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Space–time Code
A space–time code (STC) is a method employed to improve the reliability of data transmission in wireless communication systems using multiple transmit antennas. STCs rely on transmitting multiple, redundant copies of a data stream to the receiver in the hope that at least some of them may survive the physical path between transmission and reception in a good enough state to allow reliable decoding. Space time codes may be split into two main types: *Space–time trellis code Space–time trellis codes (STTCs) are a type of space–time code used in multiple-antenna wireless communications. This scheme transmits multiple, redundant copies of a generalised TCM signal distributed over time and a number of antennas ('s ...s (STTCs) distribute a convolutional code, trellis code over multiple antennas and multiple time-slots and provide both coding gain and diversity reception, diversity gain. *Space–time block codes (STBCs) act on a block of data at once (similarly to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Space Time Code
Space is the boundless three-dimensional extent in which objects and events have relative position and direction. In classical physics, physical space is often conceived in three linear dimensions, although modern physicists usually consider it, with time, to be part of a boundless four-dimensional continuum known as spacetime. The concept of space is considered to be of fundamental importance to an understanding of the physical universe. However, disagreement continues between philosophers over whether it is itself an entity, a relationship between entities, or part of a conceptual framework. Debates concerning the nature, essence and the mode of existence of space date back to antiquity; namely, to treatises like the ''Timaeus'' of Plato, or Socrates in his reflections on what the Greeks called ''khôra'' (i.e. "space"), or in the ''Physics'' of Aristotle (Book IV, Delta) in the definition of ''topos'' (i.e. place), or in the later "geometrical conception of place" as "sp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Space–time Line Code
In physics, spacetime is a mathematical model that combines the three dimensions of space and one dimension of time into a single four-dimensional manifold. Spacetime diagrams can be used to visualize relativistic effects, such as why different observers perceive differently where and when events occur. Until the 20th century, it was assumed that the three-dimensional geometry of the universe (its spatial expression in terms of coordinates, distances, and directions) was independent of one-dimensional time. The physicist Albert Einstein helped develop the idea of spacetime as part of his theory of relativity. Prior to his pioneering work, scientists had two separate theories to explain physical phenomena: Isaac Newton's laws of physics described the motion of massive objects, while James Clerk Maxwell's electromagnetic models explained the properties of light. However, in 1905, Einstein based a work on special relativity on two postulates: * The laws of physics are invaria ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
MIMO
In radio, multiple-input and multiple-output, or MIMO (), is a method for multiplying the capacity of a radio link using multiple transmission and receiving antennas to exploit multipath propagation. MIMO has become an essential element of wireless communication standards including IEEE 802.11n (Wi-Fi 4), IEEE 802.11ac (Wi-Fi 5), HSPA+ (3G), WiMAX, and Long Term Evolution (LTE). More recently, MIMO has been applied to power-line communication for three-wire installations as part of the ITU G.hn standard and of the HomePlug AV2 specification. At one time, in wireless the term "MIMO" referred to the use of multiple antennas at the transmitter and the receiver. In modern usage, "MIMO" specifically refers to a class of techniques for sending and receiving more than one data signal simultaneously over the same radio channel by exploiting multipath propagation. Additionally, modern MIMO usage often refers to multiple data signals sent to different receivers (with one or more receiv ... [...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 Channel (communications), 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 dif ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hamid Jafarkhani
Hamid Jafarkhani ( fa, حمید جعفرخانی) (born 1966, in Tehran) is an Iranian-born American electrical engineer and professor. He serves as the Chancellor's Professor in electrical engineering and computer science in the Henry Samueli School of Engineering at the University of California, Irvine (UC Irvine). His research focuses on communications theory, particularly coding and wireless communications and networks. Biography Prior to studying at the University of Tehran, he was ranked first in the nationwide entrance examination of Iranian universities in 1984. After receiving his B.S. degree in 1989, he studied at the University of Maryland College Park and obtained his M.S. degree in 1994 followed by his Ph.D. in 1997. After graduating, Jafarkhani joined AT&T Laboratories-Research in August 1997 before moving to Broadcom in July 2000 and to the University of California, Irvine in September 2001. Within the wireless communications field, Jafarkhani is best known as ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Differential Space–time Code
Differential space–time codes are ways of transmitting data in wireless communications. They are forms of space–time code that do not need to know the channel impairments at the receiver in order to be able to decode the signal. They are usually based on space–time block codes, and transmit one block-code from a set in response to a change in the input signal. The differences among the blocks in the set are designed to allow the receiver to extract the data with good reliability. The first differential space-time block code was disclosed by Vahid Tarokh and Hamid Jafarkhani Hamid Jafarkhani ( fa, حمید جعفرخانی) (born 1966, in Tehran) is an Iranian-born American electrical engineer and professor. He serves as the Chancellor's Professor in electrical engineering and computer science in the Henry Samueli S .... References Encodings {{wireless-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Noncoherent STC
