1. Submission Title: [Channel Diversity Sub group Report]
Project: IEEE P Working Group for Wireless Personal Area Networks (WPANs)
Submission Title: [Channel Diversity Sub group Report]
Date Submitted: [March 11, 2009]
Source: [Wun-Cheol Jeong, Chol Su Kang, Kuor-Hsin Chang, José A. Gutierrez, Ludwig Winkel, Rick Enns, Myung Lee, Tae Rim Park, Betty Zhao, Ghulum Bhatti, Ning Gu, Jie Shen, Wei Hong, Qin Wang]
Address []
Voice:[ ], FAX: [],
Re: [IEEE P e]
Abstract: [This document is a report of channel diversity subgroup for IEEE e.]
Purpose: [Discussion in e Task Group]
Notice: This document has been prepared to assist the IEEE P 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
Channel Diversity

2. doc.: IEEE 802.15-<doc#>
<11 January, 2008r>
<11 January, 2008r>
doc.: IEEE <doc#>
doc.: IEEE <doc#>
March, 2009
Channel Diversity Subgroup Report
ETRI, Dust Networks, Freescale, Emerson, Siemens, CUNY, MERL, Huawei, Samsung, Arch Rock, SIMIT, Vino, USTB, SIA
Channel Diversity
Page 2
<author>, <company>
<author>, <company>

3. doc.: IEEE 802.15-<doc#>
<11 January, 2008r>
<11 January, 2008r>
doc.: IEEE <doc#>
doc.: IEEE <doc#>
March, 2009
Contributors
ETRI: Wun-Cheol Jeong, Changsub Shin, Anseok Lee, Seong-Soon Joo
Dust Networks: Chol Su Kang, Kris Pister (UC Berkeley)
Freescale: Kuor-Hsin Chang, Clinton Powell
Emerson: José A. Gutierrez
Siemens: Ludwig Winkel
Rick Enns: Consultant
CUNY
MERL
Huawei
Samsung
Arch Rock
SIMIT
Vino
USTB
SIA
Channel Diversity
Page 3
<author>, <company>
<author>, <company>

4. doc.: IEEE 802.15-<doc#>
<11 January, 2008r>
<11 January, 2008r>
doc.: IEEE <doc#>
doc.: IEEE <doc#>
March, 2009
Table of Contents
Description of Channel Diversity
Anticipated Changes
Backward Compatibility
Application Support Levels
Changes to support channel diversity
Backward compatibility issues are followed
Briefly talk about application support levels
Channel Diversity
Page 4
<author>, <company>
<author>, <company>

5. Description of Channel Diversity
<11 January, 2008r>
doc.: IEEE <doc#>
March, 2009
Description of Channel Diversity
Wireless channel introduces uncertainty due to the nature of wireless medium.
“Diversity” exploits channel variations due to channel fading and mutual interferences.
Diversity schemes in Frequency/Time/Spatial Domain
PHY: Equalizer, OFDM, CDMA, Smart Antenna
MAC: ARQ, Channel Diversity, Sector Ant. MAC
NW; Path diversity
Space
In general, Diversity takes advantage of the channel variation due to the nature of wireless medium.
Since the channel variation deteriorates the transmitted signal, it is considered as a “channel impairments.” Actually, this is conventional view, though.
The channel impairments are mainly due to the physical phenomenon, multipath fading, and mutual interference from RF devices using same RF band of operation.
Coherence
Bandwidth
frequency f
time
Channel Diversity
<author>, <company>

6. Description of Channel Diversity
<11 January, 2008r>
doc.: IEEE <doc#>
March, 2009
Description of Channel Diversity
Channel Hopping – changing channel according to the predefined orthogonal (channel hopping) sequence.
Channel Adaptation – changing channel according to the channel quality measure such as CSI, packet error rate etc.
In general, Diversity takes advantage of the channel variation due to the nature of wireless medium.
Since the channel variation deteriorates the transmitted signal, it is considered as a “channel impairments.” Actually, this is conventional view, though.
The channel impairments are mainly due to the physical phenomenon, multipath fading, and mutual interference from RF devices using same RF band of operation.
Channel Diversity
<author>, <company>

7. doc.: IEEE 802.15-<doc#>
<11 January, 2008r>
<11 January, 2008r>
doc.: IEEE <doc#>
doc.: IEEE <doc#>
March, 2009
Channel Diversity
Mitigate Channel Impairments
Channel hopping/channel adaptation add frequency diversity to mitigate the effects of interference and multipath fading
If another network (like WiFi) is busy in a band of channels, retries outside of the band will work
The multipath coherence bandwidth ranges from 5 MHz for non-LOS to more than 20 MHz for near-LOS. A transmission on a faded channel can be retransmitted on other channels.
Improved coexistance
Increase Network Capacity
One timeslot can be used by multiple links at the same time by using different channels
Channel resources can be managed either in centralized or decentralized manner.
Channel Diversity
Page 7
<author>, <company>
<author>, <company>

