1,721,085 research outputs found
Analysis of Zero-Forcing Vectoring for VDSL2 and Long Reach VDSL Technologies
No full textA Normal approximation for the downstream bit rate per user in modern Fiber-to-the-Cabinet DSL-based access systems such as Very high-speed Digital Subscriber Line type 2 (VDSL2) and Long Reach VDSL (LR-VDSL) is presented in this paper. It accounts for the positions of subscribers along the main cable from the Cabinet, for the Far-end cross-talk (FEXT) fluctuations, for the transmitter power spectra of subscribers and for zero forcing vectoring. A stochastic model relating the FEXT to residual FEXT after zero forcing vectoring pre-coding is also presented. The proposed Normal model is derived by assuming Log-normal statistics of the signal-to-interference plus noise ratio per sub-carrier. Its validity is assessed by computer calculation by superimposing the cumulative distribution functions obtained from exact bit rate calculation with those obtained with the Normal model. Differences of few Mbit/s have been observed for high percentiles thus proving the effectiveness of the proposed model. We applied the model to assess coexistence among different DSL technologies such as VDSL2 and LR-VDSL sharing the same copper cable from the Cabinet and even to evaluate the downstream bit rate for G.fast with zero forcing vectoring
Spectral analysis of UWB multiple access schemes using random scrambling
No full textWith the new release of the Federal Communication Commission on matters of regulation of marketing and operation of ultra-wideband (UWB) devices, an analytical framework to enable tractable analysis of the spectrum shape of these signals is needed. We extend the framework introduced by W. A. Gardner to the case of UWB signals. We introduce a generalized UWB signal model that can be specialized to represent the traditional time-hopping (TH) technique as well as the alternative multiple access technique that we indicate as delay coded sequence (DCS). The DCS technique resembles the traditional direct sequence spread spectrum techniques, but it is not based on pulse polarity inversion. The considered matrix signal formulation allows us to easily evaluate the spectral characteristics of UWB signals under many different operating conditions: continuous or discontinuous transmissions, random or periodic scrambling operations, with or without jitter. We evaluate the spectrum of the general UWB signal under the random scrambling assumption, then we specialize it to the TH and DCS cases and discuss the variability of the spectra to some critical design parameters. We obtain an asymptotic expression of the general UWB spectrum that we use to evaluate the UWB interference power at the output of a generic receiver
Performance evaluation of high data rate UWB systems based on IEEE 802.15.3
No full textThe performance of an UWB system for high data rate transmissions is evaluated in terms of link outage probability and average aggregate network throughput. The network topology is based on a clustered structure, formed by a multitude of piconets coexisting in a given area. The piconets operate in accordance to the IEEE 802.15.3 standard. Two different modulation formats are considered and their performance compared: multiband OFDM (MBO) and direct sequence spread spectrum (DS-SS). Performance parameters are
evaluated using an effective semi-analytical procedure that allows us to account for interference due to uncoordinated piconets in the area in realistic propagation conditions. We show that when the operating band of the MBO is restricted to group A, the DSSS outperforms the MBO. The situation is reversed when the available bands for the MBO increase
Capacity Analysis of UWB systems in Realistic Multipath Channels
No full textIn this paper we combine the main results obtained within the ULTRAWAVES project on two critical issues: the characterization of the UWB propagation channel and the assessment of the capacity of an UWB system operating in a typical office environment. Based on the experimental data collected through a wide measurement campaign in a typical European office environment, we evaluate the performance of a single UWB link in a realistic multipath environment using either binary pulse position or pulse amplitude modulation. These data are used to extract the SNR specification for a target bit error probability. Then we use it to evaluate the system outage probability with a novel semi-analytic approach also described in the paper. A realistic master-slave UWB network based on DS-CDMA is considered and its capacity is expressed in terms of the average number of users served with a required outage probability level. The proposed approach is quite flexible and allows us to easily include realistic path loss models, power control mechanism and intra system interference
A physical-statistical channel modeling for mobile satellite communications with diversity
No full textEffective strategies for gradual copper-to-fiber transition in access networks
