检索结果-内蒙古大学图书馆

Effect of Diversity and Filtering on the Performance of Wavelet Packets Base Multicarrier multicode CDMA System

Journal of Signal and Information Processing 2015年第2期6卷 165-179页

作者： Maryam M. Akho-Zahieh Nasser Abdellatif Department of Electrical and Computer Engineering Applied Science Private University Amman Jordan

In Wavelet Packets Based Multicarrier multicode CDMA system, the multicode (MCD) part ensures the transmission for high speed and flexible data rate, the multicarrier (MC) part ensures the flexibility of handling multiple data rates, and wavelet packets modulation technique contributes to the mitigation of the interference problems. The CDMA system can suppress a given amount of interference. In this paper, the receiver employs suppression filter (SF) to mitigate the effect of narrow-band jammer interference and diversity techniques to reduce multiple access interference. The framework for the system and the performance evaluation are presented in terms of bit error rate (BER) over a Nakagami fading channel. Also, we investigate how the performance is influenced by various parameters, such as the number of taps of the SF, the ratio of narrow-band interference bandwidth to the spread-spectrum bandwidth, the diversity order, the fading parameter and so on. Finally, the performance of the system is compared with the performance Sinusoidal (Sin) based MC/MCD CDMA system.

关键词： Wavelet Packets Multicarrier multicode Diversity Suppression Filter

来源：评论

学校读者我要写书评

暂无评论

Downlink scheduling schemes for CDMA networks with adaptive modulation and coding and multicodes

引用

IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS 2007年第10期6卷 3668-3677页

作者： Kwan, Raymond Leung, Cyril Simon Fraser Univ Sch Engn Sci Burnaby BC V5A 1S6 Canada Univ British Columbia Dept Elect & Comp Engn Vancouver BC V6T 1Z4 Canada

For the problem of allocating radio resources in the downlink of a CDMA network studied in [1], the modulation and coding schemes, numbers of multicodes, and transmit powers used for all mobile stations (MS's) are jointly chosen so as to maximize the total transmission bit rate during each scheduling interval, subject to certain constraints. The approach employs discrete mathematical programming, which is potentially complex, and analytical solutions are not available. In this paper, sub-optimal approaches are examined. In particular, analytical expressions are derived for optimal resource allocation involving a single MS. Based on the single-MS solution, a sub-optimal, sequential optimization procedure for multiple MS's is presented. Numerical results show that when the order for allocating resources to MS's is judiciously chosen based on the MS channel conditions and/or traffic loads, the sequential solution is an attractive alternative to the more complex joint optimization. This is especially true when radio resources are scarce.

关键词： adaptive modulation and coding CDMA downlink scheduling high-speed packet data multicode

来源：评论

学校读者我要写书评

暂无评论

Performance of a new premulticoded multicarrier DS-CDMA system in Nakagami fading

引用

IEEE TRANSACTIONS ON COMMUNICATIONS 2007年第7期55卷 1363-1373页

作者： Cao, Yewen Tjhung, Tjeng Thiang Ko, Chi Chung Shandong Univ Jinan 250100 Peoples R China Inst Infocomm Res Singapore 119613 Singapore Natl Univ Singapore Dept Elect & Comp Engn Singapore 119260 Singapore

In this paper, we proposed a new multicarrier, direct sequence code division multiple access, the so-called premulticoded MC-DS-CDMA system. In this scheme, the basic MC-DS-CDMA system is augmented with a precoder and a multicode encoder at the transmitter. The multicode encoder is an inverse Walsh-Hadamard transform (IWHT) unit, while the precoder is a recently suggested "constant amplitude" encoder that guarantees that the IWHT output stream has binary level. While IWHT, multicarrier (MC) transmission, and direct sequence spreading provide us with frequency diversity, the constant amplitude precoder ensures that the transmitted waveform is spread BPSK signal, minimizing peak to average-power ratio (PAPR) problem. The multicode and (MC) combination also addresses the need for flexible high data rate services in present day wireless communications. In the receiver, after matched filtering or correlation demodulation for each subcarrier and WHT operation, a detection strategy based on minimum-mean-square-error (MMSE) criterion is used. We have derived an upper bound for the bit error rate (BER) performance in Nakagami fading channel. Numerical results are compared with those obtained from a single carrier DS-CDMA. system (SC-DS-CDMA) and a MC-DS-CDMA scheme without the precoding and IWHT units. We show that our proposed MC-DS-CDMA scheme has a much better BER performance compared with both of these schemes.

