Station de base | EPFL Graph Search

vignette|Station de radiocommunication en Géorgie Dans un système de radiocommunication mobile terrestre, une station de base est un équipement installé sur un site et muni d'une antenne émettrice-réceptrice avec lequel communiquent les appareils mobiles, pour avoir accès à un réseau de télécommunications. Le terme est utilisé dans le contexte de la téléphonie mobile, des réseaux informatiques sans fil, d'autres communications sans fil et dans l'arpentage. En arpentage, il s'agit d'un récepteur GPS à une position connue, tandis que dans les communications sans fil, il s'agit d'un émetteur-récepteur reliant un certain nombre d'autres dispositifs entre eux et / ou à une zone plus large. En téléphonie mobile, la station de base assure la connexion entre les téléphones mobiles et le réseau téléphonique (2G) ou le réseau Internet (3G et 4G). Dans ces réseaux mobiles, elles sont respectivement désignées par les termes BTS, Node B et eNode B. Dans un réseau informatique, il s'agit d'un ém

Channel State Feedback Over the MIMO-MAC

In order to exploit the full multiplexing gain of multi-antenna multi-user downlink schemes, accurate channel state information at the transmitter (i.e., at the base station) is required. We consider the design of a closed-loop channel state information feedback scheme, where user terminals feed back their channel state information simultaneously to a multi-antenna base station. The underlying information theoretic problem consists of lossy source-channel coding of multiple independent analog sources (i.e., the users' channel coefficients) over a Gaussian multiple- input multiple-output multi-access channel (MIMO-MAC). Unlike the classical source-channel coding setting, this application requires low latency, otherwise the channel state information would be outdated. Hence, source-channel codewords can span only a single fading state of the uplink (feedback) channel. Furthermore, the transmitters are ignorant of the realization of the uplink channel coefficients. In this scenario, the scaling of the maximum of the estimated downlink channel mean-square errors with the SNR dominates the performance of the multiuser downlink. This scaling is described by the distortion SNR exponent, previously introduced in a single-user MIMO setting. This paper analyzes the max-min distortion SNR exponent of the MIMO-MAC for both separated source-channel coding, and a particular hybrid digital-analog joint source-channel coding scheme. For the case of single-antenna users, we prove that the distortion SNR exponent of separated source-channel coding can be achieved by the concatenation of scalar quantization and uncoded quadrature-amplitude modulation (QAM) transmission, with lattice decoding at the base-station receiver. The resulting scheme has very low encoding latency (only a few symbols of the uplink slot) and generally outperforms currently proposed channel state feedback schemes based on analog unquantized transmission or vector quantization with fixed codebooks.

2011

Effect of intelligent antennas on radio system planning and on mitigation

Juliane Iten Chaves Simoes

Smart antennas have been recently applied to improve the capacity and the performance of second generation wireless mobile communication systems. In general, smart antennas reduce the effects of multipath fading and improve the signal-to-noise-plus-interference ratio (SNIR). Additional advantages such as channel capacity increase in urban areas, coverage extension in urban areas and spectrum efficiency in general can be obtained with the aid of smart antennas at the base station. Drawbacks are the cost, and both hardware and software complexity. Smart antennas promise a clear advantage in multi-service traffic scenario in comparison with non-adaptive antenna techniques. It is generally accepted that the adaptive antennas technique will be a key enable for the success of the European third generation mobile communication system known as Universal Mobile Telecommunication System (UMTS). The first part of this thesis presents two types of smart antenna systems: switched beam antennas and adaptive arrays. It introduces statistical models for them and investigates the performance measures of cellular radio systems with and without smart antennas deployed at base stations. Employing Monte-Carlo methodology, a tool has been developed to analyze the interference between two different systems that share the same geographical area and have neighboring frequency channels. The statistical smart antennas model has been used to verify the mitigation of the interference compared with others antennas used at the base station. These simulations have been done for TDMA, FDMA and CDMA systems. Wireless communication operating at different frequencies on the non-ionizing radiation (NIR) region of the electromagnetic spectrum has greatly increased in the last few decades, with important benefits for the population. These include mobile communication, such as cellular telephone systems. However, the radiated electromagnetic field levels increased substantially in areas where people may stay during long periods each day. This may result in long-term exposure to the population. International guidelines and standards were developed aiming at protecting the population, and limiting the maximum radiation produced. The methods used by regulation authorities to evaluate the field levels at places of sensitive use yield very conservative results. They need thus to be refined prior to the introduction of adaptive antennas. In the second part of the thesis, a 3D ray tracing tool is developed to predict the propagation for real scenarios using UMTS systems. This tool takes into account 3D radiation diagrams and multipath propagation. It was used in real scenarios to compare the real field levels with the levels obtained by the approximate methods defined by the regulation standards. Finally, this tool was used to predict the field levels in a scenario containing smart antennas. Scenario not foreseen in the method described in the standards.

