Research On Modulation Recognition Of Digital Communication Signals

Modulation recognition is an important part in cognitive radio, it is an important technology of cognitive radio based universal receiver and intelligent modem. Only accurately identify the a communication signal modulation ways and parameters, to demodulate the correct information[1]. In emergency communication field, such as the tsunami、earthquake、flood、fire and hurricane. These emergencies require the communication system real-time be very high. Because all the wireless communication are propagated through the free space, in order to realize the rapid deployment of communication network, meet the normal communication between the communication systems, modulation recognition of signal for each of the communication system is particularly important. Only correctly identifiy these information including modulation ways, transmission bandwidth of communication system, it can be rational allocate own communication band and take reasonable modulation ways for signal transmission. The core idea of cognitive radio is to make the wireless communication device having ability to find and rational use of idle spectrum, the essence is intelliget software radio. Cognitive radio can constantly aware wireless environment change, and adjust its internal communication mechanism through the adaptive to adapt the change of the wireless environment, this technique solves fundamentally the problem of lack of spectrum resource utilization rate which is the result of spectrum allocation at present. Today, in the non cooperative communication, because of low signals detection and recognition performance and far to actual application situation, this paper systematic research aiming at the key technology of non cooperative communication signal detection and modulation recognition. First, we can perceive outer singnals by the cognitive radio techonology from wireless environment. Second, analyse the received signals in time domain and transform domain, especially characteristic parameters, such as the carrier frequency, SNR, the symbol rate. Finally, through the recognition algorithm to distinction the modulation way, receiver adjust their communication mechanism according to the identification information to communicate with the sender. This subject adopts two kinds of recognition algorithm to achieve modulation recognition, through the hardware to achive instantaneous characteristic parameters identification method and verify the algorithm correctness by the actual effect.