Rapeepat Ratasuk

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.

Method for uplink acknowledgement/non-acknowledgement messages in a wireless communication system

Abstract: A method for uplink ACK/NACK for LTE TDD. The method includes receiving a frame having multiple subframes wherein a plurality of subframes being downlink subframes and at least one subframe being an uplink subframe. One uplink subframe can contain an acknowledgment/non-acknowledgment (ACK/NACK) corresponding to at least one of the plurality of downlink subframes. To transmit ACK/NACKs, one uplink subframe for ACK/NACK is used in response to one of the plurality of downlink subframes. In addition, ACK/NACK responses can be bundled into one uplink subframe for at least two of the plurality of downlink subframes. In an embodiment, multiple ACK/NACK responses can be used in one uplink subframe that corresponds to at least two of the plurality of downlink subframes in a multiple feedback configuration. One uplink subframe for ACK/NACK responses and bundling multiple ACK/NACK responses is for a bundled feedback configuration.

Method and apparatus for conveying control channel information in ofdma systems

Abstract: Various embodiments are described which can serve to mitigate interference between the control channel signaling of adjacent sectors/cells. Potentially, these techniques may have the benefit of reducing the system resource drain caused by control channels, particularly control channels in high frequency-reuse, OFDMA systems. A transmitting device (101) transmits primary control channel information to a plurality of user devices (102). The primary control channel information includes an indication that a first OFDMA resource region (e.g., 320 or 330) is assigned to at least one user device of the plurality of user devices. The transmitting device correspondingly transmits secondary control channel information to the at least one user device using the first OFDMA resource region.

TDD design for UMTS Long-Term Evolution

Abstract: Long-term evolution (LTE) will provide substantial enhancements to UMTS 3G systems including improved system capacity and coverage, low latency, reduced operating costs, multi-antenna support, flexible bandwidth operations and seamless integration with existing systems. LTE supports both frequency division duplex (FDD) and time division duplex (TDD) modes to provide deployment flexibility in accordance with operatorpsilas preference and spectrum allocation. This paper presents an overview of LTE TDD design and highlights key differences with FDD. Design challenges unique to TDD are presented together with adopted technical solutions. Finally, simulation results are provided to demonstrate typical TDD system performance with data applications.

Method and apparatus for the dynamic and contention-free allocation of communication resources

Abstract: A method and apparatus for assigning a communication resource is disclosed. The method includes allocating a channel by a base station or Node B 102. The base station or Node B detects an energy level transmitted on the channel wherein the energy level may be contention-free for a plurality of user equipment 104. The base station or Node B assigns time frequency resources for at least one of the plurality of user equipment wherein the time frequency resources are proportional to the detected energy level.

Method and apparatus for channel sounding in an orthogonal frequency division multiplexing communication system

Abstract: An Orthogonal Frequency Division Multiplexing communication system (200) is provided that triggers a transmission of an uplink sounding signal by use of a Downlink Control Information (DCI) message (600, 700) In various embodiments of the invention, the DCI message may be used to individually trigger an uplink sounding signal by a single user equipment (202) or may be used to trigger an uplink sounding signal by a group of users equipment (202-204)

Internet of Things: A Survey on Enabling Technologies, Protocols, and Applications

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.

Spatially Sparse Precoding in Millimeter Wave MIMO Systems

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.

Coverage and Rate Analysis for Millimeter-Wave Cellular Networks

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.

LTE-advanced: next-generation wireless broadband technology [Invited Paper]

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.

A Survey on Wireless Security: Technical Challenges, Recent Advances, and Future Trends

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.