基于图信号处理的OFDM系统导频设计和信道估计方法

Graph signal processing based pilot pattern design and channel estimation for OFDM system

正交频分复用(OFDM,orthogonal frequency division multiplexing)是物联网的物理层关键技术之一,导频设计和信道估计是OFDM系统的关键问题。针对物联网通信场景复杂多样导致固定导频方案性能较差的问题,提出了一种基于图信号处理(GSP,graph signal processing)的导频设计和信道估计方法。首先,将时频资源块建模为图信号,将信道估计问题转换为图信号的采样重建问题。进而考虑时频双选衰落的影响,设计加权图邻接矩阵,构造基于时频位置的图拓扑结构。在此基础上,基于图信号采样理论优化导频位置,提出一种基于加权图拓扑构造的导频图案设计方法。同时,基于图信号重建方法进行信道信息重建,提出基于图平滑性约束的信道估计方案。仿真结果表明,所提方法相较于传统方案在双选信道的高速场景下可取得更高的信道估计精度,在低速场景下则可有效节约导频资源。

Orthogonal frequency division multiplexing(OFDM)is one of the key technologies in the physical layer of the internet of things(IoT).Pilot design and channel estimation are key issues in OFDM systems.In view of the problem of performance loss by fixed pilot pattern due to the complexity and variety of IoT communication scenarios,a pilot design and channel estimation scheme based on graph signal processing(GSP)was proposed.Firstly,the time-frequency resource block was modeled as a graph signal,and the channel estimation problem was reformulated into a sampling and reconstruction problem of the graph signal.Then,considering the influence of time-frequency fading,a weighted graph adjacency matrix was designed to construct a graph topology structure based on the time-frequency position.On this basis,the pilot position is selected based on the graph signal sampling theory,a greedy pilot pattern design algorithm based on weighted graph topology was proposed.At the same time,signal reconstruction was performed based on the graph signal reconstruction method,and a channel estimation method based on the graph smoothness constraint was proposed.Compared with the conventional scheme,simulation results show that the proposed method achieves higher channel estimation accuracy in high-speed scenarios of double selective channels,and effectively reduces pilot overhead in low-speed scenarios.