doc.: IEEE 802.15-<doc#> <month year> doc.: IEEE 802.15-<doc#> SEP 2007 Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) Submission Title: [performance-analysis-reservation-based-low-power-function] Date Submitted: [September 18, 2007] Source: [Chang Sub Shin*, Gangja Jin*, Yuan Dao**, Yoh-Han Lee**, SeungHyun Whang**] Company [*ETRI, **SNR Inc] Address [161 Gajeong-dong Yuseong-gu, Daejeon, Korea] Voice:[+82-42-860-1668], FAX: [+82-42-869-1712], E-Mail:[shincs@etri.re.kr] Re: [] Abstract: [performance analysis for reservation-based-low-power-function in low rate WPAN mesh.] Purpose: [to discuss low power function] 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. <Chang Sub Shin>, <ETRI> <author>, <company>

May 2007 Performance Analysis of Reservation based Low Power Function (Low Power Support for low-rate IEEE802.15.5) ChangSub Shin*, Gangja Jin*, Yuan Dao**, Yoh-Han Lee**, Seung-Hyun Whang** * ETRI, ** SNR Inc <Chang Sub Shin>, <ETRI>

doc.: IEEE 802.15-<doc#> <month year> doc.: IEEE 802.15-<doc#> May 2007 Contents Overview of previous proposal Additional issue Time synchronization MAC PIB value Frame Format Performance Analysis Implementation result of synchronization Implementation result of low power function Reference of performance analysis <Chang Sub Shin>, <ETRI> <author>, <company>

Overview of previous proposal - 1 <month year> doc.: IEEE 802.15-<doc#> May 2007 Overview of previous proposal - 1 Synchronous and Reservation method for end-to-end multi-hop transmission Consist of active period and sleep period If a node have a packet, It transmit its REQ control packet in active period and then transmit data in sleep period REQ control packet : inform next node to transmit and prevent other neighbor node’s transmission RSP control packet : respond to REQ or RSP sender and inform next hop node to transmit <Chang Sub Shin>, <ETRI> <author>, <company>

For one-hop unicasting <month year> doc.: IEEE 802.15-<doc#> May 2007 For one-hop unicasting Other neighbor nodes Listen Sleep Sleep Data REQ RSP Sender node (A) Sleep Ack Frame Data REQ RSP Destination node (B) Sleep RSP Other node (C) Listen Sleep Sleep Other node (D) Listen Sleep Listen Period Sleep Period Duty Cycle <Chang Sub Shin>, <ETRI> <author>, <company>

For broadcasting or multicasting <month year> doc.: IEEE 802.15-<doc#> May 2007 For broadcasting or multicasting Listen Sleep Data Sender node (A) Sleep Data Neighbor node #1 Sleep Data Neighbor node #2 Sleep Data Neighbor node #3 Sleep Listen Period Sleep Period Duty Cycle <Chang Sub Shin>, <ETRI> <author>, <company>

for multi-hop unicasting <month year> doc.: IEEE 802.15-<doc#> May 2007 for multi-hop unicasting other neighbor nodes Listen Sleep Sleep Data (1) REQ RSP Sender node (A) Sleep Sleep Data Data (2) REQ RSP RSP 1st Forward node (B) Sleep Sleep Data Data (3) RSP RSP RSP 2nd Forward node (C) Listen Sleep Listen Sleep Data Listen RSP RSP Destination node (D) Sleep Listen Sleep Ack Frame Listen Period Sleep Period Duty Cycle <Chang Sub Shin>, <ETRI> <author>, <company>

Multi-hop low power and minimum end-to-end latency <month year> doc.: IEEE 802.15-<doc#> May 2007 Multi-hop low power and minimum end-to-end latency <Chang Sub Shin>, <ETRI> <author>, <company>

doc.: IEEE 802.15-<doc#> <month year> doc.: IEEE 802.15-<doc#> May 2007 Contents Overview of previous proposal Additional issue Time synchronization MAC PIB value Frame Format Performance Analysis Implementation result of synchronization Implementation result of low power function Reference of performance analysis <Chang Sub Shin>, <ETRI> <author>, <company>

