Combatting Inter-cell Interference in 802.11ac-based MU ...Β Β· AP1 NDP-A NDP Overhear AP2 NDP-A NDP...
Transcript of Combatting Inter-cell Interference in 802.11ac-based MU ...Β Β· AP1 NDP-A NDP Overhear AP2 NDP-A NDP...
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Combatting Inter-cell Interference in MU-MIMO Networks
Hang Yu, Oscar Bejarano and Lin Zhong
ECE Department, Rice University
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Guiding principlesβ’ Spectrum is precious
β’ Hardware is getting cheaper and more efficient
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0
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2002 2004 2006 2008 2010 2012 2014
2x2 MIMO
SISO
Pow
erco
nsu
mp
tio
n (
mW
)
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Mobile devices are embracing more antennas
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1-2 antennas 1-2 antennas 1-4 antennas
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How to best use client antennas?
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MobiComβ11: beamforming to achieve power efficiency
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This work: inter-cell interference
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This work: inter-cell interference
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Key insight: clients and APs can coordinately cancel inter-cell interference
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Example of two cells
Client3
AP1
Client2
Client1
Client4
AP2
1 2 1 2
1 2 3
1
1 2
1
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Cell 1 Cell 2
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A single AP delivers two streams
Client3
AP1
Client2
Client1
Client4
AP2
1 2 1 2
1 2 3
1
1 2
1
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Cell 1 Cell 2
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Coordinated interference cancellation delivers three streams
Client3
AP1
Client2
Client1
Client4
AP2
1 2 1 2
1 2 3
1
1 2
1
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Coordinated interference cancellation delivers three streams
Client3
AP1
Client2
Client1
Client4
AP2
1 2 1 2
1 2 3
1
1 2
1
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Coordinated interference cancellation delivers three streams
Client3
AP1
Client2
Client1
Client4
AP2
1 2 1 2
1 2 3
1
1 2
1
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Coordinated interference cancellation delivers three streams
Client3
AP1
Client2
Client1
Client4
AP2
1 2 1 2
1 2 3
1
1 2
1
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How to achieve coordinated interference cancellation with low overhead?
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Why is it hard?
β’ Coordination can be expensive
β’ Optimizing beamforming weights requires full channel knowledge
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Key idea: two-step optimization
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Transmitting/receiving data streams
Cancelling inter-cell interference
or
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Antenna usage optimization:To communicate data or cancel interference?
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Optimized antenna usage
Transmitting Cancelling
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Client3
AP1
Client2
Client1
Client4
AP2
1 2 1 2
1 2 3
1
1 2
1
