KR100509903B1 - Systems and methods for reducing interference caused by digital communication devices - Google Patents

Abstract

A system and method for reducing radio frequency interference associated with pulse transmission in time division multiple communication channels. In the first embodiment, the subscriber station 300 is nominally assigned all slots TN0-TN7 of each frame of the first transmission channel R0. By substantially continuing to transmit radio frequency energy, the subscriber station reduces the disturbance that occurs in pulse transmission. In the second embodiment, the subscriber station 300 is nominally assigned one or more slots TN0-TN7 of each frame of the primary channel R0 for the typical transmission of useful information, and the subscriber station 300 Is instructed to continuously transmit radio frequency energy in auxiliary channel R1 at a time other than during the assigned primary channel slots. In this way, the interference generated around the subscriber station 300 is reduced due to the substantially continuous transmission of radio frequency energy by the subscriber station 300. During jamming mode operation, one or more subscriber stations 300 may use auxiliary channel R1 at the same time.

Description

Systems and methods for reducing interference caused by digital communication devices

The present invention generally relates to a wireless communication system. More specifically, the present invention relates to novel systems and methods for reducing disturbances caused by digital communication devices.

In time division multiple access (TDMA) cellular communication systems known in the art, the available frequency spectrum is divided into a predetermined number of radio frequency channels each having a given bandwidth. Each radio frequency channel is time-divided into cycles of TDMA frames, and each frame is further divided into cycles of time intervals called a predetermined number of "slots." Thus, one slot means a finite time period on a given radio frequency channel. Communication between the air interfaces occurs during these slots with a group of modulated bits called one "burst" for each slot. A "normal burst" contains the useful information bits of a packet, with a short "guard period" before and after it, and no useful information is transmitted nominally in the guard period. During this guard period, power ramping of the transmitter occurs, where the transmitter is turned on before the transmission of the information bits and turned off after the transmission of the information bits.

Although the term " channel " corresponds to a particular fixed radio frequency bandwidth, in more general cases, a " channel " is also a temporal element in frequency-sensitive systems such as the Global System for TDMA Mobile Communication Systems (GSM). Have In other words, a "channel" (ie, communication channel) for a single function may be a sequence of slots that may occupy different frequencies at different times. In the following, the term "channel" will be used in more general and functional terms.

When a given subscriber station in a communication system enters a dedicated mode, such as during call setup or performing a location update to a base station, a subscriber station is typically assigned a specific slot of a transmission channel for transmission of that information, the slot being normal. Packaged in rows of bursts. Thus, although many subscriber stations in a given cell can transmit on a single channel (limited at least by the number of slots in one frame), individual normal bursts from each user are time-division multiplexed to the corresponding slots. . For example, a subscriber station assigned to a first slot in one frame of a given transmission channel may only interfere with the burst transmission of subscriber stations each assigned to the remaining slots of that transmission channel frame. Transmit nominally for one slot only, otherwise turn the transmitter off. Thus, a subscriber station assigned to a first slot turns on its transmitter during the guard period preceding the first slot to transmit a package of useful information during that first slot, and turns off the transmitter during the remaining slots of the frame. Likewise, a subscriber station assigned to a second slot of a frame transmits a package of useful information bits during that second slot and turns off the transmitter during the remaining slots of the frame.

Such periodic on / off switching of subscriber station transmitters generates a transmission signal that can interfere with the operation of adjacent electronic devices. Since this on / off switching modulates the amplitude of radio frequency energy transmitted, the disturbance caused by this on / off switching will be referred to as "amplitude modulation disturbance" or simply "AM disturbance". For example, in an all-European GSM cellular system, each frame is divided into eight slots with a duration of 4.615 ms and each with a duration of 577 ms. Transmission during the same slot of each frame results in a subscriber station burst repetition rate of 216.6 ms (ie 1 / 4.615 ms). Since this burst repetition rate is within the audible frequency range, it may not be desirable for other electronic devices including circuitry that can operate as an AM detector. For example, if a GSM subscriber station operates near a stereo system, the burst repetition rate may be heard as noise from the speaker.

It should be noted that other TDMA digital communication systems have different frame lengths and different number of frame slots. For example, U.S. Pat. TDMA cellular communication systems use 20 ms long cyclic TDMA frames divided into six slots. It should also be noted that for higher bandwidth signals, the TDMA system may allocate one or more slots per frame to a single subscriber station to accommodate higher rate signals. However, these systems still use burst repetition rates within the audible frequency range and can cause significant disturbances to surrounding electronic devices.

Many electronic devices, such as hearing aids and cardiac pacemakers, are also sensitive to interference from such pulse transmissions. In particular, it has been found that hearing aids designed to provide significant acoustic gain are sensitive AM detectors. Therefore, significant interference may occur when the hearing aid is operated in the vicinity of GSM and other TDMA type user communication devices. In fact, the level of acoustic disturbance or "noise" in the hearing aid wearer's ear may be sufficient to distract the caller, preventing the hearing aid wearer from effectively using the TDMA subscriber station.

Accordingly, it is an object of the present invention to provide a transmission scheme for a multiple access communication system that minimizes the possibility of AM interference with surrounding electronic devices.

