X2 Application Protocol (X2AP)
The X2AP protocol is used to handle the UE mobility within
E-UTRAN and provides the following functions:
·
Mobility Management
·
Load Management
·
Reporting of General
Error Situations
·
Resetting the X2
·
Setting up the X2
·
eNB Configuration
Update
Protocol specification
3GPP TS 36.423 - Evolved Universal Terrestrial Radio
Access Network (E-UTRAN); X2 Application Protocol (X2AP)
X2 layer 1
The main functions of X2 interface layer 1 are as following:
·
Interface to physical
medium;
·
Frame delineation;
·
Line clock extraction
capability;
·
Layer 1 alarms
extraction and generation;
·
Transmission quality
control.
Protocol specification
3GPP TS 36.421 -
Evolved Universal Terrestrial Radio Access Network (E-UTRAN); X2 layer 1
S1 Signalling Transport
S1 signalling
bearer provides the following functions:
·
Provision of reliable transfer of
S1-AP message over S1-MME interface.
·
Provision of networking and routeing
function
·
Provision of redundancy in the
signalling network
·
Support for flow control and
congestion control
L2 - Data link
layer
Support of any
suitable data link layer protocol, e.g. PPP, Ethernet
IP layer
·
The eNB and MME support IPv6 and/or
IPv4
·
The IP layer of S1-MME only supports
point-to-point transmission for delivering S1-AP message.
·
The eNB and MME support the Diffserv
Code Point marking
Transport layer
SCTP is supported
as the transport layer of S1-MME signalling bearer.
·
SCTP refers to the Stream Control
Transmission Protocol developed by the Sigtran working group of the IETF for
the purpose of transporting various signalling protocols over IP network.
·
There is only one SCTP association
established between one MME and eNB pair.
·
The eNB establishes the SCTP
association. The SCTP Destination Port number value assigned by IANA to be used
for S1AP is 36412.
Protocol
specification
3GPP TS 36.410 -
Evolved Universal Terrestrial Radio Access Network (E-UTRAN); S1 layer 1
general aspects and principles
3GPP TS 36.411 -
Evolved Universal Terrestrial Radio Access Network (E-UTRAN); S1 layer 1
3GPP TS 36.412 -
Evolved Universal Terrestrial Radio Access Network (E-UTRAN); S1 signalling transport
IETF RFC 2460:
"Internet Protocol, Version 6 (IPv6) Specification"
IETF RFC 791 (September,1981):
"Internet Protocol"
IETF RFC 2474 (December
1998): "Definition of the Differentiated Services Field (DS Field) in the
IPv4 and IPv6 Headers"
S1 layer 1
the main functions of S1 interface layer 1 are
as following:
·
Interface to physical
medium;
·
Frame delineation;
·
Line clock extraction
capability;
·
Layer 1 alarms
extraction and generation;
·
Transmission quality
control.
Protocol specification
3GPP TS 36.411 - Evolved
Universal Terrestrial Radio Access Network (E-UTRAN); S1 layer 1
Reason for SDCCH DROP in GSM Network
·
Low
Rx level DL& UL, Bad Qual (Interference ) DL & UL, and High TA
·
Drop
on LAC boundary.
·
SW congestion
·
Due
to TCH Congestion.
·
Hardware
issue, Timeslot Faulty, High VSWR, Alarm or Antenna Faulty, mismatch combining.
·
Interference
or error on E1.
·
Drop
due to radio failure.
·
SD drop due to MS faulty.
·
SD
drop due to mismatch Rxlev_access_min value & RACH busy threshold
·
SD
drop due to mismatch BA2 list, due to drop occur during HO.
Reason for TCH DROP in GSM Network
·
The
parameters SACCH
Multi-Frames and
Radio Link
Timeout are set
to too small values.
·
The
parameter RXLEV_ACCESS_MIN
is set to a too
small value.
·
The parameter RACH Min.Access Level is set to a too small value.
·
The
parameters Min
DL Power on HO Candidate Cell and Min
Access Level Offset are
inappropriately set.
·
The
length of timer T3103 (this timer is set to wait for a Handover Complete
message) is set to a too small value.
·
The
length of timer T3109 (this timer is set to wait for a Release Indication
message) is set to a too small value.
·
The
length of timer T3111 (this timer specifies the connection release delay) is
set to a too small value.
·
The
length of timer T305/T308 is set to an invalid or too great value.
·
The
parameter TCH
Traffic Busy Threshold is
set to a too small value.
·
The
parameter Call
Reestablishment Forbidden is
set to Yes.
·
The
parameters related to edge handover are inappropriately set.
·
The
parameters related to BQ handover are inappropriately set.
·
The
parameters related to interference handover are inappropriately set.
·
The
parameters related to concentric cell handover are inappropriately set.
·
The
parameters related to power control are inappropriately set.
·
T200
and N200 are set to too small values.
·
Some
neighboring cell relations are not configured.
·
The
parameter MAIO is inappropriately set.
·
The
parameter Disconnect
Handover Protect Timer is
set to a too small value.
·
The
parameter TR1N is set to a too small value.
·
The
parameters Software
Parameter 13 and MAX TA are set to too small values.
·
If a
repeater is used, the parameter Directly Magnifier Site Flag is set GSM BSS Network KPI (TCH Call Drop Rate) Optimization Manual
INTERNAL to No
·
Drop
due to hardware issue (Faulty, VSWR, ICM, Mismatch combining & Alarm)
·
Drop
due abis link error or high abis link UTL.
·
Drop
due to Co-Channel interference or due to poor Qual UL & DL.
·
Drop
due to poor level UL & DL or due to High TA.
·
Drop
due to HO Delay.
·
Drop
due to Poor Antenna installation.
·
Drop
due to poor path Imbalance ( UL & DL)
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