majorprojectcaiomorel.pdf

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Tlcom SudParis

VAP EOE

Research on new technologies for 5G:

bibliographic study about millimeter waves

Caio Morel Nogueira

January 2014


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Contents

1 Introduction p. 4

2 Generations of Mobile Wireless Technology p. 6

2.1 1G . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . p. 6

2.2 2G . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . p. 6

2.2.1 2.5 - GPRS (General Packet Radio Service) . . . . . . . . . . . p. 7

2.2.2 2.75G - EDGE (Enhanced Data rates for GSM Evolution) . . . p. 7

2.3 3G . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . p. 8

2.3.1 3.5 G - HSDPA (High-Speed Downlink Packet Access) . . . . . p.8

2.3.2 3.75 G - HSUPA (High Speed Uplink Packet Access) . . . . . . p.9

2.4 4G . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . p. 9

3 5G p.12

3.1 Migration from 4G . . . . . . . . . . . . . . . . . . . . . . . . . . . . . p. 1 2

3.2 Key terms and Features of 5G technology . . . . . . . . . . . . . . . . . p. 13

4 Radio Over Fiber (RoF) p.16

4.1 Advantages of RoF . . . . . . . . . . . . . . . . . . . . . . . . . . . . . p. 1 7

4.2 Disadvantages of RoF . . . . . . . . . . . . . . . . . . . . . . . . . . . . p. 17

5 Basic concepts of Millimeter Waves p.19

5.1 Characteristics of the 60 GHz band . . . . . . . . . . . . . . . . . . . . p. 20

5.1.1 Antenna . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . p. 21


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5.1.2 Channel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . p. 23

5.1.3 Losses from the vegetation . . . . . . . . . . . . . . . . . . . . . p. 23

5.1.4 Losses due to rain . . . . . . . . . . . . . . . . . . . . . . . . . . p. 2 5

5.1.5 Losses due to water vapor and oxygen . . . . . . . . . . . . . . p. 26

5.1.6 Loss due obstacles . . . . . . . . . . . . . . . . . . . . . . . . . p. 2 7

5.2 Regulations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . p. 28

6 Modulation and signal detection systems in RoF p.29

6.1 Evolution and trend technology of RoF . . . . . . . . . . . . . . . . . . p. 30

7 Conclusion p.32

8 Bibliography p.33


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1 Introduction

With the advent of mobile technologies, communication is now an element which is

always evolving. In addition, with the improvement of technologies and research nowadays

its possible to use communication for more than just voice, for example now we can usemobile communication for video and live streaming while the host are moving. Various

researches are going to improve this technology and this project was developed to describe

and explain some features and some new technologies which are been studied and will

be used in the next generation of mobile telecommunications, the 5G. Also, nowadays

users require a permanent wireless connection from mobile devices to a high-speed data

transmission without contact wired access points . However, wireless services do not

have enough bandwidth to provide high transmission capacity. Currently , the Ethernet

networks provide up to 1 Gb for wireless systems.

For transmissions at speeds of multiGbps , is studied possible deployment scenarios

of wireless systems operating at extremely high carrier frequencies ( EHF , extremely

highfrequency ) , which range between 30 and 300 GHz , this frequency range is known

as the band are studied millimeter wave (MMW) , which has more bandwidth in the GHz

range of North and South Korea frequency of 60 GHz has a width of 7 GHz band , in

the range of 57 - 64 GHz , and in Japan , the range is 59-66 GHz and this details will be

seen in previous chapters . Consequently , the bandwidth of wireless systems operatingaround 60 GHz are being studied as a solution for the lack of available bandwidth and to

fill the requirements related to data rate of the 5G technology.

For the development of systems operating in bands MMW is possible to see problems,

such as the cost of the electronic equipment used and the increase of the base stations

should be implemented . Moreover, the MMW signal transmission needs higher power due

to the high losses in the wireless medium , which creates drawbacks in the implementation

. It is one of the most promising solutions for access networks . The advantages of using

fiber optics to transmit signals as a means of MMW is its immunity to electromagnetic

interference , the large transmission capacity , propagation losses between 0.2-0.5 dB /


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km, depending on the type of fiber used and the wavelength of operation , these being very

low values with respect to copper and air . Moreover, the RoF systems operating in the

MMW band require small cells due to the short propagation distance , in fact , the radio

links MMW are being considered for the implementation of micro systems or cell peak

broadband access networks and internal wireless networks. The convergence of wireless

communications and optical fiber systems have become a promising technique to provide

services for broadband wireless access , in a range of applications including access network

solutions in extending coverage and capacity radio networks . In this sense, the RoF

systems provide adequate synergy between optical and radio , allowing the fusion of these

technologies, which have been instrumental in the development of telecommunications

, in which wireless networks and fiber are requiring updates, in order to respond to theexponential increase in bandwidth demand of modern information societies . It is expected

that the next generation access networks ensure the provision of broadband services and

multimedia applications to end users anytime , anywhere.


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2 Generations of Mobile WirelessTechnology

2.1 1G

The first generation of mobile communication made use of analog radio signals. In

terms of connection quality, 1G is worse than its successors. It has unreliable handoff, low

capacity, poor voice links, and no security at all since voice calls were played back in radio

towers, making these calls susceptible to be heard by third parties. However it has a few

other advantages if we compare to the second generation. The digital signal of 2G are very

reliant on location and proximity. So for large distances, the 2G signal may not be strong

enough to reach it and the 1G signal, even with a worse quality, can reach longer distances.For the technologies used by the 1G system we have frequency modulation. The mains

reasons for the development of the second generation of mobile communications was the

low capacity of 1G, the high demand of the market and the existence of several standards.