Time synchronization - methods <month year> doc.: IEEE 802.15-<doc#> May 2007 Time synchronization - methods Using MAC Primitive with timestamp value MCPS-DATA.confirm : transmitted time MCPS-DATA.indication : received time Methods Method 1 : unicast 3 way message exchange Method 2 : broadcast 3 way message exchange Method 3 : 2 successive synch packet broadcast Method 4 : 1 synch packet broadcast <Chang Sub Shin>, <ETRI> <author>, <company>

Timestamp of IEEE802.15.4 Timestamp of IEEE802.15.4 Length : 3 bytes Unit : 16 us (1 symbol) Maximum interval : 4.5 minutes Timestamp interrupt signal timing in PPDU frame Timestamp interrupt Signal timing <Chang Sub Shin>, <ETRI>

Time synchronization – method 1 B T1 T4 A (1) (2) (3) with T1, T4 time value B (4) Synch with A’s timer T2 T3 <Chang Sub Shin>, <ETRI>

Time synchronization – method 2 B C D TA4-TC3 TA4-TD3 TA1 TA4-TB3 (5) with TA1, TA4-TB3, TA4-TC3, TA4-TD3 time value A (1) (2) B (6) Synch with A’s timer (3) TB2 TB3 C (6) Synch with A’s timer TC2 TC3 (4) D (6) Synch with A’s timer TD2 TD3 <Chang Sub Shin>, <ETRI>

Time synchronization – method 3 TA1 TA2 A A (1) (2) with TA1 time value B (3) Synch with TA1 and TB1 TB1 TB2 B C D C (3) Synch with TA1 and TC1 TC1 TC2 D (3) Synch with TA1 and TD1 TD1 TD2 <Chang Sub Shin>, <ETRI>

doc.: IEEE 802.15-<doc#> <month year> doc.: IEEE 802.15-<doc#> May 2007 MAC PIB value Default MAC PIB during Listen period macMaxCSMABackoffs = 4 macMinBE = 3 Temporal MAC PIB during Sleep period macMaxCSMABackoffs = 2 macMinBE = 0 using MLME-SET.request primitive to change value <Chang Sub Shin>, <ETRI> <author>, <company>

doc.: IEEE 802.15-<doc#> <month year> doc.: IEEE 802.15-<doc#> May 2007 Frame Format <Chang Sub Shin>, <ETRI> <author>, <company>

doc.: IEEE 802.15-<doc#> <month year> doc.: IEEE 802.15-<doc#> May 2007 Contents Overview of previous proposal Additional issue Time synchronization MAC PIB value Frame Format Performance Analysis Implementation result of synchronization Implementation result of low power function Reference to performance analysis <Chang Sub Shin>, <ETRI> <author>, <company>

Test environment of time synch - 1 (1) (2) (3) (4) 1 2 3 4 Coordinator Level 1 Level 2 Level 3 Level 4 Time synch event node Time synch event node <Chang Sub Shin>, <ETRI>

Test environment of time synch - 2 <Chang Sub Shin>, <ETRI>

Test environment of time synch - 3 Hardware platform MCU : MSP430 RF : CC2420 Oscillator max skew : 20 ppm Synch packet interval every 8 second test every 3 minute test test packet interval Every 1.1 second test test result graph y-axis is sync error in microsecond unit, x-axis is in 1.1 second unit <Chang Sub Shin>, <ETRI>

Test scenario Multi-hop time synch procedure Synch error measurement Coordinator send synch packet to level 1 node. Level 1 node receiving synch packet will forward it to next level Subsequently, every each level nodes receiving synch packet will forward it to next level. Synch error measurement Periodical multi-hop time synch procedure Event node broadcast event packet to simulate an event happen at a certain time(every 8s and every 4 min) All nodes including coordinator receive the broadcast packet at the same time, and send receiving timestamp back to event node. Event node prints out the timestamps via RS232 for synch error analysis <Chang Sub Shin>, <ETRI>

