Orthogonal Frequency Division Multiplexing Transmission Technique Research Articles

A Comprehensive Review on Channel Estimation Techniques in MIMO-OFDM

In wireless communication, more than one signals are transmitted in the channel by using the concept of Orthogonal frequency division multiplexing (OFDM) which efficiently handles the inter symbol interference and utilizes the frequency and available bandwidth efficiently. Whereas for OFDM transmission technique is integrated with MIMO channel which contains multiple transmitter and receiver antenna at both ends. By using MIMO-OFDM system, different signals can be transmitted at the same time by utilizing same frequency and get separated in the space. As the transmitting antenna transmit signal in the noisy channel so, it is required to estimate the noise in the channel. The channel estimation technique in noisy channel helps in analyzing the effect of noise on the transmitted data. In this paper, a brief review is presented for channel estimation techniques for MIMO-OFDM.

TCM-coded OFDM assisted by ANN in Wireless Channels

The objective of this paper is to use Artificial Neural Network (ANN) in conjunction with M-ary PSK Trellis Coded Modulation (TCM) based Orthogonal Frequency Division Multiplexing (OFDM) as a means of achieving higher throughput and performance improvement in multi path fading channel. Simulation results are presented, that shows the superiority of the ANN-based approach, as a means to decode the signal at the receiver side, over conventional TCM decoding schemes. The performance gain is due to the adaptive learning capability of the ANN that can use the Transmitter Side Information (TSI), Receiver Side Information (RSI) and Channel Side Information (CSI) to perform decoding and symbol recovery simultaneously. 4-PSK and 8-PSK TCM-codes have been considered in this work along with OFDM transmission technique.

A Novel Filter-Bank Multicarrier Scheme to Mitigate the Intrinsic Interference: Application to MIMO Systems

Filter-bank multicarrier (FBMC) transmission system was proposed as an alternative approach to orthogonal frequency division multiplexing (OFDM) system since it has a higher spectral efficiency. One of the characteristics of FBMC is that the demodulated transmitted symbols are accompanied by interference terms caused by the neighboring transmitted data in time-frequency domain. The presence of this interference is an issue for some multiple-input multiple-output (MIMO) schemes and until today their combination with FBMC remains an open problem. We can cite, among these techniques, the Alamouti scheme and the maximum likelihood detection (MLD) with spatial multiplexing (SM). In this paper, we shall propose a new FBMC scheme and transmission strategy in order to avoid this interference term. This proposed scheme (called FFT-FBMC) transforms the FBMC system into an equivalent system formulated as OFDM regardless of some residual interference. Thus, any OFDM transmission technique can be performed straightforwardly to the proposed FBMC scheme with a corresponding complexity growth compared to the classical FBMC. First, we will develop the FFT-FBMC in the case of single-input single-output (SISO) configuration. Then, we extend its application to SM-MIMO configuration with MLD and Alamouti coding scheme. Simulation results show that FFT-FBMC can almost reach the OFDM performance, but it remains slightly outperformed by OFDM.

Mitigation of Impulsive Noise Effect on the PLC Channel With QC–LDPC Codes as the Outer Coding Scheme

In this paper, the characteristics of irregular quasicyclic-low-density parity check (QC-LDPC) codes are examined when they are applied on a highly impulsive noise channel, such as the power-line-communications (PLC) channel. We study two decoding algorithms: 1) the sum product and 2) the bit-flipping algorithm, and how they affect the system's performance. LDPC codes are introduced in combination with other coding schemes, such as Reed-Solomon and convolutional codes. We propose irregular QC-LDPC codes as outer codes for the PLC channel in combination with Reed-Solomon codes, due to their decoding characteristics. In addition, various code rates are used for each different coding scenario. We also test how common Reed-Solomon codes affect the system's performance, such as the RS(63, 53), RS(511, 431), RS(127, 107), and RS(255, 239) codes. Furthermore, we propose an altered version of the sum-product decoding algorithm to enable its operation when QC-LDPC codes are used as the outer coding scheme in combination with Reed-Solomon codes. Regarding the system's design, the orthogonal frequency-division multiplexing transmission technique is utilized. We also take Zimmermann's model into consideration for the PLC channel and Middleton's noise model.

Broad-band OFDM radio transmission for multimedia applications

Future multimedia services will require the transmission of very high data rates over broad-band radio channels. In order to provide these services to mobile users, an appropriate transmission technique has to cope with frequency-selective and time-variant radio channels. The computation complexity for an equalizer increases in a frequency-selective radio channel for high data rate applications. Furthermore, the overhead for channel estimation procedures increases in time-variant channels. To overcome these drawbacks orthogonal frequency division multiplexing (OFDM) has been considered for broadband applications in many publications. The objective of this paper is to describe the large potential, the flexibility and adaptivity of the OFDM transmission technique in frequency-selective and time variant radio channels. Several technical aspects of OFDM transmission systems are discussed, especially the topics of differential modulation for which we compare different demodulation methods and channel coding with soft decision decoding. For higher level differential modulation, multilevel coding is taken into consideration.

Multilevel differential modulation techniques (64‐DAPSK) for multicarrier transmission systems

AbstractIn Digital Video Broadcasting (DVB) applications the objective is to transmit a high data rate of 34.368 Mbit/s in a single channel. For terrestrial digital transmission the considered radio channel bandwidth is 7 or 8 MHz. In this paper we analyse the performance of a multicarrier transmission technique, the well‐known Orthogonal Frequency Division Multiplexing (OFDM) method, and consider the system parameters for this DVB application. For the OFDM transmission technique an absolute modulation scheme (64‐QAM) has been suggested. In this case and in frequency‐selective interference situations a channel estimation process and a channel equalization are necessary [4], The equalization process can be realized by a multiplier bank at the FFT output in the receiver, a so‐called frequency‐domain equalizer. Alternatively, a multilevel differential modulation technique, the so‐called Differential Amplitude and Phase Shift Keying (64‐DAPSK) is proposed in this paper, in which the phase and the amplitude are used simultaneously for differential modulation. A differential modulation technique does not require any explicit knowledge about the radio channel properties in the differential channel equalization process. In an OFDM/64‐DAPSK receiver it is therefore not necessary to implement a frequency‐domain equalizer, which reduces the computation complexity. The performance of both modulation techniques has been analysed in the uncoded case referring to Gaussian and frequency‐selective Rayleigh fading channels. The results are described in this paper.