MULTI-ANTENNA TECHNOLOGY Compact Antenna · PDF fileNeil McGowan（Ericsson ... The new antenna design can support both BF and MIMO for future LTE ... 25% is therefore one possible

next generation mobile networks

A Deliverable by the NGMN Alliance

MULTI-ANTENNA TECHNOLOGYCompact Antenna Solutions

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A Deliverable by the NGMN Alliance

MULTI-ANTENNA TECHNOLOGY Compact Antenna Solutions

Version: 3.5 Final

Date: 31st August 2012

Document Type: Final Deliverable (approved)

Confidentiality Class: P - Public

Authorised Recipients: N/A Project: Multi Antenna Technology Editor / Submitter: Ma Xin, China Mobile Contributors: China Mobile, Datang Mobile, Ericsson, Huawei, ZTE Approved by / Date: Board - 31 August 2012

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NGMN P-MATE D1-COMPACT ANTENNA SOLUTIONS 2

Document Information

Editor in Charge Ma Xin (China Mobile)

Editing Team Wuyong (Huawei）

Shi Fan（ZTE）

Zeng Zhaohua（ZTE）

Li Chuanjun（Datang）

Neil McGowan（Ericsson）

Document status: Final

Version: 3.5

Date: August 31st, 2012

Abstract

This deliverable is produced by the Next Generation Mobile Network Project MATE – Multi-ANTENNA TECHNOLOGY.

This document provides the solutions of compact antenna to reduce the difficulty of antenna deployment for information sharing. This deliverable will focus on the conclusion and summary of some basic modes from operators and vendors experiences.

This document includes basic mode and compact mode with 2 interface innovation extensions. BMA and MCIC are two interface extensions for improving the performance of interface between antenna and RRU(Remote Radio Unite). The compact solution is the combination of basic mode and interface improvement in urban/dense urban.

The intention is to provide a specific, yet generic, description of basic modes for compact antenna features.


0 EXECUTIVE SUMMARY

This document provides the solutions of compact antenna to reduce the difficulty of antenna deployment for information sharing. The basic mode including following features:

1. Dual-polar 8 path 2. Antenna‘s size reduced by half, which is easy to install in the real deployment. 3. Super wideband(3G/4G) 4. The antenna can support wideband application and cover more than 100 MHz band. 5. Support BF&MIMO(2×2、4×2、8×2) 6. The new antenna design can support both BF and MIMO for future LTE network. 7. 9 Cables.

The number of connectors and cables reached 9(min),Which is an extra challenge for installation. The extension 1&2 aim at reducing the number of connectors. Extension1 is BMA interface solution which back mounts RRU on antenna with new blind mate interface. Extension2 is MCIC interface solution which reduces the antenna and RRU connectors from 9 to 2 and makes the similar installation convenience as GSM antenna. In 4G time, we will face more challenges because of more and more scenarios with limitation of installation space. The compact antenna solution combing basic mode and 2 newly-defined interfaces will help to solve the problems .With the high efficient antenna element design, the height of antenna reduces by half with gain loss 1.5dB, which is designed to use in dense urban area. The compact antenna has been proved to have good performance in LTE trial network.


CONTENT

0 EXECUTIVE SUMMARY ............................................................................................................................................ 3

CONTENT ............................................................................................................................................................................. 4

1 INTRODUCTION AND SCOPE ................................................................................................................................... 6

2 BACKGROUND & REQUIREMENTS ......................................................................................................................... 6

3 BASIC MODE ............................................................................................................................................................ 6

3.1 BANDWIDTH ........................................................................................................................................................................... 6 3.1.1 Bandwidth to Cover 3GPP Bands .............................................................................................................................. 6 3.1.2 Frequency Range Examples ...................................................................................................................................... 8 3.1.3 Column Spacing for 3GPP Bands ............................................................................................................................ 10 3.1.4 Parameters Stored in the Multi-Antenna ............................................................................................................... 11

3.2 DUAL POLAR DESIGN .............................................................................................................................................................. 11 3.2.1 System Requirements .............................................................................................................................................. 11 3.2.2 Calibration network design ..................................................................................................................................... 13 3.2.3 Column spacing design ............................................................................................................................................ 16 3.2.4 Element beam design .............................................................................................................................................. 17 3.2.5 Broadcast beam design ........................................................................................................................................... 17 3.2.6 Scan beam design .................................................................................................................................................... 20 3.2.7 Active return loss ...................................................................................................................................................... 20

3.3 PERFORMANCE EVALUATION ................................................................................................................................................... 20 3.3.1 Spectral efficiency .................................................................................................................................................... 20 3.3.2 Broadcast beampattern .......................................................................................................................................... 24 3.3.3 Element beampattern ............................................................................................................................................. 24

3.4 TRIALS ................................................................................................................................................................................. 25 3.4.1 Introduction .............................................................................................................................................................. 25 3.4.2 Network Deployment .............................................................................................................................................. 26 3.4.3 Conclusion ................................................................................................................................................................ 26

4 EXTENSION1-BMA INTERFACE.............................................................................................................................. 26

4.1 REQUIREMENT ...................................................................................................................................................................... 27 4.2 SOLUTION ............................................................................................................................................................................ 27 4.3 COMPREHENSIVE VERIFICATION (ENVIRONMENTAL RELIABILITY, OUTDOOR USE) ............................................................................. 28 4.4 BENEFITS OF BMA ................................................................................................................................................................ 29 4.5 APPLICATIONS ON 3G NETWORK ............................................................................................................................................. 29 4.6 THE VALUE ON LTE ................................................................................................................................................................ 30

5 EXTENSION2-MCIC INTERFACE ............................................................................................................................. 30

5.1 REQUIREMENTS OF CLUSTER JOINT AND CLUSTER CABLE ............................................................................................ 30 5.2 SCHEME OF CLUSTER JOINT AND CLUSTER CABLE ......................................................................................................... 30 5.3 MAIN CHARACTERISTICS OF THE CLUSTER JOINT AND CLUSTER CABLE ............................................................................................. 30 5.4 THE STRUCTURAL STYLE OF THE CLUSTER PLUG AND JACK ............................................................................................................. 31 5.5 RELIABILITY OF CLUSTER JOINT AND CLUSTER CABLE ....................................................................................................... 32 5.6 APPLICATION ........................................................................................................................................................................ 33

