Dynamic Optimisation of Smart Antennas for Mobile Telecommunication Networks

A Multiple Switched Beam Smart AntennawithBeam Shaping AugmentationforDynamic Optimization of Capacity & CoverageinMobile Telecom Networks PhD Student: Freeborn Bobor-OyiboSupervisors: Prof David Smith &Prof. Stephen J. FotiOutline of PresentationBackground of mobile Telecommunication NetworksOverview of Smart AntennasStandard Multiple Switched Beam Smart AntennaDescription of Proposed Multiple Switched Beam Smart Antenna with Beam Shaping Augmentation Operation of 4x4 Butler Matrix Multi- Beamforming NetworkOperation of Beam Shaping networkOverall Smart Antenna Feed network operationSimulation of possible Dynamic Beam statesConclusions Future work

3G Mobile Telecom Architecture

Background of Mobile Telecom Networks Mobile telecom networks have evolved from 1G through to 3G Each generation has provided increased capacity within licensed frequency bands1G Analogue Networks provided limited capacity mainly for Voice Telephony1G uses frequency division multiple access technique (FDMA)2G Digital Networks provide improved capacity with low data rate transmission2G uses FDMA, time division multiple access (TDMA) and code division multiple access (CDMA)3G has more capacity and a higher data rate transmission capability compared to 2G for internet and video transmission (CDMA2000,WCDMA,) Mobile Telecoms is a fast growing business all over the world.At the end of 2004, worldwide cellular subscription passed the 1.4 billion mark and rapid growth is expected

Current Challenges of Mobile Telecom NetworksThere is need to increase coverage & capacity to accommodate more users with higher data rate demandsConventional ways of increasing coverage & capacity: Mast head amplifiers Receive Diversity & Transmit DiversityInfrastructural sharingHigher sectorization and Adding more cells. All of the above are useful, but limited and not dynamic.Current Challenges of Mobile Telecom Networks contdThe key problem of coverage and capacity is the varying traffic load imbalancePrevious methods to accommodate varying traffic load imbalances:Cell SpittingChannel BorrowingChannel SharingDynamic Channel AllocationNew Soft Handover SchemesCell OverlayVariable Tilt AntennasDynamic Cell-Size Control & Dynamic Sectorisation etc.All the listed techniques have limitations, hence investigation into the use of smart antenna is ongoingUnbalanced Traffic Load

Sector ASector BSector C

Sector ASector BSector C

Current Challenges of Mobile Telecom Networks contdTo accommodate the current demand of services from mobile communication users new intelligent or self-optimized and highly efficient systems will most certainly be requiredUsing the approach of a multiple switched beam antenna system and a beam shaping network, an intelligent sector optimization of varying azimuth beam shape can be established without increasing the existing electronics of the networkThe proposed technique, Multiple Switched Beams Smart Antenna with Beam Shaping Augmentation can be used to dynamically optimize coverage and capacity especially for hotspots in mobile network cell sectors. Furthermore, base stations are typically equipped with one transceiver per sector (per polarization) with a conventional sector antenna and it is cost effective not to increase the number of existing transceivers.

Current methods with Smart AntennasCooperative negotiation technique and semi-smart antenna[1]Case-base reasoning with semi-smart antenna[2]A Bubble Oscillation Algorithm for Distributed geographic load balancing in mobile networks (using smart antenna)[3]

[1]. L. Du, J. Bigham and L. Cuthbert, Towards intelligent geographic load balancing for mobile cellular networks, IEEE Transactions on Systems, Man and Cybernetics, Part C, vol. 33, no. 4, pp. 480-491, November 2003.[2]. Na, Yao and L. Cuthbert, Resource management in 3G networks using case-based reasoning International Workshop on Modeling Analysis and Simulation of Wireless and Mobile Systems, Proceedings of the 8th ACM international symposium on Modelling, analysis and simulation of wireless and mobile systems Montreal, Quebec, Canada October 2005, pp 307-312.[3]. L. Du, J. Bigham, and L. Cuthbert, "A bubble oscillation algorithm for distributed geographic load balancing in mobile networks," in The Twenty-third Annual Joint Conference of the IEEE Computer and Communications, IEEE INFOCOM'2004. Hong Kong: IEEE, March 2004.157