The standards of 1G were used in various countries, for example the NMT (Nordic Mobile

Telephone), for the Nordic countries, Eastern Europe and Russia, the AMPS (Advanced

Mobile Phone System) for the United States, the TACS (Total Access Communications

System) for the United Kingdom, C-Netz in West Germany, the Radiocom 2000 in France

and the RTMI in Italy.

2.2 2G

2G is the second generation of wireless telecommunication and its the mark of the

transition between analog signals for digital signals. In this generation the use of sms to

send data started to be available. It first appeared with the standard GSM which were

commercially launched in Finland by Radiolinja (now part of Elisa Oyj) in 1991. TheGSM service is used by over 2 billion people in more than 212 countries and territories.


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About the technologies used in 2G we can divide in Time Division Multiple Access

(TDMA) based and Code Division Multiple Access (CDMA) based standards depending

on the type of multiplexing used. Also, the 2G technology uses a CODEC (Compression-

Decompression Algorithm) to compress and multiplex digital voice data and with this a

2G network can pack more calls per amount of bandwidth than a 1G network. Another

advantage over 1G is that the 2G cellphones were usually smaller because they emitted

less radio power. And since the 2G uses digital signals it has a lot of other advantages

like it consume less battery power, so it helps mobile batteries to last long, the digital

coding improves the voice clarity and reduces noise and the digital encryption has provided

secrecy and safety to the data and voice calls.

2.2.1 2.5 - GPRS (General Packet Radio Service)

2.5G, is a cellular wireless technology developed in between the 2G, the 3G. This 2G-

systems have implemented a packet switched domain to complement the circuit switched

domain. Its important to remark that the term "2.5G" is an informal term, created only

for marketing purposes, so it was not an officially defined standards. The GPRS system

could achieve data rates between 56 kbit/s and 115 kbit/s and it can be used for several

services like Wireless Application Protocol (WAP) access, Multimedia Messaging Service

(MMS), and for Internet communication services. The data transfer of a GPRS is charged

per megabyte of traffic while the data communication in a system with circuit switching is

billed per minute of connection time. 2.5G networks may support services such as WAP,

MMS, SMS mobile games, and search and directory.

2.2.2 2.75G - EDGE (Enhanced Data rates for GSM Evolution)

EDGE is a digital mobile phone technology which gives an improvement to the 2G and

the 2.5G General Packet Radio Service (GPRS) networks. This technology is a extended

version of GSM networks. This technology permit clear and fast transmission of data and

information and was invented and introduced by Cingular (AT& T). Its main advantages

over the GSM its the flexibility to carry packet switch data and circuit switch data and

the advantages over the GPRS is that its transfers data in only a fewer seconds. Another

advantage of using EDGE technology is that its not necessary to install any additional

hardware and software in order to make use of this technology.


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2.3 3G

3G is the third generation of mobile telecommunication and its based on the Inter-

national Telecommunication Union (ITU) family of standards under the International

Mobile Telecommunications programme, IMT-2000. This technology permit several more

advanced services than its predecessor while it achieves much bigger capacity of its net-

work because of its high spectral efficiency. Services include wide area wireless voice

telephony, video calls, broadband wireless data, mobile television, GPS (global position-

ing system), all in a mobile environment.As it was explained before, the basic reason for

the development of 3G Technology is to achieve fast data transfer rates, more coverage

and growth with minimum investment.

The 3G uses as radio technologies CDMA, TDMA and FDMA. CDMA holds for

IMT-DS (direct spread), IMT-MC (multi carrier). TDMA accounts for IMTTC (time

code), IMT-SC (single carrier). FDMA has only one radio interface known as IMT-FC or

frequency code.

To compare the 2G with the 3G consider the figure 1

Figure 1: Comparative between 2G and 3G

As we can see on figure 1, the development of the 3G technology gives a big improve-

ment of data rates and also several new services.

2.3.1 3.5 G - HSDPA (High-Speed Downlink Packet Access)

This technology gives an evolution for UMTS-based 3G networks and it was devel-

oped to achieve higher data transfer speeds. Its a packet-based data service in W-CDMA

downlink with data transmission up to 8-10 Mbit/s (and 20 Mbit/s for MIMO systems)

over a 5MHz bandwidth in WCDMA downlink. HSDPA implementations includes Adap-tive Modulation and Coding (AMC), Multiple-Input Multiple-Output (MIMO), Hybrid

Automatic Request (HARQ), fast cell search, and advanced receiver design.


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2.3.2 3.75 G - HSUPA (High Speed Uplink Packet Access)

The 3.75G refer to the technologies beyond 3G mobile technologies. High Speed

Uplink Packet Access (HSUPA) is a UMTS / WCDMA uplink evolution technology. The

HSUPA technology is related to HSDPA and the two are complimentary. HSUPA will

enhance advanced person-to-person data applications with higher and symmetric data

rates, like mobile e-mail and real-time person-to-person gaming. Traditional business

applications along with many consumer applications will benefit from enhanced uplink

speed. HSUPA will initially boost the UMTS / WCDMA uplink up to 1.4Mbps and in

later releases up to 5.8Mbps.

2.4 4G

4G is the fourth generation of mobile telecommunications defined by the ITU which

has created the requirements that must be achieved to be considered a technology for 4G

as we can see next:

Be based on an all-IP packet switched network.

