다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

A key challenge of future mobile communication research is to strike an attractive compromise between wireless network's area spectral efficiency and energy efficiency. This necessitates a clean-slate approach to wireless system design, embracing the rich body of existing knowledge, especially on multiple-input-multiple-ouput (MIMO) technologies. This motivates the proposal of an emerging wireless communications concept conceived for single-radio-frequency (RF) large-scale MIMO communications, which is termed as SM. The concept of SM has established itself as a beneficial transmission paradigm, subsuming numerous members of the MIMO system family. The research of SM has reached sufficient maturity to motivate its comparison to state-of-the-art MIMO communications, as well as to inspire its application to other emerging wireless systems such as relay-aided, cooperative, small-cell, optical wireless, and power-efficient communications. Furthermore, it has received sufficient research attention to be implemented in testbeds, and it holds the promise of stimulating further vigorous interdisciplinary research in the years to come. This tutorial paper is intended to offer a comprehensive state-of-the-art survey on SM-MIMO research, to provide a critical appraisal of its potential advantages, and to promote the discussion of its beneficial application areas and their research challenges leading to the analysis of the technological issues associated with the implementation of SM-MIMO. The paper is concluded with the description of the world's first experimental activities in this vibrant research field.

https://hal-supelec.archives-ouvertes.fr/hal-00840278/document

Spatial Modulation for Generalized MIMO: Challenges, Opportunities, and Implementation

Hawaii International Conference on System Sciences

Space-air-ground integrated network (SAGIN), as an integration of satellite systems, aerial networks, and terrestrial communications, has been becoming an emerging architecture and attracted intensive research interest during the past years. Besides bringing significant benefits for various practical services and applications, SAGIN is also facing many unprecedented challenges due to its specific characteristics, such as heterogeneity, self-organization, and time-variability. Compared to traditional ground or satellite networks, SAGIN is affected by the limited and unbalanced network resources in all three network segments, so that it is difficult to obtain the best performances for traffic delivery. Therefore, the system integration, protocol optimization, resource management, and allocation in SAGIN is of great significance. To the best of our knowledge, we are the first to present the state-of-the-art of the SAGIN since existing survey papers focused on either only one single network segment in space or air, or the integration of space-ground, neglecting the integration of all the three network segments. In light of this, we present in this paper a comprehensive review of recent research works concerning SAGIN from network design and resource allocation to performance analysis and optimization. After discussing several existing network architectures, we also point out some technology challenges and future directions.

Space-Air-Ground Integrated Network: A Survey

As the explosive growth of smart devices and the advent of many new applications, traffic volume has been growing exponentially. The traditional centralized network architecture cannot accommodate such user demands due to heavy burden on the backhaul links and long latency. Therefore, new architectures, which bring network functions and contents to the network edge, are proposed, i.e., mobile edge computing and caching. Mobile edge networks provide cloud computing and caching capabilities at the edge of cellular networks. In this survey, we make an exhaustive review on the state-of-the-art research efforts on mobile edge networks. We first give an overview of mobile edge networks, including definition, architecture, and advantages. Next, a comprehensive survey of issues on computing, caching, and communication techniques at the network edge is presented. The applications and use cases of mobile edge networks are discussed. Subsequently, the key enablers of mobile edge networks, such as cloud technology, SDN/NFV, and smart devices are discussed. Finally, open research challenges and future directions are presented as well.

A Survey on Mobile Edge Networks: Convergence of Computing, Caching and Communications

Multiple heterogeneous access technologies will be intergraded in the next generation wireless system in which the seamless migration of ongoing data-flows from one access point to another is one of the fundamental issues. In this paper, an IEEE 802.21 Media Independent Handover (MIH) based handover management architecture containing four modules is proposed and the multihoming technology is adopted to achieve Make-Before-Break vertical handover. Then the paper presents the simulation of the architecture in ns-2. The results substantiate the efficacy of the architecture in improving the handover performance significantly compared with the traditional Mobile IPv6 (MIPv6) based Break-Before-Make handover scheme.

An IEEE 802.21-based multihoming architecture for Make-Before-Break vertical handover

SUMMARY

In networks with identifier/locator separation, border routers often cache recently used identifier-to-locator mappings of remote hosts and set a time to live (TTL) for each mapping. We consider two options to update the TTL of a mapping, designated as no-reset (NR) and with-reset (WR) modes. In the NR mode, once a mapping is cached, its TTL is set to a default value called cache timeout, and the mapping is removed when the TTL expires. By contrast, in the WR mode, whenever the mapping is queried, its TTL is reset to the cache timeout. Although it is not difficult to intuitively observe that the WR mode performs better than the NR mode in terms of cache hit rate, it is still of interest to evaluate what is the benefit gained by using the WR mode rather than the NR mode and what is the cost incurred to achieve this gain. Another equivalent question is what is the additional cost incurred in terms of resources for the NR mode to perform similarly to the WR mode. We model the cache hit rate and compare the performance of the WR and NR modes for flat and aggregatable identifiers by analysis and simulation, and estimate how much more cache size the NR mode requires to achieve similar cache hit rate and communication interruptions to the WR mode. The comparison results provide rational to use the WR mode, rather than the NR mode, for identifier-to-locator mapping caches. Copyright © 2012 John Wiley & Sons, Ltd.

Time to live of identifier‐to‐locator mappings: with‐reset or no‐reset

The traditional network has millions of routers, and it would be extremely expensive to entirely replace them for the future network architecture. Hence, it is desirable to design a transition scheme to connect the traditional network and SINET. In this chapter, we discuss the transition schemes for SINET. The related work on the future Internet transitions is first introduced. Then, we give our consideration and analysis for SINET’s transition solutions.

Transition Schemes to SINET

In order to evaluate the superiorities of SINET, its performance is evaluated by a thorough comparison with the recent network solutions. In this chapter, we focus on the analysis and evaluation of SINET.

Analysis and Evaluation of SINET

With the widespread use of multimedia contents via mobile nodes (MNs), IP mobile multicast becomes more important for wireless, mobile, and ubiquitous multimedia applications. Until now, many research efforts have been made to provide IP multicast for the MNs. However, the existing mobile multicast schemes mostly focus on the mobility of receivers based on the host-based mobility solution that requires the MN to participate in the mobility management. Recent work has shown that service connectivity for mobile multicast sources is still a problem and attracts very little concern. With the development of the network-based mobility support protocol, mobile multicast source support schemes in Proxy Mobile IPv6 (PMIPv6) networks are needed urgently. In this paper, we propose a base solution (BS) and also a direct multicast routing scheme (DMRS) for mobile multicast source support in PMIPv6 networks. In the BS, the multicast listener discover (MLD) proxy function is adopted to transmit multicast data through the PMIPv6 tunnel. The DMRS can provide locally optimized traffic flows and avoid inefficient routing present in the BS. We evaluate and compare the performance of the proposed schemes with the Mobile IP bidirectional tunneling (MIP-BT) and Mobile IP remote subscription (MIP-RS) schemes by theoretical analysis and also implement the proposed schemes on the test-bed. The numerical results show that the BS and DMRS outperform the MIP-BT and MIP-RS in terms of signaling cost. Meanwhile, the experimental results verify the feasibility and validity of our proposed schemes. Furthermore, we study the optimal PMIPv6 domain size to reduce the total signaling cost for the proposed schemes.

Mobile multicast source support in PMIPv6

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