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An approach to deal with the demand for increasing bandwidth and data rates from the network is to deploy an ultra-high density access network consisting of a large number of very small cells. In such a wireless network, reducing interference will contribute to meeting the targeted very-high bitrates and low latency. In this study, we evaluated the signal-to-interference ratio in an ultra-high density...
In this paper we consider transmit beamforming schemes for downlink control channel. In particular, we propose exploiting information on user location for selecting both the serving transmission/reception point (TRP) and transmit beam used for control channel transmissions. Moreover, a suppressed zero-forcing (SZF) scheme based on vertically and horizontally polarized transmit beams is proposed with...
Inbound handover (HO) or hand-in is accomplished when the user equipment (UE) performs HO from macrocell (MC) to a small cell (SC) [1] [2]. When the UE connects to a SC with a time of stay (ToS) less than a predefined time threshold, this will result in frequent unnecessary HOs and also increase service interruption which in turn will degrade the end user quality of service (QoS). In this paper, we...
A scenario consisting of several cells is considered where each cell contains a multiple-antenna enhanced remote radio head (eRRH) and several single-antenna mobile stations (MSs). All eRRHs can access the cloud with limited capacity fronthaul links. The beamforming problem aiming at maximizing the sum rate with per eRRH power constraint is considered. In this paper, a hierarchical one-shot top-down...
Our work focuses on the per user distribution of achievable rate in a cellular environment. The system considered in this work consists of clustered base stations which systematize downlink transmission. Implementation of Block Diagonalization is carried outxwithinxthe clusterxfor the removal of interference within the users. The achievable ratexperxuser has a probability distributions which superlatively...
In this paper, minimum MSE based interference alignment (IA) algorithm is developed for the interfering broadcast channel (IBC), which models the multi-cell downlink system, underlying cognitive radio, device-to-device and other scenarios. The IA precoders and decoders are computed to minimize the MSE. Cascade design is used for IA precoder design, where the first component precoder is obtained by...
In this work, decentralized coordinated scheduling in LTE-Advanced downlink networks is studied, where the base stations abstain from transmitting data on particular frequency/time resources in order to reduce the inter-cell interference experienced by users connected to neighboring base stations. The proposed decentralized scheme is derived with regard to low information exchange between the base...
This paper considers a multiuser system with one full-duplex (FD) base station (BS) serving a set of half duplex (HD) mobile users. Due to the self-interference and co-channel interference from the uplink users to the downlink users, the transmissions of the BS and uplink users have to jointly designed. In this paper, we consider such a joint design problem for maximizing the max-min-fairness (MMF)...
A secrecy transmission method with robust power control is investigated in this paper for a downlink two-tier femtocell network, where an eavesdropper attempts to wiretap the legitimate macrocell users. Considering the imperfect channel gains, a probability constraint robust optimization problem is formulated to satisfy the quality-of-service (QoS) of users. We aim to maximize the secrecy rate with...
User fairness and spectrum efficiency are conflicting objectives in cellular system optimization given that users share limited spectrum resources. Users at the cell edge are more likely to be unfairly treated due to their disadvantageous locations, where they experience high path losses and strong interferences if co-channel transmission exists. In this paper, a cell edge boundary is obtained and...
Deployment of femtocell in macrocell cellular network which forms two-tier femtocell-macrocell cellular network faces more complicated interference problems, since it uses the same licensed frequency spectrum as its macrocell. This paper addresses the interference problems for downlink transmission in such two-tier cellular communication network. In this paper, interference management using power...
This work investigates the downlink resource allocation (RA) problem in orthogonal frequency division multiplexing (OFDM)-based cognitive radio networks. The objective of this work is to develop a fair RA-algorithm that maximizes the capacity of secondary users (SUs) and in the same time limits the interference caused to the primary users. The fairness condition is formulated as a minimal data condition...
In this paper, we propose two practical and economic beamforming design methods under consideration of an effective acquisition mechanism of partial channel state information at transmitter (CSIT) for frequency-division duplex (FDD) massive MIMO systems. In contrast to previous beamforming designs with total power constraint, per-antenna power constraints are considered in this paper because of the...
In a conventional cellular wireless networks, single cell processing (SCP) is usually considered where inter-cell interference is treated as noise. As we know, interference can cause severe information leakage for secret communication, the paper studies the secrecy performance with coordination beamforming (CBf) scheme in the downlink of a two-cell multi-user MIMO (MU-MIMO) cellular network. For CBf,...
Heterogeneity and convergence are two distinctive features for new generation networks like the Long Term Evolution-Advanced (LTE-A) system. LTE-A is now being deployed and is the way forward for high speed cellular services. LTE-A enhancements the four areas of capacity, coverage, inter-cells coordination, and cost. Improvements in these areas are based on using several technologies. Multiple-Input...
In this paper, we consider the energy efficiency maximization problem in downlink multi-input multi-output (MIMO) multi-cell systems, where all users suffer from inter-cell interference. To solve this optimization problem with a nonconcave objective function and a complex-valued matrix variable, we extend the recently developed successive pseudo-convex approximation framework and propose a novel iterative...
Smartphones and other devices connected to a mobile network typically create billions of measurement samples every day. Those measurements are currently used for instantaneous resource allocation and link adaptation. There is much room for using the measurements also for network optimization with big data analytics. The measurements give valuable insight into the service quality experienced by devices...
In this paper, we describe CoMP2flex, a user-centric base station (BS) cooperation scheme that provides improvements in reliability of both uplink (UL) and downlink (DL) communications of wireless cellular networks. CoMP2flex supports not only cooperation of two BSs with same direction of traffic but also cooperation of two BSs serving bidirectional traffic. The reliability performance of CoMP2flex...
Sparse code multiple access system with multiple antennas offers unprecedented massive connectivity and capacity. To reduce the interference in a downlink multiple user SCMA (MU-SCMA) system, we propose a layer-aware interference mitigation scheme (L-AIMS). Firstly, preprocess the codewords of paired users to mitigate the intra-layer interference. Secondly, adopt the generalized singular value decomposition...
In 3GPP Rel-13, a narrowband wide-area cellular system, named Narrowband Internet of Things (NB-IoT), has been introduced to provide low-cost, low-power connectivity for the Internet of Things. This system, based on Long Term Evolution (LTE) technology, can be deployed in three operation modes - in-band within LTE carrier, in the guard-band of LTE carrier, and stand-alone. Guard-band deployment allows...
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