Sep. 2015
doc.: IEEE 802.11-15/1136r7
Discussion on Concurrent STA-to-STA
Transmissions in 11ax
Date: 2015-09-15
Authors:
Name
Company
Address
Phone
Shao-Yu Lien
National Formosa
University
+886-5-6315000 [email protected]
Der-Jiunn Deng
National Changhua
University of
Education
National Taiwan
University
No.64, Wunhua Rd.,
Huwei Township,
Yunlin County 632,
Taiwan
No.2, Shi-Da Road,
Changhua, Taiwan
+886-47232105
ext. 8411
[email protected]
No. 1, Sec. 4, Roosevelt
Road, Taipei, Taiwan
+886233663568
[email protected]
Kwang-Cheng Chen
Submission
Slide 1
email
Der-Jiunn Deng, NCUE
Der-Jiunn Deng,
Sep. 2015
doc.: IEEE 802.11-15/1136r7
Background
•
STA-to-STA (S2S) transmissions without signal relays via AP may provide
significant benefits
 Higher spectrum (reuse) efficiency, higher order MCS, power saving, etc.
•
Some mechanisms have been proposed to support frame exchanges between
two STAs
 WiFi direct, DLS/TDLS, IBSS, etc.
•
Issues of existing mechanisms
 Low spectrum efficiency
 Based on CSMA/CA
 Each STA pair has individual operations
 Concurrent TX among multiple STA pairs are not supported
 S2S TX are usually operated by STAs closely located with each other
 Low TX power can be used
Submission
Slide 2
Der-Jiunn Deng, NCUE
Der-Jiunn Deng,
Sep. 2015
doc.: IEEE 802.11-15/1136r7
Possible Scenarios of Concurrent
Transmissions in 11ax
•
To boost spectrum (reuse) efficiency, concurrent S2S transmissions might be
one of the possible solutions
•
Fig.1
UL-S2S Concurrent TX
Concurrent S2S TX may be operated with or without AP
UL
transmission
STA_4
STA_5
S2S
transmission
STA_4
 Concurrent DL pairs and S2S pairs (Fig. 2) Fig.3
 Concurrent multiple S2S pairs (Fig. 3)
AP
STA_3
STA_2
STA_3
S2S
transmission
STA_2
S2S
transmission
S2S
transmission
STA_4
STA_4
STA_1
AP
 Concurrent multiple S2S pairs (Fig. 4)
STA_3
STA_3
STA_2
S2S
transmission
STA_2
Develop mechanisms to support concurrent TX in 11ax is highly desirable in
order to enhance system throughput in dense environment
Submission
S2S
transmission
Concurrent multiple S2S Fig.4 Concurrent multiple S2S
STA_1
 Without AP
STA_5
S2S
transmission
STA_1
AP
 Concurrent UL pairs and S2S pairs (Fig. 1)
•
DL
transmission
STA_1
 With AP
Fig.2 DL-S2S Concurrent TX
Slide 3
Der-Jiunn Deng, NCUE
Der-Jiunn Deng,
S2S
transmission
Sep. 2015
doc.: IEEE 802.11-15/1136r7
Considerations on AP Centric Concurrent
Transmissions in 11ax
•
More capabilities of transmission coordination beyond CSMA/CA such as
scheduling based MU transmission on OFDMA PHY are considered to be
supported by AP in 11ax
•
In the case of S2S concurrent TX with AP, AP may provide transmission
coordination to further enhance the system performance
•
However, in concurrent TX, the system performance lies in interference
among transmission pairs
Submission
Slide 4
Der-Jiunn Deng, NCUE
Der-Jiunn Deng,
Sep. 2015
doc.: IEEE 802.11-15/1136r7
Interference in S2S Concurrent
Transmissions
•
There are multiple receivers in S2S concurrent transmissions, for example
 For UL TX from STA_1 to AP, receiver is AP
 For S2S TX from STA_3 to STA_2, receiver is STA_2
•
AP may suffer interference from STA_3
•
STA_2 may suffer interference from STA_1
•
In this case, concurrent TX are allowable if
Receiver
STA_1
Interference
 Interference level at two receivers are both acceptable
(concurrent TX opportunity)
•
UL
transmission
Interference
AP
STA_3
Receiver
STA_2
S2S
transmission
To create/find concurrent TX opportunity
 Communication ranges of S2S should be small (a smaller TX power can
be used).
 Adjustable ED mechanism supported by dynamic CCA and TPC should
Submission
be included
Slide 5
Der-Jiunn Deng, NCUE
Der-Jiunn Deng, NCUE
Sep. 2015
doc.: IEEE 802.11-15/1136r7
Adjustable ED in CCA and TPC
•
Adjustable ED mechanism supported by dynamic CCA and TPC could support
concurrent TX even when interference levels at receiver sides are high, if the
received signal strength is also high
 Concurrent TX are allowable when SINRs at all receivers are acceptable
•
How to find a concurrent TX opportunity?
Submission
Slide 6
Der-Jiunn Deng, NCUE
Der-Jiunn Deng, NCUE
Sep. 2015
doc.: IEEE 802.11-15/1136r7
More Considerations on Adjustable ED in
CCA and TPC
•
To find a concurrent TX opportunity, the following information are necessary
 AP
 Specific power level adopted by STA1, PWRsta_1
 Path loss from STA_1 to AP
 Path loss from STA_3 to AP
 STA2
 Specific power level adopted by STA3, PWRsta_3
 Path loss from STA_1 to STA_2
 Path loss from STA_3 to STA_2
•
AP may coordinate above information exchanges
UL
transmission
Receiver
STA_1
Interference
Interference
AP
STA_3
Receiver
STA_2
Submission
Slide 7
S2S
transmission
Der-Jiunn Deng, NCUE
Der-Jiunn Deng, NCUE
Sep. 2015
doc.: IEEE 802.11-15/1136r7
Considerations on AP Coordinated
Concurrent TX
•
There can be two design alternatives methods
 AP collects the information to determine the TX power level for a S2S
pair for concurrent TX
 A MAC layer signaling exchange protocol is needed to collect all
the information
 A S2S pair autonomously determines its TX power level for concurrent
TX, and then call for AP’s permission
 AP decides whether to grant the concurrent S2S TX or not
 A MAC layer signaling exchange protocol is also needed for a S2S
pair and AP to estimate SINR at their own receivers
Submission
Slide 8
Der-Jiunn Deng, NCUE
Der-Jiunn Deng, NCUE
Sep. 2015
doc.: IEEE 802.11-15/1136r7
Conclusions
•
To support concurrent S2S TX, how to find a concurrent TX opportunity is an
interesting topic
 Adjustable ED supported by dynamic CCA and TPC
 11ax might need a MAC layer signaling exchange protocol
•
Based on the potential benefits on the enhancement of spectrum (reuse) efficiency,
we may proceed to discuss the possibilities to support concurrent S2S TX in 11ax
Submission
Slide 9
Der-Jiunn Deng, NCUE
Der-Jiunn Deng, NCUE
Sep. 2015
doc.: IEEE 802.11-15/1136r7
Straw-poll
▪ Do you agree that 802.11ax should support concurrent
STA-to-STA transmissions?
Yes: 9
No: 2
Abstain:
Submission
Slide 10
Der-Jiunn Deng, NCUE
Der-Jiunn Deng, NCUE