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WO1997011545A1 - Procede d'accroissement des capacites d'un systeme tout en maintenant la largeur de bande du canal dans un systeme de communication radio - Google Patents

Procede d'accroissement des capacites d'un systeme tout en maintenant la largeur de bande du canal dans un systeme de communication radio Download PDF

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Publication number
WO1997011545A1
WO1997011545A1 PCT/US1996/010768 US9610768W WO9711545A1 WO 1997011545 A1 WO1997011545 A1 WO 1997011545A1 US 9610768 W US9610768 W US 9610768W WO 9711545 A1 WO9711545 A1 WO 9711545A1
Authority
WO
WIPO (PCT)
Prior art keywords
phases
symbol frequency
transmission
receive
data intended
Prior art date
Application number
PCT/US1996/010768
Other languages
English (en)
Inventor
James Michael Keba
Clinton C. Ii Powell
Susan Chang
Original Assignee
Motorola Inc.
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
Application filed by Motorola Inc. filed Critical Motorola Inc.
Publication of WO1997011545A1 publication Critical patent/WO1997011545A1/fr

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/10—Frequency-modulated carrier systems, i.e. using frequency-shift keying
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/10—Frequency-modulated carrier systems, i.e. using frequency-shift keying
    • H04L27/14—Demodulator circuits; Receiver circuits

