Có 20+ tài liệu thuộc chủ đề "TRUYỀN THÔNG DI ĐỘNG"
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Định vị thiết bị di động bằng công nghệ Bluetooth. Trường Đại học Công nghệ. Abstract: Giới thiệu về công nghệ Bluetooth: lịch sử phát triển, các đặc điểm và ứng dụng. Trình bày lý thuyết và đặc điểm kỹ thuật của công nghệ Bluetooth. Xây dựng được một hệ thống định vị thiết bị di động bằng công nghệ...
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It is often initiated either by crossing a cell boundary or by a deterioration in quality of the signal in the current channel. (In this chapter, a handoff is assumed to occur only at the cell boundary.) The reason why handoffs are critical in cellu- lar communication systems is that neighboring cells are always using a disjoint subset of frequency...
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A mobile station communicates with another station, either mobile or land, via a base station. A mobile station cannot communicate with another mobile station directly. To make a call from a mobile station, the mobile station first needs to make a request using a reverse control channel of the current cell. To route a call to a mobile station is...
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Heuristics for Solving Fixed-Channel Assignment Problems. The tremendous growth of the mobile users’ population coupled with the bandwidth re- quirements of new cellular services is in contrast to the limited spectrum resources that have been allocated for mobile communications. The formulation of this problem as a combinatorial one in the beginning of the 1980s led a number of computer scientists...
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The size of the set C(v) is denoted w(v) and called the weight of the node v. it is assumed that the same channel can be assigned to two different nodes in the graph if and only if their graph distance is at least r.. For our purposes, the objective of an algorithm for the channel assignment problem is, at...
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Channel Assignment and Graph Labeling. Such efficiency can be achieved by optimal frequency reuse, i.e., the simultaneous use of the same part of the ra- dio spectrum by communication links in different locations of the network. As discussed in [28], a graph model can be used for the channel assignment problem.. The nodes of the graph correspond to cells or...
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The rapid technological advances and innovations of the past few decades have pushed wireless communication from concept to reality. The aim of this chapter is to provide the reader with a comprehensive view of the role and details of the protocols that define and control access to the wireless channel, i.e., wireless media access protocols (MAC) protocols. Section 6.3 explores...
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In the near future, wireless technologies will span from broadband wide-area technolo- gies (such as satellite-based networks and cellular networks) to local and personal area networks. After a brief description of the IEEE 802.11 architecture, we will focus on the mechanisms that have been specifically designed to support delay-sensitive traffic.. The cell identifies the area covered by the centralized controller,...
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In wireline networks, fluid fair queueing has long been a popular paradigm for achieving instantaneous fairness and bounded delays in channel access. However, adapt- ing wireline fair queueing algorithms to the wireless domain is nontrivial because of the unique problems in wireless channels such as location-dependent and bursty errors, chan- nel contention, and joint scheduling for uplink and downlink in...
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The overall number of time slots required by the protocol to terminate. For each individual station, the total number of time slots in which it has to be awake in order to transmit/receive packets. The challenge is to strike a sensible balance between the two by design- ing protocols that take a small number of time slots to terminate while...
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In time slot i (1 i), every station transmits with probability p i . The first one terminates, with probability 1 – 1/n in O(log n) time slots. To address this shortcoming, Nakano and Olariu [15] improved this protocol to terminate, with probability exceeding 1 – 1/f in log log n + 2.78 log f + o(log log n +...
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11.1 INTRODUCTION. 앫 Mobile wireless environments are characterized by asymmetric communication, i.e., the downlink communication capacity is much greater than the uplink communica- tion capacity. Data broadcast can take advantage of the large downlink capacity when delivering data to clients.. The second issue is important because of the limited battery power on mobile clients, which ranges from only a few...
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12.1 INTRODUCTION. It is expected that in many countries digital broadcasting systems will mostly replace cur- rent FM radio and television technology in the course of the next one or two decades. Thus, broadcast companies and network providers have a demand for new planning methods that help to fully exploit these capabilities in the large-scale digital broadcasting networks of the...
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Industry market studies forecast an installed base of about 100 million portable computers by the year 2004, in addition to around 30 million hand-held devices and a further 100 million “smart phones.” With such increasing numbers of mobile and wireless devices acting as primary citizens of the Internet, researchers have been studying the impact of the wireless networking tech- nologies...
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14.1 INTRODUCTION. Higher relia- bility, better coverage and services, higher capacity, mobility management, power and complexity for channel acquisition, handover decisions, security management, and wire- less multimedia are all parts of the potpourri.. Safety and security management against fraud, intru- sions, and cloned mobile phones, just to mention a few, will be one of the major issues in the next...
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Mobile Ad Hoc Networks. For mobile ad hoc networks, this final limita- tion is eliminated.. Ad hoc networks are key to the evolution of wireless networks [48]. Ad hoc networks are typically composed of equal nodes that communicate over wireless links without any central control. Although military tactical communication is still considered the primary application for ad hoc networks, commercial...
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16.1 INTRODUCTION. One such challenge is to make effective use of the limited channel bandwidth. 16.2 WHAT IS BROADCAST SCHEDULING?. All of the stations share a common chan- nel. We note that as a practical matter, some existing multihop networks may violate one or more of the above assumptions.. 16.2.2 Defining Broadcast Scheduling. Regardless of the graph model utilized, if...
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17.1 INTRODUCTION. Generally, most of the nomadic computing applications today require single hop connectivity to the wired network. A scenario of MANET in a military action is illustrated in Figure 17.1. In Section 17.2, we review some existing routing protocols for MANET.. Sec- tion 17.4 reviews multicast protocols for MANET. 17.2 UNICAST ROUTING PROTOCOLS FOR MANET. The amount of information...
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18.1 INTRODUCTION. In the remainder of this paper we will assume that all our graphs, unless otherwise stated, are planar geometric networks.. Our main goal here is that of studying routing algorithms that take advantage of the lo- cation of the nodes of geometric networks. Early papers on routing ignored information regarding the physical location of the nodes of the...
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19.1 INTRODUCTION. Wireless data networks are increasingly becoming an important part of the next-genera- tion network infrastructure. One of the chief limitations of these wireless networks is the limited battery power of the network nodes. Therefore, power management is one of the challenging problems in wireless communication, and recent research has addressed this problem. The de- sign of energy-efficient routing...