September, 2005 Doc: IEEE a Zhen, Li, Kohno (NICT) SlideTG4a1 Project: IEEE P Working Group for Wireless Personal Area Networks (WPANs) Submission Title: [MAC enhancement to support ranging] Date Submitted: [Sept., 2005] Source: [Bin Zhen, Huan-Bang Li, Ryuji Kohno, Company: National Institute of Information and Communications Technology ] Contact: Bin Zhen Voice: , Abstract: [UWB MAC enhancement ] Purpose: [discussion ] Notice:This document has been prepared to assist the IEEE P 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 P

September, 2005 Doc: IEEE a Zhen, Li, Kohno (NICT) SlideTG4a2 MAC enhancement to support ranging Bin Zhen, Huan-Bang Li, and Ryuji Kohno National Institute of Information and Communications Technology (NICT)

September, 2005 Doc: IEEE a Zhen, Li, Kohno (NICT) SlideTG4a3 Requirements Requirements from ranging –No interruption and corruption Ranging response should be as fast as possible to reduce error Hidden nodes –Ranging need some data communication E.g. response delay, crystal offset –Special ranging operation Leading edge detection of preamble Accuracy timing Requirements on network –Do not break MAC architecture MAC should control channel access. PHY do not know frame structure. –GTS is optional

September, 2005 Doc: IEEE a Zhen, Li, Kohno (NICT) SlideTG4a4 Virtual carrier sense Virtual carrier sense (virtual CS) is provided by MAC –“Virtual CS is achieved by distributing reservation information announcing the impending use of the media” –Physical CS is provided by PHY The mechanism of virtual CS is network allocation vector (NAV) –the NAV maintains a prediction of future traffic on media based on duration information announced in RTS/CTS handshake –The NAV can be considered as a counter, which count down to zero at uniform rate. When the counter is zero, the Virtual CS indicate the media is free Easy to be implemented

September, 2005 Doc: IEEE a Zhen, Li, Kohno (NICT) SlideTG4a5 Virtual CS in sensor network Virtual CS has been simulated and implemented in sensor network –Sensor MAC (over Mote by USC) –EYES project –PAMAS (power aware) Virtual CS benefits energy efficiency of sensor node by reducing –packet collision due to hidden node –overhearing when neighbour talks –interleaving during message passing

September, 2005 Doc: IEEE a Zhen, Li, Kohno (NICT) SlideTG4a6 Ranging based on virtual CS Using virtual carrier to reserve media for ranging and indicate start of ranging –Ranging can be considered as a special group of long data transmission Virtual carrier sense is MAC atomic Virtual CS –RNG_RTS/RNG_CTS –RNG_INV (ranging by invitation)

September, 2005 Doc: IEEE a Zhen, Li, Kohno (NICT) SlideTG4a7 TWR through RNG_RTS/RNG_CTS Ranging initiator Ranging responder RNG_RTS RNG_CTS Ranging frame Ranging data ACK (if requested) Ranging Window (Reserved period) Contention period Other nodes NAV(RNG_RTS) NAV(RNG_CTS) PHY control period MAC control period Handshake period SIFS SIFS/LIFS

September, 2005 Doc: IEEE a Zhen, Li, Kohno (NICT) SlideTG4a8 Frame formats Frame control Rng. initiator addr. Rng. responder addr. FCS RNG_RTS Rng. duration Frame control FCS RNG_CTS Rng. preamble format Rng. duration Rng. responder addr. SS0-S 0 SSSSS 0.5, 1 or 4 (ms) Ranging frame synchronization Channel estimation Frame delimiter Ranging data Seq. number Seq. number Frame control FCSAddress field Seq. number MHRMSDU Resp. delay Relative crystal offset

September, 2005 Doc: IEEE a Zhen, Li, Kohno (NICT) SlideTG4a9 Period divisions RNG_RTS/RNG_CTS handshake period –To reserve un-interruptible and collision-free channel access for ranging between pair of nodes Other nodes enter power save mode after receiving either of RNG_RTS/RNG_CTS –To negotiate ranging parameters Preamble type (short, middle and long) Duration of ranging window –To start ranging procedure enable ranging counting and first-arrival detection enable PHY channel control Ranging window –Between ranging preamble and ACK of ranging data

