One of the candidate technologies for sixth-generation (6G) wireless communication systems is cell-free massive multiple-input multiple-output (CF-mMIMO) communication, which can control inter-cell interference in MIMO systems. This paper investigates the performance of  a full-duplex (FD) CF-mMIMO system with practical limited-capacity fronthaul links. The proposed system employs a large number $M$ distributed FD access points (APs), arbitrarily distributed $K_d$ downlink (DL) and $K_u$ uplink (UL) half-duplex (HD) single-antenna user equipments (UEs), and a central processing unit (CPU). To exploit energy efficiency (EE) and potential throughput gains of FD systems, each AP is linked to the CPU by a fronthaul link with limited capacity that handles the quantized UL/DL data to and from the CPU. On the same spectrum resource, each AP is expected to support $K$ single-antenna HD UEs, where $K = (K_u + K_d)$. Despite having a minimal signal processing complexity, our approach offers a uniform quality of service (QoS) to all UEs while providing improved spectrum efficiency and EE. Imperfect channel state information and mobility of the UEs are also considered. Closed-form expression for the outage probability is derived using the optimal uniform quantization and maximum-ratio combining/maximum-ratio transmission considering the Welch-Satterthwaite approximation. Additionally, the asymptotic and infinite-$M$ outage performance of the proposed system are analytically studied and verified via Monte-Carlo simulation.

In this paper, we investigate the two-way communication between two users assisted by a re-configurable intelligent surface (RIS). The scheme that two users communicate simultaneously in the same time slot over Rayleigh fading channels is considered. The channels between the two users and RIS can either be reciprocal or non-reciprocal. For reciprocal channels, we determine the optimal phases at the RIS to maximize the signal-to-interference-plus-noise ratio (SINR). We then derive exact closed-form expressions for the outage probability and spectral efficiency for single-element RIS. By capitalizing the insights obtained from the single-element analysis, we introduce a gamma approximation to model the product of Rayleigh random variables which is useful for the evaluation of the performance metrics in multiple-element RIS. Asymptotic analysis shows that the outage decreases at $\left(\log(\rho)/\rho\right)^L$ rate where $L$ is the number of elements, whereas the spectral efficiency increases at $\log(\rho)$ rate at large average SINR $\rho$. For non-reciprocal channels, the minimum user SINR is targeted to be maximized. For single-element RIS, closed-form solutions are derived whereas for multiple-element RIS the problem turns out to be non-convex. The latter is relaxed to be a semidefinite programming problem, whose optimal solution is achievable and serves as a sub-optimal solution.