International Journal of Emerging Technology and Advanced Engineering Website www
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International Journal of Emerging Technology and Advanced Engineering Website www

ijetaecom ISSN 2250 2459 ISO 90012008 Certified Journal Volume 4 Issue 5 May 2014 623 Performance Analysis of WiMAX Network For SISO MISO Using Adaptive Modulation and Coding Eng El Sayed Ahmed Ramadan Dr Shawki Shabaan Prof Dr El Sayed Abd Elmoat

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International Journal of Emerging Technology and Advanced Engineering Website www




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International Journal of Emerging Technology and Advanced Engineering Website: www.ijetae.com ( ISSN 2250 2459, ISO 9001:2008 Certified Journal, Volume 4, Issue 5, May 2014) 623 Performance Analysis of WiMAX Network For SISO MISO Using Adaptive Modulation and Coding Eng. El Sayed Ahmed Ramadan , Dr. Shawki Shabaan , Prof. Dr. El Sayed Abd Elmoaty lbadawy Alexandria University Faculty of Engineering Electrical Engineering Departme nt ommunication & Electronics Section Abstract although many researchers have written about WiMAX IEEE 802.16 Standard system, it needs more

attention and analysis in next generation wireless networks. Multiple Input Multiple Output Orthogonal Frequency Division Multiplexing (MIMO OFDM) has become one of the key technologies for the B 3G & 4G broadband wireless communications. This paper is aimed at studying the perfor mance analysis of OFDM and OFDMA in WiMAX IEEE 802.16m and 3GPP LTE advanced systems ommunication in hybrid environment systems. This study focuses on the analysis of SISO and MISO technology based on physical layer. As MIMO could increase the capacity of the wireless communication system compared with Single Input

Single Output (SISO) and OFDM could obtain good performances in multipath frequency selective fading channels, we combine them together with the Space Time Block Coding (STBC) scheme , so that t o enhance the system capacity. The simulation results of OFDM WiMAX IEEE 802.16e for SISO and MISO tech nology are summarized and a c omparison step between Turbo Code and Convolutional Product Code (CPC) for Mobile WiMAX is introduced in this work. Keyword OFDM OFDMA WiMAX, SISO, MISO, MIMO, Performance anal ysis of a mobile WiMAX I. NTRODUCTION The OFDMA is an extension of Orthogonal Frequency

Division Multiplexing (OFDM), which is currently the modulation of choice for high speed data access systems such as IEEE 802.1laJg/n wireless LAN (WiFi), IEEE 802.16aJd/e wireless broadband access systems (WiMAX and WiBro ) [ and satellite. Orthogonal Frequency Division Multiplexing Access OFDMA is a potential transmission technology for mobile communica tion sy stems [2 , and hence OFDMA is selected as the physical layer technology. OFDM or OFDM A systems are used in wired and broadband wireless systems such as IEEE 802.16a e, IEEE 802.1la and llg. In addition Wireless MANs (802.16) and W

ANs are used for the nex t generation internet. OFDM has a higher capacity than Co de Division Multi Access (CDMA) systems and provide access method in both wired and wireless systems for Next Generation Network (NGN). ULTIPLE INPUT multiple output (MIMO) systems offer an increase in capacity or diversity. In this work t he data transmission rate increase provided by spatial multiplexing (SM) is studded . OFDM is a popular technique for wireless high data rate transmission, because it enables the efficient use of the available bandwi dth and it is easily implemented and it divides the

frequency selective fading channel into parallel flat fading subchannels. The combination of MIMO and OFDM is a promising wireless access scheme [1]. xamples of MIM OFDM applications include the evolvin g third generation (3G) cellular systems known as long term evolution (LTE) and worldwide interoperability for microwave access (WiMAX) system. Similar to a Single Input Single Output OFDM system MIMO OFDM system is very sensitive to carrier frequency syn chronization. CFO (carrier frequency offset) introduces ICI (inter carrier interference). MIMO OFDM receiver in the presence of CFO with even