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Algorithm recursively applies to arbitrary MU-MIMO networks
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Key property:
Only # of antennas required to optimize the antenna usage
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π° , = ?
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Beamforming weight optimization
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Key property:
Partial channel knowledge required to optimize the beamforming weights
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Overview of CoaCa
β’ Coordinated optimization of AP and Client antennas
β’ Interleave 802.11ac channel sounding to achieve coordinated interference cancellation
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Channel sounding in 802.11ac
Client1
Client2
AP
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AP sends NDP-A
Client1
Client2
NDP-AAP
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AP sends NDP
Client1
Client2
NDP-AAP NDP
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Client1 reports its channel
Client1
Client2
NDP-AAP NDP
BF-R
π1β1
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AP polls Client2
Client1
Client2
NDP-AAP NDP
BF-R
BF-Pπ1β1
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Client2 reports its channel
Client1
Client2
NDP-AAP NDP
BF-R
BF-P
BF-R
π1β1 π1β2
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AP transmits to both clients
Client1
Client2
NDP-AAP NDP
BF-R
BF-P
BF-R
DATAπ1β1 π1β2
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Example of two cells
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Client3
AP1
Client2
Client1
Client4
AP2
1 2 1 2
1 2 3
1
1 2
1
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Timeline of CoaCa
Client1
Client3
Client4
AP1
AP2
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AP1 sends NDP-A
Client1
Client3
Client4
NDP-AAP1
AP2
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AP1 sends NDP-A
Client1
Client3
Client4
NDP-AAP1
AP2
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# of ant
# of ant
# of ant
# of ant
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AP1 sends NDP
Client1
Client3
Client4
NDP-AAP1 NDP
AP2
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# of ant
# of ant
# of ant
# of ant
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Clients estimate channels from AP1
Client1
Client3
Client4
NDP-AAP1 NDP
AP2
π1β1
π1β3
π‘1β4
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# of ant
# of ant
# of ant
# of ant
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AP2 sounds the channel
Client1
Client3
Client4
NDP-AAP1 NDP
AP2 NDP-A NDP
π1β1
π1β3
π‘1β4
π2β1
π2β3
π‘2β4
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# of ant
# of ant
# of ant
# of ant
# of ant
# of ant
# of ant
# of ant
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AP2 sounds the channel
Client1
Client3
Client4
NDP-AAP1 NDP
AP2 NDP-A NDP
π1β1
π1β3
π‘1β4
π2β1
π2β3
π‘2β4
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Antenna usage optimization
# of ant
# of ant
# of ant
# of ant
# of ant
# of ant
# of ant
# of ant
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AP1 polls Client1
Client1
Client3
Client4
NDP-AAP1 NDP
AP2 NDP-A NDP
π1β1
π1β3
π‘1β4
π2β1
π2β3
π‘2β4
BF-P
Compute π―1
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Antenna usage optimization
