4 Rf Propagation Models in Lte

Performance Analysis and Comparison of Radio Frequency Propagation Models for Outdoor Environments in 4G LTE Network

Asad Saeed Habib Ur Rehman Muhammad Hassan Masood

This thesis is presented as part of the Degree of Master of Sciences in Electrical Engineering

Blekinge Institute of Technology 2013

School of Engineering Blekinge Institute of Technology, Sweden Supervisor: Muhammad Shahid Examiner: Benny Lövström

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Abstract

The dissertation concerns about the path loss calculation of Radio Frequency (RF) propagation models for 4G Long Term Evolution (LTE) Network to prefer the best

Radio Frequency propagation model. The radio propagation models are very significant while planning of any wireless communication system. A comparative analysis between radio propagation models e.g. SUI model, Okumura model, Cost 231 Hata Model, Cost

231-Walfisch Ikegami and Ericsson 9999 model that would be used for outdoor propagation in LTE. The comparison and performance analysis has been made by using different geological environments e.g. urban, sub-urban and rural areas. The simulation scenario is made to calculate the lowest path loss in above defined environments by using selected frequency and height of base station antennas while keeping a constant distant between the transmitter and receiver antennas.

Dedication

To our Parents and Teachers who motivated and encouraged us to attain this Hallmark in the best way

Acknowledgment

Our thesis was an endeavour, much greater in magnitude than any of projects we have ever done. To see this endeavor turn into accomplishment was a dream that would have never come true without the support of many individuals.

First of all, we would like to thank Allah, the Almighty who did not let our faith die, who answered all of our prayers and granted us only the best ones.

Secondly, we are highly grateful to Mr. Muhammad Shahid, our project supervisor who guided, encouraged, stood by us and accepted nothing less than our best efforts.

Thirdly, we are indebted to our families and friends who were not with us on this venture of technology but were connected with each and every sentiment affiliated to it. They may not understand a word of our thesis but they know that it is important and so are they to us.

Finally we are grateful to Blekinge Tekniska Hogskolan, Karlskrona Sweden and to all our teachers we had, in the course of 2 year degree that nurtured and prepared us.

Asad Saeed, Habib Ur Rehman and Hassan Masood August 2013

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Contents

1 INTRODUCTION ...... 1

1.1 WIRELESS TECHNOLOGY: ...... 1 1.1.1 The First Generation (1G): ...... 2 1.1.2 The Second Generation (2G): ...... 2 1.1.3 The Third Generation (3G): ...... 2 1.1.4 The Fourth Generation (4G): ...... 3 1.2 THE OUTLINE OF THE THESIS: ...... 3

2 LONG TERM EVOLUTION ...... 4

2.1 INTRODUCTION: ...... 4

2.2 LTE STANDARD: ...... 5

2.3 SERVICES PROVIDED BY LTE: ...... 5

2.4 FREQUENCY BANDS ALLOCATION: ...... 5 2.4.1 Frequency Division Duplex (FDD) Bands Allocation: ...... 8 2.4.2 Time Division Duplex (TDD) Bands:...... 9 2.5 LTE TECHNICAL INFORMATION: ...... 9

2.6 MODULATION SCHEMES:...... 9 2.6.1 Analog Modulations: ...... 10 2.6.2 Digital Modulations: ...... 10 2.7 MULTIPLE ACCESS TECHNIQUES: ...... 10 2.7.1 Frequency Division Multiple Access (FDMA): ...... 10 2.7.2 Time Division Multiple Access (TDMA): ...... 11 2.7.3 Code Division Multiple Access (CDMA): ...... 11 2.8 CHANNEL EQUALIZATION: ...... 12

2.9 SINGLE CARRIER MODULATION: ...... 13

2.10 ORTHOGONAL FREQUENCY DIVISION MULTIPLEXING: ...... 14 2.10.1 Channel Bandwidths and Characteristics of LTE: ...... 14 2.10.2 LTE OFDM Cyclic Prefix (CP):...... 15 2.10.3 LTE OFDMA in the Downlink: ...... 17 2.10.4 Downlink Carriers and Resource Blocks: ...... 17

2.10.5 LTE SC-FDMA in the Uplink: ...... 18 2.11 MULTIPLE INPUT MULTIPLE OUTPUT (MIMO): ...... 19

2.12 LTE ARCHITECTURE: ...... 19 2.12.1 LTE Network Elements: ...... 20 2.12.2 Frame Structure ...... 20 2.12.3 LTE Channels and MAC Layer: ...... 22 2.12.4 LTE MAC Layer Functionality:...... 22 2.12.5 LTE Channel Architecture: ...... 23 2.13 LTE DOWNLINK CHANNELS:...... 24 2.13.1 Downlink Logical Channels: ...... 24 2.13.2 Downlink Transport Channels: ...... 24 2.13.3 Downlink Physical Channels: ...... 24 2.14 LTE UPLINK CHANNELS: ...... 25 2.14.1 Uplink Logical Channels: ...... 25 2.14.2 Uplink Transport Channels: ...... 25 2.14.3 Uplink Physical Channels:...... 25 2.15 LTE MOBILITY, CELL RANGE & ECONOMIC TARGETS: ...... 26

3 WIRELESS PROPAGATION MODELS ...... 27

3.1 INTRODUCTION: ...... 27

3.2 RADIO WAVE COMPONENTS: ...... 28

3.3 FREE SPACE MODEL: ...... 28

3.4 INDOOR RF PROPAGATION MODELS: ...... 29

3.5 OUTDOOR RF PROPAGATION MODELS:...... 30 3.5.1 Foliage models: ...... 31 3.5.2 Terrain models: ...... 31 3.5.3 City models: ...... 31 3.5.4 Band-specific models: ...... 31

4 RF PROPAGATION MODELS IN LTE ...... 33

4.1 INTRODUCTION: ...... 33

4.2 OUTDOOR RF PROPAGATION MODELS FOR LTE: ...... 34 4.2.1 SUI Path Loss Model: ...... 34 4.2.2 Ericsson 9999 Model: ...... 35 4.2.3 Okumura Model: ...... 36 4.2.4 COST 231 Hata Model: ...... 38

5 EXPERIMENTAL RESULTS ...... 39

5.1 SIMULATION OF PATH LOSS FOR DIFFERENT RF MODELS: ...... 41 5.1.1 Simulation Results of Okumura Path Loss Model: ...... 42 5.1.2 Simulation of SUI Path Loss Model:...... 43 5.1.3 COST 321 Hata Model...... 44 5.1.4 Simulation of COST-231 Walfisch-Ikegami Model ...... 45 5.1.5 Simulation of Ericsson Model ...... 46

6 CONCLUSION AND FUTURE WORK ...... ERROR! BOOKMARK NOT DEFINED.

6.1 CONCLUSION ...... 48

6.2 FUTURE WORK ...... 51

7 REFERENCES ...... ERROR! BOOKMARK NOT DEFINED.

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1 Introduction

1.1 Wireless Technology

he wireless technology has changed the world with technological development in T wireless communication and brought revolution in the wireless networks. In the beginning of new millenary, we saw an amazing world of telecommunication. Telecommunication [1] is a combination of cellular networks, computers, telephones, internet and television. Today wireless networks are used where the transmission is by means of infrared and radio waves. The great mobility is present in wireless networks and we can use the network everywhere, while in the wire networks, the availability of services in specific areas is a main problem. The demand of wireless broad band services has been increased. Wireless networks have been regularized by the Institute of Electrical and Electronics Engineers (IEEE). Different networks have different standards. The most common standards given by IEEE are IEEE 802.11 for WLAN and 802.15 for Bluetooth etc as illustrated in Figure 1.1 [1].

