e hopping sequence number (HSN) is the parameter that differentiates the hopping algorithm between two cells having the same MAList. There exist 64 possible HSNs (0 is cyclic and 1 to 63 random). The principle of SFH (spreading of interference) is assured via the HSN. Two cells having the same MAList and different HSNs hop differently; they may at a single moment use the same frequency, but shortly after those two cells will camp on different frequencies. In the case of the 1/1 model, since all three sectors use the same MAList, three different HSNs should be attributed per site, whereas with the 1/3 model the same HSN can be used for all cells with the condition that sectors are synchronised. Some simulation results have shown that according to the hopping algorithm, behind each HSN value some pairs of HSNs produce a higher probability of interference than others. Table 2.21(a) and (b) give the probability values for the best and worst performing pairs of the HSN. MAIO Planning The mobile allocation identity offset (MAIO) is the parameter that allows two TRXs belonging to the same cell (with the same MAList and the same HSN) to traffic on different frequencies at each moment. In fact MAIO is the step between the positions of the first TRX and the second TRX of the initial frequency in the hopping list. For a MAList with N frequencies, MAIO can take values of 0 to N - 1. To understand better how orthogonality can be assured between two TRXs, an example will be considered. Consider a cell with three TRXs (one BCCH and two hopping) for which the MAList is 43, 46, 49, 52 and the HSN is 5. The MAIO is fixed at 1. Then TRX3 will follow the same hopping sequence algorithm as TRX2 but with one step difference (see Figure 2.52). If the emission channel of TRX2 is in position 2 of the MAList (channel 46), then TRX3 will be in position 2+MAIO (channel 49). If the algorithm related to HSN 5 makes TRX2 hop, then the MAList is 46, 49, 46, 49, 52, 46, 49, 43, 52, etc. as TRX3 will hop to 49, 52, 49, 52, 43, 49, 52, 46, 43, etc