Jaheon Gu

Dynamic power control mechanism for interference coordination of device-to-device communication in cellular networks

Device-to-device (D2D) communication in cellular networks can bring about interference between user equipments (UEs) in cellular and D2D communications, which may decrease performance of cellular networks. In this paper, we propose dynamic power control mechanism to reduce interference and improve performance of cellular systems. The proposed mechanism excludes cellular communication UE with same resource, base station, and areas of adjacent cells from the coverage area of D2D communication UE by adjusting transmit power of the D2D communication UE. By simulations, we show that the proposed dynamic power control mechanism can improve performance of the entire communication systems.

A resource allocation scheme for device-to-device communications using LTE-A uplink resources

Abstract Device-to-device (D2D) communications enabling devices to directly communicate with each other have been considered to overcome the shortage of available radio resource and reduce heavy traffic load on cellular base station. D2D communications operating on cellular networks can improve the efficiency of utilizing radio resource by reusing the resource of cellular networks. However, it can cause interference between cellular and D2D entities using the same resource, and the interference may degrade the performance of the entire system. D2D communications have been preferred to use uplink (UL) resources of cellular networks due to asymmetric UL and downlink (DL) service loads. In Long Term Evolution Advanced (LTE-A), single carrier frequency division multiple access (SC-FDMA) has adopted as UL transmission scheme in order to achieve low a high peak-to-average power ratio (PAPR). There are the exclusivity and the adjacency constraints in SC-FDMA. In order to enable D2D communications to efficiently reuse UL resources of the cellular networks, a radio resource allocation scheme with the constraints of SC-FDMA is proposed in this paper. The proposed scheme pairs up a cellular user equipment (CUE) and a D2D pair as a resource sharing pair (RSP) by controlling transmission power of D2D user equipments (DUEs), and allocates the contiguous subchannels to an RSP based on the well-known proportional fairness (PF) scheduling algorithm. The results of performance evaluation show that the proposed scheme can maintain throughputs of CUEs and alleviate the high PAPR problem of user equipments (UEs).

Andsf-based congestion control procedure in heterogeneous networks

The mobile network operators (MNOs) have considered the provision of simultaneous multiple access in heterogeneous networks. Access network discovery and selection function (ANDSF) is introduced to provide simultaneous multiple access in heterogeneous networks to users. Since a ANDSF manages the inter-system mobility and routing policy, it can mitigate congestion of a certain access networks by restricting access or IP traffic flows toward the crowded access network. However, for congestion control by ANDSF, ANDSF should enable to manage the congestion condition among heterogeneous networks. Thus, this paper proposes messages and procedures for ANDSF to collect the congestion condition among heterogeneous networks and to decide inter-system mobility and routing policy. The proposed messages and procedures can be easily implemented by extending the messages and procedures defined in the 3GPP standards.

Mobility-based handover decision mechanism to relieve ping-pong effect in cellular networks

In order to guarantee quality of service (QoS) and seamless communications to nomadic users, it is important to prevent unnecessary handovers occurred during a short interval, so-called ping-pong effect. Considering mobility is one of the useful methods to relieve ping-pong effect in cellular networks since a mobile device can efficiently determine whether it should perform handover or not through the estimation of its moving direction or velocity. In this paper, we propose a mobility estimation method that estimates radial velocity of mobile device directed to the neighboring base stations based on the received signal strength (RSS). In addition, we propose an efficient handover decision mechanism based on the estimated mobility to relieve ping-pong effect. From performance evaluation based on simulations, we find that the proposed mobility estimation mechanism can accurately estimate mobility of moving devices and the proposed handover mechanism can effectively relieve ping-pong effect and reduce handover delay.

