In this paper, a performance analysis for the frequency-domain code-division multiple-access (CDMA) of multiple simultaneously operating piconets (SOPs) in orthogonal frequency-division multiplexing (OFDM) based ultra...
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ISBN:
(纸本)9781424402656
In this paper, a performance analysis for the frequency-domain code-division multiple-access (CDMA) of multiple simultaneously operating piconets (SOPs) in orthogonal frequency-division multiplexing (OFDM) based ultra-wideband (UWB) systems is presented. Two different strategies for the accommodation of multiples SOPs, namely, the variable spreading factor (VSF) scheme with minimal spreading and the multicode scheme with maximal spreading, were considered. The channel is assumed to be Rayleigh fading with exponentially decaying delay power profile. Furthermore, the analysis takes into account the intersymbol interference (ISI) caused by the multipath delay components exceeding the guard interval. Numerical results demonstrate that the frequency-domain CDMA can be employed to accommodate multiple SOPs while maintaining acceptable performance when a suitable subcarrier combining method is used. The VSF and multicode schemes result in a similar performance when the number of SOPS is large, while notable differences are pointed out when there are only a few SOPs.
The next generation mobile communications system is anticipated to support data rates up to and exceeding 100Mbps. In this paper, we consider a DS-CDMA high-speed downlink packet access (HSDPA) as in 3G W-CDMA systems...
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ISBN:
(纸本)0780385217
The next generation mobile communications system is anticipated to support data rates up to and exceeding 100Mbps. In this paper, we consider a DS-CDMA high-speed downlink packet access (HSDPA) as in 3G W-CDMA systems. Adaptive modulation and coding (AMC), multicode operation and hybrid automatic repeat request (HARQ) will be the enabling technologies. With such high-speed data transmissions, however, multicode operation severely suffers from destruction of orthogonality among the spreading codes since the wireless channel becomes severely frequency-selective. In this paper, we apply frequency-domain equalization (FDE) instead of conventional rake combining for receiving the packet. It is shown that the use of FDE for the reception of multicode signal gives an improved throughput irrespective of the channel's frequency-selectivity.
For efficient code sharing among users, a wireless medium access control (MAC) protocol for CDMA networks is proposed, which supports connection-oriented, as well as connectionless, services and provides the various b...
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For efficient code sharing among users, a wireless medium access control (MAC) protocol for CDMA networks is proposed, which supports connection-oriented, as well as connectionless, services and provides the various bit rates needed for the integrated multimedia services. The proposed MAC protocol allows mobile terminals to use multiple slots and spreading codes bused on contention and reservation. Optimum frequency resources are allocated to the connection-oriented and connectionless services with various bit rates. Waiting and response times in the first contention are reduced, and the overall mean delay time is typically minimized in the case of connectionless bulky traffic.
In western musical contexts at global and local levels, musicians are becoming increasingly involved in what might be termed multicode music making and are expanding their musical competences. In this article I consid...
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In western musical contexts at global and local levels, musicians are becoming increasingly involved in what might be termed multicode music making and are expanding their musical competences. In this article I consider the practical and cognitive implications of such an expanding of competences for music education at various levels. Combining ethnomusicological and music educationist perspectives, I ground the discussion in a reading of various media texts, a consideration of pedagogical trends, a field observation, and instances of autoethnography. Engaging with recent discussions of ethnomusicology's notions of bimusicality and intermusicality, I conceptualise plural musical practices according to metaphors of growth, and stretching or reforming, both within and outwards from a core of culturally grounded musical skills, values and understandings. I propose a framework for fostering the expanding of musical competences, offer brief, personal case studies and conclude by referring to emerging literature on the training of future music educators.
In 3G WCDMA, orthogonal variable-spreading-factor(OVSF) codes are valuable and scarce resources. Some single-code and multicode assignment algorithms have been proposed tosupport as many users as poss
In 3G WCDMA, orthogonal variable-spreading-factor(OVSF) codes are valuable and scarce resources. Some single-code and multicode assignment algorithms have been proposed tosupport as many users as poss
In this paper, a performance analysis for the frequency-domain code-division multiple-access (CDMA) of multiple simultaneously operating piconets (SOPs) in orthogonal frequency-division multiplexing (OFDM) based ultra...
详细信息
In this paper, a performance analysis for the frequency-domain code-division multiple-access (CDMA) of multiple simultaneously operating piconets (SOPs) in orthogonal frequency-division multiplexing (OFDM) based ultra-wideband (UWB) systems is presented. Two different strategies for the accommodation of multiples SOPs, namely, the variable spreading factor (VSF) scheme with minimal spreading and the multicode scheme with maximal spreading, were considered. The channel is assumed to be Rayleigh fading with exponentially decaying delay power profile. Furthermore, the analysis takes into account the intersymbol interference (ISI) caused by the multipath delay components exceeding the guard interval. Numerical results demonstrate that the frequency-domain CDMA can be employed to accommodate multiple SOPs while maintaining acceptable performance when a suitable subcarrier combining method is used. The VSF and multicode schemes result in a similar performance when the number of SOPs is large, while notable differences are pointed out when there are only a few SOPs.
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