Reviewed Paper Volume 2 Issue 9 May 215 International Journal of Informative & Futuristic Research ISSN (Online): 2347-1697 Analyzing Passive Optical Network Using Paper ID IJIFR/ V2/ E9/ 7 Page No. 334-3346 Subject Area Key Words OFDM, WDM PON, QAM, MATLAB Electronics & Comm. Engg. Akshita Verma 1 Vinay Thakur 2 M.Tech. Scholar Department of Electronics & Comm. Engineering Sri Sai University, Palampur- Himachal Pradesh Assistant Professor Department of Electronics & Comm. Engineering Sri Sai University, Palampur- Himachal Pradesh Abstract The main scope of this paper is to analysis the various parameters with the help of MATLAB. The increased demand for new digital services the internet service providers and governments are likely to invest in higher capacity optical networks in of customer requirements. These next generation optical networks, new advanced modulation formats and novel optical components, capable of providing high data rates. Due to the nature of dynamic traffic patterns, future designs will be required to incorporate a higher level of reconfigurability so that an efficient use of the shared optical network can be provided. The modulation format was important in wavelength division multiplexing passive optical network (WDM- PON) system. But when we talk about Orthogonal Frequency Division Multiplexing (OFDM) transmitter and receiver QAM modulation format gives us better results than others.this paper analysis and estimates the performance achieved by PON using QAM with OFDM by the use of.few parameters are, Bit error rate Bandwidth OFDM, Data rate & SNR is calculated by using MATLAB. 1. Introduction The ever increasing demand for higher internet speeds, driven by media-rich applications such as on demand HDTV, Voice over IP (VoIP), video conferencing and online gaming, will require Internet Service Providers (ISPs) to upgrade their existing networks to satisfy the needs of both residential and commercial customers as current Ethernet speeds of 1Gb/s will be upgraded to 1Gb/s. Current Core and Metropolitan Area Networks are employing optical multiplexing to help www.ijifr.com Copyright IJIFR 215 334
to meet increasing data rate requirements. The development of Wavelength Division Multiplexing (WDM) systems now allows multiple wavelengths to be propagated through fibres which in the past carried a single wavelength only. However, such a simplistic augmentation of network speeds does not account for the ever changing bandwidth demand patterns and as such network flexibility and reconfigurability will need to be incorporated into future optical communications systems. Although the capacity of Core and Metro networks has increased greatly through the use of WDM, a corresponding improvement in Access Networks (which provide the final connection to the end user) has not occurred. This is due to the fact that these networks are primarily comprised of electrical cables (telephone or co axial) and are therefore are limited in terms of data throughput and transmission distance. The natural solution to overcome this last mile bottleneck is to take advantage of the large bandwidths offered by optical fibres and to move the fibre network closer to the customer so as to eventually create an all optical communications network. This type of all optical access networks has been termed Fibre To The Home and is seen as a long term solution to meet growing bandwidth demands. Unlike Core and Metro networks whose distance bandwidth products are sufficiently large to justify high implementation costs, Access networks must be constructed in an extremely cost effective manner due to their potential for wide deployment in a price sensitive market. This presents significant financial and technical challenges in to provide adequate data rates to each user of outmost importance when designing next generation Access networks will be the selection of a highly efficient modulation format to provide maximum throughput on each optical channel. This has led to the emergence of. Inverse Fast Fourier Transform like FDM, OFDM subcarriers each have a different frequency, but the difference is that individual OFDM subcarrier spectra overlap in the frequency domain. If each subcarrier is made to be orthogonal to all other subcarriers then they can be transmitted in parallel without interference. In OFDM, subcarriers are chosen to be orthogonal to each other in frequency. This is achieved by the implementation of an Inverse Fast Fourier Transform (IFFT) at the transmitter. In practice, as OFDM signals are created digitally, an Inverse Discrete Fourier Transform (IDFT) is implemented. 2. Working To perform the various parameters there is a need of OFDM transmitter and receiver. To generate OFDM the relationship between all the carriers must be controlled to maintain that carriers are orthogonal to each other. OFDM is generated by firstly choosing the spectrum required, based on the input data, and modulation scheme used. Each carrier to be produced is assigned some data to transmit. The required amplitude and phase of the carrier is then calculated based on the modulation scheme (typically differential BPSK, QPSK, or QAM). The spectrum is then converted back to its time domain signal using an Inverse Fourier Transform. Mostly, an Inverse Fast Fourier Transform (IFFT) is used. The IFFT performs the transformation very efficiently, and provides a simple way that the carrier signals produced are orthogonal. The Fast Fourier Transform (FFT) transforms a cyclic time domain signal into its frequency spectrum. This is done by finding the equivalent waveform, generated by a sum of orthogonal sinusoidal components. The amplitude and phase of the sinusoidal components represent the frequency spectrum of the time domain signal. The IFFT performs the reverse process, transforming a spectrum (amplitude and phase of each component) into a time domain signal. An IFFT converts a number of complex data points, of length that is a power of 2, into the time domain signal of the same number of points. Each data point in frequency spectrum used for an FFT or IFFT is called a bin. 3341
