Thursday, November 26, 2009

UMTS Layers, Interfaces, Protocols - Iub interface.

Just to remind - Iub interface connects Node B (RBS) and RNC.
As for general view (general info) in this interface one can describe layers (i.e. Radio and Transport Network Layer), planes (i.e. user and control plane) and some protocols within those planes.





Figure 1. Iub Control Plane - ATM transport.

NBAP - Node Application Part
SSCF-UNI - Service Specific Coordination Function for support of signaling at the User Network Interface [ITU-T 2130]
SSCOP - Service Specific Connection Oriented Protocol
AAL5 - ATM Adaptation Layer 5

Monday, November 23, 2009

Simplified UMTS network architecture

Figure 1 shows simplified UMTS network architecture.
Simplified UMTS network architecture
Figure 1. Simplified UMTS network architecture.

Note: Not all nodes and interfaces are included in this picture.

Abbreviations used in the picture:
RNC - Radio Network Controller
MSC - Mobile Switching Center
Ue - User Equipment
SGSN - Serving Gprs Support Node
PDN - Packet Data Network
PSTN - Public Switched Telephony Network

UMTS Layers, Interfaces, Protocols - General

Previous post was a short introduction for general information regarding layers, protocols, interfaces and planes.
In UMTS one can find all mentioned objects and divisions.

As for the layers the Figure 1 shows what layers are defined for UMTS.

UMTS network protocols layers
Figure 1. UMTS network protocols layers [1]

As mentioned in each layer may have its User and Control Plane. Each layer has dedicated protocol to work in proper plane. Detailed description of theses protocols will be placed in next posts.

General Layer, Plane and Protocol Model for interfaces in UTRAN
Figure 2. General Layer, Plane and Protocol Model for interfaces in UTRAN [2]

Signaling bearers for Transport Network User Plane and for Transport Network Control Plane may be different but may be the same. It is up to configuration if the same Signaling Bearers would be used [2]


Based on:
[1] UMTS System Telefonii Komórowej Trzeciej Generacji - J. Kołakowski, J. Cichocki. WKŁ 2006
[2]  3GPP TS 25.401

Saturday, November 21, 2009

Protocols, interfaces, User Plane and Control Plane

When two devices would like to communicate with each other they would use a defined protocol. Protocol is set of rules describing how those two devices can communicate in way that receiver would understand what sender “had in mind” while sending message. Protocol description is usually description of messages (signals) that can be sent and received, it is also description for particular procedures and functions.
Now, our two devices know “how to talk” to each other, but they need to be connected somehow. For this purpose an Interface would be defined. Interface would be generally another device, with or without dedicated software, that would allow connecting, inter-working and changing messages(signals) between our devices – connected using this interface.
Sometimes when connecting two devices using interface there is a need for two protocols. First protocol would allow first device to control how works the second one. This kind of protocol is part of control plane. Second protocol would send just raw data from one device to another. This would be a part of user plane.

User and Control Plane
Figure 1. User and Control Plane.
Often when two devices connected over the interface not one protocol would be used but set of protocol divided into layers. Each layer with its specific dedicated tasks.
Sample Layer Stack
Figure 2. Sample Layer Stack.
Important to mention that each layer may has its own user and control plane. What is control plane for one protocol can be (would be) user plane for protocol located below in stack.

 User and Control Plane used with Layers
Figure 3. User and Control Plane used with Layers

Friday, October 16, 2009

Radio Interface (UMTS)

Simplified radio interface (Uu) architecture.

MAC, RLC and RRC communicate with each other using some signals/messages called primitives.



Based on 3GPP 25.321.

Tuesday, October 13, 2009

Question and Answers

Questions and Answers concerning particular and often very detailed issues given without introduction.
Comments, questions are of course welcome!!!

Q: Why AAL2 on Iu interface needs ALCAP and AAL5 does not need this signaling protocol ?
A: AAL5 is using PVC configured by O&M, hence there is no need to establish, release or maintain this connections. AAL2 is not using PVC but VC/VP which need to be established, released and maintained by separate signaling protocol i.e. ALCAP.

Q: What is the meaning of PDU and SDU and what is the difference between them ?
A: PDU is Protocol Data Unit and SDU is Service Data Unit. Difference between them and their role should describe following figure
PDU and SDU illustration

Q: What means NNI and UNI ? This two terms can be seen together with SAAL layer.
A: NNI means Network-to-Network Interface also known as Network-Node Interface. UNI means User-to-Network Interface.

