Feature comparison 2.4G-Lora VS ordinary 2.4G
The E28 series product launched by Chengdu Ebyte Electronic Technology Co., Ltd. is a transmission module with Lora spread spectrum technology designed for the 2.4GHz band. LoRa Direct Sequence Spread Spectrum technology will bring longer communication distance, and has the advantages of wider power spectrum and strong anti-interference ability. The module has a hardware FEC forward error correction algorithm, which has high coding efficiency and strong error correction capability. In the case of sudden interference, it can actively correct the interfered data packets, which greatly improves reliability and transmission distance.
what is LoRa?
Lora, short for long range, is a long-distance, low-power wireless communication technology. In 2009, French company cycleo designed an excellent spread spectrum communication algorithm. Later, the company was acquired by Semtech company of the United States, which launched Lora chip in 2013. At present, Semtech is the only supplier of Lora chips.
Advantages of LoRa
The biggest advantage of Lora is long-distance transmission, which uses spread spectrum gain, and its transmission distance is about 3 times of FSK; secondly, it has low power consumption, although its communication distance can reach 5km, it still maintains good energy-saving characteristics; thirdly, it works in free ISM frequency band, which opens a convenient door for ordinary people to use the wireless network and greatly reduces the network laying cost.
The secret of LoRa's low power consumption
Transmission rate is a key variable in system design. It will determine many attributes of the overall system performance. The wireless transmission distance is determined by the receiver sensitivity and the transmitter output power. The difference between the two is called the link budget. The output power is limited by the standard specification, so the distance can only be increased by increasing the sensitivity, and the sensitivity is affected by the data rate. For all modulation methods, the lower the rate, the narrower the receiver's bandwidth, and the higher the receiving sensitivity. The most widely used modulation method in today's cost-effective wireless transceivers is FSK or GFSK. The only feasible way to further reduce the receiver bandwidth of the FSK system is to improve the accuracy of the reference crystal.
We know that distance and power consumption are a natural contradiction in communication systems. When the transmission power is reduced, the propagation distance must be close. So how does LoRa resolve this contradiction? The fundamental reason is that LoRa improves the sensitivity of the receiver, which has a strong link budget and does not require high transmit power. LoRa receiver sensitivity is due to direct sequence spread spectrum technology. LoRa uses a high spreading factor to achieve higher signal gain. Generally, the signal-to-noise ratio of FSK needs 8dB, while LoRa only needs -20dB. Under the same data rate condition, the commercial low-cost spread-spectrum modulation method can obtain 8-10dB higher sensitivity than the traditional FSK modulation method. Compared with the FSK system, when using the same low-cost crystal, this new spread spectrum method improves the sensitivity by 30dB, which is theoretically equivalent to an increase of 5 times the transmission distance.
Why ultra-low power consumption? Isn't the existing technology such as Zigbee already ultra-low power consumption?
It is very important to choose universal and low-cost batteries in consumer and commercial products. At present, the current 2.4G communication technology in the market uses button batteries to communicate at a distance of only ten meters, and it is almost impossible to communicate after passing through a wall. If a button battery is used, the emission pulse current needs to be controlled within 10-35 mA, and the working current is controlled within 2-5 mA. In this way, a large number of CR series button batteries can be used for exterior design, commercialization, and global logistics. Provides a good foundation. And such a transmission current ensures that there is no blind zone coverage in a villa, a factory building, or a home. Currently only 2.4G-LoRa technology can do it. Based on the physical layer implementation of 2.4G-LoRa, the power consumption of RX and TX is significantly lower than Zigbee and Wireless HART; the sleep current is only 200nA level.
2.4G technology
2.4G is a wireless technology. Because its frequency band is between 2.400GHz and 2.4835GHz, it is referred to as 2.4G wireless technology for short. Is one of the three major wireless technologies on the market (including Bluetooth, 27M, 2.4G). More commonly used in wireless keyboard and mouse.
Features
1. 2.4G products are widely used, and some chips have good performance, but the price is relatively high, and it is difficult to enter mass-produced products. In order to reduce costs, JF24D modules use die bonding. Although the performance index is slightly lower than the representative nRF2401 CC2500 A7105, its price is much lower than them, which can fully meet the short-range product applications that generally require two-way data transmission and two-way remote control. . Products with single transmission and single reception are relatively simple to use. When the power is applied and the signal is transmitted, the signal is output when received. The pure hardware product transmits in one direction. It does not require the support of software programs to complete the sending and receiving functions.
2. 2.4G products are more complicated. The CPU in the chip needs the support of software programs, and the instructions of the single chip microcomputer can be used to complete the two-way transmission and reception function. Single-single-received products have low cost and are widely used, but there are serious inevitable co-channel interference. Generally, 2.4G products have frequency hopping functions that have dozens to 100 channels to avoid interference. However, the complex software programs of 2.4G products have made some engineers who do not understand microcontrollers timid. At the same time, the power consumption and cost of 2.4G products, as well as the penetrating performance of the wall, have also affected the popularity of low-end products .
2.4G-LoRa technology and 2.4G technology's most representative E28 series module SX1280 and E01 series nRF24L01 + are compared for comparison.
1. Spread spectrum: LoRa is a spread spectrum modulation technology. A coding gain can be obtained through spread spectrum modulation because the signal can be received with a negative signal-to-noise ratio. At the same time, in the absence of interference, this is equivalent to receiving under noise, and in the case of co-channel interference, this is equivalent to receiving the required signal power which is weaker than the interference signal.
2. Low bandwidth: There are two benefits to reducing bandwidth. First, the lower bandwidth reduces the impact of adjacent signals, thereby reducing the possibility of becoming a victim of interference. If we compare the bandwidth of a LORA signal to a wider band of Wi-Fi signals, we will find that even a very wide LORA signal occupies only a small portion of a Wi-Fi channel.
This brings us to a second benefit. The power of Wi-Fi signals is distributed across the Wi-Fi channel. Therefore, the energy seen in the narrower part of this channel will be a small part of this energy.
Simply put, even in the case of co-channel interference, we are only exposed to a small portion of the signal power meaning a small portion of the power of the Wi-Fi signal we receive.
3. Forward error correction and interleaving technology: Another advantage of LoRa modem is the availability of FEC (forward error correction) and interleaving technology. Forward error correction allows redundant information to be introduced into the message, allowing damaged finite bits to be modified and recovered.
Even FEC sequential bit errors (ie, adjacent corrupted bits) are the most difficult to correct. For this reason, an interleaving technique is used. This is a technique to redistribute the information in a packet so that after reconstruction, errors are less likely to come from adjacent bits.
4. Partial symbol loss immunity: In addition to all the benefits mentioned earlier in the LoRa physical layer, it is also worth noting that we may lose up to half of the LoRa symbols before losing the data in the symbols. In the case of anti-jamming, this gives us huge anti-jamming capability (in some cases over 100 decibels).
