Ofdm Systems Research Papers - Academia.edu (original) (raw)

A detailed study of the performance of MIMO-OFDM transmission on WLAN physical layer specified in IEEE 802.11n, Wi-MAX (IEEE 802.16-2009) physical layer specified in 802.16 and LTE downlink physical channel (PDSCH) has been carried out... more

A detailed study of the performance of MIMO-OFDM transmission on WLAN physical layer specified in IEEE 802.11n, Wi-MAX (IEEE 802.16-2009) physical layer specified in 802.16 and LTE downlink physical channel (PDSCH) has been carried out using MATLAB Simulink. The WLAN and Wi-MAX system incorporates Convolution coding with 1/2 and 2⁄3 rated codes. The LTE incorporates Turbo coding with 1/2 and 2/3 rated codes. Orthogonal Frequency Division Multiple (OFDM) accesses uses adaptive modulation technique such as QPSK,16-QAM and 64-QAM, on the physical layer of WLAN, Wi-MAX and LTE and the concept of cyclic prefix that adds additional bits at the transmitter end. The Error Rate (BER) derived from simulation results show that the implementation with interleaved Convolution coding and Turbo coding under QPSK modulation technique is found to be highly efficient for WLAN, Wi-MAX and LTE wireless network system. The Implementation of MIMO-OFDM multiplexing on WLAN networks with QPSK modulation at BER ~10-3 dB, exhibits significant improvement in SNR ~ 2.75 dB, Wi-MAX network SNR ~ 3.75 dB and LTE network SNR ~7.55 dB. The improvement of SNR ~4.8 dB displayed between the MIMO-OFDM implementation on WLAN and LTE network can be attributed to the Turbo coding techniques adopted in LTE networks.

A combination of multiple-input multiple-output (MIMO) signal processing with orthogonal frequencydivision multiplexing (OFDM) is regarded as a promising solution for enhancing the performance of next generation wireless local area... more

A combination of multiple-input multiple-output (MIMO) signal processing with orthogonal frequencydivision multiplexing (OFDM) is regarded as a promising solution for enhancing the performance of next generation wireless local area network (WLAN) systems.Because of the rapid growth of Digital Communication in recent years, the need for high speed data transmission is increased. Orthogonal frequency division multiplexing (OFDM) technique is suitable for high speed communication and it utilizes the bandwidth efficiently [1]. MIMO-OFDM is a combination of OFDM and MIMO (Multiple Input Multiple Output) techniques suitable for design of multiuser system and robust against channel impairments. In this paper we have implemented MIMO-OFDM for WLAN (IEEE802.11a) standard. This paper compares bit error rate (BER) performance of Simulink based MIMO-OFDM model for different modulation technique. Here we have used BPSK, QPSK and M-QAM modulation techniques.

Abstract:- This is an extension algorithm previously presented in [1] for decoded modulation systems with block codes for 8-PSK and 16-PSK constellations. The proposed algorithm presents a search mechanism of the least reliable points... more

Abstract:- This is an extension algorithm previously presented in [1] for decoded modulation systems with block codes for 8-PSK and 16-PSK constellations. The proposed algorithm presents a search mechanism of the least reliable points from the first code array and generate vectors for the Modified BCM, ZNA decoder, described in [1]. It is also presented a mapping of the 8-PSK and 16-PSK constellations in BPSK so the Modified ZNA could get the relevant results. Finally computer simulated results are compared for the 8-PSK and 16-PSK constellations, acquired from the sub-optimal algorithm proposed (Viterbi for BCM and MLD).

Channel estimator is one of the key components of the receiver in wireless communication system. It estimates channel transfer function by using channel's information from pilots in transmitted signal, so that useful data can be... more

Channel estimator is one of the key components of the receiver in wireless communication system. It estimates channel transfer function by using channel's information from pilots in transmitted signal, so that useful data can be recovered. The difficulties in channel estimation are caused by white Gaussian noise added to received signal and the complexity of channel itself as well as the system's structure in used. This study analyses IEEE 802.16e's DL PUSC (Downlink Partial Usage of Subchannels) system, and uses it as the platform to develop some proposed channel estimation methods. Two major conclusions were reached: the special system's structure limits the channel estimator and the proposed method using least square error fitting has very impressive performance and low complexity, hence it is very promising for realization.

Stochastic interdependence of a probablility distribution on a product space is measured by its Kullback-Leibler distance from the exponential family of product distributions (called multi-information). Here we investigate low-dimensional... more

Stochastic interdependence of a probablility distribution on a product space is measured by its Kullback-Leibler distance from the exponential family of product distributions (called multi-information). Here we investigate low-dimensional exponential families that contain the maximizers of stochastic interdependence in their closure. Based on a detailed description of the structure of probablility distributions with globally maximal multi-information we obtain our main

PurposeThe purpose of this paper is to propose a novel decoding algorithm, to decrease the complexity in decoding conventional block turbo codes.Design/methodology/approachIn this algorithm, the signal‐to‐noise ratio (SNR) values of... more

PurposeThe purpose of this paper is to propose a novel decoding algorithm, to decrease the complexity in decoding conventional block turbo codes.Design/methodology/approachIn this algorithm, the signal‐to‐noise ratio (SNR) values of channels are adaptively estimated. After analyzing the relationship between the statistics of the received vectors R and the channel SNR, an adaptive method of tuning the decoding complexity is presented.FindingsSimulation results show that the proposed algorithm has greatly decreased the decoding complexity and sped up the decoding process while achieving better bit error rate performance.Originality/valueSimulation experiments described in this paper show that the proposed algorithm can decrease the decoding complexity, shorten the decoding time and achieve good decoding performance.

