This paper introduces an efficient scheme to image steganography by introducing the hidden message (payload) insertion in spatial domain and transforming the stego-image to compressed domain. We apply a recently-proposed LSB method in order to obtain better statistical behavior of the stego-message and subsequently, the obtained stego-image is transformed and quantized in order to enhance the security of hiding. Performance analysis comparisons confirm a higher efficiency for our proposed method. Compared to recently-proposed approaches, our method offers the advantage that it combines an efficient LSB method with transform domain security.

This paper introduces a new method for the least significant bit (LSB) steganography in spatial domain. The new method, called one-third LSB embedding, reduces the probability of change per pixel to one-third without sacrificing the embedding capacity, as compared to previous LSB steganography techniques. This improvement results in a better imperceptibility and higher robustness against well known LSB detectors. Each bit of the message is carried through a function of three adjacent cover pixels and it is shown that no significant improvement is achieved by increasing the length of the pixel sequence employed.

We present a new subsymbol-based multistage multiuser receiver using partial parallel interference cancellation (PPIC) scheme for uplink multirate wideband UMTS-CDMA signals over a multipath fading channel. The multiuser detection process will take place during the window of the highest-rate user's symbol period which makes the proposed scheme more feasible to be implementated compared to the recently-proposed methods. Through numerical simulations, it will be shown that a considerable improvement in performance is gained through the stages of interference cancellation.

The paper introduces an analytical tool to find the large-system performance of a multistage linear partial parallel interference cancellation (PPIC) receiver using the moments of the eigenvalues of the covariance matrix for a code division multiple access (CDMA) system over a frequency-flat fading channel. The figure of merit to evaluate the performance is the signal-to-interference-plus-noise ratio (SINR) that is calculated under a large-system condition. In this case, the number of active users and the processing gain tend towards infinity while their ratio is a fixed value. It is shown that the large-system performance is a function of the system load, the partial cancellation factor (PCF), the number of interference cancellation stages, the signal-to-noise ratio (SNR), and the received powers of the interfering users. Furthermore, for practical applications, the physical meaning of the large system is described by numerical simulations.

A new closed-form expression for the partial cancellation factor (PCF) in a multistage partial parallel interference cancellation (PPIC) receiver is introduced. This approach has several advantages compared to a previously proposed method. First of all, PCFs are found directly from the moments of the eigenvalues of the correlation matrix. This results in less complexity in circuitry. In addition, there is no need that the PCFs be ordered. Therefore, a monotonically improving performance is obtained with even more reduced complexity. Finally, it is not necessary to know the number of interference cancellation stages a priori. It is shown that by choosing these PCFs, the performance of PPIC receiver converges to that of the minimum mean-squared error (MMSE) receiver.

Multiuser detection (MUD) using parallel interference cancellation (PIC) technique provides a good complexity, latency, and performance compromise. This technique is suitable for satellite systems using either code-division multiple-access (CDMA) or a combination of time-division multiple-access (TDMA) and CDMA. We offer a new scheme that is a combination of soft and hard PIC detectors whose performance is superior to that of the other famous suboptimal detectors. In soft partial parallel interference cancellation (PPIC), in the first few stages, when the performance is still poor, the accurate knowledge of power and phase cannot be of much use. However, in the following stages, accurate power and phase estimation can improve the performance. This coincides with the time when the decisions are reliable enough to be used for parameter estimation. In our scheme, after a few stages of soft interference cancellation (IC), estimation of the parameters will start. Having these estimates, in the subsequent stages hard IC is performed. The complexity of this scheme grows linearly with the number of users. Moreover, this scheme is much faster than other receivers such as successive interference cancellation (SIC). PIC detectors are usually studied in equal-power case, i.e., a perfect power control scheme is assumed. In this paper, PIC detector in a near-far condition where user signals arrive at the receiver with different power levels is also investigated.

A combination of soft and hard partial parallel interference cancellations (SHPPIC) for a multistage multiuser detector with amplitude and phase estimation is introduced in this paper. This scheme is appropriate for a digital video broadcasting-return channel via satellite (DVB-RCS) communication system when used together with the evolutionary satellite communication scheme that uses a combination of TDMA and CDMA (slotted CDMA). The outputs of the first stages are more deteriorated by multiple access interference (MAI) than by the thermal noise. This makes amplitude and phase estimation impractical in the first stages. Therefore, soft interference cancellation (IC) is used in the earlier stages since soft IC does not require the knowledge of the channel parameters. Once the performance of the soft multistage multiuser detector becomes more reliable (roughly equivalent to the performance of the decorrelator detector), the amplitude and phase of each user are estimated. Having these parameters estimated, the subsequent stages would be in the form of hard IC. The complexity of such a detector is linearly increased with the number of users. Also, a multistage hybrid interference cancellation (HIC) method for near-far conditions when the signals arrive at the receiver with different power levels, is presented.