DESIGNING A WiMAX COMMUNICATION NETWORK FOR ACCRA FOR BROADBAND WIRELESS ACCESS

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ISSN: 2278 – 1323 International Journal of Advanced Research in Computer Engineering & Technology (IJARCET)

Volume 5, Issue 4, April 2016

DESIGNING A WiMAX

COMMUNICATION NETWORK FOR

ACCRA FOR BROADBAND WIRELESS

ACCESS

Joseph Kweku Arthur

Faculty of engineering, Ghana Technology University College PMB 100, Tesano- Accra, Ghana

Abstract –WiMAX, which represents World Interoperability for Microwave Access, is a major part of broadband wireless access (BWA) network (IEEE 802.16 standard) provides fixed and mobile platform for broadband internet access anywhere atany time. The ever-growing demand for high-speed data connectivity makes broadband wireless access networks one of the hottest topics in the field of telecommunications. The various form of communication networks such as 2G, 3G and other BWA networks used to deliver data to users have some degree of limitations in terms of data rate and challenges with distance. This study aims at designing a broadband communication network for Accra the capital city of Ghana using WiMAX technology. The research work introduces readers to the practical concepts of IEEE802.16e – 2005 thus mobile WiMAX standard technology. The work also collected information and used calculations on how to plan the network and determine the number of Base Stations (BSs) and their coordinates, azimuth and mechanical tilt to provide sufficient signal coverage and capacity to the designated area. Link budget calculation was used to determine the viability of the design link and the link margin, which shows the stability of our link. The research work used calculation to determine the maximum number of subscribers that each specific Mobile WiMAX site may support.The results and the information obtained were used to design a reliable network with high data rates and increase capacity for longer distance. The design used 19 base stations (BS) to cover an area of 230 sq km. The capacity of each base station is 300Mbps and can support 256 active subscribers and a user data rate of 1Mbps

Index Terms: WiMAX, BWA, link budget, page response, end-to-end delay, WiMAX load, WiMAX delay

1 INTRODUCTION

Wireless communication is becoming a major factor in our daily lives. As one of the most important broadband wireless technologies, Worldwide Interoperability for Microwave Access (WiMAX) is anticipated to be a viable

alternative to traditional wired broadband techniques due to its cost efficiency[1]. Worldwide Interoperability for Microwave Access (WiMAX) is a certification mark for products that pass conformity and interoperability tests for the IEEE 802.16 standards. Products that pass the conformity tests for WiMAX are capable of forming wireless connections between them to permit the carrying of internet packet data. The idea of WiMAX is similar to Wi-Fi. It is a step much higher than Wi-Fi because it is focused on offering internet for a whole city. It has a much higher capacity and longer distances.

The Institute of Electrical and Electronics Engineers (IEEE) 802.16 standard, widely known as Worldwide Interoperability for Microwave Access (WiMAX), defines the Medium Access Control (MAC) and the Physical (PHY) layer specifications for the broadband wireless access networks[2]. WiMAX offers an alternative to wired networks, such as coaxial systems using cable modems, fiber optics and DSL (Digital Subscriber Line) . The IEEE 802.16 standard is a real revolution in wireless metropolitan area networks (Wireless MANs) that enables high-speed access to data, video, and voice services[3]. Worldwide Interoperability for Microwave Access (WiMAX) is a technology for point to multipoint wireless networking. The designing of a WiMAX technology in Accra is expected to meet the needs of a large variety of users who need high speed data network. Additionally, its main advantage is fast deployment, which results in cost savings. WiMAX installation can be beneficial in very crowded geographical areas like Accra, and in rural areas where there is no wired infrastructure.

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Volume 5, Issue 4, April 2016 802.16e or 802.16-2005 was also released and aimed at the

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roaming and mobile markets[2]. Below from the WiMAX Forum summarizes the 802.16 standards.