A resource allocation scheme for improving user fairness in device-to-device communication based on cellular networks

As one of solutions to radio resource shortage and heavy burden on base stations, device-to-device (D2D) communication which enables devices to directly communicate with each other has been considered. If D2D communication operates based on cellular networks, it can efficiently utilize radio resources by reusing the resources of cellular networks. However, the interference between cellular and D2D communication entities can be occurred when they share the same resource, and this may degrade entire system performance. In order to coordinate the interference, a resource allocation scheme which allocates resources to cellular mobile equipments (CMEs) and D2D pairs is proposed in this paper. The proposed scheme involves one CME and one D2D pair in a resource sharing pair (RSP) by considering interference between them, and allocates the resources to RSPs based on proportionally-fair (PF) scheduling algorithm. The proposed scheme can improve the overall performance of cellular network by improving fairness among user throughputs as maintaining total system capacity.

Mode selection scheme considering transmission power for improving performance of device-to-device communication in cellular networks

Device-to-device (D2D) communication (D2D-comm) which enables direct communications between mobile devices is considered as one of new approaches to extend capacity of cellular systems. Since radio resource sharing of conventional cellular systems is essential for D2D-comm to maximize the capacity, resource usage mode for D2D-comm should be carefully determined. In this paper, we propose a mode selection scheme which selects proper resource usage mode of each D2D pair by considering transmission power of D2D-comm user equipments (DUEs). The proposed scheme makes each D2D pair to select resource usage mode which is expected to achieve highest data rate based on its average signal-to-interference plus noise ratio (SINR) and expected amount of available radio resources. From simulations, we show that the proposed scheme can improve throughput of cellular systems with capability of D2D-comm.

Reliable cooperative scheme for public safety services in LTE-A networks

In order to enable effective public safety services in challenged environments, 3rd Generation Partnership Program is considering the use of device-to-device (D2D) communications. D2D communications can be ideal in various emergency situations where the conventional network services get suspended. We propose a D2D-based user equipment (UE) relaying process to support the out-of-range isolated UEs. The main idea is to allow UEs that have active connections with eNB to exchange data with the isolated UEs over direct D2D links. This paper proposes a mechanism that enables an ordinary UE to serve as a relay for the isolated UEs, considering the D2D link capacity and the relays radial velocity. We define the complete procedure of establishing a reliable relay link between UEs in public safety environments and analyse its performance. Copyright

FFR-based resource allocation scheme for Device-to-Device communication

Device-to-Device communication allows two cellular devices to communicate with each other without a base station. By relieving the base station from relaying data to and from different devices, D2D communication aims at increasing the system capacity. In a D2D enabled network, one of the critical issues is to effectively allocate frequency resource. In this paper, a resource allocation scheme has been proposed that increases the throughput of all devices by using Fractional Frequency Reuse.

Selection of UE relay considering QoS class for public safety services in LTE-A network

Introduction of Device-to-Device (D2D) communication in public safety (PS) environments has been well investigated by 3rd Generation Partnership Project (3GPP). The main target is to provide communication services to user equipments (UE) in the disaster struck area with the help of ordinary UEs over D2D links. UE-relaying is one of the most important application of D2D communication especially in PS environment. While selecting this type of relay, several factors have to be considered prior to the selection process. Previously, only transmission rates were considered for the selection of UE relay on the basis of received signal strength. We propose a UE relay selection scheme in this article taking into account the quality of service (QoS) class. For that, we consider two important factors which greatly affect the communication process specially in cellular networks; data rates and radial velocity. We use weighted sum model as a tool for selecting most appropriate UE relay. The efficiency of the relay selection process is also increased and we evaluate the performance with the help of system level simulations.

Heuristic Algorithm for Proportional Fair Scheduling in D2D-Cellular Systems

The effective reuse of the radio resources in D2D communication underlaying cellular system is pivotal for enhancing the total system capacity. Developing practical and effective scheduling schemes is critical to the success of D2D-based cellular systems. An optimal proportionally fair (PF) scheduling scheme that maximizes the logarithmic sum of the user data rates is proposed in this paper. Considering the fact that the computational complexity of the optimal PF scheduling is significantly high, low-complexity heuristic algorithm has also been proposed. It has been shown that the heuristic algorithm achieves high logarithmic sum of the average user data rates while maintaining low-computational complexity. Simulation results are used to verify the performance of the proposed algorithm, and to compare it with the optimal PF scheduling algorithms.