|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)|
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.
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  and the first two OFDMA femtocell papers (both attracted > 20 citations) . 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) . Prof. Zhang and his colleagues have 7 femtocell publications that have attracted over 10 citations so far -. 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.,  .
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  and Eurasip JWCN  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 -. Apart from the more practical work on radio propagation algorithms as indicated in -, CWiND members also made contributions to the more theoretical aspects of FDTD.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
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).
Fig. 7 CWiND simulation platform structure
Fig. 8 Support of 3D GIS and building
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 . CWiND researchers carried out for the first time theoretical EESM (Exponential Effective SNR (Signal to Noise Ratio) Mapping) analysis . 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.
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))
Jie Zhang, Guillaume de la Roche, et al, “Femtocells – Technologies and Deployment”, Wiley, Jan. 2010.ISBN: 978-0470742983. [21 citations]
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]
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]
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]
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]
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]
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]
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]
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]
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
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]
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
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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
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
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]
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]
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]
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 8th IEEE ICTON, GRAAL Annual Conference, Vol. 3, pp. 253-257, June 2006, Nottingham, UK. [11 citations]
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]
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]
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]
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.
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.
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]