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In this paper, a novel pilot extension scheme is proposed for massive MIMO uplink transmission, and its performance is evaluated analytically. Specifically, we divide the cell users into two groups, namely near users and far users, according to their distances to the service base stations. The far users are more motivated to mitigate the inter-cell interference than the near users at the price of...
In this paper, we propose two uplink pilot power control schemes to mitigate pilot contamination in a multi-cell massive multiple-input multiple-output (MIMO) system. These uplink pilot power control schemes can maximize the minimum signal-to-interference-plus-noise ratio (SINR) of the worst user or the mean SINR of the whole network for the downlink data transmission. Combinatorial optimization problems...
We consider wireless information and power transfer in a multi-user massive multiple-input multiple-output (MU-Massive-MIMO) system, where several distributed antenna sets, also denoted as remote radio heads (RRHs), are deployed, while the users can simultaneously perform information detection and energy harvesting. Assuming a large number of antennas and autonomous power allocation for the information...
In this work, we acknowledge the existence of the accumulation of the loopback self-interference when AF protocol is made used of in FDTW relaying and the channel estimation of the loopback channel is not done perfectly as will seen in the section to follow. The accumulation of the loopback self-interference comes from the functionality of FD antenna, which will bring back the transmitted signal to...
Superior spectral properties of Filter Bank Multi-Carrier (FBMC) techniques make them an interesting choice for future wireless systems. In order to directly apply well known pilot-symbol aided channel estimation in FBMC, however, the intrinsic imaginary interference has to be canceled. Such cancellation method is usually designed for a doubly-flat channel. In this paper, we investigate the effects...
In this paper, we analyze the performance of the fractional pilot reuse (FPR) scheme with pilot contamination mitigation in massive multiple-input multiple-output (MIMO) system. In FPR, users are classified into the cell- center and the cell-edge ones according to their signal-to- interference-plus-noise ratios (SINRs) at the receiver side. Then, the cell- edge users with low SINRs in different cells...
With the reuse of identical training sequences by users in different cells, massive MIMO is severely affected by pilot contamination due to residual error in channel estimation. In this paper, we consider the traditional structure of the training phase, where orthogonal pilot sequences are reused, and analyze a recently proposed group- blind detector in the uplink of an interference- limited network...
We propose a decentralized multi-cell aware opportunistic random access (MA-ORA) protocol that almost achieves the optimal throughput scaling in a K-cell random access network with one access point (AP) and N users in each cell. Under our MA-ORA protocol, users opportunistically transmit with a predefined physical layer data rate in a decentralized manner if the desired signal power to the serving...
This work1 analyzes the Generalized Degrees-of-Freedom (GDoF) of the 2-User Multiple-Input Single-Output (MISO) Broadcast Channel (BC) in the so-called Distributed CSIT regime, with application to decentralized wireless networks. This regime differs from the classical limited CSIT one in that the CSIT is not just noisy but also imperfectly shared across the transmitters (TXs). Hence, each TX precodes...
This paper characterizes the sources of distortion of offset-QAM based filter bank multicarrier systems when perfect channel state information at the receiver (CSIR) is not available. The statistical information of the distortion reveals that the mapping scheme, which determines how symbols are inserted in the frequency-time grid, can be optimized to reduce the impact of the estimation error. Moreover,...
Next generation (5G) mobile communication systems has a goal of ultra-high peak data rate. Ultra-Dense Network (UDN) is viewed as one of the key technologies to meet this challenge. The trend of network densification brings more complex interference. To solve this problem, a novel user-centric virtual cell design is proposed. Considering the changes of virtual cell load, we propose a load-aware virtual...
In this paper, we analyze the performance of multi-cell least-square (LS) channel estimation using pilot sequence hopping and pilot reuse strategy for pilot decontamination. We obtain achievable rates in uplink synchronous system in L-cell system using LS channel estimation and zero forcing (ZF) detection. Polynomial expansion approximation is performed to obtain a closed form bound of the asymptotic...
Superposed multicarrier transmission is a known method to improve frequency utilization efficiency when several wireless systems share the same spectrum. Obviously, an enhanced spectral efficiency comes at the expense of interference. To suppress the effect of interference, forward error correction (FEC) metric masking can be applied. In FEC, the corresponding log-likelihood (LLR) of the superposed...
Massive MIMO (multiple-input multiple-output) provides great improvements in spectral efficiency over legacy cellular networks, by coherent combining of the signals over a large antenna array and by spatial multiplexing of many users. Since its inception, the coherent interference caused by pilot contamination has been believed to be an impairment that does not vanish, even with an unlimited number...
Due to the difficulty of coordination in multi-cell random access, it is a practical challenge how to achieve the optimal throughput with decentralized transmission. In this paper, we propose a decentralized multi-cell aware opportunistic random access (MA-ORA) protocol that almost achieves the optimal throughput scaling in a multi-cell random access network with one access point (AP) and multiple...
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...
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...
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...
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