Adaptive channel prediction apparatus and method for performing uplink pre-equalization depending on downlink channel variation in OFDM/TDD mobile communication system

• US 20070211747A1
• Filed: 02/21/2007
• Published: 09/13/2007
• Est. Priority Date: 02/21/2006
• Status: Active Grant

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Kim, Jin-Kyeom
• Granted Patent: US 8,023,526 B2
• Time in Patent Office: Days
• US Class Current: 370/437
• CPC Class Codes: H04L 25/0202 Channel estimation
• CPC Class Codes: H04L 25/03159 operating in the frequency domain H04L25/03165, H04L25/03178 take precedence
• CPC Class Codes: H04L 25/03343 Arrangements at the transmitter end
• CPC Class Codes: H04L 27/0014 Carrier regulation of chaotic carriers H04L27/001; for multicarrier receivers H04L27/2657
• CPC Class Codes: H04L 27/2647 Arrangements specific to the receiver only equalisation H04L27/01

Abstract

Disclosed are an apparatus and a method for changing a channel prediction depending on the degree of downlink channel variation in predicting an uplink channel for uplink pre-equalization. N number of Doppler frequency ranges are set according to uplink channel variation degrees, and channel prediction schemes corresponding to the respective Doppler frequency ranges are established. A Doppler frequency is measured from a signal received over a downlink channel, and the Doppler frequency range, within which the measured Doppler frequency is included, is determined from among the Doppler frequency ranges. The channel prediction scheme established corresponding to the determined Doppler frequency is selected, and the uplink pre-equalization is performed by using the selected channel prediction scheme. This enables uplink pre-equalization that is suitable for a channel varying with a terminal'"'"'s moving speed or other channel environments.

Claims

1. An adaptive channel prediction method for performing uplink pre-equalization based on downlink channel variation in an OFDM/TDD mobile communication system, the method comprising the steps of:

setting N number of Doppler frequency ranges according to uplink channel variation degrees, and establishing channel prediction schemes corresponding to the respective Doppler frequency ranges;

measuring a Doppler frequency from a signal received over a downlink channel;

determining the Doppler frequency range, within which the measured Doppler frequency is included, from among the N number of Doppler frequency ranges, and selecting the channel prediction scheme established corresponding to the determined Doppler frequency; and

performing the uplink pre-equalization by using the selected channel prediction scheme.

2. The method as claimed in claim 1, wherein the channel prediction schemes established corresponding to the Doppler frequency ranges include channel prediction schemes capable of optimally predicting an uplink channel according to a reciprocity degree of the downlink/uplink channel in a TDD channel.

3. The method as claimed in claim 1, wherein the channel prediction scheme is selected from a group consisting of a linear interpolation scheme, a quadratic interpolation scheme, a cubic interpolation scheme, a linear curve fitting scheme, a quadratic curve fitting scheme and a cubic curve fitting scheme.

4. The method as claimed in claim 1, further comprising setting one of the N number of Doppler frequency ranges as a Doppler frequency range for determining if characteristics of the downlink and uplink channels are substantially the same, and establishing an uplink channel prediction scheme, which uses a channel coefficient estimated in a latest downlink period, as the channel prediction scheme corresponding to the Doppler frequency range for determining if characteristics of the downlink and uplink channels are substantially the same.

5. An adaptive channel prediction apparatus for performing uplink pre-equalization depending on downlink channel variation in an OFDM/TDD mobile communication system, the apparatus comprising:

a memory unit for storing N number of Doppler frequency ranges according to uplink channel variation degrees, and channel prediction schemes established corresponding to the respective Doppler frequency ranges;

a Doppler frequency measurement unit for measuring a Doppler frequency from a signal received over a downlink channel;

a channel prediction scheme selector for determining the Doppler frequency range, within which the measured Doppler frequency is included, from among the N number of Doppler frequency ranges, and selecting the channel prediction scheme established corresponding to the determined Doppler frequency;

a channel predictor for predicting a uplink channel by using the selected channel prediction scheme; and

a transmission equalizer for previously compensating for channel distortion based on the uplink channel predicted by the channel predictor.

6. The apparatus as claimed in claim 5, wherein the channel prediction schemes established corresponding to the Doppler frequency ranges include channel prediction schemes capable of optimally predicting an uplink channel according to a reciprocity degree of the downlink/uplink channel in a TDD channel.

7. The apparatus as claimed in claim 5, wherein the channel prediction scheme is selected from a group consisting of a linear interpolation scheme, a quadratic interpolation scheme, a cubic interpolation scheme, a linear curve fitting scheme, a quadratic curve fitting scheme and a cubic curve fitting scheme.

8. The apparatus as claimed in claim 5, wherein the memory unit stores one of the N number of Doppler frequency ranges as a Doppler frequency range for determining if characteristics of the downlink and uplink channels are substantially the same, and further stores an uplink channel prediction scheme, which uses a channel coefficient estimated in a latest downlink period, corresponding to the Doppler frequency range.