Improved self optimized variable antenna array amplitude tapering scheme to Combat Cell Size...

7/18/2019 Improved self optimized variable antenna array amplitude tapering scheme to Combat Cell Size Breathing in UMT…

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Improved self optimized variable antenna array

amplitude tapering scheme to Combat Cell Size

Breathing in UMTS and CDMA Networks

Archiman Lahiry

School of Electronics Engineering

KIIT University

Bhubaneswar, India

[email protected]

Amlan Datta

School of Electronics Engineering

KIIT University

Bhubaneshwar, India

[email protected]

Satyabrata MaitiSchool of Electronics Engineering

KIIT University

Bhubaneswar, India

[email protected]

Abstract — Cell size breathing can lead to the generation of

coverage holes in UMTS and CDMA networks and solution to

this problem was proposed before in our previous contribution

with title OMC-R controlled remote electronic variable tapered

planar array antenna. The contribution of this paper is including

both horizontal and vertical antenna amplitude taper to combat

the effect of cell size breathing as foot print depends on

horizontal as well as vertical beam width. In this paper we willintroduce an improved version of antenna array tapering using

four Node-B sector antennas. In this paper we will optimize soft

as well as softer hand-off performance by controlling and varying

the vertical and horizontal antenna array amplitude taper

simultaneously with the increasing congestion. Our contribution

of this paper is to improve soft as well as softer hand-off

performance by using a remotely re-configurable amplitude

control antenna array in the self optimizing network.

Keywords— Array amplitude tapering, Antenna footprints, Cell

size breathing, self optimizing network

Introduction

We already introduced the hardware design for OMC-Rcontrolled remote antenna array amplitude tapering [1]. In that

paper only vertical antenna array taper was introduced to

combat cell size breathing but footprint depends on both

horizontal and vertical beam width. In our new proposed work

we will use four sectored Node-B antennas with both

horizontal and vertical antenna array variable amplitude taper

to combat the cell size breathing. Here 3×12 element antenna

array will be used to combat the effect of cell size breathing

with Dolph Tchebyshev [2] tapered amplitude distribution. In

this paper we will eliminate coverage holes in soft and softer

handoff regions by using the simultaneous vertical and

horizontal antenna array amplitude taper.

The paper is organized as follows: Section I describes the

details of antenna array design and radiation patterns. Section

II explains the effect of cell size breathing. Section III

explains the vertical and horizontal antenna array amplitude

tapering scheme for unequal loading of the sectors. Section

IV explains results and guidelines of the proposed technique.

I.

ANTENNA DESIGN AND RADIATION PATTERNS

Fig. 1. Planar 3×12 elements dipole antenna array design with vertical inter

element spacing 0.613 and horizontal inter element spacing 0.34 which is

backed by a ground plane. Antenna elements distance from Ground plane

0.6 .

TABLE I.ANTENNA ARRAY HORIZONTAL AND VERTICAL BEAMWIDTHS

AFTER THE HORIZONTAL AND VERTICAL ANTENNA ARRAY

AMPLITUDE TAPERING CONTROLLED FROM THE OMC-R.

Antenna array

amplitude

distributionand side lobe level

Vertical half power

beam width of 12element antenna array

with 0.613 inter

element spacing

Horizontal beam width

of 3 element antenna

array with 0.34 inter

element spacing

Normal amplitude

distribution with

Side Lobe Level -

13.5 dB

6.89º 54.35º

Tapered with SLL -

25dB8.13º 62.55º

Tapered with SLL -

30dB 8.73º 63.48º

Tapered with SLL -35 dB

9.25º 64.02º

Tapered with SLL -

40 dB9.76º 64.33º

Tapered with SLL -

45 dB10.20º 64.51º

2015 2nd International Conference on Signal Processing and Integrated Networks (SPIN)

978-1-4799-5991-4/15/$31.00 ©2015 IEEE 77

DOI 10.1109/SPIN.2015.7095372



Fig. 2. Linear plot of the vertical radiation pattern with normal amplitude

distribution with side lobe level -13.5 dB. Number of antenna elements is 12

and inter element spacing is 0.613 . Vertical beam width is 6.89 º.

Fig. 3. Linear plot of the horizontal radiation pattern of the antenna array with

inter element spacing 0.34 . Number of antenna elements is 3 and amplitudedistribution is normal. Half power beam width is 54.35º.

Antenna array is designed according to inter site distance

and morphology. Array tapering, side lobe suppression and

main lobe broadening values totally depends on the operating

frequency, morphology inter site distance and traffic density.

P-CPICH power should be properly adjusted for small

inter site distances to implement the following scheme as this

channel is not under power control. We should take care that

the tapering should not cause overshooting.