Table 1. Summarizes the 802.16 standards [4]

Completion Date 802.16 Dec 2001 802.16a/802.16R EVd 802.16a: Jan 2003 802.16REVd: Q3 2004 802.16e 2005

Spectrum 10 to 66

GHz < 11 GHz < 6 GHz

Channel Conditions Line-of-Sight only Non-Line-of-Sight Non-Line-of-Sight Bit Rate 32 to 134Mbp s

75Mbps max 20-MHz channelization 15Mbps max 5-MHz channelizatio n Modulation QPSK; 16QAM ; 64QAM OFDM 256 subcarrier QPSK 16QAM 64QAM Same as 802.16a

Mobility Fixed Fixed

Pedestrian mobility Regional roaming Channel Bandwidths 20, 25 and 28 MHz Selectable between 1.25 and 20 MHz Same as 802.16a with uplink subchannels Typical Cell Radius

1 to 3 miles

3 to 5 Miles (30 miles max based on tower height, antenna gain and transmit power)

1 to 3 miles

In the wireless domain, WiMAX promises high data rate over long-range transmission and supports both fixed and mobile transmission. WiMAX is a standard-based technology, interoperability of the IEEE 802.16 standard, officially known as Metropolitan Area Network (Wireless MAN). WiMAX provides fixed, nomadic, portable and mobile wireless broadband connectivity[5]. The WiMAX standard delivers high-speed broadband Internet access over a wireless connection.

The MAC layer of WiMAX supports Point-to-Multipoint (PMP) and Mesh Topologies. The wireless medium access is based on either Time Division Multiple Access (TDMA) or Frequency Division Multiple Access (FDMA), with Frequency Division Duplex (FDD) and Time Division Duplex (TDD) as duplexing techniques.

Multiple PHY layer specifications are supported for Line-of-Sight (LOS) and Non-Line-Line-of-Sight (NLOS) operational environments in 10-66 GHz and 2-11 GHz frequency bands, respectively. Later on the IEEE 802.16e amendment added mobility support to WiMAX networks. WiMAX is a 3.9G standard or what is called a supper 3G network[6][7]. It is the American version, in attempt to implement a 4G standard. Long Term Evolution (LTE) on the other hand is the European attempt to implement 4G standard. LTE, just like WiMAX fell short of the 4G specifications and it is also a 3.9G standard. LTE-Advance, (LTE-A) and 802.16m are the true 4G standard. The deployment of WiMAX will not only provide services for residential and enterprise, but it can also benefits from 3G cellular towers and Wi-Fi hotspots and serve as a backhaul for both of them. The WiMAX technology will revolutionize the communications by offering affordable wireless broadband access, which will lead to the development of many areas nationwide and bridging the digital divide in Accra and other parts of Ghana.

The National communication Authority (NCA) Ghana, has recently issued 3 BWA licenses in the 2500 MHz – 2690 MHz band that could be used for either WiMAX or LTE data networks. The Authority received nine (9) applications: five (5) applications for paired frequency configuration of 2 x 15MHz, and four (4) applications for unpaired frequency configuration of 1 x 30MHz. At the end of the process, Surfline Limited and GoldKey Properties Limited each won a license for paired frequency configuration and G-Kwiknet Limited won a license for unpaired configuration; each license at a price of Six Million (US$6,000,000.00) United States Dollars for the period of 10years[8].

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 Designing a reliable wireless network using WiMAX technology for broadband wireless access and mobile applications for Accra.

 Designing architectures for a proposed fixed and a mobile WiMAX network for Accra.

Consequently, this research work will try to introduce a preliminary design of WiMAX network for Ghana and Accra to be precise.The importance of this research is to show the technological benefits of WiMAX gives; it greater system capacity, flexibility and ability to efficiently support more symmetric links compared to the other wireless networks.

WiMAX has extensive capabilities to substitute various world communication infrastructures that are in use at present. It can substitute the telephone copper wire networks and cable TV coaxial cable infrastructure in fixed wireless area and in case of cellular networks; it can substitute the entire network efficiently. The main factor here is the cost, which is considerably reduced when compared to services like the Cable, ADSL and Fiber Optics.

