Chapter 7
T1 Measurements
Introduction
This chapter provides a brief description of a T1 circuit and T1 measurements, and also ex-
plains how to setup and measure T1 performance using the Anritsu Site Master S331D with
Option 50 installed.
T1 Fundamentals
Wireless service providers use wired T1 circuits as the backhaul links to connect a Base
Transceiver Station (BTS) to a Mobile Switching Center (MSC). The quality of the service
provided over those T1 lines has a direct effect on the quality of service experienced by the
wireless service provider customers. Call setup failures, dropped calls, data errors and noise
can often be attributed to the T1 backhaul facilities. An example of a typical wireless net-
work backhaul T1 link is shown in the Figure 7-1.
In the United States, wireless service providers generally lease T1 lines from a Local Ex-
change Carrier (LEC), so it often requires a joint effort to analyze and troubleshoot a T1
line.
T1 is an American National Standard Institute (ANSI) standard, used mostly in North
America, parts of Japan and some Asian countries. Technically, a T1 line is a digital trans-
mission facility consisting of wire pairs and regenerators, or optical media, carrying a DS1
signal. T1 refers to the physical properties of the line, for example, 1.544 MHz with a spe-
cific pulse shape, etc. DS1 refers to the digital signal carrying the information at a rate of
1.544 Mb/s. The DS1 signal may be formatted using various framing patterns, most com-
monly (but not always) divided into 24 channels each carrying encoded voice or data.
7-1
T1
BACKHAUL
T1
BACKHAUL
T1
BACKHAUL
T1
BACKHAUL
T1
BACKHAUL
BTS
BTS
BTS
BTS
BTS
MSC
Figure 7-1.
Typical Wireless Network T1 Backhaul Link
