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Electromagnetic interference can degrade radio receiver severely. For this purpose, there is a need to monitor and quantify interference incidents in radio frequency bands. With this goal, a detection method is developed that is intended to be used in a portable detection system for interference detection in frequency bands, where radio transmissions are sporadically appearing. The method is used...
There are results of the experimental estimate of statistical characteristics of power, probability of observing the number and duration of radio interferences. The reviewed interferences were being received in urban areas from the narrowband radiation sources with near-omnidirectional antennas in the range of 433 MHz. There are six interference sources with a maximum power −38 dBmW in the range of...
Radio frequency interference in wireless networks affects data packets which are transmitted over WiFi networks and the data packets are lost due to poor signal strength during transmission. This study presents Access Point s' (APs') performance and analyse co-channel, adjacent channel interference of IEEE 802.11 operating at 2.4 Ghz and 5 Ghz frequency bands at the Namibia University of Science and...
In this paper, the problem of transmitting an analog Gaussian source over an additive white Gaussian noise (AWGN) channel in the presence of a Gaussian interference known only at the transmitter is investigated. Our goal is to estimate both the analog source and the channel state at the receiver simultaneously. In this work, we present different transmission schemes based on joint source-channel coding...
Contractive interference functions introduced by Feyzmahdavian et al. is the newest approach in the analysis and design of distributed power control laws. This approach can be extended to several cases of distributed power control. One of the distributed power control scenarios wherein the contractive interference functions have not been employed is the power control in MIMO systems. In this paper,...
In recent decades, due to limitation of radio spectrum and increasing users in wireless networks, spectral efficiency has been a considerable issue in literatures. In addition, energy consumption is rapidly increasing in wireless communications due to growing demand for wireless technologies especially cellular networks. Therefore, energy efficiency has become an important issue in such networks....
In this paper, we consider one of the main disadvantages of Ergodic Interference Alignment, i.e., delay. We propose two methods to solve the open problem of finding the best choice of user sets in order to minimize the delay. With these methods we are able to find the best JAP-B scheme which aims to trade off rate for delay in Ergodic Interference Alignment. First, we provide the solution based on...
This paper presents a cluster based resource allocation scheme for allocating physical resource blocks (PRBs) in downlink of OFDMA based cellular systems. The proposed scheme includes two phases of clustering and sum rate maximization. In the first phase users are clustered by using an interference graph in a way that users in each cluster are allocated the same PRB. This interference graph helps...
Multicell coordinated beamforming, where multiple base stations (BSs) collaborate with each other in the beam-vectors design to mitigate the intercell interference (ICI), has been a subject of great attention recently. With perfect channel information available at the base stations, we first present a fast converging algorithm that solves the weighted sum rate maximization (WSRM) problem. Then, the...
A multi-hop wireless transmission system employing both half duplex and imperfect full duplex relays is proposed. In this scheme, which uses Ksub-channels for transmission and reception over Rayleigh fading channels, we aim to mitigate the most dominant source of interference in each node by allocating different sub-channels to various groups of nodes. The outage probability of the proposed scheme...
In a multi-cell wireless network, users require to be properly assigned to base-stations. After assigning the base-stations to users, the power consumption and interference is controlled by means of a distributed power control algorithm. The power control and base station assignment is a challenging issue which should be jointly addressed. The conventional target-SINR tracking power control algorithm...
Device-to-device (D2D) communications as an underlay of a LTE-A (4G) network can reduce the traffic load as well as power consumption in cellular networks by way of utilizing peer-to-peer links for users in proximity of each other. This would enable other cellular users to increment their traffic, and the aggregate traffic for all users can be significantly increased without requiring additional spectrum...
We study joint routing, scheduling, and physical network coding (PNC) in fixed wireless multihop networks under a physical interference model. The objective is to quantify the throughput gain provided by PNC in wireless mesh networks. We formulate a cross-layer optimization framework to determine the optimal max-min throughput of the flows and the optimal configuration of the routing and scheduling...
We evaluate the outage probability of cognitive amplify-and-forward relay networks with cooperation between certain secondary users chosen by multi-relay selection based on the underlay approach, while adhering to the interference constraint on the primary user. A max-min strategy is employed to perform best relay or multi-relay, i.e. between two and four relays, selection. We obtain analytical expressions...
Long Term Evolution (LTE) is a standard for wireless communication of high speed data for mobile phones and data terminals. LTE is capable of delivering large data rate on the order of several megabits per second, which is even larger than the current 3G systems. This is very challenging as the wireless networks are subjected to interference, multipath and poor propagation channel characteristics...
Code-hopping multiple access (CHMA) has been an emerging multiple access technology designed to increase the number of users in Code-division multiple access (CDMA) systems. It was designed to overcome the limitations in the number of code word's required for communication in existing systems. However, it may experience degradation due to symbol perforation occurring due to code collisions when the...
A multi-reader system is presented which is capable of increasing the working range of passive RFID systems. This gain in range is obtained by using constructive superposition of the readers' RF waves. A coherent multi-reader demonstrator system has been designed that consists of two reader units and one central unit. The demonstrator system operates in the UHF band and allows for an arbitrary distributed...
We deal with the problem of frequency assignment in mobile and general radio networks, where the signal interferences are modeled using an interference graph G. Our approach uses graph theoretic and optimization techniques. The frequency assignment problem can be cast as a variant of the vertex coloring problem(called the T-colorings problem) on graphs. In this paper, we will show several previous...
Cognitive radio (CR) is a novel approach to improving the spectral efficiency of licensed radio frequency bands by opportunistically accessing unused portions of the band without introducing interference to a licensed user. To reliably identify unused portions in a dynamic environment, a collaborative spectrum sensing (CSS) approach is known to be advantageous. In this article we will consider a weighted...
In this paper, the problem of Downlink Multi-User MIMO (DL MU-MIMO) transmission from two interfering transmitters, each equipped with M antennas to multiple users each equipped with K antennas is considered. It is assumed that all users receive a single data stream of rank one from only one of the transmitters. A novel transmission/reception scheme is proposed based on the idea of Interference Alignment...
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