From request to MSC as shown in

From the figure we can see that we have old Base Transceiver Station(BTS) andBase Station Controller (BSC), and new BTS and BSC for same Mobile Station Controller5(MSC). Now, we see that what happens when the Mobile Station (MS) moves from old BSC areaand handover is required.Firstly,the MS will record the information about the best 6 cells and this will be done byscanning FCCH and SCH of the surrounding cells. This information is ‘Measurement report’which includes quality measurements.This measurement report is then forwarded to BTS. This is done over SACCH and BTS adds itsown information in it and then this whole information it transferred to the old BSC.Now, this BSC decides that whether the actual decision has to be taken or not. This is HOdecision.Once its decided that HO is required then it sends HO request to the new BSC along with therequest of the resources required for the HO.This ‘resource allocation’ is necessary as if the MSis receiving strong signals from the new cell or the new BSC areas and if there are no resourcesavailable ( resources like frequency channel or time slots or in the form of code channel) thenthere is no point of performing the HO there because there will be surely the call drop situation.If the resources are available then the BSC activates new channels (‘Channel activation’) at thenew BTS and then the new BTS acknowledges this channel activation to new BSC. The newBSC then acknowledges the HO request to MSC as shown in the figure above.Now, the HO will take place, which is initiated by ‘HO Command’from MSC.This command isforwarded to the MS through old BSC and old BTS.This HO command tells the MS that breakthe old radio link and access the new provided link by the new BTS (Hard HO-‘Break beforemake’). On receiving this command the MS now knows that now old link is to break and newlink is to be accessed. Thus,after the HO access, link is established followed by the HO completemessage to the MSC.After this the clear command is sent to old BTS to release the resources at the old BSC and BTSfollowed by final message from old BTS to MSC for successful HO.This type of HO is called”inter BSC and intra MSC” and we’ll be doing the lab based on these concepts.