Why do we need LoRa and NB-IoT when we have GPRS?

火辣西米秀

Why do we need LoRa and NB-IoT when we have GPRS? [Copy link]

Rather than a comparison between GPRS and NB-IoT, it is better to say that it is a comparison between traditional networks and emerging networks. Let's focus on the advantages of GPRS and NB-IoT in the following points.

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1. Network coverage

If we only talk about coverage, everyone knows that China Mobile's 2G coverage is almost everywhere in our country. Although people often ask when the 2G network will be phased out, but!!! It took China Mobile 20 years to achieve 2G nationwide coverage, and 4G network construction only started in 2014. Although the speed is very fast, it will take about seven or eight years to reach the coverage of 2G.

From the perspective of economic benefits, the revenue generated by NB coverage is far less affordable than the traffic revenue generated by 4G coverage. Due to the continued low price of revenue, operators have insufficient motivation to develop NB. However, on the other hand, as the cost of NB modules decreases and as NB equipment increases, the speed of NB base station coverage will steadily increase. Therefore, the construction of NB network is a gradual trend.

2. Network capacity

Many people say that NB has a large network capacity, and one cell can accommodate tens of thousands of devices, while a GPRS cell can only accommodate a few hundred devices. This is both right and wrong. The current NB cell configurations are all basic configurations with a total bandwidth of 180khz. The uplink of each device needs to occupy a bandwidth of 15khz, so from the perspective of frequency division, a cell can only allow 12 devices to transmit signals at the same time. If you want to expand the capacity, you can only think of a way from time division. In layman's terms, everyone should not transmit together, but take turns to transmit. If it is only transmitted once a day, of course it can accommodate tens of thousands of devices, but the premise is to do a good job of time division multiplexing. Therefore, it is true that the NB network capacity is large, but it must also be based on a business model of low-frequency communication.

3. Power consumption

The low power consumption of NB can be divided into two aspects. The first is the PSM mode of NB, and the second is the power consumption of normal transmission of NB. The power consumption of PSM mode is generally around 3 microamperes, which is quite low for communication chips. However, this PSM mode cannot receive paging and can only be awakened by a specific pin or timer. Therefore, the PSM mode is not very useful.

The power consumption of normal transmission is about half of that of GPRS under the same conditions, but because the upload bandwidth of NB is only 15kb, the communication time will be extended. Therefore, under normal use, the power consumption of NB will be lower than that of GPRS, but there will not be an order of magnitude difference in power consumption. Since NB's modulation and demodulation still has a better signal-to-noise ratio advantage than GPRS, NB's power consumption has an advantage under the same conditions of communication information volume. In the scenario of low-frequency communication, NB is still preferred.

4. Field advantages

NB is suitable for low-frequency services. It is best to communicate once a day, and it is best to sleep or shut down the rest of the time, so as to achieve low power consumption and even expand network capacity.

From this perspective, NB is suitable for three meters (gas meter, water meter, heat meter), trash can monitoring, manhole cover monitoring, smoke detector monitoring, street light monitoring, etc. where power supply is inconvenient and high-frequency communication is not required.

As for products such as GPS positioning and tracking, we still give priority to GPRS network.

5. Price

目前的NB模块的价格，至少要 30多块钱，资费也有些贵，贵得甚至还没补贴的起模块，这是不正常的，暂时的市场状态。 随着市场规模的扩大，NB模块价格会迅速下降。同时，无论是中国电信，还是中国移动，还是中国联通，都会逐步扩大自己的NB网络覆盖，并且逐步做到全国无死角覆盖，但是并发容量必定不会非常多，因为提升并发容量实在太费钱了，还是只能通过低频次通信来保持网络的高容量。

To sum up: the current choice, if our device is an ultra-low frequency communication, we can consider NB-IoT;

In other cases, it is recommended to give priority to GPRS or 4G

Let's talk about LoRa again:

The LoRa network mainly consists of four parts: terminal (which can have a built-in LoRa module), gateway (or base station), server and cloud. Application data can be transmitted in both directions.

price:

Since LoRa works in the unlicensed frequency band, network construction can be carried out without application, the network architecture is simple, and the operating cost is low. In the process of network construction, it is free to build a network using the LoRa communication protocol, while using the GPRS communication protocol to build a network requires the purchase of a SIM card and is charged according to the traffic volume.

Link Budget:

NB-IoT has a link budget of 164dB, GPRS has a link budget of 144dB, and LoRa provides a maximum link budget of 168dB with its unique patented technology. Generally speaking, the wireless distance range in cities is 1-2 kilometers, and the wireless distance in suburbs can reach up to 20km. Therefore, LoRa and NB-IoT have certain advantages in terms of links.

At this point, I need to give you some basic knowledge about MCL

MCL: Maximum Coupling Loss. It refers to the maximum path loss (dBm) allowed on the entire transmission link in order for the receiver to correctly demodulate the signal sent by the transmitter. According to the 3GPP standard definition, the uplink MCL of NB-IoT is -164dBm, and the uplink MCL of GPRS and broadband LTE networks is -144dBm.

NB-IoT and LoRa are still in the initial stage of development, and need investment and joint development from all parties. When large-scale deployment becomes possible, the module costs of NB-IoT and LoRa will be further reduced. In terms of technical solutions, GPRS, NB-IoT and LoRa will definitely run in parallel in the short term, each with its own advantages and disadvantages. This is why there is a need for LoRa and NB-IoT when there is GPRS.