Relaying Operation in
3GPP LTE: Challenges
and Solutions
報 告 者 ： 謝 子健
班 級 ： 碩 研 資管一 甲
學 號 ： MA490215
課 程 ： 南 台 資管 所 無 線 網 路 與 行動計 算
授 課 老 師 ： 陳偉業 教 授
Christian Hoymann, Ericsson Research Wanshi Chen and Juan Montojo, Qualcomm Inc.
Alexander Golitschek, Panasonic R&D Center
Chrysostomos Koutsimanis, Ericsson Research
Xiaodong Shen, China Mobile Research Institute
IEEE LTE-A 4G Conference, 2012
OUTLINE
◦ ABSTRACT
◦ INTRODUCTION
◦ RELAY DEPLOYMENT EXAMPLE
◦ E-UTRA
◦ CHALLENGES AND REQUIREMENTS
◦ SIMMULATION ASSUMPTIONS
◦ CONCLUSION
◦ REFERRENCE
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Abstract
Growing demand of data applications, traditional cellular networks face the
challenges of providing enhanced system capacity, extended cell coverage, and
improved minimum throughput in a cost-effective manner.
Wireless relay stations, especially when operating in a half-duplex operation,
make it possible without incurring high site acquisition and backhaul costs.
Design of wireless relay stations faces the challenges of providing backward
compatibility, minimizing complexity, and maximizing efficiency.
Provides an overview of the challenges and solutions in the design of relay
stations for 3GPP LTE advanced.
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Introduction
Recent advancements in wide area cellular networks provide high data rates for a variety of scenarios not
relying on the availability of wireless local area access networks or wired connectivity.
Mobile broadband networks deployments span scenarios from very dense urban areas to remote rural
areas, operating in a large range of carrier frequencies with different propagation characteristics and
different coverage levels.
Therefore, the ability to deploy network nodes not relying on a wired backhaul is an appealing option to
reduce total network deployment cost and operating costs.
The article is organized as follows:
◦ We present various types of relays that were discussed as part of the LTE-Advanced study.
◦ Challenges and requirements for LTE relaying are provided.
◦ Detailed solutions for LTE relaying are given, focusing on architecture and protocols, and physical and medium access
control (MAC) layer aspects, respectively.
◦ Simulation results are shown demonstrating the benefits of relaying operation.
◦ Future trends are briefly discussed. Finally, conclusions are drawn.
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Relay deployment example
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Type of Relays
Amplify-and-forward relays, or repeaters, amplify and forward the received analog signals.
Repeaters are transparent to both the UE and the eNB. Since a repeater amplifies whatever it
receives, including noise and interference, it is mainly useful in high signal-to-noise ratio (SNR)
environments.
Decode-and-forward relays decode and reencode the received signal prior to forwarding it to
the receiver. Since this class of relays does not amplify noise and interference, they are also
useful in low-SNR environments. Separate rate adaptation and scheduling for the backhaul and
access links is possible. If two or more RNs per DeNB are spatially separated, radio resources on
the access link can be reused, which paves the way to increased system capacity. However, the
decode-and-forward operation implies a larger delay than for a simple repeater.
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E-UTRAN architecture including relay
nodes
MME/S-GW
Mobility
Management
Entity/Serving
Gateway
E-UTRAN
evolved UMTS
Terrestrial Radio
Access
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CHALLENGES AND REQUIREMENTS
◦ A major challenge for the manufacturing and deployment of RNs is cost efficiency.
◦ RNs should have an advantage in operational and/or capital expenditure over the
installation of a full-fledged eNB.
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Relay DL blackhaul design
In Fig. 3, the DL data channel is
denoted physical DL shared
channel (PDSCH), and R-PDCCH
denotes the new relay physical
downlink control channel.
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Simmulation assumptions
This section discusses
performance results of an
urban cellular LTE network
with non-uniform user
distribution.
Two different outdoor
relay deployments are
considered: random
deployment and planned
deployment.
The number of RNs per
DeNB is 0, 2, and 4. More
detailed parameters are
given in Table 1.
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UL user throughput
Figure 4 shows the cumulative
distribution functions (CDFs) of the
UL user throughput for the five
different cases (0, 2, 4 relays per cell
and planned/random deployment).
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UL cell-edge user throughput vs. traffic
demand
Figure 5 shows the cell edge and
mean UL user throughput as a
function of the traffic load. For a
given traffic load, the results show
that randomly deployed relays
improve the cell edge throughput
only at low loads. However,
planned relays can greatly
improve cell edge throughput
even at high loads.
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Conclusion
Wireless relay stations in 3GPP LTE, especially when operating in half-duplex operation, make it
possible to achieve enhanced system capacity, extended cell coverage, and improved minimum
throughput.
Non-transparent half-duplex in band relays are fully backward compatible, and are deemed an
efficient, effective, and practical means to complement the existing cellular networks.
Non-transparent half-duplex relaying operation in 3GPP LTE imposes great design challenges
stemming from the support of legacy LTE UEs, and maximizing the reuse of the existing LTE
physical layer, MAC layer, and upper layer standards.
Simulations show promising gains in certain relay scenarios, most notably when the RNs are
placed close to the UE in a hotspot fashion.
The key to relay gains is a significant increase of the quality of the access and backhaul links
compared to the direct link, especially when proper deployment of relays is possible and
sophisticated cell selection is used.
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REFERENCE
iEEE Library
◦ http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=6146495&tag=1
3GPP
◦ http://www.3gpp.org/technologies/keywords-acronyms/97-lte -advanced
EUTRAN
◦ https://zh.wikipedia.org/wiki/E-UTRA
Medium Access Control
◦ http://www.erg.abdn.ac.uk/users/gorry/course/lan-pages/mac.html
OTHER
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THE END
THANKS FOR YOUR ATTENTION !
Questions?
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