Figure 1.1: IEEE and ESTI Standards for Wireless Networks.

The cellular network is most popular type of wireless networks. The cellular network is a combination of small cells. The cellular network can provide better network coverage with increasing number of users. The quality of service and mobility management is also improved in cellular networks [2]. The advancement in cellular networks is divided into different generations, which are described below

In a wireless transmission the quality of signal, degrades due to the fading effects in channel caused by the multipath propagation. In order to reduce these effects, cooperative communications is one of the best methods. The cooperative communication may employ path diversity to transfer the signal from source to destination. Here path diversity means to introduce relay in the channel [6][3].

Several relaying protocols and their combination considered to view the performance of the system [3]. The transmission relaying protocols used in this thesis are: Amplify and Forward (AF), Decode and Forward (DF) and Decode, Amplify and Forward (DAF).

1.1.1 The First Generation (1G)

The cellular networks, deployed in early 1980’s, are called First generation (1G) cellular networks. The first cellular network was introduced in Japan. The first analog cellular network distributed in Europe was Nordic Mobile Telephone (NMT) and in America it was Advance Mobile Phone System (AMPS) in 1981.

1.1.2 The Second Generation (2G)

The Second generation (2G) cellular networks were proposed in early 1991’s. The GSM and the CDMA 1 were introduced in Europe and America respectively. The GSM consists of digital circuits and almost 2 billion users are still using it in many countries. The GSM has two frequency bands 900 MHz and 1800 MHz. The GSM supports more services i.e. Caller Identification, roaming, Short Messaging Services (SMS) etc. The Enhanced Data rates for GSM Evolution (EDGE) and General Packet radio Service (GPRS) are enhancements in GSM.

1.1.3 The Third Generation (3G)

The Third Generation (3G) cellular networks including Universal Mobile Telecommunication System (UMTS) have higher data rates as compared to GSM. The 3G enables many services i.e. wireless television, wireless broadband and video

2 conferencing. In order to accomplish the goal of global coverage, UMTS was introduced. The CDMA 2000 was introduced in America.

1.1.4 The Fourth Generation (4G)

The Fourth Generation (4G) of cellular networks is currently under its development phase and will be available in coming years. It will be having a download rate of at least 10 Mbps, more effective spectral resources and other services as well. The LTE network [2] provides wireless internet facility. LTE advance is in its research phase.

1.2 The Outline of the thesis

The chapter 2 discusses the technical information and architecture of the LTE network. The LTE architecture, different modulation schemes and LTE frequency bands are explained. The LTE frame format and media access control layer functions are also described in detail. The LTE network channel allocation has also been discussed. The chapter 3 covers the RF propagation models in detail. The different propagation models with their suitable applications according to the population and area are explained. The chapter 4 starts with the RF propagation models for LTE and explain the mathematical formulations for RF outdoor propagation models used in LTE. This chapter describes the SUI path loss model, Ericson 9999 model, Okumura model and Cost 231 Hata model. The chapter 5 shows the simulation results for path loss of different propagation models. It also concludes with the thesis conclusion and the possible future works.

2 Long Term Evolution

LTE stands for Long Term Evolution. It is a 3GPP Project and is known as 4G LTE. It is standard for wireless communication of high-speed data. It is based on the GSM/EDGE and UMTS/HSPA network technologies. It is targeted to get high speed and capacity by using a different radio interface with improvements in the core network [2]. TeliaSonera was the first company to launch LTE in Oslo and Stockholm in December 2009. The comprehension of broadband Internet access anywhere and anytime was seem to be difficult but this has become possible now-a-days . LTE network is most recent wireless technology. The wireless broadband access to urban and rural areas has become possible by these networks with low rates [2].

2.1 Introduction

When it comes to the enhancement of the mobile communication and to improve the future requirements, LTE [1] is a better choice in wireless communication networks. The LTE project is initiated by 3GPP under the supervision of European Telecommunications Standards Institute (ETSI). LTE network has some features like, an uplink of 75 Mbps and a downlink of 300 Mbps with more than 200 active users per cell. The goals of LTE are; cost effectiveness, best use of new spectrum, better compatibility with other standards and improving of spectral efficiency. LTE Advanced [8] is purely a 4G technology and LTE itself is the advanced version of 3G. The evolution is illustrated in Figure 2.1.

Figure 2.1: Mobile Technologies -2G to beyond 3G [3]

2.2 LTE Standard

LTE [2] is adopted by 3GPP which operates under the ETSI. LTE is a wireless technology that can be useful to deliver IP services over large areas. Its certification indicates interoperability of the equipment built to the 3GPP, 3GPP2 or compatible standard. LTE network is a scalable wireless platform for making alternative and balancing broadband wireless networks.

2.3 Services Provided by LTE

Various services provided by LTE network, these are discussed in Table 2.1 below [2].

Table 2.1: LTE Network Services Services Details Voice Primarily Packet Data High Speed

Multimedia Mixed Media

Multicast Shared Video and Audio Channels Location Services GPS and Systems

2.4 Frequency Bands Allocation

Frequency band allocation is the most important task when planning a network. Since different regions of the world use even a single frequency for different cellular systems, so this means that we are lacking global standards for cellular communications. Almost every country has its own regulatory authority. For instance, Federal Communications

Commission (FCC) is the authority, which is responsible for the allocation of frequency bands in the US. The International Telecommunication Union (ITU) is a United Nation based organization, which is working to standardize the frequency bands all over the world [3]. In order for a user to use the same equipment and technology anywhere in the world, the same frequency bands should be used in order to set a standard. Due to historical and political reasons, there are different frequency bands allocated for cellular communication systems in US, Europe and Asia. The world is divided into three regions and all the three regions (as shown in Figure 2.2 [4]) have different frequency bands.

Figure 2.2: Different regions of frequency allocation in the world [4]

The First Region, Region 1 consists of Europe, Africa, Russia and some parts of the Middle East. The Second Region, Regions 2 covers USA, Canada and all the Latin America while in the Third Region, Region 3 China, Australia, India, Pakistan, Japan and other countries of Asia and Oceania are located. Most cellular technologies have different frequency bands in these three regions. But sometimes even in the same region there are different frequency bands for same technology.

UMTS/HSDPA/HSUPA bands  Band I (W-CDMA 2100) is used in Europe, Africa (ITU Region 1), Asia, Oceania and Brazil (part of ITU Region 2)  Band II (W-CDMA 1900) is used in North America and South America (ITU Region 2)  Band IV (W-CDMA 1700 or Advanced Wireless Services) is used in the United States of America  Band VIII (W-CDMA 900) is used in Europe, Asia and Oceania (ITU Region 1 and ITU Region 3)  Band V (W-CDMA 850) in used in Australia, Brazil, Canada, United States, some parts of South America and Asia (ITU Region 2 and ITU Region 3)  Band XII - XIV was introduced to be used in 700MHz spectrum, in USA and Canada in 2008 [3]

Frequency license is an issue with high priority while implementing a cellular network. For this purpose a higher cost have to be paid by the companies to the local regulatory authorities. The overall bandwidth of the system depends on that frequency band. Since theses authorities have predefined frequency bands for different cellular technologies the cellular companies do not have a choice for the acquisition of frequency bands.

The LTE defined 3GPP standard, spectrum bands, duplexing techniques and channel bandwidth. In DL, we use OFDM while in UL, we use SC-FDMA. The licensed spectrum band used for LTE network is different for different countries. Frequency Division Duplex (FDD) [8] and Time Division Duplex (TDD) [8] are used as duplexing techniques in LTE network.