Non-coherent space time codes are a way of transmitting data in wireless communications Wireless communication (or just wireless, when the context allows) is the transfer of information between two or more points without the use of an electrical conductor, optical fiber or other continuous guided medium for the transfer. The most .... In this multiple antenna scheme, it is assumed that the receiver only has knowledge of the statistics of channel. Non-coherent space-time transmission schemes were proposed by Tom Marzetta and Bertrand Hochwald in 1999, but these schemes are complex in terms of implementation. References Data transmission {{wireless-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Division Algebras
In the field of mathematics called abstract algebra, a division algebra is, roughly speaking, an algebra over a field in which division, except by zero, is always possible. Definitions Formally, we start with a non-zero algebra ''D'' over a field. We call ''D'' a division algebra if for any element ''a'' in ''D'' and any non-zero element ''b'' in ''D'' there exists precisely one element ''x'' in ''D'' with ''a'' = ''bx'' and precisely one element ''y'' in ''D'' such that . For associative algebras, the definition can be simplified as follows: a non-zero associative algebra over a field is a division algebra if and only if it has a multiplicative identity element 1 and every non-zero element ''a'' has a multiplicative inverse (i.e. an element ''x'' with ). Associative division algebras The best-known examples of associative division algebras are the finite-dimensional real ones (that is, algebras over the field R of real numbers, which are finite- dimensional as a vector space ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Coherent Space-time Code
Coherence, coherency, or coherent may refer to the following: Physics * Coherence (physics), an ideal property of waves that enables stationary (i.e. temporally and spatially constant) interference * Coherence (units of measurement), a derived unit that, for a given system of quantities and for a chosen set of base units, is a product of powers of base units with no other proportionality factor than one * Coherence time, the time over which a propagating wave (especially a laser or maser beam) may be considered coherent; the time interval within which its phase is, on average, predictable Mathematics * Coherence (philosophical gambling strategy), a concept in Bayesian statistics * Coherence (signal processing), a statistic that can be used to examine the relation between two signals or data sets * Coherence (statistics), a property of self-consistency across a set of assessments, or the strength of association between two series * Coherence condition in category theory, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Channel (communications)
A communication channel refers either to a physical transmission medium such as a wire, or to a logical connection over a multiplexed medium such as a radio channel in telecommunications and computer networking. A channel is used for information transfer of, for example, a digital bit stream, from one or several '' senders'' to one or several '' receivers''. A channel has a certain capacity for transmitting information, often measured by its bandwidth in Hz or its data rate in bits per second. Communicating an information signal across distance requires some form of pathway or medium. These pathways, called communication channels, use two types of media: Transmission line (e.g. twisted-pair, coaxial, and fiber-optic cable) and broadcast (e.g. microwave, satellite, radio, and infrared). In information theory, a channel refers to a theoretical ''channel model'' with certain error characteristics. In this more general view, a storage device is also a communication channel, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Maximal-ratio Combining
In telecommunication Telecommunication is the transmission of information by various types of technologies over wire, radio, optical, or other electromagnetic systems. It has its origin in the desire of humans for communication over a distance greater than that fe ...s, maximum-ratio combining (MRC) is a method of diversity combining in which: #the signals from each channel are added together, #the gain of each channel is made proportional to the rms signal level and inversely proportional to the mean square noise level in that channel. #different proportionality constants are used for each channel. It is also known as ratio-squared combining and predetection combining. Maximum-ratio combining is the optimum combiner for independent additive white Gaussian noise channels. MRC can restore a signal to its original shape. The technique was invented by American engineer Leonard R. Kahn in 1954. MRC has also been found in the field of neuroscience, where it has been shown ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
IEEE Access
IEEE Access is a peer-reviewed open-access scientific journal published by the Institute of Electrical and Electronics Engineers (IEEE). It was established in 2013 and covers all IEEE fields of interest. The founding editor-in-chief was Michael Pecht (University of Maryland) and the current editor-in-chief is Derek Abbott ( University of Adelaide). The journal won a PROSE Award in 2015 for the best new journal in science, technology, engineering, and mathematics. The journal is gold open access and charges a $1,850 Article Processing Charge which is scheduled to rise to $1,950 in 2023. Special sections The journal hosts special sections that highlight a specific topic of general IEEE interest. Associate editors propose a concentration area that emphasizes applications-oriented and interdisciplinary topics. Together with the editorial staff a "Call for Papers" is then sent to academic and industrial researchers soliciting the submissions of manuscripts that identify and discuss t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
