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Space-division Multiple Access
Space-division multiple access (SDMA) is a channel access method based on creating parallel spatial pipes (focused signal beams) using advanced antenna technology next to higher capacity pipes through spatial multiplexing and/or diversity, by which it is able to offer superior performance in radio multiple access communication systems (where multiple users may need to use the communication media simultaneously). In traditional mobile cellular network systems, the base station has no information on the position of the mobile units within the cell and radiates the signal in all directions within the cell in order to provide radio coverage. This method results in wasting power on transmissions when there are no mobile units to reach, in addition to causing interference for adjacent cells using the same frequency, so called co-channel cells. Likewise, in reception, the antenna receives signals coming from all directions including noise and interference signals. By using smart anten ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Channel Access Method
In telecommunications and computer networks, a channel access method or multiple access method allows more than two terminals connected to the same transmission medium to transmit over it and to share its capacity. Examples of shared physical media are wireless networks, bus networks, ring networks and point-to-point links operating in half-duplex mode. A channel access method is based on multiplexing, that allows several data streams or signals to share the same communication channel or transmission medium. In this context, multiplexing is provided by the physical layer. A channel access method may also be a part of the multiple access protocol and control mechanism, also known as medium access control (MAC). Medium access control deals with issues such as addressing, assigning multiplex channels to different users and avoiding collisions. Media access control is a sub-layer in the data link layer of the OSI model and a component of the link layer of the TCP/IP model. Fun ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mobile Station
A mobile station (MS) comprises all user equipment and software needed for communication with a mobile network. The term refers to the global system connected to the mobile network, i.e. a mobile phone or mobile computer connected using a mobile broadband adapter. This is the terminology of 2G systems like GSM. In 3G systems, a mobile station (MS) is now referred to as user equipment (UE). In GSM, a mobile station consists of four main components: * Mobile termination (MT) - offers common functions such as: radio transmission and handover, speech encoding and decoding, error detection and correction, signalling and access to the SIM. The IMEI code is attached to the MT. It is equivalent to the network termination of an ISDN access. *Terminal equipment (TE) - is any device connected to the MS offering services to the user. It does not contain any functions specific to GSM. * Terminal adapter (TA) - provides access to the MT as if it were an ISDN network termination wit ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Multi-user MIMO
Multi-user MIMO (MU-MIMO) is a set of multiple-input and multiple-output (MIMO) technologies for multipath wireless communication, in which multiple users or terminals, each radioing over one or more antennas, communicate with one another. In contrast, single-user MIMO (SU-MIMO) involves a single multi-antenna-equipped user or terminal communicating with precisely one other similarly equipped node. Analogous to how OFDMA adds multiple-access capability to OFDM in the cellular-communications realm, MU-MIMO adds multiple-user capability to MIMO in the wireless realm. SDMA,N. JindalMIMO Broadcast Channels with Finite Rate Feedback IEEE Transactions on Information Theory, vol. 52, no. 11, pp. 5045–5059, 2006.D. Gesbert, M. Kountouris, R.W. Heath Jr., C.-B. Chae, and T. SälzerShifting the MIMO Paradigm IEEE Signal Processing Magazine, vol. 24, no. 5, pp. 36-46, 2007.R. Tweg, R. Alpert, H. Leizerovich, A. Steiner, E. Levitan, E. Offir-Arad, A.B. Guy, B. Zickel, A. Aviram, A. Frieman ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Co-channel Interference
Co-channel interference or CCI is crosstalk from two different radio transmitters using the same channel. Co-channel interference can be caused by many factors from weather conditions to administrative and design issues. Co-channel interference may be controlled by various radio resource management schemes. Cellular mobile networks In cellular mobile communication ( GSM & LTE Systems, for instance), frequency spectrum is a precious resource which is divided into non-overlapping spectrum bands which are assigned to different cells (In cellular communications, a cell refers to the hexagonal/circular area around the base station antenna). However, after certain geographical distance, these frequency bands are re-used, i.e. the same spectrum bands are reassigned to other distant cells. The co-channel interference arises in the cellular mobile networks owing to this phenomenon of frequency reuse. Thus, besides the intended signal from within the cell, signals at the same freque ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spectral Efficiency
Spectral efficiency, spectrum efficiency or bandwidth efficiency refers to the information rate that can be transmitted over a given Bandwidth (signal processing), bandwidth in a specific communication system. It is a measure of how efficiently a limited frequency spectrum is utilized by the physical layer protocol, and sometimes by the medium access control (the channel access protocol).Guowang Miao, Jens Zander, Ki Won Sung, and Ben Slimane, Fundamentals of Mobile Data Networks, Cambridge University Press, , 2016. Link spectral efficiency The link spectral efficiency of a digital communication system is measured in ''bit/second, s/hertz, Hz'', or, less frequently but unambiguously, in ''(bit/s)/Hz''. It is the net bit rate (useful information rate excluding error-correcting codes) or maximum throughput divided by the Bandwidth (signal processing), bandwidth in hertz of a communication channel or a data link. Alternatively, the spectral efficiency may be measured in ''bit/symbol'', ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Electromagnetic Field
