How does the chosen LTE network affect the power consumption of the phone, or the disadvantages of LTE networks in the CIS

It is known that with a weak coverage of the mobile network, the mobile device spends more energy on maintaining the radio signal. With the growth of battery capacity, the magnitude of this energy became insignificant. However, with the evolution of network types, additional mechanisms are imposed that can drain the battery of a mobile device without user intervention. Below is information about the mechanisms that can change the lifetime of the phone depending on the selected LTE network.

(The discharge time is calculated without user actions).

1.User Inactivity Timer. A mobile device registered in the LTE network can be in two states: RRC_CONNECTED and RRC_IDLE. In the RRC_IDLE state, the mobile device is registered with the EMM (mobility management), but it does not have an active session. In this state, the mobile device may be called to transmit data or initiate UL (upload) traffic transmission via a request for radio resource allocation. In the RRC_CONNECTED state, the active radio channel is established between the mobile device and the tower. The average power consumption in the RRC_CONNECTED state is 300 mA. The RRC_IDLE is 4 mA. The responsibility for switching from RRC_CONNECTED to RRC_IDLE rests with the network. User Inactivity Timer - the time between the last transmitted data packet and the release of the radio channel (the RRC connection release signal generates the network). The value of User Inactivity Timer is not described in the 3gpp standard, so manufacturers of equipment for networks set this time based on their own observations. Usually, this time ranges from 10 s to one minute.

• The higher the value of User Inactivity Timer - the less often networks need to free / allocate a channel for data transmission;
• The smaller the value of User Inactivity Timer - the less time it will take a mobile device to maintain a radio channel.

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When the user is not actively using the Internet, the work of the mobile device in the network consists in periodic short polls of Internet services. A useful exchange of data occurs within a second. Then the useful power consumption is <10% of the total.

Number of requests per hour for various services in background mode:

• News (Flipboard, Daily news ...): 4 - 6 operations / hour;
• Social networks: 1 - 4 operations / hour;
• Instant messaging (Skype, Hangouts, Viber ...): 2 - 12 operations / hour;
• Geographic services: 2 - 3 operations / hour;

2.cDRX (Connected Mode Discontinuous Reception). In RRC_CONNECTED mode, there are intervals when data is not transmitted. During this time, the connected mode DRX helps reduce power consumption. The cDRX cycles the receiver on and off to save energy.



The cDRX parameters are set and controlled by the mobile device, but the network must support cDRX technology.

• 95% of the energy is stored in the RRC_CONNECTED state when there is no active data transfer (shown in the figure);
• 20% - 40% is saved in the case of active Internet services;
• 14% - with active use of the Internet by the user.

3. Handover, Redirection, Reselection. These technologies are responsible for switching the mobile device between the towers within the same network. In the RRC_IDLE state, the mobile device measures the signal power from various towers. If the results of these measurements meet the transition criteria, the mobile device will switch to the appropriate tower and remain in the RRC_IDLE state. Redirection and Handover occur when the mobile device was first in the RRC_CONNECTED state. In this state, the mobile device also measures the available towers and sends the report to the network. If there is a possibility of more optimal communication, the network switches the radio channel from one tower with a mobile device to another. In the case of a Handover, the tower to which the mobile device is switched is already prepared, while in the case of Redirection, the network sends data on the frequency on which the suitable tower is located. Handover is only possible if there is a physical interface between the two towers.

There are three ways to switch the device between the towers:

- Handover team. Requires settings for all operator towers. Possible only if there is a physical interface between the towers.
- Redirection command. It requires settings for all operator towers (unlike the previous one, only the frequency to which the device should switch is necessary). The mobile device itself will connect.
- RRC connection release command, which will transfer the mobile device to the RRC_IDLE state and the phone itself will select the optimal tower and carry out the connection procedure.



4. VoLTE (Voice over LTE). IMS (IP Multimedia Subsystem) in the case of VoIP / LTE is implemented at the AP level. Accordingly, the AP processor of the mobile device must be under load. For the VoLTE IMS module is located in the modem, so even when calling, the AP processor can be in sleep mode. This can significantly save battery power.

• ~ 33% of energy saves compared to Skype call;
• ~ 0% is equivalent to a call to the WCDMA network;

Currently in the CIS, voice services in LTE networks are performed via the CSFB (Circuit Switched FallBack) function. The mobile device receives an incoming call signal, switches to a lower level network (WCDMA / GSM) and receives a call and then joins the LTE network. Switching / searching requires additional energy costs.

The peculiarities of economic trends and rules in the post-Soviet space are forcing LTE network owners to move towards an increase in subscribers through an increase in coverage. Competition between operators occurs through ensuring the best rates and speed of the Internet. In developed countries, competition between operators occurs through the improvement of services for existing subscribers (usually tariffs are much higher). For networks in the CIS, it is typical:

• Inactivity timer in the range from 10 to 20 seconds;
• No cDRX support;
• Voice services via CSFB function;
• Redirection as a means of switching (in rare cases, a handover is partially supported, it is also possible to assign a switching function to a mobile device).

The rate of discharge of a mobile device largely depends on the quality of the network in which the device is registered. For poorly configured networks, the average LTE-phone can be discharged in 8 hours without user intervention.