Mei-Ju Shih

Handover mechanism for device-to-device communication

Device-to-Device (D2D) communication is a proximity-based technique used by Long Term Evolution-Advanced (LTE-A) systems. When a ProSe-enabled UE in D2D communication moves across a cell boundary, seamless handover is expected. However, LTE-A does not specify D2D handover procedures, and the current LTE-A handover procedures cannot support the ProSe service continuity requirements [1]. Therefore, an efficient D2D handover mechanism is necessary to meet the requirements. In this paper, a D2D handover mechanism, which considers the signal quality of D2D pairs, is proposed. The proposed mechanism includes a Joint Handover procedure and a Half Handover procedure based on a D2D handover decision method. Simulation of Urban Mobility (SUMO) [2] is adopted for the mobility model and performance evaluation simulations. The properties of this mechanism satisfy the ProSe service continuity requirements while decreasing the D2D HO failure rate as well as reducing the amount of information exchanged between the source eNB and the target eNB.

A Distributed Multi-Channel Feedbackless MAC Protocol for D2D Broadcast Communications

In Device-to-Device (D2D) broadcast communications, the design of Medium Access Control (MAC) protocol is quite challenging since it is urged on alleviating data collision under the constraints of no feedback messages, no central coordination, and half-duplex transmission. We propose a multi-channel MAC protocol for data channel competition. Theoretical and simulation results show that this protocol resolves all channel collisions in only a few iterations. Moreover, the collision resolution time is dominated by the number of channels, rather than the number of D2D transmitters. Thus, even in scenarios with densely-distributed D2D devices, the proposed protocol can guarantee short collision resolution time.

LTE-D broadcast with distributed interference-aware D2D resource allocation

Device-to-Device (D2D) communications is a promising technique to provide wireless peer-to-peer communication services and to enhance resource utilization as well as spectrum efficiency. In this paper, a distributed resource allocation scheme involving several D2D broadcast groups is proposed. However, the great amount of interference caused by sharing resources among different D2D broadcast users may significantly affect the performance of other D2D users. Therefore, an efficient resource allocation method is necessary to coordinate the interference. Specifically, we formulate the interference relationships among different D2D broadcast groups as an innovative interference-aware graph based resource allocation algorithm. This scheme aims to minimize the number of “confiict UE” meanwhile mitigate interference among different D2D broadcast groups from affecting the performance of each other. The complexity of proposed scheme is lower than that of the optimal SINR/channel capacity scheme.

Energy-aware waiting-line based resource allocation in cellular network with m2m/h2h co-existence

Since Machine-to-Machine (M2M) communications is going to be realized in advanced cellular networks, the resource allocation scheme should be re-examined to satisfy both traditional Human-to-Human (H2H) communications (e.g., voice calls) and M2M communications. Because most M2M applications are delay-tolerant and uplink-dominated, we propose a waiting-line based uplink resource allocation framework in the M2M/H2H co-existence scenario. The proposed scheme guarantees resources for H2H communications while meeting the needs of M2M communications on a first-come first-served basis. In addition, the scheme ensures the existence and uniqueness of the Bayesian Nash equilibrium and the truth-telling property. Results show that M2M devices with lower energy opportunity cost are more willing to participate in the waiting-line based scheme, and the delay in the connected mode varies according to the H2H traffic load and the total number of competitors. However, M2M devices with higher energy opportunity cost may not join this time bid resource allocation scheme. This work contributes insights into the types of resource allocation schemes, bidding with time or bidding with money, for M2M devices with different levels of energy awareness.

Performance Evaluation for Energy-Harvesting Machine-Type Communication in LTE-A System

To explore the energy efficient Machine-Type Communication (MTC) for 5G cellular systems, we developed a simulation platform to investigate the complete uplink procedures of energy-harvesting MTC devices in LTE-A (Long Term Evolution Advanced) system. Though the 3rd Generation Partnership (3GPP) has worked on LTE-A cellular standards in support of MTC transmission, the standards have not taken energy-harvesting MTC devices into their scope. Energy-harvesting technology can be the candidate to support the MTC features by allowing the devices to harvest ambient energy and support their own power usage without manual upgrade. The proposed Energy-Aware LTE-A scheme, serving as power control and admission control, prevents the devices from building the network connections greedily but ending up with energy shortage and packet loss. This scheme not only can reduce the contention level of control channels but also can decrease energy wastage on network entry procedures, thereby improving the overall energy efficiency.

