MXPA00011710A - Increasing performance in communications by embedding one signal in another signal - Google Patents

Abstract

In transmitting communication signals to a receiver via a transmission channel, the transmitter generates (44, 75) a composite signal (100) including information from which the receiver can determine (51) a channel evaluation signal and other control information. The composite signal is transmitted over the transmission channel (15). This results in improved channel capacity, reduced power transmission requirements, and reduced interference in the transmission channel.

Description

"INCREASED OPERATION IN COMMUNICATIONS BY EMBEDDING A SIGNAL IN ANOTHER SIGNAL" FIELD OF THE INVENTION The invention is generally related to improving the operation in communications and, more particularly, doing this by embedding a signal in another signal.

BACKGROUND OF THE INVENTION Figure 1 illustrates an example of a conventional wireless communication system. In the example of Figure 1, a base station 11 is bi-directionally communicated with a plurality of mobile stations 13 through radio signals passing through a transmission channel 15. This arrangement is typical of telecommunications systems cellular and other wireless communications systems. The transmission technology can be any of a variety of conventional technologies, for example, code division multiple access (CDMA), time division multiple access (TDMA), and frequency division multiple access (FDMA).

Figure 2 is a functional diagram illustrating an example of a conventional transceiver 21 that can be included in each of the mobile stations 13 and the base station 11 of Figure 1. The transceiver 21 transmits radio signals through the radio channel. transmission 15, to other communication stations, and receives radio signals through transmission channel 15, from other communication stations. The transceiver 21 includes a transmitter 17 and a receiver 19. A conventional transmitter processing apparatus at 12 provides various signals to a conventional transmission section that interleaves the signals from the transmitting processing apparatus 12 to an antenna 20 that transmits the radio signals corresponding through the transmission channel 15. The antenna 20 also receives radio signals from the transmission channel 15 and provides them to a receiving section 16 which converts the signals from the antenna 20 into signals that are admitted to a receiving processing apparatus conventional 18. The transmitter processing apparatus at 12 produces the substantive information, i.e., the message to be communicated via the transmission channel to a receiving communication station, which also provides control signals, such as pilot symbols, information of power control and other control signals. The substantive information, the pilot symbols, the power control information and other control information are also received from the transmission channel 15 and are provided from the receiving section 16 to the receiving processing apparatus 18. The power control information or symbols Power control signals (often referred to as TPC bits (Transmission Power Control) are transmitted regularly in order to compensate for changes in the transmission channel between the transmitting and receiving stations, such as fading. The pilot symbols are transmitted to help the receiver to calculate the channel and carry out the coherent detection of received signals.The pilot symbols transmitted by the transmitter are already known in the receiver, so that the receiver can evaluate the channel conditions by comparing the pilot symbols actually received with the pilot symbols waiting The pilot symbols and the power control symbols constitute a significant part of the non-information signals communicated through the transmission channel. In addition, these signals require significant transmission power. The pilot power control symbols are conventionally transmitted either in the same physical channel as the substantive information, or in a control channel that is separate from the information channel. Both power and pilot control symbols can be transmitted in either the uplink or downlink directions of the system illustrated in Figure 1. In conventional CDMA systems such as specified in IS-95, up to 20 percent of the total transmitted power is used for transmission of the pilot symbol, and the power control symbols constitute up to 10 percent of the total symbols transmitted through the channel. These figures are typical of other conventional CDMA systems such as the "Code Division Test Bed" (CODIT), and broadband CDMA standards that have been developed in Japan and Europe. Figure 3 illustrates an example of the transmission of pilot symbols and power control symbols in the transmission channel of a wireless communication system. The illustration in Figure 3 is an example of the transmission of the pilot symbols and the power control symbols through a physical channel that is separate from the physical channel used for transmission of the substantive information signals. Independently of the pilot symbols and the power control symbols are transmitted through a separate channel or through the same channel as the substantive information signals, the present invention recognizes that any reduction in the number of pilot symbols and / or symbols of The control of power to be transmitted will result in a corresponding increase in the capacity of the available channel, a corresponding decrease in the required transmission power and a corresponding decrease and interference through the transmission channel. Therefore it is desirable to provide one or more of: increased available channel capacity; decreased transmission power; and decreased interference; while means are also provided for transmitting and receiving all the desired pilot symbols and power control information. The present invention provides means for transmitting and receiving all desired pilot symbols and power control information while improving conventional systems with respect to one or more than two: the required channel capacity; the required transmission power; and the transmission channel interference. This is achieved by embedding the control information in the pilot symbols. The aforementioned advantages of the present invention can also be achieved by embedding control information of the pilot symbols other than - is not the power control information. In addition, the aforementioned technique of embedding control information in a channel evaluation signal (ie, pilot symbols) can also be advantageously applied in wired as well as wireless communication systems.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 illustrates an example of a conventional wireless communications system in which the invention can be implemented. Figure 2 illustrates an example of a conventional transceiver that can be used in the communication stations of Figure 1. Figure 3 illustrates the diagrammatic transmission of pilot symbols and power control symbols in a separate control channel in a conventional wireless communication system. Figure 4 illustrates an example of a transmitter in accordance with the present invention for use in a receiver of a wireless communication system. Figure 5 illustrates an example of a receiver according to the present invention for use in a receiver of a wireless communication system.

