Almost blank subframe in carrier aggregation
A base station transmits a message to a plurality of wireless devices in connected mode. The message comprises a subframe allocation bitmap indicating a plurality of subframes. The plurality of subframes comprises a plurality of almost blank subframes. During majority of symbols of an almost blank subframe of a base station, signals are transmitted at an almost blank subframe power level that is different from a transmit power during a non-almost blank subframe.
1. A method comprising:
transmitting, by a base station, a first message comprising a subframe allocation bitmap indicating a plurality of Almost Blank Subframes, wherein the plurality of Almost Blank Subframes consists of second, fourth, seventh, and ninth subframes of each radio frame in a plurality of radio frames;
transmitting, to a wireless device, a second message comprising:
a first measurement subframe allocation bitmap indicating a first plurality of measurement subframes of a primary carrier, wherein the first plurality of measurement subframes excludes the plurality of Almost Blank Subframes; and
a second measurement subframe allocation bitmap indicating a second plurality of measurement subframes of the primary carrier, wherein the second plurality of measurement subframes excludes the first plurality of measurement subframes; and
transmitting, by the base station, a first Almost Blank Subframe, wherein the first Almost Blank Subframe is transmitted at a power level that is lower than during a non-Almost Blank Subframe.
2. The method of claim 1 , wherein the first Almost Blank Subframe consists essentially of a common reference signal in a control region.
3. The method of claim 1 , wherein each radio frame in the plurality of radio frames is assigned a system frame number (SFN).
4. The method of claim 1 , wherein the first message further comprises:
a subframe allocation repetition period in terms of n radio frames, n being an integer greater than or equal to one; and
a subframe allocation offset i, i being an integer greater than or equal to zero.
5. The method of claim 4 , wherein the subframe allocation bitmap indicates a plurality of subframes in k frames, k being an integer and 1≦k≦n, the bitmap applying to subframes in k frames starting from frames whose SFN meets (SFN mod n=i) criterion.
6. The method of claim 4 , wherein the subframe allocation repetition period is 1, 2, 4, 8, 16, or 32 radio frames.
7. The method of claim 1 , wherein the base station broadcasts:
a system frame number represented by m bits;
the p most significant bits of the system frame number employing a plurality of subcarriers in the middle of a frequency band of a carrier; and
the (m−p) least significant bits of the system frame number by encoding control blocks in a physical broadcast channel over 2 (m−p) frames, wherein the (m−p) least significant bits are determined by sequential positions of the encoded control blocks.
8. A method comprising:
transmitting, by a base station, a first message comprising a subframe allocation bitmap indicating a plurality of Almost Blank Subframes, wherein the plurality of Almost Blank Subframes consists of third and eighth subframes of each radio frame in a plurality of radio frames;
transmitting, to a wireless device, a second message comprising:
a first measurement subframe allocation bitmap indicating a first plurality of measurement subframes of a primary carrier, wherein the first plurality of measurement subframes excludes the plurality of Almost Blank Subframes; and
a second measurement subframe allocation bitmap indicating a second plurality of measurement subframes of the primary carrier, wherein the second plurality of measurement subframes excludes the first plurality of measurement subframes; and
transmitting, by the base station, a first Almost Blank Subframe, wherein the first Almost Blank Subframe is transmitted at a power level that is lower than during a non-Almost Blank Subframe.
9. The method of claim 8 , wherein the second message further configures measurement subframes of a plurality of neighboring carriers for the wireless device.
10. The method of claim 8 , wherein the wireless device periodically reports channel state information for subframes indicated in the first measurement subframe allocation bitmap.
11. The method of claim 8 , wherein the wireless device periodically reports channel state information for subframes indicated in the second measurement subframe allocation bitmap.
12. The method of claim 8 , wherein the first Almost Blank Subframe consists essentially of a common reference signal in a control region.
13. The method of claim 8 , wherein each radio frame in the plurality of radio frames is assigned a system frame number (SFN).
14. The method of claim 8 , wherein the first message further comprises:
a subframe allocation repetition period in terms of n radio frames, n being an integer greater than or equal to one; and
a subframe allocation offset i, i being an integer greater than or equal to zero.
15. The method of claim 14 , wherein the subframe allocation bitmap indicates a plurality of subframes in k frames, k being an integer and 1≦k≦n, the bitmap applying to subframes in k frames starting from frames whose SFN meets (SFN mod n=i) criterion.
