Low-power WAN (LPWAN) has taken a long time, but demand for low-cost connection and power consumption and cost-effectiveness and cost improvement of the Internet of Things (IOT) is triggering more and more attention to LPWAN. The improvement of silicon technology has greatly reduced power consumption and can be used for battery-powered wireless sensor nodes. These nodes use the secondary GHz non-adjusted radio frequency band for long distance connections, more cost-effective than the regulating cellular frequency band.
However, promoting these LPWAN networks requires their own infrastructure, and the latter has still progressed slowly. But now I have reached a turning point. Using the sub-GHz band means that there is less base station that supports a large number of wireless nodes.
IoT network developers have a variety of options. For example, Semtech's LORA technology can be used to launch a private LPWAN network dedicated to multiple wireless nodes. Alternatively, such as a public LPWAN network such as SIGFOX, you can save the installation, connection, and management base stations. At the same time, people also develop other LPWAN networks through the new protocol (such as weightless). The selection of the LPWAN network determines the selection of the Internet of Things Node Wireless Transceivers.
LoraWan is a low-power WAN (LPWAN) specification, mainly used in regional, national or global network of wireless battery power supply nodes. The Lorawan network is a typical star topology, a gateway is a transparent bridge, transferring a message between terminal devices and back-to-open central network servers. The gateway is connected to the web server via a standard IP connection, while the terminal device is connected to one or more gateways using single-jumped wireless communication. Communication of all nodes is generally two-way, but the network architecture also supports works such as multicast, and software wireless upgrades or other large amount of distribution messages can be implemented to reduce air communication time.
Communication between nodes and gateways uses spread spectrum links to pass through different frequency channels and data rates. This will create a set of "virtual" channels, between 0.3 kbps to 50 kbps. The web server uses a self-adaptive data rate (ADR) scheme for each node separately manages data rate and RF output.
Lorawan includes several different types of nodes. The Class A node uses the minimum power, each upstream transmission follows two short downlink receiving windows. The transmission time slot of the node is based on its own communication needs, with a small change according to the random time base (Aloha Type Agreement). At any time, the server downlink communication must wait for the next scheduled uplink.
Class B nodes use the time synchronization beacon from the gateway to provide additional scheduling reception time slots. This way the server can know when the node is listening. Class C nodes contain open reception windows, only shuts down when transmitting.
These nodes can be created via SEMTECH SX1272 / 73 transceiver. These transceivers use long-range modems through the spreading protocol, and also provides high anti-interference capabilities and minimize current consumption.
The patented modulation technique can achieve a sensitivity of more than -137 dBM using low-cost crystals and materials. High sensitivity to integrate +20 DBM power amplifiers, bringing up to 157 dB link budget capabilities, which also has significant advantages relative to traditional modulation techniques (such as FSK and OOK) in blocking and selectivity. The use spread spectrum method not only solves the compromise of traditional design, anti-interference and energy consumption, but also supports high-performance FSK and GFSK modulation of other systems, including WMBUS and IEEE802.15.4G.
The SX1272 provides three channel width options 125 kHz, 250 kHz and 500 kHz, and the spreading factor ranges between 6 and 12. The SX1273 provides the same bandwidth option, but the spreading factor ranges from 6 to 9. To achieve optimal flexibility, users may need to consider spreading modulation bandwidth (BW), spread spectrum factor (sf), and error correction rate (CR).
Another LPWAN network operates from French network operators SIGFOX and its partners.
Multiple devices can be used to implement nodes. For example, Microchip's ATA8520D is a highly integrated, low-power running frequency transceiver with an integrated AVR microcontroller. The device is divided into three parts: a radio front end, a digital baseband and a low power 8-bit AVR microcontroller (868.0 MHz to 868.6 MHz and 869.4 to 869.65 MHz band). The SPI interface can be external control and device configuration.
Similarly, the ON Semiconductor's AX-SIGFOX development kit is also an ultra low power single-chip solution for nodes with uplink and downlink functions on the SIGFox network. The AX-SIGFOX chip can be used directly to operate, while also containing all the required firmware that transmits and receives European network data.
The node connection is implemented by a simple RS232 UART and uses the AT command to send frame and configure the radio parameters. The development kit includes an AX-SIGFOX full-feature module with a network usage subscription feature.
The transceiver is encapsulated in 5 mm x 7 mm QFN40, providing 10 GPIO pins, with four pins with optional voltage measurement. These pins or differential inputs in the range of 1 V or 10 V, or single-ended input in a range of 1 V, two are 10-bit resolution. Two of them have a selectable triangular integral DAC output function to connect to a sensor in the node. The three GPIO pins can also be selected as the SPI primary interface for controlling other devices in the node.
Be
One of the advantages of the SIGFOX network is to manage data in the cloud, and the company has cooperated with Microsoft to connect to the Azure Cloud Storage and Data Management Tools to implement large data deployments.
Weightless-P is an updated protocol that has just got ETSI European standard organization certification, and the Internet of Things developers can create their own LPWAN networks. The protocol can be operated on all GHz bands, but can also be used to adjust the honeycomb frequency band. It uses a 12.5 kHz channel and flexible channel allocation to allow for repetition frequencies in large deployments, while 200 BPS to 100 kbps data rates maximize network capacity. This protocol uses time synchronized base stations to achieve radio resource scheduling and utilization.
A development kit named Weightless Ignition Pack offers a WeightLesS-P network connection feature that is available. The kit includes a WeightLESS-P base station, a terminal device module, an antenna, a complete WeightLesS-P protocol stack, a terminal device, and a host, and a single cable. The kit is out of the box to deploy a WeightLess-P Internet network.
Summarize
The LPWAN network is an increasingly popular approach to the Internet of Things. Use the secondary GHz radio frequency band and spread spectrum protocol in the node to achieve low power consumption, which can greatly extend battery life, thereby reducing costs. The same secondary GHz band can also achieve longer distance, only a few base stations can be applied between multiple towns. Lorawan, Sigfox or WeightLESS-P network provides developers with a variety of implementation options, from creating a private network to a time and connect to cloud analysis on a business network.
Our other product:
