A prb is defined as consecutive ofdm symbols in the time domain and consecutive subcarriers in the frequency domain, as demonstrated in figure. A physical resource block prb, which has a bandwidth resolution of 180 khz, is the minimum amount of frequency resources that can be scheduled for transmission. N2 in this study a scheduling algorithm for cdma systems is presented which is a tradeoff between two extreme ways of scheduling. An evaluation of lte frequency selective scheduling. Engineering degree in software engineering from huazhong. These techniques effectively mitigate or even exploit channel fading and open additional degrees of freedom such as frequencydomain channeldependent scheduling. Scfdma also bears similarities to direct sequence cdma dscdma with fde in terms of. Information in this document is provided solely to enable system and software implementers.
Efficient evaluation of wireless realtime control networks. The mac sublayer scheduler runs the scheduling algorithms which determine what gets sent when and toby whom. The timesampled ofdm signal is converted into the frequency domain by means of a. In computing, scheduling is the method by which work is assigned to resources that complete. Unlike the downlink, where pure timedomain scheduling often can be used 15,16 15 16 and can be shown to be preferable from a theoretical point of view,14 14, uplink scheduling typically has to rely on sharing in the frequency domain in addition, as a single device may not have sufficient power for efficiently utilizing the. T1 fair channeldependent scheduling in cdma systems.
Dmrs, srs are not associated to any physical uplink channels and they support uplink channeldependent scheduling and link adaptation. A survey of scheduling and interference mitigation in lte. Frequency and time domain packet scheduling based on channel prediction with imperfect cqi in lte. Lte uplink system depends on a case by case analysis and. Therefore, the parameters csrs 14 and bsrs 0 configure a fullband srs transmission for the current carrier.
Two main paradigms exist in the literature, channel dependent and proportional fairness. This is accomplished via the ofdm in the downlink, making the system robust against multipath interference and providing high affinity to advanced techniques such as frequency domain channeldependent scheduling and mimo. Scheduling computing wikimili, the best wikipedia reader. Pdf on the feasibility of a channeldependent scheduling. Scfdma is implemented in lte uplink eeweb community. In order to support systems relying on channeldependent scheduling, this model can be complemented by the link measurement model that derives either ideal or realistic channel state information for the nodes, which typically will be used for scheduling users andor transmission resources. Frequency domain filters are used for smoothing and sharpening of image by removal of high or low frequency components. A frequency domain channel predictor based on kalman filter is first developed to. The ue uses pucch format 2 control information to relay an estimate of the channel properties to the base station in order to aid channel dependent scheduling. Reuse existing lte base stations with software update. Us7778151b2 efficient scheduling request channel for. Channeldependent scheduling of transmission of data packets in a wireless system is.
There are many wellknown packet scheduling algorithms designed in time domain, such as pf. It is heralded as an essential step to a brave new world of technology, but in the here and now, superfast 5g networking is already pitting china against the west. In a method for transmitting a contention free scheduling request in a cellular network, a set of n frequency opportunities is defined within a scheduling request slot. When pucch or pusch is not scheduled, sounding reference signals srs are used to test the reception quality for uplink channeldependent scheduling and are transmitted in the last symbol of the subframe.
Pdf frequency and time domain packet scheduling based on. This scheduling strategy is an example of channeldependent scheduling known. In even more advanced systems such as lte, the scheduling is combined by channeldependent packetbypacket dynamic channel allocation, or by assigning ofdma multicarriers or other frequencydomain equalization components to the users that best can utilize them. Similarly, channeldependent scheduling in the frequency domain implies that, based on knowledge about the instantaneous channel conditions also in the frequency domain, different carriers are used for transmission to or from different ues.
The allocation to subcarriers is determined by the srs bandwidth configuration. The evolution of gtechnologies the technology behind the cell phone goes back to the days of the twoway radios, or radiophones. Here is useful introduction to practitioners involved in designing lte basednetworks and systems. The scheduling gains from exploiting variations in the frequency domain are similar to those obtained.
Channeldependent scheduling of transmission of data packets in a wireless system is based on measurement and feedback of the channel quality. Pdf channeldependent scheduling of transmission of data packets in a. The itus decision regarding imtadvanced allows organizations like the 3rd generation partnership project 3gpp to finalize specifications for migration from 3g to 4g. There are three different channel types defined in ltelogical channels, transport channels, and physical channels, each associated with a service access point sap between different layers. Overview of the 3gpp long term evolution physical layer nxp. This feature encourages the use of both time and frequency domain packet scheduling algorithms.
Efficient scheduling request channel for wireless networks. An advantage of scfdma over dscdmafde is the ability to utilize channel dependent resource scheduling to exploit frequency selectivity of the. These techniques effectively mitigate or even exploit channel fading and open additional degrees of freedom such as frequency domain channeldependent scheduling. They also make it possible to control the bandwidth and form the spectrum in a flexible way. Multiuser scheduling on the downlink of an lte cellular system. These are based on efficient fft algorithms and frequency domain equalization, resulting in a lower number of multiplications per second. Channel status reports include channel quality indication cqi, rank indication ri, and precoder matrix indication pmi. In even more advanced systems such as lte, the scheduling is combined by channeldependent packetbypacket dynamic channel allocation, or by assigning ofdma multicarriers or other frequency domain equalization components to the users that best can utilize them.