Summary of the Invention

The present invention is directed to a system and method for reducing undesirable AM disturbances that occur in connection with periodic transmission in a digital wireless communication system. The invention is particularly applicable to time division multiple access communication systems such as GSM.

In the first embodiment of the present invention, all slots of each frame of the first transmission channel are nominally allocated to the first subscriber station operating in the interference reduction mode. By sufficiently continuing to transmit radio frequency energy even to the guard period of each slot, the subscriber station sufficiently eliminates AM disturbances arising from pulse transmission. The second subscriber station can be similarly arranged to operate in the disturbance reduction mode of the first embodiment. In particular, the second subscriber station is assigned nominally all slots of each frame of the second transmission channel.

In a second embodiment of the present invention, the first subscriber station is assigned one or more slots of each frame of the first transmission channel (hereinafter referred to as " main channel ") for normal transmission of useful information. However, unlike in the prior art, the first subscriber station is instructed to continuously transmit radio frequency energy to the "secondary" channel at times other than during the assigned primary channel slot. The first subscriber station does not turn off its transmitter while tuning back to the auxiliary channel frequency or back to the primary channel frequency. In this way, the substantially continuous transmission of radio frequency energy by the first subscriber station, even the transmission up to the guard period of each slot, reduces the level of AM disturbances generated around the first subscriber station. The second subscriber station can be similarly arranged to operate in the disturbance reduction mode of the second embodiment. In particular, the second subscriber station may be assigned one or more slots of each frame of the primary channel nominally for conventional transmission of useful information, and also radio frequency to the secondary channel at times other than during the assigned primary channel slots. Instructed to transmit energy continuously. Similarly, the second subscriber station does not turn off its transmitter while tuning back to the auxiliary channel frequency or back to the main channel frequency.

As can be seen in the second embodiment, one or more subscriber stations can use the auxiliary channel simultaneously during the interference reduction mode of operation. If many such subscriber stations operate simultaneously in the interference reduction mode, it is quite clear that the auxiliary channel will be filled with the interference transmission. For this reason, the auxiliary channel is chosen such that this "junk" transmission does not interfere with the information transmitted to other channels.

The present invention contemplates radio frequency energy transmission in each slot of a frame by a subscriber station only while the subscriber station is still in dedicated mode (ie, when a call is in progress or performing a location update), and the mobile station is idle. It should be noted that it is not expected to be in the idle mode (ie, when only monitoring control channels for broadcast information). However, this restriction is not strictly required for AM disturbance reduction.

1 is a diagram of three cells, shown as A, B, and C, respectively, in an exemplary cellular mobile radio system.

2 illustrates an exemplary TDMA time / frequency allocation scheme for the cellular wireless system of FIG.

3 is a block diagram of a subscriber station deployed in disturbance mode of operation for communicating over digital communication channels.

4 is a diagram of a base station for operation in the cellular mobile wireless system of FIG.

1 illustrates three cells A, B, and C in an exemplary cellular mobile radio system 10. For each cell A, B, and C, there are corresponding base stations B _A , B _B , and B _C , respectively. For illustrative purposes, base station B _A is shown in communication with three subscriber stations MA0, MA1, and MA2, each located within the cell boundary of base station B _A. Base station BB is shown in communication with one subscriber station MB0 located within the cell boundary of base station BB. Similarly, base station BC is shown in communication with one subscriber station MC0 located within the cell boundary of base station BC. Also shown in FIG. 1 is a base station controller (BSC). The BSC of FIG. 1 is connected to all three base stations BA, BB, and BC by cables 11, 12, and 13. The BSC is also connected by means of a cable (not shown) to the mobile switching center (MSC), which serves as a point of contact with the public switched telephone network (PSTN) or its equivalent. It should be noted that the present invention can be applied to non-cellular TDMA communication systems such as PCS or radio area loop systems. Thus, the subscriber station can be any type of telecommunication device, such as stationary, mobile, portable, or the like. However, for the sake of explanation it will be sufficient to describe a cellular system with three cells A, B, and C and a mobile unit for cellular operation.

The cellular wireless system 10 of FIG. 1 is designed to accommodate communication over multiple radio frequencies. An exemplary TDMA time / frequency allocation scheme for a base station of either BA, BB, or BC is shown in FIG. In Fig. 2, four reverse link (mobile station to base station) carrier frequencies R and four forward link (base station to mobile station) carrier frequencies F are shown, each with a carrier spacing of 200 Hz. The reverse link carrier frequency is 890.2-890.8 MHz, and the forward link carrier frequency is 935.2-935.8 MHz. The cycle of the TDMA frame along the time axis is represented by frame 0 and frame 1, and each time interval of duration 577 ms is defined by its time interval number TN from TN0 to TN7. The cycle of slots on the reverse link, defined by the carrier frequency of 890.2 MHz and the time interval of TN0-TN7, is indicated from R0,0 to R0,7, respectively. Likewise, the cycles of the slots on the forward link defined by the carrier frequency 935.2 MHz and the time interval from TN0 to TN7 are indicated from F0,0 to F0,7, respectively. Although the example TDMA time / frequency assignment of FIG. 2 is very similar to that of a GSM system, it should be noted that the concept is applicable to other TDMA systems with more or fewer slots per frame and with different carrier frequency spacing. . For example, U.S. Pat. No. 4, disclosed in TIA / DIA / IS 54-B. The TDMA system uses six slots per TDMA frame and a carrier frequency spacing of 30 kHz.

