We describe two classes of simple, effective techniques for reducing the average optical power requirement in intensity-modulated optical systems using multiple BPSK or QPSK subcarriers. The first class of techniques involves block coding between the information bits to be transmitted and the symbol amplitudes modulated onto the subcarriers in order to increase the minimum value of the multiple...

In coding theory it is widely known that the optimal encoding for a given alphabet of symbol codes is the Shannon entropy times the number of symbols to be encoded. However, depending on the structure of the message to be encoded it is possible to beat this optimal by including only frequently occurring aggregates of symbols from the base alphabet. We prove that the change in compressed message...

This paper studies an iterative multiuser detection and decoding for nonbinary low density parity check (LDPC) coded multicarrier M-ary frequency shift keying (MC MFSK) multiple access system to increase system spectral efficiency under specific signal-to-noise ratio. At multiuser detection side, soft metric for each symbol is quantized to 2 levels (2L) or 3 levels (3L) and then pass to the dec...

Ordet »symbol« har rod i det græske symballein, hvor sym betyder »sammen« og ballein »kaste« eller »føje« altså »sammenføje«. 1 Herudfra kan ordet tillægges en videre betydning, som skal tages op denne artikel: At føje adskilte sammen, så fuldt ud virkelige bliver nærværende et udtryk. livsverdenen vil der ofte mangle intenst ægte virkelighedsnærvær. Tingene, menneskene, andre levende væsener; ...

Bit-interleaved coded modulation with iterative detection for MIMO systems demands an efficient APP detector that delivers soft information about the coded bits. The list-sequential detector is a reduced-complexity approximation to an exhaustive APP detector. It uses a tree search employing the stack algorithm to find dominant terms of the log-likelihood ratio. The commonly used symbol-by-symbo...

Recent work has started to examine the structure of trees on a large scale to determine if they have an impact on the solutions found in genetic programming (GP) and also as measures of diversity and convergence. Much of the focus has been on the shape of evolved trees. Our work changes this focus onto the symbol space, an indication of what program functions and terminals exist, at what depth,...

Transmission of convolutionally encoded multiple descriptions over noisy channels can benefit from the use of iterative source-channel decoding. The authors first modified the BCJR algorithm in a way that symbol a posteriori probabilities can be derived and used as extrinsic information to improve the iterative decoding between the source and channel decoders. The authors also formulate a recur...

In this paper the generation and the use of reliability information for the decoding process of convolutionally encoded data in the context of a CDMA-environment is addressed. Special emphasis lies on the noncoherent detection of M-ary orthogonal symbols with a RAKE-receiver. Although symbol by symbol decisions are carried out, it is possible to characterize the reliability of the individual bi...

Accurate symbol recognition in graphic documents needs an accurate representation of the symbols to be recognized. If structural approaches are used for recognition, symbols have to be described in ternu of their shape, using structural relationships among extracted features. Unlike statistical pattern recognition, in structutul methods, slwbols are usually manually deJined from expertise knowl...

This paper describes various display devices which are useful for avionics applications. It focuses the attention of cathode ray tube based displays which has distinct advantages in terms of better luminance, contrast ration and the mature level of technology. Various writing methods have been studied which are chosen depending on application, contrast level required and on the amount of inform...