Reconfigurable antennas for WiFinetworksDaniele Piazza

Founder and CTO – Adant Technologies Inc

Company Overview

2

Adant designs, licenses, and manufactures reconfigurable (smart) antenna systems for the

wireless communications industry

AdantSF Bay Area

AdantPadova, Italy

AdantTaiwan

Adant main markets

WIRELESS NETWORKING

HOME GATEWAY

MOBILE INTERNET

RFID

Wireless ISP

3

Outline

q Reconfigurable antenna system for WiFi devices

q Advantages and challenges of using reconfigurable antennas in commercial WiFi devices

l Network capacity maximization

l Interference mitigation

l Enhanced capacity in high density environments

l Coordination and benefit with digital beamforming

l Coordination and benefit with MU-­MIMO

q Conclusions

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Active RF devices shape the antenna beams and control their direction

PCB metamaterial antenna integrates easily into any device

Reconfigurable antenna system

SW algorithms select the optimal beam shape for

maximum reliability of the wireless link

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MIMO systems – adaptive antennas

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The best wireless communication channel between TX/RX antennas is carefully selected among the large set of channels that can be generated by changing the antenna radiation patterns

SINGLE CHANNEL

STANDARD MIMO SYSTEM MIMO SYSTEM WITH RECONFIGURABLE ANTENNAS

DIFFERENT CHANNELS

CHANNEL SELECTION

TX RX

Standard static antenna

TX RX

Reconfigurable antenna

maximize channel diversity + SNR at

receiver suppress interference enhance pre-­coding

techniques

Reconfigurable HW conceptual design

q Passive metal elements can be connected or disconnected from a ground plane or connected and disconnected between each other to change the beam and null direction of the active element

q Adant patented smart antenna technology and designs allow for best radiation efficiency, good impedance matching and lowest cost

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Active antenna

Passive metallization

Reconfigurable antenna capabilities

q Each antenna in the array can generate up to 2N independentradiation patterns where N is the number of parasitic elements in the antenna

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2016-­Q2 Adant Smart Antenna PortfolioAll designs are scalable to different form factors to fit Wi-­Fi

base stations for indoor and outdoor applications

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Antennas with omnidirectional coverage

Antennas with sectorial coverage

Integration with WiFi systems

q Integration is designed to support packet by packet configuration switching

q Antenna system allows for ≤ 1 µsec switching time

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WiFi 3x3 device

CPUwith

reconfigurable antenna drivers

Antenna control circuitry

WiFichipset

GPIO

GPIO

DC bias line

ANT 1

ANT 2

ANT 3

Maximum diversity + SNR

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Q array configurations

Optimal antenna selection

TXRX

H1H2

HN

…

𝐶 = max log) 𝑑𝑒𝑡 𝑰 +𝑆𝑁𝑅2𝑁3

𝑯2𝑯2∗

y = H x + n

Configuration selection in WLAN devices

qNormally the channel matrix (𝑯)is not directly available in commercial WLAN devices

qThe problem of selecting the optimal smart antenna configuration can be separated in two steps:l Evaluating the cost function: access the required parameters and compute the value

l Smart Antenna training: optimizing the cost function

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Cost function in WLAN devices

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qCost function must be strongly correlated to the performance metric that needs to be optimized

Available parameters

Meaning

RSSI Strength of received signal per antenna

SR Packet success rate

rate Rate of data transmission(modulation and coding)

BW Bandwidth of operationPL Packet length

APSTA

DATA PACKET

ACK

Example of cost function (CF) for throughput (TP) optimization

𝐶𝐹 = 𝑓 𝑆𝑅,𝑅𝑆𝑆𝐼, 𝑟𝑎𝑡𝑒, 𝐵𝑊, 𝑃𝐿

𝜌 𝐶𝐹, 𝑇𝑃 ≥ 0.9

Test setup

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Old villa Concrete ground and ceiling

Harsh environment

Underground parking lotConcrete ground and ceiling Quasi LOS environment

q Downlink and uplink throughput is measured with an omnidirectional antenna and with a reconfigurable antenna using a 3x3 BS and 2x2 client

Measured Performance – single client

Data sample of 100 measurements

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Average TP impr.Downlink = 36%Uplink = 30%

