1,620 research outputs found
EXIT-chart aided near-capacity irregular bit-interleaved coded modulation design
No full textA near-capacity irregular Bit-Interleaved Coded Modulation based Iterative Decoding (Ir-BICM-ID) aided scheme is proposed. The irregular design of the scheme pervades the three basic components of BICM-ID, namely the encoder, the unity-rate precoder and the bit-to-symbol mapper. As a result, irregular BICM-ID schemes constituted by irregular components are created, which are capable of approaching the capacity of coded modulation. This is achieved by creating a marginally open EXtrinsic Information Transfer (EXIT) chart tunnel, and exploiting the theorem that the open tunnel’s area is characteristic of how closely the scheme operates to the channel’s capacity. The proposed Ir-BICM-ID scheme employs Irregular Convolutional Codes (IrCC), Irregular Unity-Rate Codes (IrURC) and Irregular Mappers (IrMapper)
Coded Modulation Assisted Radial Basis Function Aided Turbo Equalisation for Dispersive Rayleigh Fading Channels
No full textIn this contribution a range of Coded Modulation (CM) assisted Radial Basis Function (RBF) based Turbo Equalisation (TEQ) schemes are investigated when communicating over dispersive Rayleigh fading channels. Specifically, 16QAM based Trellis Coded Modulation (TCM), Turbo TCM (TTCM), Bit-Interleaved Coded Modulation (BICM) and iteratively decoded BICM (BICM-ID) are evaluated in the context of an RBF based TEQ scheme and a reduced-complexity RBF based In-phase/Quadrature-phase (I/Q) TEQ scheme. The Least Mean Square (LMS) algorithm was employed for channel estimation, where the initial estimation step-size used was 0.05, which was reduced to 0.01 for the second and the subsequent TEQ iterations. The achievable coding gain of the various CM schemes was significantly increased, when employing the proposed RBF-TEQ or RBF-I/Q-TEQ rather than the conventional non-iterative Decision Feedback Equaliser - (DFE). Explicitly, the reduced-complexity RBF-I/Q-TEQ-CM achieved a similar performance to the full-complexity RBF-TEQ-CM, while attaining a significant complexity reduction. The best overall performer was the RBF-I/Q-TEQ-TTCM scheme, requiring only 1.88~dB higher SNR at BER=10-5, than the identical throughput 3~BPS uncoded 8PSK scheme communicating over an AWGN channel. The coding gain of the scheme was 16.78-dB
Near-Capacity Irregular Bit-Interleaved Coded Modulation
No full textAn Irregular Bit-Interleaved Coded Modulation based Iterative Decoding (Ir-BICM-ID) aided scheme is proposed. The irregularity of the scheme pervades the three basic components of BICM-ID, namely the encoder, the unity-rate precoder and the bit-to-symbol mapper. As a result, adaptive BICM-ID schemes constituted by irregular components are created, which are capable of approaching the capacity of coded modulation. This is achieved by creating a narrow EXtrinsic Information Transfer (EXIT) chart, using a novel EXIT curve matching algorithm. The proposed Ir-BICM-ID scheme employs Irregular Convolutional Codes (IrCC), Irregular Unity-Rate Codes (IrURC) and Irregular Mappers (IrMapper)
Air flow buoyancy surrounding buildings in Malaysia / Lian Yee Cheng
No full textIn a developing country such as Malaysia, buildings have been built in fast pace. To design a durable building envelope, the air flow around a building plays an important role. The buoyancy is proven as one of the factors induced air flow pattern. The contribution of buoyancy to surrounding air flow of a building in Malaysia was comprehensively investigated in the present research. The objective of the present research is to study the significance of buoyancy in air flow movement with and without present of wind. Future development around the research building was studied as well to examine the effect of the buoyancy to the surrounding air flow. There are three research buildings for present research. The first building is the Malaysia’s Energy Commission building. Malaysia’s Energy Commission is a green building which has a unique architecture outlook makes it to be called the Diamond Building. Second building is a hospital ward tower of Sarawak International Medical Centre and the third building is Engineering Tower of University Malaya. Outdoor field