Non-orthogonal multiple access (NOMA) offers a good balance between throughput and fairness for visible light communication (VLC). This work presents a phase pre-distortion method to improve the symbol error rate performance of NOMA uplink with successive interference cancellation (SIC) decoding in VLC. Both theoretical analysis and experimental evaluation have shown that the proposed phase pre-distortion method improves the bit-error-rate (BER) performance for NOMA under both low and high relative power ratios. Specifically, at low relative power ratios, the proposed method can eliminate the possible BER floors and alleviate the power ratio requirement by 2 dB at the BER of 3.8 × 10-3.
INTRODUCTION: Opiate addicts in New Zealand are a heterogeneous, hard-to-reach group with illicit drug activity as their common characteristic. This project investigated the experience of a specific hardto-reach group: pregnant women with opiate dependency, focussing on their interactions with helping services and social networks. The aim was to explore the interactions of pregnant women on methadone with helping services and social support, with the objective to make recommendations to improve service to this hard-to-reach group. METHOD: Questions for staff and client interview schedules were constructed, informed by a literature search. Seven methadone clinic staff were interviewed and a questionnaire was distributed to 10 antenatal clinic staff known to have previously managed pregnant women on methadone. Five methadone clients were interviewed at the clinic and interviews taped for transcription with consent. FINDINGS: High risk pregnancies warrant a multidisciplinary approach, but in the hard-to-reach this ideal can itself be out of reach. Although primary care is better placed than secondary care to coordinate maternity and community support services, few opiate-dependent people have a regular general practitioner and may have perceived or actual barriers to access to care. Perceived stigma deterred these women from engaging. Women also fear that services will judge and report them, worrying about the health of their child and the powers of child protection services. CONCLUSION: A fresh consideration of the functionality of services to the hard-to-reach may be beneficial. A nursing concept of face-work throws some light on the misperception of well-intentioned services by the hard-to-reach. KEYWORDS: Pregnancy; methadone maintenance; addiction; hard-to-reach; face-work, resilience.
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