2 METHODOLOGY

2.1 General Overview of the Design

The research work is aimed at designing a WiMAX communication network for Accra the capital city of Ghana for broadband wireless access. As part of the Wireless network design process, the number of Base Stations (BSs) and their coordinates, azimuth and mechanical tilt to provide sufficient signal coverage and capacity to the designated area will be determined; BS placement within the area of interest will also be discussed. WiMAX has theoretical maximum throughput of 75Mbps for frequency less than 11GHz and a bandwidth of between 1.25MHz to 20MHz with fixed mobility and can be used for NLOS. This throughput for our network can be achieved by using 64QAM, 16QAM and QPSK modulation but 64QAM can only be utilized under optimal transmission conditions. WiMAX supports wide range of modulation algorithms to enable the efficient use of the bandwidth under all conditions; LOS and NLOS conditions and its communication range can be 50km.

2.2 The network design

The WiMAX network design will employ the WiMAX technology known as the Mobile WiMAX, which is a rapidly growing broadband wireless access technology based on IEEE 802.16-2004 and IEEE 802.16e-2005 air-interface standards. This set of standards specifically determines the rules and regulations for end-user broadband

access.Mobile WiMAXwas used because it offers the design, the required speed and most importantly the distance. Mobile WiMAXhas the capability of mobile units to hand off between base stations. True mobility is therefore enabled in addition to what 802.16d-2004 (Fixed WiMAX), already features. WiMAX is the first solution conceived to support IP data efficiently and be capable of providing wireless high-speed data to wide areas, improving spectrum efficiency over previous technologies. The geographical area of Accra will be divided into a number of hexagons, the sites are place in to achieve maximum optimization. However, there are portions of Accra that will not have continuous coverage since the population there are scattered e.gAchimota forest. To remove the blind spots in the coverage area, the cell footprints must overlap. The footprint of each cell needs to be calculated or known for the estimation of the number of base stations,

Number of required base stations =𝑆𝑒𝑟𝑣𝑖𝑐𝑒 𝐴𝑟𝑒𝑎 (𝑘𝑚 2)

𝐶𝑒𝑙𝑙 𝐹𝑜𝑜𝑡𝑝𝑟𝑖𝑛𝑡 (𝑘𝑚 2)or

𝑡𝑜𝑡𝑎𝑙 𝑎𝑟𝑒𝑎 (𝑘𝑚 2)

2.598𝑅^2 (1)

Where R = radiusof the base stations.

Base on the equation above, we have the number of

base stations = 240

2.598 ∗ 3^2=10.26

This means we will require a minimum of 10 or more base stations in order to cover the overall geographical area of Accra if a cell radius of 3km is used. The number of base stations is not determined by the size of geographical region alone, but also the capacity limitations of the area understudy. The number of users expected to be serviced on each base stations is also an important factor. So the above calculation gives only the minimum number of base station required, these limitation will be taken care of when the network coverage simulation is done hence the number of base station will increase. In thiscase cells in a three-sector base station will be used, because they are more preferred for a more precise coverage. Thesector cell coverage area of a base station with three sectors is defined by the formula:

𝐴 𝑐𝑒𝑙𝑙 = 2.59𝑅2₍₂₎

Where A cell - Coverage area of a base station and R- Radius of the cell's base station.

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2.3 Environment

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The base station will be built on towers and rooftops. The deployment of the design network will be a combination of outdoor and indoor units. In the design, obstacles between two base stationswill be avoided, to enable Line of Sight (LOS) communication.The Accra landscape does not have very high mountains and this will make the design less complex and cost effective. The subscriber station (SS) will use Non Line of sight (NLOS) in communicating with the base station. In the city of Accra, there is no heavy fog in the night and hence our design networks will not surfer much signal degradation or fading during the night. The Greater Accra Region has a total estimated land surface of 3,245 square kilometers and in terms of population; it is estimated at 4,010,054. But the capital Accra which is been used as the case study has a total land size of about 230 to 240 square kilometers and estimated population of about Two Million (2,000,000) . It is made up of eleven (11) sub metros.Figure 1 represents an administrative map of Accra[9].

Figure 1. The Administrative Map of Accra [9]

2.4 Network Topology and Link Type

The physical network layout that was chosen,depended on the nature of the land topology of Accra. The wireless network will be configured using these two logical configurations: to-point links and Point-to-multipoint links. The topology of a network is one of the major factors that determines throughput, robustness,

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reliability, security and cost. Figure 2 shows the network topology and link type.

