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Link budget

About: Link budget is a(n) research topic. Over the lifetime, 1355 publication(s) have been published within this topic receiving 19738 citation(s).
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Proceedings ArticleDOI
11 Dec 2006-
TL;DR: This work proposes light-weight cooperation in sensing based on hard decisions to mitigate the sensitivity requirements on individual radios and shows that the "link budget" that system designers have to reserve for fading is a significant function of the required probability of detection.
Abstract: Cognitive Radios have been advanced as a technology for the opportunistic use of under-utilized spectrum since they are able to sense the spectrum and use frequency bands if no Primary user is detected. However, the required sensitivity is very demanding since any individual radio might face a deep fade. We propose light-weight cooperation in sensing based on hard decisions to mitigate the sensitivity requirements on individual radios. We show that the "link budget" that system designers have to reserve for fading is a significant function of the required probability of detection. Even a few cooperating users (~10-20) facing independent fades are enough to achieve practical threshold levels by drastically reducing individual detection requirements. Hard decisions perform almost as well as soft decisions in achieving these gains. Cooperative gains in a environment where shadowing is correlated, is limited by the cooperation footprint (area in which users cooperate). In essence, a few independent users are more robust than many correlated users. Unfortunately, cooperative gain is very sensitive to adversarial/failing Cognitive Radios. Radios that fail in a known way (always report the presence/absence of a Primary user) can be compensated for by censoring them. On the other hand, radios that fail in unmodeled ways or may be malicious, introduce a bound on achievable sensitivity reductions. As a rule of thumb, if we believe that 1/N users can fail in an unknown way, then the cooperation gains are limited to what is possible with N trusted users.

1,546 citations


Book
20 Sep 2005-
Abstract: Preface. 1. Introduction. 1.1 Frequency Designations. 1.2 Modes of Propagation. 1.3 Why Model Propagation? 1.4 Model Selection and Application. 1.4.1 Model Sources. 1.5 Summary. 2. Electromagnetics and RF Propagation. 2.1 Introduction. 2.2 The Electric Field. 2.3 The Magnetic Field. 2.4 Electromagnetic Waves. 2.5 Wave Polarization. 2.6 Propagation of Electromagnetic Waves at Material Boundaries. 2.7 Propagation Impairment. 2.8 Ground Effects on Circular Polarization. 2.9 Summary. 3. Antenna Fundamentals. 3.1 Introduction. 3.2 Antenna Parameters. 3.3 Antenna Radiation Regions. 3.4 Some Common Antennas. 3.5 Antenna Polarization. 3.6 Antenna Pointing loss. 3.7 Summary. 4. Communication Systems and the Link Budget. 4.1 Introduction. 4.2 Path Loss. 4.3 Noise. 4.4 Interference. 4.5 Detailed Link Budget. 4.6 Summary. 5. Radar Systems. 5.1 Introduction. 5.2 The Radar Range Equation. 5.3 Radar Measurements. 5.4 Clutter. 5.5 Atmospheric Impairments. 5.6 Summary. 6. Atmospheric Effects. 6.1 Introduction. 6.2 Atmospheric Refraction. 6.3 Atmospheric Attenuation. 6.4 Loss From Moisture and Precipitation. 6.5 Summary. 7. Near-Earth Propagation Models. 7.1 Introduction. 7.2 Foliage Models. 7.3 Terrain Modeling. 7.4 Propagation in Built-Up Areas. 7.5 Summary. 8. Fading and Multipath Characterization. 8.1 Introduction. 8.2 Ground-Bounce Multipath. 8.3 Large-Scale or Log-Normal Fading. 8.4 Small-Scale Fading. 8.5 Summary. 9. Indoor Propagation Modeling. 9.1 Introduction. 9.2 Interference. 9.3 The Indoor Environment. 9.4 Summary. 10. Rain Attenuation of Microwave and Millimeter Wave Signals. 10.1 Introduction. 10.2 Link Budget. 10.3 Rain Fades. 10.4 The Link Distance Chart. 10.5 Availability Curves. 10.6 Other Precipitation. 10.7 Cross-Polarization Effects. 10.8 Summary. 11. Satellite Communications. 11.1 Introduction. 11.2 Satellite Orbits. 11.3 Satellite Operating Frequency. 11.4 Satellite Path Free-Space Loss. 11.5 Atmospheric Attenuation. 11.6 Ionospheric Effects. 11.7 Rain Fades. 11.8 Antenna Considerations. 11.10 Summary. 12. RF Safety. 12.1 Introduction. 12.2 Biological Effects of RF Exposure. 12.3 CC Guidelines. 12.4 Antenna Considerations. 12.5 FCC Computations. 12.6 Station Evaluations. 12.7 Summary. Appendix A: Review of Probability for Propagation Modeling. Index.