The LTE Frequency bands are planned as follow.  700 MHz and 1700 MHz in North America  900 MHz, 1800 MHz and 2600 MHz in Europe  1800 MHz, 2100 MHz and 2600 MHz in Asia  1800 MHz in Australia

2.4.1 Frequency Division Duplex (FDD) Bands Allocation

LTE network uses large number of frequency bands [2]. FDD system uses these bands. The LTE-FDD frequency bands as shown in Table 2.2 are used for simultaneous two way communications. These bands have enough separation that is required to improve the receiver efficiency but the receiver may be blocked if the signals are so close. For enabling the roll-off of the antenna filtering, the separation between signals must be competent within the received band.

Table 2.2: LTE-FDD Frequency Bands [2]

LTE Bands Regions of Use Uplink (MHz) Downlink (MHz) 1 Asia, Europe 1920 – 1980 2110 – 2170 2 Americas, Asia 1850 – 1910 1930 – 1990 Americas, Asia, 3 1710 – 1785 1805 -1880 Europe 4 Americas 1710 – 1755 2110 – 2155 5 Americas 824 – 849 869 – 894 6 Japan 830 – 840 875 – 885 7 Asia, Europe 2500 – 2570 2620 – 2690 8 Asia, Europe 880 – 915 925 – 960 9 Japan 1749.9 - 1784.9 1844.9 - 1879.9 10 Americas 1710 – 1770 2110 – 2170 11 Japan 1427.9 - 1452.9 1475.9 - 1500.9 12 USA 698 – 716 728 – 746 13 USA 777 – 787 746 – 756 14 USA 788 – 798 758 – 768 17 USA 704 – 716 734 – 746

18 Japan 815 – 830 860 – 875 19 Japan 830 – 845 875 – 890 20 Europe 832 – 862 791 – 821 21 Japan 1447.9 - 1462.9 1495.5 - 1510.9 22 3410 – 3500 3510 – 3600

Note: LTE bands 15 and 16 are reserved, but still undefined.

2.4.2 Time Division Duplex (TDD) Bands

There are several unpaired frequencies allocations associated with LTE-TDD. These band allocations as shown in Table 2.3 are unpaired. In fact, these are Time Multiplexed, so frequency is not involved in these allocations.

Table 2.3: LTE-TDD Frequency Bands [2]

LTE Band Regions of Use Allocations (MHz)

33 Asia (not Japan), Europe 1900 – 1920

34 Asia, Europe 2010 – 2025

35 Americas 1850 – 1910

36 Americas 1930 – 1990

37 1910 – 1930

38 Europe 2570 – 2620

39 China 1880 – 1920

40 Asia, Europe 2300 – 2400

41 USA 2496 – 2690

2.5 LTE Technical Information

Long Term Evolution (LTE) is a wireless technology, which describes interoperable implementations and standards of UMTS/3GPP. Here, we will discuss some technical aspects of LTE.

2.6 Modulation Schemes

Different modulation schemes are used for different types of communication in wireless technology. It is very important to select the most efficient modulation scheme that fulfills all the requirements. In modulation, a baseband signal (low frequency signal) is multiplied with a carrier signal or modulator signal (normally a high frequency signal). Signals can be transmitted for long ranges by the use of modulation. The de-modulator demodulates the signal at the other (receiver) end. There are two types of modulations, analog modulations and digital modulations. 9

2.6.1 Analog Modulations

The high frequency carrier is multiplied with the baseband signal in analog modulations. Generally, the baseband signal is a continuous signal. The following are some important types of analog modulations [6]:  Amplitude Modulation (AM)  Quadrature Amplitude Modulation (QAM)  Phase Modulation (PM)  Frequency Modulation (FM)

2.6.2 Digital Modulations

In digital modulations, a digital signal is multiplied with a carrier signal. The following are some important types of digital modulation [6]:  Frequency Shift Keying (FSK)  Phase Shift Keying (PSK)  Quadrature Differential Phase Shift Keying (QDPSK)  Multi-frequency Shift keying (MFSK)  Binary Phase Shift keying (BPSK)  Orthogonal Frequency Division Multiplexing (OFDM)  Quadrature Phase Shift keying (QPSK)  Differential Phase Shift Keying (DPSK)  Gaussian Minimum-shift keying (GMSK)

2.7 Multiple Access Techniques

In cellular communication, numbers of channel are limited within a cell. Hence, the capacity of the whole network is limited. Therefore, multiple access techniques are very important. Multiple accesses is the utilization of service by several users at the same time. These multiple access techniques are used on the physical layer. Some important multiple access techniques are described below:

2.7.1 Frequency Division Multiple Access (FDMA)

In FDMA [7], the combination of smaller frequency bands results into whole frequency band and this smaller frequency band is assigned to each user. These frequency bands

10 are allocated to the users by ensuring minimum interference between different frequency bands.

2.7.2 Time Division Multiple Access (TDMA)

In order to use shared resources in wireless networks, TDMA [7] is also used. In TDMA same frequency band is used by all users in different time intervals. In TDMA each user has a time slot and during respective time period, only one of the users can utilize the whole frequency band. TDMA is used in 2G cellular networks while a combination of TDMA and FDMA is used in GSM.

2.7.3 Code Division Multiple Access (CDMA)

CDMA [7] scheme adopts the method for transmission of data of multiple users simultaneously with a code. In FDMA scheme, the bandwidth is divided among the users, while in TDMA the time is divided among the users whereas in CDMA, both time and frequency are divided among the users. In Figure 2.3, the difference between FDMA, TDMA and CDMA is shown [7].

Figure 2.3: Comparison of FDMA, TDMA and CDMA [7]

In LTE, OFDM is used for DL and SC-FDMA is used for UL transmissions. A signal faces distortion when it is transmitted over a wireless channel in a network. The distortion can be of different types (i.e. multipath, reflection, delay etc).

When the signal reach at the receiver by traveling along these paths they are said to be time shifted (i.e. delayed). When signals are required to be transmitted without any delay, a direct line-of-sight path is chosen between the receiver and transmitter.

Figure 2.4: Multipath caused by reflections of objects

2.8 Channel Equalization

In general cases, distortions such as channel distortion are removed by SC-FDMA in time domain. So channel equalization [14] becomes practically possible (i.e. simplify) and done by any method described below:

 Channel Inversion: The channel equalizer can easily detect the channel response upon receiving data sequence since a data sequence is already known to receivers. In order to remove the delay, an incoming data signal is multiplied with the inverse of the channel response at the equalizer.  A CDMA system uses another technique at the equalizers to resolve the delay issue by combining the digital copies of the time shifted received signal but the SNR (Signal-to-Noise Ratio) will be increased in this case.

In either case, the circuit becomes more complex and symbol times become shorter with increasing data rates.

The Inter Symbol Interference (ISI) is another important issue to be discussed as it is spilled into several symbol periods. As a common equalizer, the transversal filter having finite impulse response as shown in Figure 2.5 is used. More number of samples are 12 required to compensate the delay amount since the receiver sample clock (τ) running slow. As the number of delay taps increases the adaptive algorithm becomes more complex. This approach becomes impractical for LTE data rates.

Figure 2.5: Transversal Filter Channel Equalizer [6]

2.9 Single Carrier Modulation

All cellular systems are using single carrier modulation schemes whereas in LTE, OFDM scheme is used. Here our main discussion is the dealing of single carrier systems with channel distortion. In cellular applications the amount of delay can reach up to several microseconds. Here the term “delay” means the amount of time delay of transmitted signal along different paths.

