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.

Uplink Control Channel Design for 3GPP LTE

Abstract: Long term evolution (LTE) of the UMTS Terrestrial Radio Access and Radio Access Network is aimed for commercial deployment in 2010. Goals for the evolved system include support for improved system capacity and coverage, high peak data rates, low latency, reduced operating costs, multi-antenna support, flexible bandwidth operations and seamless integration with existing systems. To reach these goals, a new design for the air interface is currently being specified in the 3GPP standards body. The Uplink (UL) for LTE is based on Single Carrier Frequency Division Multiple Access. The UL control channel carries non-data associated control signaling like CQI, ACK/NACK, Scheduling request etc. To maintain the low PA power de-rating, the single carrier property of the UL has to be maintained. As such, special consideration should be given to the UL control channel design. This paper discusses in detail the LTE UL control channel design and its performance.

Rapid channel quality based power control for high speed channels

Abstract: A method (400) and apparatus (501) provide for rapid power control based on a quality related value, e.g. channel quality indicator (CQI) value. A transmit power level can be derived from a CQI value received according to a time period, e.g. corresponding to 500 Hz. A first predicted value can be predicted based on the CQI value, at a first time within the time period and a power adjustment value can be determined based on the CQI value as well as the first predicted value at a rate that exceeds the rate of receiving the CQI values. Note that other predicted values for or corresponding to the CQI value can be predicted at other times within the time period and that power adjustment values can be determined through interpolation between predicted values for any time within the period.

Allocating downlink acknowledgement resources in wireless communication networks

Abstract: A wireless communication system includes a scheduling entity that transmits scheduling messages to first and second wireless terminals having different scheduling characteristics, wherein each scheduling message includes a reference signal cyclic shift indicator and a resource assignment. The assignment of a downlink feedback resource to the first wireless terminal is indicated by the reference signal cyclic shift indicator in the corresponding scheduling message, and the assignment of a downlink feedback resource to the second wireless terminal is indicated by a corresponding resource assignment. The scheduling entity indicates a cyclic shift that the first wireless terminal should use for its reference signal transmission using the reference signal cyclic shift indicator.

Method and apparatus for providing channel quality and precoding metric feedback in an orthogonal frequency division multiplexing communication system

Abstract: An Orthogonal Frequency Division Multiplexing communication system (100), wherein a frequency bandwidth is divided into one or more Resource Blocks Groups (RBGs) each having one or more Resource Blocks, provides for feedback of channel quality information and precoding metrics for a same at least one RBG of the one or more RBGs. More particularly, a user equipment (102) measures one or more channel quality parameters associated with at least one RBG of the one or more RBGs, determines channel quality information and a precoding metric for an RBG of the at least one RBG, and reports the channel quality information and a precoding metric determined for the RBG to a radio access network (110). In one embodiment of the invention, the RBG whose channel quality information and precoding metric are reported may be selected from the at least one RBG based on the measured channel quality parameters.

Block puncturing for turbo code based incremental redundancy

Abstract: A method of block puncturing for turbo code based incremental redundancy includes a first step (1200) of coding an input data stream into systematic bits and parity bits. A next step (1202) includes loading the systematic bits and parity bits into respective systematic and parity block interleavers in a column-wise manner. A next step (1204) includes selecting a predefined redundancy. A next step (1206) includes outputting bits from the block interleavers in a row-wise manner in accordance with the selected predefined redundancy.

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.