In prior art TDMA systems, a given mobile unit, e.g., MA0 (FIG. 1), transmits information of normal bursts to its corresponding base station BA in one or more assigned slots of each frame of the reverse link channel. For example, in a TDMA system with fixed frequency of reverse link channels, mobile unit MA0 may be assigned to transmit normal bursts in each slot marked R0,0 when MA0 is in dedicated mode. Similarly, the second mobile unit MA1 may be assigned to transmit normal bursts in each slot marked R0,1 when MA1 is in dedicated mode. The third mobile unit MA2 may be assigned to transmit normal bursts in slots related to other carrier frequencies, such as each slot indicated by R1,0. Similarly, MA0 may be assigned to receive bursts transmitted by the base station BA in each forward channel labeled F0,0. Similarly, MA1 may be assigned to receive bursts transmitted by base station BA in each forward channel labeled F0,1, and MA2 may be transmitted on a separate carrier frequency by base station BA in each forward channel labeled F1,0. May be assigned to receive bursts.

In a more general case of a frequency sensitive TDMA system such as GSM, mobile unit MA0 still transmits information of normal bursts to its corresponding base station BA in one assigned slot of each frame of the reverse link channel. However, since the reverse link channel is not fixed in frequency, when H corresponds to the hopping permutation of the frequency hopping scheme of a particular reverse link channel, MA0 is adapted to transmit normal bursts in each slot denoted RH, 0. Is assigned. Thus, for the exemplary four-frame cyclic hopping sequence {0, 1, 2, 3}, MA0 is slot R0,0 in frame 0, slot R1,0 in frame 1, slot R2,1 in frame 2 and frame 3 Transmit the normal bursts in slot R3,1. The reverse link channel used by mobile unit MA2 has a different hopping sequence, for example {1, 2, 3, 0}. In such a case, MA2 transmits normal bursts in slot R1,0 of frame 0, slot R2,0 of frame 1, slot R3,0 of frame 2, and slot R0,0 of frame 3.

In the conventional prior art TDMA system disclosed above, during the short guard period of each assigned slot and all other time intervals TN0-TN7 of each frame, the mobile units MA0, MA1, and The transmitters of the MA2 are turned off. As noted above, it is the pulse transmission of these periodic bursts that cause undesirable AM disturbances. In the present invention, such AM disturbance is eliminated due to the substantially continuous transmission of radio frequency energy.

In the first embodiment of the present invention, as will be described below, one or more of the mobile units MA0, MA1, and MA2 operate in an interference reduction mode, wherein radio frequency energy is applied across each slot of each frame of a given reverse link channel. It is allocated to transmit continuously. In other words, dedicated channels are allocated for exclusive use during operation in the interference reduction mode. For example, suppose MA0 is intended to operate in disturbance reduction mode. In the fixed frequency channel TDMA system described above, MA0 is transmitted continuously in each slot of R0,0 to R0,7 of each frame. In such fixed frequency channel systems, the disturbance caused by simultaneous transmission on the same carrier frequency by MA0 prevents either of MA1 and MA2 from effectively communicating with the base station BA in the slots marked R0, X. Therefore, all other mobile units in cell A are limited to transmissions in each assigned slot of one of the remaining carrier frequencies of 890.4 MHz to 890.8 MHz.

If the second mobile unit MA1 is also assigned to operate in the interference reduction mode at the same time as MA0, then MA1 is not in the carrier frequency of MA0 but in every slot of each frame of the individual carrier frequency, e.g. R1,0 to Transmission is continuously performed at each slot up to R1,7. Thus, the remaining mobile units of Cell A are limited to transmissions in each assigned slot of one of the remaining carrier frequencies of 890.6 MHz-890.8 MHz.

In a TDMA system with frequency-sensitive reverse link channels, the first embodiment of the present invention can be implemented in at least two ways. In the first scheme, the frequency of the dedicated channel is fixed and the remaining frequencies are frequency-sensitive as it is. In the second scheme, the dedicated channel is also frequency sensitive.

When the frequency of the dedicated channel is fixed, each mobile unit operating in the interference reduction mode as in the fixed frequency channel TDMA system described above is assigned a dedicated carrier frequency, and all other mobile units in the cell are between the other carrier frequencies. Continues frequency hopping in units per frame. In this first frequency sensitive manner, the hopping sequence for a given reverse link channel is updated to eliminate hopping to a given carrier frequency of the mobile unit operating in the interference reduction mode. For example, if the reverse link frequency R0 (890.2 MHz) operates in the interference reduction mode and is provided only to the mobile unit MA0 transmitting in each slot of R0,0 to R0,7 of each frame, then the mobile units MA1 and MA2 are given an example. For example, it is assigned to reverse link channels having a three-frame cyclic hopping sequence of {1, 2, 3} to eliminate hopping to frequency RO while the frequency RO is provided only to mobile unit MA0.

