Base station, mobile station, radio communication system, and communication control method

Abstract

One of sequence groups each specifying reference signal sequences for respective radio resource bandwidths is assigned to a base station and a different one of the sequence groups is assigned to a neighboring cell. The base station includes a scheduler configured to allocate radio resources; a reporting unit configured to report the allocated radio resources and a cyclic shift amount to a mobile station; and a demodulating unit configured to demodulate a signal received from the mobile station based on one of the reference signal sequences corresponding to one of the radio resource bandwidths and the cyclic shift amount. Cell reuse is applied to the reference signal sequences to be transmitted using one resource unit, and sequence hopping where different ones of the reference signal sequences are assigned to consecutive subframes is applied to the reference signal sequences to be transmitted using a bandwidth greater than one resource unit.

Description

TECHNICAL FIELD[0001]The present invention generally relates to a radio communication system. More particularly, the present invention relates to a base station, a mobile station, a radio communication system, and a communication control method.BACKGROUND ART[0002]A successor communication system to W-CDMA and HSDPA, i.e., Long Term Evolution (LTE), is currently being discussed by 3GPP, a standardization group for W-CDMA. In LTE, orthogonal frequency division multiplexing (OFDM) is to be used as a downlink radio access method and single-carrier frequency division multiple access (SC-FDMA) is to be used as an uplink radio access method (see, for example, 3GPP TR 25.814 (V7.0.0), “Physical Layer Aspects for Evolved UTRA,” June 2006).[0003]In OFDM, a frequency band is divided into multiple narrow frequency bands (subcarriers) and data are transmitted on the subcarriers. The subcarriers are densely arranged along the frequency axis such that they partly overlap each other but do not int...

AI Technical Summary

Benefits of technology

[0031]An aspect of the present invention provides a base station, a mobile station, a radio communication system, and a communication control method that make it possible to flexibly reuse CAZAC reference signal sequences for multiple cells in an E-UTRA system and thereby to reduce the influence of characteristic degradation caused by cross-correlation.

Problems solved by technology

However, since the correlation properties of PN sequences are poor, the accuracy of channel estimation may become low.

In other words, the interference between a pilot channel of a user and a pilot channel of another user may become high.

Still, the CAZAC sequence has problems as described below.The number of sequences is small.

If frequency bands allocated in neighboring cells partly overlap, signals interfere with each other and their quality is reduced.

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