The performance of a MIMO 4 x 4 transmission solution applied to 4th generation LTE FDD technology are evaluated inside a reverberation chamber (RC) to quantify its benefit against the LTE typical MIMO 2 x 2 transmission scheme, in different environment conditions. The implementation of MIMO 4 x 4 in live networks requires the connection of two additional cables between base station transmitters and antennas, and operators face additional costs. Throughput and modulation code scheme allocation are analyzed as a function of the signal to interference-plus-noise ratio (SINR), for both indoor and outdoor environments. Experimental results in a live network are compared to those obtained in the RC of our laboratory. Results highlight that MIMO 4 x 4 is convenient for SINR greater than 10-15 dB. These results can help mobile network operators to evaluate if the expected benefit justifies the additional costs in an operating actual network.

Testing of wireless devices and systems is becoming increasingly important in the technological development of Long Term Evolution (LTE) and 5G mobile networks. Both mobile and base station manufacturers are interested in assessing system performance and user perceived quality in realistic propagation environments, including indoor and outdoor conditions. Real-life electromagnetic environments exhibit rich multipath propagation and a strong attenuation of the wireless signal over the propagation channel. Emulating those conditions in anechoic chambers requires the careful arrangement of many interference sources in multiple configurations, which leads to complex and time-consuming measurements. The reverberation chamber (RC) is a metallic cavity where the signal created by a single source is reflected and diffused to create multipath fading. This paper gives an overview of how an RC can be tuned to emulate channel parameters, e.g., power delay profile, time delay spread, coherence bandwidth and Rician K-factor, of real-life environments The addition of absorbing material inside the RC allows for varying those parameters, thus recreating line of sight and imperfect propagation conditions experienced by the user equipment (UE). Compliant electromagnetic compatibility downlink and uplink tests are shown for selected MIMO configurations as well as for Internet of Things devices. The tests are carried out using a commercial base station connected to the live national mobile network of a mobile operator. Evaluated network parameters are throughput, signal to noise ratio, modulation schemes and other settings of both the base station and of the UE to assess the quality of the digital communication.

In this study, the authors present results of a call testing campaign using voice over long term evolution (VoLTE) technology on the radio access network of the operator Telecom Italia mobile. The quality of the voice call is expressed by means of the mean opinion score (MOS). The electromagnetic propagation environment has been reproduced within a reverberation chamber, and its effect on MOS has been evaluated by varying the signal strength, i.e. the reference signal received power and the signal-to-interference noise ratio. The aim is to find a correlation between the radio propagation environment and the perceived quality of the speech. Regardless of the networks technology, voice quality could be impacted by several factors: traffic load of LTE evolved Node B, quality of service, radio pathloss, mutual radio interference, multipath and so on. Interference and multipath are added to the useful signal in order to deteriorate the MOS, until the VoLTE calls dropped. Target of such work is to properly set the thresholds that trigger a handover of single radio voice call continuity to other radio access technologies (UMTS or GSM). Tests take also into account the adaptive multi-rate CoDec selected by the network.

High-speed trains are nowadays a reality in most of the countries. Internet services and connectivity are required by the passengers on board using smartphones and laptops. Nevertheless, the higher the speed, the bigger the issues that operators have to face to implement mobility and to reduce the effect of fast fading signal and Doppler shift, which may cause throughput reduction and problems to access the network. In the past, operators tried to optimize the cellular access to universal mobile telecommunications system cells covering railways. Now that 4G networks have become mature and deployed, a similar approach needs to be optimized and implemented to long-term evolution cells covering the same targets. We present the results of a testing campaign replicating real “high-speed train” propagation scenarios, like a train running in open space or in tunnels with the help of a reverberation chamber. The chamber was partially filled by absorbing panels and equipped with rotating stirrers in order to approach the multipath propagation and to replicate the fading conditions that is typical of smartphones in a train coach. The effects of Doppler and its fast variations are presented, together with an analysis of the efficiency of different transmission solutions for tunnels (single-input single-output cells propagating inside them). The testing sessions were performed under a collaboration program between Telecom Italia (in the paper referred as “operator”), Nokia Networks, and Università Politecnica delle Marche. After the experiments in our laboratory, some features were introduced in the operator's live network, covering the high-speed railway between the two Italian cities of Piacenza and Bologna.

