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Wireless network technology core features and capabilities
Wi-Fi is a communication technology based on the 2.4GHz band. It is good at transferring large amounts of data between two nodes, but at the same time it consumes high energy. In a star configuration, each AP is limited to no more than 15-32 clients. .
Bluetooth is another 2.4GHz technology that targets portable devices and is mainly used as a point-to-point solution, supporting only a few nodes.
Zig Bee shares the same wireless spectrum as Bluetooth and Wi-Fi but is only used to meet the special needs of low-power wireless sensor nodes.
Zig Bee: Optimization Solution for Wireless Mesh Networks
ZigBee is an open wireless mesh network technology based on global standards. Unlike traditional network architectures, such as star and peer-to-peer, mesh networks use the lowest-cost node to provide reliable coverage for all locations within a building (see the network topology options comparison below). ZigBee uses a dynamic, autonomous routing protocol based on AODV (Ad Hoc On-dem and Distance Vector) routing technology. In AODV, when a node needs to connect, it will broadcast a route request message, other nodes look in the routing table, if there is a route to the target node, it will feedback to the source node, the source node picks a reliable, hop count The smallest route, and stores information to the local routing table for future use. If a route fails, the node can simply select another alternate route. If the shortest line between source and destination is blocked due to wall or multipath interference, ZigBee can adaptively find a longer but available route.
Comparison of network topology
For example, wireless sensor networks based on the Silicon Labs EM 35x Ember ZigBee So C and Ember Z Net PRO stacks provide self-configuring and self-healing mesh network connectivity that can scale to hundreds or thousands of nodes in a single network . The rapid development of "ZigBee Certified Products" benefits from Ember App Builder, which hides the details of the protocol stack and focuses on the development tools implemented by ZAP (ZigBee Application Profiles). Through a graphical interface, developers can quickly select the properties needed for the application, and then App Builder automatically generates the required code.
In order to maximize the advantages of ZigBee network flexibility, efficient debugging tools are needed. The complexity of mesh networks makes traditional network analysis tools (such as Packets niffer) more difficult to use. In fact, because the packet may arrive at the destination through multiple hops, many intermediate transmissions are beyond the scope of the analyzer. For this problem, the only solution currently available is to use the Silicon Labs Desktop Network Analyzer, which is a powerful analysis tool that can display a complete picture of each packet in the network in a graphical interface and has built-in protocol analysis. With a visual tracking engine, developers can coordinate the tasks of network communications and devices.
In some cases, mesh networks are not a suitable choice because the node density is too low to provide effective failover support. For example, a road or rail network topology requires nodes to be deployed at a wide pitch along a narrow path. Similarly, the campus's external facilities are too sparse for adopting a mesh network. In these environments, the combination of star topology can be more distant and therefore more reliable and suitable.
Sub-GHz: Ideal for long-distance and low-power communications
Wireless propagation is inversely proportional to frequency. Sub-GHz radios have advantages in low-power, long-distance communication or wall-through capability. For many applications, 433MHz becomes a global alternative to 2.4GHz (but Japan does not allow it for wireless applications). Designs based on 868MHz and 915MHz can be used in the U.S. and European markets. There are many available frequency bands that do not require authorization or need to be authorized. For system integrators, they can choose to optimize their performance in certain specific areas or cooperate with utility companies to design systems in a wide area. In this diversification, the sub-GHz band has less spectral interference than the 2.4 GHz band. Less interference bands can improve the overall performance of the network and reduce the number of retransmissions in transmission.
Third-party and standards-based network protocol stacks are available for sub-GHz radios, but many vendors still choose proprietary solutions to address their specific needs. Many wireless protocols face the problem that the interface must constantly activate the "listening" of communications in the network. Data transmission consumes more energy than data reception, but the emission is transient and there is a long time interval, so the average long-term energy consumption is usually lower. In many wireless protocols, the receiver does not know when the message arrived. So you have to keep listening so you don't lose any data, so even if there is no message, the receiver can't turn off the energy completely. This situation will limit the node's battery autonomy, requiring regular battery replacement or charging.
Sub-GHz transceivers, such as the Silicon Labs Si446x EZ Radio PROIC, support link budgets from 119 MHz to 1050 MHz with a maximum link budget of 146dB, and consume only 50nA of current consumption in sleep mode. In order to mitigate the effects of multipath fading, the EZ Radio PRO chip supports dual antennas and integrates antenna diversity logic algorithms within the chip. By using a combination of frequency hopping and clock synchronization techniques, system integrators can implement a sub-GHz network spanning several kilometers between the coordinator and the end node, while the end node can run on a single battery for more than a decade. As a result, the system integrator can use a small number of coordinators to reliably cover a specific area and place the end node where the main power source cannot be connected.
4 wireless technologies who are more suitable for the Internet of things?
In order to better serve end users, utility companies and the Urban Council began to expand smart metering systems to address the growing problem of real-time data. Public utility companies can use smart meters to view customers' energy consumption information more frequently and effectively. They can also quickly identify, isolate, and resolve power failures. Consumers can also get relevant information through the interconnection. Indoor network equipment can report its status and energy consumption in real time, and can also respond to information sent by utility companies. With smart energy and smart home systems, consumers will be more convenient and efficient, for example, control the activation of the dishwasher at the lowest electricity rates, or promptly remind users to add detergent.