In telecommunication, inter symbol interference (ISI) is a kind of distortion in a signal in which one symbol interferes with other symbols, and makes the communication undependable. This also introduces unwanted delay at receiver side. ISI is shown in Figure 2.6 when talking about a single carrier system, the symbol time decrease by increasing data rates.

Figure 2.6: Multipath-Induced Time Delays Result in ISI [6]

A particular phase shift is caused by reflection and every different path length. All of the signals are together at the receiver. Sometimes this can cause constructive 13 interference and sometime destructive interference. Finally the composite (i.e. mixed) received signal is deformed by fading as shown in Figure 2.7

Figure 2.7: Received Signal Distorted By Fading [7]

2.10 Orthogonal Frequency Division Multiplexing

In Orthogonal Frequency Division Multiplexing (OFDM) [2], a large number of closely spaced carriers are used. The modulation of these carriers occurs at lower data rates. The interference between these carriers can take place, but Orthogonality between these causes no mutual interference. Orthogonality means to make these carriers perpendicular to each other, which means that the space between these carriers must be equal to the reciprocal of period of symbol. All the carriers occupy the transmitted data. If there is any loss of the carriers, the data can be reconstructed by using error correction techniques. This loss is due to multi-path effects. The effects of reflections and ISI can be reduced. The single frequency networks can be implemented on a same channel, in which all transmitters can transmit their information.

In LTE network, OFDM is the best efficient multiplexing scheme. It meets the exact requirements for LTE. Both TDD and FDD formats are used by OFDM which provide more advantage.

2.10.1 Channel Bandwidths and Characteristics of LTE

One of the major parameters to be decided in a wireless network is the choice of bandwidth. The number of carriers and the symbol length are the major aspects associated within the available bandwidth.

A number of channel bandwidths are reserved for LTE network. It is obvious that an increment in bandwidth also increases channel capacity.

The bandwidths for LTE network as per channel are below:

Channel Number Channel Bandwidth 1 1.4 MHz 2 3 MHz 3 5 MHz 4 10 MHz 5 15 MHz 6 20 MHz

15 KHz is spacing between each sub-carrier. For Orthogonality, the symbol rate formula is given as: 1 / 15 KHz = of 66.7 µs. Where Channel Spacing= 15 KHz

Each individual subcarrier can carry data at a max rate i.e.; 15 kilo symbols per second. It provides 20 MHz bandwidth and 18 Mbps symbol rate.

2.10.2 LTE OFDM Cyclic Prefix (CP)

The methods of adding flexibility to the system is still necessary to reduce the ISI. In order to reduce ISI a period can be added into the time slot at the beginning of a data sequence, such phenomena is called guard period. By this the copy of section of symbol from the beginning of signal to its ending and sampling of waveform at the worst time will become possible. This is called cyclic prefix (CP). All this is done so that ISI will be avoided. The length of CP should be enough long in order to reduce multipath delay, but it has a trade-off, i.e. if length of CP becomes too long the data output capacity will be reduced. Therefore selection of its length is a critical issue. The standard length of cyclic prefix (CP) is approx. 4.69 µs for LTE network. Figure 2.8, 2.9 and 2.10 describes the process of OFDM in LTE network.

Figure 2.8: OFDM Eliminates ISI [6]

Figure 2.9: Baseband FFT Resolves Subcarriers [6]

Figure 2.10: Orthogonal Frequency Division Multiplexing (OFDM) [7]

2.10.3 LTE OFDMA in the Downlink

There are 2048 different sub-carriers that are used by OFDM signal. Every mobile station must have the capability to receive all 2048 sub-carriers. But in fact, the base station supports only 72 sub-carriers. So in this way, all mobile stations can talk to any base station. In OFDM signal, three types of modulation schemes are used: 1. QPSK (= 4QAM) 2. 16QAM 3. 64QAM The exact format depends upon the prevailing conditions. There is no need of large SNR for QPSK. But it can’t send the data at fast rate.

2.10.4 Downlink Carriers and Resource Blocks

In case of DL, the sub-carriers are split-up into different resource blocks. So the system becomes able to divide into standard numbers of sub-carriers. The resource blocks comprise 12 subcarriers. The blocks also cover one time slot in a frame. This is shown in figure 2.11.

Figure 2.11: Downlink Resource Blocks [1]

2.10.5 LTE SC-FDMA in the Uplink

In UL, the SC-FDMA [14] scheme is used. This is a type of OFDMA technology. Another important issue to be addressed here is battery life of mobile equipment. All the companies are nowadays working on improving mobile equipment battery performance, but still the main objective is that the mobiles must use battery power as low as possible.

RF power amplifier transmits the signals to the base station through the antennas. The signal format and radio frequency modulation scheme play an important role in this matter. The signals have a high-peak to-average ratio which requires linear amplification. So a constant operating power level is necessary to be implemented. But unfortunately, OFDM technique has a high peak-to-average ratio.

Since the base station has a lot of equipment and high power is also available, so it is not an issue for base station. But due to small size and less equipment than the base station the mobile station has some issues. In order to overcome this problem, LTE deploys a modulation scheme known as SC-FDM.

The combination of low peak-to-average ratio with flexible subcarrier frequency allocation and the multipath interference resilience results SC-FDM. This low peak-to- average is provided by single-carrier systems and flexible subcarrier frequency allocation is provided by OFDM.

2.11 Multiple Input Multiple Output (MIMO)

The efficiency of the system will be increased by using Multiple Input Multiple Output (MIMO) [8]. In MIMO, additional signal paths are used. These different paths are distinguished by multiple (2 X 2, 4 X 4 or 4 X 2 matrices) antennas. It is comparatively easy to install more antennas at a base station. As the number of antennas is limited due to dimensions of the user equipment so installation of more antennas is a big problem for mobile equipment.

2.12 LTE Architecture

In the LTE architecture, the access side consists of Evolved UTRAN (E-UTRAN) [10] and core side consists of Evolved Packet Core (EPC). Evolved UMTS Terrestrial Radio Access Network (E-UTRAN) [10] consists of Evolved Node B (eNBs) which provide the E-UTRA control plane (RRC) protocol and user plane (PDCP/RLC/MAC/PHY) terminations towards the User Equipment (UE).

The LTE interfaces are following as shown in Figure 2.12  S1-MME, S1-U  S3, S4, S5, Rx  S6a, Gx, S8, S9  S10, S11, S12, S13, SGi

Figure 2.12: LTE Architecture [10]

2.12.1 LTE Network Elements

 The Mobility Management Entity (MME)  The Serving Gateway (SGW)  The Packet Data Network Gateway (PDN-GW)  The Home Subscriber Server (HSS)  The Policy and Charging Rules Function (PCRF)

2.12.2 Frame Structure

There are two types:

 Full and half-duplex FDD shared, the type-1 frame structure  TDD shared type-2 frame structure  The sub frame has a length of 1 ms and consists of two adjacent slots  Radio frame consists of 20 slots having length equal to 10 ms  It uses QPSK, 16QAM and 64QAM as modulation schemes  The QPSK is only used by broadcast channel  6144 bits is the maximum information block size 20

 For error detection, the CRC-24 is used

Figure 2.13: LTE Frame Structure [10]

Figure 2.14: Type-1 Frame Structure [10]

Figure 2.15: Type-2 Frame Structure [10]