8. Channel Hopping Proposals for Channel Diversity:
<11 January, 2008r>
<11 January, 2008r>
doc.: IEEE <doc#>
doc.: IEEE <doc#>
March, 2009
Channel Hopping
Slot n-2
Slot n-1
Slot n
Slot n+1
Slot n+2 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26
Channels
Proposals for Channel Diversity:
Distributed Channel Hopping (DCH)
Time Slotted Channel Hopping (TSCH)
Enhanced GTS (EGTS) Channel Adaptation
Slide 8
Channel Diversity
Page 8
Page 8
<author>, <company>
<author>, <company>

9. DCH: operation Timeslot operation Idle timeslot : No Tx and Rx
November 2008
March, 2009
DCH: operation
Timeslot operation
Idle timeslot : No Tx and Rx
Rx timeslot
Tune to its own channel
Enable receiver
Receive data frame
Turn to Tx mode
Transmit Ack frame
Tx timeslot
Jump to the receiver’s channel
Transmit data frame
Turn to Rx mode
Receive Ack frame 2
Slide 9
Channel Diversity

10. DCH: Offset Assignment
November 2008
March, 2009
DCH: Offset Assignment
Empty offset selection - example
node 1’s Neighbor offset bitmap = {1,3,6,10}
node 3’s Neighbor offset bitmap = {1,3,12,13}
node 6’s Neighbor offset bitmap = {1,2,6,9}
node 12’s Neighbor offset bitmap = {3,12}
Available offsets = {0,4,5,7,8,11,14,15}
Slide 10
Channel Diversity

11. DCH: Timeslot Allocation - sender
November 2008
March, 2009
DCH: Timeslot Allocation - sender A B C E D
Timeslot Request
D’s available timeslot :
Slide 11
Channel Diversity

12. DCH: Timeslot Allocation - receiver
November 2008
March, 2009
DCH: Timeslot Allocation - receiver A B C E D
Timeslot Response
D’s available timeslot :
E’s available timeslot :
Allocated timeslot :
Slide 12
Channel Diversity

13. TSCH: Link = (Timeslot , Channel Offset)
<11 January, 2008r>
<11 January, 2008r>
doc.: IEEE <doc#>
doc.: IEEE <doc#>
March, 2009
TSCH: Link = (Timeslot , Channel Offset)
One Slot
Time D
Chan.
offset A
BA C
CA
DA B
BA
BC E F
BE
BF
The two links from B to A are dedicated
D and C share a link for transmitting to A
The shared link does not collide with the dedicated links
Slide 13
Channel Diversity
Page 13
Page 13
<author>, <company>
<author>, <company>

14. TSCH: Channel Hopping Time Channel Offset Cycle N+2 Cycle N+1 Cycle N
<11 January, 2008r>
<11 January, 2008r>
doc.: IEEE <doc#>
doc.: IEEE <doc#>
March, 2009
TSCH: Channel Hopping
Time
BA
(ch 15)
BA
(ch25)
BA
(ch18)
CA
DA
CA
DA
CA
DA
Channel Offset
BA
BA
BA
BC
BC
BC
BE
BF
Channel resource allocation is not performed in MAC layer. It is taken care of in upper layer.
BE
BF
BE
BF
ASN=
N*4
N*4+1
N*4+2
N*4+3
(N+1)*4
Cycle N
Cycle N+1
Cycle N+2
Each link rotates through k available channels over k cycles.
Ch # = Chan Hopping Seq. Table ( ( ASN + Channel Offset) % Number_of_Channels )
Blacklisting can be defined globally and locally. (In Europe a frequency hopping system in the 2.4 GHz band can blacklist only one channel, and adaptive blacklisting is not possible)
Slide 14
Channel Diversity
Page 14
Page 14
<author>, <company>
<author>, <company>

15. EGTS(adaptation): Allocation Rule
March, 2009
EGTS(adaptation): Allocation Rule
First, choose a time slot (or slots), which has at least one vacant channel.
More than one slot can be allocated for each link (Tx & Rx pair).
Don’t assign two channels at the same time slot to a device. See Fig.1
Considering multi-hop delay (as discussed in the e).
Considering time schedule: try to assign time slots next to time slots haven been assigned to themselves. See Fig.2 time slots for A->B and B->C are successive
Then, choose a channel that is available in that time slot
Considering adjacent channel interference avoidance
Considering channel switch: try to avoid channel switch. See Fig.2 channel for A->B and B->C is the same
A->B
B->C
CH 1
CH 2
Fig.2 efficient GTS allocation
Slots
CH n
CH m
Fig.1 conflicting GTS allocation
I changed D-> C.
Slide 15
Channel Diversity 15

