IEICE Transactions on Communications
Online ISSN : 1745-1345
Print ISSN : 0916-8516
Volume E92.B, Issue 5
Displaying 1-50 of 61 articles from this issue
Special Section on Radio Access Techniques for 3G Evolution
  • Mamoru SAWAHASHI
    2009 Volume E92.B Issue 5 Pages 1431
    Published: May 01, 2009
    Released on J-STAGE: May 01, 2009
    JOURNAL RESTRICTED ACCESS
    Download PDF (30K)
  • Erik DAHLMAN, Ylva JADING, Stefan PARKVALL, Hideshi MURAI
    Article type: INVITED PAPER
    2009 Volume E92.B Issue 5 Pages 1432-1440
    Published: May 01, 2009
    Released on J-STAGE: May 01, 2009
    JOURNAL FREE ACCESS
    This paper provides an overview of the 3GPP radio-access technologies for mobile broadband — HSPA and its evolution, and LTE. The paper also discusses the current stage of the 3GPP activities on evolving LTE towards LTE-Advanced and full IMT-Advanced compliance.
    Download PDF (718K)
  • Fumiyuki ADACHI, Hiromichi TOMEBA, Kazuki TAKEDA
    Article type: INVITED PAPER
    2009 Volume E92.B Issue 5 Pages 1441-1456
    Published: May 01, 2009
    Released on J-STAGE: May 01, 2009
    JOURNAL FREE ACCESS
    Single-carrier (SC) multiple access is a promising uplink multiple access technique because of its low peak-to-average power ratio (PAPR) property and high frequency diversity gain that is achievable through simple one-tap frequency-domain equalization (FDE) in a strong frequency-selective channel. The multiple access capability can be obtained by combining either frequency division multiple access (FDMA) or code division multiple access (CDMA) with SC transmission. In this article, we review the recent research on the SC multiple access techniques with one-tap FDE. After introducing the principle of joint FDE/antenna diversity combining, we review various SC multiple access techniques with one-tap FDE, i.e., SC-FDMA, SC-CDMA, block spread CDMA, and delay-time/CDMA.
    Download PDF (2206K)
  • Yohei KOJIMA, Hiromichi TOMEBA, Kazuaki TAKEDA, Fumiyuki ADACHI
    Article type: PAPER
    2009 Volume E92.B Issue 5 Pages 1457-1465
    Published: May 01, 2009
    Released on J-STAGE: May 01, 2009
    JOURNAL RESTRICTED ACCESS
    Frequency-domain equalization (FDE) based on the minimum mean square error (MMSE) criterion can increase the downlink bit error rate (BER) performance of DS-CDMA beyond that possible with conventional rake combining in a frequency-selective fading channel. FDE requires accurate channel estimation. Recently, we proposed a pilot-assisted channel estimation (CE) based on the MMSE criterion. Using MMSE-CE, the channel estimation accuracy is almost insensitive to the pilot chip sequence, and a good BER performance is achieved. In this paper, we propose a channel estimation scheme using one-tap recursive least square (RLS) algorithm, where the forgetting factor is adapted to the changing channel condition by the least mean square (LMS)algorithm, for DS-CDMA with FDE. We evaluate the BER performance using RLS-CE with adaptive forgetting factor in a frequency-selective fast Rayleigh fading channel by computer simulation.
    Download PDF (1117K)
  • Keiichi KAMBARA, Hiroshi NISHIMOTO, Toshihiko NISHIMURA, Takeo OHGANE, ...
    Article type: PAPER
    2009 Volume E92.B Issue 5 Pages 1466-1474
    Published: May 01, 2009
    Released on J-STAGE: May 01, 2009
    JOURNAL RESTRICTED ACCESS
    Frequency-domain equalization (FDE) has been studied for suppressing inter-symbol interference (ISI) due to frequency selective fading in single carrier systems. When a high-mobility terminal is assumed in the system, channel transition within an FDE block cannot be ignored. The ISI reduction performance of FDE degrades since the cyclicity of the channel matrix is lost. To solve this problem, a method of dividing the received data block into multiple subblocks has been proposed, where pseudo cyclic prefix (CP) processing is introduced to realize periodicity in each subblock. In this method, the performance is degraded by the inherently-inaccurate pseudo CP. In this paper, we study the application of frequency-domain turbo equalization (FDTE) to subblock processing for improving the accuracy of pseudo CP. The simulation results show that FDTE with subblock processing yields remarkable performance improvements.
    Download PDF (715K)
  • Chi-Min LI, Shao-Min WEN, Pao-Jen WANG, Jia-Chyi WU, I-Tseng TANG
    Article type: PAPER
    2009 Volume E92.B Issue 5 Pages 1475-1483
    Published: May 01, 2009
    Released on J-STAGE: May 01, 2009
    JOURNAL RESTRICTED ACCESS
    In this paper, we propose a Frequency Domain Equalizer (FDE) without inserting the Guard Interval (GI) at the transmitter which is applicable to the Wide-band Code Division Multiple Access (WCDMA) and Orthogonal Frequency-Division Multiplexing (OFDM) systems. The proposed FDE adopts the Overlap-Cut (OC) method to avoid the Inter-Block Interference (IBI) and exploits the decision feedback structure to improve the Bit Error Rate (BER) performance. Without inserting the GI, the proposed FDE will be compatible to the frame format of the current High Speed Downlink Packet Access (HSDPA). Besides, it can improve the BER performance and bandwidth utilization when the GI is less than the channel length of the OFDM system.
    Download PDF (1166K)
  • Mamiko INAMORI, Takashi KAWAI, Tatsuya KOBAYASHI, Haruki NISHIMURA, Yu ...
    Article type: PAPER
    2009 Volume E92.B Issue 5 Pages 1484-1494
    Published: May 01, 2009
    Released on J-STAGE: May 01, 2009
    JOURNAL RESTRICTED ACCESS
    In this paper, the effect of the impulse response of pulse shaping filters on a fractional sampling orthogonal frequency division multiplexing (FS OFDM) system is investigated. FS achieves path diversity with a single antenna through oversampling and subcarrier-based maximal ratio combining (MRC). Though the oversampling increases diversity order, correlation among noise components may deteriorate bit error rate (BER) performance. To clarify the relationship between the impulse response of the pulse shaping filter and the BER performance, five different pulse shaping filters are evaluated in the FS OFDM system. Numerical results of computer simulations show that the Frobenius norm of a whitening matrix corresponding to the pulse shaping filter has significant effect on the BER performance especially with a small numbers of subcarriers. It is also shown that metric adjustment based on the Frobenius norm improves BER performance of the coded FS OFDM system.
    Download PDF (1515K)
  • Satoshi SUYAMA, Hiroshi SUZUKI, Kazuhiko FUKAWA, Li ZHANG
    Article type: PAPER
    2009 Volume E92.B Issue 5 Pages 1495-1503
    Published: May 01, 2009
    Released on J-STAGE: May 01, 2009
    JOURNAL RESTRICTED ACCESS
    This paper applies iterative multiuser detection employing a new channel estimation scheme to multicarrier interleave-division multiple access (MC-IDMA), called OFDM-IDMA, which is expected to offer improved spectral efficiency in mobile communications. The MC-IDMA transmitter uses both a low-rate channel code and an individual chip interleaver for each user. The MC-IDMA receiver, which this paper focuses upon, repeats the iterative multiuser detection and soft decision-directed channel estimation (SDCE) by exploiting log-likelihood ratios (LLRs) of the coded bits which the maximum a posteriori (MAP)-based channel decoders for all users provide. SDCE estimates channel impulse responses of all users by the least-mean-square (LMS) algorithm, which aims to minimize the mean squared error between the received signal and its replica. This paper investigates the performance of MC-IDMA employing SDCE and compares it with those of three MC-CDMA techniques. Computer simulations demonstrate that MC-IDMA employing SDCE outperforms time-spread MC-CDMA and frequency-spread MC-CDMA, and that it can achieve almost the same bit error rate performance as chip-interleaved MC-CDMA while requiring lower complexity.
