A capacity-approaching coded modulation scheme for non-coherent fading channels

Approaching the Shannon limit of the communication channels has been studied by many researchers to efficiently and reliably transmit data through the channels. To solve this problem, various methods and schemes have been proposed for approaching the theoretical limit for Shannon’s channel capacity. Among them, both low-density parity check (LDPC) codes and Turbo codes have been proposed to minimize the bit error rate (BER). Therefore, understanding of LDPC codes and Turbo codes is useful for their applications in modern communication systems. The study about non-coherent channels, which do not require explicit knowledge or estimation of the channel state information, has become a major issue in mobile communication. Specifically, a new signaling scheme called unitary space-time modulation has been invented which is suitable for non-coherent channels. Combining channel coding with unitary space-time modulation is expected to make good performance for non-coherent fading channels. In this thesis, non-coherent capacity of a mobile communication channel in Rayleigh flat fading is calculated for the case of coherence time of length two. Also, LDPC codes and Turbo codes are combined with unitary space-time modulation to enhance the efficiency and reliability of communication over non-coherent fading channels. The performance results are compared to the calculated channel capacity. Simulation results show that both LDPC codes and Turbo codes are well performed for non-coherent fading channels. The LDPC and Turbo coded unitary space-time modulation schemes have BER performance much better than the uncoded modulation schemes and the performance is close to the calculated channel capacity

A Compact Parallel-plane Perpendicular-current Feed for a Modified Equiangular Spiral Antenna and Related Circuits

This work describes the design and measurement of a compact bidirectional ultrawideband (UWB) modified equiangular spiral antenna with an integrated feed internally matched to a 50-Ohm microstrip transmission line. A UWB transition from microstrip to double-sided parallel-strip line (DSPSL) soldered to a short (1.14 mm) twin-line transmission line feeds the spiral. The currents on the feed travel in a direction approximately perpendicular to the direction of the currents on the spiral at the points where the feed passes the spiral in close proximity (0.57 mm). Holes were etched from the metal arms of the spiral to reduce the impedance mismatch caused by coupling between the transmission line feed and the spiral. This work also describes a low-loss back-to-back transition from coaxial line to DSPSL, an in-phase connectorized 3 dB DSPSL power divider made using three of those transitions, a 2:1 in-phase DSPSL power divider, a 3:1 in-phase DSPSL power divider, a radial dipole fed by DSPSL, an array of those dipoles utilizing the various power dividers, and a UWB circular monopole antenna fed by DSPSL. Measured and simulated results show good agreement for the designed antennas and circuits

The performance analysis of differential orthogonal space- time block codes

Ph.DDOCTOR OF PHILOSOPH