Multiplex communications – Communication techniques for information carried in plural... – Adaptive
Patent
1997-12-22
2000-09-19
Patel, Ajit
Multiplex communications
Communication techniques for information carried in plural...
Adaptive
370329, 455452, H04J 316, H04J 322
Patent
active
061222917
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND TO THE INVENTION
This invention relates, in general, to communication systems and is particularly applicable to an allocation of bandwidth for reception or transmission of information over a communication resource of such a communication system.
SUMMARY OF THE PRIOR ART
Competition and a limited availability of spectrum creates pressure on manufacturers, service providers and operators to maximise the spectrum efficiency of communications systems, generally, and particularly in relation to wireless telecommunication systems. In this respect, variable rate voice-coders (vocoders), such as implemented in the IS-95 Code Division Multiple Access (CDMA) system, provide a method of increasing spectrum efficiency. Furthermore, with specific regard to wireless systems, it is also desirable for these systems to adapt to changing system loads without the need to depart from simple frequency planning schemes. Indeed, it would be beneficial to adapt cellular frequency reuse plans, rather than to be burdened with the inflexibility of a fixed system design that has been carefully balanced by the manufacturer to take account of worst case interference problems (which may not always occur at any given point in time) for each deployment scenario.
With the move towards providing more services, such as data and multimedia, to users of wireless telecommunications networks, the use of variable information transfer rates (i.e. variable instantaneous bit rates) is becoming prevalent.
For example, in Time Division Multiplexed (TDM) systems, such as the Digital European Cordless Telephone (DECT) standard and the Global System for Mobile (GSM) cellular communication, different bit rates may be accommodated in the time-domain by using integer multiple (contiguous) slots to support the selected bit rate. Indeed, in DECT (which is a Time Division Duplex (TDD) system) it has been proposed that slots normally allocated to a reverse channel can be re-allocated to the forward channel, thereby providing an asymmetric data service. As such, transmission of more information on a fixed frequency channel in a constant power envelope system requires a greater transmission period.
Other TDM systems accommodate differing data rates by changing to different levels of modulation (such as Binary Phase-Shift Keying (BPSK), Quadrature, Phase-Shift Keying (QPSK) and forms of Quadrature Amplitude Modulation (QAM), e.g. 16-QAM and 64-QAM), whereby varying numbers of bits of information are encoded in each symbol transmitted.
Alternatively, CDMA systems support different data rates by adjusting the transmission power and, in some instances, by entering a discontinuous transmission mode. As will be understood, CDMA systems operate with a constant power spectral density in which there is an approximately constant energy per bit, so the transmission of fewer bits, in general, has the effect of reducing overall power transmission.
Consequently, by using existing techniques only, each operator or service provider wishing to offer high data rate services will require the allocation of a large amount of spectrum in each coverage area (cell) served. Therefore, a technique which would enable operators or service providers to use less spectrum without diminishing their ability to offer high data rate services would be most advantageous.
SUMMARY OF THE INVENTION
According to a first aspect of the present invention there is provided a communication system having a communication resource for supporting communications on a plurality of channels having channel bandwidths, the plurality of channels capable of supporting a plurality of differing services, the system comprising: means for determining a demand on the communication resource; and means for dynamically modifying a bandwidth of at least one channel of the plurality of channels in response to the demand, said means for dynamically modifying being arranged to modify the bandwidth to bias the communication resource with respect to a relative hierarchy that exists between on-going communications.
REFERENCES:
patent: 5231649 (1993-07-01), Duncanson
patent: 5463620 (1995-10-01), Sriram
patent: 5638363 (1997-06-01), Gittins et al.
patent: 5818830 (1998-10-01), Daane et al.
Benn Howard Peter
Chambers David
Crichton Paul
Robinson William Neil
Donato, Jr. Mario J.
Motorola Inc.
Patel Ajit
Phunkulh Bob A.
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