September, 2005 Doc: IEEE a Zhen, Li, Kohno (NICT) SlideTG4a10 Periods division (cont.) PHY control period –To measure flying time through ranging frame exchange without MAC awareness. –PHY generates ranging frame directly No data payload MAC control period –To send ranging data through normal data communication from responder to initiator –MAC generate MAC header (MHR) and MAC service data unit (MSDU) –Ranging data includes Response delay: between the end of injected ranging frame and the start of outgoing ranging frame Relative crystal offset estimate

September, 2005 Doc: IEEE a Zhen, Li, Kohno (NICT) SlideTG4a11 MSC of TWR using RNG_RTS/RNG/CTS Ranging originator Ranging responder Higher layerMACPHY MACHigher layer TWR request RNG_RTS RNG_CTS TWR indication TWR response ranging ready (rep.)ranging ready (ini.) Ranging frame Response delay (T2) Round-trip delay T1 Response delay (T2), Crystal offset ACK (if requested) TWR confirm Media reservation duration; Ranging frame; Leading edge detection; Counter d= c*(T1-T2)/2 TWR indication TWR end state Reserved period

September, 2005 Doc: IEEE a Zhen, Li, Kohno (NICT) SlideTG4a12 Channel access RNG_RTS/RNG_CTS handshake –Normal CSMA with backoff before transmission Ranging window –Both initiator and responder have no carrier sense during the ranging window All intervals between packets are SIFS –Other nodes sense a busy channel virtually or physically during the whole window

September, 2005 Doc: IEEE a Zhen, Li, Kohno (NICT) SlideTG4a13 Recovery procedure RNG_RTS/RNG_CTS handshake error –Failure of receiving RNG_CTS response trig retransmission of RNG_RTS Ranging must be finished within ranging window –No retransmission mechanism in the ranging window –Failure of receiving the expected response means the early end of ranging Ranging frame, ranging data packet and ACK The receiver of the destined node will cancel the next transmission

September, 2005 Doc: IEEE a Zhen, Li, Kohno (NICT) SlideTG4a14 Before ranging operation Ranging initiator and responder must join the same piconet, so that both of them know each other –Address Device address/associate short address –Node capability information power source, security, FFD/RFD, receiver idle –Ranging attributes Ranging window Ranging support, coherent/non-coherent receiver, or short/middle/long preamble –Security parameters Encryption and authentication

September, 2005 Doc: IEEE a Zhen, Li, Kohno (NICT) SlideTG4a15 TWR through RNG_INV Ranging initiator Ranging responder RNG_INV Ranging frame Ranging data ACK (if requested) SIFS Ranging Window (Reserved period) Contention period Other nodes NAV(RNG_BINV) PHY control period MAC control period Handshake period SIFS/LIFS

September, 2005 Doc: IEEE a Zhen, Li, Kohno (NICT) SlideTG4a16 Protocol description Normal CSMA and backoff before transmission of RNG_INV from responder RNG_INV is impliedly acknowledged by ranging frame –Initiator sends ranging frame after SIFS if channel is sensed idle –Failure of receiving ranging frame from initiator trigs re- transmission of RNG_INV with backoff Operations in the ranging window is the same as those in TWR through RNG_RTS/RNG_CTS RNG_INV Frame control Rng. initiator addr. Rng. responder addr. FCS Rng. duration Rng. preamble format Seq. number MHRMSDU

September, 2005 Doc: IEEE a Zhen, Li, Kohno (NICT) SlideTG4a17 MSC of TWR using RNG_INV Ranging originator Ranging responder Higher layerMACPHY MACHigher layer TWR request RNG_INV TWR indication TWR response ranging ready (rep.) ranging ready (ini.) Ranging frame Response delay (T2) Round-trip delay T1 Response delay (T1), Crystal offset ACK (if requested) TWR confirm Media reservation duration; Ranging frame; Leading edge detection; Counter d= c*(T1-T2)/2 TWR indication TWR end state Reserved period

September, 2005 Doc: IEEE a Zhen, Li, Kohno (NICT) SlideTG4a18 Performance Both RTS/CTS and BI are original proposed to solve hidden nodes issue –They can be used to reserve channel because of collision free property –Applying them to ranging can be considered as a special case Sender or receiver initiated ranging –RNG_INV suppresses RNG_RTS part of RNG_RTS/RNG_CTS handshake. This reduces turn-around overhead and improves channel and power efficiency UWB channel is not suitable to transmit short data due to long synchronization time

