The parallel interference cancellation (PIC) multiple input multiple output (MIMO) detection algorithm has bit error ratio (BER) performance comparable to the maximum likelihood (ML) algorithm but with complexity close to the simple linear detection algorithm such as zero forcing (ZF), minimum mean squared error (MMSE), and successive interference cancellation (SIC), etc. However, the throughput of PIC MIMO detector on central processing unit (CPU) cannot meet the requirement of wireless protocols. In order to reach the throughput required by the standards, the graphics processing unit (GPU) is exploited in this paper as the modem processor to accelerate the processing procedure of PIC MIMO detector. The parallelism of PIC algorithm is analyzed and the two-stage PIC detection is carefully developed to efficiently match the multi-core architecture. Several optimization methods are employed to enhance the throughput, such as the memory optimization and asynchronous data transfer. The experiment shows that our MIMO detector has excellent BER performance and the peak throughput is 337.84 Mega bits per second (Mbps), about 7x to 16x faster than that of CPU implementation with SSE2 optimization methods. The implemented MIMO detector has better computing throughput than recent GPU-based implementations.

In this paper, the issue of carrier frequency offset (CFO) compensation in interleaved orthogonal frequency division multiple access (OFDMA) uplink system is investigated. To mitigate the effect of multiple access interference (MAI) caused by CFOs of different users, a new parallel interference cancellation (PIC) compensation algorithm is proposed. This scheme uses minimum mean square error (MMSE) criterion to obtain the estimation of interference users, then circular convolutions are employed to restore MAI and compensate CFO. To tackle the complexity problem of circular convolutions, an efficient MAI restoration and cancellation method is developed. Simulations illustrate the good performance and low computational complexity of the proposed algorithm.

A novel low-complexity iterative receiver for coded multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) systems is proposed in this letter. The iterative receiver uses the parallel interference cancellation (PIC)-maximum ratio combining (MRC) detector for MIMO-OFDM detection, which is a popular alternative to the minimum mean square error (MMSE) detector due to its lower computational complexity. However, we have found that the conventional PIC-MRC detector tends to underestimate the magnitude of its output log likelihood ratios (LLRs). Based on this discovery, we propose to multiply these LLRs by a constant factor, which is optimized according to the extrinsic information transfer (EXIT) chart of the soft-in soft-out (SISO) detector. Simulation results show that the proposed scheme significantly improves the performance of the PIC-MRC-based receiver with little additional cost in computational complexity, allowing it to closely approach the performance of receiver using the much more complex MMSE detector.

A precoding scheme is described for multiple-input and multiple-output orthogonal frequency-division multiplexing systems with a QR-decomposition maximum likelihood detector (MLD) incorporated with a parallel interference canceller (PIC) at a receiver. Transmit antenna ranking based on received substream signal power or per-substream minimum Euclidean distances is fed back to a transmitter. Based on the ranking information, precoding matrices are determined as permutation matrices such that specific packets are transmitted from transmit antennas with higher channel quality over the whole subcarriers. The simulation results demonstrated that precoding effectively utilizes PIC by reducing the possibility that all substreams are incorrectly decoded and thus improves the transmission performance of a QR-decomposition MLD with PIC.

This letter describes unequal-power transmission for multiple-input and multiple-output (MIMO) systems with a parallel interference canceller (PIC) applied to a maximum likelihood detector (MLD) or complexity-reduced MLD at the receiver. Unequal-power transmission reduces the possibility that all substreams are incorrectly decoded. Canceling the correctly decoded substreams enables more reliable detection in the next stage. The simulation results demonstrated that unequal-power transmission improves the transmission performance of the PIC applied to MLDs or complexity-reduced MLDs, compared with equal-power transmission cases.

