Peak to average power ratio reduction and error control in MIMO-OFDM HARQ System

Currently, multiple-input multiple-output orthogonal frequency division multiplexing (MIMOOFDM) systems underlie crucial wireless communication systems such as commercial 4G and 5G networks, tactical communication, and interoperable Public Safety communications. However, one drawback arising from OFDM modulation is its resulting high peak-to-average power ratio (PAPR). This problem increases with an increase in the number of transmit antennas. In this work, a new hybrid PAPR reduction technique is proposed for space-time block coding (STBC) MIMO-OFDM systems that combine the coding capabilities to PAPR reduction methods, while leveraging the new degree of freedom provided by the presence of multiple transmit chairs (MIMO). In the first part, we presented an extensive literature review of PAPR reduction techniques for OFDM and MIMO-OFDM systems. The work developed a PAPR reduction technique taxonomy, and analyzed the motivations for reducing the PAPR in current communication systems, emphasizing two important motivations such as power savings and coverage gain. In the tax onomy presented here, we include a new category, namely, hybrid techniques. Additionally, we drew a conclusion regarding the importance of hybrid PAPR reduction techniques. In the second part, we studied the effect of forward error correction (FEC) codes on the PAPR for the coded OFDM (COFDM) system. We simulated and compared the CCDF of the PAPR and its relationship with the autocorrelation of the COFDM signal before the inverse fast Fourier transform (IFFT) block. This allows to conclude on the main characteristics of the codes that generate high peaks in the COFDM signal, and therefore, the optimal parameters in order to reduce PAPR. We emphasize our study in FEC codes as linear block codes, and convolutional codes. Finally, we proposed a new hybrid PAPR reduction technique for an STBC MIMO-OFDM system, in which the convolutional code is optimized to avoid PAPR degradation, which also combines successive suboptimal cross-antenna rotation and inversion (SS-CARI) and iterative modified companding and filtering schemes. The new method permits to obtain a significant net gain for the system, i.e., considerable PAPR reduction, bit error rate (BER) gain as compared to the basic MIMO-OFDM system, low complexity, and reduced spectral splatter. The new hybrid technique was extensively evaluated by simulation, and the complementary cumulative distribution function (CCDF), the BER, and the power spectral density (PSD) were compared to the original STBC MIMO-OFDM signal

D-BLAST MIMO Perfomance Analysis over SDR-USRP

Este artículo describe la implementación de la técnica basada en multiplexación espacial D–BLAST sobre equipos de radio definido por software (SDR) específicamente usando USRP Ettus Research x310; con el objetivo de afrontar el problema de la diversidad espacial que posee el esquema de MIMO Alamouti, al no poder incrementar el número de antenas del transmisor respecto al del receptor. El escenario de simulación fue en un ambiente indoor usando las herramientas de programación gráfica con el software Labview Communications, logrando un diseño más robusto de codificación basado en la no linealidad de ecuaciones matriciales, mitigando, de este modo, a través de la redundancia de información los efectos de la interferencia que genera el incremento propio de las antenas en el transmisor. Los resultados experimentales evaluados fueron la tasa de error de bit (BER) y la tasa de error de símbolo (SER) para determinar la efectividad de la diversidad espacial. La ganancia lograda fue alrededor de 10 dB y 7 dB en MIMO 2×2 y MIMO 3×2 respectivamente, usando la técnica D–BLAST simétrica.This paper describes the implementation of technique based on D–BLAST spatial multiplexing over Software Defined Radio (SDR) equipment; specifically, using Universal Software Peripheral Radio (USRP) Ettus Research x310; with the aim of solve the problem of spatial diversity that the MIMO Alamouti scheme has, since it is not possible to increase the number of antennas of the transmitter with respect to the receiver. The simulation scenario was in an indoor environment using graphical programming tools with the Labview Communications Software, achieving a more robust coding design based on the nonlinearity of matrix equations, in this way, the effects of interference were mitigating through the redundancy of information due to the increase of the antennas at the transmitter. The experimental results evaluated were bit error rate (BER) and symbol error rate (SER) to determine the effectiveness of spatial diversity. The gain achieved was around 10dB and 7dB in MIMO 2×2 and MIMO 3×2 respectively, using the symmetric D–BLAST technique

A comparison of time-switched transmit diversity and space-time coded systems over time-varying miso channels

