Transcript
A Scalable Multi-User Uplink for Wi-Fi Adriana B. Flores Sadia Quadri, and Edward W. Knightly NSDI, March 2016
Start of Wi-Fi AP
• • • •
Standardized in 1997 SISO Single user at a time Omni-directional transmission
Client A Scalable Multi-User Uplink for Wi-Fi Adriana Flores
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MIMO in 802.11 AP
Rx
• Multiple concurrent transmissions • MxN MIMO increases throughput by min(Tx antennas, Rx antennas)
Client
A Scalable Multi-User Uplink for Wi-Fi Adriana Flores
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MIMO in 802.11 AP
• Multiple concurrent transmissions • MxN MIMO increases throughput by min(Tx antennas, Rx antennas)
Client
Rx Rx Rx Rx
A Scalable Multi-User Uplink for Wi-Fi Adriana Flores
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MIMO in 802.11 AP
• Multiple concurrent transmissions • MxN MIMO increases throughput by min(Tx antennas, Rx antennas)
Client
Rx Rx Rx Rx
A Scalable Multi-User Uplink for Wi-Fi Adriana Flores
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Antenna Asymmetry AP
• MxN MIMO increases throughput by min(Tx antennas, Rx antennas) • Client devices often have N=1 antenna due to cost and space
Client A Scalable Multi-User Uplink for Wi-Fi Adriana Flores
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Antenna Asymmetry • MxN MIMO increases throughput by min(Tx antennas, Rx antennas) • Client devices often have N=1 antenna due to cost and space
A Scalable Multi-User Uplink for Wi-Fi Adriana Flores
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Antenna Asymmetry 8 Antennas
• MxN MIMO increases throughput by min(Tx antennas, Rx antennas) • Client devices often have N=1 antenna due to cost and space
1 Antenna
A Scalable Multi-User Uplink for Wi-Fi Adriana Flores
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Antenna Asymmetry 8 Antennas
• MxN MIMO increases throughput by min(Tx antennas, Rx antennas) • Client devices often have N=1 antenna due to cost and space
1 Antenna
A Scalable Multi-User Uplink for Wi-Fi Adriana Flores
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Antenna Asymmetry 8 Antennas
• MxN MIMO increases throughput by min(Tx antennas, Rx antennas) • Client devices often have N=1 antenna due to cost and space
1 Antenna
A Scalable Multi-User Uplink for Wi-Fi Adriana Flores
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Downlink Multi-User MIMO AP
Client
C1 C2 C3 C4
A Scalable Multi-User Uplink for Wi-Fi Adriana Flores
• MxN MIMO increases throughput by min(Tx antennas, Rx antennas) • Downlink Multi-User MIMO allows for APs to leverage antennas • Transmitter sends multiple streams concurrently to different users • Remove Interference by “ZeroForcing Beamforming” (ZFBF)
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Downlink Multi-User MIMO AP
C2 C3 C1
A Scalable Multi-User Uplink for Wi-Fi Adriana Flores
C4
• MxN MIMO increases throughput by min(Tx antennas, Rx antennas) • Downlink Multi-User MIMO allows for APs to leverage antennas • Transmitter sends multiple streams concurrently to different users • Remove Interference by “ZeroForcing Beamforming” (ZFBF)
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Downlink Multi-User MIMO AP
C2 C3 C1
A Scalable Multi-User Uplink for Wi-Fi Adriana Flores
C4
• MxN MIMO increases throughput by min(Tx antennas, Rx antennas) • Downlink Multi-User MIMO allows for APs to leverage antennas • Transmitter sends multiple streams concurrently to different users • Remove Interference by “ZeroForcing Beamforming” (ZFBF)
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Uplink Multi-User MIMO? AP
• MxN MIMO increases throughput by min(Tx antennas, Rx antennas) • Back to 1997 – SISO transmission
C2 C3 C1
A Scalable Multi-User Uplink for Wi-Fi Adriana Flores
C4
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Uplink Multi-User MIMO? AP
• MxN MIMO increases throughput by min(Tx antennas, Rx antennas) • Back to 1997 – SISO transmission
C2 C3 C1
A Scalable Multi-User Uplink for Wi-Fi Adriana Flores
C4
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Why Not Mimic Downlink MU-MIMO? AP
• • • •
Paradigm Shift Many One No connection between devices How do we remove interference?