EPFL2008

Cellular Fronthauling for Data Capacity Increase in Underserved Spaces

Adrian Schumacher

The increase in wireless data traffic continues and is a product of several factors. First, new technologies and capabilities enable new use cases for which new products emerge. Then, with the growing user adoption over time, the data traffic is further increased. As a result, the actual growth numbers vary year over year, but the trend is sustained. People nowadays also expect ubiquitous availability of mobile connectivity and use cloud services or stream music and video. Moreover, an increasing number of machines are being connected too. While mobile network operators (MNOs) deploy outdoor cellular networks, a significant portion of the mobile data traffic is consumed or originates indoors or while traveling in trains. To this end, MNOs constantly upgrade their networks to satisfy the capacity demand. Additionally, new and wider frequency bands are made available by regulators. However, the mid-band frequencies between 3 GHz and 6 GHz poorly enter buildings, and outdoor cells on millimeter-wave (mmWave) frequencies (24 GHz to 100 GHz) are practically unusable indoors and inside modern railways with their metallic hull and coated windows acting as Faraday cages. The increasing network densification with local cell sites (also inside shielded structures) can provide a partial solution. However, the required fiber and roll-out process is very costly and takes time. Moreover, providing sufficient capacity for the increasing data traffic demand inside buildings and trains is difficult where an optical fiber backhaul is too costly or impossible.State-of-the-art solutions are analyzed for solving the indoor capacity challenge. However, we found that these rely on or impact the existing outdoor cellular network and thus cannot provide additional capacity to the network that is used indoors. As a solution, we propose the mmWave bridge, an amplify-and-forward out-of-band repeater concept. It is a radio access technology (RAT) transparent and cost-efficient method to fronthaul mobile cells. Moreover, it provides wireless data capacity inside buildings, vehicles, or concealed areas outdoors, where low signal levels drastically limit the achievable capacity or prevent communication with distant base stations. The cellular signal of a base station is fronthauled over newly available mmWave frequencies outdoor without interfering with the existing cellular network. Mid-band frequencies are used indoors to provide sufficient coverage beyond rooms and, at the same time, benefit from the outdoor-to-indoor attenuation reducing possible interference.The benefits of the mmWave bridge are described, and we discuss the corresponding challenges and solutions. Moreover, a hardware prototype was developed based on commercial off-the-shelf components. We have tested our prototype in three use cases to demonstrate the functionality and compatibility with commercial infrastructure and mobile terminals and present the measurement results. We can show that the entire capacity of a mobile cell can be fronthauled over distances in relation to the mmWave frequency propagation and signal power. Finally, the amplify-and-forward out-of-band repeater concept is generalized regarding the fronthaul carrier frequency. The use of beamforming antennas on RAT-transparent repeaters without access to in-band beam control is investigated, and a solution with a minimal impact of a few percent in throughput reduction is presented.

EPFL2022