Reconfigurable antenna system improvement vs static antenna system

40% of cases where gain > 35% in download;; (30%in upload)

Measured Performance – single client

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Performance benefit is max at low SNR

Throughput Improvement vs. internal omnidirectional antennas

5 GHzDOWNLINK UPLINK

ALL THROUGHPUT RANGES 1.36x 1.30x

HIGH THROUGHPUT(>60% of MAX THROUGHPUT)

1.15x 1.04x

LOW THROUGHPUT (<30% of MAX THROUGHPUT)

1.43x 1.34×

Measured Performance – multi client

Reconfigurable antenna system improvement vs static antenna system

Average TP improvement = 30%

Data sample of 44 measurements

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Reconfigurable antennas for interference mitigation

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Q array configurations

Optimal antenna selection

TXRX

H1H2

HN

…

𝐶 = max log) 𝑑𝑒𝑡 𝑰 +𝑆𝑁𝑅2𝑁3

𝑯2𝑯2∗𝑾2

HI

Dynamically change direction of radiation to maximize power at the receiver while minimizing interference

Adant interference mitigation

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Interference test setup

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q Throughput in downlink is measured with an omnidirectional antenna and with a reconfigurable antenna using a 3x3 BS and 2x2 client

q Client (STA) is exposed to a lower amount of interference with respect to the AP

q Distance between AP and client is minimized to determine only the effect due to interference mitigation

d < 5 m

D > d

d < 5 m

D > d

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Measured Performance

Reconfigurable antenna system improvement vs static antenna system

20 different scenarios

Average TP improvement = 3.5X

High density deployment

AP 1 AP 3

AP 2 AP 46

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7

8

q Multiple APs operating on the same frequency channel

q Co-­channel interference is main cause of performance degradation

q Reconfigurable antennas provides coordinated interference mitigation capabilities to improve the network capacity

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Multiple base stations with implicit coordinationEach optimizes its own cost function with no coordination with the other base stations

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Figure.5.Aggregate)throughput)of)each)BSS,)total)per)deployment:)AP)tx)power)set)to)17dBm)

)We)repeated)a)very)similar)test)with)four)additional)deployments)targeted)to)analyzing)whether)SA)technology) may) address) the) coTchannel) interference) problem) also) with) higher) settings) of) the)transmission)power:)to)this)end)we)increased)the)transmission)power)of)ZyXEL)and)Ruckus)only)to)23dBm)keeping)the)others)to)17dBm.)This)should)increase)the)interference)between)the)two)BSSs)but)only)for)the)APs)equipped)with)SA)technology.))As)before)we)report)in)Figure)6)the)positions)of)the)clients)for)the)four)additional)deployments.)The)first)two,)3T1)and)3T2,)are)on)the)left;)the)others,)4T1)and)4T2,)are)on)the)right.)We)use)again)arrows)to)indicate)how)we)moved)nodes)from)one)deployment)to)the)next.)))

BSS1 BSS2 BSS1+BSS20

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gre

ga

te T

hro

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[Mb

/s]

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zyxelruckusciscoaruba

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zyxelruckusciscoaruba

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zyxelruckusciscoaruba

BSS1 BSS2 BSS1+BSS20

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zyxelruckusciscoaruba

Figure.5.Aggregate)throughput)of)each)BSS,)total)per)deployment:)AP)tx)power)set)to)17dBm)

)We)repeated)a)very)similar)test)with)four)additional)deployments)targeted)to)analyzing)whether)SA)technology) may) address) the) coTchannel) interference) problem) also) with) higher) settings) of) the)transmission)power:)to)this)end)we)increased)the)transmission)power)of)ZyXEL)and)Ruckus)only)to)23dBm)keeping)the)others)to)17dBm.)This)should)increase)the)interference)between)the)two)BSSs)but)only)for)the)APs)equipped)with)SA)technology.))As)before)we)report)in)Figure)6)the)positions)of)the)clients)for)the)four)additional)deployments.)The)first)two,)3T1)and)3T2,)are)on)the)left;)the)others,)4T1)and)4T2,)are)on)the)right.)We)use)again)arrows)to)indicate)how)we)moved)nodes)from)one)deployment)to)the)next.)))