6 COMPACT ANTENNA SOLUTION .......................................................................................................................... 33

6.1 COMPACT DESIGN.................................................................................................................................................................. 33 6.2 SIMULATION ......................................................................................................................................................................... 34


6.3 DESIGN REQUIREMENT AND PRODUCT ...................................................................................................................................... 36 6.4 TRIALS ................................................................................................................................................................................. 37

6.4.1 Single point throughput test(kpn) ........................................................................................................................... 37 6.4.2 Single site draw-away coverage test（CMCC） ................................................................................................... 39 6.4.3 Multi-site throughput test（CMCC） .................................................................................................................... 40

7 REFERENCES .......................................................................................................................................................... 41


1 INTRODUCTION AND SCOPE

The Multi-antenna Technology (MATE) project of NGMN Alliance, will share the information and experiences on antenna deployment and conclude some basic modes for reference for future 3G/LTE antenna deployment. The project will mainly focus on the multi antenna tech since it has been considered as the future trend for both TDD/FDD systems. This document provides the solutions of compact antenna to reduce the difficulty of antenna deployment for information sharing. This deliverable will focus on the conclusion and summary of some basic compact antenna modes from operators and vendors experience. . 2 BACKGROUND & REQUIREMENTS

Smart antenna with 8 arrays can bring maximum 9dB gain in TDD system. However, it also faced some challenges in early deployment: From the antenna side, the size of antenna reached 1300*600*300(mm). The larger size of antenna made residents worry about more electro- radiation, also made hard site choice and fixing and higher costs for network optimization etc. From the TPA/RRU side, the weight reached 30Kg each with 2 TPA or RRU is too heavy and each only support 4 RF ports with too much connectors between antenna and RRU (generally 18,max 54),not easy to install.

3 BASIC MODE

3.1 Bandwidth

3.1.1 Bandwidth to Cover 3GPP Bands

One possible choice for defining the frequency range of a given Multi-Antenna is to specify it in terms of a percentage of the center frequency of operation. The information shown in Figure 3.1-1 gives the frequency range in MHz for each 3GPP band as well as the percentage bandwidth and the duplex spacing for each band. The percentage bandwidth is calculated from the Upper frequency and the Lower frequency of the band as follows:

)2/)(()(*100%

LowerUpperLowerUpperBandwidth

+−

=

The largest required frequency range in percentage terms is for 3GPP Band 10 which is close to 25%. A bandwidth of 25% is therefore one possible choice for a common parameter for a Multi-Antenna design that can cover all 3GPP Bands. Another possible choice is a super wide bandwidth of 40% which may allow for more multi-band options and cover all the 3GPP bands with a smaller number of Multi-Antenna frequency ranges. If it is possible to scale a given Multi-Antenna design then it may make sense to specify the frequency range in percentage terms.


3GPP Band: % Bandwidth=100*(Upper-Lower)/((Upper+Lower)/2)

0.0

5.0

10.0

15.0

20.0

25.0

0 5 10 15 20 25 30 35 40 45

3GPP Band

Ban

dwid

th (%

)

0

50

100

150

200

250

300

350

400

450

500

Ban

dwid

th (M

Hz)

% BandwidthMHz BandwidthMHz Duplex Spacing

Figure 3.1-1 Bandwidth in % and MHz for each 3GPP Band and Duplex Spacing


3.1.2 Frequency Range Examples

Some examples of the frequency ranges having 25% BW (bandwidth) that could be used in multi-antennas to cover the 3GPP bands are shown in Figure 3.1-2. There are 6 frequency ranges show that are designated FR1 through FR6. Each of the FR frequency range shown covers 25%.

3GPP Multi-Antenna Frequency Range Example (25% BW)

0 5 10 15 20 25 30 35 40 45

3GPP Band

Freq

uenc

y [M

Hz]

(Log

Sca

le)

Upper

Lower

2955-3800 [FR6]

2092-2690 [FR5]

1711-2200 [FR4]

1427-1835 [FR3]

746-960 [FR2]

698-897 [FR1]

600

700

800900

1000

1500

2000

3000

4000

Figure 3.1-2 25% BW 3GPP Multi-Antenna Frequency Range Example

Some examples of the wide frequency ranges having 40% BW (bandwidth) that could be used in multi-antennas to cover the 3GPP bands are shown in Figure 3.1-3. There are 4 frequency ranges show that are designated WFR1 through WFR4. Each of the WFR frequency range shown covers 40%.


3GPP Multi-Antenna Wide Frequency Range Example (40% BW)

0 5 10 15 20 25 30 35 40 45

3GPP Band

Freq

uenc

y [M

Hz]

(Log

Sca

le)

Upper

Lower

2533-3800 [WFR4]

1793-2690 [WFR3]

1446-2170 [WFR2]

698-1047 [WFR1]

600

700

800900

1000

1500

2000

3000

4000

Figure 3.1-3 40% BW 3GPP Multi-Antenna Frequency Range Example


3.1.3 Column Spacing for 3GPP Bands

The column spacing for the Multi-Antenna design is another significant parameter. The data in Figure 3.1-4 shows the Upper and Lower column spacing in wavelengths for each of the 3GPP Bands under the assumption that the Band is covered by the highest of the 25% bandwidth frequency range choices FR1 through FR6 that covers the Band. It is assumed that the column spacing at the lowest end of each of the frequency ranges is at 0.5 wavelengths. If another column spacing is desired then the numbers would scale accordingly.

Column Spacing Using Highest Useable Frequency Range from FR1-FR6

0.45

0.50

0.55

0.60

0.65

0.70

0.75

0 5 10 15 20 25 30 35 40 45

3GPP Band

Wav

elen

ghth

s

wavelengths lowerwavelengths upper

Figure 3.1-4 Column Spacing Resulting from Example Frequency Ranges FR1-FR4

The data in Figure 3.1-5 shows the Upper and Lower column spacing in wavelengths for each of the 3GPP Bands under the assumption that the Band is covered by the highest of the 40% bandwidth frequency range choices WFR1 through WFR6 that covers the Band.


Column Spacing Using Highest Useable Frequency Range from WFR1-WFR4

0.45

0.50

0.55

0.60

0.65

0.70

0.75

0 5 10 15 20 25 30 35 40 45

3GPP Band

Wav

elen

ghth

s

wavelengths lowerwavelengths upper

Figure 3.1-5 Column Spacing Resulting from Example Wide Frequency Ranges WFR1-WFR4

3.1.4 Parameters Stored in the Multi-Antenna

It may be beneficial to store frequency range, column spacing and other parameters in the Multi-Antenna design in a way that allows them to be retrieved.