    Download PDF (672K)
  • Naoto OKUBO, Nobuhiko MIKI, Yoshihisa KISHIYAMA, Kenichi HIGUCHI, Mamo ...
    Article type: PAPER
    2009 Volume E92.B Issue 5 Pages 1504-1515
    Published: May 01, 2009
    Released on J-STAGE: May 01, 2009
    JOURNAL RESTRICTED ACCESS
    This paper compares the turbo code and rate-compatible low-density parity-check (LDPC) codes based on the block error rate (BLER) performance and decoding complexity in order to clarify which channel coding scheme is most appropriate for the channel coding scheme in the OFDM based Evolved UTRA (E-UTRA) downlink. Simulation results and the decoding complexity analysis show that although the Rate-Compatible/Quasi-Cyclic (RC/QC)-LDPC code employing an offset layered belief propagation (BP) method can reduce the computational complexity by approximately 30% for the channel coding rate of R ≥ 1/2, the required average received signal energy per bit-to-noise power spectrum density ratio (Eb/N0) is degraded by approximately 0.2-0.3dB for R=1/3, 1/2 and 3/4 compared to that for the turbo code. Moreover, the decoding complexity level of the RC/QC-LDPC code with the δ-min algorithm is almost the same or higher than that for the turbo code with a slight degradation in the required received Eb/N0. Although the decoding complexity level of the ZigZag code is lower than that of the turbo code, the code brings about a distinct loss in the required average received Eb/N0 of approximately 0.4dB. Finally, the turbo Single Parity Check (SPC) code improves the BLER performance compared to the ZigZag code, i.e., achieves almost the same BLER performance as that for the turbo code, at the cost of a two-fold increase in the decoding complexity. As a result, we conclude that the turbo code with a contention free interleaver is more promising than the LDPC codes for prioritizing the achievable performance over complexity and as the channel coding scheme for the shared data channel in the E-UTRA.
    Download PDF (1951K)
  • Nobuhiko MIKI, Hiroyuki ATARASHI, Kenichi HIGUCHI, Mamoru SAWAHASHI, M ...
    Article type: PAPER
    2009 Volume E92.B Issue 5 Pages 1516-1526
    Published: May 01, 2009
    Released on J-STAGE: May 01, 2009
    JOURNAL RESTRICTED ACCESS
    This paper presents experimental evaluations of the effect of time diversity obtained by hybrid automatic repeat request (HARQ) with soft combining in space and path diversity schemes on orthogonal frequency division multiplexing (OFDM)-based packet radio access in a downlink broadband multipath fading channel. The effect of HARQ is analyzed through laboratory experiments employing fading simulators and field experiments conducted in downtown Yokosuka near Tokyo. After confirming the validity of experimental results based on numerical analysis of the time diversity gain in HARQ, we show by the experimental results that, for a fixed modulation and channel coding scheme (MCS), time diversity obtained by HARQ is effective in reducing the required received signal-to-interference plus noise power ratio (SINR) according to an increase in the number of transmissions, K, up to 10, even when the diversity effects are obtained through two-branch antenna diversity reception and path diversity using a number of multipaths greater than 12 observed in a real fading channel. Meanwhile, in combined use with the adaptive modulation and channel coding (AMC) scheme associated with space and path diversity, we clarify that the gain obtained by time diversity is almost saturated at the maximum number of transmissions in HARQ, K' = 4 in Chase combining and K' = 2 in Incremental redundancy, since the improvement in the residual packet error rate (PER) obtained through time diversity becomes small owing to the low PER in the initial packet transmission arising from appropriately selecting the optimum MCS in AMC. However, the experimental results elucidate that the time diversity in HARQ with soft combining associated with antenna diversity reception is effective in improving the throughput even in a broadband multipath channel with sufficient path diversity.
    Download PDF (1821K)
  • Nobuhiko MIKI, Yoshihisa KISHIYAMA, Kenichi HIGUCHI, Mamoru SAWAHASHI, ...
    Article type: PAPER
    2009 Volume E92.B Issue 5 Pages 1527-1537
    Published: May 01, 2009
    Released on J-STAGE: May 01, 2009
    JOURNAL RESTRICTED ACCESS
    In the Evolved UTRA (UMTS Terrestrial Radio Access) downlink, Orthogonal Frequency Division Multiplexing (OFDM) based radio access was adopted because of its inherent immunity to multipath interference and flexible accommodation of different spectrum arrangements. This paper presents the optimum adaptive modulation and channel coding (AMC) scheme when resource blocks (RBs) is simultaneously assigned to the same user when frequency and time domain channel-dependent scheduling is assumed in the downlink OFDMA radio access with single-antenna transmission. We start by presenting selection methods for the modulation and coding scheme (MCS) employing mutual information both for RB-common and RB-dependent modulation schemes. Simulation results show that, irrespective of the application of power adaptation to RB-dependent modulation, the improvement in the achievable throughput of the RB-dependent modulation scheme compared to that for the RB-common modulation scheme is slight, i.e., 4 to 5%. In addition, the number of required control signaling bits in the RB-dependent modulation scheme becomes greater than that for the RB-common modulation scheme. Therefore, we conclude that the RB-common modulation and channel coding rate scheme is preferred, when multiple RBs of the same coded stream are assigned to one user in the case of single-antenna transmission.
    Download PDF (2307K)
  • Daisuke TAKEDA, Masao NAKAGAWA
    Article type: PAPER
    2009 Volume E92.B Issue 5 Pages 1538-1545
    Published: May 01, 2009
    Released on J-STAGE: May 01, 2009
    JOURNAL RESTRICTED ACCESS
    Vector coding (VC) is a kind of eigen mode transmission scheme which is typically considered in MIMO systems. In VC systems, several code channels corresponding to the eigenvalues of the channel matrix are created. However, any code channels with low eigenvalues will cause a degradation in performance. In this paper, adaptive modulation and coding (AMC) for a VC system is proposed. In addition to AMC, the number of code channels is adaptively changed by code channel elimination. We show that the BER performance of VC is better than that of MMSE. Secondly, we also show the throughput performance of the proposed scheme is improved compared with the maximum throughput of each individual MCS.
    Download PDF (467K)
  • Jianchi ZHU, Xiaoming SHE, Jingxiu LIU, Lan CHEN
    Article type: PAPER
    2009 Volume E92.B Issue 5 Pages 1546-1552
    Published: May 01, 2009
    Released on J-STAGE: May 01, 2009
    JOURNAL RESTRICTED ACCESS
    Codebook based multiple-input multiple-output (MIMO) precoding can significantly improve the system spectral efficiency with limited feedback and has been accepted as one of the most promising techniques for the Evolved UTRA (E-UTRA). Compared with single-user (SU) MIMO, multi-user (MU) MIMO can further improve the system spectral efficiency due to increased multi-user diversity gain. MU-MIMO is preferred for the case of a large number of users, when the total feedback overhead will become a problem. In order to reduce the feedback overhead, feedback of single channel quality indicator (CQI), e.g. rank 1 CQI, is required in E-UTRA currently. The main challenge is how to obtain CQIs of other ranks at Node B for rank adaptation with single CQI feedback. In this paper, an adaptive CQI update scheme at Node B based on statistical characteristics of CQI of various ranks is proposed. To further increase the accuracy of CQI at Node B for data transmission, an adaptive CQI feedback scheme is then proposed in which single CQI with the rank same as previously scheduled is fed back. Simulation results show that our proposed CQI update scheme can achieve 2.5-5% gain compared with the conventional method with fixed backoff. Moreover, with the proposed adaptive feedback scheme, 20-40% performance gain can be obtained and the performance can approach the upper bound.
