A Reed-Solomon Coded DS-CDMA System Using Noncoherent M-ary Orthogonal Modulation over Multipath Fading Channels

The performance of Reed–Solomon (RS) coded direct-sequence code division multiple-access (DS-CDMA) systems using noncoherent M-ary orthogonal modulation is investigated over multipath Rayleigh fading channels. Diversity reception techniques with equal gain combining (EGC) or selection combining (SC) are invoked and the related performance is evaluated for both uncoded and coded DS-CDMA systems. "Errors-and-erasures" decoding is considered, where the erasures are based on Viterbi’s so-called ratio threshold test (RTT). The probability density functions (PDF) of the ratio associated with the RTT conditioned on both the correct detection and erroneous detection of the M-ary signals are derived. These PDFs are then used for computing the codeword decoding error probability of the RS coded DS-CDMA system using "errors-and-erasures" decoding. Furthermore, the performance of the "errors-and-erasures" decoding technique employing the RTT is compared to that of "error-correction-only" decoding refraining from using side-information over multipath Rayleigh fading channels. As expected, the numerical results show that when using "errors-and-erasures" decoding, RS codes of a given code rate can achieve a higher coding gain than without erasure information. Index Terms—Direct sequence code division multiple-access, error-correction-only decoding, errors-and-erasures decoding, noncoherent $M$-ary orthogonal signaling, ratio threshold test, Reed–Solomon codes

Residue number system coded differential space-time-frequency coding.

Thesis (Ph.D.)-University of KwaZulu-Natal, Durban, 2007.The rapidly growing need for fast and reliable transmission over a wireless channel motivates the development of communication systems that can support high data rates at low complexity. Achieving reliable communication over a wireless channel is a challenging task largely due to the possibility of multipaths which may lead to intersymbol interference (ISI). Diversity techniques such as time, frequency and space are commonly used to combat multipath fading. Classical diversity techniques use repetition codes such that the information is replicated and transmitted over several channels that are sufficiently spaced. In fading channels, the performance across some diversity branches may be excessively attenuated, making throughput unacceptably small. In principle, more powerful coding techniques can be used to maximize the diversity order. This leads to bandwidth expansion or increased transmission power to accommodate the redundant bits. Hence there is need for coding and modulation schemes that provide low error rate performance in a bandwidth efficient manner. If diversity schemes are combined, more independent dimensions become available for information transfer. The first part of the thesis addresses achieving temporal diversity through employing error correcting coding schemes combined with interleaving. Noncoherent differential modulation does not require explicit knowledge or estimate of the channel, instead the information is encoded in the transitions. This lends itself to the possibility of turbo-like serial concatenation of a standard outer channel encoder with an inner modulation code amenable to noncoherent detection through an interleaver. An iterative approach to joint decoding and demodulation can be realized by exchanging soft information between the decoder and the demodulator. This has been shown to be effective and hold hope for approaching capacity over fast fading channels. However most of these schemes employ low rate convolutional codes as their channel encoders. In this thesis we propose the use of redundant residue number system codes. It is shown that these codes can achieve comparable performance at minimal complexity and high data rates. The second part deals with the possibility of combining several diversity dimensions into a reliable bandwidth efficient communication scheme. Orthogonal frequency division multiplexing (OFDM) has been used to combat multipaths. Combining OFDM with multiple-input multiple-output (MIMO) systems to form MIMO-OFDM not only reduces the complexity by eliminating the need for equalization but also provides large channel capacity and a high diversity potential. Space-time coded OFDM was proposed and shown to be an effective transmission technique for MIMO systems. Spacefrequency coding and space-time-frequency coding were developed out of the need to exploit the frequency diversity due to multipaths. Most of the proposed schemes in the literature maximize frequency diversity predominantly from the frequency-selective nature of the fading channel. In this thesis we propose the use of residue number system as the frequency encoder. It is shown that the proposed space-time-frequency coding scheme can maximize the diversity gains over space, time and frequency domains. The gain of MIMO-OFDM comes at the expense of increased receiver complexity. Furthermore, most of the proposed space-time-frequency coding schemes assume frequency selective block fading channels which is not an ideal assumption for broadband wireless communications. Relatively high mobility in broadband wireless communications systems may result in high Doppler frequency, hence time-selective (rapid) fading. Rapidly changing channel characteristics impedes the channel estimation process and may result in incorrect estimates of the channel coefficients. The last part of the thesis deals with the performance of differential space-time-frequency coding in fast fading channels

