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Author

Rapeepat Ratasuk

Other affiliations: Nokia Networks, Google
Bio: Rapeepat Ratasuk is an academic researcher from Motorola. The author has contributed to research in topics: Telecommunications link & User equipment. The author has an hindex of 31, co-authored 127 publications receiving 3589 citations. Previous affiliations of Rapeepat Ratasuk include Nokia Networks & Google.


Papers
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Patent
26 Mar 2020
TL;DR: In this paper, an apparatus and method for data transmission are presented, which comprises receiving (202) from core network data to be transmitted to user terminal, allocating (204) resource for transmitting downlink control information of the resource and a paging message to the user terminal; transmitting (206) downlink information and the paging messages to the UEs, indicating that there is data and how to acknowledge the Paging message.
Abstract: An apparatus and method for data transmission are presented. The method in an apparatus in a communication system, comprises receiving (202) from core network data to be transmitted to user terminal; allocating (204) resource for transmitting downlink control information of the resource and a paging message to the user terminal; transmitting (206) downlink control information and the paging message to the user terminal, indicating that there is data to be sent to the terminal and how to acknowledge the paging message; receiving (208) an acknowledgement from the user terminal; transmitting (210) downlink control information to the user terminal, the information indicating resource to be used in the transmission of data; transmitting (212) data to the user terminal and receiving (214) an acknowledgement from the user terminal.
Patent
24 Jul 2014
TL;DR: In this paper, the authors propose a method for long-term evolution unlicensed communication systems to benefit from dynamic trigger-based synchronization, which can include receiving, at a device, a cell search and/or synchronization command from the network on the primary cell.
Abstract: Synchronization may be valuable in many communication systems. For example, long term evolution unlicensed may benefit from dynamic trigger-based synchronization. A method can include receiving, at a device, a cell search and/or synchronization command from the network on the primary cell. The method can also include performing, by the device, cell search and/or synchronizing on a secondary cell based on the cell search and/or synchronization command.
Patent
04 Feb 2015
TL;DR: In this paper, a tri-timer design is proposed for uniform user equipment initialization for both in-coverage and out-ofcoverage device-to-device communications, incorporating an initial timer, a search timer, and an active timer.
Abstract: Methods, apparatuses, and computer program products for providing uniform user equipment initialization procedure for both in-coverage and out-of-coverage device-to device communications are disclosed herein, incorporating a novel tri-timer design: an initial timer, a search timer, and an active timer. In a method a determination is made regarding a user equipment as being a clusterhead candidate which can act as a clusterhead of a cluster. The user equipment searches for a suitable cell or cluster to join. If a suitable cell or a cluster is not found, the user equipment is selected to be a clusterhead which will act as the clusterhead of its own cluster. After selecting the user equipment to be a clusterhead and establishing its cluster, the user equipment transmits a discovery signal which alerting other user equipment to the clusterhead, to which the other user equipment can join. The user equipment as clusterhead then maintains the cluster.
Patent
15 Jan 2021
TL;DR: In this article, the authors describe a transport block size (TBS) configuration in which a terminal device transmits a preamble to a network device and receives a random access response from the network device.
Abstract: Embodiments of the present disclosure relate to methods, devices and computer readable storage medium for transport block size (TBS) configuration. In example embodiments, a terminal device transmits a random access preamble to a network device. The terminal device receives a random access response from the network device. The random access response includes a resource allocated for a reference TBS. Based on the reference TBS, the terminal device determines a TBS for transmitting data to the network device. Then, the terminal device transmits the data to the network device by using the determined TBS and the allocated resource. This TBS configuration is more flexible.
Patent
15 Apr 2021
TL;DR: In this paper, the authors present an enhanced link budget procedure for initial access, where the network device transmits configuration of random access channel and the terminal device determines the coverage enhancement and power boosting based on the configuration and measured power.
Abstract: Embodiments of the present disclosure relate to enhanced link budget procedure for initial access. According to embodiments of the present disclosure, the network device transmits configuration of random access channel and the terminal device determines the coverage enhancement and power boosting based on the configuration and measured power. Thus, collision among terminal devices is reduced.

