Chapter 8
E1 Measurements
Introduction
This chapter provides a brief description of an E1 circuit and E1 measurements, and also
explains how to setup and measure E1 performance using the Anritsu Site Master S331D
with Option 50 installed.
E1 Fundamentals
Wireless service providers use wired E1 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 E1 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 E1 backhaul facilities. An example of a typical wireless net-
work backhaul E1 link is shown in the Figure 8-1.
E1 is an International Telecommunication Union, Telecommunication Standardization Sec-
tor standard for E1 and is widely used in Europe and Asian countries. E1 is a digital signal
carrying the information at a rate of 2 Mbps, with each 2 Mbps frame containing 256 bits in
32 time slots. Each slot has 8 bits at a repetition rate of exactly 8 kHz. The first time slot is
reserved for framing, error checking and alarm signals.
ITU-T G.704 specifies a CRC-4 cyclic redundancy check for E1 performance. CRC-4 fram-
ing provides monitoring for a Bit Error Rate (BER) during normal operation. When the
equipment detects an incoming CRC-4 error, it transmits an E-bit error which is received by
the measuring equipment. Counting E-bit changes is equivalent to counting CRC errors,
which provides BER information for the data.
8-1
E1
BACKHAUL
E1
BACKHAUL
E1
BACKHAUL
E1
BACKHAUL
E1
BACKHAUL
BTS
BTS
BTS
BTS
BTS
MSC
Figure 8-1.
Typical Wireless Network Backhaul E1 Link