3.2 Dual polar design

3.2.1 System Requirements

Multiple columns smart antenna can be used to achieve spatial diversity gain and interference suppression gain compared with conventional single column antenna. Spatial diversity gain and interference suppression gain will be benefit to improve system performance and capacity. The smart antenna technology, also termed as beamforming, exploits knowledge of channel information at transmitter. It utilizes the channel information to build the beamforming matrices as pre-filters at transmitter to achieve link gain and capacity gain. In TD-SCDMA system ,for example, beamforming can offer benefits as followed, (1) increase the system capacity, since in downlink beamforming can focus as much power as possible into the direction of the desired user and avoid power into the direction of the undesired users to reduce the mean interference level in co-channel cells, and can mitigate the effects of multipath reception caused by the mobile radio propagation properties.(2) increase the cell coverage without increasing the total radiated power.(3) allow the use of dynamic channel assignment schemes which explicitly take advantage of the directional characteristics of user impinging at the NodeBs.4) obtain directional characteristics and make use of it in orientation technology.


In TD-SCDMA system, every antenna element simultaneously transmits a combination of K weighted user’s data applied by K complex weight (magnitude and /or phase). Thee knowledge of channel characteristics need to be required to build the W which is called the beamforming matrices. Here, the transmitted signals are related as followed:

=

−−−−−

−

−

−1

0

111

01

10

100

00

1

0

K

k

KN

kNN

Kn

knn

Kk

N

n

d

d

d

www

www

www

x

x

x

[ ] [ ][ ]DWX = Where , nx is transmitted signal from the nth antenna element, where 1,,1,0 −= Nn

kd is the kth user data signal,where 1,,1,0 −= Kk

knw is the nth antenna element complex weight of the kth user data signal

N is antenna element number. K is user number. When TD-SCDMA evolves to TD-LTE, the multiple columns smart antenna also can be used to substantially to improve the TD-LTE system performance by leveraging the “spatial” characteristics of the wireless channel. Dual polarized smart antenna can support:

1. single- antenna port(port 1) 2. Transmit diversity 3. open-loop spatial multiplexing 4. Closed-loop spatial multiplexing 5. Multi-user MIMO 6. Closed-loop Rank =1 pre-coding 7. single-antenna port( port 5) 8. Dual layer transmission(port 7,& port 8)

Dual polarized smart antenna with the single-antenna port (port 5) can improve the power efficiency, and Dual polarized smart antenna with Dual layer transmission (port 7 & port 8) can increase the effective date rate. So the Dual polarized smart antenna promises of higher data rates with a high spectral efficiency in TD-LTE system.


3.2.2 Calibration network design

Antenna element

load Directional coupler

power combiner/splitter

Antenna port

Calibration port

Figure 3.4 schematic diagram of calibration network for smart antenna When utilizing dual polarized smart antenna in TD-SCDMA and TD-LTE system, there are undesired RF imbalances between the N antenna element RF transmission channels from BBU to Antenna element. The undesired RF imbalances will reduce the spatial diversity gain and interference suppression gain. So the calibration network is key part of dual polarized smart antenna. Figure 3.4 shows schematic diagram of a 4 columns and 8 antenna elements calibration network, which is an example , other methods are not excluded.


Antenna element 2

load

power combiner/splitter

Antenna port

Calibration portHPA LNA

BBU

S1 Y1

HPA LNA

S2 Y2

Antenna element 1

……

UE

H1

H2

T1cal T2cal

Figure 3.5 signal calibration: transmission, reception and model using antenna calibration network A simplified signal calibration, including transmission and reception using calibration network is shown in Figure

3.5.The channel coefficients from the UE to antenna element 1 and 2 are respectively 1H , 2H . The Transmit RF

path coefficient of antenna element 1 is 1S and 1Y is the receive RF path coefficient. The Transmit RF path coefficient

of antenna element 2 is 2S and 2Y is the receive RF path coefficient. calT1 is Transmission RF path coefficient from

antenna port 1 to calibration port. calT2 is Transmission RF path coefficient from antenna port 2 to calibration port.

The UE transmits signal 1U , and the received signals at antenna port 1 and 2 at BBU are respectively r1 and r2 as: 1111 YHUr = (3-1)

2212 YHUr = (3-2) From the equations (3-1) and (3-2), according to the EBB calculation, the Beamforming coefficients are：

( ) ( )*222*

111 , YHwYHw == (3-3) Supposed the Node B transmit signal x from antenna element 1 and antenna element 2 to UE, so the UE can receive

signal 1y arriving at UE from antenna element 1,

( ) 1

*1

2111

*111111 SYHxHxSYHHxSwy ===


Similarly, the signal 2y arriving at UE from antenna element 2:

( ) 2

*2

2222

*222222 SYHxHxSYHHxSwy ===

Because there are undesired RF imbalances between the N antenna element RF transmission channels from BBU to

Antenna element, 1*

1 SY is not necessarily equal to 2*

2 SY , the signals 1y and 2y have not necessarily same phase.

So 1y and 2y can not realize MRC.

The calibration network is used to calibrate the 1y and 2y having the same phase. RXC1 and

TXC1 are the receive

calibration coefficient and transmit calibration coefficient of antenna element 1 RF transmission channel. RXC2 and

TXC2 are the receive calibration coefficient and transmit calibration coefficient of antenna element 2 RF transmission channel. The calibration principle can be represented as

calRX

calRX TYCTYC 222111 =

calTX

calTX TSCTSC 222111 =

So we can rewrite them as:

cal

calRX

RX

TYTYC

C22

1112 =

cal

calTX

TX

TSTSC

C22

1112 =

So, after compensating the calibration coefficients, The UE transmits signal 1U , and the received signals at antenna port 1 and 2 at BBU are respectively r1 and r2

11111 YCHUr RX= (3-4)

22212 YCHUr RX= (3-5) From the equations (3-4) and (3-5), according to the EBB calculation the Beamforming coefficients are：

( ) ( )*2222*

1111 , YCHwYCHw RXRX == (3-6)