Multi-carrier CDMA using convolutional coding and interference cancellation

SIGLEAvailable from British Library Document Supply Centre-DSC:DXN016251 / BLDSC - British Library Document Supply CentreGBUnited Kingdo

A wireless communications systems based on space time block coding and QAM transmission

Modern applications in wireless communications systems demand the capability of high transmission rate. Engineers have to find optimum solutions to transmit the signal over fading environments. In this study, we propose the combination of space-time diversity techniques and optimum QAM constellation design, in order to further improve performance. Specifically, we use prior knowledge of the channel behavior to design adequate mapping techniques to generate a QAM constellation from a MPSK constellation typically used in coherent space time block coding application, so that superior performance is achieved. We do this be designing QAM constellation sets that minimize the symbol error probability from the known information of the transmission medium. We study the system performance for each constellation set in both AWGN and quasi-static Rayleigh fading channels. Various multi-level QAM systems are evaluated using Monte Carlo simulation and maximum likelihood detection. System performance is assessed using bit error rate (BER) and symbol error rate (SER) versus SNR plots

NA

The integration of land, sea, and air forces within the littoral environment will require fading resistant, high data rate, non-exploitable communications. The large volumes of video and data information, i.e. Internet access, video teleconferencing and data transfer, required to support the war fighter within a Joint Task Force demands technologies that reduce the interference imposed by poor terrestrial and atmospheric conditions. In order to minimize the effect of frequency selective fading that occurs in these conditions and to provide high data rate communications, this thesis presents the analysis of a broadband cellular system featuring a multicarrier, code division multiple access (CDMA) method. The system designed complies with Federal Communication Commission broadband cellular standards and uses CDMA to reduce the probabilities of detection and interception as well as providing for multiple access, which in conjunction with the multicarrier approach enables on demand access to high data rate communications.http://archive.org/details/annalysisofbroad1094532765NAU.S. Navy (U.S.N.) author.Approved for public release; distribution is unlimited

New detection schemes for DS/CDMA with antenna arrays.

by Siu-Lung Hui, Freeman.Thesis (M.Phil.)--Chinese University of Hong Kong, 1998.Includes bibliographical references (leaves 64-[67]).Abstract also in Chinese.Chapter 1 --- Introduction --- p.1Chapter 1.1 --- Use of Antenna Arrays in Mobile Communications --- p.1Chapter 1.1.1 --- Overview --- p.1Chapter 1.1.2 --- Beamforming --- p.2Chapter 1.2 --- DS/CDMA System s and Multiple Access Interferences --- p.4Chapter 1.3 --- Multiuser Detection Schemes --- p.7Chapter 1.4 --- Outline of Thesis --- p.11Chapter 2 --- A Blind Adaptive Receiver with Antenna Arrays and M-ary Orthogonal Data Signals --- p.13Chapter 2.1 --- Introduction --- p.13Chapter 2.2 --- System Model --- p.15Chapter 2.3 --- Eigen-Analysis Algorithm --- p.21Chapter 2.4 --- Simulation Results --- p.92Chapter 2.5 --- Adaptive Algorithm --- p.27Chapter 2.6 --- Summary --- p.30Chapter 3 --- Detection with the Use of the Two-Stage Spreading Scheme --- p.32Chapter 3.1 --- Introduction --- p.32Chapter 3.2 --- System Model --- p.34Chapter 3.3 --- Blind Beamforming --- p.36Chapter 3.4 --- Blind Adaptive Multiuser Detection without Antenna Arrays --- p.38Chapter 3.4.1 --- Stochastic Gradient Descent Algorithm --- p.40Chapter 3.4.2 --- Alternative Matrix Approach --- p.41Chapter 3.5 --- Theoretical Combined Receiver Model --- p.41Chapter 3.6 --- Practical Implementation of the Receiver --- p.50Chapter 3.6.1 --- Combined Scheme with Adaptive Algorithms --- p.50Chapter 3.6.2 --- Simplified Structure --- p.52Chapter 3.7 --- Summary --- p.54Chapter 4 --- Conclusions and Future Work --- p.55Chapter A --- Correlation Properties --- p.58Chapter B --- Adaptive Algorithm --- p.62Bibliography --- p.6