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SMART ANTENNAS

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Smart Antennas

The presentation is divided into the

following:

Why?

What?

How?

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Why Smart Antennas?

- Large increase in Capacity

- Increased range

- Potential to introduce new services- More security

- Reduced Multipath propagation

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What are Smart Antennas?

- In a cellular system the radio communication is

between the user and a base station, which

provides radio coverage within a certain area,

called a cell.- The base stations are omni directional or

sectored.

- This is a waste of power as most of it will beradiated in other directions than toward the user.

- The power radiated in other directions will be

experienced as interference by other users.

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What are Smart Antennas (SA)?

- The idea of smart antennas is to use base

station antenna patterns that are not fixed, but

adapt to the current radio conditions.

- This can be visualized as the antenna directing

a beam toward the communication partner only.

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Illustration of Smart Antennas

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Sharing the Radio Spectrum

Users communicating via the same base stationhave been separated in various ways:

- by frequency as in FDMA ( frequency divisionmultiple access),

- by time as in TDMA ( time division multipleaccess),

- by code as in CDMA ( code division multipleaccess) and

- by space through SDMA ( space division multipleaccess) insmart antennas.

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The Concept

- Smart Antenna consists of a number of radiatingelements, a combining/dividing network and a

control unit.

- Control unit can be called the smart antennas

intelligence. It is realized using a digital signal

processor (DSP).

- Based on this definition of smart antenna, one can

define levels of Intelligence.

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Levels of Intelligence

1.) Switched lobe (SL)

- simplest technique, also called switched beam.

- comprises of only a basic switching functionbetween separate directive antennas or predefined

beams of an array.

- the setting that gives the best performance is

chosen.

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Levels of Intelligence

2.)Dynamically phased array (PA):

- a direction of arrival (DOA) algorithm is included for

the signal received from the user.

- continuous tracking can be achieved.

- generalization of the switched lobe concept.

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Levels of Intelligence

3.) Adaptive array (AA):

- a DOA algorithm for determining the direction

toward interference sources (e.g., other users) is

added.

- the radiation pattern can then be adjusted to null

out the interferers.

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Levels of Intelligence

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Evolution of Smart Antennas

An evolution can be foreseen in the utilization of

smart antennas. The evolution can be divided intothree phases:

- Smart antennas are used on uplinkonly. This

concept is called high sensitivity receiver(HSR).

- In the second phase, directed antenna beams areused on the downlink direction in addition to HSR.

- The last stage in the development will be fullspace division multiple access (SDMA).

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Drawbacks and Cost factors- Transceiver Complexity -- A smart antenna

transceiver is much more complex than a traditional

base station transceiver.

- Need for more powerful algorithms, processors and

control systems.- Resource Management -- New demands on network

functions such as resource and mobility management

are needed.

- Physical Size -- For the smart antenna to obtain a

reasonable gain, an array antenna with several

elements is necessary.

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Status: Trials and Testbeds

- Ericsson/Mannesmann Trial in Giessen,

Germany

- Tsunami II Trial in Bristol, UK

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Picture of an 8-element array antenna

at 1.8 GHz. (Antenna property of Telia Research AB, Sweden).

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Thank You!