May 2009 doc IEEE 802 15 09 0306

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May 2009 doc. : IEEE 802. 15 -09 -0306 -02 -004 g Project: IEEE

May 2009 doc. : IEEE 802. 15 -09 -0306 -02 -004 g Project: IEEE P 802. 15 Working Group for Wireless Personal Area Networks (WPANs) Submission Title: [Robust Multi-Channel Adaptation for Smart Utility Networks] Date Submitted: [8 May, 2009] Source: [Gahng-seop Ahn, Junsun Ryu, Myung Lee, Chang. Sub Shin, Seong-soon Joo] Companies [CUNY, ETRI] Address [140 th St. and Convent Ave, New York, NY, USA] Voice: [+1 -212 -650 -7219], FAX: [], E-Mail: [gahn@ccny. cuny. edu, junsun. ryu@gmail. com, lee@ccny. cuny. edu, shincs@etri. re. kr, ssjoo@etri. re. kr] Re: [IEEE P 802. 15. 4 g] Abstract: [This document proposes an robust multi-channel adaptation for smart utility networks] Purpose: [Discussion in 802. 15. 4 g Task Group] Notice: This document has been prepared to assist the IEEE P 802. 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 P 802. 15. Submission Slide 1 Myung Lee at al

May 2009 doc. : IEEE 802. 15 -09 -0306 -02 -004 g Robust Multi-Channel

May 2009 doc. : IEEE 802. 15 -09 -0306 -02 -004 g Robust Multi-Channel Adaptation for Smart Utility Networks CUNY, ETRI Submission Slide 2 Myung Lee at al

May 2009 doc. : IEEE 802. 15 -09 -0306 -02 -004 g Objectives •

May 2009 doc. : IEEE 802. 15 -09 -0306 -02 -004 g Objectives • MAC Modifications needed to support outdoor Low Data Rate Wireless Smart Metering Utility Network requirements – – Submission Robustness Scalability High reliability Energy efficiency Slide 3 Myung Lee at al

May 2009 doc. : IEEE 802. 15 -09 -0306 -02 -004 g Motivation •

May 2009 doc. : IEEE 802. 15 -09 -0306 -02 -004 g Motivation • Densely deployed large scale network in geographically large area – – The variance of channel condition is large. Channel Asymmetry. Common channel approach is limited Therefore, multi-channel adaptation is required. Smart Meter Concentration Point Smart Meter Submission Smart Meter Slide 4 Myung Lee at al

May 2009 doc. : IEEE 802. 15 -09 -0306 -02 -004 g Multi-channel Adaptation

May 2009 doc. : IEEE 802. 15 -09 -0306 -02 -004 g Multi-channel Adaptation 1. Asynchronous approach – Non-beacon mode – Multi-channel Meshed Tree (15. 5 based) 2. Synchronous approach – Beacon-enabled mode – EGTS: Enhanced Guaranteed Time Slots Submission Slide 5 Myung Lee at al

May 2009 doc. : IEEE 802. 15 -09 -0306 -02 -004 g 1. Asynchronous

May 2009 doc. : IEEE 802. 15 -09 -0306 -02 -004 g 1. Asynchronous Approach Submission Slide 6 Myung Lee at al

May 2009 doc. : IEEE 802. 15 -09 -0306 -02 -004 g Receiver-based Channel

May 2009 doc. : IEEE 802. 15 -09 -0306 -02 -004 g Receiver-based Channel Use (1) • Each device is listening to its designated channel. • The sender device switch to the channel of the receiver device and transmit a DATA frame. • The sender device switch back to its own channel. • The receiver device switch to the channel of the sender device and transmit a ACK frame (if requested). • The receiver device switch back to its own channel. Sender DATA ACK Submission Slide 7 Receiver Myung Lee at al

May 2009 doc. : IEEE 802. 15 -09 -0306 -02 -004 g Receiver-based Channel

May 2009 doc. : IEEE 802. 15 -09 -0306 -02 -004 g Receiver-based Channel Use (2) • If the sender knows that it can hear receiver’s channel as well. (The sender can find out whether it can hear the receiver’s channel during association or by performing multi-channel probing. ) – Each device is listening to its designated channel. – The sender device switch to the channel of the receiver device and transmit a DATA frame with a flag indicating that the sender can hear receiver’s channel. – The receiver device transmit a ACK frame (if requested) using receiver’s channel. – The sender device switch back to its own channel after it receives the ACK. Sender DATA ACK Submission Slide 8 Receiver Myung Lee at al