Synchronization error synchronization error (8s interval) Synchronization error Level 1 2 3 4 Average 2.402421899 7.057598256 -7.799226682 2.58150687 Standard deviation 7.921770027 12.98050122 15.21630921 16.99547838 <Chang Sub Shin>, <ETRI>

Absolute synchronization error absolute synchronization error (8s interval) Absolute synchronization error Level 1 2 3 4 Average 5.577437958 11.0882997 11.1094596 12.02914079 Standard deviation 6.110296955 9.752664839 12.98999719 12.26216156 Maximum 49.594659 69.464314 98.394532 82.498808 <Chang Sub Shin>, <ETRI>

synch error analysis (8second interval) error unit is us synch packets are sent every 8 seconds, and event samples are taken every 1.1 second. Theoretically, average synch error should be zero, but the skew difference will cause the average synch error deviate from zero. the standard deviation of synch error which reflects the jitter tells more about the synch accuracy. It shows the synch error is accumulated every hop. <Chang Sub Shin>, <ETRI>

synchronization error (4minutes interval) <Chang Sub Shin>, <ETRI>

synchronization error (4minutes interval) <Chang Sub Shin>, <ETRI>

synch error analysis (4minutes interval) <month year> doc.: IEEE 802.15-<doc#> May 2007 synch error analysis (4minutes interval) The difference on clock skew will slowly take effect when synch interval increases. Once synch packet is sent, synch errors reduce to zero. When time passes, each local timers of the nodes in each level increases at a slightly different rate. This rate uncertainty is caused by the frequency uncertainty of crystal oscillator which is 20 ppm according to the datasheet. In the following picture, node3 is slower than the coordinator, and other nodes are faster than coordinator at different speed. It’s possible to use skew compensation to reduce the long term drift effect caused by skew difference. But it requires extra computation overhead.  However, if the synchronization interval is very small, the synch error caused by the skew uncertainty can be negligible <Chang Sub Shin>, <ETRI> <author>, <company>

Test environment of low power function Test value Chain topology based 4 nodes test 5% Duty Cycle Period : 500, 1000, 2000, 5000 msec (4 cases)  2.5% Duty Cycle Period = 1000, 2000, 5000 msec (3 cases) procedure of multi-hop low power function Periodical multi-hop time synch procedure All nodes make synch Source node generate packet measurement Every node have timer for power consumption measurement Calculate active time and sleep time Result : end-to-end delay, power consumption <Chang Sub Shin>, <ETRI>

Implementation result of low power function - 1 <month year> doc.: IEEE 802.15-<doc#> May 2007 Implementation result of low power function - 1 <Chang Sub Shin>, <ETRI> <author>, <company>

Implementation result of low power function -2 <month year> doc.: IEEE 802.15-<doc#> May 2007 Implementation result of low power function -2 <Chang Sub Shin>, <ETRI> <author>, <company>

Reference of performance analysis - 1 Refer to “Li, J., Blake, C., Couto, D., Lee, H.I., Morris, R.: Capacity of ad hoc wireless networks. In: ACM MobiCom (2001)” MAC interference among a chain of nodes. The solid-line circle denotes a node’s valid transmission range. The dotted-line circle denotes a node’s interference range. Node 4’s transmission will corrupt node 1’s transmissions at node 2. Effective capacity of a forwarding chain topology becomes just 1/3 of the effective capacity of a single-hop connection <Chang Sub Shin>, <ETRI>

Reference of performance analysis - 2 Refer to “Tony Sun, Ling-Jyh Chen, Chih-Chieh Han, Guang Yang and Mario Gerla: Measuring effective capacity of IEEE 802.15.4 beaconless mode” Results on Multihop forwarding chain testbed effective end-to-end capacity of a chain topology decreases as the hop length increases <Chang Sub Shin>, <ETRI>