Frequency-domain Interference Cancellation Research Articles

Performance Analysis of the Downlink CP-WCDMA System with Turbo Code in Frequency Domain

Modern wireless communications require an efficient spectrum usage and high channel capacity and high throughput. Turbo code, linear equalizers, multi-user detection and wideband code-division multiple access (WCDMA) are possible solutions to achieve spectral efficiency, high channel capacity, eliminate MAI, eliminate ISI and robustness against frequency selective fading. In this paper, we combine all these techniques and investigate BER performance. We propose a low complexity receiver structure for Single-input Single-output downlink cyclic prefix CP-WCDMA systems. It employs frequency domain interference cancellation schemes to mitigate the interference caused by the multipath fading channel. Also, the proposed scheme is developed for the downlink Turbo code CP-WCDMA system to maximize the throughput of the proposed system.

직접 대역 확산 시스템을 위한 간섭 신호 제어

In this paper, we propose a frequency-domain interference cancellation algorithm for direct-sequence spread spectrum systems. In the previously proposed frequency-domain interference cancellation algorithms that protocol defines the rules concerning the collection of means of Transmission Control Protocol (TCP: Transmission Control Protocol) is the most widely used in the transport layer. Two-way traffic through the network path to the same end-to-end transfer of data in the opposite direction between pairs of nodes are infused with two or more TCP connection using the network traffic patterns from the exchanger and routers share results of approval. Per-flow input/output structure of matter using the LTS online reaction when evaluated as this is the most important factor. TCP-MT when the connection duration is one of the largest performance gains.

LTE uplink MIMO receiver with low complexity interference cancellation

In LTE/LTE-A uplink receiver, frequency domain equalizers (FDE) are adopted to achieve good performance. However, in multi-tap channels, the residual inter-symbol and inter-antenna interference still exist after FDE and degrade the performance. Conventional interference cancellation schemes can minimize this interference by using frequency domain interference cancellation. However, those schemes have high complexity and large feedback latency, especially when adopting a large number of iterations. These result in low throughput and require a large amount of resource in software defined radio implementation. In this paper, we propose a novel low complexity interference cancellation scheme to minimize the residual interference in LTE/LTE-A uplink. Our proposed scheme can bring about 2 dB gains in different channels, but only adds up to 7.2 % complexity to the receiver. The scheme is further implemented on Xilinx FPGA. Compared to other conventional interference cancellation schemes, our scheme has less complexity, less data to store, and shorter feedback latency.

Performance evaluation of cyclic prefix CDMA systems with frequency domain interference cancellation

Direct-sequence code division multiple access (DS/CDMA) systems transmitting over multipath channels suffer from intersymbol interference (ISI) and multiple access interference (MAI). Recently, DS/CDMA with frequency domain equalization (FDE) has attracted much attention for its ability to obtain an excellent performance even in strong frequency selective fading channels. However, the presence of residual interference after the FDE degrades the orthogonality among the spreading codes and hence the BER performance deteriorates. Parallel interference cancellation (PIC) is an effective method to suppress the MAI and improve the CDMA system capacity. In this paper, we propose three interference cancellation architectures for downlink cyclic prefix CDMA systems. The common thread between these three architectures is their implementation in frequency domain. A comparison between such architectures is presented. Simulation results show that the combination of PIC and FDE provides an efficient solution to suppress the MAI in downlink CDMA systems over frequency selective fading channels.

EV-do revision C: Evolution of the cdma2000* data optimized system to higher spectral efficiencies and enhanced services

Wireless packet data services are poised to be a major growth area, as wireless voice services have reached a fair level of maturity. An effort by the 3rd Generation Partnership Project 2 (3GPP2) standards body to continue to develop the successful data-optimized 1x EV-DO high rate packet data (HRPD) 3G system is under way. Alcatel-Lucent along with partners is proposing several novel techniques beyond the state of the art. Some of the key technologies are orthogonal frequency code division multiple access (OFCDMA), multi-carrier as well as wideband transmission, both frequency division duplex (FDD) and time division duplex (TDD) modes, multiple antenna techniques such as space division multiple access (SDMA) and multiple input multiple output (MIMO), interference mitigation techniques, and frequency domain interference cancellation. These are described in detail along with the resulting benefits. The design goals are to provide flexibility, backward compatibility (both loose and strict), a boost in the spectral efficiency and peak rates, a reduction in latency for real-time services, and a reduction in complexity in the base stations (BS) and mobile stations (MS). In this paper, we describe the underlying design philosophy and the associated technologies of 1x EV-DO Revision C with a focus on Alcatel-Lucent's contribution and provide associated performance results. The standard is expected to be completed in 2Q 2007. © 2007 Alcatel-Lucent.

Iterative FDIC Using 2D-MMSE FDE for Turbo-Coded HARQ in SC-MIMO Multiplexing

SUMMARY Multiple-input multiple-output (MIMO) multiplexing is an attractive technique to achieve very high-speed transmission with a limited bandwidth. Recently, we proposed an iterative frequency-domain interference cancellation (FDIC) for single-carrier MIMO (SC-MIMO) multiplexing. In our previous work, assuming that the interference from the other antennas can be perfectly cancelled in FDIC, one-dimensional minimum mean square error (1D-MMSE) frequency-domain equalization (FDE) was used. However, the residual interference remains after performing FDIC. In this paper, to improve the transmission performance with iterative FDIC, we replace 1D-MMSE FDE by 2D-MMSE FDE, which takes the residual interference from the other antennas after FDIC into account. We investigate, by computer simulation, the throughput performance of rate compatible punctured turbo coded hybrid ARQ (RCPT-HARQ) with MIMO multiplexing in a frequency-selective Rayleigh fading channel.

Frequency-domain interference cancellation and nonlinear equalization for CDMA systems

In wireless broadband communications using code division multiple access (CDMA), interference cancellation (IC) techniques have been proposed to reduce multiuser access interference (MAI); however, their performance is limited by complexity constraints that still favor the use of rake receivers. In this paper, we propose an IC architecture that makes use of a block decision feedback equalizer (DFE) to remove intersymbol interference (ISI) and whose overall complexity is much lower than equivalent (in terms of performance) existing structures. In fact, by making use of a particular block data transmission format, all filters are implemented in the frequency domain (FD), and in particular, the DFE is iteratively designed according to the reliability of the detected data in the previous iteration. Due to the strong interaction of the FD-IC and the block DFE, error propagation in the receiver is reduced by simply interleaving (INT) chips before transmission. Simulations performed for an uplink communication on a wireless multipath channel show that the combination of FD-IC, block DFE, and chip INT provides an efficient solution with good performance for CDMA systems in dispersive channels.