Co-Located Multi-Radio Coexistence Design Considerations
Document Number: IEEE S80216m-08/897r1
Date Submitted: 2008-09-02
Source:
Jing Zhu, Hujun Yin, and Sassan Ahmadi
Intel Corporation
Voice: +1-503-2647073
Email: jing.z.zhu@intel.com
Venue: IEEE 802.16m-08/033 “Call for Contributions on Project 802.16m System Description Document
(SDD)”, in response to the following topics: “Multi-Radio Coexistence”, MAC related
Base Contribution: IEEE C80216m-08/897r1
Purpose: to be discussed and adopted by TGm for the 802.16m SDD
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Background (1): Multi-Radio Usages
WiMAX
Bluetooth
Headset
Bluetooth
Headset
Wi-Fi
Wireless
Peripherals
Seamless Handover
•Mobile user terminals are rapidly evolving to devices with multiple connectivity
capabilities:
–Wi-Fi*: enabling internet/intranet access and access to peripherals like cameras, etc..
–WiMAX*: WAN access to mobile Internet, cellular type applications
–Bluetooth*: provides short range connectivity to headsets, etc.
*: other names and brands may be claimed as the properties of others
2
Usage Example: Wireless Peripherals
Wireless Peripherals over
IEEE 802.11 and 802.15
Mobile Internet over
IEEE 802.16m
Mobile Station
Base Station
Peripheral
General
Mouse
Hi precision
Mouse
Keyboard
Voice Quality
Headset
CD Quality
headphones
Aggregate
Throughput
< 8kbps
< 8kbps
< 8kbps
256 kbps
384kbps
Latency
< 10ms
< 3ms
< 50ms
< 30ms
< 100ms
3
Background (2): Problem and Solution
• Problem: Interference between co-located radios
– small separation, e.g. <20MHz between 2.4GHz and 2.3/2.5GHz
– wideband interference, e.g. receiver blocking and OOB emission
– little isolation, e.g. 10~30dB isolation on a small form-factor
device
• Solution 1: RF domain (filtering, isolation, etc.)
– costly, large in size, highly platform dependent
– not effective to wideband interference with small separation
• Solution 2: Time domain (TDM / MAC coordination)
– universal, effective, and media independent
– enabled by packet switching and spectrum efficient air-link
– but need air-interface / scheduling support
4
802.16 Rev2 Co-Located Coexistence Support
•
PSC-based Mode 1  TDM-based CLC with Wi-Fi
– BS is required to honor the configurations for the PSC in the MS MOB_SLP-REQ
message, and does not gratuitously reject or modify the configuration.
– MAP Relevance: defines that the listen and sleep interval follow the MAP
relevance. For example, the UL subframe of each listening and sleep interval
is shifted to the next frame compared to the DL subframe of that interval according
to the MAP relevance.
•
PSC-based Mode 2  TDM-base CLC with Bluetooth eSCO
– BS shall not provide any MS UL allocation in the first frame of the listening interval
– BS should provide any DL allocation as much as possible in the first frame of
listening interval
– BS shall, to all extent possible, populate the DL subframe such that DL allocations
for all MS with Co-located-Coexistence-Enabled active PSC and with allocations in
the current DL subframe, precede in time the allocations for other MS that do not
need co-located coexistence support and are allocated in the same DL subframe.
•
UL Band AMC  Reduce Interferences to Other Radios
– either lowermost or uppermost frequencies will be used for UL band AMC
subchannel allocations to achieve the maximum spectrum separation between
802.16 radio and the co-located radio in the adjacent bands.
5
PSC-based Mode 1 (w/ MAP Relevance)
FCH+MAP
Preamble
MS’s DL allocations
DL
UL
MS’s UL allocations
DL
UL
DL
UL
802.16 radio active
Sleep Window
(1 frame)
Listening Window
(2 frames)
UL MAP Relevance
FCH+MAP
MS’s UL allocations Preamble
MS’s DL allocations
DL
UL
DL
UL
DL
UL
802.16 radio active
Sleep Window
(1 frame)
Listening Window
(1 frame)
“MAP Relevance”
provides balanced
DL/UL throughput
with shorter duty
cycle, which
benefits the QOS.
Sleep Window
(1 frame)
6
PSC-based Mode 2
FCH+MAP
Preamble
MS’s DL allocations
DL
UL
MS’s UL allocations
DL
UL
DL
UL
802.16 radio active
Listening Window
Sleeping Window
2.06ms
Tx
Rx
1st
Rtx
Rx
2nd
Rtx
Rx
Rtx: retransmission
Tx: transmission
Rx: receive
Bluetooth EV3 (period=3.75ms)
7
How to improve 802.16 Rev2?
• Efficiency
– granularity is fixed to frame, e.g. 5ms, and has a direct impact on the
efficiency of TDM-based CLC operation, particularly when radio
transmissions take less than 5ms
• Flexibility
– MS determines CLC pattern, giving little flexibility for BS to adjust
according to network condition
– CLC period has to be the integer number of frames, and may not
suitable to some application.
• Scalability
– only one PSC is allowed active at any given time per MS, and difficult
to support multiple radios / applications.
• Compatibility
– power save needs to be disabled when CLC is active
• sleeping pattern is determined by 802.16m traffic
• CLC pattern is determined by co-located non 802.16m traffic
8
Design Considerations
• Type of CLC Activities
– Timing Parameters
– Definition
– Granularity Analysis
• Impact of CLC Activities
• Multiple CLC Activities
9
Co-Located Coexistence (CLC) Activity Examples
625us
Bluetooth SCO
(HV3)
Tx Rx
1
2
3
4
5
6
3.75ms
15ms (3 frames)
varied
Wi-Fi Beacon Rx
Rx
Rx
102.4ms
Wi-Fi Data Tx
Data ACK
102.4ms
Data ACK
varied
(depends on data rate and payload)
Flexible
(constrained by latency / throughput requirement)
Problem Description: Co-located Coexistence (CLC) Activities are the Tx or/and
Rx activities of one or multiple co-located radios that are not detectable over the
air, but will impact the communications to / from another co-located radio.
10
Timing Parameters
Active Period
Granularity