C2 C3 C1
A Scalable Multi-User Uplink for Wi-Fi Adriana Flores
C4
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MUSE : Multi-User ScalableE Uplink AP
• Match the number of transmitters to the number of antennas at AP • No control signaling
C2 C3 C1
A Scalable Multi-User Uplink for Wi-Fi Adriana Flores
C4
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MUSE : Multi-User ScalableE Uplink AP
• Match the number of transmitters to the number of antennas at AP • No control signaling
C2 C3 C1
A Scalable Multi-User Uplink for Wi-Fi Adriana Flores
C4
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MUSE : Multi-User ScalableE Uplink AP
• Match the number of transmitters to the number of antennas at AP • No control signaling
C2 C3 C1
A Scalable Multi-User Uplink for Wi-Fi Adriana Flores
C4
• Multiple transmitters act as a single device with multiple antennas • No control channel • Remove interference 8
Transmit Simultaneously • Association ID for user selection and grouping • Arbitrary index for each user • AP informs the network the Max ID Rx AP
AP Receiver
User 1 User 2 User 3
3 6
5
7 4
1
User 4 User 5
2
User 6 User 7
A Scalable Multi-User Uplink for Wi-Fi Adriana Flores
Time 9
Transmit Simultaneously • Association ID for user selection and grouping • Arbitrary index for each user • AP informs the network the Max ID Rx AP
AP Receiver
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User 1 User 2 User 3
3 6
7 4
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User 4 User 5 4
5
1
2
User 6 10
User 7 A Scalable Multi-User Uplink for Wi-Fi Adriana Flores
Time 9
Transmit Simultaneously • Association ID for user selection and grouping • Arbitrary index for each user • AP informs the network the Max ID Rx AP
AP Receiver
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User 1 User 2
3 6
7
7 6
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1
2
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Circular ID Vicinity
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5
User 3
1
8
User 4
3 4
User 5 4
User 6
T R G
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User 7 A Scalable Multi-User Uplink for Wi-Fi Adriana Flores
Time 9
Transmit Simultaneously • Association ID for user selection and grouping • Arbitrary index for each user • AP informs the network the Max ID Rx AP
AP Receiver
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Data
User 1 User 2
3 6
7
7 6
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1
2
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Circular ID Vicinity
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5
User 3
1
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User 4
3 4
User 5 4
User 6
Data
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User 7 A Scalable Multi-User Uplink for Wi-Fi Adriana Flores
T R G
Data Time 10
Transmit Simultaneously • Association ID for user selection and grouping • Arbitrary index for each user • AP informs the network the Max ID Rx AP
AP Receiver
A C K
A C K
A C K
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Data
User 1 User 2
3 6
7
7 6
4
1
2
2
Circular ID Vicinity
5
5
User 3
1
8
User 4
3 4
User 5 4
User 6
Data
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User 7 A Scalable Multi-User Uplink for Wi-Fi Adriana Flores
T R G
Data Time 10
Transmit Simultaneously • Association ID for user selection and grouping • Arbitrary index for each user • AP informs the network the Max ID Rx AP
AP Receiver
A C K
A C K
A C K
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Data
User 1 User 2
3 6
7
7 6
4
1
2
2
Circular ID Vicinity
5
5
User 3
1
User 4
3 4
User 5 4
User 6
T R G
Data
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User 7 A Scalable Multi-User Uplink for Wi-Fi Adriana Flores
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Data Time 10
Remove Interference AP • Environmental Multipath • Independent paths (channels) • Receiver (AP) estimate channels
C1
C2 A Scalable Multi-User Uplink for Wi-Fi Adriana Flores
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Remove Interference AP • Environmental Multipath • Independent paths (channels) • Receiver (AP) estimate channels
C1
C2 A Scalable Multi-User Uplink for Wi-Fi Adriana Flores
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Receiver Channel Estimation AP
