1215 - 1106 - ceragon - xpic - presentation v6.7.pdf

Cross Polarization Interference Cancellation (XPIC)

Introduction

Proprietary and Confidential

Introduction

Two data channels are transmitted & received over the same frequency on dual

polarization (H & V)

Crosstalk between the polarizations due to imperfect antenna isolation and

channel degradation can be effectively cancelled at the receiver using -

XPIC – Cross Polarization Interference Cancellation/Canceller

• Ideal solution for “frequency- crowded” areas

• Using one frequency for two carriers

3

V

H fx

A


Decoding the received signal

Both IDUs on each site communicate through the Backplane of the Nodal

Enclosure

M S

M S

M S

M S

H

V

Nodal Enclosure Nodal Enclosure

4


Decoding the H signal

• Each IDU accommodates 2 modems (Master and Slave)

• In each site, the Main IDU communicates with the Mate IDU via the backplane

• The Master modem (V) sends its signal (V) to the Mate Slave

• The Mate Slave produces the interference signal (v) and sends it to its H-Master

Slave

V-Master

H

V

Slave

H-Master ba

ckp

lane

ba

ckp

lane Slave

V-Master

Slave

H-Master H+v H

V V+h

Transmitter Receiver

v

Main IDU

Mate IDU

5


Decoding the H signal - continued

• By knowing the interference level (v), the Master Modem (H) can demodulate the

received horizontal signal (H)

• The vertical channel is decoded similarly

Slave

V-Master

H

V

Slave

H-Master ba

ckp

lane

ba

ckp

lane Slave

V-Master

Slave

H-Master H+v H

V V+h

Transmitter Receiver

v

Main IDU

Mate IDU

6


Guidelines

1. XPIC is supported with IP-10G IDUs in version 6.6.1 and higher

2. XPIC can only be configured in a node:

slots 1+2 and/or slots 3+4 and/or slots 5+6

3. IDU license determines the allowed script and link capacity

4. Identical configuration should be used in all IDUs participating in a link:

• XPIC Script

• Frequencies

• SW version (IDU, ODU)

• HW version (IDU, ODU)

• Protection is disabled

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If any of these conditions is not met, an

alarm will alert user. In addition, events will

inform user of which conditions are not met.


XPIC Recovery Mechanism

• The main purpose of the Recovery Mechanism is to recover link availability

due to hardware problem rather than fading issues

• The recovery mechanism maintains a working link while attempting to recover

the faulty polarization

• The mechanism applies periodic attempts to mute the problematic remote

transmitter

• The time between one attempt and another is exponentially increased to

avoid unnecessary TX Mute when interference is temporary (allowing

sufficient to recover)

• At the end of the process, if the problem still exists, the problematic link will

be permanently muted unless the user manually un-mutes it

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XPIC Recovery Mechanism

• The indication to entry the recovery mechanism is a loss of modem

preamble lock, which takes place at SNR~10dB

• The number of Mute/Un-mute attempts is user-configurable:

1.Recovery attempt time

2.Initial time between attempts

3.Multiplication factor for attempt time

4.Number of retries

5.Enable / Disable

• Users are advised to maintain Factory Defaults

Please Note:

Every recovery attempt will cause a brief traffic hit in the working link

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2+0 2U Setup

H + v

Each node includes –

• 2 x RFU-C

• Coupler

• Dual pole antenna

v

H

v

H

h/v

V + h

• 2 IDUs are installed in each node using an enclosure shelf

• We assume slot 1 is using Vertical polarization and slot 2 Horizontal polarization

10


6+0 6U Setup

• 6 IDUs are installed in each node using enclosure shelves

• Possible configurations:

• Slot 1 + slot 2

• Slot 3 + slot 4

• Slot 5 + slot 6

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Multi-Radio Configuration


What is Multi-Radio?

• Allows splitting traffic from one Ethernet port

into two links in a 2+0 configuration

• Multi-Radio saves the need to have an

external device to combine traffic from two

Ethernet ports in order to reach beyond

567Mb

• The 2+0 configuration can be either XPIC or

different frequencies

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How Does it Work?

