reference will now be made in detail to the presently preferred embodiments of the invention , examples of which are illustrated in the accompanying drawings . wherever possible , the same reference numbers will be used throughout the drawings to refer to the same or like parts . referring to fig1 a co - located multicarrier transmitter system in a linear amplifier configuration 10 comprises a first and second data source , 11a and 11b , a first and second modulator , 12a and 12b , a summation circuit 13 , a linear rf amplifier 14 , and an antenna 15 . the first and second data sources , 11a and 11b , generate a respective first and second digital bit stream which are provided to respective first and second modulators , 12a and 12b . each modulator converts the incoming digital information into a representative modulated signal or carrier . the outputs of each modulator are then combined into a single output signal by summation circuit 13 , the output of which is fed into linear rf amplifier 14 . the combined output signal is then applied to antenna 15 for transmission in a bandlimited channel . alternatively , referring to fig2 a co - located multicarrier transmitter in a composite amplifier configuration 20 comprises a first and second data source , 21a and 21b , a first and second modulator , 22a and 22b , a first and second rf amplifier , 23a and 23b , a summation circuit 24 , and an antenna 25 . the first and second digital bit streams generated respectively by the first and second data sources , 21a and 21b , are provided to first and second modulators , 22a and 22b , respectively . each modulator converts the incoming digital information into a representative modulated signal or carrier . the outputs of the first and second modulators are fed into first and second rf amplifiers , 23a and 23b , respectively . the outputs of the rf amplifiers are combined into a single output signal by summation circuit 24 , the output of which is applied to antenna 25 for transmission in a bandlimited channel . alternative embodiments of co - located transmitter systems are also possible . for example , the co - located transmitter configurations discussed above can be expanded to support more than two data sources and transmit more than two carriers in the bandlimited channel . because transmitter co - location does not give rise to the near - far problem to which the fcc mask requirements are directed , carrier spacings far closer than would ordinarily be allowed ( e . g ., 5 to 10 khz ) are achievable . moreover , the carriers need not be symmetrically or evenly spaced within the mask defining the channel . that is , the frequency spacings between adjacent carriers , while symmetric to each other , can be smaller than the frequency spacings between the band edges of the mask and the nearest respective carrier . indeed , carrier spacings may be irregular such that the carriers are asymmetrically located within the mask without incurring undue interference . referring to fig3 a , two submasks defining two subchannels , 30a and 30b , are asymmetrically located within a single mask - defined , bandlimited channel 31 , resulting in some subchannel overlap . fig3 b depicts two carriers , 32a and 32b , operating respectively over two asymmetrically - located subchannels , resulting in some carrier overlap . in accordance with this asymmetry , the frequency difference between the center frequency of each carrier and the nearest band edge of the mask is greater than half the frequency difference between the center frequencies of the two carriers . the practical implication of transmitter co - location is that a greater range of operating parameters , including the peak frequency , deviation bit rate , and carrier frequencies , are available so that multicarrier modulation in a standard bandlimited channel can be obtained without the need for stringent subchannel interference protection . in accordance with the present invention , these and other parameters can be adjusted so that the carriers generated and transmitted according to the present invention will remain within the fcc emission limits while providing optimal transmission performance . fig4 shows a fcc emissions mask which requires the power spectral density to be attenuated at least 70 db within 10 khz from center frequency . co - location of the transmitters allows for signals with a greater range of deviation and baud rates to be carried in the bandlimited channel than has been otherwise thought possible in view of fcc 70 db cutoff requirements . the present invention will be further clarified by the following examples , which are intended to be purely exemplary of the invention . fig5 a is a spectra graph of a two - carrier system in which the following parameter values were selected : a peak frequency deviation of 2400 hz , a bit rate of 6000 bps , premodulation filter cutoff frequency of 3000 hz , and carrier frequencies set to within 4590 hz of the center frequency . using this operative parameter combination , the carriers remained within the fcc mask while providing an acceptable error - rate versus signal strength performance ( fig5 b ). alternatively , fig6 a is a spectra graph of a two - carrier system using a peak frequency deviation of 1800 hz , a bit rate of 6400 bps , a premodulation filter cutoff frequency of 3200 , and carrier frequencies set to within 5150 hz of the center frequency . as depicted in fig6 b , this combination of operative parameters exhibited a higher bit error rate than the system of fig5 a . fig7 a is a spectra graph of a two - carrier system using a peak frequency deviation of 2100 hz , a bit rate of 6400 bps , a premodulation filter cutoff frequency of 3200 , and carrier frequencies set to within 4750 hz of the center frequency . as depicted in fig7 b , this combination gives significantly better performance than the system of fig6 a but performs slightly worse than the system of fig5 a . thus , according to the present invention , increased transmission capacity is achieved by operating more than one carrier in a standard bandlimited channel assigned for mobile paging use , such as in the narrowband personal communications service or the part 22 service . in the modulation technique of the present invention , carriers operating at different frequencies are fit within a single bandwidth allocation in a manner consistent with fcc mask requirements . this is achieved through the use of co - located transmitters and the selection of an optimal combination of operating parameters , including peak frequency deviation , bit rate , and carrier separation frequencies . through the multicarrier modulation technique of the present invention , the normal transmission capacity of a standard channel can be increased without the need for stringent subchannel protection levels and complicated receiver and transmitter schemes . the modulation technique of the present invention has particular application in metropolitan areas where the volume and concentration of transmission traffic is high and where the need for increased transmission capacity is acute . in addition , the modulation technique of the present invention may also be suited for use in areas where the incidence of unacceptable interference is high , such as international border regions . in that type of environment , transmissions from the respective bordering countries can be assigned to one of the carriers operating within the channel to reduce the risk of interference . it will be apparent to those skilled in the art that various modification and variations can be made to present invention without departing from the spirit or scope of the invention . other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein . thus , it is intended that the specification and examples be considered as exemplary only , with a true scope and spirit of the invention being indicated by the following claims .