Energy-Efficient Scheduling and Bandwidth-Energy Efficiency Trade-Off with Low Load

This paper presents a novel adaptation of the score-based scheduling principle along with a method for trading-off bandwidth for energy efficiency for use in Long Term Evolution (LTE) systems. The score-based principle is adapted to make use of both a relative and absolute energy efficiency metric. This results in flexible energy efficient scheduling that preserves the quality of service (QoS), as well as reduces the interference in the system. The general principle behind bandwidth expansion is to extend a user´s bandwidth by a factor of α. The target throughput is maintained by switching to a lower order modulation scheme and adjusting any other link parameters as necessary. Through a theoretical derivation, it is established that the higher the user´s employed modulation order is, the greater the possible gains are from employing such a transmission mode. The calculated improvement in expended energy ranges from approximately 43% to 98%. Simulations are used to empirically validate the theoretical results. When an expansion of bandwidth by a factor of 2 is simulated, the bandwidth expansion mode (BEM) is more efficient in 93% of the time, and the expended energy is reduced by 44%, while improving on the QoS delivered by the benchmark system.