Pulse or digital communications – Systems using alternating or pulsating current – Amplitude modulation
Reexamination Certificate
2000-02-22
2003-04-22
Pham, Chi (Department: 2631)
Pulse or digital communications
Systems using alternating or pulsating current
Amplitude modulation
C332S145000, C332S151000
Reexamination Certificate
active
06553079
ABSTRACT:
The present invention relates to a modulator and a modulation method for use, in particular but not exclusively, in cellular telecommunication networks.
In the various known cellular telecommunication networks, modulation is required in order to transmit data in the frequency band which has been allocated to the base station or mobile station in the particular cellular network. The frequencies which are typically used in cellular telecommunication networks for communication between base stations and mobile stations are relatively high frequencies which are much greater than those frequencies with which current digital technology can deal. Accordingly, digital circuitry of a cellular telecommunication network will use a base band frequency, which is much lower than the frequency used to transmit data between, for example base stations and mobile stations. After processing by the base station or mobile station, the data will be modulated onto the carrier frequency to be used.
A large number of different modulation methods are known but these modulation methods can be generally divided up into three categories. The first category uses amplitude modulation, the second category uses phase modulation whilst the third uses frequency modulation. Modulation methods which use a combination of these three known categories are known. For example quadrature amplitude modulation is a combination of amplitude and phase modulation. In the GSM standard for wireless communication, Gaussian Minimum Shift Keying (GMSK) is used which is a form of frequency modulation. However, the modulators which are currently used are generally only able to support a single modulation method. In other words, each modulator is specifically designed for a single modulation method. Thus, for every different type of modulation method used in cellular telecommunication networks, a separate modulator needs to be provided. This is disadvantageous in that a number of different modulators may need to be stocked by a manufacturer of mobile and base stations. Another problem is that it is also difficult to modify existing base and mobile stations to introduce new modulation methods. This may increase the time required in order to introduce new standards or alternatively may deter network operators from changing the modulation method used even if the new modulation method is more efficient. Additionally, during the design of new cellular network standards, it is often uncertain as to what modulation method will ultimately be used. This can increase the length of time required in order to get equipment such as base transceiver stations and mobile stations incorporating the required modulator onto the market.
According to one aspect of the present invention, there is provided a modulator for modulating input data, said modulator comprising an input for receiving data to be modulated; a plurality of memory regions arranged to contain information relating to a modulation method to be carried out by said modulator, at least one of said memory regions providing time independent modulation values and at least one of said memory regions providing time dependent modulation values, the values provided by said memory regions being dependent on the data received via said input; and processing means for providing a modulating signal based on the values provided by said memory regions.
It should be appreciated, that the above defined modulator incorporates a new manner of achieving modulation, that is having a plurality of memory regions, at least one of which provides time independent values and at least one of which provides a time dependent modulation value. This may be advantageous in achieving modulation relatively simply for otherwise quite complex modulation methods.
According to a second aspect of the present invention, there is provided a modulator for modulating input data, said modulator comprising an input for receiving data to be modulated; a plurality of memory regions arranged to contain information relating to a modulation method to be carried out by said modulator, at least one of said memory regions providing amplitude modulation values and at least one of the memory regions providing phase modulation values, the values provided by said memory regions being dependent on the data received via said input; and processing means for providing a modulation signal based on the values provided by said memory region.
In this modulator, the memory regions provide phase modulation and amplitude modulation values. Again this allows quite complex modulation methods to be implemented quite simply.
Preferably, the memory regions comprise a memory region arranged to provide time independent phase modulation values and a memory region arranged to provide time dependent phase modulation values. It should be appreciated that with this modulator, it is possible to support virtually all modulation methods which employ phase and frequency.
Preferably, the memory regions comprise a memory region arranged to provide time dependent amplitude modulation values and a memory region arranged to provide time independent amplitude modulation values. Again, these two memory regions allow any type of amplitude modulation to be supported.
In the second aspect of the invention, preferably said at least one of said memory regions providing amplitude modulation values provide at least one of the following values: time independent amplitude modulation values and time dependent amplitude modulation values. Preferably, said at least one of said memory regions providing phase modulation values provide at least one of the following values: time independent phase modulation values and time dependent phase modulation values. A separate memory region is preferably provided for each of the different types of modulation values provided.
The modulator may be arranged to be capable of supporting a plurality of different modulation methods, said memory regions being arranged to contain information relating to the selected modulation method. In this way, the modulator can support a number of different modulation methods and the same modulator can be used in different situations.
The memory regions may be arranged to store values relating to a selected modulation method whereby each memory region provides a look-up table. Alternatively, the memory regions may be arranged to store respective programs from which the values are generated. In this latter situation, a processor may be provided in order to generate the required values from the stored programs or algorithms.
Data control means may be provided, said data control means being arranged to control to which of the memory regions at input data is applied. It should be appreciated that all input data can be applied to all of the memory regions. Alternatively, only some of the input data may be applied to a given memory region. This will depend on the modulation method selected.
Preferably, register means are provided for the memory regions, said register means being arranged to store a predetermined amount of input data. Separate register means may be provided for each of the memory regions. Alternatively at least some of the memory regions may share common register means. Preferably, each value provided by said memory regions is dependent on at least some of the predetermined amount of said input data. By storing the input data in register means, it is possible to take into account the past history of a signal. This is required with some forms of modulation, for example GMSK. The input data may take the form of a series of bits and the register means may be arranged to store a predetermined number of those bits. Those predetermined number of bits of data can be applied, at the same time, to a given memory region in order to obtain the desired output value from the memory region in question.
Means may be provided for combining the outputs from the plurality of the memory regions. These combining means comprise adding means and/or multiplying means, as required by the particular modulation method employed.
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Nguyen Dung X.
Nokia Corporation
Pham Chi
Squire Sanders & Dempsey LLP
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