An electromagnetic field (also EM field or EMF) is a classical (i.e. non-quantum) field produced by (stationary or moving) electric charges. It is the field described by classical electrodynamics (a classical field theory) and is the classical counterpart to the quantized electromagnetic field tensor in quantum electrodynamics (a quantum field theory). The electromagnetic field propagates at the speed of light (in fact, this field can be identified ''as'' light) and interacts with charges and currents. Its quantum counterpart is one of the four fundamental forces of nature (the others are gravitation, weak interaction and strong interaction.) The field can be viewed as the combination of an electric field and a magnetic field. The electric field is produced by stationary charges, and the magnetic field by moving charges (currents); these two are often described as the sources of the field. The way in which charges and currents interact with the electromagnetic field is d ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Specific Absorption Rate
Specific absorption rate (SAR) is a measure of the rate at which energy is absorbed per unit mass by a human body when exposed to a radio frequency (RF) electromagnetic field. It can also refer to absorption of other forms of energy by tissue, including ultrasound. It is defined as the power absorbed per mass of tissue and has units of watts per kilogram (W/kg). SAR is usually averaged either over the whole body, or over a small sample volume (typically 1 g or 10 g of tissue). The value cited is then the maximum level measured in the body part studied over the stated volume or mass. Calculation SAR for electromagnetic energy can be calculated from the electric field within the tissue as: :\text = \frac\int_\textrm \frac d\mathbf where :\sigma is the sample electrical conductivity :E is the RMS electric field :\rho is the sample density :V is the volume of the sample SAR measures exposure to fields between 100 kHz and 10 GHz (known as radio waves). It ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mobile Phone Operator
A mobile phone operator, wireless provider, or carrier is a mobile telecommunications company that provides wireless Internet GSM services for mobile device users. The operator gives a SIM card to the customer who inserts it into the mobile device to gain access to the service. There are two types of mobile operators: * a mobile network operator (MNO) which owns the underlying network and spectrum assets required to run the service. * a mobile virtual network operator (MVNO) which buys wholesale service from an MNO and sells on to its own customers. (and for years before), the world's largest individual mobile operator by subscribers is China Mobile with over 835 million mobile subscribers. Over 50 mobile operators have over 10 million subscribers each, and over 150 mobile operators had at least one million subscribers by the end of 2009. In February 2010, there were 4.6 billion mobile subscribers, a number that is estimated to grow. Total mobile‐cellular subscriptions re ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Base Transceiver Station
A base transceiver station (BTS) is a piece of equipment that facilitates wireless communication between user equipment (UE) and a network. UEs are devices like mobile phones (handsets), WLL phones, computers with wireless Internet connectivity, or antennas mounted on buildings or telecommunication towers. The network can be that of any of the wireless communication technologies like GSM, CDMA, wireless local loop, Wi-Fi, WiMAX or other wide area network (WAN) technology. BTS is also referred to as the '' node B'' (in 3G networks) or, simply, the ''base station'' (BS). For discussion of the LTE standard the abbreviation '' eNB'' for evolved node B is widely used, and GNodeB for 5G. Though the term BTS can be applicable to any of the wireless communication standards, it is generally associated with mobile communication technologies like GSM and CDMA. In this regard, a BTS forms part of the base station subsystem (BSS) developments for system management. It may also have e ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Base Transceiver Station
A base transceiver station (BTS) is a piece of equipment that facilitates wireless communication between user equipment (UE) and a network. UEs are devices like mobile phones (handsets), WLL phones, computers with wireless Internet connectivity, or antennas mounted on buildings or telecommunication towers. The network can be that of any of the wireless communication technologies like GSM, CDMA, wireless local loop, Wi-Fi, WiMAX or other wide area network (WAN) technology. BTS is also referred to as the '' node B'' (in 3G networks) or, simply, the ''base station'' (BS). For discussion of the LTE standard the abbreviation '' eNB'' for evolved node B is widely used, and GNodeB for 5G. Though the term BTS can be applicable to any of the wireless communication standards, it is generally associated with mobile communication technologies like GSM and CDMA. In this regard, a BTS forms part of the base station subsystem (BSS) developments for system management. It may also have e ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cellular Network
A cellular network or mobile network is a communication network where the link to and from end nodes is wireless. The network is distributed over land areas called "cells", each served by at least one fixed-location transceiver (typically three cell sites or base transceiver stations). These base stations provide the cell with the network coverage which can be used for transmission of voice, data, and other types of content. A cell typically uses a different set of frequencies from neighboring cells, to avoid interference and provide guaranteed service quality within each cell. When joined together, these cells provide radio coverage over a wide geographic area. This enables numerous portable transceivers (e.g., mobile phones, tablets and laptops equipped with mobile broadband modems, pagers, etc.) to communicate with each other and with fixed transceivers and telephones anywhere in the network, via base stations, even if some of the transceivers are moving through more ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Timing Advance
In the GSM cellular mobile phone standard, timing advance (TA) value corresponds to the length of time a signal takes to reach the base station from a mobile phone. GSM uses TDMA technology in the radio interface to share a single frequency between several users, assigning sequential timeslots to the individual users sharing a frequency. Each user transmits periodically for less than one-eighth of the time within one of the eight timeslots. Since the users are at various distances from the base station and radio waves travel at the finite speed of light, the precise arrival-time within the slot can be used by the base station to determine the distance to the mobile phone. The time at which the phone is allowed to transmit a burst of traffic within a timeslot must be adjusted accordingly to prevent collisions with adjacent users. Timing Advance (TA) is the variable controlling this adjustment. Technical Specifications 3GPP TS 05.10 and TS 45.010 describe the TA value adjustment pr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
