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Orthogonal Frequency division multiplexing is the modulation technique used for the fourth generation wireless communication system. In OFDM, Signals can be modulated by multiple carriers. OFDM uses the bandwidth of the spectrum efficiently. But the limitation of the OFDM system is the high Peak to Average Power Ratio (PAPR) which results in the degradation of the signal quality. Hence reducing the...
The MIMO-OFDM technology is under the significant considerations for the development of various wireless communication systems. A WLAN for 5G is for very high throughput. The combination of Multiple Input Multiple Output with multicarrier, Orthogonal Frequency Division Multiplexing (MIMO-OFDM) delivers a significant performance improvement in terms of many parameters like transmission rate, smaller...
In wireless communication systems data recovery represents an important challenge at receiver's end. The performances of MC-CDMA systems can be improved by using OFDM technique. This paper illustrates the improvement brought in MC-CDMA OFDM systems when choosing the LDPC coding/decoding technique and the appropriate spreading sequences to separate the users. There have been tested the performances...
Orthogonal Frequency Division Multiplexing (OFDM) is a method of encoding digital data on multiple carrier frequencies. It has become a prevalent technique for wideband digital communication. Forward Error Correction (FEC) schemes for OFDM communication system is presented in this paper. Interleaver is a vital part in the communication system design. Matrix interleaver implementation which significantly...
This paper evaluates the performance of differentially encoded quadrature phase shift keying (DQPSK) modulated orthogonal frequency division multiplexing (OFDM) for underwater acoustic (UWA) communication. The combination of OFDM and the non-coherent detection scheme maintains the receiver design simple, reliable and spectrally efficient. QPSK helps achieve higher data rate as two bits are sent over...
Fountain Codes belongs to the class of rateless codes[4] which effectively improves the performance of systems used for wireless data transmission. In this paper, we present a quantitative analysis of Fountain Coded Orthogonal Frequency Division Multiplexing (OFDM) systems over Rician faded channel. Bit Error Rate (BER) performance evaluation and comparison is carried out for Fountain Coded and Convolution...
Quadrature Orthogonal Frequency Division multiple access (Q-OFDMA) has been renowned as a promising technique which provides a solution to the high PAPR (Peak to average power ratio), sensitivity to carrier frequency offset (CFO) problem and design complexity as introduced by the normal OFDMA systems. Exploiting this Q-OFDMA systems on the Multi-Input Multi-Output (MEMO) architecture, leads to a remarkable...
This report lays out the idea of introducing LPDC codes along with the spreading sequence to improve noise immunity of the signals traversing in wireless environment. With the need to make communication techniques efficient and reliable, spread spectrum has gained importance for its various added advantages. LDPC (Low Density Parity Check) have been gaining limelight in the past few years. Comprising...
This paper presents a performance evaluation of OFDM LTE downlink physical layer according to the latest 3GPP specifications. Particularly, adaptive modulation and coding (AMC) is described and analyzed. This is in conjunction with the turbo decoding algorithm Max-Log-Maximum A Posteriori (Max-Log-MAP) used in soft input soft output (SISO) decoders. The performance analysis is carried out in terms...
To achieve high data rate Multi-Carrier Code Division Multiple Access (MC-CDMA) is one suitable choice for next generation wireless communication system. MC-CDMA is the combination of CDMA and OFDM schemes, resulting into getting the advantages of both the schemes. Capacity planning is one of the major issues in designing of wireless communication system. In wireless communication system capacity...
WiMAX is an IEEE802.16 standard that provides a high speed transmission with wide coverage range. In IEEE 802.16j, the multiple Relay Stations (RS) are added to employ multihop links for WiMAX systems to extend coverage range and capacity. Many works in literature concern the RS locations based on the effective cost and the optimum user capacity. Most of them assumed the lossless transmission between...
OFDM has recently been applied widely in wireless communication system due to its high data rate transmission capability with high bandwidth efficiency. Error control codes are used to protect information from errors that can occur during transmission Reed Solomon (RS) and BCH codes is one of the most important and best known classes of non binary [5]. In the present study a simulink of RS and BCH...
A high peak-to-average power ratio (PAPR) is a major concern of an orthogonal frequency division multiplexing (OFDM) system. In this paper, a combination of pre-coding and clipping is used to reduce PAPR. This dual operation of pre-coding and clipping provides better PAPR than both conventional pre-coding and clipping method. With this technique, the PAPR can be reduced without increasing roll-off...
Unique word - orthogonal frequency division multiplexing (UW-OFDM) is a novel OFDM concept that uses deterministic sequences, which we call unique words, as guard intervals instead of the conventional cyclic prefixes. Since unique words represent known sequences, they can advantageously be used for synchronization, channel estimation, but also for improving the bit error ratio (BER) behavior of a...
In this paper, a linearly coded (LC) relaying scheme is proposed for multiuser relay network in which a number of users communicate simultaneously with a common destination with the help of one relay node, by using orthogonal frequency division multiple access (OFDMA). The proposed linear coding at the relay node enables exploiting the frequency diversity in the relay-to-destination (R-to-D) link...
A physical layer simulator for the WiMAX technology is presented in this paper. The simulator encompasses the main blocks that build the physical layer from IEEE 802.16e. It allows to understand some of the physical layer mechanisms and techniques employed in WiMAX and to simulate various transmission scenarios. BER results are presented for some distributed permutation schemes, with different digital...
In this paper, we propose a 2 × 2 cooperative multiple-input multiple-output (MIMO) orthogonal frequency-division multiplexing (OFDM) scheme based on Alamouti space-time coding. In this scheme, the the relay and the destination antennas receive the transmitted symbols from the source during the first stage. Then, both the relay and the destination generate their own decision variables using an Alamouti...
In this paper, we employ to provide a method which combines Turbo codes and Low-Density Parity-Check (LDPC) codes based on Orthogonal Frequency Division Multiplexing (OFDM) system by adaptive encoding. The technique of channel estimation is used. The code rate and encoding scheme are all adaptive selection in the light of different channel conditions, so that we can make good use of these two types...
This paper proposes an idea of developing a model of estimating timing offset error of OFDM (Orthogonal Frequency Division Multiplexing) system without the use of additional pilots relying on inherent characteristics of the OFDM signal. An analytical expression has been derived and formulated to analyze the effect of bit error rate (BER) due to timing offset introduced by the transmission channel...
In this paper, we study the performance of an Orthogonal Frequency Division Multiplexing (OFDM) WiMAX transmission system with adaptive modulation and coding (AMC) over different fading channels. An explanation necessary to understand the block diagram of the system is briefly given and a MATLAB code is written to simulate the basic processing involved in this system. The simulation is performed for...
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