If the dedicated channel is frequency sensitive, each mobile unit operating in the interference reduction mode continuously transmits in each slot of a given frame on the same assigned frequency. However, the mobile unit operating in the interference reduction mode continues frequency hopping on a frame-by-frame basis with the remaining mobile units communicating within that cell. For example, mobile unit MA0 operating in the interference reduction mode is assigned to continuously transmit in each slot of each frame of a given reverse link channel with a four frame cyclic hopping sequence of {0, 1, 2, 3}. MA0 is slots R0,0-R0,7 of frame 0, slots R1,0-R1,7 of frame 1, slots R2,0-R2,7 of frame 2, and slots R3,0 of frame 3 -Transmit continuously in R3,7. This second frequency sensitive scheme makes it unnecessary to update the hopping sequence for any channel. Thus, mobile units MA1 and MA2 may be assigned to reverse link channels with a four frame cyclic hopping sequence of {1, 2, 3, 0}, for example. If the dedicated channel is frequency sensitive, it should be noted that the mobile unit continues to transmit radio frequency energy while tuning its transmitter back to the next frequency in the hopping sequence.

In all implementations of this first embodiment, the mobile unit is assigned an exclusive dedicated transmission channel while operating in the interference reduction mode. However, in implementations with typical cyclic timing schemes of TDMA systems, only a subset of the slots of each frame of the dedicated channel need to have useful information. For example, the mobile unit may transmit meaningful information during its assigned slots and otherwise transmit a carrier that is not modulated during the remaining slots of the transmission channel. In such an implementation, the base station only needs to tune the receiver to a dedicated channel during slots containing useful information. Alternatively, the mobile unit can transmit the same repeated information, one for each slot of the frame. In another implementation, the mobile unit may transmit useful information that is not repeated in each slot of each frame of the dedicated transmission channel. In each of the above embodiments, it should be noted that the mobile unit operating in the interference reduction mode continuously transmits radio frequency energy while the guard period is nominally surrounding each burst.

In a second embodiment of the invention, one or more of the mobile units MA0, MA1, and MA2 are provided to operate in an interference reduction mode, and transmit meaningful information in one or more slots of each frame of a given reverse link channel. . With regard to this "primary channel", the operation of the disturbance reduction mode mobile unit is similar to the conventional mobile unit of the TDMA system in the prior art. However, in contrast to the conventional prior art TDMA system, the mobile unit operating in the interference reduction mode of the second embodiment also has a "secondary" channel over all time intervals TN0-TN7 independent of the slots allocated on its primary channel. Send on In addition, the auxiliary channel can be shared simultaneously by one or more disturbance reduction mode mobile units, as opposed to the first embodiment of the present invention, in which each dedicated reduction mode mobile unit is assigned an exclusive dedicated transmission channel for transmission.

For example, MA0 and MA1 are both intended to operate in the interference reduction mode, and the fixed frequency reverse link channel defined by all slots R0,0-R0,7 of each frame of carrier frequency R0 is reserved for the secondary channel. Can be. In this case, MA0 and MA1 may be assigned a primary channel that resides between the slots of the remaining carrier frequencies. In a fixed frequency channel TDMA system, for example, MA0 is allocated to transmit useful information in each slot indicated by R1,0 of each frame, and MA1 is transmitted to transmit useful information in each slot indicated by R1,1 of each frame. Can be assigned. In that case, MA0 also retunes its transmitter to continue to transmit in each slot labeled R0,1-R0,7 of the auxiliary channel. Note that both MA0 and MA1 transmit simultaneously in each slot labeled R0,2-R0,7. Each mobile unit will continue to transmit radio frequency by tuning its transmitter back to the auxiliary channel frequency or back to the main channel frequency.

In a TDMA system having frequency-sensitive reverse link channels, the second embodiment of the present invention can be implemented in at least two ways as in the first embodiment. In other words, the first embodiment is a case where the frequency of the auxiliary channel is fixed and the frequency of the remaining channels is frequency-sensitive as it is, and in the second embodiment, the frequency of the auxiliary channel is also frequency-sensitive.

If the frequency of the auxiliary channel is fixed, a fixed frequency reverse link channel defined by all slots of R0,0-R0,7 of each frame of carrier frequency R0 can be reserved as an auxiliary channel. Mobile unit MA0 operating in the interference reduction mode is allocated to transmit on the primary channel defined by the time interval TN0 and the three frame cyclic hopping sequence {1, 2, 3}. However, both MA0 and MA1 continue to transmit on the secondary channel over all time intervals that are not related to the respective primary channels. Specifically, mobile unit MA0 is slot R1,0 of frame 0 and slots R0,1-R0,7, slot R2,0 of frame 1 and slots R0,1-R0,7, slot R3,0 of frame 2 And slots RO, 1-R0,7 continuously. Similarly, mobile unit MA1 has slots R0,0, R1,1 and R0,2-R0,7 in frame 0, slots R0,0, R2,1 and R0,2-R0,7, frame 2 in frame 1. Transmit continuously in slots R0,0, R3,1 and RO, 2-R0,7. Once again, it should be noted that both MA0 and MA1 now transmit simultaneously in each slot labeled R0,2-R0,7.

