Speech and Language (eBook)

Advances in Basic Research and Practice

eBook Download: PDF | EPUB

2014 | 1. Auflage
486 Seiten
Elsevier Science (Verlag)
978-1-4832-1993-6 (ISBN)

Speech and Language: Volume 5, Advances in Basic Research and Practice is a collection of papers dealing with clinical issues, theories, and pathology of language and speech. Several papers discuss developmental apraxia of speech, relapse of stuttering therapy, the single subject research design, and the implications of the physiologic, acoustic, and perceptual aspects of coarticulation. Other papers analyze language development, language training, the three aspects of voice quality element, and the issue of disputed communication origins. One paper notes that intervention programs for stuttering produces mostly short-term benefits. The paper discusses the known risks of relapse following the end of stuttering therapy and the independent variables that influence this risk. Another paper examines voice quality in terms of perceptual, acoustic, and physiologic features of the different voice modes. By using the 'Black Box' model, in which frequency, intensity, laryngeal waveform, pharyngeal prefiltering, and formant frequency can be controlled, the paper shows that a measure of interaction among all the controls exist. For example, a voice mode represented by a laryngeal waveform and pharyngeal prefiltering still interacts with frequency and intensity. Therefore, knowledge of the differences in physiology that attend to each voice mode can be valuable in effecting changes in voice production. The collection will prove valuable for linguists, speech therapists, neurologists, neuropsychologists, neurolinguists, speech pathologists, or investigators whose works involve linguistics, learning, communications, and syntax.

Speech and Language: Volume 5, Advances in Basic Research and Practice is a collection of papers dealing with clinical issues, theories, and pathology of language and speech. Several papers discuss developmental apraxia of speech, relapse of stuttering therapy, the single subject research design, and the implications of the physiologic, acoustic, and perceptual aspects of coarticulation. Other papers analyze language development, language training, the three aspects of voice quality element, and the issue of disputed communication origins. One paper notes that intervention programs for stuttering produces mostly short-term benefits. The paper discusses the known risks of relapse following the end of stuttering therapy and the independent variables that influence this risk. Another paper examines voice quality in terms of perceptual, acoustic, and physiologic features of the different voice modes. By using the "e;Black Box"e; model, in which frequency, intensity, laryngeal waveform, pharyngeal prefiltering, and formant frequency can be controlled, the paper shows that a measure of interaction among all the controls exist. For example, a voice mode represented by a laryngeal waveform and pharyngeal prefiltering still interacts with frequency and intensity. Therefore, knowledge of the differences in physiology that attend to each voice mode can be valuable in effecting changes in voice production. The collection will prove valuable for linguists, speech therapists, neurologists, neuropsychologists, neurolinguists, speech pathologists, or investigators whose works involve linguistics, learning, communications, and syntax.

Chapter 2

High data rates in mobile communication

Abstract

A principal target for the evolution of HSPA mobile communication is to provide the possibility for significantly higher end user data rates compared to what is achievable with, for example, the first releases of the 3G standards. This includes the possibility for higher peak data rates but, even more importantly, the possibility for significantly higher data rates over the entire cell area. The initial part of this chapter discusses some of the more fundamental constraints that exist in terms of what data rates can actually be achieved in different scenarios. This is followed by a general theoretical discussion of higher-order modulation, which is a means of achieving higher data rates within a specific bandwidth, and methods for utilizing increased amounts of bandwidth.

Keywords

Shannon

Bandwidth

Signal-to-Noise Ratio

Higher-order Modulation

Multi-carrier

Chapter outline

2.1 High data rates: fundamental constraints 23

2.1.1 High data rates in noise-limited scenarios 25

2.1.2 Higher data rates in interference-limited scenarios 27

2.2 Higher data rates within a limited bandwidth: higher-order modulation 28

2.2.1 Higher-order modulation in combination with channel coding 29

2.2.2 Variations in instantaneous transmit power 30

2.3 Wider bandwidth including multi-carrier transmission 31

2.3.1 Multi-carrier transmission 32

References 34

As discussed in Chapter 1, one main target for the evolution of HSPA mobile communication is to provide the possibility for significantly higher end user data rates compared to what is achievable with, for example, the first releases of the 3G standards. This includes the possibility for higher peak data rates but, as pointed out in the previous chapter, even more so the possibility for significantly higher data rates over the entire cell area, also including, for example, users at the cell-edge. The initial part of this chapter will briefly discuss some of the more fundamental constraints that exist in terms of what data rates can actually be achieved in different scenarios. This will provide a background to subsequent discussions in the latter part of the chapter, as well as in the following chapters, concerning different means to increase the achievable data rates in different mobile communication scenarios.

2.1. High data rates: Fundamental constraints

In [1], Shannon provided the basic theoretical tools needed to determine the maximum rate, also known as the channel capacity, by which information can be transferred over a given communication channel. Although relatively complicated in the general case, for the special case of communication over a channel, for example a radio link, only impaired by additive white Gaussian noise, the channel capacity C is given by the relatively simple expression [2]

=BW⋅log21+SN

(2.1)

where BW is the bandwidth available for the communication, S denotes the received signal power, and N denotes the power of the white noise impairing the received signal.

