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Top1. Introduction
Cognitive radio network (CRN) also called smart radio network, has some significant features, such as: flexible, intelligent, reconfigurable and so on. It purposefully changes certain operating parameters (such as transmission power, the carrier frequency and modulation techniques, etc.) to adapt to the internal state of the received radio signal statistics changes in order to achieve any time, any place highly reliable communication and efficiently use limited radio spectrum resources in heterogeneous network by sensing the external environment and use of artificial intelligence techniques to learn from the environment real-time. The core idea of cognitive radio network is through intelligence of learning ability and spectrum sensing to realize dynamic spectrum allocation and spectrum sharing. In the network, secondary users dynamically search spectrum holes for communicating, a technique called dynamic spectrum access. When users occupy a primary licensed spectrum, secondary users must exit from the band. They went to search for other free ones to complete their communications (Peng et al., 2016).
In cognitive wireless networks, MAC protocol analysis and design versatility is still current hot research issues.
MAC protocol’s performance using a multi-channel way to jump the intersection is optimal. Because such agreements can give full play to the advantages of supports that multi-channel in multiplexing (Lou, 2015). However, these studies use S-ALOHA MAC protocol.
Although the use of CSMA/CA MAC protocol can avoid the shortage of S-ALOHA MAC protocol, the problem of collisions between data packets is inevitable in CSMA/CA MAC protocol (Zhou et al., 2015).
In this paper, study for the cognitive radio networks, explain the random multiple access technology which is widely used in computer systems and communication networks. The biggest advantage of this technology is to enable user occupation of public resources dynamically, make use of existing data storage area and information transfer channels to its maximum.
Because there are a lot of users in the networks, so the channel resources are limited. If every user sends messages according to no law, then the collision channel will be quite severe (Ding et al., 2015). Thus the researchers can also use the CSMA/CA protocol, in which a node listens to the channel and then sends a message if the channel is idle; the probability of such a collision would be significantly reduced (Dongfeng, 1999).
When the information is sent out, without feedback, the node will not know whether the information was successfully sent or not. On this basis, if coupled with an ACK message segment at the end of each information packet, in this way, the information has been sent successfully or not at a glance (Yingxu Wang, 2015). However, the channel collision will still occur for the existence of delay.
Therefore, the ability of conflict resolution is critical in the efficient of systems work. In various conflict resolutions algorithm, tree algorithm is a more effective decomposition method (Zhou et al., 2015). Conflict resolution for binary trees is proved to be an effective method of conflict resolution, but so far such algorithms are more complex analysis. Based on random multiple access system, a new algorithm analysis-isolated algorithm of binary trees for conflict resolution; the basic idea of the algorithm is: force the information packets to be sent at the same time slot into an activation source group, and each activation source do the same set of independent Bernoulli trials; if the result is '0', then select the left slot (the first slot) to send information; if the result is '1', then select right slot (the second slot) to send information packets (Dongfeng, 1997). When the number of terminal station which information packets selected left slot to send is 0, the system turned to the right slot to activate the right slot until the number of terminal station is zero too.