BSS1 BSS2 BSS1+BSS20

100

200

300

400

500

600

Ag

gre

ga

te T

hro

ug

hp

ut

[Mb

/s]

Deployment 1−1

zyxelruckusciscoaruba

BSS1 BSS2 BSS1+BSS20

100

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Ag

gre

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te T

hro

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hp

ut

[Mb

/s]

Deployment 1−2

zyxelruckusciscoaruba

BSS1 BSS2 BSS1+BSS20

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Ag

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zyxelruckusciscoaruba

BSS1 BSS2 BSS1+BSS20

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gre

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Deployment 2−2

zyxelruckusciscoaruba

Figure.5.Aggregate)throughput)of)each)BSS,)total)per)deployment:)AP)tx)power)set)to)17dBm)

)We)repeated)a)very)similar)test)with)four)additional)deployments)targeted)to)analyzing)whether)SA)technology) may) address) the) coTchannel) interference) problem) also) with) higher) settings) of) the)transmission)power:)to)this)end)we)increased)the)transmission)power)of)ZyXEL)and)Ruckus)only)to)23dBm)keeping)the)others)to)17dBm.)This)should)increase)the)interference)between)the)two)BSSs)but)only)for)the)APs)equipped)with)SA)technology.))As)before)we)report)in)Figure)6)the)positions)of)the)clients)for)the)four)additional)deployments.)The)first)two,)3T1)and)3T2,)are)on)the)left;)the)others,)4T1)and)4T2,)are)on)the)right.)We)use)again)arrows)to)indicate)how)we)moved)nodes)from)one)deployment)to)the)next.)))

BSS1 BSS2 BSS1+BSS20

100

200

300

400

500

600

Aggre

gate

Thro

ughput [M

b/s

]

Deployment 1−1

zyxelruckusciscoaruba

BSS1 BSS2 BSS1+BSS20

100

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gate

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ughput [M

b/s

]

Deployment 1−2

zyxelruckusciscoaruba

BSS1 BSS2 BSS1+BSS20

100

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gate

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ughput [M

b/s

]

Deployment 2−1

zyxelruckusciscoaruba

BSS1 BSS2 BSS1+BSS20

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gate

Thro

ughput [M

b/s

]

Deployment 2−2

zyxelruckusciscoaruba

)Figure.4)Positions)of)the)clients)for)the)four)deployments)with)transmission)power)set)to)17dBm..

)

We) can) see) in) Table) 5) that) ZyXEL,) in) the) first) three) deployments,) boosts) the) total) aggregate)

throughput)from)a)+25,5%)minimum)to)a)+46,7%)maximum)with)respect)to)the)second)in)the)rank)

that)is)Cisco.)Only)in)the)fourth)deployment)Cisco)does)better)with)a)+14.6%)increase)with)respect)

to)ZyXEL)that)ranks)second.)Also)this)test)confirm)that)a)specific)SA)technology)could)really)make)

the)difference)in)reducing)coTchannel)interference.)

)

Table.5)Total)aggregate)throughput)per)deployment:)AP)tx)power)set)to)17dBm.

6 Aruba6 Cisco6 Ruckus6 6ZyXEL6Depl.61#16 317,81) 425,82) 402,09) 544,98)

Depl.61#26 314,20) 439,87) 385,11) 645,36)

Depl.62#16 303,57) 452,95) 385,74) 568,57)

Depl.62#26 268,44) 333,30) 237,88) 290,68)

)

We)also)report)in)Figure)5)the)details)with)the)aggregate)throughput)per)BSS:)the)winner)in)the)total)

throughput)competition)wins)also)in)each)of)the)BSS.)

))

6

5 7

1

8

2 4

3

AP#2

AP#1

6

5 7

4

3

AP#2

AP#1

6

5 7

8

1

2 4

3

8 7 2 1

)Figure.4)Positions)of)the)clients)for)the)four)deployments)with)transmission)power)set)to)17dBm..

)

We) can) see) in) Table) 5) that) ZyXEL,) in) the) first) three) deployments,) boosts) the) total) aggregate)

throughput)from)a)+25,5%)minimum)to)a)+46,7%)maximum)with)respect)to)the)second)in)the)rank)

that)is)Cisco.)Only)in)the)fourth)deployment)Cisco)does)better)with)a)+14.6%)increase)with)respect)

to)ZyXEL)that)ranks)second.)Also)this)test)confirm)that)a)specific)SA)technology)could)really)make)

the)difference)in)reducing)coTchannel)interference.)

