Pawel Sroka

Resource allocation and packet scheduling in OFDMA-based cellular networks

In this paper a study on different Radio Resource Management (RRM) methods employed in a multi-carrier cellular system is presented. This work focuses on the rate-adaptive resource allocation (sub-carriers and power), as well as the utilitybased packet scheduling algorithms. The objective of the paper is to study the trade-off between system spectral efficiency and fairness among the users when the considered algorithms are used.

Crystallized rate regions for MIMO transmission

When considering the multiuser SISO interference channel, the allowable rate region is not convex and the maximization of the aggregated rate of all the users by the means of transmission power control becomes inefficient. Hence, a concept of the crystallized rate regions has been proposed, where the time-sharing approach is considered to maximize the sumrate.In this paper, we extend the concept of crystallized rate regions from the simple SISO interference channel case to the MIMO/OFDM interference channel. As a first step, we extend the time-sharing convex hull from the SISO to the MIMO channel case. We provide a non-cooperative game-theoretical approach to study the achievable rate regions, and consider the Vickrey-Clarke-Groves (VCG) mechanism design with a novel cost function. Within this analysis, we also investigate the case of OFDM channels, which can be treated as the special case of MIMO channels when the channel transfer matrices are diagonal. In the second step, we adopt the concept of correlated equilibrium into the case of two-user MIMO/OFDM, and we introduce a regret-matching learning algorithm for the system to converge to the equilibrium state. Moreover, we formulate the linear programming problem to find the aggregated rate of all users and solve it using the Simplex method. Finally, numerical results are provided to confirm our theoretical claims and show the improvement provided by this approach.

Distributed interference mitigation in two-tier wireless networks using correlated equilibrium and regret-matching learning

In this paper we study the interference management in two-tier cellular system from a game theoretic perspective. We extend the work given in [1], [2] to apply the game theoretic approach based on correlated equilibrium and regret-matching learning to multi-tier decentralized interference mitigation. The proposed approach requires periodic information exchange between coordinating base stations (BSs), thus several simplifications to the original algorithm are proposed. Numerical results of Monte Carlo simulations of Long Term Evolution - Advanced (LTE-A) like system are presented, with the proposed solution providing significant increase in terms of average cell throughput and user rate comparing to the state-of-the-art schemes.

System-level simulations of selected aspects of 5G cellular networks

This paper presents a system-level simulation approach developed at the Poznan University of Technology for the evaluation of selected aspects of next generation wireless systems. The details of the considered environment and propagation models are given, as well as several important aspects of the simulator implementation methodology. Selected use cases of the presented simulation platform are demonstrated in relation to different research topics in the area of next generation wireless systems. The achieved simulation results show that the problems related to the development of modern wireless systems require detailed and precise modeling of the environment in order to accurately validate system performance.

Resource and Mobility Management in the Network Layer of 5G Cellular Ultra-Dense Networks

The provision of very high capacity is one of the big challenges of the 5G cellular technology. This challenge will not be met using traditional approaches like increasing spectral efficiency and bandwidth, as witnessed in previous technology generations. Cell densification will play a major role thanks to its ability to increase the spatial reuse of the available resources. However, this solution is accompanied by some additional management challenges. In this article, we analyze and present the most promising solutions identified in the METIS project for the most relevant network layer challenges of cell densification: resource, interference and mobility management.

Crystallized rate regions in the secondary interference channels

In this paper the problem of sum-rate maximization for secondary cognitive users (SU) in presence of a primary user (PU) transmission is considered. We assume that all of the users are equipped with multiple transmit/receive antennas and that the cognitive users must not induce more interference to the primary users than it is defined in the permissive policy and expressed in terms of a spectrum mask or interference temperature constraint. We employ game-theory to find the so-called correlated equilibrium that corresponds to the playing strategy definitions for all users. Actually, the Vickrey-Clarke-Groves theory has been applied and the regret-matching algorithm has been implemented to find the optimal playing strategy for both secondary users. New cost function has been proposed that allows for fast convergence of the developed solutions to the optimal or sub-optimal point. Extensive simulation results have been carried out to corroborate the correctness of the proposed approach.

MIMO crystallized rate regions

In this paper the generalization of the concept of crystallized rate regions for MIMO/OFDM transmission is introduced. The extension from the SISO to MIMO case of the timesharing convex hull is discussed and a new definition of the cost function for the game is derived. Finally, a new game definition is provided followed by the simulation results for the MIMO case. Moreover, the OFDM transmission case is investigated, which can be treated as the special case of the MIMO system, when the channel transfer matrices are diagonal.

3GPP C-V2X and IEEE 802.11p for Vehicle-to-Vehicle communications in highway platooning scenarios

Abstract The focus of this study is the performance of high-density truck platooning achieved with different wireless technologies for vehicle-to-vehicle (V2V) communications. Platooning brings advantages such as lower fuel consumption and better traffic efficiency, which are maximized when the inter-vehicle spacing can be steadily maintained at a feasible minimum. This can be achieved with Cooperative Adaptive Cruise Control, an automated cruise controller that relies on the complex interplay among V2V communications, on-board sensing, and actuation. This work provides a clear mapping between the performance of the V2V communications, which is measured in terms of latency and reliability, and of the platoon, which is measured in terms of achievable inter-truck spacing. Two families of radio technologies are compared: IEEE 802.11p and 3GPP Cellular-V2X (C-V2X). The C-V2X technology considered in this work is based on the Release 14 of the LTE standard, which includes two modes for V2V communications: Mode 3 (base-station-scheduled) and Mode 4 (autonomously-scheduled). Results show that C-V2X in both modes allows for shorter inter-truck distances than IEEE 802.11p due to more reliable communications performance under increasing congestion on the wireless channel caused by surrounding vehicles.

The analysis of scheduling algorithms in microcellular 4G MIMO WINNER system

In this paper impact of resource scheduling algorithms on the average user throughput, average cellpsilas capacity and the quality of provided services in the microcellular 4G environment has been analyzed. Well known scheduling algorithms such as Round Robin, MaxSNR and Fair Rate have been compared with the algorithms proposed for fading channels in [1]. A simple modification of the scheduling has been proposed for all examined algorithms and its impact on the users and system performance has been analyzed. Presented results have been obtained for both uplink and downlink OFDMA transmission in the MIMO channels.

On the Context-Aware, Dynamic Spectrum Access for Robust Intraplatoon Communications

Vehicle platooning is a promising technology that allows to improve the traffic efficiency and passengers safety. Platoons that use cooperative adaptive cruise control, however, require a reliable radio link between platoon members to ensure a required distance between the cars within the platoon, thus maintaining platoon safety. Nowadays, the communication can be realized with the use of 802.11p or cellular vehicle-to-vehicle (C-V2V), but none of this technology is able to provide a reliable link especially in the presence of high traffic or urban scenarios. Therefore, in this paper, we propose a dynamic spectrum management mechanism in V2V communications for platooning purposes. A management system architecture is proposed that comprises the use of context-aware databases, sensing nodes, and spectrum allocation entity. The proposed robust system design aims to keep only the minimum necessary information transmitted over the conventional intelligent transportation system (ITS) channel, while moving the remaining data (nonsafety, service-aided, or infotainment) to an alternative channel that is selected from the available pool of spectrum white spaces. The initial analysis indicates that the proposed system may significantly improve the performance of wireless communications for the purpose of vehicle platooning.