Digital radiotelephone system, subscriber unit, and how they adapt to the increased subscriber load

 

(57) Abstract:

In a digital radiotelephone system uses a vocoder for converting analog speech signal into a digital format suitable for transmission over a radio. Under most circumstances for optimal sound quality selects the maximum data rate. If the employment of the system exceeds a specific threshold value that is defined at a fixed station system, some or all vocoders are given the command to switch to a lower data rate to increase the number of communication channels. In addition, a portable subscriber unit can autonomously switch the data rate of its vocoder depending on the charge status of the batteries. 4 C. and 6 C.p. f-crystals, 8 ill., table 1.

The invention relates to radiotelephone systems, in particular to a digital radiotelephone systems, with the possibility of adaptation to high subscriber load.

Almost every radiotelephone system serves a large number of subscribers with the Central fixed station, which provides subscribers with communication channels as they need and as subscribers Paraiso available communication channels. This problem is solved in different ways, including transferring the caller a busy signal (i.e., merely the denial of services) and the creation of cellular systems that have the ability to reduce the size of service areas (cells) and therefore to place a greater number of cells, i.e., more channels of communication within the geographic area. It is obvious that denial of service is an unacceptable solution, and the procedure of dividing cells and redistribution is characterized by low performance and lack of sensitivity for dynamic radio system.

As another way of increasing the number of channels available to subscribers, was proposed digital radio service. Two of the most promising digital method, namely the method of time-division and method of code division, increase the availability of channels due to the separation of the physical resources among the subscribers. Simply put, analog signals (such as sound) is converted into the vocoder into a digital signal format conversion with a certain sampling frequency, and a special data compression technologies. The compressed data are combined with the signal of a temporary or code division code division, expands and restores the discretized data in the process, the complementary conversion before transmission. This provides a reproduced analog signal in the receiver.

Radiotelephone network is bidirectional in the sense that the fixed station transmits and receives voice signals converted by the vocoder, and the subscriber device respectively transmits and receives the converted vocoder signals. To ensure compatibility between the transmitting and receiving devices require conversion speed and compression methods were opposite and equal. Whatever the speed was not used in the process of analog-to-digital conversion, it should be comparable with the corresponding digital to analog conversions. It should be noted that, in General, the lower the data rate in bits per vocoder, the higher the number of available channels, but the quality of the speech signal thus deteriorating.

It was suggested to do rate vocoding variables to encode speech signals at speeds that depend on the characteristics of the encoded speech signal. In order to transmit the voice signal is optimal to and stops to talk, the vocoder variable speed reduce speed, thus lowering the average speed for each speaker that allows the system to provide more communication channels.

However, even when using the above-described technology, it is impossible to get a wireless system that offers a sufficient number of effective channels of communication to servicing a large number of subscribers.

A brief description of the drawings: Fig. 1 is a simplified diagram of the radiotelephone system in which can be used in the present invention; Fig.2 is a block diagram of a transmitter system with code division multiplexing (CDMA), which can be used in the present invention, Fig.3 is a block diagram of a CDMA receiver, which can be used in this invention; Fig.4 is a block diagram of a fixed station, illustrating a hardware configuration that can be used in this invention; Fig.5-sequence of operations of the process used by the controller station according to Fig.4 to control the reduction rate of the vocoder; Fig. 6 - the sequence of operations of the process used by the controller station according to Fig.4 to control the increase rate of the vocoder; Fig.7 is a sequence agosti vocoder; Fig.8 - sequence of operations alternative process used by the controller station according to Fig.4 to control the speed of the vocoder.

The use of digital technologies to increase the capabilities of the system provides the ability to use digital compression data messages. However, reducing the speed of data transmission quality of an audio message. Since the improvement in sound quality is only possible when using higher data transmission speeds, it is desirable to use such higher speeds. At certain time intervals, for example at peak times and in certain places, for example in a crowded space, capital cities, subscriber load on the radio link exceeds the number of available channels. Because of the reduced speed data cover a smaller portion of the radio spectrum, while reducing data transmission speeds can serve more subscribers. The desire of customers to get the service is satisfied at the cost of losing sound quality at low data rates. Some subscribers may require no change in the sound quality at a higher rate to get staeblein, schematically depicted in Fig.1. Radiotelephone system with a service area 101 depicted in the geographic area of a hexagonal shape, serviced by the fixed station 103. Fixed station 103 typically includes transceivers, controllers and phone interfaces that interact to provide two-way radio communication with the subscriber device 105. A large number of subscriber devices (not shown) as a transport and portable, can be operated at a fixed station 103 in the geographic service area 101. Other service area 107 and 109 may be located near or adjacent to the service area 101, and can provide wireless services to subscribers in the service areas 107 and 109 with fixed stations 111 and 113, respectively. In a preferred embodiment of the present invention uses digital modulation for multiple access systems with code division multiplexing (CDMA), in particular such as described in EIA/TIA/IS-95 "Standard compatibility the mobile station with the base station for operating in two modes of cellular systems with spread spectrum with a broad band of frequencies".

