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

Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) Submission Title: [ BOP Location Considerations and Beacon Scheduling for Backward Compatibility to Legacy IEEE 802.15.4 Devices ] Date Submitted: [20 July , 200 6]

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

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  1. Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) Submission Title: [BOP Location Considerations and Beacon Scheduling for Backward Compatibility to Legacy IEEE 802.15.4 Devices] Date Submitted: [20 July, 2006] Source: [Ho-In Jeon (1) and Yongsik Shin(2)] Company: [Dept. Electronic Engineering, Kyung-Won University (KWU) and HNTC of IITA (1), SKtelecom (2)] Address: [San 65, Bok-Jung-Dong, Sung-Nam-Shi, Kyung-Gi-Do, Republic of Korea] Voice 1: [ +82-31-753-2533], Voice 2:[ +82-19-9101-1394] FAX: [+82-31-753-2532], E-Mail: [jeon1394@kornet.net] Re: [This work has been supported by HNRC of IITA, Korea.] Abstract: [This document proposes a routing algorithm for efficient real-time network address allocation mechanisms based on LAA concept in a Mesh Network.] Purpose: [Technical Contributions on the IEEE 802.15.5 Standard] 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. Ho-In Jeon (KWU) and Yongsik Shin (Sktelecom)

  2. BOP Location Considerations and Beacon Scheduling for Backward Compatibilityto Legacy IEEE 802.15.4 Devices Ho-In Jeon (1), and Yongsik Shin (2) (1) Kyung-Won University, HNRC of IITA Republic of Korea, and (2) SKtelecom Ho-In Jeon (KWU) and Yongsik Shin (Sktelecom)

  3. Contents • Issues of Mesh Networks • A Mesh Network Architecture • Beacon Scheduling Fundamentals with BOP Concept • Position Change of BOP for the supportability of Legacy 802.15.4 Devices • Efficiency Analysis in Data Communication • Conclusion Ho-In Jeon (KWU) and Yongsik Shin (Sktelecom)

  4. Multiple Beacons in One Superframe Beacon Scheduling for Beacon Collision Avoidance Efficient Real-Time Short Address Allocation Algorithms Routing Algorithm: Proactive or Reactive Power-Efficient Operation Mode Support of Time-Critical or Delay-Sensitive Applications Resource Reservation for Data Transmission Hidden Node and Exposed Node Problems Mobility Support for Intra- and Inter-PAN Backward Compatibility to Legacy IEEE 802.15.4 Devices Issues of Mesh Networks Ho-In Jeon (KWU) and Yongsik Shin (Sktelecom)

  5. Operating Principles of Mesh Networks • The first device becomes MPC after passive and active scan. • Devices are associated to the MPC sequentially, one by one. • When an association request is granted by multiple nodes, the new node decides to associate with the node which has lower depth. • When depth information is the same, he decides to associate with the node which transmits his beacon earlier than others. • The relation between parent and children are characterized by association request and response. • My parent and children are my neighbors. • All devices I can hear are my neighbors. 2 5 1 4 MPC 3 6 Ho-In Jeon (KWU) and Yongsik Shin (Sktelecom)

  6. Multiple Beacons in One Superframe BOP (Beacon-Only Period) Beacon CAP CFP Beacons Ho-In Jeon (KWU) and Yongsik Shin (Sktelecom)

  7. A Mesh Architecture and Beacon Scheduling • Every node sends his beacon with beacon payload containing its depth information, its Beacon Transmission Time Slot (BTTS), and BTTS’s occupied by his neighbors and neighbor’s neighbors. • The first beacon slot can be used only by the MPC for the protection of PAN’s basic information. • Solid blue line represents the Parent-Child relations based on associations, while red line represents directly reachable. • Every mesh device shall transmit his beacon during the BOP (Beacon-Only Period) at the BTTS scheduled in a distributed manner. 2 1 MPC CAP BOP 3 1 1 3 2 Ho-In Jeon (KWU) and Yongsik Shin (Sktelecom)

