JP2003506968A - Method and apparatus for supporting TDD / TTY modulation on a vocoded channel - Google Patents

Abstract

  (57) [Summary] Method and apparatus for maintaining TDD / TTY modulation over a vocoded channel A method used to encode / decode low activity communication signals for transmission by a telecommunications system (such as board sounds). Telecommunications system (100) may include any number of wireless links. Once the system (100) is notified that a low activity signal needs to be transmitted, each vocoder used to encode / decode that signal within the system 100 has a unique encoding / decoding function. Perform decryption processing. In one embodiment, the frame containing the error adversely affecting the signal is transmitted to the vocoder, and the "soft bits" contained therein are used to determine the transmitted original signal. In another embodiment, encoding the signal may include encoding the signal using redundancy with the encoded signal being spread over a multivocoder frame.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD OF THE INVENTION

In general, the present invention relates to a deaf telecommunications device (TDD) or text telephone yokes (TTY). More specifically, the present invention relates to a modification of standard vocoder operation that allows reliable transmission of TDD / TTY signals within a telecommunications system.

[0002]

[Prior art]

Many deaf or hearing-impaired people use communication terminals specially constructed and designed to allow them to communicate over standard telephone lines. Such devices, referred to as deaf telecommunications devices (TDDs) or text telephone yokes (TTYs), are collectively referred to as TDD in this application. A TDD typically includes a keyboard and a display connected to the phone through a modem (modulator / demodulator). The modem is built into the TDD and either connected directly to the telephone line or coupled by a voice coupler to a standard telephone handset. The TDD can transmit information over the telephone line using encoded voice to another TDD connected to the other end of the telephone line through another modem. These voices are called low activity communications because the frequency and amplitude envelopes remain relatively constant.

Codes and protocols that are in widespread and conventional use for TDD communications are idiosyncratic. The code set known as Baudot and the communication protocol (TDD protocol) evolved when many deaf telecommunications devices were based on mechanical or electrical equipment rather than electronic equipment. did. Therefore, the TDD protocol was created as a set of constraints that are no longer suitable for today's devices. These constraints serve to create a telecommunications network between users and devices operating under the code protocol and that protocol, which is somewhat outdated.

Traditionally, TDD communications are carried at 50 baud (45.5 baud in some countries), which represents a transfer of 6 characters / second. Other protocols now available for TDD communication include high baud rates, such as ASCII (American Standard Code for Information Exchange) and expansion board protocols. Anyway, the normal TDD communication character set consists of characters that are 5 bits long. These letters are similar to one letter in the alphabet where each letter represents a word or idea. One character is the overhead (ove
rhead) information bits, where each bit group to be transferred is 22
It has a period or unit interval equal to milliseconds. For example, under the traditional TDD protocol, a group of bits to be transferred consists of 8 bits: a start bit (1 source or zero bit), 5 bits to represent a character, and at least 1 and a half bits to mark the stopping point of a transfer group. .

Compared to modern telecommunication systems, TDD communication is done at a slower pace. A larger problem is that the TDD signal is substantially constant. These slow paced, monotonic signals disrupt (h) digital telecommunications systems that transmit higher activity signals at very high rates, especially in telecommunications systems that include wireless links.
avoc). One example of such a telecommunication system is a code division multiple access (CDMA) system having a large number of wireless subscriber units. Each subscriber unit has a transceiver and communicates through satellite repeaters or ground stations called cells within the system. Each cell comprises physical equipment called a base station. The cells cover a limited geographical area and send calls transmitted by subscriber units to and from telecommunications networks via mobile switching centers. When a subscriber moves within the geographic range of a new cell, the call routing for that subscriber is
Eventually it can be done through the new cell by a process called "handoff".

Subscriber units, commonly referred to as cell phones, transmit signals received by a base station. This signal is relayed to a mobile switching center that signals the public switched telephone network (PSTN), which includes telephone lines or other subscriber units. Similarly, signals can be sent from the PSTN via base stations and mobile switching centers to subscriber units.

The interface between the subscriber unit and the base station is the air interface
It is called (the air interface). The Telecommunications Industry Association (TIA) is a standard for CDMA call processing over air interfaces, entitled "IS-95 Mobile Station-Base Station Compatibility Standard (I-95) for Dual-Mode Broadband Spread Spectrum Cellular Systems."
S-95 Mobile Station-Base Station Com
Patiency Standard for Dual Mode Wi
deband Spread Spectrum Cellular System
The IS-95 appendix serves as the Telecommunications Service Bulletin (TSB). The standard IS-95 + TSB74 contains provisions for service negotiation on air interface, And incorporated by reference in this.

