mobile network structure

Mobile Network

Eng. Ahmed Hussein BebarsMob: 01024614238

Course Target

• After finalizing this course :

- you will have an overview for a call route and network overall

- Understanding the main difference between Mobile Generations


Agenda

• Radio InterfaceGSMUMTSLTE

• NetworkNetwork DefinitionNetwork TypesOSI ModelVLAN

• Transmission LayersAccess layerBackhaul layerCore Layer


Communication History

• 1880 : Alexander bell invented a new communication method by using electrical wire (new media) and he initialized communication by using a device called telephone

• 1917: people managed to vocally communicate through wireless (air media), since then the world started communicating through wireless and wire technology with a limited rate.

• 1946: First commercial mobile radio-telephone service by Bell and AT&T in Saint Louis, USA. Half duplex(PTT), called car telephone.


Analog To Digital • Three steps to convert from analog to Digital:

• Sampling (According to Nyquist rate)• Quantization• Coding

• Digital signal Advantages• provides us added security to our information signal.• Digital Communication system has more immunity to noise

and external interference.• Digital information can be saved and retrieved when

necessary while not possible in analog.• Digital Communication is cheaper than

Analog Communication.• The configuring process is simple compared to analog

communication system. Even though they are complex.Eng. Ahmed Hussein BebarsMob: 01024614238

Mobile Generation

Communication Media Types

• Simplex

• Duplex

half duplex

Full duplex


Communication Media Types

• Wire

• Wireless


Multiplexing Techniques In Wireless Communication

What is multiplexing?

it is a method by which multiple analog or digital signals are combined into one signal over a shared medium . The aim is to share an expensive resource.

Time-division multiplexing (TDM)


Multiplexing Techniques In Wireless Communication• FDMA (Frequency-division multiple access)

• TDMA (Frequency-division multiple access)


GSM Mobile Network Structure

• AUC Authentication Center

• BSC Base Station Controller

• BTS Base Transceiver Station

• EIR Equipment Identity Register

• HLR Home Location Register

• MS Mobile Station

• MSC Mobile services Switching Center

• NMC Network Management Center

• OMC Operation and Maintenance Center

• VLR Visitor Location Register



• MOBILE STATION (MS):

An MS is used by a mobile subscriber to communicate with the mobile network

• Base Transceiver Station (BTS):

The BTS controls the radio interface to the MS. The BTS comprises the radio equipment such as transceivers and antennas which are needed to serve each cell in the network.



• Base Station Controller (BSC):

The BSC manages all the radio-related functions of a GSM network. It is a high capacity switch that provides functions such as MS handover, radio channel assignment and the collection of cell configuration data.

• Mobile services Switching Center (MSC):

The MSC performs the telephony switching functions for the mobile network. It controls calls to and from other telephony and data systems, such as the Public Switched Telephone Network (PSTN)



• Gateway MSC (GMSC):

if a person connected to the PSTN wants to make a call to a GSM mobile subscriber. Call control through GMSC

• Home Location Register (HLR):

The HLR is a centralized network database that stores and

manages all mobile subscriptionsinformation stored in HLR:

Subscriber identity

Subscriber supplementary services

Subscriber location information

Subscriber authentication information



• Visitor Location Register (VLR):

The VLR database contains information about all the mobile subscribers currently located in an MSC service area.

• Authentication Center (AUC):

The main function of the AUC is to authenticate the subscribers attempting to use a network.

• Equipment Identity Register (EIR):

The EIR is a database containing mobile equipment identity information which helps to block calls from stolen, unauthorized, or defective MSs

Mobile Identity Number

MSISDN : Human Identity used to call a Mobile

Station

IMEI: Serial number unique to every Mobile

Station

IMSI : Network Identity unique to a

SIM 3

digits

2

digits10

digits TMSI : Identity unique in a LAI

MSRN : Mobile Station Roaming

NoCC NDC SN

98 XXX 12345

MCC MNC MSIN

404 XX 12345

TAC FAC SNR S

6 digits 2 digits 6 digits 1 digit


GSM Band


Cluster

• Cell : is the basic unit of a cellular system and is defined as the area of radio coverage given by one BTS antenna system


Cluster

• Cell Size

Large Cells Small Cells

35 Km Near about 1 KM

Remote Areas Urban Areas

High Transmission Power Low Transmission Power

Few subscribers Many Subscribers


Cluster

• Cluster: groups of frequencies can be placed together into patterns of cells called clusters. A cluster is a group of cells in which all available frequencies have been used once and only once.


