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In the context of primary/secondary spectrum sharing, we propose a randomized secondary access strategy with access probabilities that are a function of both the primary automatic repeat request (ARQ) feedback and the spectrum sensing outcome. The primary terminal operates in a time slotted fashion and is active only when it has a packet to send. The primary receiver can send a positive acknowledgment...
In Rayleigh block fading channels which represent fast-varying channels, long-term rate adaptation is required instead of instantaneous rate adaptation because the channel information fed back may be outdated. We maximize the long-term average transmission rate (LATR) in a two-hop relay network which adopts Chase combining (CC) type Hybrid Automatic-Repeat-reQuest (HARQ). The round transmission rate,...
Interference mitigation approaches in the presence of multiple receive antennas in the uplink of a multi-cell wireless communications system are studied in this paper. A formulation based on interference pricing is proposed, where it is shown that a single price per base-station can be computed and exchanged, in order to set the mobile transmit powers per cell. The work is premised on a decentralized...
In 3GPP Long Term Evolution (LTE) networks, the frequency reuse schemes such as fractional frequency reuse (FFR) and soft frequency reuse (SFR) are used to improve system capacity. The allocation of transmit power and subcarriers to each cell in these schemes are fixed prior to network deployment. This limits the potential performance of these frequency reuse schemes. In this paper, we propose to...
In this paper we propose a novel resource allocation scheme to achieve a balanced performance improvement for all users in a LTE network subject to inter-cell interference. In the proposed scheme the resource allocation process is implemented in two steps. In the first step interference coordination and scheduling are first conducted in a global manner to prevent cell-edge users from mutual interference...
This paper investigates optimal resource allocation in orthogonal frequency division multiplexing (OFDM) based multiple two-way relay systems operating with analog network coding (ANC) protocol. We formulate a joint optimization problem considering power allocation, relay selection and subcarrier paring to maximize the sum capacity under individual power constraints on each node. By applying dual...
In high criticality crisis scenarios, such as disaster management, ad hoc wireless networks are quickly assembled in the field to support decision makers through situational awareness using messaging-, voice-, and video-based applications. These applications cannot afford the luxury of stalling or failing due to overwhelming bandwidth demand on these networks as this could contribute to overall mission...
The smart grid uses data communications techniques to gather and transfer information for scheduling and decision making so that the electric power can be used more efficiently and economically. To reduce the cost of data communications in smart grid, in this paper, we assume that cognitive radio technique is used to transmit the meter data from smart meters to the data aggregator unit (DAU). Smart...
Advances in sensing and wireless communication technologies have enabled a wide spectrum of Outdoor Wireless Sensor Network (OWSN) applications. Some applications require the existence of a communication backbone federating different OWSN sectors, in order to collaborate in achieving more sophisticated missions. Federating (connecting) these sectors is an intricate task due to the huge distances between...
Video sensor networks (VSNs) offer an alternative to several existing surveillance technologies. However, unlike in conventional sensor network, video processing and transmission requires large amount of resources both in signal processing, i.e., encoding, and transmission of the encoded data. For such networks, an optimal encoding power and rate allocation method based on a power-rate-distortion...
For guaranteeing quasi-error free delivery of realtime multicast services over wireless networks, an efficient greedy algorithm is proposed for optimizing the parameters of a HARQ scheme with rateless codes under strict delay and bandwidth constraints. We take systematic Raptor codes as an example for analyzing the optimum performance of the HARQ scheme. The results show that the optimum performance...
Support-Vector Machines (SVM) have received a great interest in the machine learning community since their introduction, especially in Outlier Detection in Wireless Sensor Networks (WSN). The Quarter-Sphere formulation of One-Class SVM (QS-SVM), extends the main SVM ideas from supervised to unsupervised learning algorithms. The QS-SVM formulation is based only on Spatio-Temporal correlations between...
We consider the wireless relay network in which a base station communicates with multiple subscribers, each of which has the ability to act as a relay to forward information to a base station. Here, we propose an algorithm for joint optimization of power allocation, time scheduling, and relay selection when there is imperfect channel state information (CSI). We show that the algorithm converges with...
Exposure problem, which corresponds to the quality of coverage, is a fundamental problem in wireless sensor networks. In this paper, we exploit a cellular computing model in the physarum for solving the minimal exposure problem. We first use the road-network among all points of interesting (PoIs) in the monitoring filed to formulate the minimal exposure problem, and then convert it into the Steiner...
Deployment is a fundamental issue in wireless sensor networks. Usually the sensor locations are precomputed based on a ”perfect” sensor coverage model, whereas sensors may not always provide reliable information, either due to operational tolerance levels or environmental factors. Therefore, it is imperative to have practical considerations at the design stage to anticipate this sensing behavior....
In our earlier work, we described an optimization problem and corresponding scheduling algorithm aimed at obtaining maximum throughput guarantees in wireless networks. To further improve the short-term performance, we also proposed two adaptive versions of the optimal algorithm. Results from the simulations showed that the adaptive algorithms perform significantly better than other well-known scheduling...
Energy harvesting techniques have enabled the provisioning of alternative energy sources beside the conventional one which is typically provided by the batteries. Using such harvesting techniques together with proper energy management mechanisms, a Energy Neutral state can be achieved so that desired performance level can be supported perpetually. Existing energy neutral management mechanisms rely...
Total relay transmit power minimization in Amplify-forward (AF) MIMO relay beamforming is naturally formulated as an indefinite quadratic (nonconvex) program and then semidefinite relaxation (SDR) technique can be used to locate their optimal solutions. Indeed, SDR often gives rank-one optimal solution within a low number of relaying antennas and communicating users. However, as the antennas number...
Sensor selection is to pick out an appropriate subset of active sensors for reliable collaborative sensing. Naturally, the selected sensors should be as uncorrelated as possible to have more independent sensing outputs for information fusion. In this paper, various uncorrelation metrics are unified by the concept of Bregman divergence. The sensor selections are then systematically formulated as NP-hard...
Femtocell networks embedded in the macrocell greatly benefit capacity gain from high SINR and dedicated BS to home subscribers. However, the lack of schemes to effectively control the interference and fully utilize radio resources creates challenges to practically facilitate the additive unlicensed spectrum in femtocells. To tackle these challenges, this paper presents a solution to the interference...
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