Multi-user detector for direct sequence-code division multiple access (DS/CDMA) channels

A multi-user detection and multi-user technology, applied in the direction of electrical components, transmission systems, etc., can solve problems such as not optimal performance

Inactive Publication Date: 2004-02-25
NORTEL NETWORKS LTD
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  • Abstract
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  • Claims
  • Application Information

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Problems solved by technology

Although they have polynomial complexity in terms of the number of users and provide significa

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  • Multi-user detector for direct sequence-code division multiple access (DS/CDMA) channels
  • Multi-user detector for direct sequence-code division multiple access (DS/CDMA) channels
  • Multi-user detector for direct sequence-code division multiple access (DS/CDMA) channels

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Embodiment Construction

[0021] see figure 1 , a block diagram illustrating a multi-user detector (MUD) according to an embodiment of the present invention. The MUD 10 includes a rake receiver 12 having a plurality of outputs 14 connected to a packet combiner 16 and a parallel interference cancellation (PIC) section 18 . The output of the packet combiner 16 is used in a soft input soft output (SISO) decoder 20 . The SISO decoder 20 has multiple outputs 22 for decoding values. A plurality of outputs 22 are connected to the PIC section 18 . The output of the PIC section 18 is then input to a second packet combiner 24 whose output is used as input to a second SISO decoder 26 . The output of the second SISO decoder is input to the CRC check 28. The decision section 30 allows the received data packet to be output at 32, if no errors are found, otherwise the packet is sent to the packet buffer 48 and ARQ is sent to the transmitter requesting retransmission of the packet.

[0022] In operation, the firs...

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Abstract

The present invention combines multi-user detection with packet combining. In multi-user detection, the receiver jointly demodulates user's data by exploiting the structure of multi-user interference, the packet combining is an enhancement of standard automatic repeat request protocol, in which the erroneous packet are not discarded but preserved and combined with retransmitted ones to improve subsequent decisions. One embodiment of the two-stage detector uses a first stage in which the packets are combined and then decoded, in order to improve tentative decisions for interference cancellation. The decoder output is then used in the second stage to cancel the interference, and then the combining is performed once again, before the final decoding. For the two-stage detection we consider two decoding schemes in the first stage. One is the soft input/soft output maximum a posteriori probability decoding of the combined packets, then a soft interference cancellation is performed in the second stage. In the second embodiment, we use the hard decision Viterbi/Turbo decoding, and a hard interference cancellation in the second stage. In the simulation we include power control, quantization, and timing, phase and amplitude estimation. The results indicate that the proposed scheme with packet combining and multi-user detection employed jointly significantly improve performance in the high channel load, increasing the robustness of the system.

Description

technical field [0001] The present invention relates to a multi-user detector for Direct Sequence-Code Division Multiple Access (DS / CDMA) channels, in particular to a detector for packet retransmission. Background technique [0002] The Automatic Repeat Request (ARQ) protocol is a well-known technique used for handling transmission errors caused by noisy channels. In most implementations of the ARQ protocol, its sole purpose is error detection. When one or more errors are detected in the received data block, a retransmission request is sent back to the originating transmitter and the erroneous data block is discarded. The main disadvantage of ARQ schemes is that, especially at low signal-to-noise ratios (SNR), the number of retransmissions required before correct reception can be high, resulting in unacceptably low traffic. The bottom line is that various improvements to the ARQ protocol have been proposed in the literature [1], [2], [3] with the aim of enhancing performan...

Claims

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Application Information

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IPC IPC(8): H04B1/707
CPCH04B1/71075
Inventor 童文布朗米尔·沃伊契奇雷蒙德·皮可霍尔茨杰兰纳·达姆尼亚诺维奇
Owner NORTEL NETWORKS LTD
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