Definitions

  • This invention relates in general to radio communication systems, and more specifically to a method for increasing system capacity while maintaining channel bandwidth in a radio communication system.
  • Motorola's FLEXTM paging protocol is well known in the art.
  • the existing FLEXTM protocol supports bit rates of 1600 bits per second (bps), 3200 bps, and 6400 bps. While these rates are sufficient for a wide variety of applications, new wireless communication services such as electronic mail and faxes can benefit from a throughput beyond the 6400 bps offered by current FLEXTM paging systems.
  • An aspect of the present invention is a method for achieving an increase of fifty percent in transmission capacity in a radio communication system utilizing a modulation process comprising four- level frequency shift-keyed (FSK) modulation having a maximum bit rate of 6400 bits per second (bps) and a minimum symbol frequency spacing of 3200 Hz prior to the increase.
  • the method also maintains a channel bandwidth after the increase substantially equal to the channel bandwidth prior to the increase.
  • the method comprises the steps of changing the modulation process to include a signal utilizing eight-level FSK modulation comprising four upper symbol frequency deviations and four lower symbol frequency deviations, increasing the maximum transmitted bit rate to 9600 bps, and changing the minimum symbol frequency spacing to 1600 Hz, thereby maintaining symbol orthogonality for a complex representation of the signal.
  • a second aspect of the present invention is a method for achieving an increase of fifty percent in reception capacity in a radio communication system utilizing a modulation process comprising four- level frequency shift-keyed (FSK) modulation having a maximum bit rate of 6400 bits per second (bps) and a minimum symbol frequency spacing of 3200 Hz prior to the increase.
  • the method also maintains a channel bandwidth after the increase substantially equal to the channel bandwidth prior to the increase.
  • the method comprises the steps of changing the demodulation process to include a signal utilizing eight- level FSK demodulation comprising four upper symbol frequency deviations and four lower symbol frequency deviations, increasing the maximum received bit rate to 9600 bps, and changing the minimum symbol frequency spacing to 1600 Hz, thereby maintaining symbol orthogonality for a complex representation of the signal.
  • FIG. 1 is an electrical block diagram of a radio communication system in accordance with the preferred embodiment of the present invention.
  • FIG. 2 is an electrical block diagram of a controller utilized in the radio communication system of FIG. 1.
  • FIGs. 3 through 5 depict bandwidth occupied before and after the increase in channel capacity in accordance with the preferred embodiment of the present invention.
  • FIG. 6 is an electrical block diagram of a communication receiver utilized in the radio communication system of FIG. 1.
  • FIG. 7 is a flow chart depicting operation of the controller in accordance with the preferred embodiment of the present invention.
  • FIG. 8 is a flow chart depicting operation of the communication receiver in accordance with the preferred embodiment of the present invention. Description of the Preferred Embodiment
  • an electrical block diagram of a communication system in accordance with the preferred embodiment of the present invention comprises a fixed portion 102 and a portable portion 104.
  • the fixed portion 102 includes a plurality of base stations 116, for communicating with the portable portion 104, utilizing conventional transmission techniques well known in the art, and coupled by communication links 114 to a controller 112 which controls the base stations 116.
  • the hardware of the controller 112 is preferably a combination of the Wireless Messaging Gateway (WMGTM) Administrator! paging terminal and the RF-Conductor!TM message distributor manufactured by Motorola, Inc.
  • the hardware of the base stations 116 is preferably a Nucleus® Orchestra! transmitter manufactured by Motorola, Inc. It will be appreciated that other similar hardware can be utilized for the controller 112 and base stations 116.
  • Each of the base stations 116 transmits radio signals to the portable portion 104 comprising a plurality of communication receivers 122 via a transmitting antenna 120.
  • the radio signals comprise selective call addresses and message transactions between the base stations 116 and the communication receivers 122.
  • the controller 112 preferably is coupled by conventional telephone links 101 to a public switched telephone network (PSTN) 110 for receiving selective call messages therefrom.
  • PSTN public switched telephone network
  • the selective call messages comprise voice and data messages received from the PSTN 110 using, for example, a conventional telephone 124 coupled to the PSTN 110 in a manner well known in the art.
  • Data and control transmissions between the base stations 116 and the communication receivers 122 preferably utilize an outbound protocol such as Motorola FLEXTM digital selective call signaling protocol described more fully in U.S. Patent No. 5,168,493 issued December 1, 1992 to Nelson et al., and assigned to the assignee of the present invention and which is hereby incorporated by reference.
  • This protocol utilizes well-known error detection and error correction techniques and is therefore tolerant to bit errors occurring during transmission, provided that the bit errors are not too numerous in any one code word.
  • Transmissions comprising data and control signals from the base stations 116 preferably utilize either two, four, or eight-level frequency shift keyed (FSK) modulation in accordance with the present invention, as will be described shortly below.
  • FSK frequency shift keyed
  • an electrical block diagram of elements of the fixed portion 102 in accordance with the preferred embodiment of the present invention comprises portions of the controller 112 and the base stations 116.
  • the controller 112 comprises a processing system 210 for directing operation of the controller 112.
  • the processing system 210 preferably is coupled through a transmitter controller 204 to a transmitter 202 via the communication links 114.
  • the communication links 114 use conventional means well known in the art, such as a direct wire line (telephone) link, a data communication link, or any number of radio frequency links, such as a radio frequency (RF) transceiver link, a microwave transceiver link, or a satellite link, just to mention a few.
  • the transmitter 202 can transmit either two, four, or eight-level FSK data messages to the communication receivers 122.
  • the transmission of eight-level FSK can be any one of three embodiments. Table 1, shown below, compares two, and four-level FSK frequency deviations used in FLEXTM systems today to one embodiment of eight- level FSK frequency
  • the frequency deviations are selected orthogonal with respect to each other.
  • selecting orthogonal deviations results in a non-overlapping energy spectrum where the center of each deviation (where the energy is at a peak) occurs at a null in the frequency spectrum produced by each of the other frequency deviations.
  • Orthogonality for a complex representation of the signal is accomplished by spacing the symbol frequencies at intervals of 1 /2T, where T is the symbol duration.
  • a receiver that is designed for orthogonal reception advantageously can recover substantially all of the sensitivity that would otherwise be lost due to the higher 9600 bps bit rate utilized with the 8-Level FSK data messages.
  • a communication receiver 122 using a zero intermediate frequency (ZIF) receiver cannot easily demodulate the deviations depicted in Table 1 without great loss to sensitivity in reception.
  • ZIF receivers inherently have a notch in the passband which has a variable bandwidth (BW) dependent on component specifications chosen in the design and implementation of the ZIF receiver.
  • BW variable bandwidth
  • the above proposed frequency deviations centered at the carrier frequency ( ⁇ 800Hz) are considered difficult for utilization in a ZIF receiver.
  • Table 2 shows a second embodiment which would better support the use of a ZIF receiver.
  • This embodiment differs in two ways from the first embodiment.
  • the proposed eight-level FSK frequency deviations share frequency deviations with the existing two and four- level FSK systems.
  • a ninth frequency deviation is reserved at the carrier frequency, but no carrier is transmitted, thereby spacing the symbol frequencies that are closest to the carrier frequency far enough ( ⁇ 1600Hz) from the carrier frequency to better support a ZIF application.
  • Table 3 shows a third embodiment.
  • a carrier frequency is transmitted in the ninth frequency deviation.
