Optimization Part II: Fading Jyri Hämäläinen‚ Communications and Networking Department‚ TKK‚ 17.1.2007 Outline Modeling approaches Path loss models Shadow fading Fast fading 2 Modeling approaches 3 Fading seen by moving terminal Fast fading Power Modeling approach: +20 dB 1. Distance between TX and RX => path loss 2. Shadowing by large obstacles => shadow fading 3. Multi-path effects => fast fading - 20 dB Path loss Lognormal fading Path loss Time
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SATELLITE‚ MOBILE AND PERSONAL COMMUNICATION ASSIGNMENT =CONTENTS= PROBLEM NUMBER PAGE NUMBER 1 3 2 5 3 7 4 8 5 10 3.30 12 3.31 14 3.32
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improving the spectrum efficiency of wireless communication systems. It is well known that the use of MIMO antenna systems allows the channel capacity to scale in proportion to the minimum of the number of transmit and receive antennas in uncorrelated Rayleigh fading channels [1]‚ [2]. Of course‚ real channels do not satisfy these ideal assumptions‚ thus recent work has focused on measuring and characterizing real MIMO propagation channels [3]. In parallel‚ work is continuing on efficient spacetime coding strategies
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path length. Things to consider in designing terrestrial microwave comm. System: * Site Considerations * Sources of Path Data * Path Profile * Interferences and Restrictions * Routes and Sites to be Avoided * Effects of Fading * Diversity Methods to apply * Reliability Objectives * Equipments SITE CONSIDERATION: 1. A full description of each site by geographical coordinates‚ political subdivision‚ access roads and physical objects. 2. Any unusual
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as mobile TV‚ online gaming etc [1]. However‚ the transmission over wireless channel of high rate (i.e. bandwidth) demanding services faces fundamental limitations due to impairments inflicted by the wireless channel due to path loss‚ shadowing and fading effects. These impairments can be compensated by various ways such as by increasing transmit power or bandwidth or applying powerful error control coding (ECC). However‚ power and bandwidth are very scarce and expensive radio resources while ECC yields
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users cooperates and shares their antennas to assist the direct communication. With this approach‚ the benefits of MIMO systems can be attained in a distributed fashion. Furthermore‚ cooperative communications can efficiently combat the severity of fading and shadowing
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College of Computer & Information Science Northeastern University Wireless Networks Lecture 2 Antennas and Propagation The notes in this document are based almost entirely on Chapter 5 of the textbook [Sta05]. Rappaport’s text is also a good reference for wireless signal propagation [Rap95]. 1 Antennas An antenna is an electrical conductor or a system of conductors that radiates/collects (transmits or receives) electromagnetic energy into/from space. An idealized isotropic antenna
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multiplexing (OFDM) has been proven to be a viable technique to overcome multipath fading in wireless channels. While OFDM systems convert a multipath fading channel into a series of equivalent flat fading channels‚
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chaudhary@gmail.com 2 surbhi3jha@gmail.com 3 prabhakar.sh@gmail.com Abstract—It is the technique used to compensate for fading channel impairments. It is implemented by using two or more receiving antennas. While Equalization is used to counter the effects of ISI‚ Diversity is usually employed to reduce the depth and duration of the fades experienced by a receiver in a flat fading channel. These techniques can be employed at both base station and mobile receivers. Spatial Diversity is the most widely
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channels are far more hostile as opposed to wire alternatives‚ and the need for mobility proves especially challenging for reliable communications. OFDM is effective technique for high data rate wireless communication in multi-path channels and fading environment at reasonable complexity in wireless channels II. T HEORY A.
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