Figure 2. Network Topology and Link Type

2.4.1 Link Budget

A fundamental concept in any communications system is the link budget, or the summation of all the gains and the losses in the communication network[10]. There is the need to calculate the transmit power from the transmitter required to achieve a signal with a required Signal to Noise Ratio (SNR) at the receiver for a targeted Bit Error rate (BER). The overall link margin is given by the difference in the power received by the receiver and the receiver sensitivity. The link margin must be positive, and should be maximized (should be at least 10dB or more for reliable links).

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P received = Power of the transmitter + Gain of the transmitting antenna + Gain of the Receiving antenna – Sum of all losses.

(𝑃𝑟 = 𝑃𝑡𝑥 + 𝐺𝑡𝑥 + 𝐺𝑟𝑥 − 𝐹𝑆𝐿 − 𝐴𝑚)(3)

Now receive power in Watts will be:

𝑃𝑟 = 𝑃𝑡( 𝜆

4𝜋𝑑)²𝐺𝑟𝐺𝑡(4)

2.4.1.1 Transmit Power(Tx).

The transmit powers used in this research are 23dBm and 15dBm and it can be express in Watt. This power was chosenfor the parabolic and the panel antennas respectively. TX power is often dependent on the transmission rate. The TX power of the given devices that was used was specified in the literature provided by the manufacturer.

2.4.1.2 Antenna Gain

The shape of the antenna determines the antenna gain. Antenna gain patterns are a function of azimuth and elevation and have an associated half-power bandwidth. Antennas are passive devices that create the effect of amplification by virtue of their physical shape. Antennas have the same characteristics when receiving and transmitting. The parabolic antennas that were used has a gain of 19-24 dBm, and the sectorial antennas have roughly a 12-15 dBi gain.

2.4.1.3 Minimum Received Signal Level (RSL).

It is simply, the sensitivity of the receiver. The smallest amount of RSL is always expressed as a negative dBm (- dBm) and is the least power of signal the radio can distinguish. The minimum RSL is dependent upon rate of data; the minimum for this research is in the range of -70 to -95 dBm.

2.4.1.4 Cable Losses.

Some of the signals energy will be lost in the cables, the connectors and other devices, going from the radios to the antennas due to the imperfection in the system and dirt. These losses are dependent on the type of cable used and on its length. Signal loss for short coaxial cables including connectors is quite low, in the range of 2-3 dB. In this research, a loss per connector value of 0.25dBwas used and it is estimated that the total losses will be in the region of 2dB.

2.4.1.5 Signal-to-Noise (SNR)

Table shows modulation schemes with their corresponding SNR requirements

Table 2. Data Rates vs. Minimum SNR

Modulation& Encoding Scheme

Data Rate (Mbps)

SNR (dB)

BPSK ½ 6 8

BPSK ¾ 9 9

QPSK ½ 12 11

QPSK ¾ 18 13

16-QAM ½ 24 16

16-QAM ¾ 36 20

16-QAM 2/3 48 24

16-QAM ¾ 54 25

2.4.1.6 Path Loss

These are losses, which occur in the process of transmitting radio frequency signals from the transmitter to the receiver and it is dependent on frequency. Therefore, a lower operating frequency of 2.4GHzwas chosen for the design, to reduce the path loss, which means the signals can travel further. In a typical WiMAX link, there are two link budget calculations: one link from the BS to the SS and the other link from the SS to the BS. The general path loss can be express as:

Free Space Path Loss = 20 log (d [meters]) + 20 log (f

[MHz]) + 36.6 dB. [11](5)

At 2.4 GHz, the formula simplifies to:

Free Space Path Loss (FSPL) = 20 log (d [meters]) + 40 dB, or 100 + 20*log (d)(6)

Where FSPL is expressed in dB and d is in kilometers and d = distance and f = frequency.

These formulas are used for Line of sight (LOS) calculation where there are no many obstacles. Another formula is used for indoor calculation where LOS is difficult to achieve. At 2.4 GHz, our estimate follows this formula:

Indoor Path Loss (2.4 GHz) = 55 dB + 0.3 dB / d [meters](7)

2.4.2 Fresnel Zone

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Volume 5, Issue 4, April 2016 must be clear of any obstacle for the maximum power to

reach the receiving antenna. Objects within the Fresnel Zone such as trees, hilltops and buildings can considerably attenuate the received signal, even when there is an unobstructed line of sight (LOS) between the transmitter (TX) and receiver (RX)[12].

