The
CWiND
team
in
The
Communications
Research
Group
(CRG,
www.shef.ac.uk/eee/research/cr), the EEE Dept (www.sheffield.ac.uk/eee), the University of
Sheffield (www.sheffield.ac.uk)
1. Overview of CWiND (Centre for Wireless Network Design, www.cwind.org ) Research
The CWiND team (transferred from the University of Bedfordshire) at the CRG is a well known and
world leading research group in radio propagation, radio access network (RAN) planning and
optimisation (P&O), femtocell, and indoor wireless network P&O.
CWiND (www.cwind.org ) was founded by Prof. Jie Zhang in 2006.
Since 2003, the CWiND members have been awarded over 20 projects by the EPSRC, the European
Commission FP6/FP7 and the industry etc worth over £4.0 million to the team. These projects are
centred on new radio propagation models, UMTS/HSPA/LTE/WiMAX simulation, planning and
optimization (including self-optimisation), radio resource management (RRM), indoor wireless
network design and femtocells. Since 2006, in these areas, CWiND members have published over 40
papers in journals such as IEEE Trans on Wireless Communications/Communications/Antenna &
Propagation/Microwave Theory and Techniques/Vehicular Technology, IEEE JSAC/Com.
Mag./Network/Com. Lett/Signal Proc. Lett., IET Communications, and Wireless Networks, and some
60 papers in conferences. Since 2006, CWiND has sustained a team comprising of 15-25 postdoctoral
RFs/PhD students, many of whom had worked with Ericsson, Nokia, Vodafone, China Telecom,
Nortel, Telefornica R&D etc before joining CWiND.
2. Femtocell (small cell) research
The CWiND team is a world leading academic research group in femtocell (or small cell) research. It
is one of the three groups in the world whose work in femtocell is most widely cited. CWiND
members did some pioneering work on OFDMA femtocell simulation, interference avoidance, access
control methods, self-organisation and mobility management. He and his colleagues were awarded
the first EPSRC-funded project on femtocells (also possibly the earliest research council funded
femtocell project in Europe), authored the first technical book on femtocells: “Femtocells –
Technologies and Deployment” (Wiley, Jan. 2010) that has attracted over 20 citations so far [1] and
the first two OFDMA femtocell papers (both attracted > 20 citations) [2][3]. They also published
one of the most widely cited papers on femtocells (> 50 citations so far) – "OFDMA femtocells: A
roadmap on interference avoidance" (IEEE Communications Magazine, Sept. 2009) [4]. Prof. Zhang
and his colleagues have 7 femtocell publications that have attracted over 10 citations so far [1]-[7]. In
the last few years, CWiND researchers have also carried out a great deal of studies in heterogeneous
LTE access networks that comprise of macrocells, microcells, femtocells and relays, e.g., [10] .
3. Radio Propagation Research
The CWiND team is one of the leading European academic research groups in radio propagation
modelling. Since 2006, the CWiND members developed both empirical and deterministic propagation
models based on FDTD and 3D ray tracing/launching for indoor, outdoor, indoor to outdoor, and
outdoor to indoor scenarios. CWiND is one of the first groups (if not the first) that applied general
purpose graphic processing unit (GPU) to speed up FDTD computation. The papers on the application
of GPU for FDTD in IEEE ICCS 2008 [11] and Eurasip JWCN [5] have been widely cited. It is also
one of the testimonies listed by NVIDIA in its website. In addition, Grid-enabled 3D ray
tracing/launching algorithms are also developed, which also represent one of the earliest Grid-enabled
radio propagation algorithms (if not the earliest). These models are important to study heterogeneous
LTE access networks that involve both indoor and outdoor scenarios. CWiND members have
published extensively in this topic [11]-[22]. Apart from the more practical work on radio propagation
algorithms as indicated in [11]-[22], CWiND members also made contributions to the more
theoretical aspects of FDTD[23][24].They carried out extensive MIMO channel measurement
campaigns in indoor, indoor to outdoor and outdoor to indoor scenarios, including probably the
world’s first MIMO channel measurement campaigns in typical European residential areas.
In the following, some radio propagation prediction results in outdoor, indoor, indoor to outdoor and
outdoor to indoor scenarios based on both FDTD and 3D ray tracing/launching are shown in Figures
1-6.
Fig. 1 Outdoor 2D FDTD
Fig. 2 Outdoor 3D ray tracing/launching in
3D GIS to show best servers
Fig. 3 Indoor to outdoor 2D FDTD
Fig. 4 Indoor 3D ray tracing/launching
Fig. 5 Outdoor to indoor 3D ray tracing + 2D FDPF
Fig. 6 Indoor to outdoor 3D ray
tracing/launching
4. CWiND UMTS//HSPA/LTE/WiMAX simulation platform (CWiND simulator)
Over the last few years, CWiND members developed a UMTS/HSPA/LTE/WiMAX simulation
platform (CWiND simulator), which has over a quarter million lines of codes mainly written in C++
and is one of the most powerful system level simulators (SLSs) that are developed by a university
group. As shown in Fig. 7, its general features are as follows:

