In an embodiment of the method, uplink reference signals are assigned to
users in a group of cells. For example, a first constant amplitude
sequence having low cyclic cross correlation is assigned to each user in
a first cell of the group of cells. Here, each user is assigned the first
sequence. Also, simultaneously transmitting users in the first cell are
assigned to different sub-carriers. A second constant amplitude sequence
having low cyclic cross correlation is assigned to each user in a second
cell of the group of cells. Here, each user in the second cell is
assigned the second sequence. The first sequence and the second sequence
are different sequences, and the first cell and the second cell are
adjacent. Also, simultaneously transmitting users in the second cell are
assigned to different sub-carriers. The sub-carriers to which the
simultaneously transmitting users of the second cell are assigned overlap
in frequency with the sub-carriers to which the simultaneously
transmitting users of the first cell are assigned.