Zdenek Becvar

Czech Technical University in Prague | ČVUT · Department of Telecommunication Engineering (FEL)

Channel quality is an essential information for management of radio resources in mobile networks. To acquire the channel quality information, pilot (or reference) signals are commonly transmitted, measured, and reported to the network. However, the process of channel quality acquisition is both time and energy consuming. Moreover, the radio resourc...

In this letter, an energy-efficient algorithm for positioning of unmanned aerial vehicle-based base stations (UAV-BSs) is presented. The objective is to reduce the propulsion power consumption of UAV-BSs while not compromising the communication capacity of user equipments (UEs). As a significant step beyond state-of-the-art, we consider an effect o...

p>Most of the existing solutions for communication of connected vehicles (CVs) are focused on the optimization of resource allocation, however, not taking the driving routes of the CVs into account. In addition, no existing work considers the offloading of computing tasks from CVs to edge computing servers. In this paper, we introduce joint vehicul...

With the advent of connected and autonomous vehicles (CAVs), we observe a growing need for new resource allocation solutions in mobile networks. Currently, most of the resource allocation solutions for CAVs communication do not consider the driving routes of the cars. In this paper, we introduce joint vehicular route selection and radio and computi...

In mobile networks, unmanned aerial vehicles (UAVs) acting as flying base stations (FlyBSs) can effectively improve performance. Nevertheless, such potential improvement requires an efficient positioning of the FlyBS. In this paper, we study the problem of sum downlink capacity maximization in FlyBS-assisted networks with mobile users and with a co...

The radio resources are utilized for both transmissions of new data and for retransmission(s) of erroneous data to handle errors due to transmission over the wireless link. Hence, the more retransmissions occur, the fewer resources remain available for transmission of new data resulting in a lower goodput. This problem is even emphasized in cloud r...

Device-to-device (D2D) relaying is able to increase the network capacity, enhance the network coverage, or mitigate the interference to legacy cellular transmissions. These benefits are even emphasized if a proper incentives are offered to the users to motivate them to act as relays. We first survey the stateof- the-art incentives to show that desp...

p>Most of the existing solutions for communication of connected vehicles (CVs) are focused on the optimization of resource allocation, however, not taking the driving routes of the CVs into account. In addition, no existing work considers the offloading of computing tasks from CVs to edge computing servers. In this paper, we introduce joint vehicul...

p>Most of the existing solutions for communication of connected vehicles (CVs) are focused on the optimization of resource allocation, however, not taking the driving routes of the CVs into account. In addition, no existing work considers the offloading of computing tasks from CVs to edge computing servers. In this paper, we introduce joint vehicul...

The use of unmanned aerial vehicles (UAVs) acting as flying base stations (FlyBSs) is considered as an effective tool to improve performance of the mobile networks. Nevertheless, such potential improvement requires an efficient positioning of the FlyBS. In this paper, we maximize the sum downlink capacity of the mobile Internet of Things devices (I...

Deployment of multi-hop network of unmanned aerial vehicles (UAVs) acting as flying base stations (FlyBSs) presents a remarkable potential to effectively enhance the performance of wireless networks. Such potential enhancement, however, relies on an efficient positioning of the FlyBSs as well as a management of resources. In this paper, we study th...

Flying base stations (FlyBSs) can serve space-time varying heterogeneous traffic in the areas, where a deployment of conventional static base stations is uneconomical or unfeasible. We focus on energy consumption of the FlyBSs serving moving users. For such scenario, rotary-wing FlyBSs are not efficient due to a high energy consumption while hoveri...

Unmanned aerial vehicles (UAVs) equipped with reconfigurable intelligent surfaces (RISs) have emerged as a promising technology for numerous applications involving aerial networks. However, the UAV-RIS concept faces challenges related to the deployment of the UAV-RIS, especially in cases, where UAV-RIS is combined with emerging technologies, such a...

