A distributed system comprising a baseband unit, BBU, and two remote radio units: an RRU 0 and an RRU 1, wherein the BBU is configured to control a first logical cell, and the first logical cell comprises a physical cell covered by the RRU 0 and a physical cell covered by the RRU 1; and the physical cell covered by the RRU 0 and the physical cell covered by the RRU 1 overlap in a first area, wherein: • the RRU 0 and the RRU 1 are configured to separately send first downlink signals on a frequency f 0 to N terminals, • the RRU 0 is configured to send second downlink signals on a first frequency to the N terminals and the RRU 1 is configured to send the second downlink signals on a second frequency to the N terminals, wherein the first frequency is a difference between fo and a first offset correction amount f d_dl_0, the second frequency is a sum of fo and a second offset correction amount f d_dl_1, wherein at least one of f d_dl_0 and f d_dl_1 is not o, wherein f d_dl_0 and f d_dl_1 respectively meet the following conditions: f d _ dl _ o < 2 ∗ f d _ dl; and f d _ dl _ 1 < 2 ∗ f d _ dl, wherein the parameters f d_dl, f d_dl_0, and f d_dl_1 are all non-positive numbers, or, f d_dl, f d_dl_0, and f d_dl_1 are all non-negative numbers, • the RRU 0 and the RRU 1 are further configured to: before sending the second downlink signals, separately receive uplink signals sent by the N terminals that move from the RRU 1 to the RRU 0, wherein the N terminals are located in the first area, an i th terminal is indicated by a terminal A i, and i is any value from 1 to N, • the BBU is further configured to determine f d (i) indicating a Doppler frequency offset estimated value based on the uplink signals and is configured to determine f d_dl, wherein f d _ dl = ∑ i = 1 n a i ∗ f d i; ∑ i = 1 n a i = 1, and 0 ≤ a i ≤ 1; • the BBU is further configured to determine reference signal received power, RSRP, of the uplink signals that are received by the RRU 0 and the RRU 1, and determine a(i) according to the following formulas: RSRP _ i = RSRP 0 i + RSRP 1 i; RSRP _ sum = ∑ RSRP _ i; and a i = RSRP _ i / RSRP _ sum, wherein RSRP 0 (i) indicates RSRP of an uplink signal, among the uplink signals, received by the RRU 0 from the terminal A i among the N terminals, and RSRP 1 (i) indicates RSRP of an uplink signal, among the uplink signals, received by the RRU 1 from the terminal A i. • the RRU 0 and the RRU 1 are configured to separately send first downlink signals on a frequency f 0 to N terminals, • the RRU 0 is configured to send second downlink signals on a first frequency to the N terminals and the RRU 1 is configured to send the second downlink signals on a second frequency to the N terminals, wherein the first frequency is a difference between fo and a first offset correction amount f d_dl_0, the second frequency is a sum of fo and a second offset correction amount f d_dl_1, wherein at least one of f d_dl_0 and f d_dl_1 is not o, wherein f d_dl_0 and f d_dl_1 respectively meet the following conditions: f d _ dl _ o < 2 ∗ f d _ dl; and f d _ dl _ 1 < 2 ∗ f d _ dl, wherein the parameters f d_dl, f d_dl_0, and f d_dl_1 are all non-positive numbers, or, f d_dl, f d_dl_0, and f d_dl_1 are all non-negative numbers, • the RRU 0 and the RRU 1 are further configured to: before sending the second downlink signals, separately receive uplink signals sent by the N terminals that move from the RRU 1 to the RRU 0, wherein the N terminals are located in the first area, an i th terminal is indicated by a terminal A i, and i is any value from 1 to N, • the BBU is further configured to determine f d (i) indicating a Doppler frequency offset estimated value based on the uplink signals and is configured to determine f d_dl, wherein f d _ dl = ∑ i = 1 n a i ∗ f d i; ∑ i = 1 n a i = 1, and 0 ≤ a i ≤ 1; • the BBU is further configured to determine reference signal received power, RSRP, of the uplink signals that are received by the RRU 0 and the RRU 1, and determine a(i) according to the following formulas: RSRP _ i = RSRP 0 i + RSRP 1 i; RSRP _ sum = ∑ RSRP _ i; and a i = RSRP _ i / RSRP _ sum, wherein RSRP 0 (i) indicates RSRP of an uplink signal, among the uplink signals, received by the RRU 0 from the terminal A i among the N terminals, and RSRP 1 (i) indicates RSRP of an uplink signal, among the uplink signals, received by the RRU 1 from the terminal A i.