Have peak data rates of up to approximately 100 Mbit/s for high mobility such

as mobile access and up to approximately 1 Gbit/s for low mobility such as no-

madic/local wireless access.

Be able to dynamically share and use the network resources to support more simul-

taneous users per cell.

Using scalable channel bandwidths of 5 to 20 MHz, optionally up to 40 MHz.

Have peak link spectral efficiency of 15 bit/s/Hz in the downlink, and 6.75 bit/s/Hz

in the uplink (meaning that 1 Gbit/s in the downlink should be possible over less

than 67 MHz bandwidth).

System spectral efficiency of up to 3 bit/s/Hz/cell in the downlink and 2.25 bit/s/Hz/cell

for indoor usage.

Smooth handovers across heterogeneous networks.

The ability to offer high quality of service for next generation multimedia support.


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About the requirements, we can conclude that for the 4G technology we have basically

an improvement on data rates and improvement of spectral efficiency. However nowadays

many services are offers with a minimum implementation of 4G technology or with just

an improvement of 3G technology. 3 of these technology will be analyzed:

LTE

Developed by the 3rd generation partnership project (3GPP) this technology has as

main characteristics: Downlink with OFDM access or multiple carriers and Uplink with

single-carrier FDMA. Alto, LTE support multi-antennas technology as multiple-input

multiple-output (MIMO) and has been adopted by AT&T, T-Mobile, and Sprint. The

current work on LTE Advanced will result in real 4G speeds and bit rates.

HSPA+

Also developed by 3GPP, this technology is based on W-CDMA and uses MIMO. The

current rates are 2 to 10 Mbps, but it can offer 22 to 168 Mbps. It was adopter by AT&T

and T-Mobile and AT&T claims that HSPA+ can deliver speeds four to 10 times higher

than 3G speeds.

WiMax

This technology was developed to be fixed wireless system (IEEE 802.16a, b, c, and

d), but also it has a standard for mobility support (IEEE 802.16e). WiMax is based on

OFDM (multiple carriers) and support the use of MIMO. The main advantages are high

bandwidth and great coverage (approximately 30 miles from the antenna).

On figure 2 we can see some characteristics of each technology.

Figure 2: Characteristics of 4G technology

To conclude this first chapter we can see a resume of the evolution of mobile telecom-

munications on figure 3.


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Figure 3: Evolution of mobile telecommunications


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3 5G

5G (5th generation mobile networks or 5th generation wireless systems) is being de-

veloped to be a new revolution in mobile market. If we observe the evolution of mobile

communication on figure 3 we can see that a new generation is created in each 10 years andthe 5th generation will probably start in 2020 (Samsung has already realized some tests in

this technology). Currently 5G is not a term officially used for any particular specification

or in any official document yet made public by telecommunication companies. The lack

of an official standard makes the 5G have limitless possibilities. The 5G technology will

be a new technology that makes users able to access different Radio Access Technologies

(RATs) using one mobile. 5G has been proposed to assemble the existing wireless and

wired communication techniques into an all IP (Internet Protocol) high performance world

wide network. The 5th wireless mobile multimedia internet networks can be completed

wireless communication without limitation, which bring us perfect real world wireless,

World Wide Wireless Web (WWWW). WWWW is an attempt to make the subscriber to

experiment the great quality and quick access of internet, dynamic movement, favorable

Bit Error Ratio (BER) and great security as on wired communications in their wireless

communication devices. The 5G technologies include all type of advanced features and it

will be in huge demand in near future. 5G technology has extraordinary data capabilities

and has ability to tie together unrestricted call volumes and infinite data broadcast within

latest mobile operating system.

3.1 Migration from 4G

During the transition between two generation, its necessary to analyze what is neces-

sary to realize this migration. So in this section, some challenges will be discussed.

Multi mode user terminals: As a feature of 5G is necessary to design a single user

terminal to operate in different wireless networks. By doing this some restrictions as the

size of the device, its cost and power utilization will be mitigated. This trouble can be


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solved by using software radio approach.

Security: Its necessary to design a reconfigurable, adaptive and lightweight protec-

tion mechanisms.

Network infrastructure and QoS support: Integrating the current non-IP and

IP-based systems and providing QoS assurance for end-to-end services that engage differ-

ent systems is a challenge.

Charging and Billing: It is hard to accumulate and, handle the consumers account

information from many service providers. In the same way consumers billing is also a

difficult task.

Attacks on Application Level: Software applications which will offer an new

feature to the consumer but will commence new bugs.

3.2 Key terms and Features of 5G technology

In this section the key terms of the 5G technology and the its features will be presented:

(por referencia 5G Technology of Mobile Communication: A Survey)

Key terms of 5g Technology:

5G is a completed wireless communication with almost no limitation; somehow

people called it REAL wireless world

Additional features such as Multimedia Newspapers, also to watch T.V programs

with the clarity as to that of an HD T.V.

We can send Data much faster than that of the previous generations.

5G will bring almost perfect real world wireless or called WWWW: World Wide

Wireless Web

Using of 60 Ghz band

Real wireless world with no more limitation to access and zone issues.

Wearable devices with AI capabilities

Internet protocol version 6 (IPv6), where a visiting care-of mobile IP address is

assigned according to location and the connected network.


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One unified global standard.

Pervasive networks providing ubiquitous computing: The user can simultaneously

be connected to several wireless access technologies and seamlessly move betweenthem. These access technologies can be a 2.5G, 3G, 4G or 5G mobile networks, Wi-

Fi, PAN or any other future access technology. In 5G, the concept may be further

developed into multiple concurrent data transfer paths.

