Design of Multiservice Code (MS) in Spectral/Temporal/Spatial Domain for OCDMA System

This paper explores the design of multiservice code (MS) in spectral, time spreading and wavelength domains (3-Dimensional). The proposed 3D code is designed in such a manner that follows the ideal in phase unit cross correlation in spectral, time spreading and wavelength domains. The proposed encoder generates the MS code effectively in 3D domain and decoder suppresses the multi-user interferences successfully. Performance analyses are carried out by considering the all noises such as phase induce intensity noise(PIIN), shot noise and thermal noise. The analysis of 3D-MS code for variable code length is also performed for measurement of variation in bit error rate against the received power and number of active users in the design. The observed performances are also compared with existing codes such as 2D-MDW, 3D-PDC and 1D-MS code and the proposed code shows the better performance. The analysis of bit error rate of proposed code is carried out against the number of users at 0.622Gbits/s data rate and 0 dBm received power and comparison is also formed with the existing code such as 3D PD(M=21, N=3, P=3), 2DMDW(M=63, P=3), PDC(M=57, P=3) and 1D MS Code. It is noted that 3D MS code shows the better performance than the existing methods. Analysis is also evaluated for variable weight and variable length codes in order to observe the variation in bit error rate with variation in received power and number of simultaneous users.

Spreading-Based Voice Encryption by Means of OVSF Codes

This paper presents a new methodology to encrypt voice signals, in such a way that they simulate being a noise signal. The objective is to obtain a signal that does not generate suspicions about its content, while protecting the message. The process is based on the spread and scrambling of the signal through the use of OVSF (orthogonal variable spreading factor) codes. The security of the method is based mainly on the input value used for the randomization phase. From a computational cost point of view, the use of fixed-length codes allows for a shorter retrieval time compared to a similar method based on variable-length codes. Regarding the encrypted signal, its main characteristic is its high entropy (very close to the ideal value). Finally, in the recovery process, a signal identical to the original is obtained.

Satellite Image Compression using RICE Algorithm

Processing of satellite images is time-intensive owing to the large surface of the earth and the necessity for high resolution. Compression algorithms are an active research topic since there is no single algorithm which can achieve the best compression at the highest speed. Different compression algorithms need to be explored to enhance the speed of the analysis. Here, a lossless compression scheme using RICE algorithm is implemented using Matlab and Verilog on a satellite image according to the CCSDS (Consultative Committee for Space Data Systems) recommendation. The RICE algorithm uses a set of variable length codes. The architecture comprises of a Pre-processor, Adaptive entropy coder, Postprocessor and an Inverse mapper. The design has been implemented using Xilinx.