Monday, October 12, 2009

NAS: Non-Access Stratum

This post is to give short description of NAS protocols, procedures and functions.
NAS is a layer for communication between Ue and Core Network (CN). This communication is transparent for underlaying Access Stratum.
NAS protocols:
  • GMM - GPRS Mobility Management
  • MM - Mobility Management
  • SM - Session Management
  • CC - Call Control
  • SS - Supplementary Services
  • SMS - Short Message Services
SM, SMS, SS and CC form a group of protocols called Connection Management.


Figure - Inter protocols communication MS side [3GPP 24.007]



SM - its functions is to activate, deactivate or modify PDP contexts which are sessions for PS traffic in UMTS/GPRS networks

Figure 1 - Simplified PDP context activation procedure



Figure 2 - Inter protocol communication for PDP context activation - MS side



CC - its functions is to establish, maintain and finally release CS calls in UMTS/GPRS/GSM networks

Figure 3- Simplified CS call proceeding


Figure 4 - Inter protocol communication for CS call setup



Monday, September 14, 2009

EPS - Network architecture

This is simplified network architecture for EPS (Evolved Packet System)



There are two main parts of EPS: LTE (Long Term Evolution) and SAE (System Architecture Evolution).

Actually those two parts have also different names and LTE is known as E-UTRAN and SAE is known as EPC (Evolved Packet Core).

MME - Mobility Management Entity
S-GW - Serving Gateway
HSS - Home Subscriber Server
PCRF - Policy Control and Charging Rules Function
PDN-GW - Packet Data Networks Gateway

Saturday, September 5, 2009

CAMEL

CAMEL - Customised Applications for Mobile network Enhanced Logic
 
This is simplified CAMEL entities configuration. Based 3GPP 23.002 Release 9.

Areas

In UMTS/GSM networks the whole area covered by network coverage is divided into smaller parts. The smallest and base entity is cell that is area controlled by base station (BTS/Node B). One or more cells form UTRAN Registration Area. RNC controls URA. One or more URA forms Routing Area (RA). The area controlled by SGSN. One or more RA can be part of Location Area (LA). This is controlled by MSC/VLR.


Another concept is Service Area (SA). Service Area is a subset of Location Area. Several cells may be grouped into Service Area. This area used by RAN helps to find out UE location within LA.

Dictionary

A B C D E F G H I J K L M N R S


Location Area
Location Area is one or more cells. Location Area is controlled by VLR. Each time MS changes LA it needs to inform VLR about this with Location Update Procedure.


NAS - Non-Access Stratum
Set of protocols (i.e. MM, GMM, SM, CC, SS, SMS) and functions for communication between Ms (or Ue) and Core Network (both CS and PS domain).


Routing Area
Routing Area is one or more cells. Routing Area is controlled by SGSN. Each time Ms changes RA it needs to inform SGSN about this with Routing Area Update procedure.


Service Area

Service Area is one or more cell belonging to the same LA. It is used by RAN when location request comes from CN.

Network Architecture Release 99

This is simplified network architecture described in 3GPP 23.002 Release 99.
 

Multiple Access Methods

The problem is each wireless system has to have its bandwidth that needs to be shared among several users. That is the reason that multiple access techniques have been designed.

Descriptions:
FDMA - Frequency Division Multiple Access
TDMA - Time Division Multiple Access
CDMA - Code Division Multiple Access

FDMA - Each user has its part of overall frequency band i.e. the whole bandwidth is divided for many users. TDMA - The whole bandwidth is reserved for particular user for only specified period of time.
CDMA - User can use whole bandwidth for all time but has to use different code.
As for explanation of difference between these three multiple access technologies there is an example of room with people talking in pairs. When they would use FDMA the room (whole bandwidth) should be divided into smaller rooms and each room would represent one frequency. Walls would be the separation of these frequencies hence people in pairs would have a chance to talk at the same time without disturbing other pairs. As for TDMA each pair in the room would have some specific time to talk when other people should remain in silence. CDMA would allow to talk for all pairs but each of them would have to use different language (code).

This example as described in "UMTS". Javier Sanchez, Mamadou Thioune ISBN: 978-1-905209-71-2 January 2007, Wiley-ISTE

To increase system capacity it is common to use these technologies together. GSM would use for example TDMA together with FDMA.

