An adaptive MIMO transmission technique for LDPC coded OFDM cellular systems (original) (raw)
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Adaptive Modulation Coding For MIMO OFDM
2018
Wireless communication is one of the mainly active areas of tools progress and has become an ever-more essential and prominent part of everyday life. Several transmission modes are defined in LTE standards. A very little transmission modes are considering for LTE in physical layer parameters and wireless channel characteristics. We evaluated the act of available transmission modes in LTE. However, performance analysis can be done straightforward using evaluation of LTE. The performance of transmission modes are evaluated by calculating probability of Bit Error Rate (BER) versus Signal Noise Ratio (SNR) under the frequently used three wireless channel models (AWGN, Rayleigh and Rician). We will consider the data modulation and data rate to analyze performance that is BER vs. SNR. An important issue is in wireless application progress is selection of fading models. A comparative analysis of QPSK and 16QAM, 32 QAM and 64 QAM will also provide knowledge base which helps for application ...
Performance analysis and design optimization of LDPC-coded MIMO OFDM systems
IEEE Transactions on Signal Processing, 2004
We consider the performance analysis and design optimization of low-density parity check (LDPC) coded multiple-input multiple-output (MIMO) orthogonal frequency-division multiplexing (OFDM) systems for high data rate wireless transmission. The tools of density evolution with mixture Gaussian approximations are used to optimize irregular LDPC codes and to compute minimum operational signal-to-noise ratios (SNRs) for ergodic MIMO OFDM channels. In particular, the optimization is done for various MIMO OFDM system configurations, which include a different number of antennas, different channel models, and different demodulation schemes; the optimized performance is compared with the corresponding channel capacity. It is shown that along with the optimized irregular LDPC codes, a turbo iterative receiver that consists of a soft maximum a posteriori (MAP) demodulator and a belief-propagation LDPC decoder can perform within 1 dB from the ergodic capacity of the MIMO OFDM systems under consideration. It is also shown that compared with the optimal MAP demodulator-based receivers, the receivers employing a low-complexity linear minimum mean-square-error soft-interference-cancellation (LMMSE-SIC) demodulator have a small performance loss ( 1dB) in spatially uncorrelated MIMO channels but suffer extra performance loss in MIMO channels with spatial correlation. Finally, from the LDPC profiles that already are optimized for ergodic channels, we heuristically construct small block-size irregular LDPC codes for outage MIMO OFDM channels; as shown from simulation results, the irregular LDPC codes constructed here are helpful in expediting the convergence of the iterative receivers.
Adaptive Modulation Technique to Improve OFDM System
2015
The information rates and channel limit of a wireless Multiple Input Multiple Output (MIMO) Orthogonal Frequency Division Multiplexing (OFDM) framework can be enhanced by executing a dynamic connection adjustment calculation (Link Adaption Algorithm). Since a solitary kind of adjustment in modulation can't fulfill every working state of a correspondence framework we require versatile balance coding algorithm i.e. Adaptive Modulation Coding (AMC). We have implemented a kind of AMC plan alluded to as Spatially Adaptive Modulation and Coding (SAMC) plan. This technique implementation can be done in two stages. In the first stage, it hunt down the modulation scheme with the most extreme estimation of contention of the computed complex estimations of a parameter known as PPSNR (post processing Signal to Noise Ratio). The second stage includes the utilization of a suitable Modulation and Coding Scheme (AMC) based on the value of PPSNR yielded by the selected configuration, through a l...
Adaptive Modulation for OFDM Systems
The goal for the fourth generation (4G) of mobile communications system is to seamlessly integrate a wide variety of communication services such as high speed data, video and multimedia traffic as well as voice signals. One of the promising approaches to 4G is adaptive OFDM (AOFDM). In AOFDM, adaptive transmission scheme is employed according to channel fading condition with OFDM to improve the performance. In this paper, we have considered only adaptive modulation. First we have investigated the OFDM system performance of uncoded adaptive modulation using quadrature amplitude modulation (QAM) and phase shift keying (PSK). To further enhance the system, we employ convolutional coding to OFDM system. The obtained results show that a significant improvements in terms of bit error rate (BER) and throughput can be achieved demonstrating the superiority of the adaptive modulation schemes compared to fixed transmission schemes.
Adaptive techniques in orthogonal frequency division multiplexing in mobile radio environment
2004
In this paper, a review of various link adaptation techniques employed in the transmission of adaptive Orthogonal Frequency Division Multiplexing (OFDM) is presented. Significant research effort in coded OFDM and adaptive modulation based on second moment adaptation are simulated and presented. Results show that coded OFDM performs at least 5 dB better in terms of signal to noise ratio (SNR) requirements as compared to uncoded system in any QAM modulation. Results on second moment adaptation show that, for adaptation up to 4 bits per symbols, second moment adaptation is about 3 dB more superior than adaptation by mean channel SNR. Other related issues are discussed to formulate future research direction in an effort to achieve higher throughput, lower bit error rate and better overall system performance.
