Cyclic Delay Diversity Scheme Research Articles

Reference measurement channel RMC parameters of LTE downlink waveforms

Long-Term Evolution (LTE) is a standard for high speed wireless communication for mobile devices and data terminals, It increases the capacity and speed using a different radio interface together with core network improvements. LTE employs SC-FDMA for uplink UL transmission and OFDM for downlink DL data transmission, in this paper LTE DL implemented with MATLAB programing and Simulink, Reference measurement channel RMC on DL waveform illustrated in different Transmission scheme of single, 4 antenna and cyclic delay diversity scheme CDD, duplexing mode, resources blocks and modulation approaches leadings to a various number of total information per frame, QPSK, 16 QAM and 64 QAM modulation approaches used in the proposed system are tested under AWGN Rayleigh fading channels.

Performance Analysis of Distributed Single Carrier Systems With Distributed Cyclic Delay Diversity

This paper investigates a distributed cyclic delay diversity (CDD) transmission scheme for cyclic-prefixed single carrier systems in non-identically and identically distributed frequency selective fading channels. The distinguishable feature of the proposed scheme lies in providing a transmit diversity gain while reducing the burden of estimating the channel state information, which is a challenging task in distributed and cooperative systems. To effectively use the distributed CDD scheme at the transmitters, two sufficient conditions are derived to eliminate the intersymbol interference at the receiver and leveraged to convert the multi-input single-output channel into a single-input single-output channel. These conditions allow the system to achieve the maximum diversity for frequency selective fading channels at a full rate. To achieve this maximum diversity, a fixed number of CDD transmitters are selected based on the channel conditions, symbol block size, and maximum time dispersion of the channel, and a new two-stage transmission mode is proposed. Based on the distributed CDD and the proposed selection schemes, a new expression for the signal-to-noise ratio at the receiver is obtained with the aid of order statistics, and then closed-form expressions for the outage probability and average symbol error rate (ASER) are derived. As far as the identically distributed frequency selective fading channel model is concerned, the achievable maximum diversity gain is proved, with the aid of asymptotic analysis, to be equal to the product of the total number of transmitters in the system and the number of multipath components. Link-level simulations are also conducted to validate the analytical expressions for outage probability, ASER, and maximum achievable diversity gain.

Cooperative Transmission Scheme Using the Single Antenna in the Broadcasting and Cellular System

In this paper, the cellular system and broadcasting system use a cooperative transmission scheme. The conventional scheme is not consider the condition of a channel between a cellular base station (CBS) and a destination user. In this conventional scheme, two CBSs communicate with the user by the cooperative transmission scheme when the user is located in the cell edge. If CBS is distant from a user and the channel condition is poor, the performance of communication is degraded. The proposed scheme using the relay between CBS and the user located in the edge of CBSs improves the performance of the communication when the channel state between CBS and the user is bad. Also, space time block code and cyclic delay diversity scheme are used for the reliable transmission in the proposed scheme. The proposed scheme using the relay achieves good BER and throughput performance. Through the simulation, it is confirmed that the proposed scheme is better than the conventional scheme.

A Proposed H-STCDD Scheme in Cooperative Communication System

In this paper, the hierarchical space time cyclic delay diversity (H-STCDD) scheme is proposed. Proposed scheme uses hierarchical modulation and achieves approximately full rate. It also uses a cyclic delay diversity scheme, which improves the benefit of channel coding particularly in high SNR environment between source to relay and source to destination. According to simulation result, proposed scheme has up to 2.2 dB better BER performance than conventional cooperative scheme at BER of 10ź3 and has similar BER performance with the STCDD scheme particularly in high SNR environment between source to relay and source to destination. Throughput of the proposed scheme is better than those of other cooperative schemes. Therefore proposed scheme is more efficient than other cooperative scheme and can be efficiently used in high SNR environment between source to relay and source to destination.

