In the world of the Internet of Things, Mesh networks (mesh networks) always sound a bit "sophisticated". Nodes communicate with each other, form automatic networks, and self-repair... These features make it seem like a standard configuration for future networks.
But an interesting phenomenon is that LoRa technology, which is known for its "long distance and low power consumption", stubbornly chose the seemingly more "primitive" Star Topology.
🤔 Is this a step backward in technology or does it have a deeper meaning?
Today, let's use a vivid metaphor to thoroughly understand this "counter-intuitive" choice of LoRa.
Imagine that we are going to deliver an important notice in a huge campus.
Plan A: School Radio (Star Network)
The principal (gateway) stands in the broadcasting room and broadcasts to the entire campus through a loudspeaker (LoRa's long-distance capability). Each student (terminal node) can hear it directly in their own classroom.
Students only need to "wake up" and listen during the broadcast time. At other times, they can study or take a nap (deep sleep, ultra-low power consumption) in peace. The notice was delivered quickly and accurately.
Solution B: Message Passing Game (Mesh Networking)
The principal informed the first student in the first row of the notice. This student passed it on to the one behind him, and so on, row by row.
To ensure the smooth progress of the game, every student must always remain vigilant, listen carefully to what the previous student says, and be ready to pass it on to the next person (nodes need to be continuously monitored, which consumes a lot of power). If one person in the middle is distracted or transmits the wrong message, the information will be interrupted or distorted (network delay and packet loss).
Now, do you understand why LoRa chose the "school broadcasting" model?
All of this stems from LoRa's ultimate mission: to enable battery-powered devices to last for several years or even a decade.
In a star network, the working mode of LoRa terminal nodes is extremely simple:
Wake up：A few milliseconds.
Send data：Several hundred milliseconds.
Keep sleeping：Several hours or even days.
It's like a "lazybones", sleeping soundly all the time and only opening its eyes when it needs to report on work. This kind of "laziness" is the secret to its longevity.
However, if a Mesh network is adopted, nodes become "model workers". It not only has to send its own data, but also always "keep its ears up" to listen to the calls of its neighbors and be ready to "carry" information for them at any time. The price of such a "warm-hearted" attitude is a huge consumption of electricity.
In a LoRa network with tens of thousands of nodes (such as smart farms and smart cities), if the nodes are relays to each other, those "model" nodes close to the gateway will quickly run out of power, causing the entire network to collapse on a large scale. Who will regularly replace the batteries of tens of thousands of nodes? This is obviously unrealistic.
You might ask, "What if the signal doesn't travel far?"
This is precisely the "trump card" of LoRa.
The physical layer modulation (CSS) technology of LoRa has an astonishing communication distance. In an open environment, a terminal node can communicate directly with a gateway tens of kilometers away!
It is precisely because "one pole can reach the sky" that there is no need for a "relay race" at all.
The existence of Mesh networks is to address the coverage issues of those "inherently weak" wireless technologies such as Wi-Fi, Zigbee, and Bluetooth. Because they cannot travel far from each node, a "sea of people" tactic is needed, holding hands to send out the signal.
LoRa, by nature, is a "long-distance running champion". It is fully capable of reaching the finish line on its own and doesn't need the support of its teammates at all.
Now we can draw a conclusion:
Star network：It is a perfect architecture tailored for LoRa (long range, low power consumption). It focuses complexity on gateways and network servers, keeping terminal nodes minimalist, thereby achieving the optimization of power consumption and cost.
Mesh network：
It is an excellent solution designed for short-distance and high-density scenarios. For instance, in smart home systems, the devices are close to each other but numerous, thus requiring flexible self-organizing network capabilities.
LoRa's choice of star networks is not due to outdated technology, but rather a kind of wisdom of "decluttering". It gave up the flexibility and self-healing ability of Mesh in exchange for more valuable features such as ultra-low power consumption, ultra-high reliability and a minimalist terminal.
This is an ultimate optimization for a specific application scenario. It is the most practical and intelligent choice made by engineers after weighing the pros and cons.