Overview of Smart AntennaWhat is Smart antenna?A smart antenna consists of several antenna elements whose signals are processed adaptively in order to exploit the spatial dimension of the mobile radio channelIt is not the antenna that is smart, but the antennas systemIt is one of the promising technologies systems that will reduce interference and increase coverage and capacity simultaneously The antenna system focus its radiation patterns only towards the desire userIt employs a set of radiating elements arranged in the form of an arrayThe signals from these elements are combined to form a switchable beam pattern that can be directed to the desire userThere are basically two types of smart antennasMultiple Switched Beam fully Adaptive smart antenna.

Standard Multiple Switched Beam smart AntennaFigure 3.0a Switched beam system architectureDupDup

Dup

Dup

ReceiverReceiverReceiverReceiverSwitch

TXBeamSelectionCombining and demodulationMXM Beam-Forming Network

Standard multiple fixed beam smart antenna radiation pattern

Description of the Proposed Smart AntennaThe antenna has three major components, array columns, beam forming network (4x4 butler matrix) and a beam shaping networkEach array column has 17.5dBi gain The horizontal beam shape produced by the antenna array depends on the complex weights ( magnitude and phase) applied to each array columnThe beam shaping network can shape the antenna beam dynamically to the direction of maximum concentration of mobile users in a sector while still maintaining some coverage in the remaining area of the sector

Feed Network for +45oPolarisationD=DiplexerArray Element ColumnsDUplink 4X4 Butler Matrix (Beamforming Network)Feed Network for -45oPolarisation (Duplication of feed Network)DiplexerTransceiverXXXXXXXXXX

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DDDUplink Beam Shaping NetworkDownlink 4X4 Butler Matrix (Beamforming Network)Downlink Beam Shaping Network14Proposed Design Architecture Dynamic Optimisation of Smart Antennasfor Mobile Telecom Networks (1)

Array designGiven a linear array of equally spaced identical elements, the total horizontal radiation pattern of the array E() in the far field, is given by:E()= EL().AF()(1)E()dBi=EL()dBi+20log[AF()]Where: EL() is the horizontal pattern of the column element and AF() is the array factor.

Array design cont.And d= inter-element spacing (horizontal) (72.474mm for the specific design example presented)= Azimuth angle(zero at centre of sector) and n is the total number of element is the complex weight.

Operation of 4x4 Butler matrix multi-beam forming NetworkIt uses combination of 90 degree hybrids and fixed transmission line phase shifters to form N simultaneous independent beams from an N element arrayIt performs a spatial Discrete Fourier Transform to provide overlapping orthogonal beamsBeams overlap at about 3.9dB below the beam maximumAny signal input into one of the BM input ports will be divided equally among the output ports with a progressive phase delayThis produces the multiple beams when the Butler Matrix is connected to a linear array

BUTLER MATRIX MULTIPLE BEAMFORMER45o45o0o-90o41322314DISADVANTAGES Narrowband (Fixed Phase Dist.) Only Orthogonal Beams -13.2 dB Sidelobes -3.9 dB Beam Crossovers Network Cross- overs Reqd Network Losses PIMs(many connections) Binary No. of Beams 90o HybridsBeam PortsADVANTAGES Commercially Available Low Inter-Port Coupling Real-Time Beam Formation

Operation of Beam shaping NetworkThe beam shaping network is a variable 4-way power divider/combiner that utilizes a 2-way variable power divider/combiner to drive two 2-way power divider/combinerWhen two 3dB hybrids are arranged as shown in the figure above, the output signals are given by the equation

For equal amplitude & phase = 270 degree.Table 1.0 below shows the operation of the 2-way power divider

20Beam Shaping Network Dynamic Optimisation of Smart Antennasfor Mobile Telecom Networks (2) Input SignalTo/From Butler Matrix Beam Ports 1,2 ,3 & 4 QQ-135o QQ-135oQQ-1-2-3a1a2a3a4a5a6Operation of Beam shaping Network contTable for the Three 2-way power divider/combiner states

