Base Station Signaling in a Wireless Network

1 . A method comprising:

communicating, by a first base station, with a wireless device; and

transmitting, by the first base station, to a second base station, and for management of the wireless device, information indicating a carrier type for each of a plurality of carriers associated with the wireless device, wherein the plurality of carriers comprises:

at least one carrier of a first carrier type that comprises a reference signal in every downlink subframe of a plurality of downlink subframes; and

at least one carrier of a second carrier type that:

comprises a common reference signal in fewer than all downlink subframes of the plurality of downlink subframes based on data being in fewer than all downlink subframes of the plurality of downlink subframes, wherein the common reference signal is for wireless devices that are configured to receive signals via the at least one carrier of the second carrier type; and

supports fewer transmission modes than the at least one carrier of the first carrier type.

2 . The method of claim 1 , wherein the at least one carrier of the second carrier type selectively comprises the reference signal based on data being transmitted in one or more of the plurality of downlink subframes.

3 . The method of claim 1 , wherein the at least one carrier of the second carrier type employs a wireless-device-specific demodulation reference signal.

4 . The method of claim 1 , further comprising causing a downlink subframe of the at least one carrier of the second carrier type to become empty.

5 . The method of claim 1 , wherein the at least one carrier of the second carrier type comprises a second downlink subframe in which a control channel is configured to start at a symbol after a first symbol in the second downlink subframe.

6 . The method of claim 5 , wherein in the second downlink subframe, no common reference signal is transmitted between the first symbol in the second downlink subframe and the control channel in the second downlink subframe.

7 . The method of claim 1 , wherein the first base station is part of a long-term evolution (LTE) network.

8 . A method comprising:

communicating, by a first base station, with a wireless device; and

transmitting, by the first base station, to a second base station, and for management of the wireless device, information indicating a carrier type for each of a plurality of carriers associated with the wireless device, wherein the plurality of carriers comprises:

at least one carrier of a first carrier type that comprises a common reference signal in every downlink subframe of a plurality of downlink subframes; and

at least one carrier of a second carrier type that:

selectively comprises a common reference signal in at least one downlink subframe of the plurality of downlink subframes based on data being transmitted in one or more of the plurality of downlink subframes, wherein the common reference signal is for wireless devices that are configured to receive signals via the at least one carrier of the second carrier type; and

supports fewer transmission modes than the at least one carrier of the first carrier type

9 . The method of claim 8 , wherein the at least one carrier of the second carrier type is without the common reference signal in at least one second downlink subframe of the plurality of downlink subframes.

10 . The method of claim 8 , wherein the at least one carrier of the second carrier type is without the common reference signal, in at least one second downlink subframe of the plurality of downlink subframes, based on data being transmitted in fewer than all downlink subframes of the plurality of downlink subframes.

11 . The method of claim 8 , wherein the at least one carrier of the second carrier type employs a wireless-device-specific demodulation reference signal.

12 . The method of claim 8 , further comprising causing a downlink subframe of the at least one carrier of the second carrier type to become empty.

13 . The method of claim 8 , wherein the at least one carrier of the second carrier type comprises a second downlink subframe in which a control channel is configured to start at a symbol after a first symbol in the second downlink subframe.

14 . The method of claim 13 , wherein in the second downlink subframe, no common reference signal is transmitted between the first symbol in the second downlink subframe and the control channel in the second downlink subframe.

15 . The method of claim 8 , wherein the first base station is part of a long-term evolution (LTE) network.

16 . A first base station comprising:

one or more processors; and

memory storing instructions that, when executed by the one or more processors, configure the first base station to:

communicate with a wireless device; and

transmit, to a second base station and for management of the wireless device, information indicating a carrier type for each of a plurality of carriers associated with the wireless device, wherein the plurality of carriers comprises:

at least one carrier of a first carrier type that comprises a reference signal in every downlink subframe of a plurality of downlink subframes; and

at least one carrier of a second carrier type that:

comprises a common reference signal in fewer than all downlink subframes of the plurality of downlink subframes based on data being in fewer than all downlink subframes of the plurality of downlink subframes, wherein the common reference signal is for wireless devices that are configured to receive signals via the at least one carrier of the second carrier type; and

supports fewer transmission modes than the at least one carrier of the first carrier type

17 . The first base station of claim 16 , wherein the at least one carrier of the second carrier type selectively comprises the reference signal based on data being transmitted in one or more of the plurality of downlink subframes.

18 . The first base station of claim 16 , wherein the at least one carrier of the second carrier type employs a wireless-device-specific demodulation reference signal.

19 . The first base station of claim 16 , wherein the instructions, when executed by the one or more processors, further configure the first base station to cause a downlink subframe of the at least one carrier of the second carrier type to become empty.

20 . The first base station of claim 16 , wherein the at least one carrier of the second carrier type comprises a second downlink subframe in which a control channel is configured to start at a symbol after a first symbol in the second downlink subframe.

21 . The first base station of claim 20 , wherein in the second downlink subframe, no common reference signal is transmitted between the first symbol in the second downlink subframe and the control channel in the second downlink subframe.

22 . The first base station of claim 16 , wherein the first base station is part of a long-term evolution (LTE) network.