Reverberation chambers are successfully adopted to test last generation wireless communication systems. The aim is the replication of realistic propagation condition in outdoor and indoor situations where the multipath contribution statistically overlaps to the direct path between the base station and the user terminal. The insertion of quantified absorbing materials allows to tune the power delay profile, the Rician K-factor, and the coherence bandwidth according to real life situations.

The uplink performance of a real fourth-generation long-term-evolution (LTE) frequency-division multiplexing base station was observed by adopting a reverberation chamber as propagating environment. In the downlink direction, the reception of the LTE signal is limited to mobile station receivers. On the other hand, different reception schemes could be implemented by the base station in the uplink direction. Interference rejection and coordinated multipoint reception criteria are based on spatial diversity and are analyzed in a rich multipath environment. These options could be susceptible to impairments due to the presence of Gaussian noise, also including the more realistic case of a discontinuous noise source. The testing session was carried out under a collaboration program between TIM S.p.A., Nokia, and Università Politecnica delle Marche, and it ended up by introducing envisioned reception solutions of the base station in a live customer's cellular network.

For the first time, the carrier aggregation feature of a live fourth-generation Long-Term Evolution (4G-LTE) base station (BS) is checked, adopting a reverberation chamber as a propagating environment. For this purpose, two nonadjacent bands were chosen, i.e., 800 and 1800 MHz, and alternatively set as primary and secondary cells. The multipath conditions were tuned by adding the absorbing material inside the chamber and ranging from an empty condition with a rich multipath to a real environment such as an indoor scenario. The latter is a very interesting and popular situation as it represents one in which people use mobile phones. The multipath variation effect on the BS performance was accurately verified by introducing power compensation to account for the variation of the chamber quality factor $Q$ due to the insertion of absorbers. A complete over-the-air test was carried out by checking typical transmission quality parameters, which are of interest to manufacturers and mobile network operators. Results highlight the differences between the performance of the two bands as a function of multipath degree and signal strength.

A real 4G base station connected to live network of Telecom Italia and radiating into a reverberation chamber is used to investigate performances of fast moving terminals on board of high-speed trains. The results concern a testing campaign by replicating real high speed train propagation scenarios, like the train running in open space or in tunnels, with the aid of a reverberation chamber. This is partially filled by absorbing materials in order to approach the multipath propagation that is typical of a train coach, and equipped with two rotating paddels in order to replicate the signal fluctuations that are typical for the mentioned environments. The effects of Doppler shift and its fast variations are presented, together with an analysis of the efficiency of different transmission solutions for tunnels.

A fully operational 4G long-term evolution (LTE) base station is tested in a reverberation chamber to analyze its performance in the presence of a multipath environment, typical of wireless and vehicular communications. Transmission quality parameters are measured ranging from the empty chamber situation (very rich multipath channel) to a very high loading condition to mitigate multipath. In that way, both outdoor and indoor propagation are accounted for. A large attenuation is inserted between the transmitter and the antenna to reduce the signal received by the user to real-life values encountered in both outdoor and indoor environments. In these scenarios, operators may choose to transmit a constant power spectral density throughout all LTE spectrum, or to increase the energy of control channels at the expense of data channels in order to enforce transmission and provide better quality to the user, especially in poor radio conditions. This is called "power boosting," and its effect is analyzed in this paper.

Fourth generation (4G) cellular systems have been nowadays rolled out already in several countries in the world. With networks open to commercial use, one of the key issues is how the quality perceived by the user is influenced by multipath propagation, like it may happen in indoor locations or in any kind of places where electromagnetic waves are partially reflected by walls and other objects. In order to verify this, the signal of a real 4G base station connected to the real radio access network of Telecom Italia has been transmitted into a reverberation chamber where a client was running FTPs using a 4G capable USB dongle as a modem. This paper describe the tests that have been performed and focus on how changes in propagation conditions affected the performances perceived by the user.

The downlink transmission power of a 4G-LTE base station is quantified by means of statistical counters. They are build up analyzing the physical resource blocks allocated during transmission at different data throughputs. The analysis is performed during complete over the air tests carried out inside a reverberation chamber. The reverberation chamber allows to vary dynamic fading conditions by changing the stirrer rotating speed and the quality factor. Results are compared to direct antenna input power measurements obtained by a spectrum analyzer, in order to identify the better way to combine statistical counters. The analysis confirms the possibility to use this counters to monitor continuously the transmitted power over long time periods.