Cited by
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Journal ArticleDOI
TL;DR: An overview of the Internet of Things with emphasis on enabling technologies, protocols, and application issues, and some of the key IoT challenges presented in the recent literature are provided and a summary of related research work is provided.
Abstract: This paper provides an overview of the Internet of Things (IoT) with emphasis on enabling technologies, protocols, and application issues. The IoT is enabled by the latest developments in RFID, smart sensors, communication technologies, and Internet protocols. The basic premise is to have smart sensors collaborate directly without human involvement to deliver a new class of applications. The current revolution in Internet, mobile, and machine-to-machine (M2M) technologies can be seen as the first phase of the IoT. In the coming years, the IoT is expected to bridge diverse technologies to enable new applications by connecting physical objects together in support of intelligent decision making. This paper starts by providing a horizontal overview of the IoT. Then, we give an overview of some technical details that pertain to the IoT enabling technologies, protocols, and applications. Compared to other survey papers in the field, our objective is to provide a more thorough summary of the most relevant protocols and application issues to enable researchers and application developers to get up to speed quickly on how the different protocols fit together to deliver desired functionalities without having to go through RFCs and the standards specifications. We also provide an overview of some of the key IoT challenges presented in the recent literature and provide a summary of related research work. Moreover, we explore the relation between the IoT and other emerging technologies including big data analytics and cloud and fog computing. We also present the need for better horizontal integration among IoT services. Finally, we present detailed service use-cases to illustrate how the different protocols presented in the paper fit together to deliver desired IoT services.

6,131 citations

Journal ArticleDOI
TL;DR: This paper considers transmit precoding and receiver combining in mmWave systems with large antenna arrays and develops algorithms that accurately approximate optimal unconstrained precoders and combiners such that they can be implemented in low-cost RF hardware.
Abstract: Millimeter wave (mmWave) signals experience orders-of-magnitude more pathloss than the microwave signals currently used in most wireless applications and all cellular systems. MmWave systems must therefore leverage large antenna arrays, made possible by the decrease in wavelength, to combat pathloss with beamforming gain. Beamforming with multiple data streams, known as precoding, can be used to further improve mmWave spectral efficiency. Both beamforming and precoding are done digitally at baseband in traditional multi-antenna systems. The high cost and power consumption of mixed-signal devices in mmWave systems, however, make analog processing in the RF domain more attractive. This hardware limitation restricts the feasible set of precoders and combiners that can be applied by practical mmWave transceivers. In this paper, we consider transmit precoding and receiver combining in mmWave systems with large antenna arrays. We exploit the spatial structure of mmWave channels to formulate the precoding/combining problem as a sparse reconstruction problem. Using the principle of basis pursuit, we develop algorithms that accurately approximate optimal unconstrained precoders and combiners such that they can be implemented in low-cost RF hardware. We present numerical results on the performance of the proposed algorithms and show that they allow mmWave systems to approach their unconstrained performance limits, even when transceiver hardware constraints are considered.

3,146 citations

Journal ArticleDOI
TL;DR: A general framework to evaluate the coverage and rate performance in mmWave cellular networks is proposed, and the results show that dense mmWave networks can achieve comparable coverage and much higher data rates than conventional UHF cellular systems, despite the presence of blockages.
Abstract: Millimeter wave (mmWave) holds promise as a carrier frequency for fifth generation cellular networks. Because mmWave signals are sensitive to blockage, prior models for cellular networks operated in the ultra high frequency (UHF) band do not apply to analyze mmWave cellular networks directly. Leveraging concepts from stochastic geometry, this paper proposes a general framework to evaluate the coverage and rate performance in mmWave cellular networks. Using a distance-dependent line-of-site (LOS) probability function, the locations of the LOS and non-LOS base stations are modeled as two independent non-homogeneous Poisson point processes, to which different path loss laws are applied. Based on the proposed framework, expressions for the signal-to-noise-and-interference ratio (SINR) and rate coverage probability are derived. The mmWave coverage and rate performance are examined as a function of the antenna geometry and base station density. The case of dense networks is further analyzed by applying a simplified system model, in which the LOS region of a user is approximated as a fixed LOS ball. The results show that dense mmWave networks can achieve comparable coverage and much higher data rates than conventional UHF cellular systems, despite the presence of blockages. The results suggest that the cell size to achieve the optimal SINR scales with the average size of the area that is LOS to a user.