This thesis presents a comparison between two transmit diversity schemes, namely space-time coding and time-switched transmit diversity (TSTD) over block-fading and time-varying multi-input single-output (MISO) channels with different channel parameters. The schemes are concatenated with outer channel codes in order to achieve spatio-temporal diversity. The analytical results are derived for the error performances of the systems and the simulation results as well as outage probabilities are provided. Besides, the details of the pilot-symbol-aided modulation (PSAM) technique are investigated and the error performances of the systems are analyzed when the channel state information is estimated with PSAM. It is demonstrated using the analytical and simulation results that TSTD have a comparable error performance with the space-time coding techniques and it even outperforms the space-time codes for some channel parameters. Our results indicate that TSTD can be suggested as an alternative to space-time codes in some time-varying channels especially due to the implementation simplicity.M.S. - Master of Scienc

Análisis del Rendimiento de D–BLAST MIMO sobre SDR–USRP

Este artículo describe la implementación de la técnica basada en multiplexación espacial D–BLAST sobre equipos de radio definido por software (SDR), específicamente usando USRP Ettus Research ×310; con el objetivo de afrontar el problema de la diversidad espacial que posee el esquema de MIMO Alamouti, al no poder incrementar el número de antenas del transmisor respecto al del receptor. El escenario de simulación fue en un ambiente indoor usando las herramientas de programación gráfica con el software Labview Communications, logrando un diseño más robusto de codificación basado en la no linealidad de ecuaciones matriciales, mitigando, de este modo, a través de la redundancia de información los efectos de la interferencia que genera el incremento propio de las antenas en el transmisor. Los resultados experimentales evaluados fueron la tasa de error de bit (BER) y la tasa de error de símbolo (SER) para determinar la efectividad de la diversidad espacial. La ganancia lograda fue alrededor de 10 dB y 7 dB en MIMO 2×2 y MIMO 3×2 respectivamente, usando la técnica D–BLAST simétrica.//This paper describes the implementation of technique based on D–BLAST spatial multiplexing over Software Defined Radio (SDR) equipment; specifically, using Universal Software Peripheral Radio (USRP) Ettus Research x310; with the aim of solve the problem of spatial diversity that the MIMO Alamouti scheme has, since it is not possible to increase the number of antennas of the transmitter with respect to the receiver. The simulation scenario was in an indoor environment using graphical programming tools with the Labview Communications Software, achieving a more robust coding design based on the nonlinearity of matrix equations, in this way, the effects of interference were mitigating through the redundancy of information due to the increase of the antennas at the transmitter. The experimental results evaluated were bit error rate (BER) and symbol error rate (SER) to determine the effectiveness of spatial diversity. The gain achieved was around 10dB and 7dB in MIMO 2×2 and MIMO 3×2 respectively, using the symmetric D–BLAST technique

Self-concatenated coding for wireless communication systems

In this thesis, we have explored self-concatenated coding schemes that are designed for transmission over Additive White Gaussian Noise (AWGN) and uncorrelated Rayleigh fading channels. We designed both the symbol-based Self-ConcatenatedCodes considered using Trellis Coded Modulation (SECTCM) and bit-based Self- Concatenated Convolutional Codes (SECCC) using a Recursive Systematic Convolutional (RSC) encoder as constituent codes, respectively. The design of these codes was carried out with the aid of Extrinsic Information Transfer (EXIT) charts. The EXIT chart based design has been found an efficient tool in finding the decoding convergence threshold of the constituent codes. Additionally, in order to recover the information loss imposed by employing binary rather than non-binary schemes, a soft decision demapper was introduced in order to exchange extrinsic information withthe SECCC decoder. To analyse this information exchange 3D-EXIT chart analysis was invoked for visualizing the extrinsic information exchange between the proposed Iteratively Decoding aided SECCC and soft-decision demapper (SECCC-ID). Some of the proposed SECTCM, SECCC and SECCC-ID schemes perform within about 1 dB from the AWGN and Rayleigh fading channels’ capacity. A union bound analysis of SECCC codes was carried out to find the corresponding Bit Error Ratio (BER) floors. The union bound of SECCCs was derived for communications over both AWGN and uncorrelated Rayleigh fading channels, based on a novel interleaver concept.Application of SECCCs in both UltraWideBand (UWB) and state-of-the-art video-telephone schemes demonstrated its practical benefits.In order to further exploit the benefits of the low complexity design offered by SECCCs we explored their application in a distributed coding scheme designed for cooperative communications, where iterative detection is employed by exchanging extrinsic information between the decoders of SECCC and RSC at the destination. In the first transmission period of cooperation, the relay receives the potentially erroneous data and attempts to recover the information. The recovered information is then re-encoded at the relay using an RSC encoder. In the second transmission period this information is then retransmitted to the destination. The resultant symbols transmitted from the source and relay nodes can be viewed as the coded symbols of a three-component parallel-concatenated encoder. At the destination a Distributed Binary Self-Concatenated Coding scheme using Iterative Decoding (DSECCC-ID) was employed, where the two decoders (SECCC and RSC) exchange their extrinsic information. It was shown that the DSECCC-ID is a low-complexity scheme, yet capable of approaching the Discrete-input Continuous-output Memoryless Channels’s (DCMC) capacity.Finally, we considered coding schemes designed for two nodes communicating with each other with the aid of a relay node, where the relay receives information from the two nodes in the first transmission period. At the relay node we combine a powerful Superposition Coding (SPC) scheme with SECCC. It is assumed that decoding errors may be encountered at the relay node. The relay node then broadcasts this information in the second transmission period after re-encoding it, again, using a SECCC encoder. At the destination, the amalgamated block of Successive Interference Cancellation (SIC) scheme combined with SECCC then detects and decodes the signal either with or without the aid of a priori information. Our simulation results demonstrate that the proposed scheme is capable of reliably operating at a low BER for transmission over both AWGN and uncorrelated Rayleigh fading channels. We compare the proposed scheme’s performance to a direct transmission link between the two sources having the same throughput