tp
Active Period

ta
Active Interval
Granularity
Active Interval
Start Time
t0
11
Type of CLC Activities
Is the active period equal to the
integer number of frames?
Is the active
pattern
adjustable by
Base Station?
Yes
No
No
Type I
(Bluetooth, …)
Type II
(Wi-Fi Beacon, …)
Yes
Type III
(Wi-Fi data, …)
• 802.16 Rev2 only supports Type I
• Type I, II, and III cover current co-located multi-radio
coexistence usages, and can be extended for future
12
Granularity
Active
Period
Active
Interval
Type I
802.16 Rev2
802.16m
frame (e.g. 5ms)
frame (e.g. 5ms)
Type II
1us
Type III
frame (e.g. 5ms)
Type I
frame (e.g. 5ms)
Type II
subframe
Type III
Beacon
Transmission
Time
Wi-Fi
Beacon Interval (102.4ms)
CLC Period (100ms)
2.4ms
4.8ms
Drifting 2.4ms every 100ms due
to unmatched granularity
13
Impact of Active Interval Granularity
• Efficiency: the ratio of the actual radio active time to the
CLC active interval
tA
tA
 
ta t A 
  
• Overhead: the number of bits to describe the length of
the CLC active interval


t A 
  log 2 (    1)
 


14
Efficiency & Overhead Analysis (1): Bluetooth
Bluetooth Slot
Slot-to-Subframe Mapping for
synchronized 802.16m and Bluetooth
coexistence
625us
Idle Time: 185us
S
802.16m subframe
M
S
M
S
M
S
M
617us
Idle Time: 62.86us
5ms
Efficiency
1-slot
(tA=440us)
3-slot
(tA=1690us)
5-slot
(tA =2940us)
Overhead
(5-slot)
subframe(617us)
71%
91%
95%
3
frame (5ms)
9%
34%
59%
1
15
1
1
0.9
0.9
0.8
0.8
0.7
0.7
0.6
0.6
0.5
6Mbps
9Mbps
12Mbps
18Mbps
24Mbps
36Mbps
48Mbps
54Mbps
0.4
0.3
0.2
0.1
0
Efficiency
Efficiency
Efficiency & Overhead Analysis (2): IEEE 802.11g
6Mbps
9Mbps
12Mbps
18Mbps
24Mbps
36Mbps
48Mbps
54Mbps
50%
0.5
0.4
0.3
0.2
0.1
0
300
400
500
600
700
800
900
1000 1100
1200 1300 1400
1500
300
400
500
600
700
Payload
a) 617us (subframe)
800
900
1000 1100 1200 1300 1400 1500
Payload
b) 5ms (frame)
Overhead (6Mbps, 1500 Bytes)
Subframe (617us)
3
Frame (5ms)
1
Configuration: one frame per active interval, single user (no contention)
16
Impact of CLC Activities
• IEEE 802.16m mobile station (MS) co-located with other radios subject
to periods of time when it is
– not permitted to transmit to protect communication to co-located radio
– unable to receive due to interference by transmission from co-located radio
– unable to transmit or receive due to
• shared component requiring mutually exclusive access, e.g. switched
antenna
• unknown time boundary between Tx and Rx, e.g. 802.11 data/ack
• Concurrent Tx or Rx should be supported to maximize time available for
operation
– Wi-Fi Beacon: only RX for STA
– Bluetooth SCO/eSCO: a slot is either Tx or Rx
• CLC and Sleep Mode should be supported independently
– sleeping pattern is optimized for 802.16m traffic
– CLC pattern is optimized for non 802.16m traffic
17
Multiple CLC Activities
• Concurrent operation of multiple CLC classes should
be supported
– MS may have multiple co-located radios, and each colocated radio may have multiple applications with different