September, 2005 Doc: IEEE a Zhen, Li, Kohno (NICT) SlideTG4a19 Analyzed system parameters Real system of TWR –Data rate: 1Mbps –Ranging frame: 250 byte (1ms) –MAC command frame: 25 bytes (0.1ms) –Piconet range: 60m Normalized parameters –propagation delay= 1e-4; (0.2μs) –Normalized handshake= 0.1; 2% hidden traffics Non-persistence ranging operation 2 ^n backoff if channel is sensed busy

September, 2005 Doc: IEEE a Zhen, Li, Kohno (NICT) SlideTG4a20 Performance criteria Normalized throughput Good ranging latency –time delay to the first trial after last good ranging –Latency= (2^number_of_transmission-1)* backoff_unit-1 Ranging trial per good ranging Power consumption per good ranging –CSMA_power= ranging_trials* transmission_probability*range_frame –Handshake_power = ranging_trials* transmission_probability*handshake_frame + ranging frame

September, 2005 Doc: IEEE a Zhen, Li, Kohno (NICT) SlideTG4a21 Network throughput Single hop

September, 2005 Doc: IEEE a Zhen, Li, Kohno (NICT) SlideTG4a22 Power consumption per good ranging

September, 2005 Doc: IEEE a Zhen, Li, Kohno (NICT) SlideTG4a23 Ranging trials per good ranging

September, 2005 Doc: IEEE a Zhen, Li, Kohno (NICT) SlideTG4a24 Delay per good ranging

September, 2005 Doc: IEEE a Zhen, Li, Kohno (NICT) SlideTG4a25 Security consideration Separated ranging request, ranging operation and ranging data transmission –Handshake and ranging data are controlled by MAC –TWR is controlled by PHY No information payload in ranging frame Only MAC security mechanism is OK –Authentication before ranging handshake Ranging information can be used for verification of the claimed position

September, 2005 Doc: IEEE a Zhen, Li, Kohno (NICT) SlideTG4a26 Complexity analysis IEEE already define GTS in a superframe –Data transmission in CAP must be finished before start of GTS –Data transmission in GTS must be finished before end of GTS slot NAV computing is already available –Not much increased complexity in device

September, 2005 Doc: IEEE a Zhen, Li, Kohno (NICT) SlideTG4a27 TDOA ranging modes Key: Sync Pulse Location Pulse TDOA backhaul Mode 2 - Active controller reference node Key: Sync Pulse Location Pulse Position Report Mode 1 - Passive controller reference node SOI

September, 2005 Doc: IEEE a Zhen, Li, Kohno (NICT) SlideTG4a28 Applying virtual CS to TDOA Reference nodes must be precise clock-wise synchronized The basis of TDOA is OWR –Only PHY control period in the ranging window –No ranging data Before ranging, SOI must join same piconet with reference nodes Group RNG_INV for mode 1 Frame control Ref. node 1 addr. FCS Rng. duration Rng. preamble format Seq. number MHRMSDU Ref. node 2 addr. Ref. node 3 addr. RNG_INV for mode 2 Frame control SOI addr. FCS Rng. duration Rng. preamble format Seq. number MHRMSDU

September, 2005 Doc: IEEE a Zhen, Li, Kohno (NICT) SlideTG4a29 TDOA mode 1 Mobile node knows position SOI reserve channel using group RNG_INV TDOA mode 1 can be separated into 3 SWR which send ranging frame with defined interval (SIFS) –Only the invited reference nodes send ranging frames –SOI knows the defined interval between ranging frames before ranging Reference node SOI RNG_INV Ranging preamble SIFS Ranging window (PHY control period) Handshake period SIFS/LIFS

September, 2005 Doc: IEEE a Zhen, Li, Kohno (NICT) SlideTG4a30 TDOA mode 2 Network knows position One of the reference nodes sends RNG_INV –Master reference node RNG_INV Ranging preamble SIFS Contention period Handshake period SIFS/LIFS Reference node SOI Ranging window (PHY control period)

September, 2005 Doc: IEEE a Zhen, Li, Kohno (NICT) SlideTG4a31 Conclusions Virtual CS can be used to support ranging –Separate of TOA/TDOA measurement and ranging calculation Ranging data is managed by MAC Ranging preamble is controlled by PHY Ranging data can be protected by MAC security mechanism –Sender/receiver initiated ranging RNG_INV is better due to less handshake Support both TWR and SDS-TWR Benefits –Little disadvantage by introducing handshake mechanism –Separated ranging operation and communication operation Backward compactable with 15.4 MAC –Can be used in both beacon and non-beacon network