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WALCHAND INSTITUTE OF TECHNOLOGY

A PAPER PRESENTATION ON: 4G NETWORK Theme: Mobile, Wireless Communication Technologies and Services

By: ABBAS HASHMI ROSHAN AUTHANKAR

S.E. (C.S.E) S.E. (C.S.E)

abbas_hashmi2007@yahoo.co.in roshanauthankar@yahoo.com

ph. No.:9096265578 ph. No.:9096401214

At

Under Guidance of:

This paper focuses on the vision of 4G, its architecture and the extending horizons of 4Gnetwork.

Prof.L.M.R.J.Lobo

Abstract:-

4G is the acronym for fourth-generation wireless, the stage of broadband mobile communications

that will supersede the 3G. It is not defined by one standard, but rather represents a collection of technologies

and protocols enabling the highest throughput and lowest cost wireless network. 4G networks based on

packet radio technology represent a major change for the mobile industry. It will be a fully IP core integrated

system with wide area coverage and high throughput with high spectral efficiency. It uses the OFDM, UWB,

and MIMO wireless technology.

A 4G system is powered up with GSM services, GPRS, interactive medias-such as teleconferencing,

internet access, Wi-Max, and many more, and will be able to provide a comprehensive IP solution where

voice, data and streamed multimedia can be given to users on an “Anytime, Anywhere” basis, and at higher

data rates than ever.

Nevertheless, pioneer acknowledges that the future of 4G technology is by no means certain. 4G is a

way for the ultra-broadband mobile experience, along with highly efficient and economical devices and

technologies. Thus, we need to explorer our minds to understand it and make it more susceptible for

commercial basis.

’09

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Introduction:-

Since the first generation of so-called “analogue” mobile radio networks was created in 1980, the mobile

telephone has seen many upheavals. In 1991, with the appearance of GSM, second-generation (or 2G) mobile

telephony, it became a veritable phenomenon. Gradually, almost everyone started to have a mobile phone. 2002 saw

the arrival of UMTS, and 3G was born. To define a new generation of mobile systems that would see the light of

day by 2010, the notion of 4G was introduced in the early 2000s. The idea was to perpetuate the logic of replacing

one mobile generation with another every 10 years. The study of 4G examines drivers for network upgrades and the

technologies that will be used to improve network performance including MIMO, error correction, OFDMA,

scheduling and modulation, among others. If a new technology has interesting features, R&D endeavors to define

what is missing for it to be able to communicate with other wireless communication systems. An integrated

network-of-networks (i.e. All-IP network) is the vision for 4G mobile wireless systems architecture. This envisages

that users can benefit in several ways from this unified access platform. The advantages, however, cannot be seized

if we do not consider the dynamics and complexity in future environments. For instance, we believe that a model

based on mobility hints, cross-layer activity information, and application-specific data can contribute to an effective

network usage; what we need is a policy-based solution that can effectively expose context knowledge without a

huge overhead.

Diversity and heterogeneity in wireless systems evolution have placed the integration of hybrid mobile data

networks as an enormous barrier towards the success of seamless networking. Seamless roaming and connectivity to

highly integrated and heterogeneous networks is the key idea that springs from the 4G vision.

Rise of the 4G Network:-

Mobile networks have always focused on voice as the primary application, and that was certainly the case

for analog networks (first generation [1G]), Time Division Multiple Access (TDMA) networks (2G), and even Code

Division Multiple Access (CDMA) networks (3G). Now with the introduction of 4G networks, multimedia

applications will assume primary importance. One of the most interesting and compelling applications in this area is

mobile TV.

1G:-

The first generation of wireless mobile communications was based on analog signaling. Analog Systems,

implemented in North America, were known as Analog Mobile Phone Systems (AMPS), while systems

implemented in Europe and the rest of the world were typically identified as a variation of Total Access

Communication Systems (TACS). Analog systems were primarily based on circuit-switched technology and

designed for voice, not data.

2G:-

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The second generation (2G) of the wireless mobile network was based on low-band digital data signaling

and circuit switched technology. The most popular 2G wireless technology is known as Global Systems for Mobile

Communications. GSM technology is a combination of Frequency Division Multiple Access (FDMA) And Time

Division Multiple Access (TDMA). The first GSM systems used a 25MHz frequency Spectrum in the 900MHz

band. Today, GSM systems operate in the 900MHz and 1.8 GHz bands throughout the. While GSM technology was

developed in Europe, Code Division Multiple Access (CDMA) technology was developed in North America.

