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In this paper, we deal with channel estimation and intercarrier interference mitigation for very high mobility OFDM systems, the communication is between a BS and a train traveling at a speed of 500km/hr. The scheme proposed here uses piece-wise polynomial expansion to approximate time-variations of multipath channels. Two adjacent symbols are utilized to estimate the first and second-order parameters...
In this article, the super perfect difference (SPD) code family is presented and used in the compact spectral amplitude code (SAC) optical code-division multiple-access (OCDMA) passive optical networks (PONs). Based on the excellent properties of the SPD, such as low in-phase cross correlation (IPCC) value, cyclic shift, and excellent orthogonality, we design the SAC OCDMA PON which consists of a...
Patient Relationship Management or Customer Relationship Management for healthcare is a system design strategy said to have the potential to increase patient satisfaction and reduce healthcare costs. We outline a innovative patient relationship management information system architecture. The primary principle of this architecture is modularity, thereby reducing implementation, maintenance and evolution...
In this paper, the effect of time difference of arrival (TDoA) is investigated for distributed nodes in OFDMA-based wireless mesh networks (WMNs). In order to minimize the interferences caused by TDoA in WMNs, the optimal starting point of the FFT window at the receiver side of a node is derived by maximizing the effective SINR for each subcarrier. Also, a signal detection technique, called two dimensional...
Physicians are faced with questions and uncertainties regarding information/knowledge for the best care of their patients. There are several sources of medical information available from which they can retrieve the necessary answers, such as colleagues, textbooks or software on personal digital assistants (PDA). This case study evaluates how physicians seek medical knowledge when they face a clinical...
The social behavior in cognitive radio networks is studied using analysis tools in social networks. A recommendation system is proposed for cognitive radio, thus incurring the channel preference propagation in the corresponding random geometric network. A mean field based ordinary differential equation is used to describe the dynamics of the channel preference propagation in cognitive radio networks...
We address the problem of downlink multiuser scheduling in practical wireless networks under a desired fairness constraint. Wireless networks such as LTE, WiMAX and WiFi provide partial channel knowledge at the base station/access point by means of quantized user equipment feedback. Specifically in 3GPP's LTE, the Channel Quality Indicator (CQI) feedback provides time-frequency selective information...
Multiuser (MU) - multiple input multiple output (MIMO) techniques are attractive to increase the downlink spectrum efficiency since they allow a small number of antennas at each user station (STA). In MU-MIMO systems, the transmission performance is affected by the STA combination that is spatially multiplexed in the same frequency and same time slot. Thus, the AP needs to determine the optimum STA...
We propose a robust optimization framework for the multiple-access problem in a hospital environment. The users of e-Health applications (referred to as secondary users) coexist with active and passive medical devices (referred to as primary and protected users, respectively) under uncertainty in the channel (i.e. propagation) conditions. In particular, we design robust transmission scheduling and...
In this paper, we develop a general reduced-rate orthogonal frequency division multiplexing (OFDM) transmission scheme for inter-subchannel interference (ICI) mitigation in a high-mobility environment. By transmit and receive preprocessing, we transform the original N-subcarrier OFDM system into an equivalent K-subcarrier one with significantly reduced ICI. In particular, we develop a general structure...
The association policy in current IEEE 802.11 networks usually considers Received Signal Strength Indication (RSSI) to be the only metric to capture access link quality. However, when a Mesh Client (MC) in IEEE 802.11-based Wireless Mesh Network (WMN) needs to be associated with the most appropriate Mesh Access Point (MAP), the quality of both the access link and the routing path in mesh backhaul...
Cognitive radio systems allow secondary users to operate on underutilized licensed spectrum. When considering highly congested communication channels, however, opportunities for channel access based on time or frequency division can be limited for secondary user networks. In this research, we consider leveraging enhanced spatial diversity through directional steerable antennas to allow secondary user...
Ensuring a high customer satisfaction by monitoring Quality of Experience (QoE) aspects has become common practice for service providers. Such monitoring solutions, together with underlying QoE models, are mostly limited to measures captured in the core or access network and may thus neglect the QoE impact of recovery mechanisms deployed at client-side, e.g., FEC or ARQ. This limitation makes QoE...
In this paper, we investigate the capacity of Gaussian multiple access channels (MAC) with finite input alphabet and `quantized output'. With finite input alphabet and an unquantized receiver, the two-user Gaussian MAC rate region was studied in \cite{harsh08}. In most high throughput communication systems based on digital signal processing, the analog received signal is quantized using a low precision...
Dynamic spectrum access (DSA) is an important design aspect for the cognitive radio networks. Most of the existing DSA schemes are to govern the unlicensed user (i.e., secondary user) traffic in a licensed spectrum without compromising the transmissions of the licensed users, in which all the unlicensed users are typically treated equally. In this paper, prioritized unlicensed user traffic is considered...
With the limited wireless spectrum and the ever-increasing demand for wireless services, how to enlarge wireless network throughput is a pressing issue. To exploit the wireless spatial capacity, concurrent transmissions, if controlled appropriately, can lead to overall higher spectrum utilization and network throughput. The optimal scheduling and power control for concurrent transmissions in rate-adaptive...
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