用于接近检测 iOS 的蓝牙 LE RSSI [英] Bluetooth LE RSSI for proximity detection iOS

问题描述

我将从问题开始.

BTLE RSSI 是否是指示两个设备彼此接近的好方法?它只适用于遥控钥匙等小型设备吗?

Is the BTLE RSSI a good way to indicate two devices proximity to each other or not? does it only work with small devices like fobs etc?

问题:

我目前正在考虑制作一个应用程序，该应用程序将使用 BTLE 并允许基于接近度的连接.在这方面，它很像苹果在 Advanced Core 蓝牙主题演讲中展示的演示应用程序(当两个设备几乎接触时，它们就会连接).

I am currently looking at making an app that will use BTLE and allow connections based on proximity. In this regard it is much like the demo app that apple show in the Advanced Core Bluetooth keynote (When two devices are almost touching they then connect).

据我所知，接近度是根据中央发现外围设备时的 RSSI 值确定的.然而，当我用两台 iPad 尝试这个时，信号似乎太强了，它也太不一致而无法准确地刺入接近度，因为它与设备接近度没有太大的相关性.

As I understand it the proximity is determined based on the RSSI value when the central discovers the peripheral. When I try this however with two iPads the signal seems too strong for this it is also too inconsistent to have an accurate stab at the proximity as it doesn't show very much correlation to the devices proximity.

我已经尝试过 Apple 示例代码，它的相似之处在于设备根本不必靠近就可以将信息从一个传递到另一个.

I have tried the Apple sample code and that is similar in that the devices don't have to be close at all for the information to pass from one to another.

如果只有一种方法可以降低外围设备广告的信号强度....

If only there was a way to reduce the signal strength of the peripheral devices advertisement....

在此先感谢您的帮助.

推荐答案

Matthew Griffin 的经历与我的相符.但是 - 当我们可以测量一段相当长的时间时，有两件事帮助我们更好地校准.

The experience of Matthew Griffin matches mine. However - when we can measure for a fair period of time two things have helped us calibrate this better.

我们确实必须在天线方向和 IMU 上包裹一个简单的(卡尔曼)滤波器才能获得粗略的运行评论 - 这不是 CPU 或电池电量充足.

We did have to wrap a simple (kalman) filter on the antenna orientation and the IMU to get a rough running commentary though - and this is not very CPU or battery light.

• 使用 IMU，您可以清楚地了解行进的距离/方向 - 如果这是在很短的时间内 - 我们假设另一侧"是静止的.这对于获得当前"方向和校准当前环境噪声"的值有很大帮助.
• 同样 - 对旋转/位置更改执行相同操作.

我们发现一般来说，重新定向设备是获得方向的更好方法；并且该距离仅在移动"校准后的大约 30 到 600 秒内是可靠的，并且仅当设备没有旋转太多时.实际上，曾经需要 4-5 个其他"设备；最好不要太移动，以保持自己动态校准.

We've found that in general a re-orientation of the device is a better way to get direction; and that distance is only reliable some up to some 30 to 600 seconds after a 'move' calibration' and only if the device is not too much rotated. And in practice once needs some 4-5 'other' devices; ideally not too mobile, to keep oneself dynamically calibrated.

然而，反过来是非常可靠的 - 即我们知道什么时候不应该测量.最终的结果是，人们可以相当好地确定诸如在键盘上"和重新定位"/通过特定的门/开口或方向离开之类的东西.同样通过在房间中随机跳舞来测量场；经常改变方向 - 一旦接收器天线波瓣在静止期后得到一定程度的调整，效果就会很好.

However the converse is quite reliable - i.e. we know when not to measure. And the net result is that one can fairly well ascertain things like 'at the keyboard' and 'relocated'/moved away through a specific door/openning or direction. Likewise measuring a field by randomly dancing through the room; changing orientation a lot - does work well once the receiver antenna lobes got somewhat worked out after a stationary period.

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