Service negotiation is critical to the successful transmission of some communication, especially low activity TDD communication, through a digital telecommunications system. One problem with modern systems, including those described above, is the system for encoding vocoder-voice or TDD analog signals into digital signals and for decoding digital signals into voice or TDD analog signals. The equipment used within is essentially having difficulty in processing monotone signals and low speed dictated by the TDD protocol. In current systems, low activity communication signals such as TDD communication will likely be treated by the vocoder as background noise or signal interference and will be ignored.

What is needed is a frame error rate that can be easily integrated into existing communication systems and by invoking a protocol to be used by a vocoder during the transmission of low activity communication signals. It is an invention that can reduce (error rates).

The present invention must be compatible with wireless telecommunication modulation systems, such as CDMA systems that serve a large number of system users. The stronger (r) of CDMA systems and technologies used within multiple access communication systems.
Obust) Discussed in U.S. Pat. No. 4,901,307, entitled "Spread Spectrum Access System Using Satellite or Terrestrial Repeaters (SPREAD SPECTR).
UM MULTIPLE ACCESS COMMUNICATION SYS
TEM USING SATELLITE OR TERRESTRIAL R
EPEATORS) ", which is assigned to the assignee of the present invention and incorporated herein by reference. Further, the present invention is also Time Division Multiple Access (TDMA), Frequency Division Multiple Access (FDMA). ), And amplitude modulation (AM
It must also match other modulation systems and techniques used within other types of communication systems, such as PS) schemes.

[0011]

[Means for Solving the Problems]

Broadly, the invention includes modulation of low activity communications by a telecommunications system using coded signals and increased transmit power levels. More specifically, the present invention relates to methods of using specialized encoding, decoding, or both on low activity communication signals to minimize the frame error rate of the transmitted signal. The present invention also attempts to determine the error frame in an attempt to determine the content of the original frame.
provides decoding of low activity signals by looking at "soft bits" contained in the frame (erred frame) or adjacent to the error frame
).

Embodiments of the present invention provide a unique decoding method for TDD signals encoded using standard encoding protocols. In one embodiment, the decoder vocoders frames containing transmission errors (error frames) from a known TDD signal (voc).
The most likely vocoder processed frame transmitted can be determined by comparison with the oded frame. In another embodiment, the decoder may review adjacent frames to determine the most properly vocoder processed frame that was transmitted and received in error. In yet another embodiment, the decoder is a signal enhancer or relay that "cleans up" corrupted bits in a transmitted frame before the decoding method is applied to the transmitted frame. Can be modified to include a vessel. And while TDD communications are discussed throughout this application, it should be understood that any slow or low activity communications may be transmitted using this invention.

Another embodiment of the invention provides decoding as discussed above, but incorporates vocoder parameters that differ from the standard vocoder parameters. TD
When receiving the D signal, switch the encoder to "board coding mode", notify the decoder of protocol changes, and use the channel coding redundancy to get the correct TDD signal in the bad frame. It further improves the opportunity for the decoder to determine the exact TDD signal sent, even if included. This version of the invention separates the standard vocoder parameters by better spacing and makes it easier to distinguish them between voices.
re) ”.

Another version of the invention provides for encoding a TDD signal within a vocoder frame that uses redundancy, but is encoding over multiple vocoder frames. The information is interleaved over "N" frames so that if a frame is lost, the decoder can extract the necessary information from adjacent frames to determine the contents of the lost frame.

Yet another version of the invention provides an efficient cost system for combining the previously described encoding and decoding methods of the invention with a method for transmit power level control. Modifying the standard vocoder chipset design within a mobile station is expensive and hampers the implementation of the encoding and decoding methods described above. However, it is possible to implement a communication system in which the method described above is used in the base station of the system, but not in the mobile station. Uncorrected (unm
odified) The frame error rate for low activity communication signals transmitted to the vocoder is
Methods for controlling the transmit power level can be used to minimize.

The present invention offers its users a number of advantages. One advantage is that TDD messages can be transmitted using digital transmission media with wireless links. Yet another advantage is that the TDD device can be connected to a mobile device or subscriber unit, such as a digital cellular telephone, which is connected to a telecommunication system by a wireless link. This invention also provides a number of other advantages and benefits that will become even more apparent after reviewing the detailed description of the invention below.

[0017]

DETAILED DESCRIPTION OF THE INVENTION

The nature, objects and advantages of the present invention will become apparent to those skilled in the art after considering the following detailed description, in connection with the accompanying drawings, in which the same parts are designated by the same reference numerals here and throughout. Will.

1-7 illustrate examples of various methods and apparatus of the present invention. For ease of explanation, but without any intended limitation, these examples are described with respect to a TDD communication device attached to a digital telecommunications system incorporating a wireless link, one example of which is as follows. Described.