a small fraction of subcarrier spacing will degrade the performance of MIMO OFDM receiver severely. The paper is o rganized as follows In section II, System Model, Section III, addresse d performance analysis, Section IV, simulated results, Section V, Conclusion II. YSTEM ODEL a. OFDM Basics In order to overcome the daunting requirement for L RF radios in both the transmitter and the receiver, OFDM uses an efficient computational technique, discrete Fourier transform (DFT), which lends itself to a highly efficient implementation commonly known as the fast Fourier transform (FFT). The FFT and

its inverse, the IFFT, can create a multitude of orthogonal subcarriers using a single radio.
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International Journal of Emerging Technology and Advanced Engineering Website: www.ijetae.com ( ISSN 2250 2459, ISO 9001:2008 Certified Journal, Volume 4, Issue 5, May 2014) 624 b. Block Transmission with Guard Intervals By grouping L data symbols into a block known as an OFDM symbol. An OFDM symbol lasts for a duration of T seconds, where T=LTs. In order t o keep each OFDM symbol independent of the others after going through a wireless channel, it is necessary to introduce a guard

time between OFDM symbols This way, after receiving a series of OFDM symbols, as long as the guard time Tg is larger than the del ay spread of the channel W , each OFDM symbol will interfere only with itself. Figure 1: Block Transmission with Guard Intervals [5] c. Circular Convolution and the DFT When an input data stream is sent through a linear time invariant Finite Impulse Response (FIR) channel , the output is the linear convolution of the input and the channel : [21]. However, the paper attempt to remove the ISI within each OFDM symbo l so the computing in terms of a circular convolution

is given by , (1) , (2 The circular function mod is a periodic version of with period L. In other words, each value of is the sum of the product of L terms. In this case of circular convolution, it would then be possible to take the DFT of the channel output to get ]} ]} DFT DFT , ) which yields in the frequency domain . ) Note that the duality between circular convolution in the time domain and simple multip lication in the frequency domain is a property unique to the DFT. The L point DFT is defined as { ]} nm DFT S ) whereas its inverse, the IDFT, is defined as { ]} nm IDFT S ) Referring to

Equation , this innocent formula describes an ISI free channel in the frequency domain, where each input symbol is simply scaled by a complex value . So, given knowledge of the channel frequency response t the receiver, it is trivial to recover the input symbol by simply computing Where the estimate will generally be imperfect, owing to additive noise, co channel interference, imperfect channel estimation, and other imperfections. Nevertheless, in principle, the ISI, which is the most serious form of interference in a wideband channel, has been mitigated. The nature provides a linear

convolution w hen a signal is transmitted through a linear channel. So to reduce the ISI we must have circular convolution. This circular convolution can be faked by adding a specific prefix, the cyclic prefix (CP), onto the transmitted vector. d. An Example: O FDM in iMAX To gain an appreciation for the time and frequency domain interpretations of OFDM, WiMAX systems can be used as an example. To ground the discussion, we consider a passband OFDM system and then give specific values for the important system paramet ers.
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International Journal of Emerging Technology and

Advanced Engineering Website: www.ijetae.com ( ISSN 2250 2459, ISO 9001:2008 Certified Journal, Volume 4, Issue 5, May 2014) 625 Figure 2: pass band OFDM modulation engine [5] The inputs to this figure are L independent QAM symbols (the vector X), and these L symbols are treated as separate subcarriers. These L data bearing symbols can be created from a bit s tream by a symbol mapper and serial to parallel convertor (S/P). The L point IFFT then creates a time domain L vector x that is cyclic extended to have length, where G is the fractional overhead. This longer vector is then parallel to

serial (P/S) converte d into a wideband digital signal that can be amplitude modulated with a single radio at a carrier frequency of FC /2 Table Summary of OFDM Parameters [7] Symb ol Description Relation Example WiMAX value Nominal bandwidth B=1/T 10MHz Number of subcarriers Size of IFFT/FFT 1024 Guard fraction % of L for CP 1/8 Data subcarriers pilot/null subcarriers 768 Sample time =1/B 1 sec Guard symbo ls =GL 128 Guard time 12.8 sec OFDM symbol time T= T (L+ 115.2 sec SC Subcarrier bandwidth SC =B/L 9.76 KHz If 16 QAM modulation were used ( M = 16), the raw (neglecting coding) data