Suppose the Node B transmit signal x from antenna element 1 and antenna element 2 to UE, so the UE can receive

signal 1y arriving at UE from antenna element 1,

( ) ( ) 1

*1

211

*1111

*11111111 SYHxCCHSxCYCHHSxCwy TXRXTXRXTX ===

Similarly, the signal 2y arriving at UE from antenna element 2:


( ) ( )

( ) 1*

12

222

21

1*

1

1*

12

22

11

*

2

11

2*

22

22*

2222*

22222222

SYHxT

TCC

SYHxT

TCT

TC

SYHxCCHSxCYCHHSxCwy

cal

calTXRX

cal

calTX

cal

calRX

TXRXTXRXTX

=

=

===

So we can see that the signals 1y and 2y have same phase. 1y and 2y can realize MRC. We note the

22

21

cal

cal

T

T

is related with MRC performance. So we defined the antenna calibration key parameter as : Number Parameter specification 1 Difference in transmission coefficient between any 2 antenna element

port to calibration port in magnitude(dB) <0.5

2 Difference in transmission coefficient between any 2 antenna element port to calibration port in phase(deg)

< 5

At the same time, we should control the transmission loss from antenna element port to calibration port for calibration signal transmission and reception; we defined another calibration parameter as: Number Parameter specification 3 Calibration port directional coupler (dB) >15 4 Transmission loss from antenna element port to calibration port (dB) -26 ±2

3.2.3 Column spacing design

Column to column spacing at multiple columns smart antenna has a strong relationship to overall spatial correlation. As the column spacing is reduced, the column – to – column correlation would increase. The high column – to – column correlation is used to increase the gain of composite array. Typically, in multiple columns smart antenna

application, the column spacing is approximately 2λ . As the percentage of bandwidth increases, the column spacing needs to adjust. For example, the column spacing of TD-LTE 1880-1920/2010-2025/2500-26900 MHz 4 columns 8

antenna elements dual polarized smart antenna is designed as λ7.0 。 Figure 3.6 shows schematic diagram of 4

columns 8 antenna elements dual polarized smart antenna. 4 columns 045± polarized antennas vertically oriented,

and spaced at a distance, d . Antenna element 1,2,3,4 is 045+ polarized, and antenna element 5,6,7,8 is

045− polarized.


1 5 2 6 3 7 4 8

d

Figure 3.6, schematic diagram of 4 columns 8 antenna elements dual polarized smart antenna

3.2.4 Element beam design

The Element beam performance of 4 columns 8 antenna elements dual polarized smart antenna is the inherent properties of the antenna. So Element beam design is very important for Broadcast beam and scan beam. Broadcast beam and scan beam depend on the Element beam performance. We defined the element beam reference parameters & values as follows:

1 Vertical beamwidth(0) - 2 Upper side suppression(USLS)（dB） 16 3 Lower Null Fill（dB） - 4 gain(dBi) 17(for higher band) 5 Horizontal beamwidth(0) 65 6 Horizontal FBR（dB） 23 7 Horizontal pattern Cross-polarization ration（on

Axis）（dB） 18

8 Horizontal pattern Cross-polarization ration（In range of ±60degree）（dB）

10

3.2.5 Broadcast beam design

In a tri-sector mobile network structure (see Figure 3.7), base stations serve 3 contiguous hexagonal cells with three directional 4 columns 8 antenna element dual polarized smart antennas;


RR

Main beams ofTri-sector antenna

Main beams ofTri-sector antenna

Figure 3.7 Tri-sector cell configuration

The respective ideal broadcast beam patterns idealG are given as follows:

( )( )( )( )

( )

≤<<≤−−−

≤<−<≤−−

=

=

60063sin

3sin2

3663sin

6sin3

02

πθθππθπ

π

πθππθπθπ

π

θ

θ

orR

orR

R

d .

So , ( ) ( )( )RdGideal 2log35 10 θθ =

Figure 3.8 shows the ideal pattern:

-60 -40 -20 0 20 40 60-12

-10

-8

-6

-4

-2

0

angle(degree)

patte

rn g

ain(

dB)

Ideal broadcast beam pattern for Tri-sector cell configuration

Figure 3.8 ideal broadcast beampattern for Tri-sector cell configuration


The 65 degree beam pattern is taken to be:

dBH

HG

mdB

mdB

28,65

180180),12min()(

3

2

365

==

≤≤−

−=

θ

θθθθ

(4.2)

This 65degree pattern is displayed in the Fig.3.9

-60 -40 -20 0 20 40 60-12

-10

-8

-6

-4

-2

0

angle(degree)

patte

rn g

ain(

dB)

Ideal broadcast beam pattern versus 65 degree beam pattern

ideal broadcast beam pattern65 degree beam pattern

Figure 3.9, ideal broadcast beam pattern versus 65 degree beam pattern.

The ideal broadcast beam pattern and 65 degree beam pattern are shown in Figure 3.9, the 65 degree beam pattern can track ideal broadcast beam pattern well. So we need to optimize a fixed beamforming matrix BCHW to let dual

polarized smart antenna transmit a 65 degree broadcast beam pattern to cover the whole sector. So, we defined the 65 degree broadcast beam reference parameters as follows:

1

65 degree broadcast beam

gain（dBi） 16.5 2 Horizontal beamwidth(0) 65 3 Horizontal gain attenuation at ±60°（dB） 9 4 Horizontal FBR（dB） 28 5 Horizontal pattern Cross-polarization ration（on Axis

）（dB） 18

6 Horizontal pattern Cross-polarization ration （ In range of ±60degree）（dB）

10

7 Ripple（dB） 2


3.2.6 Scan beam design

Scan beam performance is decided by element beam performance and beam weight. The element beam performance is the inherent properties of the antenna and is very key performance. The scan beam is composite performance of antenna element with corresponding weight. So we only need to verify smart antenna scan beam performance through 0 degree and 60 degree scan beam. 0 degree scan beam reference parameters are defined as follows:

1 0 degree scan beam

gain(dBi) 22.5 2 Horizontal beamwidth(0) 21 3 Horizontal FBR（dB）） 33 4 Horizontal side lobe level（dB） -12 5 Horizontal pattern Cross-polarization

ration（on Axis）（dB） 22

60 degree scan beam specification is defined as follows: 1 60 degree

scan beam

gain（dBi） 19.5 2 Horizontal beamwidth(0) 23 3 Horizontal side lobe level（dB） -4

3.2.7 Active return loss

Active return loss will be different for each element due to mutual coupling, Active return loss decide the antenna element transmission loss, 0.5dB transmission loss can be allowed, so we defined the active return loss as follows:

1

Active return loss

Active return loss of antenna element (Relative to 50 ohms）（dB） ≤-10

3.3 Performance evaluation

In this subsection, the performance of deploying dual polarized antenna in typical LTE deployments will be evaluated.

