Wireless Communications

What will 5G be? What it will not be is an incremental advance on 4G. The previous four generations of cellular technology have each been a major paradigm shift that has broken backward compatibility. Indeed, 5G will need to be a paradigm shift that includes very high carrier frequencies with massive bandwidths, extreme base station and device densities, and unprecedented numbers of antennas. However, unlike the previous four generations, it will also be highly integrative: tying any new 5G air interface and spectrum together with LTE and WiFi to provide universal high-rate coverage and a seamless user experience. To support this, the core network will also have to reach unprecedented levels of flexibility and intelligence, spectrum regulation will need to be rethought and improved, and energy and cost efficiencies will become even more critical considerations. This paper discusses all of these topics, identifying key challenges for future research and preliminary 5G standardization activities, while providing a comprehensive overview of the current literature, and in particular of the papers appearing in this special issue.

What Will 5G Be

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

The vision of next generation 5G wireless communications lies in providing very high data rates (typically of Gbps order), extremely low latency, manifold increase in base station capacity, and significant improvement in users’ perceived quality of service (QoS), compared to current 4G LTE networks. Ever increasing proliferation of smart devices, introduction of new emerging multimedia applications, together with an exponential rise in wireless data (multimedia) demand and usage is already creating a significant burden on existing cellular networks. 5G wireless systems, with improved data rates, capacity, latency, and QoS are expected to be the panacea of most of the current cellular networks’ problems. In this survey, we make an exhaustive review of wireless evolution toward 5G networks. We first discuss the new architectural changes associated with the radio access network (RAN) design, including air interfaces, smart antennas, cloud and heterogeneous RAN. Subsequently, we make an in-depth survey of underlying novel mm-wave physical layer technologies, encompassing new channel model estimation, directional antenna design, beamforming algorithms, and massive MIMO technologies. Next, the details of MAC layer protocols and multiplexing schemes needed to efficiently support this new physical layer are discussed. We also look into the killer applications, considered as the major driving force behind 5G. In order to understand the improved user experience, we provide highlights of new QoS, QoE, and SON features associated with the 5G evolution. For alleviating the increased network energy consumption and operating expenditure, we make a detail review on energy awareness and cost efficiency. As understanding the current status of 5G implementation is important for its eventual commercialization, we also discuss relevant field trials, drive tests, and simulation experiments. Finally, we point out major existing research issues and identify possible future research directions.

Next Generation 5G Wireless Networks: A Comprehensive Survey

An apparatus and method to feedforward non-quantized precoding weights in an OFDM communication system includes a first step ( 300 ) of sending feedback information from a subscriber station (SS) to a base station (BS). A next step ( 302 ) includes deriving non-quantized weight information from the feedback information. A next step ( 304 ) includes transmitting symbols carrying the non-quantized weight information and non-precoded pilot symbols by the BS. A next step ( 305 ) includes receiving the information and symbols by the SS. A next step ( 306 ) includes estimating the non-quantized weights from the symbols carrying the non-quantized weight information and the non-precoded pilot symbols by the SS. A next step ( 308 ) includes decoding data from the BS by the SS using the estimated non-quantized weight information.

Feedforward of non-quantized precoding weights in a wireless communications system

Third generation wireless communication systems, such as High Rate Packet Data (HRPD-A), also known as 1xEV-DO Revision A, and High Speed Downlink/Uplink Packet Access (HSDPA/HSUPA) have been standardized to support high-speed data and Internet access in cellular systems. Advanced techniques such as adaptive modulation and coding, Hybrid ARQ (H-ARQ), fast scheduling and a de- centralized architecture have been included in these systems to achieve high peak data rate and significantly higher sector and user throughput. It is shown that approximately 35-40 Erlangs could be supported with a delay bound of around 250 msec for mobile-to-mobile call for HRPD-A and around 90- 100 Erlangs for HSDPA/HSUPA combination with a similar delay bound of HRPD-A.

Voice over IP (VOIP) over cellular: HRPD-A and HSDPA/HSUPA

A method for blindly detecting a precoding matrix index used to transmit a data or control signal is provided. The method includes receiving at a mobile station (102) a common reference signal and user specific data and control signal weighted by precoding matrix. An objective function is applied to the received reference signal and user specific data and control signal that minimizes the objective function for each of at least one rank used to transmit the received user specific data and control signal and each of known possible modulation constellations used to transmit the received data/control signal to determine the precoding matrix index (PMI).

Method for blindly detecting a precoding matrix index

In a network, where a packet is to be transmitted on a channel to a communication device with a time offset between a shared control channel and a shared data channel, the packets can be ordered (401). A margin can be determined (403) between a power need of a data channel of a packet and a total available transmit power of the network infrastructure device. Scheduling packets (405) is responsive to the margin, and determines the next packet to be sent, where the control channel of the next packet has a power need less than the powe margin (407). Resources are allocated (409) responsive to the margin to further determine the subsequent packet. The subsequent pack is transmitted (411) on the channel, wherein the data channel of the current packet and the control channel of the subsequent packet are at least partially contemporaneous.

Downlink resource allocation for time offset downlink packets

Long-term evolution (LTE) of the UMTS network provides 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 achieve these enhancements, a new design for the air interface including state-of-art multi-antenna technology was developed. This article describes multi-antenna schemes for UMTS LTE and provides system performance of different multi-antenna schemes under various scenarios.

Amitava Ghosh

Papers

Feedforward of non-quantized precoding weights in a wireless communications system

Voice over IP (VOIP) over cellular: HRPD-A and HSDPA/HSUPA

Method for blindly detecting a precoding matrix index

Downlink resource allocation for time offset downlink packets

Multi-Antenna Systems for LTE eNodeB