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In this paper, the application of non-orthogonal multiple access (NOMA) into $K$-tier heterogeneous networks (HetNets) is investigated. A new promising transmission framework is proposed, in which massive multiple-input multiple-output (MIMO) is employed in macro cells and NOMA is adopted in small cells. For maximizing the biased average received power at mobile users, a massive MIMO and NOMA based...
In this paper, we propose a novel iterative algorithm based on successive convex approximation for the nonconvex energy efficiency optimization problem in massive MIMO networks. The stationary points of the original problem are found by solving a sequence of successively refined approximate problems, and the proposed algorithm has the following advantages: 1) fast convergence as the structure of the...
Caching is an effective technique to improve user perceived experience for massive content delivery in wireless networks. An essential problem in cache-aided wireless networks is to find what and how much gain can be achieved by caching. This paper provides a study of the fundamental storage- latency tradeoff for a cache-aided MIMO interference network with 3 transmitters and 3 receivers and each...
We propose a novel model for the NLOS interference power distribution in a cellular system employing MIMO beamforming transmission in mmWave spectrum. The proposed model is a mixture of the Inverse Gaussian and the Inverse Weibull distributions, both are two-parameter medium-to-heavy tail distributions. To estimate the parameters of the mixture model, we design an expectation maximization algorithm...
We propose a novel algorithm to design user load- achieving pilot sequences that mitigate pilot contamination in multi-cell massive multiple-input multiple-output (MIMO) networks. To this end, we first derive expressions for the user load and the load region of the network considering both small- scale and large-scale propagation effects. We then develop the pilot sequence algorithm for multi- cell...
Under the conditions where performance in a massive MIMO network is limited by pilot contamination, the uplink signal-to-interference ratio (SIR) exhibits different distributions when using different pilot allocation schemes. By utilising different sets of orthogonal pilot sequences, as opposed to reused sequences amongst adjacent cells, the resulting SIR distribution is more favourable with respect...
This paper studies the deployment of multiple- input multiple-output (MIMO) full-duplex (FD) relaying systems in a multi-cell environment, where a multi-antenna amplify-and-forward (AF) FD relay station serves multiple half-duplex (HD) multi-antenna users. The fundamental challenges of loopback self-interference (LI) and multiple co-channel interferers (CCI) at the relay and destination when incorporating...
In this paper, we consider a heterogeneous network in which a macro-cell tier is overlaid with a very dense tier of small cells. The macro-cell base station (BS) that applies a massive MIMO scheme not only serves the macro user equipment but also provides a wireless backhual for small-cell access points (APs). These APs serve their associated small-cell user equipment. A reverse time division duplex...
The maximal ratio combining (MRC) receiver has excellent performance in the uplink of massive multiple-input-multiple-output (MIMO) systems under favorable propagation, but the performance degrades very much in a harsh channel because of interference. Theoretical analysis showing this phenomenon is given for a particular class of fading channel. A novel receiver, exploiting preemphasis/deemphasis...
This paper considers a robust precoder design for MIMO-OFDM systems with insufficient cyclic prefix (CP). Interference alignment is utilized to formulate the precoder design problem as a bit error rate (BER) minimization problem subject to a total power constraint. To this end, the precoder is designed to be robust to the errors in the available channel estimates, by considering the worst-case BER...
In this paper, we look into the issue of intra-cell uplink (UL) pilot orthogonalization and schemes for mitigating the inter-cell pilot contamination with a realistic massive multi-input multi-output (MIMO) orthogonal frequency-division multiplexing (OFDM) system model. First, we show how to align the power-delay profiles (PDP) of different users served by one BS so that the pilots sent within one...
In traditional cellular networks, cell edge users suffer from severe interference. This paper considers a cell free network scenario that multiple base stations (BSs) serve a group of users without cell boundary. Each user can only be served by its own BS according to the traditional cellular network paradigm, while in the user centric cell free network, users can be associated with multiple nearby...
Superposed transmission on the broadcast channel delivers multiple private messages simultaneously to the intended users. Superposed transmission is employed in non-orthogonal multiple access to increase the aggregate throughput and connectivity of wireless cellular systems. Rate-adaptive constellation Expansion Multiple Access (REMA, a.k.a. RA-CEMA) is a non-orthogonal multiple access scheme which...
We consider training-based channel estimation for cloud radio access networks (CRANs), in which a large amount of remote radio heads (RRHs) and users are randomly scattered over a certain service area. In this model, assigning orthogonal training sequences to all users, if possible, will cause a substantial overhead to the overall network. Instead, we introduce the notion of local orthogonality, in...
Massive multiple-input multiple-output (MIMO) is one of the promising technologies to be used in the future fifth generation (5G) wireless networks for its capability to increase the system throughput, improve spectral efficiency and energy efficiency. To achieve these benefits of the massive MIMO, there are many challenges that need to be handled. One of these challenges is the pilot contamination...
This paper proposes a novel multi-user multiple-input and multiple-output (MU-MIMO) selection and beamforming technique for a geosynchronous orbit (GSO) satellite communication (SATCOM) system. The MU-MIMO technique employs beam-forming and adaptive power allocation schemes in order to support a large numbers of users. Additionally, this paper provides a solution for the scenario where satellite ground...
The paper provides the optimal power allocation in two-tier multi-antenna cognitive femtocell radio networks. The multiple antennas are used to serve a dual objective: avoid the interference and enhance throughput via multi-input multi-output (MIMO) transmission towards the receivers. A method is presented in order to achieve the optimal power allocation for the femtocell base station (FBS). The simulation...
Establishing the fairness is an important issue in communication networks. CSMA/CA used in IEEE 802.11 standard is well known for unfair behavior towards distant nodes. In this paper, first, we present a multi-user multiple input multiple output (MU-MIMO) MAC protocol for the uplink of a network and propose a modified version with better fairness performance. Then, we evaluate the performance of our...
In this paper1 we consider the Network MIMO channel under the so-called Distributed Channel State Information at the Transmitters (D-CSIT) configuration where the precoder is designed in a distributed manner at each Transmitter (TX) on the basis of local versions of Channel State information (CSI) of various quality. In that setting, a novel transmission scheme has been developed in [1] and surprisingly...
Today's wireless environment is very dense to support enhanced performance, which is become heterogeneous in cell, applications, services, standards and technologies. This dense deployment of heterogeneous cells has a large impact on the power consumption of network. Thus, issue of energy efficiency need to be considered in perspective of deploy of several base station (BS) in the area. In 5G standard,...
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