Cognitive radio technology, also known as smartradio: allowing different radio tech-

nologies to share the same spectrum efficiently by adaptively finding unused spec-

trum and adapting the transmission scheme to the requirements of the technolo-

gies currently sharing the spectrum. This dynamic radio resource management isachieved in a distributed fashion, and relies on software defined radio. See also the

IEEE 802.22 standard for Wireless Regional Area Networks.

High altitude stratospheric platform station (HAPS) systems.

Features of 5G Technology:

5G technology will offer high resolution for crazy cell phone user and bi-directional

large bandwidth shaping.

The advanced billing interfaces of 5G technology will makes it more attractive and

effective.

5G technology will provide subscriber supervision tools for fast action.

The high quality services of 5G technology based on Policy to avoid error.

5G technology will provide large broadcasting of data in Gigabit which supporting

almost 65,000 connections.

5G technology will offer transporter class gateway with unparalleled consistency.

The traffic statistics by 5G technology will make it more accurate.

Through remote management offered by 5G technology a user can get better and

fast solution.

The remote diagnostics will be a great feature of 5G technology.

The 5G technology will provide up to 25 Mbps connectivity speed.


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The 5G technology will support virtual private network.

The new 5G technology will take all delivery service out of business prospect

The uploading and downloading speed of 5G technology will touch the peak.

The 5G technology network will offer enhanced and available connectivity just about

the world.


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4 Radio Over Fiber (RoF)

One possibility studied to achieve the high levels of data rate required by the 5G

technology, is the use of fiber optics because its has low losses and so is possible to have

high data rates. When we have the transition between fiber and radio we use a systemcalled Radio over Fiber. The technique of radio over fiber (RoF) is basic the transmission

of radio signals (RF) in optical fiber, where the RF carrier is modulated in an optical

carrier. RF signals are thus transmitted in optical fiber from a central station (CS) and

several base stations (BS) or Radio Access Point (RAP) and then sent to the transmitting

antenna and radiated for various devices.

Figure 4: Example of RoF

One way to increase the capacity of wireless communication systems is reducing the

size of the cells (which is a requirement for 5G systems), by reducing the power radiated

by and the use of antennas operating bands in the 60 GHz the attenuation zone where the

atmosphere is greater. Thus, to implement a communication system is required a higher

number of base stations because the covering areas have higher dimensions. Installation

and maintenance cost of such a system can be prohibitive, however technology of RoF is

a solution to this problem. Centralizing the processing of RF signals allows the sharing ofequipment, dynamic resource allocation, as well as operation and simplified maintenance,

reducing costs. Thus, the RoFs allows to simplify the BS Architecture, as they only have


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to perform optoelectronics conversion functions and amplification.

4.1 Advantages of RoF

The technique RoF is recognized for having as main advantages the ability to central-

ized operation , the use of small BS, simplicity and low power consumption . Networks

based in such systems take advantage of the huge bandwidth of the optical fiber. Current

systems use only a fraction of the capacity offered by the fiber. The low attenuation on

fiber allows the transmission of RF signals over long distances reducing the need to use

repeaters. There are three transmission windows in fiber with a low optical attenuation

at wavelengths of 850 nm, 1310 nm and 1550 nm . The current fibers have attenuation

between 0.2 dB / km ( 1550 nm ) and 0.5 dB / km ( 1310 nm ) . Compared to coaxial

cables , these losses are much smaller , especially at high frequencies , since the losses

increase with frequency. Thus, the use optical signals can transmit signals much greater

distances and with the benefit of using lower transmission power. Once the signals are

transmitted in the form of light in the optical fiber, there is a important property in trans-

mission, the immunity to radio frequency interference and immunity to eavesdropping ,

which allows for secure communication and more privacy (colocar referencia broadband).

This technology reduces the cost of deploying of wireless networks, enabling its integra-

tion with current fiber optic networks and using techniques of wavelength multiplexing

(WDM) . The use of simple and small base stations ( BS) and small , transferring some

of the equipment and complex transactions for central stations , allows you to share these

resources with various BS and thereby reduce costs.

4.2 Disadvantages of RoF

Despite the numerous advantages of this technology , there are some limitations in

implementation of these systems . The carriage of analog signals suffers from distortion

of intermodulation due to the nonlinearity of the optical / microwave components , and

require an available bandwidth greater than the frequency of the RF carrier. Furthermore,

the dynamic range of an analog optical link decreases linearly with distance transmission

, due to the attenuation of the optical fiber. The RoF systems are fundamentally analog

systems , where noise and distortion are characteristics that affect communication . Thereare several sources of noise in systems analog communication, such as laser intensity noise

( RIN ) , the quantum noise photodiode and thermal noise of the amplifier . In RoF


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systems using single-mode fiber (SMF) , the transmission distance is limited by chromatic

dispersion , while in systems that use multimode fiber (MMF ) modal dispersion limited

transmission distance and bandwidth .


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5 Basic concepts of MillimeterWaves

As it was explained before the main objective of this project is to realize a bibliographic

study on millimeter waves because its related to 5G. Also, we are interested in the 60Ghz

band because future systems are supposed to operate in the unlicensed band (from 57 to

64 GHz) and could support data rates above 1 Gbit/s which is something important for

the 5G technology. The main advantage of this frequency band is the large bandwidth

available without comparably restrictive power limits as for UWB transmission. We can

explain the benefits of using 60GHz band by analyzing the Shannon equation for capacity

in equation 5.1:

C=B log2(1 +

PSPN

) (5.1)

where C is the capacity of the channel, B the bandwidth and the relation PSPN

is the

Signal-to-Noise ratio. And since we want a high capacity (1 Gbit/s) and also a low

power consumption its necessary a large bandwidth. Two bands with sufficiently large,

unlicensed bandwidth are available: The Ultra Wideband (UWB) and the 60 GHz band.