Table 2.3: Sub-Frame Number Configuration

Sub-frame Number Switch-Point Periodicity Configuration 0 1 2 3 4 5 6 7 8 9 0 D S U U U D S U U U 5ms 1 D S U U D D S U U D 5ms 2 D S U D D D S U D D 5ms 3 D S U U U D D D D D 10ms 4 D S U U D D D D D D 10ms 5 D S U D D D D D D D 10ms 6 D S U U U D S U U D 10ms

2.12.3 LTE Channels and MAC Layer

Figure 2.16: LTE Channels and MAC Layer [11]

2.12.4 LTE MAC Layer Functionality

MAC layer performs the functions as shown in Figure 2.17

 The mapping between Logical and Transport channels  The error correction via Hybrid Automatic Repeat Request (ARQ)  The prioritization of Logical Channels  The handling of priority by dynamic scheduling

Figure 2.17: LTE MAC Layer Functions [10]

2.12.5 LTE Channel Architecture

Figure 2.18: LTE Channel Architecture [12] It consists of:  RLC layer  MAC layer  Physical layer

2.13 LTE Downlink Channels

Figure 2.19: Downlink Channels [10]

2.13.1 Downlink Logical Channels

 Multicast Traffic Channel (MTCH)  Multicast Control Channel (MCCH)  Dedicated Control Channel (DCCH)  Dedicated Traffic Channel (DTCH)  Common Control Channel (CCCH)  Broadcast Control Channel (BCCH)  Paging Control Channel (PCCH)

2.13.2 Downlink Transport Channels

 Downlink Shared Channel (DL-SCH)  Multicast Channel (MCH)  Broadcast Channel (BCH)  Paging Channel (PCH)

2.13.3 Downlink Physical Channels

 Physical Multicast Channel (PMCH)  Physical Broadcast Channel (PBCH)

 Multicast Control Channel (MCCH)  Physical Hybrid ARQ Indicator Channel (PHICH)  Dedicated Traffic Channel (DTCH)  Physical Downlink Control Channel (PDSCH)  Physical Downlink Shared Channel (PDSCH)

2.14 LTE Uplink Channels

Figure 2.20: Uplink Channels [10]

2.14.1 Uplink Logical Channels

 Dedicated Traffic Channel (DTCH)  Dedicated Control Channel (DCCH)  Common Control Channel (CCCH)

2.14.2 Uplink Transport Channels

 Uplink Shared Channel (UL-SCH)  Random Access Channel (RACH)

2.14.3 Uplink Physical Channels

 Packet Uplink Control Channel (PUCCH)  Physical Uplink Shared Channel (PUSCH)  Physical Radio Access Channel (PRACH) 25

2.15 LTE Mobility, Cell Range & Economic Targets

 The high mobility can be optimized for mobile [11]  The surety for quality of real-time services and voice over total speed range  The excellent performance surety for speeds up to 120 km/h  The best throughput, spectrum efficiency and mobility with cell range up to 30 km  Surety of well mobility maintenance for speeds up to 350 km/h  Some degradation in throughput and spectrum efficiency should be permitted  The reduction in capital & optional Expenditures (i.e. CAPEX and OPEX)  The avoidance of complicated architectures and unnecessary interfaces  The maximum reuse of existing sites  The optimized terminal complexity and power consumption  The optimization of backhaul protocols  The multi vendor environment

3 Wireless Propagation Models

Wireless Propagation Models [13] are very important in cellular networks. The available resources are very limited in cellular networks and we have to make use of them in the best possible manner. An optimized solution is required in order to make use of the spectrum efficiency. This is good in order to improve coverage, capacity and Quality of Service (QoS). The core principle of choosing preeminent and efficient wireless propagation model is to make light of the cost of network while maintaining the QoS in network. In wireless propagation model, we have parameters like path loss, antenna gain, attenuation (rain or fog), SNR etc.

3.1 Introduction

The propagation means transmit the required signal intensity in the given time period and geographic/climatic region over desired distance/area/volume. The wireless propagation model is the relation between the signal radiated and signal received as a function of distance and other variables as shown in figure 3.1.

Figure 3.1: Radio Transmission [14] 27

3.2 Radio Wave Components

 Direct wave The wave in free space is called direct wave.  Attenuated wave The wave attenuated by walls, buildings, atmosphere, is called attenuated in wireless communication. Its frequency is equal or greater than 10 MHz.  Reflected wave The wave after reflection from ionosphere, ground, passive antenna, wall etc is called as reflected wave. Its frequency is equal or less than 100 MHz.  Refracted wave The wave which goes through standard refraction, sub refraction, super refraction, ducting, ionized layer refraction, is known as refracted wave. Its frequency is equal or less than 100 MHz.  Diffracted wave The wave which results after ground diffraction, mountain diffraction, spherical earth diffraction etc, is called diffracted wave. Its frequency is equal or less than 5 GHz.  Surface wave Its frequency is equal or less than 30 MHz.  Scatter wave Tropo scatter wave, ionized-layer scatter wave, precipitation-scatter wave are the types of scatter wave.

3.3 Types of RF/Wireless Propagation Models

The following are the types of RF propagation models.

3.3.1 Free Space Model

The Path loss between receiver and transmitter plays a critical role while discussing Quality of Service (QoS). This formula is valid up to a distance of 55m [13]. It doesn’t take in to account any clutter loss or reflections. Free Space Loss formula is given as:

4πd Free Space Loss =20 log ( 3 . 1 ) (dB) 10 λ Where 휆 = 푊푎푣푒푙푒푛푔푡푕 (푚) 푑 = 푇푟푎푛푠푚푖푡푡푒푟 푡표 푅푒푐푒푖푣푒푟 푠푒푝푎푟푎푡푖표푛 (푘푚)

Figure 3.2: Simple Radio Link Model [14]

The Free Space model [13] means no reflection, no absorption or no other propagation effects. This is an ideal model. Generally, there are two types of Wireless/RF Propagation Models.

 Indoor RF Propagation Models  Outdoor RF Propagation Models

3.4 Indoor RF Propagation Models

Figure 3.3: Indoor Propagation [13]

The following indoor Propagation Models are used in Wireless Communication:

 Log-distance path loss model  ITU Model for Indoor Attenuation  Keenan-Motley Model  Path Loss Slope Model

The Indoor Propagation can be affected due to following reasons:

 Effects of obstructions  Energy Spreading  Effects of Ground  Wavelength  Frequency  Polarization  Environment  Climate  weather  Time

3.5 Outdoor RF Propagation Models

Figure 3.4: Outdoor Propagation [14]

In Wireless Communication the following Outdoor Propagation Models are used:

3.5.1 Foliage models

 Updated ITU model Single Vegetative Obstruction Model One Woodland Terminal Model  Early ITU Model  Weissberger's modified exponential decay model

3.5.2 Terrain models

 ITU Terrain Model  Longley–Rice Model  Egli Model

3.5.3 City models

 Lee Model (Point to Point)  Lee Model (Area to Area)  COST 231 Hata model  Hata Model (for Open Areas)  Hata Model (for Suburban Areas)  Hata Model (for Urban Areas)  Okumura Model  Young Model

3.5.4 Band-specific models

 The ISM Band (i.e. 2.4 GHz, well used in LTE)

Outdoor Propagation can be affected as follows:

 Energy Spreading  Troposphere effects For Clear air For Non-clear air

 Ionosphere effects  Wavelength  Effects of obstructions  Frequency  Polarization  Environment  Effects of Ground  Climate  weather  Time

4 RF Propagation Models in LTE

Long Term Evolution (LTE) is a 3GPP standard for wireless communication networks. It is adopted by 3rd Generation Partnership Project (3GPP) which operates under the ETSI. LTE is a possible replacement of Digital Subscriber Line (DSL). The goals for LTE are reformed spectrum opportunities, lowering costs, best use of new spectrum, improving services, improving spectral efficiency and better integration with other open standards [8]. LTE is such type of wireless technology in which all IP centric services can be delivered over a large coverage area. Its certification indicates interoperability of the equipment built to the 3GPP, 3GPP2 or compatible standard. It is a scalable wireless platform for making alternative and complementary broadband networks. It is not purely 4G technology. It is actually an enhanced version of 3G (one can say it 3.9G). But LTE Advanced is purely a 4G technology, which is still under its deployment phase.

