Joel Grotz - Academia.edu (original) (raw)

Papers by Joel Grotz

arXiv (Cornell University), Feb 2, 2023

2022 IEEE 96th Vehicular Technology Conference (VTC2022-Fall)

2022 IEEE International Mediterranean Conference on Communications and Networking (MeditCom)

Non-geostationary (Non-GSO) satellite constellations have emerged as a promising solution to enab... more Non-geostationary (Non-GSO) satellite constellations have emerged as a promising solution to enable ubiquitous high-speed low-latency broadband services by generating multiple spot-beams placed on the ground according to the user locations. However, there is an inherent trade-off between the number of active beams and the complexity of generating a large number of beams. This paper formulates and solves a joint beam placement and load balancing problem to carefully optimize the satellite beam and enhance the link budgets with a minimal number of active beams. We propose a two-stage algorithm design to overcome the combinatorial structure of the considered optimization problem providing a solution in polynomial time. The first stage minimizes the number of active beams, while the second stage performs a load balancing to distribute users in the coverage area of the active beams. Numerical results confirm the benefits of the proposed methodology both in carrier-to-noise ratio and multiplexed users per beam over other benchmarks.

2022 11th Advanced Satellite Multimedia Systems Conference and the 17th Signal Processing for Space Communications Workshop (ASMS/SPSC)

For multi-beam high throughput (MB-HTS) geostationary (GEO) satellite networks, the congestion ap... more For multi-beam high throughput (MB-HTS) geostationary (GEO) satellite networks, the congestion appears when user's demands cannot be fully satisfied. This paper boosts the system performance by formulating and solving the power allocation strategies under the congestion control to admit users. A new multi-objective optimization is formulated to balance the sum data throughput and the satisfied user set. After that, we come up with two different solutions, which efficiently tackle the multi-objective maximization problem: The modelbased solution utilizes the weighted sum method to enhance the number of demand-satisfied users, whilst the supervised learning solution offers a low-computational complexity design by inheriting optimization structures as continuous mappings. Simulation results verify that our solutions effectively copes with the congestion and outperforms the data throughput demand than the other previous works.

IEEE Transactions on Broadcasting

To adjust for the non-uniform spatiotemporal nature of traffic patterns, next-generation high thr... more To adjust for the non-uniform spatiotemporal nature of traffic patterns, next-generation high throughput satellite (HTS) systems can benefit from recent technological advancements in the space-segment in order to dynamically design traffic-adaptive beam layout plans (ABLPs). In this work, we propose a framework for dynamic beamforming (DBF) optimization and adaptation in dynamic environments. Given realistic traffic patterns and a limited power budget, we propose a feasible DBF operation for a geostationary multibeam HTS network. The goal is to minimize the mismatch between the traffic demand and the offered capacity under practical constraints. These constraints are dictated by the traffic-aware design requirements, the on-board antenna system limitations, and the signaling considerations in the K-band. Noting that the ABLP is agnostic about the inherent inter-beam interference (IBI), we construct an interference simulation environment using irregularly shaped beams for a large-scale multibeam HTS system. To cope with IBI, the combination of on-board DBF and on-ground precoding is considered. For precoded and non-precoded HTS configurations, the proposed design shows better traffic-matching capabilities in comparison to a regular beam layout plan. Lastly, we provide trade-off analyses between system-level key performance indicators for different realistic non-uniform traffic patterns.

This paper aims to design joint precoding and onboard beamforming of a multiple gateway multibeam... more This paper aims to design joint precoding and onboard beamforming of a multiple gateway multibeam satellite system, either in a hybrid space-ground mode, or in a totally on-board one. In such an architecture, with employing high throughput full frequency reuse pattern over both user and feeder links, each gateway serves a cluster of adjacent beams such that the adjacent clusters are served through a set of gateways that are located at different geographical areas. However, such a system brings in two challenges to overcome. First, the interference in both user and feeder links is the bottleneck of the whole system and applying interference mitigation techniques becomes necessary. Second, as the data demand increases, the ground and space segments should employ extensive bandwidth resources in the feeder link accordingly. This entails embedding an extra number of gateways aiming to support a fair balance between the increasing demand and the corresponding required feeder link resourc...

