14,229 research outputs found
Two-Layered Superposition of Broadcast/Multicast and Unicast Signals in Multiuser OFDMA Systems
We study optimal delivery strategies of one common and independent
messages from a source to multiple users in wireless environments. In
particular, two-layered superposition of broadcast/multicast and unicast
signals is considered in a downlink multiuser OFDMA system. In the literature
and industry, the two-layer superposition is often considered as a pragmatic
approach to make a compromise between the simple but suboptimal orthogonal
multiplexing (OM) and the optimal but complex fully-layered non-orthogonal
multiplexing. In this work, we show that only two-layers are necessary to
achieve the maximum sum-rate when the common message has higher priority than
the individual unicast messages, and OM cannot be sum-rate optimal in
general. We develop an algorithm that finds the optimal power allocation over
the two-layers and across the OFDMA radio resources in static channels and a
class of fading channels. Two main use-cases are considered: i) Multicast and
unicast multiplexing when users with uplink capabilities request both
common and independent messages, and ii) broadcast and unicast multiplexing
when the common message targets receive-only devices and users with uplink
capabilities additionally request independent messages. Finally, we develop a
transceiver design for broadcast/multicast and unicast superposition
transmission based on LTE-A-Pro physical layer and show with numerical
evaluations in mobile environments with multipath propagation that the capacity
improvements can be translated into significant practical performance gains
compared to the orthogonal schemes in the 3GPP specifications. We also analyze
the impact of real channel estimation and show that significant gains in terms
of spectral efficiency or coverage area are still available even with
estimation errors and imperfect interference cancellation for the two-layered
superposition system
Content-Specific Broadcast Cellular Networks based on User Demand Prediction: A Revenue Perspective
The Long Term Evolution (LTE) broadcast is a promising solution to cope with
exponentially increasing user traffic by broadcasting common user requests over
the same frequency channels. In this paper, we propose a novel network
framework provisioning broadcast and unicast services simultaneously. For each
serving file to users, a cellular base station determines either to broadcast
or unicast the file based on user demand prediction examining the file's
content specific characteristics such as: file size, delay tolerance, price
sensitivity. In a network operator's revenue maximization perspective while not
inflicting any user payoff degradation, we jointly optimize resource
allocation, pricing, and file scheduling. In accordance with the state of the
art LTE specifications, the proposed network demonstrates up to 32% increase in
revenue for a single cell and more than a 7-fold increase for a 7 cell
coordinated LTE broadcast network, compared to the conventional unicast
cellular networks.Comment: 6 pages; This paper will appear in the Proc. of IEEE WCNC 201
Control-data separation architecture for cellular radio access networks: a survey and outlook
Conventional cellular systems are designed to ensure ubiquitous coverage with an always present wireless channel irrespective of the spatial and temporal demand of service. This approach raises several problems due to the tight coupling between network and data access points, as well as the paradigm shift towards data-oriented services, heterogeneous deployments and network densification. A logical separation between control and data planes is seen as a promising solution that could overcome these issues, by providing data services under the umbrella of a coverage layer. This article presents a holistic survey of existing literature on the control-data separation architecture (CDSA) for cellular radio access networks. As a starting point, we discuss the fundamentals, concepts, and general structure of the CDSA. Then, we point out limitations of the conventional architecture in futuristic deployment scenarios. In addition, we present and critically discuss the work that has been done to investigate potential benefits of the CDSA, as well as its technical challenges and enabling technologies. Finally, an overview of standardisation proposals related to this research vision is provided
Achieving Large Multiplexing Gain in Distributed Antenna Systems via Cooperation with pCell Technology
In this paper we present pCellTM technology, the first commercial-grade
wireless system that employs cooperation between distributed transceiver
stations to create concurrent data links to multiple users in the same
spectrum. First we analyze the per-user signal-to-interference-plus-noise ratio
(SINR) employing a geometrical spatial channel model to define volumes in space
of coherent signal around user antennas (or personal cells, i.e., pCells). Then
we describe the system architecture consisting of a general-purpose-processor
(GPP) based software-defined radio (SDR) wireless platform implementing a
real-time LTE protocol stack to communicate with off-the-shelf LTE devices.
Finally we present experimental results demonstrating up to 16 concurrent
spatial channels for an aggregate average spectral efficiency of 59.3 bps/Hz in
the downlink and 27.5 bps/Hz in the uplink, providing data rates of 200 Mbps
downlink and 25 Mbps uplink in 5 MHz of TDD spectrum.Comment: IEEE Asilomar Conference on Signals, Systems, and Computers, Nov.
8-11th 2015, Pacific Grove, CA, US
V2X Meets NOMA: Non-Orthogonal Multiple Access for 5G Enabled Vehicular Networks
Benefited from the widely deployed infrastructure, the LTE network has
recently been considered as a promising candidate to support the
vehicle-to-everything (V2X) services. However, with a massive number of devices
accessing the V2X network in the future, the conventional OFDM-based LTE
network faces the congestion issues due to its low efficiency of orthogonal
access, resulting in significant access delay and posing a great challenge
especially to safety-critical applications. The non-orthogonal multiple access
(NOMA) technique has been well recognized as an effective solution for the
future 5G cellular networks to provide broadband communications and massive
connectivity. In this article, we investigate the applicability of NOMA in
supporting cellular V2X services to achieve low latency and high reliability.
Starting with a basic V2X unicast system, a novel NOMA-based scheme is proposed
to tackle the technical hurdles in designing high spectral efficient scheduling
and resource allocation schemes in the ultra dense topology. We then extend it
to a more general V2X broadcasting system. Other NOMA-based extended V2X
applications and some open issues are also discussed.Comment: Accepted by IEEE Wireless Communications Magazin
DyMo: Dynamic Monitoring of Large Scale LTE-Multicast Systems
LTE evolved Multimedia Broadcast/Multicast Service (eMBMS) is an attractive
solution for video delivery to very large groups in crowded venues. However,
deployment and management of eMBMS systems is challenging, due to the lack of
realtime feedback from the User Equipment (UEs). Therefore, we present the
Dynamic Monitoring (DyMo) system for low-overhead feedback collection. DyMo
leverages eMBMS for broadcasting Stochastic Group Instructions to all UEs.
These instructions indicate the reporting rates as a function of the observed
Quality of Service (QoS). This simple feedback mechanism collects very limited
QoS reports from the UEs. The reports are used for network optimization,
thereby ensuring high QoS to the UEs. We present the design aspects of DyMo and
evaluate its performance analytically and via extensive simulations.
Specifically, we show that DyMo infers the optimal eMBMS settings with
extremely low overhead, while meeting strict QoS requirements under different
UE mobility patterns and presence of network component failures. For instance,
DyMo can detect the eMBMS Signal-to-Noise Ratio (SNR) experienced by the 0.1%
percentile of the UEs with Root Mean Square Error (RMSE) of 0.05% with only 5
to 10 reports per second regardless of the number of UEs
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