Short-range wireless ad hoc network protocols: development status and trends?
At present, most foreign chip manufacturers are walking on two legs, launching not only 2.4GHz ZigBee chips, but also Sub-1GHz radio frequency chip technology. Although ZigBee technology is still developing and improving, it has never jumped out of the 2.4GHz platform, and the technical system of the entire protocol stack has not undergone major changes. At the user interface layer, it has begun to abandon the idea of profile and turn to more standard and open IPv6 technology. .
As a low-rate, low-cost sensor network, ZigBee technology can still be applied in some fields, but its application in situations with higher transmission (transmission network characteristics) requirements has been rejected from the proposal stage, as follows:
(1) Penetration and diffraction performance are poor. The gain of PA and LNA is difficult to make very high. The noise coefficient is large. It is very sensitive to the digital noise of the user's circuit board. The stability is not good. The product has poor noise immunity and is not solid. ;
(2) It is incapable of transmitting large data packets such as voice, pictures and video clips;
(3) Insufficient mixed transmission capabilities for diversified data types such as voice, GPS, and pictures;
(4) There is almost no usability for transmitting data blocks of tens of K bytes under the multi-hop model;
(5) Insufficient adaptive adjustment capabilities when the network topology changes rapidly.
Many domestic manufacturers are also developing ad-hoc network technology based on 433MHz, but most manufacturers design protocol stacks for engineering projects, especially power meter reading, as their main target market. This type of protocol stack is essentially a wide area network with great limitations in application and poor versatility. It can only be used as a supplement to ZigBee technology in specific markets.
These wireless ad hoc network protocol stack products almost all have a common problem, which is that they are only positioned in wide area networks and use time slot expansion to define the access time slot of each node. The communication efficiency is very low, even if there are only a few nodes. Network, it takes several minutes to collect data once.
In fact, communication is a local behavior in many situations. What users pursue is real-time communication and transmission efficiency. The delay caused by adding a relay is usually acceptable to users, but there is a premise. It requires that the delay increases linearly. In other words, you have to try your best to transmit without wasting any time. This is an important difference between LAN and WAN.
Our wireless ad hoc network protocol stack adopts distributed computing and asynchronous frequency conversion communication technology, and combines the multiple access mechanisms of TDMA and FDMA to provide high bandwidth, low latency, and large capacity networking features, perfectly unifying The heterogeneous problems of local area network and wide area network, sensor network and transmission network realize the smooth extension of network coverage in a way that is completely consistent with people's intuition.
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