Parismita Gogoi

Channel Estimation Technique for STBC Coded MIMO System with Multiple ANN Blocks

In this work, a channel estimation technique based on Artificial Neural Networks (ANN) has been proposed as an alternative to pilot based channel estimation technique for Space-Time Block Coded Multiple-Input Multiple-Output (STBC- MIMO) systems over Rayleigh fading channels. ANNs, due to their high degree of adaptability, can be used for modelling the nonlinear phenomenon of channel estimation and for decoding the degraded symbols over severely faded channel. Two different ANN structures, namely Multilayer Perceptron (MLP) and Recurrent Neural Networks (RNN) have been trained and tested extensively for estimating the channel in STBC- MIMO systems with Binary Phase Shift Keying (BPSK) modulation scheme. Simulated results in terms of Bit Error Rates (BER) vs. Signal to Noise Ratio (SNR) have been used to compare the effectiveness of the learning capability of the two ANN structures over wireless fading channel. RNN structures are found to outperform the MLP, both in terms of training performance and BER results and thus proving its nonlinear dynamic adaptive behaviour. General Terms

STBC coded MISO and MIMO set-up in frequency selective wireless fading channels for BPSK and QPSK modulation schemes

Diversity methods provide the receiver with independently faded copies of the transmitted signal with the expectation that at least one of these replicas will be received correctly. There are ranges of techniques available through which these faded copies can be recovered and used as part of arrangements for better reception. This paper proposes a method based on Space-Time Block Coding (STBC) with Multiple-Input Single-Output (MISO) and Multiple-Input Multiple-Output (MIMO) set-up for use in wireless channels. A special version of STBC called Alamouti code is used for exploiting the performance of MISO and MIMO in frequency-selective fading environment. Performance differences are observed with and without STBC in frequency selective faded channels. A comparison is made between the diversity gain of MISO and MIMO systems in terms of BER for two specific modulation schemes, namely BPSK and QPSK. The obtained results demonstrate that spatial diversity along with the power of STBC significantly improves the error performance in frequency selective wireless fading channels.

Pilot assisted channel estimation technique for Alamouti STBC- MISO and MIMO Set-up with BPSK and QPSK modulation

The combination of coding with spatial diversity opens up new dimensions in wireless communications, and can offer effective solutions to the challenges faced in realizing reliable high-speed links. Use of Space-Time Block Coding (STBC) with Multiple-Input Multiple-Output (MIMO) set-up proves to be an efficient method for this task. In wireless environment there is no prior knowledge of the channel state information (CSI) and hence it is required to employ some estimation techniques to obtain an estimate of the channel. Channel estimation is thus an important step in receiver design. This paper proposes an estimation technique based on block type pilot symbols having an orthogonal nature for use in Space-Time Block Coding (STBC) with Multiple Antennas set-up for use in wireless channels. Results have been obtained for known channel case and pilot estimated channel information for two distinct modulation schemes, namely Binary Phase Shift Keying (BPSK) and Quadrature Phase Shift Keying (QPSK) respectively. The Bit Error Rate (BER) performance curves from the estimation technique show a result which is closely approaching the known channel case, proving its effectiveness.

Recurrent neural network based channel estimation technique for STBC coded MIMO system over Rayleigh fading channel

Artificial Neural Networks (ANN)s, due to their high degree of adaptability, can be used to model nonlinear phenomenon of channel estimation. In this work, a channel estimation technique based on Recurrent Neural Network (RNN) has been proposed as an alternative to pilot based channel estimation technique for STBC- MIMO systems over Rayleigh fading channels. Learning property of ANN is fully exploited for decoding the degraded symbols over severely faded channel. This technique is found to be more bandwidth efficient compared to pilot-based channel estimation techniques. Simulated results in terms of bit error rates (BER) vs. signal to noise ratio (SNR) depict the effectiveness of the learning capability of ANNs for the task of channel estimation over wireless fading channel.

Performance analysis of MIMO over MIMO-LTE for MQAM considering Rayleigh fading distribution

LTE (Long Term Evolution) is a 3GPP (Third Generation Partnership Project) wireless standards which uses the standard OFDMA (Orthogonal Frequency Division Multiple Access) modulation, MU-MIMO (Multiuser Multiple Input Multiple Output) technology and different multipath fading models. LTE allows the operator to use spectrum more efficiently to deliver high speed data. This paper characterizes the downlink performance of LTE. The requirement for high data rate applications demanded a system to provide users with the MIMO technology which constitutes a breakthrough in wireless communication and is defined in the LTE standard. There are many metric to characterize the performance, but one of the most convenient and informative metric is the BER (Bit Error Rate). So the performance is characterized in terms of BER. In this paper the LTE system is modeled and simulated using MATLAB and the BER for 2×2 and 4×4 MIMO-LTE using 16QAM and 64QAM modulation schemes for Rayleigh fading environment are obtained against different SNR values.