Hardware Components and Interconnects FIG. 1 illustrates one type of telecommunications system 100 that includes a wireless link and a TDD communication device (TDD) 200 as used in the present invention. As shown in detail in FIG. 2, a TDD typically includes a keyboard and display that is connected to the phone through a modem (modulator / demodulator). The modem is built into the TDD and either connected directly to the telephone line or coupled by a voice coupler to a standard telephone handset. The TDD can transmit information over the telephone line using encoded voice to another TDD, such as the TDD 102 shown in FIG. 1, connected to the opposite end of the telephone line through another modem. .

In a digital telecommunications system using a wireless link, TDD 200 may be combined with a subscriber unit 104 used within telecommunications system 100 to transmit received signals. An exemplary embodiment of subscriber unit 104 is a digital signaling telephone, such as the Q-800 manufactured by Qualcomm, Inc., and commonly referred to as a cell telephone. Subscriber unit 10 as shown in FIG.
4 includes a notifying apparatus 106 communicatively connected to the circuitry of the subscriber unit 104. The hard wire 108 is TDD200.
Subscriber unit 1 via notification device 106 or device port
04 may be used to connect. An example of such a notification device or device port is U.S. patent application, entitled "TDD / T Through Vocodered Channels."
Method and apparatus for establishing TY service (METHOD AND APPA
RATUS FOR ESTABLISHING TDD / TTY SERVI
CE OVER VOCODED CHANNELS), Application No. 09/114
, 344, filed Jul. 13, 1998, assigned to the assignee of the present invention and incorporated herein by reference.

Device ports may be configured to receive low activity communication device attachments such as plugs, connectors or receivers. These items are commonly used today to connect telephones and computing devices and are readily available from electronics suppliers. The device port interfaces with the attachment to communicatively connect a low activity communication device (not shown), such as the TDD 200, to the subscriber unit 104 of the telecommunications system 100. The device port allows information to be exchanged between the low activity communication device and the subscriber unit 104. Notification device 10 regardless of whether the device port or hardwire is used.
6 allows the system 100 to be notified that a TDD signal needs to be transmitted.

Returning to FIG. 1, after notification device 106 receives the low activity communication signal, subscriber unit 104 processes the signal. Very basically, the signal for transmission is formed by including the information contained in the low activity signal. The telecommunications system 100 is informed that a low activity signal is being sent so that the system is readable.
herable) Respond to ensure transmission. For example, the analog signal received from the analog circuit 228 shown in FIG. 2 digitizes the signal, sets the transmit power level to protect against signal fading during transmission, compresses the signal. And will undergo signal or "voice" processing, including filtering and filtering. These functions include subscriber units 10 including vocoders.
4 circuits (not shown). Depending on the signal received, a variable rate vocoder (collectively referred to in this application as a vocoder) dynamically determines and negotiates services within telecommunications system 100 to provide for successful signal transmission and decoding. You can (negotiate). This negotiation is like the rate, transmit power, and compression techniques that the vocoder will use,
Includes establishing values for multiple parameters. A more thorough discussion of the processing of signals for transmission in telecommunications systems is provided by the Electronics Industry Association standard TIA / E.
IA / IS-95-A entitled "Mobile Station-Base Station Compatibility Standard (Mobile Station for Dual Mode Wideband Spread Spectrum Cellular Systems).
-Based Station Compatibility Standard
d for Dual-Mode Wideband Spread Spec
Other Cellular Standards, known as "IS-95", incorporated herein by reference, and including standard vocoder protocols are well known.

However, when a low activity signal is received, the vocoder can identify the signal as either noise, a pause, or a signal not intended to be transmitted. Simply, the vocoder does not know the low activity signal received and thus does not know what service is used. By notifying system 100 that a low activity signal is being sent, the vocoder will establish the service necessary to ensure the most likely transmission and decoding of the signal.

The low activity communication signal may be transmitted over the wireless link 114 using the antenna 112 after being processed and service determined. The digitized signal is transmitted to another antenna 1 at a remote location, such as base station 118.
16 and is processed by base station circuitry (not shown) including vocoder 120. Various base station circuit arrangements for telecommunications systems are well known, and a further understanding is provided by the above referenced TIA / EIA / IS-95-
Can be found in A. By processing the signal after receipt, the low activity signal, which reflects the information contained in the transmitted low activity signal, can be delivered to the low activity device 102 through the communication link 120. . Second notification device 106 is shown coupled to base station 118. This provides a low activity signal to be returned from the low activity communication device 102 to the TDD communication device 200.

Communication link 120 is shown bifurcated to emphasize that base station 118 may not be directly connected to low activity device 102. Base station 118 is typically connected to a standard PSTN switching center commonly used by telephone companies for telephone call coordination, and low activity equipment 1
02 is connected to PSTN. In another example, a second mobile station (not shown) connected to the low activity device 102 may be linked to the base station 118. Further, the telecommunications system may include a mobile switching center as described above.

