Localization has become a prominent use case for 6G mobile networks, and the integrated localization and communication (ILAC) system represents an inevitable trend. To design and manage such ILAC systems effectively and efficiently, quantification of its performance bound, i.e., an analytical model that reveals the trade-off between communication and localization performance, is a crucial yet unresolved task. To address this, we proposed an analytical framework for an ILAC system that achieves communication and localization. Specifically, we derived a closed-form expression of the capacity loss versus localization Cramer-Rao lower bound (CRB) loss through time-domain and frequency-domain resource allocation. Through simulations, we validated our analytical model and observed that frequencydomain resource allocation is preferable in scenarios with fewer antennas at the next generation nodeB (gNB) and a larger distance between user equipment (UE) and gNB. Conversely, time-domain resource allocation is preferable in scenarios with more antennas and a smaller distance between UE and the gNB

Reconfigurable intelligent surface (RIS), which provides indirect line-of-sight (LoS) transmission paths between the receiver and its blocked transmitter, has been proposed as one of the promising technologies for network performance enhancement. Recent works indicate that both the numbers of RISs and unit cells per RIS have a significant impact on network performance. However, with a given total number of unit cells, the joint analysis of these two factors considering blockage effect has not been investigated. In this paper, the coverage probability of a three-dimensional downlink millimeter wave RIS-assisted network is analyzed. We first derive the acceptable area where a LoS RIS is capable to satisfy the signal-to-noise ratio threshold at the receiver. Next, we model the centers of building blockages and human-body blockages as two independent Poisson point processes and derive the probability that indirect LoS transmissions exist. Then, we derive and validate the analytical upper and lower bounds of the coverage probability as the functions of network parameters and blockage densities. We also derive and validate the closed-form coverage probability when RISs are much closer to UE than BS. Finally, we propose a general network cost model for RIS-assisted network. Results show that in terms of coverage enhancement, densely deployed small-scale RISs outperform sparsely deployed large-scale RISs in scenarios with dense blockages or short transmission distances, while sparsely deployed large-scale RISs are preferable in scenarios with sparse blockages or long transmission distances.

Both reconfigurable intelligent surfaces (RISs) and ultra-dense (UD) small-cell (SC) base stations (BSs) are investigated for indoor mmWave wireless coverage enhancement. To explore which deployment strategy is more cost-effective, the costs of deploying both RISs and UD SCs are defined and calculated. Through jointly analyzing coverage probability and network cost in typical indoor environments, we conclude that the same network coverage can be achieved by multiple deployment strategies. To achieve certain level of coverage probability with the lowest network cost, a proper number of BSs are crucial for RIS-assisted networks.

Deploying the 5 G new radio network on the unlicensed mmWave band (NR-U) is a promising solution to meet the constantly increasing traffic demand of the cellular network. However, the coexistence issue on the unlicensed mmWave spectrum between NR-U and Wireless Gigabit (WiGig) networks becomes a significant concern. The coexistence schemes between LTE and Wi-Fi networks cannot be readily applied to support the coexistence between NR-U and WiGig networks due to the directional beamforming and propagation characteristic of the mmWave band. The directional transmission complicates the coexistence problem but opens up possibilities for increased system capacity via concurrent multi-user MIMO (MU-MIMO) transmission at the expense of interference management. To this end, we consider an NR-U and WiGig coexisting scenario and aim to maximize the total NR-U throughput on the unlicensed spectrum via resource allocation and inter-beam interference mitigation. The optimization problem is formulated into an integer nonlinear programming (INLP) problem and is further transformed into a many-to-one matching game for tractability. We propose a matching-based concurrent algorithm (MBCA) to solve it and the inter-beam interference is mitigated via the forbidden pairs (FPs). In comparison to the exhaustive search-based algorithm (ESA), simulation results show that FP effectively mitigates inter-beam interference and achieves near-optimal performance. The proposed algorithm also outperforms the state-of-art algorithms in existing research.

Transmissive reconfigurable intelligent surfaces (RISs) are a promising solution for coverage enhancement of the future outdoor-to-indoor (O2I) millimeter wave (mmWave) network. In this work, the coverage probability of the multiple transmissive RIS-aided O2I mmWave network is investigated. Firstly, the system model of the three-dimensional O2I mmWave network considering random blockages is proposed. Moreover, the spatial correlation of blockages is analyzed to derive the accurate blockage probability. Furthermore, based on the blockage probability, the closed-form approximation of the signal-to-noise ratio (SNR) coverage probability is derived and verified. Finally, the impact of blockage density, the number and locations of RISs on the coverage probability is analyzed. According to the numerical results, the highest coverage enhancement caused by four small-scale RISs with appropriate locations reaches $69.5$ % higher compared with a large-scale RIS located at the center of the building envelope.

Although the almost blank subframes (ABSFs) proposed in heterogeneous cellular networks can enhance the performance of the cell range expansion (CRE) user equipments (UEs), it significantly degrades the macro-cell total throughput. To address this problem, the low power subframes (LPSFs) are encouraged to be applied in the macro-cell center region by the further-enhanced inter-cell interference coordination. However, the residual power of the LPSF, which interferes with the CRE UEs, and the proportion of the LPSF affect the downlink throughput together. To achieve a better rate coverage probability, the appropriate LPSF power and the proportion are required. In this paper, the analytical results of the overall signal to interference and noise ratio coverage probability and the rate coverage probability are derived under the stochastic geometric framework. The optimal region bias ranges for maximizing the rate coverage probability are also analyzed. The results show that the ABSF still outperform the LPSF in terms of rate with the optimal range expansion bias, but lead to a heavier burden on the backhaul of the pico-cell. However, with a static range expansion bias, the LPSF provide better rate coverage than the ABSF. In addition, in a low-range expansion scenario, the reduced power of the LPSF has negligible effect on the rate coverage with the optimal resource partitioning.