  8. Beacon Payload Info. for Beacon Scheduling • When a node sends his beacon with beacon payload shown below, the receiver nodes can obtain the information of the BTTS occupied by its neighbors and its neighbor’s neighbors. • The beacon scheduling is performed by choosing the smallest time slot of the BOP slots which avoids the time slots occupied by neighbors and its neighbor’s neighbors. <Information contained in the beacon payload> Ho-In Jeon (KWU) and Yongsik Shin (Sktelecom)

  9. Beacon Scheduling 14 16 17 12 18 13 11 15 19 2 5 9 20 1 6 PNC 8 10 4 3 7 Ho-In Jeon (KWU) and Yongsik Shin (Sktelecom)

  10. Beacon Scheduling 14 16 17 12 13 11 15 2 5 9 1 6 8 10 PNC 4 3 7 Deep Sleep BOP BOP CFP CAP 1 1 3 4 5 6 2 9 13 2 7 8 12 14 15 10 11 10 16 17 16 Ho-In Jeon (KWU) and Yongsik Shin (Sktelecom)

  11. Beacon Scheduling Performed! 4 14 2 6 16 3 17 12 18 11 13 7 10 11 3 6 15 19 2 5 2 9 10 5 9 1 20 1 2 6 6 MPC 4 8 10 4 3 7 8 3 7 Deep Sleep BOP CFP BOP CAP 1 3 4 5 6 1 2 9 13 18 7 2 8 12 14 15 20 10 11 10 16 19 17 16 Ho-In Jeon (KWU) and Yongsik Shin (Sktelecom)

  12. Concerns about Beacon Scheduling • Efficiency in data communications • The size of the BOP (Beacon-Only Period) may become too large as the mesh network grows having many nodes, and thus the efficiency in data communication can be very low. • Power consumption may be too much. • Backward compatibility to legacy IEEE 802.15.4 devices • Legacy IEEE 802.15.4 devices listen his parent’s beacon and perform the CSMA/CA immediately. • During the BOP, the legacy IEEE 802.15.4 devices may hear many other beacons which will not confuse it. • It will wait until BOP end in order to send his data. Ho-In Jeon (KWU) and Yongsik Shin (Sktelecom)

  13. Efficiency in Data Communication • The efficiency of the data communications is defined as the ratio of the period where actual data can be effectively transferred to the Superframe Duration. (See 15-06-0266-00-0005) • The legacy IEEE 802.15.4 device has efficiency of 99.6%. • Mesh network with 64 beacons transmitted without beacon scheduling algorithm having SO = 3 and BO = 4 provides 33.3%. • Mesh network with 64 beacons transmitted without beacon scheduling algorithm having SO = 4 and BO = 5 provides 66.7%. • Mesh network with 32 beacons transmitted without beacon scheduling algorithm having SO = 4 and BO = 5 provides 87.5%. • Mesh network with 16 beacons transmitted without beacon scheduling algorithm having SO = 4 and BO = 5 provides 93.75%. Ho-In Jeon (KWU) and Yongsik Shin (Sktelecom)

  14. 802.15.4 Superframe Structure and Timing Efficiency = 99.6% Beacon Beacon CFP CAP GTS #1 GTS #2 Inactive 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 0 1 2 SlotD (Slot Duration) SlotD = aBaseSlotDuration × 2SO [symbols] = 60 × 2SO [symbols] = 0.96 × 2SO [msec] SD (Superframe Duration) SD = aBaseSuperframeDuration * 2SO [symbols] = 960 * 2SO [symbols] = 15.36 * 2SO [msec] BI (Beacon Interval) = aBaseSuperframeDuration * 2BO [symbols] = 960 * 2BO [symbols] = 15.36 * 2BO [msec] Ho-In Jeon (KWU) and Yongsik Shin (Sktelecom)

  15. Superframe Timing with SO = 3 and BO = 4 BOP Efficiency = 33.3% when BTTS = 64 aUnitBackoffPeriod = 320 usec ………. B3 Inactive B1 B2 B64 B1 CAP 0.192[msec]: Rx-Tx Turnaround Time 0.896[msec] 1.280[msec] Duration of BOP with 64 Beacons = 1.280 x 64 = 81.920 [msec] Duration of CAP with 64 Beacons = 12.288 - 81.920 = 40.960 [msec] SD (Superframe Duration) = aBaseSuperframeDuration * 2SO [symbols] = 15.36 * 2SO [msec] = 122.88 [msec] BI (Beacon Interval) = aBaseSuperframeDuration * 2BO [symbols] = 960 * 2BO [symbols] = 15.36 * 2BO [msec] = 245.76 [msec] Ho-In Jeon (KWU) and Yongsik Shin (Sktelecom)