It supports heterogeneous radio access technologies (RATs) such as WCDMA/HSPA/LTE
/WiMAX and heterogeneous access points e.g., NB/HNB, eNB/HeNB, i.e., both macrocell and
femtocells.

It supports antenna formats from various manufacturers. It is linked to various radio propagation
models, such as empirical (e.g., COST231-Hata) and deterministic models based on FDTD and
3D ray tracing and launching algorithms. In addition, channel measurement data can be input to
the simulator to carry out propagation model tuning and validation.

It supports both outdoor full 3D GIS (3D view & operation, etc) and indoor 3D building data (Fig
8). Its 3D outdoor and indoor capability makes it well suited to evaluate adaptive spatial
multiplexing as well as transmit diversity of MIMO and make it well suited to study femto/macro
scenarios. In addition, traffic maps are supported on top of GIS.

It has a good GUI (CWiND Core) to support user interactions with the simulator. Unlike the radio
propagation and simulation modules, the CWiND core is developed in Matlab. Apart from the
GUI, users can also write Matlab M files to interact with the simulator. Such a design facilitates
both computational efficiency and easy use.

It supports both static Monte Carlo and dynamic simulation; hence, RRM (Radio Resource
Management) and MM (Mobility Management) can be well studied.

It outputs various system performance metrics (e.g., throughput, connection rate, outage
probability, handover success rate, etc.) and problem states such as frequency collision, pilot
pollution, etc., in graphs and tables.