CDMA uses spread spectrum technology to break up speech into Small, digitized segments and encodes them to

identify each call. While GSM and other TDMA-based systems have become the dominant 2G wireless

technologies, CDMA technology is recognized as providing clearer voice quality with less background

noise, fewer dropped calls, enhanced security, greater reliability and greater network capacity. 2G wireless

technology can handle some data capabilities such as fax and short message service at the data rate of up to 9.6 kbps,

but it is not suitable for web browsing and multimedia applications.2Gsystem fueled with General Packet Radio

Services (GPRS) is identified as 2.5G, a stepping stone towards 3G.

Mobile

Data

<300 bps 9.6k - 64kbps(packet) 64kbps – 384kbps

2Mbps(indoor)

2 Mbps 20 Mbps(best

effort)

PSTN

Data

28.8kbps 64kbps ~1 Mbps(flat rate) ~20Mbps?

Growing stage

Analog

AMPS, NMT,NTT…. (1st generation)

Digital

GSM, PDC, IS-95…. (2nd generation)

4th generation

IMT-2000 (3rd generation)

‘80s ‘90s 2000s

Initial stage

Expansion stage

Mature stage

(Fig 1: Evolutions of Mobile Systems with respect to time)

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3G:-

Third Generation (3G) mobile devices and services transform wireless communications into on-line, real-

time connectivity. 3G wireless technology allows an individual to have immediate access to location-specific

services that offer information on demand. The concept of 3G wireless technology represents a shift from voice-

centric services to multimedia-oriented (voice, data, video, fax) services. 3G wireless technology represents the

convergence of various 2G wireless telecommunications systems into a single global system that includes both

terrestrial and satellite components. One of the most important aspects of 3G wireless technology is its ability to

unify existing cellular standards, such as CDMA, GSM, and TDMA, under one umbrella. Subscribers are likely to

access 3G wireless services initially via dual band terminal devices. W-CDMA networks will be used for high-

capacity applications and 2G digital wireless systems will be used for voice calls. 3G wireless networks consist of a

Radio Access Network (RAN) and a core network. The core network consists of a packet-switched domain, which

provide the same functionality that they provide in a GPRS system, and a circuit-switched domain, which includes

3G MSC for switching of voice calls. The access network provides a core network technology independent access

for mobile terminals to different types of core networks and network services. The implementation of 3G wireless

systems raises several critical issues, such as the successful backward compatibility to air interfaces as well as to

deployed infrastructures.

Rise of the 4G Network: Enabling the Internet Everywhere Experience

Mobile networks have always focused on voice as the primary application, and that was certainly the case

for analog networks [1G], Time Division Multiple Access networks (2G), and even Code Division Multiple Access

networks (3G). Now with the introduction of 4G networks, multimedia applications will assume primary

importance. One of the most interesting and compelling applications in this area is mobile TV. Given the enormous

success of mobile services and the popularity of TV, this combination is a natural one. Variations on this theme

include broadcast, multicast, and unicast of both real-time and stored content. Enabling these types of services on a

broad scale clearly introduces some significant challenges, including latency, throughput, and network capacity.

Characteristics of 4G mobile networks:-

The study examines drivers for network upgrades and the technologies that will be used to improve

network performance including MIMO, error correction, OFDMA, scheduling and modulation, among others. They

must be engineered from the beginning to be all-IP end-to-end-representing a major change from the circuit-

switched architectures that have dominated in the past and an essential step toward enabling multimedia

applications. We will see a move away from closed RAN architectures and toward open systems with

interoperability. The Internet has always been based on the concept of open systems, and this concept is being

introduced in the mobile world. Base stations will be built by RAN vendors and mobile gateways will be built by IP

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vendors. Open interfaces will allow network integrators to bring these pieces together to build a robust mobile

network.

The advantages of 4G:-

New radio technologies can be more easily introduced into the network. A spectrally efficient system (in

bits/s/Hz and bits/s/Hz/site), High network capacity: more simultaneous users per cell,A nominal data rate of 100

Mbit/s while the client physically moves at high speeds relative to the station, and 1 Gbit/s while client and station

are in relatively fixed positions as defined by the ITU-R, Smooth handoff across heterogeneous networks, Seamless

connectivity and global roaming across multiple networks, High quality of service for next generation multimedia

support (real time audio, high speed data, HDTV video content, mobile TV, audio, high speed data, HDTV video

content, mobile TV, etc)Interoperability with existing wireless standards, and Support for interactive multimedia,

voice, streaming video, Internet, and other broadband services Seamless switching, and a variety of Quality of Service

driven services Better scheduling and call admission control techniques.