3.3.1 Spectral efficiency

Cell average and cell edge spectral efficiency [2] are the key metrics to evaluate the capacity and coverage that could be provided by a specific antenna configuration in specific scenarios. In this subsection, the spectral efficiency of both dual polarized and uni-polarized antennas are evaluated under the TD-LTE deployment. The Urban Micro (UMi), Urban Macro (UMa) and Rural Macro (RMa) defined in [3] are employed as test scenarios to access the performance of dual-polarized antennas compared to uni-polarized antennas. The UMi scenario is an urban micro-cellular environment with high user density and pedestrian and low-speed users. The UMa scenario represents the urban macro-cellular environment with continuous coverage for fast-speed users. And RMa scenario aims to evaluate the macro cells environment with very high speed vehicular and trains. These three scenarios are typical for future TD-LTE deployment, and therefore it is appropriate to employ them to demonstrate the spectral efficiency performance with dual-polarized antennas. Table 1 listed the basic parameters of each of the scenario.

Table 3.1 Basic parameters of UMi, UMa, and RMa


Deployment sceanrio UMi UMa RMa Total BS TX power at antenna feedpoint

44 dBm for 20 MHz 49dBm for 20 MHz 49dBm for 20 MHz

Carrier Frequency 2.5 GHz 2GHz 800 MHz Operating Bandwidth 20 MHz (TDD) 20 MHz (TDD) 20 MHz (TDD) Inter-site distance 200 m 500m 1732 m UE speed 3 km/h 30km/h 120 km/h. In the evaluation, the 3GPP LTE Rel-8 transmission modes are employed. The evaluated Rel-8 features include downlink (DL) codebook based closed-loop spatial multiplexing, and the single-layer beamforming (BF) (i.e., transmission mode 4 and 7 defined in [4]), and uplink (UL) SIMO without MU-MIMO. These features are feasible in TD-LTE deployment, and it is therefore necessary to evaluate the performance of using dual-polarized antennas with such features. The evaluation could convince the use of dual-polarized antennas in the near-future deployments. The simulation assumptions are listed in Table 3.2, and the evaluation result follows.

Table 3.2 Simulation assumption

Parameters Value Deployment scenario UMi, UMa, and RMa Network Layout Hexagonal grid Duplex TDD Network synchronization Synchronized User load Average 10 UEs per cell (sector) Bandwidth 20 MHz for TDD Channel model ITU channel model (generic model, see Annex 1 in [3]) Scheduler Proportional Fair

Antenna configuration at base station (BS)

(1) Dual-polarized: columns with ±45deg linearly polarized antennas; columns separated by 0.5 wavelengths (illustrated for 4Tx: xx) (2) Uni-polarized: Vertically-polarized, with 0.5 wavelengths between antennas (illustrated for 4Tx: ||||)

Antenna configuration at mobile station (MS)

Vertically-polarized, with 0.5 lambda spacing

Downlink transmission scheme

4x2 codebook-based SU-MIMO, with rank adaptation. 8x2 single-layer beamforming (BF)

Uplink transmission scheme 1x4 SIMO without MU-MIMO

Uplink Power control Open loop, as in [4], with fractional pathloss compensation and P0 fitted to the environment.

Link adaptation

Non-ideal, Downlink: Non-ideal based on non-ideal CQI/PMI/RI reports and non-ideal sounding transmission. - For codebook-based SU-MIMO: Non-frequency selective PMI and frequency

selective CQI report with 5ms periodicity, subband CQI with measurement error: N(0,1) per PRB;

- For single-layer BF: Sounding-based precoding, frequency selective CQI report with 5ms periodicity, subband CQI with measurement error: N(0,1) per PRB

Uplink: Non-ideal based on delayed SRS-based measurements. Receiver type MMSE

Overhead consumptions Downlink overhead: • Overhead for CRS • Overhead for antenna port 5 DRS (only for single-layer BF)


• Overhead for DL CCH of 3 OFDM symbols • Overhead for SCH/BCH Uplink overhead: • Overhead for DL feedback (ACK/NAK, CQI, PMI) on PUCCH • Overhead for DMRS: 2 symbols DMRSs per subframe • Overhead for SRS

TDD uplink-downlink configurations

Configuration 1: DL subframes : special slots : UL subframes = 2:1:2; 5ms switching period.

In Fig. 3.1, Fig. 3.2 and Fig. 3.3, the DL spectral efficiency of dual-polarized antennas compared to uni-polarized antennas are shown, in UMi, UMa, and RMa, respectively. The 4x2 codebook-based SU-MIMO is employed to compare the performance of dual-polarized and uni-polarized antenna. It can be seen that in all three test scenarios, the DL performance of both antenna configurations are quite similar. It implies that the use of half-sized dual-pol antenna does not lead to performance loss compared to uni-pol antennas. Further, when increasing the size of the dual-pol antenna to the size of uni-pol antenna and employing the single-layer BF, the 8x2 dual-pol configuration outperforms the 4x2 dual-pol, and even the 4x2 uni-pol antennas. This implies that, given the same antenna size, the dual-polarized antenna could further improve the performance compared to its uni-pol counterpart.

(a) DL cell average spectral efficiency in UMi (b) DL cell edge spectral efficiency in UMi

Fig. 3.1 DL spectral efficiency in UMi

(a) DL cell average spectral efficiency in UMa (b) DL cell edge spectral efficiency in UMa

Fig. 3.2 DL spectral efficiency in UMa


(a) DL cell average spectral efficiency in RMa (b) DL cell edge spectral efficiency in RMa

Fig. 3.3 DL spectral efficiency in RMa The UL spectral efficiency evaluation results of UMi, UMa and RMa are shown in Fig. 3.4, Fig.3. 5, and Fig.3. 6, respectively. The results show that the dual-polarized antenna has better performance than the uni-polarized antenna in all test scenarios. It implies that for UL system, the dual-polarized antenna even contributes benefit over the uni-pol antenna system. The above evaluation results suggest that the dual-polarized antenna, although half-sized compared to the uni-pol antenna given the same number of elements, has similar spectral efficiency to uni-pol antennas, and therefore the deployment of dual-polarized antenna in the near-future TD-LTE systems could be convinced.

