<month year> doc.: IEEE 802.15-09-0117-00-0007 July 2009 Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) Submission Title: [VLC MAC considerations based on TCD] Date Submitted: [16 July, 2009] Source: [Ying Li, Sridhar Rajagopal, Farooq Khan, Taehan Bae, Jaeseung Son, Eun Tae Won] Company [Samsung Electronics] Address [1301 E. Lookout Drive, Richardson, TX 75082, USA] Voice:[1-972-761-7903], FAX: [1-972-761-7909], E-Mail:[ yli2@sta.samsung.com] Re: [] Abstract: [MAC design considerations for VLC are discussed.] Purpose: [Contribution to IEEE 802.15.7 VLC TG] 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. Ying Li, Samsung Electronics <author>, <company>

Samsung MAC considerations based on TCD July 2009 Samsung MAC considerations based on TCD Application focus Indoor/Outdoor Infrastructure/Mobile 1- 100 Mbps Multiple topologies (Peer to peer/star) Mobility Uni/bi-directional/broadcast data transfer Ying Li, Samsung Electronics

Focus for presentation July 2009 Focus for presentation Band plan Guard colors Device discovery and capabilities MAC PDU types for data, dimming/visibility support Dimming support Rate adaptation Resource allocation Ying Li, Samsung Electronics

Band plan design for communicating supported channels July 2009 Band plan design for communicating supported channels Source: http://www.ecse.rpi.edu/~schubert/Light-Emitting-Diodes-dot-org/chap17/F17-03%20Chromaticity%20diagram%20(Gage).jpg Ying Li, Samsung Electronics

July 2009 Notes from CIE diagram Center colors are narrower in width than outer colors. Human eye is more sensitive to center colors pB, R occupy 100~200 nm while G occupies ~ 30 nm LED manufacturers make LEDs depending on human color perception and not frequency band => Non-linear widths needed for band plan Ying Li, Samsung Electronics

Human eye response to wavelength July 2009 Human eye response to wavelength Ying Li, Samsung Electronics

Proposed Band Plan (based on CIE diagram) July 2009 Proposed Band Plan (based on CIE diagram) Frequency band (nm) Spectral width (nm) Color Proposed Code 380 450 70 pB 000 510 60 B, BG 001 560 50 G 010 600 40 yG,gY, Y,yO,O 011 650 rO 100 710 R 101 780 110 Reserved 111 Red – popular LED for comm. Non-uniform distribution based on CIE diagram Human eye most sensitive to green color and visible LEDs are designed to match human eye sensitivity Provides support for up to 7 independent and parallel channels – can consider expansion to more channels Ying Li, Samsung Electronics

Bandplan issue: Leakage from other LED colors July 2009 Bandplan issue: Leakage from other LED colors Source: http://www.theledlight.com/technical3.html Ying Li, Samsung Electronics

White LED spectrum (Blue + Phosphor) July 2009 White LED spectrum (Blue + Phosphor) Blue LED (GaInN) Light sensitivity to human eye Yellow Phosphor yttrium aluminum garnet (YAG) – leakage if not used at RX Source: Maxim, Application Note 3070 : Standard and White LED Basics and Operation Ying Li, Samsung Electronics

July 2009 Need for guard colors Many LEDs (such as white) may not support saturated colors and may transmit in multiple bands Spectrum affected by leakage may be unusable For FDD mode, adjacent bands may be impacted by spectral leakage from own transmitter Significant variations in LED spectral width and peak wavelengths for different manufacturers and costs LED peak wavelength can change with forward current variations. Ying Li, Samsung Electronics

