In this paper, we propose a novel cooperative roadside unit (RSU) broadcast approach that can effectively enhance the vehicles’ packet-reception rates of the messages broadcast cooperatively by nearby RSUs. To enable message-aggregation among RSUs, we propose a new vehicular-message format based on the software-defined multiplexing code which can aggregate multiple messages without any need of packet form. To facilitate our proposed new cooperative scheme, RSUs must be organized into clusters. We formulate this RSU clustering problem as a graph partitioning problem, which aims to make individual cluster sizes as close to each other as possible. Furthermore, we design a new heuristic algorithm to efficiently solve this problem. This heuristic algorithm is also compared with the random clustering and minimum-degree clustering schemes in terms of the modified Gini index. The theoretical analysis of our proposed cooperative RSU broadcast scheme is also conducted to guarantee that our proposed new cooperative RSU-broadcast approach can improve the packet reception rate. Furthermore, we simulate the vehicular environment with the simulation tools SUMO and NS-3 as benchmarks. The simulation demonstrates that our proposed new cooperative RSU-broadcast system will increase the packet reception rate and the number of successfully received packets over the conventional non-cooperative broadcast system.

Nowadays, wireless local-area networks (WLANs) are widely deployed in residential and commercial areas. How to ensure full coverage is always an important challenge during the deployment of access-points (APs) and routers. In this study, we investigate the full Line of Sight (LoS) coverage problem. We will focus on how to achieve the full LoS coverage using a minimal number of APs/routers in an arbitrary polygonal/prismatic field-of-interest, which may be simply or multiply connected subject to a certain restricted link-range. We propose a new visibility-polygon-based approach for doing so. The performance of our proposed new approach is then evaluated in terms of the coverage efficiency, the total number of APs/routers, and the peak link-distance ratio for achieving the full LoS coverage. Meanwhile, we also compare our proposed new approach with the existing schemes. Compared to the existing schemes, our proposed novel visibility-polygon-based approach can achieve the full LoS coverage by requiring the same number of APs/routers but much less computation time.

The well-known soft-focus effect, which relies on either special optical filters or manual post-production techniques, has been intriguing and powerful in photography for quite a while. Nonetheless, how to impose the soft-focus effect automatically simply using sophisticated image-processing (computational photography) algorithms has never been addressed in the literature to the best of our knowledge. In this work, we would like to make the first-ever attempt to design an automatic, optical-filter-free approach to create the appropriate soft-focus effects desired by individual users. Our approach is first to investigate the physical optical filter, namely Kenko Black Mist No. 5, and estimate the corresponding kernel matrix (i.e., the system impulse response matrix) using our proposed novel irradiance-domain kernel-matrix estimation framework. Furthermore, we demonstrate that it is not feasible to find a kernel matrix that precisely characterizes the soft-focus effect by just using a pixel-value-domain image (a regular photo) in post production. To combat the aforementioned problem, we establish a novel pixel-value-to-pseudo-irradiance map such that the pseudo irradiance-domain image can be obtained directly from any pixel-value-domain image. Finally the soft-focus effect can be created from the two-dimensional convolution between the pseudo irradiance-domain image and the estimated kernel. To evaluate our proposed automatic scheme for soft-focus effect, we compare the results from our proposed new scheme and the physical optical filter in terms of the DCT-KLD (Kullback-Leibler divergence of discrete cosine transform) and the conventional PSNR (peak-signal-to-noise ratio). Experiments show that our proposed new scheme can achieve very small DCT-KLDs and very large PSNRs over the ground truth, namely the results from the physical optical filter.

Nowadays, wireless local-area networks (WLANs) are widely deployed in residential and commercial areas. The coverage quality is essential to users. The full coverage appears to be one of the most crucial problems to be considered during the network and access-point/router deployment (placement). We formulate the light-of-sight (LoS) coverage problem using the visibility-graph framework. In this work, for arbitrary multiply-connected or simply-connected polygonal/prismatic fields-of-interest subject to an arbitrary link-range restriction, we investigate how the full LoS coverage can be achieved by a minimum number of access-points/routers. Based on the new mathematical lemmas we derive, we design a novel graph-theoretical approach accordingly. Our proposed new scheme can be deemed the first-ever systematic approach to the best of our knowledge. Our proposed new approach is also evaluated in terms of the coverage efficiency, the number of access-points/routers, and the peak link-distance ratio for full LoS coverage in comparison with the existing solution to the art gallery problem.