![]() For example, if the last power level in the 3600E access point has a power value of 4dbm (total power), then it actually means the power value is -2dbm (per path). For example, Cisco 3500, 1140, and 1250 series access points allow the configuration of last power levels because those access points report the "per path power" to the controller, whereas all next generation acess points such as Cisco 3700, 3600, 2600, and 1600 series access points report "total power value" to the controller, thereby decreasing the allowed power levels for newer generation products. These power values are derived based on the regulatory compliance limits and minimum hardware limitation which varies across different Cisco access points. If the 8th power level is configured on those channels, the configuration would fail since the controller considers the 7th power level as the lowest acceptable valid power level. In certain cases, Cisco access points support only 7 power levels for certain channels, so that the Cisco Wireless Controller considers the 7th and 8th power levels as the same. For example, 1 = maximum power level in a particular regulatory domain, 2 = 50% power, 3 = 25% power, 4 = 12.5% power, and so on. However, power level 1 is always the maximum power level allowed per country code setting, with each successive power level representing 50% of the previous power level. The number of available power levels varies based on the access point model. The integer corresponds to a power level that varies depending on the regulatory domain in which the access points are deployed. The transmit power level is assigned an integer value instead of a value in mW or dBm. The signal-to-noise ratio (SNR) and signal loss are expressed in dB.TX power level 1 is always maximum power level of access point. If power value A changes to 10000 mW, the calculation result changes to the following: 10lg(10000/10) = 30 dB. For example, if power value A is 100 mW and power value B is 10 mW, 10lg(100/10) equals to 10 dB, indicating that power value A is 10 dB greater than power value B. When A and B represent two power values, dB represents the ratio of the two power values. Therefore, the new concepts dB and dBm are introduced.ĭB is a relative unit for expressing the ratio of two values. ![]() As the energy attenuates exponentially, it is difficult to measure the energy attenuation by the power. For example, a 100 mW energy source attenuates to 1 mW, 0.1 mW, 0.01 mW, or even lower after being transmitted over a certain distance. However, the energy of electromagnetic waves attenuates quickly. In an antenna system, the antenna also needs to consume electric power to convert the electric energy into electromagnetic waves for transmission. For example, a 10 W bulb consumes 10 W of electric power when it is on for 1 hour. In our daily life, the power is typically the rate of doing work or the rate of using energy. For details about how to calculate the maximum transmission distance, see Coverage Calculation. Then, the maximum transmission distance can be calculated according to its relationship with the path loss. RSSI = Radio transmit power + TX antenna gain – Path loss – Signal attenuation caused by obstacles + RX antenna gainĪfter other factors except the path loss are determined, the path loss can be determined. The RSSI is calculated as follows (regardless of factors such as the interference and line loss): Uplink signal strength = 7 - 6 + 5 - 4 + 3 - 2. ![]() Uplink signal strength: signifies the strength of signals received by an AP from a wireless terminal. It is calculated as follows:ĭownlink signal strength = 1 - 2 + 3 - 4 + 5 - 6. As a result, wireless terminals receive weak signals or even fail to receive signals.ĭownlink signal strength: signifies the strength of signals received by a wireless terminal from an AP. Weak signal strength means that the RSSI is lower that the edge field strength. It is the value of the EIRP minus the transmission path loss and signal attenuation caused by obstacles. ![]() RSSI: signifies the signal strength at a location in the coverage area of a wireless network. During WLAN planning, ensure that the sum of the transmit power and antenna gain does not exceed the maximum value allowed by the country code.ĮIRP: signifies the strength of signals transmitted from an antenna. Radio transmit power: 1 signifies the radio transmit power of the AP 7 signifies the radio transmit power of the wireless terminal.
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