  • the carrier signal can be used by a communication receiver 122 utilizing a coherent receiver design.
  • FIG. 3 depicts bandwidth occupied by the existing FLEXTM four- level FSK system.
  • FIG. 4 depicts the first embodiment described above of a FLEXTM eight-level FSK system in accordance with the present invention.
  • Fig. 5 depicts the second embodiment of a FLEXTM eight-level FSK system in accordance with the present invention without a carrier present at the ninth frequency deviation.
  • the channel bandwidth depicted in FIGs. 4 and 5 is substantially the same as that of the existing FLEXTM protocol depicted in FIG. 3 (i.e., approximately ⁇ 12KHz) and that the power is well inside the FCC out-of-band envelope 130.
  • Simulations to determine bandwidth requirements of the third embodiment according to the present invention similarly show that the channel bandwidth thereof also is substantially the same as that of FIG.
  • the processing system 210 is also coupled to an input interface 218 for communicating with the PSTN 110 through the telephone links 101 for receiving selective call originations.
  • the processing system 210 preferably includes a conventional computer system 212, and a conventional mass storage medium 214.
  • the conventional mass storage medium 214 also includes subscriber user information such as, for example, communication receiver 122 addressing, communication capability, programming options, etc.
  • the conventional computer system 212 is programmed by way of software included in the conventional mass storage medium 214.
  • the conventional computer system 212 preferably comprises a plurality of processors such as VME Sparc processors manufactured by Sun Microsystems, Inc. These processors include memory such as dynamic random access memory (DRAM), which serves as a temporary memory storage device for scratch pad processing such as, for example, storing messages originated by callers using the PSTN 110, and for protocol processing of messages destined for the communication receivers 122, just to mention a few.
  • DRAM dynamic random access memory
  • the conventional mass storage medium 214 is preferably a conventional hard disk mass storage device.
  • FIG. 6 is an electrical block diagram of the communication receiver 122 in accordance with the preferred embodiment of the present invention.
  • the communication receiver 122 comprises a receiver antenna 302 for intercepting RF signals from the base stations 116.
  • the receiver antenna 302 is coupled to a receiver element 304 which includes a receiver utilizing conventional demodulation techniques for receiving the communication signal transmitted by the base station 116.
  • the RF signals received from the base stations 116 use two, four, or eight-level FSK, as will be described shortly below.
  • Radio signals received by the receiver element 304 produce demodulated information, which is coupled to a processing unit 310 for processing received messages.
  • a conventional power switch 308, coupled to the processing unit 310, is used to control the supply of power to the receiver element 304, thereby providing a battery saving function.
  • the processing unit 310 is coupled to a microprocessor 316, a random access memory (RAM) 312, a read-only memory (ROM) 314, and an electrically erasable programmable read-only memory (EEPROM) 318.
  • the processing unit 310 is similar to the M68HC08 micro ⁇ controller manufactured by Motorola, Inc. It will be appreciated that other similar processors can be utilized for the processing unit 310, and that additional processors of the same or alternative type can be added as required to handle the processing requirements of the processing unit 310. It will be also appreciated that other types of memory, e.g., EEPROM or FLASH, can be utilized for the ROM 314, as well as the RAM 312. It will be further appreciated that the RAM 312 and the ROM 314, singly or in combination, can be integrated as an integral portion of the microprocessor 316.
  • the processing unit 310 is programmed by way of the ROM 314 to process incoming messages on the outbound channel. During received message processing, the processing unit 310 decodes in a conventional manner an address in the demodulated data of the received message, compares the decoded address with one or more addresses stored in the EEPROM 318, and when a match is detected, the processing unit 310 proceeds to process the remaining portion of the message. Once the processing unit 310 has processed the message, it stores the message in the RAM 312, and a call alerting signal is generated to alert a user that a message has been received. The call alerting signal is directed to a conventional audible or tactile alerting device 322 for generating an audible or tactile call alerting signal.
  • the message can be accessed by the user through user controls 320, which provide functions such as lock, unlock, delete, read, etc. More specifically, by the use of appropriate functions provided by the user controls 320, the message is recovered from the RAM 312, and then displayed on a display 324, e.g., a conventional liquid crystal display (LCD) and /or played out by the audio amplifier 326 and audio speaker 328 combination.
  • FIG. 7 is a flow chart 400 depicting operation of the controller 112 in accordance with the preferred embodiment of the present invention. The flow chart 400 begins with step 402 where the controller 112 receives one or more messages from the PSTN 110 destined for one or more communication receivers 122.
  • step 404 the controller 112 processes the messages, and identifies the communication receivers 122 to which the messages are intended.
  • the controller 112 determines the communication capability of the selected communication receivers 122.
  • the controller 112 sends the messages to the transmitter 202 with transmission instructions.
  • the transmission instructions comprise the transmission phases to be utilized by the transmitter when transmitting a message to a particular communication receiver 122.
  • Table 4 below shows the reception phase (used by the communication receivers 122) to the transmission phase (used by the base stations 116) mapping.
  • the instructions given in step 406 determine the transmission phases to be used by the transmitter 202 when transmitting a message to a communication receiver 122 as defined by Table 4.
  • step 410 the transmitter 202 selects coherent or ZIF (noncoherent) transmission in accordance with the communication receiver 122 selected. Once the modulation mode selection is made the message is transmitted to the communication receiver 122.
  • FIG. 8 is a flow chart 500 depicting operation of the communication receiver 122 in accordance with the preferred embodiment of the present invention.
  • the flow chart 500 begins with step 502 where the communication receiver 122 is prompted to receive a message in accordance with events in the FLEXTM protocol well known to one of ordinary skill in the art.
  • the communication receiver 122 determines the modulation format and multiplex factor from the FLEXTM protocol as indicated in SYNCl word (not shown) in the FLEXTM protocol.
  • the communication receiver 122 uses Table 4 to determine the reception phases in accordance with the programming of the communication receiver 122.
  • step 506 a determination is made from one of four operational quantities which define the multiplex factor utilized by the communication system 102, 104 for transmission and reception.
  • the operational quantity is "one”
  • the communication receiver 122 proceeds to step 508 and maps reception phases 0 through 5 to transmission phase "a" (i.e., the 1600 bps column of Table 4).
  • the operational quantity is "two”
  • the communication receiver 122 proceeds to step 510 and maps reception phases 0, 1, & 2 to transmission phase "a”, and reception phases 3, 4, & 5 to transmission phase "b” (i.e., the 3200 bps column of Table 4).
  • the communication receiver 122 proceeds to step 512 and maps reception phases 0 & 1 to transmission phase "a,” reception phase 2 to transmission phase “b,” reception phases 3 & 4 to transmission phase “c,” and reception phase 5 to transmission phase “d” (i.e., the 6400 bps column of Table 4).
  • the communication receiver 122 proceeds to step 514 and maps reception phase 0 to transmission phase "a,” reception phase 1 to transmission phase “b,” reception phase 2 to transmission phase “c,” reception phase 3 to transmission phase “d,” reception phase 4 to transmission phase "e,” and reception phase 5 to transmission phase “f” (i.e., the 9600 bps column of Table 4).
  • the communication receiver 122 proceeds to step 516 where it demodulates the received signal in accordance with its programming, and stores the message in the RAM 312.
  • step 518 the user is alerted to the pending message, and subsequently reads the message by using appropriate functions provided on the user controls 320.

