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The power control problem is considered with the CR user QoS requirement and the interference to primary user under the threshold which the primary user can tolerate. We model the power control as a optimize problem which each CR user SINR must not less than minimum SINR requirement and the total interference must less than predefined threshold. Firstly we consider the network can satisfy the CR user...
There is an increasing need for a cognitive radio (CR) that is capable of observing its environment and modifying its transmission characteristics to transmit on unused frequency bands in ways that cause no harmful interference to the primary users (PU). In this paper, we assume that the PU transmits using a conventional OFDM system. We present a non-contiguous OFDM (NC-OFDM) and a multi-block OFDM...
In this paper, we investigate the energy consumption of a wireless cognitive radio (CR) network, where each node is equipped with CR and the network is an OFDMA system operating on time slots. In particular, we investigate the energy consumption efficiency in CR network using a joint adaptive modulation and power allocation algorithm. We also investigate the optimum network area for green communication.
In this paper we consider cognitive radios (CR) that employ orthogonal frequency division multiplexing (OFDM) modulation at the physical layer and present an algorithm for transmitter adaptation subject to specified quality of service (QoS) constraints. The proposed algorithm explicitly considers multipath channels between the CR transmitter and its intended receiver, and performs joint spectral shaping...
The ever-increasing demand for precious radio spectrum along with the inefficient usage of licensed band has led to the advent of the cognitive radio (CR) technology, which aims to provide opportunistic spectrum usage to unlicensed users and thus lead to the co-existence and interference control problem among heterogeneous systems. In this paper, an interference minimization and subcarrier power allocation...
Cognitive radio (CR) is a promising technology for the efficient use of available spectrum. Reliable detection of primary user (PR) signals and spectrum sensing are the most important challenges which meet the implementation of the CR. In CR's communications, the PR user must be protected from the interference from the CR users. This can be achieved only by using an optimal spectrum sensing. In this...
This paper addresses the subcarrier and power allocation problem in the uplink of an OFDMA system under the cognitive radio environment. The objective is to maximize the sum-rate of secondary users, without causing adverse interference to the primary users. We formulate the optimization problem subject to the individual power constraints and the interference constraints. Since the problem cannot be...
In an environment of shared radio spectrum, multiple systems may interfere with each other and cause significant impacts on system coexistence. In this paper we propose an adaptive subband selection technique based on orthogonal frequency division multiplexing (OFDM) to avoid interference for better system coexistence when multiple systems are operating in the same unlicensed industrial, scientific...
Spectrum awareness is the key technique for Cognitive Radio (CR). A special spectrum sensing scheme is necessary for Cognitive UWB radio (CUWB) because of its lower radio power and ultra wide bandwidth. Although CUWB transmitter and receiver could respectively detect the spectrum holes, they couldn't communicate with each other probably if they are out of the communication range or there isn't common...
Traditional communications systems imply an a priori association of the frequency band, the service assigned to it and the used technology. Breaking this static association can provide much more flexible, efficient and easy-to-use dynamic systems able to cope with the requirements and constraints of the environment and the users. Cognitive radio and software defined radio modify this current communication...
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