Energy efficient design for tactile internet

Ensuring the ultra-low end-to-end latency and ultrahigh reliability required by tactile internet is challenging. This is especially true when the stringent Quality-of-Service (QoS) requirement is expected to be satisfied not at the cost of significantly reducing spectral efficiency and energy efficiency (EE). In this paper, we study how to maximize the EE for tactile internet under the stringent QoS constraint, where both queueing delay and transmission delay are taken into account. We first validate that the upper bound of queueing delay violation probability derived from the effective bandwidth can be used to characterize the queueing delay violation probability in the short delay regime for Poisson arrival process. However, the upper bound is not tight for short delay, which leads to conservative designs and hence leads to wasting energy. To avoid this, we optimize resource allocation that depends on the queue state information and channel state information. Analytical results show that with a large number of transmit antennas the EE achieved by the proposed policy approaches to the EE limit achieved for infinite delay bound, which implies that the policy does not lead to any EE loss. Simulation and numerical results show that even for not-so-large number of antennas, the EE achieved by the proposed policy is still close to the EE limit.