It supports parallel and distributed computing (e.g., Grid computing), various computational
intensive modules such as radio propagation, simulation and optimisation can be done in parallel
computers or the Grid (it evolved to cloud computing).
Data
Resource
XML
Propagation
Model
Prediction
CWiND
Core
API
for
propagation
API
for
prediction
model
WiMAX
API for Network
UMTS/HSPA
API for Network
LTE/LTE-A
API for Network
Fig. 7 CWiND simulation platform structure
Fig. 8 Support of 3D GIS and building
5. CWiND Research in RAN P&O
CWiND members have done a great deal of research in UMTS/HSPA/LTE/WiMAX RAN P&O,
self-organising network (SON), radio resource management etc, e.g., analysis
[25][26][27][28][29][30][31]. CWiND researchers carried out for the first time theoretical EESM
(Exponential Effective SNR (Signal to Noise Ratio) Mapping) analysis [32][33][34]. This result is
important in the context of 4G mobile communications that are multi-carrier systems as EESM is
widely used to obtain effective SNR used for link adaptation in such systems.
6. Current Research Interests and Collaborations
Our current main research interests include: femtocell, indoor and indoor <=> outdoor radio
propagation modelling, indoor wireless network planning and optimisation, SON, CoMP,
heterogeneous networks (macrocell, femtocell and relay), ICT for energy, smart building, smart city
and smart grids.
We are interested in working with industrial and academic groups from the UK, Europe and the
rest of the world to apply for funding from UK research councils, EU FP7 and other sources. Please
feel free to contact us if you think we can contribute to your applications.
Selected publications (number of citations were checked at the end of Feb. 2011))
[1] Jie Zhang, Guillaume de la Roche, et al, “Femtocells – Technologies and Deployment”, Wiley, Jan.
2010.ISBN: 978-0470742983. [21 citations]
[2] D. López Pérez, A. Valcarce, G. De La Roche, J. Zhang, “Access Methods to WiMAX Femtocells: A
downlink system-level case study,” in IEEE ICCS (International Conference on Communication
Systems), Guangzhou, China, November 2008. [20 citations]
[3] D. López-Pérez, G. De La Roche, A. Valcarce, A. Jüttner, J. Zhang, “Interference Avoidance and
Dynamic Frequency Planning for WiMAX Femtocells Networks,” IEEE ICCS (International
Conference on Communication Systems), Guangzhou, China, November 2008. [24 citations]
[4] D. Lopez, A. Valcarce, G. De La Roche and J. Zhang, "OFDMA femtocells: A roadmap on
interference avoidance," IEEE Communications Magazine, vol. 47, no 9, pp. 41 - 48, Sept. 2009.
(ranked in 47 of top 100 documents accessed in IEEExplore in Oct. 2009. Widely regarded as the
ground breaking work on interference avoidance in OFDMA based (e.g., LTE and WiMAX)
femtocells). [52 citations]
[5] A. Valcarce, G. De La Roche, A. Juttner, D. Lopez, and J. Zhang, "Applying FDTD to the coverage
prediction of WiMAX femtocells," in Eurasip Journal of Wireless Communications and Networking,
Feb. 2009, Article ID 308606. [27 citations]
[6] G. De La Roche, A. Valcarce, D. López-Pérez and J. Zhang, "Access Control Mechanisms for
Femtocells," IEEE Communications Magazine, vol. 48, no 1, pp. 33 - 39, Jan. 2010. [14 citations]
[7] D. López-Pérez, A. Jüttner and J. Zhang, "OFDMA femtocells: A self-organizing approach for
frequency assignment," in IEEE PIMRC (Personal, Indoor and Mobile Radio Communications),
Tokyo, Japan, September 2009. [12 citations]
[8] Valcarce, D. López Pérez, G. De La Roche and J. Zhang, "Limited Access to OFDMA femtocells," in
IEEE PIMRC (Personal, Indoor and Mobile Radio Communications), Tokyo, Japan, September 2009.
[9 citations]
[9] D. Lopez-Perez, A. Ladanyi, G. de La Roche, and J. Zhang. “Intracell Handover for Interference and
Handover Mitigation in OFDMA Two-Tier Networks,” EURASIP Journal of Wireless
Communications and Networking. Special issue on Femtocells, March 2010. [5 citations]
[10] F. Gordejuela-Sanchez and J. Zhang, “Planning and optimization of multihop relaying networks,” in
Evolved Cellular Network Planning and Optimisation for UMTS and LTE, L. Song and J. Shen Ed.
CRC Press, Taylor & Francis Group, Aug. 2010. ISBN-13: 978-1439806494
[11] A. Valcarce, G. De La Roche, J. Zhang. “A GPU approach to FDTD for Radio Coverage Prediction,”
in IEEE International Conference on Communication Systems (ICCS), Guangzhou, China, November
2008. [11 citations]
[12] Alvaro Valcarce and Jie Zhang, "Empirical Indoor-to-Outdoor propagation model for residential areas
at (0.9 - 3.5) GHz," IEEE Antennas and Wireless Propagation Letters, vol. 9, pp. 682 – 685, Jul. 2010
[13] G. de la Roche, P. Flipo, Z. Lai, G. Villemaud, J. Zhang, and J-M. Gorce. “Implementation and
Validation of a New Combined Model for Outdoor to Indoor Radio Coverage Predictions,” EURASIP
Journal on Wireless Communications and Networking, Article ID 215352, 2010.
