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Proportional-fair Scheduling
Proportional-fair scheduling is a compromise-based scheduling algorithm. It is based upon maintaining a balance between two competing interests: Trying to maximize total throughput of the network (wired or not) while at the same time allowing all users at least a minimal level of service. This is done by assigning each data flow a data rate or a scheduling priority (depending on the implementation) that is inversely proportional to its anticipated resource consumption.Guowang Miao, Jens Zander, Ki Won Sung, and Ben Slimane, Fundamentals of Mobile Data Networks, Cambridge University Press, , 2016. Weighted fair queuing Proportionally fair scheduling can be achieved by means of weighted fair queuing (WFQ), by setting the scheduling weights for data flow i to w_i = 1 / c_i, where the cost c_i is the amount of consumed resources per data bit. For instance: * In CDMA spread spectrum cellular networks, the cost may be the required energy per bit in the transmit power control (the incre ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Scheduling Algorithm
In computing, scheduling is the action of assigning ''resources'' to perform ''tasks''. The ''resources'' may be processors, network links or expansion cards. The ''tasks'' may be threads, processes or data flows. The scheduling activity is carried out by a process called scheduler. Schedulers are often designed so as to keep all computer resources busy (as in load balancing), allow multiple users to share system resources effectively, or to achieve a target quality-of-service. Scheduling is fundamental to computation itself, and an intrinsic part of the execution model of a computer system; the concept of scheduling makes it possible to have computer multitasking with a single central processing unit (CPU). Goals A scheduler may aim at one or more goals, for example: * maximizing ''throughput'' (the total amount of work completed per time unit); * minimizing ''wait time'' (time from work becoming ready until the first point it begins execution); * minimizing '' latency' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Guowang Miao
Guowang Miao is an associate professor at KTH Royal Institute of Technology, Sweden, working on design and optimization of wireless communications and networking and the author of ''Fundamentals of Mobile Data Networks'' and ''Energy and Spectrum Efficient Wireless Network Design''. Education Guowang Miao received his bachelor's degree from Tsinghua University and his master's degree and Ph.D. from Georgia Institute of Technology, Atlanta. Career Guowang Miao's initial career saw work at intel, Intel Labs and Samsung Research America. He won an Individual Gold Award from Samsung, Samsung Telecom America, in 2011, for his work on LTE-A standardization. In 2012, he joined the KTH Royal Institute of Technology as an assistant professor. In 2015, he became an associate professor at the same institute, where he also published above 80 research papers, some of which are Essential Science Indicators (ESI) highly cited with several of them patented. He also served as a technical program ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Weighted Fair Queuing
Weighted fair queueing (WFQ) is a network scheduling algorithm. WFQ is both a packet-based implementation of the generalized processor sharing (GPS) policy, and a natural extension of fair queuing (FQ). Whereas FQ shares the link's capacity in equal subparts, WFQ allows schedulers to specify, for each flow, which fraction of the capacity will be given. Weighted fair queuing is also known as packet-by-packet GPS (PGPS or P-GPS) since it approximates generalized processor sharing "to within one packet transmission time, regardless of the arrival patterns." Parametrization and fairness Like other GPS-like scheduling algorithms, the choice of the weights is left to the network administrator. There is no unique definition of what is "fair" (see for further discussion). By regulating the WFQ weights dynamically, WFQ can be utilized for controlling the quality of service, for example, to achieve guaranteed data rate. Proportionally fair behavior can be achieved by setting the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
CDMA
Code-division multiple access (CDMA) is a channel access method used by various radio communication technologies. CDMA is an example of multiple access, where several transmitters can send information simultaneously over a single communication channel. This allows several users to share a band of frequencies (see bandwidth). To permit this without undue interference between the users, CDMA employs spread spectrum technology and a special coding scheme (where each transmitter is assigned a code). CDMA optimizes the use of available bandwidth as it transmits over the entire frequency range and does not limit the user's frequency range. It is used as the access method in many mobile phone standards. IS-95, also called "cdmaOne", and its 3G evolution CDMA2000, are often simply referred to as "CDMA", but UMTS, the 3G standard used by GSM carriers, also uses "wideband CDMA", or W-CDMA, as well as TD-CDMA and TD-SCDMA, as its radio technologies. It can be also used as a channe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Transmit Power Control
Power control, broadly speaking, is the intelligent selection of transmitter power output in a communication system to achieve good performance within the system.Guowang Miao, Jens Zander, Ki Won Sung, and Ben Slimane, Fundamentals of Mobile Data Networks, Cambridge University Press, , 2016. The notion of "good performance" can depend on context and may include optimizing metrics such as link data rate, network capacity, outage probability, geographic coverage and range, and life of the network and network devices. Power control algorithms are used in many contexts, including cellular networks, sensor networks Wireless sensor networks (WSNs) refer to networks of spatially dispersed and dedicated sensors that monitor and record the physical conditions of the environment and forward the collected data to a central location. WSNs can measure environmental c ..., wireless LANs, and Digital subscriber line, DSL modems. Transmit power control Transmit power control is a technical mec ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Link Adaptation