16. A method comprising:
transmitting, by a base station, a first message comprising a subframe allocation bitmap indicating a plurality of Almost Blank Subframes, wherein the plurality of Almost Blank Subframes consists of second, fourth and eighth subframes of each radio frame in a plurality of radio frames;
transmitting, to a wireless device, a second message comprising:
a first measurement subframe allocation bitmap indicating a first plurality of measurement subframes of a primary carrier, wherein the first plurality of measurement subframes excludes the plurality of Almost Blank Subframes; and
a second measurement subframe allocation bitmap indicating a second plurality of measurement subframes of the primary carrier, wherein the second plurality of measurement subframes excludes the first plurality of measurement subframes; and
transmitting, by the base station, a first Almost Blank Subframe, wherein the first Almost Blank Subframe is transmitted at a power level that is lower than during a non-Almost Blank Subframe.
17. The method of claim 16 , wherein the second message further configures measurement subframes of a plurality of neighboring carriers for the wireless device.
18. The method of claim 16 , wherein the wireless device periodically reports channel state information for subframes indicated in the first measurement subframe allocation bitmap.
19. The method of claim 16 , wherein the wireless device periodically reports channel state information for subframes indicated in the second measurement subframe allocation bitmap.
20. The method of claim 16 , further comprising:
transmitting, by the base station and in response to a decrease in traffic load of the base station by an amount greater than a first value, a third message comprising a second subframe allocation bitmap indicating a second plurality of Almost Blank Subframes, wherein the second plurality of Almost Blank Subframes consists of second, fourth, seventh, and ninth subframes of each radio frame in a second plurality of radio frames.
21. The method of claim 16 , further comprising:
transmitting, by the base station and in response to an increase in traffic load of the base station by an amount greater than a first value, a third message comprising a second subframe allocation bitmap indicating a second plurality of Almost Blank Subframes, wherein the second plurality of Almost Blank Subframes consists of third and eighth subframes of each radio frame in a second plurality of radio frames.
22. The method of claim 1 , wherein the second message further configures measurement subframes of a plurality of neighboring carriers for the wireless device.
23. The method of claim 1 , wherein the wireless device periodically reports channel state information for subframes indicated in the first measurement subframe allocation bitmap.
24. The method of claim 1 , wherein the wireless device periodically reports channel state information for subframes indicated in the second measurement subframe allocation bitmap.
25. The method of claim 16 , wherein the first Almost Blank Subframe consists essentially of a common reference signal in a control region.
26. A method comprising:
transmitting, by a base station, a first message comprising a subframe allocation bitmap indicating a plurality of Almost Blank Subframes, wherein the plurality of Almost Blank Subframes consists of third, seventh, and ninth subframes of each radio frame in a plurality of radio frames;
transmitting, to a wireless device, a second message comprising:
a first measurement subframe allocation bitmap indicating a first plurality of measurement subframes of a primary carrier, wherein the first plurality of measurement subframes excludes the plurality of Almost Blank Subframes; and
a second measurement subframe allocation bitmap indicating a second plurality of measurement subframes of the primary carrier, wherein the second plurality of measurement subframes excludes the first plurality of measurement subframes; and
transmitting, by the base station, a first Almost Blank Subframe, wherein the first Almost Blank Subframe is transmitted at a power level that is lower than during a non-Almost Blank Subframe.
27. The method of claim 26 , wherein the second message further configures measurement subframes of a plurality of neighboring carriers for the wireless device.
28. The method of claim 26 , wherein the wireless device periodically reports channel state information for subframes indicated in the first measurement subframe allocation bitmap.
29. The method of claim 26 , wherein the wireless device periodically reports channel state information for subframes indicated in the second measurement subframe allocation bitmap.
30. The method of claim 26 , further comprising:
transmitting, by the base station and in response to a decrease in traffic load of the base station by an amount greater than a first value, a third message comprising a second subframe allocation bitmap indicating a second plurality of Almost Blank Subframes, wherein the second plurality of Almost Blank Subframes consists of second, fourth, seventh, and ninth subframes of each radio frame in a second plurality of radio frames.
31. The method of claim 26 , further comprising:
transmitting, by the base station and in response to an increase in traffic load of the base station by an amount greater than a first value, a third message comprising a second subframe allocation bitmap indicating a second plurality of Almost Blank Subframes, wherein the second plurality of Almost Blank Subframes consists of third and eighth subframes of each radio frame in a second plurality of radio frames.
32. The method of claim 26 , wherein the first Almost Blank Subframe consists essentially of a common reference signal in a control region.