• Known set of training signals • Enable distributed usage • Fixed size (# Streams = # Rx antennas) • User has assigned set of training signals • Assignment through Association ID • No control signaling (coordination) required A 1
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IDs
5 A Scalable Multi-User Uplink for Wi-Fi Adriana Flores
3 4
C1
B
2
6
A
D
C
B C2 12
Receiver Channel Estimation AP
• Known set of training signals • Enable distributed usage • Fixed size (# Streams = # Rx antennas) • User has assigned set of training signals • Assignment through Association ID • No control signaling (coordination) required A 1
7
IDs
5 A Scalable Multi-User Uplink for Wi-Fi Adriana Flores
3 4
B
C1
B
2
6
A
D
C
C2 12
Group Adaptation • Association ID Reassignment • AP learning process: which users are most likely to transmit AP Receiver 1 7 6
3
7
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Association IDs
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2 3 4
2 1 A Scalable Multi-User Uplink for Wi-Fi Adriana Flores
Time 13
Group Adaptation • Association ID Reassignment • AP learning process: which users are most likely to transmit AP Receiver 4 7 6
3
7
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Association IDs
5
4
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2 3 1
2 1 A Scalable Multi-User Uplink for Wi-Fi Adriana Flores
Time 13
Group Adaptation • Association ID Reassignment • AP learning process: which users are most likely to transmit AP Receiver 1 4 7 6
3
7
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Association IDs
5
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2 3 41
2 14 A Scalable Multi-User Uplink for Wi-Fi Adriana Flores
Time 13
MUSE Implementation Trigger Cables • OTA experiments WARPLab • 1 to 4 concurrent spatial streams • Evaluation Setup: Clients • Clients: single WARP board with independent RF clocks • Time synchronized through triggering cables • Conference room 645sq ft or 60 sq m • Evaluate over 20 locations
AP A Scalable Multi-User Uplink for Wi-Fi Adriana Flores
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MUSE Scalability • Scalability can be limited by inter-stream interference and channel correlation between users • MUSE PHY ability to achieve full-rank capacity and permit scaling • Setup: 395%
• 1x1, 2x2, 3x3, 4x4 • 2000 packets • 24 Mbps
290%
197%
A Scalable Multi-User Uplink for Wi-Fi Adriana Flores
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MUSE Scalability • Scalability can be limited by inter-stream interference and channel correlation between users • MUSE PHY ability to achieve full-rank capacity and permit scaling • Setup: 395%
• 1x1, 2x2, 3x3, 4x4 • 2000 packets • 24 Mbps
290%
Tx Beamforming is NOT needed for distributed uplink multi-user transmission
197%
A Scalable Multi-User Uplink for Wi-Fi Adriana Flores
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MUSE Scalability • Empirical capacity with estimated channels
𝐶 𝑏𝑝𝑠 𝐻𝑧 = 𝑙𝑜𝑔2 det 𝐼𝑁 + (𝑆𝑁𝑅 𝑀)(𝐻𝐻∗ ) 33.48
26.11
18.45
9.6 193 Mbps to 669 Mbps
A Scalable Multi-User Uplink for Wi-Fi Adriana Flores
[1] Foschini, Gerard J. "Layered space-time architecture for wireless communication in a fading environment when using multi-element antennas."Bell labs technical journal 1.2 (1996).
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[1]
Conclusion MUSE
AP
• Scalable Multi-User MIMO uplink WLAN • Match the number of transmitters to the number of antennas at AP • No control signaling
• • • • •
Emulate Single Multi-Antenna device Transmit Simultaneously ID-Based Grouping and Synchronization Enable distributed and dynamic Rx channel estimation Leverage environmental multipath Standard compatible
C2
C3
C1 C4
A Scalable Multi-User Uplink for Wi-Fi Adriana Flores
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Conclusion MUSE
AP
• Scalable Multi-User MIMO uplink WLAN • Match the number of transmitters to the number of antennas at AP • No control signaling
• • • • •
Emulate Single Multi-Antenna device Transmit Simultaneously ID-Based Grouping and Synchronization Enable distributed and dynamic Rx channel estimation Leverage environmental multipath Standard compatible
C2
C3
C1 C4
A Scalable Multi-User Uplink for Wi-Fi Adriana Flores
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