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Pilot contamination problem mainly comes from the linearity of channel estimation algorithms, e.g. zero forcing, and MMSE, which can be overcame by applying nonlinear channel estimation algorithms. Therefore, the alternating projection (AP) algorithm is back to our sights. Since an AP based channel estimation uses the unknown data symbols (blind) for channel estimation, the concern of pilot contamination...
The 2 user MIMO interference channel with arbitrary antenna configurations is studied under arbitrary levels of partial CSIT for each of the channels, to find the degrees of freedom (DoF) achievable by User 2 while User 1 achieves his full interference-free DoF. The goal is to gain new insights due to the inclusion of MIMO (multiple antennas at both transmitters and receivers) into the signal space...
In this work, we develop a new pilot-aided channel estimation for filter bank multi-carrier (FBMC) systems. The proposed method is different from previous approaches in the sense that it uses the intrinsic interference rather than cancelling it. By doing so, we can obtain a virtual power boosting effect without increasing power budget. The estimation, detection, and peak-to-average power ratio (PAPR)...
When the femtocell base station has perfect channel state information, it can adopt beamforming to avoid interference. However, the perfect channel assumption may not be practicable due to the channel-state information delay, channel estimator error, and bandwidth wastage while reporting channel parameters. In this paper, we proposed an angle of arrival (AOA) based beamforming structure for orthogonal...
This paper aims to minimize the total transmit power consumption for Massive MIMO (multiple-input multiple-output) downlink cellular systems when each user is served by the optimized subset of the base stations (BSs). We derive a lower bound on the ergodic spectral efficiency (SE) for Rayleigh fading channels and maximum ratio transmission (MRT) when the BSs cooperate using non-coherent joint transmission...
While massive MIMO based underlay cognitive radio (CR) networks are a promising concept in the next generation of wireless networks to increase spectral efficiency, reusing the same pilot sequences in both networks cause pilot contamination leading to residual interference. Thus, this paper investigates the affects of pilot contamination on a random CR network underlaid upon a random primary network...
This paper provides indications and simulative performance evaluations of how a wireless system can profit from being able to support various subcarrier spacings concurrently. We show that with using this degree of freedom high Doppler, low latency and extended coverage scenarios are improved. In our investigations we consider different options for multi-carrier numerology, frame design and pilot...
Massive MIMO is an energy efficient technique which utilizes frequency spectrum efficiently and provides secure and sturdy system. Therefore it is going to be backbone of future broadband network. Multi-cell Massive MIMO system reused orthogonal pilot sequence which results in pilot contamination. Pilot contamination causes poor channel estimation at the BS and degrades the performance of the system...
In this paper, the parameters estimation for the interference rejection combining (IRC) technique with the inter-cell interference (ICI) and narrowband interference (NBI) in single-carrier frequency-division multiple access (SC-FDMA) systems is considered. Due to the characteristics of the interferences in uplink SC-FDMA systems is quite different from that in downlink orthogonal frequency-division...
In this paper, we propose an efficient data exchange mechanism with a dedicated detection approach for Device-to-Device (D2D) communications. By involving in a third device as Relay Node (RN), both devices of interest can communicate with each other. Within an inband relay mode, Interleave Division Multiple Access (IDMA) is exploited to enable the third device to detect and decode the data of both...
In massive multiple-input multiple-output (MIMO) system with time-shifted pilots, the interference from other cell groups, where the pilots are staggered with the ones in the target cell group, can be eliminated when the number of antennas at base station (BS) is infinite. However, with only hundreds of antennas at the BS in practice, both intra-group interference and inter-group interference can...
Massive MIMO is a promising technology for 5G. While its advantages of increasing capacity and reducing output power are clear, understanding its SNR requirements in practical cases lacks sufficient theoretical support. This paper computes the relative power levels of the different signal, interference and noise terms in a Massive MIMO system using Maximum-Ratio Transmission (MRT). This brings light...
This paper presents a high-level overview of the Fundamental Limits studies for the DARPA SSPARC program. It focuses on the key techniques and insights that have resulted from this effort and presents possible future research directions that have been suggested by these studies1.
We propose a pilot decontamination method for noncooperative cellular massive MIMO systems using pilot and data alignment in the time-frequency plane. In this method, pilot and data channels are assigned such that the terminals in any two adjacent cells operate over non-overlapping pilot channels but the terminals may share data channels. The former condition is imposed to circumvent pilot contamination...
A heterogeneous system of a Massive multiple- input-multiple-output (MIMO) macro cell with low power ancillary small cells can achieve higher spectral and energy efficiency than a Massive MIMO macro cell alone. The performance of such heterogeneous system is examined in this paper. A few small cells are used to enhance the spectral and energy efficiency of the overall system. Macro Massive MIMO base...
Although the technical merits of the heterogeneous cloud radio access networks (H-CRAN) architecture have been well demonstrated in terms of data rate enhancement and ubiquitous wireless service provisioning, solely relying on the H-CRAN may not be sufficient to further support full automation and everything-to-everything (X2X) connection for the next generation wireless applications. Recently, the...
LTE is designed to support user velocities of up to 500 km/h where experiments are expensive, time-consuming and dangerous. Fortunately, such experiments can be emulated at lower velocities by time-stretching the transmit signals. This method preserves the spatial properties of the mobile radio channel but performs a spectral compression. In this paper, we propose a new set of methods that preserve...
This paper presents a cooperative multiple-input multiple-output (MIMO) scheme for a wireless sensor network consisting of inexpensive nodes, organised in clusters and transmitting data towards sinks. The transmission is affected by hardware imperfections, imperfect synchronisation, data correlation among nodes of the same cluster, channel estimation errors and interference among nodes of different...
Full duplex transmission is envisioned as one of the potential breakthrough for a Generation (5G) radio access technology. In this paper, we evaluate the performance of full duplex transmission in a network of dense small cells by using real channel measurements. A large measurement campaign is carried out in an indoor office and an open hall scenario, and such measurements are then fed to...
In this paper we investigate the physical layer security for downlink MU-MIMO systems where the transmitter and the eavesdropper are equipped with multiple antennas, while the legitimate users have single antenna. This is a more challenging topic because the eavesdropper appears to be more powerful than the legitimate users. We propose a transmission scheme able to enhance secure transmission for...
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