Hiroaki Aminaka

Device-to-device relay selection based on effective path throughput to fill coverage hole in public safety LTE

There is desire for public safety networks to meet the increasing demands for sharing images or videos among first responders and incident commanders more effectively. Long term evolution (LTE) is considered to be a candidate for achieving such broadband services. However, out-of-coverage areas tend to happen at the cell edge areas or inside buildings because the cell areas of each base station for public safety networks is larger than those of commercial one. This paper proposes a relay selection scheme for the relay communication using device-to-device (D2D) communication as a means to fill coverage holes in public safety LTE (PS-LTE). The scheme, based on effective path throughput from an out-of-coverage terminal to a base station via an in-coverage relay terminal, enables the optimal relay terminal to be selected. System level simulation results reveal that the proposed scheme can increase the user ratio, satisfying the throughput requirement for video transmission. Additionally, an evaluation intended for actual parties of firefighters shows that the proposed scheme enables 99% of out-of-coverage users to achieve the requirement throughput for transmitting video images.

Interleaved Resource Mapping for Autonomous Device-to-Device Discovery in Public Safety LTE

Device-to-device (D2D) discovery is an important function for public safety long term evolution (PS-LTE) to detect user equipment (UE) located in proximity. When many UEs are gathered at a disaster site or an incident command post, in-band emission (IBE) of discovery signals can cause significant interference resulting in discovery errors. In order to reduce the effect of IBE, a radio resource mapping method is proposed for autonomous D2D discovery in a PS-LTE system configured to repeatedly transmit discovery signals over different subframes. The proposed method interleaves discovery resources so that retransmission on resources with a certain frequency gap follows transmission on adjacent resources. Simulation results revealed that the proposed method takes 10% less time to detect UEs than a conventional method does.

Scheduling for Device-to-Device Communication Considering Spatial Reuse and User Fairness in Public Safety LTE

Public safety networks are desired to meet increasing demands for sharing images or videos among first responders and incident commanders. Long term evolution (LTE) is considered a candidate to achieve such broadband services. However, in the case of a disaster or a big sporting event, the traffic suddenly increases sharply as the number of active public safety users increases. This paper reports methods for allocating radio resources for device-to-device (D2D) communication as a means to enhance system capacity of the public safety LTE (PS-LTE). The methods allow spatial reuse of the resources among D2D communicating public safety users satisfying certain sharing conditions. Two practical scheduling algorithms that take into account both spatial reuse of the resources and fairness between the D2D communicating users are described. System level simulation results reveal that the methods can increase the number of users that satisfy the throughput requirement for video transmission.