Cluster

• Three types of frequency reuse patterns

7 Cell reuse pattern

4 cell reuse pattern

3 cell reuse pattern

• D=R (3N)

• where N is Cluster size

• R Cell Diameter

• By frequent reuse of frequency more capacity can be achieved

Cluster

• MSC SERVICE AREA: An MSC service area is made up of a number of LAs (Location Area) and represents the geographical part of the network controlled by one MSC

• A Location Area (LA): is defined as a group of cells


GSM Access Method (TDMA/FDM)

• In GSM, a TDMA frame consists of 8 time slots. This means that a GSM radio carrier can carry 8 calls.


Transmission Problems

• PATH LOSS



• MULTIPATH FADING: occurs when there is more than one transmission path to the MS or BTS



• MULTIPATH FADINGTime dispersion is another problem relating to multiple paths to the Rx

antenna of either an MS or BTS. However, in contrast to Rayleigh fading, the reflected signal comes from an object far away from the Rx antenna. Time dispersion causes Inter-Symbol Interference (ISI) where consecutive symbols (bits) interfere with each other making it difficult for the receiver to determine which symbol is the correct one. An example of this is shown in the figure below where the sequence 1, 0 is sent from the BTS.


Solutions To Transmission Problems

• CHANNEL CODING

Channel coding is used to detect and correct errors in a received bit stream. It adds bits to a message. These bits enable a channel decoder to determine whether the message has faulty bits, and to potentially correct the faulty bits.


Solutions To Transmission Problems

• Interleaving: Interleaving is frequently used in digital communication and storage systems to improve the performance of forward error correcting codes attenuation factor.For example:

Transmission without interleaving

With interleaving:


GSM Transmission Process

• STAGE ANALOG TO DIGITAL (A/D) Sampling

Quantization: GSM8,192 levels are used.

Coding: Coding involves converting the quantized values into binary. Every value is represented by a binary code of 13 bits (213 = 8192). For example, a quantized value of 2,157 would have a bit pattern of 0100001101101



• STAGE SEGMENTATION AND STAGE 3: SPEECH CODING

it is an application of data compression of digital audio signals containing speech

The GSM speech coder produces a bit rate of 13 kbits/s per subscriber. When it is considered that 8 subscribers use one radio channel, the overall bit rate would be 8 x 13 kbits/s = 104 kbits/s



• STAGE CHANNEL CODING

Channel coding in GSM uses the 260 bits from speech coding as input to channel coding and outputs 456 encoded bits. The 260 bits are split according to their relative importance



• First level of interleaving

The channel coder provides 456 bits for every 20 ms of speech. These are interleaved, forming eight blocks of 57 bits each, as shown in the figure below



• Second level of interleaving

If only one level of interleaving is used,

a loss of this burst results in a total loss

of 25%.



• STAGE CIPHERING/ENCRYPTION

The purpose of ciphering is to encode the burst so that it cannot be interpreted by any other device than the intended receiver. The ciphering algorithm in GSM is called the A5 algorithm



• STAGE MODULATION & TRANSMISSION

The bits must be sent over the air using a carrier frequency. as previously explained, GSM uses the GMSK modulation technique, The bits are modulated onto a carrier frequency and transmitted (e.g. 912.2 MHz).