Shown in FIG. 2 is a schematic block diagram of the circuitry of a typical TDD device 200, either standard TDD or extended TDD, operating in accordance with the present invention. Figure 2
The TDD device 200 is provided with a keyboard 202 into which a user can enter data characters. The output of keyboard 202 is connected to a processor 204 which serves to control the circuit elements contained within FIG. The characters sent and received by the processor 204 are also displayed on the display 206. Optionally, the same characters sent and received can be reproduced on a device such as printer 208. While it is standard for TDD to have some sort of visual display so that the user can see the characters typed in and received, some TDD devices may not have a printer. The keyboard 202 thus serves as an input source of data characters to the processor 204, while either or both of the display 206 and the printer 208 serve as local destinations for data stream characters.

The processor 204 can be connected by any suitable data or address bus that would typically be used by one schooled in the art for this type of application. . In FIG. 2, the bus 210 includes a read only memory (ROM) 212 and a nonvolatile random access memory (NVRA).
M) Connect to 214. Dedicated control lines 216 and 218 provide ROM 212 that provides interactive control of these units from processor 204.
And NVRAM 214. ROM 212 is intended to permanently store programs that dictates the operation of processor 204 as well as some data used by the programs. For example, special strings for machine-to-machine communication and for synchronizing two TDDs in extended operating mode.
) May be accumulated. The NVRAM 214 is used as a buffer for the TDD device 200.
Used as a floating storage location for data coming in or out of, and for the storage of standard messages as entered by the user through the keyboard 202 and designated as intended for rapid. . Other circuitry may be used, such as connecting the microprocessor 204 with the ROM 212 and NVRAM 214 in a single integrated circuit. Also connected to the processor 202 in FIG. 2 is a telephone keypad 22.
0, which allows the entry of a telephone number for dialing by the processor 202 through the telecommunication system 100. Standard telephone handset 22
4 rests on a cradle 226 that incorporates a switch (not shown) that indicates whether the handset 224 is in use and therefore removed from the cradle 226.

The processor 204 is communicatively coupled to the telecommunications system 100 via analog circuitry 228. This connection is shown as a hardwire connection 230, but may be any type of connection that allows the analog circuit 228 to be communicatively linked to the telecommunications system 100. The analog circuitry 228 provides a connection between the handset and the processor 202 that allows both board and dialing tones to be received by the telecommunications system 100. The analog circuitry 228 provides an interface for voice information to and from the handset 224. TDD device 200
Analog circuit 228 is connected to telecommunications system 100 using a connector such as the devices discussed above.

Notwithstanding the particular preceding description, a person of ordinary skill in the art who shares the benefit of this disclosure will appreciate that the apparatus discussed above may be used in telecommunication systems of different configurations without departing from the scope of the invention. It will be appreciated that it may be implemented. As a particular example, multiple subscriber units 104 may be linked to base station 118, or low activity communication device 200 may be integrated with subscriber unit 104.

Operation After the TDD signal is received, throughout the signal processing, the vocoder used by the system 100 is notified that a low activity signal has been received for transmission.
), Or 1/8 rate traffic channel frames can be used to detect and transmit the signal. However, as discussed below, application of the following methods for quarter to full rate traffic channel transmission may be undertaken.

FIG. 3 shows a typical variable rate vocoder frame format for a traffic channel using rate setting 1. A variable rate vocoder uses the well-known Code Excited Linear Prediction (CELP) technique to form one frame every 20 ms, which is a full, half, or quarter according to speech activity. Or can be initialized with a 1/8 rate format.If a board tone is received, the standard vocoder currently in use is assumed to be able to detect that it is sending a variable rate. Vocoders will usually detect low activity and will use the 1/8 rate format, typically the board signal will be treated as noise and generally ignored.

All rates refer to that each bit contained in each frame is not repeated. Half-rate corresponds to sending the same number of bits per frame, but each bit is repeated once in the frame, ie each unique bit will appear twice in the frame. A quarter rate corresponds to each unique bit appearing four times per frame, and so on. The more repetitive the information bits, the less total information is sent per frame. The given bit is only sent once, so
Signals at all rates are sent with higher power. This total rate power level is referred to as the reference power for the purposes of this application. Since the bits are repeated at a lower rate, the power is accumulated over the frame for each repeated bit, so
The reduced power level is used. Assuming a fixed minimum power is used for transmission, a full rate transmission will contain more frame errors than a half rate transmission of the same information.

The power level is typically set based on a selected frame error rate (FER) for a transmitted signal received at a remote location, such as a subscriber unit, which corresponds to the target of the transmitted signal. . The desired FER is selected because the real FER is increased using the present method when a low activity signal is being sent. This selected FER
Range between 0.1% and 1.0% error rate, but may be larger or smaller if necessary to preserve the quality of the transmitted signal. Preferably, 0.2% FER is desirable for low activity signals.