rate of this WiMAX system would be illustrat ed in equation 8: log Mbps MHz 24 125 16 log 768 1024 10 ach L data carrying subcarriers of bandwidth B/L carries log M) bits of data. An additional overhead pena lty of (1+G) must be paid for the cyclic prefix, since it consists of redundant information and sacrifices the transmission of actual data symbols See igure 3, 4. Figure .OFDM Time Frequency Sub Carriers [5] Figure 4 . LTE A TDD multiple acces s schemes In UL and DL 6]
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International Journal of Emerging Technology and Advanced Engineering Website: www.ijetae.com ( ISSN 2250

2459, ISO 9001:2008 Certified Journal, Volume 4, Issue 5, May 2014) 626 Figure 5 A generic MIMO OFDM System Figure 6. Convolutional encoder and tail biting In IEEE 802.16e 2005 1] Figure 7. Channel Coding data Randomizer 1] Figure 8. Channel C oding FEC Reed Solomon Encoder Fig.9. Turb o Encoder in IEEE 802.16 e 2005 7] Fig.10 SISO, MISO, MIMO system 3]
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International Journal of Emerging Technology and Advanced Engineering Website: www.ijetae.com ( ISSN 2250 2459, ISO 9001:2008 Certified Journal, Volume 4, Issue 5, May 2014) 627 Fig.11 . WiMAX network reference model [5]

Fig.12. Space Time Coded 2x2 MIMO OFDM Transcei ver structure Fig.13. The First Stage of WiMAX Model Standard 1] Fig. 14 Simulink Diagram of WiMAX Simulator SISO [7 Fig. 15 Simul ink Diagram of WiMAX Simulator ISO [7] Figure : Fundamental turbo encoder
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International Journal of Emerging Technology and Advanced Engineering Website: www.ijetae.com ( ISSN 2250 2459, ISO 9001:2008 Certified Journal, Volume 4, Issue 5, May 2014) 628 Figure : Turbo encod er with generator polynomials [6] Figure Turbo encoder in details Figure : Convolutional encoder Figure 20 : Convolutional coding

Figure 21 Coded Block [6] III. ERFORMANCE NALYSIS WIMAX ETWORK ESCRIPTION NALYSIS Th e complete channel encoding and decoding setup in figure 22 . Shows standards, 802.16 OFDM PHY layer baseband transmitters are composed of three major parts: channel coding, modulation, and OFDM transmitter. Since the receiver complimentary operations are a pplied in the reverse order. Channel coding refers to the class of signal transformations designed to improve the communications performance by enabling the transmitted signal to better withstand the effects of various channel impairments, such as noise, f

ading, and jamming The goal of channel coding is to improve the bit error rate (BER) performance of power limited and bandwidth limited channels by adding structured redundancy in the transmitted data. In the IEEE 802.16 standard, the channel coding includ es randomization, forward error correction (FEC), and interleaving. The FEC block is composed by Reed Solomon encoder, Convolutional coding and puncture (used to adjust different data rates). These are the mandatory blocks on the standard. Convolutional Tu rbo Coding (CTC) is optional as well as CTC interleaving, so they are not implemented

in this model. Modulation is the process of mapping the digital information to analog form so it can be transmitted over the channel. In an OFDM system the changing of ph ase and amplitude can be done but the frequency cannot change because they have to be kept orthogonal. The modulation used in 802.16 is Gray mapped B PSK, Q PSK, 16 QAM, and 64 QAM. The OFDM transmitter is composed of three parts: assemble OFDM frame, cre ate an OFDM signal by performing an IFFT / FFT, and add cyclic prefix (guard interval used to cancel inter symbol interference). For the channel, an AWGN channel and a

