Buffer status reporting in small cell networks
The invention provides for association of data streams (and/or logical channels) with individual carriers (cells), and independent buffer status reporting per carrier for terminals with more than one uplink carrier configured. In a “Small Cell” scenario for 3GPP LTE, a terminal may be simultaneously served by a macro cell and one or more small cells. These may operate at different frequencies, have different traffic loading and support different QoS (Quality of Service). The invention allows independent control of traffic on the uplinks to the macro cell and the small cells, which can be used to optimize the user experience in relation to the available resources at any given time/location, and allows particular data to be routed via particular cells.
1. A wireless communication method wherein:
a terminal transmits first and second data streams to a network, the network providing a plurality of cells serving the terminal; wherein
the first data stream is associated with both a first one and a second one of the cells, and the second data stream is associated with a second one of the cells;
the terminal detects that there is data waiting for transmission in at least one of the first and second data streams; and
the terminal transmits to the network at least one signalling message including at least one of a buffer status report, scheduling request and physical random access channel signature relating to the cell or cells associated with the at least one of the first data and second streams.
2. The method according to claim 1 wherein the terminal determines via which of the cells to send the at least one signalling message.
3. The method according to claim 2 wherein the terminal makes said determination based at least on channel conditions with respect to each cell.
4. The method according to claim 1 wherein a said signalling message is transmitted via the first cell.
5. The method according to claim 1 wherein a said signalling message is transmitted via the second cell.
6. The method according to claim 1 wherein two signalling messages are both transmitted via the same cell.
7. The method according to claim 1 wherein the at least one signalling message includes a buffer status report.
8. The method according to claim 1 wherein the at least one signalling message includes a scheduling request.
9. The method according to claim 1 wherein the at least one signalling message includes a PRACH signature.
10. The method according to claim 1 wherein each data stream is further associated with a logical channel and/or a logical channel group.
11. The method according to claim 1 wherein the association between a data stream and a cell is changed by signalling from the network to the terminal.
12. The method according to claim 1 wherein the first and second cells are controlled by different base stations.
13. A wireless communication network providing a plurality of cells serving a terminal, the terminal arranged to transmit first and second data streams to the network, wherein
the first data stream is associated with both a first one and a second one of the cells, and the second data stream is associated with a second one of the cells; and
the terminal is further arranged to detect that there is data waiting for transmission in at least one of the first and second data streams and to transmit to the network at least one signalling message including at least one of a buffer status report, scheduling request and physical random access channel signature relating to the cell or cells associated with the at least one of the first and second data streams.
14. A terminal in a wireless communication network, the network providing a plurality of cells serving the terminal, the terminal arranged to transmit first and second data streams to the network, wherein
the first data stream is associated with both a first one and a second one of the cells, and the second data stream is associated with a second one of the cells; and
the terminal is further arranged to detect that there is data waiting for transmission in at least one of the first and second data streams and to transmit to the network at least one/or signalling message including at least one of a buffer status report, scheduling request and physical random access channel signature relating to the cell or cells associated with the at least one of the first and second data streams.
15. A base station providing at least one serving cell of a terminal having a plurality of serving cells, the cells used by the terminal to transmit first and second data streams, wherein
the first data stream is associated with both a first one and a second one of the cells, and the second data stream is associated with a second one of the cells; and
the base station is arranged to receive from the terminal at least one signalling message including at least one of a buffer status report, scheduling request and physical random access channel signature relating to the cell or cells associated with the at least one of the first and second data streams.