In the present invention, specialized encoding and decoding techniques control the frame error rate. In an environment where the disclosed technique falls short of the desired FER, the transmit power level (where FER is defined as the total number of erroneous frames even after restoration of the vocoder frame information) should be adjusted in It can also be used with specialized encoding and decoding techniques. Typically, the vocoder will be locked at full rate and the transmit power will be increased to transmit a low activity signal. It should be understood that any increase needed would still be less than the increase needed if this encoding / decoding technique were not implemented. A. Decoder Using Soft Bits In one embodiment, when a TDD call is received, the system 100 announces or detects the type of call. System 100 processes the call for transmission from TDD unit 200 using well-known standard processing techniques. The frame is remote,
When received at base station 118, for example, the call is decrypted using the present invention.
If a frame error occurs in the physical layer, that is, if the frame is IS-
If the checksum as described in 95 is not passed, the frame is still transmitted to the vocoder 120 for decoding. Transmitting the false frame to the vocoder is not currently done in the standard IS-95 embodiment. The bits contained in the false frame are not all likely to be in error, and the information is individually picked from them to recover the information contained in the false frame (g
leaned), so it is called “soft bit”.

However, the vocoder decoder in the present invention detects or is notified that a TDD call has been received and looks up the received vocoder parameters.
ng at) and these parameters with a TDD modulated signal or speech "signature" as found in the space of vocoder parameters to handle false frames. This is the TD that received the accumulated and vocoder processed TDD sound.
Compare with D sound. This comparison will probably be a decision made as to which TDD signal was received.

For example, the vocoder display of the board sound “0” is in sequence 16 “0”
Assume that the representation of the board tone "1" is represented as 16 "1". The method defines them as voice-parameter-spacing.
pace) ・ Think of it as a signature. For the following example, the three layers are identified as follows:

[Equation 1]

[0037] Suppose the vocoder decoder receives the following parameters:

[Equation 2]

The decoder recognizes board sound boundaries and recognizes that the receive parameters for the second board '0' are closer to '0' than '1'. Decoder is board sound '0
'Determine and fix suspected error bits before decryption.
For the next board sound '1', the decoder has a vocoder parameter of'0 '
Admit that you are approaching 1'and thus modify that bit. The decoder now uses the following sequence to form the corrected TDD signal:

[Equation 3]

This example shows an error transition (tra) that should occur at a frame boundary that is not always
nsitions). If these transitions are within one frame (fall withi
If n), another version of the invention can be used as follows.

If the vocoder decoder receives an erroneous frame that contains erroneous bits in its frame, the vocoder may examine adjacent non-errored or “good” frames to recover the erroneous frame. The adjacent frame will contain a portion of the board sound that was lost in the false frame. For example, suppose the following signals are received:

[Equation 4]

The vocoder parameters for the second board sound '0' make an accurate decision on the voice, as the number of '0's is almost the same as the number of'1's in the vocoder frame parameter. Too ambiguous for To make a better decision, the vocoder examines the next adjacent frame (vocoder frame 3) and decides that the speech will appear to continue as a '0' in this frame. The decoder therefore determines that this is a board '0' note in the second half of vocoder frame 2.

After determining in tasks 402 and 404 whether a low activity signal is being received, as shown in the flowchart of FIG. 4, the decoder continuously monitors the receive board sound boundaries in task 408. Update. Otherwise, any non-low activity signal is processed using traditional methods. If an erroneous frame is received when detected at the physical layer, the frame is assigned the indicator N, and at task 410 the vocoder examines the erroneous frame. If the frame parameters are quite distinct, then a "trusted" decision can be made as to whether the frame is a board '0' or '1', and then a false frame. Are modified to reflect the parameters of the decision. The reliable decision is to get the original frame parameters within the established probability. For the purposes of this invention, the desired probability would certainly be in the range of 51%. If so, the method returns to task 402 and determines the next signal.

If a reliable decision cannot be made as shown in task 412, the vocoder reviews the next adjacent frame N + 1 or, alternatively, N-1. If this frame is good at task 416, the decision to correct the erroneous frame is made at task 418 based on parameters contained in frame N + 1, or alternatively frame N-1. If neither next adjacent frame is good, then the next most reliable decision is made based on the parameters contained in the next adjacent frame N + 1, and the parameters of frame N are modified accordingly. . B. Encoder and Decoder Using Soft Bits The decoder embodiment in this embodiment of the invention is similar to that disclosed above. However, the encoder also utilizes "soft bits" to further reduce the error rate and improve the accuracy and reliability of the decoded signal.

When the vocoder coder detects a board sound to be transmitted, the coder switches to "board sound coding mode". In this mode, the encoder determines whether the speech received for encoding is a "0" or a "1". The encoder then makes this decision
The vocoder frames are used, but with channel coding redundancy, sent to the combiner to improve the opportunity for the combiner to determine its own board sound. Even if the decoder receives speech in the wrong frame, it will, with a greater probability, determine the exact speech sent, because of the forwarded decision.

