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Mobile Communication has been developed rapidly since last few decades. The growth of the wireless broadband technologies in the modern years was the answer of increasing demand for mobile Internet and wireless multimedia application such as live TV, live Movies, video conferencing etc. Mobile communication plays a vital role in telecommunication industry. During a common wide area radio access technology and supple network architecture WiMAX and LTE has facilitate convergence of mobile and fixed broadband network. Since 2007, the IEEE 802.16 working group has been developing a new improvement if the IEEE 802.16 standards as a higher level air interface to meet the requirement of ITU-R/IMT-advanced for 4G system as well as for the next generation. In 4G mobile technology, assures the high mobility with high level speed of data rates and high capacity IP based services and application. This paper describes the 4G wireless system, its architecture, security services, benefits and challenges of 4G wireless technology.

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International Journal of Engineering and Management Research, Volume-3, Issue-2, April 2013

ISSN No.: 2250-0758

Pages: 35-43

www.ijemr.net

4G Wireless Technology: A Brief Review

Ashish Kumar1 , Ankit Aswal2 , Lalit Singh3

1,3Department of CS&E, BT Kumaon Institute of Technology, Dwarahat, Almor, Uttarakhand, INDIA.

Department of ECE, BT Kumaon Institute of Technology, Dwarahat, Almora, Uttarakhand, INDIA.

ABSTRACT

Mobile Communication has been developed rapidly since

last few decades. The growth of the wireless broadband

technologies in the modern years was the answer of increasing

demand for mobile Internet and wireless multimedia

application such as live TV, live Movies, video conferencing

etc. Mobile communication plays a vital role in

telecommunication industry. During a common wide area

radio access technology and supple network architecture

WiMAX and LTE has facilitate convergence of mobile and

fixed broadband network. Since 2007, the IEEE 802.16

working group has been developing a new improvement if the

IEEE 802.16 standards as a higher level air interface to meet

the requirement of ITU-R/IMT-advanced for 4G system as

well as for the next generation. In 4G mobile technology,

assures the high mobility with high level speed of data rates

and high capacity IP based services and application. This

paper describes the 4G wireless system, its architecture,

security services, benefits and challenges of 4G wireless

technology.

Keywords— WiMAX, LTE (Long Time Evolution), OFDMA

(Orthogonal Frequency Division Multiplex Access), MIMO

(Multiple Input Multiple Output), MME (Mobility Management

Entity).

I. INTRODUCTION

The mobile and wireless communication technologies have

been enhancing rapidly day by day. Gadgets continue to

shrivel in size and at the same time rising in processing

power. Users generally insist in more sophisticated and

worthwhile applications. Hence, capacity improvement is

the paramount necessity in wireless communications [1].

The evolution of various mobile services initiating from

the 1G (first generation) to 4G (fourth generation) is begun

as follows:

1G: First generation (1G) was a wireless network which

basically constituted an analog cellular system along with

circuit switched network architecture. These wireless

networks only supported basic voice telephony and were

mainly confronted by low capacity and limited coverage

region. Hence in telecommunications sector an increased

requirement for high frequency ranges paved the way for

the development of digital transmission techniques from

analog transmission techniques [2].

2G: In the early 1990s, second generation (2G) wireless

technology arrived to meet the capacity requirements of

burgeoning voice plus telephony, limited circuit switched

data services and text messaging. This technology utilized

digital transmission system which is capable of

compressing the signal much more efficiently and

effectively as compared to analog system and at the same

time allows the transmission of more packets in the same

bandwidth with lesser power [2].

2.5G: 2.5G, an interim step being taken after 2G and prior

to 3G, was basically an improvement of the two chief 2G

technologies. This technology provided an enhanced

capacity on the 2G RF (radio frequency) channels and also

presented higher throughput data rates, up to 384 kbps [3].

3G: 3G, third generation of mobile and wireless

technology, supersedes 2G technology and precedes 4G

technology. 2.5G was a transitory bridge between 2G and

3G for providing high data rates. Hence 3G wireless

technology was introduced for bestowing higher data-

transmission speeds, superior network capacity and more

sophisticated and enhanced network services. In May 2001

NTT DoCoMo launched the first pre-commercial 3G

network, branded as FOMA, in Japan. Subsequently after

the first pre-commercial launch, NTT DoCoMo launched

the first commercial 3G network in Japan in Oct. 2001.

4G: 4G, the fourth-generation of wireless service, is an

enhancement from 3G and is presently the most extensive,

widespread, expeditious and high-speed wireless service.

Presently 4G is available only in limited regions. 4G

wireless service has been devised to deliver high speed

irrespective of the technology which drives 4G. For

instance Sprint employs a technology called WiMax for its

4G services, whereas Verizon Wireless employs Long

Term Evolution, or LTE. On an average, 4G wireless

technology is expected to provide data rates from four to

ten times higher than today's conventional 3G networks.

II. FOURTH GENERATION

NETWORKS

The 4G is the most innovative wireless

technology which has replaced the 3G systems. The vital

characteristics of the 4G networks include accessing

information with a flawless connection anytime, anywhere

with a wide range of services, receiving greater amounts of

information, pictures, data, video, and so on. The future 4G

network infrastructures assimilate numerous networks

employing the use of IP (Internet protocol) as a common

protocol to ensure that every user will be able to opt for

every application and environment. In this era of emerging

trends in mobile and wireless communications, 4G focuses

on ensuring a flawless service, have larger bandwidth,

higher data rates, and smoother and faster handoff across a

wide range of wireless networks and systems.