The orthogonal carriers required for the OFDM signal can be easily generated by setting the amplitude and phase of each frequency bin, then performing the IFFT. Since each bin of an IFFT corresponds to the amplitude and phase of a set of orthogonal sinusoids, the reverse process guarantees that the carriers generated are orthogonal. Figure 1: OFDM Transmitter and Receiver RF Frequency is a rate of oscillation in the range of oscillation around 3 khz to 3 GHz, which corresponds to the frequency of radio waves and alternating currents which carry radio signals and OFM requires the RF final amplifier on the output of the transmitter. One of the enabling techniques for OFDM is the insertion of a Cyclic Prefix.Let us consider one OFDM symbol which contains N orthogonal subcarriers. As each subcarrier is at a different frequency the effect of dispersion is to introduce a delay spread across all transmitted subcarriers. The receiver FFT window size is the same as the transmitted IFFT size (i.e. the size of one OFDM symbol).consider just two subcarriers within an OFDM symbol which are aligned in time at the transmitter. Assume, for simplicity, that one subcarrier arrives at the receiver exactly within the FFT window. Therefore the other (lower frequency) subcarrier has been delayed due to dispersion by a time td that the received version of Subcarrier 1 is a truncated version of the original transmitted subcarrier. Note also that inter (OFDM) symbol interference has occurred. As a full copy of Subcarrier 1 is not received, the subcarriers can no longer be described as orthogonal. The solution to this problem is to append a portion from the end of each subcarrier (within each OFDM symbol) to the start of it.this is known as the Cyclic Prefix (CP) and once the length of the CP is greater than the maximum delay spread caused by dispersion, tmax, then a complete copy of every subcarrier will be received and orthogonality is preserved. The addition of a CP at the transmitter and reception after propagation through a dispersive channel the CP being added to an entire OFDM subcarrier containing N subcarriers. When the CP is employed at the receiver to ensure a full copy of a particular subcarrier is obtained it that the received version is a time shifted version of the transmitted subcarrier. In essence, the received subcarrier is a copy of the transmitted subcarrier with an added phase shift. As 3342
each subcarrier is delayed by a different amount of time it follows that each received subcarrier, in one OFDM symbol, has a different phase shift relative to the corresponding transmitted subcarrier. This phase shift, as well as other frequency selective effects caused by the channel, affect the received data and need to be accounted for. Quadrature amplitude modulation (QAM) is both an analog and a digital modulation scheme. It conveys two analog message signals, or two digital bit streams, by changing (modulating) the amplitudes of two carrier waves, using the amplitude-shift keying (ASK) digital modulation scheme or amplitude modulation (AM) analog modulation scheme. The two carrier waves, usually sinusoids, are out of phase with each other by 9 and are thus called quadrature carriers or quadrature components hence the name of the scheme. The modulated waves are summed, and the final waveform is a combination of both phase-shift keying (PSK) and amplitude-shift keying (ASK), or (in the analog case) of phase modulation (PM) and amplitude modulation. In the digital QAM case, a finite number of at least two phases and at least two amplitudes are used. PSK modulators are often designed using the QAM principle, but are not considered as QAM since the amplitude of the modulated carrier signal is constant. QAM is used extensively as a modulation scheme for digital telecommunication systems. Arbitrarily high spectral efficiencies can be achieved with QAM by setting a suitable constellation size, limited only by the noise level and linearity of the communications channel. QAM is being used in optical fibre systems as bit rates increase; QAM16,QAM, QAM64. Figure 2: QAM OFDM Symbol Rate and Subcarrier Spacing the conversion of data from a serial bit stream to an OFDM symbol. The bit stream is divided into groups of bits which will each be assigned a specific QAM symbol. As 16 QAM is used, 4 bits are allocated to each QAM symbol. Serial to parallel conversion also takes place as the QAM symbols are arranged as inputs to the 6 point IFFT. The QAM inputs are processed by the IFFT as discussed in the previous section and the resultant output symbol, the OFDM symbol, is 6 times longer in time than each input QAM symbol. More generally, if N parallel streams of QAM data are fed to the IFFT, then the OFDM symbol period, T ofdm, is set to the original QAM stream symbol period, T data, multiplied by N (since an OFDM symbol contains information about all input QAM symbols over one IFFT operation. Tofdm = Tdata * N 42=11 111 11 11 11 111 3343
