IEEE Wireless Communications • June 2010
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COORDINATED AND DISTRIBUTED MIMO
INTRODUCTION
In the Third Generation Partnership Project
(3GPP), the specifications for the Universal
Mobile Telecommunications System (UMTS)
Long-Term Evolution (LTE) called the evolved
universal terrestrial radio access (UTRA) and uni-
versal terrestrial radio access network (UTRAN)
were completed as Release 8 [1, 2]. Release 8
LTE supports only efficient packet-based radio
access and radio access networks that provide
Internet Protocol (IP)-based functionalities with
low latency and low cost. After the completion of
the specifications, commercial equipment is under
development aiming at the forthcoming launch of
broadband radio access services.
The principle behind international standard-
ization of International Mobile Telecommunica-
tion (IMT)-Advanced and the new spectra for
IMT were agreed upon at the Radiocommunica-
tion Assembly 2007 (RA ’07) and the World
Radiocommunication Conference 2007 (WRC
’07) in the International Telecommunication
Union — Radiocommunication Sector (ITU-R),
respectively [3]. With the circular letter (CL) to
invite proposals for IMT-Advanced radio inter-
face technologies as the motivation, the 3GPP
initiated a Study Item (SI, i.e., feasibility study)
for LTE-Advanced in March 2008. In the 3GPP,
LTE-Advanced represents LTE enhancement in
Release 10 and beyond. The system require-
ments for LTE-Advanced were agreed upon in
[4]. The technical components to achieve the
system requirements were discussed in the 3GPP,
and summarized in a technical report [5]. Based
on Release 8 LTE and agreements on LTE-
Advanced, the 3GPP submitted its final proposal
to the ITU-R as a complete submission in Octo-
ber 2009. Following the SI, Work Items (WIs,
i.e., specification work) for the LTE-Advanced
radio interface in Release 10 were initiated and
it is expected that the specifications will be com-
pleted according to the IMT-Advanced stan-
dardization schedule. In addition to multiple
access schemes, advanced multiple-input multi-
ple-output (MIMO) channel transmission tech-
niques and elaborate coordination among
multiple cell sites called coordinated multipoint
(CoMP) transmission/reception were adopted as
key techniques for LTE-Advanced at the Tech-
nical Specification Group — Radio Access Net-
work (TSG-RAN) Working Group 1 (WG1)
meeting in the 3GPP [5].
In this article we present the purpose for
CoMP based on the system requirements, and
actual CoMP transmission and reception
schemes for LTE-Advanced based on the discus-
sion in the 3GPP. In the rest of the article we
first address major radio access techniques
including intercell interference coordination
(ICIC) in the Release 8 LTE, which form the
basis for the radio interface for LTE-Advanced.
Then we explain the necessity for CoMP trans-
mission and reception to satisfy the system
requirements in terms of capacity and cell edge
user throughput through tighter intercell orthog-
onality as well as intracell orthogonality among
simultaneously accessing sets of user equipment
(UE) in LTE-Advanced. To achieve intercell
MAMORU SAWAHASHI, TOKYO CITY UNIVERSITY
YOSHIHISA KISHIYAMA, AKIHITO MORIMOTO, DAISUKE NISHIKAWA, AND MOTOHIRO TANNO,
NTT DOCOMO, I
NC.
ABSTRACT
This article presents an elaborate coordina-
tion technique among multiple cell sites called
coordinated multipoint transmission and recep-
tion in the Third Generation Partnership Project
for LTE-Advanced. After addressing major radio
access techniques in the LTE Release 8 specifica-
tions, system requirements and applied radio
access techniques that satisfy the requirements
for LTE-Advanced are described including
CoMP transmission and reception. Then CoMP
transmission and reception schemes and the
related radio interface, which were agreed upon
or are currently being discussed in the 3GPP, are
presented. Finally, system-level simulation evalu-
ations show that the CoMP transmission and
reception schemes have a significant effect in
terms of improving the cell edge user throughput
based on LTE-Advanced simulation conditions.
COORDINATED MULTIPOINT
TRANSMISSION/RECEPTION TECHNIQUES FOR
LTE-ADVANCED
The authors present
an elaborate
coordination
technique among
multiple cell sites
called coordinated
multi-point
transmission and
reception in the
3rd generation
partnership project
for LTE-Advanced.
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