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%. / This thesis is about battery saving in LTE

Det är intressant att veta varför användare tvångsavslutar mobila appar regelbundet eftersom flera källor pekar på att det kan sluka mer batteri än om användare inte gör detta. Representanter från Google och Apple bekräftar att regelbunden tvångsavslutning på Android- och iOS-enheter kan vara batterikrävande. Relaterat till detta är hur batteriikonen är utformad i mobila operativssystem där tidigare forskning menar att användare har svårt att med säkerhet veta hur länge deras batteri kommer räcka. Det finns även forskningsrapport från 2009 som skriver att flertalet användare i deras studie inte visste att det fanns energisparande funktioner att använda sig av i operativssystemen. Min genomförda studie utgick från en förstudie som kontrollerade varför användare tvångsavslutade appar på sina mobila enheter. Det visade sig finnas flera anledningar till att användare utför regelbunden tvångsavslutning av appar på mobila enheter. Det visade sig i min förstudie att 46% av alla som deltog i förstudien tvångsavslutade appar regelbundet. Den näst största anledningen, enligt min förstudie, till regelbunden tvångsavslutning är för att användare vill ha kontroll över vilka appar som är öppna. Detta gäller för 7% alla användare som deltog. Den största anledningen till regelbunden tvångsavslutning av mobila appar är för att användarna vill spara batteri. Dessa användare utgör 28% av alla användare som deltog i förstudien. Utifrån datan från förstudien gjordes intervjuer med smartphone-användare för att ta reda på ytterligare information om hur användare tänker kring funktionen. Flera av användarna som intervjuades tvångsavslutade appar på sin smartphone och de berättar även varför de gör detta. Av de som tvångsavslutar i intervjuerna tvångsavslutar de flesta för att de tror att det sparar batteri. Denna undersökning är gjord för att få fram data kring om användare faktiskt tvångsavslutar appar på mobila enheter och varför de gör detta. Denna rapport ska vara en del i att hjälpa formgivare att designa gränssnitt utifrån denna tillhandahållna data. / I have observed some users that force-quit apps regularly. It's interesting to know why users do this because multiple sources indicate that it probably use more battery-power than not doing it. Representatives from both Google and Apple confirm that force-quitting apps regularly on Android and iOS devices may be more battery-demanding. Relative to this is how the battery-icon is designed in the mobile operative system where a research report that users have a hard time know for certainty how much battery there is left. There is also a research from 2009 that report that users in their studie did not know that there was energysaving funktions available to use in the mobile operatingsystem. My study started with a pilot study that checked why users force-quit apps on their mobile devices. There are several reasons why users force-quit apps regularly on mobile devices. It was shown in the study that 46% of all participants in the pilot-study force-quitted apps regularly on mobile devices to save battery power. My pilot-study shows that the second biggest reason for force-quitting regularly is that users want to have control over which apps are open. That is 7% of all the participants in the pilot-study. The main reason that users force-quit apps regularly is to save battery power. This category of users constitutes 28% of all the participants in the pilot-study. Based on the data from the pilot-study, interviews with smartphone users were made to find out more about what users think about this function. Multiple participants in the interviews do force-quit apps on their smartphone. They even told us why they do it. Most of the participants in the interviews that force-quit apps do it because they think it will save battery. This research is made to get data about if users force-quit apps on mobile devices and why they do it. This research report is made to help and inform designers to design interfaces from this data provided.