(a) UL cell average spectral efficiency in UMi (b) UL cell edge spectral efficiency in UMi

Fig. 3.4 UL spectral efficiency in UMi

(a) UL cell average spectral efficiency in UMa (b) UL cell edge spectral efficiency in UMa

Fig. 3.5 UL spectral efficiency in UMa


(a) UL cell average spectral efficiency in RMa (b) UL cell edge spectral efficiency in RMa

Fig. 3.6 UL spectral efficiency in RMa

3.3.2 Broadcast beampattern

The broadcast beampattern is a key parameter that impact on the coverage of the network. The use of dual-polarized antenna should not degrade the coverage compared to the uni-polarized antenna. To confirm this issue, the broadcast pattern of the dual-pol and uni-pol antennas are measured in microwave anechoic chamber, and the derived patterns are plotted in Fig. 3.7. It is clearly seen that the beam width and the sidelobe level of the two types of antennas are quite close to each other. Therefore, the network coverage of dual-polarized antenna can achieve that of uni-polarized antenna.

(a) Uni-polarized antenna (b) Dual-polarized antenna

Fig. 3.7 Broadcast beam of uni-pol and dual-pol antenna

3.3.3 Element beampattern

The element pattern would impact the ultimate synthesized array pattern in either case of Beamforming or preoding. A good element pattern should ensure the coverage at desired directions. To make sure the BF or precoding performance with dual-polarized antenna comparable to that of uni-polarized antenna in practical applications, the element patterns are measured in microwave anechoic chamber and compared. The derived element patterns are illustrated in Fig. 3.8. It is observed that the element directional gain is quite close to each other, which confirms the solid basis of BF and precoding performance in dual-polarized antenna systems.


(a) Uni-polarized antenna (b) Dual-polarized antenna

Fig. 3.8 Element pattern of uni-pol and dual-pol antenna

3.4 Trials

3.4.1 Introduction

Since the first prototype of dual-polarized smart antenna was announced at the end of September in 2007, the China Mobile has organized several large-scale field trials in more then 5 cities jointly with main equipment manufacturers. During the trials, a significant amount of radio channel characteristics based on dual-polarized antennas have been collected and analysed and extensive experience of wireless network optimization has been obtained.

Figure 3.4-1 Field Trials

The field trials were designed to evaluate coverage and beam-forming gain comparisons between systems employing compact smart antennas and conventional 8 antennas. For this purpose, performance tests of broadcast channel and dedicated channel have been conducted and corresponding test data have been analysed. The basic wireless performance of compact smart antenna has thereafter been verified and its impact to TD network has been analysed. The above experimental data provides solid base for future network planning and optimization when compact smart antennas are deployed.

Table 3.4-1 Performance of Trial


Trial -type Trial -item Trial -site

City A City B City C City D City E City F

Single eNodeB wireless

performance trial

Broadcasting covering ability of the remote trial √ √ √ √ √

Services covering ability of the remote trial √ √ √ √

Broadcasting covering ability of the designated

trial √ √

Services covering ability of the designated trial √ √

Single-UE BF ability trial √ √ √ √ √ √ Single eNodeB with 2 cell of the data handoff trial √

Capacity trial √ √

Multiple-UE BF ability trial √ Multiple eNodeB network

performance trial

Multiple-UE BF ability trial √ √ √ √

Capacity trial √ √ √ √

Whole-network-ergodicity √ √ √ √

3.4.2 Network Deployment

The dual-polarized antenna has been applied in TD-SCDMA networks in large scale with more than 80% share. Dual-polarized compact antenna plays the important role in TD-LTE network deployment. It can easily support MIMO and BF algorithm. Compared with traditional smart antenna, dual-polarized compact antenna is better choice for network deployment.

3.4.3 Conclusion

The dual-polarized antenna is a better choice for compact smart antenna and its deployment will become a trend in the future in dense urban, medium urban and suburb area: a) The capacity of 4* 4 dual- polarized antennas is equivalent to 8 single polarized antennas, with both of them can

reaching the full capacity. b) No coverage loss is observed within the normal cell coverage although many worried about it for long time. c) Compared with conventional single polarized smart antenna, the size of dual- polarized antenna reduces by

more than 50%, giving rise to advantages in reduced wind resistance, installation difficulty and user’s fear of potential radiation. Considering factors such as coverage, antenna size, antenna weight and installation, 4+4 dual-polarization antenna is preferred over alternatives.

4 EXTENSION1-BMA INTERFACE

For compact antenna, one of the solutions to reduce the antenna deployment is RRU miniaturization and integrated with antenna. Here we call it Integrative Antenna-Array with RRU Device, and a new design: BMA interface will be talked below.


4.1 Requirement

As the usual network used in TD-SCDMA, we got some troubles with the traditional multi-antenna plus RRU module during the station building process 1) Installation problems

It is difficult to take a waterproof on both antenna and RRU during the installation with multi-antenna as there is too much ports (18 ports for 8-channel antenna), for which is a normal requirement. And it is also a trouble for maintenance later.

2) Restriction of station address Additional space needed for RRU installation, and additional pole or the others for wall-install.

3) Waste of the energy sources A 1.2dB additional inter-loss with the jumpers takes in for connection of the antenna and RRU

4) More cost Waterproof materials and jumpers ,also as the additional time and space takes in during the installation and maintenance increase the cost

5) Potential risk of the reliability Waterproof for so many ports and jumpers with the environment which including the solarization and wind and rain .

6) Ugly visual impressions Site outdoor equipments: antennas, RF jumpers, RRU (Remote Radio Unit), the visual effect is not good. Therefore, the proposed BMA-based interface to the antenna and RRU interconnect design, which for fast installation, compact installation, quick release, high reliability, installation requirements, improved network construction speed and reduced antenna system failure rate, also gives better visual effects.

Here is a picture of the traditional antenna’s installation.

