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The performance of a cognitive radio based Transmitter Pre-processing (TP) assisted Multi-Carrier (MC)-Code Division Multiple Access (CDMA) system over correlated frequency-selective channels for downlink communication is presented in this paper. The Singular Value Decomposition (SVD) helps us understand the need for TP. Channel State Information (CSI) is collected via feedback channels and this SVD...
Spread spectrum (SS) modulation is one of the most commonly used methods for data hiding. However, the capacity of SS-based methods is rather limited. To improve the hiding efficiency, this paper presents a method that employs the parallel combinatory spread spectrum (PCSS), in which the hidden data can be transmitted in parallel with a combination of a few pseudo noise sequences. An informed embedding...
In this paper an analytical approach is presented to determine the impact of frequency offset, timing jitter and additive white Gaussian noise (AWGN) on the bit error rate (BER) performance of a multi-carrier direct-sequence code division multiple access (MC-DS-CDMA) system over a Rayleigh Fading Channel. The analysis developed the pdf (probability density function) at the receiver considering combined...
Code-hopping multiple access (CHMA) has been an emerging multiple access technology designed to increase the number of users in Code-division multiple access (CDMA) systems. It was designed to overcome the limitations in the number of code word's required for communication in existing systems. However, it may experience degradation due to symbol perforation occurring due to code collisions when the...
A robust pointing error compensated algorithm for code-division multiple access (CDMA) signals is proposed. Theoretically, minimum variance distortionless response (MVDR) beam-former can achieve the maximum power. However, it is very sensitive to pointing error for the large SNR. In order to deal with the desired signal cancellation problem, the differential rooting method is used to estimate the...
The effects of random network coding on code division multiple access/time division duplex (CDMA/TDD) platforms are studied and evaluated. A multi-hop mesh network with both single source and multiple receiving nodes is assumed. Two scenarios are evaluated for their efficiency. The study focuses on the effects of uncontrolled parameters such as the minimum number of neighbors and the network connectivity,...
This paper investigates the application of the Generalized Likelihood Ratio Test detector to the Global Navigation Satellite System array-based acquisition problem. We consider an unstructured channel model which includes colored noise with an arbitrary covariance matrix. We show that the proposed test function is a Constant False Alarm Rate detector and we provide closed form expressions for false...
Interference reduction is vital for being able to effectively communicate with mobile users in rugged terrain and mountainous regions.12 It is proposed to outfit a high flying airborne node with a Code Division Multiple Access (CDMA) base station in order to provide line of sight communications and continual coverage to the remote users. One approach to increasing capacity and coverage zones for the...
In today's cellular networks, it becomes harder to provide the resources for the increasing and fluctuating traffic demand exactly in the place and at the time where and when they are needed. Moreover, a cellular network which can cover indoor areas and hot-spots is a complicated and expensive task. Therefore, a new hierarchical topology is put forward to solve the problem, and the topology have application...
In spread spectrum communication systems a major role is played by the spreading sequences adopted to assign each user the possibility of communicating over the system itself. Spreading sequences with low correlation, large family size, and high linear complexity are desirable, in order to ensure low inter-user interference effects, a sufficiently high number of simultaneous users, and an adequate...
The conventional amplify-and-forward cooperative system is capable of achieving a superior performance with the aid of Multiple-Symbol Differential Sphere Detection (MSDSD), when compared to conventional differential detection (CDD) for transmission over time-selective channels. However, the conventional broadcast/cooperative twin-phase based relaying protocol encounters a 50% throughput loss imposed...
The uplink of an asynchronous Detect and Forward CDMA wireless network interference tolerance is investigated in this paper where relays and base station use Adaptive Multiuser Detection to detect incoming signals. Relays exchange data and channel information with the base station to achieve diversity gains. Due to non orthogonality of random spreading waveforms, Multiple Access Interference occurs,...
We consider the problem of fair resource allocation in interference channels, for the case of one-dimensional cells. We propose simple interference channel models based upon the deterministic channel model, assuming zero queuing delay. This enables study of how the interference induces coupling among the rates available in the channels and evaluation of resource allocation. A sequence of models of...
In this paper, Cognitive Radio CDMA networks have been modeled and performances of primary user (PU) and secondary user (SU) have been investigated. PUs communicate to BS in our assumed model. However, SUs form pair wise ad hoc networks to maximize their data rates. In the process, they may interfere heavily in uplink at the BS. An efficient signal strength based algorithm has been proposed for gradual...
In this paper a novel Space Time Diversity Generalized Decorrelating Discrete Time Rake (STD-GD-DTR) for Upstream DS-CDMA system is proposed. The chosen algorithm for estimating the correct data is Maximum likelihood. In this method, a robust receiver based on maximum likelihood estimation is represented in which, space time diversity technique has been combined with generalized decorrelating discrete-time...
In this paper, discrete event simulation by batch-means of a M/M/∞ queuing system is utilised to simulate a cellular CDMA system. The details of the simulation model, warm-up period, and simulation run time are discussed. The warm-up period is studied because it affects the accuracy of the results in simulation of communication systems. During the warm-up period-when the simulation system has not...
The IMT-2000 standard UMTS of (Universal Mobile Telecommunications System) is based on Wideband CDMA (Code Division Multiple Access). To access a shared transmission channel for multiple users, UMTS exploit Code Division Multiple Access (CDMA). Multi-user interference is a critical issue in CDMA, limited user, cell Capacity and limiting spectral efficiency dramatically. The manner of used multiple...
The technology of Direct Sequence Code Division Multiple Access (DS-CDMA) has been chosen for mobile communication systems because of numerous advantages. A major advantage is that it can provide a better capacity compared to the other possible technologies of multiple access. In spread spectrum system the signal bandwidth is increased to a value much larger than is needed to transmit the underlying...
We consider a wireless communication model where a large number of transmitter-receiver pairs share a common Rayleigh fading channel without any coordination between them. The performance of a simple coexistence etiquette is analyzed in details, where packets are allowed to be transmitted from a given terminal only if the signal-to-interference-plus-noise ratio (SINR) at their intended receiver exceeds...
Linear and nonlinear receiver structures based on Minimum Mean Square Error (MMSE) linear combiner are proposed to mitigate the effect of multiuser interference in uplink Direct Sequence overloaded Code Division Multiple Access (DS-CDMA) system. The proposed mitigation algorithm exploits the inherent multi-path diversity and diminishes the effects of both Inter Symbol Interference (ISI) and Multiuser...
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