717 citations


Proceedings ArticleDOI
18 May 1998-
TL;DR: A space-time coded orthogonal frequency division multiplexing (OFDM) modulated physical layer is designed which combines coding and modulation and is attractive for delay-sensitive applications.
Abstract: There has been an increasing interest in providing high data-rate services such as video-conferencing, multimedia Internet access and wide area network over wideband wireless channels. Wideband wireless channels available in the PCS band (2 GHz) have been envisioned to be used by mobile (high Doppler) and stationary (low Doppler) units in a variety of delay spread profiles. This is a challenging task, given the limited link budget and severity of wireless environment, and calls for the development of novel robust bandwidth efficient techniques which work reliably at low SNRs. To this end, we design a space-time coded orthogonal frequency division multiplexing (OFDM) modulated physical layer. This combines coding and modulation. Space-time codes were previously proposed for narrowband wireless channels. These codes have high spectral efficiency and operate at very low SNR (within 2-3 dB of the capacity). On the other hand, OFDM has matured as a modulation scheme for wideband channels. We combine these two in a natural manner and propose a system achieving data rates of 1.5-3 Mbps over a 1 MHz bandwidth channel. This system requires 18-23 dB (resp. 9-14 dB) receive SNR at a frame error probability of 10/sup -2/ with two transmit and one receive antennas (resp. two transmit and two receive antennas). As space-time coding does not require any form of interleaving, the proposed system is attractive for delay-sensitive applications.

595 citations


Journal ArticleDOI
Y. P. Zhang1, Duixian Liu2Institutions (2)
TL;DR: Antenna-on-chip (AoC) and antenna-in-package (AiP) solutions are studied for highly integrated millimeter-wave (mmWave) devices in wireless communications and the systems level pros and cons are highlighted from the electrical and economic perspectives for system designers.
Abstract: Antenna-on-chip (AoC) and antenna-in-package (AiP) solutions are studied for highly integrated millimeter-wave (mmWave) devices in wireless communications. First, the background, regulations, standard, and applications of 60-GHz wireless communications are briefly introduced. Then, highly integrated 60-GHz radios are overviewed as a basis for the link budget analysis to derive the antenna gain requirement. Next, in order to have deep physical insight into the AoC solution, the silicon substrate's high permittivity and low resistivity effects on the AoC efficiency are examined. It is shown that the AoC solution has low efficiency, less than 12% due to large ohmic losses and surface waves, which requires the development of techniques to improve the AoC efficiency. After that, the AiP solution and associated challenges such as how to realize low-loss interconnection between the chip and antenna are addressed. It is shown that wire-bonding interconnects, although inferior to the flip-chip, are still feasible in the 60-GHz band if proper compensation schemes are utilized. An example of the AiP solution in a low-temperature cofired ceramic (LTCC) process is presented in the 60-GHz band showing an efficiency better than 90%. A major concern with both AoC and AiP solutions is electromagnetic interference (EMI), which is also discussed. Finally, the systems level pros and cons of both AoC and AiP solutions are highlighted from the electrical and economic perspectives for system designers.

429 citations


Journal ArticleDOI
Peter Hall1, Yang Hao2, Yuriy I. Nechayev1, Akram Alomainy2  +12 moreInstitutions (3)
TL;DR: Investigations into channel characterization and antenna performance at 2.45 GHz show that for many channels, an antenna polarized normal to the body's surface gives the best path gain.
Abstract: On-body communication channels are of increasing interest for a number of applications, such as medical-sensor networks, emergency-service workers, and personal communications. This paper describes investigations into channel characterization and antenna performance at 2.45 GHz. It is shown that significant channel fading occurs during normal activity, due primarily to the dynamic nature of the human body, but also due to multipath around the body and from scattering by the environment. This fading can be mitigated by the use of antenna diversity, and gains of up to 10 dB are obtained. Separation of the antenna's performance from the channel characteristics is difficult, but results show that for many channels, an antenna polarized normal to the body's surface gives the best path gain. Simulation and modeling present many challenges, particularly in terms of the problem's scale, and the need for accurate modeling of the body and its movement.

418 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
20221
202160
202092
2019103
2018106
201790

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Topic's top 5 most impactful authors

Emmeric Tanghe

11 papers, 120 citations

Hendrik Rogier

9 papers, 74 citations

Hyoungsuk Yoo

8 papers, 142 citations

Sathaporn Promwong

8 papers, 57 citations

David Plets

7 papers, 52 citations