Performance analysis and design optimization of LDPC-coded MIMO OFDM systems (original) (raw)
Related papers
Performance of Concatenated Optimized Irregular LDPC Code with Alamouti Coded MIMO-OFDM Systems
2013
Multiple input multiple output (MIMO) communication systems along with orthogonal frequency division multiplexing (OFDM) have a great potential for future 4G broadband wireless communications. Recently, low density parity check codes (LDPC) achieves good error correcting performance and capacity near Shannon's limit. In this paper, we considered the performance analysis of serially concatenated regular and irregular LDPC codes with Alamouti space time block coded (STBC) and space frequency block coded (SFBC) MIMO-OFDM systems for high data rate wireless transmission. Currently, most of the research related to this area is concentrated on the impact of increase in code rate and diversity of the system but not on increase in coding gain. In this paper, we analyzed the impact of increasing coding gain. Performance analysis and design optimization is carried out using density evolution (DE) tool with mixture of Gaussian approximations over Rayleigh independent and identically distributed (i.i.d) channels
Practical performance of MIMO-OFDM-LDPC with low complexity double iterative receiver
2009 IEEE 20th International Symposium on Personal, Indoor and Mobile Radio Communications, 2009
This paper considers MIMO-OFDM transmission with low density parity check (LDPC) codes. We employ a low complexity minimum mean-square-error (MMSE) softinterference-cancelation (SIC) based double iterative receiver (DIR). Results are presented for a real system implementation at 5.2 GHz. We achieve zero packet errors at 90% of the measured indoor locations, when transmitting at 600 Mbit/s, with 15 bit/s/Hz spectral efficiency and 26 dB signal-to-noise ratio. We show that the proposed receiver actually outperforms a list sphere detection (LSD) based single iterative receiver (SIR) at high coding rates, in practice. Investigations reveal that the LSD-SIR is adversely affected by the non-Gaussian noise present at the receiver, while at the same time the MMSE-SIC-DIR is better able to handle transmitter noise present in the practical system.
IEEE Transactions on Communications, 2002
We consider a space-time coded (STC) orthogonal frequency-division multiplexing (OFDM) system with multiple transmitter and receiver antennas over correlated frequencyand time-selective fading channels. It is shown that the product of the time-selectivity order and the frequency-selectivity order is a key parameter to characterize the outage capacity of the correlated fading channel. It is also observed that STCs with large effective lengths and ideal built-in interleavers are more effective in exploiting the natural diversity in multiple-antenna correlated fading channels. We then propose a low-density parity-check (LDPC)-code-based STC-OFDM system. Compared with the conventional space-time trellis code (STTC), the LDPC-based STC can significantly improve the system performance by exploiting both the spatial diversity and the selective-fading diversity in wireless channels. Compared with the recently proposed turbo-code-based STC scheme, LDPC-based STC exhibits lower receiver complexity and more flexible scalability. We also consider receiver design for LDPC-based STC-OFDM systems in unknown fast fading channels and propose a novel turbo receiver employing a maximum a posteriori expectation-maximization (MAP-EM) demodulator and a soft LDPC decoder, which can significantly reduce the error floor in fast fading channels with a modest computational complexity. With such a turbo receiver, the proposed LDPC-based STC-OFDM system is a promising solution to highly efficient data transmission over selective-fading mobile wireless channels.
An adaptive MIMO transmission technique for LDPC coded OFDM cellular systems
2004 IEEE 59th Vehicular Technology Conference. VTC 2004-Spring (IEEE Cat. No.04CH37514)
In this paper, an adaptive MIMO transmission scheme using QAM and LDPC code is proposed for an OFDM cellular system employing FDD. By approximating the LLR distribution to a Gaussian distribution, only two parameters, the mean and the normalized standard deviation, are required to be sent to the transmitter, which requires only a few more bits than those required in currently used single carrier cellular systems, such as cdma2000-1x EV-DO. It is shown by computer simulation that the proposed adaptive transmission scheme can provide up to 2 ∼ 3dB gain over the conventional system using the mean SNR only, at the expense of only 3 more bits in the feedback information.