Logical Channels


Logical Channels

• Broadcast Control Channel (BCCH)

Logical Channels

• Common Control Channels (CCCH)

Logical Channels

• Dedicated Control Channels (DCCH's)

Logical Channels

• Traffic Channels

Once call set-up procedures have been completed on the control physical channel, the MS tunes to a traffic physical channel. It uses the Traffic Channel (TCH) logical channel. There are two

• Types of TCH:

Full rate (TCH): transmits full rate speech (13 kbits/s). A full rate TCH occupies one physical channel.

Half rate (TCH/2): transmits half rate speech (6.5 kbits/s). Two half rate TCH's can share one physical channel, thus doubling the capacity of a cell.


Sample Traffic Case: Call To MS

• The MSC/VLR knows which LA the MS is located in. A paging message is sent to the BSC's controlling the LA.

• The BSC’s distributes the paging message to the BTS's in the desired LA. the BTS's transmit the message over the air interface using PCH.

• When the MS detects a PCH identifying itself, it sends a request for a signaling channel using RACH.

• The BSC uses AGCH to inform the MS of the signaling channel (SDCCH and SACCH) to use.

• SDCCH and SACCH are used for call set-up. A TCH is allocated and the SDCCH is released.


Sample Traffic Case: Call To MS

• The MS and BTS switch to the identified TCH frequency and timeslot, the MS generates ring tone, If the subscriber answers, theconnection is established. During the call, signals can be sent andreceived by the MS using SACCH.


Handovers

• Types of GSM handover

Intra-BTS handover

Inter-BTS Intra BSC handover

Inter-BSC handover

Inter-MSC handover


Handovers

• Handover Mechanism

Hard Handover

Soft Handover

Handovers

• The mobile measures up to 32 adjacent cells for

Signal Strength (Rx Level)

Signal Quality (Rx Quall)

updated every 480 m/s and sends to BTS

• Handover based on

Rx Level

interference

Rx Qual

Timing Advance

Power Budget

BTS Components

BTS Components

• GSM RBS (Radio Base Station) Node

BTS Components

• GSM Antenna

BTS Components

• Power Cabinet

BTS Components

• Transmission Cabinet

UMTS Evolution

3G Network


3G Network

• Radio Network Subsystem (RNS): The RNS also known as the UMTS Radio Access Network, UTRAN, is the equivalent of the previous Base Station Subsystem or BSS in GSM.

• Core Network: The core network provides all the central processing and management for the system. It is the equivalent of the GSM Network Switching Subsystem or NSS


3G Network

• The GPRS Core Network:

is the central part of the General Packet Radio Service (GPRS)which allows 2G, 3G and WCDMA mobile networks totransmit IP packets to external networks such as the Internet.


3G Network

• Serving GPRS Support Node (SGSN) function

Session management: The SGSN manages the data sessions providing the required quality of service and also managing what are termed the PDP (Packet data Protocol) contexts

Billing: The SGSN is also responsible billing

3G Network

• Gateway GPRS Support Node (GGSN)

Aims to provide IP Telephony ultra broadband internet accessand game services

4G NetworkIt uses OFDM (Orthogonal frequency Division Multiplexing) techniques to

access wireless mediaSupports flexible channel BW between 5 MHz to 20 MHz with data rate up

to 100 Mb/S

4G Network

•Radio Access Network (RAN) in any type of network is verycritical logic components. It is mainly responsible for forwarding therequest to the allocated radio channel, its consist from e-Node B

•PGW (PDN): which is similar to the function GGSN networkelement for border gateway EPC network, providing user sessionmanagement and load control, data forwarding, IP addressassignment

•PCRF: PCRF (Policy and Charging Rules Function Policy andCharging Rules Function units) policy and charging control is apolicy decision point service data and IP bearer resources.

4G Network

•MME: MME (Mobility Management Entity, the mobilitymanagement entity) is the key to the control node LTE accessnetwork, which is responsible for idle mode UE (UserEquipment) positioning, paging process, including repeaters,simply MME is responsible for signaling processing section

•SGW (Serving Gateway): The SGW routes and forwards userdata packets

.

