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 (mmW) frequencies between 30 and 300 GHz are a new frontier for cellular communication that offers the promise of orders of magnitude greater bandwidths combined with further gains via beamforming and spatial multiplexing from multielement antenna arrays. This paper surveys measurements and capacity studies to assess this technology with a focus on small cell deployments in urban environments. The conclusions are extremely encouraging; measurements in New York City at 28 and 73 GHz demonstrate that, even in an urban canyon environment, significant non-line-of-sight (NLOS) outdoor, street-level coverage is possible up to approximately 200 m from a potential low-power microcell or picocell base station. In addition, based on statistical channel models from these measurements, it is shown that mmW systems can offer more than an order of magnitude increase in capacity over current state-of-the-art 4G cellular networks at current cell densities. Cellular systems, however, will need to be significantly redesigned to fully achieve these gains. Specifically, the requirement of highly directional and adaptive transmissions, directional isolation between links, and significant possibilities of outage have strong implications on multiple access, channel structure, synchronization, and receiver design. To address these challenges, the paper discusses how various technologies including adaptive beamforming, multihop relaying, heterogeneous network architectures, and carrier aggregation can be leveraged in the mmW context.

Millimeter-Wave Cellular Wireless Networks: Potentials and Challenges

Multiple transmit antennas in a downlink channel can provide tremendous capacity (i.e., multiplexing) gains, even when receivers have only single antennas. However, receiver and transmitter channel state information is generally required. In this correspondence, a system where each receiver has perfect channel knowledge, but the transmitter only receives quantized information regarding the channel instantiation is analyzed. The well-known zero-forcing transmission technique is considered, and simple expressions for the throughput degradation due to finite-rate feedback are derived. A key finding is that the feedback rate per mobile must be increased linearly with the signal-to-noise ratio (SNR) (in decibels) in order to achieve the full multiplexing gain. This is in sharp contrast to point-to-point multiple-input multiple-output (MIMO) systems, in which it is not necessary to increase the feedback rate as a function of the SNR

MIMO Broadcast Channels With Finite-Rate Feedback

There is considerable pressure to define the key requirements of 5G, develop 5G standards, and perform technology trials as quickly as possible. Normally, these activities are best done in series but there is a desire to complete these tasks in parallel so that commercial deployments of 5G can begin by 2020. 5G will not be an incremental improvement over its predecessors; it aims to be a revolutionary leap forward in terms of data rates, latency, massive connectivity, network reliability, and energy efficiency. These capabilities are targeted at realizing high-speed connectivity, the Internet of Things, augmented virtual reality, the tactile internet, and so on. The requirements of 5G are expected to be met by new spectrum in the microwave bands (3.3-4.2 GHz), and utilizing large bandwidths available in mm-wave bands, increasing spatial degrees of freedom via large antenna arrays and 3-D MIMO, network densification, and new waveforms that provide scalability and flexibility to meet the varying demands of 5G services. Unlike the one size fits all 4G core networks, the 5G core network must be flexible and adaptable and is expected to simultaneously provide optimized support for the diverse 5G use case categories. In this paper, we provide an overview of 5G research, standardization trials, and deployment challenges. Due to the enormous scope of 5G systems, it is necessary to provide some direction in a tutorial article, and in this overview, the focus is largely user centric, rather than device centric. In addition to surveying the state of play in the area, we identify leading technologies, evaluating their strengths and weaknesses, and outline the key challenges ahead, with research test beds delivering promising performance but pre-commercial trials lagging behind the desired 5G targets.

