1,721,032 research outputs found
Millimeter-wave transmission for small-cell backhaul in dense urban environment: a solution based on MIMO-OFDM and Space-Time Shift Keying (STSK)
No full textNext generation wireless standards will exploit the wide bandwidth available at the millimeter-wave (mm-Wave) frequencies, in particular the E-band (71-76 GHz and 81-86 GHz). This large available bandwidth may be converted into multi-gigabit capacity, when efficient and computationally-affordable transceivers are designed to cope with the constrained power budget, the clustered fading and the high level of phase noise, which actually characterize mm-wave connections. In this paper, we propose a viable Multiple-Input Multiple-Output (MIMO) solution for high bit-rate transmission in the E-band with application to small-cell backhaul based on Space-Time Shift Keying (STSK) and Orthogonal Frequency Division Multiplexing (OFDM). STSK provides an efficient trade-off between diversity and multiplexing without inter-channel interference (ICI) and without the need for large antenna arrays. These features make STSK theoretically preferable over other throughput-oriented space-time coding techniques, namely Spatial Multiplexing (SMUX) and Spatial Modulation (SM), which were recently considered in the literature for mm-wave MIMO applications. In this paper we consider the most significant channel impairments related to small-cell backhaul in dense urban environment, namely the correlated fading with and without the presence the line-of-sight (LOS), the phase noise, the rain attenuation and shadowing. Additionally, we consider small-size MIMO systems (2×2 and 4×4), and low-cost base station equipments in the perspective of easily-deployable small-cell network components. Comparative results, obtained by intensive simulations targeted at assessing link performance and coverage, have clearly shown the superior performance of STSK against counterpart techniques, although obtained at the cost of a somewhat reduced spectral efficiency
Feeder Link Precoding for Future Broadcasting Services: Architecture and Performance
Full text link5G systems are becoming a reality and the evolution towards Beyond 5G (B5G) and 6G systems is already being defined, also to cope with the ever increasing capacity demanded by on-ground users. This will pose challenging requirements on the feeder link of future satellite systems, which risks to become a bottleneck for the overall system performance. In this paper, we propose a novel architecture of linear precoding for the feeder link of a broadcast satellite system operating with full frequency reuse to significantly enhance the achievable capacity. The architecture has been simulated and tested in a challenging multi-frequency scenario, where Ku, Ka, Q/V, and W band have been considered for transmission. The numerical performance analysis and the open issues related to the practical realisation of the proposed architecture are also thoroughly discussed
A serial acquisition scheme based on statistical-hypothesis-testing for asynchronous DS/CDMA systems
No full textOne of the most critical problem in the asynchronous DS/CDMA reception consists of the effective acquisition of the initial pseudo-noise (PN) synchronism. In particular the multi-user interference (MUI) contrasts the operation to synchronise correctly the system. In this paper1, an adaptive PN acquisition scheme based on a statistical hypothesis testing and able to reduce the detrimental effects on acquisition process of multi-access interference present on the channel will be presented. The application considered for the proposed algorithm concerns with the transmission over an AWGN channel, performed by a DS/CDMA system. The results shown can prove the robustness of the proposed method in presence of different level of MUI, provided a reliable estimation of the channel conditions
A higher-order-statistics based blind interference cancellator for asynchronous DS/CDMA systems
No full textIn this work1, a novel DS/CDMA receiver using a High Order Statistics (HOS)-based interference cancellator is presented. In particular, the use of the Shen-Nikias algorithm for multilevel signal estimation in interference-dominated communication systems is proposed. The information signal coming out from the matched filter receiver can be regarded as a multilevel signal corrupted by heavy interference due to other system users (multi-user interference) or introduced by external noise sources. In the proposed analysis we considered only the presence of multiuser interference together with AWGN noise. A heuristic, however reasonable, assumption about the autoregressive nature of the multi-user interference is considered in the paper. BER performance analysis evidences a clear improvement with respect to the conventional matched filter case, thus confirming the validity of the basic assumptions made about statistical properties of MUI and proposing HOS-based techniques as valuable alternatives to other state-of-the-art DS/CDMA detection algorithms
An SDR-Based Satellite Gateway for Internet of Remote Things (IoRT) Applications
Full text linkInternet-of-Things (IoT) represents a breakthrough for the current ICT market. In many IoT applications, sensors and actuators are distributed over very wide areas, sometimes not reached by terrestrial networks. In such scenarios, the satellite plays a significant role. In this paper, a Software-Defined Radio (SDR) - based satellite gateway for Internet-of-Remote-Things (IoRT) is proposed. The use of SDR allows to decrease equipment cost and provides higher flexibility. The proposed architecture has been implemented by using a standalone SDR platform and Commercial Off-The-Shelf (COTS) modules for covering the main terrestrial IoT standards. Extensive proof-of-concept results are presented and discussed. Uplink and downlink tests showed the correct functionality implementation and transmitted signal generation, while the integration tests allowed to assess the reliability of the end-to-end information processing. Reconfigurability tests confirmed the capability of the gateway of dynamically updating in real-time its protocol settings. The overall test results showed the validity of the proposed SDR-based gateway for IoRT applications
Mm-Wave STSK-aided single carrier block transmission for broadband networking
No full textMillimeter wave (mm-Wave) communications has been considered as a strong candidate for future wireless standards, due to the large available bandwidth in the order of gigahertz. As a result, a plethora of future services and application-oriented scenarios can be conceived, under suitable propagation conditions. Accurate physical (PHY) layer design plays a vital role in the deployment of robust transmission systems able to efficiently exploit the large bandwidth portions available in the mm-Wave frequencies. In this paper, we propose Space-Time Shift Keying (STSK) MIMO coding combined with Cyclic-Prefixed Single Carrier (CP-SC) block transmission for broadband data exchange over frequency-selective mm-Wave channels. STSK allows to exploit transmit and receive diversity with better performance when compared with state-of-the-art MIMO techniques only relying on receive diversity, such as, for example Spatial Modulation (SM). The performance of CP-SC-STSK and CP-SC-SM have been assessed in the presence of phase noise and imperfect channel estimation, considering 2 and 4 elements MIMO systems and LoS indoor vs. nLoS outdoor 73 GHz multipath channels. We show that the STSK-based solution using MMSE Frequency-Domain Equalization (FDE) is very robust against the aforementioned impairments and clearly outperforms CP-SC-SM at the price of a slight increase of receiver complexity and a throughput reduction of 50% when 4 × 4 MIMO systems are considered
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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