    Download PDF (431K)
  • Takashi ISOGAI, Mamoru SAWAHASHI, Hidekazu TAOKA, Kenichi HIGUCHI
    Article type: PAPER
    2009 Volume E92.B Issue 5 Pages 1553-1562
    Published: May 01, 2009
    Released on J-STAGE: May 01, 2009
    JOURNAL RESTRICTED ACCESS
    This paper investigates the influence of channel estimation error on the precoding matrix selection and signal detection for MIMO multiplexing using precoding in the downlink OFDM radio access. In a simulation, we assume codebook-based unitary precoding and signal detection that employs a minimum mean squared error (MMSE) based interference suppression filter. The simulation results clarify the effect of the channel estimation error with respect to the precoding matrix selection and signal detection from the viewpoints of the number of streams, i.e., rank order, the number of transmit antennas, the modulation scheme and channel coding rate, and codebook size, i.e., quantization for precoding matrix feedback information.
    Download PDF (1704K)
  • Tetsuya YAMAMOTO, Kazuki TAKEDA, Fumiyuki ADACHI
    Article type: PAPER
    2009 Volume E92.B Issue 5 Pages 1563-1572
    Published: May 01, 2009
    Released on J-STAGE: May 01, 2009
    JOURNAL RESTRICTED ACCESS
    Frequency-domain equalization (FDE) based on the minimum mean square error (MMSE) criterion can provide a better bit error rate (BER) performance than rake combining. To further improve the BER performance, cyclic delay transmit diversity (CDTD) can be used. CDTD simultaneously transmits the same signal from different antennas after adding different cyclic delays to increase the number of equivalent propagation paths. Although a joint use of CDTD and MMSE-FDE for direct sequence code division multiple access (DS-CDMA) achieves larger frequency diversity gain, the BER performance improvement is limited by the residual inter-chip interference (ICI) after FDE. In this paper, we propose joint FDE and despreading for DS-CDMA using CDTD. Equalization and despreading are simultaneously performed in the frequency-domain to suppress the residual ICI after FDE. A theoretical conditional BER analysis is presented for the given channel condition. The BER analysis is confirmed by computer simulation.
    Download PDF (1104K)
  • Boonsarn PITAKDUMRONGKIJA, Kazuhiko FUKAWA, Satoshi SUYAMA, Hiroshi SU ...
    Article type: PAPER
    2009 Volume E92.B Issue 5 Pages 1573-1581
    Published: May 01, 2009
    Released on J-STAGE: May 01, 2009
    JOURNAL RESTRICTED ACCESS
    This paper proposes a MIMO-OFDM precoder that can minimize a BER upper bound of the maximum likelihood detector (MLD) under a non-cooperative downlink multicell co-channel interference (CCI) environment. Since there is no cooperation among base stations (BSs), it is assumed that information on the interference can be estimated at a mobile station (MS) and then fed back to the desired BS for the precoder. The proposed scheme controls its precoding parameters under a transmit power constraint so as to minimize the BER upper bound, which is derived from the pairwise error probability (PEP) averaged with respect to CCI plus noise. Computer simulations demonstrate that the proposed precoder can effectively improve BER performance of cell edge users and is superior in terms of BER to the eigenmode and the minimum mean squared error (MMSE) precoded transmissions which aim to maximize the channel capacity and to minimize MSE, respectively.
    Download PDF (487K)
  • Koichi ISHIHARA, Yasushi TAKATORI, Kentaro NISHIMORI, Kazuyasu OKADA
    Article type: PAPER
    2009 Volume E92.B Issue 5 Pages 1582-1588
    Published: May 01, 2009
    Released on J-STAGE: May 01, 2009
    JOURNAL RESTRICTED ACCESS
    In this paper, we propose a novel multiuser detection (MUD) method that is robust against timing offset between wireless terminals (WTs) for the multiuser multiple-input multiple-output (MU-MIMO) orthogonal frequency division multiplexing (OFDM) uplink. In the proposed method, MUD is carried out in the frequency-domain using overlapping fast Fourier transform (FFT) windows. After the inverse FFT (IFFT) operation, the samples obtained at both ends of each FFT window are discarded to suppress the effect of inter-block interference (IBI). Thus, it realizes an MUD regardless of the arrival timing differences of the signals from the WTs. The achievable bit error rate (BER) performance of the proposed MUD method is evaluated by computer simulations in a frequency selective fading channel.
    Download PDF (1074K)
  • Hidekazu TAOKA, Akihito MORIMOTO, Hiroyuki KAWAI, Kenichi HIGUCHI, Mam ...
    Article type: PAPER
    2009 Volume E92.B Issue 5 Pages 1589-1599
    Published: May 01, 2009
    Released on J-STAGE: May 01, 2009
    JOURNAL RESTRICTED ACCESS
    This paper presents the best transmit diversity schemes for three types of common/shared control signals from the viewpoint of the block error rate (BLER) performance in the Evolved UTRA downlink employing OFDM radio access. This paper also presents the coverage performance of the common/shared control signals using transmit diversity with respect to the outage probability that satisfies the required BLER performance, which is a major factor determining the cell configuration. Simulation results clarify that Space-Frequency Block Code (SFBC) and the combination of SFBC and Frequency Switched Transmit Diversity (FSTD) are the best transmit diversity schemes among the open-loop type transmit diversity candidates for two-antenna and four-antenna transmission cases, respectively. Furthermore, we show through system-level simulations that SFBC is very effective in reducing the outage probability at the required BLER for the physical broadcast channel (PBCH), for the common control signal with resource block (RB)-level assignment such as the dynamic broadcast channel (D-BCH) and paging channel (PCH), and in increasing the number of accommodated L1/L2 control signals over one transmission time interval duration, using mini-control channel element (CCE)-level assignment.
    Download PDF (1689K)
  • Qiyue YU, Fumiyuki ADACHI, Weixiao MENG
    Article type: PAPER
    2009 Volume E92.B Issue 5 Pages 1600-1607
    Published: May 01, 2009
    Released on J-STAGE: May 01, 2009
    JOURNAL RESTRICTED ACCESS
    Code division multiple access (CDMA) technique is used widely since it can flexibly support multi-rate multi-media services by changing the number of orthogonal spreading codes. In this paper, we present a new adaptive code assignment algorithm, which consists of three steps: reserved-space, improved-crowded-first-space, and multi-code combination to fully use the code space. Compared with the existing algorithms, the proposed algorithm can avoid the code blocking problem and lower its total blocking probability while keeping its computational complexity relatively low. Simulation results show that increasing the free space reduces the average total blocking probability while increasing the blocking probability of high rate users.
    Download PDF (1711K)
  • Satoshi NAGATA, Motohiro TANNO, Yoshihisa KISHIYAMA, Kenichi HIGUCHI, ...
    Article type: PAPER
    2009 Volume E92.B Issue 5 Pages 1608-1618
    Published: May 01, 2009
    Released on J-STAGE: May 01, 2009
    JOURNAL RESTRICTED ACCESS
    This paper presents a comparison of hierarchical and non-hierarchical synchronization channel (SCH) structures in terms of the initial cell search time and neighboring cell search time in order to establish the optimum SCH structure in the Evolved UTRA downlink. Computer simulation results show that in a 19-cell configuration, the cell search time at 90% in the cumulative distribution function (CDF) using the hierarchical SCH structure is less than half that using the non-hierarchical SCH structure in a neighboring cell search under low signal-to-interference plus noise power ratio (SINR) conditions, although both structures achieve almost the same cell search time in the initial cell search. This is due to the cross-correlation based SCH symbol timing detection in the hierarchical SCH structure, which is affected less by noise than the auto-correlation based detection in the non-hierarchical SCH structure. Thus, we conclude that the hierarchical SCH structure is superior to the non-hierarchical SCH structure based on the cell search time performance especially in the neighboring cell search.
