SMART ANTENNA SMART ANTENNA SYSTEMSSYSTEMS IN BWA IN BWA

Submitted by M. Venkateswararao

Abstract

• One of the most rapidly developing areas of communications is “Smart Antenna” systems. The elegance of their applications in various fields such a 4G telephony system, best suitability of multi carrier modulations such as OFDMA etc..,

•The signal that is been transmitted by a smart antenna cannot tracked or received any other antenna thus ensuring a very high security of the data transmitted. This paper also deals the required algorithms that are need for the beam forming in the antenna patters.

INTRODUCTION

• The rapid growth of the Internet user base and of

bandwidth-hungry applications in recent years has

created a need for ‘last mile’ broadband access

• We define “broadband” access as one that provides at

least 5 Mbps peak (burst) rate per user in the downlink

direction and 500 Kbps peak (burst) rate in the uplink.

• These include rapid deployment, high data

(Mbps/sq.mile) scalability, low maintenance.

BLOCK DIAGRAM

b1 b6b5b4b2 b3 ....

b1 b4

...b6b3

b2 b5 ...

...

SIG

NA

L P

RO

CE

SS

ING

b1 b6b5b4b2 b3 ....

SIG

NA

L P

RO

CE

SS

ING b2 b5 ...

b2 b5 ...

...b6b3

C1

C3

C2

A1

A3

A2

B3

B2

B1

A1 C1

B3

B2

B1

A3

A2

C3

C2

Smart Antenna Array:• Antenna array with a digital signal

processing capability to transmit and receive in an adaptive and spatially sensitive manner.

“Smart” >> digital signal processing facility

USAGE

Applications to:

• cellular and wireless networks

• radar

• electronic warfare (EWF) as a countermeasure to electronic jamming

• satellite systems

WHY SMART ANTENNA ARRAYS?

Higher Capacity

Higher Coverage

Higher bit rate

Improved link quality

Spectral efficiency

Mobility

Elements of a Smart Antenna

• Number of radiating elements

• A combining/dividing network

• Control unit

Aim :

• To maximize the antenna gain in the desired direction

• To minimize the gain in directions of interferers

Smart Antennas for Base Stations

• The idea of smart antennas is to use base station antenna patterns that are not fixed, but adapt to the current radio conditions

• Can be visualized as the antenna directing a beam toward the communication partner only

Types of Smart Antennas

Switched lobe (SL):

( also called “switched beam” )

• simplest technique

• comprises only a basic switching function between separate directive antennas or predefined beams of an array

Types of Smart Antennas - cont’d

Dynamically phased array (PA):

• continuous tracking can be achieved by including a direction of arrival (DoA) algorithm for the signal received from the user

• can be viewed as a generalization of the switched lobe concept

BWA ARCHITECTURES

SINGLE (MEGA) CELL

• In mega cell architecture, a large service area with

a radius of up to 30 miles is covered by one or two cells.

The base station antenna is typically located on a very high

tower or hill top (height of 500 to 1200 ft) to provide line of

sight (LOS) paths to subscribers.

• A high gain CPE rooftop mounted antenna pointing

towards the base station is used. Frequency reuse in angle

(and polarization) may be possible with sectorization [Fig.

1(a)], particularly on the uplink.

Macro Cell

•Macro cellular systems use spatial frequency reuse

to cover the service area. The BTS heights are

similar to cellular infrastructure.

• LOS propagation is usually not possible, and cell

ranges are therefore much smaller (1 – 4 miles) due

to higher path loss.

SMDA(Space Division Multiple Access)

• More than one user can be allocated to the same physical communications channel simultaneously in the same cell

• Separated by angle only

• In a TDMA system, two users will be allocated to the same time slot and carrier frequency at the same time and in the same cell

SDMA (Space Division Multiple Access)

SMART ANTENNA ADVANTAGES

Array Gain: Multiple antennas coherently combine the signal energy improving the carrier-to-noise ratio (C/N). Available both on transmit and receive.

Diversity Gain: Spatial diversity obtained from multiple antennas helps combat channel fading. Available on transmit and receive.

Spatial Multiplexing: Spatial multiplexing uses multiple antennas at both ends to create multiple channels and improves spectrum efficiency (bps/Hz).

Conclusion

• A large market opportunity is opening up for providing broadband

wireless access to residential, SOHO and business markets.

Successful BWA systems need to be scalable, should have high

spectrum efficiency, should offer high bit rates and should be easy

to deploy at the infrastructure and subscriber end.

• Use of multiple antennas at both ends of the wireless link along with

efficient modulation, radio resource management, coding and

diversity can increase spectrum efficiency

REFERENCES

1. “Smart Antenna Systems Tutorial”, The International Engineering Consortium, http://www.iec.org/online/tutorials/smart_ant/

2. Lehne, P.H. and Pettersen M., “An Overview of Smart Antenna Technology for Mobile Communications Systems”, IEE Communications Surveys, Fourth Quarter 1999, vol. 2, no.4, http://www.comsoc.org/livepubs/surveys/public/4q99issue/pdf/Lehne.pdf

3. Schüttengruber, W., Molisch A.F. and Bonek E., “Smart Antennas for Mobile Communications Tutorial”, http://www.nt.tuwien.ac.at/mobile/research/smart_antennas_tutorial/index.en.html