Urban Dense Networks



Growing demand for mobile broadband

Mobile broadband usage has surged exponentially in the last few years. Some reports indicate that the global mobile data traffic more than doubled between 2015 and 2016. By 2022, the total mobile traffic is predicted to cross 70 exabytes (1 exa is sixth power of 1000(1018)) ) [1]. The rapid growth in the demand for broadband internet is fuelled by a substantial increase in the number of mobile subscribers using data-hungry applications.  Most of these mobile subscribers are located in the densely populated cities of the world. Catering to the rising demands of these urban subscribers has been a challenge for the mobile network operators as the infrastructure has almost hit a ceiling.

How are mobile signals transmitted

The most common way to transmit mobile signals is by using what are called ‘base stations’. There is a good chance that you have seen these base stations – they are the big tall towers erected in and around cities. These towers are powerful enough to transmit signals to large areas called ‘macro cells’. However, with more urban subscribers demanding large amounts of data in each cell,  base stations have reached their full capacity. Deploying additional infrastructure in the crowded cities has also been a challenge due to logistical constraints.

Small is beautiful

One way to address this is to shrink both the cell and the node that serves it. We can have a number of small nodes each serving a relatively smaller geographical area called a ‘small cell’. Such nodes are so small in size that they can be attached to a light pole, and if required, deployed indoors too. Interestingly, in urban areas, it turns out that a number of small cells deliver better reception and capacity than a single macro cell. But the real advantage of small cells lies in the ease of deployment – when compared to macro cells, it’s much easier to set and scale up small cell infrastructure.

There are other options too. Instead of deploying small cells, one can shrink the macro cells to a certain extent, depending on cell site availability and acquisitions. One more option is to use a mix of macro and small cells – have small cells in highly crowded  areas like stadia, and retain macro cells elsewhere.  

Supporting the new network

The mobile infrastructure in cities require macro and small cells to work in tandem. Features like Coordinated Multi Point (CoMP), Inter Cell Interference Coordination (ICIC), and Dual Connectivity ensure seamless coordination among the cells. Since these features demand cells to be ‘in touch’ with each other, they require inter-cell backhaul connectivity. Though it is possible, at least in principle, to connect cell-sites by optical fiber and copper cables, the realities of a busy city force the operators to look elsewhere

lThe wireless backhaul

To overcome the limitations of physical connectivity in backhaul, the mobile network operators are looking at wireless options. Certain bands in high frequency millimeter wave spectrum are considered to be very good for high capacity backhaul needs. Moreover, in many countries these bands are unlicensed and light licensed. The availability of large bandwidths in these bands – 7 GHz to 10 GHz – make them ideal candidates for providing multi gigabit capacity wirelessly. Of course, millimeter wave based backhaul products might well enable the network operators to cash in on the exciting opportunities right in front of them.

 

[1] https://www.ericsson.com/en/mobility-report/latest-mobile-statistics

 

Posted by: Sanjeev Shankar,Madhukara Putty