    Download PDF (1871K)
  • Hidekazu TAOKA, Fumiaki ITO, Keiji TAKAKUSAKI, Mamoru SAWAHASHI
    Article type: PAPER
    2009 Volume E92.B Issue 5 Pages 1619-1626
    Published: May 01, 2009
    Released on J-STAGE: May 01, 2009
    JOURNAL RESTRICTED ACCESS
    This paper experimentally investigates the effect of frequency error compensation provided by demodulation automatic frequency control (AFC) using the Synchronization Channel (SCH) in downlink OFDM radio access. The implemented OFDM receiver compensates for the frequency error caused by the difference in frequency between a base station (BS) and a user equipment (UE) using a time-division multiplexed SCH signal and that caused by the Doppler shift generated by the mobility of a user using reference signals with staggered multiplexing. Experimental results show that even when the standard oscillator frequency of the UE cannot be made to track the more accurate frequency of a BS, demodulation AFC can suppress the residual frequency error to a sufficiently low level, i.e., within 0.3ppm, using the SCH so that the degradation in the block error rate of the physical broadcast channel control signals is slight, i.e., within approximately 0.1dB, with respect to the case without frequency error for speeds greater than 350km/h.
    Download PDF (2375K)
  • Daisuke NISHIKAWA, Yoshihisa KISHIYAMA, Kenichi HIGUCHI, Mamoru SAWAHA ...
    Article type: PAPER
    2009 Volume E92.B Issue 5 Pages 1627-1633
    Published: May 01, 2009
    Released on J-STAGE: May 01, 2009
    JOURNAL RESTRICTED ACCESS
    This paper presents the optimum control interval for intra-cell fractional transmission power control (TPC) for a shared data channel employing frequency domain channel-dependent scheduling and adaptive modulation and coding (AMC) in the Evolved UTRA uplink using single-carrier (SC)-FDMA radio access. The simulation results show that the best attenuation factor in the fractional TPC is approximately 0.6 for achieving the maximum user throughput when the maximum target received signal power, P0 is -60dBm. Then, we show that the optimum averaging interval for the desired signal level, which corresponds to a substantial control interval for the fractional TPC, is approximately 100-200msec regardless of the maximum Doppler frequency up to 222Hz and the distance at the shadowing correlation of 0.5. Throughout the simulation results, we verify that slow intra-cell fractional TPC associated with fast AMC is effective in achieving the maximum cell throughput and cell-edge user throughput.
    Download PDF (1274K)
  • Daisuke NISHIKAWA, Yoshihisa KISHIYAMA, Kenichi HIGUCHI, Mamoru SAWAHA ...
    Article type: PAPER
    2009 Volume E92.B Issue 5 Pages 1634-1640
    Published: May 01, 2009
    Released on J-STAGE: May 01, 2009
    JOURNAL RESTRICTED ACCESS
    This paper proposes the use of inter-cell transmission power control (TPC) with overload indicator (OLI) signaling to user equipment (UE) in addition to intra-cell TPC for the Evolved UTRA uplink. In the proposed inter-cell OLI transmission method, a cell site (Node B) selects UEs offering high-level interferences to the cell site based on the measured path loss difference, and then, the cell site transmits the OLI signal to the selected UEs. The simulation results show that the inter-cell TPC improves both the average user throughput and cell-edge user throughput at 5% in the cumulative distribution function (CDF) curve, assuming the same sector throughput. For instance, when the sector throughput is 1Mbps using 1.08MHz bandwidth, the inter-cell TPC with the proposed UE-common OLI scheme increases the average user throughput and the 5%-cell edge user throughput by approximately 41% and 53%, respectively, compared to the case with intra-cell TPC only. Furthermore, when the inter-cell TPC with the proposed UE-individual OLI is employed, the corresponding average user throughput and the 5% user throughput are increased by approximately 87% and 94%, respectively.
    Download PDF (1297K)
  • Wei PENG, Fumiyuki ADACHI
    Article type: PAPER
    2009 Volume E92.B Issue 5 Pages 1641-1648
    Published: May 01, 2009
    Released on J-STAGE: May 01, 2009
    JOURNAL RESTRICTED ACCESS
    As the demand for reliable high speed data transmission increases, the capacity of downlink cellular multiple-input multiple-output (MIMO) systems is of much interest. Unfortunately, the capacity analysis regarding the frequency reuse factor (FRF) is rarely reported. In this paper, theoretical analyses for both ergodic and outage capacities for cellular MIMO systems are presented. The FRF is considered and a hybrid frequency reuse scheme is proposed. It is shown by the numerical results that the proposed scheme can greatly alleviate the coverage problem of single-frequency-reuse cellular systems.
    Download PDF (372K)
  • Akihito MORIMOTO, Yoshihisa KISHIYAMA, Motohiro TANNO, Kenichi HIGUCHI ...
    Article type: PAPER
    2009 Volume E92.B Issue 5 Pages 1649-1659
    Published: May 01, 2009
    Released on J-STAGE: May 01, 2009
    JOURNAL RESTRICTED ACCESS
    This paper investigates the best cell-common reference signal (RS) structure and transmit diversity scheme for Multimedia Broadcast Multicast Service (MBMS) signals considering frequency diversity in a single-frequency network (SFN) in the OFDM based Evolved UTRA downlink. Link-level simulation results show that cyclic delay diversity (CDD) is the most promising transmit diversity scheme for the MBMS signals considering the RS overhead. It is also elucidated that the required average received signal energy per symbol-to-noise power spectrum density ratio (Es/N0) using CDD is reduced by approximately 0.5dB even though the MBMS signal obtains a sufficient frequency diversity gain in SFN operation. Furthermore, we clarify the achievable data rate for the MBMS signal at the cell edge of the centered MBMS cell that satisfies the required block error rate (BLER) using two-antenna transmit CDD and diversity reception by system-level simulation. Then, the simulation results show that the offered data rates with the required BLER of less than 10-2 at 95% coverage are 0.211 (0.17), 0.243 (0.196), 1.168 (1.084), and 2.754 (2.754)bps/Hz with the number of cells providing MBMS, NMBMS = 1, 3, 21, and 57, respectively, employing transmit CDD with two antennas (single-antenna transmission) for ISD = 500m.
    Download PDF (2285K)
  • Satoshi NAGATA, Yoshiaki OFUJI, Yoshihisa KISHIYAMA, Nobuhiko MIKI, Ke ...
    Article type: PAPER
    2009 Volume E92.B Issue 5 Pages 1660-1668
    Published: May 01, 2009
    Released on J-STAGE: May 01, 2009
    JOURNAL RESTRICTED ACCESS
    This paper proposes block-wise resource block (RB)-level distributed OFDMA transmission with ND-block division in order to obtain the frequency diversity effect even for low-rate traffic (here ND indicates the number of virtual RBs within one physical RB) in Evolved UTRA downlink. More specifically, we propose a constraint rule such that distributed transmission is multiplexed into a different physical RB from that of localized transmission in order to achieve the same resource assignment and independent decoding between the distributed and localized transmissions. Based on the proposed rule, a virtual RB for distributed transmission is segmented into ND blocks with the size of 1/ND of the original virtual RB. Then, the ND virtual blocks with the size of 1/ND are mapped together into each ND physical RB in a distributed manner, resulting in a large frequency diversity effect. Numerical calculations show that the block-wise RB-level distributed transmission can reduce the number of control signaling bits required for resource assignment compared to the subcarrier-level distributed transmission scheme, which provides the best performance. Moreover, a system-level simulation shows that the loss in the cell throughput employing the block-wise RB-level distributed transmission compared to that using the subcarrier-level transmission is only within 3-4% when the channel load is 0.5 and 1.0, i.e., the maximum loss is 3-4% at approximately 90% in the cumulative distribution function (CDF).
