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Caching is an effective technique to improve user perceived experience for massive content delivery in wireless networks. An essential problem in cache-aided wireless networks is to find what and how much gain can be achieved by caching. This paper provides a study of the fundamental storage- latency tradeoff for a cache-aided MIMO interference network with 3 transmitters and 3 receivers and each...
With the explosive growth of mobile traffic demand, device-to-device (D2D) communication offers a promising approach to reduce cellular congestion by offloading users' traffic to D2D network. In this paper, we consider a relay- assisted D2D communication in underlay cellular networks, where D2D users access a proportion of the spectrum occupied by cellular users. This poses two fundamental issues...
Wireless covert systems use low probability of detection (LPD) techniques to hide transmission and protect the transmitter. Traditionally, spread spectrum has been used to hide the covert signal in noise. Recently, research has focused on covert systems that sense the RF channel and hide their transmission in the RF band of a primary network (PN). A widely used metric to quantify covertness is the...
Energy efficiency is one of the major challenges of 5G networks. As data rates are expected to increase by 1000x from 4G to 5G, energy efficiency will need to improve by about the same amount. Recently, energy harvesting techniques have attracted lots of attention from the scientific community, due to their ability to increase network lifetime. More specific, energy harvesting from ambient radio frequency...
Recent advancements in manufacturing and favorable regulatory positions make millimeter wave (mmWave) a target for next-generation wireless networks. For a variety of use-cases, it is reasonable to assume users will be clustered around a central point (e.g. WiFi hotspot) rather than uniformly located. In this paper, we develop analytic expressions for the capacity of clustered mmWave ad hoc networks...
The capacity of frequency-flat multiuser MIMO downlinks is achieved with nonlinear dirty paper coding (DPC). Linear processing techniques, such as block diagonalization (BD), offer relatively low computational cost with respect to DPC and can also achieve capacity in certain cases. However, BD is not easily translated to frequency-selective channels since the channel matrix has a space-time structure...
In this paper, we jointly consider mode selection, admission control, partner assignment, and power allocation to investigate the sum rate maximization problem in underlay SCMA device-to-device (D2D) networks. Due to its mixed combinatory, we first decouple the problem to devise efficient algorithms. In particular, we propose a channel gain based mode selection criterion and a greedy-style partner...
This paper considers a robust precoder design for MIMO-OFDM systems with insufficient cyclic prefix (CP). Interference alignment is utilized to formulate the precoder design problem as a bit error rate (BER) minimization problem subject to a total power constraint. To this end, the precoder is designed to be robust to the errors in the available channel estimates, by considering the worst-case BER...
In this paper, a novel non-orthogonal multiple access (NOMA)-based device-to-device (D2D) communications framework is proposed. A major novelty of the proposed framework is that it introduces the new concept of ``D2D group" which utilizes NOMA transmission, enabling one D2D transmitter to communicate with multiple D2D receivers simultaneously. Based on the considered framework, a resource allocation...
In this paper, a general 3-D model for K-tier heterogeneous networks (HetNets) is proposed to investigate the performances of device-to-device (D2D) communications in highrise centers. The new model is based on stochastic geometry, where a 3-D Mat'ern hard- core process (MHCP) is used to describe the different cells positions in the network with realistic constraints. We derive the expressions of...
Game theory, as a powerful conceptual framework, has in the past decade or so been widely applied to wireless communications in a variety of contexts. One such context is power control, where a game-theoretic formulation is particularly well-motivated since the distributed power control paradigm makes it natural to treat each wireless link (consisting of a transmitter and a receiver) as a player equipped...
Covert systems are designed to operate at a low probability of detection (LPD) in order to provide system protection at the physical layer level. The classical approach to covert communications hides the signal in noise; however, the increasing demand for modern covert systems that provides better protection against intercept receivers (IRs) has shifted the focus to the design of Ad-Hoc covert networks...
In this paper, we propose joint spectral shaping and power allocation for an orthogonal frequency division multiplexing (OFDM)-based cognitive radio (CR). The objective is to maximize its downlink transmission rate subject to the constraint on the interference introduced to the primary user (PU) spectrum band that coexists side-by-side in overlay approach. Considering that the CR transmitter (base...
We study a three-node network with a full-duplex base-station communicating with one uplink and one downlink half-duplex node. In this network, both self-interference and inter-node interference are present. We use an antenna-theory-based channel model to study the spatial degrees of freedom of such network, and study if and how much does spatial isolation outperforms time-division (i.e. half-duplex)...
Within the context of faster-than-Nyquist signaling, a low-complexity multicarrier system based on short-length filters and zero-forcing turbo equalization is introduced. Short-length filters allow a reduced-size block processing while zero-forcing equalization allows a linear reduced-complexity implementation. Furthermore, rectangular and out-of-band energy minimization pulse shaping demonstrates...
Recent advances in Milimeter wave (mmWave) band mobile communications may provide solutions to the increasing traffic demand in modern wireless systems. Even though mmWave bands are scarcely occupied, the design of a prospect transceiver should guarantee the efficient coexistence with the incumbent services in these bands. To that end, in this paper, two underlay cognitive transceiver designs are...
A required feature for the next generation of wireless communication networks will be the capability to serve simultaneously a large number of devices with heterogeneous CSIT qualities and demands. In this paper, we consider the overloaded MISO BC with two groups of CSIT qualities. We propose a transmission scheme where degraded symbols are superimposed on top of spatially-multiplexed symbols. The...
In underlay Device-to-Device (D2D) communication, where a D2D pair reuses the cellular spectrum and creates interference to regular cellular users, there exists a tradeoff between the achieved D2D rate and the interference to cellular users. In this work, we present stochastic optimization solutions to allocate the D2D transmission power over multiple resource blocks (RBs), to maximize the D2D rate,...
A two-stage downlink beamforming design is proposed for multicell multi-input single-output channels with limited backhaul capacity and local channel state information (CSI). The first stage is to maximize the signal-to-leakage-plus-noise ratio with local CSI. Each base station (BS) then calculates the corresponding channel gains and shares them with all other BSs, which typically requires low-rate...
The research is devoted to the reduction of multiple access interference (MAI) in chaos-based asynchronous direct sequence code division multiple access (DS-CDMA) communication systems by use of spreading sequences which are selected from a large set of generated chaotic sequences. For the generation of binary chaotic spreading sequences different 1-dimensional maps are examined. As selection criteria...
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