There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

Mathematical Handbook for Scientists and Engineers

This chapter contains sections titled: Introduction Overview of Multicarrier CDMA Systems Channel Model Performance of MC-CDMA System Performance of Overlapping Multicarrier DS-CDMA Systems Performance of Multicarrier DS-CDMA-I Systems Performance of AMC DS-CDMA Systems Performance of SFH/MC DS-CDMA Systems Chapter Summary and Conclusion 
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Overview of Multicarrier CDMA

A main drawback of frequency division multiplexing (OFDM) system is the high peak-to-aver-age power ratio (PAPR). High PAPR leads to amplifier nonlinearity, inter-modulation and low inefficiency. As a simplest approach, traditional clipping method can reduce PAPR of OFDM signals, but it causes large unwanted out-of-band radiation. In this paper, a new clipping method is proposed, which can reduce PAPR without out-of-band radiation. It is based on the traditional clipping to generate the error signal. Zero out-of-band radiation is achieved by filtering the error signal. Although the proposed method produces more inband noise, by using noise cancel algorithm, the ideal unclipped signal′s BER performance can be achieved.

New OFDM peak-to-average power reduction scheme

This paper proposes broadband packet wireless access employing Variable Spreading Factor-Orthogonal Frequency and Code Division Multiplexing (VSF-OFCDM) with two-dimensional spreading that prioritizes time domain spreading in the forward link and multi-carrier/DS-CDMA (MC/DS-CDMA) in the reverse link for the system beyond IMT-2000. Based on the wireless access scheme, we propose major radio air interfaces in the physical layer to achieve our target maximum throughput beyond 100 Mbps and 20 Mbps in the forward and reverse links, respectively. Furthermore, we present key technologies such as the adaptive radio link parameter control coupled with link adaptation, pilot channel assisted coherent detection in both links, adaptive antenna array beam forming transmitter and receiver, cell search, and channel coding. Finally, simulation results elucidate that VSF-OFCDM using die proposed radio link parameters achieves a throughput above 100 Mbps at the average received signal energy per symbol-to-background noise power spectrum density ratio (Ea/No) of approximately 13 dB (101.5 MHz bandwidth, without antenna diversity reception, 12-path Rayleigh fading channel). Furthermore, MC/DS-CDMA realizes a throughput above 20 Mbps at the average received Ea/No of approximately 8 dB (40 MHz bandwidth, with antenna diversity reception, 6-path Rayleigh fading channel).

Broadband packet wireless access based on VSF-OFDM and MC/DS-CDMA

In mobile communication systems, the received signal power varies due to fading, shadowing and path loss, resulting in the transmission performance degradation. Transmit antenna diversity is a promising technique to improve the transmission performance. For the downlink transmission, the outage probability in a service area can be improved by distributing the transmit antennas over the service area instead of using all of them at the same location (i.e., a base station). This is because the slowly varying local average received signal power due to the shadowing and distance-dependent path losses can be mitigated. In this paper, we evaluate the channel capacity distribution obtainable a distributed antenna system (DAS) using maximal ratio transmission (MRT) diversity. We discuss the effects of the number of antennas, path loss exponent, and shadowing loss standard deviation on the distribution of channel capacity. Keywords-Maximal ratio transmission, distributed antenna systems, channel capacity

A Study on Channel Capacity of Distributed Antenna System Using Maximal Ratio Transmission

あらまし 送信アンテナを空間的に十分離して配置する分散アンテナネットワーク(DAN) は伝搬損失,シャドウ イング損失および周波数選択性フェージングの影響によって生じる問題を解決可能な無線ネットワークである.本 論文では,シングルキャリア周波数分割マルチアクセス(SC-FDMA) DAN の 2 次元注水(2D-water filling : 2D-WF) 重みを用いる下りリンク送信ダイバーシチにおける周波数スケジューリングについて提案している.ここで, 2D-WF 重みは送信アンテナ次元では最大比送信(MRT)規範に基づく電力配分を,周波数次元では注水定理に基づく 電力配分を行う送信重みである.モンテカルロ数値計算により周波数スケジューリングがチャネル容量の分布に与 える影響について検討を行っている. キーワード 分散アンテナネットワーク,送信ダイバーシチ,チャネル容量,周波数スケジューリング

http://www.mobile.ecei.tohoku.ac.jp/paper/pdf/rcs_2010/10_rcs_2010_matsuda.pdf

Channel Capacity of SC-FDMA Distributed Antenna Network Using Transmit Diversity

Iterative MMSE Detection and Interference Cancellation for Uplink SC-FDMA MIMO using HARQ

あらまし 周波数領域等化を用いる DS-CDMA において,複数のアンテナに異なる遅延を与えて同一信号を同時に送 信し,等価的にパス数を増やすことで大きな,周波数ダイバーシチ効果を得ることのできる遅延送信ダイバーシチ(DTD)が 提案されている.しかし DTD では,各アンテナに与える遅延時間が大きくなると,最大パス遅延がガードインターバル(GI)よ り長くなり符号間干渉を生じるため,平均 BER 特性が劣化してしまう.最近,アンテナごとに異なる循環遅延を与えて同時に 送信する Cyclic Delay Transmit Diversity (CDTD)が提案されている.CDTDでは,DTD と異なり各アンテナに与える循環遅 延の量に制限がないために,DTD より大きな周波数ダイバーシチ効果を得ることができる.本論文では,周波数領域等化を 用いる DS-CDMAに CDTD を適用したときの平均 BER特性を計算機シミュレーションによって明らかにし, DTD を用いる ときの BER特性と比較している. キーワード DS-CDMA,遅延送信ダイバーシチ (DTD),Cyclic Delay Transmit Diversity (CDTD),周波数領域等化

Application of Cyclic Delay Transmit Diversity to DS-CDMA using Frequency-domain Equalization

Multi-user single-carrier (SC) MIMO multiplexing has been attracting a lot of attention due to its low peak-to-average power ratio (PAPR). As the transmission rate increases, the channel becomes frequency-selective and the bit error rate (BER) performance degrades significantly due to intersymbol interference (ISI). Frequency-domain equalization (FDE) provides a good BER performance since the frequency diversity gain can be obtained. In this paper, we evaluate, by computer simulation, the uplink capacity of multi-user SCMIMO multiplexing using FDE in a frequency-selective fading channel. Zero-forcing detection (ZFD) and minimum mean square error detection (MMSED) are considered. The uplink capacity is found from the complimentary cumulative distribution function (CCDF) of the local average BER, obtained by computer simulation. It is shown that larger uplink capacity can be achieved in a frequency-selective fading channel rather than in a frequency-nonselective fading channel and that almost the same capacity is obtained by ZFD and MMSED. It is also shown that ZFD and MMSED can provide almost 1.3 times larger uplink capacity than MMSEFDE+antenna diversity reception using 8-element receive antenna array.

https://www.mobile.ecei.tohoku.ac.jp/paper/pdf/inter_2008/16_in_2008_chiba.pdf

Adachi Fumiyuki

Papers

A Study on Channel Capacity of Distributed Antenna System Using Maximal Ratio Transmission

Channel Capacity of SC-FDMA Distributed Antenna Network Using Transmit Diversity

Iterative MMSE Detection and Interference Cancellation for Uplink SC-FDMA MIMO using HARQ

Application of Cyclic Delay Transmit Diversity to DS-CDMA using Frequency-domain Equalization

Uplink capacity of a single-carrier multi-user mimo multiplexing in a frequency-selective channel