Downlink/uplink decoupling technology to support spectrally and energy efficient wearable communications in LTE

The key technical challenge of developing communication solutions for wearable devices is to meet the stringent energy consumption constraints while supporting diverse traffic types and quality of service (QoS) requirements in potentially densely populated deployment scenarios. In this work, we first present a new wearable communication architecture we refer to as LTE-W (LTE for Wearables) for wireless personal area networks (PANs) underlaying a cellular network. Within a single PAN, the client device with highest communication/ computation capabilities, usually a high-end hand-held device like a smartphone or a tablet, becomes the PAN header (nUE) and will assist other wearable devices (wUEs) to communicate with base station (BS) as a relay. Although two types of links are present, i.e., the cellular-PAN link and the intra-PAN link, the air interface for intra-PAN communication is defined as an integrated part of the cellular air interface for enhanced end-toend radio access and control. In LTE-W, the LTE RAT is considered to be the baseline and is proposed to be further enhanced in 5G systems to 5G-W. Based on our LTE-W architecture, we propose downlink (DL)/uplink (UL) decoupling transmission technology. For the scenario where all links support the LTE RAT, three options (transmission schemes) for DL transmission are possible: Option D1 where the BS transmits to wUEs only through the nUE, Option D2 where dynamic switching between direct and relay transmission takes place and Option D0 as DL direct transmission from the BS to wUEs. Regarding UL transmission, two options exist: Option U1 where all wUEs transmit to the BS only through the nUE and Option U0 as UL direct transmission from the wUEs to the BS. In this paper, the defined DL and UL LTE-W transmission schemes are analyzed and evaluated through simulation. We further propose several LTE-W DL/UL transmission modes with different combinations of DL and UL transmission options by investigating those modes with DL and UL transmissions decoupled. Under this strategy, high-end wUEs and low-end wUEs can have different transmission mode solutions. For example, high-end wUEs can directly receive from the BS in the DL for maximum spectral efficiency while they can only transmit to the nUE in the UL for maximum energy efficiency; in the case of low-end wUEs, DL transmission can take place either exclusively or partially through the nUE in order to maximize energy efficiency. System-level simulation results demonstrate the effectiveness of the proposed technologies under the LTE-W architecture. Keywords—Long-term evolution; wearables; personal area network; relay; energy efficiency; system-level simulation.