ee 4105 communication engg-ii 4105_… · rappaport data ... history of mobile cellular chapter 1:...

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EE 4105 Communication Engg-IIDr. Mostafa Zaman Chowdhury

Slide # 1

Dept. of Electrical and Electronic Engineering, KUET

2Dept. of Electrical and Electronic Engineering, KUET

References

Wireless and Cellular Telecommunications by William C. Y. Lee

Wireless Communications: Principles and Practice by Theodore S.

Rappaport

Data Communications and Networking by Behrouz A. Forouzan


Mobile Communication History and

Evolution

History of Mobile Cellular

Chapter 1: Wireless and Cellular Telecommunication


1G to 6G

1st Generation(1984) Analog cellular (basic voice service) AMPS

2nd Generation(CDMA(1996)) Digital cellular (enhanced voice service) GSM and cdmaOne(IS-95A, IS-95B(1999))

3rd Generation(2000(cdma2000), 2002(WCDMA)) Voice, data, image(384Kbps), limited video IMT-2000 (cdma2000 1x, EV-DO, EV-DV and WCDMA, HSDPA, HSUPA, HSPA, 3GPP

LTE) WiBro, WiBro Evolution Problems: limited mobility and up to 2Mbps~100Mbps bandwidth 3GPP, 3GPP2, IEEE 802

4th Generation (IMT-Advanced(2010)) Broadband multimedia applications and virtual reality (VR) applications Full mobility and higher bandwidth (100Mbps, 1Gbps ) Combination of 3GPP and IEEE 802.16m or Dual Mode LTE-Advanced

5th Generation (2020) Future Internet and Networks Sense

6th Generation Communication (2030) AI based network Global connectivity 1 Tb/s

Dept. of Electrical and Electronic Engineering, KUET 5

Predicted Service Requirements for 6G wireless

Enhanced mobile broadband (eMBB)

Ultra-reliable low latency communications (URLLC)

Massive machine-type communication (mMTC)

AI integrated communication

Tactile internet

High throughput

High network capacity

High energy efficiency

Low backhaul and access network congestion

Enhanced data security



Issue 4G 5G 6G

Per device peak data

rate

1 Gbps 10 Gbps 1 Tbps

E2E latency 100 ms 10 ms 1 ms

Maximum spectral

efficiency

15 bps/Hz 30 bps/Hz 100 bps/Hz

Mobility support Up to 350

km/hr

Up to 500 km/hr Up to 1000

km/hr

Satellite integration No No Fully

AI No Partial FullyAutonomous vehicle No Partial Fully

XR No Partial Fully

Haptic

Communication

No Partial Fully

A comparison among 4G, 5G, and 6G

Cellular Network Evolution

1G 2 G 2.5 G 3G 4GService

Systemanalog digital PCS IMT-2000 IMT-Advanced

Multiplexi

ngFDMA

TDMA

CDMA

TDMA

CDMACDMA OFDMA

Data rate

2.4Kbps (14.4Kbps)

(144Kbps)

(384Kbps~14.4Mbps) 100Mbps(mobile)

1Gbps(stationary)

Roaming No Limited Limited Global Global

Technolo

gy

AMPS GSM

IS-95(CDMA)

PCS-1800

(GSM)

IS-95C

cdma2000, EVDO

WCDMA, HSDPA,

LTE, LTE-Advanced,

WiBro Evolution

Mobile WiMAX,

Femtocell, VLC,..


4G Evolution Path


Cellular communication

Mobile communication

Wireless communication

Advantages

Disadvantages


Network Type/Systems


Circuit-Switched Systems

In a circuit-switched system, each traffic channel is

dedicated to a user until its cell is terminated.

Circuit switching is a methodology of implementing a

telecommunications network in which two network nodes

establish a dedicated communications channel (circuit)

through the network before the nodes may communicate.

The circuit guarantees the full bandwidth of the channel

and remains connected for the duration of the

communication session. The circuit functions as if the

nodes were physically connected as with an electrical

circuit.

Analog system

digital system


Circuit-Switched Systems: Analog

Consists of three subsystem

a mobile unit : A mobile

telephone unit contains a

control unit, a transceiver, and

an antenna system.

a cell site : provides interface

between the MTSO and the

mobile units. It has a control

unit, radio cabinets, antennas,

a power plant, and data

terminals.

mobile telephone switching

office (MTSO): The switching

office, the central coordinating

element for all cell sites,

contains the cellular processor

and cellular switch.


