A new divide-and-conquer scheme has been proposed with Adaptive Modulation in CDMA system to improve the spectrum efficiency of the wireless communication system. The proposed method results in increase in average throughput achieved and simultaneously decrease in the outage probability of the system when the user density is high. The proposed scheme is compared with the existing algorithms and...

A new type of adaptive optics system is proposed for astronomical imaging. It replaces the wavefront sensing and modulation hardware pieces of conventional adaptive optics with numerical processing capabilities of digital holography of incoherent sources. OCIS codes: (010.1080) Active or adaptive optics; (090.1000) Aberration compensation; (090.1995) Digital holography; (110.0115) Imaging throu...

Spectral efficiency is one of primary concern in the design of any wireless data communications systems, where fading is the main problem. An approach that can be taken to overcome the problem of fading is to adapt the modulation scheme according to the instantaneous propagation channel conditions. In this paper, we present a simplified mathematical model to calculate the probability of SER for...

The three most important factors in choosing a speech output processing method for a particular application are flexibility, bit rate and cost. Flexibility enables the user to change the binary speech patterns according to his needs; bit rate is the amount of binary information necessary to produce a certain length (I s) of continuous speech; and cost includes not only the LSl chip itself, but ...

In this letter, we analyze power and rate adaptation in a point-to-point link with Rayleigh fading and impulsive interference. We model the impulsive interference as a BernoulliGaussian random process. Adaptation is used to maximize the average spectral efficiency by changing power and rate of the transmission subject to an average power and instantaneous probability of error constraints. Witho...

In this contribution, adaptive modulation is applied in conjunction with a Decision Feedback Equalizer (DFE) in order to mitigate the eeects of the slowly varying wideband multi-path Rayleigh fading channel. An upper-bound mean BER and Bits Per Symbol (BPS) performance is introduced for this scheme by utilizing the pseudo-SNR at the output of the DFE in order to switch the modulation schemes on...

In this paper, we propose a joint transmit and receive linear filtering based on minimum mean square error criterion (joint Tx/Rx MMSE filtering) for single-carrier (SC) multiple-input multiple-output (MIMO) transmission. Joint Tx/Rx MMSE filtering transforms the MIMO channel to the orthogonal eigenmodes to avoid the inter-antenna interference (IAI) and performs MMSE based transmit power alloca...

Future mobile communication requires 100 Mbps data rate, video and audio streaming, asymmetric, multiple access, adaptive modulation and code rate, dynamic packet arrangement, adaptive antenna and IPv6 utilization facility to enhance lossless communication. We propose an Adaptive Modulation and Rate Coding Multi Carrier Code Division Multiple Access (AMRC-MC-CDMA) technique is a promising way t...

We study the performance of cognitive radio networks (CRNs) when incorporating adaptive modulation at the physical layer. Three types of CRNs are considered, namely opportunistic spectrum access (OSA), spectrum sharing (SS) and sensing-based SS. We obtain closed-form expressions for the average spectral efficiency achieved at the secondary network and the optimal power allocation for both conti...

We consider different high rate space-time modulation methods and related (re)transmission strategies in a MIMO channel. The proposed matrix modulators exploit the MIMO channel in increasing the peak rate via power-efficient parallel transmission, whereas the self-orthogonalizing retransmission and signal combining strategies improve ultimate throughput.