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This paper considers a coordinated robust design of beamforming and power allocation under per-BS power constraints in a multicell multiuser downlink network with only imperfect channel state information (CSI) is available at both base stations (BS) and mobile users (MU). Our goal is to maximize the weighted sum rate while taking imperfect CSI into account. Due to the intractability of the original...
In this letter, we consider energy efficient beamforming for the broadcast multiple antenna channel. The optimization problem is formulated as maximizing the ratio of the achievable sum-rate to the total power consumption subject to given power and SINR constraints, which is non-convex and hard to tackle. In contrast to existing approaches, we first derive a virtual uplink problem that is dual to...
Low-complexity and high-performance multiple-input and multiple-output (MIMO) channel estimation scheme is investigated. Pilot blocks are constructed using quadriphase complementary sequences (QCSs) which enable both one-sided (OSD) and two-sided (TSD) channel estimation (CE). And OSD-CE and TSD-CE are combined to provide improved performance in frequency-selective fast and slow fading channels and...
A hybrid system consisting of a cellular network and a device-to-device (D2D) network is considered in this paper where the D2D users operate in an underlay mode and reuse the spectrums with the cellular users. Most researches focus on reusing the uplink spectrums but how to share the downlink frequency bands is seldom addressed. To share the downlink spectrums and avoid the interference to the primary...
In this paper, we address the preamble-based channel estimation problem for orthogonal frequency-division multiplexing (OFDM) systems using multiple amplify-and-forward (AF) relays. We first establish a linear minimum mean-square-error (LMMSE) channel estimator which directly estimates the overall channels from the source to the destination. Then, based on the assumption that the channel correlations...
Spectrum sensing is an essential mechanism for a cognitive radio system. However, the security aspects of spectrum sensing receive little attention so far. In this paper, we identify two kinds of untrusted secondary users which are called dasiaAlways Yespsila users and dasiaAlways Nopsila users. These untrusted secondary users can degrade detection performance greatly, especially when conventional...
Spectrum sensing is an essential mechanism in a cognitive radio network. However, the detection performance will be greatly degraded when few untrusted secondary users exist which can be identified as 'Always Yes' users and 'Always No' users. In this paper, we propose an energy detector with double thresholds combined with revised data fusion rules to find these untrusted users and counteract their...
In a wireless regional area network (WRAN), the presence of wireless microphone (WM) signals must be detected as primary users. However, very narrow bandwidth and low power makes it difficult to sense WM signals especially when these WM signals are distributed in a wideband spectrum. In this paper, a singular value decomposition (SVD)-based approach is presented to sense and estimate multiple WM signals...
In a wireless regional area networks (WRAN) network, the presence of a wireless microphone (WM) signal must be detected as a primary user. However, very narrow bandwidth and low power makes it difficult to sense a WM signal. In this paper, a singular value decomposition (SVD)-based approach is presented to sense and estimate a WM signal. After performing SVD on the received data matrix, the presence...
This paper presents approaches of link to system mapping for OFDM/multi-carrier mobile communications systems. Mainly, the effective SINR method is highlighted, which includes EESM and MI-ESM. It is shown how the multi-state channels are integrated into a single state in system simulator with effective SINR approach and why the effective SINR can represent the characteristics of multiple sub-carrier...
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