Sampling frequency needed for maximum 20mhz lte bandwidth fft size 2048 subcarrier spacing 15khz 30. Downlink resource allocation relies on the channel quality index cqi reported by the user. An evaluation of lte frequency selective scheduling. An evaluation of lte frequency selective scheduling frank rayal. Long term evolution is standardized by the 3rd generation partnership project to provide a high data rate up to 100 mbps and 50 mbps for downlink and uplink transmission respectively and can operate in. The benefits of lte ca are increased terminal peak data. The incorporated scheduling mechanisms can significantly contribute to this goal. Putting it other way, sr is an uplink physical layer message from ue to network, saying i have some data to send to you. In persistent scheduling mode, ue can send the data to. It is found that only a limited amount of feedback information is needed to. Guest post by faris alfarhan channel dependent scheduling is commonly used in cellular systems. Study of downlink scheduling algorithms in lte networks. Low complexity estimation of frequency selective channels.
Lte uses the scfdma radio access technology for its uplink transmission. Release 8 scfdma only allowed carriers along contiguous block of spectrum but lteadvanced in release 10 allows frequencyselective scheduling in uplink. This is no coincidence, and has been arranged for multirat interworking. In this paper, the physical layer phy of lte transceiver is analyzed in downlink and uplink transmissions. Create an uplink ltem transmission consisting of the physical uplink shared channel pusch and associated demodulation reference signals dmrs including repetitions and frequency hopping. Long term evolution lte is a cellular technology developed to support data tra c at potentially high rates. Tshiteya dikamba,downlink scheduling in 3gpp long term evolution.
With tdd the uplink and downlink operate in same frequency band whereas with tdd the uplink and downlink operate in different frequency bands. In persistent scheduling mode, ue can send the data to network anytime since network is sending ul grant all the time. With new multimedia services, mobile data volume has increased 10. Clustered scfdma was chosen in preference to pure ofdm to avoid a significant increase in papr. This scheme is similar to scfdma but has the advantage that it allows non contiguous clustered groups of subcarriers to be allocated for transmission by a single ue, thus enabling uplink frequency. Used to sound uplink channel to support frequency selective scheduling. Scheduling policies in time and frequency domains for lte. Frequency diversity scheduling allocates whole system bandwidth to a user in order to conquer deep fading of the subband when user with highmobility. Cylic shifts and subcarrier offsets and used to define transmission combs for ues or in other words.
Lteadvanced introduces clustered scfdma in the uplink, allowing frequencyselective. Analysis and simulation of lte downlink and uplink transceiver. Oct 19, 2016 lte advanced uplink scheduling network simulator ns3 projects phdprojects. Lte advanced introduces clustered scfdma in the uplink, allowing frequency selective scheduling of component carriers for better link performance. Jul 04, 2014 5 figure below is the lte uplink allocation structure from a time and frequency perspective. A method for downlink frequency selective scheduling in lte mac based on channel quality feedback is disclosed. Access sdma which can be used in the downlink direction.
The pre4g 3gpp long term evolution lte technology is often branded 4g lte, but the first lte release does not fully comply with the imtadvanced requirements. Lte frequency selective scheduling performance and improvements assessed by measurements. Litjens2 1 university of twente, enschede, the netherlands 2 tno ict, delft, the netherlands abstract. Downlink scheduling and resource allocation for 5g mimo. 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. Frequency selective scheduling provides benefits to both fdd and tdd lte networks. Novel scheduling algorithm for 3gpp downlink lte cellular. Long term evolution lte, lte uplink scheduling technique, coexistence, wifi, 5ghz unlicensed frequency band. 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. The downlink physical resource of the lte is represented as a timefrequency resource grid consisting of multiple resource blocks rb. He has served for various ieee conferences as a technical program committee member.
The main objective of the thesis work is to design a parallel processing algorithm for lte uplink in a multi processor system and evaluate the performance of this algorithm with respect to throughput, efficiency as. Putting it other way, sr is an uplink physical layer. As a result, resources assigned to the same user must be contiguous in the frequency domain. Downlink scheduling and rate capping for lteadvanced. In ul, the ue has no dedicated resources to transmit directly when new data arrived in the buffer from higher layer.
In particular, a novel optimalmultiuser scheduler is proposed. Resource allocation in lte is made complex, especially when. We accurately model the lte mac layer, and selectively abstract the phy layer. Pratschner et al complexity estimation of frequency selective channels for the ltea uplink 675 fig. This scheme is similar to scfdma but has the advantage that it allows non contiguous clustered groups of subcarriers to be allocated for transmission by a single ue, thus enabling uplink frequency selective scheduling and better link performance. Frequencydomain packet scheduling for low papr in 3gpp. 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. Getting started with open broadcaster software obs duration. Master of science computer science, december 20, 67 pp.
However, the proper scheme for an uplink is the singlecarrier frequency domain multiple access due to the peaktoaveragepowerratio papr constraint. Wireless software and hardware platforms for flexible and unified radio and network control sven zehl. Ofdma in the downlink and scfdma in the uplink, lte possesses a robust and. Lte advanced uplink scheduling network simulator ns3 projects phdprojects. Lte has a theoretical net bit rate capacity of up to 100 mbits in the downlink and 50 mbits in the uplink if a 20 mhz channel is used and more if multipleinput multipleoutput mimo, i.
