Ravikumar V. Pragada

Architecture and protocols for LTE-based device to device communication

The evolution of cellular wireless communications has involved the introduction of technologies such as multiple antennas, OFDM, higher spectral efficiency through better modulation, denser deployments and carrier aggregation. A different approach to enhancing the cellular network by using direct communication between UEs is presented in this paper. Direct device-to-device (D2D) communication can be used for several purposes including network traffic offloading, public safety, and social applications such as gaming. The architectural and protocol enhancements required to extend the current 3GPP LTE-Advanced system to incorporate D2D communication are described, including the logical functions of a D2D server in the core network, the procedures for devices to discover each other and obtain D2D services, the steps involved in establishing and maintaining a D2D call and procedures for efficient mobility between a traditional cellular mode and a D2D mode of operation.

System Architecture for a Cellular Network with Cooperative Mobile Relay

This paper describes a comprehensive system architecture that enables mobile-to-mobile communications for the purpose of enhancing the capacity of the cellular network. The architecture is developed using LTE Release-10 as the baseline. The impact on the protocol stack is discussed in detail. Neighbor discovery mechanisms are described to enable users to identify potential helper mobiles to enable a cooperative mobile relay. Resource partitioning for the mobile-to-mobile link is detailed and changes to the design of the HARQ entity structure and timing are discussed.

Measurement and Characterization of Various Outdoor 60 GHz Diffracted and Scattered Paths

This paper investigates diffracted and scattered waves in unlicensed millimeter wave mobile-to-mobile, access and backhaul radio links. Narrowband 60 GHz measurements of diffraction at building corners, and scattering by a car, lamppost and building, as well as blocking by humans are presented. Semi-analytical corner diffraction and human blocking models are proposed and verified based on the measurements. Analysis of the diffraction and scattering shows that the contributions from vehicular and lamppost scattered paths can be dominant compared to corner diffracted paths. Measurements also show that the majority of power from building scattering arrives in and near the horizontal plane containing the transmit and receive antennas.

mm Wave Initial Cell Search Analysis under UE Rotational Motion

Millimeter wave (mmW) communication has emerged as a promising component of the access link for 5G cellular systems. In order to overcome the higher free-space path loss at these frequencies, high gain, and therefore highly directional, antennas are being proposed at both ends of the link. Furthermore, in order to maintain a mobile connection with an acceptable quality of service (QOS), these highly directional antennas also need to be electronically steerable. This required dual-end steerability adds significant system complexity in terms of both initial access and connected mode procedures. Therefore, these various procedures which were originally designed for the current sub 6 GHz systems need to be re-investigated in light of this added complexity. Traditionally, sub 6 GHz mobility studies mainly focused on translational motion; however, with the dual-end highly directional links being proposed for mmW communications, rotational motion also becomes a concern. In this paper, we study the effects these steerable links have on initial network access procedures, especially in the presence of user equipment (UE) rotational motion.