The principle of radio wave transmission and the main dissemination model, in plain words, is the answer to a question: what is going on in the middle of a signal from the antenna to the other end? Look at the foundation, but many communication engineers are still being bypassed by models when they reach the budget chain. I've been taking students for years with an individual meeting, and i've been able to explain the logic between the communication machine and the matching model, and then i'm going to do the engineering selection, and i'm not going to come up with the blind formula。
What's the radio wave transmission model
The most basic is the free space dissemination model, also known as the friis formula. It assumes that there is no shield between the two points and that the signal power decreases inversely by distance. Use it to calculate the millimetre wave link budget for the open area. However, the real environment could not be so clean, and engineering would introduce a logarithmic distance path loss model with a set of revised parameters for cities, villages and rooms. 3gp has specially calibrated 5g different frequency bands and scenes in 38. 901 and 37. 901These parameters directly determine whether the overlay plan will runI don't know。
It's a statistical model. The okumura-hata model drew the median decay curve for cities, suburbs and open areas, with a frequency range of 150 mhz to 1,500 mhz, largely dependent on 2g and 3g for base station planning. At sub-6ghz and above, especially the millimetre wave, the radio-tracking model became useful. It geometrically model buildings, road reflectors, and distillation edges, with a high degree of precision in output certainty multi-routing paths, but with a high degree of computing power, which is generally used to simulate the intensive deployment of small base stations and the millimetre beam beam-shaped landscape and is not suitable for full-network planning。
How do we calculate the loss of radio transmission
The most common thing on the project is the budget for the link. The core equation is: the receiving power equals the launch power plus the launch antenna gain plus the receiving antenna gain minus loss of path, minus feedback and other losses plus the system surplus. The amount of path loss filled depends entirely on which dissemination model you choose. For a free space formula, l=20lg(f)+20lg(d)+32. 44(db), f takes mhz, d takes km, and just take it. But don't think you're done with an averageThe actual design must be superseded with a decay residualOtherwise, the error rate indicator would not have been achieved。
Decline in two layers. Slow decline or shadow decline, described as a logarithmic normal distribution, with standard deviations typically ranging from 8 to 10 db, reflecting the randomity of terrain fluctuations and building barriers. The rapid decline reflects the rapid ups and downs of the signal caused by multiple paths, using the rayeleigh distribution (non-vision range) or the rician distribution (the presence of a direct fraction). The budget is closed only when the statistical features of these two layers are folded over the average path loss and the remaining amount is left in the reliability of the target link. It is not a small probability that a millimetre wave-fixed return will be carried out without sufficient residual coverage to break through a wall。
The dissemination model is not "best," it's "best of the right." when the frequency is changed, the scene changes, the distance pulls, the model changes. The bottom-level physical apparatus is ingested, and the model is chosen with a background and does not lead to the nose by a bunch of parameters in the simulation software。