In Fig.2 depicts a block diagram of A, for example, sound, entered into the vocoder 201 for converting into digital form and processing prior to transmission. The output signal from the vocoder 201 is entered into the encoder 203 associated with the mixer 205, and is mixed with the radio frequency carrier produced by the oscillator carrier frequency 207. The selected output signal of the mixer 205 is transmitted to the amplifier 209 for further transmission. The vocoder 201 and the encoder 203 is managed by the resource controller 211. The resource controller 211 may be a General-purpose computer with associative memory 213. Clock generator 215 provides an output clock signal for the encoder 203, a velocity-dependent synchronization, uploaded ZU 213 in accordance with the resource controller 211. Cipher 217 serves as a buffer that contains the code that is loaded from the memory 213 in accordance with the resource controller 211. Cipher is usually a pseudo-random number used to generate a repeating sequence of digital numbers to encode the output of the vocoder 201. The generator carrier frequency 207 also is programmed to the frequency specified by the value loaded from the memory 213. Thus, the encoder 203 together with input cipher 217 provides pseudolocal and resource controller 211. Many of the frequencies that define the resources link in the table of frequencies in the memory 213. This frequency table can be created after launch, depending on the assigned frequency spectrum and bandwidth allocated to a system in which the transmitter. Because different, not creating interference signals extended range can be transmitted on the same frequency, but at different ciphers, on the same frequency without mutual interference can be multiple communication channels.

Similar to the CDMA transmitters can be used on both fixed station and the subscriber device. In a preferred embodiment, the subscriber device may include a detector parameter 219, which is typically used to determine the conditions of the batteries and transfer this data to the resource controller 211.

Receiver for multiple access systems with code division multiplexing (CDMA), which can be used in the subscriber device according to the present invention, shown in the flowchart of Fig.3. The generator carrier frequency 301 generates a signal to the mixer 303 so that the received signals can be converted in podczeck, is depicted in Fig.2, the pseudorandom number generator of the decoder 305 in conjunction with a clock generator 307 and the buffer cipher 309 retrieves data generated by the vocoder 201, and transmits the data to the vocoder 311. Sync codereuse pseudo-random number and a specific carrier frequency is carried out in the usual way controller 313 and the associated memory 315.

Similar receivers can be included in the fixed station 103, a simplified block diagram of which is shown in Fig.4. Transceivers and vocoders depicted in blocks 401 and 403. These transceivers together with all the other connected to the antenna system 405 for transmitting signals in the service area and receive from it. To the antenna system 405 is also connected to the signal Converter 407, which filters and combines the whole range of radio frequencies used by all transmitting devices operating at a given fixed station. The output signal of the inverter 407 is transmitted to the detector of the employment spectrum 409 to determine the number of user devices operating at this time, and transmitting signals at a fixed station. In a preferred embodiment, the detector shareenum received signals in the busy operating frequency range of the fixed station. This signal is an output signal to the controller station 411, which among other functions compares this output signal from the detector employment 409 with a threshold value corresponding to a known number of subscriber devices, representing a particular system operator percentage of the total bandwidth of a given fixed station. If the threshold is blocked, the controller station 411 generates one or more output signals for vocoders transceiver devices 401 and/or vocoder transmitting-receiving device 403, giving the command to the selected vocoder to reduce its sample rate. A corresponding message is transmitted to the controller of the subscriber device associated with the selected transceiver device, instructing the subscriber unit to operate with a speed corresponding to the speed of the vocoder at a fixed station.

Characteristic feature of the present invention is that the data rate vocoder fixed station and associated vocoder subscriber device can be adjusted in accordance with the number of subscriber devices served with this fixed is. ontroller station 411 measures the level of the output signal of the detector employment 409 (operation 501), and determines whether exceeds this level threshold employment, set in the fixed station (503). If this threshold is not exceeded, the controller station 411 is returned to its other functions, including periodic re-measurement of the level detector of employment. If this threshold is exceeded, the search (505) on the list of low-priority devices stored in the fixed station, and identifies devices that are serviced at the moment. Defined (507), milestones whether the low priority of subscribers served at the moment, vocoders fixed station, a subscriber unit to a low data rate. If there is a low-priority subscribers, vocoders which operate with high data rate is identified (509) specific low-priority subscriber, a serving transceiver and associated vocoders. After that related vocoders given command (511) to reduce the data rate. If you find that all low-priority subscribers currently have to work with a low data rate (507), then of Semenych (513).