关键词： DS-CDMA MMSE detection multicarrier CDMA multicode

来源：评论

学校读者我要写书评

暂无评论

Performance of a CDMA system employing AMC and multicodes in the presence of channel estimation errors

引用

IEEE TRANSACTIONS ON COMMUNICATIONS 2008年第2期56卷 189-193页

作者： Kwan, Raymond Leung, Cyril Univ British Columbia Dept Elect & Comp Engn Vancouver BC V6T 1Z4 Canada

The impact of channel state estimation errors in a CDMA system employing adaptive modulation and coding in conjunction with multicodes is studied. The channel is modelled as a finite-state Markov chain and the performances using (1) a simple moving average (SMA) filter (2) a hidden Markov model (HMM) filter to estimate the channel state are compared. The results show that the HMM filter is more robust and provides a significant throughput improvement over the SMA filter, especially when the channel estimate is quite noisy or the normalized Doppler rate is small.

关键词： CDMA adaptive modulation and coding multicode imperfect channel estimation Rayleigh fading hidden Markov model

来源：评论

学校读者我要写书评

暂无评论

Adaptive modulation and coding with multicodes over Nakagami fading channels

Adaptive modulation and coding with multicodes over Nakagami...

引用

IEEE Wireless Communications and Networking Conference

作者： Kwan, R Leung, C Univ British Columbia Dept Elect & Comp Engn Vancouver BC V6T 1Z4 Canada

ISBN: (纸本)0780389662

Adaptive Modulation and Coding (AMC) has been adopted in the 3GPP standard in order to improve spectral efficiency. In order to increase the granularity of the adaptation and to provide higher bit rates, multicode transmission is employed. Since the use of AMC requires knowledge of the channel state, the accuracy of this information is important. In practice, errors in estimating the channel state are inevitable, resulting in performance degradation. In this paper, the average bit rate performance of AMC with multicodes is studied for a CDMA system experiencing Nakagami fading and channel estimation errors. The results are obtained in terms of the generalized Marcum Q-function. Numerical results are provided to illustrate the performance degradations due to inaccuracies in estimating the channel.

关键词： adaptive modulation and coding multicode imperfect channel estimation CDMA Nakagami fading

来源：评论

学校读者我要写书评

暂无评论

Performance analysis of multirate MC-CDMA in Rayleigh-fading channels with delay power spectrum exceeding the guard interval

引用

IEEE JOURNAL ON SELECTED AREAS IN COMMUNICATIONS 2006年第3期24卷 542-553页

作者： Kunnari, E Finatti, J Univ Oulu Ctr Wireless Commun FI-90014 Oulu Finland

Multicarrier code-division multiple access (MC-CDMA) is a promising multiplexing technique for future mobile radio systems, which require multirate transmission capability to efficiently support various services with wide range of data rates. In this paper, a generic performance analysis for the multicode and variable spreading factor multirate schemes in MC-CDMA is presented. Results comparing and pointing out notable differences in the error rate performance of these multirate schemes in conjunction with six different combining techniques are presented for the synchronous downlink and both the synchronous and asynchronous uplink. Furthermore, the analysis takes into account also the intersymbol interference caused by the multipath delay components exceeding the guard interval, which is commonly omitted in the literature.

关键词： delay spread multicarrier code-division multiple access (MC-CDMA) multicode multirate transmission subcarrier combining variable spreading factor (VSF)

来源：评论

学校读者我要写书评

暂无评论

Adaptive radio resource management for maximizing reward and balancing loads in 4G hybrid universal mobile telecommunications system and long term evolution communications

引用

WIRELESS COMMUNICATIONS & MOBILE COMPUTING 2015年第3期15卷 510-526页

作者： Chang, Ben-Jye Liang, Ying-Hsin Cao, Kai-Xiang Natl Yunlin Univ Sci & Technol Dept CSIE Touliu Taiwan Nan Kai Univ Technol Dept MAA Caotun Taiwan

The universal mobile telecommunications system (UMTS) and long term evolution (LTE)/LTE-advanced specifications have been proposed to offer high data rate for the forwarding link under high-mobility wireless communications. The keys include supporting multi-modes of various coding schemes (e.g., VSF-OFCDM, OFDM, OFDMA), multiple-input multiple-output, relay networks, and so on. To balance loads among different communication interfaces is one of the most important issues that should be addressed for achieving efficient radio resource allocations. In a shared packet service, the 3GPP UMTS adopts the VSF-OFCDM interface to allocate orthogonal codes of an OVSF code tree in two-dimension (2D) spreading at the time and frequency domains. However, it easily leads to high packet loss rate and high bandwidth waste rate, because it does not consider interference and the adaptive modulation and coding scheme simultaneously. Conversely, although the LTE/LTE-advanced interface offers a high data rate, it suffers from unbalanced loads and moderate reward. This paper thus proposes an adaptive radio resource allocation for balancing loads between the UMTS and LTE/LTE-advanced interfaces according to various interference and mobility environments. In addition, an adaptive multi-code allocation is proposed for the UMTS to minimize the bandwidth waste rate while guaranteeing quality of service. Numerical results indicate that the proposed approach outperforms other approaches in fractional reward loss and system utilization. Copyright (c) 2013 John Wiley & Sons, Ltd.