The unmanned aerial vehicles (UAVs) acting as flying base stations (FlyBSs) are considered as an efficient way to enhance the capacity of mobile networks. The enhancement provided by such network requires a dynamic positioning of the FlyBSs with respect to the users demands on communication. However, the power consumption of the FlyBS is a challeng...

A relaying can significantly improve performance of contemporary mobile networks in terms of capacity and/or energy consumption. Nevertheless, an incorporation of conventional relay stations into the mobile networks is usually expensive in terms of both capital and operational expenditures for the mobile operators. With an evolution of Device-to-de...

In this letter, we maximize the minimum downlink capacity of moving users in the mobile networks based on non-orthogonal multiple access (NOMA) with flying base stations (FlyBSs) considering practical constraints on the speed, altitude, and transmitting power of the FlyBSs. We propose a geometrical approach allowing us to reflect the users’ movemen...

To ensure a seamless mobility of users in the scenario with flying base stations (FlyBSs) and static ground base stations (GBSs), an efficient handover mechanism is required. In this paper, we introduce new framework simultaneously managing cell individual offset (CIO) for handover of both FlyBSs and mobile users. Our objective is to maximize capac...

Unmanned aerial vehicles (UAVs) acting as flying base stations (FlyBSs) are considered as an efficient tool to enhance the capacity of future mobile networks and to facilitate the communication in emergency cases. These benefits are, however, conditioned by an efficient control of the FlyBSs and management of radio resources. In this paper, we prop...

Flying base stations (FlyBSs) enable ubiquitous communications in the next generation mobile networks with a flexible topology. However, a deployment of the FlyBSs intensifies interference, which can result in a degradation in the throughput of cell-edge users. In this paper, we introduce a flexible soft frequency reuse (F-SFR) that enables a self-...

While an integration of flying base stations (FlyBSs) into future mobile networks has received plenty of attention, a backhaul link (i.e., the link between a static base station and the FlyBS) is often either fully disregarded or oversimplified. However, the backhaul link and an access link between the FlyBS and users should be managed together to...

The Multi-Access Edge Computing (MEC) constitutes computing over virtualized resources distributed at the edge of mobile network. For mobile users, an optimal allocation of communication and computing resources changes over time and space, and the resource allocation becomes a complex problem. Moreover, for delay constrained applications, the resou...

The cloud radio access network (C-RAN) can potentially reduce a network's deployment cost and energy consumption. However, a connection between a centralized baseband unit and distributed remote radio heads, known as a fronthaul, introduces an additional delay to both control and user planes. This delay is a serious limiting factor for radio resour...

Transparent flying relay stations (FlyRSs), represented by transparent relays mounted on unmanned aerial vehicles (UAVs), have the potential to improve cellular network’s capacity and coverage at little extra complexity and energy cost, especially when compared with non-transparent relays. As the transparent relays do not transmit reference signals...

Device-to-device communication (D2D) is expected to accommodate high data rates and to increase the spectral efficiency of mobile networks. The D2D pairs can opportunistically exploit channels that are not allocated to conventional users in a dedicated mode. To increase the sum capacity of D2D pairs in the dedicated mode, we propose a novel solutio...

Device-to-device (D2D) relaying is a concept, where some users relay data of cell-edge users (CUEs) experiencing a bad channel quality to a base station. While this research topic has received plenty of attention, a critical aspect of the D2D relaying remains a selfish nature of the users and their limited willingness to relay data for others. Thus...

6G will exploit satellite, aerial and terrestrial platforms jointly to improve radio access capability and to unlock the support of on-demand edge cloud services in the three dimensional space (3D) by incorporating Mobile Edge Computing (MEC) functionalities on aerial platforms and low orbit satellites. This will extend the MEC support to devices a...

Efficient transmission protocols are required to minimize the energy consumption of mobile devices for ubiquitous connectivity in the next-generation of wireless networks. In this article, we analyze the energy consumption performance of a two-hop opportunistic device-select relaying (ODSR) scheme, where a device can either transmit data directly t...