data such as air velocity, surface temperature and ambient conditions were collected during physical measurement. Three dimensional air flow simulation was then carried out using the Computational Fluid Dynamics (CFD) software ANSYS. Qualitative and quantitative analyses of the simulation results have been carried out to investigate the influence of the buoyancy effect on the air flow surrounding buildings. The result shows that the air flow surrounding the green building has a maximum velocity of 0.69 ms-1, hospital ward tower is 0.25ms-1 and engineering tower is 0.19ms-1 which is dominated by the buoyancy effect when no wind is present. The buoyancy strength is quantified by a dimensionless number, Archimedes number. If natural wind is present, the buoyancy effect is negligible
A Wideband Radial Basis Function Decision Feedback Equaliser Assisted Burst-by-Burst Adaptive Modem
No full textThe performance of radial basis function-based decision feedback equalized (RBF DFE) burst-by-burst adaptive quadrature amplitude modulation (AQAM) is presented for transmissions over dispersive wide-band mobile channels. This scheme is shown to give a significant improvement in terms of the mean bit error rate (BER) and bits per symbol (BPS) performance compared to that of the individual fixed modulation modes. The structural equivalence of the RBF DFE to the optimal Bayesian equalizer enables it to potentially outperform the conventional Kalman-filtered AQAM DFE scheme. Index Terms—Adaptive modulation, decision feedback equalization, radial basis function, wide-band modem
Iterative Soft Interference Cancellation Aided Minimum Bit Error Rate Uplink Receiver Beamforming
No full textIterative multiuser receivers constitute an effective solution for transmission over Multiple Access Interference (MAI) infested channels, when invoking a combined multiuser detector and channel decoder. Most reduced-complexity methods in this area use the Complex-valued Minimum Mean Squared Error (CMMSE) Multiuser Detector (MUD). Since the desired output of BPSK systems is real-valued, minimizing the Mean Square Error (MSE) between the beamformer’s desired output and the real part of the beamformer output has the potential of significantly improving the attainable Bit Error Rate (BER) performance. We refer to this MMSE design as the Real-valued MMSE (RMMSE) receiver. In this paper, we explore a new Soft-Input Soft-Output (SISO) interference cancellation multiuser detection algorithm based on the novel Minimum BER (MBER) criterion. We demonstrate that the MBER turbo receiver outperforms both the CMMSE and the RMMSE algorithms, particularly in so-called ‘overloaded’ beamforming systems, where the number of receiver antennas is lower than the number of users supported
Iterative decoding of multilevel and bit-interleaved coded modulation
No full textA comparative study of various codeq. modulation schemes is carried out in terms of their different block length, number of iterations and complexity, quantified by the number of trellis states as well as the EXtrinsic Information Transfer (EXIT) charts are used for analysing their decoding convergence and Bit Error Ratio (BER). A threeDimensional (3-D) EXIT chart is introduced for MultiLevel Coding (MLC) invoking MultiStage Decoding (MSD). Based on this 3-D EXIT chart, we design a precodedMLC scheme employing both MSD and Parallel Independent Decoding (PID). In order to provide space diversity, we study the new arrangement of Bit-Interleaved Coded Modulation with Iterative Decoding (BICM-ID) and MLC combined with Space Time Block Codes (STBC) invoking a novel Sphere Packing (SP) modulation scheme. An equivalent-capacIty-based design of MLCs based on this SP modulation is proposed. We use the Binary Switching Algorithm (BSA) to optimise our cost function for the sake of obtaining appropriate bit-to-SP-symbol mapping schemes. A hybrid mapping scheme is introduced for achieving unequal error protection. Furthermore, bit-to-SP-symbol mapping to 256 constellation points is designed for a serially concatenated BICM-ID aided twin-antenna STBC arrangement for creating a system, which is capable of outperforming an identical-throughput 16-level Quadrature Amplitude Modulation (16QAM) scheme. Furthermore, the benefits of MLC