Figure 4. Fresnel Zone.

2.4.3 Frequency Band

The mobile WiMAX network design will operate in theunlicensed frequency band of 2.4GHz called the Industrial, Scientific, and Medical (ISM) Band. The 2.4 GHz ISM band has an inherently stronger signal with a longer range and can travel through walls.The ISM bands were originally reserved internationally for non-commercial use of RF electromagnetic fields for industrial, scientific, and medical purposes. However, this frequencywas chosen for this work because of its strong signal properties.

2.4.4 Antenna and Advanced Antenna Systems

Two types of antennas were used in this design and they were chosen base on their gain, transmitand receive powers, voltage standing wave ratio (VSWR), impedance and frequency. The sample antenna shown in Figure 5 are the cross-polarized sector antenna panel type and parabolic dish antenna. The sector panel antennas are often used outdoors to cover a sector of a cell while the parabolic can be used for both between sites and users. They operate within the frequency range of 2.4 - 2.5GHz band and it has again of 17.5dBi and 30dBi and offers excellent maximum front-to-back ratio of greater than 32dB. The antenna has a nominal impedance of 50 ohms. The polarization of the antenna is vertical with an azimuth of 60º and elevation of 6º beam widths. The antennas have a very good voltage standing wave ratio (VSWR) of less than 1.5 and operate at a power of 200W to 250W. The antenna uses a multiple

input multiple output (MIMO) array modulation scheme. Spatial multiplexing (SM) or MIMO (Multiple In signal and Multiple Out signal) are improvements over the previous solution that uses simultaneous transmit and receive diversity[1].

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Figure 5. Typical WiMax Sector Antenna and parabolic dish Antenna

2.5 Link Budgetcalculations

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The table below shows the antenna parameters that were used in the link budget calculation between two sites.

Table 3. Parameter for panel antenna.

Element Value

Transmit output 15dBm

Cable and connectors for TX

-1dB

Antenna TX 18dBi

FSL 109.54

Antenna RX 18dBi

Cable and connectors for RX

-1dB(0.25dB per connector)

Receive Sensibility -85dBm

Total: (margin) 24.46dBm

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Volume 5, Issue 4, April 2016 FSPL = 100 + 20*log (d), where FSPL is expressed

in dB and d is in kilometers and d = distance and f = frequency. Therefore if the distance is 3Km then:

FSPL = 100 + 20 log 3 = 109.54dB then calculating for the Power received

(Pr = Ptx + Gtx + Grx − FSL − Am)

(Pr = 15 + 18 + 18 − 109.54 − 2 = −60.54dBm Maximum Channel Noise (MCN) (dBm) = Received Power (dBm) – SNR (dB)MCN dBm = Pr dBm − SNR dB = MCN = −60.54 − 25 = −85.45dBm

Link Margin (dB) = Received Power (dBm) - Receive Sensitivity (dBm)

−60.54 − − 85 = 24.46dBm

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At 3km, the link margin will be sufficient to provide 54Mbps data rate and ensure 99% link availability based on Rayleigh’s Fading Model shown in Table 4.Table 4 shows the Rayleigh Fading Model, and its relationship with link availability as a percentage of time.

Table 4. Rayleigh Fading Model

Time Availability (%) Fade Margin (dB)

90 8

99.0 18

99.9 28

99.99 38

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99.999 48

Table 5. Parameter for parabolic antenna

Element Value

Transmit output 23dBm

Cable and connectors for TX

-1dB(0.25dB per connector)

Antenna TX 24dBi

FSL 109.54

Antenna RX 24dBi

Cable and connectors for RX

-1dB (0.25dB per connector)

Receive Sensibility -72dBm

Total: (margin) 2896dBm

From Metro_1 to Metro_5 link: Distance (d) = 4km.