In summary, the 4G system shares and utilizes network resources to meet the minimal requirements of all the 4G

enabled users.

ARCHITECTURE:-

The overall 4G architecture discussed in this paper is IPv6-based, supporting seamless mobility between

different access technologies. Mobility is a substantial problem in such environment, because inter-technology

handovers have to be supported. In our case, we targeted Ethernet (802.3) for wired access; Wi-Fi (802.11b) for

wireless LAN access; and W-CDMA - the radio interface of UMTS- for cellular access (Fig. 1). With this diversity,

mobility cannot be simply handled by the lower layers, but needs to be implemented at the network layer. An "IPv6-

based"mechanism has to be used for interworking, and no technology-internal mechanisms for handover, neither on

the wireless LAN nor on other technology, can be used. So, in fact no mobility mechanisms are supported in the W-

CDMA cells, but instead the same IP protocol supports the movement between cells. Similarly, the 802.11 nodes are

only in BSS modes, and will not create an ESS: IPv6 mobility will handle handover between cells.

Summarizing Fig 2, the key entities are:

-A user - a person or company with a service level agreement (SLA) contracted with an operator for a specific set

of services. Our architecture is concerned with user mobility, meaning that access is granted to users, not to specific

terminals.

-A MT (Mobile Terminal) - a terminal from where the user accesses services. Our network concept supports

terminal portability, which means that a terminal may be shared among several users, although not at the same time.

-AR (Access Router) - the point of attachment to the network, which takes the name of RG (Radio Gateway) - for wireless access (WCDMA or 802.11).

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-PA (Paging Agent) - entity responsible for locating the MT when it is in "idle mode" while there are packets to be delivered to it .

-QoS Broker - entity responsible of managing one or more ARs/AGs, controlling user access and access rights according to the information provided by the AAAC System.

-NMS (Network Management System) - the entity responsible for managing and guaranteeing availability of resources in the Core Network, and overall network management and control.

This network is capable of supporting multiple functions:

•Inter-operator information interchanges for multiple-operator scenarios;

•Confidentiality both of user traffic and of the network control information;

•Mobility of users across multiple terminals;

•Mobility of terminals across multiple technologies;

•QoS levels guaranties to traffic flows (aggregates);

•Monitoring and measurement functions, to collect information about network and service usage;

•Paging across multiple networks to ensure continuous accessibility of users.

We presented an architecture for supporting end-to-end QoS. This QoS architecture is able to support

multi-service, multi-operator environments, handling complex multimedia services, with per user and per service

(Fig 2: General Network Architecture)

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differentiation, and integrating mobility and AAAC aspects. It seems to provide a simple, flexible, QoS architecture

able to support multimedia service provision for future 4G networks. Security will be an essential part of a 4G

network architecture. The Internet Everywhere Experience will allow the mobile subscriber to access a whole host

of Internet related services, but with that flexibility comes the risk associated with Internet connectivity. Next

generation solutions must have a carefully thought out security approach that protects both the network and the

subscriber.

The Technologies Hired For 4G:-

OFDM: To exploit the frequency selective channel property

Orthogonal Frequency Division Multiplexing (OFDM) and OFD Multiple Access (OFDMA). OFDM

transmits data by splitting radio signals that are broadcast simultaneously over different frequencies. OFDMA, used

in mobile WiMax, also provides signals that are immune to interference and can support high data rates. It is said to

use power more efficiently than 3G systems while using smaller amplifiers and antennas. This all translates to

expected lower equipment costs for wireless carriers. The beauty of OFDM lies in its simplicity. One trick of the

trade that makes OFDM transmitters low cost is the ability to implement the mapping of bits to unique carriers via

the use of IFFT. Unlike CDMA, OFDM receiver collects signal energy in frequency domain, thus it is ableto protect

energy loss at frequency domain. In a relatively slow time-varying channel, it is possible to significantly enhance the

capacity by adapting the data rate per subcarrier according to SNR of that particular subcarrier.

