1. A method comprising: providing, by the apparatus, a modulo 3 grouping and a modulo 30 grouping for physical layer cell identifiers in a cellular communication system, wherein the modulo 3 grouping is associated with first synchronization signal assignments and the modulo 30 grouping is associated with second synchronization signal assignments, and wherein a combination of a first synchronization signal and a second synchronization signal determines a physical layer cell identifier of a cell; allocating, by the apparatus, a modulo 3 group to each of a plurality of cells of the cellular communication system; allocating, by the apparatus, and after the allocation of the modulo 3 groups, a modulo 30 group to each of the plurality of cells of the cellular communication system, wherein the allocation of the modulo 30 groups incorporates the allocated modulo 3 group as a precondition to reduce a search space for the modulo 30 grouping; allocating, by the apparatus, to each cell a first synchronization signal and a second synchronization signal on the basis of said allocation of the modulo 30 group; using, by the apparatus, the allocated first synchronization signal and allocated second synchronization signal to assign a unique physical layer cell identifier to each cell; and sending, by the apparatus, the assigned unique physical cell identifiers to the cells to be used by the cells to perform at least cell synchronization with user equipment.