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This paper considers a design of signal constellations for trans-modulation (constellation rearrangement: CoRe) in a relay system with the multiple links in which the same signal is decoded-and-forwarded to the destination over N time slots, each assigned to the different relay node. Demonstrating that the minimal accumulated squared Euclidean distance (MASED) is not an ultimate design metric to minimize the bit error rate (BER), we choose the BER for the joint log-likelihood ratio (LLR) combining scheme as a design metric, so as to find bit-to-symbol mapping for the multiple relay links. To handle the prohibitive amount of computational complexity associated with an exhaustive search over enumeration of all possible mappings, which grows exponentially with the number of relay links, genetic algorithm is employed for searching for the sub-optimal bitto-symbol mappings in the multiple relay links. We show that a new type of CoRe design without the Gray-mapping constraint is critical for warranting the LLR-combining gain over the multiple relay links, e.g., approximately 4dB gain for 4 relay links at high SNR as compared to the CoRe design for hybrid ARQ.

Usual holographic imaging of moving objects re quires a high power pulsed laser to deliver sufficient energy on the photographic sensitive emulsion in a short time. We have developed a method for obtaining holograms of moving objects with low power cw lasers. It involves two steps. The first step consists of taking a hologram of a moving object with a relatively high intensity reference beam to match the middle portion of the H-D curve in a short time. The intensity of the object image generated by this hologram is too low to be recognized. The second step is the amplification of the holographic image by the technique of amplified reconstruction. One application of our research can be the imaging of the microstructure of living cells inside the body through an optical fiber. After taking an amplified image hologram, we may phase conjugate the image to the original object side. The image can then be viewed by under a microscope to demonstrate the detailed structure of the object. The image quality and resolution will be discussed.

The wavefront of a beam reflected from a metal surface has random variations in phase due to microsurface roughness. If this beam is multiply reflected from the surface, the combined beams will average out the random variations in intensity, while increasing the contrast of fringes that arise due to macrovariations in surface flatness. We present results of holographic interferometric experiments using a multiply reflected object beam at a glancing angle in the surface of machined metal surfaces.