Incorporating the 4G potentials with the existing mobile

technologies by the use of enhanced technologies is the

major concept. The major characteristics of 4G services of

user interest include application adaptability and high

dynamism which implies that different services can be

delivered and available to users' personal preferences and

support the user traffic, air interfaces, quality of service,

and radio environment. Effective and efficient connection

with the network applications can be achieved in numerous

forms and at different levels [4].

Enhanced Features of 4G Wireless Technology are as

follows:

• Wider and extensive mobile coverage region.

• Larger bandwidth - higher data rates.

• Terminal Heterogeneity and Network

Heterogeneity.

• Smoother and quicker handoff.

• WLAN for hot spots, an extension of 2G and 3G.

• Better scheduling and call admission control

techniques.

• Global roaming and inter- working among various

other access technologies.

• Supports interactive multimedia, video, wireless

internet, voice and various other broadband

services.

• User Friendliness and Personalization.

III. BENEFITS AND CHALLENGES

A. Benefits of 4G networks

The benefits of 4G networks assist in ensuring a

larger range of services and use-cases. However, the

commercial models and eco-systems have not yet been

established that are required in driving adoption from a

user and service provider perspectives.

1) Technology Performance Improvement: Delivers

higher uplink and downlink throughput besides lesser

latency and network capabilities. It has been universally

believed that there will be a prolong growth in mobile data

traffic significantly in the coming years. It is also a matter

of fact that the majority of the core transport and

throughput bottlenecks will undoubtedly be delivered by

the technology itself despite of the 4G technology used

(LTE or WiMAX) in comparison to 3G. 4G technologies

provide at least two times more effective and efficient use

of spectrum, enhanced support for real-time applications,

and greater max speeds. Though there exist further

network and capacity confronts such as edge or gateway

management, signalling management which are needed to

be fully addressed to increase benefits from the upgrade [5].

2) New Mobile Application Enablement: It enables new

mobile applications to enhance the existing ones

(Streaming Music). Several 4G services such as digital

storage or smart home monitoring will get enhanced by the

improved 4G bandwidth and latency. Other services such

as MMS, digital picture frames and various near-field

communication applications will notice no significant

improvement in riding on a 4G network. Hence, it is very

crucial to have a very close look at the services and

applications which are likely to be enhanced by 4G

advancements. We can see that services which gain the

most from the 4G technology's deployment are video

streaming, MMOG/gaming and expertise applications such

as interactive learning [5].

3) Addressable Device Expansion: Network potentials and

chipset scale could expand the connectivity to various

innovative gadgets. Handset technologies persist in

evolving along a huge range of features and value added

services by means of smart phones and more specialized

gadgets. A carrier controlled service experience has been

conventionally supported by the Terminal operating model.

Commercial operating systems such as Windows Mobile

or RIM have attracted heavy data users and hence fostered

network congestion by reducing some control [5]. In

addition, the increasingly growing open eco-systems,

further enabled by 4G, offer a challenging opportunity for

operators since third parties develop services, applications

and customization tools in order to meet user needs.

Gadgets are becoming highly configurable because of open

standards and more expertise gadgets such as net books,

eReaders, tablets etc. are coming into the market. To meet

lesser user segment needs we believe that vendors must

think of a micro-segmentation based device roadmap;

various new distribution channels are requisite to support

the acceptation of Converged Mobile Gadgets and 4G

applications [5].

4) Differentiated Customer Experience: It enables in

managing the user expectation and experience with new

features and services. We consider the user's experience in

gaining a profound understanding of how these services are

completely facilitated and how it mingles into the fabric of

our living, the necessity or capability to deploy expertise or

configured gadgets to support enhancement, and finally,

how to make money and when to share the income from

the service delivery. Till now, it has been inadequate in

understanding the experience of a 4G user and it is

uncertain that how greatly the user experience will alter as

many more and various 4G services arrive [5]. We are

much aware of the fact that user expectations regarding

price points are retuning with growing expectations to pay

"a little for a little" which confronts the present costing and

monetization approaches. We also believe that users are

expecting an additional bunching of services and

applications into a "solution" which assists the way they

live. Hence, accomplished adoption of 4G services will be

highly reliant in resolving the most probable Use-Cases for

4G services.

5) Business Model Evolution: 4G wireless technology

will be the key in facilitatng the alternative partnership and

monetization models. The previous couple of years or so

have exposed the industry to the myth of all you can eat

pricing models, or flat rate voice and data plans. This has

motivated performance consistent with Pareto's data usage

rule where 4% of users generally utilize more than 70% of

the bandwidth. The consequential network bottlenecks

restrain access in regions with a high tally of smart gadgets

[5]. The bandwidth requirements of several 4G use cases

suggests that the above problem will only get worse if

present pricing methods move further. One alternative

presently being considered by operators motivates in

moving towards the tiered pricing based on conventional

aspects such as time, speed and quality of service. An

additional capable service model is bandwidth on demand

and the associated pricing method to charge premium

pricing for these burst requirements. This may be proved

advantageous in planning high bandwidth utilizing events

such as video streaming or LIVE TV.

