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  Communication method, receiver and base stationUSPTO Application #: 20070072551Title: Communication method, receiver and base station Abstract: A multi-user receiver which uses at least two antenna elements and in which the influence of interference is reduced, the receiver comprises: means (200) for pre-filtering a wideband antenna signal, the pre-filtering means being determined on the basis of a spatial covariance matrix estimate, which spatial covariance matrix estimate is obtained from wideband antenna signals by sampling, arranging sampled values into a signal vector and by multiplying the signal vector by its conjugate transpose vector, means (210, 218) for removing the whitening from signals of predetermined users by using an inverse matrix of the matrix used in the whitening filter, means (202, 204, 206, 208, 210) for performing multi-path combining and multi-antenna combining. (end of abstract) Agent: Squire, Sanders & Dempsey L.L.P. - Tysons Corner, VA, US Inventors: Kari Pajukoski, Esa Tiirola, Juha Ylitalo USPTO Applicaton #: 20070072551 - Class: 455063100 (USPTO) Related Patent Categories: Telecommunications, Transmitter And Receiver At Separate Stations, Distortion, Noise, Or Other Interference Prevention, Reduction, Or Compensation The Patent Description & Claims data below is from USPTO Patent Application 20070072551. Brief Patent Description - Full Patent Description - Patent Application Claims
REFERENCE TO RELATED APPLICATIONS [0001] This is a divisional application of application Ser. No. 10/760,532, filed Jan. 21, 2004, which claims the benefit of Patent Application No. 20031609, filed Nov. 6, 2003 in Finland. The disclosure of the prior applications is hereby incorporated by reference herein in its entirety FIELD [0002] The invention relates to a method for reducing the influence of interference in a multi-user receiver, when the multi-user receiver receives signals from users having different data rates using at least two antenna elements. The invention also relates to a multi-user receiver and a base station. BACKGROUND [0003] Several combining techniques have usually been used to combine diversity antennas or different antenna branches in antenna arrays to create nulls towards interfering signals while maintaining a large antenna gain towards the desired signal, thus reducing interference. One example of combining techniques is interference rejection combining (IRC). Conventionally the IRC is carried out at symbol level after despreading operations. This requires that the IRC operations need to be implemented separately for each user, thus increasing the complexity of a receiver. For simplifying the receiver structure, the IRC technique is combined with a maximal ratio combining (MRC) technique, whereupon an IRC filter acts as a pre-whitening filter in WO 02/075950. The IRC technique is also examined in Esa Tiirola, Juha Ylitalo: Performance of Smart Antenna Receivers in WCDMA Uplink with Spatially Coloured Interference, IST Mobile Communications Summit 2001, Barcelona, Spain, 9.-12.9.2001, which is incorporated herein by reference. While the IRC technique is used in a pre-whitening filter, the pre-whitening is carried out by antenna weighting, which is performed on all users. Thus there arises a problem: the high bit rate users are seen as relatively high level interferers to low bit rate users and therefore taken into account when determining whitening weights. As a consequence of this, in whitening, the combining of antenna signals is not optimal from the high data rate user's point of view. The use of a non-optimal solution will diminish the uplink coverage of high data rate users and at the same time increase the user terminal's battery consumption for the high bit rate users. BRIEF DESCRIPTION OF THE INVENTION [0004] The invention provides an improved method, receiver and base station. [0005] According to an embodiment, there is provided a method for reducing the influence of interference in a multi-user receiver, when the multi-user receiver receives signals from users having different data rates using at least two antenna elements, the method comprises: creating a spatial covariance matrix estimate from wideband antenna signals by sampling, arranging sampled values into a signal vector and by multiplying the signal vector by its conjugate transpose vector, determining a whitening filter on the basis of the spatial covariance matrix estimate, whitening received signals by using the whitening filter, removing the whitening from signals of predetermined users by using an inverse matrix of the matrix used in the whitening filter, conveying whitened signals and the signals from which the whitening has been removed to a receiver element, which carries out multi-path combining and multi-antenna combining. [0006] According to another embodiment, there is provided a multi-user receiver which uses at least two antenna elements and in which the influence of interference is reduced, the receiver comprises: means for pre-filtering a wideband antenna signal, the pre-filtering means being determined on the basis of a spatial covariance matrix estimate, which spatial covariance matrix estimate is obtained from wideband antenna signals by sampling, arranging sampled values into a signal vector and by multiplying the signal vector by its conjugate transpose vector, means for removing the whitening from signals of predetermined users by using an inverse matrix of the matrix used in the whitening filter, means for performing multi-path combining and multi-antenna combining. [0007] According to another embodiment, there is provided a multi-user receiver which uses at least two antenna elements and in which the influence of interference is reduced, the receiver comprises: one branch with a whitening arrangement, another branch without a whitening arrangement and a switching arrangement conveying received signals to the branch with the whitening arrangement or to the branch without the whitening arrangement depending on the used bit rate, a receiver element performing multi-path combining and multi-antenna combining. [0008] According to another