    Download PDF (2468K)
  • Hidekazu TAOKA, Yoshihisa KISHIYAMA, Kenichi HIGUCHI, Mamoru SAWAHASHI
    Article type: PAPER
    2009 Volume E92.B Issue 5 Pages 1669-1679
    Published: May 01, 2009
    Released on J-STAGE: May 01, 2009
    JOURNAL RESTRICTED ACCESS
    This paper presents comparisons between common and dedicated reference signals (RSs) for channel estimation in MIMO multiplexing using codebook-based precoding for orthogonal frequency division multiplexing (OFDM) radio access in the Evolved UTRA downlink with frequency division duplexing (FDD). We clarify the best RS structure for precoding-based MIMO multiplexing based on comparisons of the structures in terms of the achievable throughput taking into account the overhead of the common and dedicated RSs and the precoding matrix indication (PMI) signal. Based on extensive simulations on the throughput in 2-by-2 and 4-by-4 MIMO multiplexing with precoding, we clarify that channel estimation based on common RSs multiplied with the precoding matrix indicated by the PMI signal achieves higher throughput compared to that using dedicated RSs irrespective of the number of spatial multiplexing streams when the number of available precoding matrices, i.e., the codebook size, is less than approximately 16 and 32 for 2-by-2 and 4-by-4 MIMO multiplexing, respectively.
    Download PDF (2469K)
  • Daichi IMAMURA, Yoshihiko OGAWA, Takashi IWAI, Tomohumi TAKATA, Katsuh ...
    Article type: PAPER
    2009 Volume E92.B Issue 5 Pages 1680-1687
    Published: May 01, 2009
    Released on J-STAGE: May 01, 2009
    JOURNAL RESTRICTED ACCESS
    In this paper, we study and propose an inter-cell co-channel interference (CCI) mitigation method for pilot signals using cyclic shift Zadoff-Chu (CS-ZC) sequences for SC-FDMA-based uplink without tight scheduler coordination among cells. Firstly, we investigate the issue of severe detection performance degradation created by the lack of orthogonality among the pilot signals without alignment of the allocated frequency resource positions among cells when using the conventional CS-ZC sequences generation scheme. Secondly, we identify the primary factor causing the issue. Thirdly, we propose a frequency-dependent CS-ZC sequence generation scheme by allocating the same spectrum elements of the ZC sequence to the overlapped subcarriers among cells to mitigate the inter-cell CCI of the pilot signals without alignment of the frequency resource positions among cells. Finally, we confirm the validity of the proposal using uplink data BLER evaluation under a multipath fading condition by computer simulation compared to the conventional method, and show that the proposal achieves around 0.9dB and 0.6dB better performance at 10% BLER than the conventional method for 1 RB and 2 RBs frequency offsets in 3 RBs transmission bandwidth, respectively.
    Download PDF (2109K)
  • Yoshihisa KISHIYAMA, Kenichi HIGUCHI, Mamoru SAWAHASHI
    Article type: PAPER
    2009 Volume E92.B Issue 5 Pages 1688-1694
    Published: May 01, 2009
    Released on J-STAGE: May 01, 2009
    JOURNAL RESTRICTED ACCESS
    This paper presents the optimum physical random access channel (PRACH) structure in terms of the number of control signaling bits accommodated and the transmission bandwidth based on the link budget in order to satisfy the coverage requirement for the single-carrier (SC)-FDMA based E-UTRA uplink. First, we present the design concept of the PRACH structure considering the purposes of the random access procedure in the E-UTRA. Simulation evaluations including a system-level simulation show that a PRACH comprising a 0.5-msec preamble sequence can convey a 6-bit control signal at the cell edge when the inter-site distance (ISD) is 500m under full channel load conditions with one-cell frequency reuse. It is also shown, however, that a PRACH longer than one-sub-frame, e.g., 1.0msec, is necessary to support the ISD of 1732m assuming the same conditions. We also show that the best transmission bandwidth for the PRACH is approximately 1.08-4.5MHz from the viewpoint of the misdetection probability, and a 1.08-MHz transmission bandwidth is suitable considering other aspects such as flexible resource assignment in the time domain and a small number of options in the transmission bandwidth.
    Download PDF (737K)
  • Teruo KAWAMURA, Yoshihisa KISHIYAMA, Kenichi HIGUCHI, Mamoru SAWAHASHI
    Article type: PAPER
    2009 Volume E92.B Issue 5 Pages 1695-1704
    Published: May 01, 2009
    Released on J-STAGE: May 01, 2009
    JOURNAL RESTRICTED ACCESS
    This paper proposes efficient single-carrier (SC) based multiplexing schemes for Layer 1 (L1)/Layer 2 (L2) control signals in SC-FDMA radio access using DFT-Spread OFDM in the Evolved UTRA uplink. L1/L2 control signals are necessary for key packet access techniques such as downlink scheduling, link adaptation, hybrid automatic repeat request (ARQ) with soft combining, and for uplink feedback control signals. We first propose a SC-based multiplexing scheme for L1/L2 control signals within a shared data channel for a set of user equipment (UE) that transmits both an uplink shared data channel and L1/L2 control signals within the same subframe. We also propose a multiplexing scheme for L1/L2 control signals without uplink data transmission that takes advantage of intra-subframe frequency hopping (FH) using multiple exclusively-assigned time-frequency resource blocks (RBs) to obtain a frequency diversity gain. Furthermore, we propose an orthogonal CDMA-based multiplexing scheme using cyclic shifts of a constant amplitude zero auto-correlation (CAZAC) sequence for L1/L2 control signals from different UEs within the same narrowband time-frequency RB. Computer simulation results show that the proposed SC-based multiplexing scheme for the L1/L2 control signals within the shared data channel achieves a higher user throughput than a multicarrier-based multiplexing scheme. The results also show that the proposed multiplexing scheme for the L1/L2 control signals that takes advantage of the intra-subframe FH for the UE without uplink data transmission achieves high quality reception through large frequency diversity gain. Furthermore, we show that the proposed cyclic-shift based orthogonal CDMA multiplexing is effective in the multiplexing of multiple L1/L2 control signals from different UEs within the same RB.
    Download PDF (1773K)
  • Shohei TSUCHIDA, Mamoru SAWAHASHI, Hidekazu TAOKA, Kenichi HIGUCHI
    Article type: PAPER
    2009 Volume E92.B Issue 5 Pages 1705-1713
    Published: May 01, 2009
    Released on J-STAGE: May 01, 2009
    JOURNAL RESTRICTED ACCESS
    This paper presents field experiments on open-loop transmit diversity in downlink OFDM based radio access conducted in a measurement course in Yokosuka city near Tokyo. The experimental results obtained under actual propagation channel conditions show that Space Frequency Block Code (SFBC) and the combination of SFBC and Frequency Switched Transmit Diversity (FSTD) (or Cyclic Delay Diversity (CDD)) are the most promising open-loop transmit diversity schemes for two- and four-antenna transmission, respectively, from the viewpoint of the required average received signal-to-noise power ratio (SNR).
