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This paper presents a new algorithm for solving the frequency assignment problem in cellular mobile systems. The proposed algorithm is based on a Taboo search starting with a sequential local search method. Instead of using a minimum number of frequencies and reusing them a maximum number of times, our algorithm assembles to maximum the frequencies while avoiding deadlock. This algorithm introduces...
Spectrum management has been identified as a crucial step towards enabling the technology of the cognitive radio network (CRN). Most of the current works dealing with spectrum management in the CRN focus on a single task of the problem, e.g., spectrum sensing, spectrum decision, spectrum sharing or spectrum mobility. In this work, we argue that for certain network configurations, jointly performing...
Next generation wireless networks will be heterogeneous, where several primary users (PU e.g. licensed users) and secondary users (SU e.g. unlicensed users) can operate in the same dynamic and reconfigurable networks at a given time. The major challenge in this heterogeneous radio environment is to enable the coexistence between PU and SU which will further improve the efficient use of radio spectrum...
Femto-cells promise substantial gains in system spectral efficiency due to an enhanced reuse of radio resources. Femto-cells may be employed in a co-channel fashion such that the bandwidth used by the macro-cell is reused by the femto-cell. Femto-cells maintain an exclusive list of user equipments (UEs) that they serve. In this case, a foreign macro UE trapped inside a femto-cell experiences heavy...
Supporting secondary users through a collateral network dedicated to spectrum sensing has been recently proposed as a mean to overcome spectrum sensing limitations of secondary devices. Building on this idea, we propose a protocol for a Wireless Sensor Network (WSN) to support secondary devices of an Opportunistic Spectrum Access (OSA) network. We examine the fundamental tradeoff between the statistics...
In next generation broadband wireless networks, the orthogonal frequency division multiple access (OFDMA) technique provides a flexible physical interface for mobile users (MS) to share the radio resources. Since OFDMA allows MSs in different cells to reuse the same frequency subchannels to increase network spectrum utilization, MSs at the edge of a cell suffer from severe inter-cell interference...
Cognitive radio (CR) technology provides great flexibility in spectrum utilization with orthogonal frequency-division multiplexing (OFDM) as its candidate transmission technique. In this paper, we propose a simple spectrum shaping scheme for OFDM-based CRs to enhance spectral compactness and ensure bandwidth efficiency. By mapping antipodal symbol pairs onto adjacent subcarriers at the edges of the...
The microcellular system and distributed antenna system (DAS) are two promising systems to provide high data rate for future wireless communications, especially for the cell edge of the macrocell, because both systems can reduce the radio transmission distance. The cell edge spectrum efficiency is theoretically compared between the two systems in a network topology with seven macrocells, each of which...
The development of mobile communication services has lead to the increase the use of wireless spectrum. However, the persuasion of the overly crowded spectrum is not due to the scarcity of usable radio frequencies but to the current static spectrum management policy. This reveals many idle frequency bands in both time and space. The cognitive radio network (CRN) is a key solution to exploit the existing...
Spectrum sharing concepts have been widely employed in the design of practical systems with the aim to improve the utilization efficiency of the radio spectrum. Motivated by this, a comprehensive capacity study of spectrum sharing systems undergoing α-μ fading is performed in this paper. More specifically, assuming identical fading parameters, a closed-form expression for the delay-limited capacity...
This paper presents an ultra wideband (UWB) microwave sensor using a stepped-FM scheme. Impulse-radio UWB sensor requires high speed A/D in order to synchronize and detect the nanosecond pulse echo. Also it may be difficult to use the bandwidth wider than 500MHz without causing interference with other wireless systems. Our suggested scheme which does not require any high speed A/D devices can coexist...
Optimum channel/frequency allocation problem in a general mobile radio networks is well-known to be NP-complete. The optimum general solution for a mobile radio network for even 2-channel case is not known. In this paper, we focus on the case L=2k where L is the number of channels/frequencies and k is a positive integer. In order to minimize the sum of the network level interference, we show that...
In this paper, we consider a dynamic spectrum sharing system consisting of a primary user, whose licensed spectrum is allowed to be accessed by a secondary user as long as it does not violate the prescribed interference limit inflicted on the primary user. Assuming the Nakagami-m block-fading environment, we aim at maximizing the performance of secondary user's link in terms of average spectral efficiency...
In split spectrum macrocell-femtocell networks, certain portion of the available spectrum resources are dedicated to each tier in order to avoid interference problems among the tiers. In such a setting, effective partitioning of the spectrum resources carries critical importance for maximizing the total capacity and satisfying quality of service (QoS) requirements of the users within each tier. This...
The underutilization of spectrum coupled with developments in network technologies has prompted a number of proposals for managing spectrum. Dynamic spectrum access radio technology, which is based on cognitive radio technology, promises to increase spectrum sharing and thus overcome the lack of available spectrum for new communication services. In this paper, the pricing and the transmission power...
Dynamic transmission power based dynamic spectrum allocation (DSA) schemes are extensively adopted in cognitive ratio (CR) networks due to their flexible spectrum access strategies to improve spectrum utility. However such DSAs suffer from high sensitivity to the environment change. Based on the protocol model of wireless communications, a notion of interference threshold (IT) is introduced into the...
We investigate the dynamic connectivity of cognitive radio ad-hoc networks (secondary networks) coexisting with licensed networks (primary networks) that experience time-varying on-off links. It is shown that there exists a critical density λs* such that if the density of secondary networks is larger than λs*, the secondary network percolates at all time t >; 0, i.e., there exists always an infinite...
Global navigation satellite systems (GNSS) are highly susceptible to interference, due to their low signal power. This paper studies the impact of DVB-T on the GPS L1 and Galileo E1 frequency band. An analytical tool has been developed to evaluate the probability of detection in the presence of interference, taking into account the possible effects of fading on the GNSS signal. Further, the tracking...
Next generation wireless networks will be heterogeneous, where several primary users (PU e.g. licensed users) and secondary users (SU e.g. unlicensed users) can operate in the same dynamic and reconfigurable networks at a given time. The major challenge in this heterogeneous radio environment is to enable the coexistence between PU and SU which will further improve the efficient use of radio spectrum...
Recently, a new cognitive radio network architecture named after hierarchical spectrum sharing network (HSSN) is proposed to improve the utilization of the spectrum resource by taking the time and spatial dimensions of spectrum resource into account. For testing and verifying performance and reliability of algorithms and protocols for HSSN, evaluating HSSN network performance and the level of interference...
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