The advantage of the 60 GHz band over other technologies in small distances can be seen

on figure 5.

The use of millimeter wave has more advantages as:

License: It is also an unlicensed band, so it can be used freely.

Bandwidth: They can handle large band widths (5-9 GHz), which also implies higher

speeds.

Equipment: The equipiment for base stations are small (antennas) and they can be

easily installed.

Maintenance and installation: The installation and maintenance of the equipment


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Figure 5: Advantages of 60 GHz

of the base station are simple.

Coverage: They can help cover areas which is usually not possible due to the density

of users and it can serve more users in the MHz band due to the higher bandwidth.

But it also has a disadvantage:

Propagation conditions: The MMW, unlike the lower frequency waves are char-

acterized by having high attenuation by vegetation and atmospheric absorption, so can

only operate over short distances and highly directional, although this does not is alwaysa disadvantage since it can protect the information in this way.

5.1 Characteristics of the 60 GHz band

This section presents the physical conditions of communication in the unlicensed

60GHz band. Some properties of this band came from the fact that the free space wave-

length at 60GHz of60GHz = 5mm(according to the equation 5.2 )is much smaller than

at frequencies previously used. In this

= c

f (5.2)

where is the wavelength, c the speed of light in vacuum ( 3108m/) and f the fre-

quency. So are called "millimeter wave" frequencies whose wavelengths in vacuum is of the

order of millimeters, which in practice corresponds to the frequencies included between

30 GHz and 300 GHz. In this range of frequency is important to analyze the attenuationof the signal because it increases for high frequency as we can see on equation 5.4:


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A= (4d

)2 (5.3)

and if we convert to dB we have:

A= 87.56 + 20logf+ 20logd (5.4)

Considering a distance of one kilometer, the attenuation in the frequency of 2.4 GHz

is 100 dB, whereas the frequency of 60 GHz the attenuation is 128 dB. In this case we

have 630 times greater attenuation for the same distance. Furthermore, for millimeter

wave there are additional transmission loss factors (which will be described after), such

as absorption by molecules of oxygen, water vapor and other gases which comprise the

atmosphere.

5.1.1 Antenna

The small wavelength has a strong influence on the performance of the antennas in

the 60GHz band. As an antenna to obtain power from an electromagnetic field depends

more on the effective area Ae than on directivity or gain we will start by analyzing thisparameter which is defined by the equation 5.5

Ae=2

0G

4 (5.5)

if we consider a lossless isotropic radiator (with gain G = 1, that is 0 dBi). Aedecreases

quadratically with decreasing wavelengths so the size of a simple antenna, which is related

to its effective area, decreases if we increase the frequency. Also we can analyze the power

obtained by a receiving antenna from electromagnetic wave of power spectral density S

by the equation 5.6:

Pr,max=S Ae,r (5.6)

where Pr,max is the maximum power that can be received from the incident wave by

a lossless receiving antenna in case of power match. The consequence is that a receiving

antenna with a given gainGr,1at 60GHz obtains less power from a field of electromagneticpower density S than an antenna with the same gain Gr,1 at lower frequencies. This can

be seen if we put the equations 5.5 and 5.6:


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Pr,max=S20Gr,14

(5.7)

The electromagnetic power density S(r) in free space, which was originated by the

transmit antenna, must to follow a different law: it decays equally fast at all frequencies

as a function of distance r as we can see in equation 5.8.

S(r) =PtGt,14r2

(5.8)

where Gt,1 is the gain of the transmitting antenna and Pt the transmit power. So

according to equation 5.6, the antennas need to have the same effective area at 60 GHz

as at lower frequencies (and not the same gain) to receive the same power. And for an

antenna with smaller effective area (often considered for the 60 GHz band) is, if we consider

the possibility for a higher gain, followed by a higher path loss. The Friis transmission

formula, which results when putting together the equations 5.5, 5.6 and 5.8 shows this:

PrPt

=GrGt0

4r

2

(5.9)

As this equation is often used for antennas which are characterized by their gain, thebigger loss at 60GHz is usually assigned to the channel and not to the antenna. However,

as illustrated by 5.5, the part of the transmission formula including 0 is introduced by

the antenna, whose effective area depends on the wavelength according to the equation

5.5. As the gain of an antenna of the same effective area is higher at higher frequencies, in

the 60 GHz band a much higher antenna directivity is required to obtain the same path

loss as at lower frequencies. In practice, this often results in the use of aperture antennas,

parabolas or antenna arrays.

The higher directivity of 60GHz links demands a continuous effort to align the antenna

beams for mobiles. The standards for communication in the 60GHz band consequently

provide beam steering technology in the different communication layers.

Another approach to increase the total antenna area can be the use of Multiple-Input

Multiple-Output (MIMO) systems, where each antenna is associated with a separate

transceiver circuit. While complexity increases in this situation, a high level of integration

can make these kind of solution feasible.


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5.1.2 Channel

The basic phenomena for the signal attenuation in the radio links are:

Fading: Is generally due to obstruction in the path of a signal obstacles in adverse

propagation conditions such as attenuation due to gases or, signal propagation , etc..

