WO1997039535A2 - Systeme de gestion des largeurs de bande pour un reseau a repeteurs tele-alimentes - Google Patents

Systeme de gestion des largeurs de bande pour un reseau a repeteurs tele-alimentes Download PDF

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Publication number
WO1997039535A2
WO1997039535A2 PCT/US1997/005985 US9705985W WO9739535A2 WO 1997039535 A2 WO1997039535 A2 WO 1997039535A2 US 9705985 W US9705985 W US 9705985W WO 9739535 A2 WO9739535 A2 WO 9739535A2
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WIPO (PCT)
Prior art keywords
signal
sideband
site
translating
frequency
Prior art date
Application number
PCT/US1997/005985
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English (en)
Other versions
WO1997039535A9 (fr
WO1997039535A3 (fr
Inventor
Dana J. Jensen
Steven J. Pfiefer
James K. Lyon
Mark D. Dvorak
Original Assignee
E.F. Johnson Company
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from US08/628,981 external-priority patent/US5991309A/en
Priority claimed from US08/631,866 external-priority patent/US5896560A/en
Application filed by E.F. Johnson Company filed Critical E.F. Johnson Company
Priority to AU27263/97A priority Critical patent/AU2726397A/en
Publication of WO1997039535A2 publication Critical patent/WO1997039535A2/fr
Publication of WO1997039535A3 publication Critical patent/WO1997039535A3/fr
Publication of WO1997039535A9 publication Critical patent/WO1997039535A9/fr

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04H—BROADCAST COMMUNICATION
    • H04H20/00—Arrangements for broadcast or for distribution combined with broadcast
    • H04H20/65—Arrangements characterised by transmission systems for broadcast
    • H04H20/67—Common-wave systems, i.e. using separate transmitters operating on substantially the same frequency
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
    • H04B1/60—Supervising unattended repeaters
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
    • H04B1/68—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission for wholly or partially suppressing the carrier or one side band
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L12/00—Data switching networks
    • H04L12/02—Details
    • H04L12/12—Arrangements for remote connection or disconnection of substations or of equipment thereof
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W84/00—Network topologies
    • H04W84/02—Hierarchically pre-organised networks, e.g. paging networks, cellular networks, WLAN [Wireless Local Area Network] or WLL [Wireless Local Loop]
    • H04W84/04—Large scale networks; Deep hierarchical networks
    • H04W84/08—Trunked mobile radio systems

Definitions

  • the present invention relates generally to a bandwidth management system, and more particularly, to a system for managing signals transceived between repeaters and their respective mobile units so that the signals may be communicated between remote repeaters to enhance the coverage area of a repeater network.
  • Remote repeater networks are used in a variety of applications, including police, fire, and emergency mobile radio communications environments.
  • a number of mobile transceivers are in communication with a repeater which is in proximity to the mobiles.
  • the area of coverage ofthe repeater system is increased by linking the repeaters.
  • One way to link the repeaters uses a microwave link.
  • subaudible signalling is employed in mobile trunked radio communication systems.
  • the subaudible signalling increases the audio bandwidth ofthe signals which must be communicated between the mobile transceivers and their respective repeaters.
  • the subaudible signalling increases the audio bandwidth ofthe signals transmitted between repeaters.
  • the bandwidth of each microwave multiplexed channel must be increased to handle the subaudible signalling.
  • Existing microwave multiplexing systems are not adapted to transceive subaudible signals.
  • bandwidth management system should introduce little distortion while performing frequency translations. Furthermore, the bandwidth management system should function with existing multiplexer systems to eliminate the need to modify or replace inter-repeater links.
  • the present system provides a bandwidth management system capable of performing frequency translations on signals of a first spectral content to convert them to signals of a second spectral content, transfer the converted signals, and then deconvert the signals to their original spectral content.
  • the bandwidth management system will be described using an example of a repeater-based system having subaudible signalling which is not within the passband of a microwave multiplexer. Therefore, the embodiments herein describe a system for positioning the subaudible signalling within the passband ofthe microwave multiplexer. However, these examples are for purposes of demonstrating the present bandwidth management system, and are not intended in a limiting or exclusive sense.
  • the present bandwidth management system is also applicable for any signal bandwidth management application, and the use ofthe present system in a repeater network is intended to demonstrate the present system and is not intended in a limiting or exclusive sense.
  • the present bandwidth management system is also applicable for performing a variety of spectral translations using the methods and apparatus disclosed and the spectral translations demonstrated herein are not intended to be exclusive or limiting.
  • the signal is divided into a low frequency component and a high frequency component.
  • the high frequency component is not modified, however, the low frequency component is translated upband of the high frequency component to position it within the passband ofthe microwave multiplexer.
  • the upband translation ofthe low frequency component produces an upper and lower sideband signal at the carrier frequency.
  • the lower sideband is removed with a low pass filter.
  • the lower sideband is removed with a bandpass filter.
  • a single sideband representation of the low frequency component is moved upband without using a low pass or bandpass filter.
  • a single sideband generation method using Weaver's method is inco ⁇ orated to generate a translated single sideband representation of the low frequency component which is upband ofthe high frequency component.
  • Deconversion of the translated signals may be performed by the inverse operation of any ofthe upconversion methods. Also included is an embodiment whereby spectral distortions are reduced in the step of deconverting the spectral signals. In this embodiment, a signal from a common reference, such as a global positioning satellite, is incorporated in the deconversion step to prevent distortion to the deconverted signals.
  • Figure 1 is a block diagram of one environment in which the present bandwidth management system may be practiced;
  • Figure 2A shows a frequency spectrum of a first composite signal;
  • Figure 2B shows a frequency spectrum of a translated version of the first composite signal in Figure 2A;
  • Figure 3 is a block diagram of one embodiment of a frequency translation system
  • Figure 4 is a block diagram of one embodiment of a frequency translation system
  • Figure 5 is a block diagram of one embodiment of a frequency translation system
  • Figure 6A shows a frequency spectrum of a first composite signal
  • Figure 6B shows a frequency spectrum of an output from a mixer having an input signal as shown in Figure 6A;
  • Figure 6C shows the frequency spectrum after filtering
  • Figure 6D shows the frequency spectrum after mixing a second time
  • Figure 7A shows a frequency spectrum of a first composite signal
  • Figure 7B shows a converted frequency spectrum of the first signal
  • Figure 8A shows the lower frequency portion of the first signal
  • Figure 8B shows a mixed version of the lower frequency portion
  • Figure 8C shows a filtered version ofthe mixed version of Figure
  • Figure 9A shows a block diagram of one embodiment of an upconversion system
  • Figure 9B shows a block diagram of one embodiment of a downconversion system
  • Figure 10 shows a block diagram of one embodiment of a mixer system for upconversion
  • Figure 1 1 shows a block diagram of one embodiment of a mixer system for downconversion
  • Figure 12 shows a block diagram of one embodiment of a mixer system for upconversion
  • Figure 13 shows a block diagram of one embodiment of a mixer system for down conversion
  • Figure 14 shows signal timing according to one embodiment of the reconstruction system.
  • the bandwidth management system is described using an example of a repeater-based system having subaudible signalling which is not within the passband of a microwave multiplexer. Therefore, the embodiments herein describe a system for positioning the subaudible signalling within the passband ofthe microwave multiplexer. However, these examples are for pu ⁇ oses of demonstrating the present bandwidth management system, and are not intended in a limiting or exclusive sense.
  • the present bandwidth management system is also applicable for any signal bandwidth management application, and the use of the present system in a repeater network is intended to demonstrate the present system and is not intended in a limiting or exclusive sense.
  • the present bandwidth management system is also applicable for performing different spectral translations, such as multi band, low pass, and high pass signal translation.
  • Figure 1 shows one environment in which the present invention may be practiced.
  • two remote repeater sites 1 10 and 120 are in communication with central site 100 over the microwave equipment including transceivers 104 , 1 14, and 124 and multiplexers 102, 112, and 122.
  • Other links may be used without departing from the scope of the present invention.
  • the system in Figure 1 shows two channels, A and B, to demonstrate the present system. Other numbers of channels are possible without departing from the scope ofthe present invention.
  • Mobile transceivers (not shown in Figure 1 ) communicate with the repeater site which provides the best signal. Inter-site communications are possible using a system of subaudible signalling, such as the system described in U.S. Patent No.
  • control data In such a trunked radio system the spectral content of the control data typically extends from nearly DC to 300Hz.
  • the control data is transmitted with voice information, data information, or both.
  • the control information transmitted by central site 100 provides commands and information to the radio units serviced by repeater sites 1 10 and 120.
  • control information having a bandwidth of approximately DC to 300 Hz is generated at central site 100 and must be communicated, along with a 300Hz to 3000Hz audio signal, to the repeater sites 1 10 and 120.
  • Other spectral subdivisions may be managed by the present bandwidth management system without departing from the spirit and scope of the present invention, and the present system is not limited to the stated frequency subdivisions.
  • the present bandwidth management system allows the use of existing link equipment, whose passband extends from 300Hz to 3400Hz.
  • the use of existing equipment allows flexibility in the design of systems since many companies can supply such equipment.
  • Using existing, rather than specially designed, and therefore more costly, equipment also reduces overall system cost.
  • the information we wish to pass consists of a high frequency component which extends from 300Hz to 3000Hz, and a low frequency component which extends from nearly DC to approximately 300Hz.
  • the low frequency component is a data signal
  • the high frequency component is an audio signal.
  • Figure 2A shows the original composite signal and the passband of the existing multiplexing equipment. It is apparent that the data signal will not be passed by the existing multiplexing equipment. If the entire composite signal is shifted upband by 300 Hz, then the entire composite signal falls within the passband of the existing multiplexing equipment.
  • the whole signal spectrum (composite signal) is translated upband by 300Hz.
  • the data signal extends from 300Hz to 600Hz and the audio signal extends from 600Hz to the top ofthe multiplexer passband. If the multiplexer passband is less than 3300 Hz, then the upper portion ofthe audio signal will be attenuated. This compromise may be acceptable for the benefit of transferring the data signal. Shifting the entire spectrum up by 300Hz provides the same amount of isolation between the data and audio signals as exhibited by the composite signal.
  • fy is equal to the amount of frequency shift desired for the input signal x(t)/2.
  • fy is equal to a 300 Hz tone is used to translate the x(t)/2 input signal, which is the composite signal, upband by 300 Hz.
  • Other tone frequencies may be used to translate the composite signal to different frequencies. Therefore, if the composite signal, shown in Figure 2A, is the input signal, x(t)/2, then the output signal using a 300 Hz tone is shown in Figure 2B.
  • Figure 4 Another system for translating the composite signal is demonstrated by Figure 4, which uses Weaver's method to translate the composite signal in frequency.
  • the x(t) signal is the composite signal.
  • the frequencies of fl is set to 3000 Hz, f2 is 3300 Hz, so that fl-f2 is equal to the desired frequency shift.
  • the low pass filter bandwidth is equal to f 1 (3000 Hz in this example).
  • Other frequencies may be used as long as the difference between fl and f2 is equal to the desired frequency shift.
  • FIG. 5 Yet another system of translating the composite signal is a double mixing system as shown in Figure 5.
  • the composite signal of Figure 2 A also shown in Figure 6A, is translated upband by 3000 Hz by setting fl to 3000 Hz and mixing it with the input signal.
  • the resulting signal is shown in Figure 6B.
  • Filter 1 is a high pass or band pass filter which is used to produce the signal of Figure 6C.
  • This signal is then translated to 300 Hz by mixing it with a 2700 Hz signal as £2.
  • the resulting signal is filtered with a low pass filter or band pass filter to remove the 5.7 KHz signal component.
  • the final signal is shown in Figure 2B.
  • bandwidth management provides that the central site 100 contains a system which translates the data signal such that it resides above 3000Hz but below 3400Hz, so that it is within the passband ofthe multiplexer 1 12 (or 122). This is illustrated in Figures 7A and 7B. At the remote site the data signal is shifted back to its original spectral position
  • FIGS 8A, 8B, and 8C One method for upband translation ofthe data signal is shown in Figures 8A, 8B, and 8C.
  • a single frequency will represent the data signal translated.
  • the data spectrum is a Fourier series of single frequency signals, whose summation reproduces the time domain form ofthe data signal.
  • cos(2 ⁇ f x t) to be representative ofthe data signal.
  • Multiplying the data signal by another tone, such as cos(2 ⁇ 3000t) gives 0.5cos(2 ⁇ [3000 - fjt) + 0.5cos(2 ⁇ [3000 + fjt).
  • the data signal now has the form of a double sideband signal whose center frequency is higher than the original data frequency, as illustrated in Figure 8B.
  • the lower sideband is eliminated using a highpass filter.
  • a bandpass filter is used to eliminate the lower sideband.
  • the upper sideband, shown in Figure 8C may now be added to the audio signal which extends from 300 Hz to 3000 Hz.
  • the resulting combined signal extends from 300 Hz to 3300 Hz, as shown in Figure 7B.
  • FIG. 9A One system for performing the upband frequency translations described is shown in Figure 9A.
  • the input signal cos(2 ⁇ f x t), which is representative ofthe data signal, is multiplied by the tone, cos(2 ⁇ 3000t), to produce the signal of Figure 8B.
  • the filter removes the lower sideband to generate the signal of Figure 8C.
  • the inverse of this method is applied at the remote site to move the data spectrum back to its original position, as shown in Figure 7A.
  • Multiplying the data signal, represented by cos(2 ⁇ [3000 + fjt) by cos(2 ⁇ 3000t) produces 0.5cos(2 ⁇ f x t) + 0.5cos(2 ⁇ 6000t).
  • the second term is removed using a lowpass filter, and the original data signal represented by the first term is recovered.
  • Figure 9B One system used to perform the down frequency translation.
  • Single Sideband Translation System Figure 10 shows one system for translating the data signal upband ofthe audio signal, however, the shifting process does not create a double sideband signal which requires filtering, as in the last embodiment.
  • the desired single sideband signal is:
  • This embodiment requires wideband 90 degree phase shifting, which can be difficult
  • the inverse of this system is applied to the
  • Figure 11 is used.
  • the output is then £ x, cos(2 ⁇ // + 0, ) , which was the original data signal, as shown in Figure 8A.
  • the audio signal may then be added to the data signal to reconstruct the original composite signal, as shown in Figure 7A.
  • Figure 12 shows another system for performing the upband translation ofthe data signal using Weaver's method.
  • the signal will be a Fourier series of frequencies which correspond to the time domain version ofthe data signal.
  • the signals at points (a) and (b) are:
  • this system is used to down translate the data signal spectrum.
  • the input signal is cos[2 ⁇ (f x - f , + f 2 )t], which is mixed with the frequency f 2 , lowpass filtered with bandwidth f,, mixed with f,, and then summed.
  • the output is cos(2 ⁇ f x t) which is the original data signal.
  • the only difference between moving the data upband and moving it downband is the order in which the mixing frequencies are applied. For upband translation the first mix is with f, then f 2 , while the opposite order is used for the downband translation process.
  • system of Figure 12 is used to move the data spectrum upband so it will be passed by existing multiplexer equipment while the system of Figure 11 is used to perform the downband translation.
  • system of Figure 11 is used to perform the downband translation.
  • any combination of the described embodiments, and their equivalents, may be combined. These embodiments may be implemented with either digital signal processing software or using actual circuit elements.
  • An additional embodiment ofthe present invention provides a system whereby the deconversion ofthe translated spectrum is coordinated to minimize distortions in the reconstructed signals.
  • This embodiment is particularly useful is in a simulcast system.
  • Simulcast systems have remote receivers which demodulate two or more signals in overlapping broadcast regions. Distortions in the reconstructed signals complicate demodulation by a receiver in the overlap area.
  • a sinusoidal data signal cos(2 ⁇ f x t)
  • This tone has been moved above the audio spectrum using the system of Figure 12, so it is described by cos(2 ⁇ [3000 + fjt).
  • the downband translation ofthe data portion is performed by the system shown in Figure 13, which is described below.
  • the upband translation process takes place at the central site 100.
  • the signal is then transmitted over multiplexer 102 and microwave equipment 104 to a remote site, for example, remote site 110.
  • This transmission takes some amount of time t, mk due to the time required to propagate a signal from the central site 100 to the remote site 1 10 as well as time delays associated with the multiplexers 102 and 112 and microwave equipment 104 and 1 14.
  • This time delay means there is an associated phase delay which is:
  • This signal must be moved back to its original spectral position. Doing so requires mixing it with a tone of frequency 3000Hz since, for this example, the data spectrum was moved up by 3000Hz.
  • GPS global positioning system
  • phase term ⁇ represents the phase relationship between the tones, since synchronization of the mixing frequencies to both be 3000Hz does not determine the phase relationship between these tones. That is, the 3000Hz tone at the remote site 110 is generally an unknown number of degrees out of phase with respect to the 3000Hz tone at the central site 100.
  • the result from the mixing process at the remote site is:
  • the second term is removed using a lowpass filter, as shown in Figure 13. If phase is
  • variable phase (time) delay which is set to ⁇ link before it is mixed with
  • This phase adjusted signal is the cos(2 ⁇ 3000t + ⁇ ) signal of Figure 13. This ensures that the data waveform will be properly reconstructed.
  • phase offset i.e. [ ⁇ li ⁇ k - ⁇ ] .
  • a decision based recovery method where the received signal is used to determine what data has been sent.
  • this method suffers the drawback that the recovery produces jitter due to the ambiguity of when the data changes state. If this ambiguity is too large they may sum at each location in such a way as to produce a large offset and provide unacceptable data distortion in the simulcast region.
  • Another approach is to transmit a pilot tone, along with the data signal, that indicates when state changes occur. This requires that some signal energy ofthe audio signal and data signal be sacrificed. Performance will suffer since the noise floor will increase because the channel energy is finite.
  • a pilot tone also increases the DSP filtering complexity and affects system timing.
  • One approach is to derive system synchronization using an outside source GPS. The GPS provides fixed one pulse per second and 10 MHz clocks that can be used to provide the required synchronization. The transmitting and receiving ends both use modulation frequencies that are integers to insure that they divide into one second without remainder. That is, f2 is required to be an integer.
  • Each site begins generating a tone of frequency f 2 on a one second boundary, as shown in Figure 14, so that all sites are phase aligned.
  • the f 2 frequencies at the channel controller and the remote site do not have to be equal. They both, however, reach zero at the one second mark, as illustrated.
  • GPS synchronization may be applied to any of the frequency conversion methods described herein.
  • the present system applies in situations where the frequency translations are different and any combination ofthe systems taught herein may be adapted for a variety of different systems.

Abstract

Système de gestion des largeurs de bande destiné à un réseau à répéteurs télé-alimentés, qui permet de modifier un premier signal de façon à créer un second signal à l'intérieur de la largeur de bande d'une liaison de communication, de transférer le second signal par la liaison de communication et de reconstruire le premier signal au niveau de l'extrémité éloignée de la liaison. Le système présente, pour effectuer la conversion et la reconstruction du signal, plusieurs modes de mélange. Il présente une caractéristique d'étalonnage permettant de corriger les distorsions de phase introduites dans la reconstruction du signal d'origine, la caractéristique d'étalonnage contenant, pour la reconstruction, des signaux provenant d'un système mondial de radiorepérage (GPS).
PCT/US1997/005985 1996-04-12 1997-04-11 Systeme de gestion des largeurs de bande pour un reseau a repeteurs tele-alimentes WO1997039535A2 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU27263/97A AU2726397A (en) 1996-04-12 1997-04-11 Bandwidth management system for a remote repeater network

Applications Claiming Priority (12)

Application Number Priority Date Filing Date Title
US63067396A 1996-04-12 1996-04-12
US1531196P 1996-04-12 1996-04-12
US1530996P 1996-04-12 1996-04-12
US08/628,981 US5991309A (en) 1996-04-12 1996-04-12 Bandwidth management system for a remote repeater network
US08/631,866 1996-04-12
US08/631,866 US5896560A (en) 1996-04-12 1996-04-12 Transmit control system using in-band tone signalling
US60/015,309 1996-04-12
US08/630,673 1996-04-12
US08/628,981 1996-04-12
US60/015,311 1996-04-12
US2776396P 1996-10-07 1996-10-07
US60/027,763 1996-10-07

Publications (3)

Publication Number Publication Date
WO1997039535A2 true WO1997039535A2 (fr) 1997-10-23
WO1997039535A3 WO1997039535A3 (fr) 1997-12-24
WO1997039535A9 WO1997039535A9 (fr) 1998-02-12

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PCT/US1997/005891 WO1997039542A2 (fr) 1996-04-12 1997-04-11 Systeme de gestion de la radiodiffusion par reseau d'emetteurs
PCT/US1997/005985 WO1997039535A2 (fr) 1996-04-12 1997-04-11 Systeme de gestion des largeurs de bande pour un reseau a repeteurs tele-alimentes
PCT/US1997/005984 WO1997039543A2 (fr) 1996-04-12 1997-04-11 Systeme de calcul de temporisation de liaison pour un systeme de repeteurs radio
PCT/US1997/005893 WO1997039541A1 (fr) 1996-04-12 1997-04-11 Systeme de commande d'emission utilisant la signalisation multifrequence

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PCT/US1997/005984 WO1997039543A2 (fr) 1996-04-12 1997-04-11 Systeme de calcul de temporisation de liaison pour un systeme de repeteurs radio
PCT/US1997/005893 WO1997039541A1 (fr) 1996-04-12 1997-04-11 Systeme de commande d'emission utilisant la signalisation multifrequence

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WO1997039542A2 (fr) 1997-10-23
AU2450297A (en) 1997-11-07
WO1997039542A3 (fr) 2001-09-13
WO1997039543A3 (fr) 1998-02-05
AU2726297A (en) 1997-11-07
AU2726397A (en) 1997-11-07
AU2662997A (en) 1997-11-07
WO1997039543A2 (fr) 1997-10-23
WO1997039541A1 (fr) 1997-10-23
WO1997039535A3 (fr) 1997-12-24

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