Femtocell base stations are required to set proper downlink transmit power under various building environment. Conventional power setting techniques use a fixed power offset over received power level of the strongest macrocell base station to expand indoor femtocell coverage along with mitigating the interference leakage to the outdoors. However, the power offset has not been adequately optimized for various interference conditions, leading to degradation of macrocell or femtocell throughput. We propose an auto-tuning scheme of the power offset adaptive to the various interference conditions such as size of buildings where femtocell mobile stations exist, and distance to a street where macrocell mobile stations exist. The proposed scheme automatically tune the power offset so that the femtocell throughput can increase while maintaining the macrocell throughput based on macrocell mobile stations' interference detection reports and their totalization. According to the LongTerm Evolution system level simulations, the proposed scheme tuned the power offset to a proper level depending on various building conditions and can improve the throughput. If the power offset is commonly tuned among femtocells in macrocell, a newly deployed femtocell can employ a proper setting from the beginning of its operation.
Traffic collision is an extremely serious issue in the world today. The World Health Organization (WHO) reported the number of road traffic deaths globally has plateaued at 1.25 million a year. In an attempt to decrease the occurrence of such traffic collisions, various driving systems for detecting pedestrians and vehicles have been proposed, but they are inadequate as they cannot detect vehicles and pedestrians in blind places such as sharp bends and blind intersections. Therefore, mobile networks such as long term evolution (LTE), LTE-Advanced, and 5G networks are attracting a great deal of attention as platforms for connected car services. Such platforms enable individual devices such as vehicles, drones, and sensors to exchange real-time information (e.g., location information) with each other. To guarantee effective connected car services, it is important to deliver a data block within a certain maximum tolerable delay (called a deadline in this work). The Third Generation Partnership Project (3GPP) stipulates that this deadline be 100 ms and that the arrival ratio within the deadline be 0.95. We investigated an intersection at which vehicle collisions often occur to evaluate a realistic environment and found that schedulers such as proportional fairness (PF) and payload-size and deadline-aware (PayDA) cannot satisfy the deadline and arrival ratio within the deadline, especially as network loads increase. They fail because they do not consider three key elements -radio quality, chunk size, and the deadline -when radio resources are allocated. In this paper, we propose a deadline-aware scheduling scheme that considers chunk size and the deadline in addition to radio quality and uses them to prioritize users in order to meet the deadline. The results of a simulation on ns-3 showed that the proposed method can achieve approximately four times the number of vehicles satisfying network requirements compared to PayDA.
In LTE, uplink (UL) transmit power control is important to mitigate the UL aggregate interference from all femtocells to the macrocell, which is increased as the number of femtocells is increased. We propose an UL power control method for LTE femtocells adaptively setting target received power by using the aggregation of the resource usage of femtocells. With this method, when the aggregate resource usage is small, the UL throughput of femtocells is improved by increasing the UL transmit power. When the aggregate resource usage is large, the UL throughput of macrocells is maintained by decreasing the UL transmit power. With LTE system level simulations, it is shown that while in the full buffer traffic condition the decline in the UL throughput of macrocells due to introducing femtocells was suppressed, in the FTP traffic condition the UL throughput of femtocells was improved by 24% at the largest in comparison with the method using the number of active HeNBs.
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