5G Network

•The 5G mobile phones will have access to different wireless technologies at the same time and the terminal should be able to combine different flows from different technologies. 5G is predicted to be an intelligent technology capable of interconnecting the entire world without limits. Mobile data rate 1 Gb/S

Network

• What is a network?

It's collection of Devices connected to apply applications

Network

• Why we study network in our course

Network

• Network Topology

Network Types

• LAN

• MAN

• WAN


OSI Model

• OSI (Open Systems Interconnect)

• Why a layered network Model?

• Reduce Complexity

• Standardized interface

• Accelerate Evolution

• Simplify learning and teaching


OSI Model

• Physical layer


OSI Model

• Data Link Layer


OSI Model

• Network Layer


OSI Model

• Transport Layer


OSI Model

• Session Layer

OSI Model

• Presentation Layer

OSI Model

• Application Layer

OSI Model

• Data Encapsulation Process


Network Address

• How to data send over network and addressing used


Network Address

• MAC

MAC (Media Access Controller): it's addressing used in layer 2 to allow transmit data between source and destination

each device has unique address


Network Address

• MAC types:• Unicast MAC: from specific source MAC to destination MAC

• Broadcast MAC: destination MAC address write FF:FF:FF:FF:FF:FF

• Multicast MAC: this address assign by Organization called IANA that assign multicast MAC, for example network games that have Multicast MAC address to allow group from users play it on network when setup this games on their PC's automatically multicast MAC address will assign on NIC

Network Address

• IP (Internet Protocol)

Every host (computer, networking device, peripheral) must have a unique address. An IP address consists of two parts (Network ID & Host ID)

Network Address

• IP (Internet Protocol)

IPv4 has 32bits these bits divided between network and host ID according to 3 classes from address:


Network Devices

• Computer

Function: The function of a computer server is to store, retrieve and send computer files and data to other computers on a network.


Network Devices

• Switch

• It’s allow host connect together through the same LAN Network

• Use MAC address to forward traffic between ports


Network Devices

• Router

• It use to reroute traffic from Network to another


VLAN


VLAN

• Router

• there are two port types:Access port: port member in specific VLAN

Trunk port: port Member in all VLAN and it created between switches to allow users in the same VLAN connected

• Tagged Protocol:

to identify frame by use tagging use protocol IEEE802.1Q to tagged all frame transmitted over network


VLAN

• Video Lab


Transmission

Mobile network transmission divided to three layers:

• Access layer: from Site to HUB, where hub is first point to multiplex more than one site to transmit it again to next point, there are three technology method use to support data transmission

Microwave (cheaper and most used)

DSL (there are two types from it ADSL & SDSL and we use SDSL in our network, this solution use for micro sites)

Fiber


Transmission

• Backhaul layer: from HUB to BSC and RNC, in this point use high data rate to allow BSC and RNC to communicate with BTS, there are many nodes and technology use in this layer

DXX (Digital Cross Connection) use PDH system

ADM (Add drop Multiplexer) use SDH technology

Tellabs smart router use MPLS technology

PTN use MPLS technology

• Core layer: this layer use to allow MSC communicate together and GMSC connect to another network, this layer use Router carry huge traffic may be reach to 10 G on port, inside this part we use one technology is MPLS


• Microwave: it's cheaper and easy installation method to transmit data from point to point there are many vendors supply this technology such as Ericsson and Huawei and SIAE and NEC

Ericsson Nodes: such as TN traffic Node) and CN (Compact Node) and PT (Packet transport)

Huawei Nodes: such as RTN950 and RTN 980

SIAE Nodes: ALC (Access Link Compact) PDH and ALC +2 and ALC +2e and Alpho in old MW transmit PDH technology only but today we target packet also to support another mobile generation such as 3G and 4 G as show in below

Access Layer


Access Layer

• DSL (Digital Subscriber line): its technology used to support data traffic over traditional telephone cable we use HDSL (High Digital Subscriber line) in our network to support 2.048 Mb/S in Upload and download and use 4 wire

• Fiber cable: this technology depend on light phoneme to reflect inside fiber and transfer high data rate there are two types single mode and multi mode and main difference between them in coverage distance also there are two main connector types as show in below


