Serial hierarchical scheduling algorithm for factor graph iterative equalization
A technology of layered scheduling and serial scheduling, applied in code conversion, error correction/detection using block codes, shaping network in transmitter/receiver, etc. Code Diffusion, etc.
Active Publication Date: 2020-08-28
TOEC TECH
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There are three situations where the channel is not ideal: the first situation is that the signal reaches the receiving end through multiple paths and different delays due to reflection, scattering and other reasons during transmission, resulting in inter-symbol interference; the second situation is due to limited The channel filtering characteristics of bandwidth are not ideal, such as the unideal group delay and unideal amplitude-frequency characteristics of transponders in satellite communications, which distort the waveform of the transmission channel and cause delay expansion, which can be equivalent to multiple path transmission, resulting in intersymbol interference
The third case is that the transmission filter and the reception filter are used in the communication system to limit the signal bandwidth. When the receiving end cannot accurately sample, inter-symbol interference will occur.
Moreover, in iterative equalization, due to the existence of a large number of short loops with a length of 4, flood scheduling will increase the correlation of external information, resulting in error diffusion and affecting the performance of the receiver
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[0074] Specific embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings.
[0075] original symbol s k The set of constellation points is defined as Ω, and the number of constellation points is |Ω|=2 θ , θ is the modulation order, generally an integer of 1-6. the s k After passing through the ISI and AWGN channels, it reaches the receiving end and becomes y k . The equalizer at the receiving end according to y k Perform iterative equalization processing, and send the posterior probability soft information result to the demapping module.
[0076] The intersymbol interference system can be expressed as a transversal filter model, such as figure 1 shown.
[0077] The coefficients of the transversal filter are represented by a vector h, and the order of the transversal filter is the dimension (|h|) of the h vector. Here it is assumed that |h|=L 1 +L 2 +1, and define
[0078] In a digital communication system,...
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The invention provides a serial hierarchical scheduling algorithm for factor graph iterative equalization. The serial hierarchical scheduling algorithm comprises the following steps: 1) processing a channel convolution matrix H to realize system serial scheduling; 2) initializing extrinsic information transmitted to an equalization function node Ek by a variable node si and posterior probability information p(-1)(sk|Y, H) of a sending symbol sk to be equal to 1; 3)For i=0:L1+L2; 4) updating the external information in the ith layer of factor graph according to a formula; 5) updating the external information transmitted to the variable node by the equalization function node in the ith layer of factor graph according to the formula; 6) updating the posterior probability p(i)(sk|Y,H) of the symbol variable node according to the formula; 7) End For. Aiming at the problem of high complexity of the iterative equalization algorithm, the confidence propagation algorithm in iterative equalization is scheduled, so that the convergence rate of the iterative equalization algorithm is increased, the complexity of the iterative equalization algorithm is reduced, and the practicability of the factor graph iterative equalization algorithm is improved.
Description
technical field [0001] The invention relates to the field of wireless communication, in particular to a serial hierarchical scheduling algorithm for factor graph iterative equalization. Background technique [0002] In a communication system, the channel is often non-ideal, and channel distortion always occurs, and the most common distortion is inter-symbol interference (ISI). In order to eliminate or weaken the impact of ISI on the communication system, the signal can be pre-distorted at the sending end or equalized at the receiving end. [0003] Intersymbol Interference (ISI) in communication systems is caused by channel imperfections. There are three situations where the channel is not ideal: the first situation is that the signal reaches the receiving end through multiple paths and different delays due to reflection, scattering and other reasons during transmission, resulting in inter-symbol interference; the second situation is due to limited The channel filtering cha...
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Login to View More IPC IPC(8): H04L25/03H03M13/11
CPCH04L25/03006H04L25/0391H03M13/1148H04L2025/03363H04L2025/03611
Inventor 张建军董悦曹晓冬范玉进
Owner TOEC TECH