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This paper studies the impact of in-phase and quadrature imbalance (IQI) on the downlink of a single-cell multiuser multiple-input multiple-output (MU-MIMO) system with large antenna arrays. Moreover, we consider a time-division duplex (TDD) system where we assume uplink/downlink channel reciprocity in the downlink precoding design. We study the impact of uplink/downlink channel mismatch on the downlink...
In this paper, the problem of sequential beam construction and adaptive channel estimation based on reduced rank (RR) Kalman filtering for frequency-selective massive multiple-input multiple-output (MIMO) systems employing single-carrier (SC) in time division duplex (TDD) mode are considered. In two-stage beamforming, a new algorithm for statistical pre-beamformer design is proposed for spatially...
In the studies of 5th generation (5G) wireless communication systems, an alternative method to orthogonal frequency division multiplexing (OFDM) used for 4th generation (4G) systems is still being investigated. OFDM with offset quadrature amplitude modulation (OFDM/OQAM) is one of these alternatives. Due to the reasons such as absence of cyclic prefix (CP) in its structure and perfect separation between...
Time-shifted pilot scheme can efficiency combat pilot contamination. However, when the number of base station (BS) antennas is finite, the pilot interference due to the downlink transmission symbols cannot be mitigated in the time-shifted scheme. This paper proposed a novel two-stage channel estimation algorithm based on time-shifted pilot to reduce the effect of pilot interference. In the first stage,...
This paper investigates the joint design of pilot assignment and pilot contamination precoding (PCP) to combat pilot contamination in multi-cell multi-user massive MIMO systems. The system performance of the downlink transmission in massive MIMO with PCP is investigated and an optimization problem is formulated to find the best pilot assignment solution in PCP assisted massive MIMO systems that can...
This paper investigates the channel estimation error effects on the opportunistic relay selection strategy. The opportunistic relay selection strategy is based on selecting the maximum sum-rate of half/full-duplex relay terminal among N. The investigation considers a dual-hop multiple half/full-duplex bi-directional wireless relaying networks in the system model. According to Monte-Carlo simulation...
Vandermonde-subspace frequency division multiplexing (VFDM) is a newly-proposed spectrum sharing technology, where perfect channel state information (CSI) is required. In this paper, considering complex Gaussian distributed channel estimation error, we study the interference leakage from small cell (SC) to macro cell (MC) due to imperfect CSI. The probability density function (PDF) of the upper bound...
Multiple-input multiple-output (MIMO) multi-carrier code division multiple access (MC-CDMA) wireless systems are sensitive to multi-user interference (MUI), which increases with increase in the number of users. In order to study its effect, pilot based linear channel estimators are derived considering also the effect of MUI in frequency-selective MIMO MC-CDMA wireless systems. The proposed schemes...
This work addresses the problems of frequency synchronization and channel estimation for OFDM/OQAM systems in Rayleigh fading channel. A two-step preamble based approach using a new frame structure is proposed. The first step is coarse carrier frequency offset (CFO) estimation and the second step is joint fine CFO (FCFO) and channel estimation. We also propose a FCFO estimator under the assumption...
Performance of OFDM (Orthogonal Frequency Division Multiplexing) systems is limited by inter carrier interference (ICI) under high Doppler scenarios such as that encountered in high speed trains like TGV. The use of multiple receive antennas is known to be a very effective way to combat ICI. In a recent publication, the authors explored the use of transmit (Tx) antennas for ICI mitigation. It considered...
In this paper, the self-interference mitigation performance of in-band full-duplex multiple-input multiple-output (MIMO) nodes is considered in the context of models for realistic hardware characteristics in which antennas are reused to transmit and receive simultaneously. The use of MIMO indicates a self-interference channel with spatially diverse inputs and outputs. Consequently, there are both...
We design jamming resistant receivers to enhance the robustness of a massive MIMO uplink channel against jamming. In the pilot phase, we estimate not only the desired channel, but also the jamming channel by exploiting purposely unused pilot sequences. The jamming channel estimate is used to construct the linear receive filter to reduce impact that jamming has on the achievable rates. The performance...
This work considers the downlink of a multicell massive MIMO system in which L base stations (BSs) of N antennas each communicate with K single-antenna user equipments randomly positioned in the coverage area. Within this setting, we are interested in evaluating the sum rate of the system when MRT and RZF are employed under the assumption that each intracell link forms a MIMO Rician uncorrelated fading...
In massive multiple-input multiple-output (MIMO) systems, superimposed (SP) and time-multiplexed (TM) pilots exhibit a complementary behavior, with the former and latter schemes offering a higher throughput in high and low inter-cell interference scenarios, respectively. Based on this observation, in this paper, we propose an algorithm for partitioning users into two disjoint sets comprising users...
A cyclic prefix orthogonal frequency division multiplexing (CP-OFDM) system that transmits information over a time-varying fading channel is considered. In channels with large Doppler spreads, the frequency orthogonality assumption of OFDM is not valid. Hence, inter-carrier interference (ICI) is introduced, which leads to higher bit error rates (BERs). We propose a channel equalizer based on the BCJR...
The performance of multiuser multiple input multiple output (MIMO) downlink communication system is degraded under the assumption of rapid movement of user terminals with a certain speed. Though several methods have been proposed to improve this situation, they consume extra-degrees of freedom for the extension of the zero forcing (ZF) area and/or heavy computational load for the frequent update of...
The Cognitive Radio (CR) is an emerging technology for modern wireless communication system that offers a great solution to scarcity of radio spectrum. The Cognitive Radio Network (CRN) is an intelligent wireless communication organization that is aware of its environment. Here, heterogeneous nodes meet spectrum sensing challenges due to the variation of transmission power, spectrum allocation and...
Block by block differential encoding is proposed for two-way relay network using amplify and forward protocol at the relays. In order to achieve bandwidth efficiency the bits are mapped into 16-ary differential amplitude phase shift keying (DAPSK) symbols. Phase estimation and reference carrier estimation at the receiver is avoided by using this non-coherent detection technique. The symbols are mapped...
Next generation wireless promises high data rate using advanced MIMO techniques. Large-Scale antenna system, or massive MIMO, has been proposed as a strong candidate for broadband next generation wireless applications. However, pilot contamination is one of the major challenges that limits the promised massive gains. In this paper, a new pilot assignment procedure is proposed to mitigate the pilot...
Massive MIMO promises large spectral and power efficiency. However, pilot contamination, a well known challenge in massive MIMO, limits these aspired gains. In this paper, we propose a pilot hopping sequence along with a pilot reuse strategy for pilot decontamination. A simple hopping scheme is proposed and simulated in an uplink L-cells system where every user is assigned distinct pilot sequences...
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