In this letter, parallel interference cancellation (PIC) in code division multiple access (CDMA) was performed with two different structures by using a neural network (NN). In the first structure (receiver-1) the NN was used as a front-end stage of a one stage PIC circuit. In the second structure (receiver-2), the NN was used instead of the one stage PIC circuit and it was trained as a multiple access interference (MAI) detector to perform the PIC process by subtracting the MAI from the outputs of the matched filter. The PIC is a classical technique in multi user detection process and its bit error rate (BER) performance is not good in one stage for most of the applications. For improving its BER performance, generally a multi stage PIC which has the high computational complexity is used. In this study, we have gotten a better BER performance than a three stages PIC receiver with both proposed receivers that have the lower computational complexity.

In this paper, we propose an adaptive multistage fuzzy-based partial parallel interference cancellation (FB-PPIC) multiuser detector for multi-carrier direct-sequence code-division multiple-access (MC-CDMA) communication systems over frequency selective fading channels. The partial cancellation tries to reduce the cancellation error in parallel interference cancellation (PIC) schemes due to the wrong interference estimations in the early stages and thus outperforms the conventional PIC (CPIC) under the heavy load for MC-CDMA systems. Therefore, in this paper, the adaptive cancellation weights are inferred from a proposed multistage fuzzy inference system (FIS) to perform effective PPIC multiuser detection under time-varying frequency selective fading channels in MC-CDMA systems. Simulation results show that the proposed adaptive four-stage FB-PPIC scheme outperforms both CPIC and constant weight PPIC (CW-PPIC) schemes, especially in near-far environments.

In this paper, two types of multi-stage partial parallel interference cancellation (PIC) receivers are considered for multi-rate DS-CDMA system: multi-stage PIC receiver with partial cancellation factors and multi-stage PIC receiver with decision thresholds. Bit error rate (BER) of the multi-stage partial PIC receivers is obtained by simulation in a Rayleigh fading channel. It is shown that the multi-stage partial PIC receivers achieve smaller BER than the matched filter (MF) receiver, multi-stage PIC receiver, group-wise successive interference cancellation (GSIC) receiver, and extended GSIC receiver (EGSIC) for the multi-rate DS-CDMA system in a Rayleigh fading channel.

This paper introduces an improved multistage parallel interference cancellation (PIC) technique that uses the reverse-link synchronous transmission technique (RLSTT) to improve the estimation of data at the initial stage. Because the subtraction of an interfering signal based on an incorrect bit decision quadruples the interference power for that signal, the relatively high decision bit error rate (BER) may lead to a poor cancellation or even a higher BER at the following stages. The RLSTT is a robust approach which takes into account the fact the tentative decision at the earlier stages is less reliable than the following stages and makes the earlier cancellation more reliable. The analysis demonstrates that a better transmission performance can be achieved by using the RLSTT at the initial stage of PIC.

In [3], the decision feedback channel estimation (DFCE) for M-ary orthogonal modulation in direct sequence/code division multiple access (DS/CDMA) systems was proposed. However, the performance of the DFCE in the multiuser environment is severely degraded due to multiple access interference (MAI). In this letter, to overcome this problem, we modify the DFCE as multistage configurations using a multistage parallel interference cancellation (PIC) scheme. According to the results of our simulations, the performance of coherent demodulation using the proposed multistage DFCE is significantly improved in comparison with conventional demodulation in [3].

In this paper, the improvement technique for a nonlinear parallel interference cancellation (PIC) receiver for a DS-CDMA system is studied, which cancels only the estimated multiple access interference (MAI) from specific users at each receiver stage. This technique was introduced as a PIC receiver using null zone hard decision in the proceeding of IEEE MILCOM '94, but the numerical results has not been fully provided with varying decision threshold. In this paper, the performance of the PIC receiver using null zone hard decision is shown in a Rayleigh fading channel. Also, a new PIC receiver with an adaptive decision threshold is proposed. In the proposed new PIC receiver, the decision threshold for partial cancellation is adjusted according to the statistic of its matched filter (MF) outputs. The BER of the proposed PIC receiver is obtained by simulation and compared with those of the conventional PIC receiver and the PIC receiver using null zone hard decision in a Rayleigh fading channel. It is shown that the proposed PIC receiver achieves better performance than the conventional PIC receiver and the PIC receiver using null zone hard decision in a Rayleigh fading channel.