Utilizing unused network capacity for battery lifetime extension of LTE devices

The average operational time of today´s smart phones with one filling of the accumulator is one of the most important performance parameters for the customers of new devices. Nevertheless, this value is remaining constant or even decreasing in the last few years due to the continuously increasing complexity. On the other hand, for ensuring the fulfillment of the high user-requirements even under worst case conditions, novel cellular systems such as Long Term Evolution (LTE) are usually over-dimensioned in terms of the maximum available capacity. In this paper, a novel approach is presented which allows for trading in unused cell capacity for battery lifetime extension of the mobile devices. The basic idea in this context is to increase the robustness of the submitted uplink (UL) signal by decreasing the order of the modulation and coding scheme used. If the provided data rate is kept constant, this comes along with an increasing number of allocated Resource Blocks (RB) and therefore a decreased overall cell capacity. Nevertheless, the more robust signal allows for reducing the uplink transmit power while the Quality of Service (QoS) parameters are still met. The results for exemplary Voice over IP (VoIP) traffic show that for users originally submitting at the maximum available transmit power, the consumed energy of the LTE chip-set can be reduced by up to 27.5 % applying this novel approach.