Acronym

LOF
: Loss of frame alignment [3]

LOS: Loss of Signal [2]

AIS: Alarm Indication Signal [2]

RDI
:
Remote Defect Indication
[2]

Reference

1. G.704

2. G.775

3. G.706

2M E1
传输简介

一个
E1
的帧长为
256
个
bit,
分为
32
个时隙，一个时隙为
8
个
bit

每秒有
8k
个
E1
的帧通过接口，即
8K*256=2048kbps

每个时隙在
E1
帧中占
8bit
，
8*8k=64k
，即一条
E1
中含有
32
个
64K

2M E1
帧结构
[1]

其中偶数帧传送
Frame containing the frame alignment signal
。奇数帧传送
Frame not containing the frame alignment signal
。

E1
传输几种告警

Receiving LOF

Frame alignment will be assumed to have been lost when three consecutive incorrect frame alignment signals have been received.

Frame alignment will be assumed to have been lost when bit 2 in time slot 0 in frames not containing the frame alignment signal has been received with an error on three consecutive occasions.

Receiving LOS

A LOS defect at 2048 kbit/s, 6312 kbit/s, 8448 kbit/s, 34 368 kbit/s and 139 264 kbit/s interfaces is detected when the incoming signal has "no transitions", i.e. when the signal level is less than or equal to a signal level of Q dB below nominal, for N consecutive pulse intervals, where 10 <= N <= 255.

Receiving AIS/Transiting AIS

An AIS defect at a 2048 kbit/s interface is detected when the incoming/outgoing signal has two (2) or less ZEROs in each of two consecutive double frame periods (512 bits).

Receiving
RDI

A Remote Defect Indication (
RDI
) defect at 2048 kbit/s path termination functions is detected when the incoming signal has the "Remote alarm indication" bit set to binary
ONE
("1") for z consecutive double frame periods, where z = 2 .. 5. z is not provisionable.