Phase Shifter Numbers (i=)ia1Phase(a1 )

a2

Phase(a2 )(1),(2)&(3)000N/A1-900(1) &(2)18001000N/A(2)&(3)20800.97-1400.242-140(1),(2),(3)27000.707-4500.707-1350(2) &(3)33200.242-1400.97-140Simulation of possible Dynamic Beam StatesTo verify the performance of the proposed smart antenna over the up and downlink sub-bands for a specific UK 3G network operator (orange, UK) the feed network was modelled using microwave office software.Two designs were modelled, one for downlink frequency and another for the uplink frequency band.The orange UK sub-bands have been assumed as practical example.The circuit was configured using ideal transmission lines.Table below gives a summary of the dynamic operating states of the networkThe feed network was modelled in all operating states to get the various beams need for the antenna to dynamically optimize coverage & capacity.

Simulation continueThe result from the microwave office model for the complex weights with an inter-element spacing of /2 (d=72.474mm) was put into an array analysis software programThe condition at which this beams are form is shown in table 2.0 aboveIt is seen that beams are virtually invariant over each of the bands base upon the ideal network model and the narrow uplink and downlink bands

Overall Smart Antenna Feed Network OperationBeam StateComplex weights: Values are for Downlink with corresponding values for Uplink in ( ) Phase Shifter Settingsw1w2w3w4123Amp (dB)Phase (deg)Amp (dB)Phase (deg)Amp (dB)Phase (deg)Amp (dB)Phase (deg)Phase (deg)Phase (deg)Phase (deg)B1 only-6.02(-6.07)135(138.8)-6.02(-6.01)90(93.8)-6.02(-6.02)45(49.23)-6.02(-6.07)0(4.15)-180-180AnyB2 only-6.02(-6.09)180(-176.1)-6.02(-6.06)-45(-40.83)-6.02(-5.99)90(94.02)-6.02(-6.02)-135(-131.2)-1800AnyB3 only-6.02(-6.07)-135(-130.8)-6.02(-6.02)90(94.18)-6.02(-6.0)-45(-41.18)-6.02(-6.07)-180(-176.2)0Any-180B4 only-6.02(-6.08)-180(-176)-6.02(-6.04)-135(-131.3)-6.02(-6.00)-90(-56)-6.02(-6.04)-45(-40.79)0Any0BB-9.03(-9.099)-135(-130.7)-4.26(-4.292)-9.7(-5.64)-4.26(-4.26)-9.7(-5.64)-9.03(-9.01)-135(-130.7)-270-270-270RHSB-18.36(-18.43)-104(-98.53)-5.77(-5.83)56.59(60.44)-3.14(-3.16)-3.9(-0.025)-6.29(-6.26)-104(-100.1)-270-208-208LHSB-6.28(-6.35)-165.9(-162)-3.14(-3.16)-65.98(-62.07)-5.77(-5.76)-5.44(-1.35)-18.36(-18.32)-165.9(-163.4)-270-332-332

25 Dynamic Optimisation of Smart Antennasfor Mobile Telecom Networks (1)

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27 Dynamic Optimisation of Smart Antennasfor Mobile Telecom Networks (3)

Dynamic Optimisation of Smart Antennasfor Mobile Telecom Networks (4)

29 Dynamic Optimisation of Smart Antennasfor Mobile Telecom Networks (5)

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Conclusions This research has explored the importance of using smart antenna systems for traffic load balancing especially in hotspots of wireless networks. We have successfully designed, simulated and analysed a multiple switched beam smart antenna with beam shaping augmentation for dynamic optimization of capacity and coverage for the up and downlinks of 3G mobile telecommunication networks. Only one transceiver/polarizationSimple to operate

Future workUse propagation model in conjunction with Antenna model to produce beam footprint contours & quantify coverage & capacityProduce Non-Ideal antenna model & Analyze including realistic vertical column arrays and mutual coupling.

Sample Footprint of Smart Antenna

Foot print of four multiple beam smart antenna (standard) using orange network planner Glasgow city35Thanks for your attention.EL ( =17.5dBi + 20[ ] AF (=