optical OFDM

Main objectives of this paper is to design the PSK and QAM system for Symbol Error Rate (SER) performance analysis and to estimate the channels in OFDM. PSK & QAM syatems are designed for 64 Sbcarriers. In this paper we will compare the SER for both techniques for same modulation rate and same number of subcarrier. In this paper we will show how Symbol error rate is reduced as modulation rate increases for PSK & QAM. We will use three algotihms LS, LMMSE & Modified MMSE to compare the result parameters. Modified MMSE gives better results than LS & LMSE but computational complexity will be increased that is its major drawback.

LTE was proposed in 2004 Toronto conference to fulfill the requirement of achieving higher speed and lower packets latency in UMTS 3G systems. LTE which is abbreviated as long term evolution is an basically a transmission mode of providing the communication channel/communication link between the mobile portable device’s connected with each other to establish the connection between the two. LTE is composed of many new technologies compared with the previous generation of cellular systems. These new technologies are used to generate more efficiency with regards to spectrum and higher data rates as expected by designers. The currently agreed LTE architecture adopts a flat architecture, inheriting four functional elements named as Evolved Radio Access Network, User Equipment (UE) and hosts the physical layer (PHY), Medium Access Control (MAC), Radio Link Control (RLC), and Packet Data Control Protocol (PDCP) layers, Serving Gateway (SGW) and Mobility Management Entity. To do this work it has various numerous number of techniques through which it establish the link between the two. The technologies were named as OFDM, MIMO, and FDMA, SC-FDMA and so on. as it keep and maintains accuracy while providing the medium cascade to perform the task as it make use of TDD,FDD,QAM as multiplexing technologies.

This paper describes the physical implementation of an all-optical implementation security architecture for optical code division multiple access networks based on lattice cryptography. Our design is mainly based on the use of loop-based optical delay lines and fiber brag grating. The encryption process is achieved by delaying a pulse in the optical delay line according to the structure of the codewords. The number of loops is defined by the position of the pulse in codeword. We demonstrate that our implementation is less complex and more flexible than classical approachs such as fixed length optical delay lines. In addition, a performance evaluation using eye diagrams shows that our architecture is more robust against eavesdropping security attacks.

http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=5970837&tag=1

Orthogonal Frequency Division Multiplexing (OFDM)
has recently been proposed as a modulation technique for optical networks, because of its good spectral efficiency, flexibility, and tolerance to impairments. We consider the planning problem of an OFDM optical network, where we are given a traffic matrix that includes the requested transmission rates of the connections to be served. Connections are provisioned for their requested rate by elastically allocating spectrum using a variable number of OFDM subcarriers and choosing an appropriate modulation level, taking into account the transmission distance. We introduce the Routing,
Modulation Level and Spectrum Allocation (RMLSA) problem, as opposed to the typical Routing and Wavelength Assignment (RWA) problem of traditional WDM networks, prove that is also NP-complete and present various algorithms to solve it. We start by presenting an optimal ILP RMLSA algorithm that minimizes the spectrum used to serve the traffic matrix, and also present a decomposition method that breaks RMLSA into its two substituent subproblems, namely, (i) routing and modulation level, and (ii) spectrum allocation (RML+SA), and solves them sequentially. We also propose a heuristic algorithm that serves connections one-by-one and use it to solve the planning problem by sequentially serving all the connections in the traffic matrix. In the sequential algorithm, we investigate two policies for defining the order in which connections are considered. We also use a simulated annealing meta-heuristic to obtain even better orderings. We examine the performance of the proposed algorithms through simulation experiments and evaluate the spectrum utilization benefits that can be obtained by utilizing OFDM elastic bandwidth allocation, when compared to a traditional WDM network.

OFDM (orthogonal frequency-division multiplexing) signals used in 802.11a and 802.11g wireless LAN systems include provisions for equalization in the receiver to correct for some types of system and channel impairments. High data rate wireless communication has improved by a factor of minimum four while migrating from one generation to next generation. And now we have entered into an era, where fast, accurate and secured data transmission is of maximum value. The Orthogonal Frequency Division Multiplexing (OFDM) put its need in the communication for the effective bandwidth utilization with large data transmission. In this paper, we present a proposed OFDM based wireless LAN architecture and its implementation using Verilog for an efficient physical layer implementation of an OFDM technique. Our architecture improves resources utilization, compared with the other architecture.

In wireless communication demand of high data rate transmission is increases rapidly on the other side limited amount of spectrum makes it difficult. For such cases signal modulation is a dominant method for transforming the information signal over the air and the choice of modulation scheme is crucial for wireless communication. In wireless communication, conventional FDM (Frequency Division Multiplexing) does not utilize the bandwidth because there is no frequency subband overlap. OFDM is a technique which provides the full bandwidth utilization by overlapping the sub carriers. In this paper the BER performance for QAM and PSK has been analyzed in the presence of AWGN noise. Further we will investigate the effect of QAM-OFDM for different orders in the presence of frequency selective Rayleigh fading channel through MATLAB simulation.