Impact of DRX on VoIP Performance and Battery Life in LTE
Independent thesis Advanced level (degree of Master (Two Years))Student thesis
Along with higher data rates and application-enriched user terminals, LTE has even higher requirements to conserve the battery power in mobile devices compared to the WCDMA terminals. In LTE, Discontinuous Reception (DRX) has been introduced as one of the key solutions to conserve battery power in mobile terminal. It is very meaningful to investigate the possible impact of DRX on power consumption and also the VoIP performance. This study evaluates several different parameter settings for DRX, and tries to find a reasonable trade-off between VoIP performance and battery life. This study report proposes DRX parameter setting to achieve maximum possible power saving with minimum VoIP degradation. Based on the assumed power saving model and simulation scenario presented in chapter 4 and chapter 5 of this report respectively, the proposed parameter settings can achieve up to ~60% of the terminal power saving. Furthermore, it is concluded that longer DRX cycles are not suitable for VoIP traffic since they introduces longer delays and degrades the VoIP performance particularly in downlink.
This study has evaluated different DRX parameter settings for VoIP traffic both in uplink and downlink and found out different gains in terms of power saving and network performance. It is shown that key parameters include On-duration Timer, Inactivity Timer and length of DRX cycle. These three parameters have major impact on both VoIP and power saving. Different combinations of these parameters show different results. DRX affects downlink and uplink in a different manner. In the downlink, a user cannot be scheduled and thus receive any DL data during the period of inactivity. Downlink assignments can only be sent when receiving UE is awake. This is one reason that length of DRX cycle and length of On-duration period is more important parameters in downlink. It is found out that increasing the length of DRX cycle, keeping relatively constant average awake time of terminal, introduces larger delays in downlink and thus degrades the performance. On the other hand, uplink is affected by DRX only when there is fragmentation. In uplink, whenever a user has available data it can a scheduling request, which is independent of DRX state and can be sent even if UE is sleeping, and thus can get UL scheduling grant. However, if the grant is fragmented, UE might not always be able to receive remaining fragments due to DRX state. That is why Inactivity Timer plays a more important role in UL. If poor radio conditions are expected, it is important to have larger Inactivity Timer period. From the power saving point of view, the length of On-duration Timer and Inactivity Timer should be chosen as smaller as possible. However, these parameters should not be reduced below a certain threshold. For example reducing On-duration Timer below 2ms shows a major degradation in VoIP performance while not showing a comparable gain in receiver power. This study has proposed a DRX parameter setting to achieve maximum power saving with minimum VoIP degradation. Based on the assumed power saving model and the simulation settings presented in chapter 4 and chapter 5 of this report respectively, the proposed DRX settings show that ~60% of total power can be saved while keeping the VoIP capacity loss <= 12%.
Place, publisher, year, edition, pages
2009. , 54 p.
Battery saving, LTE, DRX
IdentifiersURN: urn:nbn:se:bth-1135Local ID: oai:bth.se:arkivexFDF799B97B6BE90BC12575370071918BOAI: oai:DiVA.org:bth-1135DiVA: diva2:828296
Nilsson, Magnus G
This thesis is about battery saving in LTE2015-05-252009-01-072015-06-30Bibliographically approved