Calculating for the Free Space Propagation Loss (FSPL) = 100 + 20log⁡(d)

FSPL = 100 + 20 log 4 = 112.04dB

Calculating for the Power Received (Pr⁡) = 23 + 24 + 24 − 112.04 − 2 = 43.04dBm

Calculating the Maximum Channel Noise (MCN) dBm = Pr dBm − SNR dB

MCN dBm = −43.04 dBm − 25 dB = −68.04dBm Determine the

Link Margin dB = recieve signal(dBm) − receiver sensitivity(dBm) LM = −43.04 − (−72) = 28.96dB

At 4km, the link margin will be sufficient to provide 54Mbps data rate and ensure 99.9% link availability based on Rayleigh’s Fading Model shown in Table 4.

From Metro_10 to Metro_9 link: Distance (d) = 4.30km.

FSPL = 100 + 20 log 4.5 = 112.67dB

Calculating for the Power Received (Pr⁡) = 23 + 24 + 24 − 112.67 − 2 = −41.67dBm

MCN dBm = −41.67 dBm − 25 dB = −66.67dBm Determine the

Link Margin dB = recieve signal(dBm) − receiver sensitivity(dBm) LM = −41.67 − (−72) = 30.33dB

At 4.5km, the link margin will be sufficient to provide 54Mbps data rate and ensure 99% link availability based on Rayleigh’s Fading Model shown in Table 4.

From Metro_5 to Metro_10 link: Distance (d) = 3.5km

FSPL = 100 + 20 log 3.5 = 110.88dB

MCN dBm = −41.88 dBm − 25 dB = −66.88dBm

Determine the

Link Margin dB =

recieve signal(dBm) − receiver sensitivity(dBm) LM = −41.88 − (−72) = 30.12dB

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Volume 5, Issue 4, April 2016 From Metro_2 to Metro_12 link: Distance (d) =

2.50km

FSPL = 100 + 20 log 5 = 113.98dB

MCN dBm = −44.98 dBm − 25 dB = −69.98dBm

Determine the

Link Margin dB =

recieve signal(dBm) − receiver sensitivity(dBm) LM = −44.98 − (−72) = 27.02dB

At 5km, the link margin will be sufficient to provide 54Mbps data rate and ensure 99% link availability based on Rayleigh’s Fading Model shown in Table 4

2.6 Plotting of base stations

The names for the different cell sites where chosen based the structures on the ground and the co-ordinates (longitude and latitude) were picked from Google map. The sites were placed to achieve high coverage as shown figure 6a, figure 7b and figure 8c. Asset planning tool was used in the coverage prediction of the sites. MapInfo and Google Earth were used to plot the physical location of the sites in Accra. The path loss formula for the macrocell modelswas used for the sites. The propagation model used for the enhancedmacrocell models has a pathloss formula as follow:

Path Loss (dB) = k1 + k2log(d) + k3(Hms) + k4log(Hms) + k5log(Heff) + k6log(Heff)log(d) + k7(diffn) + C_Loss. (8)

Where:

d – Distance from the base station to the mobile station (km).

Hms– Height of the mobile station above ground (m). This figure may be specified either globally or for individual clutter categories.

Heff– Effective base station antenna height (m). Diffn– Diffraction loss calculated using either the Epstein-Peterson, Bullinton, deygout or Japanese Atlas knifeedge techniques.

k1 and k2 – Intercept and Slope. These factors correspond to a constant offset (in dB) and a multiplying factor for the log of the distance between the base station and the mobile.

k3 – Mobile Antenna Height Factor. Correction factor used to take into account the effective mobile antenna height.

k4 – Multiplying factor for Hms.

k5 – Effective Antenna Height Gain. This is the multiplying factor for the log of the effective antenna height.

k6 – multiplying factor for log(Heff)log(d).

k7 – multiplying factor for diffraction loss calculation.

C_loss– Clutter specification taken into account in the calculation process.

The propagation model can be tuned by modifying the k-factors. For improved near and far performance, dual slope attenuation can be introduced by specifying both near and far values for k1 &k2 and the crossover point.