In the simplified example, if the encoder detects that the board '1' should be transmitted, it sends consecutive 1's to the decoder. This sequence can be of any length, but if necessary must be sufficient for the decoder to operate as discussed in Section A above. This version of the invention replaces the standard vocoder parameters with vocoder "signatures", which are better spaced apart (ie, more distinguishable), and thus, even when frames are in error. It makes it easier to decide between two voices. C. Soft Bit-Free Encoder and Decoder This embodiment of the invention is another version of the method described in Sections A and B, but the decoder does not process any erroneous vocoder frames to process. Is not given a soft bit.

In this case, when the vocoder encoder detects a '1' or '0' board tone,
Vocoders also use redundancy to encode speech within vocoder frames, but the encoding may be done over many vocoder frames. The multiple '1's and'0's are interleaved across multiple frames M so that the decoder can extract the required information from adjacent frames if one frame is lost. The example below shows interleaving that occurs over 4 frames, but any number of frames may be used. Assume that the encoder detects the following board sounds for transmission:

[Equation 5]

In this example, the vocoder frame parameters for each frame are segmented,
There, 4 bits represent the detection board sound within a particular vocoder frame. The whole 1
The 6 bits represent the detected board sound from the last 4 vocoder frames:

[Equation 6]

To describe board sounds that do not correspond to vocoder frame boundaries, the invention uses the following 4-bit sequence, where XXYY is the code in the current vocoder frame followed by the board code'Y '. Show that it reflects the board code'X 'that is:

[Equation 7]

D. Modified Vocoder With Increased Transmit Power In another embodiment, the high cost of modifying a chipset within a mobile station to achieve the encoding and decoding processes discussed in Sections A, B and C above. Is advantageously minimized.

The encoding and decoding methods of clauses A, B, and C are standards that communicate communicatively with a signal enhancer, such as an estimator or a repeater or some other device capable of performing signal enhancement functions. It can be conveniently achieved by the use of a vocoder. In addition, A,
The methods of Sections B and C can be achieved by the use of modified vocoders. Modifying the vocoder to further incorporate a signal enhancing function, i.e., to make an estimate of whether the incorrect bits received by the communication unit were originally transmitted as multiple '0's or'1's. What can be done will be apparent to those skilled in the art.

The system of FIG. 5 illustrates one embodiment of the present invention. Base station 550 to mobile station 5
The transmission to 10 is called the forward link, and the transmission from mobile station 510 to base station 550 is called the reverse link. On the reverse link, unmodified vocoder 520 at mobile station 510 encodes the board signal into standard vocoder parameters and sends the vocoder parameters to base station 550. The modified vocoder 560 receives this coded board signal and undoes the incorrect bits (res
to enhance this board signal. A clean version of the board signal is then generated. On the forward link, unmodified vocoder 580 at base station 550 encodes the board signal using standard vocoder parameters and sends the vocoder parameters to mobile station 510. The modified vocoder 530 receives the encoded board signal and expands the board signal to undo the bad bits. A clean version of this signal is then generated.

However, using signal enhancers or modified vocoders on both the forward and reverse links to achieve the decoding methods discussed in Sections A, B and C is not provided by. Can be very expensive. In yet another embodiment of the present invention, power is used to adjust the signal transmission power level from the base station to the mobile station on the forward link by using a signal enhancer in the base station and on the forward link. By using control techniques, the frame error rate of the system can be reduced.

On the reverse link of the communication system of FIG. 6, base station 655 recovers the original board signal contained within the vocoder coded frame according to the methods discussed in Sections A, B and C. However, on the forward link, base station 655 is assigned to the assignee of the present invention and is incorporated herein by reference.
114,344, entitled "TDD / TTY Through Vocodered Channels."
Method and apparatus for establishing service (METHOD AND APPARA
TUS FOR ESTABLISHING TDD / TTY SERVICE
The coded board signal is transmitted using a power control technique as discussed in "OVER VOCODED CHANNELS".

FIG. 7 is a flow diagram of a method for controlling transmit power between a base station and a mobile station. The method begins at task 702, where a board signal is received by mobile station 605. After the signal is received, the vocoder used by mobile station 605 is locked in full rate at task 704 during processing of the signal. In this example, the transmit power is not reduced from the transmit power used by the telecommunications system for full rate transmission in task 710. The power level is typically set based on the selected FER for the transmitted signal as received at mobile station 605. The desired FER is selected because the actual character error rate of the board signal when it is being sent is about 9 to 10 times that of the FER. This selected FER range is between 0.1% and 1.0% error rate, but may be lower if necessary for quality protection of the transmitted signal. Preferably 0.2%
FER is desirable for board signal transmission. If the FER exceeds the selection range at task 712, mobile station 605 informs base station 655 during task 706 that system adjustments are needed to reduce the FER. Therefore, adjustments are made in task 708. Adjustment typically involves increasing the transmit power during full rate transmission, but may also include adjusting other known parameters to reduce FER. If in task 712 F
If the ER is acceptable, signaling can continue at task 714, and dynamic coordination to the telecommunications system continues throughout transmission of all transmitted signals 710. Otherwise, when the board signal has been transmitted, the vocoder is released and the telecommunications system returns to normal operation.

