A PHY-MAC Cross-Layer Approach for Sleep Scheduling in LTE/LTE-A Uplink

To support mobility, wireless mobile devices are powered by batteries; however, a battery can only store a limited amount of energy. Take a 3G handheld device for example, according to the real test, the wireless interface consumes the largest proportion of the total amount of power (up to 40%). In particular, the 4G wireless communications adopt OFDMA and MIMO as the wireless access technology, where the former improves the bandwidth efficiency and the latter enhances throughput. In this case, the wireless interface in a mobile device will consume much more power than that for 3G devices. To save power, we have designed a PHY-MAC cross-layer sleep scheduling method which considers power saving, energy efficiency, and QoS at the same time over the 4G LTE/LTE-A wireless networks. Several papers have been published or submitted and three master theses have been accomplished. In this paper, we discuss a cross-layer design of sleep scheduling in 3GPP LTE/LTE-A wireless networks. The design jointly considers the Medium Access Control (MAC) layer multi-user sleep scheduling (via the settings of DRX/DTX parameters) and the physical layer power and radio resource allocations. The new approach enables UEs to gain longer battery life time and better utility of radio resource while guarantee the delay, packet drop rate, and maximum transmit power constraints. The design is validated through comparisons with simulation results and we find significant improvement on power saving.