Cyclic division algebras: a tool for space-time coding

Multiple antennas at both the transmitter and receiver ends of a wireless digital transmission channel may increase both data rate and reliability. Reliable high rate transmission over such channels can only be achieved through Space–Time coding. Rank and determinant code design criteria have been proposed to enhance diversity and coding gain. The special case of full-diversity criterion requires that the difference of any two distinct codewords has full rank. Extensive work has been done on Space–Time coding, aiming at finding fully diverse codes with high rate. Division algebras have been proposed as a new tool for constructing Space–Time codes, since they are non-commutative algebras that naturally yield linear fully diverse codes. Their algebraic properties can thus be further exploited to improve the design of good codes. The aim of this work is to provide a tutorial introduction to the algebraic tools involved in the design of codes based on cyclic division algebras. The different design criteria involved will be illustrated, including the constellation shaping, the information lossless property, the non-vanishing determinant property, and the diversity multiplexing trade-off. The final target is to give the complete mathematical background underlying the construction of the Golden code and the other Perfect Space–Time block codes

Interference-Mitigating Waveform Design for Next-Generation Wireless Systems

A brief historical perspective of the evolution of waveform designs employed in consecutive generations of wireless communications systems is provided, highlighting the range of often conflicting demands on the various waveform characteristics. As the culmination of recent advances in the field the underlying benefits of various Multiple Input Multiple Output (MIMO) schemes are highlighted and exemplified. As an integral part of the appropriate waveform design, cognizance is given to the particular choice of the duplexing scheme used for supporting full-duplex communications and it is demonstrated that Time Division Duplexing (TDD) is substantially outperformed by Frequency Division Duplexing (FDD), unless the TDD scheme is combined with further sophisticated scheduling, MIMOs and/or adaptive modulation/coding. It is also argued that the specific choice of the Direct-Sequence (DS) spreading codes invoked in DS-CDMA predetermines the properties of the system. It is demonstrated that a specifically designed family of spreading codes exhibits a so-called interference-free window (IFW) and hence the resultant system is capable of outperforming its standardised counterpart employing classic Orthogonal Variable Spreading Factor (OVSF) codes under realistic dispersive channel conditions, provided that the interfering multi-user and multipath components arrive within this IFW. This condition may be ensured with the aid of quasisynchronous adaptive timing advance control. However, a limitation of the system is that the number of spreading codes exhibiting a certain IFW is limited, although this problem may be mitigated with the aid of novel code design principles, employing a combination of several spreading sequences in the time-frequency and spatial-domain. The paper is concluded by quantifying the achievable user load of a UTRA-like TDD Code Division Multiple Access (CDMA) system employing Loosely Synchronized (LS) spreading codes exhibiting an IFW in comparison to that of its counterpart using OVSF codes. Both system's performance is enhanced using beamforming MIMOs

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

Pembangunan model kualiti bagi modul pengajaran kendiri (MPK) menggunakan kaedah quality function deployment (QFD)

Kajian ini bertujuan untuk membangunkan satu Model Kualiti menggunakan kaedah Quality Function Deployment (QFD) yangmerupakan salah satu teknik dalam Total Quality Management (TQM). Objektifkajian ini adalah untuk melihat bagaimanakah QFD dapat digunakan dalam proses pembangunan Modul Pengaj aran Kendiri (MPK). Di samping itu, kajian ini turut mengkaji tentang ciri-ciri MPK yang dapat memenuhi kehendak pelajar melalui pembangunan matrik QFD. Responden kajian ini adalah terdiri daripada 98 orang pelajar semester satu Diploma Akauntansi di sebuah politeknik. Kajian berbentuk tinjauan mengguriakan borang soal selidik bagi mendapatkan kajian terhadap pasaran dilakukan untuk mendapatkan kriteria modul yang dapat memenuhi keperluan pelajar di samping mengenalpasti permasalahan yang dihadapi oleh mereka di dalam menggunakan modul. Data yang diperolehi dianalisis menggunakan perisian SPSS Version 11.0 (Statistical Package For Social Sciences) bagi mendapatkan peratusan dan skor min. Dapatan kajian menunjukkan bahawa kaedah QFD dapat digunakan sebagai salah satu alat kawalan kualiti dalam proses pembangunan MPK melalui pembangunan empat buah Rumah Kualiti. Basil kajianjuga mendapati bahawa dalam Rumah Kualiti 1 antara elemen modul yang dapat memenuhi kehendak pelajar mengikut hirarki matrik QFD adalah modul dalam bentuk cetakan, penekanan kepada elemen-elemen modul bercetak dalam Rumah Kualiti 2, spesifikasi bahagian isi kandungan dalam Rumah Kualiti 3 dan perincian dalam isi kandungan bagi kawalan kualiti dalam Rumah Kualiti 4. Dengan adanya cadangan model ini, diharap kajian ini akan dapat menjadi panduan kepada pensyarah dan para pembangun modul untuk menggunakan kaedah QFD sebelum menghasilkan sesebuah MPK

