Coverage extension in wireless communication
In a wireless communication system, two cells (cell 1 , cell 2 ) co-exist in the same time/frequency resources with the same Cell ID. The two cells are differentiated by one being a legacy cell and the other being a cell in which coverage extension by means of signal repetition is applied. There is a corresponding difference in broadcast control channels transmitted by a base station ( 11 ) providing the two cells, for example a difference in one or more of the contents of the PBCH, or the repetition factor on the PBCH, and/or a difference in a higher-level ID. The second cell is intended for machine type communication where coverage enhancement is required.
1. A transmission method for use in a wireless communication system the method comprising:
providing by a base station a first cell having a Cell ID and comprising a first set of resources;
providing by the base station a second cell having a Cell ID and comprising a second set of resources;
transmitting a broadcast channel in each of the first and second cells to a terminal, wherein
the broadcast channel for the second cell is different from that for the first cell, the Cell ID of the first cell is the same as the Cell ID of the second cell, and at least some of the first set of resources are the same as some of the second set of resources; and
transmitting by a terminal on a Random Access Channel (RACH) in the second cell with a number of repetitions applied to RACH transmission based on information broadcast by the second cell, or the number of repetitions applied to a channel transmitted by the second cell.
2. The method according to claim 1 wherein the broadcast channel transmitted by the second cell differs in a number of repetitions from the broadcast channel transmitted by the first cell.
3. The method according to claim 1 wherein the broadcast channel transmitted by the second cell differs in information content from the broadcast channel transmitted by the first cell.
4. The method according to claim 1 wherein the second cell is provided for coverage extension with respect to a coverage area of the first cell.
5. The method according to claim 1 wherein the wireless communication system is based on Long-Term Evolution (LTE) and the broadcast channel includes a Physical Broadcast Channel, PBCH.
6. The method according to claim 1 wherein the wireless communication system is based on LTE and the broadcast channel includes a System Information Block, SIB.
7. The method according to claim 1 wherein additional channels are transmitted in the first and second cells, at least some of said broadcast channels and/or said additional channels being transmitted using the same antennas of a plurality of antennas of the base station.
8. The method according to claim 1 wherein different antenna configurations of the same base station are used for transmission of the broadcast channels of the first and second cells.
9. The method according to claim 8 wherein the broadcast channel in the second cell is transmitted using beamforming with a time-varying beamforming pattern.
10. A wireless communication system comprising:
a base station arranged to provide a first cell having a Cell ID and comprising a first set of resources and a second cell having a Cell ID and comprising a second set of resources; wherein
the first and second cells each transmit a broadcast channel to a terminal, the broadcast channel for the second cell is different from that for the first cell,
the Cell ID of the first cell is the same as the Cell ID of the second cell, and at least some of the first set of resources are the same as some of the second set of resources; and
the terminal is configured to transmit on a Random Access Channel (RACH) in the second cell, with a number of repetitions applied to RACH transmission based on information broadcast by the second cell, or the number of repetitions applied to a channel transmitted by the second cell.
11. A base station comprising:
a processor configured to execute instructions to:
provide a first cell having a Cell ID and comprising a first set of resources and a second cell having a Cell ID and comprising a second set of resources;
a transmitter configured to transmit information on broadcast channel in each of the first and second cells to a terminal, wherein the broadcast channel for the second cell is different from that for the first cell; and
the Cell ID of first cell is the same as the Cell ID of the second cell, and at least some of the first set of resources are the same as some of the second set of resources, wherein by information broadcast by the second cell, or the number of repetitions applied to a channel transmitted by the second cell, the base station informs the terminal of a number of repetitions to be applied to Random Access Channel (RACH) transmission in the second cell.
12. A terminal for use in a wireless communication system comprising:
a receiver configured to receive information on broadcast channels by a first and second cell provided by a base station; and
a transmitter configured to transmit on a Random Access Channel (RACH) in the second cell with a number of repetitions applied to the RACH transmission based on information on the broadcast channel in the second cell transmitted from the base station, or the number of repetitions applied to a channel in the second cell transmitted from the base station,
wherein the first cell has a Cell ID and comprises a first set of resources and the second cell has a Cell ID and comprises comprising a second set of resources, the broadcast channel for the second cell is different from that for the first cell, the Cell ID of the first cell is the same as the Cell ID of the second cell, and at least some of the first set of resources being the same as some of the second set of resources.
13. A non-transitory computer-readable recording media storing computer-readable instructions which, when executed by a processor of a base station in a wireless communication system, cause the base station to provide functions of:
providing a first cell having a Cell ID and comprising a first set of resources and a second cell having a Cell ID and comprising a second set of resources; and
transmitting information on a broadcast channel in each of the first and second cells to a terminal, wherein the broadcast channel for the second cell is different from that for the first cell, the Cell ID of the first cell is the same as the Cell ID of the second cell, and at least some of the first set of resources are the same as some of the second set of resources, and wherein
by information broadcast by the second cell, or the number of repetitions applied to a channel transmitted by the second cell, the base station informs the terminal of a number of repetitions to be applied to Random Access Channel (RACH) transmission in the second cell.