Cross-Layer Adaptation Technology to Enable Just-Enough Services for mHealth in OFDM-Based Mobile Networks

Link adaptation plays a unique role to handle uncertainties and variations while delivering emerging mHealth services in mobile networks. In terms of typical link adaptation strategies, AMC (Adaptive Modulation and Coding) is designed to maximize spectrum efficiency in the physical layer, and HARQ (Hybrid Automatic Repeat reQuest) is conceived for enhancing transmission reliability in the combination of physical and upper layers. In reality, the fundamental goal of a link adaptation technique should utilize just-enough radio resources to deliver QoS (Quality of Service)-benchmarked services, since the radio resources are always limited in any mobile networks, and QoS requirements are the baseline of any kinds of mobile services. Motivated by this fundamental goal, we propose a novel cross-layer link adaptation to integrate AMC and HARQ mechanisms, in which they are sharing link feedback information by a CQI-Judgement support mechanism. To be specific, this proposal is a cross-layer combination of transmission reliability inspection and transmission pattern recognition, in which AMC is a coarse self-adaptive mechanism and HARQ is applied for the fine self-adaptation. To facilitate this proposal, we conceive an implementation scheme to realize the CQI-Judgement support mechanism, namely, BLER-oriented WMS (Weighted Mean Scheme) judgement, and the advanced version by using NLMS (Normalized Least Mean Square) model with occasional channel measurement. System-level simulation experiments demonstrate that the proposal can finely tailor just-enough radio resources to accommodate QoS-benchmarked mHealth services in LTE-Advanced mobile networks. Results show that the proposal can obtain gains 8.4% in terms of system throughput. Obviously, this proposal is open to integrate any potential advances in the future, for example, ARQ in the RLC (Radio Link Control) layer, power control in the physical layer, etc.