    Download PDF (2781K)
  • Naoto OKUBO, Yoshiaki OFUJI, Sadayuki ABETA, Takehiro NAKAMURA
    Article type: PAPER
    2009 Volume E92.B Issue 5 Pages 1714-1724
    Published: May 01, 2009
    Released on J-STAGE: May 01, 2009
    JOURNAL RESTRICTED ACCESS
    This paper investigates the uplink throughput performance and the interference power to other cells using an Evolved UTRA (E-UTRA) laboratory and field experimental system. In E-UTRA uplink, the near-far problem is not an issue since the orthgonality among the users within the target cell is maintained. Therefore, the fractional transmission power control (TPC), in which the target level of TPC is adjusted according to the path loss level, can be adopted. Thus, it is expected the high cell throughput and the large coverage area by combining fractional TPC, adaptive modulation and channel coding (AMC), and variable resource block (RB) allocation. The indoor and field experimental results show that the peak throughput of approximately 45Mbps is achieved by allocating a wider bandwidth and setting higher target level for the UE located near the cell site while keeping the adjacent cell interference level almost the constant. We also showed that the system capacity can be improved by 50% in simple cell model by applying the AMC and the fractional TPC.
    Download PDF (1777K)
  • Hidekazu TAOKA, Kenichi HIGUCHI, Mamoru SAWAHASHI
    Article type: PAPER
    2009 Volume E92.B Issue 5 Pages 1725-1734
    Published: May 01, 2009
    Released on J-STAGE: May 01, 2009
    JOURNAL RESTRICTED ACCESS
    This paper presents experimental results in real propagation channel environments of real-time 1-Gbps packet transmission using antenna-dependent adaptive modulation and channel coding (AMC) with 4-by-4 MIMO multiplexing in the downlink Orthogonal Frequency Division Multiplexing (OFDM) radio access. In the experiment, Maximum Likelihood Detection employing QR decomposition and the M-algorithm (QRM-MLD) with adaptive selection of the surviving symbol replica candidates (ASESS) is employed to achieve such a high data rate at a lower received signal-to-interference plus background noise power ratio (SINR). The field experiments, which are conducted at the average moving speed of 30km/h, show that real-time packet transmission of greater than 1Gbps in a 100-MHz channel bandwidth (i.e., 10bits/second/Hz) is achieved at the average received SINR of approximately 13.5dB using 16QAM modulation and turbo coding with the coding rate of 8/9. Furthermore, we show that the measured throughput of greater than 1Gbps is achieved at the probability of approximately 98% in a measurement course, where the maximum distance from the cell site was approximately 300m with the respective transmitter and receiver antenna separation of 1.5m and 40cm with the total transmission power of 10W. The results also clarify that the minimum required receiver antenna spacing is approximately 10cm (1.5 carrier wave length) to suppress the loss in the required received SINR at 1-Gbps throughput to within 1dB compared to that assuming the fading correlation between antennas of zero both under non-line-of-sight (NLOS) and line-of-sight (LOS) conditions.
    Download PDF (2122K)
  • Motohiro TANNO, Akihito MORIMOTO, Kenichi HIGUCHI, Mamoru SAWAHASHI
    Article type: PAPER
    2009 Volume E92.B Issue 5 Pages 1735-1742
    Published: May 01, 2009
    Released on J-STAGE: May 01, 2009
    JOURNAL RESTRICTED ACCESS
    This paper proposes a handover method that uses a combination of bicast and forwarding (BIFO) of IP packets to achieve a short handover delay. BIFO achieves a lower amount of IP packet traffic in the backhaul for future IP-based radio access networks (RANs) than the bicast only method. To validate the effect of the proposed BIFO, we implement prototype experimental equipment comprising a RAN_access router (RAN_AR), Node Bs associated with a radio control server (RCS), and user equipment (UE) including a controller. The experimental results show that BIFO achieves a shorter handover delay than the conventional bicast method or forwarding method by taking advantage of the respective merits of bicast and forwarding. The results also confirm that BIFO achieves the handover delay time in the control plane of approximately 10-20msec.
    Download PDF (1675K)
  • Motohiro TANNO, Yoshihisa KISHIYAMA, Hidekazu TAOKA, Nobuhiko MIKI, Ke ...
    Article type: PAPER
    2009 Volume E92.B Issue 5 Pages 1743-1750
    Published: May 01, 2009
    Released on J-STAGE: May 01, 2009
    JOURNAL RESTRICTED ACCESS
    This paper proposes applying the Layered Orthogonal Frequency Division Multiple Access (OFDMA) radio access scheme and its radio access techniques to LTE (Long-Term Evolution)-Advanced to satisfy its system requirements, which are much stricter than those of the Evolved Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access (UTRA) and UMTS Terrestrial Radio Access Network (UTRAN). Layered OFDMA comprises layered transmission bandwidth assignment (bandwidth is assigned to match the required data rate), a layered control signaling structure, and support for layered environments for both the downlink and uplink. Especially in the uplink, an adaptive multi-access scheme with hybrid single-carrier and multicarrier based radio access is applied. Layered OFDMA radio access will support all the functionalities specified in Release 8 LTE and later enhancements. Key radio access techniques such as fast inter-cell radio resource management that takes advantage of remote radio equipment (RRE) so as to realize inter-cell orthogonality, multi-antenna transmission with more antennas, and coverage enhancing techniques are used to achieve a high level of capacity and cell-edge spectrum efficiency.
    Download PDF (1037K)
  • Meilong JIANG, Narayan PRASAD, Yan XIN, Guosen YUE, Amir KHOJASTEPOUR, ...
    Article type: PAPER
    2009 Volume E92.B Issue 5 Pages 1751-1759
    Published: May 01, 2009
    Released on J-STAGE: May 01, 2009
    JOURNAL RESTRICTED ACCESS
    The 3GPP Long Term Evolution Advanced (LTE-A) system, as compared to the LTE system, is anticipated to include several new features and enhancements, such as the usage of channel bandwidth beyond 20MHz (up 100MHz), higher order multiple input multiple output (MIMO) for both downlink and uplink transmissions, larger capacity especially for cell edge user equipment, and voice over IP (VoIP) users, and wider coverage and etc. This paper presents some key enabling technologies including flexible uplink access schemes, advanced uplink MIMO receiver designs, cell search, adaptive hybrid ARQ, and multi-resolution MIMO precoding, for the LTE-A system.
    Download PDF (957K)
  • Le LIU, Takamichi INOUE, Kenji KOYANAGI, Yoshikazu KAKURA
    Article type: PAPER
    2009 Volume E92.B Issue 5 Pages 1760-1768
    Published: May 01, 2009
    Released on J-STAGE: May 01, 2009
    JOURNAL RESTRICTED ACCESS
    The 3GPP LTE-Advanced has been attracting much attention recently, where the channel bandwidth would be beyond the maximum bandwidth of LTE, 20MHz. In LTE, single carrier-frequency division multiple access (SC-FDMA) was accepted as the uplink access scheme due to its advantage of very low cubic metric (CM). For LTE-A wideband transmission, multicarrier access would be more effective than single carrier access to make use of multi-user diversity and can maintain the physical channel structure of LTE, where the control information is transmitted on the edges of each 20MHz. In this paper, we discuss the access schemes in bandwidth under 20MHz as well as over 20MHz. In the case of bandwidth under 20MHz, we propose the access schemes allowing discontinuous resource allocation to enhance average throughput while maintaining cell-edge user throughput, that is, DFT-spread-OFDM with spectrum division control (SDC) and adaptive selection of SC-FDMA and OFDM (SC+OFDM). The number of discontinuous spectrums is denoted as spectrum division (SD). For DFT-S-OFDM, we define a parameter max SD as the upper limit of SD. We evaluate our proposed schemes in bandwidth under 20MHz and find that SC+OFDM as well as SDC with common max SD or UE-specific max SD can improve average throughput while their cell-edge user throughput can approach that of SC-FDMA. In the case of bandwidth over 20MHz, we consider key factors to decide a feasible access scheme for aggregating several 20MHz-wide bands.
