Where is the application boundary of narrowband wireless ad hoc network technology?

In an earlier article, "Why did the ZigBee wireless ad hoc network technology fail to achieve the desired success?", we mentioned that ZigBee wireless ad hoc network technology has some limitations in use and did not achieve the desired success. As it has obtained the full support of almost all international semiconductor giants, its overwhelming advertising campaign has educated the market and users, enabling people to fully realize the enormous potential of ad hoc network technology and investing in the development of ad hoc network technology. There are more and more enterprises, but there is a basic problem that needs to be understood. It is not a problem in the technical implementation (source code design) of the ZigBee wireless ad hoc network itself, but the technical scope planned by the ZigBee wireless ad hoc network is insufficient. Too, there are many applications that cannot be included. In other words, if you design the source code along the technical specifications of the ZigBee wireless ad hoc network, the performance of the designed network may not be as good as that of the existing products.

So, we need to re-examine the application boundary of wireless ad hoc network technology? Yes, I do think so, at least in some developing countries in the Asia Pacific region. In all wireless applications, there are several key factors that require special attention

First, the distance of wireless communication is determined by the hardware chip in most cases, and it is not related to the networking protocol itself. Imagine that the radius of a network constructed by multi-hop is only 100 meters. It is hard to accept. Second, the reliability of wireless communication is often more confusing than the first problem, and it is easier for people to feel deceived. Why do you say so? Because the communication distance is easily measured, only two nodes need to be received and received. Within a few minutes, the communication capability of the system can be tested. However, the reliability test is much more complicated. The following situations often occur:

1. The demo system made of three or five nodes is very reliable, dozens of batch networking, hundreds of nodes are unstable

2. Dozens of nodes are relatively stable when the traffic volume is small, but they are unstable when communications are frequently sent and received.

3. The network is still stable in a short time. If it is running for a long time, it will easily crash and fail to recover, forming a botnet.

So reliable transmission is the most basic starting point for wireless. If a system can sometimes transmit data, and sometimes it is not very agile, then this product cannot be well promoted. Why do you say so? Because everybody doesn't know when you're OK, when it suddenly hangs up. However, in a situation where everyone can accept, that is, you can clearly point out, under what circumstances I am OK, under what circumstances I can not rely on. Everyone using European and American products often has an impression that the design of a certain place is ugly and difficult to use, but as long as you follow his steps, it is very awkward, but the results obtained are evenly consistent, or they are always correct. It's always wrong. The communication reliability of wireless products is sometimes related to the distance. For example, when the communication distance is far away, the signal itself becomes unstable. In this case, the instability of the network is usually acceptable, such as at high speed. Calls on the train or in the deep basement are easy to drop, but few people go to the telecommunications operators. This is just like people have more traffic jams. Everyone can tolerate the slow movement, but they can't stand running fast. It was a car accident.

In addition to the reliability of communications, it is not difficult to find that wireless networking technology actually has 4 X 3 = 12 dimensions, and some communication periods only support a few of them, as follows:

1. Differences between wireless sensor networks and wireless transmission networks

The wireless sensor network is basically an uplink-based network. The data only flows vertically upwards. The node has a low transmission density, a single data type, a small data packet, and a low reliability requirement. It loses one data and sends it several times. , as long as it is effective once. But the wireless transmission network is different, communication is very frequent, the message is various (voice, data, GPS, command, diagnosis, etc.), the data has a horizontal flow within the network, sometimes there is multicast, unicast and even The entire network broadcasts, the data reliability demand is very high, cannot have the wrong data, the heavy data, or leaks the data, the packet length changes indefinitely, sometimes several tens of bytes, sometimes several hundred bytes or even thousands Bytes, sometimes continuous data flow. For example, an instrument, usually reported once a day is a few dozen bytes of data, but the need to do a summary when the month, the reported data reached several kilobytes. This is a hybrid model between wireless sensor networks and wireless transmission networks.

2. Differences between wireless LAN and wireless wide area network

Generally speaking, the wireless wide area network refers to a network with more node data than 255 nodes. A wireless local area network is a network with 255 nodes or less. Of course, this is a relatively broad definition, and it is relatively good for practical applications. understanding. The typical application of the wireless wide area network is the wireless super table. Although the actual number of nodes may not reach 255, the technical architecture of the 1024-node node is taken into account at least from the model; and the wireless ordering machine is the wireless local area network. One of the typical applications. What is the difference and commonality between the two? People usually understand that because of the large number of nodes in the wireless wide area network, the data transmission can be slower and the efficiency can be lower. Even if you ensure success once a day is acceptable, but the wireless LAN requires you to be very fast. To support 10 devices to communicate once, this is a very obvious difference in efficiency. Of course it would be better if you could unite the two.

3. The difference between static and dynamic networks

Obviously, a static network is where all nodes in the network are stationary. Wireless meter reading is such an application. A dynamic network is where all nodes in the network are dynamically changing. Car networking (car-borne radio networking) ) It belongs to this kind of network. There is also a semi-mobile network. As the name implies, semi-mobile is the base station and the relay is not moving. The mobile station, the ordering machine and our mobile phone belong to this kind of network.

4. The difference between the constant current network and the dormant network

In wireless applications, the power supply of the equipment is sufficient, and a network with 220V of utility power or sufficient supply of large batteries can be called a regular network. Such a network does not need to consider the problems of hibernation and energy saving. The active wake-up network is usually a battery-supplied network that wakes up and performs data communication triggered by a GPIO or timer; the passively awakened network is usually powered by a battery or restricted mains (such as a smart home panel). If the master station needs to communicate with a sleeping node, it usually only needs to wake up the node through wireless electromagnetic waves, and the rest of the nodes can remain in a sleep state without wasting energy or inadvertently causing other adverse effects.

From the analysis above, it can be seen that wireless ad hoc networks have at least four major categories in terms of applications. Each major category has at least three branches, that is, at least 12 network forms. Most of the wireless ad hoc network protocols on the market today, even the famous ZigBee wireless ad hoc network, only support a few of them, and there are a large number of features that are not standardized in the protocol stack. It is no wonder that users use It's always not a good idea, but then again, if all these features are supported, how large is the protocol stack? The existing ZigBee wireless ad hoc network protocol stack has been very large and bloated, and has been widely criticized by users. Further expansion will require a large amount of Flash and SRAM chips. How can the cost be controlled?

When ZigBee wireless ad hoc network was just born, it thought that it had found itself excited by the immense market that Wi-Fi and Bluetooth “have”. It was not expected that after years passed, people discovered that there was a A bigger market left by ZigBee wireless ad hoc network is waiting for everyone, but this time you are sure that you are really excited?