1,342 citations

Journal ArticleDOI
TL;DR: An overview of the techniques being considered for LTE Release 10 (aka LTEAdvanced) is discussed, which includes bandwidth extension via carrier aggregation to support deployment bandwidths up to 100 MHz, downlink spatial multiplexing including single-cell multi-user multiple-input multiple-output transmission and coordinated multi point transmission, and heterogeneous networks with emphasis on Type 1 and Type 2 relays.
Abstract: LTE Release 8 is one of the primary broadband technologies based on OFDM, which is currently being commercialized. LTE Release 8, which is mainly deployed in a macro/microcell layout, provides improved system capacity and coverage, high peak data rates, low latency, reduced operating costs, multi-antenna support, flexible bandwidth operation and seamless integration with existing systems. LTE-Advanced (also known as LTE Release 10) significantly enhances the existing LTE Release 8 and supports much higher peak rates, higher throughput and coverage, and lower latencies, resulting in a better user experience. Additionally, LTE Release 10 will support heterogeneous deployments where low-power nodes comprising picocells, femtocells, relays, remote radio heads, and so on are placed in a macrocell layout. The LTE-Advanced features enable one to meet or exceed IMT-Advanced requirements. It may also be noted that LTE Release 9 provides some minor enhancement to LTE Release 8 with respect to the air interface, and includes features like dual-layer beamforming and time-difference- of-arrival-based location techniques. In this article an overview of the techniques being considered for LTE Release 10 (aka LTEAdvanced) is discussed. This includes bandwidth extension via carrier aggregation to support deployment bandwidths up to 100 MHz, downlink spatial multiplexing including single-cell multi-user multiple-input multiple-output transmission and coordinated multi point transmission, uplink spatial multiplexing including extension to four-layer MIMO, and heterogeneous networks with emphasis on Type 1 and Type 2 relays. Finally, the performance of LTEAdvanced using IMT-A scenarios is presented and compared against IMT-A targets for full buffer and bursty traffic model.

1,044 citations

Journal ArticleDOI
10 May 2016
TL;DR: The security requirements of wireless networks, including their authenticity, confidentiality, integrity, and availability issues, and the state of the art in physical-layer security, which is an emerging technique of securing the open communications environment against eavesdropping attacks at the physical layer are discussed.
Abstract: Due to the broadcast nature of radio propagation, the wireless air interface is open and accessible to both authorized and illegitimate users. This completely differs from a wired network, where communicating devices are physically connected through cables and a node without direct association is unable to access the network for illicit activities. The open communications environment makes wireless transmissions more vulnerable than wired communications to malicious attacks, including both the passive eavesdropping for data interception and the active jamming for disrupting legitimate transmissions. Therefore, this paper is motivated to examine the security vulnerabilities and threats imposed by the inherent open nature of wireless communications and to devise efficient defense mechanisms for improving the wireless network security. We first summarize the security requirements of wireless networks, including their authenticity, confidentiality, integrity, and availability issues. Next, a comprehensive overview of security attacks encountered in wireless networks is presented in view of the network protocol architecture, where the potential security threats are discussed at each protocol layer. We also provide a survey of the existing security protocols and algorithms that are adopted in the existing wireless network standards, such as the Bluetooth, Wi-Fi, WiMAX, and the long-term evolution (LTE) systems. Then, we discuss the state of the art in physical-layer security, which is an emerging technique of securing the open communications environment against eavesdropping attacks at the physical layer. Several physical-layer security techniques are reviewed and compared, including information-theoretic security, artificial-noise-aided security, security-oriented beamforming, diversity-assisted security, and physical-layer key generation approaches. Since a jammer emitting radio signals can readily interfere with the legitimate wireless users, we also introduce the family of various jamming attacks and their countermeasures, including the constant jammer, intermittent jammer, reactive jammer, adaptive jammer, and intelligent jammer. Additionally, we discuss the integration of physical-layer security into existing authentication and cryptography mechanisms for further securing wireless networks. Finally, some technical challenges which remain unresolved at the time of writing are summarized and the future trends in wireless security are discussed.

948 citations