Marvell Semiconductor)

29. Possible functional splits
May 2015
doc.: IEEE /0496r1
Possible functional splits
NRT-RT
split
PHY-MAC
split
Volker Jungnickel (Fraunhofer HHI)
Edward Au (Marvell Semiconductor)