    Download PDF (1384K)
  • Zhenjie FENG, Taiyi ZHANG, Runping YUAN
    Article type: PAPER
    2009 Volume E92.B Issue 5 Pages 1769-1777
    Published: May 01, 2009
    Released on J-STAGE: May 01, 2009
    JOURNAL RESTRICTED ACCESS
    In this paper, we consider an amplify-and-forward (AF) relay network where a source node transmits information to a destination node through the cooperation of multiple relay nodes. It is shown in prior works that the outage behavior and average throughput of the selection AF (S-AF) scheme where only the best relay node is chosen to assist can outperform the conventional all-participate AF (AP-AF) scheme. Assuming multiple antennas at the destination node and single antennas at other nodes in this paper, we propose a relay selection scheme according to the criterion of maximizing receive signal to noise ratio (SNR), where a group of relays is chosen to assist in the transmission simultaneously in a manner similar to cyclic delay diversity (CDD). Compared with S-AF, the proposed scheme achieves better outage behavior and average throughput. It can be seen from simulation results that the performance improvement of symbol error rate (SER) is significant compared with S-AF.
    Download PDF (350K)
  • Moohong LEE, Byungjik KEUM, Young Serk SHIM, Hwang Soo LEE
    Article type: PAPER
    2009 Volume E92.B Issue 5 Pages 1778-1785
    Published: May 01, 2009
    Released on J-STAGE: May 01, 2009
    JOURNAL RESTRICTED ACCESS
    An interference cancellation (ICAN) scheme for mobile communication radio repeaters is presented. When a radio repeater has a gain that is larger than the isolation between its transmit and receive antennas, it oscillates due to feedback interference signals. To prevent feedback oscillation of a radio repeater, we first formulate a feedback oscillation model of the radio repeater and then derive an ICAN model from that model. From the derived ICAN model, we show that the stability and the signal quality of the repeater depend on the repeater's gain and delay, the propagation delay on feedback paths, feedback channel characteristics, and the capability of the feedback channel estimation algorithm. It is also shown that the stability condition of the repeater does not guarantee the quality of the repeater's output signal. To guarantee repeater's stability and signal quality, an ICAN scheme based on an iterative algorithm is subsequently proposed. The simulation results confirm the relationship between the stability and signal quality of the repeater and the impact of the aforementioned factors. Using the proposed ICAN scheme, a mean error vector magnitude (quality indicator) of about 6.3% for the repeater's output signal was achieved.
    Download PDF (415K)
  • Salma Ait FARÈS, Fumiyuki ADACHI, Eisuke KUDOH
    Article type: PAPER
    2009 Volume E92.B Issue 5 Pages 1786-1795
    Published: May 01, 2009
    Released on J-STAGE: May 01, 2009
    JOURNAL RESTRICTED ACCESS
    In this paper, we propose a novel scheme of cooperative relaying network based on data exchange between relays before forwarding their received data to destination. This inter-relay data exchange step is done during an additional middle-slot in order to enhance the transmit signals from relays to the destination under low transmit power condition. To reduce the propagation errors between relays as well as the required transmit power during this data exchange, only the relay possessing the highest SNR is engaged into exchanging data by forwarding its received signal to the other relays. As for the remaining non-selected relays, i.e. with low SNR, the transmitted signal is estimated by using both signals received separately at different time slots (i.e., 1st and 2nd slot) from source and the ‘best’ selected relay, respectively, emulating virtual antenna array where appropriate weights for the antenna array are developed. In addition, we investigate distributed transmit beamforming and maximum ratio combining at the relays and the destination, respectively, to combine coherently the received signals. At the relay optimal location and for low SNR condition, the proposed method has significant better outage behavior and average throughput than conventional methods using one or two time slots for transmission.
    Download PDF (560K)
  • Jianming WU, Shunji MIYAZAKI, Kazuhisa OHBUCHI, Tomohiko TANIGUCHI
    Article type: PAPER
    2009 Volume E92.B Issue 5 Pages 1796-1807
    Published: May 01, 2009
    Released on J-STAGE: May 01, 2009
    JOURNAL RESTRICTED ACCESS
    In this paper, we investigate the system performance of decode and forward based bi-directional relaying based on symbol-wise XOR operation. This technique gives more freedom in selecting the modulation and coding scheme at relay stations, and significantly relaxes the transmission bottleneck. However, the performance degradation occurs when the modulation orders of both links differ from each other. To mitigate such an impact, we exploit a repetition coding scheme in conjunction with a redundant modulation code scheme by overlapping MCS levels. To this end, a system level simulation proves that the proposed scheme achieves about 43% capacity gain over bit-wise XOR based bi-directional relaying and gives additional 10% gain over symbol-wise XOR based bi-directional relaying.
    Download PDF (2201K)
  • Mohammad Azizur RAHMAN, Shigenobu SASAKI, Hisakazu KIKUCHI, Hiroshi HA ...
    Article type: LETTER
    2009 Volume E92.B Issue 5 Pages 1808-1812
    Published: May 01, 2009
    Released on J-STAGE: May 01, 2009
    JOURNAL RESTRICTED ACCESS
    A simple exact error rate analysis is presented for random binary direct sequence code division multiple access (DS-CDMA) considering a general pulse shape and flat Nakagami fading channel. First of all, a simple model is developed for the multiple access interference (MAI). Based on this, a simple exact expression of the characteristic function (CF) of MAI is developed in a straight forward manner. Finally, an exact expression of error rate is obtained following the CF method of error rate analysis. The exact error rate so obtained can be much easily evaluated as compared to the only reliable approximate error rate expression currently available, which is based on the Improved Gaussian Approximation (IGA).
    Download PDF (172K)
  • Haris GACANIN, Fumiyuki ADACHI
    Article type: LETTER
    2009 Volume E92.B Issue 5 Pages 1813-1817
    Published: May 01, 2009
    Released on J-STAGE: May 01, 2009
    JOURNAL RESTRICTED ACCESS
    The use of frequency-domain interleaving on a frame-by-frame basis for orthogonal frequency division multiplexing (OFDM) combined with time division multiplexing (OFDM/TDM) is presented. In conventional OFDM, FDE is not designed to exploit the channel frequency-selectivity and consequently, the frequency diversity gain cannot be obtained. To further improve the bit error rate (BER) performance of conventional OFDM an interleaving technique may be applied, but FDE cannot be fully exploited. In this letter, the OFDM/TDM signal (i.e., several concatenated OFDM signals) frequency components are interleaved at the transmitter and then, minimum mean square error frequency-domain equalization (MMSE-FDE) is applied at the receiver to obtain a larger frequency diversity gain. It is shown that frequency-domain interleaving on a frame-by-frame basis for OFDM/TDM using MMSE-FDE achieves improved BER performance in comparison with conventional OFDM due to enhanced frequency diversity gain.
    Download PDF (218K)
  • Hyunkyu YU, Taeyoung KIM, Jaeweon CHO, Hokyu CHOI, Dong Seek PARK, Seo ...