Given that what we are aware of today, 4G wireless

technology will need an extension of pricing models to

favour lower up-front prices (subscriptions, one time

purchases, ad-based, fermium and per-use). Though, open

development manifestoes and collaborative solution

deployment/development methods may influence how

manifold charging models may work. Undoubtedly new

4G service eco-system and use-cases arrangements head to

the significant query of who will generate the bill for the

services and how will the income be shared [5].

B. Challenges

1) Security and Privacy: Security measures must be

instituted in the development of 4G Wireless Networks

which will facilitate the safest possible technique for data

transmission. Explicitly, "The 4G core delivers mobility,

security, and QoS by means of reusing the existing

methods while still working on a few mobility and

handover concerns" [5]. Hence, for securing data, to be

transmitted across the network, from hackers and further

security contraventions it is obligatory for the organization

to develop an efficient and effective series of tools which

will support the utmost 4G security measures. As a result

of the nature of the 4G wireless network, there is a more

possibility of security intrusions, and hence, manifold

levels of security, including increased necessities for

validation, will be essential for protecting data and

information transmitted across the network. One of the

major objectives of 4G wireless networks is to envelope

very wide geographic region with flawless service. Clearly,

smaller local area networks will operate on different

operating systems. The heterogeneity of these networks

that exchange different sorts of data complicates the

privacy and security concerns. Moreover, since new

gadgets and services are being introduced for the first time

in 4G wireless networks, the encryption and decryption

schemes being used for 3G wireless networks are not

suitable for 4G wireless networks. To prevail over these

issues, two methods can be followed. The former method

relies on modifying the current privacy and security

methods so as to employ them to heterogeneous 4G

wireless networks. The latter method relies in developing

new, fresh dynamic reconfigurable, lightweight and

adaptive mechanisms whenever the existing employed

methods fail to get adapted to 4G wireless networks [5].

2) Quality of Service: Regarding the network quality,

various telecommunication service providers assure the

users for the enhanced connectivity, and the utmost

possible data quality which is transmitted across the

network, just as Ericsson's 4G Wireless Networks for

TeliaSonera [5]. With the data rates of almost 10 times

higher as compared to today's conventional mobile

broadband networks and real-time performance, it allows

users to be connected always, even "on the move".

Consequently, it is essential for service providers to

develop an efficient and effective method to the 4G

Wireless Networks which will improve quality, bestows

effectual security measures, and will make sure that all

users are provided with widespread options for

downloading music, video, and picture files without any

delays. The major confront for 4G wireless networks is

incorporating IP- based and non-IP-based gadgets. We

know that gadgets which are non-IP address based are

usually used for services such as VoIP. In contrast, gadgets

which are IP address based are generally used for

delivering data [5].

IV. EVOLUTION OF MOBILE WIMAX

TECHNOLOGY

Mobile WiMAX has turned out to be a vital part

of today's modern and digitized world. As a result, people

are now showing more dependency on mobile computing.

The demand for downloading and transporting the data on

mobile devices moving with high speed has stirred up the

development of new techniques so as to meet the various

requirements of mobile computing. In the field of wireless

networks our world has witnessed numerous revolutionary

changes in the last two decades. Today wireless network

has become an essential part of peoples' life in their day to

day requirements and is becoming more popular by each

passing day due to the necessity of mobility along with

high speed broadband access. Presently, new and fast

emerging technologies are being introduced in the field of

wireless networks which allow high speed broadband

wireless access. Mobile WiMAX, stands for Worldwide

Interoperability for Microwave Access, is a sophisticated

next generation mobile broadband wireless network based

on IEEE 802.16e-2005[7] which supports 4G. Primarily it

was developed for the solutions of problems faced by

wired networks but later it became the part of 4G wireless

network with the improvements from 802.16-2004,

802.16e-2005 to 802.16m. IEEE 802.16e -2005 is an

improvement to IEEE 802.16 -2004[8] and the latter was

the fixed data transmission technique for broadband

connection to MAN. Wireless MAN-OFDMA

specification assists in providing an enhanced air interface

for operation in either unlicensed or licensed bands.

Nowadays user wants to remain online every time and also

want speedy transmission of data at low price without any

data loss. Presently a large number of PDAs (Personal

Digital Assistance) in the market are capable of supporting

wireless data transmission flawlessly with mobility. In the

upcoming future such type of requirement will raise

immensely, therefore developers (for example WiMAX

Forum) are looking for such type of requirements for

making these gadgets more supportive in accordance with

the user necessities. WiMAX (802.16e- 2005) is the

solution for such type of problems. WiMAX can support

data rates up to 75 Mbps with a range of nearly about 30

miles.

Architecture of WiMAX

The IEEE 802.16e-2005 standard includes

specified air interface for WiMAX without having an end-

to-end WiMAX network. The WiMAX Forum's Network

Working Group, using IEEE 802.16e- 2005 as the air

interface, is creditworthy for devising the end-to-end

network requirements, protocols, and architecture for

WiMAX. For providing architecture framework for

WiMAX deployments and to certify interoperability

among several WiMAX equipments and operators a

network reference model has been developed by the

WiMAX NWG. The network reference model is based on

an IP service model for supporting fixed, nomadic, and

mobile deployments.