Combination of radio frequency (RF) and visible light communication (VLC) bands for device-to-device (D2D) communication is seen as a promising way to both increase the system capacity and cope with an overcrowded RF bands. The main concern, however, is a proper mobility management and selection of the band that is beneficial at the moment. While t...

6G will exploit satellite, aerial and terrestrial platforms jointly to improve radio access capability and to unlock the support of on-demand edge cloud services in the three dimensional space (3D) by incorporating Mobile Edge Computing (MEC) functionalities on aerial platforms and low orbit satellites. This will extend the MEC support to devices a...

Device-to-device (D2D) communication allows a direct transmission between two devices. In this way, cellular user equipment’s are not always obliged to route the data conventionally through a cellular base station. This paper focuses on multi-hop D2D communication, where D2D relays are exploited to delivery of data from a source to a destination. W...

Device-to-device (D2D) communication, which enables a direct connection between users while bypassing the cellular channels to base stations (BSs), is a promising way to offload the traffic from conventional cellular networks. In D2D communication, optimizing the resource allocation requires the knowledge of D2D channel gains. However, such knowled...

This letter focuses on the selection between radio frequency (RF) and visible light communications (VLC) bands for users exchanging data directly with each other via device-to-device (D2D) communication. We target to maximize the energy efficiency of D2D communication while the outage is minimized. Since the VLC channel can vary quickly due to the...

The concept of device-to-device (D2D) communication, combining common radio frequency (RF) and visible light communication (VLC), is seen as a feasible way how to cope with spectrum crunch in the RF domain and how to maximize spectral efficiency in general. In this paper, our objective is to decide when RF should be utilized or if VLC proves to be...

Device-to-device (D2D) communication, which enables a direct connection between users while bypassing the cellular channels to base stations (BSs), is a promising way to offload the traffic from conventional cellular networks. In D2D communication, one recurring problem is that, in order to optimally allocate resources across D2D and cellular users...

Simultaneous random access attempts from massive machine-type communications (mMTC) devices may severely congest a shared physical random access channel (PRACH) in mobile networks. This paper presents a novel two-phase random access (TPRA) procedure to deal with the congestion caused by mMTC devices accessing the PRACH. During the first phase, the...

In this letter, the goal is to maximize sum capacity of device-to-device (D2D) communication through a reuse of each radio channel by multiple D2D pairs while each D2D pair can access multiple channels. Since existing approaches cannot be easily extended to enable reuse of multiple channels by multiple D2D pairs in scenario with a high interference...

Time-varying requirements of users on communication push mobile operators to increase density of base stations. However, the dense deployment of conventional static base stations (SBSs) is not always economical, for example, when periods of peak load are short and infrequent. In such cases, several flying base stations (FlyBSs) mounted on unmanned...

To satisfy requirements on future mobile network, a large number of small cells should be deployed. In such scenario, mobility management becomes a critical issue in order to ensure seamless connectivity with a reasonable overhead. In this paper, we propose a fuzzy logic-based scheme exploiting a user velocity and a radio channel quality to adapt a...

Energy consumption is a major limitation of low power and mobile devices. Efficient transmission protocols are required to minimize an energy consumption of the mobile devices for ubiquitous connectivity in the next generation wireless networks. Opportunistic schemes select a single relay using the criteria of the best channel and achieve a near-op...

Device-to-device (D2D) communication is an effective technology enhancing spectral efficiency and network throughput of contemporary cellular networks. Typically, the users exploiting D2D reuse the same radio resources as common cellular users (CUEs) that communicate through a base station. This mode is known as shared mode. Another option is to de...

Machine type communication (MTC) devices stay in idle mode to save energy and should perform random access (RA) procedure to obtain radio resources for data transmission. The RA procedure introduces access delay and extra power consumption for the MTC devices. Thus, RA needs to be optimized. In this paper, we develop low complexity analytical model...

