Joint-Detection and Interference Cancellation Based Burst-by-Burst Adaptive CDMA Schemes

Spread adaptive quadrature amplitude modulated (AQAM) code-division multiple access (CDMA) is proposed as a powerful means of exploiting the time-variant channel capacity fluctuations of wireless channels. It is studied in comparison to variable spreading factor (VSF)-based techniques. These adaptive-rate transmission methods are compared in the context of joint detection and interference cancellation assisted adaptive CDMA (ACDMA) systems. More explicitly, we exploit the time-variant channel quality of mobile channels by switching either the modulation mode (AQAM) or the spreading factor (VSF) on a burst-by-burst basis. The most appropriate modulation mode or spreading factor is chosen based on the instantaneous channel quality estimated. The chosen modem mode or spreading factor is communicated to the remote communicator either through explicit signalling or extracted at the receiver using blind detection techniques. The multiuser joint detector (JD) and the successive interference cancellation (SIC) receiver are compared in the context of these adaptive schemes, with the conclusion that the JD outperformed the SIC receiver in the ACDMA schemes at the cost of increased complexity. Finally, the performance of the uncoded AQAM JD-CDMA scheme is also compared to that of adaptive trellis coded modulation (TCM) assisted AQAM JD-CDMA, which allows us to incorporate adaptive channel coding without any bandwidth expansion.We also show that in the particular scenario studied, adaptiveTCM outperformed adaptive turbo TCM since the system was designed for maintaining a low turbo-interleaver delay. Index Terms—Burst-by-burst adaptive code-division multiple access (CDMA), joint detection CDMA, parallel interference cancellation (PIC), successive interference cancellation (SIC), successive and parallel interference cancellation

Prior dengue virus exposure shapes T Cell immunity to Zika Virus in humans

While progress has been made in characterizing humoral immunity to Zika virus (ZIKV) in humans, little is known regarding the corresponding T cell responses to ZIKV. Here we investigate the kinetics and viral epitopes targeted by T cells responding to ZIKV and address the critical question of whether pre-existing dengue virus (DENV) T cell immunity modulates these responses. We find that memory T cell responses elicited by prior infection with DENV or vaccination with Tetravalent Dengue Attenuated Vaccines (TDLAV) recognize ZIKV-derived peptides. This cross-reactivity is explained by the sequence similarity of the two viruses, as the ZIKV peptides recognized by DENV-elicited memory T cells are identical or highly conserved in DENV and ZIKV. DENV exposure prior to ZIKV infection also influences the timing and magnitude of the T cell response. ZIKV-reactive T cells in the acute phase of infection are detected earlier and in greater magnitude in DENV-immune patients. Conversely, the frequency of ZIKV-reactive T cells continues to rise in the convalescent phase in DENV-naive donors, but declines in DENV pre-exposed donors, compatible with more efficient control of ZIKV replication and/or clearance of ZIKV antigen. The quality of responses is also influenced by previous DENV exposure, and ZIKV-specific CD8 T cells form DENV pre-exposed donors selectively up-regulated granzyme B and PD1, as compared to DENV-naïve donors. Finally, we discovered that ZIKV structural proteins (E, prM and C) are major targets of both the CD4 and CD8 T cell responses, whereas DENV T cell epitopes are found primarily in nonstructural proteins

Lung adenocarcinoma promotion by air pollutants

A complete understanding of how exposure to environmental substances promotes cancer formation is lacking. More than 70 years ago, tumorigenesis was proposed to occur in a two-step process: an initiating step that induces mutations in healthy cells, followed by a promoter step that triggers cancer development1. Here we propose that environmental particulate matter measuring ≤2.5 μm (PM2.5), known to be associated with lung cancer risk, promotes lung cancer by acting on cells that harbour pre-existing oncogenic mutations in healthy lung tissue. Focusing on EGFR-driven lung cancer, which is more common in never-smokers or light smokers, we found a significant association between PM2.5 levels and the incidence of lung cancer for 32,957 EGFR-driven lung cancer cases in four within-country cohorts. Functional mouse models revealed that air pollutants cause an influx of macrophages into the lung and release of interleukin-1β. This process results in a progenitor-like cell state within EGFR mutant lung alveolar type II epithelial cells that fuels tumorigenesis. Ultradeep mutational profiling of histologically normal lung tissue from 295 individuals across 3 clinical cohorts revealed oncogenic EGFR and KRAS driver mutations in 18% and 53% of healthy tissue samples, respectively. These findings collectively support a tumour-promoting role for PM2.5 air pollutants and provide impetus for public health policy initiatives to address air pollution to reduce disease burden