Circuit-Switched Systems: Digital (e.g., GSM) (1/3)

Consists of four

elements: mobile station,

base transceiver station

(BTS), base station

controller (BSC), and

switching subsystems,


GSM Architecture


MS: consists of two parts, mobile equipment (ME) and

subscriber identify module (SIM). SIM contains all

subscriber-specific data stored on the MS side.

BTS: Besides having the same function as the analog BTS,

it has the Transcoder/Rate Adapter Unit(TRAU), which

carries out coding and decoding as well as rate adaptation

in case data rate varies.

BSC: A new element in digital systems that performs the

Radio Resource (RR) management for the cells under its

control. BSC also handles handovers, power management

time and frequency synchronization, and frequency

reallocation among BTSs.



Switching subsystems:

MSC: The main function of MSC is to coordinate the setup of calls between MS and

PSTN users.

VLR (Visitor Location Register): A database of all mobiles roaming in the MSC’s

area of control.

HLR(Home Location Register):A centralized database of all subscribers registered

in a Public Land Mobile Network (PLMN).

AUC (Authentication Center): Provides HLR with authentication parameters and

ciphering keys that are used for security purposes.

EIR (Equipment Identity Register): A database for storing all registered mobile

equipment numbers.

IWF (Interworking function): Provides the subscriber with data services that can

access data rate and protocol conversion facilities and interfaces with public and

private data networks.

EC (Echo Canceller): Used on the PSTN side of the MSC for all voice circuits.

XC (Transcoder): Usually installed in each BTS. But for the cost reason, it can be

installed in BSC or MSC.

OMC(Operational and Maintenance Center): This function resided in analog MSC

but became a separated entity in digital systems.



Packet-Switched Systems: (2.5G+ e.g., UMTS)

Packet switching is a digital networking communications method that

groups all transmitted data – regardless of content, type, or structure –

into suitably sized blocks, called packets

delivery of variable bitrate data streams (sequences of packets) over a shared

network which allocates transmission resources as needed using statistical

multiplexing or dynamic bandwidth allocation techniques


UMTS Architecture

SD

Mobile Station

MSC/

VLR

Base Station

Subsystem

GMSC

Network Subsystem

AUCEIR HLR

Other Networks

Note: Interfaces have been omitted for clarity purposes.

GGSNSGSN

BTSBSC

Node

BRNC

RNS

UTRAN

SIMME

USIMME

+

PSTN

PLMN

Internet


Packet-Switched Systems: (2.5G+ e.g., UMTS)

There are six elements: MS, Node B, RNC, SGSN, GGSN, and GF

MS: Provides the voice and packet data services. It is also called UE

(User Equipment).

Node B: The name for base station in GSM.

RNC (Radio Network Controller): Controls the radio resources of the

Node Bs that are connected to it. Its function is similar to BSC. A

device PCU (Packet Control Unit) converts the data stream into packet

format

SGSN (Service GPRS Support Node): Analogous to MSC/VLR in the

circuit-switched system. This includes mobility management, security,

and access control functions. It interfaces to HLR.

GGSN (Gateway GPRS Support Node): The point of interface with

external packet data networks such as the Internet.

CGF (Changing Gateway Function): Mainly for billing


LTE Architecture

Reff: https://sites.google.com/site/lteencyclopedia/lte-

network-infrastructure-and-elements


https://sites.google.com/site/lteencyclopedia/lte-network-infrastructure-and-elements

Access Network

eNode B Functionalities

the eNodeB supports a set of legacy features, all related to physical

layer procedures for transmission and reception over the radio

interface

Modulation and de-modulation

Channel coding and de-coding

Radio Resource Control: this relates to the allocation, modification

and release of resources for the transmission over the radio

interface between the user terminal and the eNodeB

Radio Mobility management: this refers to a measurement

processing and handover decision.


Evolved Packet Core (EPC)

The MME (Mobility Management Entity)

Security procedures

Terminal-to-network session handling

Idle terminal location management

The HSS (Home Subscriber Server)

is the concatenation of the HLR (Home Location Register) of GSM

User identification and addressing

User profile information

Mutual network-terminal authentication


Evolved Packet Core (EPC)

The Serving Gateway

the Serving GW is the termination point of the packet data interface

towards E-UTRAN

When terminals move across eNodeB in E-UTRAN, the Serving GW

serves as a local mobility anchor, meaning that packets are routed

through this point for intra E-UTRAN mobility and mobility with

other 3GPP technologies, such as 2G/GSM and 3G/UMTS.