active patterns.
– The state of MS should be the superset of all active CLC
classes.
CLC Class A
No No
Tx& Tx&
Rx Rx
No
Rx
CLC Class B
Sleeping Window
PSC Class A
No
Tx
No
Tx
PSC Class B
State of MS as a whole
No
No
Tx&
Tx
Rx
No
Tx
No No
Tx& Tx&
Rx Rx
Subframe
State of MS as a whole
Frame
Frame k
Frame k+1
18
Recommendations
• Support Type I, II, and III CLC Activity
• Granularity of CLC Activity
– active period: frame or microsecond (Type-II only)
– active interval: subframe
• Consider the Impact of CLC Activity on Tx and Rx
separately
• Support Multiple CLC Activities
• Support Sleep Mode and CLC Independently
– sleep mode can also be used to support CLC
19
Proposal: Explicit Co-located Coexistence Control
2
BS
MS
3
MOB_CLCRSP
MOB_CLCRSP (Update)
1
MOB_CLC-REQ
•Static Control
1 MS: send out MOB_CLC-REQ to report Type-I or/and Type-II CLC activities
2 BS: respond with MOB_CLC-RSP to accept or reject the request
– If “accept”, not provide MS allocation to the impacted intervals
– Otherwise”, indicate the limits
•Dynamic Control
1 MS: send out MOB_CLC-REQ to report a set of parameters for Type-III CLC activities
2 BS: respond with MOB_CLC-RSP to accept or reject the request
– If “accept”, provide the information of CLC active intervals
– Otherwise, indicate the limits
3
BS: update the information with MOB_CLC-RSP
20
Proposed Text for SDD
Insert the following text into Chapter 8:
8.1.4 Multi-Radio Coexistence Support Protocol Structure
Fig.8 shows an example of multi-radio device with co-located IEEE 802.16m MS, IEEE 802.11
device, and IEEE 802.15.1 master. The multi-radio coexistence functional block of the IEEE
802.16m MS obtains the information about other co-located radio’s activities via inter-radio
interface, which is internal to multi-radio device and out of the scope of IEEE 802.16m.
IEEE 802.16m provides protocols for the multi-radio coexistence functional blocks of MS and BS
to communicate with each other via air interface. MS generates management messages to report
its co-located radio activities to BS, and BS generates management messages to respond with
the corresponding actions to support multi-radio coexistence operation. Furthermore, the multiradio coexistence functional block at BS communicates with the scheduler functional block to
operate properly according to the reported co-located coexistence activities.
IEEE
802.16m BS
air interface
Multi-Radio Device
IEEE
802.15.1
device
IEEE
802.15.1
device
IEEE
802.16m
MS
IEEE
802.11
STA
IEEE 802.11
STA
inter-radio interface
Fig.8 Example of Multi-Radio Device with Co-Located IEEE 802.16m MS, IEEE 802.11
STA, and IEEE 802.15.1 device
21
References
[1] IEEE 802.19-08/0021, “IEEE 802 Air-Interface Support for CoLocated Coexistence”, July 2008
[2] IEEE 802.16 Rev2/D4, April 2008
[3] IEEE 802 Tutorial on “WPAN/WLAN/WWAN Multi-Radio
Coexistence”, Nov 2007
[4] WiMAX Forum, “Proposal for WiMAX-Bluetooth and WiMAX-WiFi
Coexistence,” September 2007
22