CC2640主要是for BLE的, 目前支持4.x的1Mbps 和5.0的2Mbps. 为了提高距离,可以考虑5.0的长距特性
Increased Receiver Performance with LE-Coded PHY
Link budget [dB]= TX Power [dBm] - Sensitivity level [dBm]
Example for CC2640R2F @ 125 kbps: 5 dBm - (-103 dBm) = 108 dB
6 dB improvement in link budget compared to 1 Mbps – same low current
Hi. My name is Fredrik. I'm an applications engineer with Texas Instruments supporting Bluetooth Low Energyprojects. I'm here on Lake [INAUDIBLE] today with the peripheral end of our Bluetooth Low Energy long rangeBluetooth 5 link. My colleague Espen is up in the hills there. And I will now take the peripheral and see how far outon the lake I can go while still maintaining a connection. And for that, I brought my skates.
I have now skated a bit out on the lake. Espen is at the top of the hill behind me. The green LED on the board isflashing. You may not be able to see that on this film. But that means that we still have a reliable BLE connection.The distance from Espen to me is at this point about 1 and 1/2 kilometers.
So we have just shown you that with the CC2640R2F, we can get up to 1.5 kilometers of range running Bluetooth 5coded PHYs. And that's pretty impressive for Bluetooth. So how does this work? Well, there's several ways you canimprove your link budgets. One obvious is, of course, to increase the output power in your system. But that willalso increase your current consumption. So what Bluetooth sync chose to do was to improve the sensitivity of yourreceiver instead. And the way they did that was through coding.
So what is coding? Consider regular Bluetooth Low Energy. The data rate is 1 megabit per second. And the over theair symbol rate is 1 mega symbol per second. So that means that for each data bit that you put into thetransmitter, you get one physically modulated symbol over the air. With coding, that is different. So you basicallyuse more symbols to represent each data bit. For low energy coded PHYs, there's two stages. So we can either usetwo symbols per data bit, and this will give us a data rate of 500 kilobits per second. Or we can use eight symbolsto represent each data bit. And this will give us a data throughput of 125 kilobits per second.
So how does this work? Well, consider a data bit stream. And let's take one random bit in that bit stream. So we ranforward error correction on the data bits. So in this case, let's take a one going through formal error correction willyield two bits instead. And for the s equal 2, or two symbols per data bit, we use these two directly to representthis single data bit. Now for the eight symbols per data bit, or as Bluetooth sync calls it, s equals 8 [INAUDIBLE],each of these are again expanded by 1 to 4. So a 1 is always represented as 1100, and a 0 is always represented asa 0011. So now we have one data bit being converted to eight symbols. The basic idea here is that this will make iteasier for your receiver to interpret your data stream over noise. And that improves sensitivity.
For the CC2640R2F, the sensitivity when running eight-symbol coding is minus 103 dBm. Comparing that to thealready best in class sensitivity for 1 megabit per second BLE at minus 97 dBm means that you get a 6 dBimprovement in link budget. A very important factor here is that the receiver current consumption is the same asbefore. And for the CC2640, that is 6 milliamps. So in other words, without increasing the current consumption inyour system, you get a 6 dB improvement in your link budget.
As I mentioned earlier, another way to increase the link budget is to increase the TX output power. Many BLEapplications transmit at 0 dBm to optimize the power consumption. At 0 dBm, CC2640 consumes 6 milliamps. Forthis demonstration, we chose a TX power of 5 dBm, which increases the peak current consumption from 6 to 9milliamps. This is a moderate increase, and will in most cases still allow the system to use the same power supplyarchitecture and energy source. For example, like coin cell battery.
To conclude, we have shown you that by using the new Bluetooth 5 coded PHY, we can achieve a BLE range ofmore than 1.5 kilometers while still maintaining a peak current consumption below 10 milliamps. Thank you forwatching. Please visit our Bluetooth Low Energy web page for more information on how to get started with theCC2640R2F.
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