May 2009 doc. : IEEE 802. 15 -09 -0306 -02 -004 g Channel Selection

May 2009 doc. : IEEE 802. 15 -09 -0306 -02 -004 g Channel Selection • A PAN can be configured to use a block of channels – – Cmax channels among all Ctotal channels. Motivation: to reduce the active scanning time. Considering adjacent channel interference and coherent bandwidth. For example, if there are 16 channels (channel 11 to channel 26): • PAN 1 uses channel 11, 17, 23. • PAN 2 uses channel 13, 19, 25. • PAN 3 uses channel 15, 21. Submission Slide 9 Myung Lee at al

May 2009 doc. : IEEE 802. 15 -09 -0306 -02 -004 g Multi-channel Active

May 2009 doc. : IEEE 802. 15 -09 -0306 -02 -004 g Multi-channel Active Scan A device perform active scan for all Cmax channels twice at worst case. For example, Cmax = 4, Coordinator’s designated channel is C 4, New device’s good channel is C 3. Channel Coordinator C 1 C 4 T New Device Channel C 1 C 2 C 3 C 4 C 3 T C 2 C 3 C 4 C 1 Beacon Request Beacon Association Request Association Response Submission Slide 10 Myung Lee at al

May 2009 doc. : IEEE 802. 15 -09 -0306 -02 -004 g Channel selection

May 2009 doc. : IEEE 802. 15 -09 -0306 -02 -004 g Channel selection based on link quality (optional) A device perform active scan for all Cmax channels twice and choose the best RSSI among the received beacons. For example, Cmax = 4, Coordinator’s designated channel is C 4, New device’s good channel is C 1, C 3. Channel Coordinator C 1 C 4 T New Device Channel C 1 C 2 C 3 C 4 C 1 C 4 C 2 C 3 C 4 C 1 T C 2 C 3 C 4 C 1 Beacon Request Beacon Association Request Association Response Submission Slide 11 Myung Lee at al

May 2009 doc. : IEEE 802. 15 -09 -0306 -02 -004 g Multi-channel Hello

May 2009 doc. : IEEE 802. 15 -09 -0306 -02 -004 g Multi-channel Hello • A device can send a multi-channel hello message to its one-hop neighbors to inform its designated channel. – The device should send the same hello message on each channel sequentially starting from its designated channel. – Optional: The device can request hello reply by setting a flag in the hello message. Two Neighbor Example: Cmax = 4, Coordinator’s designated channel is C 4, New device’s good channel is C 3. Channel C 4 C 3 C 4 Neighbor 1 T New Device Channel C 3 C 4 C 1 C 2 C 3 Hello Reply Neighbor 2 Channel Submission C 2 C 3 C 2 Slide 12 Myung Lee at al

May 2009 doc. : IEEE 802. 15 -09 -0306 -02 -004 g Three-way Handshake

May 2009 doc. : IEEE 802. 15 -09 -0306 -02 -004 g Three-way Handshake Channel Probing • • • The requesting device sends a channel probe request frame to one of its neighbors on the designated channel of the neighbor (e. g. , brown) indicating the channel to probe (e. g. , red). The neighbor sends a channel probe reply frame back on the requester’s channel (e. g. , green). The neighbor sends a channel probe frame using the channel indicated in the probe request (e. g. , red). Requester Neighbor Channel Probe Request Channel Probe Reply Channel Probe Submission Slide 13 Myung Lee at al

May 2009 doc. : IEEE 802. 15 -09 -0306 -02 -004 g Recovery from

May 2009 doc. : IEEE 802. 15 -09 -0306 -02 -004 g Recovery from Bad Channel Condition • Recovery from the case when the designated channel of a device has gone bad – The neighboring devices can immediately find a backup route bypassing the device (for example, using the feature of 15. 5 meshed tree). – The device can check the condition of its designated channel and switch to a better channel. (Using the channel probing). Smart Meter X ? X Concentration Point Smart Meter Submission Slide 14 Myung Lee at al

May 2009 doc. : IEEE 802. 15 -09 -0306 -02 -004 g Channel Adaptation

May 2009 doc. : IEEE 802. 15 -09 -0306 -02 -004 g Channel Adaptation • The device can check the condition of its designated channel using three-way handshake channel probing with one of its neighbors. • If the channel condition is bad, the device can probe other channels and switch to a better channel. • After switching the channel, the device shall broadcast a multi-channel hello to its one-hop neighbors. Smart Meter X ? X Smart Meter Concentration Point Smart Meter Submission ! Concentration Point Smart Meter Slide 15 Myung Lee at al