Performance analysis of adaptive filter channel estimated MIMO OFDM communication system
International Journal of Electrical and Computer Engineering (IJECE), 2018
Advanced Communication Systems are wideband systems to support multiple applications such as audio, video and data so and so forth. These systems require high spectral efficiency and data rates. In addition, they should provide multipath fading and inter-symbol interference (ISI) free transmission. Multiple input multiple output orthogonal frequency division multiplexing (MIMO OFDM) meets these requirements Hence, MIMO-OFDM is the most preferable technique for long term evaluation advanced (LTE-A). The primary objective of this paper is to control bit error rate (BER) by proper channel coding, pilot carriers, adaptive filter channel estimation schemes and space time coding (STC). A combination of any of these schemes results in better BER performance over individual schemes. System performance is analyzed for various digital modulation schemes. In this paper, adaptive filter channel estimated MIMO OFDM system is proposed by integrating channel coding, adaptive filter channel estimation, digital modulation and space time coding. From the simulation results, channel estimated 2×2 MIMO OFDM system shows superior performance over individual schemes. 1. INTRODUCTION Advanced mobile systems aim on supporting high data rate services over multiple systems for multi-media applications involving voice, data, pictures and video. They should provide services without interruptions for private and public networks. These services require interference free transmission over frequency selective fading channels. OFDM is a promising technique for Long Term Evaluation-Advanced (LTE-A), Worldwide Interoperability for Microwave Access (Wi-MAX) systems, IEEE 802.11ac, and IEEE 802.15 [1]. A good channel estimation procedure is necessary in order to make reliable decisions and to coherently demodulate the received data. OFDM systems require effective and exact channel estimation for time-varying channels. The principal motto of this paper is to improve the OFDM system performance by proper channel coding, suitable digital modulation schemes, adaptive filter channel estimation techniques and multiple antennas at the transmitter and receiver. By using all these, an integrated OFDM system is proposed to enhance system performance [2-3]. Gosh [4] formulated a closed form expression for impulse noise performance in a multicarrier QAM system and showed that it is better than single carrier systems for moderate values of impulse power and probability. Dong et al. [5] determined the power and rate adaptation analytically with channel state information in the presence of carrier frequency offset (CFO) for an OFDM system. Sabbaghian et al. [6] developed a new code based on dual BCH code for reduction of PAPR in multi
In the rapid growing field of wireless communications, there is an increasing demand of higher rates with longer transmission ranges for new broadband applications. It was a big challenge for modern wireless communications networks to provide services like video, voice, data including mobility. The project presents the analysis of Space-Time Block Codes used for Multiple-Input Multiple-output MIMO-OFDM technology is a combination of multiple-input multiple-output antenna technology with orthogonal frequency division multiplexing. Adaptive modulation schemes for fading channels are usually required to fulfill certain long-term average error rate targets. The error rate level is depend on the modulation type, SNR value and channel behavior. To transmit the faithful data over these systems the error rate performance is further improved using forward error correction codes (FEC). Error rate performance is evaluated for these codes under different modulation schemes like QPSK, BPSK, and QAM techniques.
Bit Error Rate Performance Analysis of Channel Estimated Adaptive OFDM System
Modern communication systems are designed to support multiple applications such as data, voice, video and multimedia transmission, hence they require high data rate, spectral efficiency and inter symbol interference (ISI) free transmission. Orthogonal frequency division multiplexing (OFDM) meets the above requirements but fluctuations in Signal to Noise Ratio is quite common due to variations in envelope of OFDM signal which degrades system performance. System performance can be improved either by using Space time coding or Adaptive modulation (AM) schemes. In this work, adaptive modulation is considered due to its low complexity and optimum spectrum utilization over space time coding. In this scheme, channel state information (CSI) is fed to the transmitter to adopt the order of modulation in order to maintain constant bit error rate (BER) irrespective of the channel conditions. Here channel estimation has done using Least Square (LS), Minimum Mean Square Error (MMSE) and interpolation along with comb type pilot symbol assisted channel estimation algorithms. In this work, a new scheme has implemented to improve the BER performance by integrating channel estimation and adaptive modulation and this new scheme results superior performance over individual methods. Keywords: Bit Error Rate (BER), Channel Estimation, Comb type pilot, Least Square (LS), Minimum Mean Square Error (MMSE), adaptive modulation and Signal to Noise Ratio (SNR) .
Adaptive MIMO OFDMA for Future Generation Cellular Systems in a Realistic Outdoor Environment
2006 IEEE 63rd Vehicular Technology Conference, 2006
This paper presents a downlink performance evaluation of a candidate physical layer for future generation cellular communications systems employing link adaptive MIMO-OFDMA. Adaptation between various modulation and coding schemes in combination with both space-time block codes (STBC) and spatial multiplexing (SM) on the basis of channel knowledge is considered. By means of ray-tracing software, a detailed example coherent time-variant channel trace is generated. Subsequent application of physical layer simulation software to this channel trace yields PER and throughput results for all available link adaptation parameters. Various channel parameters are considered against this data and the SNR and H matrix determinant are found to have the most significant influences on the system throughput. Subsequently, LA algorithms are proposed whereby the system adapts according to SNR only and both SNR and H matrix determinant. The performance of these algorithms is compared to the optimal case.
Channel adaptive OFDM systems with packet error ratio adaptation
MIMO-OFDM systems with pre-filtering as well as bit and power loading have gained a lot of interest recently. These systems are based on theoretically optimal solutions maximizing the uncoded throughput and constraining the maximum uncoded BER. In this paper, we extend the existing frameworks to coded systems with bit and packet error ratio adaptation. We evaluate the performance of this approach in a standard compliant WiMAX link level simulator.