A method performed by a random access channel planning node in a communication network, the method comprising: identifying a coverage overlap area of a candidate cell with each of the neighboring cells of the candidate cell in a radio access network; using the identified coverage overlap area to determine a root sequence index for the candidate cell having a minimum root sequence index collision factor; and initiating a command to the candidate cell to set the root sequence index for the candidate cell to the determined root sequence index having the minimum root sequence index collision factor; wherein the using comprises: preparing a first list of root sequence indexes for neighboring cells having coverage overlap areas with the candidate cell; deriving a second list of the root sequence indexes from the first list, wherein the number of root sequence indexes in the second list is based on a defined number of root sequence indexes for generating a defined number of preambles for the candidate cell; calculating a root sequence index collision factor for the candidate cell for each root sequence index in the second list; and determining the root sequence index having the minimum root sequence index collision factor for the candidate cell; the method characterized in that the deriving a second list of the root sequence indexes from the first list comprises calculating a subset of the root sequence indexes, L CAND, from the first list to generate a defined number of random access channel preambles for the candidate cell; and wherein each root sequence index for the candidate cell, P RSI, is included in the subset, L CAND, so that an absolute value of a difference between each root sequence index for the candidate cell, P RSI, and each root sequence index for a neighbor cell, N RSI, having a coverage overlap area with the candidate cell, N n, is less than R RSI, the defined number of root sequence indexes for generating a defined number of preambles for the candidate cell. identifying a coverage overlap area of a candidate cell with each of the neighboring cells of the candidate cell in a radio access network; using the identified coverage overlap area to determine a root sequence index for the candidate cell having a minimum root sequence index collision factor; and initiating a command to the candidate cell to set the root sequence index for the candidate cell to the determined root sequence index having the minimum root sequence index collision factor; wherein the using comprises: preparing a first list of root sequence indexes for neighboring cells having coverage overlap areas with the candidate cell; deriving a second list of the root sequence indexes from the first list, wherein the number of root sequence indexes in the second list is based on a defined number of root sequence indexes for generating a defined number of preambles for the candidate cell; calculating a root sequence index collision factor for the candidate cell for each root sequence index in the second list; and determining the root sequence index having the minimum root sequence index collision factor for the candidate cell; the method characterized in that the deriving a second list of the root sequence indexes from the first list comprises calculating a subset of the root sequence indexes, L CAND, from the first list to generate a defined number of random access channel preambles for the candidate cell; and preparing a first list of root sequence indexes for neighboring cells having coverage overlap areas with the candidate cell; deriving a second list of the root sequence indexes from the first list, wherein the number of root sequence indexes in the second list is based on a defined number of root sequence indexes for generating a defined number of preambles for the candidate cell; calculating a root sequence index collision factor for the candidate cell for each root sequence index in the second list; and determining the root sequence index having the minimum root sequence index collision factor for the candidate cell; the method characterized in that the deriving a second list of the root sequence indexes from the first list comprises calculating a subset of the root sequence indexes, L CAND, from the first list to generate a defined number of random access channel preambles for the candidate cell; and wherein each root sequence index for the candidate cell, P RSI, is included in the subset, L CAND, so that an absolute value of a difference between each root sequence index for the candidate cell, P RSI, and each root sequence index for a neighbor cell, N RSI, having a coverage overlap area with the candidate cell, N n, is less than R RSI, the defined number of root sequence indexes for generating a defined number of preambles for the candidate cell.