Nortel Networks 411-2021-111 manual Stsr cell site configuration, Control Channel redundancy

3-8Cell Site Layouts

120° STSR cell site configuration

The Metrocell in a 120° STSR configuration uses at least two equipment frames, one CE Frame and one RF frame (see Figure 3-4). Each TRU/DPA Shelf and its associated ATC on the RF frame support one of the three sectors. With only one RF frame, the maximum number of Voice Channels (VCH) supported by each sector is six since two of the eight TRUs on the TRU shelf have to be assigned as the Control Channel (CCH) and the Locate Channel Receiver (LCR). A 120° STSR Metrocell with one RF Frame requires six antennas; one TX/RX antenna and one RX only antenna for each sector (see Figure 3-6). As traffic grows, two additional RF frames can be added to accommodate more VCHs (see Figure 3-5).

A 120° STSR Metrocell with three RF Frames requires six antennas. It may be three TX/RX antennas and three RX only antennas or six TX/RX antennas depending on the number of channels in each RF Frame. An RF Frame with 20 channels or less in one sector requires one duplexer in the RF Frame and one TX/RX antennas for that sector. The outputs of the three combiners are combined through one phasing transformer (located at ATC 2) and connected to Duplexer position 2 in that RF Frame. The output of the duplexer is then connected to the main TX/RX Antenna of that sector).

An RF Frame with 21 channels or more in one sector requires two duplexers in the RF Frame and two TX/RX antennas for that sector. The outputs of ATC 1 and ATC 2 are combined through one phasing transformer (located at ATC

2)and connected to Duplexer position 2 in that RF Frame. The output of the duplexer is then connected to main TX/RX Antenna of that sector. The output of ATC 3 is connected to Duplexer position 3 and then to the diversity TX/RX Antenna of that sector. This arrangement is used to meet the requirement of a minimum of 21 channel spacing (630 kHz) between the channels in one RF

Frame. Figure 3-5 shows the frame layout and Figure 3-7 shows the block diagram of a 120° STSR Metrocell with three RF Frames.

Control Channel redundancy

Control Channel (CCH) redundancy is commonly provided with a Locate Channel Receiver (LCR) backup. With one RF Frame, the CCH of each sector is assigned to position 1 on the TRU/DPA Shelf of that sector and the LCR is assigned to position 4 on the same shelf. With three RF Frames, the CCH of each sector is assigned to position 1 on TRU/DPA Shelf 1 of that sector and the LCR is assigned to position 4 on the same shelf. This arrangement will have the CCH and the LCR supplied on a different DC power feed and a TCM card. No RF coaxial switch is required since the cavity of the LCR position on the ATC will tune to the CCH frequency when backup is required.

411-2021-111 Standard 01.01 June 1996