In Fig. 6 shows a complementary procedure to return the data transfer rate in vocoders to normal high speed. Plant controller 411 receives a signal from the detector employment 409 and measures (601) level detector of employment. Defined (603), if the level detector is below the return threshold employment (i.e., the threshold below which you want the switch to the high sampling rate to provide hysteresis). If the detector does not return below the threshold of employment, procedures controller station returned to its other functions. The level detector is below the return threshold employment encourages plant controller 411 search (605) on the list of high-priority subscriber devices served at this time. If not all high-priority subscriber unit returned to the high speed data transmission (607), the correlation (609) between high-priority subscriber devices and serving their transceivers. Then the command is given (611) related vocoders to increase their data transfer rate. If all high-priority subscriber unit returned to the high speed data transmission (607), then all in the normal operation mode.

Alternatively, subscribers may be given the command to switch to the low data rate increments. As shown in Fig.7, if it is determined that not all low-priority subscribers operate at a low data rate (507), is an arbitrary choice (707) number of M subscribers (which may be M = I). These selected low-priority subscribers are correlated with service transceivers (705) and related vocoders given command (509) go on a low speed data transmission.

If all low-priority subscribers are low-speed data subscribers list is searched high priority subscribers at the moment (707). Defined (709) whether all high-priority callers are working with a low data rate. If not, you can make a selection (711) K high priority subscribers, working with high speed data transfer (which may mean K = 1 and/or M-K). These selected subscribers are correlated with serving their transceivers, and related vocoders given command (715) go on a low speed data transmission.

To gradually return to service the version, is depicted in Fig.8. If defined (607) that not all high-priority callers returned to work at high speed, is an arbitrary choice (803) N high-priority subscribers (possibly N = 1), using a low data rate. These selected subscribers are correlated with serving their transceivers (805), and related vocoders given command (611 ) go for high speed data transfer.

If all high priority subscribers have high speed data transmission, according to the list of subscribers to search those low-priority customers who currently are served by the system (807). Defined (809), whether there were any low-priority subscribers, working with a low data rate, and if so, selects a random number L such subscribers (811). The number of subscribers can be L = 1 and L M. the Selected low priority subscribers are correlated with serving their fixed transceiver (813), and related vocoders are given the command to switch to high speed data transmission (815).

In systems where priority subscribers can be assigned additional levels priorityareas data while the other vocoders selected subscribers may not be given the command to switch to high speed data transmission. For example, subscribers using radio system for communications related to public safety, may always require the highest quality sound. On the other hand, some subscribers may require only minimal communication capabilities, and they may accept slightly lower quality sound for a smaller monthly fee. For a system that uses these classes of priority, is characterized by release from the commands to change the speed of data transmission according to Fig. 5 - 8.

The subscriber device in the preferred embodiment, also has a selectable rate vocoder depending on the specific operating parameters of the subscriber device. This quality is especially useful for portable subscriber units for which the importance of battery life, but can be used and other parameters of the portable device to run speed changes of the vocoder. Changing the operating characteristics of the device depending on the detected type of batteries are described in U.S. patent 5164652, and determining the status for the e energy. To extend battery life detector parameter batteries dynamically determines the remaining charge of the battery. If overlap threshold low charge level, the detector parameter 219 subscriber unit transmits a signal to the resource controller 211. Returny controller 211 generates and transmits a control message to reduce the data rate to the appropriate vocoder fixed station and also instructs the vocoder 201 subscriber device to reduce the data rate. For a subscriber using a portable subscriber unit provides increased battery life by reducing the quality of the audio signal converted by the vocoder.

Vocoders variable speed that can be used in the present invention, is described in the standard IS-96 Telecommunication Inductry Association (TIA) TR-45.5. Transmitting vocoder samples of the audio signal and generates a coded audio packet for transmission to the receiving vocoder. The receiving vocoder decodes adopted sound package in the sample audio signal. The vocoder according to the present invention uses an encoding algorithm linear prediction with coded excitation (CELP). about the time of analysis by the method of synthesis. The vocoder uses a variable bit rate of the output data depending on the loading of the channel system. During the processing of the vector is taken from the codebook of random Gaussian vectors (for 1/8 frequency generated random vector). This vector is multiplied by the gain, and then filtered by a filter with a long main tone (long term pitch filter) whose characteristics depend on the parameters of the fundamental tone. The output signal is filtered by filter formant synthesis, also referred to as linear coded filter with prediction to generate the speech signal. The speech signal is also filtered by the adaptive postfilter. In the encoding procedure the sampling of the input speech signal is 8 kHz. This sampled speech signal is divided into cycles of vocoder 20 MS, consisting of 160 samples. The coefficients of the linear encoder filter with prediction adjusted once in each cycle regardless of the selected baud rate. The number of bits used to encode the parameters of a linear coding with prediction is a function of the selected data transfer rate. In each cycle parameters main tone adjusted pererasti data. Similarly, the parameters codebook adjusted variable number of times, where the number of corrections is a function of the selected data transfer rate.