embodiment, there is provided a multi-user receiver in which the influence of interference is reduced, comprising: a pre-filter whitening a wideband antenna signal, the pre-filter being determined on the basis of a spatial covariance matrix estimate which spatial covariance matrix estimate is obtained from wideband antenna signals by sampling, arranging sampled values into a signal vector and by multiplying the signal vector by its conjugate transpose vector, a whitening removing arrangement removing the whitening from signals of predetermined users by using an inverse matrix of the matrix used in the whitening filter, a receiver element performing multi-path combining and multi-antenna combining. [0009] According to another embodiment, there is provided a base station comprising a multi-user receiver which receiver uses at least two antenna elements and in which base station the influence of the interference is reduced, the base station comprises: means for pre-filtering a wideband antenna signal, the pre-filtering means being determined on the basis of a spatial covariance matrix estimate, which spatial covariance matrix estimate is obtained from wideband antenna signals by sampling, arranging sampled values into a signal vector and by multiplying the signal vector by its conjugate transpose vector, means for removing the whitening from signals of predetermined users by using an inverse matrix of the matrix used in the whitening filter, means for performing multi-path combining and multi-antenna combining. [0010] According to another embodiment, there is provided a base station comprising a multi-user receiver which uses at least two antenna elements and in which base station the influence of the interference is reduced, the base station comprises: one branch with a whitening arrangement, another branch without a whitening arrangement and a switching arrangement conveying received signals to the branch with the whitening arrangement or to the branch without the whitening arrangement depending on the used bit rate, an element performing multi-path combining and multi-antenna combining. [0011] According to another embodiment, there is provided a base station comprising a multi-user receiver which uses at least two antenna elements and in which base station the influence of the interference is reduced, the receiver comprises: a pre-filter whitening a wideband antenna signal, the pre-filter being determined on the basis of a spatial covariance matrix estimate, which spatial covariance matrix estimate is obtained from wideband antenna signals by sampling, arranging sampled values into a signal vector and by multiplying the signal vector by its conjugate transpose vector, a whitening removing arrangement removing the whitening from signals of predetermined users by using an inverse matrix of the matrix used in the whitening filter, an element performing multi-path combining and multi-antenna combining. [0012] The method and system of the invention provide several advantages. In one embodiment of the invention, the whitening performed by a pre-whitening filter can be removed from predetermined users and therefore the signals can be combined optimally. In another embodiment of the invention, the predetermined users are conveyed to by-pass a pre-whitening filter, thus preventing disadvantages caused by whitening. LIST OF DRAWINGS [0013] In the following, embodiments of the invention will be described in greater detail with reference to the preferred embodiments and the accompanying drawings, in which [0014] FIG. 1 shows an example of a method for reducing the influence of interference in a multi-user receiver, [0015] FIG. 2 illustrates an example of a receiver structure for reducing the influence of interference in a multi-user receiver, [0016] FIG. 3 shows an example of a receiver structure for reducing the influence of interference in a multi-user receiver. DESCRIPTION OF EMBODIMENTS [0017] With reference to FIG. 1, let us examine an embodiment of a method for reducing the influence of interference in a multi-user receiver. The method may be used in several kinds of radio receivers, such as a base station of a communication system, for instance a base station used in a wideband code division multiple access system (WCDMA), such as UMTS (universal mobile telecommunications system). The receiver may, for example, be a Rake receiver or a receiver having diversity antennas. The embodiment is directed to a receiver having a pre-whitening filter in the front-end of an MRC receiver. [0018] The embodiment is especially suitable for systems where there are users having different bit rates, for example, the majority of users use low bit rate services and some users use high bit rate services and the receiver uses several antenna elements. Data rates, which are classified as low or high, vary according to the current system; the data rates tend to increase due to technology development. In this application, the concept of high bit rate users means users having a relatively high bit rate and low bit rate users mean users having a relatively low bit rate. It is possible to set a bit rate threshold and classify users exceeding it as high bit rate users. Continue reading... Full patent description for Communication method, receiver and base station Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Communication method, receiver and base station patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. Start now! - Receive info on patent apps like Communication method, receiver and base station or other areas of interest. ### Previous Patent Application: Apparatus and method to provide multiple wireless communication paths to and from remotely located equipment Next Patent Application: Method and apparatus for mitigating multiuser access interference Industry Class: Telecommunications ### FreshPatents.com Support Thank you for viewing the Communication method, receiver and base station patent info. IP-related news and info Results in 2.51701 seconds Other interesting Feshpatents.com categories: Daimler Chrysler , DirecTV , Exxonmobil Chemical Company , Goodyear , Intel , Kyocera Wireless , |
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