Figure 4.1 traditional multi-antenna’s installation

4.2 Solution

1) With adoption of BMA design, we left out the jumpers that connected between the antenna and RRU. 2) RRU and antenna design guide ensured the RRU and the antenna can be inserted through the blind smooth

and reliable way to connect; 3) No additional installation space as RRU installed on the back of the antenna, only the antenna installation

space is enough 4) Through a simple screw for the RRU installation on the back of the antennas, we complete the three

functions: radio connection, the interface waterproof, RRU fixation, which greatly reduces on-site assembly


time;

VS

Figure 4.2 Jumper connection VS BMA connection

4.3 Comprehensive verification (environmental reliability, outdoor use)

BMA blind plug on the antenna interface system which is interconnected with the RRU takes rigorous testing of the following: blind test for antenna plug and RRU interface vibration waterproof damp heat cyclic Variant wind tunnel icing installation strength dry heat performance contrast field installation, rain, wind, temperature changes and operational After more than 1 year of a variety of environmental, reliability testing, the results fully validate the interpolation technique based on blind multi-channel antenna and RF unit RRU and other high-reliability interconnect and installation, maintenance convenience. Blind plug design based on multi-antenna system has been large-scale application of TD-SCDMA network construction. Some testing pictures:


vibration wind tunnel

Icing field installation

4.4 Benefits of BMA

BMA blind plug interface using multi-channel antenna in the network construction, to bring good out of the following: 1) greatly reduce the installation time: the interface of the antenna based on blind plug and RRU, field installation

saved 90% (8-channel antenna, for example) install time than traditional design 2) saves installation, maintenance, material costs

No RF jumper, waterproof clay, tape, shrink tube and other materials, and without Pole mounting during the installation

3) save the installation, maintenance labor costs： Blind plug interface significantly reduces the installation and dismantling time, thereby reducing installation and maintenance labor costs. Also reduced due to business interruption caused by failure；

4) reduce the RF loss: no feed cable connection, reducing the RF loss, increase system sensitivity, improve the coverage results. RF loss reduction also help save energy；

5) site installation becomes compact, simple and better visual effects 6) improve the reliability of the system: blind plug the interface cable to avoid the problems caused by connection

reliability, waterproof reliability issues

4.5 Applications on 3G network

In China, the TD-SCDMA network based on BMA antenna plug in the parts has arranged more than 13,700 pcs (estimated value), running time more than 2 years, and come out good results after stood on sun, wind, rain, salt spray, high and low temperature and other environmental challenges outside the field.


4.6 The value on LTE

For the LTE-based wireless cellular networks with MIMO technology, still using multi- antenna, LTE-based multi- antenna system installation remain the following questions:

1) Installation time-consuming, laborious； 2) Feeder cable connector on both sides to do waterproof； 3) Waterproof of connector installation reliability because cables by hand, people working 4) Extra loss by RF jumper ,resulting in the power amplifier to enhance or reduce coverage 5) Limited of the installation address, leading to difficult to install the amplifier unit 6) Scattered layout of the antenna, multiple feed cable, amplifier, resulting in poor visual

Therefore, with blind insertion of the BMA-based multi- antenna, the LTE wireless communication system is able to play it fast station, quick service, and improve network reliability. 5 EXTENSION2-MCIC INTERFACE

5.1 REQUIREMENTS OF CLUSTER JOINT AND CLUSTER CABLE

Multiple antenna wireless system products require cable connections between multi-channel RRU and multi-port antenna. As an example, in current 8 channel TD-SCDMA or TD-LTE system, 9 cables are employed to connect RRU and antenna unit. Connection with multiple cables makes deployment of multiple antenna system highly complicated and costly. Therefore, it is one of the key multiple antenna techniques to reduce the number of cables between RRU and antenna unit. Cluster connection using cluster joint and cluster cable forms a good solution to solve the above problem. By cluster connection, electrical and mechanical connections using multiple cables are realized by a pair of connectors and cable bundling. The cluster connection simplifies outside panel structure and reduces both installation time and cost.

5.2 SCHEME OF CLUSTER JOINT AND CLUSTER CABLE

Antenna

RRU

Antenna

RRU

5.3 Main characteristics of the cluster joint and cluster cable

Each plug or jack contains multiple connectors to enable bundled cable connection, making plug-in or plug-out operation efficient.

Figure 5.1 9 cables are used between antenna unit and RRU

Figure 5.2 the cluster joint and cluster cable are used between antenna unit and RRU


The conductor of each connector inside the plug has the elastic contact end with elastic range of 0.3mm in the axial direction to ensure both reliable conducting and required isolation among connectors. The asymmetric design of keyway and key’s positions inside plug or jack ensures correct connection of each component cable. Specially designed mechanism guarantees no inadvertent plugging either a 4-core plug into a 5-core jack or a 5-core plug into 4-core jack. Sealing on both head face and rear port of cluster joint ensures the waterproofing after plug-in. The supreme reliability of the cluster joint benefits from similarity to DIN type connector in connection design and adoption of SMA type connector size.

5.4 The structural style of the cluster plug and jack

Figure5. 4-1 4 core cluster plug and jack


Figure 5.4-2 5 core cluster plug and jack

Figure5. 4-3 picture of 4-core or 5-core cluster plug

5.5 Reliability OF CLUSTER JOINT AND CLUSTER CABLE

Electrical Characteristics and enginnering reliability are two factors of the cluster joint and cluster cable in reliability. Table 5.5 Electrical requirement

Experiment Experimental evidence

PartⅠ electrical indexes

GJB1215A-2005 4.5.8

and 4.5.9

EIA-364-106

Part Ⅱ

water test GB/T 2423.38 IEC 60068-2-18:2000

salt spray test GB/T 2423.17 IEC 60068-2-11:1981

cable retentivity GJB1215A-2005 4.5.7 IEC 60966-1-1999 9.1

Part Ⅲ bend test GJB1215A-2005 4.5.6 IEC 60966-1-1999 9.2


endurance GJB681A-2002 4.5.13 IEC 61196-1 9.5

Part Ⅳ

temperature variation

GB/T 2423.22 IEC 60068-2-14:1984

moisture resistance

GJB360A-96 method 106 MIL-STD-202G METHOD

106G

vibration GB/T 2423.10 IEC 60068-2-6:1995 Electrical Characteristics: Impedance: 50Ω Frequency range: DC-3.00GHz Power Voltage: 500v (max) Dielectric Withstand Voltage <750V VSWR <1.2 Center Contact Resistance<3.00mΩ Outer Contact Resistance < 2.0mΩ Reliability Volume deployment of TD-SCDMA systems in recent years has enabled cluster connection technique to undergo continuous improvement and optimization, making such technique to meet very high engineering standard.