  16. Superframe Timing with SO = 4 and BO = 5 BOP Efficiency = 66.7% when BTTS = 64 aUnitBackoffPeriod = 320 usec ………. B3 Inactive B1 B2 B64 B1 CAP 0.192[msec]: Rx-Tx Turnaround Time 0.896[msec] 1.280[msec] Duration of BOP with 64 Beacons = 1.280 x 64 = 81.920 [msec] Duration of CAP with 64 Beacons = 245.76 - 81.920 = 163.840 [msec] SD (Superframe Duration) = aBaseSuperframeDuration * 2SO [symbols] = 15.36 * 2SO [msec] = 245.76 [msec] BI (Beacon Interval) = aBaseSuperframeDuration * 2BO [symbols] = 960 * 2BO [symbols] = 15.36 * 2BO [msec] = 491.52 [msec] Ho-In Jeon (KWU) and Yongsik Shin (Sktelecom)

  17. Superframe Timing with SO = 4 and BO = 5 BOP Efficiency = 87.5% when BTTS = 32 aUnitBackoffPeriod = 320 usec ………. B3 Inactive B1 B2 B32 B1 CAP 0.192[msec]: Rx-Tx Turnaround Time 0.768[msec] 0.960[msec] Duration of BOP with 64 Beacons = 0.960 x 32 =30.720 [msec] Duration of CAP with 64 Beacons = 245.76 – 30.720 = 215.040 [msec] SD (Superframe Duration) = aBaseSuperframeDuration * 2SO [symbols] = 15.36 * 2SO [msec] = 245.76 [msec] BI (Beacon Interval) = aBaseSuperframeDuration * 2BO [symbols] = 960 * 2BO [symbols] = 15.36 * 2BO [msec] = 491.52 [msec] Ho-In Jeon (KWU) and Yongsik Shin (Sktelecom)

  18. Superframe Timing with SO = 4 and BO = 5 BOP Efficiency = 93.75% when BTTS = 16 aUnitBackoffPeriod = 320 usec ………. B3 Inactive B1 B2 B16 B1 CAP 0.192[msec]: Rx-Tx Turnaround Time 0.704[msec] 0.960[msec] Duration of CAP with 64 Beacons = 245.76 – 15.36 = 230.40 [msec] Duration of BOP with 64 Beacons = 0.960 x 16 = 15.36 [msec] SD (Superframe Duration) = aBaseSuperframeDuration * 2SO [symbols] = 15.36 * 2SO [msec] = 245.76 [msec] BI (Beacon Interval) = aBaseSuperframeDuration * 2BO [symbols] = 960 * 2BO [symbols] = 15.36 * 2BO [msec] = 491.52 [msec] Ho-In Jeon (KWU) and Yongsik Shin (Sktelecom)

  19. Backward Compatibility to Legacy Device • We can move all the beacons except MPC’s at the end of the inactive period, forming new BOP and its location. • The node 2 sends his beacon at the beginning of BST in the inactive period. • The same beacon scheduling algorithm is applied to the rest of the devices. • Each device has to wait for about one superframe period until it can send his beacon to his children. • The legacy device turned on in the POS area works just like regular environment in the star topology. Ho-In Jeon (KWU) and Yongsik Shin (Sktelecom)

  20. Beacon Scheduling Performed! 4 14 2 6 16 3 17 12 18 11 13 7 10 11 3 6 15 19 2 5 2 9 10 5 9 1 20 1 2 6 6 MPC 4 8 10 4 3 7 8 3 7 Deep Sleep BOP CFP BOP CAP 1 3 4 5 6 1 2 9 13 18 7 2 8 12 14 15 20 10 11 10 16 19 17 16 Ho-In Jeon (KWU) and Yongsik Shin (Sktelecom)