The whole network may be logically segregated

into three major parts: (1) mobile stations employed by the

end user for accessing the network, (2) the access service

network (ASN) consisting of one or more base stations and

one or more ASN gateways forming the radio access

network on the edge, and (3) the connectivity service

network (CSN) for providing IP connectivity and entire IP

core network functions. A basic demonstration of IP-based

WiMAX network architecture is shown in Figure 1. The

following architecture allows for three distinct business

articles: (1) network access provider (NAP), which owns

and operates the ASN; (2) network services provider (NSP),

that provides the IP connectivity and WiMAX services to

users by utilizing the ASN infrastructure which is provided

by one or more NAPs; and (3) application service provider

(ASP), that can provide various value-added services such

as multimedia applications using IMS (IP multimedia

subsystem) and corporate VPN (virtual private networks)

that run on top of IP. This division among NAP, NSP, and

ASP is devised to permit a richer ecosystem for WiMAX

service business, which leads to more competition and

hence better services.

The IEEE has created the 802.16m Task Group

for developing the subsequent improvement to the 802.16e

standard. This article mainly emphasise on the

improvement of the IEEE Wireless MAN standards. There

are several research and development following the IEEE

802.16e standard related to Mobile WiMAX networks.

Figure 1: IP Based WiMAX Network Architecture [9] [10]

Air Interface Features of WiMAX

The term WiMAX is generally employed as a

name for the family of IEEE standards since 1999 created

by the 802.16 working group. The TABLE I presents the

various aspects for 802.16e explaining that 802.16e allows

for a broad range of design alternatives that offers

flexibility in meeting the necessities of most deployment

scenarios. The significant parametric quantities of WiMAX

RAN (Radio Access Network) are being explained in the

subsection.

TABLE I

SUMMARY OF WIMAX AIR INTERFACE FEATURES

age

Flexibility

frequency

Flexible

channel

√ √ √

duplexing

channelisation

modulation

cyclic prefix

reuse

hybrid ARQ √ √ √

MIMO

service

support

(√)Primary benefit (√) Secondary benefit

V. EVOLUTION OF LONG TERM

EVOLUTION

LTE Overview

LTE has improved the Universal Mobile

Telecommunication Services (UMTS) in a series of points

on account of the requirements of future generation cellular

technology and rising mobile communication services

necessities. Such improvements are generated owing to

LTE background needs, motivations and objectives, as

presented in section 2.1. The concise account concerning

LTE technique and specifications is also being covered in

the following subsections.

LTE Background:

LTE was first proposed in Toronto conference in

2004 for attaining higher speed and lesser packets latency

in UMTS 3G wireless systems. Therefore, LTE must fulfil

a set of high-level requirements which are shown below

[11 ]:

• Reduced cost per bit.

• Simple architecture and open interfaces.

• Flexible use of existing and future frequency

bands.

• Reasonable consumption of terminal power.

• Improved user experience -more services with

lower cost and higher speed.

As for the motivations and objectives, 3GPP LTE aspires

to deliver superior performance as compared to HSPA

technique. The major performance objectives are listed

below [12]:

• 2 to 4 times higher spectral efficiency than HSPA

Release 6.

• Peak rates exceed 100 Mbps in Downlink and 50

Mbps in Uplink.

• Round trip time is less than 10 ms.

• Optimized packet-switching.

• High-level mobility and security.

• Efficient and optimized terminal power

consumption.

• Flexible frequency with 1.5 MHz to 20 MHz

allocations.

LTE Technology:

LTE is constituted of several new technologies as

compared to the previous generations of wireless systems.

These new technologies are employed in generating more

efficiency with respect to the spectrum and enhanced data

rates as expected by designers. Here we presented only the

snapshots of the techniques which will be explained in

detail in the third section.

OFDM (Orthogonal Frequency Division

Multiplex) [13 ]: During the transmission of packets, for

achieving high data bandwidth, LTE incorporates OFDM

technology which provides a high-degree of resilience to

interference and reflections simultaneously. Moreover, the

access schemes can be further divided into two access

methods that are used in the Downlink and Uplink

respectively. The former one that is used for the Downlink

is OFDMA (Orthogonal Frequency Division Multiplex

Access); the latter one that is used for the Uplink is SC-

FDMA (Single Carrier- Frequency Division Multiplex

Access). These access schemes have the advantages of

smaller ratio of peak to average power and more steady

power capable of getting higher RF power amplifier

efficiency in the mobile handsets.

1. MIMO (Multiple Input Multiple Output)

[12 ] [ 14 ]: MIMO operations consist of spatial multiplexing

in addition to pre-coding and transmit diversity. These

operations deal with the problems of multiple signals rising

from various reflections that were faced by prior

telecommunications systems. In addition, use of MIMO

also improves the throughput by means of the additional

signal paths subsequent to those operations. To distinguish

different paths MIMO needs two or more dissimilar

antennas with unlike data streams, such as the schemes

employing 2 x 2, 4 x 2, or 4 x 4 antenna matrices.

LTE Architecture:

The presently agreed LTE architecture employs a

flat architecture, that can be demonstrated by the use of

four functional elements as discussed below (see also

Figure 2) [15]:

A. Evolved Radio Access Network (RAN): It primarily

constitutes a single RAN node termed as eNodeB

(eNB). The eNB hosts the physical layer (PHY),

Medium Access Control (MAC), Radio Link Control

(RLC), and Packet Data Control Protocol (PDCP)

layers and interfaces with the User Equipment (UE).

Its functions include admission control, radio resource

management, scheduling and enforcement of

negotiated UL QoS and compression/decompression

of Downlink/Uplink user plane packet headers.

B. Serving Gateway (SGW): It works as the mobility

anchor between LTE and other 3GPP technologies for

the user plane during inter-eNB handovers.