July 2009 Guard colors We define “guard color” channels for each channel used for transmissions. For every channel color, we define a list of guard colors that cannot be used simultaneously for TX or RX when that channel is in use for TX due to leakage. For example, white led (blue + phosphor) Color code : 001 Guard codes : 011, 100 The criteria used for defining a guard color channel could be based on out-of-band leakage, exceeding a certain value (for example, 10 -20 dB) over the in-channel value that causes a considerable loss in receiver sensitivity in those channels. The guard colors are defined on a per channel basis and could be also be defined as a N-bit number with a ‘1’ in the location where the channel cannot be used. Example: Guard colors (011,100) for 001 can be represented as: 00011000 Ying Li, Samsung Electronics

July 2009 Exchanging capabilities and channel selection during device discovery process Device 1 (host/master) Device 2 Transmit on M1 channels Send channel colors supported, guard channels, application requirements Exchange capabilities Device 1 – M1 colors Device 2 - M2 colors K = M1 ∩ M2 – common colors CQI – Color Quality Indicator report Transmit on K channels Send channel colors supported, guard channels, application requirements Send RX CQI report for K channels Send TX CQI report for K channels Channel selection Inform channel(s) used for TX and RX and access (TDD/FDD) Data transfer on agreed channel(s) Ying Li, Samsung Electronics

Capabilities Information Element for device discovery July 2009 Capabilities Information Element for device discovery PHY capabilities: Colors supported Data rates Guard colors for each supported color MAC capabilities: Uni-directional traffic support Bi-directional traffic support P2P support P2MP support Dimming support Visibility support Ying Li, Samsung Electronics

Two types of MAC PDU MAC packet data unit (PDU) July 2009 Two types of MAC PDU MAC packet data unit (PDU) Regular PDU, for Data/Signaling Padding PDU, for Visibility support The padding PDUs can be used for other purposes, such as the channel quality measurement. Ying Li, Samsung Electronics

Visibility/Dimming Support July 2009 Visibility support Visibility of the beam can be used to assist pointing and device alignment Addition to VLC data/signaling, visibility padding can be used to support the visibility The pattern of visibility support can be adaptive so that the blinking can be an indicator of the link quality Dimming support Infrastructure may have dimmers Dimming padding duty cycle should match up the dimmer requirements Visibility padding can be treated as a special case of dimming padding Ying Li, Samsung Electronics

Infrastructure VLC Device VLC when Dimming July 2009 Dimming cycle patterns of infrastructure should be notified to VLC RX device, so that the VLC device could adapt to the dimming pattern Infrastructure VLC may receive a dimming request from a dimmer triggered by user Propose to use a link adaptation timer that delays the time between the dimming request and the actual dimming of the light source. With this knowledge of an incoming dimming, the link between the devices can be adapted to work at a new (lower) data rate (if dimmed) without requiring the link to be interrupted or possible link failure. Infrastructure VLC Device VLC Device User Dimmer Link adaptation and communication Dim light Dimming request Dimming pattern. Updated scheduling & resource allocation due to dimming Link adaptation timer Uninterrupted communication with adapted link Actual dimming Ying Li, Samsung Electronics

Rate Control/Adaptation July 2009 Rate Control/Adaptation To maximize the throughput and to provide the flexibility of transmission rate, the transmission rate control is needed. The transmission rate is adaptively adjusted according to the channel quality. Schemes to support rate control The data rate supported can be indicated, e.g., in the frame header The transmission rate can be estimated from the channel quality which can be measured/estimated by, e.g., the preambles used for synchronization the padding for the visibility/dimming Ying Li, Samsung Electronics

QoS provision: Resource Allocation for Various Traffic July 2009 QoS provision: Resource Allocation for Various Traffic Schemes for resource request Real-time, fixed size: use pre-allocated resource Real-time, variable size data: use real-time polling, periodically Non real-time with different priorities: use non-real-time polling, regularly, even during congestion. Best effort data: if there is no polling resource available, use contention based resource request. Ying Li, Samsung Electronics

July 2009 Summary Band plan supporting 7 independent color channels proposed (can consider more channels) Guard colors proposed for interference mitigation due to leakage Two MAC PDU types defined for data and visibility/dimming Link adaptation notification and timer for dimming Ying Li, Samsung Electronics