(7.3) Where L represents the path loss between the sender and the receiver. Using a logarithmic representation of Eq. (7.3) leads further to Eq. (7.4): 20 log(f) + (7.4) Using the equations listed above we attempt to derive some useful rules of thumb. 7.4 Deployment Considerations Assuming a certain constant maximum allowed path loss L, we are interested in calculat- ing the maximum distance between the sender and the receiver, depending on the carrier frequency. Using Eq. (7.3) we arrive at Eq. (7.5): (7.5) Where the term c can be regarded as a constant K. This shows that the maximum distance d, between sender and receiver is indirectly pro- portional to the carrier frequency. In other words, doubling the carrier frequency from f to 2f reduces the maximum distance by a factor of 2. However, in order to use the above result for actual deployments and the related cost analysis, we need a more important parameter, which is the related number of base stations or RUs required to cover a certain area. For reasons of simplicity, we assume a perfect circular coverage by a base station (even though in practice most deployments today use three-sector base stations). The coverage area can be calculated by: Where r represents the radius. Inserting d from Eq. (7.4) into the formula for the area of a circle leads to Eq. (7.6): Acircle = (7.6) Where the constant K and It have been combined to create a new constant K1 = K2. From Eq. (7.6), we further deduce that the coverage area is indirectly proportional to the square of the carrier frequency. In other words, doubling the carrier frequency from f to 2f, decreases the coverage area by a factor of 4, which means that for the case of deploying a technology on the double carrier frequency, four times more NG-RAN base station sites are needed. This is of course nothing more than a back-of-the-envelope cal- culation, but it does illustrate the network densification problem mentioned in previous chapters. Another interesting aspect is the question about the actual loss or gain in dB