On the evolution of downlink physical layer in multi-antenna 3GPP LTE / LTE-A: A review

3GPP (Third Generation Partnership Project) started LTE (Long Term Evolution) as a project in 2004 and later it was introduced as the 4th generation of mobile communication standard in 3GPP Release 8. LTE uses some new technologies such as OFDMA (Orthogonal Frequency Division Multiple Access) with MU-MIMO (Multiuser Multiple Input Multiple Output) in the downlink and SC-FDMA (Single Carrier Frequency Division Multiple Access) in the uplink. The benefit of LTE is that it provides better performance in multimedia applications, higher data rates, improved system capacity and coverage, reduced latency, enhanced voice communication. To fulfill all this aim a better understanding of the physical layer of LTE is required. Therefore in this paper a holistic overview of the downlink physical layer of LTE been discussed.

Interference cancellation in massive MIMO base stations with certain precoding techniques in faded environment

Precoding design for MIMO wireless system has gained momentum currently as a new emerging research area and has been established in various wireless standards. In this paper, certain linear and nonlinear precoding methods are investigated to address the transmission problems of MU-MIMO systems in faded channels. It is studied how various precoding techniques at the transmitter side is improving the Bit error rate (BER), with full channel knowledge at the receiver end. Error performances prove that nonlinear DPC or TH technique achieves the capacity region of the multiple antennas, as compared to linear methods. DPC method seems to outperform all other techniques in terms of error performance and capacity limits.

Performance Analysis of MIMO-LTE for MQAM over Fading Channels

LTE (Long Term Evolution) is a 3GPP (Third Generation Partnership Project) wireless standards which uses the standard OFDMA (Orthogonal Frequency Division Multiple Access) modulation, MU-MIMO (Multiuser Multiple Input Multiple Output) technology and different multipath fading models. LTE uses the spectrum more efficiently to deliver high speed data. This paper characterizes the downlink performance of LTE. The MIMO technology which provides high data rate applications to the users made a breakthrough in wireless communication and is defined in the LTE standard. The performance is characterized in terms of BER (Bit Error Rate). In this paper the LTE system is modelled and simulated using MATLAB and the BER for 2×2 and 4×4 MIMO-LTE using 16QAM and 64QAM modulation schemes for Rayleigh fading environment are obtained against different SNR values.

Kalman filter and semi-blind technique-based channel estimation for coded STBC multi-antenna set-ups in faded wireless channels

Alamoutis space-time block coding STBC with diversity gains provide improved performance in faded channels. Alamoutis transmit diversity scheme, however, relies on the availability of accurate channel state information CSI. If the assistance of channel estimation is considered, the overall performance can be further enhanced. In this work, we report the performance of three separate approaches to deal with coded multi-antenna setups. These are STBC Coded MISO-MIMO Set-up with BPSK and QPSK, pilot assisted channel estimation with Walsh-Hadamard code and semi-blind channel estimation using Kalman filter KF. The first two proposed techniques are able to obtain an error performance closer to a known CSI in severely faded channel. The semi-blind estimation technique using KF with Walsh-Hadamard coded pilot symbols incorporates orthogonality to facilitate decoupling of multiple data blocks after STBC decoding. The simulated results prove the effectiveness of the channel estimators in time varying Rayleigh faded channel.

Hybrid channel estimation scheme for IEEE 802.11n-based STBC MIMO system

In this paper, we have proposed a Kalman Filter (KF) - Recurrent Neural Network (RNN) based channel estimator block for Multiple-Input Multiple-Output (MIMO) multipath fading channels based on the IEEE 802.11n channel models for indoor wireless local area networks (WLAN). Two transmit antennas and two receive antennas are used here. The estimator block has been simulated in STBC coded MIMO multipath fading channel scenario with and without CSI, and figure of merit in terms of Bit Error Rate (BER) has been obtained. The design criteria and performance curve shown in the paper clearly proves the effectiveness of the proposed hybrid estimator, both in terms of performance and hardware realizability.