As wireless operators map their plans for 4G, one concept that is gaining substantial ground is the notion of heterogeneous networks. Current 2G/3G wireless networks are largely homogeneous and rely on network topology that is dominated by macro-cells. This type of network is ideal when coverage is the primary concern rather than spectral efficiency and capacity.
Mobile network operators are rolling out 4G networks in response to the tremendous increase in data demand brought forth by the explosion of data hungry devices and applications such as smart phones, tablets, and USB wireless modems. The shift towards a network topology that is more agile and closely aligned with network demand is an attractive proposition. This topology would include components of lower power such as indoor or outdoor pico-cells, femtocells and other small cells using a variety of technologies and bands. The key benefit is the increase in the spectral efficiency and capacity per unit area. This is ultimately achieved by increasing the number of cells in areas where demand justifies it. In fact, the value proposition of heterogeneous networks is entirely dependent on that very fact: where demand justifies it.
While macro-cell dominated networks are all about coverage and interference management, heterogeneous networks bring another critical component to the table: the expected demand. This component has a technical and economical implication. Indeed, standard macro-cells are not going to disappear anytime soon due to the need to offer coverage everywhere — a basic expectation of today's wireless consumer. This in turn leads to the need to carefully plan the interaction between cells of all types in a network irrespective of their power levels, locations, capacity, band and technology.
Like traditional networks, heterogeneous networks will continue to require careful radio network planning but some of the fundamentals of how this planning is done will change. A greater emphasis will be put on understanding indoor performance and areas of high demand as a mean to plan additional small cells that will offload capacity from the macro-cellular cells. When smaller cells are in the same band, as envisioned in LTE release 10, then interference mitigation will need to be considered both during planning and operation (i.e., SON). The economical dimension will have to be taken into account alongside the more traditional, but increasingly complex, technical dimension. As network demand rapidly evolves, network operators have to review and shorten their design cycle in order to be able to gain the most from a more agile network topology. A key aspect of this is a review of methods and procedures that will include increased utilization of automated solutions in order to minimize the level of effort required to manage a network where the number of cells is growing rapidly.
Heterogeneous networks provide an opportunity for deployment flexibility as well as increased capacity in the areas of high demand. As traffic demand continues to rise, along with the expectations of mobile consumers, the introduction of heterogeneous networks represents an attractive solution for meeting capacity and performance goals. Advanced network planning solutions are going to prove pivotal for operators to gain the agility required to extract all the benefits from such strategy.
