When planning for mobile network and small cell deployments, mobile operators must have a clear plan. Without one, backhaul networks may create bottlenecks in the network, both from a roll-out and network capacity point of view.
Backhaul solutions must be considered in the early phase of a small cell project and should also influence the small cell site selection. Most small cell backhaul networks will have a mix of different backhaul solutions such as optical fiber and wireless backhaul, with both line-of-sight (LOS) and non-line-of-sight (NLOS) connections. Regardless, network planning is a crucial starting point, as there are many variables that must be accounted for, especially in dense urban areas. Additionally, mobile operators that plan small cell and backhaul effectively and early can reduce time-to-market and overall costs for the network roll-out.
So, where should mobile operators start? 3D maps can be used to visualize relevant parts of a city and better understand whether microwave links should provide backhaul for macro cells and small cells. Many mobile operators often find that combining this 3D building data with Google Maps or Bing Maps also provides a good understanding of the layout of dense urban areas. Accurate 3D building data, which can also be used in analyses and calculations, combined with input about structural features from Google and Bing Maps, means that mobile operators will be able to rely on the most detailed information possible in their network planning efforts.
As I described during a recent webinar, the number of small cells being deployed is growing exponentially, and will continue to do so, as this technology provides network capacity relief, helping improve the end user quality of experience (QoE) and reducing operating costs.
However, mobile operators can't just put a small cell on the top of every lamp post and expect flawless quality of service (QoS). They also need to take into account the proportional cost of backhauling small cells, which is typically higher than for macro cells. Thus, the biggest issue faced by mobile operators is determining how a small cell can be connected to the existing backhaul and connection points. Typically, the macro sites are on the top of tall buildings, while small cells are about five meters off the ground on lamp posts or other low structures. In cities, that often means that buildings block the direct LOS between the macro site and the small cell, and mobile operators cannot necessarily rely on traditional network planning methodologies.
Whether a connection has clear LOS, near line-of-sight (nLOS) or NLOS, microwave links in the frequency range 20-80 GHz can be used — that is, the V- and E-bands. These high frequency bands are pushed by some network equipment vendors such as Ericsson as a viable option to sub-6 GHz NLOS systems.
One solution to NLOS connections on high frequencies is to “bounce” the signal off a building via a reflection point. In this case, 3D maps are a crucial aspect of the network planning process, as they allow mobile operators to take a 360-degree look at potential reflection points to ensure they are clear of obstacles and at the correct height. Local context is also important — a glass building will serve as an excellent reflection point, whereas brick will scatter the signal. Due to high antenna gains and the short distances between cell sites in urban areas, it is possible to allow quite high signal loss and still obtain the required signal level to ensure optimal quality of service (QoS).
To learn more about small cell backhaul planning, especially for NLOS connections on higher frequencies, you can listen to a replay of the webinar here.