    Article type: LETTER
    2009 Volume E92.B Issue 5 Pages 1818-1821
    Published: May 01, 2009
    Released on J-STAGE: May 01, 2009
    JOURNAL RESTRICTED ACCESS
    This letter deals with coding and multiplexing strategies for DL/UL MAP transmission in IEEE 802.16m. Separate coding gives a better choice against the joint coding due to the individual users' link adaptation gain. As a multiplexing option, frequency-domain multiplexing outperforms time-domain one in the system-level performance thanks to its flexible power sharing capability between overhead channels and user traffic channels. Overall system-wide performance results are presented with the system level simulation for the various options.
    Download PDF (256K)
  • Hongxing LI, Hanwen LUO, Xinbing WANG, Ming DING, Wen CHEN
    Article type: LETTER
    2009 Volume E92.B Issue 5 Pages 1822-1824
    Published: May 01, 2009
    Released on J-STAGE: May 01, 2009
    JOURNAL RESTRICTED ACCESS
    This letter investigates a subchannel and power allocation (SPA) algorithm which maximizes the throughput of a user under the constraints of total transmit power and fair subchannel occupation among relay nodes. The proposed algorithm reduces computational complexity from exponential to linear in the number of subchannels at the expense of a small performance loss.
    Download PDF (101K)
  • Mingju LI, Lei DU, Lan CHEN
    Article type: LETTER
    2009 Volume E92.B Issue 5 Pages 1825-1827
    Published: May 01, 2009
    Released on J-STAGE: May 01, 2009
    JOURNAL RESTRICTED ACCESS
    In LTE, AC barring check is performed before RRC connection. In some cells with a low access probability, the UEs keep retrying access which results in higher connection failure and longer access delay. We therefore propose balancing the UEs by adjusting the cell reselection criteria based on the access probability, so that the UEs shall be more encouraged to reselect a cell with a higher access probability.
    Download PDF (298K)
Regular Section
  • Wen-Long CHIN, Sau-Gee CHEN
    Article type: PAPER
    Subject area: Transmission Systems and Transmission Equipment for Communications
    2009 Volume E92.B Issue 5 Pages 1828-1833
    Published: May 01, 2009
    Released on J-STAGE: May 01, 2009
    JOURNAL RESTRICTED ACCESS
    Conventional symbol time (ST) synchronization algorithms for orthogonal frequency-division multiplexing (OFDM) systems are mostly based on the maximum correlation result of the cyclic prefix. Due to the channel effect, the estimated ST is not accurate enough. Hence, one needs to further identify the channel impulse response (CIR) so as to obtain a better ST estimation. Overall, the required computational complexity is high because it involves time-domain (TD) correlation operations, as well as the fast Fourier transform (FFT) and inverse FFT (IFFT) operations. In this work, without the FFT/IFFT operations and the knowledge of CIR, a low-complexity TD ST estimation is proposed. We first characterize the frequency-domain (FD) interference effect. Based on the derivation, the new method locates the symbol boundary at the sampling point with the minimum interference in the FD (instead of the conventional maximum TD correlation result). Moreover, to reduce the computational complexity, the proposed FD minimum-interference (MI) metric is converted to a low-complexity TD metric by utilizing Parseval's theorem and the sampling theory. Simulation results exhibit good performance for the proposed algorithm in multipath fading channels.
    Download PDF (754K)
  • Anas BASALAMAH, Takuro SATO
    Article type: PAPER
    Subject area: Network
    2009 Volume E92.B Issue 5 Pages 1834-1840
    Published: May 01, 2009
    Released on J-STAGE: May 01, 2009
    JOURNAL RESTRICTED ACCESS
    For wireless multicast applications like multimedia conferencing, voice over IP and video/audio streaming, a reliable transmission of packets within short delivery delay is needed. Moreover, reliability is crucial to the performance of error intolerant applications like file transfer, distributed computing, chat and whiteboard sharing. Forward Error Correction (FEC) is frequently used in wireless multicast to enhance Packet Error Rate (PER) performance, but cannot assure full reliability unless coupled with Automatic Repeat Request forming what is knows as Hybrid-ARQ. While reliable FEC can be deployed at different levels of the protocol stack, it cannot be deployed on the MAC layer of the unreliable IEEE802.11 WLAN due to its inability to exchange ACKs with multiple recipients. In this paper, we propose a Multicast MAC protocol that enhances WLAN reliability by using Adaptive FEC and study it's performance through mathematical analysis and simulation. Our results show that our protocol can deliver high reliability and throughput performance.
    Download PDF (569K)
  • Fan LISHENG, Kazuhiko FUKAWA, Hiroshi SUZUKI, Satoshi SUYAMA
    Article type: PAPER
    Subject area: Wireless Communication Technologies
    2009 Volume E92.B Issue 5 Pages 1841-1851
    Published: May 01, 2009
    Released on J-STAGE: May 01, 2009
    JOURNAL RESTRICTED ACCESS
    This paper proposes joint maximum a posteriori (MAP) detection and spatial filtering for MIMO-OFDM mobile communications; it offers excellent receiver performance even over interference-limited channels. The proposed joint processor consists of a log likelihood generator and a MAP equalizer. The log likelihood generator suppresses cochannel interference by spatially filtering received signals and provides branch metrics of transmitted signal candidates. Using the branch metrics, the MAP equalizer generates log likelihood ratios of coded bits and performs channel decoding based on the MAP criterion. In the first stage, the log likelihood generator performs spatio-temporal filtering (STF) of the received signals prior to the fast Fourier transform (FFT) and is referred to as preFFT-type STF. Estimation of parameters including tap coefficients of the spatio-temporal filters and equivalent channel impulse responses of desired signals is based on the eigenvalue decomposition of an autocorrelation matrix of both the received and transmitted signals. For further improvement, in the second stage, the generator performs spatial filtering (SF) of the FFT output and is referred to as postFFT-type SF. Estimation of both tap coefficients of the spatial filters and channel impulse responses employs the recursive least squares (RLS) with smoothing. The reason for switching from preFFT-type STF into postFFT-type SF is that preFFT-type STF outperforms postFFT-type SF with a limited number of preamble symbols while postFFT-type SF outperforms preFFT-type STF when data symbols can be reliably detected and used for the parameter estimation. Note that there are two major differences between the proposed and conventional schemes: one is that the proposed scheme performs the two-stage processing of preFFT-type STF and postFFT-type SF, while the other is that the smoothing algorithm is applied to the parameter estimation of the proposed scheme. Computer simulations demonstrate that the proposed scheme can achieve excellent PER performance under interference-limited channel conditions and that it can outperform the conventional joint processing of preFFT-type STF and the MAP equalizer.
    Download PDF (712K)
  • Kazuto YANO, Makoto TAROMARU, Masazumi UEBA
    Article type: PAPER
    Subject area: Wireless Communication Technologies
    2009 Volume E92.B Issue 5 Pages 1852-1859
    Published: May 01, 2009
    Released on J-STAGE: May 01, 2009
    JOURNAL RESTRICTED ACCESS
    This paper introduces our proposed pre-FFT type MMSE-AAA for an OFDM packet transmission system to suppress sporadic interference. The AAA scheme controls an antenna weight to minimize the mean square error between its output signals of two periods with identical transmitted waveform and iterates the weight updating process in an OFDM symbol to rapidly converge the weight. The average PER performance of the proposed AAA with the presence of a sporadic inter-system/intra-system interference signal is evaluated through computer simulations that assume an exponentially decaying 12-path LOS fading channel and IEEE 802.11a data frame transmission. Simulation results show that the proposed AAA can effectively suppress sporadic inter-system interference that is irrelevant to its arrival timing. Sporadic intra-system interference can also be suppressed by the proposed AAA more efficiently than inter-system interference as long as the interference arrives between 13% and 90% of the OFDM symbol duration after the beginning of an OFDM symbol of the desired signal.
    Download PDF (864K)
feedback
Top