Performance analysis of channel codes in multiple antenna OFDM systems

Multiple antenna techniques are used to increase the robustness and performance of wireless networks. Multiple antenna techniques can achieve diversity and increase bandwidth efficiency when specially designed channel codes are used at the scheme’s transmitter. These channel codes can be designed in the space, time and frequency domain. These specially designed channel codes in the space and time domain are actually designed for flat fading channels and in frequency selective fading channel, their performance may be degraded. To counteract this possible performance degradation in frequency selective fading channel, two main approaches can be applied to mitigate the effect of the symbol interference due to the frequency selective fading channel. These approaches are multichannel equalisation and orthogonal frequency division multiplexing (OFDM). In this thesis, a multichannel equalisation technique and OFDM were applied to channel codes specially designed for multiple antenna systems. An optimum receiver was proposed for super-orthogonal space-time trellis codes in a multichannel equalised frequency selective environment. Although the proposed receiver had increased complexity, the diversity order is still the same as compared to the code in a flat fading channel. To take advantage of the multipath diversity possible in a frequency selective fading channel, super-orthogonal block codes were employed in an OFDM environment. A new kind of super-orthogonal block code was proposed in this thesis. Super-orthogonal space-frequency trellis-coded OFDM was proposed to take advantage of not only the possible multipath diversity but also the spatial diversity for coded OFDM schemes. Based on simulation results in this thesis, the proposed coded OFDM scheme performs better than all other coded OFDM schemes (i.e. space time trellis-coded OFDM, space-time block coded OFDM, space-frequency block coded OFDM and super-orthogonal space-time trellis-coded OFDM). A simplified channel estimation algorithm was proposed for two of the coded OFDM schemes, which form a broad-based classification of coded OFDM schemes, i.e. trelliscoded schemes and block-coded schemes. Finally in this thesis performance analysis using the Gauss Chebychev quadrature technique as a way of validating simulation results was done for super-orthogonal block coded OFDM schemes when channel state information is known and when it is estimated. The results obtained show that results obtained via simulation and analysis are asymptotic and therefore the proposed analysis technique can be use to obtain error rate values for different SNR region instead of time consuming simulation.Thesis (PhD)--University of Pretoria, 2012.Electrical, Electronic and Computer Engineeringunrestricte

Turbo Decoding and Detection for Wireless Applications

A historical perspective of turbo coding and turbo transceivers inspired by the generic turbo principles is provided, as it evolved from Shannon’s visionary predictions. More specifically, we commence by discussing the turbo principles, which have been shown to be capable of performing close to Shannon’s capacity limit. We continue by reviewing the classic maximum a posteriori probability decoder. These discussions are followed by studying the effect of a range of system parameters in a systematic fashion, in order to gauge their performance ramifications. In the second part of this treatise, we focus our attention on the family of iterative receivers designed for wireless communication systems, which were partly inspired by the invention of turbo codes. More specifically, the family of iteratively detected joint coding and modulation schemes, turbo equalization, concatenated spacetime and channel coding arrangements, as well as multi-user detection and three-stage multimedia systems are highlighted

Improving the performance of free space optical systems: a space-time orthogonal frequency division modulation approach

Free space optical (FSO) communication systems are known for high capacity and information security. The overall system performances of FSO systems are however significantly affected by atmospheric turbulence induced fading. This paper, therefore, proposes a technique to mitigate this effect through the introduction of an additional degree of error correction capacity by exploiting the spectral dimension in the coding space. A space-time trellis coded orthogonal frequency division modulation (OFDM) scheme was developed, simulated and evaluated for optical communication through a Gamma-Gamma channel. The evaluation of the coding gain obtained from the simulation results, the mathematical analysis and the truncation error analysis shows that the proposed technique is a promising and viable technique for improving the error correction performance of space-time codes for free space optical communication links

Super-orthogonal space-time turbo coded OFDM systems.

Thesis (Ph.D.)-University of KwaZulu-Natal, Durban, 2012.The ever increasing demand for fast and efficient broadband wireless communication services requires future broadband communication systems to provide a high data rate, robust performance and low complexity within the limited available electromagnetic spectrum. One of the identified, most-promising techniques to support high performance and high data rate communication for future wireless broadband services is the deployment of multi-input multi-output (MIMO) antenna systems with orthogonal frequency division multiplexing (OFDM). The combination of MIMO and OFDM techniques guarantees a much more reliable and robust transmission over a hostile wireless channel through coding over the space, time and frequency domains. In this thesis, two full-rate space-time coded OFDM systems are proposed. The first one, designed for two transmit antennas, is called extended super-orthogonal space-time trellis coded OFDM (ESOSTTC-OFDM), and is based on constellation rotation. The second one, called super-quasi-orthogonal space-time trellis coded OFDM (SQOSTTCOFDM), combines a quasi-orthogonal space-time block code with a trellis code to provide a full-rate code for four transmit antennas. The designed space-time coded MIMO-OFDM systems achieve a high diversity order with high coding gain by exploiting the diversity advantage of frequency-selective fading channels. Concatenated codes have been shown to be an effective technique of achieving reliable communication close to the Shannon limit, provided that there is sufficient available diversity. In a bid to improve the performance of the super orthogonal space-time trellis code (SOSTTC) in frequency selective fading channels, five distinct concatenated codes are proposed for MIMO-OFDM over frequency-selective fading channels in the second part of this thesis. Four of the coding schemes are based on the concatenation of convolutional coding, interleaving, and space-time coding, along multiple-transmitter diversity systems, while the fifth coding scheme is based on the concatenation of two space-time codes and interleaving. The proposed concatenated Super-Orthogonal Space-Time Turbo-Coded OFDM System I. B. Oluwafemi 2012 vii coding schemes in MIMO-OFDM systems achieve high diversity gain by exploiting available diversity resources of frequency-selective fading channels and achieve a high coding gain through concatenations by employing the turbo principle. Using computer software simulations, the performance of the concatenated SOSTTC-OFDM schemes is compared with those of concatenated space-time trellis codes and those of conventional SOSTTC-OFDM schemes in frequency-selective fading channels. Simulation results show that the concatenated SOSTTC-OFDM system outperformed the concatenated space-time trellis codes and the conventional SOSTTC-OFDM system under the various channel scenarios in terms of both diversity order and coding gain