4.1 Introduction

In the previous chapter, RF Propagation Models [13] were discussed in perspective of general cellular networks. Here, the focus will be on best choice of RF Models in LTE network. There is a similarity between architectures of LTE and general cellular networks. Hence, RF model is of great importance in LTE as well. The main function of choosing best RF Model is to ensure the QoS. The optimal solution in designing and planning a network is critical due to the limitation of resources. We will discuss outdoor RF Propagation Models in LTE Network. We are taking two frequency bands for LTE (i.e. 1900MHz and 2100 MHz)

4.2 Outdoor RF Propagation Models for LTE

The following RF propagation models are used as outdoor propagation:

4.2.1 SUI Path Loss Model

The Stanford University Interim (SUI) Path Loss model [1] has been developed by IEEE for IEEE 802.16. This model is used for frequencies above 1900 MHz. As LTE will be using frequency band of 2100 MHz and 2600 MHz, so it is a suitable solution for LTE network. In this propagation model, we have three different types of areas. These are called as terrain A, B and C. Terrain A represents an area with highest path loss which describes an urban area. Terrain B represents an area with moderate path loss which describes a sub-urban area. Terrain C represents the least path loss. Table 4.1 presents the terrains and the factors used in SUI model.

The Path Loss is given by:

d PL (SUI)=A+10γlog10 +Xf+Xh+S (4.1) d0 Where

푃퐿 (푆푈퐼) = 푃푎푡푕 퐿표푠푠, 푖푛 푆푈퐼 푀표푑푒푙, 푚푒푎푠푢푟푒푑 푖푛 푑퐵

퐴 = 퐹푟푒푒 푆푝푎푐푒 퐿표푠푠, 푚푒푎푠푢푟푒푑 푖푛 푑퐵

푑 = 푇푟푎푛푠푚푖푡푡푒푟 푡표 푅푒푐푒푖푣푒푟 푠푒푝푎푟푎푡푖표푛 (푘푚)

푑0 = 100푚 푈푠푒푑 푎푠 푎 푅푒푓푒푟푒푛푐푒

푋푓 = 퐶표푟푟푒푐푡푖표푛 푓푎푐푡표푟 푓표푟 푓푟푒푞푢푒푛푐푦

푋푕 = 퐶표푟푟푒푐푡푖표푛 푓푎푐푡표푟 푓표푟 퐵푆 푕푒푖푔푕푡

푆 = 푆푕푎푑표푤푖푛푔

훾 = 푃푎푡푕 푙표푠푠 푐표푚푝표푛푒푛푡

휸 factor is given as: c γ= a-bbh+ (4.2) hb

Where

푕푏 = 퐻푒푖푔푕푡 표푓 퐵푎푠푒 푆푡푎푡푖표푛 퐵푆 34

Where a, b and c describes the terrain, and there values are selected from Table 4.1 [1].

Table 4.1: Different Terrains and Parameters for SUI Model [1]

Parameters Terrain A Terrain B Terrain C

A 4.6 4 3.6

B 0.0075 0.0065 0.005

C 12.6 17.1 20

Where

푇푒푟푟푖푎푛 퐴 = 푈푟푏푎푛 퐴푟푒푎 푇푒푟푟푖푎푛 퐵 = 푆푢푏 − 푈푟푏푎푛 퐴푟푒푎 푇푒푟푟푖푎푛 퐶 = 푅푢푟푎푙 퐴푟푒푎

The frequency correction factor is given as:

f X = 6.0 log (4.3) f 10 2000

For terrain A and B, correction factor of BS height is explained in following expression h X = -10.8 log r (4.4) h 10 2000

For terrain C, the correction factor for BS height is given by the following expression: h X = -20 log r (4.5) h 10 2000

The shadowing factor is given by:

2 S= 0.65 log10 f - 1.3 log10 f+α (4.6)

Where

훼 = 5.2 푑퐵 푓표푟 푇푒푟푟푎푖푛 퐴 푎푛푑 퐵 푎푛푑 6.6 푑퐵 푓표푟 (푇푒푟푟푎푖푛 퐶) 푕푟 = 퐻푒푖푔푕푡 표푓 푅푒푐푒푖푣푒푟 퐴푛푡푒푛푛푎

4.2.2 Ericsson 9999 Model

The Ericsson 9999 Model [15] is in fact an extend version of Hata Model and implemented by Ericsson in which we can adjust parameters according to the given scenario. The Path Loss is given by: 35

PL (Eric)=Z1+Z2+Z3+Z4-Z5+Z6 (4.7)

Where

푃퐿 (퐸푟푖푐 ) = 푃푎푡푕 퐿표푠푠, 푖푛 퐸푟푖푐푠푠표푛 푀표푑푒푙, 푚푒푎푠푢푟푒푑 푖푛 푑퐵

푍1 = 푎0

푍2 = 푎1푙표푔10(푑)

푍3 = 푎2푙표푔10 (푕푏 )

푍4 = 푎3푙표푔10 푕푏 푙표푔10(푑) 2 푍5 = 3.2{푙표푔10 11.75푕푟 } 2 푍6 = 44.49 푙표푔10 푓 − 4.78{푙표푔10 푓 }

Where

푎0 , 푎1 , 푎2 and 푎3 are values, which are changed according to the environments (i.e. areas). For different areas, the parameters are described in following Table 4.2 [21].

Table 4.2: Parameters and Terrains for Ericsson 9999 Model [21]

Parameters Rural Area Sub-Urban Area Urban Area

풂ퟎ 45.95 43.20 36.2

풂ퟏ 100.6 68.93 30.2

풂ퟐ 12.0 12.0 12.0

풂ퟑ 0.1 0.1 0.1

4.2.3 Okumura Model

Okumura model [16][18] is one of the most widely used models used for signal prediction in urban areas. This model is applicable for frequencies from 150 MHz to 1920 MHz and a distance of 1 km to 100 km. It can be used for base station antenna heights ranging from 30m to 1000m. For dense cities, it is the best model. Okumura gives overview of correction factors for open, sub-urban and quasi areas. Okumura model is used to calculate path loss for up to 3 GHz. But we will discuss it at 2100 MHz and 2600 MHz frequencies.

