In this study, we propose a novel mobile tracking method based on Multi-Criteria Decision Making (MCDM), in which uncertain parameters—the received signal strength, the distance between the mobile and the base station, the moving direction, and the previous location—are used in the decision process using the aggregation function in the fuzzy set theory. Through numerical results, we show that our proposed mobile tracking method provides a better performance than the conventional method using the received signal strength.
Since random early detection (RED) was proposed in 1993, many active queue management (AQM) algorithms have been proposed to support better end-to-end Transmission Control Protocol (TCP) congestion control. In this article, the authors introduce and analyze a feedback control model of the TCP/AQM dynamics. Then they suggest the concept of an AQM algorithm that can detect and avoid congestion proactively. Finally, they propose the proportional-integral (PI) proportional-derivative (PD) controller using proportional-integral-derivative (PID) feedback control to overcome the reactive control behavior of existing AQM proposals. The PI-PD controller is able to provide proactive congestion avoidance and control using an adaptive congestion indicator and a control function. A comparative simulation study under a variety of network environments shows that the PI-PD controller outperforms RED and the PI controller in terms of the queue length dynamics, the packet loss rates, and the link utilization.
The femtocell access point of LTE-Advanced system, which can be deployed under macrocell coverage, was applied to the paper. The paper consists of two analyses which are the interference impact by the femtocell and the macrocell at a user equipment and the load impact to the control plane in evolved packet core network by X2 and S1 handover signaling messages. On the results of investigations by performance simulations with regard to the receiving power and signal-to-noise ratio at a user equipment side, the unavailable zone to the inbound handover from macrocell to femtocell occurred due to a severe intercell interference depending on a femtocell topology. Therefore, we found that an intercell interference coordination between macrocell and femtocell in order to make an inbound handover is needed and that X2 interface is the better solution rather than S1 interface for an inbound handover by investigating the X2 and S1 handover procedure of 3GPP. Ultimately, it is shown that the X2 interface between macrocell and femtocell can play an important role in an high reliable inbound handover and a simple interference control implementation on femtocell environment.
Abstract Background Nontuberculous mycobacteria (NTM) species rarely cause vertebral osteomyelitis (VO). The clinical characteristics and radiological findings of NTM VO are not well described since the number of cases are limited. Here we present the clinical characteristics of culture positive NTM VO, compared to those of tuberculous (TB) VO. Methods We performed a retrospective, multicenter study at 5 hospitals. Patients with radiologic findings consistent with VO, and positive NTM or TB cultures on biopsy were included. Demographic characteristics and symptoms were collected, along with laboratory, radiologic, and pathologic findings. Results Nineteen patients with NTM VO and 105 patients with TB VO were included. M. intracellulare (52.6%) and M. abscessus (26.3%) were the most common NTM pathogens. The mean age of patients was significantly older in the NTM VO group (68.0 vs. 58.5 years, P = .01). Previous steroid or immunosuppressant use was more frequent in the NTM VO group (21.1% vs. 2.9%, P = .01; 15.8% vs. 2.9%, P = .046, respectively), as was a history of vertebral surgery (47.4% vs. 13.3%, P < .001). Symptoms and laboratory findings were similar between the 2 groups, although the proportion of patients with positive interferon-gamma release assays (IGRA) was significantly higher in the TB VO group (14.3% vs. 86.4%, P < .001). Radiologic findings were also similar, with lumbar involvement being the most common (57.9% and 44.8%, respectively). Chronic granulomatous inflammation was more frequently seen in TB VO patients (33.3% vs. 64.0%, P = .04), while inflammation alone was more common in NTM VO. Although there was no significant difference in survival after 1 year, survival at last follow-up (median, 24 months) was significantly lower in the NTM VO group (75.0% vs. 98.8%, P = .02). Conclusion NTM VO should be considered in older patients with a history of immunosuppression or previous vertebral surgery. The pathologic findings and radiologic findings of NTM VO were similar to that of TB VO. Granulomatous inflammation and positive IGRA tests were more common in TB than NTM VO. Disclosures All Authors: No reported disclosures.
In this paper, we evaluate handover (HO) performance when user equipment (UE) moves between femto cell and macro cell in long term evolution (LTE) systems. The focus is on the HO performance for inbound and outbound mobility which corresponds to handoff between the femtocell and the macro cell. Due to the severe signal-to-interference noise ratio (SINR) degradation near the edge area of femtocell, HO triggering for inbound and outbound mobility needs to be carefully selected than that of the macro cell. Too late HO triggering leads to radio link failures (RLF), whereas too early HO triggering causes ping-pong HO. In this paper, we take the neighbouring cell configurations into account to keep the allowable RLF rate and low ping-pong rates. We propose a cell-types adaptive handover margins algorithm, which assigns different handover margins in line with neighbouring cell types. Simulation results indicate that the low ping-pong rate and the low RLF rate are achieved simultaneously by using the proposed algorithm.
Component carriers (CCs) in a Long Term Evolution - Advanced (LTE-A) system are limited by maximum 100 radio bearers (RBs) on a 20 MHz CC due to a fixed 15 KHz subcarrier bandwidth. However it is able to be changed in the future, so that a study regarding heterogeneous CCs which have diverse RBs above 100 on a CC is needed at this moment. To support non-contiguous carrier aggregation (CA) with the these conditions, a heterogeneous joint CC packet scheduling algorithm interacting with a radio resource control (RRC) is considered in this paper. The performance of the joint CC packet scheduling algorithm on heterogeneous CCs with different channel characteristics has been analyzed and compared through computer simulations as well. According to the results, we found that an 800 MHz CC exhibits approximately 4 dB better channel gains than a 2.1 GHz CC. We also obtained a capacity increase of about 15-40% for a joint CC maximum rate (MR) algorithm and about 2-28 % for a joint CC proportional fair (PF) algorithm when the number of users is increased. On the other hand, in a round-robin (RR) scenario, we were unable to notice any differences between the independent CC and joint CC packet scheduling policies. Furthermore, looking at the impacts of different amounts of RBs on 800 MHz + 2.1 GHz CCs, we can conclude that a one-to-one RB ratio with respect to the MR, PF, and RR algorithms has a better performance compared to other cases, and thus, owing to the better channel gain, the smaller the RBs of the 800 MHz CC, the better the performance achieved.
In this paper, we exploit how to provide quality of service at the downlink in the OFDMA wireless communication systems. The OFDMA, also referred to as multiuser-OFDM, is considered as a strong candidate wireless system for the next generation mobile communications. Since there are a variety of traffic demands for real-time and non-real-time traffics in the next generation mobile communications, especially at the downlink from a base station, scheduling of such downlink traffic packets is expected to be a key function for QoS provisioning to users. One such scheduling algorithm designed not only to support multiple users simultaneously but also to offer real-time and non-real-time services to a user at the same time is the urgency and efficiency based packet scheduling (UEPS) algorithm [S. Ryu et al., 2005]. The UEPS algorithm uses the time-utility function as a scheduling urgency factor and the relative status of the current channel to the average one as an efficiency indicator of radio resource usage. The design goal to maximize throughput of non-real-time traffics with satisfying QoS requirements of real-time traffics.
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