High capacity multiuser multiantenna communication techniques

One of the main issues involved in the development of future wireless communication systems is the multiple access technique used to efficiently share the available spectrum among users. In rich multipath environment, spatial dimension can be exploited to meet the increasing number of users and their demands without consuming extra bandwidth and power. Therefore, it is utilized in the multiple-input multiple-output (MIMO) technology to increase the spectral efficiency significantly. However, multiuser MIMO (MU-MIMO) systems are still challenging to be widely adopted in next generation standards. In this thesis, new techniques are proposed to increase the channel and user capacity and improve the error performance of MU-MIMO over Rayleigh fading channel environment. For realistic system design and performance evaluation, channel correlation is considered as one of the main channel impurities due its severe influence on capacity and reliability. Two simple methods called generalized successive coloring technique (GSCT) and generalized iterative coloring technique (GICT) are proposed for accurate generation of correlated Rayleigh fading channels (CRFC). They are designed to overcome the shortcomings of existing methods by avoiding factorization of desired covariance matrix of the Gaussian samples. The superiority of these techniques is demonstrated by extensive simulations of different practical system scenarios. To mitigate the effects of channel correlations, a novel constellation constrained MU-MIMO (CC-MU-MIMO) scheme is proposed using transmit signal design and maximum likelihood joint detection (MLJD) at the receiver. It is designed to maximize the channel capacity and error performance based on principles of maximizing the minimum Euclidean distance (dmin) of composite received signals. Two signal design methods named as unequal power allocation (UPA) and rotation constellation (RC) are utilized to resolve the detection ambiguity caused by correlation. Extensive analysis and simulations demonstrate the effectiveness of considered scheme compared with conventional MU-MIMO. Furthermore, significant gain in SNR is achieved particularly in moderate to high correlations which have direct impact to maintain high user capacity. A new efficient receive antenna selection (RAS) technique referred to as phase difference based selection (PDBS) is proposed for single and multiuser MIMO systems to maximize the capacity over CRFC. It utilizes the received signal constellation to select the subset of antennas with highest (dmin) constellations due to its direct impact on the capacity and BER performance. A low complexity algorithm is designed by employing the Euclidean norm of channel matrix rows with their corresponding phase differences. Capacity analysis and simulation results show that PDBS outperforms norm based selection (NBS) and near to optimal selection (OS) for all correlation and SNR values. This technique provides fast RAS to capture most of the gains promised by multiantenna systems over different channel conditions. Finally, novel group layered MU-MIMO (GL-MU-MIMO) scheme is introduced to exploit the available spectrum for higher user capacity with affordable complexity. It takes the advantages of spatial difference among users and power control at base station to increase the number of users beyond the available number of RF chains. It is achieved by dividing the users into two groups according to their received power, high power group (HPG) and low power group (LPG). Different configurations of low complexity group layered multiuser detection (GL-MUD) and group power allocation ratio (η) are utilized to provide a valuable tradeoff between complexity and overall system performance. Furthermore, RAS diversity is incorporated by using NBS and a new selection algorithm called HPG-PDBS to increase the channel capacity and enhance the error performance. Extensive analysis and simulations demonstrate the superiority of proposed scheme compared with conventional MU-MIMO. By using appropriate value of (η), it shows higher sum rate capacity and substantial increase in the user capacity up to two-fold at target BER and SNR values