The PDN (Packet Data Network) Gateway

anchor point for sessions towards the external Packet Data

Networks, the PDN GW also supports Policy Enforcement features

The PCRF (Policy and Charging Rules Function) Server

The Policy Decision Function (PDF)

The Charging Rules Function (CRF)


LTE vs UMTS

Functional changes compared to the current UMTS

architecture


Multiple access


The Multiple Access Problem

The base stations need to serve many mobile terminals at

the same time (both downlink and uplink)

All mobiles in the cell need to transmit to the base station

Interference among different senders and receivers

So we need multiple access scheme


Multiple Access:

Enable many mobile users to share simultaneously radio spectrum.

Provide for the sharing of channel capacity between a number of

transmitters at different locations.

Aim to share a channel between two or more signals in such way

that each signal can be received without interference from another.


Multiple Access Schemes

• Frequency Division Multiple Access (FDMA)• Time Division Multiple Access (TDMA)• Code Division Multiple Access (CDMA)

3 orthogonal Schemes:


Frequency Division Multiple Access

Each mobile is assigned a separate frequency channel for the duration of the call

Sufficient guard band is required to prevent adjacent channel interference

Usually, mobile terminals will have one downlink frequency band and one uplink frequency band

Different cellular network protocols use different frequencies Frequency is a precious and scare resource. We are running out

of it Cognitive radio

frequency


FDMA


Features of FDMA

If an FDMA channel is not in sue, then it sits idle and can’t

be used by other users.

Transmit simultaneously and continuously.

FDMA is usually implemented in narrowband systems.

Its symbol time is large as compared to the average delay spread.

For continuous transmission, fewer bits are needed for

overhead purposes (such as synchronization and framing

bits) as compared to TDMA.

FDMA uses duplexers since both TX and RX operate at the

same time.


Time Division Multiple Access

• Time is divided into slots and only one mobile terminal transmits during each slot

– Like during the lecture, only one can talk, but others may take the floor in turn

• Each user is given a specific slot. No competition in cellular network

– Unlike Carrier Sensing Multiple Access (CSMA) in WiFi

Guard time – signal transmitted by mobile terminals at different locations do no arrive at the base station at the same time


TDMA

Transmitter share a common channel.

Only one transmitter is allowed to transmit at a time.

Synchronous TDMA: access to the channel is restricted to regular.

Asynchronous TDMA: a station may transmit at any time that the

channel is free.


Features of TDMA

TDMA systems divide the radio spectrum into time slots.

Each user occupies a cyclically repeating time slot.

Transmit data in a buffer-and-burst method, thus the

transmission for any user is not continuous.

TDMA has TDD and FDD modes

Share a single carrier frequency with several users.

Data transmission is not continuous, but occurs in bursts.

No duplexers is required since users employ different time

slots for transmission and reception.

TDMA can allocate different numbers of time slots per

frame to different users, allowing bandwidth be supplied

on demand to different users


Combined used of synchronous TDMA and

FDMA


Code Division Multiple Access

Use of orthogonal codes to separate different transmissions

Each symbol of bit is transmitted as a larger number of

bits using the user specific code – Spreading

Bandwidth occupied by the signal is much larger than the

information transmission rate

But all users use the same frequency band together

Orthogonal among users


CDMA


Example of CDMA


Orthogonal Frequency Division

Multiplexing(OFDM

It is a special kind of FDM

The spacing between carriers

are such that they are

orthogonal to one another

Therefore no need of guard

band between carriers.

Each terminal occupies a subset

of sub-carriers

Subset is called an OFDMA

traffic channel

Each traffic channel is assigned

exclusively to one user at any

time41Dept. of Electrical and Electronic Engineering, KUET

user1

user2

user3

user4

Advantages of OFDMA

Multi-user Diversity

broadband signals experience frequency selective fading

OFDMA allows different users to transmit over different portions

of the broadband spectrum (traffic channel)

Different users perceive different channel qualities, a deep faded

channel for one user may still be favorable to others


Interference Management


Why Interference Management is Required?

Interference is one of the main obstacle for the

femtocell network deployment

Many femtocells around a small area

Huge interference if there is no proper planning

Interference causes

Reduced throughput

Increased outage probability

Decreased QoS/QoE

Inefficient interference management system

Decreased frequency utilization

Increased cost


Interference Scenarios for Femtocells Overlaid

by Macrocells

Macrocell downlink

Macrocell uplink

Femtocell downlink

Femtocell uplink

Macrocellular BS

FAP-2

FAP-1

Femto

UE-1

Femto

UE-2

Macro

UE-1

Macro

UE-2

Femto

UE-3

Signal Interference


Quality of Service (QoS)

Quality of Experience (QoE)


QoS

What is QoS?

