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To address the risk that, in a fusion reactor, the conventional single-null divertor (SND) configuration may not be able to handle the power exhaust, alternative divertor configurations, such as the Snowflake divertor (SFD), are investigated in TCV. The expected benefits of the SFD-minus in terms of power load and peak heat flux are discussed and compared to experimental measurements. In addition, key results obtained during the last years are summarized. (C) 2017 Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license. (http://creativecommons.org/licenses/by-nc-nd/4.0/)

Spectrum scarcity is impeding practical implementations of emerging wireless multimedia applications requiring significantly more frequency spectrum. Cognitive radio (CR) has emerged as a promising solution to the current spectral congestion problem by imparting intelligence to the conventional software defined radio that allows spectrum sharing through opportunistic spectrum access. The principal objective of CR is to optimize the use of under-utilized spectrum through robust and efficient spectrum sensing (SS). This paper introduces cognitive functionality and provides an in-depth comparative survey of various spectrum awareness techniques in terms of their sensing accuracy and computational complexities along with their merits and demerits. Specifically, key challenges in SS are highlighted and possible solutions are discussed. A classification of SS is presented to address the sensing method selection criterion. Both non-cooperative and cooperative sensing schemes are reviewed and open research problems are highlighted to identify future research directions.

This paper presents second order statistical properties of the mobile to mobile Nakagami Hoyt channel model under non-isotropic condition. The spatial-time correlation function, the power spectral density (PSD), level crossing rate (LCR) and the average duration of fade (ADF) of the Nakagami Hoyt channel have been derived under the assumption that both the transmitter and receiver are non-stationary having non-omnidirectional antennas. Design of simulator using the Inverse Fast Fourier Transform (IFFT) based computation method has been applied for this model. The simulator and analytical results have been corroborated.

The tagged user analysis (TUA) is a generic approximate method developed to analyze random access protocols for finite-user finite-buffer systems that avoids complexities of Markovian analysis by using available queueing results. In this paper, TUA method is extended to the analysis of finite buffer S-ALOHA operating over flat fading radio channels when the user population is spatially distributed. The expressions for system performance indices are derived. It is shown that for moderate number of active users, the simulation and analytical results have a close fit.

The performance and design of a deterministic interleaver for short frame turbo codes is considered in this paper. The main characteristic of this class of deterministic interleaver is that their algebraic design selects the best permutation generator such that the points in smaller subsets of the interleaved output are uniformly spread over the entire range of the information data frame. It is observed that the interleaver designed in this manner improves the minimum distance of first few spectral lines of minimum distance spectrum. Finally we introduce a circular shift in the permutation function to reduce the correlation between the parity bits corresponding to the original and interleaved data frames to improve the decoding capability of MAP decoder. The design is focused on combining good permutations with de-correlation property. Our solution to design a deterministic interleaver outperforms the semi-random interleavers and the deterministic interleavers reported in the literature.

Recently, sharing the radio access network (RAN) has become an important issue for 3G and beyond mobile wireless operators. In addition to user and service considerations, there are economic and technical advantages to 3G and beyond shared networks. This is driving optimizations in the deployment and development of national 3G and 4G rollouts. However, shared 3G and 4G networks exhibit many of the resource management opportunities and challenges as more complex heterogeneous traffic and sharing techniques are considered. In this paper, we propose a roaming-based sharing adaptive partitioning with borrowing (APB) scheme where an operator is allowed to borrow from the unutilized resources originally belonging to other operators sharing the same RAN. This algorithm controls the resource sharing between the operators in addition to controlling the admission control (CAC) within each operator's domain. The borrowing margin is specified either as a fixed portion or an adaptive percentage of the unutilized resource. Furthermore, the APB CAC function makes a distinction between newly originating calls and handoff calls by assuming a higher priority level for handoff calls in the form of possibility of queuing. Therefore, the prescribed call admission control scheme provides a higher quality of service for the handoff requests of real-time services expected in 3rd and 4th G wide band code division multiple access (WCDMA) systems. Simulation results indicate that APB provides higher resource utilization under all load conditions leading in turn to increased revenue. In addition, a higher quality of service for traffic is provided especially when an operator is allowed to borrow from the unutilized resources.

In this paper, R-ALOHA systems with propagation delay, finite buffer capacity and finite user population are analyzed using Tagged User Approach. The system throughput, message response time, message delay-time distribution and message blocking probability are obtained. It is assumed that each message consists of a random number of packets with a general distribution, and each user have a finite buffer capacity. To maintain the fairness to all users, it is assumed that each message in the buffer is transmitted independently that is, a user has to release the reserved slot after finishing the transmission of a message even if it has more messages waiting in the buffer. The analysis can be extended to R-ALOHA systems with infinite buffer capacity straightforwardly. The accuracy of the analysis is verified by simulations.

In this paper, a new approach is proposed to analyze the performance of buffered random multiple access protocols called tagged user analysis (TUA). In TUA, each user is modeled as an independent queueing system, which operates at its own equilibrium probability. As a result, the classical queueing theory can be employed to analyze the queueing behavior of each user. On the basis of the behavior of the tagged user, the performance of the whole system is analyzed. TUA is a unified method of analyzing most of random access methods including the heterogeneous random multiple access techniques that are difficult to analyze otherwise. Furthermore, TUA can also handle those systems where user terminals may have arbitrary packet size (in slots) distribution, arbitrary arrival processes such as batch packet arrivals in Bernoulli, arbitrary service principle such as priority queueing, last came first served, and random service. In this paper, in addition to analyzing for the distributions of several performance indices, their mean values are obtained.

We survey recent advances in equalization and diversity combining for counteracting multipath and interuser interference in digital portable wireless systems. These two techniques are complementary, and, given sufficient excess bandwidth and/or number of receiving antenna array elements, they can eliminate interference among an arbitrary number of interfering users′ signals. Recent evaluations of adaptive decision feedback equalizers applied to suppressing interference in TDMA and CDMA radio systems are summarized.