User guide

Upgrading a BH Link to BH20 Installing Components
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pmp-0229 (Mar 2013)
b. Listen to the alignment tone for
◦ pitch, which indicates greater signal power (RSSI/dBm) by higher pitch.
◦ volume, which indicates better signal quality (lower jitter) by higher volume.
c. Adjust the module slightly until you hear the highest pitch and highest volume.
d. If the Configuration web page of the BHS contains a 2X Rate parameter, set it back
to Enable.
19. When you have achieved the best signal (highest pitch, loudest volume), lock the BHS in
place with the mounting hardware.
Installing a PTP 200 Series BHS
To install a PTP 200 Series (OFDM) BHM, use the procedure provided under Installing a PMP 400 Series
SM on Page 402, with the following additional treatment for a setting that is unique to PTP 200 Series
wireless Ethernet bridges.
OFDM technology uses a cyclic prefix, where a portion of the end of a symbol (slot) is repeated at the
beginning of the symbol (slot) to allow multipathing to settle before receiving the desired data. A 1/4 cyclic
prefix means that for every 4 bits of throughput data transmitted, an additional bit is used, A 1/8 cyclic
prefix means that for every 8 bits of throughput data transmitted, an additional bit is used.
PTP 200 Series modules (OFDM BHs) are settable for either 1/8 or 1/4 cyclic prefix. The use of 1/8 cyclic
prefix provides about 11% higher maximum throughput and is recommended for most cases.
The Cyclic Prefix is set on the Configuration => Radio page of the BHM. The default on a new unit or
after the unit has been reset to factory defaults is 1/4 Cyclic Prefix. In most deployments, 1/8 Cyclic Prefix
will provide a high quality, higher throughput link. In cases with severe multipathing or obstructions, 1/4
Cyclic Prefix may yield better overall results.
To perform and possibly adjust the setting, use Procedure 27: Setting the Cyclic Prefix in a PTP 200 Series
wireless Ethernet bridge on Page 412.
Upgrading a BH Link to BH20
To replace a pair of 10-Mbps BHs with 20-Mbps BHs, you can minimize downtime by temporarily using
the 10-Mbps capability in the faster modules. However, both interference and differences in receiver
sensitivity can make alignment and link maintenance more difficult than in the previous 10-Mbps link. The
effects of these factors are greater at greater link distances, particularly at 5 miles or more.
In shorter spans, these factors may not be prohibitive. For these cases, set the first replacement module to
1X Rate and establish the link to the 10-Mbps BH on the far end. Similarly, set the second replacement
module to 1X Rate and re-establish the link. With both of the faster modules in place and with an
operational link having been achieved, reset their modulation to 2X Rate (20 Mbps).