Design guidelines for spatial modulation

A new class of low-complexity, yet energyefficient Multiple-Input Multiple-Output (MIMO) transmission techniques, namely the family of Spatial Modulation (SM) aided MIMOs (SM-MIMO) has emerged. These systems are capable of exploiting the spatial dimensions (i.e. the antenna indices) as an additional dimension invoked for transmitting information, apart from the traditional Amplitude and Phase Modulation (APM). SM is capable of efficiently operating in diverse MIMO configurations in the context of future communication systems. It constitutes a promising transmission candidate for large-scale MIMO design and for the indoor optical wireless communication whilst relying on a single-Radio Frequency (RF) chain. Moreover, SM may also be viewed as an entirely new hybrid modulation scheme, which is still in its infancy. This paper aims for providing a general survey of the SM design framework as well as of its intrinsic limits. In particular, we focus our attention on the associated transceiver design, on spatial constellation optimization, on link adaptation techniques, on distributed/ cooperative protocol design issues, and on their meritorious variants

Performance Analysis of Super-Orthogonal Space-Time Trellis Coded MIMO-OFDM Systems over the One-Ring Channel

Masteroppgave i informasjons- og kommunikasjonsteknologi 2007 – Høgskolen i Agder, GrimstadWith the rapid development of wireless communications, the available bandwidth for wireless applications becomes more and more insufficient. Therefore, how to improve data rate without expending bandwidth becomes a main goal in modern communication system design. Recently, two wireless communication schemes, which can be used to effectively combat with multi-path fading, are widely investigated around the world. One is the multiple-input multiple-output (MIMO) technology and another is the orthogonal frequency division multiplexing (OFDM). As a result, a combined system, MIMO-OFDM, can be used for wireless communications to jointly explore the advantages of the above two strategies. In the study of MIMO-OFDM systems, the space-time block codes (STBC) and the spacetime trellis codes (STTC) are two efficient coding approaches. The former can be used to offer a full diversity gain, and the later can provide the systems with a large coding gain. Since 2003, super-orthogonal space-time trellis codes (SOSTTC), a new coding method processing the merits of both STBC and STTC, have been developed. However, whether or not it can perform just as well in a MIMO-OFDM system over a frequency-selective channel is still unknown. In addition, a communication channel plays a very important role on a communication system. A channel model is used to describe a realistic communication channel and its various model parameters are considered to influence the system performance such as symbol error rate (SER) as well as bit error rate (BER). Therefore, the effects on SER and BER, caused by changing channel parameters, are worth to be investigated. In the thesis, a new SOSTTC scheme for 16QAM constellation which can be used for high speed wireless communications is applied to a MIMO-OFDM system. To examine the performance of the proposed MIMO-OFDM system based on SOSTTC, the one-ring MIMO channel model is studied by evaluating the effects of antenna spacing, channel profiles and maximum Doppler frequency shift. In MATLAB simulations, the SER and the BER performance results show that enlargement of the antenna spacing can bring a higher diversity gain, and the enlargement of the antenna spacing at base station can achieve better system performance than at the mobile station. In the channel profiles, the model E can gain more 1.5dB on the SER than the other models at a SER of 10−2. In addition, the larger maximum Doppler frequency shift can cause more data errors by assuming non-perfect channel state information (CSI). Finally, by using SOSTTC, the system performance on SER can be improved by 0.5 to 1dB at a SER of 5×10−4, comparing it with the STBC in the same MIMO-OFDM system. According to the above results, it will be more efficient to increase antenna spacing at the base station and it is necessary to adjust the coding scheme and signal power to avoid performance decrease in a different communication environment and at a different speed of the mobile unite. Moreover, the SOSTTC can be integrated with MIMO-OFDM system to increase system performance. Keywords: MIMO-OFDM, SOSTTC, 16QAM, One-ringMIMO channel model, SER, BER

OFDM ido tsushin shisutemu ni okeru doitsu chaneru kansho jokyo hoshiki ni kansuru kenkyu

制度:新 ; 報告番号:甲3396号 ; 学位の種類:博士(国際情報通信学) ; 授与年月日:2011/9/15 ; 早大学位記番号:新571