No full textIn this paper, we analyze the improvements that can be achieved with the introduction of low-cost technical arrangements and devices into the present Fiber-To-The-Cabinet (FTTC) networks aiming: to support statistical multiplexing of groups of copper pairs shared among subscribers at protocol layer two, and to relay signals along the main cable. With simple calculations, we prove the bit rate per user can be increased well beyond, that achieved with present Fiber-To-The-Home (FTTH) network standards. Crosstalk performance degradation with respect to ideal case are analysed in the case of VDSL2 35b and G.fast technologies. Costs of the considered solutions are compared with those of FTTH networks. We show that in a short-medium term the low cost of investments required for updating the FTTC network can extend the life of existing copper-based networks providing at the same time a significant performance improvement with respect to the current FTTC configuration. This facilitates the smooth transition to FTTH supported by the re-investing of the acquired revenues. The solution considered in this paper moves in the direction of rendering feasible the European Gigabit Society (EGS) vision, whose objectives are extremely challenging (if not unreachable within the foreseen 2025 timeframe) with an all-fiber approach. In fact, as shown in this paper the Gigabit-ready hybrid copper-fiber approach technology provides a feasible path to significantly reduce “gigabit” deployment costs so to gradually move toward all-fiber EGS vision
Satellite-Based Capillary 5G-mMTC Networks for Environmental Applications
No full textBesides traditional 5G MBB and ULLRC services, 5G networks will also embody connections to billions of Internet of Things (IoT) objects. Future IoT 5G-mMTC applications for environmental monitoring, remote metering, and surveillance over metropolitan areas are among the main enablers of the Smart City concept. The role of satellite to transfer large amount of data gathered from (any type of) sensors spread over geographical metropolitan areas in a country can be helpful to promote the implementation of smart applications aimed for example to optimize usage of resources (e.g., energy), transportation flows, centralized control of critical infrastructures, etc., at a nation-wide scale. One of the main limitations of this scenario consists in the availability of sensors devices incorporating transmission facilities to directly connect to the satellite. In this paper, we assess the achievable performance of a FttC-based capillary network extended to include terrestrial radio stations (RSs) collecting data from surrounding IoT devices. RS data are then transferred using one (or more) copper pair(s) to the satellite modem installed at the cabinet as well as at the central office. Performance of the considered network architecture is expressed in terms of the blocking probability for satellite access
Analysis of UWB system capacity in a realistic multipath environment with coexistence constraints
No full textUltra-wideband (UWB) wireless technology is envisaged to play a key role in B3G wireless systems, guaranteeing very high bit rates, low power consumption, low costs and location capabilities. The availability of low cost and efficient devices makes UWB technology very competitive on the communications market. However, its worldwide acceptance mainly relies on coexistence issues because of the necessity of sharing the spectrum with other radio systems. The reduction, due to coexistence constraints, in the capacity of an UWB system in a realistic multipath channel is investigated. Link performance of an UWB system that exploits either partial or selective Rake combining at the receiver is evaluated over experimental impulse responses of an UWB indoor channel in an office building. Using these results, system performances are evaluated through a semi-analytical procedure in terms of outage probability and system capacity. Results on system capacity account for the limitations imposed by the current regulation, leading us to introduce the concept of `UWB systems limited by coexistence'
Future Technologies for Train Communication: The Role of LEO HTS Satellites in the Adaptable Communication System
No full textThe railway sector has been characterized by important innovations regarding digital technologies for train-to-ground communications. The actual GSM-R system is considered an obsolescent technology expected to be dismissed by 2030. The future communication systems in the rail sectors, such as Adaptable Communication Systems (ACS) and Future Railway Mobile Communication Systems (FRMCS), can manage different bearers as 4G/5G terrestrial technologies and satellites. In this environment, the new High Throughput Satellite (HTS) Low-Earth Orbit (LEO) constellations promise very interesting performances from data rate and coverage points of view. The paper analyzes the LEO constellations of Starlink and OneWeb using public data. The Rome–Florence railway line is considered for simulations. The results evidence the LEO satellite can provide interesting performance in terms of visibility, service connectivity, and traffic capacities (up to 1 Gbps). This feature enables the LEO to fully manage a high amount of data, especially in the railway scenarios of the next years when video data applications will be more present
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