Multiplex communications – Diagnostic testing – Determination of communication parameters
Reexamination Certificate
1998-03-18
2001-04-17
Ton, Dang (Department: 2661)
Multiplex communications
Diagnostic testing
Determination of communication parameters
C370S468000
Reexamination Certificate
active
06219341
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention generally relates to wireless communication and, in particular, to a method for multiplexing a plurality of user signals over a communication channel having a fixed frequency range in an efficient manner with -respect to channel bandwidth utilization.
It is known in the art to utilize radio frequency communication channels to transfer digital data between devices. Digital data is encoded on the channel such that a parameter of the communication channel is modulated in accordance with the values of the digital data bit sequence to be transferred. Many applications of such communication channels permit multiple, simultaneous access to the channel by a plurality of digital data streams, for example, a plurality of digitized voice data streams or a plurality of computer digital data streams. The plurality of digital data streams is multiplexed over the communication channel by subdividing the channel into a plurality of subchannels each characterized by unique communication parameters which may be de-multiplexed at the opposite end of the communication channel.
A variety of communication parameters is known to be useful for such subdivision of the communication channel. For example, time division multiple access, also referred to herein as TDMA, multiplexes the subchannels onto the channel by assigning each subchannel a period of time during which the subchannel uses the channel exclusively. Frequency division multiple access techniques, also referred to herein as FDMA, assign each subchannel a sub-range of the fixed frequency range. Code division multiple access techniques, also referred to herein as CDMA, assign a signature to each subchannel which describes the pulse amplitude modulation, also referred to herein as PAM, to be used by the subchannel for communication. Well-known digital signal processing techniques may be applied to de-multiplex such multiplexed signals on the communication channel.
A variety of techniques have been applied to many of these known modulation methods to further improve the utilization of the channel bandwidth. It is a continuing problem to improve the bandwidth utilization of a channel so as to maximize the data throughput over the channel. In particular, it is a continuing problem to dynamically adjust the multiplexing techniques to adapt to particular signaling patterns, usage, and power. As mobile transmitters and receivers are moved relative to one another, channel bandwidth utilization efficiency may change. It is a problem to adapt presently known multiplexing techniques to such dynamic environmental factors.
SUMMARY OF THE INVENTION
The present invention solves the above and other problems thereby advancing the state of the useful arts by providing methods for multiplexing a plurality of digital data streams over a communication channel in a manner which is efficient in bandwidth utilization and dynamically adaptable to changes in the communication power and other parameters. The present invention thereby provides bandwidth efficient multiple access also referred to herein as BEMA.
As compared to prior multiplexing techniques, the receiver operable in accordance with the present invention uses successive cancellation decoding techniques. Signature waveforms are specifically designed for each receiver (subchannel) presently using the multiplexed communication channel. The dynamically designed signature waveforms are dynamically allocated to the transmitters operable in accordance with the methods of the present invention. Unlike the teaching of prior multiplexing techniques, the signature waveform used between a particular transmitter and receiver operable in accordance with the present invention is not statically assigned or otherwise pre-determined or pre-designed to be orthogonal or quasi-orthogonal. Rather, the signature waveforms are designed so as to meet receiver performance specifications for each user (subchannel). The dynamically designed waveforms may be dynamically re-allocated and re-designed in response to changes in the traffic conditions, received power levels, number of transmitters and other parameters.
In particular, the methods of the present invention provide for design of a signature waveform which modulates signal characteristics in a manner dynamically determined to be efficient in view of presently measured channel characteristics.
To this end, in an embodiment of the present invention, a method for improving channel bandwidth utilization in a communication system is provided. The method comprises the steps of: providing an available communication channel; evaluating available channel bandwidth for a plurality of signals applied to the available communication channel; determining signal power characteristics of the plurality of signals; defining signature waveforms; and multiplexing the plurality of signals onto the communication channel based on the signature waveforms.
In an embodiment,. the plurality of signals are digital data sequences.
In an embodiment, the available channel has a fixed frequency range.
In an embodiment, signaling power parameters are assigned to each receiving device.
In an embodiment, signature waveforms are designed for each receiving device.
In an embodiment, the signature waveforms to transmitters are dynamically allocated.
In an embodiment, the signature waveforms are designed to meet receiver performance specifications for each user.
In an embodiment, the signature waveforms are re-designed based on changes in traffic conditions in the communication channel.
In an embodiment, the signature waveforms are re-designed based on received power levels.
In an embodiment, the signature waveforms are re-designed based on the number of transmitters.
In an embodiment, extra received power is used to assign signals with smaller bandwidths.
In an embodiment, the number of users is increased by using extra received power to assign signals with smaller bandwidths.
It is, therefore, an advantage of the present invention to provide a method for improving channel bandwidth utilization in a communication system.
Another advantage of the present invention is to provide a method for designing signature waveforms for each receiving device in a communication system.
Additional features and advantages of the present invention are described in, and will be apparent from, the detailed description of the presently preferred embodiments and from the drawings.
REFERENCES:
patent: 5729607 (1998-03-01), DeFries et al.
patent: 5812947 (1998-09-01), Dent
Bell Boyd & Lloyd LLC
Ton Dang
University Technology Corporation
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