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In mobile communication systems such as LTE, Hybrid-ARQ (HARQ) schemes based on Turbo codes have proved to be very effective in ensuring reliable transmission. However, several modified HARQ and Turbo decoding strategies have been recently developed to further improve performance. This paper proposes an enhanced coding scheme for LTE which couples a modified Turbo coding strategy with Reliability...
In this paper, the performance of the Least Squares (LS) estimator along with turbo codes in OFDM is evaluated for the SUI channel models in the presence of AWGN. Turbo codes are used in this paper because of its BER performance close to Shannon limit. The iterative turbo decoder exchanges soft information between the component decoders. Maximum A Posteriori (MAP) and its simplified version Max-Log-MAP...
Cloud-Txn is a new broadcasting approach, which proposes the usage of the layer-division-multiplexing (LDM) to meet the requirements of the new generation digital TV services. Cloud Txn has been proposed as one of the candidate technologies for the Next Generation DTV systems. This technology is considered as an attractive alternative to the commonly used Time Division (TDM) and Frequency Division...
Vehicular wireless channels are highly time-varying and the pilot pattern in the 802.11p orthogonal frequency-division multiplexing frame has been shown to be ill suited for long data packets. The high frame error rate in off-the-shelf chipsets with noniterative receiver configurations is mostly due to the use of outdated channel estimates for equalization. This paper deals with improving the channel...
This paper considers the coded OFDM system and instead of discarding the cyclic prefix (CP) at the receiver, we utilize the CP observation for joint detection, decoding and channel estimation. In particular, detection and decoding are performed iteratively between an equalizer and a soft-input soft-output (SISO) decoder based on the turbo principle, and the expectation-maximization (EM) algorithm...
We consider the two-way relaying of orthogonal space time block codes (OSTBCs) with imperfect channel information. We derive a maximum likelihood (ML) decoder of OSTBC, by assuming perfect channel knowledge at both user nodes. The decoding of OSTBC data at a user terminal is performed by replacing the exact channel state information (CSI) by the estimated CSI, in the ML metric. An approximate closed-form...
We investigate the influence of channel estimation error on the achievable system-level throughput performance of non-orthogonal access with successive interference cancellation (SIC) in the cellular downlink. The channel estimation error in non-orthogonal access causes residual interference in the SIC process, which decreases the achievable user throughput. Furthermore, the channel estimation error...
n this paper, we introduce a three-phase transmis- sion scheme for cloud radio networks against eavesdropper. We study the security and reliability performance of this scheme in the form of intercept probability and outage probability, respectively. Channel estimation error is considered in our study instead of assumption of perfect channel state information. It is found that the security-reliability...
This paper presents a comparative study of single-carrier (SC)-frequency division multiple access (FDMA) and OFDMA using turbo soft interference cancellation (SIC) from the viewpoint of throughput for multiple-input multiple-output (MIMO) spatial division multiplexing (SDM). In turbo SIC, interference from other transmission streams is generated based on the log-likelihood ratio (LLR) at the turbo...
With the widespread deployment of LTE 4G systems and large number of connected devices due to the Internet of Things, M2M services using LTE is under consideration by many cellular operators. To provide ubiquitous network coverage for M2M services, 3GPP will introduce coverage enhancement feature in Rel-13. In this paper we analyze features which will extend the range of an LTE system by up to 15dB...
Channel quality parameters are needed to achieve efficient utilization of radio resources. These parameters include channel amplitude gain, channel frequency offset, channel random phase, channel multipath as well as channel noise variance. Usually, signal-to-noise ratio (SNR) at the demodulator output is used as channel quality indicator to link bit error rate (BER). In applications such as power...
Reactive jamming is considered the most powerful jamming attack as the attack efficiency is maximized while the risk of being detected is minimized. Currently, there are no effective anti-jamming solutions to secure OFDM wireless communications under reactive jamming attack. On the other hand, MIMO has emerged as a technology of great research interest in recent years mostly due to its capacity gain...
Today's smartphones and tablets contain multiple cellular modems to support 2G/3G/4G standards, including Long Term Evolution (LTE). They run on complex multi-processor hardware platforms and have to meet hard real-time constraints. Dataflow modeling can be used to design an LTE receiver. Static dataflow allows a rich set of analysis techniques, but is too restrictive to model the dynamic behavior...
In this paper a receiver making use of a complexity-optimized Decision feedback equalization (DFE) structure and adaptive noise filtering is presented. Vehicular transmission systems such as IEEE 802.11p are facing serious challenges originating from the vehicular channel. Due to the channels high Doppler frequencies and long path delays, channel estimation and equalization is a pivotal aspect of...
This paper presents the soft-input soft-output (SISO) linear programming (LP) decoder. It is shown that the soft information gleaned from a pseudo-codeword solution to the LP optimization is not only useful, but that it can be used to form a superior channel estimate compared to the output from a SISO belief propagation (BP) decoder in certain situations.
In the setting of the time-selective two-user multiple-input single-output (MISO) broadcast channel (BC), recent work by Tandon et al. considered the case where — in the presence of error-free delayed channel state information at the transmitter (delayed CSIT) — the current CSIT for the channel of user 1 and of user 2, alternate between the two extreme states of perfect current CSIT and of no current...
We propose a factor-graph-based approach to joint channel, impulse, symbol and bit estimation (JCISB) of LDPC-coded orthogonal frequency division multiplexing (OFDM) systems in impulsive noise environments. Impulsive noise arises in many modern wireless and wireline communication systems, such as cellular LTE and powerline communications, due to uncoordinated interference that is much stronger than...
Several researches investigate the performance of the conventional adaptive equalizers for the medium data rates HF waveforms (up to 8 PSK) and show that they are suitable for mitigating the HF channel. However, the performance of these types of equalizers is very bad for the high data rates HF waveforms (up to 64QAM). Most of the later researches in the high data rates HF waveforms are based on the...
The performance of a multicell large scale antenna system (LSAS) is conveniently characterized by capacity lower-bounds that explicitly account for channel-estimation error, the type of linear spatial multiplexing/de-multiplexing (conjugate beamforming or zero-forcing on the forward link and matched-filtering or zero-forcing on the reverse link), power-control, non-coherent inter-cell interference,...
Code for a compound discrete memoryless channel (DMC) is required to have small probability of error regardless of which channel in the collection perturbs the codewords. Capacity of the compound DMC has been derived classically: it equals the maximum (over input distributions) of the minimal (over channels in the collection) mutual information. In this paper the expression for the channel dispersion...
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