Existing methods for resource allocation have no means for efficient utilization of the. Downlink packet scheduling in lte cellular networks. For the uplink, frequency hopping, if configured, always takes place between only two narrowbands. Lte advanced uplink scheduling network simulator ns3. These methods do not ensure that the ues that possess channel quality feedbacks are allocated. In lte, orthogonal frequency division multiple access ofdma in the downlink and single. Used to sound uplink channel to support frequency selective scheduling srs parameters are ue specific and configured semistatically 1 symbol in subframe used for srs periodicity. Existing methods for resource allocation have no means for efficient. Ca allows aggregation of up to 5 cells for a terminal. Long term evolution is standardized by the 3rd generation partnership project to provide a high data rate up to 100 mbps and 50 mbps for downlink and uplink transmission respectively and can operate in different bandwidths ranging from 1. Numerical results show that the system performance improves with increasing correlation among ofdma subcarriers. The introduction of clustered scfdma in the uplink allows frequency selective scheduling within a component carrier for better link performance, and the pucch and pusch can be scheduled together. Long term evolution lte carrier aggregation ca was introduced by the release10 3gpp specifications.
Furthermore lte operates both frequency division duplexing fdd and time division duplexing tdd and can be deployed in different bandwidths. Feb 02, 2012 a method for downlink frequency selective scheduling in lte mac based on channel quality feedback is disclosed. Multiuser scheduling on the downlink of an lte cellular system. Us20120026986a1 downlink frequency selective scheduling. Abstractlte long term evolution is a next generation standard by 3rd generation partnership project 3gppp consortium. Downlink frequency selective scheduling based on channel. Sr scheduling request sr is a special physical layer message for ue to ask network to send ul grant dci format 0 so that ue can transmit pusch.
Also similar to the downlink, in case of ce mode a, frequency hopping can be dynamically disabled by means of a frequencyhopping flag in the scheduling grant. The interlayer interference on the unit circle is cancelled when summed over all points. In this section the concept of ofdma and dftofdm as used in the uplink and downlink are presented. Downlink scheduling in 3gpp long term evolution lte. Srs are employed for channel sounding to enable frequency selective scheduling. Scfdma is implemented in lte uplink eeweb community. Scheduling is the process through which enb decides which ues should be given resources to send or receive data. Simulations of the physical layer of lte transceiver are obtained with the use of lte system toolbox by mathworks. Single carrier frequency division multiple access scfdma is a promising technique for high data rate uplink communication and has been adopted by 3gpp for it next generation cellular system, called long term evolution lte. Exploring the physical layer frontiers of cellular uplink europe pmc.
Srs is uplink counterpart of cqi report for downlink scheduling. However, the first commercial deployments focus on the aggregation of two cells in the downlink. The interlayer interference on the unit circle is cancelled when summed over all. Mobile data traffic trends and estimates have shown that demand for mobile data will grow enormously in near future. However, scfdma allocates carriers across a contiguous block of spectrum, which limits scheduling flexibility. The key features of the 3gpp lte uplink ul are that it is based on a modi. 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.
Camarda abstract future generation cellular networks are expected to provide ubiquitous broadband access to a contin. Cylic shifts and subcarrier offsets and used to define transmission combs for ues or in other words schedule reference signals of ue, cell edge user cannot use. Also, the pucch and pusch can be scheduled together to reduce latency. In this paper, the physical layer phy of lte transceiver is analyzed in downlink. On the performance of lte downlink scheduling algorithms. Pdf on the frequencyselective scheduling gain in sdma. I want to use scenario c2 in winner ii channel models. Uplink scheduling for lte video surveillance systems. Lte provides an uplink speed of up to 50 megabits per second mbps and a. The challenge of scheduling user transmissions on the downlink of a long term evolution lte cellular communication system is addressed. How to calculate central frequency in lte uplink frequency. 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.
The vienna ltea uplink simulator is a 3gpp ltea standard compliant matlabbased. Downlink scheduling for multiclass traffic in lte springerlink. Uplink data transmission scheduling non persistent scheduling. 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. Table i phaseshift forpossiblenumbers oflayers l we have to sum, or average, over. Research program nprp grant from the qatar national. Create an uplink lte m transmission consisting of the physical uplink shared channel pusch and associated demodulation reference signals dmrs including repetitions and frequency hopping. Oct 09, 20 guest post by faris alfarhan channel dependent scheduling is commonly used in cellular systems.
There is provided mechanisms for frequency selective scheduling of wireless devices in a communication network. Lte frequency selective scheduling performance and. Frequency selective scheduling 87% faster networkwide tokyo photo kpi analysis. Basics of scheduling in lte all about wired and wireless.
When compared to prerelease devices, catm devices offer lower cost and complexity, enhanced coverage by the introduction of repetitions and an. Tshiteya dikamba,downlink scheduling in 3gpp long term evolution lte, delft university of technology, march 2011. However, clustered scfdma increases peak to average power ratio par by several db, adding to transmitter linearity issues. Nakkeeran department of electronics engineering, school of engineering and technology, pondicherry university, puducherry605014, india email. Uplink signal optimization lte optimization engineering. The main objective of the thesis work is to design a parallel processing. Resource scheduling algorithms in long term evolution lte. Study of downlink scheduling algorithms in lte networks s. Mtc, which will substantially impact the uplink scheduling operation. Single carrier frequency division multiple access scfdma is a promising technique for high data rate uplink communication and has been adopted by 3gpp for it next generation cellular system, called long term evolution. Though ofdma technology mitigates interference of users in same cell, it increases interference of cell edge user as base stations use same frequency. Most of the existing works for lte uplink scheduling have tried to maximize the total throughput.
Srs parameters are ue specific and configured semistatically. Instead of exploiting the frequency diversity of the. 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. Thus, we developed a frequency diversity fairness scheduling algorithm to balance fairness of. The introduction of clustered scfdma in the uplink allows frequency selective scheduling within a component carrier for better link performance, and the pucch and pusch can be scheduled together to reduce latency. Channel dependent scheduling is commonly used in cellular systems. Scfdma is a modified form of ofdm with similar throughput performance and complexity. It is also used to send acknowledgement responses and retransmission requests ack and nack.
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