Cassio Ribeiro

Device-to-device communication as an underlay to LTE-advanced networks

In this article device-to-device (D2D) communication underlaying a 3GPP LTE-Advanced cellular network is studied as an enabler of local services with limited interference impact on the primary cellular network. The approach of the study is a tight integration of D2D communication into an LTE-Advanced network. In particular, we propose mechanisms for D2D communication session setup and management involving procedures in the LTE System Architecture Evolution. Moreover, we present numerical results based on system simulations in an interference limited local area scenario. Our results show that D2D communication can increase the total throughput observed in the cell area.

Resource Sharing Optimization for Device-to-Device Communication Underlaying Cellular Networks

We consider Device-to-Device (D2D) communication underlaying cellular networks to improve local services. The system aims to optimize the throughput over the shared resources while fulfilling prioritized cellular service constraints. Optimum resource allocation and power control between the cellular and D2D connections that share the same resources are analyzed for different resource sharing modes. Optimality is discussed under practical constraints such as minimum and maximum spectral efficiency restrictions, and maximum transmit power or energy limitation. It is found that in most of the considered cases, optimum power control and resource allocation for the considered resource sharing modes can either be solved in closed form or searched from a finite set. The performance of the D2D underlay system is evaluated in both a single-cell scenario, and a Manhattan grid environment with multiple WINNER II A1 office buildings. The results show that by proper resource management, D2D communication can effectively improve the total throughput without generating harmful interference to cellular networks.

Mode Selection for Device-To-Device Communication Underlaying an LTE-Advanced Network

Device-to-Device communication underlaying a cellular network enables local services with limited interference to the cellular network. In this paper we study the optimal selection of possible resource sharing modes with the cellular network in a single cell. Based on the learning from the single cell studies we propose a mode selection procedure for a multi-cell environment. Our evaluation results of the proposed procedure show that it enables a much more reliable device-to-device communication with limited interference to the cellular network compared to simpler mode selection procedures. A well performing and practical mode selection is critical to enable the adoption of underlay device-to-device communication in cellular networks.

Power Optimization of Device-to-Device Communication Underlaying Cellular Communication

We address resource sharing of the cellular network and a device-to-device (D2D) underlay communication assuming that the cellular network has control over the transmit power and the radio resources of D2D links. We show that by proper power control, the interference between two services can be coordinated to benefit the overall performance. In addition, we consider a scenario with prioritized cellular communication and an upper limit on the maximum transmission rate of all links. We derive the optimum power allocation for the considered resource sharing modes. The results show that cellular service can be effectively guaranteed while having a comparable sum rate with a none power control case in most of the cell area.

Device-to-Device Communications; Functional Prospects for LTE-Advanced Networks

In this paper the possibility of device-to-device (D2D) communications as an underlay of an LTE-A network is introduced. The D2D communication enables new service opportunities and reduces the eNB load for short range data intensive peer-to-peer communication. The cellular network may establish a new type of radio bearer dedicated for D2D communications and stay in control of the session setup and the radio resources without routing the user plane traffic. The paper addresses critical issues and functional blocks to enable D2D communication as an add-on functionality to the LTE SAE architecture. Unlike 3G spread spectrum cellular and OFDM WLAN techniques, LTE-A resource management is fast and operates in high time-frequency resolution. This could allow the use of non-allocated time-frequency resources, or even partial reuse of the allocated resources for D2D with eNB controlled power constraints. The feasibility and the range of D2D communication, and its impact to the power margins of cellular communications are studied by simulations in two example scenarios. The results demonstrate that by tolerating a modest increase in interference, D2D communication with practical range becomes feasible. By tolerating higher interference power the D2D range will increase.

Interference-avoiding MIMO schemes for device-to-device radio underlaying cellular networks

An underlaying direct Device-to-Device (D2D) communication mode in future cellular networks, such as IMT-Advanced, is expected to provide spectrally efficient and low latency support of e.g. rich multi-media local services. Enabling D2D links in a cellular network presents a challenge in transceiver design due to the potentially severe interference between the cellular network and D2D radios. In this paper we propose MIMO transmission schemes for cellular downlink that avoid generating interference to a D2D receiver operating on the same time-frequency resource. System simulations demonstrate that substantial gains in D2D SINR of up to 15 dB and around 10% total cell capacity gains can be obtained by using the proposed scheme.

Advances in D2D communications: Energy efficient service and device discovery radio

Device-to-Device communications with automated connectivity to sensors, machines and other users is an important enabler for a multitude of use cases with local social networks as one example. In this paper we focus on the main challenges to build a seamless user experience. In particular, we present a novel device beaconing scheme to facilitate service and device discovery. Moreover, the mechanism enables the exchange of small data packets and facilitates the connection setup of a suitable transport radio. We discuss the energy efficiency of the proposed device discovery mechanism and evaluate the capability to form a network in a residential scenario with different device densities.

Performance impact of fading interference to Device-to-Device communication underlaying cellular networks

We consider Device-to-Device (D2D) communications underlaying a cellular network to accommodate local services. The system aims to optimize the overall cell throughput while giving priority to the cellular service. In this paper, we study the impact of a fading environment to a D2D enabled cellular network. The results show that the system experiences an increased cellular service outage probability and a decreased cell throughput. We also show that a conservative optimization scheme can effectively control the cellular service outage. Even when using the conservative scheme the cell throughput increases significantly compared to cellular-only transmission which shows high potential of underlay D2D communications.

Performance of linear multi-user MIMO precoding in LTE system

For scenarios with a large number of users to be served in one cell, high capacity gains can be achieved by transmitting independent data streams to different users sharing the same time-frequency resources. This technique is known as Multi-User MIMO (MU-MIMO). In this paper we investigate the performance of MU-MIMO operation in 3GPP LTE for different frequency granularities of the precoder at the OFDM transmitter. We also investigate the impact of channel correlation on the performance of the receiver when it is unaware of the interfererpsilas precoding vector. The performance is evaluated by means of semistatic system simulations.

On efficient discovery of next generation local area networks

In this paper we propose an energy efficient idle scanning method of local area networks, which could be provided within the framework of Automated Network Discovery and Service Function in 3GPP Long Term Evolution. Further, we combine it with a proposal to utilize an accelerometer, to limit the amount of scans during times when the UE is not moving. We evaluate the scanning strategies in a residential scenario where a model for varying access point density is applied based on the uptake of the 802.11n technology. We further extend this scenario by proposing a mobility model. The results show that without assistance the UE will spend a significant amount of energy on scanning in areas with low density of access points, which will result in insufficient stand-by performance. Further, our studies show that the proposed assistance with channel knowledge is an effective way to keep the energy consumption at a tolerable level.