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Cognitive radio is an intelligent radio wireless communication technology in order to increase the spectrum efficiency. In this paper one of the most important cognitive radio task i.e. spectrum sensing is explained in detail. Spectrum sensing used to detect the presence of the primary users in a licensed spectrum, which is a fundamental problem for cognitive radio. Increasing efficiency of the spectrum...
Viterbi sequence detectors and Turbo decoders are widely used in the receivers of mobile communications systems. They are offer an efficient means of implementing a near-maximum likelihood receiver. However, Viterbi sequence estimators are usually based on the assumption of Gaussian noise and/or interference statistics. It is becoming clear that for third generation and enhanced second generation...
A distributed system consists of several autonomous nodes, where some of the nodes may be overloaded due to a large number of job arrivals while others nodes are idle without any processing. Load Balancing is used for effectively distributing the load among the nodes. Centralized load balancing schemes are not scalable as the load balancing decision depends on a central server. In contrast fully distributed...
By assuming the impulse statistics, channel coding has long served as an effective tool against fairly frequent occurrence of strong impulses, which impedes the guaranteed quality of service of communication systems. Nevertheless, impulse statistics are generally hard to be modeled and likely to be time-varying, posing a great challenge to system design. Our previous work reveals that, without assuming...
In ultra-wideband (UWB) communications for power electronic systems, large power consumption and logic resource are occupied by multi-parallel sliding-block Viterbi decoders. A novel add-select-delay-compare architecture for Viterbi decoder is proposed to minimize these consumptions. In this architecture, a nested iteration of add-select and compare-select with balanced settling path is utilized to...
Wireless Mesh Networks (WMN) are considered as robust architecture to provide reliable connectivity to fixed and mobile users. The redundant infrastructure provided by WMN can be efficiently utilized using multipath routing. However, the performance gain of multipath routing mainly depends on efficient path selection protocols. The omni-directional wireless medium, unstable link quality and mutual...
In the light of the mice-elephant phenomenon of the Internet traffic, TCP congestion control algorithm shows unfairness against flows of small sizes (small flows). In this context, we find it motivating to study the influence of TCP's initial window (IW) size on the response times of small flows. In our previous works, we proposed a function that determines IW-size for each flow based on its size;...
In this paper, we consider K-user multiple-input single-output interference channels with a cognitive relay. Assuming that data of all transmitters and channel state information are known at the cognitive relay, we design a linear precoder for the cognitive relay with the aim of maximizing the sum-rate without changing the transmitter operations at all transmitters. We first define the receiver set...
The use of wireless sensor networks (WSNs) can be advantageous in applications that serve in hostile environments such as security surveillance and military battlefield. The operation of a WSN typically involves collection of sensor measurements at an in-situ Base-Station (BS) that further processes the data and either takes action or reports findings to a remote command center. Thus the BS plays...
Wireless communications in the terahertz (THz) frequency band, 0.1-10THz, promises a rapid increase of channel capacity in next- generation networks. However, the advantages of this technology depend not only on the single link performance, but also on the possibility of several THz links to coexist in the same area. Thus, the efficiency of spatial channel reuse has to be studied. Due to the presence...
There are many examples in the literature of scorecards derived from clinical data. These scorecards are proposed for use by health professionals to stratify patients into risk categories and are often compared using receiver operating characteristic (ROC) curves and their associated areas (AUC). This paper analyses random scorecards and shows that the underlying distributions and therefore statistical...
Received Signal Strength (RSS) and Round Trip Time (RTT) are two common metrics for a wireless receiver to tell the proximity of a remote wireless transmitter. A large RSS or a small RTT normally indicates a close transmitter, and vice versa. Both metrics are effective in a benign environment. However, when the transmitter modifies the send time or transmit power to hide its real distance, they may...
Iterative receiver combining multiple-input multiple-output (MIMO) detection with channel decoding is an attractive solution to greatly improve the error rate performance of wireless communication systems. However, such iterative process poses significant challenges for efficient receiver design. In this paper, a modification of soft-input soft-output K-Best decoder is proposed to provide high throughput...
The list demapper has been widely implemented in a coded multiple-input multiple-output (MIMO) receiver, where only a part of total signal vectors are examined in the calculation of likelihood ratio for low complexity. Generally, the list is generated either in the original or the lattice-reduced domain. In the latter, thanks to the operation of lattice reduction (LR), a better-conditioned MIMO channel...
In this paper, we propose a spectrum map aided routing protocol for a distributed cognitive radio network. We assume the presence of dedicated sensors that capture the spatio-temporal spectrum usage statistics to create the radio environment map. We exploit the map to find not only the best hops along a route but also the best available channel in terms of the expected performance. Through the use...
Non-Gaussian impulsive interference mitigation is of great interest in robust and reliable communication over wired and wireless channels. One of the most popular impulsive noise cancellation methods used along with the orthogonal frequency division multiplexing (OFDM) is blanking nonlinearity. Although its simplicity and efficiency, the blanking method suffers from inter-carrier interference (ICI)...
In multiple-input multiple-output (MIMO) systems adopting space shift keying (SSK), the use of adaptive precoder on transmitter offers the opportunity to improve its performance significantly. One major challenge in precoder operation is the difficulty in obtaining the full channel state information on transmitter (CSIT). In this work, we investigate the precoder design for SSK-MIMO systems with limited...
This paper proposes an experimental evaluation of the communication in an Organization-based Multi-Agent System. We defined a set of criteria to evaluate the quality of interactions between agents at run time. The originalities and the advantages of our proposal are threefold: (1) the adaptation of a set of criteria and their corresponding metrics to evaluate communication in an Organization-based...
We propose Plena, a packet length adaptation scheme exploiting recently proposed Error Estimating Codes for low power sensor networks. We carefully consider two low power MAC protocols, i.e., X-MAC and LPP, in modeling the energy consumptions of different packet lengths. Based on the modeling and analysis, we give closed form solutions for the optimal packet length in terms of energy efficiency. We...
We study achievable information rates for nonlinear channels with memory, in the context of satellite communication with QAM modulation. The complete channel model can be described by a Volterra expansion, but large alphabet size and/or large channel memory length may prohibit optimal soft-output demodulator processing, say with the BCJR algorithm. Thus we focus on reduced-state receivers and their...
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