User Manual

Table Of Contents

ADCP-75-191 • Preliminary Issue B • November 2005

Page 1

1 DESCRIPTION

The Reverse Link Monitor (RLM) is an optional add-on feature that is available for the

Digivance 800 and 1900 MHz LRCS product line. The RLM feature provides an alarm indication

if there is a loss of gain in the reverse path RF signal. The standard Digivance product provides

an alarm indication if there is an internal component failure or an optical failure but does not

provide an alarm if a loss of gain occurs in the reverse path RF signal.

The RLM feature works by injecting a pilot tone at the STM and then measuring the level of the

tone at the Host Unit. An RLM fault is reported if the reverse path signal level at the Host Unit

RF output drops more than 10 dBm. This generates a major alarm which triggers the operation of

the normally open and normally closed alarm contacts provided by the Host Unit. The RLM

feature is available on both non-diversity and diverstiy systems. On diversity systems, an RLM

fault in either the primary or diversity return path will trigger an RLM alarm.

The RLM alarm generates an alarm message which may be accessed through the Element

Management System (EMS) software, the Network Operations Center-Network Element

Manager (NOC-NEM) interface, or the Simple Network Management Protocol (SNMP)

manager. The Host Unit (LED) indicators on both the Host Unit and the Remote unit (STM)

turn red when an RLM alarm is reported. The RF output of the Remote Unit is not muted for an

RLM alarm.

2 HARDWARE AND SOFTWARE REQUIREMENTS

The RLM feature requires that both the Host Unit and the Remote Unit Spectrum Transport

Unit (STM) be equipped with the internal components that support RLM. This is an option that

must be specified when either unit is ordered. There are no external markings that indicate if the

Host Unit or STM supports RLM. Host Units and STM’s equipped with the RLM feature are

compatible with hardware that does not support the RLM feature. However, the RLM feature

will not function unless both units are equipped to support the RLM feature.

The EMS and SNMP agent software has been upgraded to support the RLM feature. Only EMS

software Version 7.0 and SNMP Agent software Version 7.1 can report when an RLM alarm has

been generated. The upgraded versions of the EMS and SNMP agent software are compatible

with any earlier versions of the Host Unit and STM that are not equipped with the RLM feature.

Earlier versions of the EMS and SNMP agent software (Version 3.01 and Version 5.0) do not

support RLM alarm reporting but are otherwise compatible with RLM equipped hardware.

3 APPLICATION

The RLM feature is primarily designed for simulcast applications where a single Base

Transceiver Station (BTS) is configured to serve multiple Host Units as shown in Figure 1. The

BTS monitors the level of the reverse path RF signal and generates an alarm if the level drops

below a specified threshold. When a single Host Unit is connected to the BTS, a drop in the

reverse path signal level will generate an alarm by the BTS. When several Host Units are linked

to the same BTS, a drop in the reverse path signal level from one of the Host Units will not

generate an alarm if the reverse path RF signal levels from the remaining units are within

specifications. The RLM feature provides selective alarming that cannot be provided by the

BTS in a simulcast application.