Already from (2.1) it should be clear that the two fundamental factors limiting the achievable data rate are the available received signal power, or more generally the available signal-power-to-noise-power ratio S/N, and the available bandwidth. To further clarify how and when these factors limit the achievable data rate, assume communication with a certain information rate R. The received signal power can then be expressed as

=Eb⋅R

(2.2)

where Eb is the received energy per information bit. Furthermore, the noise power can be expressed as

=N0⋅BW

(2.3)

where N0 is the constant noise power spectral density measured in W/Hz.

Clearly, the information rate can never exceed the channel capacity. Together with the above expressions for the received signal power and noise power, this leads to the inequality

≤C=BW⋅log21+SN=BW⋅log21+Eb⋅RN0⋅BW

(2.4)

or, by defining the radio link bandwidth utilization γ = R/BW,

≤log21+γ⋅EbN0

(2.5)

This inequality can be reformulated to provide a lower bound on the required received energy per information bit, normalized to the noise power density, for a given bandwidth utilization γ

bN0≥minEbN0=2γ−1γ

(2.6)

The rightmost expression, that is, the minimum required Eb/N0 at the receiver as a function of the bandwidth utilization, is illustrated in Figure 2.1. As can be seen, for bandwidth utilizations significantly less than one, that is, for information rates substantially smaller than the utilized bandwidth, the minimum required Eb/N0 is relatively constant, regardless of γ. For a given noise power density, any increase of the information data rate then implies a similar relative increase in the minimum required signal power S = Eb · R at the receiver. On the other hand, for bandwidth utilizations larger than one, the minimum required Eb/N0 increases rapidly with γ. Thus, in case of data rates in the same order as or larger than the communication bandwidth, any further increase of the information data rate, without a corresponding increase in the available bandwidth, implies a larger, eventually much larger, relative increase in the minimum required received signal power.

Figure 2.1 Minimum required Eb/N0 at the receiver as a function of bandwidth utilization.

2.1.1. High data rates in noise-limited scenarios

From the discussion above, some basic conclusions can be drawn regarding the provisioning of higher data rates in a mobile communication system when the thermal noise level is greater than the level of other sources of interference, and hence noise is the main source of radio link impairment (a noise-limited scenario):

• The data rates that can be provided in such scenarios are always limited by the available received signal power or, in the general case, the received signal-power-to-noise-power ratio. Furthermore, any increase of the achievable data rate within a given bandwidth will require at least the same relative increase of the received signal power. At the same time, if sufficient received signal power can be made available, basically any data rate can, at least in theory, be provided within a given limited bandwidth.

• In case of low bandwidth utilization, that is, as long as the radio link data rate is substantially lower than the available bandwidth, any further increase of the data rate requires approximately the same relative increase in the received signal power. This can be referred to as power-limited operation (in contrast to bandwidth-limited operation, see below) as, in this case, an increase in the available bandwidth does not substantially impact what received signal power is required for a certain data rate.

• On the other hand, in case of high bandwidth utilization, that is, in case of data rates in the same order as or exceeding the available bandwidth, any further increase in the data rate requires a much larger relative increase in the received signal power unless the bandwidth is increased in proportion to the increase in data rate. This can be referred to as bandwidth-limited operation as, in this case, an increase in the bandwidth will reduce the received signal power required for a certain data rate.

Thus, to make efficient use of the available received signal power or, in the general case, the available signal-to-noise ratio, the transmission bandwidth should at least be of the same order as the data rates to be provided.

Assuming a constant transmit power, the received signal power can always be increased by reducing the distance between the transmitter and the receiver, thereby reducing the attenuation of the signal as it propagates from the transmitter to the receiver. Thus, in a noise-limited scenario, it is at least in theory always possible to increase the achievable data rates, assuming that one is prepared to accept a reduction in the transmitter/receiver distance, that is, a reduced range. In a mobile communication system, this would correspond to a reduced cell size and thus the need for more cell sites to cover the same overall area. Providing data rates in the same order as or larger than the available bandwidth,...

Erscheint lt. Verlag	28.6.2014
Sprache	englisch
Themenwelt	Sachbuch/Ratgeber ► Gesundheit / Leben / Psychologie ► Krankheiten / Heilverfahren
	Geisteswissenschaften ► Sprach- / Literaturwissenschaft ► Sprachwissenschaft
	Medizin / Pharmazie ► Gesundheitsfachberufe ► Logopädie
	Medizin / Pharmazie ► Medizinische Fachgebiete ► Allgemeinmedizin
	Sozialwissenschaften ► Politik / Verwaltung
ISBN-10	1-4832-1993-3 / 1483219933
ISBN-13	978-1-4832-1993-6 / 9781483219936

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