How to choose LoRa module product

TheLoRa module has become a rising star of the Internet of Things communication technology with its "long distance, low power consumption" advantage. With its obvious advantages: large-capacity, global unified standards, free frequency bands, low cost and flexibility, like WiFi, it has become the primary choice of "private Internet of Things" (NB-IoT, like GPRS, is "public objects," public objects. The solution of the Internet). How to choose the most suitable LoRa module product to become the top -level design of the Internet of Things. For this reason, we discuss together.

1. Construction elements

Demand is the source of the project! In the same way, building an Internet of Things first requires the following needs:

1.1 Distance

Because of the long -distance characteristics, the mainstream of the LoRa Internet of Things is the "star network", which means that the distance refers to the communication distance between the farthest node and the gateway, as shown in the figure above.

Under the same conditions of "transmitting power + communication rate + antenna", the communication distance of the LoRa module is seriously dependent on terrain and environment, such as: high altitude gas balloons reaches 40km; 2 mountain heads or iron tower communication reaches 15km, and communication in open areas has reached reaching the open area communication reaches the open area. 5km ... Because the wireless communication environment is different, it can only be based on the "empty vision"; other environments shall prevail.

3 methods with insufficient communication distance:

① Reducing the communication rate can increase the receiving sensitivity;

② Replace the high-gain antenna and adjust the direction of the antenna;

③ Increase the gateway and effectively cover the signal blind spots.

LinkLabs announced a method of calculating the LoRa network distance. As shown in the figure above, it is very interesting. Drag some variables on the left, and the effective communication distance will be automatically calculated on the right.

The link of this method is: https://www.link-labs.com/symphony 

1.2 Scale

The scale is the popular saying of "node number", which is a variable that is easy to count.

1.3 Bandwidth

The bandwidth here, the more popular name is the demand for "network throughput", and its unit is "Bit per second".

Such as: 100 nodes, each node, 37 bytes are reported every 60 seconds, because the Lorawan protocol generally needs to add 13 bytes of "metadata" (frame head and test), then the "bandwidth" required is:

(37 + 13) X 8 bit / 60S x 100 = 667 bps

1.4 Power consumption

If the terminal and sensor (or the driver) are powered by the battery, energy saving will be an important indicator.

Thanks to Lorawanclass A's "Synchronous" feature, the end of the terminal is very good.

Generally, energy consumption is calculated by "mode + current + duration".

Taking the Lorawan node of Rymi as an example, in different working mode, the power consumption is as follows:

Dormation = 1.6ua, listening = 13mA, launch (17dbm) = 88mA.

There is a LORAAWAN terminal and sending a data frame for about 10 minutes, about 1000ms; according to the agreement, after the sending, it can be awakened within 1 second. The listening time is 160ms and the receiving time is 1000ms; other times are in Sleep dormant. In 10 minutes (600 seconds), the energy consumption is as follows:

Send: 1000ms *88ma = 88mA.S

Receive: 1160ms *13ma = 15.08ma.s

Dormation: (600-1-1.16) S* 1.6ua = 0.96ma.s

Average power consumption: (88 +15.08 + 0.96) MA.S / 600S = 0.17ma

The total electrical energy of AA batteries (Nanfu or Shuanglu) is about 2400mAh, and the time for working is: 2400mAh / 0.17ma = 14118h = 1.6 years.

1.5 Topology

When the scale of network nodes increases, this requires more gateways to support it. This will use the "multi -star type" network -level connection. For details, please refer to the "Middle/Large Lorawan" below.

1.6 Cost

Cost is a more complicated topic. In addition to formal costs (procurement equipment, deployment construction, etc.), it also has intangible costs (development debugging, technical support, etc.).

A simple method of calculating costs is to get all the costs of a LoRa IoT (formal cost + intangible cost). Except for the number of nodes, you can get "single -point construction costs".

There are 2 basic principles for LORA IoT costs:

Large quantity: This is the basic principle of the market economy, not explained.

Industry maturity: The industry is high in the early stage, because cost (R & D/manufacturing/marketing/support, etc.) has not been "diluted".

2. Point -to -point (single -cell animal)

The LoRa point -to -point system has a small amount of application scenarios in reality, such as: use the handheld machine to "name" the energy meter meter (electric/water/gas/hot meter), remote control valve, etc. Of course, its limitations are obvious:

1. There is no avoidance mechanism: there is no LBT (Listenbeface Talk) mechanism, if 2 or more nodes are sent at the same time, the radio signal will be damaged and the communication fails;
2. Receive nodes cannot be low power consumption: receiving nodes must wait for the signal of the node at any time to sleep;
3. Unable to automatically organize network: Can't solve conflict and low power consumption, networking has become the air tower.

3.TDMA (Fish Age)

If the needs of networking meet the following conditions, you can use the Lora-TDMA system.

1) The number of nodes is small;

2) There is a regular law of reporting and issuing communication;

3) The requirements for bandwidth are very low.

The advantage of LoRa-TDMA is: low cost implementation of small-scale networking.

At the same time, its disadvantages are also obvious: network capacity is limited, and delay increases linearly with the number of nodes. As shown in the figure below, when n = 10, a node needs to wait for (10 x slot) to be reported before reporting; when n = 100, you need to wait for the time of (100 x slot) before the report is allowed.

4. Small Lorawan (Dinosaur Age)

If the number of nodes is small, but there are requirements for real -time and throughput, it is a suitable solution to choose a small Lorawan.

Its advantages are: 8 channels, allowing 8 nodes to be reported at the same time; standards are unified, and the equipment of each manufacturer can be connected.

If you look closely, you will find that in the Lorawan architecture, there is always the existence of Lorawan Server. It brings complexity, although the cloud server can only reduce complexity.

Small Lorawan: Server Localization

Small Lorawan: Server Cloud

5. Mid -size Lorawan (mammalian)

When you need to improve "real -time" or "network capacity", adding the LoRaWan gateway is a good choice.

As shown in the figure below, adding one or more gateways in a LoRaWan network will not bring any conflict. Because it has only one "brain" -LoRaWan Server, it will execute the following "smart" logic:

Report to reduce redundancy: If a packet is received by multiple gateways, Server will recognize this "repeated" packet based on ID and FCNT, only one of the copies.

Selected gateway: Server always selects the right gateway (often the "best signal strength"), allowing it to launch down the data frame.

Middle -size Lorawan: Server Localization

Middle -size Lorawan: Server Cloud

6. Large Lorawan (Modern Humans)

The original intention of Lorawan-the "telecommunications-level" IoT for regions and countries and the world, which is an ambitious plan.

As shown in the figure below, with the help of 3G/4G technology, many Lorawan gateways are connected to Server; Customer server provides massive storage and intelligent computing; convenient data access and interaction for authorized terminals (PC, smartphones, tablets, etc.).

At present, LoRa and NB-IoT (China), EMTC (US), SIGFOX (France) and other telecommunications-level solutions have strong competition; at the same time, it provides valuable solutions for the construction of "large-scale IoT".

Large Lorawan: Server localized

Large Lorawan: Server Cloud