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arXiv 2203.07549cs.ITmath.IT
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具有OTFS调制的无小区大规模MIMO:功率控制和资源分配

Cell-Free Massive MIMO with OTFS Modulation: Power Control and Resource Allocation

Mohammadali Mohammadi, Hien Quoc Ngo, Michail Matthaiou

摘要:

我们考虑了无小区的大规模多输入多输出(MIMO)系统的下行链路与正交时频空间(OTFS)调制。两种基于导频的信道估计方案,即基于叠加导频的信道估计(SP-CHE)和基于嵌入导频的信道估计(EP-CHE),被应用于估计接入点(AP)处的信道。SP-CHE方案在延迟-多普勒域中将低功率导频叠加到数据符号上,以避免由于EP-CHE方案中使用的空保护间隔而导致的频谱效率(SE)损失。在SP-CHE方案的情况下,我们考虑一个最大最小公平性优化问题,以联合优化每个用户导频/数据功率分配系数和每个AP功率控制系数。然后通过两个解耦的子问题迭代求解复杂的非凸问题。此外,一个最大-最小公平性问题投EP-CHE方案,其中优化变量是每个AP的功率控制系数。数值结果表明,所提出的资源分配方法提供了最多42和5倍的增加,在95%可能的每用户SE的SP-CHE和EP-CHE计划,分别与均匀功率控制和相关的阴影衰落信道。

英文摘要:

We consider the downlink of cell-free massive multiple-input multiple-output (MIMO) systems with orthogonal time frequency space (OTFS) modulation. Two pilot-based channel estimation schemes, namely superimposed pilot-based (SP-CHE) and embedded pilot-based channel estimation (EP-CHE), are applied to estimate the channels at the access points (APs). The SP-CHE scheme superimposes low power pilots onto the data symbols in the delay-Doppler domain to avoid the spectral efficiency (SE) loss due to null guard intervals used in the EP-CHE scheme. In the case of SP-CHE scheme, we consider a max-min fairness optimization problem to jointly optimize the peruser pilot/data power allocation coefficients and per-AP power control coefficients. The complicated non-convex problem is then iteratively solved through two decoupled sub-problems. Moreover, a max-min fairness problem is cast for the EP-CHE scheme, where the optimization variables are the per-AP power control coefficients. Numerical results show that the proposed resource allocation approaches provide at most 42 and 5-fold increase in the 95%-likely per-user SE for the SP-CHE and EP-CHE scheme, respectively, compared with the uniform power control and in correlated shadowing fading channels.

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