Simultaneously, it directs and forwards the user data

packets. While Downlink data approaches UE the

SGW functions in controlling the termination of the

Downlink data path and imitates the user traffic during

lawful and rational interception. In addition it also

manages and stores UE information such as network

internal routing information, parameters of the IP

bearer service.

C. Mobility Management Entity (MME): It is the key

control- node for the LTE access network which tracks

and pages the idle mode UE, even during

retransmission. MME chooses the SGW for a UE at

first attach and at the time of intra-LTE handover

which involves Core Network (CN) node relocation.

During the authentication of the user, it interacts with

the HSS (a master user database which supports IP

Multimedia Subsystem including subscriber

information) [16 ] through the specified interface.

D. Packet Data Network Gateway (PDN GW): It has two

major tasks in terms of functionality. Foremost, the

PDN GW supports the connectivity to the UE and also

to the external packet data networks by the entry and

exit of UE traffic. The other major role of the PDN

GW is to act as a mobility anchor between 3GPP and

non-3GPP technologies, for instance, WiMAX and

3GPP2 (CDMA 1X and

EvDO).

Figure 2: High Level Architecture for 3GPP LTE

For the LTE architecture to run typically and efficiently it

has to have the ingenious physical and transport channels

between Downlink and Uplink, as all packets transmissions

inevitably involve both the two links. And then the design

of the channels for enabling dynamic resource deployment

becomes significant. The LTE PHY Downlink and Uplink

are reasonably different and are dealt separately within the

specification documents [17]. Hence for achieving the

different objectives in transmission the physical and

transport channels for Downlink and Uplink are also

different which are simply introduced in the following

subsections.

Physical and Transport Channels for Downlink [12] [18]

Physical Channels:

• Physical Broadcast Channel (PBCH): It is used for

holding the system information for UEs require in

accessing the network.

• Physical Control Format Indicator Channel (PCFICH):

It is employed in managing the transmission format.

• Physical Downlink Control Channel (PDCCH): The

primary objective of this channel is to carry the

scheduling information.

• Physical Hybrid ARQ Indicator Channel (PHICH):

This channel is used in reporting the status of Hybrid

ARQ.

• Physical Downlink Shared Channel (PDSCH): It is

employed for unicast and paging.

• Physical Control Format Indicator Channel (PCFICH):

It is used for supplying information for decoding the

PDSCH by UE.

Transport Channels:

• Broadcast Channel (BCH) : This channel maps to

Broadcast Control Channel (BCCH)

• Downlink Shared Channel (DL-SCH): This is the most

important channel for transferring downlink data and

is used by many logical channels.

• Paging Channel (PCH) : This channel is used convey

the Paging Control Channel (PCCH)

• Multicast Channel (MCH): This channel is used in

transmitting Multicast Control Channel (MCCH)

information.

Physical and Transport Channels for Uplink [ 12] [18]

Physical Channels:

• Physical Uplink Control Channel (PUCCH): For

sending Hybrid ARQ acknowledgement.

• Physical Uplink Shared Channel (PUSCH): This

channel is on the Uplink and is the counterpart of

PDSCH.

• Physical Random Access Channel (PRACH): This UL

channel is used for random access functions.

Transport Channels:

• Uplink Shared Channel (UL -SCH): It is similar to

Downlink Shared Channel (DL-SCH).

• Random Access Channel (RACH): It is used for

random access requirements.

VI. ORTHOGONAL FREQUENCY

DIVISION MULTIPLEX ACCESS IN

WIMAX AND LTE

The Orthogonal frequency division multiple

access (OFDMA), a multi-carrier transmission technique

for providing high speed bi-directional wireless data

communication, has recently been accepted as an

outstanding multiple access technique for the downlink

receivers of the next generation. Each and every proposal

that has been considered for the 4G wireless technologies

has adopted orthogonal frequency division multiple access.

IEEE 802.16e based WiMAX and 3GPP based LTE are the

two chief competitors in the 4G marketplace that are likely

to dominate the 4G Wireless landscape [2]. Both WiMAX

and LTE employs the use of orthogonal frequency division

multiple access (OFDMA). In WiMAX OFDMA is

employed both on the uplink (UL) and the downlink (DL)

and, whereas LTE uses OFDMA only on the downlink

(DL). There are numerous reasons in opting for OFDMA.

Some of them are multipath handling potential, scalability

of operation in different bandwidths, ability to handle

different data rates and the ease in combining with multiple

antennas techniques [2]. To support higher data rates is the

key necessity in modern wireless systems. Hence, the use

of OFDM has been considered appropriate for the above

reasons. Frequency diversity (FD) and channel feedback

can be used efficiently for improving robustness and

throughput. Owing to its capability in handling multipath,

4G cellular networks have adopted OFDM as the basic

technique. An integrated radio and core network furnishing

different services is envisioned for the next generation

wireless systems. The use of OFDMA technique assists in

splitting resources into smaller granular units for allocation

to various services as required. OFDMA is considered

crucial for attaining high spectral efficiencies in 4G

wireless systems owing to its ability to incorporate well

with MIMO technology (also called as MIMO-OFDM) [2].

