Channel estimation is a practical challenge for intelligent reflecting surface (IRS) aided wireless communication. As the number of IRS reflecting elements or IRS-aided users increases, the channel training overhead becomes excessively high, which results in long delay and low throughput in data transmission. To tackle this challenge, we propose in this paper a new anchor-assisted channel estimation approach, where two anchor nodes, namely A1 and A2, are deployed near the IRS for facilitating its aided base station (BS) in acquiring the cascaded BS-IRS-user channels required for data transmission. Specifically, in the first scheme, the partial channel state information (CSI) on the element-wise channel gain square of the common BS-IRS link for all users is first obtained at the BS via the anchor-assisted training and feedback. Then, by leveraging such partial CSI, the cascaded BS-IRS-user channels are efficiently resolved at the BS with additional training by the users. While in the second scheme, the BS-IRS-A1 and A1-IRS-A2 channels are first estimated via the training by A1. Then, with additional training by A2, all users estimate their individual cascaded A2-IRS-user channels simultaneously. Based on the CSI fed back from A2 and all users, the BS resolves the cascaded BS-IRS-user channels efficiently. In both schemes, the quasi-static channels among the fixed BS, IRS, and two anchors are estimated off-line only, which greatly reduces the real-time training overhead. Simulation results demonstrate that our proposed anchor-assisted channel estimation schemes achieve superior performance as compared to existing IRS channel estimation schemes, under various practical setups. In addition, the first proposed scheme outperforms the second one when the number of antennas at the BS is sufficiently large, and vice versa.
翻译:智能反射表面(IRS)辅助无线通信的频道估算是智能反射表面(IRS)辅助无线通信的一个实际挑战。随着IRS反映元素或IRS辅助用户数量的增加,频道培训管理管理费用变得过高,导致数据传输方面出现长期拖延和低输送量。为了应对这一挑战,我们在本文件中建议采用一个新的锚辅助频道估算方法,在IRS附近部署两个锚点,即A1和A2, 在获得数据传输所需的连锁BS-IRS-用户用户频道时,在获得数据传输所需的级联BS-IRS用户用户用户用户频道用户频道用户频道用户频道时,在第一个办法中,部分频道状态信息(CSI)显示部分BS-IR连接在数据传输方面出现延误。 在第二个办法中,BS-IR-IS服务器服务器服务器服务器用户在第二个方案下大幅下降,在A-2级联级联的服务器系统用户之前首先通过A-S高级频道估算其通用的BS-IR-IRA-IS连接度数据,然后又通过A2级联路段进行更多培训。