5.6 Application

1) Application of Cluster connection technique in TD-SCDMA

Cluster connection technique has been applied in TD-SCDMA networks in large volume. The following product forms have been verified in real networks:

a) RRU with Cluster joint + Dual polarized antenna with N connectors.

b) RRU with N connector + Antenna with cluster joint.

c) RRU with Cluster joint + Antenna with cluster joint.

2) Application of cluster connection technique in TD-LTE

For the same reason as that in TD-SCDMA networks, cluster connection using cluster joint and cluster cable play the same important role in TD-LTE network deployment. In particular, the technique is highly desirable in sites where TD-LTE and TD-SCDMA system co-exist. 6 COMPACT ANTENNA SOLUTION

6.1 Compact design

The compact antenna solutions with basic mode and 2 interface innovations have improved the smart antenna deployment problems in 3G network. It will be also a good solution in 4G network for multi-antenna application which has been used in TDD LTE trials. The network deployment will face bigger challenge than 3G because of the limitation of antenna installation space, especially in dense urban area. The enhanced compact solution is design to solve the problem. The distance between sites in dense urban is 300~500meters. For this kind of area, the coverage limitation is not the main issue. The interference control is main job for network optimization. Thus, the antenna gain will have the space to reduce in order to balancing the antenna compact size requirement and performance.


Enhanced compact solution has 3 main features: -- high efficient antenna element design with antenna height reducing by half but the gain loss 1.5dB -- inheriting basic mode design (dual polar, wideband, etc) --with MCIC interface, thus only 2 connectors

Figure 6.1 one possible antenna design mode

6.2 Simulation

Simulation of antenna element:

Figure6.2 element simulation


Figure6.3 element simulation From the simulation, the gain of it can reach 13.1 dBi (min) with only 4 antenna element. The gain will reach 15 dBi (min) with 8 antenna element for one array. Simulation for service beam:

Figure 6.4 service beam simulation


Figure 6.5 service beam simulation

Simulation for broadcast beam：

Figure 6.5 broadcast beam simulation

6.3 Design requirement and product

The product of compact solution has passed the lab test and the field trial in CMCC’s TD LTE trial network. The figure 6.6 shows the antenna product (without MCIC interface):


Figure 6.6 Compact antenna product (two compact antenna compared with 1 basic solution antenna) Main design requirements:

Dual-polar 8 path Super wideband(3G/4G) Enhanced high efficient antenna element design Support BF&MIMO 2 Cables(MCIC interface) Half height with gain-1.5dB Solution for urban/dense urban

6.4 Trials

6.4.1 Single point throughput test(kpn)

Single point throughput test was finished in KPN’s TD-LTE network in Dusseldorf. Site configuration:


Figure 6.7 Testing enviornment and testing point There is only one site for TM2&TM7 comparison test and TM3 test. Frequency Band is 2.6 GHz. Bandwidth is 10 MHz and . The name of the site is E-plus office building. In the point2, with compact antenna, we compared the throughput in TM7 which support beamforming feature and TM2.

Figure 6.8 DL RSRP (dbm) & SINR (db)

Figure 6.9 DL throughput (Kbps) of TM2 & TM7 from Network Side


Figure 6.10 DL throughput (kbps) of TM2 from UE Side

Figure 6.11 DL throughput (kbps) of TM7 from UE side From the figures above we can see that in the test point 2, TM7 has remarkable performance improvement compared to TM2.

6.4.2 Single site draw-away coverage test（CMCC）

CMCC finished the compact antenna coverage test in the following test environment: 1. Band: 2570~2590 MHz (20M) 2. Mode: TM2/3/7 adaptive 3. Site distance: >500m, urban area 4. single site with no loading 5. Type: vehicle draw-away coverage test from near point to far point until drop call 6.Height: 30m After the compact antenna test case was finished, We re-installed basic antenna, and repeated the test.


Figure 6.12 compact antennas Coverage test

Figure 6.13 Basic antenna Coverage test The line with colors is the GPS points. Figure6.7 and 6.8 shows the coverage difference of two types of antenna based on the drop link point. We also recorded the throughput of two types of antennas. We found that within the 400m distance, the throughputs are very similar.

Figure 6.14 Coverage differences of two antennas For the drop call point, we can find that compact antenna is around 10~15% less than basic antenna. However, considering the coverage information of other test area for compact antenna, we find that also in some scenarios, the coverage abilities of two antennas are much more similar. We believe in urban and dense urban area with no coverage limitation but interference limitation, the basic performance of system throughput should be similar.

6.4.3 Multi-site throughput test（CMCC）

We also compared the throughput in different system loading for two antennas in another testing area in different city. Testing area is not the typical dense urban area but similar to urban area limited to the site choice difficulty. The site distance is between 600~900m.


Throughput: Mbps in near test point

Uplink-Basic Uplink-Compact Downlink-Basic Downlink-Compact

0% loading 14.24 15.51 27.42 33.87

50%loading 14.80 15.23 20.42 24.05

70%loading 11.54 12.96 12.42 15.09

We can read from table in the near point, Compact antenna’s performance is better then that of basic antenna.

Throughput: Mbps in far test point

Uplink-Basic Uplink-Compact Downlink-Basic Downlink-Compact

0% loading 11.94 15.42 8.41 13.64

50%loading 6.75 10.9 8.76 13.75

70%loading 3.88 8.66 8.49 6.27

We can read from table in the far point, Compact antenna’s performance is similar or better then that of basic antenna.

7 REFERENCES

[1] MIMO and Smart Antennas for 3G and 4G Wireless Systems; Practical Aspects and Deployment Considerations; 3G Americas May 2010 [2] ITU-R, M.2134, Requirements related to technical performance for IMT-Advanced radio interface(s) [3] ITU-R, M.2135, Guidelines for evaluation of radio interface technologies for IMT advanced. [4] 3GPP TS 36.213, v10.0.0, Evolved Universal Terrestrial Radio Access (E-UTRA); Physical layer procedures.

MULTI-ANTENNA TECHNOLOGY Compact Antenna · PDF fileNeil McGowan（Ericsson ... The new antenna design can support both BF and MIMO for future LTE ... 25% is therefore one possible

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