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

Systems and methodologies are described that facilitate supporting multiple access modes for a base station in a wireless communication environment. The base station can leverage hybrid, closed, or open access mode. A whitelist of a mobile device that successfully registers on the base station can be selectively updated to include a CSG ID of the base station (708). For example, the CSG ID of the base station can be added to the whitelist when the base station operates in closed access mode, while adding the CSG ID can be skipped when the base station operates in hybrid access mode. According to another example, the CSG ID can be selectively added based upon a received accept cause value. Additionally or alternatively, a CSG ID and an access mode indicator can be transmitted from a base station to a network node for implementing access control and/or paging optimization at the network node.

Support for multiple access modes for home base stations

Certain aspects of the present disclosure provide methods and apparatus for implementing Automatic Neighbor Relation (ANR) functions for relay nodes (RNs), home base stations (eg, home evolved Node Bs (HeNBs), and related entities (eg, donor evolved Node Bs (DeNBs) and HeNB gateways) X2 is designed to be an end-to-end protocol between two evolved Node Bs (eNBs) However, for the case of RNs or HeNBs, this protocol may involve a proxy function (eg, where the DeNB acts a proxy for the RN) This creates several issues, such as how to manage a potentially very large set of cells under a gateway and how to route S1 messages used for X2 endpoint discovery Therefore, certain aspects of the present disclosure generally relate to methods and apparatus for maintaining the X2 connections intelligently and hiding the large number of nodes from the X2 endpoints based on various triggers

Automatic neighbor relation (anr) functions for relay nodes, home base stations, and related entities

In this paper, we present a practical UMTS-WLAN interworking architecture based on 3GPP standards, and propose a seamless handoff scheme that guarantees low delay and low packet loss during UMTS-WLAN handoff. For low handoff delay, the proposed handoff scheme performs pre-registration and pre-authentication processes before the layer 2 handoff. Moreover, it uses packet buffering and forwarding functions in order to reduce packet loss during the handoff period. Numerical and simulation results show that the proposed scheme performs well with respect to signaling cost, handoff delay, and packet loss compared with conventional schemes.

A seamless handoff scheme for UMTS-WLAN interworking

A method and an apparatus for adaptively transmitting and receiving channel quality information of each AMC sub-band in application of an AMC technology in a broadband OFDM-based system are provided A speed status of the UE is determined, a determination is made based on a determined speed status whether to receive the channel quality information of the UE, a channel quality information transmission mode is reported to indicate a type of the channel quality information, to the UE when it is determined to receive the channel quality information of the UE The channel quality information is received from the UE according to the channel quality information transmission mode and radio resources are allocated to the UE in consideration of the received channel quality information

Method and apparatus for transmitting/receiving channel quality information in a wireless communication system

A seamless handoff system and method reduces delay and packet loss during handoff of user equipment (UE) from a Wireless Local Area Network (WLAN) network to a Universal Mobile Telecommunication System (UMTS) network. The handoff system and method performs pre-registration and pre-authentication processes before the occurrence of a handoff, buffers packets being delivered to a UE during a handoff period, and forwards the buffered packets to the UE after completion of the handoff, thereby reducing packet loss that can occur during handoff.

Osok Song

Papers

Support for multiple access modes for home base stations

Automatic neighbor relation (anr) functions for relay nodes, home base stations, and related entities

A seamless handoff scheme for UMTS-WLAN interworking

Method and apparatus for transmitting/receiving channel quality information in a wireless communication system

System and method for seamless handoff of wlan-umts interworking