Scattering: Scattering is a physical phenomenon waves which separate two wave with

different frequency when they pass through a material. For millimeter wave is considered

minimum, if compared with other variables such as transmission distance , although this

is mainly due to the size of the wavelength .

Refraction: Refraction is the change of direction experienced by a wave passingfrom one material medium to another. Only occurs if the wave is incident obliquely on

the surface of separation of the two mediums and if they have different refractive indices

. The refractive originates from the change of speed of the wave propagation and to the

millimeter waves happens mainly with vegetation .

Absorption: Every atom has a discrete number of energy levels. At the environment

temperature is in its lowest energy level called the ground state. When a radio Electro-

magnetic interacts with an atom of the shock wave energy can be absorbed if exactly

matches the energy required to carry the chemical species in question from the ground

state to one of the higher energy levels.

Beside this, there are others lost which should be analyzed.

5.1.3 Losses from the vegetation

Vegetation is one of the factors causing higher losses compared to others which affect

millimeter waves . These losses depend mainly on the following factors : frequency ,

type of foliage, vegetation density ( leaf density ) , the movement that is generated due

to wind, the distance that the signal pass through the vegetation , the beam width and

the polarization of the signal . The foliage affect because the leaves vary in size and

shape depending on the type of vegetation. The vegetation density is focused primarily

on whether the vegetation is only trunks and branches or if there are leaves and how

they are populated . Of course this depends on the season ( summer or winter) . If the

vegetation has leaves , the attenuation depends on the its size. If they are larger than

the wavelength of the signal is most likely greater attenuation. It also affects how many

sheets are together in the same space .


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It is also important to consider the geometric dimensions of the plant (the height,

thickness of the trunk and the section where there are branches with leaves). It should

also be noted that vegetation is not uniform and this makes it complicated to calculate

the theoretical attenuation of vegetation . The ITU in recommendation ITU -R P.833

- 4 describes an empirical model of attenuation vegetation for frequencies above 5 GHz

This is a function of factors before mentioned and is expressed as follows :

Aveg =Rd + k(1 + exp(R0 R)

k d) (5.10)

where:

R0= af (5.11)

and

R= b

fc (5.12)

f is the frequency in GHz, d the distance in meters,

k= k0 10log10(A0(1 expAmin

A0)(1 exp Rff)) (5.13)

and the parameters a,b,c,k0, Rf and A0 can be seen on table 1.

Parameter With foliage Without foliagea 0.2 0.16b 1.27 2.59c 0.63 0.85k0 6.57 12.6Rf 0.0002 2.1A0 10 10

Table 1: Parameters of losses caused by vegetation

Amin is defined as the product of the minimum width of vegetation illuminated and

minimum height , corresponding to the smaller of the zones lighted of the antenna in the

front and rear parts of the vegetation areas.


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5.1.4 Losses due to rain

Many MMW links do not work properly because the calculation of rates of rain in

an area is not properly applied. It is for this very reason that the rainfall intensity (rain

rate in mm / h) should be carefully evaluated, since many cities have microclimates

where rates of temperature and rainfall differ significantly from one location to another.

This calculation becomes critical when links are designed in the bands of MMW because

they are so sensitive to environmental effects. The ITU-R Recommendation P.838-2

to calculate the attenuation caused by rain from values of rain intensity at the known

frequency range of 1 to 400 GHz from the following equation:

YR=kR (5.14)

where YR is the atenuation in dB/km, R is the intensity of rain and k and for the

polarization horizontal and vertical can be calculated by:

logk=3

j=1

(ajexp[(logf bj

cj)2]) + mklogf+ ck (5.15)

=4

i=1

(aiexp[(logf bi

ci)2]) + mlogf+ c (5.16)

and the values for a, b, c, mk,ck,m,c can be obtained from the tables 2 and 3.

a b c mk ck m cj = 1 0.3364 1.1274 0.2916 1.9925 -4.4123 - -2 0.7520 1.6644 0.5175 1.9925 -4.4123 - -3 -0.9466 2.8496 0.4315 1.9925 -4.4123 - -

i= 1 0.5464 0.7741 0.4011 - - -0.08016 0.89932 0.2237 1.4023 0.3475 - - -0.08016 0.89933 -0.1961 0.5769 0.2372 - - -0.08016 0.89934 -0.02219 2.2959 0.2801 - - -0.08016 0.8993

Table 2: Coefficients for vertical polarization

Also in the same recommendation a table with sample values for the coefficients

and K in the equation 5.14. As we are interested in the 60 GHz band only this will be

show on table 4.


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a b c mk ck m cj = 1 0.3023 1.1402 0.2826 1.9710 -4.4535 - -2 0.7790 1.6723 0.5694 1.9710 -4.4535 - -

3 -1.0022 2.9400 0.4823 1.9710 -4.4535 - -i= 1 0.5463 0.8017 0.3657 - - -0.07059 0.87562 0.2158 1.4080 0.3636 - - -0.07059 0.87563 -0.1693 0.6353 0.2155 - - -0.07059 0.87564 -0.01895 2.3105 0.2938 - - -0.07059 0.8756

Table 3: Coefficients for horizontal polarization

Frequencia KH Kv h v60 0.7039 0.6347 0.8266 0.8263

Table 4: Coefficients for the estimation of attenuation due to rain

5.1.5 Losses due to water vapor and oxygen

The molecular absorption experienced during the propagation of radio waves through

the atmosphere , at wavelengths of the order of millimeters , is mainly due to water vapor

and oxygen present in the atmosphere. However, the waste gas contribute to a significant

attenuation in the absence of water vapor at frequencies above 70 GHz. Other residual

gases have absorption lines . Among them are the oxide of nitrogen ( N2O) , dioxide of

sulfur (SO2 ), ozone (O3) , dioxide of nitrogen (N O2 ) and ammonia (N H3) , but due to

their low concentration in the atmosphere are negligible effects on the spread.

