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EditorialAdvanced MIMO Techniques in the Heterogeneous
Networks
Xiang Zhang,1 Lin Zhang,2 Guangyue Lu,3 Xiaoli Chu,4 and Yulong
Zou5
1 Beijing Key Lab of New Generation Broadband Wireless Mobile
Communication Technology, Standard andVerification, China Academy
of Telecommunication Research of MIIT (CATR), Beijing 100191,
China
2 Faculty Development Center, Beijing University of Posts and
Telecommunications (BUPT), Beijing 100876, China3 School of
Telecommunications and Information Engineering, Xi’an University of
Posts and Telecommunications, Xi’an 710121, China4The
Communications Group, Department of Electronic and Electrical
Engineering, University of Sheffield, Mappin Street,Sheffield S1
3JD, UK
5McGill University, 3480 Rue University, Montreal, Canada H3A
0E9
Correspondence should be addressed to Xiang Zhang;
[email protected]
Received 3 August 2014; Accepted 3 August 2014; Published 12
August 2014
Copyright © 2014 Xiang Zhang et al. This is an open access
article distributed under the Creative Commons Attribution
License,which permits unrestricted use, distribution, and
reproduction in any medium, provided the original work is properly
cited.
Since the first commercial long term evolution (LTE) wasdeployed
in South Korea, 300 operators have commerciallylaunched LTE
networks in 107 countries reported by theglobal mobile suppliers
association. At least 20% of networkoperators are investing to
deploy LTE-Advanced techniques.The downlink throughput for
LTE-Advanced category 6(CAT6) user equipment (UE) is 300Mbps.
However, with thedevelopment of mobile internet service, the peak
rate andspectrum efficiency of the cellular network need to be
furtherenhanced. Multiple input multiple output (MIMO)
andheterogeneous network (HetNets) are adopted in LTE and thefifth
generation (5G) system to improve user experience. Byemploying
multiple antennas in both base station (BS) andUE, a new space
domain is introduced inMIMOarchitecture.Multiantenna precoding and
receiving can achieve array gainand diversity gain. As the spectral
efficiency in a singlelink between the BS and UE approaches
theoretical limits,the demand of mobile traffic data requires
increasing thenode density to further improve cell capacity.
Therefore,heterogeneous network performance optimization is of
greatimportance in the wireless network, especially for scenario
ofMIMO technique in the heterogeneous network.
To fully realize the potential of advanced antenna tech-nologies
and to solve the problems of heterogeneous net-work performance
optimization, this special issue aims toattract the attention of
investigators to contribute original
research articles. We have received a total of 11
submissions,out of which 9 papers were accepted for publication
afterpeer reviewing. The accepted papers cover a broad area
ofadvanced MIMO topics.
Different from the traditional wireless network, whichonly uses
macrocell to provide outdoor coverage, plentyof small cells are
adopted in the LTE-A and 5G stage toenhance the data rate in the
hot spot area. Therefore manualoptimization is not very efficient.
One potential solution toaddress these issues is to introduce the
extensively attractedself-organizing network (SON).There are three
papers in thisspecial issue focusing on SON technology.The paper
entitled“Capacity analysis and optimization in heterogeneous
networkwith adaptive cell range control” by X. Gu et al. proposedan
adaptive cell specific offset updating algorithm. System-level
simulations results indicate that the proposed algorithmcan ensure
a nearly optimal performance in all tested trafficload situations.
The paper entitled “Cell outage detection andcompensation in
two-tier heterogeneous networks” by W. Xueet al. developed a cell
outage detection and compensationmethods in two-tier HetNets where
macrocell and picocellscoexisted. In the paper “Advanced load
balancing based onnetwork flow approach in LTE-A heterogeneous
network,” Dr.S. Jia et al. first evaluated the negative impact of
unbalancedload among cells through the Markova model. Then,
theyproposed a novel algorithm named optimal solution-based
Hindawi Publishing CorporationInternational Journal of Antennas
and PropagationVolume 2014, Article ID 193954, 2
pageshttp://dx.doi.org/10.1155/2014/193954
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2 International Journal of Antennas and Propagation
load balancing. System-level simulation shows that the pro-posed
scheme can provide up to 20% gain in load distributionindex.
Due to deployment of small cell in HetNets, macro celland small
cell may be overlapped in some scenario. There-fore, interference
cancellation needs to be well investigated.The paper entitled “High
energy efficient heterogeneous net-works: cooperative and cognitive
techniques” by H. Wanget al. introduced both the cooperative
communication andcognitive radio techniques to mitigate the
interference inHetNet, while the authors of the paper entitled
“Coordinatedbeamforming with altruistic precoding and user
selection forMU-MIMO system” proposed an altruistic
precodingmethodto minimize the sum of interference. Furthermore,
the lowerbound of the capacity and local optimal solution for
multicelluser selection problem were also discussed.
In the paper entitled “Performance analysis of jointbase-station
multiantenna multibeam and channel assignmentscheme for
hierarchical cellular system,” P. Yang et al. intro-duced a joint
base-station multiantenna multibeam andchannel assignment scheme
for hierarchical cellular. Multi-beam base-station antenna
splitting and dynamic channelallocation scheme are studied.
Full duplexing mode is a hot topic recently because ofits
potential use in 5G. The paper entitled “Full-duplex modein
amplify-and-forward relay channels: outage probability andergodic
capacity” by R. Hu et al. investigated the outageprobability and
ergodic capacity performances for full-duplexmode in two-way
amplify-and-forward relay channel scenar-ios.
In the paper entitled “Model of handover and trafficbased on
cellular geometry with smart antenna,” the authorsdiscussed the
impact of the width of the smart antenna beamsin terms of dwell
time and traffic performance.
The paper entitled “Miniaturization design for 8 × 8
Butlermatrix based on back-to-back bilayer microstrip” by Y. Zhai
etal. presented a low-cost compact 8 × 8 Butler matrix basedon a
novel bilayer microstrip configuration. Some measuredresults were
also shown in this paper.
Acknowledgment
Before the end of this editorial, we would like to thank
theanonymous reviewers for their great efforts in reviewing
thesubmitted papers, without which this special issue would nothave
been published as scheduled.
Xiang ZhangLin Zhang
Guangyue LuXiaoli ChuYulong Zou
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