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This work presents the generation, dynamic phase modulation and phase detection of interfering composite optical vortices. This technique demonstrates a new method for encoding information onto an optical beam for potential use in underwater communication as well as sensing applications including object detection and channel characterization.
Channel aggregation (CA) techniques can offer flexible channel allocation and improve overall system performance in multi-channel cognitive radio networks (CRNs). Although many CA techniques have been proposed and studied, the impact of guard-band on CA for channel access has not been addressed in-depth. In this paper, we study the guard-band allocation mechanisms in discontinuous-orthogonal frequency...
In LTE uplink systems, single-carrier frequency-division multiple access (SC-FDMA) has been employed. In SC-FDMA, orthogonal frequency resources are assigned to different users to avoid intra-cell interference. However, inter-cell interference (ICI) caused by the users in neighboring cells significantly deteriorates the performance. Cooperation among base stations must be used to deal with ICI for...
Multi-cell coordinated beamforming (CB) can mitigate inter-cell interference. However, previous study on CB focuses on systems with only one receive antenna. This paper considers CB for systems with multiple receive antennas. To take fairness among scheduled users into account, CB is designed to maximize the harmonic sum of signal-to-interference-plus-noise ratio (SINR). We develop an iterative algorithm...
In this paper, we propose a novel routing protocol which is integrated with channel assignment for multi-channel multi-hop wireless ad hoc networks. In such a network, each node is equipped with three transceivers. One is always tuned on a control channel which is responsible for control and broadcast messages, and the other two perform as transmitter and receiver respectively for traffic flows on...
An attractive approach to overcome capacity limitations in a densely deployed WLAN environment is to enable transmission concurrency. In this paper, we propose a co-channel concurrent transmission scheme, referred to as C2SMA/CA, which determines whether to allow multiple concurrent transmissions based on interference estimation using positional information. A distributed multi-link concurrency scheduling...
Cognitive radio (CR) technology provides great flexibility in spectrum utilization with orthogonal frequency-division multiplexing (OFDM) as its candidate transmission technique. In this paper, we propose a simple spectrum shaping scheme for OFDM-based CRs to enhance spectral compactness and ensure bandwidth efficiency. By mapping antipodal symbol pairs onto adjacent subcarriers at the edges of the...
A thorough analysis of the electromagnetic compatibility of power lines and neighboring railway is presented. The railway is located close to the transmission line that consists of a combination of overhead and underground conductors and cables. Electromagnetic interference caused by high voltage power lines can endanger the proper operation of the signal and protection systems of the railways and...
A novel robust adaptive beamformer, with new robust constraints on array magnitude response was proposed by utilizing the autocorrelation sequence of array weight vector and the worst-case optimization technique. The proposed adaptive beamformer was formulated as a linear programming problem with second-order cone semi-infinite constraints, which can be eliminated by using the sampling technique....
Many advanced adaptive beamformers are robust against arbitrary array steering vector (ASV) mismatches within a presumed uncertainty set. Adaptive array tolerating significant steering direction error usually requires a large size of ASV uncertainty set. In such case, however, the output signal-to-interference-plus-noise ratios (SINRs) of robust methods degrade quickly with the increasing size of...
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