Monday, August 24, 2009

Abbreviations

A B C D E F G H I J K L M N P R S T U W V

3GPP
Third Generation Partnership Project

AAL
ATM Adaptation Layer
ADCH
Associated DCH
ADSL
Asymetric Digital Subscriber Line
ALCAP
Access Link Control Application Part
ARFCN
Absolute Radio Frequency Channel Number
ARQ
Automatic Repeat reQuest
ATM
Asynchronous Transfer Mode

BCCH
Broadcast Control Channel
BCH
Broadcast Channel
BER
Bit Error Rate
BICC
Bearer Independent Call Control
BLER
Block Error Rate
BPSK
Binary Phase Shift Keying
BSC
Base Station Controller
BSS
Base Station Subsystem
BTS
Base Transceiver Station

CAMEL
Customised Applications for Mobile network Enhanced Logic
CC
Call Control
CCCH
Common Control Channel
CDM
Code Division Multiplexing
CDMA
Code Division Multiple Access
CN
Core Network
CM
Connection Management
CPICH
Common Pilot Channel
CQI
Channel Quality Indicator
CRC
Cyclic Redundancy Check
C-RNTI
Cell Radio Network Temporary Identifier
CS
Circiut Switch
CRNC
Controlling Radio Network Controller

DCH
Dedicated Channel
DNS
Domain Name Server
DL-SCH
Downlink Shared Channel
DRNC
Drift Radio Network Controller
DS-CDMA
Direct sequence Code Division Multiple Access
DRX
Discontinuous Reception
DTCH
Dedicated Traffic Channel
DTX
Discontinuous Transmission

ECGI
E-UTRAN Cell Global Identifier
E-DCH
Enhanced Dedicated Channel
EDGE
Enhanced Data Rate for GSM Evolution
EIR
Equipment Identity Register
EUL
Enhanced Uplink
EPC
Evolved Packet Core

FACH
Forward Access Channel
FDD
Frequency Division Duplex
FDMA
Frequency Division Multiple Access
FP
Frame Protocol
F-PDCH
Fractional-PDCH

GERAN
GSM/EDGE Radio Access Network
GGSN
Gateway GPRS Support Node
GMLC
Gateway Mobile Location Center
GMM
GPRS Mobility Management
GPRS
General Packet Radio Service
GSM
Global System for Mobile Communication
GTP
GPRS Tunneling Protocol

HLR
Home Location Register
HSDPA
High Speed Data Packet Access
HS-DSCH
High Speed Downlink Shared Channel
HSS
Home Subscriber Server

IMEI
International Mobile Equipment Identity
IMSI
International Mobile Subscriber Identity
IMS
IP multimedia system
ISDN
Integrated Services Digital Network
ISUP
ISDN User Part

LTE
Long Term Evolution

MAC
Medium Access Control
MCC
Mobile Country Code
MGW
Media Gateway
MM
Mobility Management
MME
Mobility Management Entity
MNC
Mobile Network Code
MSC
Mobile Switching Center
MSIN
Mobile Subscriber Identification Number
MSISDN
Mobile Subscriber ISDN Number
MSS
Mobile softswitch solution

NBAP
Node B Application Part

PCCH
Paging Control Channel
PCH
Paging Channel
PDSCH
Physical Downlink Shared Channel
PLMN
Public Land Mobile Network
PSTN
Public Switched Telephone Network

RAN
Radio Access Network
RLC
Radio Link Control
RNTI
Radio Network Temporary Identifier
RANAP
Radio Access Network Application Part
RNSAP
Radio Network Subsystem Application Part

SM
Session Management
SRB
Signaling Radio Bearer
SCCP
Signaling Connection Control Part
SCCOP
Service Specific Connection Oriented Protocol
SCTP
Stream Control Transmission Protocol
SGSN
Serving GPRS Support Node

TDMA
Time Division Multiple Access
TDM
Time Division Multiplexing

UMTS
Universal Mobile Telecommunication System
UTRAN
UMTS Terrestrial Radio Access Network

WCDMA
Wideband Code Division Multiple Access

VLR
Visitor Location Register

Monday, August 17, 2009

GPRS Network Architecture

Simplified GPRS network architecture.

GPRS - General Packet Radio Service
SGSN - Serving GPRS Support Node
GGSN - Gateway GPSR Support Node
PLMN - Public Land Mobile Network

Friday, July 31, 2009

GSM Network Architecture

Simplified GSM network architecture


Description:
Ms - Mobile Station
BTS - Base Transceiver Station
MSC - Mobile Switching Center
HLR - Home Location Register
VLR - Visitor Location Register
EIR - Equipment Identity Register
G-MSC - Gateway MSC

Thursday, July 30, 2009

Welcome Everyone.

This blog has been created as a place for some general and some detailed information about mobile networks such as GSM, GPRS, UMTS and LTE.

Best Regards