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Cross Polarization InterferenceCancellation (XPIC)

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Topics of Discussion

What is XPIC?

Examples

Design Considerations

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Some carriers transport system designers arenot aware that more than one RF channel maybe assigned to a path

Some also believe that if you do assign asecond channel on a path that another antenna

is required

And most do not know about XPIC and what itallows a design engineer to accomplish

General Comments

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Disclaimers

This presentation is not a sales pitch for NEC

equipment

According to Dick Laine at Harris Corporation a

similar capability is available for their Megastar

Radio

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UPDATE 18 March 2004

Alcatel has XPIC capable equipment. It is

available in the ETSI high capacity radios suchas the 9600 LH and UH, as well as the 9600

USY ("MDR-9000"). Contact your Alcatel

representative for additional information.

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Disclaimers

The presenter only has experience with NEC

XPIC equipment

Becky Holland and Bruce Blain of NEC wrote

an article for RadioResourceMagazine

Information from that article is presented

with the permission of Bruce Blaine

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What is XPIC?

Cross Polarization Interference

Cancellation (XPIC)

How does microwave radio having XPIC

capabilities effectively double the potential

capacity of a microwave path?

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What is XPIC?

It allows the assignment of the same frequency

to both the vertical and horizontal polarizationon a path

Where available frequencies are limited then it

is possible to assign the same frequency twiceon the same path using both polarizations

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What is XPIC?

Using standard microwave equipment from anyof the major manufacturers, if a full block ofeight frequencies were available for a 6 GHzlower band path then eight frequencies couldbe assigned in each direction on the path, fourper polarization

Using equipment with XPIC capability sixteenfrequencies may be assigned each way on thesame path, eight per polarization

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What is XPIC?

Standard Frequency Assignments

4 FrequenciesHorizontal

4 FrequenciesVertical

XPIC Frequency Assignments

8 FrequenciesHorizontal

8 Frequencies - Vertical

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Design Considerations

The use of XPIC requires very high crosspolarization discrimination antennas such as

Andrew HSX-40 dB Cross Polarizationdiscrimination

XPIC should be considered in the initial system

designretrofitting the equipment with therequired intra bay cables is not easy after theequipment is installed, in fact NEC engineerstold me that it cannot be retrofitted in the field

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Design Considerations

NEC prefers to have ATPC operational on

paths using XPIC equipment

ATPC must be turned ON for both directions of

a path

Adjacent frequencies on a path should be

receiving at nearly the same level in order for

XPIC equipment to work properly

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Design Considerations

For Example, if 13T requires ATPC to clear an

interference case then 12T and 14T are alsorequired to use ATPC at the same levels

Designers must employ XPIC for the protection

channel and the first operational channel forthe remaining channels 2 through 7 XPIC may

be applied on a per channel basis

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Design Considerations

For circulator coupled XPIC equipment anadditional 7.1 dB of loss for the transmittersand 7.2 dB of loss for the receivers must betaken into account in the path calculations

XPIC equipment will work with one transmit

antenna and if required a diversity antenna.The three-antenna configuration required bysome equipment manufacturers because ofintermodulation is not required

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Discussion, Questions, Comments