multipath Rayleigh fading channel are used for simulation. See Figures (7, , 11, 13) Page no. (4, 5).
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International Journal of Emerging Technology and Advanced Engineering Website: www.ijetae.com ( ISSN 2250 2459, ISO 9001:2008 Certified Journal, Volume 4, Issue 5, May 2014) 629 igure 22 . IEEE 802.16 OFDM PHY Layer Baseband Block Diagram IV. IMULATED ESULTS Results of Analysis of the WiMAX system Results of Study the Modulation Characteristic It is getting close to ideal ness when we use BPSK an d get far from ideal ness as we use 64QAM in AWGN channel. See figure ( 23 In

BPSK we can see the SNR near to zero in 8 =zero in 11. In QPSK we can see the SNR near to zero in 11 & =zero in 14. In 16 QAM we can see the SNR near to zero in 19 &=zero in 21 . In 64QAM we can see the SNR near to zero in 24 &=zero in 27. The results of the impact study OFDM on different types of modulation We can see the effect of the OFDM amendments reducing the BER as shown in Figure 24: In BPSK we can see the SNR near t o zero in 10. In QPSK we can see the SNR near to zero in11. In 16 QAM we can see the SNR near to zero in15. In 64QAM we can see the SNR near to zero in 20. Results of

study of WiMAX system using one type of modulation: The WiMAX system works BPSK m odulation: Figure 25 shows the variability of BER with SNR in the WiMAX system works amending BPSK orthogonal, and notes the lack of stability, the inverse proportionality between SNR and BER. (G = 0.25, BW = 3.5MHZ) The WiMAX system works 64QAM modulatio The figure 26 shows the diversity of BER with SNR in the WiMAX system works 64QAM modulation orthogonal, and we note the lack of stability, because we forcing the system to deal with all the SNR in the same way without taking into account the state of th e

channel affects the higher Order even more. (G = 0.25, BW = 3.5MHZ
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International Journal of Emerging Technology and Advanced Engineering Website: www.ijetae.com ( ISSN 2250 2459, ISO 9001:2008 Certified Journal, Volume 4, Issue 5, May 2014) 630 Table 1. Parameter s Channel Coding Per Modulation 7] Table2 Specifies Model Parameters for a Simulation Run [7] Results of Study fading impact on the signal: Table 3 shows t he relationship of the effect of different types of fading on the BER in the presence of different values of the SNR, we note that the highest BER Produce the type

frequency selective fading Followed by frequency flat fading And then the ideal sit uation i n the absence of fading . In figure 27 we can see Comparison between different types of fading. Results of Study the WiMAX system for Use AMC or use one type of modulation: Figure shows clearly shows that the use of AMC reduces the value of the BER and gives better results than using higher and lower modulation in WiMAX system. Results of Study impact of various modulation on WiMAX System by using different types of ntenna The system uses SISO antenna with fading: From Table 5 Represents the a L ow SNR

threshold for rate control (dB) for WiMAX system which uses an antenna from Type SISO were obtained after experiments conducted specifically to deduce values idealism see figure 29 to show: Relationship between SNR and BER and its impact on Differen t modulations in WIMAX system use SISO antenna with fading The system uses MISO antenna with fading Table 6 is a Low SNR threshold for rate control (dB) for WiMAX system which uses an antenna from Type MISO were obtained after experiments conducted speci fically to deduce values idealism. See figure30 to show: Relationship between SNR and BER and

its impact on different modulations in WIMAX system use MISO antenna with fading. The system uses SISO antenna without fading: In this case we note that the curv es of modulation less distortion and more accurate than in the previous two types, for lack of the effects of fading signal, but this case remain imaginary and unfounded on the fact. See figure 31 to show: Relationship between SNR and BER in case of SISO ntenna without fading And we put the most important results that have been obtained are the values of the Low SNR thresholds for rate control (dB) and can be summarized in the

