624 research outputs found
Optimal Precoders for Tracking the AoD and AoA of a mm-Wave Path
In millimeter-wave channels, most of the received energy is carried by a few
paths. Traditional precoders sweep the angle-of-departure (AoD) and
angle-of-arrival (AoA) space with directional precoders to identify directions
with largest power. Such precoders are heuristic and lead to sub-optimal
AoD/AoA estimation. We derive optimal precoders, minimizing the Cram\'{e}r-Rao
bound (CRB) of the AoD/AoA, assuming a fully digital architecture at the
transmitter and spatial filtering of a single path. The precoders are found by
solving a suitable convex optimization problem. We demonstrate that the
accuracy can be improved by at least a factor of two over traditional
precoders, and show that there is an optimal number of distinct precoders
beyond which the CRB does not improve.Comment: Resubmission to IEEE Trans. on Signal Processing. 12 pages and 9
figure
Distributed Radar-aided Vehicle-to-Vehicle Communication
Establishing high-rate vehicle-to-vehicle (V2V) linkswith narrow beamwidth is challenging due to the varying networktopology. A too narrow beam may miss the intended receiver,while a too broad beam leads to SNR loss. We propose toharness the high accuracy of radar detections to establish V2V links. In particular, we develop a distributed method where eachvehicle associates local radar detections with GPS informationcommunicated by nearby vehicles. The method relies on thetransformation of relative to global coordinates, the definition ofa suitable metric, and solving an optimal assignment problem. Wedemonstrate that the proposed approach avoids time-consumingchannel estimation and provides high SNR, under the conditionthat reliable relative and absolute location information is present
MAC Aspects of Millimeter-Wave Cellular Networks
The current demands for extremely high data rate wireless services and the spectrum scarcity at the sub-6 GHz bands are forcefully motivating the use of the millimeter-wave (mmWave) frequencies. MmWave communications are characterized by severe attenuation, sparse-scattering environment, large bandwidth, high penetration loss, beamforming with massive antenna arrays, and possible noise-limited operation. These characteristics imply a major difference with respect to legacy communication technologies, primarily designed for the sub-6 GHz bands, and are posing major design challenges on medium access control (MAC) layer. This book chapter discusses key MAC layer issues at the initial access and mobility management (e.g., synchronization, random access, and handover) as well as resource allocation (interference management, scheduling, and association). The chapter provides an integrated view on MAC layer issues for cellular networks and reviews the main challenges and trade-offs and the state-of-the-art proposals to address them
Millimeter-wave Wireless LAN and its Extension toward 5G Heterogeneous Networks
Millimeter-wave (mmw) frequency bands, especially 60 GHz unlicensed band, are
considered as a promising solution for gigabit short range wireless
communication systems. IEEE standard 802.11ad, also known as WiGig, is
standardized for the usage of the 60 GHz unlicensed band for wireless local
area networks (WLANs). By using this mmw WLAN, multi-Gbps rate can be achieved
to support bandwidth-intensive multimedia applications. Exhaustive search along
with beamforming (BF) is usually used to overcome 60 GHz channel propagation
loss and accomplish data transmissions in such mmw WLANs. Because of its short
range transmission with a high susceptibility to path blocking, multiple number
of mmw access points (APs) should be used to fully cover a typical target
environment for future high capacity multi-Gbps WLANs. Therefore, coordination
among mmw APs is highly needed to overcome packet collisions resulting from
un-coordinated exhaustive search BF and to increase the total capacity of mmw
WLANs. In this paper, we firstly give the current status of mmw WLANs with our
developed WiGig AP prototype. Then, we highlight the great need for coordinated
transmissions among mmw APs as a key enabler for future high capacity mmw
WLANs. Two different types of coordinated mmw WLAN architecture are introduced.
One is the distributed antenna type architecture to realize centralized
coordination, while the other is an autonomous coordination with the assistance
of legacy Wi-Fi signaling. Moreover, two heterogeneous network (HetNet)
architectures are also introduced to efficiently extend the coordinated mmw
WLANs to be used for future 5th Generation (5G) cellular networks.Comment: 18 pages, 24 figures, accepted, invited paper
Cloud Cooperated Heterogeneous Cellular Networks for Delayed Offloading using Millimeter Wave Gates
Increasing the capacity of wireless cellular network is one of the major challenges for the coming years. A lot of research works have been done to exploit the ultra-wide band of millimeter wave (mmWave) and integrate it into future cellular networks. In this paper, to efficiently utilize the mmWave band while reducing the total deployment cost, we propose to deploy the mmWave access in the form of ultra-high capacity mmWave gates distributed in the coverage area of the macro basestation (Macro BS). Delayed offloading is also proposed to proficiently exploit the gates and relax the demand of deploying a large number of them. Furthermore, a mobility-aware weighted proportional fair (WPF) user scheduling is proposed to maximize the intra-gate offloading efficiency while maintaining the long-term offloading fairness among the users inside the gate. To efficiently link the mmWave gates with the Macro BS in a unified cellular network structure, a cloud cooperated heterogeneous cellular network (CC-HetNet) is proposed. In which, the gates and the Macro BS are linked to the centralized radio access network (C-RAN) via high-speed backhaul links. Using the concept of control/user (C/U) plane splitting, signaling information is sent to the UEs through the wide coverage Macro BS, and most of users’ delayed traffic is offloaded through the ultra-high capacity mmWave gates. An enhanced access network discovery and selection function (eANDSF) based on a network wide proportional fair criterion is proposed to discover and select an optimal mmWave gate to associate a user with delayed traffic. It is interesting to find out that a mmWave gate consisting of only 4 mmWave access points (APs) can offload up to 70 GB of delayed traffic within 25 sec, which reduces the energy consumption of a user equipment (UE) by 99.6 % compared to the case of only using Macro BS without gate offloading. Also, more than a double increase in total gates offloaded bytes is obtained using the proposed eANDSF over using the conventional ANDSF proposed by 3GPP due to the optimality in selecting the associating gate.
WiFi Assisted Multi-WiGig AP Coordination for Future Multi-Gbps WLANs
Wireless Gigabit (WiGig) access points (APs) using 60 GHz unlicensed
frequency band are considered as key enablers for future Gbps wireless local
area networks (WLANs). Exhaustive search analog beamforming (BF) is mainly used
with WiGig transmissions to overcome channel propagation loss and accomplish
high rate data transmissions. Due to its short range transmission with high
susceptibility to path blocking, a multiple number of WiGig APs should be
installed to fully cover a typical target environment. Therefore, coordination
among the installed APs is highly needed for enabling WiGig concurrent
transmissions while overcoming packet collisions and reducing interference,
which highly increases the total throughput of WiGig WLANs. In this paper, we
propose a comprehensive architecture for coordinated WiGig WLANs. The proposed
WiGig WLAN is based on a tight coordination between the 5 GHz (WiFi) and the 60
GHz (WiGig) unlicensed frequency bands. By which, the wide coverage WiFi band
is used to do the signaling required for organizing WiGig concurrent data
transmissions using control/user (C/U) plane splitting. To reduce interference
to existing WiGig data links while doing BF, a novel location based BF
mechanism is also proposed based on WiFi fingerprinting. The proposed
coordinated WiGig WLAN highly outperforms conventional un-coordinated one in
terms of total throughput, average packet delay and packet dropping rate.Comment: 6 pages, 8 Figures, IEEE International Symposium on Personal Indoor
and Mobile Radio Communications (PIMRC) 201
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