Ability of a network to provide a service at an assured service level

QoS management

Network planning − Network dimensioning

• Number of radio, transmission element and core network

− Details network planning

• Requirement of coverage, capacity and QoS

QoS provisioning− A process that deploys QoS in networks and MT

− Radio, core and transport QoS

QoS monitoring− Measure QoS and improve it further

QoS optimization − A process to improve the overall network quality

− Performance measurements, analysis of measurement results and

update of network quality


QoS Requirements for HSDPA Networks

▣ QoS Requirements target for audio and video services

Medium Application Key performance parameters and target values

E2E delay Jitter Loss

AudioConversational

voice

< 150 ms (

preferred)

< 400 ms limit

< 1 ms < 3% PLR

Audio Voice messaging

< 1 s for play back

< 2 s for record

< 1 ms < 3% PLR

AudioHigh quality

streaming audio< 10 s <<1ms < 3% PLR

Video Videophone

< 150 ms

(preferred)

< 400 ms limit

Lip-synch:<100 ms

< 1% PLR

Video One-way video <10 s < 1% PLR


QoS Requirements for HSDPA Networks

▣ QoS requirement target for data services

Medium Application Key performance parameters and target values

E2E one-way delay Jitter Information loss

DataWeb-browsing

HTML

<2 s /page (preferred)

< 4 s/page (acceptable)N.A 0

DataBulk data

Transfer /retrieval

< 15 s (preferred)

< 60s acceptable)N.A 0

DataHigh priority

Transaction/services

< 2 s (preferred)

< 4 s (acceptable)N.A 0

Data Command/control < 250 ms N.A 0

Data Still image< 15 s (preferred)

<60 s acceptable)N.A 0

Data Interactive games < 200 ms N.A 0

Data Telnet < 250 ms N.A 0

DataE-mail (server

access)

< 2 s (preferred)

< 4s (acceptable)N.A 0

DataE-mail (server to

server transfer)

Can be several

minutesN.A 0


An Example of QoS class identifier (QCI) for

LTE Network

QCI Service Type Priority PDB(ms) PER Examples service

1 GBR 2 100 10−2

Conversational voice (VoIP)

2 GBR 4 150 10−3

Conversational video (live streaming)

3 GBR 5 300 10−6

Non-Conversational video (buffered streaming)

4 GBR 3 50 10−3

Real-time gaming

5 Non-GBR 1 100 10−6

IMS signaling

6 Non-GBR 7 100 10−3

Voice, Video (live streaming), interactive gaming

7 Non-GBR 6 300 10−6

Video streaming(buffered streaming)

8 Non-GBR 8 300 10−6

TCP based (e.g. www, email), chat, FTP, p2p file sharing

9 Non-GBR 9 300 10−6

TCP based (e.g. www, email), chat, FTP, p2p file sharing


Standardized QCI

PDB: packet delay budget

PER: Packet error rate, GBR: Guaranteed bit rate

Mobility Management


Why Mobility Management is Needed?

Moving entity?

Mobile terminal

Mobile user

Mobile network

Moving scope?

Intra/Inter-domain, Micro/Macro-mobility

Horizontal, Vertical

Active session?

Location management (for Paging)

Handoff (Session mobility)

More network coverage in same area

Cost

QoS

Reliability


Handoff Management Requirements

Reduction of signaling and processing overhead

Minimize packet loss and delay (seamless HO)

QoS guarantees during the process and transfer of

context

Use of any “triggers” or metrics available to decide when

and where (planned HO)

Efficient use of network and MT resources

Enhanced scalability, reliability and robustness

Allow inter-technology handoff (VHO)


Soft Handoff Process

MS continually scan for pilot signals from neighbor cells

When a pilot from a neighbor cell crosses a threshold, MS requests a

handoff

BS commands MS to perform handoff


Signal of ASignal of B

BS A BS B

HO

region

Distance

DistanceSignal

strength

Handover Steps

System Discovery

MT must know which wireless networks are reachable

Periodic beacons from AP

Signal measurements

Gathering handoff metrics : bandwidth, cost, delay, SNR, power, etc.

Periodic network scanning

Handoff Decision

MT evaluates the reachable wireless networks to make a decision

Price

Power consumption

Bandwidth availability

Handoff Execution

If MT decides to perform a HO, it executes the HO procedure required to be

associated with the new wireless network

Wireless Networks & Communications Lab. Dept. of Electrical and Electronic Engineering, KUET

ee 4105 communication engg-ii 4105_… · rappaport data ... history of mobile cellular chapter 1:...

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