following tables In Appendix A at this paper (pages no. 15 16 17 ) See Fig ures ( 10 12, 14 and 15 page no. ( , 5 6) Results of Comparison between Turbo Code and Convolutional Product Code (CPC) for Mobile WiMAX In this paper, a simulation of physical layer of WiMAX was made as described in section II by matlab. AWGN will be assumed only. The Figure 32 ,33 ,34, and 35 (Page no. 14 show the BER versus the received SNR obtained at different modulation and different number of OFDMA sub carriers.
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International Journal of Emerging Technology and Advanced Engineering Website:

www.ijetae.com ( ISSN 2250 2459, ISO 9001:2008 Certified Journal, Volume 4, Issue 5, May 2014) 631 Figure 32 shows the relation between SNR and BER at 16QAM and 128 subcarrie rs. From this figure, we conclude that SNR will be improved by approximately 3 dB at BER equals to 10 2 compared to turbo code and by approximately 2 dB at BER equals to 10 2 compared to the combination between the two code methods. Also, improvement will be obtained when the number of subcarriers increases to 512 as shown in Figure 33 When different modulation is used, CPC still gives better results as shown in Figure 34

and 35 This improvements comes from using CPC method in which the overall code rate is not 1/3 as in turbo coding method. summaries of the most important results that have been proven in research: 1. Increased energy transmitted is reduced the BER and increase the coverage area and it appears in the Constellation and the Power Spe ctrum but the excessive increase may cause serious diseases to humans and the environment. 2. The best cases if you can use standard IEEE802.16 be activated Amplifier nonlinearity and the Pre distortion in the event of frequent changes in the amendment. 3.

Deformation signal is more clarity in cases of low signaling amendments. 4. Fading effects cannot be ignored, especially when low SNR. 5. Use Two OFDM symbols per burs allowance for one in the WiMAX system uses SISO antenna increases data transm ission rates. 6. Curve of modification in general representation Simulation not much different from the Theory and is close when using low order and away whenever we use high order in the modulation. 7. The lower degree of modification the BER is decrea sed. 8. Using the OFDM reduces the BER effectiveness. 9. Very difficult to get BER values stable in

the case of using one type of modulation. 10. CP directly affects the rate of data transmission. 11. The lower SNR is advisable to use modified of Low Order. 12. AMC in case of transmission from one ID to another in ascending sequence regularly top Throughput will be higher CP settles then. 13. system is trying to access to self stability, trying to improve the error value with the passage of ti me, which increases the rate of data transmission through the control system and guessing including AMC. 14. There are values to AMC cannot give effective results because it is less than the Threshold

may exceed the critical points. 15. The use of Wi MAX antenna type Mays is not the best option in all cases, and idealism is approaching when using kind of MIMO antennas. 16. Difficult to adjust the AMC at low values of righteousness with Bits high when all cases, but there must be a mechanism based Tr ade off increase the BER or reduce the Bits for QoS above the long term. V. ONCLUSION The key contribution of this paper was the implementation of the IEEE 802.16 OFDM PHY layer using MATLAB in order to evaluate the PHY layer performance under referen ce channel model. The implemented PHY layer

supports all the modulation and Coding schemes as well as CP lengths defined in the specification. To keep matters simple we avoided doing oversampling of the data samples before using the channel model. Though, that can be implemented by minor modifications. On the receiver side, We have assumed perfect channel estimation to avoid the effect of any particular estimation method on the simulation results and then we add noise to study the effects, though the inser tion of pilot subcarriers in the OFDM symbols makes use of any comb type estimator possible. The developed simulator can be easily

modified to implement new features in order to enhance the PHY layer performance. Simulation was the methodology used to inve stigate the PHY layer performance. The performance evaluation method was mainly concentrated on the effect of channel coding on the PHY layer. The overall system performance was also evaluated under different channel conditions. Scatter plots were generate d to validate the model in terms of general trends in reception quality as we very different parameters. Acknowledgements The authors would like to thank Dr Amr Hassan Yassin for his helpful comments. REFERENCES [1]