)

Table.5)Total)aggregate)throughput)per)deployment:)AP)tx)power)set)to)17dBm.

6 Aruba6 Cisco6 Ruckus6 6ZyXEL6Depl.61#16 317,81) 425,82) 402,09) 544,98)

Depl.61#26 314,20) 439,87) 385,11) 645,36)

Depl.62#16 303,57) 452,95) 385,74) 568,57)

Depl.62#26 268,44) 333,30) 237,88) 290,68)

)

We)also)report)in)Figure)5)the)details)with)the)aggregate)throughput)per)BSS:)the)winner)in)the)total)

throughput)competition)wins)also)in)each)of)the)BSS.)

))

6

5 7

1

8

2 4

3

AP#2

AP#1

6

5 7

4

3

AP#2

AP#1

6

5 7

8

1

2 4

3

8 7 2 1

AP with Adant reconfigurable antenna system

Deployment 1 Deployment 2 Deployment 3

Deployment 3Deployment 1 and 2

Explicit coordination

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A. Michaloliakos, W. C. Ao, and K. Psounis, “Joint user-­beam selection for hybrid beamforming in asynchronously coordinated multi-­cell networks”, in Proceedings of Information Theory and Applications Workshop (ITA), San Diego, California, USA, February 2016.

AP 1

AP 3

AP 2

AP 4

4

3

2

qJoint user-­beam selection

AP 1 AP 3

AP 2

AP 46

47

8

Coordination schemes performance

8 20 400

10

20

30

40

50

60

Number of stations

Avg.

Thr

ough

put p

er u

ser [

Mbp

s]

SU−MISOMU−MIMOCoor. MU−Hybrid 1x PowerCoor. MU−Hybrid 2x PowerCoor. MU−Hybrid 8x PowerCoor. MU−MIMO

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AP density: 1 AP/BS per 112.5/45/22.5 sq m (~10/7/5m between APs/BSs) User density: 1 active user per 4.5 sq m(~10% of users active)

30x30m hall, 200 users,

A. Michaloliakos, W. C. Ao, and K. Psounis, “Joint user-­beam selection for hybrid beamforming in asynchronously coordinated multi-­cell networks”, in Proceedings of Information Theory and Applications Workshop (ITA), San Diego, California, USA, February 2016.

Smart antenna and digital beamforming

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The reconfigurable antenna selects the best wirelesschannel and the precoding matrix optimizes thatchannel for maximum SNR at the receiver

Q array configurations

TXRX

H1H2

HN

…

Simply Better Wireless.

Page 2

Using All the Tools You Can

Since these RF fundamentals matter so much now to the

performance of your network, and to the experience of your

users, we’re ready to take up the challenge of getting you

enough knowledge to make good Wi-Fi network design

decisions nonetheless. To build the foundation in “how stuff

works” required to accurately assess claims and likely per-

formance benefits for multi-antenna systems, we’re going to

go back to the basics here, using lots of pictures and defin-

ing carefully the necessary jargon along the way to try to help

make things very clear.

We start with an old-fashioned single-antenna access point,

shown in Figure 1, with a common omni-directional antenna,

or an “omni”. When this device transmits, as the antenna’s

name suggests, it sends the same signal in all directions in the

horizontal plane (we’ll worry about what happens in the verti-

cal direction in section 4). While this approach has a certain

satisfying design simplicity, it has substantial performance

disadvantages. The vast majority of this radio energy is com-

pletely wasted, since an access point can only talk to one client

at a time. Beyond mere waste, this excess energy causes prob-

lems in the form of more self-interference in the WLAN, step-

ping on neighboring APs and their clients and reducing the

possibility of channel reuse nearby. Meanwhile, the tiny frac-

tion of transmit energy that actually reaches the client yields a

lower throughput rate, as we’ll show shortly, than would be the

case if the energy could be focused more tightly (since client

throughput is directly related to available signal strength).

