Clock Estimation Method with Low Oversampling Rate for Bidirectional Relay Channel Physical Layer Network Coding

Abstract

The invention discloses a clock estimation method with a low oversampling rate for two-way relay channel physical layer network coding. Communication nodes use communication signals with known waveforms to send training sequences containing cyclic prefixes and cyclic suffixes to the relay through different communication channels. node; the relay node oversamples the received multi-channel superimposed signal to obtain a sampled signal, and the sampled signal is filtered by a matched filter to output the same phase sampling points to form a receiving vector; the likelihood function is calculated by using the training sequence and the receiving vector, and the communication The waveform of the signal is known and the training sequence is orthogonal, and the likelihood functions of different communication signals are separated, which effectively realizes the estimation of time offset with low complexity and low oversampling rate. The clock estimation performance of the method of the present invention is good, and when the low oversampling rate reaches 2, compared with the estimation algorithm of traditional time offset, when the signal-to-noise ratio is greater than 5dB, the mean square error performance of the estimation algorithm of the present invention is at least better by one Magnitude.

Description

technical field [0001] The invention relates to a low oversampling rate clock estimation method, in particular to a low oversampling rate clock estimation method for two-way relay channel physical layer network coding, which belongs to the field of digital communication. Background technique [0002] Shengli Zhang et al first proposed the concept of Physical-Layer Network Coding (PNC) in 2006. As soon as the concept was proposed, it quickly attracted widespread attention and attention from academia and industry. The main idea adopted by PNC is: adopt appropriate mapping mechanism in the relay node, and map the superimposed electromagnetic signals into the XOR of the corresponding digital bit stream, so that the interference becomes a part of the operation of the network coding algorithm. It can greatly improve the throughput of the system. For example, in the two-way relay channel, the system throughput of PNC can be increased by 100% compared with the traditional routing s...

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Problems solved by technology

[0004] Some materials disclose the PNC synchronization problem of two-way relay, and mainly study the impact of non-synchronization on system performance in two aspects of carrier phase and carrier frequency error and time synchronization error. The research results show that in the QPSK modulation mode, in the two cases The total loss of the non-synchronous average power is about 3 ~ 4dB, but there are few materials to disclose the clock estimation method of PNC

Although some data disclose that PNC can reduce the bit error rate performance loss by using the belief propagation (Belief Propagation, BP) algorithm in the case of asynchronous clock, and it is proved that if combined with channel coding, the performance can be reduced when there is asynchronous symbol clock and carrier phase loss, but this is at the expense of increasing system complexity and reducing system information transmission efficiency

[0005] In view of the above-mentioned problems existing in the prior art, for the communication network system with two-way relay channel physical layer network coding, when the signals transmitted by the nodes at both ends reach the relay node at unknown and different times, it is urgent to develop a A clock estimation method with low oversampling rate and low complexity based on two-way relay channel physical layer network coding, and the oversampling rate involved in the clock estimation method is not limited by the actual situation during engineering implementation

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