Maninder Singh and Kiran Ahuja , 20 11, performance evaluation of adaptive Modulation techniques of WIMAX network with cyclic prefix, international Journal of advanced engineering sciences and technologies Vol no. 3, issue no. 1, 034 038. [2] Dr. Techn. Markus Rupp, February 2007, Imple mentation of a WiMAX simulator in Simulink.
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International Journal of Emerging Technology and Advanced Engineering Website: www.ijetae.com ( ISSN 2250 2459, ISO 9001:2008 Certified Journal, Volume 4, Issue 5, May 2014) 632 [3] Hadj Zerrouki, 2010, High Throughput of WiMAX MIMO OFDM Including

Adaptive Modulation and Coding, International Journal of Computer Science and Information Security, Vol. 7, No. 1, 2010 . [4] Mustafa Ergen, "Mobile Broadband including WiMAX and LTE", Springer, Berkeley, CA, USA, 2009. [5] *)DLVDO$-XEDLU0,PUDQ+DVDQ0G2EDLG8OODK3HUIRUPDQFH Evaluation of IEEE 802.16e (Mobile WiMAX) in OFDM Physical /D\HU%OHNLQJH,QVWLWXWHRI7HFKQRORJ\$XJXVW 200 9. [6] Imran Hussain, Sadia Hussain, Imtiaz Khokhar3 &

Raja Iqball, "OFDMA as the Technology for the Ne xt Generation Mobile Wireless Internet", Proceedings of the Third International Conference on Wireless and Mobile Communications (lCWMC'07), 2007. [7] My M.SC thesis May 2014 Applications and Performance Analysis of a Mobile WiMAX Network Supervised By: Prof. Dr. El Sayed Abd Elmoaty Elbadawy and Dr. Shawki Elsaysd Shabaan Fig. 23 [7] Fig. 24 [7] Fig.26a. AMC and Cell Coverage/ QoS links [6 Fig. 25 [7] Fig. 26 [7]
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International Journal of Emerging Technology and Advanced Engineering Website: www.ijetae.com ( ISSN 2250 2459, ISO

9001:2008 Certified Journal, Volume 4, Issue 5, May 2014) 633 Fig.26b. AMC's handling with the coverage area [3 Fig. 27 [7] Fig. 28 [7] WIMAX Results with and without using the AMC Scheme [7] [7]
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International Journal of Emerging Technology and Advanced Engineering Website: www.ijetae.com ( ISSN 2250 2459, ISO 9001:2008 Certified Journal, Volume 4, Issue 5, May 2014) 634 Fig. 29 [7] Fig. 30 7] Fig. 31 [7] [7] [7] Comparison between Turbo Code and Convolutional Product Code (CPC) for Mobile WiMAX [7] (See Figures 6 , 9 , 1 6 , 17 , 18 , 19 , 20 , 21 [7] (Pages no. 4 , 5 , 6


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International Journal of Emerging Technology and Advanced Engineering Website: www.ijetae.com ( ISSN 2250 2459, ISO 9001:2008 Certified Journal, Volume 4, Issue 5, May 2014) 635 Fig . 32 [7] Fig. 33 7] Fig. 34 [7] Fig. 35 7]
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International Journal of Emerging Technology and Advanced Engineering Website: www.ijetae.com ( ISSN 2250 2459, ISO 9001:2008 Certified Journal, Volume 4, Issue 5, May 2014) 636 Appendix A The most important results that have been obtained represent the Low SNR thresholds for rate control: Of the most important results that have been

obtained are the values o f the Low SNR thresholds for rate control (dB) and can be summarized in the following tables [7] SISO Without fading: [7]
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International Journal of Emerging Technology and Advanced Engineering Website: www.ijetae.com ( ISSN 2250 2459, ISO 9001:2008 Certified Journal, Volume 4, Issue 5, May 2014) 637 SISO With fading: [7] MISO With fading: [7]
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International Journal of Emerging Technology and Advanced Engineering Website: www.ijetae.com ( ISSN 2250 2459, ISO 9001:2008 Certified Journal, Volume 4, Issue 5, May 2014) 638