Introduction: the communication reliability of wireless products is sometimes related to distance. For example, when the communication distance is far away, the signal itself is very unstable. In this case, the network is unstable and people are usually acceptable.
ZigBee ad hoc network technology has some limitations, and has not achieved the expected success. But because of its access to the international semiconductor giant almost all the support of the overwhelming advertising education market and users, to make people fully aware of the enormous potential of ad hoc network technology into research and development, from the network technology more and more enterprises, but there is a basic issue that is not ZigBee ad hoc network technology implementation (source code design) itself what problem, but the technical scope of ZigBee ad hoc network planning is not enough, there are many causes of the application can not be included. In other words, if you design the source code along the technical specifications of the ZigBee ad hoc network, the performance of the designed network may not be as good as the performance of the existing products.
So, do we need to re-examine the boundaries of the application of MANETs? 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 need special attention, the first one is the wireless communication distance, the problem in most cases is determined by the hardware chip, and protocol itself is, imagine a building through multi hop network coverage radius is only a few hundred m, it is unacceptable. The second problem is reliability, but this problem is often more confusing than the first one, which makes it easier for people to feel cheated by the pit. Why do you say that?. Because the communication distance is easy to measure, you only need to send two nodes at a time, you can test the communication ability of the system in a few minutes, but the reliability test is much more complex, often appear the following situation:
(1) the demo system made up of 35 nodes is very reliable, and dozens of nodes in the batch network, hundreds of nodes are unstable
(2) dozens of nodes are relatively stable when the communication is not large, but the communication is unstable when sending and receiving frequently
(3) the network is stable for a short time, and it can easily collapse and can not be recovered for a long time, forming a botnet
So reliable transmission is the basic starting point of wireless. If a system can sometimes transmit data, and sometimes not very bright, then this product can not be a good promotion. Why do you say that? Because no one knows when you OK, and when you suddenly hang up. But in one case, you can take it, and that's what you can point out explicitly: what happens to me when I'm OK and under what circumstances I'm unreliable. People often use the European and American products to have an impression, the design of a place is ugly, difficult to use, but you just follow his steps to do, although it is difficult, but the result is consistent, or always right, or always wrong.
The communication reliability of wireless products and sometimes distance are related, such as when the communication distance, the signal itself is floating is not stable, in this case the network instability often is acceptable, like in the high-speed train or deep in the basement of the phone easily dropped, but very few people to swear to telecom operators, it is like a traffic congestion, we can endure slowly forward, but can't stand running very fast, but an accident.
In addition to the reliability of communication, it is not difficult to find that the wireless networking technology actually has 4 X 3 = 12 dimensions, and some communication periods only support a few dimensions, as follows:
(1) the difference between the transmission network and the sensor network
Sensor network is basically uplink network, the data is only vertical upward flow, node sending density is very low, data type is single, data packet is small, reliability requirements are low, lost a data, send several times, as long as once effective enough. But the transmission network is not the same, the communication is very frequent, various messages (voice, data, GPS, command, diagnosis, data) have horizontal flow within the network, sometimes even the whole network multicast, unicast broadcast, data reliability is very high, can not be wrong data, data, or leakage the data packet length changes, sometimes dozens of bytes, sometimes hundreds or even thousands of bytes bytes, sometimes it is a continuous data stream. For example, a meter, usually reported one time a day data, that is, dozens of bytes, but to a month when you need to do summary, the data reported to reach several K bytes. This is a hybrid model between sensor networks and transmission networks.
(2) the difference between LAN and WAN
Generally speaking, Wan refers to the node data is more, more than 255 nodes of the network, LAN is 255 nodes below the network, of course, this is a relatively broad definition, specific to the actual application of a better understanding. The typical application of wide area network is wireless hyper - list, although the number of nodes in reality may be less than 255, but at least from the model to take into account the technical architecture of 1024 nodes; and wireless order machine is one of the typical applications of lan. What are the differences and commonalities between the two? People usually understand Wan because the number of nodes, the data transmission can be a little slower, the efficiency can be a little lower, even if you once a day to ensure success is acceptable, but LAN requires you very quickly, a second you will have to support 10 communications equipment at once, this is the difference of efficiency is very obvious. Of course, it would be better if you could unify the two
(3) difference between static network and dynamic network
Obviously, all the nodes in the network is static within the network are stationary, wireless meter reading is this application; all nodes in the network is a dynamic network in the dynamic change, car Networking (car radio network) is belong to this network. There is also a semi mobile network, as the name suggests, half mobile is the base station and relay does not move, from the station in the mobile, the order machine and our mobile phones are belong to this 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 the network with 220V power supply or sufficient battery supply can be called the constant current network, so the network does not need to consider the problem of sleep and energy saving. Active wake up network