nrf9160 throughput

[Ben Li]

 I'm trying to build a proof of concept for a BLE gateway that captures data from BLE sensors and sends it to the cloud via LTE-M connection. I'm hoping that the gateway can support 20 concurrent BLE connections for the proof of concept. However, I'm concerned on nRF91's data rate. I am afraid it leave the throughput on the cellular side lacking compared to what it receives from the BLE peripheral. Is there anyway to get around this? Or should I use a third party GSM like sim7600?

My idea is to connect two NRF9160 together to handle the throughput. Or I can connect nrf52840 with a LTE CAT4 module like Maduino Zero 4G LTE. Both options need to be battery backed and runs without connecting to PC eventually.

Would that work?

Best,

Ben Li

[Albrecht Markus Schellenberger]

Hello Ben Li, 

Ben Li said:

I think what I'm trying to say is that the throughput of the modem on nrf9160 seems to be very low. Just like what other people said  nRF9160 DK maximum throughput I'm not sure the UL rate of 50kbps is going to be enough for my case (20 concurrent BLE connections). I am afriad that when the application sends more data than how much the modem can transmit, I will experience the some issues with the data trasmission. (like it´s waiting to send the buffer to the cellular tower or the socket disconnects.) 

The above-mentioned data rates are not nRF9160 specific, we are talking about designed limits according to the specifications of the LTE-M / NB-IoT protocol. In LTE-M, data rates up to 4 Mbps can be achieved while NB-IoT is specified for 127 kbps up to this point. The nRF9160 acts according to those standards, which it is designed for. And I guess this what my colleague Simon means with “The nRF9160 isn't really designed for high throughput use cases, but rather low power solutions.” 

However, if one would consider those data rates as low or high throughput depends on how you look at it and what you compare it to. 

Ben Li said:

I've been told by Simon about this issue on my last ticket  nRF6943 or nRF9160 DK (BLE Cellular gateway) but I still want to consider using nRF9160DK because I'm not sure how to connect nRF52 with SIMCOM GSM. So I'm wondering if nRF9160 cellular modem is capable of supporting high throughput. I have also been told by my supervisor that LTE-CAT M1 doesn't have enough UL and DL rate, what's why I'm considering using LTE CAT4. What do you think about that?

The nRF9160 does not support LTE protocols, no.  

One challenge that I see from what you are describing here is that the gateway has to buffer lots of data, filter and transfer it within certain time frames. Since the nRF9160 has a shared memory for data exchange between the application and modem core, this can be handled quite fast. On the other hand, if an external modem is used, the data rates of the interface that communicates with this modem might limit the throughput. Additionally, how fast an external modem will act on certain requests might have to be considered as well. 

I might not have an universal answer for you here, Ben Li. At a certain point you should test and compare the devices you are considering for your project and see which ones give you the most promising results.

Cheers, 

Markus