16. EGTS(adaptation): Allocation Bitmap Table (ABT)
March, 2009
EGTS(adaptation): Allocation Bitmap Table (ABT)
Each node maintains a Neighborhood Allocation Bitmap Table (ABT)
Example (MO = SO = 3)
ABT size = 14 bytes
0: Vacant, 1: Allocated (self or neighbors)
Row: time slot, Column: channel
Slide 16
Channel Diversity

17. EGTS(adaptation): ABT sub-block
March, 2009
EGTS(adaptation): ABT sub-block …
Entire bitmap may be too big to be transmitted by Beacon or EGTS command frames
Example (MO = 7, SO = 3)
ABT size = 224 bytes
0: Vacant, 1: Allocated.
Row: time slot, Column: channel
Solution:
Send a ABT sub-block (with an index indicating beginning & ending of a block)
Example: 28 bytes sub-block.
Slide 17
Channel Diversity 17

18. EGTS: Three-way-handshake for Allocation
March, 2009
EGTS: Three-way-handshake for Allocation
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)
Schedule Update
Those nodes who are reachable by EGTS Rep and EGTS Notify.
Beacons do not carry EGTS allocation information
Entire EGTS bitmap may be too big.
Periodically sending EGTS bitmap is energy consuming.
Slide 18
Channel Diversity

19. EGTS(adaptation): Allocation Example
March, 2009
EGTS(adaptation): Allocation Example
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 { … }
Every node that hears the broadcasts updates its allocation bitmap table (ABT)
3. EGTS notify, broadcast
Payload :
Dst addr (1)
new allocated ABT sub-block { … }
EGTS request, unicast
Payload :
Number of slots
ABT sub-block { … }
Assuming slot (9,21) is
already assigned from node 4
for transmitting frames to node 3
Slide 19
Channel Diversity 19

20. EGTS: Duplicated Allocation Notification
March, 2009
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.
Slide 20
Channel Diversity

21. EGTS: Deallocation & Expiration
March, 2009
EGTS: Deallocation & Expiration
EGTS Expiration
If an allocated EGTS is not used for longer than N beacon intervals, the allocation expires.
Each destination device maintains a counter table for EGTS Expiration.
EGTS Deallocation
Deallocation also uses three-way-handshake (request, reply, notify).
Deallocation is performed
when a source device finds out EGTS expiration.
when a destination device does not need to use EGTS any longer.
ABT Table
Slide 21
Channel Diversity

22. Anticipated Changes to Standard
March, 2009
Anticipated Changes to Standard
Channel Diversity

23. MAC PIB Supporting Channel Hopping
March, 2009
MAC PIB Supporting Channel Hopping
DCH:
Channel Hopping Sequence
Channel Offset Value
Beacon Index
Allocation Bitmap Table
TSCH:
Default Channel Hopping Sequence
Channel Hopping Sequence Tables
Channel Diversity

24. TSCH MAC Primitives Supporting Channel Hopping
March, 2009
TSCH MAC Primitives Supporting Channel Hopping
SET-SLOTFRAME Request parameters
slotframe size
channel page
channel map
SET-LINK Request parameters
Timeslot number
Channel offset
Channel Diversity

25. EGTS MAC Primitives and Commands Supporting Channel Diversity
March, 2009
EGTS MAC Primitives and Commands Supporting Channel Diversity
A new parameter in a MAC Primitive
MLME-GTS.request
(GTSCharacteristics, SecurityLevel, KeyIdMode, KeySource, KeyIndex, EGTSCharacteristics)
MLME-GTS.confirm
(GTSCharacteristics, status, EGTSCharacteristics)
MLME-GTS.indication
(DeviceAddress, GTSCharacteristics, SecurityLevel, KeyIdMode,
KeySource, KeyIndex, EGTSCharacteristics)
A new command frame : EGTS Request
Sub-fields: MHR fields, Commands frame identifier, EGTSCharacteristics
Channel Diversity

26. Backward Compatibility
March, 2009
Backward Compatibility
Channel Diversity

27. Backward Compatibility
March, 2009
Backward Compatibility
Backward Compatibility is provided if the proposed protocol can coexist with legacy protocol.
No changes on the existing frame format
Only additions that are optional
New frame format, primitives, and PIB attributes
Two modes in : Beacon enabled mode and non-beacon enabled mode
Channel Diversity

28. 802.15.4 March, 2009 Factory Automation ISA, HCF Contention-Free
E-GTS
TDMA
ZigBee,
Contention Access
Contention Access
beacon-enabled PAN
nonbeacon-enabled PAN
Overhead Reduction/Security
Low Energy
Channel Diversity
Channel Diversity

29. Application Support Levels
March, 2009
Application Support Levels
Channel Diversity

30. Application Support Levels
March, 2009
Application Support Levels
EGTS joint proposal can fully support all application domains because EGTS joint proposal can handle all required MAC behaviors.
Channel Diversity