2018 9th Advanced Satellite Multimedia Systems Conference and the 15th Signal Processing for Space Communications Workshop (ASMS/SPSC), 2018

Soaring demand for high data rate services entails high throughput satellite (HTS) systems with m... more Soaring demand for high data rate services entails high throughput satellite (HTS) systems with multi beam architecture, and full frequency and time resources reuse. However, interference among simultaneously served users is the primitive factor that is needed to be addressed before enacting HTS system with this architecture. beamforming has been proposed as a potential technique to mitigate the interference in the literature. Different types of beamforming techniques proposed including beamforming at payload (on-board), beamforming at gateway and hybrid beamforming. On-board beamforming prevails over other techniques due to its advantages-channel information at payload is more recent than gateway and sharing overhead of channel and symbols across multiple gateways is reduced in a multigateway architecture to name a few. Despite these advantages, beamforming at gateway is usually preferred due to the heavy processing cost incurred in beamforming. beamforming processing cost can be split into two factors: design cost and implementation cost. While design cost accounts for the cost involved in design of beamformer, implementation cost accounts for multiplications and additions involved in applying calculated beamformer coefficients to data symbols. Through our study, we noticed that the major contributing factor to processing cost is the implementation cost which accumulates for every data symbol rather than design cost which is incurred only once per channel coherence time which usually relatively longer than many data symbols. Furthermore, implementation cost is dominated by the multiplications involved. Hence, in this work, we address the issue of implementation cost from the perspective of on-board multiplications. We formulate the problem of minimizing on-board implementation cost (multiplications) of a beamformer as a second order cone programming problem with help of 1 norm constraint on the beamforming matrix subjected to minimum signal-to-interference-noise ratio of simultaneously users and classical total power constraint. We show the efficacy our algorithm over the traditional power minimization method through Monte-Carlo simulations. Index Terms-High throughout satellite systems, interference, beamforming and second order cone programming

2020 IEEE Aerospace Conference, 2020

In this paper we propose a Revenue Management framework for satcom operators and show with a proo... more In this paper we propose a Revenue Management framework for satcom operators and show with a proof-ofconcept simulation that predicts a significant gain in revenues. New satellite operators, highly variable demand for data, digital payloads, and new phased array technologies are likely to remake the current satcom landscape. One of the challenges operators old and new will face is how to manage demand and capacity. Airlines faced a similar situation with deregulation in the 1970s-their response with tiered pricing and seat inventory control to allocate capacity (known as Revenue Management), which may offer lessons for the satcom market. The satcom industry shares many characteristics with the airline industry, such as inflexible capacity, low marginal sales cost, perishable inventory, heterogenous customers, and variable and uncertain demand. Generally, those characteristics favor the implementation of a Revenue Management system. However, the details of how Revenue Management can be used by satcom operators still need to be explored, which is the focus of this paper.

Advances in Communications Satellite Systems Proceedings of The 36th International Communications Satellite Systems Conference (ICSSC-2018), 2019

This study aims at designing precoding in multiple satellite multibeam systems with overlapping c... more This study aims at designing precoding in multiple satellite multibeam systems with overlapping coverage areas where the multiple satellites have the same footprints and overlap in their coverage. Besides, high throughput full frequency reuse pattern among satellites is used. In such an architecture, the key objective lies in the collaboration between satellites and obtains: i) reliable multibeam infrastructure to serve unforeseen changes in the traffic demand through establishing supportive secondary satellites, ii) multiple satellites can provide service to higher spatial diversity by keeping the size of the payload affordable, iii) employing multiple satellites provides hardware redundancy to guarantee uninterrupted service delivery. However, intra-satellite and inter-satellite interference are the bottleneck of the whole network and employing interference mitigation techniques, particularly precoding techniques, is essential. In this paper, we analytically and numerically study designing precoding technique that: a) properly mitigates intra-satellite and inter-satellite interference, b) since the performance of precoding is sensitive to the quality of Channel State Information (CSI), proper low complex CSI exchange mechanism among the satellites is developed.