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Figure 9. Coverage simulation of the network

3 RESULTS AND ANALYSIS

For the simulation and analysis of the network, OPNET Modeller version 14.5 with WiMAX Module capability was used[13]. The network model design describes the implementation of a mobile WiMAX network. This network model is shown in Figure 10, where the whole WiMAX network is implemented on the map of Accra. Three user profiles were considered, these profiles are Video, Email, Web Browsing and All profiles. These users are connected to only one base station. Different topologiesare built with different user profile.

Figure 10. WiMAX network implementation

As shown in Figure 10, the network model contains four application servers to provide service to the clients and one remote client for access in into the system. These

servers are; Web server with an application of Web browsing (light), the Video Server with an application of Video Conferencing (Light), an FTP Server with an application of File Transfer (Light) and email server with an email application. These severs are connected to a hub which is a networking device that connects the network devices together. Between the WiMAX BTS and the hub is the router, which takes incoming packet, analyses the packets and then directs them to the appropriate locations. The links used to connect the nodes are Ethernet 100BaseT link. In this network the "Physical Layer Enabled", is enabled. When this attribute is set the simulation accounts for physical layer effects, (frame-by-frame modellingis also performed).

In the coverage area of WiMAX BTS (cell) there are WiMAX Subscriber Stations (SS), these SS are distributed randomly throughout the cell. The subscriber stations (SS), which are closer to the base station (BS) have very good channel condition and have very high modulation scheme and better coding rate. The Subscriber Stations (SS) which are far from the Base Station (BS) will use the modulation scheme that could be set to a medium modulation coding schemes. The Subscriber Stations (SS) which are very far from Base Station (BS) i.e. near the edges of the cell may use a more robust modulation and coding scheme.

3.1 Network Simulation Parameters

3.1.1 Wireless Application Node Configuration

In the network design, the Application Configuration node is defined by using Application Specifications types. Here three or four applications are defined (Application Definition attributes, these applications are File Transfer (Light Load), Video Conferencing (Light Load) and Voice over IP Call (PCM Quality)). It is possible that all the three or four applications Voice, Video and Data are supported by the Subscriber Stations (SSs).

3.1.2 Wireless Profile node configuration

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3.1.3 WiMAX Configuration Node. (WiMAX config)

This node is used to store profiles of PHY and service classes, which can be referenced by all WiMAX nodes in the network. It defines the profile sets that can be used by the base station on the UL and the DL for Adaptive Modulation and Coding. It has the attribute that allows the configuration of parameters that make up a service class. A service class groups the QoS requirements of a service flow. Therefore, the service classifications were done in the WiMAX config node. The specified duration of the frame in milliseconds in this design is 5ms.We also used its attribute to specify duration of an OFDMA symbol. The duration of the OFDMA symbols is related to the frequency separation between subcarriers.

3.1.4 WiMAX Base Station (BS) Parameters

The maximum power transmission from the base station is kept at 23dBm and the again is set to 24dBi. The base stations (BS) nodes and their associated subscriber station (SS) nodes are configured with the same PHY profile and this is referenced with the one configured in WiMAX config. It is where the minimum and the maximum receiver sensitivity is set and mobility configuration are also done here. Error! Reference source not found.below lists some of the network setting for the BS and user nodes.

Table 6. Network configuration

Configuration parameter

Base station Work station

Antenna gain dB 24 dB -1 dB

Transmitted power

23dBm 0.5 W

PHY profile Wireless OFDMA 20MHz

Wireless OFDMA 20MHz PHY profile type OFDM OFDM

Efficiency mode Physical layer enable

Number of subcarrier 2048

Duplexing technique TDD

Frame duration 5 ms

Channel bandwidth 20 MHz

3.2 Implementation

OPNET Modeller 14.5 was used to simulate the designed networks to show the way video conferencing (light), emails, web browsing and all user profiles are used at the same time on the WiMAX network. Different scenarios were implemented and their simulated results

were analyzed. The user nodes starts sending data packets to their destinations through the WiMAX base station.

3.3 Simulation Results and Analysis

The duration of the simulation for all the scenarios was one hour to eliminate statistical errors. This research analyses the performance of WiMAX for video conferencing, web browsing, Email. There are different QoS parameters that are analysed. They include throughput, end-to-end delay, packet sent and packet receive, WiMAX delay, HTTP page response time and WiMAX load. In this section we will analyse the results by showing the graph for the WiMAX parameters we have chosen, also the results with respect to each node are analysed.