Selective Random CDD Enhanced Joint Cooperative Relay and HARQ for Delay-Tolerant Vehicular Communications

We propose a selective random cyclic-delay diversity (CDD) enhanced joint cooperative relay and hybrid automatic repeat request (HARQ) scheme for two-hop vehicular communications. Our innovation mainly concentrates on design of the second-hop transmissions. On one hand, the CDD technique is applied across multiple relay nodes to artificially create frequency selectivity and then achieve diversity gain by applying channel coding. The employment of CDD does not necessarily require channel state information (CSI) at the transmitters and thus also decreases overhead caused by CSI feedback. On the other hand, retransmission for the second hop is performed based on relay selection. Particularly, the CDD is constructed only over selected relay nodes with qualified channel qualities to achieve a better frequency selective channel. As the selection results vary with random channel fading, our scheme is termed selective random CDD. Our scheme is presented based on a generic model and further applied into two scenarios, respectively: (1) car-to-car communications in high-way vehicular networks; (2) downlink transmission for the high velocity mobile station in cellular networks. Simulation results show that our proposed selective random CDD scheme can achieve higher throughput as well as lower transmission delay than the conventional cooperative beamforming based transmission scheme.

A Random Beamforming Technique for Omnidirectional Coverage in Multiple-Antenna Systems

A random beamforming (RBF) technique is proposed to achieve omnidirectional coverage for broadcast channels in multiple-antenna systems. In the proposed scheme, the time and frequency resources for communication are divided into many time-frequency blocks (TFBs). A random pattern is employed on each TFB, with the average power in all directions over many TFBs being equal. The design criteria and detailed design of the random pattern sequence are given. We propose a basic RBF scheme and an Alamouti-enhanced scheme, as well as the corresponding structures of the transmitter and the receiver. Simulations are carried out for an eight-element unitary linear array with half-waveform separation in a fast-fading channel, showing that the proposed scheme greatly outperforms the cyclic delay diversity scheme and is robust to calibration errors and failures of radio-frequency chains.

CDD-DSF 릴레이 기법을 적용한 MC-CDMA 시스템의 다중경로 레일리 페이딩 채널에 대한 평균 비트 오류율 분석

본 논문에서는 CDD-DSF 릴레이 기법을 적용한 MC-CDMA 시스템을 다중경로 레일리 페이딩 채널에 대해 제안한다. 일반적인 DSF 기법들과는 다르게 CDD 방법의 적용시 각 릴레이는 하나의 채널을 통하여 신호를 전송한다. 따라서 릴레이들과 수신단 사이의 채널들은 넓게 시간 확산된 하나의 채널로 간주된다. 그리고 릴레이 네트워크의 협력 다이버시티는 제안된 CDD 기법의 MC-CDMA 시스템에서 주파수 다이버시티로 획득된다. 또한 CDD-DSF 릴레이 기법에 대한 평균 오류율을 의사 분석기법을 통하여 제시한다. 성능분석 및 모의실험 결과를 통하여 제안된 CDD-DSF 기법이 주파수 효율 저하 없이 협력 다이버시티를 획득할 수 있음을 확인한다.

On the Optimal Cyclic Delay Value in Cyclic Delay Diversity

In this paper, we propose a method to determine the optimal cyclic delay value of cyclic delay diversity (CDD) in orthogonal frequency division multiplexing (OFDM) systems. As the cyclic delay value increases, we can get signal to interference and noise ratio (SINR) gain by the diversity effect, while SINR loss increases because of channel estimation errors. If the optimal cyclic delay value obtained by the proposed method is applied to a CDD scheme, we can minimize the required SINR for a given frame error rate (FER) under the above-mentioned trade-off.

Cyclic space-frequency filtering for BICM-OFDM systems with multiple co-located or distributed transmit antennas

