Raymond Knopp

Bio: Raymond Knopp is an academic researcher from Institut Eurécom. The author has contributed to research in topics: Communication channel & MIMO. The author has an hindex of 32, co-authored 230 publications receiving 6832 citations. Previous affiliations of Raymond Knopp include École Polytechnique Fédérale de Lausanne & McGill University.

An SDN/NFV based framework for management and deployment of service based 5G core network

Abstract: The traffic explosion and the rising of diverse requirements lead to many challenges for traditional mobile network architecture on flexibility, scalability, and deployability. To meet new requirements in the 5G era, service based architecture is introduced into mobile networks. The monolithic network elements (e.g., MME, PGW, etc.) are split into smaller network functions to provide customized services. However, the management and deployment of network functions in service based 5G core network are still big challenges. In this paper, we propose a novel management architecture for 5G service based core network based on NFV and SDN. Combined with SDN, NFV and edge computing, the proposed framework can provide distributed and on-demand deployment of network functions, service guaranteed network slicing, flexible orchestration of network functions and optimal workload allocation. Simulations are conducted to show that the proposed framework and algorithm are effective in terms of reducing network operating cost.

Sensor networks for cognitive radio : theory and system design

Abstract: Following current trends towards dynamic spectrum allocation and cognitive radio, this paper proposes a new approach and innovative techniques to support the coexistence of licensed and unlicensed wireless users in a same area. Theproposed concept, called Sensor Network aided Cognitive Radio, consists of a wireless sensor network able to assist the cognitive network by providing information on the current spectrum occupancy. This concept, that will address various operational scenarios in the future networks, involves a set of advanced wireless communications techniques like spectrum sensing, interference management, cognitive radio reconfiguration management, cooperative communications, end-to-end protocol design and cross-layer optimisation. All these enabling techniques together will form a compound system able to improve the spectrum use in a significant way. The main target scenario we consider is the use of nomadic cognitive radios in urban and suburban areas. Our objective is to develop a proof-of-concept – scheduled in 2010 – of the Sensor Network aided Cognitive Radio technology by implementing such techniques and integrating them on a hardware radio platform, which will allow us to assess the efficiency of the technology in a realistic environment.

Contention Based Access for Machine-Type Communications over LTE

Abstract: To enable the efficient and low latency machine-type communications (MTC) over long term evolution (LTE), a contention based access (CBA) method is proposed. With CBA, UEs transmit packets on the randomly selected resource without having any UE specific scheduled resources. To address the problem of collision caused by CBA in high traffic load, eNB exploits the MU-MIMO detection technique to decode radio network temporary identifier (RNTI) of the collided UEs and use this information to perform a regular scheduling in subsequent subframe. Detailed low layer signaling enhancement to implement CBA technique in current LTE specification (Rel. 10) is also presented. Simulation results demonstrate that the CBA significanlty outperforms the existing uplink channel access methods.

Channel allocation algorithms for multi-carrier systems

Abstract: This study focuses on orthogonal channel allocation strategies, yielding multiuser diversity with a deterministic channel, for use in an N-user system with N parallel sub-channels. The techniques are applicable, for instance, in orthogonal frequency division multiple-access (OFDMA) systems with dynamic sub-carrier allocation. We show that multiuser diversity, and thus an increase of aggregate data rates with the size of the user population, can still be successfully achieved even under a hard fairness constraint. Furthermore, we provide algorithms which perform channel allocation yielding a variable-rate with constant power and fixed-rate with variable power. We show the effect of system bandwidth (and thus sub-channel correlation) on multiuser diversity. The techniques considered here do not require phase information in the channel allocation process, which, from a practical point-of-view, is particularly important for time-division duplex systems exploiting channel reciprocity.

On the achievable rates of ultra-wideband PPM with non-coherent detection in multipath environments

Abstract: In this work we investigate the achievable rates of ultra-wideband (UWB) systems using a m-ary pulse position modulation (PPM) with non-coherent receivers in multipath fading environments. We derive a random coding bound on the achievable information rates and highlight the influence of system parameters (bandwidth, delay spread). We also investigate the effect of the use of hard decisions prior to channel decoding and characterize its impact on system performance.

I and i

Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

User cooperation diversity. Part I. System description

Abstract: Mobile users' data rate and quality of service are limited by the fact that, within the duration of any given call, they experience severe variations in signal attenuation, thereby necessitating the use of some type of diversity. In this two-part paper, we propose a new form of spatial diversity, in which diversity gains are achieved via the cooperation of mobile users. Part I describes the user cooperation strategy, while Part II (see ibid., p.1939-48) focuses on implementation issues and performance analysis. Results show that, even though the interuser channel is noisy, cooperation leads not only to an increase in capacity for both users but also to a more robust system, where users' achievable rates are less susceptible to channel variations.

Massive MIMO for next generation wireless systems

Abstract: Multi-user MIMO offers big advantages over conventional point-to-point MIMO: it works with cheap single-antenna terminals, a rich scattering environment is not required, and resource allocation is simplified because every active terminal utilizes all of the time-frequency bins. However, multi-user MIMO, as originally envisioned, with roughly equal numbers of service antennas and terminals and frequency-division duplex operation, is not a scalable technology. Massive MIMO (also known as large-scale antenna systems, very large MIMO, hyper MIMO, full-dimension MIMO, and ARGOS) makes a clean break with current practice through the use of a large excess of service antennas over active terminals and time-division duplex operation. Extra antennas help by focusing energy into ever smaller regions of space to bring huge improvements in throughput and radiated energy efficiency. Other benefits of massive MIMO include extensive use of inexpensive low-power components, reduced latency, simplification of the MAC layer, and robustness against intentional jamming. The anticipated throughput depends on the propagation environment providing asymptotically orthogonal channels to the terminals, but so far experiments have not disclosed any limitations in this regard. While massive MIMO renders many traditional research problems irrelevant, it uncovers entirely new problems that urgently need attention: the challenge of making many low-cost low-precision components that work effectively together, acquisition and synchronization for newly joined terminals, the exploitation of extra degrees of freedom provided by the excess of service antennas, reducing internal power consumption to achieve total energy efficiency reductions, and finding new deployment scenarios. This article presents an overview of the massive MIMO concept and contemporary research on the topic.

Opportunistic beamforming using dumb antennas

Abstract: Multiuser diversity is a form of diversity inherent in a wireless network, provided by independent time-varying channels across the different users. The diversity benefit is exploited by tracking the channel fluctuations of the users and scheduling transmissions to users when their instantaneous channel quality is near the peak. The diversity gain increases with the dynamic range of the fluctuations and is thus limited in environments with little scattering and/or slow fading. In such environments, we propose the use of multiple transmit antennas to induce large and fast channel fluctuations so that multiuser diversity can still be exploited. The scheme can be interpreted as opportunistic beamforming and we show that true beamforming gains can be achieved when there are sufficient users, even though very limited channel feedback is needed. Furthermore, in a cellular system, the scheme plays an additional role of opportunistic nulling of the interference created on users of adjacent cells. We discuss the design implications of implementing. this scheme in a complete wireless system.