If the auxiliary channel is frequency sensitive, it can be defined by all time intervals TN0-TN7 and the four frame cyclic hopping sequence {0, 1, 2, 3}. Mobile unit MA0 operating in the interference reduction mode may be assigned to transmit on the primary channel defined by the time interval TN0 and the four-frame cyclic hopping sequence {1, 2, 3, 0}. Similarly, mobile unit MA1 operating in the interference reduction mode may be assigned to transmit on the primary channel defined by the time interval TN1 and the four-frame cyclic hopping sequence {1, 2, 3, 0}. Specifically, mobile unit MA0 is slots R1,0 and R0,1-R0,7 of frame 0, slots R2,0 of frame 1, and R1,1-R1,7, slots R3,0 of frame 2 And in slots R0,0, and R3,1-R3,7 of R2,1-R2,7 and frame3. Similarly, mobile unit MA1 has slots R0,0, R1,1 and R0,2-R0,7 of slot 0, slots R1,0, R2,1, and R1,2-R1,7, frame 2 of frame1. Transmit in slots R2,0, R3,1 and R2,2-R2,7 and slots R3,0, R0,1 and R3,2-R3,7 in frame3. In addition, both MA0 and MA1 are now transmitting on the auxiliary channel simultaneously over the time interval TN2-TN7. In addition, the mobile unit continues to transmit radio frequency energy while tuning its transmitter back to the next frequency in the hopping sequence.

This second embodiment allows more efficient use of the frequency spectrum since the auxiliary channel is shared by multiple mobile units. However, even when there is only one mobile unit operating in the interference reduction mode in one cell (i.e., when the auxiliary channel is not yet shared), the second embodiment has a significant difference from the first embodiment. In particular, in the first embodiment, at least one slot of the dedicated channel contains useful information for proper demodulation by the base station. However, in the second embodiment, no slot of the auxiliary channel need to contain useful information. Therefore, the base station does not need to tune the receiver to the auxiliary channel at any time. In fact, one auxiliary channel may be shared by several base stations.

It is contemplated that the present invention will be particularly useful for deaf people using digital communication devices. In other words, since such users often rely on electronic hearing aids, the reduction in disturbance levels associated with the operation according to the invention minimizes the impact on hearing aid operation. Various permit schemes can be formulated as a means to ensure that only mobile units associated with the selected competent person (eg, deaf) can belong to the form of disturbance reduction expected by the present invention. For example, only suitable hearing impaired users can purchase a mobile unit (eg, a cellular telephone) that is previously authorized to operate in a reduced interference mode. Alternatively, appropriate hearing impaired users may obtain permission from the cellular service provider after purchasing a mobile unit capable of interference reduction mode operation, and then broadcast radio of interference reduction mode service selection from the cellular service provider during call setup. Can be received.

3 is a block diagram of a mobile unit 300 arranged for communication on a digital communication channel in the interference reduction mode of the present invention. In mobile unit 300, speech is digitized by A / D-D / A converter 302 and encoded in speech codec 304 as is known in the art. Channel codec 307 introduces redundancy into the data flow to detect and correct signal errors introduced during transmission, increasing its speed by adding information calculated by the source data. In burst generator 308, the flow of coded words generated by channel codec 306 is multiplexed with signal bits from microprocessor 324, inserted as needed, and trained sequence sequences as needed. It is formatted into individual bursts by adding sequence bits and tail bits. The mobile unit 300 uses the signal generated by the microprocessor 324 to signal to the base station the intention to operate in the interference reduction mode. Bursts generated by burst generator 308 are modulated onto an intermediate frequency by modulator 310. The resulting analog waveform is upconverted to the carrier frequency by the transmitter 312, directed to the antenna 316 by the duplexer 314, and broadcasted to the base station. When the mobile unit 300 is operating in the disturbance reduction mode as described above, the microprocessor 324 can generate radio frequency energy regardless of whether meaningful information is provided to the modulator 310 by the burst generator 308. Command the transmitter 312 to continue transmitting. Even in systems with frequency sensitive reverse link channels, microprocessor 324 also instructs transmitter 312 to tune back to the next frequency of the hopping sequence.

The signal received by the antenna 316 is directed by the duplexer 314 to the receiver 318. Receiver 318 bandpasses the signal captured by antenna 316, selects the appropriate signal, and downconverts it to an intermediate frequency. Demodulator 320 extracts the received bursts from the modulated frequency signal and passes the resulting digital signal to demultiplexer 322. Demultiplexer 322 extracts the demodulated signal, sorts the information received from the different slots and frames into its appropriate logical channels, and passes the reconstructed code words to channel codec 306. The channel codec 306 then reconstructs source information from code words generated by the demultiplexer 322 using any redundancy added to detect and correct possible errors. A command to the mobile unit 300 to assign the mobile unit 300 to the primary channel, in the second embodiment to the secondary channel, is provided to the mobile unit 300 via a signal message from the base station, and the channel codec 306 Is passed to the microprocessor 324. The encoded digital speech is sent to the speech codec 304 by the channel codec 306 and decoded by the channel codec 306 and converted into an analog speech waveform by the converter 302 as is known in the art.