Link adaptation, comprising adaptive coding and modulation (ACM) and others (such as Power Control), is a term used in wireless communications to denote the matching of the modulation, coding and other signal and protocol parameters to the conditions on the radio link (e.g. the pathloss, the interference due to signals coming from other transmitters, the sensitivity of the receiver, the available transmitter power margin, etc.). For example, WiMAX uses a rate adaptation algorithm that adapts the modulation and coding scheme (MCS) according to the quality of the radio channel, and thus the bit rate and robustness of data transmission. The process of link adaptation is a dynamic one and the signal and protocol parameters change as the radio link conditions change—for example in High-Speed Downlink Packet Access (HSDPA) in Universal Mobile Telecommunications System (UMTS) this can take place every 2 ms. Adaptive modulation systems invariably require some channel state information ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
EVDO
Evolution-Data Optimized (EV-DO, EVDO, etc.) is a telecommunications standard for the wireless transmission of data through radio signals, typically for broadband Internet access. EV-DO is an evolution of the CDMA2000 ( IS-2000) standard which supports high data rates and can be deployed alongside a wireless carrier's voice services. It uses advanced multiplexing techniques including code-division multiple access (CDMA) as well as time-division multiplexing (TDM) to maximize throughput. It is a part of the CDMA2000 family of standards and has been adopted by many mobile phone service providers around the world particularly those previously employing CDMA networks. It is also used on the Globalstar satellite phone network. EV-DO service was discontinued in much of Canada in 2015. An EV-DO channel has a bandwidth of 1.25 MHz, the same bandwidth size that IS-95A ( IS-95) and IS-2000 ( 1xRTT) use, though the channel structure is very different. The back-end network ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Signal-to-noise Ratio
Signal-to-noise ratio (SNR or S/N) is a measure used in science and engineering that compares the level of a desired signal to the level of background noise. SNR is defined as the ratio of signal power to the noise power, often expressed in decibels. A ratio higher than 1:1 (greater than 0 dB) indicates more signal than noise. SNR, bandwidth, and channel capacity of a communication channel are connected by the Shannon–Hartley theorem. Definition Signal-to-noise ratio is defined as the ratio of the power of a signal (meaningful input) to the power of background noise (meaningless or unwanted input): : \mathrm = \frac, where is average power. Both signal and noise power must be measured at the same or equivalent points in a system, and within the same system bandwidth. Depending on whether the signal is a constant () or a random variable (), the signal-to-noise ratio for random noise becomes: : \mathrm = \frac where E refers to the expected value, i.e. in this ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dynamic Channel Allocation
In radio resource management for wireless and cellular networks, channel allocation schemes allocate bandwidth and communication channels to base stations, access points and terminal equipment. The objective is to achieve maximum system spectral efficiency in bit/s/Hz/site by means of frequency reuse, but still assure a certain grade of service by avoiding co-channel interference and adjacent channel interference among nearby cells or networks that share the bandwidth. Channel-allocation schemes follow one of two types of strategy:Guowang Miao, Jens Zander, Ki Won Sung, and Ben Slimane, Fundamentals of Mobile Data Networks, Cambridge University Press, , 2016. # Fixed: FCA, fixed channel allocation: manually assigned by the network operator # Dynamic: ## DCA, dynamic channel allocation ## DFS, dynamic frequency selection ## Spread spectrum Static Channel Allocation In Fixed Channel Allocation or Fixed Channel Assignment (FCA) each cell is given a predetermined set of frequency ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Scheduling (computing)
In computing, scheduling is the action of assigning ''resources'' to perform ''tasks''. The ''resources'' may be processors, network links or expansion cards. The ''tasks'' may be threads, processes or data flows. The scheduling activity is carried out by a process called scheduler. Schedulers are often designed so as to keep all computer resources busy (as in load balancing), allow multiple users to share system resources effectively, or to achieve a target quality-of-service. Scheduling is fundamental to computation itself, and an intrinsic part of the execution model of a computer system; the concept of scheduling makes it possible to have computer multitasking with a single central processing unit (CPU). Goals A scheduler may aim at one or more goals, for example: * maximizing '' throughput'' (the total amount of work completed per time unit); * minimizing ''wait time'' (time from work becoming ready until the first point it begins execution); * minimizing '' latenc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Round-robin Scheduling
Round-robin (RR) is one of the algorithms employed by process and network schedulers in computing. Guowang Miao, Jens Zander, Ki Won Sung, and Ben Slimane, Fundamentals of Mobile Data Networks, Cambridge University Press, , 2016. As the term is generally used, time slices (also known as time quanta) are assigned to each process in equal portions and in circular order, handling all processes without priority (also known as cyclic executive). Round-robin scheduling is simple, easy to implement, and starvation-free. Round-robin scheduling can be applied to other scheduling problems, such as data packet scheduling in computer networks. It is an operating system concept. The name of the algorithm comes from the round-robin principle known from other fields, where each person takes an equal share of something in turn. Process scheduling To schedule processes fairly, a round-robin scheduler generally employs time-sharing, giving each job a time slot or ''quantum'' (its allowan ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Proportional-fair Rule
In operations research and social choice, the proportional-fair (PF) rule is a rule saying that, among all possible alternatives, one should pick an alternative that cannot be improved, where "improvement" is measured by the sum of relative improvements possible for each individual agent. It aims to provide a compromise between the utilitarian rule - which emphasizes overall system efficiency, and the egalitarian rule - which emphasizes individual fairness. The rule was first presented in the context of rate control in communication networks. However, it is a general social choice rule and can also be used, for example, in resource allocation. Definition Let X be a set of possible `states of the world' or `alternatives'. Society wishes to choose a single state from X. For example, in a single-winner election, X may represent the set of candidates; in a resource allocation setting, X may represent all possible allocations of the resource. Let I be a finite set, representing a c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