Burst-by-Burst Adaptive Joint-Detection CDMA/H2.63 Based Video Telephony

Since wireless channels exhibit dramatic near-instantaneous channel-quality fluctuations, it is unrealistic to expect that a transceiver relying on time-invariant modulation and coding modes is capable of delivering as good a performance as a near-instantaneously adaptive arrangement. Hence, a near-instantaneously adaptive joint-detection code division multiple access (CDMA)-based video transceiver is proposed for wireless video telephony. Specifically, the transceiver is capable of reconfiguring itself in 1, 2, and 4 bits/symbol direct-sequence CDMA modes and delivers an unimpaired video quality associated with a peak signal-to-noise ratio (PSNR) of 34–41 dB for channel SNRs in excess of about 5 dB over the COST207 bad urban channel model at video rates between 5–26.9 kbits/s using 176 144 pixel quarter common intermediate format (QCIF) and 128 96 pixel sub-QCIF (SQCIF) video formats. Index Terms—CDMA, H.263, reconfigurable modulation, video telephony, wireless video

Single- and Multi-Carrier DS-CDMA: Multi-USer Detection, Space-Time Spreading, Synchronisation, Standards and Networking

This volume is dedicated to a range of CDMA and MC-CDMA transmission aspects of systems designed for communicating over fading wireless channels. Currently, a technical in-depth book on this subject, which has a similar detailed exposure of the recent advances in CDMA, M-ary CDMA and MC-CDMA, is unavailable. A further attraction of the joint treatment of these topics is that it allows the reader to view their design trade-offs in a comparative context. Divided into five main parts: Part I – provides a detailed introduction to the subject of CDMA systems designed for employment in various application Part II – deals with the currently hot topic of genetic algorithm assisted multiuser detection Part III – gives a detailed account of new, reduced-complexity M-ary CDMA schemes Part IV – considers a range of novel MC-CDMA schemes which have the potential of supporting numerous design objectives Part V – provides an overview of the 3G wireless system proposals and characterises the expected network capacity gains attained with the aid of adaptive CDMA systems By providing an all-encompassing self-contained treatment this groundbreaking volume will have appeal to researchers, postgraduate students, academics practising research and development engineers working for wireless communications and computer networking companies, as well as senior undergraduate students and technical managers in the field

Burst-by-Burst Adaptive Multiuser Detection CDMA: A Framework for Existing and Future Wireless Standards

This paper provides a broad overview of the multiuser detection literature of the past few years in a nonmathematical, easily accessible approach. The treatment is then extended to the comparative study of channel-quality controlled burst-by-burst (BbB) adaptive code division multiple access (CDMA) detection such as parallel interference cancellation, successive interference cancellation, and joint detection (JD). It is demonstrated that the best complexity versus performance tradeoff is constituted by the JD receivers. Furthermore, the BbB-adaptive variable spreading factor-based schemes considered were outperformed by the adaptive quadrature amplitude modulation-based JD-CDMA schemes investigated. For example, at a channel signal-to-noise ratio per bit value of $E_b=N_0$ = 14 dB the latter scheme provides an average bit per symbol (BPS) throughput of 3.39, while the former provides an average BPS throughput of only 2.83, although the complexity of the latter is lower. In conclusion, BbB-adaptive CDMA schemes provide an attractive performance versus complexity tradeoff and are amenable to employment in both existing and future generations of wireless systems. Keywords—Adaptive CMDA systems, adaptive transceivers, interference cancellation, multiuser detection

Single-Carrier Space-Time Trellis and Space-Time Block Coding for Dispersive Rayleigh Fading Channels

In this contribution we propose a novel Space-Time Coding (STC) scheme for transmissions over dispersive Rayleigh fading channels, which invokes a Joint-Detection assisted Minimum Mean Square Error based Decision Feedback Equalizer (JD-MMSE-DFE)for jointly detecting the channel-impaired wideband signals of multiple transmit antennas. The performance of the proposed scheme was investigated using Quadrature-Phase-Shift-Keying (QPSK) when communicating over channels exhibiting multi-path components. It was shown that the scheme advocated outperforms conventional STC due to benefitting from the multi-path diversity of the dispersive channel

TCM, TTCM, BICM and BICM-ID Assisted Joint Detection Based CDMA

In this contribution we studied the performance of Trellis Coded Modulation (TCM), Turbo Trellis Coded Modulation (TTCM), Bit-Interleaved Coded Modulation (BICM) and Iterative Decoding assisted BICM (BICM-ID) schemes applied in a Code-Division Multiple Access (CDMA) system in the context of 8-level Phase Shift Keying (8PSK) and 16-level Quadrature Amplitude Modulation (16QAM) for transmissions over dispersive Rayleigh fading channels. A Minimum Mean Square Error based Decision Feedback Equalizer (JD-MMSE-DFE) was utilised for multiuser detection and for mitigating the effects of both intersymbol interference as well as that of the multiuser access interference in the system. It was found that TCM is the best scheme when using a short interleaver, while TTCM is best scheme when using long interleaver, compared to the other investigated schemes at the same decoding complexity

Multi-Mode Joint-Detection CDMA/H.263 Based Video Telephony

A multi-mode joint-detection CDMA-based video transceiver is proposed for wireless video telephony, which substantially outperforms the matched-filtering-based bench-marker video transceiver. For channel SNRs in excess of about 5 dB near-unimpaired video quality is maintained by the proposed scheme