4 illustrates a base station 400 designed for operation in the cellular mobile wireless system of FIG. 1, which may support mobile units 300 operating in an interference reduction mode. In many respects, the voice processing operation of base station 400 is similar to that of mobile station 300. Although the base station 400 may include several transmitter 412 and receiver 418 resources, it will be sufficient to describe the operation of the base station 400 in the case of a single transmitter 412 and a single receiver 418. Receiver 418 includes bandpass filters that select the desired carrier frequency from all signals received by antenna 416. Receiver 418 also down converts the desired signal to an intermediate frequency. Demodulator 420 extracts the bit stream from the down-converted signal and passes the resulting digital signal to demultiplexer 422. Demultiplexer 422 extracts the demodulated signal, sorts the received information from the different slots and frames into its appropriate logical channels, and passes the reconstructed code words to channel codec 406. The channel codec 406 then reconstructs the source information from the code words generated by the demultiplexer 422 using any redundancy added to detect and correct possible errors. Channel codec 406 also separates any signal for base station 400 and sends it to controller 424.

Base station controller interface 402 is a logical interface for both digitized voice and control messages between base station controller and base station 400. Many control messages are transparent to base station 400 and only pass through channel codec 406. For example, if the mobile unit 300 signals that it intends to operate in the interference reduction mode, this message may be passed through the base station 400 to the base station controller, where it may be passed to the subscriber database for authorization. Any control message from the base station controller intended for the base station 400 itself is communicated to the controller 424 by the channel codec 406. For example, based on cell loading conditions, the base station controller may cause the mobile unit 300 to operate in a disturbance reduction mode, and the mobile unit 300 may be assigned to a specific dedicated channel (in the case of the first embodiment) or the primary channel and The base station 400 may also be instructed to transmit on an auxiliary channel (in the case of the second embodiment). The message intended for the mobile unit 300 is delivered to the burst generator 408, inserted, multiplexed with the signal message generated by the controller 424 as needed, and formatted into a burst. The modulator 410 modulates the bursts to an intermediate frequency, and the transmitter 412 upconverts the signal and transmits it to the antenna 414.

The foregoing description of the preferred embodiments is provided to enable any person skilled in the art to practice the invention. It will be readily apparent to those skilled in the art of the possibility of various modifications of these embodiments, and the generic concept defined herein may be applied to other embodiments without using inventive capabilities. Accordingly, the invention is not limited to the embodiments presented herein but is to the maximum extent not inconsistent with the principles and novel features disclosed herein.

Claims (55)