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Digital Transmission Methods That Use Modulated Carrier Waves (AREA)

Abstract

Cette invention concerne un procédé permettant d'accroître de cinquante pourcent la capacité de transmission d'un système de communication radio (102, 104) à l'aide d'un processus de modulation. Ce processus consiste en une modulation de transmission par déplacement de fréquence (FSK) à quatre niveaux possédant un train binaire maximal de 6400 bits par seconde et un espacement minimal des fréquences de symboles de 3200 Hz, ceci avant que la capacité ne soit accrue. Ce procédé permet également de conserver, après l'accroissement, une largeur de bande de canal sensiblement égale à celle existant avant ledit accroissement. Le procédé comprend les étapes suivantes: modifier le processus de modulation (412, 414) de manière à inclure un signal faisant appel à une modulation FSK à huit niveaux et comprenant quatre déviations supérieures des fréquences de symboles et quatre déviations inférieures des fréquences de symboles; accroître le train binaire maximal transmis à 9600 bits par seconde; et, enfin, ramener l'espacement minimal des fréquences de symboles à 1600 Hz. Ce système permet ainsi de conserver l'orthogonalité des symboles pour une représentation complexe du signal.
PCT/US1996/010768 1995-09-18 1996-06-24 Procede d'accroissement des capacites d'un systeme tout en maintenant la largeur de bande du canal dans un systeme de communication radio WO1997011545A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US52982695A 1995-09-18 1995-09-18
US08/529,826 1995-09-18

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WO1997011545A1 true WO1997011545A1 (fr) 1997-03-27

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PCT/US1996/010768 WO1997011545A1 (fr) 1995-09-18 1996-06-24 Procede d'accroissement des capacites d'un systeme tout en maintenant la largeur de bande du canal dans un systeme de communication radio

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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4601045A (en) * 1984-08-03 1986-07-15 Larse Corporation Modulator-demodulator method and apparatus with efficient bandwidth utilization
US5208835A (en) * 1990-09-24 1993-05-04 In-Situ, Inc. Automatic frequency control system and method for frequency-shift-key data transmission systems
US5524122A (en) * 1993-09-13 1996-06-04 U.S. Philips Corporation System and method for adapting the transmission rate to the line quality and modem suitable for such a system

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4601045A (en) * 1984-08-03 1986-07-15 Larse Corporation Modulator-demodulator method and apparatus with efficient bandwidth utilization
US5208835A (en) * 1990-09-24 1993-05-04 In-Situ, Inc. Automatic frequency control system and method for frequency-shift-key data transmission systems
US5524122A (en) * 1993-09-13 1996-06-04 U.S. Philips Corporation System and method for adapting the transmission rate to the line quality and modem suitable for such a system

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