Access Layer

SC connector Subscriber

Connector Or

square

connector Or

Standard

Connector

Snap 2.5mm

LC

connector

Lucent

Connector

Snap

(push-pull

coupling

like RJ45)

1.25mm


Transmission Technology

• PDH (Plesiochronus Digital Hierarchy ): is a technology used in telecommunications networks to transport large quantities of data over digital transport equipment such as microwave radio systems

• There are three systems:

E1

T1

J1


• SDH (Synchronous digital Hierarchical): is a standard technology for synchronous data transmission on optical media

• The world convert from PDH system to SDH system due to below reasons

PDH ( Plesiochronus Digital Hierarchy) disadvantage:

1. World divided to island (European use E1 and America use T1)

2. Less synchronized, E2 rate 8.448 MB/S not equal four E1 rate (4x2.048 Mb/S = 8.192 Mb/Sec), we add stuffing bit for Multiplex and DE multiplex E1

3. Low data rates

4. The maximum capacity for PDH is 140 Mbps, which is limited in bandwidth


• First frame structure is STM1 with rate 155 Mb/S

SDH Level Rate

STM1 155 Mb/S

STM4 622Mb/S (4x155)

STM16 2488 Mb/S

STM64 9953 Mb/S



Microwave

• Its electromagnetic signal use to carry traffic by use modulation and send it to long distance , it's cheap technology use to transfer data

• The microwave spectrum is

usually defined as

electromagnetic energy

ranging from

approximately 1 GHz to 100

GHz in frequency

• in Mobile network we use frequency band from 7 GHz to 40 GHz and now we use e-band 80 GHz


Microwave B.W

• By international regulations frequency bands are divided into below parts:

• for example we use BW 17 GHz it divided to Sub band (group of frequency inside 17 GHz BW) and it divided to two band high band and low band and each band divided to channel called channel B.W

• each channel in high band has mirror to it in low band to send and receive data simultaneous (full duplex) and distance between them called duplex distance

Microwave B.W


Transmission problem

• frees space loss: it is the loss in signal strength of an electromagnetic wave that would result from a line-of-sight path through free space


• Free space formula (FSPL) equation:

• A = 92.4 + 20 log d + 20 log f

• d = distance in km

• f = frequency in GHz

• Relation between frequency and loss value:



• Fading:

• It's random variation of the received level, the variation is irregular and the reasons for this are various

• Fading Mechanism:

• Rain Fading

• Multipath fading


• Video show problem:

Rain Fading

• Solution:

Lower frequency band

Increased system gain (increased fade margin) Larger antennas, increased transmitter output power.

Vertical antenna polarization

(Shorter hop…)

Rain Fading

• Is the propagation phenomenon that results in radio signals reaching the receiving antenna by two or more paths

Multipath Fading

Multipath Fading

• Solution:

Increased system gain Larger antennas, Increased transmitter output power.

Space or Frequency diversity

(Shorter hop…)

First Fresnel Zone

• The 1st Fresnel zone shall be free from obstacles at k = 4/3

Microwave polarization

• Single polarized

• Vertical: Most recommend it resist rain fading

• Horizontal

• Dual Polarized:

Send data in two polarization Vertical and horizontal to get double capacity, this solution use technique XPIC Technology

Modulation Techniques

• In telecommunications, modulation is the process of conveying a message signal

• QAM:


• There is relation between Modulation and channel spacing to get total link capacity

Modulation Techniques


Link Performance

• Performance: these counters use to measure link quality and troubleshooting

BER (Bit Error rate): is the number of bit errors per unit time A block in which one or more bits are in error

Errored Second, ES: A one-second period in which one or more blocks are in error.

Severely Errored Second, SES: A one-second period which contains >30% error blocks.

UAS (Unavailable error second): after count 10 SES through one second

Ethernet Carriers

• E-line: service connecting two customer Ethernet ports over Microwave.