Other Embodiments While what is presently considered to be the preferred embodiment of the invention is set forth herein,
It will be apparent to those skilled in the art that various changes and modifications can be made without departing from the scope of the invention as defined by the appended claims.

[Brief description of drawings]

FIG. 1 is a block diagram of hardware components and interconnections of a telecommunications system incorporating a wireless link in accordance with one embodiment of the present invention.

FIG. 2 illustrates a typical prior art TDD communication device used in accordance with one embodiment of the present invention.

FIG. 3 shows a traffic channel frame format for rate setting 1 used by a variable rate vocoder.

[Figure 4]   FIG. 6 is a flow diagram of one method aspect according to one embodiment of the invention.

FIG. 5 illustrates a block diagram of a wireless telecommunications system configured in accordance with one embodiment of the present invention.

FIG. 6 illustrates a block diagram of a wireless telecommunications system configured in accordance with one embodiment of the present invention.

FIG. 7 is a flow diagram of one method for controlling transmit power level between a base station and a mobile station.

[Explanation of symbols]

100 ... Telecommunications system, 102 ... TDD, 104 ... Subscriber unit, 10
6 ... Notification device, 108 ... Hard wire, 112 ... Antenna, 116 ... Antenna,
118 ... Base station, 200 ... Communication device.

─────────────────────────────────────────────────── ─── Continued front page    (81) Designated countries EP (AT, BE, CH, CY, DE, DK, ES, FI, FR, GB, GR, IE, I T, LU, MC, NL, PT, SE), OA (BF, BJ , CF, CG, CI, CM, GA, GN, GW, ML, MR, NE, SN, TD, TG), AP (GH, GM, K E, LS, MW, MZ, SD, SL, SZ, TZ, UG , ZW), EA (AM, AZ, BY, KG, KZ, MD, RU, TJ, TM), AE, AG, AL, AM, AT, AU, AZ, BA, BB, BG, BR, BY, BZ, C A, CH, CN, CR, CU, CZ, DE, DK, DM , DZ, EE, ES, FI, GB, GD, GE, GH, GM, HR, HU, ID, IL, IN, IS, JP, K E, KG, KP, KR, KZ, LC, LK, LR, LS , LT, LU, LV, MA, MD, MG, MK, MN, MW, MX, MZ, NO, NZ, PL, PT, RO, R U, SD, SE, SG, SI, SK, SL, TJ, TM , TR, TT, TZ, UA, UG, UZ, VN, YU, ZA, ZW F-term (reference) 5K028 BB06 CC02 CC05 EE08 HH00                       KK01 KK12 MM05 MM09 SS04                       SS14                 5K067 AA21 CC10 EE02 EE10 EE71                       FF02 FF23 HH21                 5K101 KK19 LL11 MM05 SS00

Claims (17)