Fig. 4. Linear plot of the vertical radiation pattern with Dolph Tchebyshev

tapered amplitude distribution with side lobe level -25 dB. Half power beam

width is 8.13º.

Fig. 5. Linear plot of the vertical radiation pattern with Dolph Tchebyshev

tapered amplitude distribution with side lobe level -30 dB. Half power beam

width is 8.73º.

Antenna array amplitude control is a very excellent and

efficient method to combat cell size breathing [3] in UMTS or

CDMA network as the side lobe level and main lobe beamwidth can be controlled according to our requirements of

morphology which may be dense urban, urban or rural. We

should reduce the pilot power to avoid pilot pollution caused

due to overshooting cells. Antenna down tilt angles [4] should

be optimized properly to avoid overshooting.


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Fig. 6. Linear plot of the vertical radiation pattern with Dolph Tchebyshevtapered amplitude distribution with side lobe level -35 dB. Half power beam

width is 9.25º.

Fig. 7 Linear plot of the vertical radiation pattern with Dolph Tchebyshev

tapered amplitude distribution with side lobe level -40 dB. Half power beamwidth is 9.76º.

Dolph Tchebyshev is best antenna array amplitude

tapering scheme for base station antennas as it suppress all the

side lobes to equal level. Suppressing side lobes will eliminate pilot pollution [5] and it will overlap the footprints of the cells

in soft and softer handoff regions.

Fig. 8. Linear plot of the vertical radiation pattern with Dolph Tchebyshevtapered amplitude distribution with side lobe level -45 dB. Half power beam

width is 10.20º.

Fig. 9. Antenna array horizontal pattern for -25 dB side lobe level with Dolph

Tchebyshev tapered amplitude distributions. HPBW is 62.55º.

Fig. 10. Antenna array horizontal pattern for -30 dB side lobe level with

Dolph Tchebyshev tapered amplitude distributions. HPBW is 63.48º.


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Fig. 11. Antenna array horizontal pattern for -35 dB side lobe level withDolph Tchebyshev tapered amplitude distributions. HPBW is 64.02º.

Fig. 12. Antenna array horizontal pattern for -40 dB side lobe level withDolph Tchebyshev tapered amplitude distributions. HPBW is 64.33º.

Fig. 13. Antenna array horizontal pattern for -45 dB side lobe level with

Dolph Tchebyshev tapered amplitude distributions. HPBW is 64.51º.

All the radiation patterns from -13.5 dB side lobe level to -

45dB side lobe level are given in this section. The effects of

the cell size breathing will be analyzed in the next section and

after that we will propose the solution of the problem.

II.

ANTENNA FOOTPRINT ANALYSIS

In this section we will analyze the effect of cell breathing

in busy hour in the soft and softer handoff regions and then we

will propose the solution of the problem in next section.

Fig.14. Four sectored Node-B scheme for improving the softer handoff performance. The loading of four individual sectors are extremely low or

nearly zero percent.

Fig. 15 Effect of Node-B loading on the softer handoff regions. Here coverageholes are generated due to the loading.

In this section we will completely concentrate on the

effects of cell size breathing in both soft and softer handoffregions. Therefore with the increased antenna array tapering

we can easily eliminate all the coverage holes in soft and

softer handover regions. Horizontal antenna array amplitude

tapering will improve the softer handoff performance.


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Vertical antenna array amplitude tapering will improve the

soft handoff performance.

Fig. 16. Case of two Node-B’s with soft and softer handoff regions with no

loading state.

Fig. 17 Case of two Node-B’s with soft and softer handoff regions with

heavily loaded sectors.

The Fig. 14, Fig. 15, Fig. 16 and Fig. 17 illustrates the

effect of cell site loading or cell size breathing in soft and

softer handoff regions. In next section we will propose the

solution for enhancing both soft and softer handoff

performance by applying vertical and horizontal antenna arrayamplitude tapering simultaneously.

III.

SOLUTION TO THE PROBLEM

The solution to the problem is increasing the side lobe

suppression in both horizontal and vertical directions

simultaneously to increase horizontal and vertical beam width

with the increased loading of each sector. This method will

increase the footprints in soft and softer handoff regions.

Based on antenna height, inter site distance and vertical beam

widths the antenna down tilt angles should be properly

measured to avoid pilot pollution. Antenna array tapering

effects will be analyzed in this section. The proposed method

is extremely effective in combating the cell size breathing inall kinds of morphology. The loading of all sectors are always

non uniform therefore tapering implemented in all the sectors

will also be non uniform based on loading of each sector.

Fig. 18. Horizontal variable amplitude tapering scheme to vary the horizontal beam width. The tapering is made proportional to loading. This will increase

inter sector footprint overlapping in softer handoff region.

Fig. 19. The vertical variable amplitude tapering scheme to vary the vertical beam width. The tapering is made proportional to loading. This will increase

inter site footprint overlapping in soft handoff region.

