# An Energy-Efficient Coverage Algorithm for Macrocell--Small Cell Network Systems
## 4 Proposed Algorithm
If processing has been completed for all users, we will switch off the SBSs that have not been used (according to the recorded data) and complete the execution of the algorithm. In addition, in our design, if coverage holes are present during the relay process, the SBSs in the centers of these holes will be \"directly activated first\", with their power levels being set to \(P_{\text{s}}^{\text{(low)}}\) during the execution of the algorithm, thus providing coverage for these holes. In this manner, the coverage holes that are present during the relay process will be covered, and thus no locations or areas will exist where signal coverage is lacking during the relay process. Next, if the algorithm determines that SBSs are being used to provide coverage during the relay process, these SBSs will include the SBSs in the centers of the holes. If the MBS takes over the role of providing coverage during the relay process, a user will switch to the SBSs in the centers of the holes for coverage when he or she enters the holes, and revert back to the MBS upon leaving them. Along user \(i\)'s direct path (comprising the starting point, relay process, and end point), the determination of A, B, and C, and the notational representation of these statuses, are described below (and are categorized into the \"end point will not fall within a coverage hole\" and \"end point will fall within a coverage hole\" scenarios for discussion):  
(1) Determination of A, B, and C when the end point will not fall within a coverage hole  
The system first determines if user \(i\) at the starting point has an SBS that provides him or her with coverage. If it is present, A would be represented by S; if it is not present, A would be represented by N. The system then determines if an SBS that provides the user with coverage is present at the end point area. If it is present, C would be represented by S; if it is not present, C would be represented by N. Finally, the system determines if SBSs providing support overlay are present during the relay process. If they are present, B would be represented by S; if they are not present, B would be represented by N.  
However, when B is represented by S, it would be revised in the following manner, unless A and C are also both represented by S. If A and/or C are represented by N, the SBSs in the relay process area that are closest to A and/or C would amplify their power levels, in an attempt to provide coverage to  
Figure 4: Flow chart of the proposed coverage algorithm. A and/or C. If this attempt is successful, B would then be represented by Y instead of S; if the attempt is not successful, B would then be represented by X instead of S. However, when B is represented by N, and A and C are both represented by S and able to compensate or cover the relay process via the amplification of their power levels, A and C would then be represented by Y instead of S; otherwise, A and C would be represented by X instead of S.  
Determination of A, B, and C when the end point will fall within a coverage hole  
In this situation, the determination principles are similar to those used when the end point will not fall within a coverage hole. The following points indicate the differences: (1) if there is at least one available SBS next to a coverage hole center, a user at the end point would obtain coverage from the SBS closest to the coverage hole center (with its power level being set to \(P_{\text{s}}^{\text{(high)}}\)), at which point C would be represented by D; (2) if there is no available SBS next to a coverage hole center, a user at the end point would obtain coverage from the SBS deployed in the coverage hole (with its power level being set to \(P_{\text{s}}^{\text{(low)}}\)), at which point C would be represented by O.