High data rate communication systems usually implement Orthogonal Frequency Division Multiplexing (OFDM) to face frequency selectivity. High Peak to Average Power Ratio (PAPR) is an OFDM disadvantage that causes Bit Error Rate (BER)... more

High data rate communication systems usually implement Orthogonal Frequency Division Multiplexing (OFDM) to face frequency selectivity. High Peak to Average Power Ratio (PAPR) is an OFDM disadvantage that causes Bit Error Rate (BER) degradation and out-of-band (OOB) radiation when OFDM signal pass through nonlinear Power Amplifier (PA). In order to overcome this problem larger Input Back-Off (IBO) is required. However, large IBO decreases the PA efficiency. PAPR reduction techniques are used to reduce the required IBO, so that PA efficiency is saved. Several PAPR reduction methods are introduced in literature, among them Tone Reservation based on Null Subcarriers (TRNS) is downward compatible version of Tone Reservation (TR) with small excess in the average power and low computational complexity compared to others. As will be shown, TRNS is the best practical one of the four downward compatible techniques. Performance of TRNS is controlled by three parameters; number of peak reduction tones (PRTs), predefined threshold (Amax), and number of iterations (Itr). In order to increase PAPR reduction gain, enhance BER performance, and reduce the required IBO to follow the given power spectral density (PSD), we have to choose the values of these parameters adequately. Results showed that, we have to reduce the threshold value to the average (i.e. Amax =0 dB). Also, we have to increase number of PRTs. However, we have to maintain the spectrum shape. Finally, we have to choose moderate number of iterations (e.g. Itr ≈50), as excessive increase in number of iterations is not useful, especially at high PAPR values.

Channel estimator is one of the key components of the receiver in wireless communication system. It estimates channel transfer function by using channel's information from pilots in transmitted signal, so that useful data can be... more

Channel estimator is one of the key components of the receiver in wireless communication system. It estimates channel transfer function by using channel's information from pilots in transmitted signal, so that useful data can be recovered. The difficulties in channel estimation are caused by white Gaussian noise added to received signal and the complexity of channel itself as well as the system's structure in used. This study analyses IEEE 802.16e's DL PUSC (Downlink Partial Usage of Subchannels) system, and uses it as the platform to develop some proposed channel estimation methods. Two major conclusions were reached: the special system's structure limits the channel estimator and the proposed method using least square error fitting has very impressive performance and low complexity, hence it is very promising for realization.

ABSTRACTModern wireless orthogonal frequency division multiple access (OFDMA) systems incorporate dynamic resource allocation (DRA), adaptive modulation and coding (AMC), and power control (PC) to exploit multiuser diversity and achieve... more

ABSTRACTModern wireless orthogonal frequency division multiple access (OFDMA) systems incorporate dynamic resource allocation (DRA), adaptive modulation and coding (AMC), and power control (PC) to exploit multiuser diversity and achieve higher system throughput. In the literature, only a few proposed algorithms deal with the contiguous DRA problem according to which a contiguous collection of resources can be allocated to each user. This paper formulates this high complexity problem, provides a suitable decision metric and a simple yet efficient solution. The proposed algorithm allocates in each step a contiguous collection of resources to the pending user that leads to the highest estimated correctly received number of bits. Simulation results show that, in this way, considerably improved performance can be achieved in terms of overall system throughput, spectral efficiency, and served traffic. Copyright © 2010 John Wiley & Sons, Ltd.

Abstract: The objective of this deliverable is to perform a first assessment of wireless access/multiple access technologies for the WINNER system concept. The study of multiple access schemes is the responsibility of Task 4 within the... more

Abstract: The objective of this deliverable is to perform a first assessment of wireless access/multiple access technologies for the WINNER system concept. The study of multiple access schemes is the responsibility of Task 4 within the WINNER workpackage 2. The work requires the collection and assessment of the numerous ideas and proposals available. The technologies and combinations of technologies are also assessed and compared, to identify the most promising strategies and combinations. The latter work is primarily performed by multi-link simulation and system-level simulation

In this World of Digital era the demand of mobile Internet and wireless multimedia applications are growing faster than ever. To satisfy the user requirements and to overcome the limitations of existing wireless technologies, have led the... more

In this World of Digital era the demand of mobile Internet and wireless multimedia applications are growing faster than ever. To satisfy the user requirements and to overcome the limitations of existing wireless technologies, have led the researchers to come up with more advanced and efficient technology. Orthogonal Frequency Division Multiplexing (OFDM) based WiMAX (Worldwide Interoperability for Microwave Access) is the outcome in this direction which promises to solve the last mile access technology to provide high speed internet access in the residential as well as small and medium sized enterprise sectors. In this paper we have analyzed the effect of Block Interleaving on the Bit Error Rate (BER) performance of the WiMAX Physical layer baseband system conforming to the parameters established by IEEE 802.16 standards for different digital modulation schemes. From the analysis it was observed that addition of interleaving with forward error correction (FEC) improves the system pe...