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Massive MIMO systems, where base stations are equipped with hundreds of antennas, are an attractive way to handle the rapid growth of data traffic. As the number of users increases, the initial access and handover in contemporary networks will be flooded by user collisions. In this work, we propose a random access procedure that resolves collisions and also performs timing, channel, and power estimation...
Device-to-device (D2D) communication is one of the most promising solutions to the dramatic increase of wireless networks traffic load. In D2D communications, mobile nodes can communicate in a semi-autonomous way, with minimal or no control by the base station (BS). In this context, we address the problem of the coexistence of cellular and D2D tiers in the uplink frequencies, where a D2D source is...
Computation offloading manages resource-intensive and interactive applications on mobile devices where much processing is replicated with multiple users in the same environment. In this paper, we consider the scenario where duplicated computation tasks are processed on specific mobile users and computation results are shared through Device-to-Device (D2D) multicast channel. Our goal is to find an...
Efficient transmission power control is indispensable for cellular networks. It not only provides a high energy efficiency, but also maintains reliable connections. With the emergence of 5G mobile technology, the presence of device-to-device (D2D) communications within the cellular network has stimulated research on radio resource sharing. In this paper, we consider an underlay D2D network operating...
Hardware calibration is a necessary procedure to establish the reciprocity of the uplink (UL) and downlink channels (DL) in a time division duplex (TDD) mode of operation. In practice, any calibration scheme is prone to errors. Such errors result in a residual mismatch between UL and DL channels, which, in turn, can significantly affect the quality of DL transmission. In this paper, we study the effects...
This paper investigates the performance of bidirectional dynamic networks (BDN) with massive multiple input multiple output (MIMO) systems. In BDN, dynamic allocation of the number of uplink and downlink remote radio heads (RRHs) is proposed, which offers a flexible solution to balance the data traffic asymmetry without requiring the time synchronization. Intuitively, the interference between the...
The idea of combining spatial modulation (SM) with massive multiple-input multiple-output (MIMO) system, i.e. massive SM-MIMO, has recently attracted plenty of academic interest, as it could simultaneously harness the advantages of SM and massive MIMO. However, the spectral efficiency (SE) analysis for massive SM-MIMO is still lack of exploring. To this end, a novel SE expression is derived in this...
In Uplink Coordinated multipoint (Uplink CoMP) schemes as in LTE [1], multiple base-stations (EnodeBs) receive signals from the same user equipment (UE). Combining this information appropriately using the backhaul is known to yield high gains, especially when the interference avoidance is used across the EnodeBs in CoMP. We consider a load-balanced, dense, small-cell deployment where a UE may be connected...
Device-to-Device (D2D) communications are considered as one of the key technologies for 5G wireless communication systems. In this paper, a frequency reuse scheme, in which multiple D2D links share spectrum resources with multiple cellular links simultaneously, is studied. Two novel concepts are introduced, namely the D2D pool and the cellular pool. D2D links in the D2D pool reuse uplink resource...
In this paper, we present a stochastic geometry based framework to analyze the coverage probability and ergodic rate with different channel allocations for device-to-device (D2D) communications. Different from existing works, we assume there are two different kinds of users, cellular users and D2D users, in the muti-channel uplink cellular network. Specifically, cellular users can upload data to the...
Device-to-device (D2D) enabled cloud radio access networks (C-RANs) are potential solutions for further improving spectral efficiency (SE) and decreasing latency by allowing direct communication between two user equipments. Due to the acquirement of global channel state information (CSI) and the execution of centralized algorithms in the uplink D2D enabled C- RANs, heavy burdens are put on fronthaul...
In this paper, we consider device-to-device (D2D) communication underlaying cellular networks, where D2D users harvest radio frequency (RF) power from uplink cellular transmissions. This paper addresses two important issues for energy harvesting-based D2D cellular networks. The first is how the energy harvested from cellular ambient RF signals affects the D2D spectral efficiency. Using tools from...
This paper considers training-based transmissions in massive multi-input multi-output (MIMO) systems with one-bit analog-to-digital converters (ADCs). We assume that each coherent transmission block consists of a pilot training stage and a data transmission stage. The base station (BS) first employs the linear minimum mean-square-error (LMMSE) method to estimate the channel and then uses the maximum-ratio...
We develop a novel opportunistic beamforming scheme referred to as doubly opportunistic beamforming (DOBF), which is doubly selective in both users and beams. The sum-rate performance of the proposed scheme is investigated in less-known finite networks where the number of transmit antennas and the number of active users are finite and of the same order of magnitude in the bursty traffic model. We...
This paper presents a theoretical model for estimating the uplink capacity of a communication in a threedimensional(3D) millimeter-wave (mmWave) scenario. The model is developed considering realistic channel conditions, including path-loss attenuation, shadowing, and angular dispersion, which comply with recent measurement campaigns carried out in mmWave environment. The analysis also incorporates...
In this paper, we investigate the user pairing scheme in virtual multiple-input multiple-output (V- MIMO) systems, which can significantly improve system performance and spectral efficiency (SE) using multiuser diversity. Considering the development of green communication, we want to find the upper bound of energy efficiency (EE) under the constraint of SE. Firstly, the optimal transmit power allocation...
This paper investigates secrecy and connection performance for uplink transmission in a two-tier heterogeneous network with non-uniformly deployed low- power small base stations (BSs). All BSs and the eavesdropper are equipped with multiple antennas. We propose an aggregate interference approximation approach to characterize the statistics of interference generated by users associated with small BSs...
Non-orthogonal multiple access (NOMA) is a promising multiple access technique for future wireless communications as it results in high spectral efficiency. NOMA differs from recently adopted orthogonal multiple access techniques in that it superimposes multiple data flows at the same time and same frequency band but with different power levels, and resorts to the successive interference cancellation...
This paper presents the performance analysis of the self-interference cancellation (SIC) methods in full-duplex large-scale multiple-input multiple-output systems. To mitigate self-interference (SI), we assume that the full duplex-base station (BS) uses SI-subtraction or spatial suppression. Analytical and numerical results confirm that the SI-subtraction outperforms the spatial suppression for SIC...
The rapid development of the Internet of Things (IoT) has brought big challenges to the traditional cellular networks such as super dense devices and deep fading channels. These new challenges will lead to a significant transmission efficiency degradation and increase the device's power consumption, especially in the uplink. A huge pressure will be also imposed to the enhanced Node B's (eNB) scheduler...
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