[14] D. Umansky, G. De La Roche, Z. Lai, G. Villemaud, J-M. Gorce and J. Zhang, “A New Deterministic
Hybrid Model for Indoor-to-Outdoor Radio Coverage Prediction,” The Fifth European Conference on
Antennas and Propagation, EuCap, IEEE, Rome, Italy, April 11-15, 2011.
[15] G. De La Roche, D. Umansky, Z. Lai, G. Villemaud, J-M. Gorce and J. Zhang, “Antenna Height
Compensation for an Indoor to Outdoor Channel model based on a 2D Finite Difference Model,” 29th
Progress In Electromagnetics Research Symposium (PIERS), Marrakesh, Morocco, March 2011.
[16] Z. Lai, N. Bessis, G. de la Roche, P. Kuonen, J. Zhang, and G. Clapworthy, “The Characterization and
Human-Body Influence on Indoor 3.525 GHz Path Loss Measurement,” In International Workshop on
Planning and Optimization of Wireless Communication Networks (IEEE WCNC2010 Workshop),
Sydney, Australia, April 2010.
[17] G. de la Roche, P. Flipo, Z. Lai, G. Villemaud, J. Zhang, and J-M Gorce, “Combination of Geometric
and Finite Difference Models for Radio Wave Propagation in Outdoor to Indoor Scenarios,” In
European Conference on Antennas and Propagation (EuCAP 2010), Barcelona, Spain, April 2010.
[18] Z. Lai, N. Bessis, G. de la Roche, P. Kuonen, J. Zhang, and G. Clapworthy, “On the use of an
Intelligent Ray Launching for Indoor Scenarios,” In European Conference on Antennas and
Propagation (EuCAP 2010), Barcelona, Spain, April 2010.
[19] G. de la Roche, P. Flipo, Z. Lai, G. Villemaud, J. Zhang, and J-M Gorce, “Combined Model for
Outdoor to Indoor Radio Propagation,” In COST2100 Management Meeting, TD(10)10045, Athens,
Greece, February 2010.
[20] Z. Lai, N. Bessis, G. de la Roche, P. Kuonen, J. Zhang, and G. Clapworthy, “A New Approach to Solve
Angular Dispersion of Discrete Ray Launching for Urban Scenarios,” In Loughborough Antennas and
Propagation Conference (LAPC 2009), Loughborough, UK, November 2009.
[21] G. de la Roche, J-M. Gorce and J. Zhang, "Optimized implementation of the 3D MR-FDPF method for
Indoor radio propagation predictions," in 3rd European Conference on Antennas and Propagation
(EuCAP 2009 ), Berlin, Germany, March 2009.
[22] Z. Lai, N. Bessis, G. de la Roche, H. Song, J. Zhang and G. Clapworthy, "An Intelligent Ray
Launching for Urban Propagation Prediction," in 3rd European Conference on Antennas and
Propagation (EuCAP 2009), Berlin, Germany, March 2009.
[23] A. Valcarce, H. Song and J. Zhang, "Characterization of the Numerical Group Velocity in Yee’s FDTD
Grid," IEEE Transactions on Antennas and Propagation, Vol. 58, no. 12, Dec. 2010, pp. 3974 - 3982
[24] A. Valcarce, H. Song and J. Zhang. “On the design of dispersion-robust pulsed sources for wideband
finite-difference time-domain electromagnetic simulations.” IEEE Transactions on Microwave Theory
and Techniques, vol. 58, no. 11, 2838 – 2849, Nov. 2010
[25] R. Kwan, C. Leung, and J. Zhang, "Multiuser Scheduling on the Downlink of an LTE Cellular
System," Research Letters in Communications, vol. 2008, Article ID 323048, 4 pages, 2008.
doi:10.1155/2008/323048. [20 citations]
[26] J. Yang, M. Aydin, J. Zhang, C. Maple, "UMTS Base Station Location Planning: a Mathematical
Model and Heuristic Optimisation Algorithms,” IET Communications, October 2007, vol. 1 (5),
pp.1007-1014. [14 citations]
[27] L. Zhao, J. Zhang, and H. Zhang, “Using Incompletely Cooperative Game Theory in Wireless Mesh
Networks,” IEEE Network, vol. 22 (1), pp. 39-44, 2008. [11 citations]
[28] J. Zhang, J. Yang, M. E. Aydin and J. Wu, “Mathematical Modelling and Comparisons of Four
Heuristic Optimization Algorithms for WCDMA Radio Network Planning,” Proc. of 8 th IEEE ICTON,
GRAAL Annual Conference, Vol. 3, pp. 253-257, June 2006, Nottingham, UK. [11 citations]
[29] R. Kwan, M. E. Aydin, C. Leung, J. Zhang, " Multiuser Scheduling in HSDPA," IET Communications,
vol. 3, no. 8 , pp. 1363-1370, Aug. 2009 [8 citations]
[30] R. Kwan, C. Leung, J. Zhang, "Proportional Fair Multiuser Scheduling in LTE,” IEEE Signal
Processing Letters, vol. 16, no. 6, pp. 461-464, June 2009. [7 citations]
[31] F. Gordejuela-Sanchez, A. Juttner and J. Zhang, “A multiobjective optimization framework for IEEE
802.16e network design and performance analysis,” IEEE Journal on Selected Areas in
Communications (J-SAC), vol. 27, no. 2, pp. 202-216, February 2009 special issue on Broadband
Access Networks. [3 citations]
[32] H. Song, R. Kwan and J. Zhang, " Approximations of EESM Effective SNR Distribution," IEEE
Transactions on Communications, vol. 59, no. 2, pp. 603-612, Feb. 2011.
[33] H. Song, R. Kwan and J. Zhang, "General Results on SNR Statistics involving EESM-based Frequency
Selective Feedbacks," IEEE Transactions on Wireless Communications, vol. 9, no. 5, pp. 1790 – 1798,
May 2010.
[34] H. Song, R. Kwan, J. Zhang, "On statistical characterization of EESM effective SNR over frequency
selective channels," IEEE Transactions on Wireless Communications, vol.8, no. 8, pp. 3955-3960,
Aug. 2009. [4 citations]