Wireless Communications Research Group
Heterogeneous Cellular Networks
As the wireless data traffic continues to increase as well as the way we use the cellular network changes towards multimedia applications, cellular system development has reached practical limits in many densely populated scenarios. This change has led cellular operators to opt for increased heterogenity in the design of cellular networks to improve spectral efficiency and traffic offloading. As radio link improvements such as coding, adaptive transmission and communication over multiple antennas are reaching their theoretical limits, there is a shift from centrally planned tower mounted base stations (BS) called macro BS to multiple smaller tiers inside the macro tier. This new paradigm is known as Heterogeneous cellular networks.
As depicted in the figure above, the typical heterogeneous cellular network consists of planned macro base station deployments whic transmit at high power with overlaid smaller cells such as micros, picos and femtos. These smaller cells are low powered and are deployed to eliminate coverage gaps in the indoor and outdoor environments. Smaller cells also help to increase the capacity and spectral efficiency as well as offloading cellular traffic from the macro cell. Pico cells are typically deployed by cellular operators in scenarios which are likely to have high number of users (traffic), whereas femtocells are unplanned and are privately maintained by the cell owner. They are connected through the main network via an internet backhaul link.
The group is investigating several challanges which can arise when small cells are deployed in heterogeneous cellular networks. As small cells are are co-channeled (i.e., they transmit at the same carrier frequency as the macrocell), they introduce co-channel (intercell) interference in addition to the interference coming from out of the cell. We are also investigating the interaction between different components of hetrogeneous cellular network and how this leads to the promised gains in the spectral efficiency and capacity.
Some Key Papers:
- A. Ghosh, N. Mangalvedhe, R. Ratasuk, B. Mondal, M. Cudak, E. Visotsky, T. A. Thomas, J. G. Andrews, P. Xia, H. S. Jo, H. S. Dhillon and T. D. Novlan, "Heterogeneous Cellular Networks: From Theory to Practice", IEEE Communications Magazine June 2012, Vol. 12.
- A. Damnajanovic, J. Montojo, Y. Wei, T. Ji, T. Luo, M. Vajapeyam, T. Yoo, O. Song and D. Malladi, "A Survey on 3GPP Heterogeneous Networks", IEEE Communications Magazine June 2011, Vol. 11.
- J. G. Andrews, "Interference Cancellation for Cellular Systems: A Contemporary Overview", IEEE Communications Magazine, April 2005, Vol. 05.
- J. G. Andrews, H. Claussen, M. Dohler, S. Rangan and M. C. Reed, "Femtocells: Past, Present, and Future", IEEE Journal on Selected Areas in Communications, Vol. 30, No. 3, April 2012.
- M. Haenggi, J. G. Andrews, F. Baccelli, O. Dousse and M. Franceschetti, "Stochastic Geometry and Random Graphs for the Analysis and Design of Wireless Networks", (Invited Paper) IEEE Journal on Selected Areas in Communications, Vol. 27, No. 7, 2009.
- H. S. Dhillon, R. K. Ganti, F. Baccelli and J. G. Andrews, "Modelling and Analysis of K - Tier Downlink Heterogeneous Cellular Networks", IEEE Journal on Selected Areas in Communications, Vol. 30, No. 3, April 2012.
- P. Dmochowski, P. Smith and M. Shafi, "Capacity Analysis for Closed and Open Access Femto Cell Networks", in Proc. 23rd IEEE International Symposium on Personal, Indoor and Mobile Radio Communications (PIMRC), September 2012, pp. 1722-1727.
- P. Dmochowski, P. Smith, M. Shafi, J. Andrews, R. Mehta, "Interference Models for Heterogenous Sources", in Proc. IEEE International Conference on Communications (ICC), June 2012, pp. 4049-4054.