Imtadvanced defines true fourth generation 4g mobile technology, succeeding the imt2000 standard for 3g mobile technology. Guest post by faris alfarhan channel dependent scheduling is commonly used in cellular systems. Depending on the selected cqi reporting scheme, the accuracy and. To efficiently support various qos classes of services, lte adopts a hierarchical channel structure. Single carrier frequency division multiple access scfdma is a novel method of radio transmission under consideration for deployment in future cellular systems. You can use time domain, frequency domain, and sequence domain parameters to create sets of orthogonal interferencefree srs transmissions. Orthogonal frequency division multiplexing ofdm is a common. Frequency and time domain packet scheduling based on channel. The challenge of scheduling user transmissions on the downlink of a longterm. Frequency domain filters are different from spatial domain filters as it basically focuses on the frequency of the images.
Frequency domain scheduling for ofdma with limited and noisy. Downlink 2 ch mimo peak rate of 100 mbps in 20 mhz channel b. The nomenclature of the generations generally refers to a change in the fundamental nature of the service, nonbackwards compatible transmission technology, and new frequency bands. The downlink scheduling is performed at the enodeb based on the channel quality information fed back from ues, and then the downlink resource assignment information is sent to ues on the pdcch channel. In this phase, procedural software code is used to specify the internal. Frequency domain filters and its types geeksforgeeks. Lte course orthogonal frequency division multiplexing. This article provides an overview of the lte radio interface, together with a more indepth description of its features such as spectrum flexibility, multiantenna transmission, and intercell interference control. However, they require advanced dynamic channel allocation and adaptive traffic scheduling. Frequency division duplex fdd and unpaired time division. Myung currently works as a senior engineer at qualcommflarion technologies, bedminster, new jersey. Pdf in this paper, we investigate the frequencydomain packet scheduling fdps problem for 3gpp.
Signal generation using phaseshift based precoding lg. Uplink phy layer of lte uplink transmission scheme lte uplink transmission is based on socalled dfts ofdm transmission which is a singlecarrier transmission scheme that allows for flexible bandwidth assignment orthogonal multiple access not only in the time domain but also in the frequency domain. The solution to 4 depends on the channel state dependent. A phaseshift based precoding scheme used in a transmitting side and a receiving side that has less complexity than those of a spacetime coding. Unlike the downlink, where pure time domain scheduling often can be used 15,16 15 16 and can be shown to be preferable from a theoretical point of view,14 14, uplink scheduling typically has to rely on sharing in the frequency domain in addition, as a single device may not have sufficient power for efficiently utilizing the. Channelaware scheduling and resource allocation is essen. Design of a computationally efficient dynamic systemlevel. Program committee cochair of the international conference on game.
The number of resource blocks for the different lte bandwidths is listed in table 1. Pdf frequencydomain packet scheduling for 3gpp lte uplink. Frequency domain scheduling for ofdma with limited and noisy channel feedback. An overview of the lte physical layerpart ii ee times. Ran, baseband processing is performed by software running in cloudcomputing platforms. Link adaptation and channeldependent scheduling in the frequency domain. Such radios were used extensively from world war ii through about 1973. The time sampled ofdm signal is converted into the frequency domain by means of a. However, efficient exploitation and realistic evaluation of such schemes call for more complex channel and link performance models, which conventional packetlevel network.
Jindal, distortionrate analysis for distributed estimation with wireless sensor networks, eurasip journal on advances in signal processing, special issue on distributed signal processing techniques for wireless sensor networks, may 2008. Sometimes it is possible of removal of very high and very low frequency. In addition to channel dependent time domain scheduling, channel dependent frequency domain scheduling has been shown to provide substantial gains over purely distributed or randomly localized frequency hopped scheduling in ofdmabased systems. In this paper, we investigate the frequencydomain packet scheduling fdps problem for 3gpp lte uplink ul. The resource block size is the same for all bandwidths. Lte performs channeldependent scheduling in both time and frequency, with a resolution of. Frequency domain channel dependent scheduling means that different sub carriers or more correct scheduling blocks, are used for different terminals. Myung served in the republic of korea air force between 1996 and 1999 and then worked as a software engineer for arraycomm, california between 2001 and 2002.
His research interests include 3gpp long term evolution and single carrier fdma. Sawahashi, optimum resource block bandwidth for frequency domain channeldependent scheduling in evolved utra downlink ofdm radio access, in proceedings of the ieee vehicular technology conference vtc 06, vol. Detailed presentation that covers the following topics. This article presents an overview of the lte physical layer with a focus on essential aspects of the physical layer for fdd mode, which is the dominant mode of operation.
Fundamental constraints from the shannon limit multipath radio propagation time varying multipath channel cellular systems and frequency reuse 4g enabling technologies ofdmofdma scfdma mimo fast channeldependent scheduling fractional frequency reuse ofdm orthogonal subcarriers ofdm implementation using. In lte, orthogonal frequency division multiple access ofdma in the downlink and single carrier frequency division multiple access scfdma in the uplink allow scheduling to be performed orthogonally in both the frequency and time domains. The blocks can be assigned consecutively, randomly or based on measurements. Scheduling strategy an overview sciencedirect topics.
Suyash tripathi, vinay kulkarni, and alok kumar introduction the journey which initially started with umts 99 aiming for high peak packet data rates of 2mbps with support for both voice and data services is approaching a new destination known as long term evolution. Us20080080472a1 efficient scheduling request channel for. Part ii spans reference signals to synchronization sequences. In frequency domain, one resource block is a formation of 12 subcarriers length. Instead of studying a specific scheduling policy, we provide a unified approach to. In the evolved utra umts terrestrial radio access downlink, orthogonal frequency division multiplexing ofdm based radio access was adopted because of its inherent immunity to. On the feasibility of a channeldependent scheduling for the scfdma in 3gpplte mobile environment based on a prioritizedbifacet hungarian method. We investigate channeldependent scheduling schemes to achieve. Engineering degree in software engineering from huazhong university of.
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