A system for reducing interference in a time division multiple access communication system having a plurality of communication devices, wherein the plurality of communication channels are divided into cycles of time intervals. (a) the plurality of communications to continuously transmit an information signal in at least one of the predetermined time intervals in a first one of the plurality of communication channels, and continuously transmit radio frequency energy for the remainder of the time intervals. Means for instructing a first communication device of the device; And (b) in the first communication device, in response to the command means, continuously transmit the information signal in the first communication channel for at least one of the predetermined time intervals, Means for continuously transmitting radio frequency energy during the remainder, wherein the disturbance is reduced closer to the first communication device due to the continuous transmission. The method of claim 1, The instructing means instructs the first communication device to continuously transmit radio frequency energy in the first communication channel during the rest of the time intervals, wherein the transmitting means is in the first communication channel during the rest of the time intervals. And continuously transmitting radio frequency energy in the system. The method of claim 1, The instructing means instructs the first communication device to continuously transmit radio frequency energy in a second of the communication channels during the remainder of the time intervals, wherein the transmitting means is adapted to perform the rest of the time intervals during the rest of the time intervals. Continuously transmitting radio frequency energy in a second communication channel. The method of claim 2, (a) continuously transmitting an information signal in at least one of the predetermined time intervals in a second one of the plurality of communication channels, and continuously transmitting radio frequency energy in the second communication channel during the remainder of the time intervals. Means for instructing a second one of the plurality of communication devices to transmit; And (b) in the second communication device, in response to the command means, continuously transmit the information signal in the second communication channel for at least one of the predetermined time intervals, And means for continuously transmitting radio frequency energy in the second communication channel during the remainder, wherein the disturbance is reduced closer to the second communication device due to the continuous transmission. The method of claim 3, wherein (a) continuously transmit an information signal in at least one of the predetermined time intervals in one of the plurality of communication channels, and continuously transmit radio frequency energy in the second communication channel during the remainder of the time intervals. Means for instructing a second communication device of the plurality of communication devices; And (b) in the second communication device, in response to the command means, continuously transmit the information signal during at least the one of the predetermined time intervals, and in the second communication channel during the remainder of the time intervals. Means for continuously transmitting radio frequency energy, wherein the disturbance is reduced closer to the second communication device due to the continuous transmission. A method for reducing disturbances in a time division multiple access communication system having a plurality of communication devices, wherein the plurality of communication channels are divided into cycles of time intervals. (a) the plurality of communications to continuously transmit an information signal in at least one of the predetermined time intervals in a first one of the plurality of communication channels, and continuously transmit radio frequency energy for the remainder of the time intervals. Instructing a first communication device of the device; And (b) in the first communication device, in response to the command step, continuously transmit the information signal in the first communication channel for at least one of the predetermined time intervals, Continuously transmitting radio frequency energy during the remainder, wherein the disturbance is reduced closer to the first communication device due to the continuous transmission. The method of claim 6, The commanding further comprises instructing the first communication device to continuously transmit radio frequency energy in the first communication channel during the remainder of the time intervals, wherein the transmitting step is performed during the remainder of the time intervals. Continuously transmitting radio frequency energy in the first communication channel. The method of claim 6, The commanding further comprises instructing the first communication device to continuously transmit radio frequency energy in a second of the communication channels during the remainder of the time intervals, wherein the transmitting step comprises the time interval Continuously transmitting radio frequency energy in the second communication channel during the remainder of the channel. The method of claim 7, wherein (a) continuously transmitting an information signal in at least one of the predetermined time intervals in a second one of the plurality of communication channels, and continuously transmitting radio frequency energy in the second communication channel during the remainder of the time intervals. Instructing a second one of the plurality of communication devices to transmit; And (b) in the second communication device, in response to the command step, continuously transmitting the information signal in the second communication channel for at least one of the predetermined time intervals, Continuously transmitting radio frequency energy in the second communication channel during the remainder, wherein the disturbance is reduced closer to the second communication device due to the continuous transmission. The method of claim 8, (a) continuously transmit an information signal in at least one of the predetermined time intervals in one of the plurality of communication channels, and continuously transmit radio frequency energy in the second communication channel during the remainder of the time intervals. Instructing a second one of the plurality of communication devices; And (b) in the second communication device, in response to the command step, continuously transmitting the information signal during at least the one of the predetermined time intervals, and in the second communication channel during the remainder of the time intervals. Continuously transmitting radio frequency energy, wherein the disturbance is reduced closer to the second communication device due to the continuous transmission. A communication device operating in a time division multiple access communication system in which a plurality of communication channels are divided into cycles of time intervals, (a) a transmitter; And (b) instructing the transmitter to continuously transmit an information signal for at least one of the predetermined time intervals in a first one of the plurality of communication channels, and continuously transmit radio frequency energy for the remainder of the time intervals. Wherein the disturbance is reduced closer to the communication device due to continuous transmission. The method of claim 11, And the controller instructs the transmitter to continuously transmit radio frequency energy in the first communication channel for the remainder of the time intervals. The method of claim 11, And the controller instructs the transmitter to continuously transmit radio frequency energy in a second one of the plurality of communication channels for the remainder of the time intervals. A system for reducing interference in a time division multiple access communication system having multiple communication devices, wherein multiple communication channels are time and frequency divided into cycles of slots, the method comprising: (a) continuously transmit an information signal during at least one predetermined slot of a first communication channel of the plurality of communication channels, and continuously transmit radio frequency energy during the remaining slots of the first communication channel. Means for instructing a first communication device of the plurality of communication devices; And (b) in the first communication device, in response to the command means, continuously transmit the information signal during the predetermined at least one slot of the first communication channel, and the remaining slots of the first communication channel. And means for continuously transmitting radio frequency energy, wherein the disturbance is reduced closer to the first communication device due to the continuous transmission. The method of claim 14, Said cycle of slots comprises eight slots, each