BLE modules for building applications

[PHYSEE]

I am working in a project to create a mesh wireless sensor network(WSN). I am very interested in doing so using mesh BLE devices. However, this topic is completely new for me and I have faced some challenges to fully determine the performance of BLE in a similar application to mine. Thus, I would like to ask some technical questions hoping to get better understanding for my project.

1. The sensors will be operating inside buildings, very close to aluminium windows frames and other metals. Thus, I would like to know what Is an estimated range in meters of BLE modules inside building applications?
2. Following the previous questions, what would be the size of the antenna to reach that range and power consumption? Can it be a PCB antenna?
3. Is there any limitation related to the number of nodes I can implement in the mesh wireless sensor network? 
4. Finally, what is a good estimation of the Throughput of the BLE module for this kind of application?

PS: I do understand that giving exact numbers without knowing all details of the application is difficult but ballparks numbers based on your experience would be very insightful.

Thank you for your help, and looking forward to your answers.

[DheerajPK_41 · Accepted solution]

Hi,

First of all, Please go through the below link to get everything (Supported chips, modules, software, documentations, etc.) about Bluetooth LE Mesh. https://www.cypress.com/products/bluetooth-low-energy-mesh 

Coming to your questions.

1. Bluetooth Mesh is a networking specification build on to of Bluetooth LE stack. So The basic range and behavior is same as Bluetooth LE. If you check the Module sections (in the above link), you can see that the range is 75 meters (least) up 1Km (for Long range modules). It can vary based on the environments and obstacles nature.

2. Yes. It can be PCB antenna.

For example, in CYBT-213043-02 we have PCB antenna and its location dimensions are 12mm (L) x 4.55mm (W). Please check the datasheet for more info.

3. As per the mesh specification, 32767 elements can be added to a mesh network. A Node can have multiple elements containing multiple models. There is indeed a RAM limitation for number of elements/models/subscriptions/publications per node. Please check 

https://community.cypress.com/t5/WICED-Smart-Bluetooth/Max-number-of-GATT-Proxy-and-max-number-of-No... 

https://www.bluetooth.com/specifications/mesh-specifications/

4. Bluetooth LE Mesh is mainly designed for low data transfer application such as a Light Bulb with a on/off switch or a discrete sensor arrays, etc. The spec says, 

"The transport layer provides up to 11 octets for a non-segmented message, leaving up to 10 octets that are available for parameters when using a 1-octet opcode, up to 9 octets available for parameters when using a 2-octet opcode, and up to 8 octets available for parameters when using a vendor-specific 3-octet opcode.

The transport layer provides a mechanism of SAR capable of transporting up to 32 segments. The maximum message size when using the SAR is 384 octets."

Thanks,

-Dheeraj

[PHYSEE]

Thanks for your reply and for the links that you share.

I was checking the datasheet of one of you BLE modules (CYBT-413034-02), and i did not find in which conditions are those 75 meters measured.

Also, I guess that you have used any of those BLE modules inside building with many obstacles for the signal. So, base on your experience which range have you been able to reach inside buildings with those modules? 

thanks.

[DheerajPK_41]

Hi,

The range mentioned in the website is Line-Of-Sight range, without any obstacles. 

We have tested Bluetooth LE Mesh in our labs/floors which contains numerous wireless devices, racks and other obstacles. And we could cover the entire lab and floor using the inbuild antenna without any issues. I remember we could cover the entire floor using 3 mesh nodes diagonally - Meaning we can expect the range more than 50 meters easily without any thick obstacles in between the modules. But, we did not record the exact range numbers. 

Based on the obstacles nature (thickness, material, etc.) and other interferences in the surroundings, these range can get changed. 

Thanks,

-Dheeraj