Co-Channel Operation; Xpic - Alcatel-Lucent 9500 MXC User Manual

Chapter 3. 9500 MXC Nodes

Co-channel Operation

XPIC

Vol. II-3-102
This section provides data on Co-channel Dual Polarization (CCDP) operation
with Cross-Polarization Interference Cancellation (XPIC). This allows two radio
links of identical capacity and modulation to operate over the same path, on the
same frequency channel, by operating one link on horizontal polarization, and the
other on vertical. In this way, one frequency channel can be used to support two
same-path links (double the capacity), compared with one link for a standard
(non-CCDP) radio.
• Co-channel operation requires paired RAC 40 plug-ins with companion ODU
300s.
Refer to:
• XPIC on page 3-102
• RAC 40 Operating Guidelines on page 3-104
For CCDP operation XPIC is required to provide the additional cross polarization
discrimination needed to avoid unacceptable co-channel interference.
• Standard high performance shielded antennas typically exhibit 30 dB cross
polarization discrimination (XPD) whereas 40 dB is typical for
purpose-designed, high polarization discrimination antennas.
• Correct end-end polarization alignment is essential to achieve a path XPD to
closely match the antenna XPD. Refer to Additional Procedures for CCDP
XPIC links on page 5-7 of Chapter 5, Volume III.
• XPIC provides up to an additional 20+ dB of XPD, which is achieved by
cancelling interference caused in the wanted signal by taking a sample of the
unwanted signal received on the opposite polarization. For an explanation of
XPIC operation, refer to RAC 40 in Appendix F.
• In a non-XPIC STM1/75E1/64E1 system, ETSI specifies that a co-channel
interfering signal 37 dB below the wanted signal (37 dB C/I) shall not
degrade Rx threshold by more than 1 dB. In an XPIC system ETSI specifies
a 17dB C/I for a 1 db threshold degradation.
• While high performance dual polarized antennas when correctly aligned
may provide up to 30 dB of isolation between received H and V signals, such
isolation may reduce dramatically during fading conditions, which is when
the XPIC function provides maximum benefit.
• Each RAC 40 operates with an ODU300ep or ODU 300hp.
Figure 3-56 shows the relative difference between conventional adjacent channel
alternate polarization (ACAP) operation, and CCDP, for same-path operation.
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