36th International Satellite Communications Systems Conference (ICSSC2018), 2018

Precoding techniques for mulit-beam satellite systems have received a considerable attention in r... more Precoding techniques for mulit-beam satellite systems have received a considerable attention in recent years as a tool to mitigate the interference among the beams, and hence increasing the throughput. Our goal is to compare two main categories of precoding schemes, namely, the conventional linear block level precoding and the symbol level precoding. Focusing on power minimization problem with signal to interference plus noise ratio (SINR) constraints, symbol level precoding (SLP) has significant gains with respect to the zero forcing (ZF). However, the lower transmit power is achieved with a price: A higher computational complexity. Therefore, several sub-optimal SLP techniques have been proposed in the literature to overcome the complexity. While ZF has the lowest complexity among the techniques chosen in this paper, it is not an optimal linear block level precoder as far as power minimization is concerned. Therefore, in order to have a more complete picture, one needs also to consider optimal block level precoders. Our results indicate that in order to have a fair comparison, one needs to consider two different scenarios, namely, low and high SINR threshold regimes. While for low SINRs the optimal linear block level precoding scheme may provide a good solution with reasonable complexity, for high SINR threshold, the SLP techniques become more attractive. Our results also indicate that the performance of SLP highly depends on the chosen constellation space, and therefore a final conclusion can be achieved only after appropriately optimizing the constellation set.

2019 IEEE Global Communications Conference (GLOBECOM), 2019

This paper designs dynamic on-board signal processing schemes in a multiple gateway multibeam sat... more This paper designs dynamic on-board signal processing schemes in a multiple gateway multibeam satellite system where full frequency reuse pattern is considered among the beams and feeds. In particular, we deploy on-board Joint Precoding, Feed selection and Signal switching mechanism (JPFS) so that the following advantages are realized, I) No need of Channel State Information (CSI) exchange among the gateways and satellite, since the performance of precoding is highly sensitive to the quality of CSI, II) In case one gateway fails, rerouting signals through other gateways can be applied without any extra signal processing, III) Properly selecting on-board feed/s to serve each user which generates maximum gain toward corresponding user, IV) Flexibly switching the signals received from the gateways to requested users where each user can dynamically request traffic from any gateway, and V) Multiple user with multiple traffic streams can be dynamically served at each beam. However, deploying such JPFS architecture imposes high complexity to the satellite payload. To tackle this issue, this study aims at deploying JPFS that can provide affordable complexity at the payload. In addition, while increasing the data demand imposes extensive bandwidth resources requirement in the feeder link, the proposed JPFS design works efficiently with available feeder link resources even if the data demand increases. The proposed design is evaluated with a close-to-real beam pattern and the latest broadband communication standard for satellite communications.

International Journal of Satellite Communications and Networking, 2020

The fifth generation (5G) wireless networks have to deal with the high data rate and stringent la... more The fifth generation (5G) wireless networks have to deal with the high data rate and stringent latency requirements due to the massive invasion of connected devices and data-hungry applications. Edge caching is a promising technique to overcome these challenges by prefetching the content closer to the end users at the edge node's local storage. In this paper, we analyze the performance of edge caching 5G networks with the aid of satellite communication systems. Firstly, we investigate the satellite-aided edge caching systems in two promising use cases: a) in dense urban areas, and b) in sparsely populated regions, e.g., rural areas. Secondly, we study the effectiveness of satellite systems via the proposed satellite-aided caching algorithm, which can be used in three configurations: i) mono-beam satellite, ii) multi-beam satellite, and iii) hybrid mode. Thirdly, the proposed caching algorithm is evaluated by using both empirical Zipf-distribution data and the more realistic Movielens dataset. Last but not least, the proposed caching scheme is implemented and tested by our developed demonstrators which allow real-time analysis of the cache hit ratio and cost analysis.

2005 IEEE 61st Vehicular Technology Conference

Data-aided multi-user burst frequency synchronization under interference limited conditions is an... more Data-aided multi-user burst frequency synchronization under interference limited conditions is analyzed. It is assumed that a unique-word based synchronization mechanism is used to achieve synchronization. In a first approach this unique-word is assumed to be located at the beginning of the burst structure. The interference represents frequency-adjacent bursts that are coarsely time synchronous. This corresponds to a typical multi frequency

