Fifth lecture and space wireless propagation loss calculation
5.1 Link Budget Uplus and Downlink have its own transmit power loss and path decline. In cellular communication, in order to determine effective coverage, the maximum path decline must be determined, or other restriction factor. In the uplink, the limit factor from the mobile station to the base station is the acceptance sensitivity of the base station. For the downlink, the main limit factor from the base station to the mobile station is the transmit power of the base station. By optimizing the balance between the uplink, there is a good communication quality within the radius of the cell. Generally, the link balance (uplink or downstream) of each cell in the network is improved by utilizing base station resources, thereby working in the best state. In the end, it can also cause the handover and call to create better. Fig. 51 is a base station link loss calculation, which can be used as a reference. Figure 5-01 Calculation of the upper and downlink balance. For GSM systems for achieving two-way communication, the upper and downlink balances are important to ensure that the main factors of the same traffic and communication quality in both directions are also related to the actual coverage of the cell. Downlink is a link to the base station, the mobile station is received. Uplink (UPLINK) refers to a link to a mobile station, a base station. The algorithm for the upper and downlink balances is as follows: Downlink (represented by DB value): PINMS = Poutbts - LDuPLBTS - LPBTS GABTS CORI GAMS GDMS - LSLANTBTS - LPDOWN: PINMS is the power received by the mobile station; PoutBTS is the output power of BTS; lduPLBTS is the loss of the bosser, the duplexer, and the like; the LPBTS is a fever of the antenna of BTS, and the gabt is the gain of the base station emission antenna; CORI is the direction of the base station antenna Coefficient; GAMS is the gain of the mobile station receiving antenna; GDMS is a diversity gain of the mobile station receiving antenna; LSlantBTS is a polarization loss of the bipolarized antenna; LPDOWN is a downlink path loss; uplink (represented by DB): PINBTS = Poutms - LDuPLBTS - LPBTS GABTS CORI GAMS GDBTS -LPUP [GTA]: PINBTS is the power received by the base station; Poutms is the output power of the mobile station; lduPLBTS is a zipper, duplexer, etc. LPBTS is a fever of the antenna of BTS; Gabts is the gain of the base station receiving antenna; the CORI is the direction coefficient of the base station antenna; GAMS is the gain of the mobile station transmitting antenna; GDBTS is the branch gain of the base station receives the gain of the base station The GTA is the resulting gain in the case of using the tower; LPUP is uplink. According to the mudity, that is, for any mobile station position, the uplink loss is equal to the downlink loss, ie: LPDOWN = LPUP set the system margin is DL. The deterioration amount of the mobile station is DNMS. The deterioration amount of the base station is DNBTS. The receiver sensitivity of the mobile station is Mssense. The receiver sensitivity of the base station is btssense, Lother is other losses, such as buildings through loss, vehicle losses, human loss, etc.
Thus, for any point in the coverage area, it should be satisfied: PINMS - DL - DNMS - LOTHER> = MSSENSE PINBTS - DL - DNMS - LOTHER> = BTSSENSE The purpose of the downlink balance is to adjust the transmit power of the base station, so that the cover area boundary Point (point far from the base station) is satisfied: PINMS - DL - DNMS - LOTHER = MSSENSE, the calculation formula for the maximum transmit power of the base station: Poutbts <= mssense - btssense Poutms GDBTS - GDMS LSLANTBTS - GTA DNMS - DNBTS 5.2 Determination of various types of loss ◆ The penetration loss of buildings in the building refers to the attenuation of electric waves through the outer structure of the building, which is equal to the field of buildings and buildings. The difference in medals. The construction of buildings and the structure of the building, the types and sizes of doors and windows, and the floor has a big relationship. Throughout the loss of loss with the height of the floor, generally -2dB / layer, therefore, generally considering the penetration loss of the layer (under layer). Below is a set of data for the 900MHz band, integrated national test results: --- Medium urban urban area general reinforced concrete frame building, through the loss in the medium value of 10dB, standard deviation is 7.3dB; suburban building, penetration For 5.8 dB, standard deviation is 8.7 dB. --- General reinforced concrete framework building in large urban urban area, throughout the loss is 18dB, standard deviation is 7.7dB; the same type of building in the suburbs is 13.1 dB, the standard deviation is 9.5 dB. --- Building a metal housing structure or special metal frame structure in large urban urban area, and the cross-wear loss is 