[Claims] 1. A method for communicating a announced low activity communication signal in a telecommunications system, the telecommunications system comprising a mobile station and a base station, the method comprising: an original sequence of bits. Transmitting an original frame represented by; receiving a first transmission frame, the first transmission frame comprising a first transmission sequence of bits, the first transmission sequence of the bits being substantially the bits; The first transmitted sequence of the bits to form an extended sequence of bits; and the extended sequence of bits to process the extended sequence of bits to obtain the extended sequence of bits of the original frame. Obtain additional information used to identify the original sequence. 2. The method of claim 1, wherein the step of processing the extended sequence of bits further comprises: comparing the bits of the extended sequence of bits to a known low activity communication signal bit sequence. Determining if the extended sequence of bits is statistically reliable; and, if the extended sequence of bits is statistically reliable, then modify the extended sequence of bits to modify the original sequence in the original frame; Check the original sequence of the bits. 3. The method of claim 1, wherein the extended sequence of bits is labeled as frame N, and the step of processing the extended sequence of bits further comprises: A low activity communication signal bit sequence to form a comparison result; if the comparison result is statistically reliable, then modify the extended sequence of bits based on the comparison result, Reflects the known low activity communication signal bit sequence; but if the comparison result is statistically unreliable, then process frame N + 1 adjacent to frame N so that frame N + 1 has some error However, if the frame N + 1 is error-free, then the bit sequence contained in frame N + 1 is determined. Modifying the extended sequence of the bits in the frame N based on the bit sequences included in and frame N + 1; the defined low activity communication signal to determine the cans. 4. The comparison result is statistically reliable if the probability that the known low activity communication signal bit sequence will reflect the original sequence of the bits is 51% or more. A method according to claim 3. 5. The method of claim 1, wherein the step of transmitting the original frame is performed by a mobile station and the step of receiving the first transmission frame is performed by a base station. 6. The method further comprises the step of replacing standard vocoder encoding / decoding parameters used by a plurality of vocoders with a vocoder signature, wherein the ordered bits contained in the vocoder signature are standard. 2. The method of claim 1, wherein the replacement step precedes the transmitting step at a distance further apart than the arranged bits contained in the vocoder parameters. 7. The method of claim 6, wherein the step of replacing standard vocoder parameters further comprises: communicating to the first vocoder that a low activity communication signal is being transmitted; and Encode the low activity communication signal with a second vocoder, the second vocoder determines if the bit is a 1 or a 0, and the performed encoding is the channel code in the information bit field of the original frame. To improve the likelihood of the first vocoder to decode the original frame, the encoding also means that a low activity communication signal is being transmitted. Notify the vocoder. 8. The method of claim 6, wherein the step of processing the extended sequence of bits further comprises: comparing the extended sequence of bits with a known low activity communication signal bit sequence; And modifying the extended sequence of the bits based on the comparison to confirm the original sequence of the bits. 9. A method for communicating an advertised low activity communication signal in a telecommunications system, the telecommunications system including a mobile station and a base station, the method comprising: Transmitting one original frame, said first original frame being represented by a first original sequence of bits; receiving a first transmission frame at a base station, said first transmission frame being first bit The first transmission sequence of the bits is arranged substantially the same as the first original sequence of the bits, comparing the first transmission sequence of the bits within the base station. , Forming an extended sequence of bits; transmitting the extended sequence of bits to a first vocoder in the base station; transmitting the extended sequence of bits to the first vocoder To obtain additional information used to ascertain the first original sequence of bits in the first original frame; and a second original frame from the base station with increased transmit power. Send at the level. 10. The method of claim 9, wherein the step of transmitting the second original frame from the base station at an increased transmit power level further comprises the steps of: Lock all vocoders used to process all rates; and transmit the second original sequence at an increased transmit power level to obtain a minimum target frame error rate for the second original sequence of the bits. To maintain. 11. The method of claim 9, wherein the bits of the extension sequence are labeled as frame N, and the step of processing the bits of the extension sequence further comprises: known bits of the extension sequence. A low activity communication signal bit sequence to form a comparison result; and if the comparison result indicates that it is statistically reliable, then modify the bits of the extended sequence based on the comparison result. And reflect the known low activity communication signal bit sequence; but if the comparison result is not statistically reliable, then process frame N + 1 adjacent to frame N to determine what frame N + 1 is. Determines whether the frame N + 1 contains an error; if the frame N + 1 has no error, the bits included in the frame N + 1 Modifying the extended sequence of bits of frame N based on the bit sequences included in and frame N + 1; the defined low activity communication signal to determine the Sequence. 12. The comparison result is statistically reliable if the probability that the known low activity communication signal bit sequence will reflect the original sequence of the bits is 51% or more. A method according to claim 11. 13. The method of claim 11, wherein the step of transmitting the second original frame from the base station at an increased transmit power level further comprises the steps of: Lock all vocoders used to process all rates; and transmit a second original sequence of the bits at an increased transmit power level and a minimum target frame error rate for the second original sequence of the bits. To maintain. 14. The method of claim 13, wherein the minimum target frame error rate is 1.0% or less. 15. An apparatus for communicating a low activity communication signal in a telecommunications system, the apparatus comprising: for encoding an original frame of the low activity communication signal into an original sequence of bits. Means for transmitting an original sequence of bits; means for receiving a first transmission frame; the first transmission frame comprising a first transmission sequence of bits; and a first of the bits. The signal transmission sequence is extended by the signal enhancer to form a clean signal. 16. The apparatus of claim 15, wherein the apparatus further comprises: means for comparing the extended sequence of bits with a known low activity communication signal bit sequence; extended sequence of the bits. Means for determining whether the bit is statistically reliable; means for checking the statistical reliability of the extended sequence of the bits; and modifying the extended sequence of the bits to modify the bits in the original frame. A means to confirm the original sequence of. 17. An apparatus for communicating a announced low activity communication signal in a telecommunications system, the apparatus comprising: encoding an original frame of the low activity communication signal into an original sequence of bits. A vocoder for transforming; a transmitter for transmitting the original sequence of the bits; a receiver for receiving a first transmit frame, the first transmit frame comprising a first transmit sequence of bits; And a signal enhancer for extending the first transmission sequence of the bits to form a clean signal.