Throughput Analysis of Arq Schemes Using State Transition Diagrams

Automatic-Repeat-Request (ARQ) schemes have been widely used and various methods and representations have been used in their analysis. In this paper, the schemes are represented by ztransform based transition diagrams to yield easily retractable expressions. The approach has enabled the analysis of the Selective Repeat-Stutter 2 (SR-ST2) scheme having variable selective repeat mode retransmissions and the Selective Repeat-Stutter-Go Back N (SR-ST-GBN) scheme having variable stutter mode retransmissions. Using the SR-ST-GBN scheme, it is also shown that it is possible to choose the design parameters of ARQ-based communication systems in order to achieve maximum throughput.Keywords: Automatic-Repeat-Request, throughput, throughput efficienc

A new automatic repeat request protocol based on Alamouti space-time block code over Rayleigh fading channels.

Masters Degree. University of KwaZulu-Natal, Durban.Spatial and multiplexing diversity of multiple-input multiple-output (MIMO) schemes improves link reliability and data rates of wireless networks. MIMO-based space-time block codes (STBCs) improve wireless network reliability by using different copies of the receiver’s original data. Recently automatic repeat request (ARQ) technique was introduced for MIMO schemes to enhance the system's link reliability. ARQ improves the link reliability by using acknowledgments and timeouts to ensure efficient transmission of data over an insecure system. In this dissertation, we propose a new ARQ protocol based on Alamouti space-time block code (STBC) over Rayleigh fading channels. The proposed system transmits data by employing two transmit antennas ( ) and four receive antennas , and it is developed by applying the recent technique called uncoded space-time labeling diversity (USTLD). The main idea behind the proposed technique is to use two distinct mappers to improve the error performance of the system. The theoretical expression of the proposed technique is derived employing the union bound approach, and the theoretical analysis is validated with the simulation results. Furthermore, the results revealed that there is a symbol error probability (SEP) performance improvement of 4 dB for 16-QAM and 4.90 dB for 64-QAM when one mapper is employed as compared to the Alamouti system at a SEP of . The results also revealed that when the proposed system uses two mappers, there is a SEP performance improvement of 7.98 dB for 16-QAM and 9.8 dB for 64-QAM compared to the Alamouti system at a SEP of

Resource Allocation, Scheduling and Feedback Reduction in Multiple Input Multiple Output (MIMO) Orthogonal Frequency-Division Multiplexing (OFDM) Systems

The number of wireless systems, services, and users are constantly increasing and therefore the bandwidth requirements have become higher. One of the most robust modulations is Orthogonal Frequency-Division Multiplexing (OFDM). It has been considered as an attractive solution for future broadband wireless communications. This dissertation investigates bit and power allocation, joint resource allocation, user scheduling, and limited feedback problem in multi-user OFDM systems. The following dissertation contributes to improved OFDM systems in the following manner. (1) A low complexity sub-carrier, power, and bit allocation algorithm is proposed. This algorithm has lower computational complexity and results in performance that is comparable to that of the existing algorithms. (2) Variations of the proportional fair scheduling scheme are proposed and analyzed. The proposed scheme improves system throughput and delay time, and achieves higher throughput without sacrificing fairness which makes it a better scheme in terms of efficiency and fairness. (3) A DCT feedback compression algorithm based on sorting is proposed. This algorithm uses sorting to increase the correlation between feedback channel quality information of frequency selective channels. The feedback overhead of system is successfully reduced

MIMO Systems

In recent years, it was realized that the MIMO communication systems seems to be inevitable in accelerated evolution of high data rates applications due to their potential to dramatically increase the spectral efficiency and simultaneously sending individual information to the corresponding users in wireless systems. This book, intends to provide highlights of the current research topics in the field of MIMO system, to offer a snapshot of the recent advances and major issues faced today by the researchers in the MIMO related areas. The book is written by specialists working in universities and research centers all over the world to cover the fundamental principles and main advanced topics on high data rates wireless communications systems over MIMO channels. Moreover, the book has the advantage of providing a collection of applications that are completely independent and self-contained; thus, the interested reader can choose any chapter and skip to another without losing continuity