USE OF OFDMA IN WIMAX AND LTE

A. Frame Structure

In WiMAX, frame duration of 5 ms is used along

with time division duplexing (TDD). The frame is then

divided into OFDM symbols (for e.g., 48). Some of them

are allocated for downlink (DL) and the rest for uplink

(UL) transmissions. The first symbol in the frame is used

for preamble transmission. For control and data

transmissions sub channels are then formed out of a group

of subcarriers [2]. The base station (BS) announces a

schedule after every frame period (i.e., 5 ms) to convey the

downlink (DL) and uplink (UL) allocation.

In LTE, the frame duration of 10 ms is divided to

form sub frames of 1 ms duration. A sub frame is used to

form two slots each of 0.5 ms duration. The base station

(BS) programs transmissions after every 1 ms and the

subcarriers form resource blocks for allocation on the

downlink (DL) [2].

B. Subcarrier's resource mapping

Subcarrier (also known as resource elements in

LTE) is the smallest granular unit in the frequency domain

and OFDM symbol duration is the smallest granular unit in

the time domain [2].

In an OFDM symbol, groups of subcarriers are

considered together since subcarriers are too large in

number to handle the allocation plane. For supporting

numerous services, a group of OFDM symbols are handled

together for minimizing the signaling overhead and

achieving granularity in the achievable rates.

C. Frequency Diversity

In WiMAX sub channels are formed by grouping

24 subcarriers, present in different parts of the spectrum, in

the PUSC (partially used subcarriers) sub channelization

method. This pseudorandom selection of the positions of

the subcarriers over the entire band depends on the

CELL_ID. For sending all the basic control messages

diversity based sub channelization approach is employed

[2].

In LTE, a RB (resource block) constitutes the

similar 12 adjacent subcarriers for 7 OFDM symbols.

However, a different RB can be used in the second slot of

the sub frame to leverage FD (frequency diversity) instead

of using the similar RB in the second part of the sub frame

[2].

D. Multiuser Diversity

For achieving multiuser diversity in WiMAX,

groups of adjacent subcarriers are spread out over a few

OFDM symbols in the BAMC approach. The subcarriers

are then arranged into groups of 9 adjacent subcarriers

called as bins. A group of four bins is termed as a band

where each bin constitutes 8 data and 1 pilot subcarrier.

The base station chooses 2 bins in one of these bands and

assigns the same bin over 3 consecutive OFDM symbols

which results in 48 data subcarriers for a BAMC slot.

BAMC sub channelization approach is the most

widespread approach desired for WiMAX certification [2].

In LTE, the BTS opts for the RB for sending data

to a user. It makes use of the channel feedback from the

mobile device to schedule a RB for the user in a frame.

The base station receives configuration from the channel

feedback in LTE for its scheduled downlink (DL). Usually,

160 ms is the maximum gap between feedback messages

and is 2 ms is the minimum duration between feedback

messages and the channel status report is requested from

the mobile by the BTS in a periodic feedback. In LTE

simultaneous use of FD and MUD for different users is

possible whereas in WiMAX, it cannot coexist in time [2].

E. Interference Diversity

Sub channel formation in WiMAX depends on the

CELL_ID. Sub channels will be different for different

users. Hence, the user experiences interference diversity

which is likely to provide improved performance as

compared to the dominant interferer case. Note that

interference diversity leverages only in the case of PUSC

transmissions. Hence interference diversity cannot be used

for BAMC transmissions [2].

In LTE, RBs are allocated to the users

independent of the CELL_ID. The interference on the

downlink (DL) will not be randomly distributed across

RBs of adjacent cells. Hence there is no interference

diversity on the downlink (DL) in LTE [2].

VII. CONCLUSION

This paper presents a brief account on the 4G

wireless technology and networks, the evolution of

WiMAX and LTE Network architecture and the OFDMA

technique. We have observed that the count of wireless

broadband users have surpassed the count of fixed

broadband users. Hence, in a world going digitized and

wireless, the technologies with higher throughputs are

getting more importance with each passing day. For an

accomplished and sophisticated 4G wireless network,

coverage and capacity are most vital elements. LTE-

Advanced and WiMAX are the most feasible technologies

for a successful 4G deployment. Therefore the need of

today's world is a novel technology which is affordable in

cost with higher throughput, better coverage and capacity.

REFERENCES

[1] Bill Krenik "4G Wireless Technology:When will it

happen? What does it offer?" IEEE Asian Solid-State

Circuits Conference November 3-5, 2008.

[2] R. Mayuri, P. Manish " 4G Wireless Technology: A

Survey Paper". In: Proceedings of the National

Conference "NCNTE-2012" at Fr. C.R.I.T., Vashi,

Navi Mumbai, Feb. 24-25, 2012.

[3] K.Deepak, M. Mahak, K. J. Mohd, Y. Manoj "Beyond

3G: 4G Mobile Communication". International Journal

of Innovations in Engineering and Technology (IJIET).

Vol-1, Issue- 2. ISSN: 2319 – 1058.

[4] Augustine C. Odinma, Lawrence I. Oborkhale and

Muhammadou M.O. Kah, "The Trends in Broadband

Wireless Networks Technologies ",The Pacific Journal

of Science and Technology, Volume 8. Number 1. May

2007.

[5] V. K. Pushpendra, S. Jayant "4G WIRELESS

NETWORKS: BENEFITS AND CHALLENGES".

Vol-2, Issue-6. ISSN:2249 -0558.

[6] E. Buracchini, "The Software Radio Concept," IEEE

Commun. Mag., vol. 38, no. 9, 2000, pp. 138–43.