Technological evolution of mobile user equipments (UEs), such as smartphones or laptops, goes hand-in-hand with evolution of new mobile applications. However, running computationally demanding applications at the UEs is constrained by limited battery capacity and energy consumption of the UEs. Suitable solution extending the battery life-time of th...

Future mobile networks are supposed to serve high data rates required by users. To accommodate the high data rates, a direct communication between nearby mobile terminals (MTs), known as Device-to-device (D2D) communication, can be exploited. Furthermore, a communication in high frequency bands, such as, visible light communication (VLC), is also f...

The small cell base stations (SCs) with cognitive capabilities are seen as an efficient way to cope with interference between the SCs and macrocells (MBSs). The cognitive SCs may access the spectrum by means of overlay or underlay mode. An efficiency of the overlay mode fully depends on the activity of macrocell users (MUEs), since insufficient res...

The femto access points (FAPs) with cognitive capabilities, also known as cognitive FAPs, are able to efficiently mitigate interference in two-tier heterogeneous networks. Hence, the concept of cognitive FAPs can be seen as one of the key enablers for future 5G networks, where high density of FAPs is foreseen. However, conventional overlay and unde...

Increasing demands of mobile users on communication and new types of devices, such as sensors, machines, and vehicles, impose high load on cellular networks. Since requirements are expected to rise in a near future, new ways for cellular network offloading are needed. A promising solution for vehicles and vehicular users is to offload data to vehic...

Small Cell Cloud (SCC) consists of Cloud-enabled Small Cells (CeSCs), which serve as radio end-points for mobile user equipments (UEs) and host computation offloaded from mobile UEs. SCC hereby brings advantages of a centralized cloud computation to the users' vicinity. The SCC architecture provides a mechanism for distribution of computation deman...

Convergence of mobile networks and cloud computing enables to offload heavy computation from a user equipment (UE) to the cloud. The offloading can reduce energy consumption of the UEs. Nevertheless, delivery of data to a centralized cloud leads to high latency and to overloading backhaul network. To overcome these constrains, computing capabilitie...

Running computationally demanding real-time applications at the mobile user equipment (UE) is complicated because of limited battery life time of the UEs. One solution is to offload demanding computing tasks to a centralized cloud. Nevertheless, this option introduces significant delay consisting in delivery of the offloaded tasks to the cloud and...

Direct communication between two or more devices without the intervention of a base station, known as device-to device (D2D) communication, is a promising way to improve performance of cellular networks in terms of spectral and energy efficiency. The D2D communication paradigm has been largely exploited in non-cellular technologies such as Bluetoot...

Opportunistic device-to-device (D2D) communication is the approach proposed to offload mobile data traffic for cellular networks. In opportunistic D2D communication, the network has to appoint relaying users to distribute content(s) to normal subscribers under a given delay-tolerance threshold. In general, the total number of relaying users is fixe...

The use of femtocells with cognitive capabilities is considered as a promising way for interference mitigation. The femto access point (FAP) accesses the spectrum either in overlay or underlay fashion. In the former case, the FAPs utilize only radio resources currently not occupied by the macrocell. In the latter case, the whole bandwidth may be us...

To avoid call drops after handover due to unavailability of radio resources at a target handover cell, call admission control procedure reserves a specific amount of resources for users performing handover to this cell. If a high amount of resources is reserved, the available capacity for users served by the cell is lowered. Contrary, if a low amou...

Requirements of current services and applications on computational power are still increasing. Hence, the utilization of these by the mobile user equipment (UE) having limited battery lifetime is quite a challenge. To cope with this problem, the mobile cloud computing can be exploited to offload high complex applications to the cloud. Nevertheless,...

In future 5G networks, in-band interference is perceived as one of the most critical performance bottlenecks. While current solutions classically treat interference as an additional source of noise, recent advances in information theory show that interference is not necessarily an opponent, but might be cancelled or supressed. In this paper, we pro...