蓝牙LE的txPower到底是什么?如何使用? [英] What exactly is txPower for Bluetooth LE and how is it used?
问题描述
由于我打算开发使用信标的Android应用程序，因此我试图了解txPower的确切含义以及如何使用它.
我在网上看到了2个定义:
1.信标的发射功率.
2.接收功率距离信标1米.
这两个定义如何相关? 另外，当使用QuickBeacon之类的应用程序从设备传输信标信号时，如何确定将功率(txPower)设置为什么?
大多数信标格式在传输中仅包含一个字节，表明您在一米外时的预期信号电平.该字节有时称为 txPower (发射功率的缩写)，有时也称为测得的功率.
请勿将此与某些信标模型上的第二个配置设置混淆，该设置使您可以更改发射机实际发送其广播的强度.这通常称为发射功率，这就是为什么测量功率是一个不太容易混淆的术语.
测得的功率场用于进行距离估计.如果电话发现其信号电平与信标发射的测得的功率场相同，则知道它正好相距一米.如果它具有更强的信号，则表明它更接近.如果信号较弱，则表明信号距离较远.使用公式，您可以粗略了解以米为单位的距离.
要使此距离估算值准确，需要将测得的功率场适当地设置为一米处的预期信号电平.它通常由制造商预先配置到信标中，但通常是可调整的.您为什么要调整它?如果将信标放置在机柜中，则它可能会使信号衰减.如果将信标靠在金属墙上，则可能会由于反射而增加信号.因此，建议您在安装后通过测量和设置其测得的功率值来校准信标.
校准涉及使用电话来测量信标信号电平(使用称为接收信号强度指示器"或RSSI的测量值，以dBm为单位进行测量).要进行校准，请将手机与典型性能良好的蓝牙接收器(最好是iPhone 6，但Nexus设备也可以正常使用)保持距离信标一米，并在30秒内测量平均信号强度.许多信标配置应用程序和工具，例如为iOS定位和 Android 具有校准实用程序. >
一旦有了校准值，就需要按照制造商的说明在信标中配置它.这将为您提供更准确的距离估计.
I am trying to understand what exactly txPower is and how to use it, since I am planning to develop and Android app that uses Beacons.
I have seen 2 definitions online:
1.The transmitted power of the beacon.
2.The received power 1 meter away from the beacon.
How are these two definitions related? Also, when transmitting a Beacon signal from a device using an app such as QuickBeacon, how do I determine what to set the power (txPower) to?
Most beacon formats contain a single byte in the transmission that indicates what the expected signal level should be when you are one meter away. This byte is sometimes called txPower (short for transmitted power) and sometimes measured power.
Do not confuse this with a second configuration setting on some beacon models that lets you vary how strongly the transmitter actually sends its broadcasts. This is typically called transmit power, which is why measured power is a less easily confused term.
The measured power field is used to make distance estimates. If the phone sees that its signal level is the same as the measured power field transmitted by the beacon, it knows it is exactly one meter away. If it has a stronger signal, it knows it is closer. If it has a weaker signal it knows it is further away. Using a formula, you can get a rough idea of the distance in meters.
Making this distance estimate accurate requires having the measured power field set properly to the expected signal level at one meter. It is often pre-configured into the beacon by the manufacturer, but it is typically adjustable. Why would you want to adjust it? If you place the beacon inside a cabinet, it might attenuate the signal. If you place the beacon against a metal wall, it might increase the signal due to reflections. For this reason, it is recommended that you calibrate a beacon by measuring and setting its measured power value after installation.
Calibration involves using a phone to measure the beacon signal level (using a measurement called the Received Signal Strength Indicator or RSSI, which is measured in dBm). To calibrate, you hold a phone with a typically performing bluetooth receiver (ideally an iPhone 6, but Nexus devices work well too) exactly one meter away from the beacon, and measure the average signal strength over 30 seconds. Many beacon configuration apps and tools like Locate for iOS and Android have calibration utilities.
Once you have the calibration value, you need to configure it inside your beacon per the manufacturer's instructions. This will give you more accurate distance estimates.
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