If the water is heated above its boiling point , it turns to steam , or water gaseous state.

However, not all vapors are equal. Steam properties vary depending on the pressure and

the temperature to which it is subject . On this basis there are several types of steam:

saturated steam, wet steam and superheated steam. The computing attenuation by

water vapor can be based on the ITU -R Recommendation P.676 -6 , which provides the

maximum frequency range up to 1000 GHz and proposes a pressure of 1013 hPa and a

temperature of 15 C for the case of water vapor density of 7.5 g/m3 and dry atmosphere.

In the spectrum of absorption due to atmospheric gases, as we can see on figure 6, a peak

around 60GHz is seen. However, while the absorption in this frequency band is quite high

relative to other frequencies, since we have this in logarithmic scale, it remains below 0.2

dB at 10m and is thus negligible with respect to free space loss in a WPAN context. The

same is true for attenuation due to rain, which is on the same order of magnitude as oxygen

attenuation. Besides, this second mechanism applies only to outdoor environments.


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Figure 6: Absorption of mm-waves due to atmospheric gases at sea level and 15.000 feet

altitude

5.1.6 Loss due obstacles

For the calculation of the received power when there are obstacles in the trajectory

specifically for the frequency 60 GHz we use a model. This equation includes a term that

is not included in other to perform the calculation of the received power which is known

as: partition dependent attenuation, and thus generates a model that assumes free space

propagation with additional losses based obstacles traversed by a single beam going fromthe transmitter to the receiver. this model is as follows:

PR(d) =PT+ GT+ GR 20log10(4d

)

N

i=1

(aiXi) (5.17)

where PR(d)is the received power in dBm, d is the distance of the transmitter to the

receiver in meters, PTis the transmitting power in dB, GTis the antenna gain transmit-

ting,GR is the gain of the receiving antenna, Xi are the values of the attenuation in dB

for the i-th partition inserted that crosses a line from transmitter to receiver, ai is the

number of times that the beam intercepts each partition, N is the number of partitions

on the link and is the wavelength in cm. Partitions refer to the types of materials

which may include an office environment: drywall, office whiteboards, transparent glass,

metal mesh objects the first Fresnel zone, and so on. On tables ?? and 6 we can see the

influence of these materials for 60 GHz:


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drywall white blackboard office clear glassAverage attenuation (dB) 6.0 9.6 3.6Standard deviation (dB) 3.4 1.3 2.2

Average attenuation standardized (dB / cm) 2.4 5.0 11.3Table 5: Loss due obstacles

glass with mesh metal object in the officeAverage attenuation (dB) 10.2 1.2Standard deviation (dB) 2.1 1.8Average attenuation standardized (dB / cm) 31.9 -

Table 6: Loss due obstacles

5.2 Regulations

This band is unlicensed but there are some regulation which must be followed and

this regulations depend on the region. We can see the regulation on the allocation of the

band on figure 7 and the power emission specification of table 7.

Figure 7: Unlicensed band around 60 GHz for different countries and regions

Region Max Tx Power (dBm) Max EIRP (dBm) Gain (dBi)Australia 13 51.76 -Australia (indoor) 13 43 -Canada 27 43 -

Europe 10 55 30 (Min)Europe (indoor) - 40 30 (Min)Germany 40 - 35 (Min)Japan 10 - 47 (Max)Korea - 10 -USA 27 43 -

Table 7: Emission Power specifications around 60Ghz for different countries and regions


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6 Modulation and signal detectionsystems in RoF

Another important part to be analyzed in this project is how the RoF systems works

with Millimeter Waves. The modulation in the RoF system is generated from an electrical

and an optical modulation. First, there is the electrical in amplitude , phase or frequency

as in a conventional electrical system . The electrical signal must have the specifications

required by wireless applications , such as GSM , UMTS , WLAN , WiMAX , among

others. In this RoF architecture , the optical carrier is modulated by a radio signal with

a radio frequency carrier (RF ) , then transmitted by a fiber optic link between a CS

and a set of BSs . The process of electrical - optical conversion is done by using laser

modulation , the electrical signal enables the laser module optical intensity in an " On- Off" state , and commonly a photodetector is used in the receiver , where the signal

is converted from the optical domain to the electrical domain before being amplified and

radiated by an antenna . These systems are known as IM / DD ( intensity modulation /

direct detection ) . The IM / DD systems are the simplest and the most widely deployed

, but to achieve higher than 10 GHz frequency modulate this technique causes problems ,

because the bandwidth of this device is limited. For this reason, to achieve greater than

10 GHz the IM / DD systems use external modulation . In this type of modulation the

Mach Zender modulator (MZM) and the electro - absorption modulator (EAM) is widely

used . Another method used for transmission and transport of RF signals by the optical

fiber is the form remote heterodyne generation . It is a method in which more than one

optical signal is generated by the light source , one is modulated by the signal that carries

the information , then its mixed by a photodetector or an external mixer to form the

signal RF output. The optical heterodyne generation has the advantage of generating

high frequency signals and is only limited by the bandwidth of the photodetector. The

generation of heterodyne detection supports higher power (high link gain ) and higher

carrier to noise ratio (CNR , carrier-to-noise ration ), since under certain conditions the

optical powers of the two optical fields interfere , which contributes to increase the power


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of the generated optical signal.