[7] IEEE 802.16e- 2005,IEEE Standard for Local and

metropolitan area networks-Part 16:Air Interface for

Fixed and Mobile Broadband Wireless Access

Systems-Amendment 2:Physical and Medium Access

Control Layers for Combined Fixed and Mobile

Operation in Licensed Band and Corrigendum 1,

http://standards.ieee.org/getieee802/download/802.16e-

2005.pdf

[8] IEEE 802.16- 2004, IEEE standard for local and

metropolitan area networks-part 16: Air Interface for

Broadband Wireless Access systems

http://standards.ieee.org/getieee802/download.

[9] P. Marichamy, S. Chakrabati, S. L. Maskara,

"Overview of handoff schemes in cellular mobile

networks and their comparative performance

evalution," IEEE VTC'99, vol.3, pp.1486 -1490, 1999.

[10] Jeffrey G. Andrews, Arunabha Ghosh, Rias

Muhamed, "Fundamentals of WiMAX Understanding

Broadband Wireless Networking ," publisher Prentice

Hall ,pp. 496,Inc. 2007.

[11] "3GPP Long Term Evolution," http://www.radio-

electronics.com/info/cellulartelecomms/lte-long-term-

evolution/3g-lte-basics.php [3G LTE introdution]

[12] Holma, Harri; Toskala, Antti; "LTE for UMTS :

OFDMA and SC-FDMA Based Radio Access," Wiley,

2009

[13] "3GPP Long Term Evolution," http://www.radio-

electronics.com/info/cellulartelecomms/lte-long-term-

evolution/lte-ofdm-ofdma-scfdma.php [3G LTE

OFDMA and SC-FDMA principles]

[14] "3GPP Long Term Evolution," http://www.radio-

electronics.com/info/cellulartelecomms/lte-long-term-

evolution/lte-mimo.php [3G LTE MIMO principle]

[15] "Long Term Evolution: A Technical Overview"

Motorola Whitepaper

http://business.motorola.com/experiencelte/pdf/LTETec

hnicalOverview.pdf [An overall introduction of LTE

technologies]

[16] http://en.wikipedia.org/wiki/Home_Subscriber_Se

rver [Including brief Home Subscriber Server

introduction]

[17] Zyren, Jim; "Overview of the Long Term

Evolution Physical Layer," Doc Num.

3GPPEVOLUTIONWP, Rev 0, 2007

http://www.freescale.com/files/wireless_comm/doc/whi

te_paper/3GPPEVOLUTIONWP.pdf

[18] "3GPP Long Term Evolution," http://www.radio-

electronics.com/info/cellulartelecomms/lte-long-term-

evolution/physical-logical-transport- channels.php [3G

LTE Physical and Transport Channels brief overview.

... LTE network was designed to deliver a peak data rate of 100Mbps in the downlink and 50Mbps in the uplink. This requirement was exceeded in the eventual system, which delivers peak data rates of 300Mbps and 75Mbps for the downlink and uplink, respectively [3]. ...

... It Increases handoff dropping probability. 3 Delay Aware Call Admission Control (DACAC) scheme [15] It guarantees QoS for different service type. ...

Background Internet is being used extensively throughout the world from last decade. In India internet service has entered into new generation called 4G. Medical students are particularly vulnerable group for problematic internet use on account of the time they spend online. This might have negative effects on their physical, psychological and social health. Hence they are more prone to internet addiction. Aims To compare use and effect of internet service among medical students before and after the availability of 4G service. Study design Institution based cross sectional study. Methods and material Predesigned validated questionnaires were provided to the medical students in the year 2014. The questionnaire included demographics, pattern of internet use and Young's internet addiction test. Again in the year 2018 the similar procedure was carried out after introduction of 4G service. The data was collected and compared. Analysis was done using SPSS 25. Statistical analysis Descriptive statistics, Chi² test and Mann–Whitney test was applied. Results Among 424 medical students 207 students were assessed in the year 2014 and 217 students in 2018.There was a significant change of pattern of use. Also significant increase in number of female users and severity of internet addiction in 2018. The ill effect of internet was on rise after availability of 4G service. Conclusions The prevalence of internet addiction and its ill effect on behavior among medical students was higher after availability of 4G service in same college. So appropriate preventive and interventional strategies need to be developed in professional institutions.

Ekkharin Srilaphat
Thada Jantakoon

This research aimed at proposing an ubiquitous flipped classroom instructional model with learning process of scientific to enhance problem-solving skills for higher education (UFC-PS model). The UFC-PS model was developed based on the review of the literature, the expert's interview and evaluated by five experts. The research results were found that the UFC-PS model consists of three components were (1) Ubiquitous Learning Environment, (2) Ubiquitous Scaffolding, and (3) flipped classroom through scientific inquiry. The experts also evaluated which step of the UFC-PS model was most suitable for the development of the respective aspects of problem-solving skills.

Deepak Kanojia

Based on the study, 4G mobile technologies is in a determining and Standardization stage. Since 4G is still in the cloud of the sensible standards creation, ITU and IEEE form several task forces to work on the possible completion for the 4G mobile standards as well. 3GPP LTE is an Evolution standard from UMTS, and WiMAX is another candidate from IEEE. These technologies have different characteristics and try to meet 4G characteristics to become a leading technology in the future market. Under these circumstances, this paper will present about the current trends and its underlying technologies to implement the 4G mobile technology. This paper also shows some of the possible scenarios that will benefit the 4th generation technology.