Performance studies of a multi-band OFDM system using a simplified LDPC code
2004
Ultra-wideband (UWB) is a promising radio technology for networks delivering extremely high data rates at short ranges. Multi-band orthogonal frequency division multiplexing (MB-OFDM) is a suitable solution to implement high speed data in ultra wideband spectrum by dividing the available spectrum into multiple bands. MB-OFDM achieves adaptability as well as high performance, low-power and low-cost characteristics through the usage of OFDM. Due to the importance of error correcting codes for OFDM systems, it is essential to employ a powerful error correcting code for the MB-OFDM system to improve the performance. Recently, low-density parity-check (LDPC) code has attracted great attention because it achieves bit error rate near to the Shannon limit. In this paper, we design and evaluate the performance of the MB-OFDM system using LDPC code. In order to simplify the implementation of the LDPC encoder and decoder, we introduce a joint code and decoder design approach to construct a class of (3, k)-regular LDPC code which exactly fits to a partly parallel decoder implementation. The simulations show that the performance of such a simplified LDPC coded MB-OFDM system is better than that of a convolutional coded MB-OFDM system, and is very close to that of the conventional LDPC coded MB-OFDM system. The implementation complexity of the simplified LDPC code is carefully examined subsequently in the paper.
Wireless Personal Communications
In this paper, we study the design of expectation-maximization (EM)-based iterative receivers for low-density parity check -coded multiple-input multiple-output orthogonal frequency-division multiplexing systems with the presence of carrier-frequency offset (CFO). First, starting from the maximum-likelihood principle, we devise a novel EM-based pilot-aided scheme for joint estimation of CFO and channel coefficients. Then, this estimator is incorporated into the initialization step of the iterative receiver. Simulation results show the effectiveness of our receiver design in combating CFO over unknown frequency selective fading channels.
Various Diversity Combining Techniques with LPDC Codes in MIMO-OFDM
OFDM with MIMO is the most efficient and commonly used technology. In MIMO system multiple antennas arrays used across transmitter and receiver side. OFDM with MIMO technology provide reliable communication and efficient manner of signal reception across receiver. In MIMO technology Bit rate error very high due to Multi-path fading effect of channel. In this paper new technique is proposed to reduce Bit rate. The proposed technique uses LDPC filter with OFDM along diversity methods. LDPC filter is used in OFDM to reduce bit rate error and calculate performance in terms of BER for receive combing technique such as MRC. Since MRC provide excellent reduction in BER as compare to SC and EGC. The proposed technique is implemented in MATLAB and result shows that proposed technique will reduce bit rate error in MIMO-OFDM.
IEEE Transactions on Vehicular Technology, 2011
A low-density parity-check (LDPC)-coded multiple-inputmultiple-output (MIMO) system is able to achieve excellent bit-error-rate (BER) performance over fading channels. The two types of MIMO systems examined in this paper are the transmit antenna selection/generalized selection combining (TAS/GSC) and orthogonal space-time block code (STBC). The approximate BER expressions of these two systems with LDPC codes using binary phase-shift keying signals over a Rayleigh fading channel are derived based on the Gaussian approximation (GA) approach. These expressions provide a computationally efficient method of analyzing the system performance, as compared with density evolution (DE) and simulation. The stability conditions for both systems using the DE and GA approaches are also presented. Index Terms-Gaussian approximation (GA), generalized selection combining (GSC), low-density parity-check (LDPC) codes, space-time block code (STBC), transmit antenna selection (TAS).
Iterative estimation and decoding for an LDPC-coded OFDMA system in uplink environments
2004 IEEE International Conference on Communications (IEEE Cat. No.04CH37577), 2004
In this paper, we propose an LDPC-coded OFDMA system with a resource allocation method suitable for the uplink of mobile cellular environments. At the receiver of the proposed system, an iterative channel estimation and decoding (IED) method with a Wiener filter adapting to the channel variation rate is employed to support high mobility without boosting the pilot power. For practical applications, the channel variation rate is also estimated with pilot symbols to select Wiener filter coefficients for every received packet dynamically allocated. It is shown that the proposed system supports the mobility up to 250 km/h and exhibits more than 1 dB performance gain over the system with conventional non-iterative receiver.