of said eight slots having a duration of about 577 kHz and a frequency bandwidth of about 200 kHz. The method of claim 15, The first communication channel is fixed in frequency, and the remaining ones of the plurality of communication channels are frequency sensitive. The method of claim 15, Wherein each channel of the plurality of communication channels is frequency sensitive. The method of claim 14, The cycle of slots comprises six slots, each of the six slots having a duration of about 3.33 kHz and a frequency bandwidth of about 30 kHz. The method of claim 18, And wherein said first communication channel is fixed in frequency. The method of claim 18, Wherein each of the plurality of communication channels is frequency fixed. The method of claim 14, (a) continuously transmitting an information signal during at least one predetermined slot of a second communication channel of the plurality of communication channels, and during a remaining slot of the second communication channel in the second communication channel; Means for instructing a second one of the plurality of communication devices to continuously transmit energy; And (b) in the second communication device, in response to the command means, continuously transmit the information signal during the predetermined at least one slot of the second communication channel, and in the second communication channel the second communication. Means for continuously transmitting radio frequency energy during the remaining slots of the channel, wherein the disturbance is reduced closer to the second communication device due to the continuous transmission. The method of claim 21, Said cycle of slots comprises eight slots, each of said eight slots having a duration of about 577 kHz and a frequency bandwidth of about 200 kHz. The method of claim 22, The first and second communication channels are frequency fixed, and the remainder of the plurality of communication channels is frequency sensitive. The method of claim 22, Each of said plurality of communication channels is frequency sensitive. The method of claim 21, The cycle of slots comprises six slots, each of the six slots having a duration of about 3.33 kHz and a frequency bandwidth of about 30 kHz. The method of claim 25, And said first and second communication channels are fixed in frequency. The method of claim 25, Wherein each of the plurality of communication channels is frequency fixed. A system for reducing interference in a time division multiple access communication system having multiple communication devices, wherein multiple communication channels are time and frequency divided into cycles of slots, the method comprising: (a) continuously transmitting an information signal during at least one predetermined slot of a primary communication channel of the plurality of communication channels, and continuously transmitting radio frequency energy during the remaining slots of an auxiliary communication channel of the plurality of communication channels; Means for instructing a first one of the plurality of communication devices to transmit to the network; And (b) in the first communication device, in response to the command means, continuously transmit the information signal during the predetermined at least one slot of the primary communication channel, and wirelessly during the remaining slots of the secondary communication channel. Means for continuously transmitting frequency energy, wherein the disturbance is reduced closer to the first communication device due to the continuous transmission. The method of claim 28, Said cycle of slots comprises eight slots, each of said eight slots having a duration of about 577 kHz and a frequency bandwidth of about 200 kHz. The method of claim 29, The auxiliary communication channel is fixed in frequency, and the remaining channels of the plurality of communication channels are frequency sensitive. The method of claim 29, Each of said plurality of communication channels is frequency sensitive. The method of claim 28, Said cycle of slots comprises six slots, each of said six slots having a duration of about 3.33 kHz and a frequency bandwidth of about 30 kHz. The method of claim 32, The auxiliary communication channel is fixed in frequency. The method of claim 32, Wherein each of the plurality of communication channels is frequency fixed. The method of claim 28, (a) continuously transmitting an information signal during at least one predetermined slot of one of the plurality of communication channels and continuously transmitting radio frequency energy during the remaining slots of the auxiliary communication channel. Means for instructing a second communication device of the plurality of communication devices; And (b) in the second communication device, in response to the command means, continuously transmit the information signal during the predetermined at least one slot of the one of the plurality of communication channels, and the auxiliary communication Means for continuously transmitting radio frequency energy during the remaining slots of the channel, wherein the disturbance is reduced closer to the second communication device due to the continuous transmission. 36. The method of claim 35 wherein Said cycle of slots comprises eight slots, each of said eight slots having a duration of about 577 kHz and a frequency bandwidth of about 200 kHz. The method of claim 36, The auxiliary communication channel is fixed in frequency, and the remaining ones of the plurality of communication channels are frequency sensitive. The method of claim 36, Each of said plurality of communication channels is frequency sensitive. 36. The method of claim 35 wherein The cycle of slots comprises six slots, each of the six slots having a duration of about 3.33 kHz and a frequency bandwidth of about 30 kHz. The method of claim 39, The auxiliary communication channel is fixed in frequency. The method of claim 39, Wherein each of the plurality of communication channels is frequency fixed. A communication device operating in a time division multiple access communication system in which a plurality of communication channels are time and frequency divided into cycles of slots, (a) a transmitter; And (b) the transmitter to continuously transmit an information signal during at least one predetermined slot of a first communication channel of the plurality of communication channels, and continuously transmit radio frequency energy during the remaining slots of the first communication channel. And a controller instructing the communication device, wherein the disturbance is reduced closer to the communication device due to continuous transmission. The method of claim 42, Said cycle of slots comprises eight slots, each of said eight slots having a duration of about 577 kHz and a frequency bandwidth of about 200 kHz. The method of claim 43, The first communication channel is fixed in frequency, and the remaining channels of the plurality of communication channels are frequency sensitive. The method of claim 43, Wherein each of the plurality of communication channels is frequency sensitive. The method of claim 42, Said cycle of slots comprises six slots, each of said six slots having a duration of about 3.33 kHz and a frequency bandwidth of about 30 kHz. The method of claim 46, And said first communication channel is fixed in frequency. The method of claim 46, Wherein each of the plurality of communication channels is frequency fixed. A communication device operating in a time division multiple access communication system in which a plurality of communication channels are time and frequency divided into cycles of slots, (a) a transmitter; And (b) continuously transmitting an information signal during at least one of said predetermined slots of a primary communication channel of said plurality of communication channels, and continuously transmitting radio frequency energy during the remaining slots of an auxiliary communication channel of said plurality of communication channels. And a controller instructing the transmitter to transmit, wherein the disturbance is reduced closer to the communication device due to continuous transmission. The method of claim 49, Said cycle of slots comprises eight slots, each of said eight slots having a duration of about 577 kHz and a frequency bandwidth of about 200 kHz. 51. The method of claim 50 wherein The auxiliary communication channel is fixed in frequency, and the remaining channels of the plurality of communication channels are frequency sensitive. 51. The method of claim 50 wherein Wherein each of the plurality of communication channels is frequency sensitive. The method of claim 49, Said cycle of slots comprises six slots, each of said six slots having a duration of about 3.33 kHz and a frequency bandwidth of about 30 kHz. The method of claim 53 wherein The auxiliary communication channel is fixed in frequency. The method of claim 53 wherein Wherein each of the plurality of communication channels is frequency fixed.