Methods, base station system, radio unit and radio head of a wireless communication network, for increasing signal quality of signals sent from the radio head to the radio unit

Abstract

Disclosed is a method performed by a base station system of a wireless communication network, for increasing signal quality of signals sent from a radio head (RH) to a radio unit (RU) over a metallic conductor. The base station system comprising a baseband unit (BBU), the RU and the RH and the RU is connected to the RH via the metallic conductor. The method comprises, at the RH: amplifying, by an amplification unit, a signal to be transmitted from the RH to the RU; changing the signal amplification level of the amplification unit; and transmitting the amplified signal to the RU. The method further comprises, at the RU: receiving the amplified signal and compensating, by a compensating unit capable of adapting its amplification level, for the change in signal amplification level performed at the RH such that the strength of the signal is transparent to the base station system.

1 . A method performed by a base station system of a wireless communication network, the base station system comprising a baseband unit (BBU), a radio unit (RU), and a radio head (RH), wherein the RU is connected to the RH via a metallic conductor, the method comprising, at the RH:
 amplifying a signal to be transmitted from the RH to the RU;   changing a signal amplification level; and   transmitting the amplified signal to the RU,   the method further comprising, at the RU:   receiving the amplified signal; and   compensating for the change in signal amplification level performed at the RH.   
     
     
         2 . The method according to  claim 1 , wherein the signal to be transmitted is amplified to a signal strength level approximately equal to a maximum allowed signal strength level of the metallic conductor, or is amplified by a maximum possible gain of the amplifier, when the signal strength level to which the signal is amplified with maximum possible gain is below the maximum allowed signal strength level of the metallic conductor. 
     
     
         3 . The method according to  claim 1 , further comprising transmitting information of a current signal amplification level at the RH to the RU. 
     
     
         4 . The method according to  claim 1 , further comprising:
 receiving, at the RU, information of a current amplification level at the RU from the RH; and   controlling the compensating according to the received information.   
     
     
         5 . The method according to  claim 4 , wherein the receiving of information comprises, at a first point of time, receiving information from the RH of a current amplification level at the RH and at a second point of time later than the first point of time, receiving information from the RH of a current amplification level at the RH, and comparing the amplification level at the second point of time with the amplification level at the first point of time to detect a difference in amplification level, and wherein the compensating is controlled according to the detected difference in amplification level. 
     
     
         6 . The method according to  claim 4 , wherein the information of the current amplification level is received over a carrier frequency outside a frequency band used for the reception of the signal. 
     
     
         7 . The method according to  claim 1 , further comprising, after the compensating has been performed, detecting sudden changes in signal strength, and adjusting the detected changes such that the signal strength is reduced at the detected changes. 
     
     
         8 . The method according to  claim 1 , wherein the compensating for the signal amplification change performed at the RH is only performed if under normal operating conditions, and, if under a special operating condition differing from the normal operating conditions, the compensating for the signal amplification change performed at the RH is only partially performed. 
     
     
         9 . The method according to  claim 8 , further comprising, after the compensating has been performed, detecting sudden changes in signal strength, and adjusting the detected changes such that the signal strength is reduced at the detected changes. 
     
     
         10 . A base station system of a wireless communication network, the base station system comprising a baseband unit (BBU), a radio unit (RU), and a radio head (RH), the RU being connected to the RH via a metallic conductor, the BBU being connected to the RU, wherein the RH comprises:
 an amplifying unit to amplify a signal to be transmitted from the RH to the RU and to change its amplification level; and   a transmitting unit to transmit the amplified signal to the RU, and the RU comprises:   a receiving unit to receive the amplified signal; and   a compensating unit to adapt its amplification level to compensate for the change in signal amplification level performed at the RH.   
     
     
         11 . The base station system according to  claim 10 , comprising a plurality of the RHs and a plurality of the RUs, and further comprising a combiner to combine an output signal from each of the compensating units of the plurality of RUs, and an automatic gain control (AGC) unit connected to the combiner to receive the combined output signals. 
     
     
         12 . The base station system according to  claim 10 , wherein the amplifying unit amplifies the signal to be transmitted to a signal strength level approximately equal to a maximum allowed signal strength level of the metallic conductor, or amplifies the signal to be transmitted by a maximum possible gain of the amplifier, when the signal strength level to which the signal is amplified with maximum possible gain is below the maximum allowed signal strength level of the metallic conductor. 
     
     
         13 . The base station system according to  claim 10 , wherein the transmitting unit further transmits information of a current signal amplification level at the RH to the RU. 
     
     
         14 . The base station system according to  claim 10 , wherein the receiving unit further receives information of a current amplification level at the RH from the RH, and the compensating unit compensates for the change in signal amplification level performed at the RH according to the received information. 
     
     
         15 . The base station system according to  claim 10 , wherein the receiving unit receives information of a current amplification level by, at a first point of time, receiving information from the RH of a current amplification level at the RH, and at a second point of time later than the first point of time, receives information from the RH of a current amplification level at the RH, and the compensating unit compares the amplification level at the second point of time with the amplification level at the first point of time to detect a difference in amplification level, and compensates according to the detected difference in amplification level. 
     
     
         16 . The base station system according to  claim 14 , wherein the receiving unit receives the information of the current amplification level over a carrier frequency outside a frequency band used for the reception of the signal. 
     
     
         17 . The base station system according to  claim 10 , further comprising a glitch adjustment unit arranged after the compensating unit in a propagation direction of the signal, to detect sudden changes in signal strength, and to adjust the detected changes such that the strength of the signal is reduced at the detected changes. 
     
     
         18 . The base station system according to  claim 13 , wherein the compensating unit compensates for a signal amplification adjustment performed at the RH only if under normal operating conditions, and, if under a special operating condition differing from the normal operating conditions, the compensating unit only partially compensates for the signal amplification adjustment performed at the RH. 
     
     
         19 . A non-transient computer-readable storage medium that stores instructions, which when run in a radio head (RH) operable in a base station system of a wireless communication network, wherein the base station system comprises a baseband unit (BBU), a radio unit (RU), and the RH, the RH being connected to the RU via a metallic conductor, the instructions causing the RH to perform the following operations:
 amplifying a signal to be transmitted from the RH to the RU;   changing a signal amplification level; and   transmitting the amplified signal to the RU for subsequent compensation for the signal amplification level change at the RH.   
     
     
         20 . The non-transient computer-readable storage medium according to  claim 19 , the instructions further causing:
 receiving information of a current amplification level at the RU from the RH; and   controlling the compensating according to the received information.