Multi-user receiving apparatus converting SC-FDMA received signals of all users to signals in a frequency domain commonly

• US 20070070879A1
• Filed: 09/22/2006
• Published: 03/29/2007
• Est. Priority Date: 09/27/2005
• Status: Active Grant

• Current Assignee: NEC Corporation
• Original Assignee: NEC Corporation
• Inventors: Kimata, Masayuki, Kakura, Yoshikazu, Yoshida, Shousei, Oketani, Kengo
• Granted Patent: US 7,668,076 B2
• Time in Patent Office: Days
• US Class Current: 370/208
• CPC Class Codes: H04L 2025/03414 Multicarrier
• CPC Class Codes: H04L 27/2662 Symbol synchronisation
• CPC Class Codes: H04L 5/023 Multiplexing of multicarrier modulation signals multicarrier modulation H04L27/2601

Abstract

A multi-user receiving apparatus is provided for achieving a reduction in the amount of processing for single-carrier FDMA signals and an improvement in reception characteristics. A DFT unit converts single-carrier FDMA received signals of all users to signals in a frequency domain commonly. A demapping unit selects part of sub-carriers for each user from sub-carriers supplied from the DFT unit. A reception filter separates a user signal and suppresses noise. A demodulator demodulates the user signal, and detects a timing thereof.

Claims

1. A multi-user receiving method in a base station with which a plurality of mobile stations each assigned to a respective user simultaneously communicate in accordance with a single-carrier frequency division multiple access scheme, said method comprising the steps of:

converting SC-FDMA received signals of all users to signals in a frequency domain commonly;

selecting part of the sub-carriers for each user contained in the signals in a frequency domain; and

performing reception processing.

2. A multi-user receiving apparatus in a base station with which a plurality of mobile stations each assigned to a respective user simultaneously communicate in accordance with a single-carrier frequency division multiple access scheme, said apparatus comprising:

a DFT unit for converting SC-FDMA received signals of all users to signals in a frequency domain commonly;

a demapping unit for selecting part of the sub-carriers for each user contained in the signals in a frequency domain supplied from said DFT unit; and

a plurality of user receivers each associated with one of a plurality of users, and each including a reception filter for limiting the frequency band of each user signal, supplied from said demapping unit, to separate the user signal and to suppress noise, and a demodulator for demodulating the output of said reception filter and for detecting a reception timing to generate a timing control signal.

3. The apparatus according to claim 2, wherein said demapping unit selects part of sub-carriers for each user from the sub-carriers supplied from said DFT unit to convert the carrier frequency of each user to zero frequency.

4. The apparatus according to claim 2, wherein said reception filter has a raised cosine roll-off characteristic with a variable bandwidth corresponding to the transmission rate of each user signal

5. The apparatus according to claim 2, wherein said demodulator includes:

a reference signal generator for generating a pilot reference signal in a frequency domain of each user from pilot symbols;

a transmission channel estimator responsive to the received pilot signal, the band of which has been limited by said reception filter, and to the pilot reference signal generated by said reference signal generator, for calculating a transmission channel estimate;

an equalization processing unit responsive to the received signal, the band of which has been limited by said reception filter, and to an equalization weight calculated from the transmission channel estimate for equalizing the received signal; and

a timing detector for detecting a reception timing from a transmission channel response resulting from an IDFT of the transmission channel estimate to generate a timing control signal.

6. The apparatus according to claim 5, wherein said reference signal generator performs DFT on pilot symbols, limits the frequency band of the DFT signal with a transmission/reception filter, and generates a pilot reference signal by which pilot symbol pattern characteristics included in the received pilot signal, together with characteristics of the transmission/reception filter are cancelled in the calculation of a transmission channel estimate.

7. The apparatus according to claim 5, wherein said equalization processing unit equalizes the received signal in accordance with a minimum mean square error method or a zero forcing method.

8. The apparatus according to claim 5, wherein said timing detector calculates power or amplitude of a transmission channel response resulting from an IDFT of the transmission channel estimate to generate a delay profile, detects from the delay profile a path with a high level, the timing of which indicates a reception timing, and generates a timing control signal.

9. The apparatus according to claim 5, wherein said timing control signal is fed back to a mobile station and used in transmission timing control for synchronizing reception timings of packet signals among the users.