In this letter, we consider downlink transmission of a multiuser multiple-input multiple-output (MU-MIMO) system with zero-forcing (ZF) precoders in the presence of multiple attackers. We propose a cooperative pilot spoofing attack (CPSA), where the attackers collaboratively impair the channel estimations in the uplink channel training phase, aiming at deteriorating the downlink throughput of the whole cell. We first evaluate the impacts of CPSA on the channel estimation and the downlink ZF precoding design, and then we derive an analytical expression for the achievable downlink sum-rate. Furthermore, we investigate the optimal attack strategy to minimize the achievable downlink sum-rate. We show that the optimization problem under consideration is a convex one so the global optimum could be obtained conveniently. Numerical results show that the CPSA attack results in a severe performance deterioration with the increase in the attacking power and the number of attackers.

中文翻译：

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MU-MIMO 系统中的协作导频欺骗


在这封信中，我们考虑在存在多个攻击者的情况下使用迫零（ZF）预编码器的多用户多输入多输出（MU-MIMO）系统的下行链路传输。我们提出了一种协作导频欺骗攻击（CPSA），攻击者在上行链路信道训练阶段协同损害信道估计，旨在恶化整个小区的下行链路吞吐量。我们首先评估 CPSA 对信道估计和下行 ZF 预编码设计的影响，然后导出可实现的下行总速率的解析表达式。此外，我们研究了最佳攻击策略以最小化可实现的下行链路总速率。我们证明所考虑的优化问题是凸问题，因此可以方便地获得全局最优值。数值结果表明，随着攻击力和攻击者数量的增加，CPSA攻击会导致性能严重恶化。