Diversity Combining

	Diversity Combining Diversity combining is the technique applied to combine the multiple received signals of a diversity reception device into a single improved signal. Various techniques Various diversity combining techniques can be distinguished: * Equal-gain combining: All the received signals are summed coherently. * Maximal-ratio combining is often used in large phased-array systems: The received signals are weighted with respect to their SNR and then summed. The resulting SNR yields \sum_^SNR_k where SNR_k is SNR of the received signal k. * Switched combining: The receiver switches to another signal when the currently selected signal drops below a predefined threshold. This is also often called "Scanning Combining". * Selection combining: Of the N received signals, the strongest signal is selected. When the N signals are independent and Rayleigh distributed, the expected diversity gain has been shown to be \sum_^\frac, expressed as a power ratio. Therefore, any additional gain diminishes ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu]
	Diversity Scheme In telecommunications, a diversity scheme refers to a method for improving the reliability of a message signal by using two or more communication channels with different characteristics. Diversity is mainly used in radio communication and is a common technique for combatting fading and co-channel interference and avoiding error bursts. It is based on the fact that individual channels experience different levels of fading and interference. Multiple versions of the same signal may be transmitted and/or received and combined in the receiver. Alternatively, a redundant forward error correction code may be added and different parts of the message transmitted over different channels. Diversity techniques may exploit the multipath propagation, resulting in a diversity gain, often measured in decibels. Diversity techniques The following classes of diversity schemes can be identified: * Time diversity: Multiple versions of the same signal are transmitted at different time instants. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu]
	Diversity System Diagram Diversity, diversify, or diverse may refer to: Business Diversity (business), the inclusion of people of different identities (ethnicity, gender, age) in the workforce Diversity marketing, marketing communication targeting diverse customers Supplier diversity, the use of diverse suppliers Politics Diversity (politics), the political and social policy of encouraging tolerance for people of different cultural and racial backgrounds * Diversity Immigrant Visa or Green Card Lottery, a United States immigration program * Diversity jurisdiction, a concept under which U.S. federal courts can hear suits between parties from different states * Diversity training, the process of educating people to function in a diverse environment * Cultural diversity, the respect of different cultures and interculturality * Functional diversity (disability), a term for special needs, disability, impairment and handicap * Gerodiversity, a multicultural approach to issues of aging * Multicultur ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu]
	Transmit Diversity Transmit diversity is radio communication using signals that originate from two or more independent sources that have been modulated with identical information-bearing signals and that may vary in their transmission characteristics at any given instant. It can help overcome the effects of fading, outages, and circuit failures. When using diversity transmission and reception, the amount of received signal improvement depends on the independence of the fading characteristics of the signal as well as circuit outages and failures. Considering antenna diversity, in many systems additional antennas may be expensive or impractical at the remote or even at the base station. In these cases, transmit diversity can be used to provide diversity benefit at a receiver with multiple transmit antennas only. With transmit diversity, multiple antennas transmit delayed versions of a signal, creating frequency-selective fading, which is equalized at the receiver to provide diversity gain. Sinc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu]
	Ambient Noise Level In atmospheric sounding and noise pollution, ambient noise level (sometimes called background noise level, reference sound level, or room noise level) is the background sound pressure level at a given location, normally specified as a reference level to study a new intrusive sound source. Ambient sound levels are often measured in order to map sound conditions over a spatial regime to understand their variation with locale. In this case the product of the investigation is a sound level contour map. Alternatively ambient noise levels may be measured to provide a reference point for analyzing an intrusive sound to a given environment. For example, sometimes aircraft noise is studied by measuring ambient sound without presence of any overflights, and then studying the noise addition by measurement or computer simulation of overflight events. Or roadway noise is measured as ambient sound, prior to introducing a hypothetical noise barrier intended to reduce that ambient noise lev ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu]
picture info	Los Angeles, California Los Angeles ( ; es, Los Ángeles, link=no , ), often referred to by its initials L.A., is the largest city in the state of California and the second most populous city in the United States after New York City, as well as one of the world's most populous megacities. Los Angeles is the commercial, financial, and cultural center of Southern California. With a population of roughly 3.9 million residents within the city limits , Los Angeles is known for its Mediterranean climate, ethnic and cultural diversity, being the home of the Hollywood film industry, and its sprawling metropolitan area. The city of Los Angeles lies in a basin in Southern California adjacent to the Pacific Ocean in the west and extending through the Santa Monica Mountains and north into the San Fernando Valley, with the city bordering the San Gabriel Valley to it's east. It covers about , and is the county seat of Los Angeles County, which is the most populous county in the United States with an estimat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu]
picture info	San Rafael, California San Rafael ( ; Spanish for " St. Raphael", ) is a city and the county seat of Marin County, California, United States. The city is located in the North Bay region of the San Francisco Bay Area. As of the 2020 U.S. census, the city's population was 61,271, up from 57,713 in 2010. San Rafael was founded by the Spanish in 1817, when Vicente Francisco de Sarría established Mission San Rafael Arcángel, initially as an ''asistencia'' (sub-mission). San Rafael Arcángel was upgraded to full mission status in 1822, a month before Alta California declared independence from Spain as part of Mexico. Following the American Conquest of California, the community of San Rafael incorporated as a city in 1874. History San Rafael was once the site of several Coast Miwok villages: ''Awani-wi'', near downtown San Rafael, ''Ewu'', near Terra Linda and ''Shotomko-cha'', in Marinwood. Spanish period Mission San Rafael Arcángel was founded as the 20th Spanish mission in the colonial pro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu]
	Selective Calling In a conventional, analog two-way radio system, a standard radio has ''noise squelch'' or ''carrier squelch'', which allows a radio to receive all transmissions. Selective calling is used to address a subset of all two-way radios on a single radio frequency channel. Where more than one user is on the same channel (co-channel users), selective calling can address a subset of all receivers or can direct a call to a single radio. Selective calling features fit into two major categories—''individual calling'' and ''group calling''. Individual calls generally have longer time-constants: it takes more air-time to call an individual radio unit than to call a large group of radios. Selective calling is akin to the use of a lock on a door. A radio with carrier squelch is unlocked and will let any signal in. Selective calling locks out all signals except ones with the correct "key", in this case a specific digital code. Selective calling systems can overlap; a radio may have (group call) ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu]