Patent EA-000776-B1 (EA)
Title: Transmission of digital and analog signals in the same band
Inventor: BOSSARD BERNARD
IPC: H04W16/24
Filed: 1997-07-01
Abstract: 1. A method of transmitting a plurality of signals within a given broad frequency band from a transmitting location, for selective reception by a subscriber receiver located within a cell, comprising: transmitting a first plurality of signals at respectively different carrier frequencies, said first plurality of signals occupying mutually exclusive individual channel bands within a given broad band, and  transmitting at least one additional signal within a respective other individual channel band lying within said given broad band, the sum of the width s of the mutually exclusive individual channel bands and the other individual channel band being greater than the given broad band, the step of transmitting at least one additional signal comprising transmission with at least two diversity characteristics different from characteristics of the first plurality of signals, said diversity characteristics being selected from t he group including carrier frequency, modulation type, and polarization such that a receiver in a given location receiving the first plurality of signals and the at least one additional signal can selectively receive any one of the transmitted signals. 2. A method as claimed in claim 1, characterized in that the first plurality of signals are digital transmitted signals, and the at least one additional signal is an analog signal occupying substantially the entire given band, transmitted at a carrier frequency different from the carrier frequency of any of the first plurality of signals.  3. A method as claimed in claim 2, characterized in that the method includes transmitting additional signals in a respective plurality of contiguous given bands occupying a broad band, in at least a plurality of said contiguous given bands the analog signal being a respective FM signal occupying substantially all of the respective given band. 4. A method as claimed in claim 2, characterized in that the method includes transmitting additional signals in a respective plurality of contiguous given bands occupying a broad band, at least one of the first plurality of individual signals being a digital signal having an individual band which occupies portions of two adjoining given bands. 5. A method of transmitting a plurality of signals within a frequency band from a transmitting location, for selective reception by a subscriber receiver located within a cell, comprising: transmitting analog signals occupying substantially all of said frequency band, said analog signals including program signals representing at least one communicated program transmitted at a program carrier frequency within the band and occupying one program channel, characterized in that the method further comprises: transmitting digital signals representing at least one digital communication, at a first bit rate, using at least a first carrier frequency which is within said program channel, said digital signals being entirely within said band and occupying substantially less of said frequency band than the analog signals representing said one communicated program, and selecting said first carrier frequency, said first bit rate, and a given transmission power of the digital transmission such that a subscriber receiver can selectively receive and reliably detect either said one communicated program or said digital communication. 6. A method as claimed in claim 5, characterized in that said digital signals represent a plurality of digital communications including said one digital communication, using a plurality of digital carrier frequencies within said program channel each transmitted at said given transmission power. 7. A method as claimed in claim 6, characterized in that said digital signals include five T-l channels transmitted having a velocity of 1,5 Mbit/s. 8. A method as claimed in claim 5, characterized in that said analog signals and said digital signals are transmitted with a same polarization. 9. A method as claimed in claim 5, characterized in that said analog signals are transmitted over a given coverage angle in said cell, and said digital signals are transmitted in a first sector having a coverage angle less than said given coverage angle. 10. A method as claimed in claim 9, characterized in that said given coverage angle is 360 degree . 11. A method as claimed in claim 10, characterized by further comprising transmitting further digital signals at frequencies within said program channel in a second sector, with a polarization different from said same polarization. 12. A method as claimed in claim 5, characterized in that said analog signals and said digital signals are transmitted with mutually different polarizations. 13. A method as claimed in claim 12, characterized in that said analog signals and said digital signals are transmitted over a first sector in which the analog signals have a first polarization, further comprising: transmitting said analog signals over a second sector adjoining said first sector with a polarization different from said first polarization,  and transmitting further digital signals in said second sector with said first polarization. 14. A method as claimed in claim 13, characterized in that said further digital signals include at least a second digital communication not transmitted in said first sector. 15. A method as claimed in claim 13, characterized in that the method further comprises: transmitting said analog signals over third and fourth sectors, arranged such that the polarization of the analog signals is different in adjoining sectors, and each of the sectors is approximately a 90 degree  sector, and  transmitting third and fourth digital signals in the third and fourth sectors respectively.  16. A method as claimed in claim 15, characterized in that the method further includes transmitting additional signals from transmitting location in adjoining cells, characterized in that the cells are arranged such that sectors in adjoining cell s facing each other transmit signals of like modulation and like polarization toward each other. 17. A method as claimed in claim 5, characterized in that said digital signals are a first plurality of digital signals, said analog signal and said first plurality of digital signal are transmitted over a first sector having a sector angle not substantially greater than 180 degree , and said analog signal and a second plurality of digital signals are transmitted over a second sector adjoining but not substantially overlapping said first sector, at least said second plurality of digital signals being transmitted with a polarization different from the polarization with which the first plurality is transmitted. 18. A method of transmitting a digital signal to a receiver, comprising: transmitting an analog signal using a given carrier frequency, said analog signal occupying substantially all of a frequency band, transmitting the digital signal using a first carrier frequency which is within said frequency band, at a given bit rate, said carrier frequency and bit rate being s elected such that the digital signal occupies a portion of said frequency band entirely to one side of the given carrier frequency, and a region occupying at least approximately 10% of said frequency band centered about said given carrier frequency is substantially free from the digital signal, and selecting the power level of transmission of the digital signal such that the signal power level of the digital signal received by the receiver, over said portion of the frequency band, is no more than 6 dB greater than the signal power level of the analog signal over said portion. 19. A method as claimed in claim 18, characterized in that a plurality of said digital signals are transmitted over corresponding separate portions of said frequency band, and the total signal power level of the respective digital signals received by the receiver is less than the total received analog signal power level. 20. A method as claimed in claim 19, characterized in that the respective received signal power level of each of said digital signals is at least 12 dB less than the received analog signal power level in the corresponding separate portion of the frequency band. 21. A method as claimed in claim 19, characterized in that the digital signals and the analog signal are transmitted from a same transmitter location with a same polarization. 22. A method as claimed in claim 21, characterized in that the analog signal is transmitted omnidirectionally with a given polarization, said digital signal is transmitted over a first sector having a beam angle less than 180 degree , and a plurality o f further digital signals are transmitted over a second sector with a polarization different from said given polarization, said plurality of further digital signals being transmitted at carrier frequencies within said band, and said first and second sectors having no substantial angular overlap. 23. A method as claimed in claim 22, characterized in that said second sector is wider than said first sector. 24. A method as claimed in claim 22, characterized in that at least another plurality of digital signals are transmitted in a third sector having no substantial overlap with said first or second sectors, and adjoining sectors have mutually different polarizations. 25. A method as claimed in claim 19, characterized in that the analog signal is an FM signal having a substantially constant power level, and the digital signal is a quadrature phase shift keyed signal. 26. A method as claimed in claim 25, characterized in that the analog signal occupies a band of more than 3.3 MHz, and the digital signal occupies an approximately 1.5 MHz wide portion of the band. 27. A method as claimed in claim 26, characterized in that the analog sign al is a television signal which occupies a band greater than 16 MHz wide. 28. A transmitter arrangement comprising: means for transmitting an analog signal using a given carrier frequency, from a given locat