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Satellite selection is an important technology in Global Navigation Satellite Systems (GNSS), for which the dilution of precision (DOP) serves as the key performance metric. Selecting a satellites set with lower DOP often results more accurate positioning and timing. In this paper, the characteristics of DOP for dual-GNSS constellations is studied, where an uncertain clock offset is assumed between...
Massive Multi-input Multi-output (MIMO) technique shows great potentials in improving energy and spectral efficiency while suffers high costs of the requirement for large amount of radio frequency (RF) chains. In this paper, we develop an ${l_{1/2}}$-regularity based downlink transmit antenna selection scheme for massive MIMO systems with limited RF chains. With the objective to minimize the transmission...
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...
The emergence of Internet of Things (IoT), which connects billions of smart devices together wirelessly, has brought great pressure on capacity of current wireless networks. Fortunately, a new technology, three-dimension multiple-input multiple-output (3D-MIMO), with a large number of active antennas equipped in a 2D planar array, has been shown significant potential in improving system capacity....
Due to its high data rate support and other salient features, LTE-Advanced (LTE-A) has been chosen as a promising technology for Internet of Things with billions of devices being connected and managed. Sufficient frequency resource and appropriate interference coordination techniques are eagerly needed to accommodate the network requirements. In this paper, to deal with the inter-cell interference...
The amorphous cells have emerged as a new paradigm to meet the fast increasing wireless capacity and coverage demands. Compared with the traditional cellular networks with hexagon-based deployments, the amorphous cells support mobile base stations (MBS) to form dynamic cell topologies, which can adapt to the group-movement behaviors of network loads. These amorphous cells are required to be self-organized...
Nowadays, the Internet of Things (IoT) becomes a new technological marvel. However, its realization imposes a tremendous request on the capacity of the access network. In this paper, vertical sectorization which is recognized as a potential way to increase the capacity for cellular wireless communication systems is studied. Unlike the traditional method which uses two antenna arrays with different...
Energy detection based spectrum sensing, focusing on threshold design, is studied for cognitive radio networks in this paper. Our objective is to maximize the secondary user's throughput by dynamically controlling the energy detection threshold according to the instantaneous channel sate between secondary sender and receiver. An optimization problem is formulated and transformed to convex optimization...
Power allocation for the multiple-channel cognitive systems is studied in this paper. Our objective is to maximize the throughput of the cognitive link while providing delay guarantee for the secondary user. By using the effective capacity theory, the problem is modeled as effective capacity maximization problem with average power constraint, which turns out to be a constrained convex optimization...
A high-rate beamforming design is reported for amplify-and-forward wireless relay networks with simultaneous information and power transfer. To achieve high sum rate, a new relay beamformer is designed to support multi-pair source–destination communication links as well as an energy receiver simultaneously, instead of serving one information transmitter at a time. An energy-harvesting constrained...
In this study, the authors present a novel low backhaul load cooperative transmission framework for the two-cell multiple-input–single-output systems. In this framework, the neighbouring two base stations (BSs) take turns to transmit data in two consecutive slots. In each slot, only one BS is active, transmitting the preprocessed data symbols of both its own serving user and the cooperative user in...
We consider the uplink of a single-cell multiuser MIMO-OFDM system with MRC receiver and large antenna arrays at the base station. Assuming that the channels are perfectly estimated by the uplink pilots, we analyze the uplink spectral efficiency, taking the pilot overhead into consideration. The closed-form expression for the uplink spectral efficiency is derived and the optimal number of users in...
Physical (PHY) layer security has recently become a hot issue in wireless communication. In this paper, an approach to a generalized anti-eavesdropping space-time network coding (GAE-STNC) for cooperative communications is proposed to achieve the physical layer security and overcome the problem of imperfect synchronization while still guaranteeing full diversity. Based on the assumption of channel...
Adaptive codebook makes the codebook-based precoding vectors change adaptively with the channels by including the spatial covariance. However, the large intervals of the long-term (typically 20ms or even longer) feedback often incur a sharp performance loss in high-speed scenarios. In this paper, per-cell codebook design for separately quantizing local channel state information (CSI) and the dynamic...
Inter-cell interference is a serious problem in multicell OFDMA systems. In this paper, an iterative interference price based power allocation algorithm with inter-cell interference coordination is proposed for downlink multi-cell OFDMA systems. In the algorithm, each base station announces a price for interference and performs power allocation based on the price information received from other base...
Power minimization problem under minimum rate constraint for each user is studied in this paper for multiuser OFDM systems. By thoroughly analyzing the necessary conditions for the optimum solution of the resource allocation problem, we deduce a heuristic Lagrange relaxation (LR) based resource allocation algorithm. Different from existing LR schemes which obtain Lagrange multipliers through exhaustive...
In this paper, we consider asynchronous two-way wireless relay networks with amplify-and-forward protocol (AF- TWRN), where the distributed space-time code (DSTC) is utilized without synchronization among relays to assist the communication between two terminals. We analyze the pairwise error probability (PEP) behavior of DSTC for AF-TWRN under frequency-selective channels. From our analysis, it is...
In this paper, we study the asynchronous cooperative diversity schemes employing the amplify-and-forward (AF) protocols over the frequency-selective channel. We consider three time-division-multiple-access (TDMA) based cooperation protocols and derive the corresponding pairwise error probabilities (PEP). From our analysis, it is seen that of the paths from the source to relays and from relays to the...
In this paper, we design a new type of distributed space-time code (DSTC) for space-time cooperation scheme without the timing synchronization assumption. The construction of proposed DSTC is based on the construction of a special generator matrix. Both theoretical analysis and numerical results show that our DSTC can achieve full diversity for the asynchronous space-time cooperation.
In most cooperative communications works, perfect synchronization among relay nodes is assumed in order to achieve cooperative diversity. However, this assumption is not realistic due to the distributed nature of each relay node. In this paper, we propose a new distributed space-time coded transmission (DSTCT) scheme for asynchronous cooperative communications under frequency-selective channels. First,...
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