  21. BOP Position Change for Legacy Devices Deep Sleep BOP CFP BOP CAP 1 3 4 5 6 1 2 9 13 18 7 2 8 12 14 15 20 10 11 10 16 19 17 16 BST (BOP Start Time) Deep Sleep Superframe Deep Sleep for Legacy Device Deep Sleep forMesh Device CFP BOP CAP BOP 1 3 4 5 6 1 9 13 2 9 13 18 7 8 12 14 15 20 10 11 16 19 17 Ho-In Jeon (KWU) and Yongsik Shin (Sktelecom)

  22. Beacon Scheduling for Legacy Devices 14 16 17 12 13 11 15 2 5 9 1 6 MPC 8 10 4 3 7 BST (BOP Start Time) Deep Sleep Superframe Deep Sleep for Legacy Device Deep Sleep forMesh Device CFP BOP CAP BOP 1 1 3 4 5 6 9 13 2 9 13 7 8 12 14 15 10 11 16 17 Ho-In Jeon (KWU) and Yongsik Shin (Sktelecom)

  23. Beacon Scheduling for Legacy Devices 4 14 2 6 16 3 17 12 18 11 13 7 10 3 6 15 11 19 2 5 2 9 10 5 9 1 20 1 2 6 6 MPC 4 8 10 4 3 7 8 3 7 BST (BOP Start Time) Deep Sleep Superframe Deep Sleep for Legacy Device Deep Sleep forMesh Device CFP BOP CAP BOP 1 3 4 5 6 1 9 13 2 9 13 18 7 8 12 14 15 20 10 11 16 19 17 Ho-In Jeon (KWU) and Yongsik Shin (Sktelecom)

  24. New Legacy Device in the POS of MPC 14 16 17 12 18 13 15 11 L1 19 2 L2 5 9 20 1 6 MPC 8 10 4 3 7 BST (BOP Start Time) Deep Sleep Superframe Deep Sleep for Legacy Device Deep Sleep forMesh Device CFP BOP CAP BOP 1 3 4 5 6 1 9 13 2 9 13 18 7 8 12 14 15 20 10 11 16 19 17 Ho-In Jeon (KWU) and Yongsik Shin (Sktelecom)

  25. Observations • Legacy devices can join in the mesh network. • The new position of BOP is in the inactive period. • The legacy device will not be interfered by other beacons except its MPC beacon because it is in the deep sleep mode. • The optimum size of the BOP which is adaptive in terms of the size of the network may be very important from the power consumption point of view. • They have to wake up to be able to listen to the beacon during the BOP located in the inactive period. • The efficiency in the data communication becomes as good as that of original network. Ho-In Jeon (KWU) and Yongsik Shin (Sktelecom)

  26. New Legacy Devices in the POS of Routers 14 16 17 12 18 13 15 11 L1 19 L3 L4 2 L2 5 9 20 1 6 MPC 8 10 4 3 7 BST (BOP Start Time) Deep Sleep Superframe Deep Sleep for Legacy Device Deep Sleep forMesh Device CFP BOP CAP BOP 1 3 4 5 6 1 9 13 2 9 13 18 7 8 12 14 15 20 10 11 16 19 17 Ho-In Jeon (KWU) and Yongsik Shin (Sktelecom)

  27. Legacy Devices in the POS of Routers • Legacy devices will scan passively and actively, listen to the first beacon and be associated with this device. • He will follow his parent’s beacon information only. • No other beacons will affect his behavior. • So, the star topology around the legacy device’s parent will maintain anyway. • The overall functionality will be the same as the original behavior of the legacy devices. Ho-In Jeon (KWU) and Yongsik Shin (Sktelecom)

  28. Conclusions • Addressed some issues of Mesh Networks • Defined a new Mesh Network Architecture • Introduced Beacon Scheduling fundamentals with BOP concept • Proposed the position change of BOP for the supportability of Legacy IEEE 802.15.4 Devices • Legacy device in the POS of MPC • Legacy device in the POS of mesh routers • Provided the efficiency analysis in Data Communication Ho-In Jeon (KWU) and Yongsik Shin (Sktelecom)

  29. Acknowledgment • This work has been supported by HNRC of IITA. Ho-In Jeon (KWU) and Yongsik Shin (Sktelecom)

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