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In Cognitive Radio Networks (CRNs), when the Primary Users (PUs) appear, the SUs have to evacuate the licensed spectrum in use or reduce the transmit power so that no harmful interference is introduced to the PUs. In this paper, we explore the multiple Secondary Users (SUs) coexistence system in CRNs based on power control mechanism and interference temperature model. We propose an optimal solution...
This paper presents the performance analysis of a realistic Smart Utility Network (SUN) system with low duty signaling design. The main focus of this paper is to evaluate the performance of the SUN system based on the specifications in an on-going industrial standardization activity, the IEEE 802.15.4g. For this purpose, a theoretical framework is constructed to model the transceiver with low duty...
Cognitive radio networks are receiving a lot of research attention lately. Most user equipment in state-of-the-art wireless communication systems are equipped with two antennas. In this paper, we take advantage of the two transmit antennas in an underlay cognitive radio network scenario. Secondary users use the two transmit antennas in order to insert a null in the direction of the primary base station,...
The increasing density and data rate of unlicensed band wireless devices in small office and home (SOHO) environments has led to significant inter- and intra-radio interference problems. Multiple competing standards such as the IEEE 802.11b/g, Bluetooth and ZigBee, all of which operate in the 2.4 GHz ISM band, can interfere with each other when used in typical indoor environments, potentially causing...
An interference management method for coordinating downlink transmission in a Multiple-Input Multiple-Output (MIMO) cellular network is proposed. The problem is to efficiently manage inter-cell interference in a multi-cell environment, by so-called transmitter cooperation, in order to reduce the diminishing effects of interference on the networks performance. To allow for application in deployable...
Cognitive radios share the whitespace in the absence of licensed users. For spectrum sharing, avoiding the interference among multiple secondary users is a fundamental problem (known as dynamic spectrum allocation problem). This paper proposes a factor graph based approach to solve the dynamic spectrum allocation problem in an efficient manner. With the proposed DWA-Tree (Distributed Wave Algorithm),...
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,...
This paper presents a respiratory rate monitoring sensor using stepped-FM ultra-wideband impulse-radio (UWB-IR), which does not require high speed A/D devices unlike conventional UWB-IR sensors. This sensor is also capable of co-existing with other narrowband systems operating in overlaid frequency band, since it can be designed to have any spectrum hole without causing interference with other wireless...
A novel design of micostrip bandstop filter (BSF) based on branch-line coupler structure is presented. The present BSF is obtained by modifying the branch-line coupler with open-circuits at the coupled and isolated ports. The usefulness of the present topology is demonstrated by comparing the filter performances with a standard two transmission line (TTL) signal interference BSF of same total electrical...
In this paper, a module has been presented which can perform a seamless interoperation between Bluetooth and Wi-Fi interfaces. The work is really challenging to achieve as both the interfaces work in the frequency band of 2.4 GHz creating a high possibility of interference. The challenge of implementing such an interoperable application atop OSGi framework has been discussed in this paper as well...
We consider the use of Blind Interference Alignment (BIA) in a cellular environment as a means for supporting downlink Multi-User MIMO (MU-MIMO) transmission without the need for channel state information at the transmitter (CSIT). This “CSIT-blind” characteristic of BIA is of particular interest for Frequency Division Duplex (FDD) systems, since it allows one to eliminate overheads and impairments...
In this paper we propose a power control policy over an imperfect fading channel within a cognitive spectrum sharing area. In particular, our proposed scheme maximizes the secondary user effective capacity subject to the average interference power and the secondary user transmit power constraints. We also investigate the minimization of average interference power at the Primary Receiver (PR) under...
Power conservation for maximizing the lifetime of the limited battery powered ad hoc networks are one of the most important factors in a network design. Transmitting at high power may assure network connectivity but sacrifice network lifetime and increases the interference as well. Meanwhile transmitting at lower power reduces the interference on the expense on network robustness. We investigate the...
We consider smart “cognitive” femtocells, that can decode the base station control channel and make decision on their transmission opportunities based on the scheduling and resource allocation of the overlaying macrocell. The operation of such femtocells is somehow reminiscent of “Type II” relays, as specified in the IEEE 802.16j standard. Under certain system assumptions, we consider the tradeoff...
The law of the time to transmit a packet from a node to its intended receiver, in a wireless network with randomly deployed, multiple-antennas equipped nodes, whose communication is impaired by fading and interference, is investigated. SINR-based coverage at the physical layer is assumed, and the useful signal strength is shaped through either cooperative or non-cooperative beamforming. In particular,...
We develop a tractable, flexible, and accurate model for downlink heterogeneous cellular networks. It consists of K tiers of randomly-located base stations (BSs), where each tier may differ in terms of the average transmit power, the supported data rate and the BS density. This allows elements spanning traditional, micro, pico, and femtocell BSs to be simultaneously considered. Assuming a mobile user...
In this paper, we propose a precoding algorithm called flexible coordinated beamforming for the MIMO interference relay channel (IRC-FlexCoBF), where two base stations equipped with multiple antennas transmit to two user terminals simultaneously with the assistance of an amplify-and-forward relay that also has multiple antennas. The case of multiple data stream transmission is considered. The relay...
The degrees of freedom of a cellular system in a fading environment are determined. An arbitrary number of base stations with multiple antennas and an arbitrary, but similar per cell, number of users with multiple antennas is considered. Two distributed algorithms which possibly achieve interference alignment are presented. Simulations show that the proposed algorithms achieve the optimal degrees...
We consider the 3-user Gaussian interference channel and provide an outer bound on its capacity region. Under some conditions, which we call the mixed strong-very strong interference conditions, this outer bound is achievable. These conditions correspond to the case where at each receiver, one transmitter is causing strong interference and the other is causing very strong interference. Therefore,...
In the K-user single-input single-output (SISO) frequency-selective fading interference channel, it is shown that the maximal achievable multiplexing gain is almost surely K/2 by using interference alignment (IA). However, when the signaling dimensions are limited, allocating all the resources to all users simultaneously is not optimal. So, a group based interference alignment (GIA) scheme is proposed,...
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