Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs)

1. Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) Submission Title: [Traffic-based Wake-up Mechanisms for WBAN] Date Submitted: [January, 2009] Source:[Kyung sup Kwak1, M.A. Ameen1, Sana Ullah1, SeokHo Kim1,Xizhi An1, Bumjung Kim1, Jaewook Kwak1 , Youjin Kim2,Youngwoo Choi2, Hyungsoo Lee2, Jaeyoung Kim2] Company [Inha University1, Electronics and Telecommunications Research Institute (ETRI)2] Address [428 Hi-Tech, Inha University, 253 Yonghyun-dong, Nam-gu, Incheon, 402-751, Republic of Korea]1,[ETRI, 161 Gajeong-dong, Yuseong-gu, Daejeon, 305-700, Republic of Korea]2 Voice:[], FAX: [], E-Mail:[kskwak@inha.ac.kr(other contributors are listed in “Contributors”slides)] Re: [] Abstract: [We propose a low-power wake-up mechanism based on the wake-up patterns of sensor nodes. We further provide an innovative solution towards the reliable communication of on-demand and emergency traffics using wake-up radio] Purpose: [To be considered in IEEE 802.15.6] 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. <ETRI>, <Inha Univ.>

2. Contributors

3. Introduction • Energy waste in Sensor Networks • Idle Listening • Collision • Overhearing • Over-emitting • Others • Suitable wake-up mechanisms can save significant amount of energy in Wireless BAN and increase the network lifetime. • Device wake-ups only when necessary, otherwise it sleeps thereby saving energy. • Coordinated and controlled data transmission can reduce energy consumption. Table 1. Power Characteristics for a Mica2 Mote Sensor [2]

4. WBAN Traffic Classification • Data traffic in a WBAN is classified into: • Normal traffic: Based on normal operation between device and coordinator using a defined patterns. • On-demand traffic: Initiated by Coordinator to know certain information. • Emergency traffic: In case of critical condition. MAC Mapping Gather Information Normal traffic Send Classification On-demand traffic Emergency traffic Fig 1. Traffic classification in a WBAN

5. Features of WBAN Devices • BNC: BAN Netwotk Coordniator • On AC power supply • It can wake-up all the time. • It can support normal, emergency, and on-demand traffics. • On battery power supply • It has certain limitations and should adopt low-power scavenging techniques. • It should calculates its own wake-up pattern based on the BN’s wake-up patterns. • It should maintain the traffic-based wake-up table. • BN: BAN Node(Device) • They are operating on limited power and support a default normal wake-up state. • Wake-up and sleep according to traffic-based wake-up table. • BN wake-ups upon receiving an ‘on demand’ request from a BNC. • BN wakes-ups by itself to handle emergency events.

6. WBAN Characteristics: Traffic & Device • A network consists of low-power invasive and non-invasive BNs . • BNs can be • Full functional: When deal with Multi-Phys. • Reduced functional: Mostly in the in-body networks. • One WBAN device is selected as a BNC. • One-hope coverage range is around 3m. • The traffic characteristic in a WBAN vary low to high with periodic or non-periodic, and vice versa. • The dynamic natures of BNs does not urge synchronized periodic wake-up periods • Communication flows: • Normal Traffic: • BNs BNC • Emergency Traffic: • BNs BNC • On-Demand Traffic: • BNC BNs • BNs BNs Fig 2. WBAN Characteristics

7. Wake-up States • Sleep State: • Default state of BNs. • Wake-up State: • Normal Wake-up State • Based on the traffic-based wake-up pattern maintained by the BNC. • On-demand Wake-up State • Initiated by BNC. • BNC can wake up any BN with an ‘on demand’ request instead of waiting for its wake-up pattern. • Emergency(Self) Wake-up State • To handle time critical events • Initiated by BNs. • BNs are triggered to handle emergency events.

8. Proposed Wake-up Solution Table 2. A wake-up solution to the heterogeneous traffic in a WBAN Traffic Device Normal Traffic: A traffic-based wake-up table is used to handle the normal traffic requirements in a WBAN Emergency and On-Demand Traffic: A Wake-up by radio concept is used to accommodate emergency and on-demand traffics in a reliable manner.

9. Wake-up by Traffic-Based Patterns(1) • Each BN has a wake-up pattern. • The initial wake-up pattern is pre-defined (by the company) or created and modified (by the BNC). • The wake-up patterns indicate the traffic nature of BNs. • The patterns are subjected to change at anytime by the BNC. • Each BN repeats its pattern in multiple number of superframe size(x). Table 2. An example of a traffic-based wake-up table • Y is a wake-up pattern of the BNC and is based on wake-up patterns of BNs

10. Wake-up by Traffic-Based Patterns(2) • BNs repeat their wake-up patterns in a periodic manner. • The traffic levels are classified into high, medium, and low for example • BNs having frequent wake-up patterns are designated as high traffic nodes. • BNs with the same wake-up patterns contend for the channel. • In case of TDMA, • the wake-up patterns represent the corresponding data slots • The data slots are active according to wake-up patterns, i.e, 10 * x would allow to use the BN-1 TDMA data slot after 10 TDMA super frames. 10 * x 10 * x 10 * x 10 * x BN-1 18 * x 18 * x BN-2 43 * x BN-3 9 * x 9 * x 9 * x 9 * x BN-4 Fig 3. Superframe based Wake-up Patterns Wake-up Contention

11. WBAN Device Wake-up radio circuit Other Circuits Wake-up by Radio: Concept • Wake-up Radio Concept • Radio-triggered hardware component in sensor devices. • Wake-up radio can be adopted in a WBAN. • Wake-up radio signal contains enough energy to trigger a wake-up process [1]. • Hardware Implementation • Extremely low-power detection circuit in WBAN devices. • Wake-up radio circuit is on all the time, while all other circuits can be switched off when sensor device is sleeping. Fig 1. Typical WBAN device

12. Wake-up by Radio for On–demand/Emergency • Two Radio channels • Primary Radio: for sending data and control packets. • Wakeup Radio: To wake-up WBAN devices. • How to wake-up a Device? • Directed wake-up using multiple frequency support • Hardware costs for using multiple frequency support is fairly low [1]. • Unique frequency can be used by subdividing it. • Broadcast wake-up tone • Directed wake-up tone without Power source

13. Summary • The traffic is mainly classified into normal, emergency, and on-demand traffics. • A traffic-based wake-up technique is proposed to handle the normal traffic requirements. • The BN’s wake-up patterns are used to predict the BNC’s wake-up pattern. • A wake-up radio concept is used to accommodate the emergency and on-demand traffics. • This hybrid approach provides innovative solution towards low-power and reliable communication in a WBAN. • Future work includes the design and implementation of the proposed solutions.

14. References • Gu, L. and Stankovic, J. A. 2005. Radio-Triggered Wake-Up for Wireless Sensor Networks. Real-Time Syst. 29, 2-3 (Mar. 2005), 157-182 • Miller, M.J.; Vaidya, N.H., "A MAC protocol to reduce sensor network energy consumption using a wakeup radio," IEEE Transactions on Mobile Computing, vol.4, no.3, pp. 228-242, May-June 2005