Claims
1 . Base station (100) for a cellular communications
network, wherein said base station (100) is configured to control at least one antenna system (110) which comprises a plurality of antenna elements (110a, 110b, 110c, .., 110T| ) , wherein at least two antenna elements (110a, 110b) are arranged at different vertical positions (pa, pb) with reference to a virtual horizontal plane (P) , characterized in that said base station (100) is configured to transmit specific pilot signals (Dl, D2) on orthogonal radio resources associated with said specific pilot signals (Dl, D2) via different ones of said at least two antenna elements (110a, 110b) , wherein said base station (100) is configured to receive feedback information from a terminal (200) , wherein said feedback information depends on or characterizes a phase shift between said pilot signals (Dl, D2) as detected by said terminal
(200) , and to control a tilt angle 0) for downlink and/or uplink transmissions to/from said terminal (200) depending on said feedback information.
2 . Base station (100) according to claim l , wherein said
base station (100) is configured to transmit a) a first pilot signal (Dl) on a first radio resource via a first antenna element (110a) , and b ) a second pilot signal (D2) on a second radio resource, which is orthogonal to said first radio resource, via a second antenna element (110b) .
3 . Base station (100) according to one of the preceding
claims, wherein said base station (100) is configured to employ at least one of the following resources as

orthogonal radio resources: transmission time slots, subcarriers, orthogonal codes.
4 . Base station (100) according to one of the preceding
claims, wherein said base station (100) is configured to transmit a first pilot signal (Dl) via a first antenna element (110a) during a first downlink transmission time slot (tsl) , and to transmit a second pxlot sxgnal (D2) via a second antenna element (110b) during a second, preferably subsequent, downlink transmission time slot (ts2 ) .
5 . Base station (100) according to one of the preceding
claims, wherein said base station (100) is configured to transmit a first pilot signal (Dl) via a first antenna element (110a) on a first subcarrier (scl) , and to transmit a second pilot signal (D2) via a second antenna element (110b) on a second subcarrier (sc2) , wherein said first and second pilot signals (Dl, D2) are preferably transmitted simultaneously.
6 . Base station (100) according to one of the preceding
claims, wherein said base station (100) is configured to transmit a first pilot signal (Dl) via a first antenna element (110a) using a first spreading code, and to transmit a second pilot signal (D2) via a second antenna element (110b) using a second spreading code, which is orthogonal to said first spreading code, wherein said first and second pilot signals (Dl, D2) are preferably transmitted simultaneously
7 . Base station (100) according to one of the claims 2 to
6, wherein saxd £xrst pilot signal (DD is identxcal to said second pilot signal (D2) .
8 • Base station (100) aoco rdxng to claim if wherein said
base station (100) is configured to control the tilt

angle (0) for both downlink transmissions and uplink transmissions with said terminal (200) depending on said feedback information, and to use different tilt angle values for uplink transmission and downlink transmissions
Base station (100) according to one of the preceding claims, wherein said base station (100) is configured to periodically transmit said pilot signals (Dl, D2) , wherein a time interval between two subsequent transmissions of pilot signals (Dl, D2) from the same antenna element (110a) ranges between about 1 millisecond and about 20000 milliseconds, preferably between 10 milliseconds and 1000 milliseconds.
Terminal (200) for a cellular communications network, characleriZed ID that SaXl texminal (200) is cQnf?gUred. tO receX^e at Xeast two pilot signal S ©X, D2) which are transmitted from a base station (200) of said cellular communications network on orthogonal radio resources associated with said pilot signals
(Dl, D2) via different antenna elements (110a, 110b) that are arranged at different vertical positions (pa, pb) with reference to a virtual horizontal plane (P) , wherein said terminal (200) is further configured to determine a phase shift between said pilot signals
(Dl, D2) and to transmit feedback information to said base station (100) , wherein said feedback information depends on or characterizes said phase shift between said pilot signals (Dl, D2) as determined by said terminal (200) .
Terminal (200) according to claim 10, wherein said terminal (200) is configured to

a . transmit determined phase shifts between received pilot signals (Dl, D2) to the base station (200) , and/ or
b . determine a desired tilt angle 0) for downlink transmissions from said base station (100) to said terminal (200) depending on said phase shift
and transmit said desired tilt angle 0) to the base station (200) , and/or
c . determine an index value denoting one of a
plurality of predefined tilt angle values that may be used by the base station (200) and that relates to the determined phase shift and transmit said index value to the base station (100) .
12. Terminal (200) according to one of the claims 10 to 11, wherein said terminal (200) is configured to receive further pilot signals from a further base station of said cellular communications network, to determine a phase shift between said further pilot signals, and to transmit feedback information depending on said further phase shift to said base station (100) .
13. Method of operating a base station (100) for a cellular communications network, wherein said base station (100) is configured to control at least one antenna system (110) which comprises a plurality of antenna elements (110a, 110b, 110c, .., llOT)) , wherein at least two antenna elements (110a, 110b) are arranged at different vertical positions (pa, pb) with reference to a virtual horizontal plane (P) , characterized in that said base station (100) transmits specific pilot signals (Dl, D2) on