Method of parallel interference cancellation and an apparatus thereof

• US 20050163198A1
• Filed: 05/30/2003
• Published: 07/28/2005
• Est. Priority Date: 05/30/2002
• Status: Active Grant

• Current Assignee: Huawei Technologies Co., Ltd. (Huawei Investment & Holding Co., Ltd.)
• Original Assignee: Huawei Technologies Co., Ltd. (Huawei Investment & Holding Co., Ltd.)
• Inventors: Wei, Limei, Wang, Guolin
• Granted Patent: US 7,277,473 B2
• Time in Patent Office: Days
• US Class Current: 375/148
• CPC Class Codes: H04B 1/71075 Parallel interference cancellation
• CPC Class Codes: H04B 1/7115 Constructive combining of multi-path signals, i.e. RAKE receivers

Abstract

The invention discloses a method for parallel interference cancellation (PIC) in a mobile communication system. Every user signal is processed through multiple stages of PIC to remove multiple address interference (MAI) partly, it is characterized that any middle stage and final stage of PIC takes multipath de-spread results of this stage and last stage of the same user to make successive combination to obtain a multipath de-spread result having combined for this stage of the said user. A PIC device for said method includes multiple stages of structure that is mainly consisted of a RAKE receiver, a hard decision unit, a reliability coefficient generator, a signal regenerator, a MAI estimation and interference cancellation device, a de-spreader, a front-back stage combiner, and a channel estimation and multipath combiner etc.

Claims

1. A Parallel Interference Cancellation (PIC) method, comprises,

A) in the first stage of PIC, making multipath de-spread, channel estimation and multipath combination for a user input signal by a RAKE receiver, sending a multipath de-spread result to next stage,

making estimation and cancellation of Multiple Address Interference (MAI) of the user of this stage based on a multipath combination result and a channel estimation result, and obtaining an output signal of the said user of this stage;

B) in any middle stage of PIC, making multipath de-spread for output signal of last stage to obtain a multipath de-spread result of this stage, combining the multipath de-spread result of this stage and that of last stage of the said user to obtain a combined multipath de-spread result, sending the combined multipath de-spread result to next stage;

making channel estimation and multipath combination of this stage based on the combined multipath de-spread result, and then making estimation and cancellation of Multiple Address Interference (MAI) of this stage of the said user based on the multipath combination result and the channel estimation result of this stage, and obtaining an output signal of the said user of this stage;

C) in the final stage of pic, making multipath de-spread for output signal of last stage to obtain a multipath de-spread result of this stage, combining the multipath de-spread result of this stage and that of last stage of the said user to obtain a combined multipath de-spread result, making channel estimation and multipath combination based on the combined multipath de-spread result to obtain a soft output of the said user.

2. The Parallel Interference Cancellation (PIC) method according to claim 1, the step of combining the multipath de-spread result of this stage and that of last stage of the said user comprises, combining the multipath de-spread result of this stage and that of last stage by a formula

3. The Parallel Interference Cancellation (PIC) method according to claim 1, the step of making estimation and cancellation of MAI based on the multipath combination result and the channel estimation result further comprises,

making decision calculation based on the said multipath combination result;

calculating a regenerated signal based on the decision calculation result and the channel estimation result;

accumulating regenerated signals of other users to calculate the MAI of the said user;

removing the said MAI from the user input signal to obtain an output signal of this stage of the said user.

4. The Parallel Interference Cancellation (PIC) method according to claim 3, the decision calculation is a hard decision calculation or a soft decision calculation.

5. The Parallel Interference Cancellation (PIC) method according to claim 1, the step of making estimation and cancellation of MAI based on the multipath combination result and the channel estimation result further comprises,

calculating a hard decision based on the multipath combination result, and calculating a reliability coefficient of the hard decision result based on the said multipath combination result and the said channel estimation result;

calculating a regenerated signal based on the hard decision result, the reliability coefficient and the said channel estimation result;

accumulating regenerated signals of other users to calculate MAI of the said user;

removing the said MAI from the user input signal to obtain an output signal of this stage of the said user.

6. A parallel interference cancellation device that is a multiple stages of structure;

of which a first stage of the PIC includes N first stage user processing units and a first stage MAI estimation and interference cancellation device, any middle stage of the PIC includes N user processing units and a MAI estimation and interference cancellation device, and a final stage of the PIC structure includes N final stage user processing units;

wherein

the first stage user processing unit includes a RAKE receiver, a decision unit and a signal regenerator;

the RAKE receiver receives an input signal of a user and makes multipath de-spread, channel estimation and multipath combination;

a multipath combination result is sent to the decision unit, and a channel estimation result is sent to the signal regenerator., and a multipath de-spread result is exported to a front-back stage combiner of next stage;

a decision result of the decision unit is sent to the signal regenerator and a regenerated signal of said signal regenerator is sent to the first stage MAI estimation and interference cancellation device that makes estimation and cancellation of MAI and outputs the said user output signal of this stage;

the middle stage user processing unit includes a de-spreader, a front-back stage combiner, a channel estimation and multipath combiner, a decision unit and a signal regenerator;

the de-spreader makes multipath de-spread for the said user output of the last stage MAI estimation and cancellation device to obtain a multipath de-spread result of this stage;

the front-back stage combiner combines a multipath de-spread result of this stage and that of last stage of the said user to obtain a combined result, and then sends it to the said channel estimation and multipath combiner and a front-back stage combiner of next stage of the said user;

a multipath combination result of the channel estimation and multipath combiner is sent to the decision unit, and a channel estimation result of the channel estimation and multipath combiner is sent to the signal regenerator;

a decision result from the decision unit is sent to the signal regenerator, and a regenerated signal is sent to the MAI estimation and interference cancellation device of this stage, which makes estimation and cancellation of MAI and outputs the said user output signal of this stage;

the final stage user processing unit includes a de-spreader, a front-back stage combiner and a channel estimation and multipath combiner;

the de-spreader makes multipath de-spread for the said user output of last stage MAI estimation and cancellation device to obtain a multipath de-spread result of this stage;

said front-back stage combiner combines the multipath de-spread result of this stage and that of last stage of the said user to obtain a combined result, the combined result is sent to the channel estimation and multipath combiner, which makes channel estimation and multipath combination for the combined result and then outputs a final output signal of this user.

7. The parallel interference cancellation device according to claim 6, the first stage user processing unit further includes a reliability coefficient generator;

the multipath combination result and the channel estimation result of the RAKE receiver are sent to the reliability coefficient generator, respectively, and a result of said reliability coefficient generator is sent to the signal regenerator.

8. The parallel interference cancellation device according to claim 6, the middle stage user processing unit further includes a reliability coefficient generator;

the multipath combination result and the channel estimation result of the channel estimation and multipath combiner are sent to the reliability coefficient generator, respectively, and a result of said reliability coefficient generator is sent to the signal regenerator.

9. The parallel interference cancellation device according to claim 6, the decision unit is a hard decision unit or a soft decision unit.