We investigate the creation of linear block codes using Hadamard matrices for block fading channels. The aforementioned codes are very easy to find and have bounded cross correlation spectrum. The optimality is with respect to the metric-spectrum which gives a performance for the codes very close to optimal codes. Also, we can transform these codes according to different characteristics of the channel and can use selective transmission methods.

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Yes / Multiple-input multiple-output (MIMO) systems require simplified architectures that can maximize design parameters without sacrificing system performance. Such architectures may be used in a transmitter or a receiver. The most recent example with possible low cost architecture in the transmitter is spatial modulation (SM). In this study, we evaluate the SM and quasi-orthogonal space time block codes (QOSTBC) schemes for MIMO systems over a Rayleigh fading channel. QOSTBC enables STBC to be used in a four antenna design, for example. Standard QO-STBC techniques are limited in performance due to self-interference terms; here a QOSTBC scheme that eliminates these terms in its decoding matrix is explored. In addition, while most QOSTBC studies mainly explore performance improvements with different code structures, here we have implemented receiver diversity using maximal ratio combining (MRC). Results show that QOSTBC delivers better performance, at spectral efficiency comparable with SM.

In this thesis, space-time block codes originally developed for multiple antenna systems are extended to cooperative multi-hop networks. The designs are applicable to any wireless network setting especially cellular, adhoc and sensor networks where space limitations preclude the use of multiple antennas. The thesis first investigates the design of distributed orthogonal and quasi-orthogonal space time block codes in cooperative networks with single and multiple antennas at the destination. Numerical and simulation results show that by employing multiple receive antennas the diversity performance of the network is further improved at the expense of slight modification of the detection scheme. The thesis then focuses on designing distributed space time block codes for cooperative networks in which the source node participates in cooperation. Based on this, a source-assisting strategy is proposed for distributed orthogonal and quasi-orthogonal space time block codes. Numerical and simulation results show that the source-assisting strategy exhibits improved diversity performance compared to the conventional distributed orthogonal and quasi-orthogonal designs.Motivated by the problem of channel state information acquisition in practical wireless network environments, the design of differential distributed space time block codes is investigated. Specifically, a co-efficient vector-based differential encoding and decoding scheme is proposed for cooperative networks. The thesis then explores the concatenation of differential strategies with several distributed space time block coding schemes namely; the Alamouti code, square-real orthogonal codes, complex-orthogonal codes, and quasiorthogonal codes, using cooperative networks with different number of relay nodes. In order to cater for high data rate transmission in non-coherent cooperative networks, differential distributed quasi-orthogonal space-time block codes which are capable of achieving full code-rate and full diversity are proposed. Simulation results demonstrate that the differential distributed quasi-orthogonal space-time block codes outperform existing distributed space time block coding schemes in terms of code rate and bit-error-rate performance. A multidifferential distributed quasi-orthogonal space-time block coding scheme is also proposed to exploit the additional diversity path provided by the source-destination link.A major challenge is how to construct full rate codes for non-coherent cooperative broadband networks with more than two relay nodes while exploiting the achievable spatial and frequency diversity. In this thesis, full rate quasi-orthogonal codes are designed for noncoherent cooperative broadband networks where channel state information is unavailable. From this, a generalized differential distributed quasi-orthogonal space-frequency coding scheme is proposed for cooperative broadband networks. The proposed scheme is able to achieve full rate and full spatial and frequency diversity in cooperative networks with any number of relays. Through pairwise error probability analysis we show that the diversity gain of the proposed scheme can be improved by appropriate code construction and sub-carrier allocation. Based on this, sufficient conditions are derived for the proposed code structure at the source node and relay nodes to achieve full spatial and frequency diversity. In order to exploit the additional diversity paths provided by the source-destination link, a novel multidifferential distributed quasi-orthogonal space-frequency coding scheme is proposed. The overall objective of the new scheme is to improve the quality of the detected signal at the destination with negligible increase in the computational complexity of the detector.Finally, a differential distributed quasi-orthogonal space-time-frequency coding scheme is proposed to cater for high data rate transmission and improve the performance of noncoherent cooperative broadband networks operating in highly mobile environments. The approach is to integrate the concept of distributed space-time-frequency coding with differential modulation, and employ rotated constellation quasi-orthogonal codes. From this, we design a scheme which is able to address the problem of performance degradation in highly selective fading environments while guaranteeing non-coherent signal recovery and full code rate in cooperative broadband networks. The coding scheme employed in this thesis relaxes the assumption of constant channel variation in the temporal and frequency dimensions over long symbol periods, thus performance degradation is reduced in frequencyselective and time-selective fading environments. Simulation results illustrate the performance of the proposed differential distributed quasi-orthogonal space-time-frequency coding scheme under different channel conditions.