3.3.1 WiMAX throughput (bits/sec)

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The WiMAX throughput is the successful data that reached to the desire channel. The rate at which a user or the network sends or receives data, the data can be shared out on the logical link or physical link. It can be measured in bytes/s (Bps) or bits/s (bps) or packet per second.

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Figure 11. WiMAXThroughput Vs Simulation time for video conferencing users

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Figure 13. WiMAX Throughput Vs Simulation time per video conferencing users

Figure 14.WiMAX Throughput Vs Simulation time for all profile users

Figure 15. Throughput Vs Simulation time for SISO and MIMO for the BS

In figure 15, the throughput of the two systems is compared and it shows that the performance of MIMO configured system provides better throughput than SISO system configuration.

3.3.2 WiMAX Traffic Sent and Receive (bits/sec)

[image:11.595.66.292.290.463.2]

Traffic sent and received is an important outcome for this network design; traffic sent by the base station (BS) is near about same, but the traffic received at the BS is so high. The traffic sent for video conferencing users has an average of 170kbps per user and the received is 129kbps, which is less than the traffic sent. . The traffic sent and traffic received graphs are shown below.

Figure 16. WiMAX Traffic Sent (bits/sec) for video conferencing user.

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[image:12.595.66.291.65.247.2]

[image:12.595.336.559.68.260.2]

Figure 18. HTTP traffic Sent (bytes/sec)

Figure 19. WiMAX Traffic sent (bits/sec) for a web browsing user.

[image:12.595.64.290.280.463.2]

Figure 20. WiMAX Traffic Receive (bits/sec) for a web-browsing user.

Figure 21. HTTP traffic received (bytes/sec)

3.3.3 Page response

The page response time and the object response time are parameters that are present only in Data Servers, such as FTP Servers, this parameter explain the interval between request send by client or server and the response which it is getting back from either client or server. From the Figure 22 we can justify that the average page response time and the object respone time of 0.1359sec and 0.03936sec respectively are good

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[image:13.595.56.286.67.271.2]

Figure 23. HTTP Object Response Time (seconds).

3.3.4 End-to-End Delay

[image:13.595.327.552.69.255.2]

It was realized from the research that the end-to-end delay increases with an increase in the number of users that are connected to the network at a given time. The packet end-to-end delay is the time required by for a packet to transfer over a network from basis to end. It was observed that when the users are less, the value is around 0.5sec. However, when the users increase the maximum end-to-end delay is at over 1.5 (sec).

[image:13.595.330.570.423.597.2]

Figure 24. End to End Delay for more users

Figure 25. End-to-End Delay for few user

3.3.5 WiMAX load

In this research, WiMAX load refers to the quantity of data (traffic) being accepted by the network. It was observed that, the WiMAX load increases with increasing number of user’s. When the number users are less the amount of data carried is below 5kbps. However, when the number of users increase the quantity of load also increases. When the MIMO system comes in, the response of the site is instant but when the MIMO is removed, there is a delay.

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[image:14.595.56.305.69.295.2]

[image:14.595.326.564.181.411.2]

Figure 27. WiMAX load for few users

Figure 28. WiMAX load for MIMO

Figure 29. WiMAX load for non-MIMO

3.3.6 WiMAX Delay (sec)

In terms of WiMAX Delay, it was realized that when the number of users increase the WiMAX delay performance decreases. For few users the system has an average delay of around 0.022sec, but when the users increase the WiMAX delay recorded the highest of 3.5sec.

[image:14.595.58.297.322.763.2]

Figure 30. WiMAX Delay (sec) for few users

Figure 31. WiMAX Delay (sec) for more users

4 CONCLUSION

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Volume 5, Issue 4, April 2016 100 video conferencing and web browsing users per site

have an end-to-end delay of 1.5 seconds and 0.07 seconds respectively. As the number of users increase, for the various profiles, the duration of response also increases. The network has 99.99% link availability and that will be sufficient to provide 54Mbps. The average distance covered by a base station was improved to 15 km in WiMAX.

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