• E-LAN: multipoint service connecting a set of customer endpoints, giving the appearance to the customer of a bridged Ethernet network connecting the sites.

Ethernet Carriers

• Ethernet frame over microwave

Ethernet over PDH

Native Ethernet

Ethernet Over SDH


Comparison between Ethernet Carriers

Parameter Ethernet Over PDH Native Ethernet

Frame Size Support frame 2048 byte Support frame 9 Kbyte (Jumbo

frame)

Mapping Protocol PDH-IME (n*E1) RL-IME framing and segment

Throughput 95 Mb/Sec per PDH-IME with

ETU card 30 Mb/Sec for total

PDH-IME with NPU3 card

The following maximum bit rate

over the radio hop is supported by

MMU2 H:

a. 406 Mbps in a 56 MHz

channel

b. 812 Mbps in a 56 MHz

channel with XPIC and

Adaptive Modulation

Latency end to end latency contribution

between two Ethernet ports on two

nodes connected with Ethernet over

PDH mapping with 95 Mbps link

capacity is:

a. 0,2 ms for 64 Byte frame size

b. 0,6 ms for 2048 Byte frame

size

NPU3 has an average latency

contribution of 1,5 ms for all frame

sizes.

Typical end to end latency

contribution between two Ethernet

ports on two nodes connected with

Ethernet over packet Link with 135

Mbps link capacity is: 0,15 ms for

64 Byte frame size 0,35 ms for

2048 Byte frame size

Ethernet frame Header Increased 6 % Increased 0.5 ,0.6 %

Microwave component

• Indoor

• Outdoor


Microwave component

• Outdoor Unit

• Reflector and Radom

This part used to reflect

electromagnetic wave also

diameter of this part control lobe width degree

(gain).


Microwave component

• Reflector Size & Beam width relation

• Reflector types:

• HP (High Performance)

• SHP (Super High Performance)


Microwave component

• Horn Types:• Single

• Dual


Microwave component

• RAU (Radio Access Unit): This part responsible for radio Modulation (GHZ) to start transmit wave through Horn and reflector


Microwave component

• Integrated Power Splitter (IPS): this Module use to support RAU protection

• Asymmetric

• Symmetric


Microwave component

• IF cable: it's connection between outdoor unit and indoor unit,


Protection Types

• Microwave Protection:

1+0: Microwave use one RAU to transmit and received if there is problem in RAU all data dropped

1+1: Microwave use two RAU one of them protected and another as protection if there is problem in one RAU another RAU can transmit and received

• Data protection:

MSP (Multiplex Section Protection): it is port protection

SNCP (Sub network connection Protection) it is path protection


TN Types

• AMM (Access Module Modem):

TN2P

TN6P

TN6PC

TN6PD


TN Types

• AMM (Access Module Modem):TN20P

TN20P

TN20PB


TN Modules

• MMU (Modem Module Unit): Function: Modulate base band signal to IF (Intermediate

Frequency) Signal and send it to RAU


TN Modules

• Node Processor Unit (NPU): Function: The NPU handles the control functions of the system. It

also provides traffic and management interfaces


TN Modules

• LTU (Line termination Unit): Function: It is card support output traffic

There are two types:

Traditional

Channelized STM


TN Modules

• ETU (Ethernet Terminal Unit): Function: Module card used to Support Ethernet over PDH by use

PDH-IME Protocol


TN Ethernet

• Ethernet Connection types:E-LAN

E-Line

• Ethernet Over radio Microwave:Ethernet Over PDH

Native Ethernet


Radio Link Configuration

• Radio Link Parameter Configured:

Radio Link Configuration

• RSL (Received Signal Level):

TN Management

• DCN (Data Communication Network):

TN Management

• Configure Basic NE:

TN Management

• Configure OSPF:

Alignment

• Antenna Radial Pattern Envelope :


Alignment

• RSL=40*(Volt value)-120

• The following fig show relation between volt and RSL value

• RSL: Received Signal Level (dBm)


Operator NMC Basic chart

NMC

Access teamTransmission

TeamCore Team

Service Team