OFDM is more resistant to frequency selective fading than single carrier systems. The OFDM transmitter

simplifies the channel effect, thus a simpler receiver structure is enough for recovering transmitted data. If we use

BW=2R

+R

+R

+R -2R/3

-R/4 -3R/4

BW=2R

BW=2R

BW=2R

BW=3R/2

BW=4R/2

-R

-R

-R

-R +R +R

+R

+R/3 -R/3 2R/3 R/3 -R/3

+R/4 3R/4

N=1

N=2

SC BW=R

N=2

SC BW=2R/3

-R

-R

(Fig 3: Spectrum Efficiency of OFDM Compared to Conventional FDM)

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coherent modulation schemes, then very simple channel estimation (and/or equalization) is needed, on the other

hand, we need no channel estimator if differential modulation schemes are used. The orthogonality preservation

procedures in OFDM are much simpler compared to CDMA or TDMA techniques even in very severe multipath

conditions. OFDM can be used for high-speed multimedia applications with lower service cost. OFDM can support

dynamic packet access. Single frequency networks are possible in OFDM, which is especially attractive for

broadcast applications. The increasing requirement of data rate and quality of service for wireless communications

calls for new techniques to increase spectrum efficiency and to improve link quality. OFDM has proved to be very

effective in mitigating adverse multipath effects of a broadband wireless channel. Multiple Input Multiple Output

(MIMO) technique has proved its potential by increasing the link capacity significantly via spatial multiplexing and

improving the link capacity via space-time coding. Numerous research works are being published on MIMO

enhanced OFDM based wireless systems. It is obvious that MIMO technique will be effectively used with OFDM

based systems for providing mobile multimedia in future with reasonable data rate and quality of service (in terms

bit error rate, BER).

Orthogonality and OFDM:-

The use of orthogonal subcarriers would allow the subcarriers’ spectra to overlap, thus increasing the

spectral efficiency. As long as orthogonality is maintained, it is still possible to recover the individual subcarriers’

signals despite their overlapping spectrums. If the dot product of two deterministic signals is equal to zero, these

signals are said to be orthogonal to each other.

Orthogonality can also be viewed from the standpoint of stochastic processes. If two random processes are

uncorrelated, then they are orthogonal. Given the random nature of signals in a communications system, this

probabilistic view of orthogonality provides an intuitive understanding of the implications of orthogonality in

OFDM. If the input signal has some energy at a cer tain frequency, there will be a peak in the correlation of the input

signal and the basis sinusoid that is at that corresponding frequency. This transform is used at the OFDM transmitter

to map an input signal onto a set of orthogonal subcarriers, i.e., the orthogonal basis functions of the DFT. Similarly,

the transform is used again at the OFDM receiver to process the received subcarriers. The signals from the

subcarriers are then combined to form an estimate of the source signal from the transmitter. The orthogonal and

uncorrelated nature of the subcarriers is exploited in OFDM with powerful results. Since the basis functions of the

DFT are uncorrelated, the correlation performed in the DFT for a given subcarrier only sees energy for that

corresponding subcarrier. The energy from other subcarriers does not contribute because it is uncorrelated. This

separation of signal energy is the reason that the OFDM subcarriers’ spectrumscan overlap without causing

interference.

MIMO:- To attain ultra high spectral efficiency

MIMO uses signal multiplexing between multiple transmitting antennas (spacemultiplex) and time or

frequency. It is well suited to OFDM, as it is possible to process Independent time symbols as soon as the OFDM

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waveform is correctly designed for the channel. This aspect of OFDM greatly simplifies processing. The signal

transmitted by m antennas is received by n antennas. Processing of the received signals may deliver several

performance improvements: range, quality of received signal and spectrum efficiency. In principle, MIMO is more

efficient when many multiple path signals are received. The performance in cellular deployments is still subject to

research and simulations. However, it is generally admitted that the gain in spectrum efficiency is directly related to

the minimum number of antennas in the link.

Spatial multiplexing involves deploying multiple

antennas at the transmitter and at the receiver. Independent

streams can then be transmitted simultaneously from all the

antennas. This increases the data rate into multiple folds

with the number equal to minimum of the number of

transmit and receive antennas. This is called MIMO (as a branch of intelligent antenna).

Multiple-input multiple-output (MIMO) wireless LAN technology supports two or more radio signals in a

single radio channel, increasing bandwidth. MIMO does this by using multiplexing. MIMO is expected to support

data rates as high as 315Mbps in 36MHz of spectrum.