Master of Engineering (Research) / The latest wireless communication techniques such as highspeed wireless internet application demand higher data rates and better quality of service (QoS). However, transmission reliability is still degraded by harsh propagation channels. Multiple-input multiple-output (MIMO) systems can increase the system capacity and improve transmission reliability. By transmitting multiple copies of data, a MIMO system can effectively combat the effects of fading. Due to the high hardware cost of a MIMO system, antenna selection techniques have been applied in MIMO system design to reduce the system complexity and cost. The Nakagami-m distribution has been considered for MIMO channel modeling since a wide range of fading channels, from severe to moderate, can be modeled by using Nakagami-m distribution. The Rayleigh distribution is a special case of the Nakagami-m distribution. In this thesis, we analyze the error performance of two MIMO schemes: maximal-ratio combining with transmit antenna selection (the TAS/MRC scheme) and space-time block codes with transmit antenna selection (the TAS/STBC scheme) over Nakagami-m fading channels. In the TAS/MRC scheme, one of multiple transmit antennas, which maximizes the total received signal-to-noise ratio (SNR), is selected for uncoded data transmission. First we use a moment generating function based (MGF-based) approach to derive the bit error rate (BER) expressions for binary phase shift keying (BPSK), the symbol error rate (SER) expressions for M-ray phase shift keying (MPSK) and M-ray quadrature amplitude modulation (MQAM) of the TAS/MRC scheme over Nakagami-m fading channels with arbitrary and integer fading parameters m. The asymptotic performance is also investigated. It is revealed that the asymptotic diversity order is equal to the product of the Nakagami fading parameter m, the number of transmit antenna Lt and the number of receive antenna Lr as if all transmit antenna were used. Then a Gaussian Q-functions approach is used to investigate the error performance of the TAS/STBC scheme over Nakagami-m fading channels. In the TAS/STBC scheme, two transmit antennas, which maximize the output SNR, are selected for transmission. The exact and asymptotic BER expressions for BPSK are obtained for the TAS/STBC schemes with three and four transmit antennas. It is shown that the TAS/STBC scheme can provide a full diversity order of mLtLr.

Master of Engineering (Research) / The latest wireless communication techniques such as highspeed wireless internet application demand higher data rates and better quality of service (QoS). However, transmission reliability is still degraded by harsh propagation channels. Multiple-input multiple-output (MIMO) systems can increase the system capacity and improve transmission reliability. By transmitting multiple copies of data, a MIMO system can effectively combat the effects of fading. Due to the high hardware cost of a MIMO system, antenna selection techniques have been applied in MIMO system design to reduce the system complexity and cost. The Nakagami-m distribution has been considered for MIMO channel modeling since a wide range of fading channels, from severe to moderate, can be modeled by using Nakagami-m distribution. The Rayleigh distribution is a special case of the Nakagami-m distribution. In this thesis, we analyze the error performance of two MIMO schemes: maximal-ratio combining with transmit antenna selection (the TAS/MRC scheme) and space-time block codes with transmit antenna selection (the TAS/STBC scheme) over Nakagami-m fading channels. In the TAS/MRC scheme, one of multiple transmit antennas, which maximizes the total received signal-to-noise ratio (SNR), is selected for uncoded data transmission. First we use a moment generating function based (MGF-based) approach to derive the bit error rate (BER) expressions for binary phase shift keying (BPSK), the symbol error rate (SER) expressions for M-ray phase shift keying (MPSK) and M-ray quadrature amplitude modulation (MQAM) of the TAS/MRC scheme over Nakagami-m fading channels with arbitrary and integer fading parameters m. The asymptotic performance is also investigated. It is revealed that the asymptotic diversity order is equal to the product of the Nakagami fading parameter m, the number of transmit antenna Lt and the number of receive antenna Lr as if all transmit antenna were used. Then a Gaussian Q-functions approach is used to investigate the error performance of the TAS/STBC scheme over Nakagami-m fading channels. In the TAS/STBC scheme, two transmit antennas, which maximize the output SNR, are selected for transmission. The exact and asymptotic BER expressions for BPSK are obtained for the TAS/STBC schemes with three and four transmit antennas. It is shown that the TAS/STBC scheme can provide a full diversity order of mLtLr.

In this dissertation a computationally efficient cognitive multiple-input multiple-output (MIMO) orthogonal frequency division duplexing (OFDM) detector is designed to decode perfect space-time coded signals which are able maximize the diversity and multiplexing properties of a rich fading MIMO channel. The adaptive nature of the cognitive detector allows a MIMO OFDM communication system to better meet to needs of future wireless communication networks which require both high reliability and low run-time complexity depending on the propagation environment. The cognitive detector in conjunction with perfect space-time coding is able to achieve up to a 2 dB bit-error rate (BER) improvement at low signal-to-noise ratio (SNR) while also achieving comparable runtime complexity in high SNR scenarios.

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ITC/USA 2007 Conference Proceedings / The Forty-Third Annual International Telemetering Conference and Technical Exhibition / October 22-25, 2007 / Riviera Hotel & Convention Center, Las Vegas, Nevada / Next generation satellite communication systems require efficient coding schemes that enable high data rates, require low overhead, and have excellent bit error rate performance. A newly rediscovered class of block codes called Low Density Parity Check (LDPC) codes has the potential to revolutionize forward error correction (FEC) because of the very high coding rates. This paper presents a brief overview of LDPC coding and decoding. An LDPC algorithm developed by Goddard Space Flight Center is discussed, and an overview of an accompanying VHDL development by L-3 Communications Cincinnati Electronics is presented.