# of ant
# of ant
# of ant
# of ant
# of ant
# of ant
# of ant
# of ant
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Client1 reports its channel vector
Client1
Client3
Client4
NDP-AAP1 NDP
AP2 NDP-A NDP
BF-Rπ1β1
π1β3
π‘1β4
π2β1
π2β3
π‘2β4
π1β1π―1BF-P
Compute π―1
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Antenna usage optimization
# of ant
# of ant
# of ant
# of ant
# of ant
# of ant
# of ant
# of ant
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AP2 polls Client4
Client1
Client3
Client4
NDP-AAP1 NDP
AP2 NDP-A NDP
BF-R
BF-P
π1β1
π1β3
π‘1β4
π2β1
π2β3
π‘2β4
π1β1π―1BF-P
Compute π―1
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Antenna usage optimization
# of ant
# of ant
# of ant
# of ant
# of ant
# of ant
# of ant
# of ant
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Client4 reports to both APs
Client1
Client3
Client4
NDP-AAP1 NDP
AP2 NDP-A NDP
BF-R
BF-P
BF-R
π1β1
π1β3
π‘1β4
π2β1
π2β3
π‘2β4
π1β1π―1BF-P
Compute π―1
π‘2β4
π‘1β4
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Antenna usage optimization
# of ant
# of ant
# of ant
# of ant
# of ant
# of ant
# of ant
# of ant
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Client3 overhears Client4
Client1
Client3
Client4
NDP-AAP1 NDP
Overhear
AP2 NDP-A NDP
BF-R
BF-P
BF-R
π1β1
π1β3
π‘1β4
π2β1
π2β3
π‘2β4
π1β1π―1BF-P
Compute π―1
π‘1β4
π‘2β4
π‘1β4
44
Antenna usage optimization
# of ant
# of ant
# of ant
# of ant
# of ant
# of ant
# of ant
# of ant
![Page 45: Combatting Inter-cell Interference in 802.11ac-based MU ...Β Β· AP1 NDP-A NDP Overhear AP2 NDP-A NDP BF-R BF-P BF-R DATA DATA π 1β1 π1β3 π‘1β4 π2β π2β3 π‘2β4](https://reader033.fdocuments.us/reader033/viewer/2022042812/5faeb986e155e85fc23e9dca/html5/thumbnails/45.jpg)
Beamforming weight of Client3
AP1
1 2
AP2
1 2
Client1
1 2 3
Client2
1
Client3
1 2 Client4
1
π―3 = π‘1β4β₯ π1β3
β₯
π1β3
π‘1β4
45
![Page 46: Combatting Inter-cell Interference in 802.11ac-based MU ...Β Β· AP1 NDP-A NDP Overhear AP2 NDP-A NDP BF-R BF-P BF-R DATA DATA π 1β1 π1β3 π‘1β4 π2β π2β3 π‘2β4](https://reader033.fdocuments.us/reader033/viewer/2022042812/5faeb986e155e85fc23e9dca/html5/thumbnails/46.jpg)
Channel alignment by Client3
AP1
1 2
Client3
1 2 Client4
1
π―3 = π‘1β4β₯ π1β3
β₯
π1β3
π‘1β4
46
![Page 47: Combatting Inter-cell Interference in 802.11ac-based MU ...Β Β· AP1 NDP-A NDP Overhear AP2 NDP-A NDP BF-R BF-P BF-R DATA DATA π 1β1 π1β3 π‘1β4 π2β π2β3 π‘2β4](https://reader033.fdocuments.us/reader033/viewer/2022042812/5faeb986e155e85fc23e9dca/html5/thumbnails/47.jpg)
Channel alignment by Client3
AP1
1 2
Client3
1 2 Client4
1
π―3 = π‘1β4β₯ π1β3
β₯
π‘1β4π1β3
π‘1β4
47
![Page 48: Combatting Inter-cell Interference in 802.11ac-based MU ...Β Β· AP1 NDP-A NDP Overhear AP2 NDP-A NDP BF-R BF-P BF-R DATA DATA π 1β1 π1β3 π‘1β4 π2β π2β3 π‘2β4](https://reader033.fdocuments.us/reader033/viewer/2022042812/5faeb986e155e85fc23e9dca/html5/thumbnails/48.jpg)
Channel alignment by Client3
AP1
1 2
Client3
1 2 Client4
1
π―3 = π‘1β4β₯ π1β3
β₯
π‘1β4
π°1
π1β3
π‘1β4
48
![Page 49: Combatting Inter-cell Interference in 802.11ac-based MU ...Β Β· AP1 NDP-A NDP Overhear AP2 NDP-A NDP BF-R BF-P BF-R DATA DATA π 1β1 π1β3 π‘1β4 π2β π2β3 π‘2β4](https://reader033.fdocuments.us/reader033/viewer/2022042812/5faeb986e155e85fc23e9dca/html5/thumbnails/49.jpg)
Channel alignment by Client3
AP1
1 2
Client3
1 2 Client4
1
π―3 = π‘1β4β₯ π1β3
β₯
π°1
π1β3(1) π1β3(2)π1β3