• Every bit is transmitted either over the master or the slave

• The distribution is proportional to the available bandwidth in every link

• If both links have the same capacity, half the data is sent through each

link

• If the links use different modulations, data is distributed proportionally in

order to maximize the available bandwidth

• If the links have different capacity, data is distributed proportionally in

order to maximize the available bandwidth

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Packet to send:

101010111010010100

Master

Slave

Master

Slave

EMS Configuration


Logging in

1. Log in to the EMS

2. Execute the following steps to Main IDU and

Extension IDU on both ends of the link

3. When configuring an IDU, make sure the relevant

unit is selected (a black line will highlight selected IDU)

Main

Extension

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Versions

Check that your IDUs and ODUs are installed with the required version

(6.6.1 or higher)

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XPIC Script

Apply the required script to both IDUs (Main & Ext.) on both ends:

1. Expand the “+” icon next to the script in the MRMC Table

2. Click the “Apply” button

3. IDU will automatically restart to apply the new script

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XPIC Script - 2

When IDUs complete the reset process, verify XPIC script is successfully

assigned.

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XPIC Configured

Verify Main View in GUI shows icon next to IDUs

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Radio Parameters

1. Verify that no alarms exist in the system.

2. Clear the defected blocks counter and verify that there are no errors in the

system.

3. Read the MSE and XPI and verify that they fit the link design (if no values

are defined, verify that they are below 34dB and above 25dB, respectively).

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Radio Parameters – scroll down to bottom of page

Configure Radio Parameters and verify both links (H+V) are operational

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Troubleshooting


Link Commissioning

1. Make sure IF Cables are identical in length (H and V)

2. Commission the “H” link as a single link system with “V” channel muted,

verify RSL and MSE are as expected

3. Commission the “V” link as a single link system with “H” channel muted,

verify RSL and MSE are as expected

4. Check stability of RSL readings

5. Upon confirming the above steps, proceed to configure XPIC as explained

in previous slides

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Improving XPI Levels

• When XPI levels < 25, antenna feeders need to be re-aligned.

• One of the parameters that impacts the XPI is the antenna XPD

(Cross Polarization Discrimination) -

• In the following steps, we shall measure the antenna XPD to determine the

XPD of each antenna – 1. Mute “H” transmitters on both ends: “H” link is irrelevant now

2. Measure RSL on “H” receivers: we measure the “v” interference now

3. Measure RSL on “V” receivers – calculate the difference between V and H

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v H

v H

RSL = -70dBm

TX = OFF

RSL = -50dBm

TX = OFF

In this example, the XPD is

not good enough:

The difference is only 20dB

We need to aim for a bigger

difference (better XPI)


Improving XPI Levels

4. Re-align the antenna feeders to read a bigger difference:

RSLH – RSLV > 25dB

5. Un-mute the “H” transmitters

6. Repeat steps 1-4 for the “V” link

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v H

v H

RSL = -78dBm

TX = OFF

RSL = -50dBm

TX = OFF

In this example, the XPD is

much better:

The difference 28dB

That means, XPI = 28dB


XPIC Events (EMS Event Log)

• During the XPIC mechanism, events are displayed in the EMS Event log to

allow detailed description and effective troubleshooting

• Various cases are encoded as a single event with a bitmask code –

• Event title = “Insufficient conditions for XPIC”

• Bitmask Codes -

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XPIC Events (EMS Event Log)

The following events indicate changes in the XPIC state:

• Remote TX Mute (try # n) was Set by XPIC Recovery on Slot # n

• Remote TX Un-mute (try # n ) was Set by XPIC Recovery on Slot # n

• XPIC Recovery Started on Slot # n

• XPIC Recovery Finished Successfully on Slot # n

• XPIC Recovery Finished Unsuccessfully on Slot # n. Remote Mute was Set

• XPIC Recovery on Slot # n Stopped Due to an External Event

• XPIC Recovery (XRSM) was disabled

• XPIC Recovery (XRSM) was enabled

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XPIC Events (EMS Event Log) - Example

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XPIC Performance Monitoring

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Thank You

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1215 - 1106 - ceragon - xpic - presentation v6.7.pdf

Documents

h signal

master modem v

master modem h

interference signal

horizontal signal h

mate slave

modems master

idu license