May, 2009 doc.: IEEE 802.15-09-0321-00-0006 Project: IEEE P802.15 Working Group for Wireless Personal Area Networks ( etworks (WPANs WPANs) ) Project: IEEE P802.15 Working Group for Wireless Personal Area N Submission Title: [Distributed TDMA Scheduling for SOP] Date Submitted: [4th May, 2009] Source: [Seung-Hoon Park / Jeongsik In / Sridhar Rajagopal / Eui-Jik Kim / Ranjeet Kumar Patro / Noh- Gyoung Kang / Chihong Cho / Giriraj Goyal / Ashutosh Bhatia / Thenmozhi Arunan / Kiran Bynam / Arun Naniyat / Farooq Khan / YongSuk Park / Eun-Tae Won] Company [Samsung Electronics Co. Ltd.] Address [416, Maetan-3dong, Yeongtong-gu, Suwon-si, Gyeonggi-do, 443-742, Korea] Voice: [+82-31-279-4579], FAX: [+82-31-279-5130], E-Mail: [shannon.park@samsung.com] Re: [Responses to Call for Intent in Wireless Body Area Networks] Abstract: [This document proposes the method to schedule time resource for SOP of BAN] Purpose: [To propose scheduling algorithm for SOP to support BAN high data rate applications] 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. Submission Slide 1/23 Seung-Hoon Park et al., Samsung
May, 2009 doc.: IEEE 802.15-09-0321-00-0006 Distributed TDMA Scheduling for SOP Submission Slide 2/23 Seung-Hoon Park et al., Samsung
May, 2009 doc.: IEEE 802.15-09-0321-00-0006 Motivation � High data rate service [1] – Streaming service with see-through goggle – Video recording & storage � BAN piconet environment – Frequent encounter with other piconets � Time resource sharing is required – QoS requirement � Collision affects packet error rate – UWB band opened globally is narrow [2] � A few number of frequency bands Submission Slide 3/23 Seung-Hoon Park et al., Samsung
May, 2009 doc.: IEEE 802.15-09-0321-00-0006 Possible Solutions for SOP � FDMA – How to allocate bands ? � Frequent change of band makes the system complex � Direct spread spectrum, frequency hopping, or time hopping – Only low data rate can be supported � Contention-based access (CSMA) – Not delay bounded – Hidden node – Channel sensing is not easy at UWB, implant (MICS) or body shadowing condition � Contention free allocation (TDMA, polling) – Bandwidth efficient with dynamic slot allocation Submission Slide 4/23 Seung-Hoon Park et al., Samsung
May, 2009 doc.: IEEE 802.15-09-0321-00-0006 Inter-piconet Collision � Collision types – Piconet A ↔ Piconet B – TDMA ↔ TDMA � Can not avoid collision without any control – TDMA ↔ CSMA � Piconet B can reduce collision ratio by channel sensing � low receiver sensitivity is required – CSMA ↔ CSMA � Same as the condition of CSMA in single piconet Submission Slide 5/23 Seung-Hoon Park et al., Samsung
May, 2009 doc.: IEEE 802.15-09-0321-00-0006 CSMA/CA Performance CSMA/CA Throughput Performance CSMA/CA PER Performance 10000 1 Rx.Sen. -98 dBm Rx.Sen. -98 dBm 9000 0.9 Rx.Sen. -108 dBm Rx.Sen. -108 dBm Rx.Sen. -118 dBm Rx.Sen. -118 dBm 8000 0.8 7000 0.7 Throughput [kbps] 6000 0.6 PER 5000 0.5 4000 0.4 3000 0.3 2000 0.2 1000 0.1 0 0 1 2 3 4 5 1 2 3 4 5 # of piconets # of piconets * Rx. Sensitivity of 802.15.4a UWB PHY is 85dBm (for 1Mbps) or 91dBm (for 250kbps). Submission Slide 6/23 Seung-Hoon Park et al., Samsung
May, 2009 doc.: IEEE 802.15-09-0321-00-0006 TDMA � Contention free allocation � Pros – Guaranteed QoS – High channel efficiency – Very low power consumption � Cons – Inter-piconet collision induces much performance degradation � How to sync and schedule ? Submission Slide 7/23 Seung-Hoon Park et al., Samsung
May, 2009 doc.: IEEE 802.15-09-0321-00-0006 TDMA Performance TDMA Throughput Performance TDMA PER Performance 10000 1 TDMA 100% Duty Cycle TDMA 100% Duty Cycle 9000 0.9 TDMA 20% Duty Cycle TDMA 20% Duty Cycle 8000 0.8 7000 0.7 Throughput [kbps] 6000 0.6 PER 5000 0.5 4000 0.4 3000 0.3 2000 0.2 1000 0.1 0 0 1 2 3 4 5 1 2 3 4 5 # of piconets # of piconets Submission Slide 8/23 Seung-Hoon Park et al., Samsung
May, 2009 doc.: IEEE 802.15-09-0321-00-0006 Centralized Piconet Merging Submission Slide 9/23 Seung-Hoon Park et al., Samsung
May, 2009 doc.: IEEE 802.15-09-0321-00-0006 Centralized Piconet Merging Sync Root Superframe CSMA TDMA Approach Timer Offset Sync Root Time sync unification Superframe Unified Sync Root TDMA reschedule Submission Slide 10/23 Seung-Hoon Park et al., Samsung