IEEE Communications Magazine, 2015

Multibeam satellite networks in Ka band have been designed to accommodate the increasing traffic ... more Multibeam satellite networks in Ka band have been designed to accommodate the increasing traffic demands of the coming years. However, these systems are spectrum limited due to the current spectrum allocation policies. This paper investigates the potentials of applying cognitive radio techniques in satellite communications in order to increase the spectrum opportunities for future generation of satellite networks without interfering operation of incumbent services. These extra spectrum opportunities can potentially amount to 2.4 GHz of bandwidth in downlink, and to 2 GHz of bandwidth in uplink for high density fixed satellite services (HDFSS). 1-Introduction The Ka band is mainly considered by the SatCom industry for deployment of satellite high speed broadband networks in un-served and under-served areas. To determine the market demand for Ka band, recent R&D studies in Europe [1], [2], show the potential demand for satellite broadband services in rural areas in order to meet the objectives of the Digital Agenda for Europe, i.e. universal availability of broadband speeds of at least 30 Mb/s throughout Europe, with at least 50% of households having access to data rates above 100 Mb/s. Moreover, some studies conclude that the average number of total European households which choose a satellite broadband connection in 2020 is expected to be between 5 to 10 Million [2]. This represents a market potential for several satellite systems and creates the need to access extra spectrum, including the frequency bands shared with other services, in order to accommodate the increasing bandwidth and data rate demand [3]. It is foreseeable that spectrum congestions can make future Ka band deployments more difficult. High Throughput Satellites (HTS) already suffer from spectrum scarcity in Ka band in order to deliver meaningful performance. Only 500 MHz of exclusive Geostationary Satellite Orbit (GSO) incumbent spectrum is available in all ITU Regions for downlink. The access to a further 2.4 GHz of spectrum in Ka band as discussed in this paper, potentially allows satellite operators to meet the demand for HDFSS without prior individual frequency coordination. This in turn justifies the need to investigate cognitive radio (CR) techniques in the SatCom context, in order to allow exploitation of the shared frequency bands while guaranteeing acceptable interference to the incumbent users [3]. Another important aspect to be taken into account is the long-term and persistent interference from the terrestrial services which affects the core business of satellite operators. In this context, CR based solutions can provide relief as well as a measurable utilization and revenue increase to the SatCom business.

Vehicular Technology, IEEE Conference, 2005

This paper investigates the usage of established interference cancellation techniques applied to ... more This paper investigates the usage of established interference cancellation techniques applied to the simultaneous reception of geostationary satellite broadcast signals from two or more satellites. In particular the reduction of interference from adjacent satellites is of interest, which would allow a reduction of the antenna size and the requirements on the directivity of the installation. The rejection of unwanted adjacent

The objective of this paper is to discuss the applicability and benefits of Cognitive Radio techn... more The objective of this paper is to discuss the applicability and benefits of Cognitive Radio techniques in the context of satellite communication systems operating in the Ka band where spectrum chunks are allocated to Fixed Satellite Services with other services. The paper reports about ongoing technical analysis and standardization activities in the context of the FP7 ICT project "CoRaSat", which aims to assess the potential gain of Cognitive Radio techniques to improve the spectrum use and to assess the need for the implementation of possible adaptations to the existing regulatory framework.

IEEE Transactions on Wireless Communications, 2010

We address fixed satellite broadcast reception with the goal of decreasing the aperture of the re... more We address fixed satellite broadcast reception with the goal of decreasing the aperture of the receiving antenna. The front-end antenna size is commonly determined by the presence of interference from adjacent satellites. A small antenna aperture leads to interference from neighboring satellites utilizing the same frequency bands. We propose a reception system with M multiple input elements and with subsequent

IEEE Transactions on Consumer Electronics, 2008

The problem of fixed satellite broadcast reception is considered. The possibility of reducing the... more The problem of fixed satellite broadcast reception is considered. The possibility of reducing the requirements on the antenna front-end dimensions is investigated. Interference processing and mitigation techniques are employed to cope with the increased level of adjacent system interference at the satellite broadcast receiver resulting from the less directive antenna. A novel satellite reception front-end antenna based on a multiple input receiver is proposed to adapt the interference processing methods to the broadcast reception scenario. The potential performance of the devised scheme is thoroughly discussed and assessed by extensive software simulations. 1

2015 European Conference on Networks and Communications (EuCNC), 2015

The Digital Agenda for Europe (DAE) sets forth ambitious requirements for broadband communication... more The Digital Agenda for Europe (DAE) sets forth ambitious requirements for broadband communications, in which Satellite Communications (SatCom) play a major role. In this context, spectrum sharing techniques offer unprecedented opportunities to increase capacity and reduce costs in order to allow SatCom to meet the DAE objectives. The EU FP7 Project CoRaSat is assessing Cognitive Radio (CR) techniques for Ka-band SatCom scenarios, showing that coexistence between Fixed Satellite Service (FSS) and Broadcasting Satellite System (BSS)/Fixed Service (FS) links would introduce significant benefits in non-exclusive frequency bands. In this paper, spectrum awareness and exploitation techniques are analyzed. Simulation results show that significant improvements can be obtained in both spectrum utilization (up to 2.4 GHz of additional spectrum) and available throughput (up to 600% increase).