Cable Implications

5G and Network Densification

The term “densification” refers to installation of more cellular antennas in a given geographic area. One example is the increasing use of small-cell technology with 4G mobile technology. The deployment of 5G networks will bring a new wave of mobile network densification, especially in urban areas. For some countries or some carriers, the total number of 4G cell sites is published. Dividing this number into the country’s square km of land area gives an indication of the average 4G cell-site radius for the entire country. For Japan, this average is about 0.8 km. For the US, it is 3.3 km, and for China it is 2.1 km. As noted, the average radius will be smaller in urban areas, and larger in rural areas.

The table shows the inter-site distance for 5G in different environments. This distance would be twice the radius. Even without knowing the distribution of urban and rural areas, the table suggests that the number of 5G sites will be a multiple of 4G sites. For urban areas, some carriers have estimated a multiple of 10, meaning that a 5G network will require 10 times more antennas than a 4G network. Looking at the range of densities in different countries, another estimate is that urban 5G networks may require 6 to 25 times more cell sites than 4G networks, depending on the country and city size.

Network Topology and Fibre Counts

A white paper published in late 2017 by the US Fiber Broadband Association concluded that 5G networks covering the US’s 25 largest metro areas would require 2.2 million km of optical cable, in terms of route-km. This conclusion was based on the assumption that cell-site spacing would be 750 feet (229 metres), and that this spacing is required throughout all 25 cities. The calculation also relies on assumptions about the cable architecture.

The association’s conclusion identifies the amount of cable needed to connect the cell sites, not the fibre-km. The 2.2 million km must be multiplied by an average fibre count to arrive at the fibre requirement. The average count over the entire cable plant should be at least six, and it more likely is in the range of 12 to 24, if not higher. This suggests a potential market for 24 million fibre-km, or more, to cover these 25 cities, based on the assumptions about density and cable architecture.

Cable Types

The 5G latency and capacity requirements suggest that fibre will be necessary for backhaul links. Backhaul speeds of 100 Gbps are likely, which are impossible with twisted pair copper. The backhaul link might be done with microwave or millimeter wave wireless systems, but this will necessitate frequency licenses and line-of-sight engineering. Most carriers have acknowledged that fibre is likely to be most effective for backhaul.

For the previous generations, most mobile network operators have used coaxial cable for fronthaul applications. In recent years, however, there have been advances in miniaturizing the digital-to-analog electronics so that some of the base station functions can be remoted to the radio head, and other functions can be hauled over fibre from further away. These developments mean that 5G cell sites may have new architectures – new approaches for optimizing the location of digital electronics and the radio heads. This in turn may mean that fibre can be used for both backhaul and fronthaul functions, along with conductors for powering the antennas. It also may mean that there will be increasing demand for hybrid cables, containing both fibres and conductors for power. Finally, the use of fibre on the towers also may lead some carriers or network-construction companies to consider bend-insensitive fibre in the cables, allowing for tighter bends and greater ease-of-handling.