Furthermore, the RoF links which are phase modulated (PM) have advantages over

the IM / DD systems , and allows the implementation of a more simple BSs . However,the links RoF - PM requires a combined coherent optical receiver DSP modules for de-

tecting and demodulating linear signals . Coherent detection in optical systems have been

demonstrated to perform demodulation of linear MMW signals coded on the phase of an

optical carrier . The main advantages offered by the RoF -PM systems with coherent

detection over RoF IM / DD systems are:

1) more free dynamic range of stimulus

2 ) optical data transmission more effectively spectral in advanced modulation formats

3) higher bandwidth and channel selectivity

4 ) lower requirements on the power transmission signal .

The main advantages of the digital coherent receiver compared to conventional re-

ceivers :

1) effective cost and reduced size

2) adaptive compensation of the imperfections in the channel in the electronic domain

using signal processing techniques

3) design versatility and robustness in operation , allowing different formats using the

same receiver hardware in.

6.1 Evolution and trend technology of RoF

End users of wireless and wired networks are demanding large volumes of information

at high speeds. In this scenario, based RoF systems and fiber to the home ( FTTTH

, Fiber to the Home) are the most promising candidates to support these requirements

of access networks . Access networks of next generation progress towards convergence of

wired and wireless services, in order to efficiently provide services of high bandwidth at

low cost. The RoF systems lead the progress of the access networks through significant

advances in areas such as : the increase in transmission capacity and bandwidth and lower

costs of fixed and mobile networks.

Nearly two decades ago began the study of MMW RoF systems , but these are not

modulated MMW signal within the optical carrier in the fiber , so its necessary a complex


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BS for conversion. Using radio signals over fiber distributed antenna systems (F - DAS

) moves the electronic processing of the antenna to a central station , opening new op-

portunities for the creation of hybrid networks , which have not yet been fully exploited

. Change the location of the equipment means that the ability can now be reassigned to

any point in the network , instead of being fixed by the equipment that is installed in a

particular BS .

The huge bandwidth offered by fiber have other benefits besides high capacity to

transmit microwave signals . The large optical bandwidth enables the processing of signals

at high speed which could be more difficult to do in electronic systems , such as the

MMW signal filtering can be achieved by converting the electrical signal to optical and

perform filtering using optical component networks based on optical fiber Bragg ( FBG

fiber Bragg Gratting ) or Mach Zender interferometer (MZI , Mach Zender interferometer

) . However, the major problem when transmitting signals on optical fiber mmw is the

signal degradation due to fiber dispersion . One of them, the chromatic dispersion is

the most important phenomenon affecting these systems, because it causes intersymbol

interference ( ISI ) due to temporal broadening of the pulses at the receiver . This

phenomenon depends on the spectral components of the light source , the frequency of

the carrier and the length of the fiber . Mmw wireless systems with channel bandwidth

above 10 GHz could easily provide multi - Gbps capabilities even with simple formats or

qpsk and ask modulation .

The main challenges of photonic systems based on mmw are to improve the perfor-

mance of devices that integrate , adapt these systems to the spectral region of operation

, increase the conversion efficiency of the devices optoelectronic and increase dynamic

range, offset dispersions of the fiber, and in turn, reduce the costs of these technological

advances.


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7 Conclusion

Throughout this project, we tried to analyze, understand and reflect on the present

value of the mobile telecommunications systems and technologies that support them. Was

given special attention to the study of its evolution and features of new technology forthe 5G. Among the technologies we had special interest in millimeter waves because of its

great potential of study and development.

In the first chapter was given the motivation of the project and a little introduction

about the subject. The second chapter explains the evolution of mobile telecommuni-

cation with the difference among each generation, advantages, disadvantages and some

technologies. In the third chapter was finally introduced the new 5G technology, with

its feature and requirements. In fourth chapter was initiated the relation with optical

technology, starting with some basic concepts of RoF. Then, in the fifth chapter was dis-

cussed about the basics of millimeter wave technology and finally in the sixth chapter was

explained about modulation and signal generation for millimeter waves.

After finishing this project its possible to analyze and see the importance of the study

of RoF technology because it has a great future for 5G.


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8 Bibliography

[1] Young Kyun, Kim; Prasad, Ramjee (2006), 4G Roadmap and Emerging Commu-

nication Technologies. Artech House 2006.

[2] Q. Zhao and J. Li, Rain attenuation in millimeter wave ranges, in Proc. IEEE Int.

Symp. Antennas, Propag. EM Theory, Oct. 2006.

[3] T. S. Rappaport, J. N. Murdock, and F. Gutierrez, State of the art in 60 GHz

integrated circuits &systems for wireless communications, Proc. IEEE.

[4] T. S. Rappaport, S. Sun, R. Mayzus, H. Zhao, Y. Azar and F. Gutierrez Millimeter

Wave Mobile Communications for 5G Cellular: It Will Work!, Proc. IEEE.

[5] Christopher R. Anderson, and Theodore S. Rappaport, In-Building WidebandPartition Loss Measurements at 2.5 and 60 GHz, IEEE Transactions on Wireless Com-

munications.

[6] N. Guerrero, Digital Photonic Receivers for Wireless and Wireline Optical Fiber

Transmission Links, Ph. D. dissertation, Dept. Fotonik, Denmark Tech. Univ., Copen-

hagen, 2011.

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