Application of MIMO technology for wireless data transmission channels

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A competition of ideas for the reconstruction of a diorama was announced in Belgorod. This was reported by the press service of the Belgorod administration.

Order to hold an open competition for the best conceptual idea to create an exposition of the Belgorod State Historical and Art Museum-diorama “Battle of Kursk. Belgorod direction ”was signed by the head of the Belgorod city administration Yuri Galdun.

According to the source, the collection of ideas will start on March 6, 2021. Acceptance of proposals will end on April 13 at 17:00. According to the results of the competition, the winners will receive a prize: 1st place - 2.5 million rubles, 2nd place - 1.5 million rubles, 3rd place - 1 million rubles.

Citizens of the Russian Federation with specialized education in the field of history, culture, architecture, design, landscape architecture, as well as design organizations and architectural bureaus can become participants. It is necessary to submit graphic materials (2 PVC tablets 1 x 1 sq. M), an explanatory note, 3D visualization of design solutions, technical and economic indicators and an approximate calculation of the cost of implementation.

Let us remind you that the renovation of the museum started last year. First, an unusual lighting appeared on the facade of the building. The workers then proceeded to the interior decoration. The exhibits had to be transported, and the painting itself had to be packed. The work was planned to be completed by the May holidays, but Vyacheslav Gladkov instructed to turn the diorama into one of the best museums in the country and attract the best specialists to the work.

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In Belgorod for the best idea for the reconstruction of the diorama will pay 2.5 million rubles

In wireless communication systems, various measures are taken to ensure communication reliability, increase network capacity and data transfer rate. Among the diversity reception methods, which allow avoiding signal fading, there are spatial, time and frequency diversity, the use of directional transmission, and the combination of different types of polarizations.

One of the biggest challenges in mobile devices is signal fading. When moving, the phase instability and attenuation coefficient take on a random character due to reflections from all kinds of obstacles (walls, rain, mountains, trees, etc.). Accordingly, it is necessary to frequently update the channel state information (CSI) in order to timely correct channel distortions. In open-loop MIMO systems, the channel is estimated only at the receiving end. In closed-loop MIMO systems, channel information is also sent to the transmitting side via the return channel. Based on the received information, the transmitter reallocates the power in the transmitting paths so as to increase the power of the paths in the channels with a high degree of fading, as well as to correct for the amplitude and phase in the formation of the antenna beamforming.

As mentioned, the main ways to prevent signal attenuation are frequency, time and space diversity. It can be seen from the table that the main parameter when choosing the diversity method is the bandwidth of the simultaneously fading frequencies and the coherence time.

Table. Basic methods for avoiding channel fading Diversity Description Frequency difference of carrier frequencies exceeds the bandwidth of simultaneously fading frequencies; their duration significantly exceeds the channel coherence period Spatial antennas at the receiving and transmitting ends are located far enough from each other to expand the possibilities of radio channel variation

When using multiple antennas, space diversity is performed at both the receiver and transmitter sides. The gain from using multiple antennas increases with the number of antennas. However, a trade-off has to be found between bit rate and space diversity.

Several types of transmission are used: an array of antennas sends different data over different channels (multiplexing), or the same signal over different channels, or a combination of them (see Fig. 1).

Fig. 1. Principle of data transmission in systems with multiple antennas (MIMO): a) space diversity; b) spatial multiplexing; c) combined method

Standard MIMO configurations include 2x2, 3x3, 4x4 (802.1n / ah) and 8x8 (802. 1ax / ac).

Transfer to multiple users

The concept of spatial multiplexing can be applied to an array of receivers equipped with one or more antennas (see Figure 2). This allows you to increase the efficiency of the system while maintaining the reliability of communication. The Wi-Fi standard supports multi-user MU-MIMO technology in versions 802.1ac / ax (downstream only); it is also included in 4G LTE (release 8) and LTE-A (release 10). Unlike single user systems, MU-MIMO systems are more susceptible to intra-channel interference, often requiring near-ideal channel conditions and low signal-to-noise ratio.

Fig. 2. Multiplexing can be used not only for transmission to one user terminal with several receivers, but also for transmission to multiple users (only in one direction)

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