[Chinese Instrument Network Encyclopedia Knowledge] Nodes in the low-power wireless Internet of Things must spend most of their time sleeping in order to reduce power consumption to support long battery life. If a node wants to initiate communication, it must wake up the target node before communicating with the target node before it can communicate effectively. In this paper, a channel coding correlation algorithm is proposed, which has the characteristics of strong anti-jamming capability, low power consumption, rapid identity recognition, implicit time stamp, and simple implementation. The performance is better than the existing wake-up method or algorithm.
Existing wake-up method There are three existing wake-up methods, namely: 1RSSI (field strength) awakening method: the carrier can be transmitted during Ts. The intensity of the received field strength from the node test is awakened if it exceeds the set threshold, otherwise it continues to sleep. 2 Sniff wake-up method: During the Ts period, the 010101010 bit stream is sent. The number of 01 or 10 received from the node count is awakened if the number exceeds the set value. Otherwise, it continues to sleep. 3 Packet awake method: Repeatedly sending a data packet during Ts, one of the data packets received from the node is awakened, otherwise it continues to sleep.
Fatal drawbacks of methods 1 and 2 are that they cannot identify illegal signals and are prone to false wake-ups due to interference. The probability of false wake-up cannot be calculated and evaluated, resulting in a significant reduction in system reliability and loss of energy compensation. That is, these two methods have serious problems that cannot resist interference. Another drawback is that it can only achieve wake-up on the radio, increasing the power consumption of nodes that do not need to participate in communications.
The biggest disadvantage of Method 3 is the large power consumption. In order to reliably detect the frame synchronization signal of the data packet, the value of the detection window t needs to be set to 2 times the total transmission bandwidth of the data packet, resulting in increased power consumption.
Auto-correlation-based wake-up method The new wake-up method needs to reduce the power consumption while increasing the anti-interference ability, thereby overcoming the two biggest defects in the existing methods. The highly autocorrelated codec wakeup method not only completely replaces existing methods, overcomes existing defects, but also adds some new useful functions. We call this new method the HAC dynamic cyclic code awakening method, hereinafter referred to as the dynamic code awakening method.
Highly autocorrelation coding method, the best devaluation Barker code, but because Barker code is too short and not much, can not be used. Then the pseudo-random sequence code is a very good encoding method that can be used. It not only has a high degree of autocorrelation, but also can provide unlimited encoding. Applying this coding method flexibly to the wake-up link of the wireless Internet of things is very appropriate. The specific method is as follows:
For the sender, if the target node is to be woken up, a series of continuous bit streams is generated by encoding, and the length of the bit stream is related to the communication baud rate and the wake-up duration Ts.
It generates the equation: an=c1an-1⊕c2an-2⊕...⊕cn-1a1⊕cna0
When the node sends the current symbol an of the wake-up sequence, an is derived from the first n symbols through a specific operation. This particular operation is determined by the taps C0~Cn. That is, the symbol an has the correlation with the preceding n symbols an-1 to a0. The value of n is called the order. The receiving node can decide whether to wake up by deciding the correlation.
For the target node, regardless of the location of the probe window during which the master node sends the wake-up signal, it can arbitrarily intercept a small segment of received symbols from the air for decoding, and any symbol can be used as a start bit. When n symbols are received, decoding can be started. If the values ​​of C0~Cn of the transmitting side and the receiving side are the same, the decoder starts to output 0 continuously and does not output 1. Output 0 indicates the currently received symbol, and the preceding n symbols satisfy the agreed relevant characteristics. If M 0s are continuously output, it is considered that the wake-up signal is scanned and the node is awakened. If 1 is received, it is immediately Quit detection and go to sleep to save power. M can be from 8 to 20 according to the actual application requirements. In practical applications, order n can take values ​​from 9 to 22. In special applications, such as high speed, n can be longer.
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