The patent's assignee is
News editors obtained the following quote from the background information supplied by the inventors: "In a UMTS (Universal Mobile Telecommunications System) network, for the purposes of improving spectral efficiency and improving the peak data rate, system features based on W-CDMA (Wideband Code Division Multiple Access) are maximized by adopting HSDPA (High Speed Downlink Packet Access) and HSUPA (High Speed Uplink Packet Access). For this UMTS network, for the purposes of further increasing high-speed data rates, providing low delay and so on, long-term evolution (LTE) has been under study (non-patent literature 1).
"In the third-generation mobile communication system, it is possible to achieve a transmission rate of maximum approximately 2 Mbps on the downlink by using a fixed band of approximately 5 MHz. Meanwhile, in a system of the LTE scheme, it is possible to achieve a transmission rate of about maximum 300 Mbps on the downlink and about 75 Mbps on the uplink by using a variable band which ranges from 1.4 MHz to 20 MHz. Furthermore, in the UMTS network, for the purpose of achieving further broadbandization and higher speed, successor systems of LTE have been under study (for example, LTE-Advanced (LTE-A)). Accordingly, in the future, it is expected that these multiple mobile communication systems will coexist, and configurations (base station apparatus, mobile terminal apparatus, etc.) that are capable of supporting these multiple systems will become necessary.
"In the downlink of the LTE system, a CRS (Cell-specific Reference Signal) is defined. This CRS is used to demodulate transmission data, and, besides, used to measure downlink channel quality (CQI: Channel Quality Indicator) for scheduling and adaptive control, and furthermore used to measure an average downlink propagation path state for cell search and handover (mobility measurement). Meanwhile, in the downlink of a successor system of LTE (LTE-A system), a CSI-RS (Channel State Information--Reference Signal) is under study for dedicated use of CSI (Channel State Information) measurement."
As a supplement to the background information on this patent application, VerticalNews correspondents also obtained the inventors' summary information for this patent application: "Technical Problem
"Now, the CSI-RS is used only in CSI measurement, so that, compared to the RS to be used in data demodulation and so on, its abundance ratio (density) in a predetermined period is set low. In future systems, need for further improvement of the accuracy of measurement by increasing the abundance ratio of reference signals such as the CSI-RS and so on is anticipated.
"The present invention has been made in view of the above, and it is therefore an object of the present invention to provide a base station apparatus, a mobile terminal apparatus and a communication control method, whereby it is possible to transmit and receive reference signals adequately even when the abundance ratio of reference signals in a predetermined period is increased.
"Solution to Problem
"A base station apparatus according to the present invention is a base station apparatus to transmit reference signals to a first mobile terminal apparatus which can receive a reference signal for measuring a channel state, and to a second mobile terminal apparatus which can receive a reference signal that is set in a predetermined period at a lower abundance ratio than the first mobile terminal apparatus, and this base station apparatus has: a reference signal allocation section that allocates the reference signals, to reference signal resources which are defined for transmission of the reference signals and which can be muted, at an abundance ratio which allows the first mobile terminal apparatus reception; and a reference signal reporting section that reports resources where the reference signals are allocated, to the first mobile terminal apparatus, and that, when reporting the resources where the reference signals are allocated, to the second mobile terminal apparatus, reports part of the resources as resources to be muted.
"Advantageous Effects of Invention
"According to the present invention, the first mobile terminal apparatus is able to receive reference signals that are allocated at a high abundance ratio in a predetermined period and measure the channel state with high accuracy. Also, a second mobile terminal apparatus is able to disregard the reference signals of muted resources, among the reference signals that are allocated at an abundance ratio which the first mobile terminal apparatus is able to receive, and measure the channel state. Consequently, the second mobile terminal apparatus is not influenced by the increase of reference signals. In this way, even when the abundance ratio of reference signals is increased in a predetermined period, it is possible to receive the reference signals adequately.
BRIEF DESCRIPTION OF DRAWINGS
"FIG. 1 provides diagrams to explain CSI-RS allocation patterns in resource blocks;
"FIG. 2 provides diagrams to explain muting in CQI measurement using CSI-RSs;
"FIG. 3 provides diagrams to show examples of a muting reporting method;
"FIG. 4 is a diagram to show an example of a CSI-RS arrangement configuration when the abundance ratio is increased;
"FIG. 5 provides diagrams to show examples of a CSI-RS position information signaling method;
"FIG. 6 is a diagram to show a modified example of a CSI-RS pattern;
"FIG. 7 is a diagram to explain a system configuration of a radio communication system;
"FIG. 8 is a diagram to explain an overall configuration of a base station apparatus;
"FIG. 9 is a diagram to explain an overall configuration of a mobile terminal apparatus
"FIG. 10 is a function block diagram corresponding to the first reporting method by a base station apparatus;
"FIG. 11 is a function block diagram showing the first reporting method by the first and second mobile terminal apparatuses;
"FIG. 12 is a function block diagram corresponding to a second reporting method by a base station apparatus; and
"FIG. 13 is a function block diagram corresponding to a second reporting method by the first and second mobile terminal apparatuses."
For additional information on this patent application, see: Abe, Tetsushi;
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