BER BW -1-1i,-3+1i,3-1i,3+3i,-3+1i ISSN (Online): 2347-1697 Incoming Bit Stream 16-QAM Assignment Serial to IIRL OFDM Symbol Tofdm = Tdata x 6 1+3i,X1,X2,X3,X4,X5,X6 This gives an OFDM symbol rate of R ofdm =1/(Tdata *N)=Rdata/N The extremely low subcarrier spacing facilitated by the fact that subcarriers can overlap and still be uniquely detectable, is one of those major advantages of OFDM and is the main reason for its popularity in RF communications. Spectral efficiency can be even further increased my maximizing the level of QAM used on each subcarrier. Another key advantage of OFDM, particularly for applications in optical communications, is its tolerance to large amounts of chromatic dispersion. There are no. of bits and no. of samples to check the total no. of data points. Cyclic prefix is used with the appropriate value and also take the symbol rate. RF frequency is taken then time delays required. Design a OFDM transmitter with the of and bit stream, it contains no. of channels, no. of bits &. The loop is of 15 and then adds QAM modulation with bits &. Construct IFFT input. Add CP which is the multiplication of no. of samples & cyclic prefix size. Take two real and imaginary parts I and Q. Now define these parts with the help of RF. Count the values. After then Design a OFDM receiver then remove CP & construct FFT after that the data carrying subcarriers with high & low gets extracted. Equalization of the bits and EVM parameter used for the calculation of Tx & Rx are then done. EVM stands for error vector magnitude. After storing of data, iteration takes place 15 times as the ratio of loop is 1:15. After that QAM Demodulation is applied then reshaping of bits and channels is done by using conversion of binary. At the end BER, BW, Data Rate SNR is calculated. Now Rx constellation of all channels is shown in the figure. 3. Results And Discussions ANALYSIS: Wavelength Division Multiplexing to optical networks has led to a more efficient use of optical fibers. However, as operators seek to further increase network capacity, more optical channels are required to allow for higher data rates and a greater number of users to be reached. It is done with MATLAB.QAM modulation is used. Few parameters are calculated Bit error rate, Bandwidth, Data Rate & SNR. Methods normally used are Computational. Results: BER-, BW Ofdm-2.3878e+1, Data rate- 1.1719e+1 & SNR-63.9576. 1 v/s BER 2.5 x 11 v/s BW.8.6 2.4.2 1.5 -.2 -.4 1.5 -.6 -.8-1 3344
Datarate SNR ISSN (Online): 2347-1697 12 x 19 v/s Datarate 7 v/s SNR 1 6 8 5 4 6 3 4 2 1 2 Figure 4: Output 4. Conclusion and Future Scope This paper analysis and estimates the performance achieved by PON using QAM with OFDM by the use of. Few parameters i.e Bit error rate, Bandwidth OFDM, Data rate & SNR are calculated by using MATLAB. The values by using the QAM are: BER-, BW Ofdm- 2.3878e+1, Data rate-1.1719e+1, SNR-63.9576. We can use the different of the QAM in OFDM systems. Orthogonal frequency-division multiplexing (OFDM) is a method of encoding digital data on multiple carrier frequencies. We are using QAM in these systems. 5. References [1] [Biswanath Mukherjee WDM Optical Communication Networks: Progress and Challenges IEEE Journal On Selected Areas In Communications, VOL. 18, NO. 1, OCTOBER 2. [2] Manushree Bhardwaj1, Arun Gangwar2, Devendra Soni A Review on OFDM: Concept, Scope & its Applications IOSR Journal of Mechanical and Civil Engineering (IOSRJMCE) ISSN : 2278-1684 Volume 1, Issue 1 (May-June 212), PP 7-11 [3] Mérouane Debbah Short introduction to OFDM. [4] Harpal Singh (Student),Harjinder Singh (Assistant professor) Analyzing The Performance Of 1Gb/s DPSK Multicast Overlaid WDM-PON Architecture Using Numerous Modulation Techniques Department of Electronics and Communication, Punjabi University, Patiala, India IJISET - International Journal of Innovative Science, Engineering & Technology, Vol. 1 Issue 5, July 214. [5] Pandey, G.; Agarwal, N. WDM PON enhanced capacity architecture for unicast, multicast and broadcast through efficient sideband carrier modulation WOCN, page 1-6. IEEE, (212). [6] Ahmed Muddassir Khan, Zhang Jie A Simple and Cost-effective Design for Simultaneous Transmission of Point-to-point and Broadcast Services in WDM-PON International Journal of Future Generation Communication and Networking Vol. 6, No. 3, June, 213. [7] Li Li,Jijun Zhang Analysis the Speciality of Modulation Format in WDM-PON System Journals of computers,vol. 6,211. [8] S. Rajalakshmi#1, Ankit Srivastava*2 Analysis of TDM and WDM PON using Different Coding Schemes for Extended Reach International Journal of Computer Science and Network Security, VOL.11 No.7, July 211. [9] Gurtej Singh Toor1, Harjinder Singh2, Amandeep singh Bhandari Review Paper On Papr Reduction Techniques In Ofdm System International Journal For Technological Research In Engineering Volume 1, Issue 8, April-214 ISSN (Online): 2347-4718 3345
[1] Megha Gupta, Prof. Rajesh Nema, Dr. Ravi Shankar Mishra, Dr. Puran Vol. 1, Issue 3 -Bit Error Rate Performance in OFDM System Using MMSE & MLSE Equalizer Over Rayleigh Fading Channel Through The BPSK, QPSK,4 QAM & 16 QAM Modulation Technique International Journal of Engineering Research and Applications (IJERA)ISSN: 2248-9622 Department of Electronics & Communication,NRI Institute of Information Science & Technology Bhopal (M.P.) [11] [Jijun Zhang1 and Aihan Yin Analysis the Speciality of Modulation Format in WDM-PON System Departments of Electronic Information and Electrical Engineering, Anyang Institute of Technology/ Anyang, China 3346