5G : A tutorial overview of standards, trials, challenges, deployment, and practice

This paper explores the addition of frequency-domain transmit antenna arrays to the cyclic-prefix CDMA (CP-CDMA) system concept. CP-CDMA is a novel type of single carrier DS-CDMA that employs OFDM-style cyclic prefixes to facilitate efficient frequency-domain receiver processing in broadband CDMA cellular systems. CP-CDMA is intended for high-bandwidth, high-delay-spread cellular channels, such as those envisioned for systems that evolve from current 3G CDMA standards. This paper examines both single-data stream (i.e., maximal ratio transmission) and multiple data stream (i.e., spatial multiplexing also known as multiple-input, multiple-output or MIMO) techniques for CP-CDMA systems that operate with high code usage and multi-level modulation in broadband high delay-spread channels. In the proposed algorithms, both the transmit and receive array processing is performed completely in the frequency-domain to allow the tracking of frequency-selective MIMO channels. Simulation results are presented to show the efficacy of the proposed methods.

https://ieeexplore.ieee.org/iel5/8066/22307/01040347.pdf

Transmit array processing for cyclic-prefix CDMA

A transmitter for implementing a stream transmission method is disclosed. Optionally, the transmitter first determines an equal weighting of a plurality of stream weights and transmits a plurality of transmission signals as a function of a plurality of data streams and the equal weighting of the plurality of stream weights. Thereafter, the transmitter reiterates as needed a determination of an unequal weighting of the plurality of stream weights and a transmission of the plurality of transmission signals as a function of the plurality of data streams and the unequal weighting of the plurality of stream weights.

Stream transmission method and device

Disclosed are a method, information processing system and wireless communications device for suppressing interference. The method includes receiving a transmission from each of a target ( 104 ) and interfering device ( 106 ). A set of pilot sequences ( 604 ) for an interfering device ( 106 ) and the target device ( 104 ) are determined. A channel estimate ( 608 ) for the target device ( 104 ) and the interfering device ( 106 ) is determined. A set of combining weights ( 610 ) associated with each pilot sequence for the interfering device ( 106 ) is determined as a function of the determined channel estimates ( 608 ) of the target device ( 104 ) and the interfering device ( 106 ). At least one pilot symbol estimate ( 612 ) for each pilot sequence in the set of pilot sequences for the interfering device is determined as a function of the received transmission and the determined set of combining weights ( 610 ).

Interference suppression for partial usage of subchannels uplink

It has been recognized that a primary method of further enhancing the spectral efficiency of LTE Release-8 is to improve support for multi-user (MU) MIMO transmission in the downlink in an efficient manner. This paper investigates the performance improvements due to the enhanced support of single-cell MUMIMO within the framework of LTE evolution (specifically LTE Release-9 and Release-10 also known as LTE-Advanced) considering a 4Tx-2Rx system. A realistic estimate of achievable MU-MIMO full-buffer throughput performance is provided with respect to variations in the propagation environment, feedback accuracy, antenna polarizations, antenna calibration as well as receiver type. It is observed that a closely spaced uniform linear array (ULA) at the base station and interference rejection capability at the mobile is essential to maximize MU-MIMO gains. Further, channel reciprocity based spatial channel feedback in a TDD scenario can provide significantly higher MU-MIMO throughput compared to codebook based feedback.

MU-MIMO system performance analysis in LTE evolution

Obtaining channel state information (CSI) at the base station in an OFDM system can significantly improve both the capacity and reliability of the downlink. However, this CSI will suffer from estimation error plus possible quantization error for certain feedback methods and will also become outdated because of time variations in the channel. If the channel variations are reasonably slow and the estimation (or quantization) errors are small, then per-subcarrier maximal ratio transmission (MRT) is the optimal single-stream beamforming technique (MRT is designed to match the instantaneous channel and hence is a short-term transmit beamformer). When the estimation (or quantization) error is high, then eigen beamforming (EBF) is typically better than MRT because it uses long-term statistics that can be estimated more accurately by averaging over many samples. In addition, if the channel variations are high, then EBF is typically better than MRT because again EBF is matched to the long-term channel statistics (e.g., channel covariance matrix) that do not change rapidly. Since MRT is better than EBF under some conditions and EBF is better than MRT in others, it may be necessary for the base to choose between the two. This paper introduces three methods to switch between MRT and EBF and shows through simulation results that the methods are fairly effective at choosing the best method under various channel conditions.

Timothy A. Thomas

Papers

Transmit array processing for cyclic-prefix CDMA

Stream transmission method and device

Interference suppression for partial usage of subchannels uplink

MU-MIMO system performance analysis in LTE evolution

Methods for Switching Between Long Term and Short Term Transmit Beamforming in OFDM