Increasing Coverage of nRF51822 BLE module

RE: Increasing Coverage of nRF51822 BLE module

NK — Sun, 12 Oct 2014 19:34:20 GMT

Hi @Vaio,

if you have managed to make any progress on this question [with regards to increasing coverage/range of NRF51822] - whether by means of reducing the data-rate in the Gazelle proprietary protocol as discussed in one of the answers below, or some other manner, could you kindly share your experience? Thanks.

RE: Increasing Coverage of nRF51822 BLE module

Håkon Alseth — Thu, 20 Mar 2014 10:47:25 GMT

The restriction is that you have to disable the SoftDevice before using the radio for other purposes, ie: break your BLE connection. It is not concurrent dual RF protocol. This could create issues for some multi-protocol applications. It usually takes in the range of 5-10 ms to switch protocol, depending on your configuration, but you will also have the re-connection time in BLE mode, which depends on the masters scanning period.

The nRF24L-series is proprietary RF only, no BLE. However, it is compatible with nRF51 over-the-air using for instance Gazell. You do not need two 51-kits for checking range, you could do with either the nRF51-dongle included or a nRF24LE1 (Note: LE1 has slightly reduced sensitivity compared to nRF51).

Since you have the motherboard already, it does not matter if you go for ev-kit or dev-kit. They're priced the same as well. It depends on what you prefer, I guess.

BR Håkon

RE: Increasing Coverage of nRF51822 BLE module

Vaio — Wed, 19 Mar 2014 14:06:49 GMT

Thanks Håkon,

At this moment, it has it's restrictions

Can you elaborate on them?

Let me summarize what we wanna implement again: Base Station: send out a beacon regularly (via custom 2,4 GHz protocol, 250 kbps) Mobile Station:

check for presence of this beacon periodically, e.g. 10 times per minute (via custom 2,4 GHz protocol)
act as BLE peripheral, by advertising periodically (every few seconds), and wait for connection requests from a Master (eg smartphone)

It seems periodic BLE advertising is contradicting to scanning for BS beacons (ESB || GZLL) at the same time from the MS?

We don't have nRFgo motherboards yet; nRF24L-series is 2.4 GHz only (no BLE), correct? We don't need that, so EVkit(s) will be fine.

For a pure coverage test, wouldn't a single EVkit do the trick? (as it includes Tx board + Rx dongle). Why would I need two? If we go on and develop both the BS and MS side (as per the requirements above), I would of course need two EVkits.

RE: Increasing Coverage of nRF51822 BLE module

Håkon Alseth — Mon, 17 Mar 2014 19:38:20 GMT

forgot to mention; does not matter if it's a devkit or an evkit. Both will do the trick, however the devkit requires that you have nRFgo motherboards. If you do not have/need nRFgo motherboards for nRF24L-series development, I would go for the EVkits.

-H

RE: Increasing Coverage of nRF51822 BLE module

Håkon Alseth — Mon, 17 Mar 2014 19:33:35 GMT

Hi,

ESB and GZLL examples can be found in the nRF51 SDK. Note that they are setup with 2Mbit data-rate by default, so you will have to set the desired datarate on both receiver and transmitter.

You're looking into running both BLE and proprietary on one firmware. This is possible (we do it on some of our reference designs, like nRFready Desktop 2.) At this moment, it has it's restrictions. In order to use proprietary communication, you will have to disable the SoftDevice. There's an example in the SDK, called "ble_app_gzll" which switches between gazell and BLE.

For a range test, I would setup a transmitter (based on Enhanced Shockburst example) which sends quickly, let's say every 5 ms. On your receiver, toggle a LED for each 50 packets received.

Note: you will have to set the automatic re-transmit delay to >2700 us for 250kbit on-air mode, as stated here in the documentation: devzone.nordicsemi.com/.../a00896.html

Best regards Håkon

RE: Increasing Coverage of nRF51822 BLE module

Vaio — Mon, 17 Mar 2014 15:57:41 GMT

Thanks for clarification. In this case, I'd like to test the 2.4 GHz proprietary protocol w/ 250 kbps. ESB and Gazell are provided by Nordic and can be easily used on the devboards I assume?

What remains unclear to this point: could I use the custom protocol (for presence detection of a mobile device near the base station, long range), and switch the nRF51822 later to use it with BLE protocol (to synchronize some data to a smartphone, shorter range)? I.e., can we switch the protocols during runtime (= controlled from our firmware)? I suppose this is not possible in parallel, but at least sequentially?

Using a proprietary protocol, then you can go over this limit, but you have to make sure that you're within teleregulatory requirements.

I suppose you refer to region-specific regulations? Afaik, for Europe this should be limited to 100mW (20dBm) EIRP in the 2,4 GHz band then.

In terms of testing, can you clarify/confirm what would be required for such a 2.4 GHz custom protocol range test? It seems either 2 evaluation kits (probably cheaper?), or alternatively 1 development kit (more flexible?) would do the trick?

Thanks, Mike

RE: Increasing Coverage of nRF51822 BLE module

Håkon Alseth — Fri, 14 Mar 2014 09:10:32 GMT

Hi,

Note that ~200m LOS is with 250 kBit data rate. With BLE this might be 50-100 meters line-of-sight.

You're correct. BLE can only do 1MBit data-rate, so if BLE does not satisfy your range requirements, then I would recommend checking out our proprietary protocols (ESB or Gazell) and set the on-air data rate to 250 kBit. You could also add an RF PA, but note that BLE does not allow more than +10 dBm output power. Using a proprietary protocol, then you can go over this limit, but you have to make sure that you're within teleregulatory requirements.

Using a good antenna (like a WiFi antenna) will most likely give you better coverage, but it may not be enough. What I would do is to test this out with both BLE and 250kBit proprietary protocol, and see if the range is acceptable.

Best regards Håkon

RE: Increasing Coverage of nRF51822 BLE module

Vaio — Thu, 13 Mar 2014 11:22:10 GMT

Thanks Håkon,

in our setup the BS would be the transmitter (always advertising), and the MS the receiver (checking for the BS beacon's presence, e.g. once per minute). The MS doesn't even need to make an actual connection to the BS - it is sufficient to detect its presence.

The BS is connected to the wall, so no power problems there. The MS of course has very tight power requirements. Since we only check for presence e.g. once per minute, this should hopefully allow for multiple weeks of battery runtime.

Of course, coverage in buildings is hard to say. 200m LOS sounds promising however. Regarding decreasing the data rate: it seems for BLE, using 1 Mbps is the only valid datarate. Were u referring to a custom protocol (where 250kbps can be used)?

Other than decreasing the datarate, can sbdy think of any other means to extend the range? (could we equip the BS with a better antenna for instance, to get closer to the allowed +20 dBM?)

Best Rgds, Mike

RE: Increasing Coverage of nRF51822 BLE module

Håkon Alseth — Tue, 11 Mar 2014 11:40:34 GMT

Hi,

Power-wise, I do not believe that you will run into issues, as the base station will act as a master device (always in RX mode) and it's most likely connected to the wall.

We're usually reluctant to say anything on the range, as this varies in different environments. If you're in a building where the walls are thick and made of concrete, this will reduce range across different rooms.

If you reduce the on-air datarate (supports 2M, 1M, 250k), you should get better coverage. When running on 2 MBit on-air datarate, the range is around 10-15 meters in an office environment. 250 kBit in an open area (outside, line-of-sight), you will get more than 200 meters. This is with a well-tuned design.

However, in buildings you will always have walls, wifi, and other factors that comes into play.

The best way to test this is to get two eval-kits, set them up with 250 kBit mode and test it in your natural application environment.

Best regards Håkon