Mingyu Zhou

Evolving LTE with Flexible Duplex

Both TDD and FDD systems obtain their own merits and application limit. As the increasing of service requirement and traffic load, more and more telecommunication systems are operating in both FDD and TDD bands. It is foreseen that convergence of TDD and FDD will be the evolution trend of mobile communication systems. The paper proposes Flexible Duplex to enhance network efficiency and flexibility to well support non-uniform and varying traffic as well as various scenarios adaptively, which is the most important phase of the duplex evolution roadmap. With flexible duplex, those resources reserved for UL (DL) in conventional system can be re-allocated for DL (UL) with high flexibility. Based on the LTE system, seen as the global common 4G system, the system design to support flexible duplex is interpreted, characterized in the symmetrical DL/UL transmission to enable the inter-direction interference cancellation and simplify the receiver complexity. Several scenarios can benefit from the technique and evident gain is proved with simulation results.

Precise interference estimation for the uplink of LTE heterogeneous networks

Link adaptation mechanism is introduced in long term evolution (LTE) networks. With link adaptation, a base station (BS) selects a modulation and coding scheme (MCS) for each transmission based on signal to interference and noise ratio (SINR) estimation of the link. In the uplink, MCS is selected in advance of actual data transmission, which means a BS need to predict the SINR level. However, interference level may change drastically along with time as different sets of user equipments (UE) can be scheduled in neighbor cells every ms. The fluctuation of interference level poses serious challenge to SINR prediction and the effectiveness of link adaptation, especially for heterogeneous networks (HetNet). To solve the problem it has been proposed to exchange resource allocation information among neighbor BSs via backhaul so that the interference level can be predictable. However, such schemes are sensitive to backhaul delays. In this paper, a novel technique, i.e. precise interference estimation (PIE), is proposed to enhance the efficiency of link adaptation. The proposed scheme doesnt rely on backhaul for resource allocation information exchanging. Extensive system level simulations are carried out to evaluate the performance of the proposed scheme and significant gains can be observed.