27dB. Since my country's urban environment is very different from abroad, it is generally 8 --- 10dB higher than foreign name names. For 1800 MHz, although its wavelength is shorter than 900 MHz, the through ability is larger, but the diffusion loss is even greater. Therefore, in fact, the penetration loss of 1800 MHz buildings is larger than 900 MHz. In mentioned in GSM Specification 3.30, the penetration of buildings in urban environments is generally 15dB, and the countryside is 10 dB. Generally, it is 5 --- 10dB of throughout the same area of 900 MHz. ◆ Human body loss For the handset, when located in the waist and shoulders of the user, the received signal field will reduce 4 --- 7dB and 1 --- 2dB, respectively, when the antenna leaves the human body. The general human loss is set to 3dB. ◆ The vehicle caused by the vehicle inside the car cannot be ignored. Especially in the economically developed cities, some of the time of people are spent in the car. The inner vehicle is 8 --- 10dB. ◆ The feeder loss is often used in GSM900. It is 7/8 "feeder. In the case of 1000 MHz, the loss per 100 meters is 4.3dB; in the case of 2000MHz, the loss per 100 meters is 6.46dB, more 2.6 DB. 5.3 Wireless Propagation Characteristics
The propagation of mobile communication is shown in Fig. 5-02, and the overall average is weakened, but the signal level has undergone the effect of fast and slow fading. Slow fading is a substantial change from the accepted site surrounding the topography, so that the signal level has a substantial change in the range of several tens of meters. If the mobile station moves without any obstacle, the signal level is only transmitted with the emission The distance between the machine is related. So, a certain point signal level is a average signal level in the range of tens of meters. The change in this signal is distributed normally. Standard deviations are different from different terrains, usually around 6-8 dB. Fast fading is superimposed on slow decline signals. This decline is very fast, up to dozens of times per second. In addition to the terrain object, it is also related to the speed of the mobile station and the wavelength of the signal, and the amplitude is large, but dozens of DB, the change in signal is contained. Fast fading tends to lower the voice quality, so keep the reserves of fading. Figure 5-02
The spread of radio waves in free space is the most basic and simple in radio wave propagation research. Free space is an ideal space that meets the following conditions: 1. Uniform unlimited unlimited space, 2. Each sameness, 3. Electrical conductivity is zero. The application of electromagnetic field theory can be introduced. Under free space propagation conditions, the expression of the transmission loss LS is: LS = 32.45 20LGF 20LGD free space Basic transmission loss LS is only related to frequency f and distance D. When F and D are doubled, the LS increases by 6 dB, whereby the GSM1800 base station propagation loss is 6 DBs than the GSM900 base station in the free space, as shown in Figure 5-03. Figure 5-03 The main feature of the land mobile channel is multipath propagation. The actual multipath propagation environment is very complicated. It often simplifies when researching the issue, and is from the simplest case. Only the two-diameter model of Direct wave from the base station to the mobile station and the two-diameter model of the ground reflected wave are the simplest propagation model. The two diameter models are shown in Figure 5-04, and the application of electromagnetic field theory can be launched, and the expression of the transmission loss LP is: LP = 20Lg (D2 / (H1 * H2)) Figure 5-04 5.4 Common two electric wave propagation models ◆ Okumura Electric Wave propagation attenuation calculation mode GSM900MHz mainly uses CCIR recommended Okumura radio wave propagation attenuation calculation mode. This mode is a comparative factor such as a medium-value field strength or path loss in a large-scale terrain region, and corrects other propagation environments and terrain conditions. Basic transmission loss on different terrain is predicted separately according to the following formula. L (urban) = 69.55 26.16LGF-13.82LGH1 (44.9-6.55LGH1) LGD-A (H2) -S (a) L (suburbs) = 64.15 26.16LGF-2 [LG (f / 28)] 2 -13.82LGH1 (44.9-6.55LGH1) LGD-A (H2) L (Country Highway) = 46.38 35.33LGF- [LG (F / 28)] 2-2.39 (LGF) 2-13.82LGH1 (44.9-6.55LGH1) LGD-A (H2) L (open area) = 28.61 44.49LGF-4.87 (LGF) 2-13.82LGH1 (44.9-6.55LGH1) LGD-A (H2) L (forest area) = 69.55 26.16LGF-13.82LGH1 (44.9-6.55LGH1) LGD-A (H2) where: F ---- Working frequency, MHZH1 --- Base station antenna height, MH2 - mobile station antenna height, MD --- to the base station, KMA (H2) - Mobile antenna height gain factor, DBA (H2) = (1.1LGF-0.7) H2-1.56LGF 0.8 (medium, small cities) = 3.2 [LG (11.75H2)] 2-4.97 (large City S (a) --- Downtown Building Density Correction Factor, DB; S (A) = 30-25LGA (5%