π‘1β4π1β3π―3
49
![Page 50: Combatting Inter-cell Interference in 802.11ac-based MU ...Β Β· AP1 NDP-A NDP Overhear AP2 NDP-A NDP BF-R BF-P BF-R DATA DATA π 1β1 π1β3 π‘1β4 π2β π2β3 π‘2β4](https://reader033.fdocuments.us/reader033/viewer/2022042812/5faeb986e155e85fc23e9dca/html5/thumbnails/50.jpg)
AP2 polls Client3
Client1
Client3
Client4
NDP-AAP1 NDP
Overhear
AP2 NDP-A NDP
BF-R
BF-P
BF-R
π1β1
π1β3
π‘1β4
π2β1
π2β3
π‘2β4
π1β1π―1
Compute π―3
BF-P
BF-P
Compute π―1
π‘1β4
π‘2β4
π‘1β4
50
Antenna usage optimization
# of ant
# of ant
# of ant
# of ant
# of ant
# of ant
# of ant
# of ant
![Page 51: Combatting Inter-cell Interference in 802.11ac-based MU ...Β Β· AP1 NDP-A NDP Overhear AP2 NDP-A NDP BF-R BF-P BF-R DATA DATA π 1β1 π1β3 π‘1β4 π2β π2β3 π‘2β4](https://reader033.fdocuments.us/reader033/viewer/2022042812/5faeb986e155e85fc23e9dca/html5/thumbnails/51.jpg)
Client3 reports its channel vector
Client1
Client3
Client4
NDP-AAP1 NDP
Overhear
AP2 NDP-A NDP
BF-R
BF-P
BF-R
BF-R
π1β1
π1β3
π‘1β4
π2β1
π2β3
π‘2β4
π1β1π―1
π2β3π―3
Compute π―3
BF-P
BF-P
Compute π―1
π‘1β4
π‘2β4
π‘1β4
51
Antenna usage optimization
# of ant
# of ant
# of ant
# of ant
# of ant
# of ant
# of ant
# of ant
![Page 52: Combatting Inter-cell Interference in 802.11ac-based MU ...Β Β· AP1 NDP-A NDP Overhear AP2 NDP-A NDP BF-R BF-P BF-R DATA DATA π 1β1 π1β3 π‘1β4 π2β π2β3 π‘2β4](https://reader033.fdocuments.us/reader033/viewer/2022042812/5faeb986e155e85fc23e9dca/html5/thumbnails/52.jpg)
Client3 reports its channel vector
Client1
Client3
Client4
NDP-AAP1 NDP
Overhear
AP2 NDP-A NDP
BF-R
BF-P
BF-R
π1β1
π1β3
π‘1β4
π2β1
π2β3
π‘2β4
π1β1π―1
Compute π―3
BF-P
BF-P
Compute π―1
π‘1β4
π‘2β4
π‘1β4
52
BF-R
π2β3π―3
Beamforming weight optimizationAntenna usage optimization
# of ant
# of ant
# of ant
# of ant
# of ant
# of ant
# of ant
# of ant
![Page 53: Combatting Inter-cell Interference in 802.11ac-based MU ...Β Β· AP1 NDP-A NDP Overhear AP2 NDP-A NDP BF-R BF-P BF-R DATA DATA π 1β1 π1β3 π‘1β4 π2β π2β3 π‘2β4](https://reader033.fdocuments.us/reader033/viewer/2022042812/5faeb986e155e85fc23e9dca/html5/thumbnails/53.jpg)
Both APs transmit simultaneously
Client1
Client3
Client4
NDP-AAP1 NDP
Overhear
AP2 NDP-A NDP
BF-R
BF-P
BF-R
DATA
DATA
π1β1
π1β3
π‘1β4
π2β1
π2β3
π‘2β4
π1β1π―1
Compute π―3
BF-P
BF-P
Compute π―1
π‘1β4
π‘2β4
π‘1β4
53
Beamforming weight optimizationAntenna usage optimization
BF-R
π2β3π―3
# of ant
# of ant
# of ant
# of ant
# of ant
# of ant
# of ant
# of ant
![Page 54: Combatting Inter-cell Interference in 802.11ac-based MU ...Β Β· AP1 NDP-A NDP Overhear AP2 NDP-A NDP BF-R BF-P BF-R DATA DATA π 1β1 π1β3 π‘1β4 π2β π2β3 π‘2β4](https://reader033.fdocuments.us/reader033/viewer/2022042812/5faeb986e155e85fc23e9dca/html5/thumbnails/54.jpg)
No additional frames
Client1
Client3
Client4
NDP-AAP1 NDP
Overhear
AP2 NDP-A NDP
BF-R
BF-P
BF-R
DATA
DATA
π1β1
π1β3
π‘1β4
π2β1
π2β3
π‘2β4
π1β1π―1
Compute π―3
BF-P
BF-P
Compute π―1
π‘1β4
π‘2β4
π‘1β4
54
Beamforming weight optimizationAntenna usage optimization
BF-R
π2β3π―3
# of ant
# of ant
# of ant
# of ant
# of ant
# of ant
# of ant
# of ant
![Page 55: Combatting Inter-cell Interference in 802.11ac-based MU ...Β Β· AP1 NDP-A NDP Overhear AP2 NDP-A NDP BF-R BF-P BF-R DATA DATA π 1β1 π1β3 π‘1β4 π2β π2β3 π‘2β4](https://reader033.fdocuments.us/reader033/viewer/2022042812/5faeb986e155e85fc23e9dca/html5/thumbnails/55.jpg)
Will APs/clients acquire enough channel knowledge?