关键词： adaptive radio resource management adaptive modulation and coding load balancing resource block 2D-spreading multiple input multiple output multicode LTE-A

来源：评论

学校读者我要写书评

暂无评论

Constant Amplitude Encoders and Decoders with Error Correction (EC) for CDMA Systems

引用

IEICE TRANSACTIONS ON COMMUNICATIONS 2013年第8期E96B卷 2131-2138页

作者： Kim, Suil Bae, Sukneung Kim, Junghwan Univ Sci & Technol Hefei Peoples R China Univ Toledo Toledo OH 43606 USA

multicode CDMA systems convert a high-rate serial data stream into low-rate parallel data streams prior to transmission, but reducing the peak-to-average-power-ratio (PAPR) is a prerequisite. In this paper, we propose constant amplitude coding schemes with forward error correction (EC) capability. The proposed schemes overcome the adverse nonlinear effects of the high power amplifier (HPA) by using the transmitted signal of constant amplitude and parity channel. In the first scheme, we add the EC capability to the previously reported constant-amplitude rate 4/4 (Suil's) scheme, which can transmit data without energy loss. Next, we propose a rate 12/16 decoder with EC capability, which is slightly different from the previous work through the addition of EC capability. Lastly, we propose a new high-rate EC capable 16/16 scheme without energy loss, which makes it superior to the conventional 12/16 scheme which experiences excessive energy loss due to redundancy. Computer simulation results confirm that new 4/4 decoder along with 12/16 decoder and 16/16 encoder/decoder can effectively reduce the inherent problem of high PAPR in the multicode CDMA signal transmission. Our methods also yield better BER performance than other constant amplitude coding-schemes.

关键词： constant amplitude coding multicode CDMA PAPR

来源：评论

学校读者我要写书评

暂无评论

Improving the performance in a multimedia CDMA cellular system with resource reservation

引用

IEICE TRANSACTIONS ON COMMUNICATIONS 2001年第4期E84B卷 727-738页

作者： Hwang, BJ Wu, JS Nieh, YC Van Nung Inst Technol Dept Elect Engn Chungli 32054 Taiwan Natl Cent Univ Dept Elect Engn Chungli 32054 Taiwan

The Direct-Sequence Code Division Multiple Access (DS-CDMA) is one of the most likely candidates: for the 3rd generation mobile communication systems. On the other hand, a network supporting integrated data transfer and providing predictable qualities of service (QoS) to such application is an attractive issue. This paper proposes several schemes based on the majority rule concerned with resource reservation ta investigate the performance of a CDMA cellular system. The admission control is based on the residue capacity and required signal-to-noise ratio (SNR) for multimedia traffic including voice, data and video. The system performance is explored with variable spreading gain and multi-code CDMA systems under the proposed schemes, Moreover, several system parameters including the handoff probability (lifetime in a cell) and the traffic load are investigated to study the impact to system performance. The results show the trade-off between the blocking probability of new calls and dropping probability of handoff calls under diversified situations. However, it is inefficient under resource reservation due to unused capacity. In this paper, we also propose a resource-borrowing scheme to improve system performance. Simulation results show that our proposed algorithm really improves the system performance in a multimedia CDMA cellular system with resource reservation.

关键词： CDMA multicode resource reservation

来源：评论

学校读者我要写书评

暂无评论

Performance analysis of a new multi-code high-speed mobile radio transmission scheme using cyclic modified M-sequence

引用

IEICE TRANSACTIONS ON COMMUNICATIONS 2000年第9期E83B卷 2056-2067页

作者： Harada, H Minist Posts & Telecommun Commun Res Lab Yokosuka Kanagawa 2390847 Japan

This paper proposes a new parallel high speed mobile radio transmission scheme using cyclic-shifted-codes generated from a modified M-sequence. The modified M-sequence is biased with constant direct current (dc) on an M-sequence and is inserted the guard chips before and after this biased M-sequence. The proposed system has the following features: i) Orthogonality of the codes is kept not only between direct waves of each parallel channels but also between direct and delayed waves within the guard chips;ii) It is possible to reduce the number of kinds of codes allocated to one user;and iii) It is easy to recover both code and chip timings. In this paper, moreover, the performance of the proposed system was evaluated in terms of bit error rate (BER) under additive white Gaussian noise (AWGN), non-selective one path Rayleigh fading and double-spike Rayleigh fading channels. As a result, the proposed transmission scheme can transmit several Mbps in a high-speed double-spike Rayleigh fading channel with better quality in comparison with a conventional multicode CDM transmission scheme based on M-sequences.

关键词： multicode CDMA synchronization Rake receiver multimedia wireless broadband communication

来源：评论

学校读者我要写书评

暂无评论

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案：

请选择收藏分类：

通借通还

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：