PID designs employing Generalised Low Density Parity Check (GLDPC) codes are investigated, which results in a low-delay scheme useful for multimedia transmission. A stopping criterion is designed for this scheme for the sake of terminating the iterative decoding process, once the target BER is attained. We then contrive coding schemes for the wireless Internet by introducing a BICM-ID scheme combined with Luby Transform (LT) coding constructed for the AWGN-contaminated Binary Erasure Channel (BEC). An improved robust LT packetdegree distribution is introduced for determining the specific number of LT source packets combined with modulo-2 additions in order to create an LT-encoded packet. Furthermore, a Log-Likelihood Ratio (LLR) based reliability estimation scheme is invoked in order to achieve a performance improvement based on this amalgamated design. Finally, a near-capacity Irregular Bit-Interleaved Coded Modulation with Iterative Decoding (Ir-BICM-ID) scheme was designed with the aid of an EXIT chart. An Irregular Convolution Code (IrCC) is proposed for the sake of introducing a diverse range of outer code EXIT functions. By contrast, the inner code is based on the serially concatenated components constituted by an Irregular Unity-Rate Code (IrURC) and an Irregular Mapper (IrMapper). An EXIT chart matching algorithm is invoked for constructing an Ir-BICM-ID scheme, which exhibits a narrow but still open EXIT tunnel and hence approaches the theoretical capacity limit.EThOS - Electronic Theses Online ServiceGBUnited Kingdo
H-ARQ-Aided Systematic Luby Transform Codes
No full textHybrid Automatic-Repeat-Request (H-ARQ) Aided Systematic Luby Transform (SLT) Coded Modulation is proposed, where SLT codes are used both for correcting erroneous bits and for detecting as well as retransmitting erroneous Internet Protocol (IP) based packets. Erroneous IP packet detection is implemented using syndrome checking with the aid of the SLT codes’ Parity Check Matrix (PCM). Optimizing the mapping of SLT-encoded bits to modulated symbols and then using iterative decoding for exchanging extrinsic information between the SLT decoder and the demapper substantially improves the achievable Bit Error Ratio (BER) performance of the scheme. Quantitatively, at Eb/N0 in excess of 3.8 dB, this scheme is capable of achieving a BER 10?5 and up to 1.5 times higher throughput in comparison to less sophisticated benchmarker schemes such as SLT codes, dispensing with ARQ-assistance or joint SLT coded modulation and H-ARQ-SLT codes, when communicating over AWGN channels, using 16-QAM and a half-rate SLT code
Peranan dan sikap wanita dalam pekerjaan di sektor awam (Satu kajian perbandingan antara wanita berkahwin dan bujang) / Yee Guat Lian
No full textDalam usaha untuk membuat latihan ilmiah ini, pengkaji telah menjalankan kajian luarnya si Suruhanjaya Perkhidmatan Awam Malaysia. Kajian ini adalah bertujuan untuk melihat sejauhmana peranan dan sikap wanita dalam pekerjaan khususnya kaum wanita di sektor awam. Berhubung dengan itu, pengkaji telah membahagikan latihan ilmiah ini kepada 6 bab. Bab I pengkaji telah menghuraikan bidang serta tujuan kajian. Di samping itu, pengkaji juga menerangkan metode kajian yang digunakan serta masalah-masalah yang dihadapi oleh pengkaji semasa menjalankan kajian luar. Bab II pengkaji telah membuat huraian mengenai teori dan konsep-konsep yang digunakan di dalam latihan ilmiah ini khususnya konsep peranan dan sikap. Bab III adalah bab di mana pengkaji menghuraikan latar belakang responden serta faktor-faktor yang mendorong penglibatan wanita dalam pekerjaan. Bab IV pula pengkaji telah membincangkan sejauhmana penglibatan wanita memberi kesan ke atas hubungan dengan suami, anak-anak dan juga keluarga di kampung. Di samping itu, dalam bab yang sama pengkaji menghuraikan pola perbelanjaan oleh wanita-wanita ini. Bab V pengkaji telah meninjau penglibatan wanita dalam kegiatan-kegiatan sosial yang terdapat di tempat kerja sama ada yang bercorak formal atau informal. Dalam bab ini juga, pengkaji menghuraikan implikasi penglibatan wanita dalam pekerjaan ke atas saiz famili. Bab VI merupakan rumusan keseluruhan kajian di mana dikaitkan antara teori dan konsep dengan dapatan
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