The Path Loss is given by:

PL (Okum)=+Amn f,d -G hb -G hr -GAREA (4.8)

Where

푃퐿 (푂푘푢푚 ) = 푃푎푡푕 퐿표푠푠, 푖푛 푂푘푢푚푢푟푎 푀표푑푒푙, 푚푒푎푠푢푟푒푑 푖푛 푑퐵

퐿푓 = 퐹푟푒푒 푆푝푎푐푒 푙표푠푠

"퐺 푕푏 " is called Base Station (BS) antenna height gain factor, which is given by: h G h =20log b (4.9) b 10 200

퐺 푕푟 is called Mobile Station (MS) antenna height gain factor, which is given by: h G h =10log ( r ) (4.10) r 10 3

퐺퐴푅퐸퐴 = 퐺푎푖푛 푑푢푒 푡표 푡푕푒 푡푦푝푒 표푓 푒푛푣푖푟표푛푚푒푛푡

퐴푚푛 푓, 푑 = 푀푒푑푖푎푛 푎푡푡푒푛푢푎푡푖표푛 푟푒푙푎푡푖푣푒 푡표 푓푟푒푒 푠푝푎푐푒

The values of 퐺퐴푅퐸퐴 gain and Amn (f, d) factor, for different areas, are determined from graph as shown in Figure 4.1 [20].

Figure 4.1: Correction Factor and Median Attenuation for Okumura Model [20]

From above figure, we construct the following table.

Table 4.3: Different Terrains and Parameters for Okumura Model

Open Sub-Urban Quasi Open Parameters Frequencies Area Area Area At 2100 MHz 32 13 28 (Correction Factor) At 2600 MHz 34 13.5 29.5 At 2100 MHz 36 34 30.5

(Median Attenuation) At 2600 MHz 38 35 32

4.2.4 COST 231 Hata Model

Hata Model [17] is introduced as an empirical formulation of the graphical path loss data provided by Okumura and is valid from 150 MHz to 1500 MHz. Hata model is used to calculate the median path loss at following conditions.

 Distance between Tx and Rx of 20 km.  The height of transmitter antenna ranges from 30 m to 200 m.  The height of receiver antenna ranges from 1 m to 10 m.  Frequency range is 150 MHz to 1500 MHz.

An extend version of Hata Model is known as COST 231 Hata Model [18]. In three different areas (i.e. sub-urban, urban and rural), it is used to calculate path loss. It provides simple and easy ways for calculations.

The path loss model equation is given as:

PL(dB) = 46.3 + 33.9 log (f) - 13.02 log (hb) – a(hr) +[44.9 - 6.55 log (hb)]. log(d) + c (4.11)

The path loss is also given by: PL=N1+N2-N3-N4+N5+N6 (4.12) Where 38

푃퐿 = 푃푎푡푕푙표푠푠, 푖푛 퐶푂푆푇 231퐻푎푡푎 푀표푑푒푙, 푚푒푎푠푢푟푒푑 푖푛 푑퐵 N1=46.3 N2=33.3 log f N3=13.82 hb log (4.13) N4=ahm

N5= 44.9-6.55 log hb log d (4.14) 푁6 = 퐶푚 ahm parameter is given by:

For Urban Area: ahm=32 log 11.75hr *2 -4.799 (4.15)

For Rural and Suburban Areas: ahm= {1.11 log (f) - 0.7}hr - {1.5 log (f) -0.8} (4.16)

The Cm parameter, for different areas, is described in Table 4.4 [22]

Table 4.4: Different Terrains and Parameters for COST 231 Hata model [22]

Parameters Rural Area Sub-Urban Area Urban Area

3dB 0dB 3dB

4.2.5 COST 231-Walfisch Ikegami Model

Another important and popular outdoor Propagation Model for LTE is COST 231- Walfisch Ikegami Model. This empirical model is a combination of the models from J. Walfisch and F.Ikegami. It is also called as an extension of COST 231 Hata Model [18].

It is considered for both line of sight conditions. It is designed for 800 MHz to 2 GHz and is especially suitable for predictions in dense urban conditions [19]. The case of line

39 of sight is approximated by a model using free-space approximation up to 20 m and the following equation:

PL= 42.64 + 26 log (d) + 20 log (f) (4.17)

The path loss model equation for non line of sight takes into accounts various scattering and diffraction properties of the surrounding buildings which is shown below

PL= Lo + 퐿푅푇푆 + 퐿푀퐷푆 (4.18)

퐿표 = 32.45 +20 log (d) + 20 log (f) (4.19)

퐿푅푇푆 = -16.9 - 10 log (w) + 10 log (w) +20 log (푕푏 - 푕푟 ) + 퐿표푟푖 (4.20)

−10 + 0.354푎 푓표푟 0 < 푎 < 35

퐿표푟푖 = 25 + 0.075 푎 − 35 푓표푟 35 < 푎 < 55 (421) 4 − 0.114 푎 − 55 푓표푟 55 < 푎 < 90

(3.18)

5 Experimental Results

The radio propagation model describes the behaviour of the signal when it is being transmitted from the transmitter towards the receiver. It gives a relation to the distance between the transmitter & receiver and the path loss. From the above relation, one can get an idea about the acceptable path loss and the maximum cell range. The path loss depends on different terrains and environment (urban, rural, dense urban, suburban, open, forest, sea etc) frequencies, atmospheric situation, and distance between transmitter and receiver.

5.1 Simulation of Path Loss for different RF Models

The path loss is calculated by using path loss equations discussed earlier for RF Propagation Models. The resulted graphs are plotted by using MATLAB. In our calculations, we use different parameters such as carrier frequencies, distance between transmitter and receiver, receiver height and base station height. The simulation parameters for the propagation models are given in the Table 5.1.

These parameters are used in the simulation scenario to achieve the given results. All the propagation models are almost available to be used both in LOS & NLOS environment. To make our scenario more practical in the simulations, NLOS is used in urban, suburban & rural conditions. But for rural area in COST 231 W-I model LOS condition is considered because it does not provide any specific parameters.

TABLE 5.1: Simulation Parameters

Parameters Values

Base station transmitter power 43 dBm

Mobile transmitter power 30 dBm

Transmitter antenna height 20 m & 70 m in urban, suburban and rural area

Receiver antenna height 2 m

In suburban and rural (8.2 dB) and In urban Correction for shadowing area (10.6 dB) Operating frequency 1900 MHz & 2100 MHz

Distance between Tx-Rx 8 km

Building to building distance 50 m 15 m Average building height 25 m

Street width Street orientation angle 300 in urban and 400 in suburban

5.1.1 Simulation Results of Okumura Path Loss Model

Figure 5.1 & Figure 5.2 gives simulation results for the path loss in Okumura model for 2100 MHz & 1900 MHz respectively.

Figure 5.1: Path Loss simulation results for Okumura Model (1900 MHz)

Figure 5.2: Path Loss simulation results for Okumura Model (2100 MHz)

5.1.2 Simulation of SUI Path Loss Model

It is used for frequencies above 1900 MHz. In this propagation model, three different types of terrains or areas are considered. These are called as terrain A, B and C. Terrain A represents an area with highest path loss, and it is dense populated area. The suburban environment is represented as Terrain B that has a moderate path loss. Rural area is given as Terrain C and has the least path loss. Table 5.2 shows us the different terrains and factors used in SUI model. For 2100 and 1900 MHz, the results for path loss of urban, sub-urban and rural regions are shown in the Figure 5.1 and Figure 5.2.

TABLE 5.2: Terrains and parameters

Parameters Terrain A Terrain B Terrain C A 4.5 4 3.7 b(1/m) 0.0076 0.0064 0.005 c(m) 12.5 17.3 20

Figure 5.1: Path Loss simulation results for SUI Model (1900 MHz)

Figure 5.2: Path Loss simulation results for SUI Model (2100 MHz)

5.1.3 COST 321 Hata Model

The numerical results of path loss, for urban, sub urban and rural areas, for 1900 MHz 2100 MHz, is shown in the Figure 5.3 & Figure 5.4 shows the calculation of path loss in COST Hata model for 1900 MHz & 2100 MHz respectively.