Modified quasi-orthogonal space-time block coding in distributed wireless networks

Cooperative networks have developed as a useful technique that can achieve the same advantage as multi-input and multi-output (MIMO) wireless systems such as spatial diversity, whilst resolving the difficulties of co-located multiple antennas at individual nodes and avoiding the effect of path-loss and shadowing. Spatial diversity in cooperative networks is known as cooperative diversity, and can enhance system reliability without sacrificing the scarce bandwidth resource or consuming more transmit power. It enables single-antenna terminals in a wireless relay network to share their antennas to form a virtual antenna array on the basis of their distributed locations. However, there remain technical challenges to maximize the benefit of cooperative communications, e.g. data rate, asynchronous transmission and outage. In this thesis, therefore, firstly, a modified distributed quasi-orthogonal space-time block coding (M-D-QO-STBC) scheme with increased code gain distance (CGD) for one-way and two-way amplify-and-forward wireless relay networks is proposed. This modified code is designed from set partitioning a larger codebook formed from two quasi-orthogonal space time block codes with different signal rotations then the subcodes are combined and pruned to arrive at the modified codebook with the desired rate in order to increase the CGD. Moreover, for higher rate codes the code distance is maximized by using a genetic algorithm to search for the optimum rotation matrix. This scheme has very good performance and significant coding gain over existing codes such as the open-loop and closed-loop QO-STBC schemes. In addition, the topic of outage probability analysis in the context of multi-relay selection from $N$ available relay nodes for one-way amplify-and-forward cooperative relay networks is considered together with the best relay selection, the $N^{th}$ relay selection and best four relay selection in two-way amplify-and-forward cooperative relay networks. The relay selection is performed either on the basis of a max-min strategy or one based on maximizing exact end-to-end signal-to-noise ratio. Furthermore, in this thesis, robust schemes for cooperative relays based on the M-D-QO-STBC scheme for both one-way and two-way asynchronous cooperative relay networks are considered to overcome the issue of a synchronism in wireless cooperative relay networks. In particular, an orthogonal frequency division multiplexing (OFDM) data structure is employed with cyclic prefix (CP) insertion at the source in the one-way cooperative relay network and at the two terminal nodes in the two-way cooperative network to combat the effects of time asynchronism. As such, this technique can effectively cope with the effects of timing errors. Finally, outage probability performance of a proposed amplify-and-forward cooperative cognitive relay network is evaluated and the cognitive relays are assumed to exploit an overlay approach. A closed form expression for the outage probability for multi-relay selection cooperation over Rayleigh frequency flat fading channels is derived for perfect and imperfect spectrum acquisitions. Furthermore, the M-QO-STBC scheme is also proposed for use in wireless cognitive relay networks. MATLAB and Maple software based simulations are employed throughout the thesis to support the analytical results and assess the performance of new algorithms and methods

Reduction of Peak to Average Power Ratio using Selective Mapping Technique of an OFDM Signal: An Analysis

Orthogonal Frequency Division Multiplexing (OFDM) is a optimistic and very popular modulation technique in multicarrier domain which is quite promising regarding the issues of interferences present in next generation mobile communication systems. It deployed in the area where high data rate and low latency required while efficiency will be as better as possible. The critical problem in OFDM system is maintaining low PAPR (peak to average power ratio) because it reduces the performance of system. There are several techniques which are used to overcome problem of high PAPR in OFDM modulation system. One of the techniques is Selective Mapping (SLM) which comes in distortion less criteria. In this paper analysis of PAPR reduction of an OFDM system for distortion less transmission criterion is shown. We have also used some mathematical equations to calculate and simulate its performance. It’s also shown that SLM method grants the user a better PAPR reduction while having high complex circuitry