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Switching transients generated by a selection diversity combiner corrupt receiver filters and increase the system outage as well as corrupting channel estimation. In order to produce an accurate (transient-free) channel estimate and reduce the internal outage, one prefers small switching rates. Therefore, knowledge of the switching rate provides useful information for system engineers in the design...
In this paper, a novel general small-scale fading model for wireless communications, that describes the nonhomogeneous nature of the propagation medium, is introduced. Its probability density function (PDF) is given by a simple, exact, and closed-form expression. Namely, the η - λ - μ includes the λ - μ, the η - μ, the gamma, the exponential, the Hoyt, the Nakagami-m, the Rayleigh, and the one-sided...
This paper proposes the distributed space-time block code (D-STBC) over frequency selective fading channel that achieves both spatial diversity gain and low decoding complexity with decoupling property in amplify-and-forward (AF) relay networks. These two goals are simultaneously achieved by our proposed code design, where the source permutates and conjugates the transmitted data before sending to...
Relays can improve wireless links by providing an extra path to the direct path which together form a virtual multiple antenna system. Network Coded-Distributive Antenna System (NC-DAS) and Plain-Distributive Antenna System (PDAS) are examples of realizations of such scenario. Although the asymptotic diversity gain for both the schemes is comparable, the network coded scheme can further take advantage...
Free probability theory, which has became a main branch of random matrix theory, is a valuable tool for describing the asymptotic behavior of multiple systems, especially for large random matrices. In this paper, using free probability theory, a new cooperative scheme for spectrum sensing is proposed, which shows how asymptotic free behavior of random matrices and the property of Wishart distribution...
In this paper, we exploit cooperative spectrum sensing technique for applications in a relay based cognitive radio network. Relays are assigned in cognitive radio networks to transmit the primary user's signal to a cognitive coordinator. This research is focused on the detection of primary user in single or multiple cognitive relay scenarios. The performance of energy detector is analyzed for independent...
The distribution of the received signal power ?? of a multiple-input multiple-output system, with the associated 2 ?? 2 complex Wishart matrix having n degrees of freedom, is investigated under the channel inversion power allocation scheme. Exact closed-form expressions are derived for the probability density function and the cumulative distribution function of ??. The analysis covers systems with...
In a protocol assisted switched diversity (PASD) system, the time separated repetition blocks are accumulated in order to increase decoding reliability. In this paper, we consider transmit antenna selection (TAS) protocols in a PASD system. To minimize system complexity we assume the feedback information is limited to the SNR of the current pair of antennas. We propose three TAS protocols : the random...
Emulation of fading channels is a key step in the design and verification of wireless communication systems. Testing wireless transceivers with actual fading channels is inconvenient due to unrepeatable and uncontrollable channel conditions. In this paper we present a compact field-programmable gate array (FPGA) implementation for a circuit that generates temporally-correlated fading variates for...
Ergodic capacity is not a suitable information-theoretic measure for delay sensitive applications over fading channels. On the other hand, delay-limited capacity becomes zero for Rayleigh channels. In this case, the Capacity with Probabilistic Delay Constraint becomes useful. In, the maximum constant source rate that may be supported in a wireless system with a probability ?? of exceeding certain...
Space-time modulation exploiting diversity or/and coding gains has been a major focus in high-speed wireless communications systems against channel fading. We employ noncoherent space-time modulation in cyclic-prefix (CP) based single-carrier (SC) block systems over frequency selective Rayleigh block fading channels, where channel order, upper-bounded by the CP length, is assumed known. Capitalizing...
A partial interference cancellation (PIC) group decoding based space-time block code (STBC) design criterion was recently proposed by Guo and Xia, where the decoding complexity and the code rate trade-off is dealt when the full diversity is achieved. In this paper, we propose a systematic design of STBC that satisfy the criterion, i.e., achieve full diversity with the PIC group decoding for any number...
We derive new exact closed-form expressions for the symbol error rate (SER) of cooperative selection diversity (CSD) with amplify-and-forward (AF) transmission using channel-state-information (CSI)-based gain relaying. We consider the general fading condition of independent but not necessarily identically distributed (i.n.d.) Nakagami-m fading. We also present a closed-form expression for i.n.d. Rayleigh...
In a cellular system, when multiple-input multiple-output (MIMO) techniques are employed, the interference scenario is quite complicated. In this paper, considering realistic propagation conditions including both path loss and Rayleigh fading, and considering the existence of unequal-power interferers, we analyze the statistical distributions of the post-processing SIRs for downlink space-time block...
In relay networks, partial channel state information at the transmitter due to feedback delay can severely degrade the beamforming performance. In this paper, the decremental effect of transmit beamforming with feedback delay on the downlink performance of a two hop Amplify-and-Forward (AF) relay network over Rayleigh fading channels is investigated. The source is equipped with multiple antennas while...
Cognitive radio with spectrum sharing feature is a promising technique to address the spectrum under-utilization problem in dynamically changing environments. In this paper, achievable capacity gain of spectrum sharing systems over dynamic fading environments is studied. For the analysis, a theoretical fading model called hyper fading model that is suitable to the dynamic nature of cognitive radio...
An adaptive power control scheme for cognitive radio system (CRS) in Rayleigh fading channel is proposed. The transmit power of a secondary user (SU) is adjusted in Rayleigh fading to maximize the constant output signal-to-noise ratio (SNR) at an SU receiver while keeping the interference to a primary user (PU) under given constraints. To calculate the maximum constant output SNR at the SU receiver...
When transmitting at a fixed-rate to a wireless mobile terminal with strict latency requirements channel inversion is often used but at the cost of a significant loss in efficiency. Further, many such systems utilize limited packet buffering at the mobile terminal. In this paper we propose a method to recapture the lost spectral efficiency by exploiting the local buffer. Specifically, in severe channel...
We investigate the incremental relaying protocol in conjunction with relay-selection cooperative diversity networks with an aim to make efficient use of the degrees of freedom of the channels by exploiting a limited feedback signal from the destination. In particular, whenever the direct link from the source to the destination is not favorable to decoding, the destination will request the help from...
In this paper, we investigate amplify-and-forward (AF) incremental-best-relay cooperative diversity to make efficient use of the channel spectrum by exploiting a limited feedback from the destination terminal, e.g., a single bit indicating the success or failure of the direct transmission. If the destination provides a negative acknowledgment via feedback; in this case only, the best relay among M...
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