Figure 5.3: Path Loss simulation results for Hata COST 231 Model (1900 MHz)

Figure 5.4: Path Loss simulation results for Hata COST 231 Model (for 2100 MHz)

5.1.4 Simulation of COST-231 Walfisch-Ikegami Model

COST-231 Walfisch-Ikegami model is an extension of COST Hata model. For 1900 and 2100 MHz, the results for path loss in COST-231 Walfisch-Ikegami Model are shown in the Figure 5.5 and Figure 5.6

Figure 5.5: Path loss simulation results for COST-231 Walfisch-Ikegami Model (1900 MHz)

Figure 5.6: Path loss simulation results for COST-231 Walfisch-Ikegami Model (2100 MHz)

5.1.5 Simulation of Ericsson Model

In this model, we can adjust the parameters according to the given scenario. Figure 5.7 & Figure 5.8 represents the path loss for Ericsson 9999 model.

Figure 5.7: Path Loss simulation results for Ericsson 9999 Model (1900 MHz)

Figure 5.8: Path Loss simulation results for Ericsson 9999 Model (2100 MHz)

6 Conclusion and Future Work

6.1 Conclusion

The resulted path losses for required three terrains, urban, sub urban and rural are achieved. Simulation results show that SUI model has the lowest path loss calculation (61.98dB to 80.57dB) in urban area for 1900 MHz and 2100 MHz respectively. On the other hand, COST Hata model has the highest path loss of 216.9 dB here for 2100 MHz in urban environment as shown in Table 5.3.

Table 5.3: Comparative analysis of RF Propagation Models (Urban Environment)

Model Frequency Distance Base station Receiver Path loss (MHz) (Km) height (m) height(m) (dB) Okumura 1900 8 20 2 83.22 Okumura 1900 8 70 2 72.34 Okumura 2100 8 20 2 83.22 Okumura 2100 8 70 2 72.45 SUI 1900 8 20 2 61.98 SUI 1900 8 70 2 64.48 SUI 2100 8 20 2 63.24 SUI 2100 8 70 2 80.57 COST 231 1900 8 20 2 215.4 COST 231 1900 8 70 2 200.5 COST 231 2100 8 20 2 216.9 COST 231 2100 8 70 2 202 Ericsson 1900 8 20 2 110.2 Ericsson 1900 8 70 2 103.8 Ericsson 2100 8 20 2 110.8 Ericsson 2100 8 70 2 104.3 WalfischIkegami 1900 8 20 2 158 WalfischIkegami 1900 8 70 2 158 WalfischIkegami 2100 8 20 2 156.5 WalfischIkegami 2100 8 70 2 156.6

Likewise, in sub urban area the results are more or less the same. The lowest path loss of 64.48 dB for 1900 MHz and 65.74 dB for 2100 MHz has been calculated for SUI model. COST Hata model gives the highest path loss of 210.7 dB for 1900 MHz frequency. COST Walfisch-Ikegami model gives path loss of 155.2 and 160.2 for 1900 MHz and 2100 MHz frequencies respectively in sub-urban environment as shown in Table 5.4.

Table 5.4: Comparative analysis of RF Propagation Models (Sub-Urban Environment)

Model Frequency Distance Base station Receiver Path loss (MHz) (Km) height (m) (m) (dB) Okumura 1900 8 20 2 101.2 Okumura 1900 8 70 2 90.34 Okumura 2100 8 20 2 101.2 Okumura 2100 8 70 2 90.34 SUI 1900 8 20 2 64.48 SUI 1900 8 70 2 64.48 SUI 2100 8 20 2 65.74 SUI 2100 8 70 2 65.74 COST 231 1900 8 20 2 210.7 COST 231 1900 8 70 2 195.8 COST 231 2100 8 20 2 212.1 COST 231 2100 8 70 2 197.2 Ericsson 1900 8 20 2 145.2 Ericsson 1900 8 70 2 138.7 Ericsson 2100 8 20 2 145.8 Ericsson 2100 8 70 2 139.7 WalfischIkegami 1900 8 20 2 155.3 WalfischIkegami 1900 8 70 2 155.3 WalfischIkegami 2100 8 20 2 160.2 WalfischIkegami 2100 8 70 2 160.2

In rural area SUI model gives the lowest path loss of 54.53 dB for 1900 MHz and 55.79 dB for 2100 MHz. COST Hata 231 model gives the highest path loss 212.1 dB for 2100 MHz and COST Walfisch-lkegami model gives path loss of 131.7 dB and 132.5 dB for 1900 MHz and 2100 MHz respectively as shown in Table 5.5.

Table 5.5: Comparative Analysis of RF Propagation Models (Rural Environment)

Model Frequency Distance Base station Receiver Path loss (MHz) (Km) height (m) (m) (dB) Okumura 1900 8 20 2 90.22 Okumura 1900 8 70 2 79.34 Okumura 2100 8 20 2 90.22 Okumura 2100 8 70 2 79.34 SUI 1900 8 20 2 92.93 SUI 1900 8 70 2 54.53 SUI 2100 8 20 2 94.19 SUI 2100 8 70 2 55.79 COST 231 1900 8 20 2 210.7 COST 231 1900 8 70 2 195.8 COST 231 2100 8 20 2 212.1 COST 231 2100 8 70 2 197.2 Ericsson 1900 8 20 2 173.8 Ericsson 1900 8 70 2 167.3 Ericsson 2100 8 20 2 174.4 Ericsson 2100 8 70 2 167.9 WalfischIkegami 1900 8 20 2 131.7 WalfischIkegami 1900 8 70 2 131.7 WalfischIkegami 2100 8 20 2 132.5 WalfischIkegami 2100 8 70 2 132.5

Ericsson Model has more path loss as compared to COST Walfisch-Ikegami model in rural environment. In the same way, Ericson model gives more path loss in sub urban and rural terrains as compared to urban terrain, which is an abnormal behaviour. This behaviour is because the Ericsson model was meant to design for urban and dense urban areas and it does not give precise information concerning sub urban and rural environment. Therefore respective values can be overlooked. Here COST Walfisch- Ikegami is also essential as it shows additional parameters that are used to describe some environmental properties.

In all three terrains described above the base station height has no major effect on the path loss of SUI model but all the other model shows a variation in path loss when the base station heights are changed. In this regard Okumura model has the preeminent 50 variations. It is very important to note that all of these models are described by their empirical formulae that are the path loss equations. Some models are specifically designed for a particular terrain. For example all cost models are made for highly urban and dense urban areas and these models also uses some other parameters (antenna polarization, building heights, and angle of antenna etc.) that is why they are giving a very high path loss so they will be used for specific areas depending on our environment conditions. COST Walfisch-Ikegami model uses some other parameters as discussed earlier so it shows a higher path loss from the other models for all the areas.

From the above calculations we conclude that when the height of the base station changes the value of the path loss decreases for these models. Hence it is cleared that height of the base station plays a vital role in determining the path loss for these propagation models in LTE. On the other hand, when frequency increases path loss increases but this change is not very remarkable. So, frequency and height has a major effect on path loss in the scenario these are implemented in this research work.

6.2 Future Work

Following suggested works in this field would be innovative.

 In future, our simulated propagation model results can be tested and verified practically in Indoor environments

 Further study can also be made for these propagation models in LTE Advance.

 Also, we can build a software or tool dedicated for cell planning in LTE Network by using the propagation models described in our simulations.

 We can also add traffic capacity and coverage features in that tool.

 We can use also used a frequency of 2600 MHz for some areas to calculate the path loss.

7 Bibliography

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