May 2009 doc. : IEEE 802. 15 -09 -0306 -02 -004 g Optimizing the

May 2009 doc. : IEEE 802. 15 -09 -0306 -02 -004 g Optimizing the Channel Diversity • Channel diversity has its cost. – The device have to switch its channels frequently if each neighbors are using a different channel. • To minimize the number of diverse channels, – Among the good channels, choose the channel that is being used by the majority of its neighbors. Smart Meter Submission Smart Meter Smart Meter Slide 16 Smart Meter Myung Lee at al

May 2009 doc. : IEEE 802. 15 -09 -0306 -02 -004 g 2. Synchronous

May 2009 doc. : IEEE 802. 15 -09 -0306 -02 -004 g 2. Synchronous Approach Submission Slide 17 Myung Lee at al

May 2009 doc. : IEEE 802. 15 -09 -0306 -02 -004 g EGTS: Enhanced

May 2009 doc. : IEEE 802. 15 -09 -0306 -02 -004 g EGTS: Enhanced Guaranteed Time Slots • • Beacon-enabled mode Robust and reliable communication – – – • Dynamic channel diversity – • Multi-channel support for GTS (Guaranteed Time Slot). Co-channel interference avoidance (EGTS three-way handshake). Adjacent channel interference avoidance (Passive RSSI monitoring). Detection of bad channel condition and reallocation of the slot to a better channel. Beacon collision avoidance – Submission Bit-map assisted beacon scheduling. Slide 18 Myung Lee at al

May 2009 doc. : IEEE 802. 15 -09 -0306 -02 -004 g EGTS Multi-channel

May 2009 doc. : IEEE 802. 15 -09 -0306 -02 -004 g EGTS Multi-channel Extension • • • Common channel : Beacon and CAP use a fixed common channel for all nodes. Multi-channel: EGTS uses multi-channel for a different set of source and destination. EGTS slot = tuple (time slot, channel) Allocates each link (Tx & Rx pair) with one or more slots. When MO = SO (to be explained in the following), 112 slots (7 time slots * 16 channels) are available in a superframe. EGTS Submission Slide 19 Myung Lee at al

May 2009 doc. : IEEE 802. 15 -09 -0306 -02 -004 g EGTS Mesh

May 2009 doc. : IEEE 802. 15 -09 -0306 -02 -004 g EGTS Mesh Extension • Multi-channel aspect is omitted in this figure for simplicity • EGTS allocation do not rely on PAN coordinator. – Allows EGTS for peer-to-peer connection. – Allows EGTS for nodes beyond one hop distance from PAN coordinator. Submission Slide 20 Myung Lee at al

May 2009 doc. : IEEE 802. 15 -09 -0306 -02 -004 g Flexible Multi-superframe

May 2009 doc. : IEEE 802. 15 -09 -0306 -02 -004 g Flexible Multi-superframe • For low duty cycle • Active • • • Beacon, CAP During EGTS time slots that are allocated to the node Inactive • • • During EGTS time slots that are not allocated to the node BLE in CAP periods Beacon slot where none of the neighbors are transmitting a beacon. Active / awake Inactive / sleep BO = 6, SO = 3, MO = 5 Node Submission Slide 21 Myung Lee at al

May 2009 doc. : IEEE 802. 15 -09 -0306 -02 -004 g CAP Period

May 2009 doc. : IEEE 802. 15 -09 -0306 -02 -004 g CAP Period Reduction in MSF • Motivation: Lower duty cycle, more GTS slots. • Each multi-superframe (MSF) has only one CAP period. • • Beacon indicates the next CAP period time. Every node synchronizes the CAP period. • Number of slots in a multi-superframe S = 16 channels * (7 + (2(MO – SO)-1) * 15) time slots • The allocation pattern of these S slots is repeated every multi-superframe. BO = 6, SO = 3, MO = 5 Submission Slide 22 Myung Lee at al

May 2009 doc. : IEEE 802. 15 -09 -0306 -02 -004 g EGTS Allocation

May 2009 doc. : IEEE 802. 15 -09 -0306 -02 -004 g EGTS Allocation Bitmap Table (ABT) • Each node maintains a Neighborhood Allocation Bitmap Table (ABT) • Example (MO = SO = 3) • ABT size = 14 bytes • • 0: Vacant, Row: time slot, 1: Allocated (self or neighbors) Column: channel 00000000 01000100 000000001000 00000100 00000000 0100000000 Submission Slide 23 Myung Lee at al