The table lists the main parameters used for each speed. The number of bits per block adjustment LPC in the table means the number of bits in a given bit rate to encode the LPC coefficients. Each block of main tone corresponds to the adjustment of the primary colors in each cycle and the number in each block of the primary current is equal to the number of bits used to encode the adjusted settings of the main tone. For example, at a frequency of 1 parameters of the primary colors are adjusted 4 times, once for each quarter cycle of the speech signal, each time we use 10 bits to encode the new settings of the main tone. As shown, this is done in different number of times for other speeds. Each block adjustments codebook corresponds to adjusting the codebook at each cycle, and the number in each block codebook corresponds to the number of bits used to encode the adjusted parameter code dictionary. For example, when the on signal, each time we use 10 bits to encode the parameters. The number of adjustments decreases with decreasing speed.

1. Digital radiotelephone system that includes a fixed station 103 that contains the transceiver device 401 and the first vocoder 401 for converting the first analog signal into a digital signal at the first set speed transmission of data intended for transmission of signals in the service area 101 and receive from it while servicing multiple user devices 105 within the service area 101, and the first subscriber device 105 from a variety of subscriber devices 105 contains a second vocoder 201, converts the second analog signal into a digital signal at the first set speed data transfer, characterized in that it contains the detector system busy 409, connected to the transceiver device 401 that is designed to generate an output signal related to a certain number of the set of subscriber devices 105 that are serviced by the fixed station 103 in the service area 101, and the detector threshold 409, 411, designed to control the mentioned output th preset speed data transmission at the second set speed data transfer.

2. The system under item 1, characterized in that the transmitter 401 is designed to transfer the signal from the detector threshold 409, 411 to the second vocoder 201 through a fixed station 103.

3. The system under item 1 or 2, characterized in that the above-mentioned detector threshold 409, 411 provides the first threshold, when the overlap which mentioned output signal is generated by the command at least one of the first and second vocoders 401, 201 to reduce the first set of data transmission speed to the second speed data transfer.

4. System according to any one of paragraphs.1 to 3, in which the second vocoder 201 in each of the multiple subscriber devices 105 is designed to convert the second analog signal into a digital signal at the first set speed data transfer, characterized in that it contains the first group of subscriber devices 105, which is pre-assigned priority level, the priority list of subscribers and the device poll list to select the first group of subscriber devices 105 and the detector threshold 409, 411 is designed for monitoring the output signal and developing a team of at least one of the first and second vocoders viavai radiotelephone system, consisting of a fixed station 103 at least one transceiver device 401 and the first vocoder for converting the first analog signal into a digital signal at the first set speed data transmission when servicing multiple user devices 105 within the service area 101 of the fixed station 103, and each of the multiple subscriber devices 105 contains a second vocoder 201 for converting the second analog signal into a digital signal at the first set speed data transfer, characterized in that it contains the detector working parameter 219, designed to control operating characteristics of the subscriber device 105 and generate a signal when the overlap of the set threshold values, as well as the resource controller 211, used for receiving signal detector working parameter 219 and developing a team of at least one of the first and second decoders 401, 201 on the transition from the first speed data transmission at the second set speed data transfer.

6. The device under item 5, characterized in that the detector is working parameter 219 contains the detector charge status of the batteries.

7. Postema contains a fixed station with a transceiver device and the first vocoder for converting the first analog signal into a digital signal at the first speed data and signaling in the service area and receive from it, when servicing a variety of subscriber devices includes a second vocoder to convert the second analog signal into a digital signal at the first set speed data transfer, characterized in that it comprises the operation of determining the employment spectrum transceiver device and generate an output signal associated with some of the many subscriber devices served by a fixed station in the service area, and generate commands in response to the generated output signal at least one of the first and second vocoders on the transition from the first speed data transmission at the second set speed.

8. The method according to p. 8, characterized in that it includes the operation the development of this team at least one of the first and second vocoders to reduce the first set of data transmission speed to the second speed data at exceeding the mentioned output signal of the first threshold.

9. The method according to p. 8, characterized in that it comprises the operation of generating the commands at least one of the first and second vocoders to increase the speed of data transmission with the second set the s ' signal of the second threshold.

10. Adaptation mode subscriber device used in a digital radiotelephone system containing a fixed station at least one transceiver device and the first vocoder for converting the first analog signal into a digital signal at the first set speed data transmission, and a fixed station serves a variety of subscriber devices within the service area, and each of the multiple subscriber devices includes a second vocoder, designed for converting the second analog signal into a digital signal at the first set speed data transfer, characterized in that it comprises the operation of determining the working parameter of the subscriber device, whereby control of the operating characteristics and produce a signal when exceeding the threshold value, and operation of generation in response to this command signal, at least one of the first and second vocoders on the transition from the first speed data transmission at the second set speed data transmission.

 

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