Cell throughputcapacity and fairness by taking the scheduling into account. The problem of allocating resources to multiple users on the downlink of a long term evolution lte cellular communication system is discussed. Dci format 60b is a more compact dci format used for scheduling grants for devices operating in ce mode b. Challenges, improvement, and analysis mohamad omar kayali, zeinab shmeiss, haidar safa, and wassim elhajj. Downlink scheduling and rate capping for lteadvanced carrier. Performance evaluation of ofdma in frequency selective. Ofdma which enables channel dependent frequency selective scheduling, and that it allows for multiuser mu scheduling wherein multiple users can be assigned the same timefrequency resource. One constraint in lte downlink scheduling is that all sbs belonging to a single user can be assigned to only one modulation and coding scheme mcs in each transmission time interval tti or scheduling period 4, page 326. Lte frequency selective scheduling performance and improvements assessed by measurements abstract. Lte downlink physical layer channels long term evolution. Each lte subchannel corresponds to 12 successive and equallyspaced subcarriers with subcarrier spacing of 15 khz i. Frequency selective scheduling provides benefits to both fdd and tdd lte networks.
Apr 07, 2014 lte schedulers a definitive approach 1. In all cases, user mobility is shown to decrease the performance of fss due to the cqi reporting delay. A method for downlink frequency selective scheduling in lte mac based on channel quality feedback is disclosed. The long term evolution provides a high data rate and can operate in different. The physical uplink control channel format 1 is a transmission channel used to carry information regarding scheduling requests in which the ue requests resources to transmit ulsch. For frequency selective scheduling to be applicable, the cqi must be reported for all of the carriers resource blocks. It involves frequency division multiplexing fdm and multi. Downlink packet scheduling in lte cellular network. The long term evolution provides a high data rate and can operate in different bandwidths ranging from 1. Elrabaie 2, mohammed abdelnaby 3 department of electronics and electrical communications, faculty of electronic engineering, menoufia university, menouf. Scheduling algorithm for highmobility user in lte downlink. Frequency network lte systems and for normal cyclic prefix cp. User classification and scheduling in lte downlink systems. Abstract scheduler is the backbone of intelligence in a lte network.
Channel aware scheduling algorithms for 3gpp lte downlink. In ul, the ue has no dedicated resources to transmit directly when new data arrived in the buffer from higher layer. It is also used to send acknowledgement responses and retransmission requests ack and nack. The different physical layer channels on downlink are as below, physical downlink. The downlink transmission utilizes orthogonal frequency division multiple access ofdma as the physical layer technique which enables high data rate transmission in frequency selective fading scenarios. 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. Feb 02, 2012 a method for downlink frequency selective scheduling in lte mac based on channel quality feedback is disclosed. In lte, orthogonal frequency division multiple access ofdma in the. Which resource blocks and how many the user gets at a given point in time depend on advanced scheduling mechanisms in the frequency and time dimensions. Jul 25, 2016 round robin scheduling algorithm duration.
Qoedriven lte downlink scheduling for multimedia services ali alfayly abstract the significant growth in multimedia services and traffic e. Dl fss feature is implemented on multan city serving sites 10 enodebs. Scheduling ues within frequency selective environment without much argument scheduling of lte a required more than what is obtainable in lte scheduling, thus, in multiuser network deployment lte a lte there is need for determining. In this article, the aim is to evaluate the gain achieved from frequency selective scheduling fss in lte networks by means of statistical models and simulations. Scheduling algorithms implementation for lte downlink s. Downlink packet scheduling in lte cellular networks. Scheduling policies in time and frequency domains for lte. Liveaction network performance software 69,472 views. In an lte cell, a base station or enodebenb allocates radio resources to a number of user equipments ues, i. A generalized packet scheduler in lte downlink network is shown in fig. Existing methods for resource allocation have no means for efficient utilization of the resources and allocation of the available downlink bandwidth to the ue with low computation overhead.
Lte random or initial accessrach procedure duration. Full text of enhanced pf scheduling algorithm for lte. Numerical results show that the system performance improves with increasing correlation among ofdma subcarriers. An optimal maximum throughput multiuser scheduler is proposed and its performance is evaluated. Carrier frequency synchronization in the downlink of 3gpp lte. Resource scheduling algorithms in long term evolution lte. The scheduling strategy is based on a certain metric.
Indicator computed from its downlink instantaneous channel condition to the serving en cqi, a quantized and scaled measure of sinr. Fdd has the advantage of having more instantaneous cqi feedback from the subscriber, so it is more advantageous in the case of severe multipath or high user mobility. It adopts a scalable radio resource bandwidth of 1. Tutorial, survey and evaluation framework 1241 enb mme sgw mme sgw enb enb s1 s 1 s1 s 1 x2 x2 x2 eutran fig. Lte frequency selective scheduling performance and improvements assessed by measurements. Smart scheduler features and benefits lte radio technology is highly nsn. On the performance of lte downlink scheduling algorithms. The scheduling mechanisms in lte are similar to those used in hspa, and enable optimal performance for different services in different radio environments. Study of downlink scheduling algorithms in lte networks s. Scheduling algorithms implementation for lte downlink.