55
![Page 56: Combatting Inter-cell Interference in 802.11ac-based MU ...Β Β· AP1 NDP-A NDP Overhear AP2 NDP-A NDP BF-R BF-P BF-R DATA DATA π 1β1 π1β3 π‘1β4 π2β π2β3 π‘2β4](https://reader033.fdocuments.us/reader033/viewer/2022042812/5faeb986e155e85fc23e9dca/html5/thumbnails/56.jpg)
56
Theorem 1:
At most, a AP needs:
channel knowledge from its served clients, or
clients it interferes with and holds the cancellation responsibility
![Page 57: Combatting Inter-cell Interference in 802.11ac-based MU ...Β Β· AP1 NDP-A NDP Overhear AP2 NDP-A NDP BF-R BF-P BF-R DATA DATA π 1β1 π1β3 π‘1β4 π2β π2β3 π‘2β4](https://reader033.fdocuments.us/reader033/viewer/2022042812/5faeb986e155e85fc23e9dca/html5/thumbnails/57.jpg)
57
Theorem 1:
At most, a AP needs:
channel knowledge from its served clients,
clients it interferes with and holds the cancellation responsibility
![Page 58: Combatting Inter-cell Interference in 802.11ac-based MU ...Β Β· AP1 NDP-A NDP Overhear AP2 NDP-A NDP BF-R BF-P BF-R DATA DATA π 1β1 π1β3 π‘1β4 π2β π2β3 π‘2β4](https://reader033.fdocuments.us/reader033/viewer/2022042812/5faeb986e155e85fc23e9dca/html5/thumbnails/58.jpg)
58
Theorem 1:
At most, a AP needs:
channel knowledge from its served clients,
or clients it interferes with and holds the cancellation responsibility
![Page 59: Combatting Inter-cell Interference in 802.11ac-based MU ...Β Β· AP1 NDP-A NDP Overhear AP2 NDP-A NDP BF-R BF-P BF-R DATA DATA π 1β1 π1β3 π‘1β4 π2β π2β3 π‘2β4](https://reader033.fdocuments.us/reader033/viewer/2022042812/5faeb986e155e85fc23e9dca/html5/thumbnails/59.jpg)
Clients report necessary channels
Client1
Client3
Client4
NDP-AAP1 NDP
Overhear
AP2 NDP-A NDP
BF-R
BF-P
BF-R
DATA
DATA
π1β1
π1β3
π‘1β4
π2β1
π2β3
π‘2β4
π1β1π―1
Compute π―3
BF-P
BF-P
Compute π―1
π‘1β4
π‘2β4
π‘1β4
59
BF-R
π2β3π―3
# of ant
# of ant
# of ant
# of ant
# of ant
# of ant
# of ant
# of ant
![Page 60: Combatting Inter-cell Interference in 802.11ac-based MU ...Β Β· AP1 NDP-A NDP Overhear AP2 NDP-A NDP BF-R BF-P BF-R DATA DATA π 1β1 π1β3 π‘1β4 π2β π2β3 π‘2β4](https://reader033.fdocuments.us/reader033/viewer/2022042812/5faeb986e155e85fc23e9dca/html5/thumbnails/60.jpg)
Theorem 2:
At most, a client needs:
channel knowledge from clients in the same cell;
if ordered properly, channel knowledge from previous clients.
60
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Theorem 2:
At most, a client needs:
channel knowledge from clients in the same cell;
if ordered properly, channel knowledge from previous clients.
