Slide title In CAPITALS 50 pt Slide subtitle 32 pt Dynamic and Persistent Scheduling for Voice over IP Traffic in the Long-Term Evolution Uplink Master’s Thesis Presentation Author: Mira Heiskari Supervisor: Professor Riku Jäntti Instructor: M.Sc. (Tech.) Anna Larmo Oy L M Ericsson Ab, Jorvas, Finland

Top right corner for field-mark, customer or partner logotypes. See Best practice for example. Slide title 40 pt Slide subtitle 24 pt Text 24 pt Bullets level pt © Ericsson AB Agenda  Long-Term Evolution  Voice over IP  Uplink Scheduling  Background and Goals  Simulation Setup  Simulation Results  Conclusions  Future Work

Top right corner for field-mark, customer or partner logotypes. See Best practice for example. Slide title 40 pt Slide subtitle 24 pt Text 24 pt Bullets level pt © Ericsson AB Long-Term Evolution (LTE)  An evolution of the 3G WCDMA technology, currently under specification process in the 3GPP  The recommendations are estimated to be ready by September 2007  First live networks are expected to come to markets in  Target data rates for LTE: around 100 Mbps in the downlink and 50 Mbps in the uplink  Main changes compared to today networks: –Simplified network architecture  less interfaces –Support for packet-switched domain only –Reduced control and user plane latencies –Multi-antenna solutions

Top right corner for field-mark, customer or partner logotypes. See Best practice for example. Slide title 40 pt Slide subtitle 24 pt Text 24 pt Bullets level pt © Ericsson AB Voice over IP (VoIP)  VoIP is a general term for delivering speech traffic using the Internet Protocol (IP) on the network layer  Speech frames are packed to IP packets, and then sent over the packet-switched network to the receiver  LTE has only packet-switched domain  VoIP is a suitable technology for transferring speech in LTE networks  In VoIP traffic, the speech packet that needs to be scheduled and transmitted comes every 20 ms

Top right corner for field-mark, customer or partner logotypes. See Best practice for example. Slide title 40 pt Slide subtitle 24 pt Text 24 pt Bullets level pt © Ericsson AB Uplink (UL) Scheduling  The UL scheduler monitors the users’ requests and distributes the available resources among various users  The scheduler has only limited information about the UE’s demands Example of dynamic scheduling Example of persistent scheduling

Top right corner for field-mark, customer or partner logotypes. See Best practice for example. Slide title 40 pt Slide subtitle 24 pt Text 24 pt Bullets level pt © Ericsson AB Background and Goals  3GPP standardization organization is planning to make the scheduling in LTE more effective  Based on theoretical calculations done in the thesis, signaling load could be reduced significantly with persistent scheduling –In dynamic scheduling, the resources are distributed in 1 ms intervals –In persistent scheduling, longer transmission period is allocated for user with the one grant –Persistent grant could be valid for a continuous or discontinuous time for a specified frequency domain resource –Also modulation and coding scheme would be persistent throughout the validity time of the grant (i.e., link adaptation disabled)  How the persistent scheduling will effect to the traffic performance of a user?  The practical part of the thesis was done with computer simulations

Top right corner for field-mark, customer or partner logotypes. See Best practice for example. Slide title 40 pt Slide subtitle 24 pt Text 24 pt Bullets level pt © Ericsson AB Simulation Setup  The simulations were done with a detailed LTE network simulation tool developed by Ericsson Research  The author of the thesis implemented the scheduling patterns used in the simulations for the persistently scheduled users  One user moving slowly in a single-cell network  no handovers or interference from others  The simulations investigated the effects of uplink scheduling patterns to the traffic performance in terms of: –Hybrid ARQ (HARQ) retransmissions –Delay –Number of used sub-frequency bands –Used modulations

Top right corner for field-mark, customer or partner logotypes. See Best practice for example. Slide title 40 pt Slide subtitle 24 pt Text 24 pt Bullets level pt © Ericsson AB Simulation Scenarios  There were three simulation cases: 1)Dynamic scheduling 2)Persistent scheduling with fixed Transport Block size (TbSize) 316 bits 3)Persistent scheduling with fixed TbSize 355 bits  All cases were tested with max. 2 and 5 HARQ retransmissions  In dynamic scheduling, the user got a scheduling grant with updated link adaptation (LA) parameters every 20 ms  In persistent scheduling, the LA parameters were saved when sending the first VoIP packet, and the same parameters were used throughout the whole call  The persistent scheduling pattern was granted for the whole duration of a VoIP call during the first VoIP packet  only one signaling message needed

Top right corner for field-mark, customer or partner logotypes. See Best practice for example. Slide title 40 pt Slide subtitle 24 pt Text 24 pt Bullets level pt © Ericsson AB Results The number of used HARQ retransmissions were significantly larger for the persistently scheduled users

Top right corner for field-mark, customer or partner logotypes. See Best practice for example. Slide title 40 pt Slide subtitle 24 pt Text 24 pt Bullets level pt © Ericsson AB Conclusions  The results showed quite clearly that the persistent user experienced worse results in all examined areas, even in a simple simulation scenario  All (persistently scheduled) users had a good link quality in the beginning  The lack of link adaptation for the persistently scheduled users was the main reason for lower traffic performance results  Fixed parameters used in the persistent scheduling should be selected for a poorer link quality, in order to have better traffic performance for the users, when the link quality decreases  Scheduling grant should be given for a shorter period, not for the whole duration of the call  link adaptation would exist with certain frequency

Top right corner for field-mark, customer or partner logotypes. See Best practice for example. Slide title 40 pt Slide subtitle 24 pt Text 24 pt Bullets level pt © Ericsson AB Future Work  Developments for simulations: –number of users –number of cells –varying the mobility of the users  Before planning the simulation parameters more exact, the scheduling patterns should be modified to more flexible direction, in order to get better results  Different resource allocation methods than dynamic scheduling for other traffic types (e.g., Web traffic)

Top right corner for field-mark, customer or partner logotypes. See Best practice for example. Slide title 40 pt Slide subtitle 24 pt Text 24 pt Bullets level pt © Ericsson AB