23 . A first base station comprising:

one or more processors; and

memory storing instructions that, when executed by the one or more processors, configure the first base station to:

communicate with a wireless device; and

transmit, to a second base station and for management of the wireless device, information indicating a carrier type for each of a plurality of carriers associated with the wireless device, wherein the plurality of carriers comprises:

at least one carrier of a first carrier type that comprises a common reference signal in every downlink subframe of a plurality of downlink subframes; and

at least one carrier of a second carrier type that:

selectively comprises a common reference signal in at least one downlink subframe of the plurality of downlink subframes based on data being transmitted in one or more of the plurality of downlink subframes, wherein the common reference signal is for wireless devices that are configured to receive signals via the at least one carrier of the second carrier type; and

supports fewer transmission modes than the at least one carrier of the first carrier type

24 . The first base station of claim 23 , wherein the at least one carrier of the second carrier type is without the common reference signal in at least one second downlink subframe of the plurality of downlink subframes.

25 . The first base station of claim 23 , wherein the at least one carrier of the second carrier type is without the common reference signal, in at least one second downlink subframe of the plurality of downlink subframes, based on data being transmitted in fewer than all downlink subframes of the plurality of downlink subframes.

26 . The first base station of claim 23 , wherein the at least one carrier of the second carrier type employs a wireless-device-specific demodulation reference signal.

27 . The first base station of claim 23 , wherein the instructions, when executed by the one or more processors, further configure the first base station to cause a downlink subframe of the at least one carrier of the second carrier type to become empty.

28 . The first base station of claim 23 , wherein the at least one carrier of the second carrier type comprises a second downlink subframe in which a control channel is configured to start at a symbol after a first symbol in the second downlink subframe.

29 . The first base station of claim 28 , wherein in the second downlink subframe, no common reference signal is transmitted between the first symbol in the second downlink subframe and the control channel in the second downlink subframe.

30 . The first base station of claim 23 , wherein the first base station is part of a long-term evolution (LTE) network.

31 . One or more non-transitory, computer-readable media storing instructions that, when executed, configure a first base station to:

communicate with a wireless device; and

transmit, to a second base station and for management of the wireless device, information indicating a carrier type for each of a plurality of carriers associated with the wireless device, wherein the plurality of carriers comprises:

at least one carrier of a first carrier type that comprises a common reference signal in every downlink subframe of a plurality of downlink subframes; and

at least one carrier of a second carrier type that:

selectively comprises a common reference signal in at least one downlink subframe of the plurality of downlink subframes based on data being transmitted in one or more of the plurality of downlink subframes, wherein the common reference signal is for wireless devices that are configured to receive signals via the at least one carrier of the second carrier type; and

supports fewer transmission modes than the at least one carrier of the first carrier type

32 . The one or more non-transitory, computer-readable media of claim 31 , wherein the at least one carrier of the second carrier type is without the common reference signal in at least one second downlink subframe of the plurality of downlink subframes.

33 . The one or more non-transitory, computer-readable media of claim 31 , wherein the at least one carrier of the second carrier type is without the common reference signal, in at least one second downlink subframe of the plurality of downlink subframes, based on data being transmitted in fewer than all downlink subframes of the plurality of downlink subframes.

34 . The one or more non-transitory, computer-readable media of claim 31 , wherein the at least one carrier of the second carrier type employs a wireless-device-specific demodulation reference signal.

35 . The one or more non-transitory, computer-readable media of claim 31 , wherein the instructions, when executed, further cause the first base station to cause a downlink subframe of the at least one carrier of the second carrier type to become empty.

36 . The one or more non-transitory, computer-readable media of claim 31 , wherein the at least one carrier of the second carrier type comprises a second downlink subframe in which a control channel is configured to start at a symbol after a first symbol in the second downlink subframe.

37 . The one or more non-transitory, computer-readable media of claim 36 , wherein in the second downlink subframe, no common reference signal is transmitted between the first symbol in the second downlink subframe and the control channel in the second downlink subframe.

38 . The one or more non-transitory, computer-readable media of claim 31 , wherein the first base station is part of a long-term evolution (LTE) network.

39 . A system comprising:

a first base station and a second base station,

wherein the first base station is configured to:

communicate with a wireless device; and

transmit, to the second base station and for management of the wireless device, information indicating a carrier type for each of a plurality of carriers associated with the wireless device, wherein the plurality of carriers comprises:

at least one carrier of a first carrier type that comprises a common reference signal in every downlink subframe of a plurality of downlink subframes; and

at least one carrier of a second carrier type that:

selectively comprises a common reference signal in at least one downlink subframe of the plurality of downlink subframes based on data being transmitted in one or more of the plurality of downlink subframes, wherein the common reference signal is for wireless devices that are configured to receive signals via the at least one carrier of the second carrier type; and

supports fewer transmission modes than the at least one carrier of the first carrier type,

wherein the second base station is configured to receive the information indicating the carrier type for each of the plurality of carriers associated with the wireless device.

40 . The system of claim 39 , wherein the at least one carrier of the second carrier type is without the common reference signal in at least one second downlink subframe of the plurality of downlink subframes.

41 . The system of claim 39 , wherein the at least one carrier of the second carrier type is without the common reference signal, in at least one second downlink subframe of the plurality of downlink subframes, based on data being transmitted in fewer than all downlink subframes of the plurality of downlink subframes.

42 . The system of claim 39 , wherein the at least one carrier of the second carrier type employs a wireless-device-specific demodulation reference signal.

43 . The system of claim 39 , wherein the first base station is further configured to cause a downlink subframe of the at least one carrier of the second carrier type to become empty.

44 . The system of claim 39 , wherein the at least one carrier of the second carrier type comprises a second downlink subframe in which a control channel is configured to start at a symbol after a first symbol in the second downlink subframe.

45 . The system of claim 44 , wherein in the second downlink subframe, no common reference signal is transmitted between the first symbol in the second downlink subframe and the control channel in the second downlink subframe.

46 . The system of claim 39 , wherein the first base station is part of a long-term evolution (LTE) network.