61
![Page 62: Combatting Inter-cell Interference in 802.11ac-based MU ...Β Β· AP1 NDP-A NDP Overhear AP2 NDP-A NDP BF-R BF-P BF-R DATA DATA π 1β1 π1β3 π‘1β4 π2β π2β3 π‘2β4](https://reader033.fdocuments.us/reader033/viewer/2022042812/5faeb986e155e85fc23e9dca/html5/thumbnails/62.jpg)
Theorem 2:
At most, a client needs:
channel knowledge from clients in the same cell;
if ordered properly, channel knowledge from previous clients.
62
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Clients report in the optimal order
Client1
Client3
Client4
NDP-AAP1 NDP
Overhear
AP2 NDP-A NDP
BF-R
BF-P
BF-R
BF-R
DATA
DATA
π1β1
π1β3
π‘1β4
π2β1
π2β3
π‘2β4
π1β1π―1
π2β3π―3
Compute π―3
BF-P
BF-P
Compute π―1
π‘1β4
π‘2β4
π‘1β4
63
# of ant
# of ant
# of ant
# of ant
# of ant
# of ant
# of ant
# of ant
![Page 64: Combatting Inter-cell Interference in 802.11ac-based MU ...Β Β· AP1 NDP-A NDP Overhear AP2 NDP-A NDP BF-R BF-P BF-R DATA DATA π 1β1 π1β3 π‘1β4 π2β π2β3 π‘2β4](https://reader033.fdocuments.us/reader033/viewer/2022042812/5faeb986e155e85fc23e9dca/html5/thumbnails/64.jpg)
Will CoaCa APs/clients interoperate with unmodified 802.11ac clients?
64
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Clients passively report channels
65
Client1
Client3
Client4
NDP-AAP1 NDP
Overhear
AP2 NDP-A NDP
BF-R
BF-P
BF-R
BF-R
DATA
DATA
π1β1
π1β3
π‘1β4
π2β1
π2β3
π‘2β4
π1β1π―1
π2β3π―3
Compute π―3
BF-P
BF-P
Compute π―1
π‘1β4
π‘2β4
π‘1β4
# of ant
# of ant
# of ant
# of ant
# of ant
# of ant
# of ant
# of ant
![Page 66: Combatting Inter-cell Interference in 802.11ac-based MU ...Β Β· AP1 NDP-A NDP Overhear AP2 NDP-A NDP BF-R BF-P BF-R DATA DATA π 1β1 π1β3 π‘1β4 π2β π2β3 π‘2β4](https://reader033.fdocuments.us/reader033/viewer/2022042812/5faeb986e155e85fc23e9dca/html5/thumbnails/66.jpg)
Clients do not collide with APs
66
Client1
Client3
Client4
NDP-AAP1 NDP
Overhear
AP2 NDP-A NDP
BF-R
BF-P
BF-R
BF-R
DATA
DATA
π1β1
π1β3
π‘1β4
π2β1
π2β3
π‘2β4
π1β1π―1
π2β3π―3
Compute π―3
BF-P
BF-P
Compute π―1
π‘1β4
π‘2β4
π‘1β4
Fake client ID
# of ant
# of ant
# of ant
# of ant
# of ant
# of ant
# of ant
# of ant
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Correctness of the two-step optimization
Client1
Client3
Client4
NDP-AAP1 NDP
Overhear
AP2 NDP-A NDP
BF-R
BF-P
BF-R
DATA
DATA
π1β1
π1β3
π‘1β4
π2β1
π2β3
π‘2β4
π1β1π―1
Compute π―3
BF-P
BF-P
Compute π―1
π‘1β4
π‘2β4
π‘1β4
67
Beamforming weight optimizationAntenna usage optimization
BF-R
π2β3π―3
# of ant
# of ant
# of ant
# of ant
# of ant
# of ant
# of ant
# of ant
![Page 68: Combatting Inter-cell Interference in 802.11ac-based MU ...Β Β· AP1 NDP-A NDP Overhear AP2 NDP-A NDP BF-R BF-P BF-R DATA DATA π 1β1 π1β3 π‘1β4 π2β π2β3 π‘2β4](https://reader033.fdocuments.us/reader033/viewer/2022042812/5faeb986e155e85fc23e9dca/html5/thumbnails/68.jpg)
Interoperability with unmodified 802.11ac clients
Client1
Client3
Client4
NDP-AAP1 NDP
Overhear
AP2 NDP-A NDP
