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

Driven by the visions of Internet of Things and 5G communications, recent years have seen a paradigm shift in mobile computing, from the centralized mobile cloud computing toward mobile edge computing (MEC). The main feature of MEC is to push mobile computing, network control and storage to the network edges (e.g., base stations and access points) so as to enable computation-intensive and latency-critical applications at the resource-limited mobile devices. MEC promises dramatic reduction in latency and mobile energy consumption, tackling the key challenges for materializing 5G vision. The promised gains of MEC have motivated extensive efforts in both academia and industry on developing the technology. A main thrust of MEC research is to seamlessly merge the two disciplines of wireless communications and mobile computing, resulting in a wide-range of new designs ranging from techniques for computation offloading to network architectures. This paper provides a comprehensive survey of the state-of-the-art MEC research with a focus on joint radio-and-computational resource management. We also discuss a set of issues, challenges, and future research directions for MEC research, including MEC system deployment, cache-enabled MEC, mobility management for MEC, green MEC, as well as privacy-aware MEC. Advancements in these directions will facilitate the transformation of MEC from theory to practice. Finally, we introduce recent standardization efforts on MEC as well as some typical MEC application scenarios.

A Survey on Mobile Edge Computing: The Communication Perspective

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

Driven by the visions of Internet of Things and 5G communications, recent years have seen a paradigm shift in mobile computing, from the centralized Mobile Cloud Computing towards Mobile Edge Computing (MEC). The main feature of MEC is to push mobile computing, network control and storage to the network edges (e.g., base stations and access points) so as to enable computation-intensive and latency-critical applications at the resource-limited mobile devices. MEC promises dramatic reduction in latency and mobile energy consumption, tackling the key challenges for materializing 5G vision. The promised gains of MEC have motivated extensive efforts in both academia and industry on developing the technology. A main thrust of MEC research is to seamlessly merge the two disciplines of wireless communications and mobile computing, resulting in a wide-range of new designs ranging from techniques for computation offloading to network architectures. This paper provides a comprehensive survey of the state-of-the-art MEC research with a focus on joint radio-and-computational resource management. We also present a research outlook consisting of a set of promising directions for MEC research, including MEC system deployment, cache-enabled MEC, mobility management for MEC, green MEC, as well as privacy-aware MEC. Advancements in these directions will facilitate the transformation of MEC from theory to practice. Finally, we introduce recent standardization efforts on MEC as well as some typical MEC application scenarios.

This article explores network densification as the key mechanism for wireless evolution over the next decade. Network densification includes densification over space (e.g, dense deployment of small cells) and frequency (utilizing larger portions of radio spectrum in diverse bands). Large-scale cost-effective spatial densification is facilitated by self-organizing networks and intercell interference management. Full benefits of network densification can be realized only if it is complemented by backhaul densification, and advanced receivers capable of interference cancellation.

Network densification: the dominant theme for wireless evolution into 5G

As the spectral efficiency of a point-to-point link in cellular networks approaches its theoretical limits, with the forecasted explosion of data traffic, there is a need for an increase in the node density to further improve network capacity. However, in already dense deployments in today's networks, cell splitting gains can be severely limited by high inter-cell interference. Moreover, high capital expenditure cost associated with high power macro nodes further limits viability of such an approach. This article discusses the need for an alternative strategy, where low power nodes are overlaid within a macro network, creating what is referred to as a heterogeneous network. We survey current state of the art in heterogeneous deployments and focus on 3GPP LTE air interface to describe future trends. A high-level overview of the 3GPP LTE air interface, network nodes, and spectrum allocation options is provided, along with the enabling mechanisms for heterogeneous deployments. Interference management techniques that are critical for LTE heterogeneous deployments are discussed in greater detail. Cell range expansion, enabled through cell biasing and adaptive resource partitioning, is seen as an effective method to balance the load among the nodes in the network and improve overall trunking efficiency. An interference cancellation receiver plays a crucial role in ensuring acquisition of weak cells and reliability of control and data reception in the presence of legacy signals.

A survey on 3GPP heterogeneous networks

Systems and methodologies are described that facilitate distributing and/or utilizing a Closed Subscriber Group (CSG) Identifier (ID) that identifies a CSG corresponding to a base station and a CSG indication that distinguishes between the base station permitting access to members of the CSG and permitting access to members and non-members of the CSG For instance, the CSG ID can uniquely identify the CSG corresponding to the base station A mobile device can receive the CSG ID and the CSG indication from the base station Further, the received CSG ID can be compared to CSG IDs included in an allowed CSG list to recognize whether the mobile device is a member or a non-member of the CSG Moreover, a preference for selecting the base station as compared to a disparate base station can be generated as a function of the received CSG ID and CSG indication

Registration and access control in femto cell deployments

Local breakout is provided by one or more nodes (e.g., a local access point and/or a local gateway) in a wireless network to facilitate access to one or more local services. In conjunction with local breakout, multiple IP points of presence relating to different levels of service may be provided for an access point. For example, one point of presence may relate to a local service while another point of presence may relate to a core network service. IP point of presence may be identified for an over-the-air packet to indicate a termination point for the packet. Also, different mobility management functionality may be provided at different nodes in a system whereby mobility management for a given node may be provided by a different node for different types of traffic. Thus, an access terminal may support multiple NAS instances. In addition, different types of paging may be provided for different types of traffic. Furthermore, messages associated with one protocol may be carried over another protocol to reduce complexity in the system.

Providing multiple levels of service for wireless communication

A method and terminal apparatus for transmitting a status report comprising a received status of packet data in a mobile communication system are provided, in which whether transmission of an implicit Negative Acknowledge (NACK) signal is required for requesting retransmission of at least one non-received data packet whose sequence number is unidentified is determined, if transmission of the implicit NACK signal is required , the implicit NACK signal including a sequence number of the last packet is generated among successfully received data packets, and a status report including the implicit NACK signal is transmitted to the transmitter, and if transmission of the implicit NACK signal is not required, a status report is transmitted to the transmitter including at least one of an ACK signal comprising a sequence number of a successfully received data packet and an explicit NACK signal comprising a sequence number of a non-received data packet whose sequence number is identified.

Method and apparatus for transmitting and receiving status report comprising received status of packet data in a mobile communication system

Systems, methodologies, and devices are described that manage employment of network (NW)-initiated resource allocation and user equipment (UE)-initiated resource allocation for a UE. To employ NW-initiated resource allocation, a core network can transmit an indicator to the UE indicating that Policy and Charging Control (PCC) is supported by a network associated with the UE. The UE receives the indicator and other information, such as indicator regarding whether the current access network supports NW-initiated resource allocation and whether the current application prefers NW-initiated resource allocation, determines that NW-initiated resource allocation is to be employed, and the core network initiates resource allocation for the UE. If any indicator is not received by the UE, or the UE receives an indicator that indicates PCC is not supported or not preferred, the UE determines that UE-initiated resource allocation is to be employed, and transmits a request for resource allocation to the core network.

Osok Song

Papers

A survey on 3GPP heterogeneous networks

Registration and access control in femto cell deployments

Providing multiple levels of service for wireless communication

Method and apparatus for transmitting and receiving status report comprising received status of packet data in a mobile communication system

Managing network-initiated quality of service setup in mobile device and network