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In this paper a new scheme for deriving the channel reliability factor to be passed to the turbo decoder is derived in the framework of a Long Term Evolution (LTE) air interface and for a realistic Wiener channel interpolator. Our results show that a performance gain can be achieved with a limited increase in complexity by accounting for the imperfect channel knowledge in the channel reliability factor...
Cooperative diversity networks have been receiving a lot of attention recently as an attractive way to combat frequency-selectivity of wireless channel, as it consumes neither time nor frequency resources. In the conventional cooperative strategies, relays employ either a decode-and-forward (DF) or an amplify-and-forward (AF) relaying protocol. In this paper, we investigate a new hybrid cooperative...
4G wireless systems predominately employ multiple input multiple output (MIMO) with an orthogonal frequency division multiplexing (OFDM) system. Like other 4G systems long term evolution (LTE) also employs MIMO-OFDM physical layer. MIMO helps in increasing the throughput whereas OFDM converts a frequency selective fading channel to multiple flat fading sub-channels facilitating easy equalization....
We present an algorithm and architecture of a soft-output sphere decoder with an optimized hardware implementation for 2??2 MIMO-OFDM reception. We introduce a novel table look-up approach for symbol enumeration that simplifies the implementation of soft-output decoders. The HW implementation is targeted towards WLAN (IEEE 802.11n) with stringent latency and throughput requirements. The current implementation...
OFDM data with line rates of 5.4 Tbit/s or 10.8 Tbit/s are generated and decoded with a new real-time all-optical FFT receiver. Each of 75 carriers of a comb source is encoded with 18 GBd QPSK or 16-QAM.
We experimentally demonstrate the transmission of a spectrally-efficient 44-Gb/s CO-OFDM signal whose subcarriers are trellis-coded with 32-QAM over a 990-km dispersion-managed SSMF link, and show the performance improvements obtained through the coded-modulation and self-phase-modulation compensation.
The performance of a wireless communication system is analyzed considering multi-carrier OFDM with Multiple- Input-Multiple-Output (MIMO) wireless channel and Space-Time Block Coding (STBC). Bit Error Rate (BER) expression for MIMO-OFDM system without and with STBC is presented considering fading and timing jitter with QPSK, DPSK and DQPSK modulation schemes. The performance results are evaluated...
A simple soft-demapping scheme for rectangular quadrature amplitude modulation (R-QAM) signals is developed for a low-cost 60 GHz OFDM baseband chip design, conforming to the IEEE802.15.3C standard. The scheme is equally applicable to a generic bit-interleaved orthogonal frequency division multiplexing (OFDM) modulation for both square QAM (S-QAM) and R-QAM constellations. The channel coding employs...
In this work we investigate Multi-User Multiple-Input Multiple-Output (MU-MIMO) systems within the frame of an Orthogonal Frequency Division Multiplexing (OFDM) communication scheme. We look at the case where several User Terminals (UT), each of them having one transmit antenna, are grouped together and communicate in Up-Link (UL) with the Base Station (BS) equipped with two or four antennas. We perform...
A space-time coding scheme based on interleave division multiplexing (EDM) is investigated over an orthogonal frequency division multiplexing (OFDM) link that employs multiple transmit antennas. The performance of an iterative receiver structure for the proposed scheme over a quasi-static channel is evaluated via simulation, and its advantages are shown by comparison to other space-time schemes in...
Based on the high peak to average power ratio of orthogonal frequency division multiplexing systems, several methods of reducing the peak to average power ratio were analyzed. Then a method based on Golay complementary sequences was proposed to realize the low peak to average power ratio. The high peak to average power ratio sequences were encoded into Golay complementary sequences, peak to average...
In this paper, we introduce carrier interferometry OFDM (CI/OFDM) into the underwater acoustic transmission field, and put the emphasis on how to deal with BER during communication with LDPC approach. We also analyze the error distribution of the received CI/OFDM signal, and propose a kind of CI-OFDM-LDPC joint algorithm to solve this problem. The result shows that even if the BER reaches a level...
This article at first introduces the development of the channel coding technology driven by the Shannon's theory, and the tendency that the coding and modulation will be combined. Then it elaborates on the channel coding problems under the wireless channel. At last it discusses the development direction of the coding technology, that is, when considering the specific wireless communication environment,...
Time variation of wireless fading channels introduces interference in block-based transmissions such as orthogonal frequency division multiplexing (OFDM) or single-carrier frequency domain equalization (SC-FDE). The interference, called inter-carrier interference (ICI) in OFDM or residual inter-symbol interference (ISI) in SC-FDE, impacts the bit error rate performance resulting in an error floor...
This paper proposes novel techniques for the synchronous pipelined two-stage radix-4 Viterbi decoder for 200 Mbps MB-OFDM UWB on FPGA. MB-OFDM UWB requires rate-1/3, 64-state Viterbi decoder to be implemented with 200 Mbps data rate and low power. To obtain low power, traceback method is used instead of register exchange method and to obtain high speed, radix-4 Viterbi decoder with two stages is used...
Receivers for horizontally encoded LTE based MIMO-OFDM systems are considered in this paper. Adaptive modulation and coding (AMC) is used as well as precoding. The linear minimum mean square error (LMMSE), successive interference cancellation (SIC) and K-best list sphere detectors (LSD) are compared. The receivers were designed and implemented for 2??2 and 4??4 antenna systems and meet the decoding...
This paper presents turbo coded orthogonal frequency division multiplexing performance which uses fading channel rayleigh distributed. Channel coefficients are generated by jakes method. Iterative decoding causes iteratively transfer of extrinsic LLR which yields correct polarity and realibility of soft decision. The size of block interleaver rules increasing weight codeword and declining bit error...
The frequency bands used by secondary systems such as cognitive radio (CR) and ultra-wideband (UWB) systems are subject to various forms of non-Gaussian noise and interference including co-channel interference caused by the primary user and other secondary systems and man-made impulsive noise. For secondary systems employing the popular combination of bit-interleaved coded modulation (BICM) and orthogonal...
The ever-increasing demand for precious radio spectrum along with the inefficient usage of licensed band has led to the advent of the cognitive radio (CR) technology, which aims to provide opportunistic spectrum usage to unlicensed users and thus lead to the co-existence and interference control problem among heterogeneous systems. In this paper, an interference minimization and subcarrier power allocation...
This paper proposes a low-complexity algorithm to calculate log likelihood ratios (LLRs) of coded bits, which is necessary for channel decoding in coded MIMO-OFDM mobile communications. An approximate LLR needs to find a pair of transmitted signal candidates that can maximize the log likelihood function under a constraint that a coded bit be equal to either one or zero. The proposed algorithm can...
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