In this paper, we introduce cyclic space-frequency (CSF) filtering for orthogonal frequency division multiplexing (OFDM) systems using bit-interleaved coded modulation (BICM) and multiple transmit antennas for fading mitigation, and discuss the extension to orthogonal frequency division multiple access (OFDMA) systems. CSF filtering is a simple form of space-frequency coding (SFC) and may be viewed as a generalization of cyclic delay diversity (CDD) where the cyclic delays are replaced by CSF filters. CSF is applicable to both traditional multiple-input multiple-output systems with co-located transmit antennas and cooperative diversity systems with decode-and-forward relaying and distributed transmit antennas. Similar to CDD and in contrast to other SFC schemes, CSF filtering does not require any changes to the receiver compared to single-antenna transmission. Based on the asymptotic pairwise error probability of the overall system we derive an optimization criterion for the CSF filters for co-located and distributed transmit antennas, respectively. We show that the optimum CSF filters are independent of the interleaver if they do not exceed a certain length. If this length is exceeded, the adopted interleaver has to be carefully taken into account in the CSF filter design. For several special cases we derive closed-form solutions for the optimum CSF filters and for the general case we provide various CSF filter design methods. Our simulation results show that CSF filtering can achieve significant performance gains over existing CDD schemes.

Cyclic space-frequency filtering for BICM-OFDM systems with multiple co-located or distributed transmit antennas

In this paper, we introduce cyclic space-frequency (CSF) filtering for orthogonal frequency division multiplexing (OFDM) systems using bit-interleaved coded modulation (BICM) and multiple transmit antennas for fading mitigation, and discuss the extension to orthogonal frequency division multiple access (OFDMA) systems. CSF filtering is a simple form of space-frequency coding (SFC) and may be viewed as a generalization of cyclic delay diversity (CDD) where the cyclic delays are replaced by CSF filters. CSF is applicable to both traditional multiple-input multiple-output systems with co-located transmit antennas and cooperative diversity systems with decode-and-forward relaying and distributed transmit antennas. Similar to CDD and in contrast to other SFC schemes, CSF filtering does not require any changes to the receiver compared to single-antenna transmission. Based on the asymptotic pairwise error probability of the overall system we derive an optimization criterion for the CSF filters for co-located and distributed transmit antennas, respectively. We show that the optimum CSF filters are independent of the interleaver if they do not exceed a certain length. If this length is exceeded, the adopted interleaver has to be carefully taken into account in the CSF filter design. For several special cases we derive closed-form solutions for the optimum CSF filters and for the general case we provide various CSF filter design methods. Our simulation results show that CSF filtering can achieve significant performance gains over existing CDD schemes.

Analysis of Cyclic Delay Diversity on DVB-H Systems over Spatially Correlated Channel

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> The objective of this work is to research and analyse the performance of Cyclic Delay Diversity (CDD) with two transmit antenna on DVB-H systems operating in spatially correlated channel. It is shown in this paper that CDD can achieve desirable transmit diversity gain over uncorrelated channel with or without receiver diversity. However, in reality, the respective signal paths between spatially separated antennas and the mobile receiver is likely to be correlated because of insufficient antenna separation at the transmitter and the lack of scattering effect of the channel. Under this spatially correlated channel, it is apparent that CDD cannot achieve the same diversity gain as obtained under the uncorrelated channel. In this paper, a new upper bound on the pairwise error probability (PEP) of the CDD with spatial correlation of two transmit antennas is derived. The upper bound is used to study the CDD theoretical error performance and diversity gain losses over a generalized spatially correlated Rayleigh channel. This theoretical analysis is validated by the simulation of DVB-H systems with two transmit antennas and the CDD scheme. Both the theoretical and simulated results give the valuable insight that the CDD ability to perform well with a certain amount of channel correlation. </para>

On space-frequency coding using cyclic delay diversity for OFDM-based transmission systems

We present a space-frequency coding scheme using cyclic delay diversity (CDD) for an orthogonal frequency division multiplexing (OFDM)-based transmission system. CDD is a simple multiple transmit antenna approach for increasing the frequency selectivity of the channel seen at a single antenna receiver. This is due to the insertion of virtual echoes caused by antenna specific cyclic delays in the time domain at the transmitter. On each antenna a shifted version of the signal is sent, with these shifts being performed in the frequency domain. This allows the receiver to apply optimum demodulation, and thus exploit the diversity introduced by CDD. We optimize the selection of the time domain cyclic delays in the CDD so as to get full spatial diversity with the proposed space-frequency codes with CDD (SFC-CDDs) scheme. Moreover, we show simulation results for SFC-CDD, which confirm theoretical results with respect to the achieved spatial diversity, and present a comparison with the well-known Alamouti scheme implemented as SFC.