With the following technique we get excellent results. The

effect of the implemented scheme is illustrated in end of thissection. The contribution of this paper is on soft and softer

handoff performance enhancement. The main contribution of

this paper is application of reconfigurable remote amplitude

control antenna array for the footprint overlapping in soft and


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softer handoff region. This is the extended version of our

published IEEE paper.

Fig. 20. The footprints before and after the antenna array amplitude tapering.

Red Boundary is after tapering and blue boundary is before tapering.

IV.

CONCLUSION

The contribution of paper is soft as well as softer handoff

performance enhancement. We solved the problem caused due

to loading in soft and softer handoff region by vertical and

horizontal variable antenna array amplitude tapering scheme

implemented simultaneously and final antenna array

amplitude tapering guideline is mentioned in the TABLE II.

TABLE II.

ARRAY TAPERING BASED ON MORPHOLOGY, PENETRATIONLOSS, TRAFFIC DENSITY AND THE PILOT CHANNEL POWER.

Morphology(Coverage

area type)

Building penetration

losses

Traffic

density(loading

or channel

utilization)

Side lobe

suppressionAccording to

Morphology,

Path loss, penetration

losses and

Traffic

density

Pilot

channel

(P-CPICH)

Power

DenseUrban

Maximum Maximum

Maximum

tapering orside lobe

suppression

Minimum

Urban Moderate Moderate

Moderate

tapering or

side lobesuppression

Moderate

Rural Minimum Minimum

Minimumtapering or

side lobe

suppression

Maximum

The scheme is automated from OMC-R. The technique is

implemented according to Node-B sector loading percentage

detected at OMC-R. Our contribution of this paper is to

improve the soft as well as the softer handoff performance.

We achieved the following performance by remotely tapering

the antenna array amplitudes simultaneously in both the

vertical and horizontal plane. We are able to counter the

effect of cell size breathing so effectively that no coverage

holes are generated in entire radio network. This method is

increasing the footprint overlapping in both soft as well assofter handoff regions. We have to carefully set the pilot

channel (P-CPICH) transmit power as mentioned in the table

II to avoid the chances of pilot pollution. We have to set the

pilot channel transmit power according to the inter-site

distance morphology and total no of subscribers in the cell site

coverage area. Traffic density and pilot channel transmit

power will have an inverse relationship. We will also vary the

side lobe suppression according to the morphology and traffic

density as mentioned in table II to counter the cell breathing

effectively.

The proposed technique is better than beam forming as the

foot increases uniformly in all the directions including soft and

softer handoff regions. We are using variable attenuators in

the transmission lines of all the antenna elements except thecentral elements of the antenna array to control the antenna

array amplitude taper remotely from OMC-R (operations and

maintenance center for radio) where the entire network’s radio

parameters are defined. OMC-R is the centralized database

from where we can detect the total loading of each and every

Node-B. We are making the process automated by defining an

algorithm at OMC-R to increase the antenna array amplitude

taper proportionally with the loading of each and every sector

of Node-B. This is the contribution related to the application

of a remotely reconfigurable amplitude control antenna in self

optimizing network to enhance the soft and softer handoff

performance.

R EFERENCES

[1] Archiman Lahiry, Sushanta Tripathy, Amlan Datta “ W-CDMA BusyHour Handoff Optimization using OMC-R Controlled Remote

Electronic Variable Tapered Planar Array”, Presented at 3rd IEEE

International Conference On Communication and Signal Processing

(ICCSP), 3-5 April, 2014, Melmaruvathur, Tamilnadu, India, pp.031-

035.

[2] Constantine A. Balanis, Antenna Theory Analysis and Design, Wiley

India Pvt. Ltd., Third Edition, 2012, pp. 331-346.

[3] Gilbert Micallef, Preben Mongensen, Hans-Otto-Scheck, “Cell size

breathing and possibilities to introduce cell sleep mode”, Presented at IEEE European wireless conference (EW), 12-15April, 2010, Lucca,

pp.111-115.

[4] Iana Siomona, “P-CPICH power and antenna tilt optimization in UMTSnetworks”, Presented at Telecommunications, 2005 advanced industrial

conference on telecommunications/service assurance with partial and

intermittent resources conference/e-learning on telecommunications workshop, 17-20 July, 2005, Lisbon, Portugal, pp.268 – 273.

[5] Jarno Neimela, Jukka Lempiamen, “Mitigation of pilot pollution through

base station antenna configuration in W-CDMA”, Presented at 60th IEEE Vehicular technology conference (volume: 6), 26-29 September,

2004, Los Angeles, CA, USA, pp. 4270-4274.


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Improved self optimized variable antenna array amplitude tapering scheme to Combat Cell Size...

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