First tier of co-channel base stations

Consider a cellular system that uses a 7-cell hexagonal reuse cluster. The base stations employ 120ı wide-beam directional antennas and they all have the same antenna height and transmit with the same power level. Consider the forward channel (base-to-mobile). Ignore shadowing and envelope fading and consider only the path loss. A mobile station will experience the lowest co-channel interference ratio, , when it is located in the corner of a cell.

(a) Considering only the first tier of co-channel base stations, what is the worst case with a path loss exponent of 4?

(b) Considering the first two tiers of co-channel base stations, what is the worst case with path loss exponent of 4?

(c) From parts a) and b) what conclusions can you make about the effect of the second-tier co-channel base stations?

(d) What happens if the path loss exponent is equal to 3?

Solution: