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In this paper we consider a constant envelope pilot signal based carrier frequency offset (CFO) estimation in massive multiple-input multiple-output (MIMO) systems. The proposed algorithm performs spatial averaging on the periodogram of the received pilots across the base station (BS) antennas. Our study reveals that the proposed algorithm has complexity only linear in (the number of BS antennas)...
Delay-tolerant sensor networks (DTSNs) require efficient MAC transmission strategies that include energy constraint, relaxed latency, mobility support and diverse traffic load. Reservation-based and contention-based MAC schemes are used to improve throughput and energy consumption. In this paper, we propose a traffic adaptive, energy-efficient MAC protocol to achieve better data transmissions and...
We present a multi-user multiple-input multiple-output (MIMO) cognitive radio system consisting of a secondary receiver that deploys spatial multiplexing to decode signals from multiple secondary transmitters, under the presence of primary transmissions. The secondary receiver carries out minimum mean-squared error detection to decode the secondary data streams, while it performs spectrum sensing...
Maximizing the lifetime is an important issue in the design of applications and protocols for wireless sensor networks (WSNs). Clustering sensor nodes is an effective topology control approach helping achieve this goal. In this paper, we present an energy efficiency protocol to prolong the network lifetime based on an improved particle swarm optimization (PSO) algorithm. The protocol takes both energy...
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...
Peer-to-peer (P2P) cache techniques for information-centric networks (ICN) provide the local data resources services for mobile users by storing the popular data contents in their peer mobile users' cache stations, so that a mobile user can obtain these data contents directly from its peer mobile users instead of the remote service provider. Retrieving the requested data content from the nearby storage...
In this paper, we introduce a new model for RF-powered cognitive radio networks with the aim to improve the performance for secondary systems. In our proposed model, when the primary channel is busy, the secondary transmitter is able either to backscatter the primary signals to transmit data to the secondary receiver or to harvest RF energy from the channel. The harvested energy then will be used...
The visible light communication (VLC) technology is able to provide indoor users with high quality of service and low cost. However, the performance of the VLC is limited in shaded or strong sun- light areas. In this paper, we combine the VLC network with Device-to-Device (D2D) technology. We consider that some mobile users accessible to the VLC network is able to relay the transmitted data to the...
In this paper, we investigate the problem of jammer selection for securing Cooperative Cognitive Radio Networks (CCRNs) with the Multiple-Input Multiple- Output (MIMO) capability. In the CCRN under our consideration, there exist a pair of Primary Users (PUs), a relay node, a number of Secondary User (SU) pairs, and an eavesdropper. The PUs need to select a pair of SUs as jammers to interfere with...
Due to the unique spatial and temporal focusing effects, time-reversal (TR) communication can be utilized in the cloud radio access network, where it creates a tunneling effect such that the traffic load in the front-haul links can be alleviated in both downlink and uplink. Although the basic TR waveforms are simple to use, they cannot provide the optimal performance in some cases. While the cloud...
5G wireless standards require a much lower latency than what current wireless systems can guarantee. The main challenge to fulfill this requirement is the capability to support short packet transmission, in contrast to most of the current standards which use a long data packet structure. In this paper, we propose an efficient receiver technique that exploits information obtained during the data transmission...
We consider training-based channel estimation for cloud radio access networks (CRANs), in which a large amount of remote radio heads (RRHs) and users are randomly scattered over a certain service area. In this model, assigning orthogonal training sequences to all users, if possible, will cause a substantial overhead to the overall network. Instead, we introduce the notion of local orthogonality, in...
This paper proposes a new Reverse Direction (RD) Medium Access Control (MAC) protocol to improve the throughput and energy efficiency of IEEE 802.11 Wireless Local Area Networks (WLANs). The proposed protocol allows a source device to transmit a burst of data frames to the intended destination device in a single channel access opportunity. After the successful reception of each data frame, the destination...
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