May, 2009 doc.: IEEE 802.15-09-0321-00-0006 Problems of Centralized Piconet Merging � BAN Piconet – Piconet is moving – High density in the specific location � Fine synchronization is very difficult � Centralized approach is apt to failed – Sync root node is changed frequently – Low scalability � Long latency � Large signal overhead Submission Slide 11/23 Seung-Hoon Park et al., Samsung
May, 2009 doc.: IEEE 802.15-09-0321-00-0006 Problems of Centralized Piconet Merging Submission Slide 12/23 Seung-Hoon Park et al., Samsung
May, 2009 doc.: IEEE 802.15-09-0321-00-0006 Resolving Approach � Distributed scheduling – Only local consensus is required � No sync root – Exchanging time information between neighboring piconets � Loose synchronization – Just avoiding slot allocation over the slot duration allocated by neighboring piconet – No need to fitting at slot level Submission Slide 13/23 Seung-Hoon Park et al., Samsung
May, 2009 doc.: IEEE 802.15-09-0321-00-0006 Distributed TDMA Scheduling Superframe TDMA reschedule without Time sync unification Submission Slide 14/23 Seung-Hoon Park et al., Samsung
May, 2009 doc.: IEEE 802.15-09-0321-00-0006 Local Time Offset Exchange ST C ST B ST A A B T1 C T2 T3 D A D C D B TDMA schedule Table A Addr # hop Offset Slot Start Slot Dur Seqno TDMA Schedule Advertisement Message A 0 0 ST A D A SN A Addr # hop Slot Start Slot Dur Seqno B 1 T1 ST B + T1 D B SN B C 1 T2 ST C + T2 D C SN C TDMA schedule Table B TDMA schedule Table C Addr # hop Offset Slot Start Slot Dur Seqno Addr # hop Offset Slot Start Slot Dur Seqno – T1 ST A – T1 – T2 ST A – T2 A 1 D A SN A A 1 D A SN A B 0 0 ST B D B SN B B 1 T3 ST B + T3 D B SN B – T3 ST C – T3 C 1 D C SN C C 0 0 ST C D C SN C Submission Slide 15/23 Seung-Hoon Park et al., Samsung
May, 2009 doc.: IEEE 802.15-09-0321-00-0006 Offset Calculation � Existing synchronization method – IEEE 802.11 � Time stamping – IEEE 802.15.4 � Beacon Tx. time control � Any method can be used Submission Slide 16/23 Seung-Hoon Park et al., Samsung
May, 2009 doc.: IEEE 802.15-09-0321-00-0006 TDMA Schedule Table Calculation Sequence number is used to reject obsolete information Hop distance between A delivered through another path. and B. ( TDMA sched info can TDMA schedule Table A be propagated in multi Addr # hop Offset Slot Start Slot Dur Seqno hop ) A 0 0 ST A D A SN A B 1 T1 ST B + T1 D B SN B Slot duration does C 1 T2 ST C + T2 D C SN C not change node to node. Timer value of A – Timer value of C. Received The slot start time received from C ( Timer values can be from C can be converted into the equivalent communicated using any time of A ’ s timer by adding the existing sync method ) offset with respect to C, T2. Submission Slide 17/23 Seung-Hoon Park et al., Samsung
May, 2009 doc.: IEEE 802.15-09-0321-00-0006 Simulation Setup � 10Mbps system � # of nodes = 8 � CSMA/CA parameters – CCA threshold = 10dB – Rx. Sensitivity = -98dBm � Time information broadcasting – Sent at beacon time with robust coding Submission Slide 18/23 Seung-Hoon Park et al., Samsung
May, 2009 doc.: IEEE 802.15-09-0321-00-0006 Simulation Results Comparison of Throughput Performance Comparison of PER Performance 10000 1 TDMA 100% Duty Cycle TDMA 100% Duty Cycle 9000 0.9 TDMA 20% Duty Cycle TDMA 20% Duty Cycle CSMA Rx.Sen. -98 dBm Rx.Sen. -98 dBm 8000 0.8 proposed DTS proposed DTS 7000 0.7 Throughput [kbps] 6000 0.6 PER 5000 0.5 4000 0.4 3000 0.3 2000 0.2 1000 0.1 0 0 1 2 3 4 5 1 2 3 4 5 # of piconets # of piconets Submission Slide 19/23 Seung-Hoon Park et al., Samsung
May, 2009 doc.: IEEE 802.15-09-0321-00-0006 Conclusion � TDMA – Bandwidth efficient – Dynamic bandwidth allocation possible – Delay bounded – Mixable with other types of channel access mechanisms � CSMA, low duty cycle overlapping, or etc � Distributed TDMA scheduling – Support dynamically changing multiple piconets � Uncoordinated interference problem – When two piconets are out of the communication range while still in the interference range of each other – Partially solved with multi hop coordination – Fundamentally solved with two level Tx power control Submission Slide 20/23 Seung-Hoon Park et al., Samsung
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