Enrico Buracchini

Since early 1980 an exponential blowup of cellular mobile systems has been observed, which has produced, all over the world, the definition of a plethora of analog and digital standards. In 2000 the industrial competition between Asia, Europe, and America promises a very difficult path toward the definition of a unique standard for future mobile systems, although market analyses underline the trading benefits of a common worldwide standard. It is therefore in this field that the software radio concept is emerging as a potential pragmatic solution: a software implementation of the user terminal able to dynamically adapt to the radio environment in which it is, time by time, located. In fact, the term software radio stands for radio functionalities defined by software, meaning the possibility to define by software the typical functionality of a radio interface, usually implemented in TX and RX equipment by dedicated hardware. The presence of the software defining the radio interface necessarily implies the use of DSPs to replace dedicated hardware, to execute, in real time, the necessary software. In this article objectives, advantages, problem areas, and technological challenges of software radio are addressed. In particular, SW radio transceiver architecture, possible SW implementation, and its download are analyzed

Jim Zyren

Overview Long Term Evolution (LTE) is the next step forward in cellular 3G services. Expected in the 2008 time frame, LTE is a 3GPP standard that provides for an uplink speed of up to 50 megabits per second (Mbps) and a downlink speed of up to 100 Mbps. LTE will bring many technical benefits to cellular networks. Bandwidth will be scalable from 1.25 MHz to 20 MHz. This will suit the needs of different network operators that have different bandwidth allocations, and also allow operators to provide different services based on spectrum. LTE is also expected to improve spectral efficiency in 3G networks, allowing carriers to provide more data and voice services over a given bandwidth. This technical white paper provides an overview of the LTE physical layer (PHY), including technologies that are new to cellular such as Orthogonal Frequency Division Multiplexing (OFDM) and Multiple Input Multiple Output (MIMO) data transmission.

In this paper various handoff schemes have been discussed and their performance are compared based on simulation results. Also a timer based priority handoff scheme is suggested which will work over a wide range of performance requirements. The timer value can be varied dynamically with traffic pattern which is expected to result in improvement in performance

3GPP Long Term Evolutionradioelectronics.com/info/cellulartelecomms/lte-long-term- evolution/3g-lte-basics.php [3G LTE introdution] [12] Holma, Harri; Toskala, Antti LTE for UMTS : OFDMA and SC-FDMA Based Radio Access 3GPP Long Term Evolution Long Term Evolution: A Technical Overview

Jeffrey G Andrews
Arunabha Ghosh
Rias Muhamed

Jeffrey G. Andrews, Arunabha Ghosh, Rias Muhamed, " Fundamentals of WiMAX Understanding Broadband Wireless Networking, " publisher Prentice Hall,pp. 496,Inc. 2007. [11] " 3GPP Long Term Evolution, " http://www.radioelectronics.com/info/cellulartelecomms/lte-long-term- evolution/3g-lte-basics.php [3G LTE introdution] [12] Holma, Harri; Toskala, Antti; " LTE for UMTS : OFDMA and SC-FDMA Based Radio Access, " Wiley, 2009 [13] " 3GPP Long Term Evolution, " http://www.radioelectronics.com/info/cellulartelecomms/lte-long-termevolution/lte-ofdm-ofdma-scfdma.php [3G LTE OFDMA and SC-FDMA principles] [14] " 3GPP Long Term Evolution, " http://www.radioelectronics.com/info/cellulartelecomms/lte-long-termevolution/lte-mimo.php [3G LTE MIMO principle] [15] " Long Term Evolution: A Technical Overview " Motorola Whitepaper http://business.motorola.com/experiencelte/pdf/LTETec hnicalOverview.pdf [An overall introduction of LTE technologies] [16] http://en.wikipedia.org/wiki/Home_Subscriber_Se rver [Including brief Home Subscriber Server introduction] [17] Zyren, Jim; " Overview of the Long Term Evolution Physical Layer, " Doc Num. 3GPPEVOLUTIONWP, Rev 0, 2007

IEEE Standard for Local and metropolitan area networks-Part 16:Air Interface for Fixed and Mobile Broadband Wireless Access Systems-Amendment 2:Physical and Medium Access Control Layers for Combined Fixed and Mobile Operation in Licensed Band and Corrigendum 1

IEEE 802.16e-2005,IEEE Standard for Local and metropolitan area networks-Part 16:Air Interface for Fixed and Mobile Broadband Wireless Access Systems-Amendment 2:Physical and Medium Access Control Layers for Combined Fixed and Mobile Operation in Licensed Band and Corrigendum 1, http://standards.ieee.org/getieee802/download/802.16e- 2005.pdf

4G Wireless Technology:When will it happen? What does it offer? " IEEE Asian Solid-State Circuits Conference

Bill Krenik

Bill Krenik " 4G Wireless Technology:When will it happen? What does it offer? " IEEE Asian Solid-State Circuits Conference November 3-5, 2008.

4G Wireless Technology: A Survey PaperNCNTE-2012

R Mayuri
Manish C R I T Fr
Navi Vashi
Mumbai

R. Mayuri, P. Manish " 4G Wireless Technology: A Survey Paper ". In: Proceedings of the National Conference "NCNTE-2012" at Fr. C.R.I.T., Vashi, Navi Mumbai, Feb. 24-25, 2012.

Source: https://www.researchgate.net/publication/265014886_4G_Wireless_Technology_A_Brief_Review

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