BF-R
BF-P
BF-R
DATA
DATA
π1β1
π1β3
π‘1β4
π2β1
π2β3
π‘2β4
π1β1π―1
Compute π―3
BF-P
BF-P
Compute π―1
π‘1β4
π‘2β4
π‘1β4
68
Beamforming weight optimizationAntenna usage optimization
BF-R
π2β3π―3
# of ant
# of ant
# of ant
# of ant
# of ant
# of ant
# of ant
# of ant
![Page 69: Combatting Inter-cell Interference in 802.11ac-based MU ...Β Β· AP1 NDP-A NDP Overhear AP2 NDP-A NDP BF-R BF-P BF-R DATA DATA π 1β1 π1β3 π‘1β4 π2β π2β3 π‘2β4](https://reader033.fdocuments.us/reader033/viewer/2022042812/5faeb986e155e85fc23e9dca/html5/thumbnails/69.jpg)
Implementation
β’ WARP V3 platformβ’ Up to four antennas on each AP/client
β’ Layered prototyping: FPGA/C/MATLAB
β’ WARPLab framework with modificationsβ’ Standard MIMO processing in FPGA
β’ Two-step optimization in MATLAB
69
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Experimental setup
β’ Single interference domain
β’ MU-MIMO network with two cells
β’ Four cases with different node and antenna configurations
β’ 20 repeated experiments for each case
β’ CoaCa compared with 802.11ac
70
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AP1 AP2
71
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Case 1: two streams for CoaCa (no gain)
AP1
Client1
AP2
Client2
Client3
Client4
Cell 1 Cell 2
72
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Case 1: CoaCa achieves similar capacity
0
5
10
15
20
25
0 5 10 15 20 25
Cap
acit
y b
y 1
1ac
(b
its/
s/H
z)
Capacity by CoaCa (bits/s/Hz)
Measured
Expected
73
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Case 2: three streams for CoaCa (50% gain)
AP1
Client1
AP2
Client2
Client3
Client4
Cell 1 Cell 2
74
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Case 2: CoaCa improves capacity by 40%
0
7
14
21
28
35
0 7 14 21 28 35
Cap
acit
y b
y 1
1ac
(bit
s/s/
Hz)
Capacity by CoaCa (bits/s/Hz)
Measured
No gain
Expected
75
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76
Max # of streams β max capacity
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77
Trivial gain for larger-scale networks
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Related works
β’ Inter-cell interference in 802.11 networksβ’ K. C. Lin, S. Gollakota, and D. Katabi. βRandom Access
Heterogeneous MIMO networksβ. In Proc. ACM SIGCOMM, 2011.
β’ Network-MIMOβ’ H. Rahul, S. Kumar, and D. Katabi. βJMB: Scaling Wireless
Capacity with User Demandsβ. In Proc. ACM SIGCOMM, 2012.β’ H. V. Balan, R. Rogalin, A. Michaloliakos, and K. Psounis.
βAchieving High Data Rates in a Distributed MIMO Systemβ. In Proc. ACM MobiCom, 2012.
β’ X. Zhang, K. Sundaresan, M. A. Khojastepour, S. Rangarajan, and K. G. Shin. βNEMOx: Scalable Network MIMO for Wireless Networksβ. In Proc. ACM MobiCom, 2013.
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CoaCa: practical solution to combat inter-cell interference in
802.11ac-based MU-MIMO networks
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