May 2009 doc. : IEEE 802. 15 -09 -0306 -02 -004 g Three-way-handshake EGTS

May 2009 doc. : IEEE 802. 15 -09 -0306 -02 -004 g Three-way-handshake EGTS Allocation (1) • Source Requesting destination • Three command frames are transmitted during CAP period – EGTS request • Unicast from a source to a destination. • Providing locally available slots (28 byte ABT sub-block). • Required number of slots (depending on data rate). – EGTS reply • Broadcast from the destination. • Select appropriate slots in the sub-block and announce the assigned EGTS slots to all neighbors (28 byte ABT sub-block). – EGTS notify • Broadcast from the source • Announce the assigned EGTS slots to all neighbors (28 bytes ABT sub-block) Submission Slide 24 Myung Lee at al

May 2009 doc. : IEEE 802. 15 -09 -0306 -02 -004 g EGTS Allocation

May 2009 doc. : IEEE 802. 15 -09 -0306 -02 -004 g EGTS Allocation Example (from node 3) Slot = tuple (time slot, channel) MO = SO Node 1 assigns slot (10, 15) for Node 3 2. EGTS reply, broadcast Payload : Dst addr (3) new allocated ABT sub-block {000000001000000 … 00000000 } Every node that hears the broadcasts updates its allocation bitmap table (ABT) 1. EGTS request, unicast Payload : Number of slots ABT sub-block {00000100000000 … 00000000 } 3. EGTS notify, broadcast Assuming slot (9, 21) is already assigned from node 4 for transmitting frames to node 3 Submission Slide 25 Payload : Dst addr (1) new allocated ABT sub-block {000000001000000 … 00000000 } Myung Lee at al

May 2009 doc. : IEEE 802. 15 -09 -0306 -02 -004 g EGTS Duplicated

May 2009 doc. : IEEE 802. 15 -09 -0306 -02 -004 g EGTS Duplicated Allocation Notification • Duplicated allocation can happen • Some nodes may miss some of EGTS reply or notify. (Broadcast is not reliable) • New joining node requests a slot not knowing the slot allocation state in the area. • Send EGTS collision notification during CAP period • The existing owner of the slot detects duplicated allocation by hearing neighbor’s EGTS reply or notify. • EGTS duplicated allocation notification (Unicast) from the existing owner. • Duplicated slot id (time slot, channel). • ABT sub-block (28 bytes) around the colliding time slot. • Forces the source and the destination nodes to retry three-way-handshake EGTS allocation. Submission Slide 26 Myung Lee at al

May 2009 doc. : IEEE 802. 15 -09 -0306 -02 -004 g Hybrid Slot

May 2009 doc. : IEEE 802. 15 -09 -0306 -02 -004 g Hybrid Slot Allocation • Proactive: tree-based slot allocation – Tree establishment (Beacon scheduling) and slot allocation are arranged simultaneously • Reactive: mesh-based slot allocation – Assign slots on-demand basis – Path reliability: backup route in the face of route failure – Peer-to-peer communication Submission Slide 27 Myung Lee at al

May 2009 doc. : IEEE 802. 15 -09 -0306 -02 -004 g Discussion: Issue

May 2009 doc. : IEEE 802. 15 -09 -0306 -02 -004 g Discussion: Issue of EGTS in 15. 4 g • EGTS set up (as proposed in 15. 4 e) is still based on common channel approach! • • Common channel : Beacon and CAP use a fixed common channel for all nodes. Multi-channel: EGTS uses multi-channel for a different set of source and destination. EGTS Submission Slide 28 Myung Lee at al

May 2009 doc. : IEEE 802. 15 -09 -0306 -02 -004 g 1. Common

May 2009 doc. : IEEE 802. 15 -09 -0306 -02 -004 g 1. Common Channel Frequency Hopping • Common Channels: Beacon, CAP • Objective: Reliable communication in the face of time-varying and frequency-dependant radio conditions. • Pre-defined hopping sequence: Example: 15 → 20 → 25 → 15 → … • Trade-off is longer scanning time for new joining nodes. Submission Slide 29 Myung Lee at al

May 2009 doc. : IEEE 802. 15 -09 -0306 -02 -004 g 2. Beacon

May 2009 doc. : IEEE 802. 15 -09 -0306 -02 -004 g 2. Beacon Frequency Hopping • No common channel: Each node is listening to its designated channel. Each node broadcast beacons on each available channel sequentially. • Objective: Robust communication in the face of asymmetric channel conditions. • Pre-defined hopping sequence: Example: 15 → 20 → 25 → 15 → … • Trade-off is longer scanning time for new joining nodes. Submission Slide 30 Myung Lee at al