Frequency selective scheduling illustration for two users in downlink lte. Downlink scheduling and rate capping for lteadvanced. This paper proposes the design of a scheduling framework for the downlink of the long term evolution lte system with the objective of meeting the quality of service qos requirements as defined by the qos architecture of the 3g partnership project 3gpp specifications. Frequency selective scheduling to minimize fading impact lets nsn. The use of orthogonal frequency division multiple access ofdma in long term evolution lte and lte advanced systems facilitates the potential for. The analysis reveals that ftgs provides a good tradeoff between cell capacity and fairness in different scenarios, both. The lte network adopts orthogonal frequency division multiple access ofdma for downlink transmissions. Computer science department huawei technologies ucla, ca 90095 shanghai, china abstractwith the power consumption issue of mobile handset taken into account, singlecarrier fdma scfdma has been. Long term evolution lte is a 4g wireless broadband technology developed by the third generation partnership project 3gpp, an industry trade group. To overcome the effect of multi path fading problem available in umts, lte uses orthogonal frequency division multiplexing ofdm for the downlink that is, from the base station to the terminal to transmit the data over many narrow band careers of 180 khz each instead of spreading one signal over the complete 5mhz career bandwidth ie. Study of downlink scheduling algorithms in lte networks.
Lte is the evolution for existing 3g mobile networks which offers higher capacity, efficient utilization of radio resources, lower latency. Performance evaluation of ofdma in frequency selective fading channel in 3gpp lte downlink interface air. Future generation cellular networks are expected to provide ubiquitous broadband access to a continuously growing number of mobile users. Camarda abstract future generation cellular networks are expected to provide ubiquitous broadband access to a contin. Scheduling based on metrics which depends only on own sinr and distance specific models for the common basic scheduling algorithms, round robin, proportional fair and maxsinr. Long term evolution lte carrier aggregation ca was introduced by the release10 3gpp specifications. A variety of scheduling strategies is available in lte. Introduction the long term evolution lte of the umts 3gppts 36. Downlink scheduling for multiclass traffic in lte springerlink. Instead of exploiting the frequency diversity of the. A generalized packet scheduling model in lte downlink in lte, p acket scheduling is performed in enodeb. Proportional fair frequencydomain packet scheduling for 3gpp lte uplink sukbok lee. Downlink scheduling in 3gpp long term evolution lte assignment. Basics of scheduling in lte all about wired and wireless.
Ioannis pefkianakis adam meyerson shugong xu songwu lu. Voip, video streaming and video gaming in current and emerging mobile networks including the latest 4g long term evolution lte networks and the rising user expectation for high quality of experience. However, one of the drawbacks of ofdma is its vulnerability to carrier frequency. Abuali et al uplink scheduling in lte and lte advanced. Downlink scheduling in 3gpp long term evolution lte. Nakkeeran department of electronics engineering, school of engineering and technology, pondicherry university, puducherry605014, india email. We define the computational architecture and describe the exact computations that need to be done at each time. The comparison of data rates between 3g and 4g technologies is discussed below.
Smart downlink scheduling for multimedia streaming over. As a core functionality of lte downlink radio resource management, packet scheduling algorithms plays a vital role. Elrabaie 2, mohammed abdelnaby 3 department of electronics and electrical communications, faculty of electronic engineering, menoufia university. Future generation cellular networks are expected to deliver an omnipresent broadband access network for an endlessly increasing number of subscribers. The benefits of lte ca are increased terminal peak data. International journal of inventive engineering and sciences ijies issn. In the frequency domain, the total available system bandwidth is divided into subchannels. A timefrequency radio resource spanning over one subchannel of 12. A scheduler is a key element in the base station bs and it assigns. Ofdma as the physical layer technique which enables high data rate transmission in frequency selective fading scenarios.
Long term evolution lte 1 has been standardized as the successor of the universal mobile telecommunication system umts. Downlink frequency selective scheduling based on channel. Some studies on lterelated scheduling have been reported in 6, 7 and the references therein. Their modification enabled pf to support scheduling in frequency domain. In this paper the potential of downlink frequency selective scheduling fss is addressed based on measurements in an experimental 3gpp long term evolution lte system setup. Downlink packet scheduling in lte cellular network projects. Ca allows aggregation of up to 5 cells for a terminal. On the analysis of packet scheduling in downlink 3gpp lte system. Schematic presentation of frequency selective environment with links indicating different carrier. User classification and scheduling in lte downlink systems with heterogeneous user mobilities abstract. Litjens2 1 university of twente, enschede, the netherlands 2 tno ict, delft, the netherlands abstract.