WiMAX:-

Fourth-generation network technology is not so much a new modulation technology as it is a way of

architecting networks. These networks are using a variety of mobile packet radio technologies along with Wi-Fi to

offer a ubiquitous broadband experience for the mobile subscriber, the all new WiMax. More recently, the topic of

WiMAX, a particular 4G technology which promises to deliver 70 Mb/s data speeds over a 50 km radius has been

the focus of much attention and hype. WiMAX has been at the forefront of the move to all-IP end-to-end networks

based on open systems, and this technology is already being deployed in fixed wireless applications and OFDMA

and MIMO are seen as critical ingredients. Mobile WiMAX is an IEEE specification also known as 802.16e and

designed to support as high as 12Mbps data-transmission speeds. It uses OFDMA and is the next-generation

technology.

The technologies used in WiMAX such as Orthogonal Frequency Division Multiple Access (OFDMA) and

Multiple-Input Multiple-Output (MIMO) allow higher transmission efficiency per available spectrum. These

technologies also support more powerful and effective resource management. Sprint, a leading name in the field,

took the wraps off its Xohm wireless network in Baltimore, which uses Samsung WiMAX technology on the 2.5

GHz spectrum, offers faster download speeds than current 3G wireless networks. For instance, while AT&T's fastest

HSDPA network claims speeds up to 3.6Mbps, Xohm promises even more.

(Fig 4: A MOMO having transmitters and receivers antennas)

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IEEE 802.11 standard:

IEEE 802.11 is a set of standards implementing WLAN

computer communication in the 2.4, 3.6 and 5 GHz spectrum

bands. They are maintained by the IEEE LAN/MAN Standards

Committee IEEE 802.2.

802.11b: Known as Wi-Fi, 802.11b is currently the

leading market standard for wireless local-area networking. This

version transfers data at 11 Mbits/s at distances of up to 300 ft. It operates at 2.4 GHz, so it shares spectrum with

cordless phones, Bluetooth products, and many other unlicensed devices. It uses the complementary-code-keying

(CCK) modulation scheme.

802.11a: Also known as Wi-Fi, 802.11a has yet to be

widely accepted in the industry. It operates in the 5-GHz range at

a 54-Mbit/s data rate and uses orthogonal-frequency-division-

Multiplexing (OFDM) modulation, which is a faster data-

transmission scheme than CCK. But it's not backward-compatible

with 802.11b.

802.11g: Like 802.11b, this version uses OFDM. It runs

at 2.4 GHz and is expected to operate at 54 Mbits/s when it becomes an official standard, which the IEEE expects by

July. It is backward-compatible with 802.11b. The "g" standard is still in the draft stage, but judging by the products

that appeared at the recent International Consumer Electronics

Show, "g" will likely be the standard of choice for most wireless

network manufacturers. Some vendors are covering their bets by

using chips that combine 802.11a, b, and g for 54-Mbit/s data

rates over the 2.4- and 5.2-GHz bands. At least one company has

announced a combination Wi- Fi/Bluetooth chip. Motorola,

Nokia, and Samsung, among other manufacturers, plan to

integrate Wi-Fi into their cell phones.

802.11n: It is a proposed amendment which improves

upon the previous 802.11 standards by adding multiple-input multiple-output (MIMO) and many other newer

features. The TGn workgroup is not expected to finalize the amendment until December 2009. Enterprises, however,

have already begun migrating to 802.11n networks based on Draft 2 of the 802.11n proposal.

Release date October 1999

Op. frequency 2.4 GHz

Throughput (Typ) 4.5 Mbit/s

Net bit rate 11 Mbit/s

Range indoor ~38 m

Release date October,1999

Op. frequency 5 GHz

Throughput (Typ) 23 Mbit/s

Net bit rate 54 Mbit/s

Gross bit rate 72 Mbit/s

Range indoor ~35 m

Release date June 2003

Op. frequency 2.4 GHz

Throughput (Typ) 19 Mbit/s

Net bit rate 54 Mbit/s

Gross bit rate 72 Mbit/s

Range indoor ~38 m

(Table 1: 802.11b)

(Table 2: 802.11a)

(Table 3: 802.11g)

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A common strategy for many businesses is to set up 802.11n networks to support existing 802.11b and 802.11g

client devices and while gradually moving to 802.11n clients as

part of new equipment purchases.

Applications:-

4G will open the door to a variety of mobile apps-

Some analysts agree there is no “killer app” for 4G

today. But with the mobile speeds being proposed with 4G,

customers could participate in live video conferences while on the

go or access bandwidth-intensive applications.

Forrester’s Pierce says the real jewel of 4G will be its ability to prioritize business traffic and offer

customers classes of service that they have come to expect from other business-grade IP services.