Next we introduce another omni antenna to begin to explore

the options this might provide us for better control of the

radio signal. As shown in Figure 2, the combination of two

copies of the same signal transmitted from two neighbor-

ing omni antennas creates a set of intersecting troughs and

peaks, much like the wave rings you would get by tossing

two separate rocks into a still pond at the same time. In some

locations, the peaks of the signal from transmit antenna 1

(“Tx 1”, in the jargon) line up in space and time with the peaks

from Tx 2 — this is referred to as constructive combination. In

other locations, the peaks of Tx 1’s signal are lined up with the

troughs of signal from Tx 2, which yields destructive combina-tion. If a receive (Rx) antenna is placed in the zone of perfect

constructive combination, it would pick up roughly twice the

signal strength of a single Tx antenna’s output, without doing

any intelligent work on its own — its analog receive electron-

ics simply sum the signals received automatically. In contrast,

a zone of complete destructive combination would yield zero

FIGURE 1: Radio signal distribution pattern from an access point with one omni-directional antenna.

Omni Transmit (Tx)Pattern

FIGURE 2: Fundamental concepts in multi-antenna processing for increased signal strength (technology often broadly categorized as “beamforming”)

ConstructiveCombination

Tx Antenna 1

In Phase

180º Outof Phase

Tx Antenna 2

Time2x signal

Signal strength

ReceiveAntenna (Rx)

DestructiveCombination

No signalTx 1

Tx 2

Rx

Maximum signal strength at receiver and channel selection

y = H Bx

Smart antenna and digital beamformingOptimal combined radiation patterns to improve link of interest (power at receiver) and interference mitigation (null steering towards interfering sources)

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Combined beamforming and reconfigurable antenna digital

beamforming only

Optimal control of radiation nulls and radiation in the intended direction

AP

Test setupDownlink throughput is measured with an omnidirectional antenna and with a reconfigurable antenna system using an AP with digital beamforming

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Old villa Concrete ground and ceiling

Harsh environment

Underground parking lotConcrete ground and ceiling Quasi LOS environment

Measured Performance

40%

Data sample of 100 measurements29

25% of cases where gain >40%

Reconfigurable antenna system improvement vs static antenna system

Average TP impr. = 32%

Advantages of Adant and TXBF

Adant smart antenna system significantly improves AP performance with and without TXBF

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Results based on >50 independent measurements in two different environments

Average benefit vs. standard antenna systemTXBF OFF TXBF ON

35% 32%

EXAMPLE Standard Omni Antennas

Adant smart antenna system

TXBF OFF 100 Mbps 135 MbpsTXBF ON 130 Mbps 170 Mbps

Reconfigurable antennas and MU-­MIMO

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The reconfigurable antenna creates the wirelesschannel to enable the possibility of simultaneoustransmission to multiple users through the properprecoding matrix

TXRX 1

H1H2

HN

…

RX 2

HNB2 = 0

HNB1 = 0

Grouping and reconfigurable antennas

Grouping OK Grouping NOT possible

Client A

Client B

Client C

Omnidirectionalradiation

Client A

Client B

Client C

Omnidirectional radiation

SCENARIO A SCENARIO B

Grouping OK Grouping OK

STANDARD ANTENNA

RECONFIGURABLE

ANTENNA Client A

Client B

Client C

Smart antenna configuration

AP

AP

AP

AP

Client A

Client B

Client C

Smart antenna configuration

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Test setupqDifferent combinations of three MU-­MIMO clients are connected to a 4x4 commercial grade AP MU-­MIMO capable based on QCA 9990 chipset

qAggregate downlink throughput is measured with an omnidirectional antenna and with a reconfigurable antenna system

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Data sample of >40 measurements

Measured Performance

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45% of cases where gain >30%

Reconfigurable antenna system improvement vs static antenna system

Average TP improvement = 30%

ConclusionsqReconfigurable antenna systems significantly enhance WiFi networks by:l Maximizing network capacity l Mitigating interference through implicit or explicit coordination between base stations

l Enhancing based band pre-­coding techniques like MU-­MIMOqAntenna selection speed and uplink benefit highly depend on the level of integration that can be achieved with the WiFi chipset

qAdditional benefits that Adant is further exploring in using reconfigurable antennas in WiFinetworks are relative to the possibility of l Enhancing security of the networkl Providing reliable localization services

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