Optimal resource reservations to provide quality-of-service guarantee in M2M communications

Machine-to-Machine (M2M) communications characterize a huge number of devices and small data transmission, which render admission control and resource allocation two key components to guarantee similar quality of service (QoS) for homogeneous devices. In view of this, we propose a pricing model based on option pricing and auction, aiming to guarantee the required QoS (i.e., throughput in this study) in the successive reserved time slots. We also introduce the concept of TotalPayment, referring to the price paid by the device when entering a M2M network, based on which we further suggest the optimal value of TotalPayment and its corresponding optimal range of strike price. The combination of QoS guarantee, admission control and market modelling in M2M network is an innovative business concept.

To Wait or To Pay: A Game Theoretic Mechanism for Low-Cost M2M and Mission-Critical M2M

When it comes to machine-to-machine (M2M) communications in advanced cellular networks, the resource allocation scheme should be re-examined to satisfy both low-cost M2M and mission-critical M2M. Because most M2M applications are uplink-dominated, we propose a mixed waiting-time auction and price-based dedicated uplink resource allocation framework for the low-cost and mission-critical M2M. The prioritized framework guarantees resources for traditional human-to-human (H2H) communications while meeting the needs of low-cost and mission-critical M2M devices on the basis of either time bids or direct price. In addition, the scheme ensures the existence and uniqueness of the Bayesian Nash equilibrium and the interregional and waiting-time-based truth-telling properties. This indirect mechanism holds with Bayesian-Nash incentive compatibility, interim efficiency, interim individual rationality, and weak budget balance. The results show that low-cost M2M devices with lower energy awareness are more willing to participate in the waiting-time auction, while mission-critical M2M with higher energy awareness turn to directly pay for guaranteed access. The delay in connected mode and the optimal price vary according to the M2M/H2H traffic loads and resource pool partitions. This paper contributes insights that with proper mechanism design, low-cost M2M and mission-critical M2M can be served together, while the operator is financially compensated.

Energy-Efficient D2D Discovery for Energy-Harvesting Proximal IoT Devices

Device-to-Device (D2D) communication is a promising concept used to improve user experience and enhance resource utilization in cellular networks, enabling two close-by D2D devices to establish a direct local link and bypass a base station. The proximity of two D2D devices allows for high data rate, low latency, and low energy consumption. D2D communication for proximity-based services (ProSe) is one of the most popular issues discussed in the 3rd Generation Partnership Project (3GPP). D2D devices require to discover each other (i.e. D2D discovery) before D2D communication. It can be applied to various important fields such as the environment and habitat monitoring, disaster management, and emergency response. In this work, we consider D2D communication is adopted for Internet-of-Things (IoT) devices for local operation. These devices may be randomly deployed and expose to uncontrolled, harsh and hostile environments. Thus, energy-harvesting technology is considered to enable devices to gather energy from the ambient sources and recharge their batteries. We investigate the constraints of an LTE-A system to serve energy-harvesting D2D devices. We develop a low complexity algorithm for D2D discovery resource allocation. Moreover, Sleep-Coordinative Mechanism (SCM) and Saving-before-Activity Mechanism (SBA) are proposed to realize energy-harvesting D2D discovery under the resource and energy constraints. Simulation results show that the combination of SCM and SBA effectively achieves almost 100% discovery rate with fewer time slots and lower energy consumption.

UE autonomous resource selection for D2D communications: Explicit vs. implicit approaches

With the increasing demand for wireless traffic, Device-to-Device (D2D) communications underlaying the cellular network is beneficial to offload traffic and further improve throughput and latency. 3GPP has introduced D2D communications for proximity-based services since Rel-12. The assumption of half-duplex mode and lack of a feedback mechanism make UE autonomous resource selection challenging in terms of collision minimization, which is significant when the eNB is out of function or when UEs move out of coverage. However, the existing design (i.e., Mode 2 communications) fails to address this problem. In this paper, we comprehensively explore UE autonomous resource allocation based on the specified frame structure including Scheduling Assignment (SA) and data transmission. Moreover, we propose the enhanced explicit approach and enhanced implicit approach by utilizing the sensing result to minimize collisions. Simulation results show that the proposed approaches outperform Rel-12 Mode 2 in terms of data collision probability and throughput. The enhanced implicit approach achieves low data collision probability and high throughput by SA admission control to prohibit excess transmissions. The pros and cons among the proposed approaches and Rel-12 Mode 2 are compared. The insights can be further adopted for Vehicle-to-Vehicle (V2V) communications and D2D communications enhancement.