At the present rates of 15-30 Mbit/s, 4G is capable of providing users with streaming high-definition

television, but the typical cellphone's or smartphone's 2" to 3" screen is a far cry from the big-screen televisions and

video monitors that got high-definition resolutions first and which suffer from noticeable pixelation much more than

the typical 2" to 3" screen. A cellphone may transmit video to a larger monitor, however. At rates of 100 Mbit/s, the

content of a DVD-5 (for example a movie), can be downloaded within about 5 minutes for offline access.

4G is being developed to accommodate the quality of service (QoS) and rate requirements set by

forthcoming applications like wireless broadband access, Multimedia Messaging Service (MMS), video chat, mobile

TV, HDTV content, Digital Video Broadcasting (DVB), minimal service like voice and data, and other streaming

services for "anytime-anywhere".

Mobile TV is just one example of the Internet Everywhere experience. At the heart of this experience are

all-IP end-to-end mobile networks based on open systems. These networks will emerge from several different

sources. WiMAX has emerged out of the IEEE 802.16 committee, Universal Mobile Telecommunications Service

(UMTS) SAE/LTE out of the Third-Generation Partnership Project (3GPP), and 3GPP2 is working on a Radio

Access Network (RAN) evolution for CDMA. It is expected that all three of these technologies, along with.

Limitations of 4G:-

Although the concept of 4G communications shows much promise, there are still limitations that must be

addressed. One major limitation is operating area. Although 2G networks are becoming more ubiquitous, there are

still many areas not served. Rural areas and many buildings in metropolitan areas are not being served well by

existing wireless networks. This limitation of today’s networks will carry over into future generations of wireless

systems.

Release date 2009

Op. frequency 5 GHz and/or 2.4 GHz

Throughput (Type) Unknown

Net bit rate 600 Mbit/s(using 440 MHz channels)

Range indoor ~70 m

(Table 4: 802.11n)

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The hype that is being created by 3G networks is giving the general public unrealistic expectations of

always on, always available, anywhere, anytime communications. The public must realize that although high-speed

data communications will be delivered, it will not be equivalent to the wired Internet – at least not at first. If

measures are not taken now to correct perception issues, when 3G and later 4G services are deployed, there may be

a great deal of disappointment associated with the deployment of the technology, and perceptions could become

negative. If this were to happen, neither 3G nor 4G may realize its full potential. Another limitation is cost. The

equipment required to implement a next generation network is still very expensive. Carriers and providers have to

plan carefully to make sure that expenses are kept realistic. Also, a 4G handset will be required to transmit on the

appropriate band anywhere in the world. This implies five or more conventional power amplifiers for a broadband

cellular RF interface seeking to cover all 10 LTE bands – adding several pounds to the bill of materials.

A further issue is that 3G and 4G standards use complex modulation schemes that increase data throughput in the

operators’ spectrum but have a dramatic impact on the power consumption of RF transmitters and hence handset

battery life.

Conclusions:-

In this paper, we presented a heterogeneous IP-based wireless access network handoff architecture that

supports uplink and downlink traffic services with different bandwidth. This IP-based network uses the Internet

standard, hierarchical mobile IP to support mobility of mobile nodes. We also illustrated the issues in the integration

of cellular networks with 802.11 such as WLAN, and a multipath handoff scheme. It provides two end-to-end

mobility supports to utilize disparity of available bandwidths in wireless cells improving system capacity and getting

transmission efficiency. For future work, the performance of the proposed architecture and algorithm will also be

evaluated through simulations.

4G networks will eventually deliver on all the promises. At times, it seems that technological advances are

being made on a daily basis. These advances will make high speed data/voice-over-Internet-protocol (VoIP)

networks a reality. This evolution will give the general public as well as the public safety community amazing

functionality from the convenience of a single handheld device.

References:

[1]Pei L, Zhifeng T, Zinan L, Erkip E, Panwar S. Cooperative Wireless Communications: a Cross-Layer Approach.

IEEE Wireless Communications, vol. 13, no. 4, pp. 84-92, August, 2006.

[3]Frattasi S, Fathi H, Fitzek FHP, Katz M, Prasad R. Defining 4G Technology from the User Perspective. IEEE

Network Magazine, vol. 20, no. 1, pp. 35-41, January-February, 2006.

[4]IEEE 802.16 Broadband Wireless Access Working Group. Tapped Delay Line Channel Model and Parameter

Settings for Link-Level 802.16 Simulations. June, 2006.