A method for transmitting pilot symbols in a Multiple Input Multiple Output, MIMO, communications system, wherein the MIMO communications system includes a base station and a plurality of mobile stations, comprising: selecting a pilot symbol pattern comprising clusters (304, 306, 308, 301, 324, 326, 328, 330) of contiguous pilot symbols according to a condition of a communications channel, selecting either the pilot symbol pattern for a time selective channel, wherein each cluster span multiple frequency tones but is located in the same symbol period, the pilot symbol pattern for a frequency selective channel, wherein each cluster span in time multiple symbol periods but is located in the same frequency tone, or the pilot symbol pattern for a combination of a time selective channel and a frequency selective channel comprising both clusters as in the pilot patterns for a time-selective channel spanning multiple frequency tones but located in the same symbol period and clusters as the in pilot patterns for a frequency-selective channel spanning multiple symbol periods but located in the same frequency tone; defining a hop region (300, 320), wherein a hop region includes symbols that are assigned to the mobile stations for communication with a sector of the base station over a reverse link, the location of the hop region within a set of subcarriers and symbols in each hop period being determined according to a hopping sequence; and sending an instruction to the mobile stations for placing the pilot symbols of the selected pilot symbol pattern within the hop region, wherein prior to transmission of the pilot symbols according to the pattern, the pilot symbols of the pilot pattern are multiplied with some sequences of a plurality of sequences that are orthogonal or quasi-orthogonal to each other sequence of the plurality of sequences, such that a receiver of the multiplied pilot symbols in each cluster can receive the multiplied pilot symbols of different mobile stations so that they are orthogonal or quasi-orthogonal with respect to the multiplied pilot symbols from each other mobile station in the same cluster, wherein the different mobile stations use said selected one pilot pattern. selecting a pilot symbol pattern comprising clusters (304, 306, 308, 301, 324, 326, 328, 330) of contiguous pilot symbols according to a condition of a communications channel, selecting either the pilot symbol pattern for a time selective channel, wherein each cluster span multiple frequency tones but is located in the same symbol period, the pilot symbol pattern for a frequency selective channel, wherein each cluster span in time multiple symbol periods but is located in the same frequency tone, or the pilot symbol pattern for a combination of a time selective channel and a frequency selective channel comprising both clusters as in the pilot patterns for a time-selective channel spanning multiple frequency tones but located in the same symbol period and clusters as the in pilot patterns for a frequency-selective channel spanning multiple symbol periods but located in the same frequency tone; defining a hop region (300, 320), wherein a hop region includes symbols that are assigned to the mobile stations for communication with a sector of the base station over a reverse link, the location of the hop region within a set of subcarriers and symbols in each hop period being determined according to a hopping sequence; and sending an instruction to the mobile stations for placing the pilot symbols of the selected pilot symbol pattern within the hop region, wherein prior to transmission of the pilot symbols according to the pattern, the pilot symbols of the pilot pattern are multiplied with some sequences of a plurality of sequences that are orthogonal or quasi-orthogonal to each other sequence of the plurality of sequences, such that a receiver of the multiplied pilot symbols in each cluster can receive the multiplied pilot symbols of different mobile stations so that they are orthogonal or quasi-orthogonal with respect to the multiplied pilot symbols from each other mobile station in the same cluster, wherein the different mobile stations use said selected one pilot pattern.