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.

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

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.

Spatially Sparse Precoding in Millimeter Wave MIMO Systems

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.

Coverage and Rate Analysis for Millimeter-Wave Cellular Networks

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.

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

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.

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

A wireless communication system as described here employs control signaling for contention-based uplink access from user equipment devices to a base station. Contention-based access configuration is performed via physical downlink control channel signaling. Configuration data sent to the user equipment devices identifies multiple contention-based access zones, along with minimum power headroom values for each contention-based access zone. A probability factor may also be used to lower collision possibility by influencing whether the user equipment devices perform contention-based uplink access. An uplink grant message can be used to acknowledge contention-based transmission; contention resolution is achieved implicitly via the uplink grant.

Method and apparatus for determining when to use contention-based access for transmitting data in a wireless network

Enhanced uplink technology is currently being considered for standardization in 3GPP W-CDMA (Release-6) with the standard scheduled for completion in the 4/sup th/ quarter of 2004. Enhanced uplink technology under consideration includes advanced techniques such as adaptive modulation and coding (AMC), hybrid ARQ (HARQ), fast rate control or fast scheduling by the node-B (base station), higher peak rates (up to 2 Mbps) and a reduced transition latency between CELL_DCH, CELL_FACH and CELL_PCH states. These techniques reduce overall delay, and increase throughput significantly compared to release-99/4/5 3GPP W-CDMA. In this paper, the physical layer aspects of enhanced uplink for 3GPP W-CDMA FDD are discussed in detail with accompanying link and system simulation results. These results show that the sector and user throughput of the enhanced uplink (EU) can be improved by more than 50% compared to release-99/4/5 3GPP W-CDMA.

Overview of enhanced uplink for 3GPP W-CDMA

In this paper, we investigate the performance of a quasi-static method used to predict link-level error performance in dynamic system simulations. Two flavors of the quasi-static approach are used to model the link characteristics: (a) static curves with fudge factors; and (b) short-term frame error curves. For the fudge factor based method, we examine the various factors (or penalties) required for the method to work properly, their limitations in capturing the various features of the high-speed packet data channel, and their effects on the overall accuracy of the technique. Here, we concentrate on three important penalties: puncturing penalty, Doppler penalty, and demapping penalty. The quasistatic method based on short-term frame error curves is used to generate frame erasures for voice and control channels associated with high-speed packet data channels. From simulation results, it is shown that both variations of the quasi-static method can provide accurate prediction of link-level performance at certain operating ranges, provided that the penalties are correctly obtained. At low frame error rates and moderate to high speeds, however, the quasi-static method often fails to accurately reflect frame error performance at the link level.

Quasi-static method for predicting link-level performance

A user equipment (102) and method for contention-based uplink access to a base station. Contention-based configuration data identifies multiple contention-based access zones along with minimum power headroom values for each contention-based access zone (602, 604). The user equipment compares available power headroom to the minimum power headroom values and identifies candidate contention-based resource zones (606). The user equipment selects one of the candidate contention-based resource zones for use (608).

Method and apparatus for using contention-based resource zones for transmitting data in a wireless network

Standardization work is nearly complete on long term evolution (LTE) of the UMTS Terrestrial Radio Access and Radio Access Network which 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 including state-of-art multi-antenna technology needs to be deployed. This paper provides a look at different multi-antenna schemes for LTE downlink and uplink. The paper also discusses various Node-B antenna configurations and summarizes the performance of different multi-antenna schemes under various scenarios.

Rapeepat Ratasuk

Papers

Method and apparatus for determining when to use contention-based access for transmitting data in a wireless network

Overview of enhanced uplink for 3GPP W-CDMA

Quasi-static method for predicting link-level performance

Method and apparatus for using contention-based resource zones for transmitting data in a wireless network

Multi-antenna system design for 3GPP LTE