The physical layer channels are widely divided into data, control and random access channels. The challenge of scheduling user transmissions on the downlink of a long term evolution lte cellular communication system is addressed. On the analysis of packet scheduling in downlink 3gpp lte. On the analysis of packet scheduling in downlink 3gpp lte system oana iosif, ion banica. In particular, a novel optimalmultiuser scheduler is proposed. An evaluation of lte frequency selective scheduling. Instead of exploiting the frequency diversity of the channel, frequencyselective scheduling leverages the channels time and frequency selectivity to allocate valuable radio resources in an optimal manner. The ue with the best channel conditions gets the highest priority. Similar to downlink scheduling assignments, the resource assignment included in dci formats 60a and 60b is split into two parts. Long term evolution lte 1 has been standardized as the. Thus, we developed a frequency diversity fairness scheduling algorithm to balance fairness of.
Frequency selective scheduling nfss and the scheduling. Downlink resource scheduling in an lte system intechopen. An evaluation of lte frequency selective scheduling frank rayal. Lte physical layer has different channels defined on both uplink and downlink, each with a predefined purpose. The lte access network can host only two kinds of node. Scheduling decisions can be made each tti time transmission interval that in lte is equal to 1 ms.
Lte frequency selective scheduling performance and. May 29, 20 lte physical layer has different channels defined on both uplink and downlink, each with a predefined purpose. In order to evaluate performance of scheduling algorithms, we simulate the lte environment under several scenarios with different parameters including antenna configuration, antenna type, network topology, mobility, carrier frequency, channel model and the number of ues. The pgw interconnects lte network with the rest of the world, providing connectivity among ues and external packet data networks. Having evaluated various scheduling policies with a simpler although complete design, future work includes the implementation of other interesting features offered by lte specifications, for example, asynchronous and adaptive harq for downlink, power shaping, and frequency selective scheduling. Challenges, improvement, and analysis mohamad omar kayali, zeinab shmeiss, haidar safa, and wassim elhajj department of computer science american university of beirut beirut, lebanon email. Scheduling is the process through which enb decides which ues should be given resources to send or receive data.
In lte systems with heterogeneous user mobilities, lowmobility users favor frequency selective scheduling while highmobility users benefit from frequency diversity scheduling. Downlink packet scheduling in lte cellular network projects phdprojects. Though ofdma technology mitigates interference of users in same cell, it increases interference of cell edge user as base stations use same frequency. This applies in the nonmultipleinputmultipleoutput mimo configuration. To conclude, frequency selective scheduling provides a great potential in lte, but is constrained to a number of limiting factors mentioned in this article. On the frequencyselective scheduling gain in sdmaofdma.
However, we observe that the fd version of ftgs can dramatically reduce the inter scheduling time and the service time of highlayer packets in case of frequency selective channels, thus alleviating the aforementioned problem. System model the lte system is based on a flat architecture, known as. We present a design of a complete and practical scheduler for the 3gpp long term evolution lte downlink by integrating recent results on resource allocation, fast computational algorithms, and scheduling. These physical channels are fed using the transportation channels of higher layers. Guest post by faris alfarhan channel dependent scheduling is commonly used in cellular systems. An ofdma system takes advantage of both frequency diversity fd gain and frequencyselective scheduling fss gain. The ofdma and scfdma shared channel transmissions incorporated in lte offer great flexibility for integrating adaptive scheduling. Master of science computer science, december 20, 67 pp. Tshiteya dikamba,downlink scheduling in 3gpp long term evolution lte, delft university of technology, march 2011. Frequency diversity scheduling allocates whole system bandwidth to a user in order to conquer deep fading of the subband when user with highmobility. Research program nprp grant from the qatar national. The downlink physical resource of the lte is represented as a timefrequency resource grid consisting of multiple resource blocks rb.
Estimation of the capacity usage for gbr sources in lte. Scheduling principle,frequency and time domain in lte. However, the first commercial deployments focus on the aggregation of two cells in the downlink. It is found that only a limited amount of feedback information is needed to. Analysis of practical frequency selective scheduling algorithms in. Oct 04, 2017 downlink packet scheduling in lte cellular network projects phdprojects. Multiuser scheduling on the downlink of an lte cellular system. Further evolution of lte scheduling 3gpp is working with enhanced. On the other hand, if a cqi value is used to represent each sb.
The resources are mainly shared in an equal manner. Smart downlink scheduling for multimedia streaming over lte networks with hard handoff article pdf available in ieee transactions on circuits and systems for video technology 2511. Scheduler types in lte scheduling quality strategies throughput a variety of scheduling strategies is available in lte. Long term evolution lte is a cellular technology developed. Lte performance evaluation based on two scheduling. Enhanced pf scheduling algorithm for lte downlink system mohamad i. Long term evolution lte offers revolutionary performance when compared to its predecessors, gsmedge and umt. Lte nodes, and to manage handover among lte and other 3gpp technologies. We also survey representative schemes in the literature that have addressed the scheduling problem, and offer an evaluation methodology to be used as a basis for comparison between scheduling proposals in the literature.
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