Figure 6 illustrates an exemplary implementation of the extractor of Figure 5. Figure 6A illustrates another example of the extractor of Figure 5. Figure 7 is a functional diagram illustrating an example of the operation of the transmitter of Figure 4. The Figure 8 is a functional diagram illustrating the exemplary operations of the extractor of Figures 5 and 6. Figure 9 is a functional diagram illustrating an additional exemplary operation of the extractor of Figures 5 and 6. Figure 10 shows numerical examples of the operation of the transmitter and receiver of Figures 4 to 6. Figure 11 illustrates an example of a composite signal including the pilot symbol information and the power control information in accordance with the invention.

DETAILED DESCRIPTION Figures 4 and 5 of the example respectively illustrate the examples of a transmitter and a receiver according to the present invention for use in communications stations of a communication system - wireless, for example in the transceivers, of the mobile stations and the base station of FIG. 1. The transmitter of the example of FIG. 4 includes a composite signal generator 44 coupled between the transmission section 14 and the processing section of FIG. transmission 12 of Figure 2. The composite signal generator 44 produces a composite signal that includes information about conventional pilot symbols and power control symbols received from conventional outputs 23 and 27 of the transmitter processing section conventional 12. The composite signal generator 44 includes an encoder 41 for encoding the power control symbols that are sent conventionally at 27 from the processing section of the transmitter 12. The encoder 41 allocates a code to represent the power control information and outputs this code at 43. The power control information encoded at 43 is used then to modulate the pilot symbols that are conventionally sent at 23 from the processing section of the transmitter. A modulator 45 receives as inputs the pilot symbols of the output 23 and the encoded power control information 43. The encoded power control information 43 is used to modulate the symbols - pilot from the output 23, and the output of the modulator 45 is connected to the conventional input 24 of the transmission section 14. The composite signal represents pilot symbols modulated by the power control information, so that the power control information is embedded in the pilot symbol information. The transmitting section 14 processes the composite signal at the input 24 in the same conventional manner as it processes the pilot symbols conventionally received from the output 23 of the transmission processing section 12 in the prior art Figure 2. The power control information conventionally sent at 27 of the transmitter processing apparatus 12 will typically indicate that either the transmitting power needs to be increased or decreased, that is, increase the power or decrease the power. The transmit processing processing 12 conventionally selects either the up or down transmission, in response to the current channel conditions. Because the power control symbols are not actually transmitted, the apparatus 12 only needs to provide at 27 an indication of rising power or falling power instead of an actual power control symbol. In any case, the encoder 41 can provide the information 43 as will be described below. Using Figure 3 as an example, because each unit 31 of the pilot information includes four pilot symbols namely lili in Figure 3, the encoder 41 in this example provides at 43 a power control information code including four symbols that they will be modulated at 45 with the four pilot symbols. Columns 111 and 112 of Figure 10 illustrate the output 43 of the encoder 41 in response to both an indication of "rising power" and "falling power" at the output 27 of the transmitting processing section 12. In particular, if the conventional output 27 indicates a "rising power", then the encoder 41 sends 1111, and if the output 27 indicates a "falling power", then the output of the encoder 43 is 1100. It will be noted that the "ascending" code 1111 is orthogonal with respect to the "descending" code 1100. This orthogonal relationship facilitates the best operation to demodulate the modulated (composite) signal in the receiver, as will be seen below. Column 113 of Figure 10 shows composite signals output from modulator 45 and received at input 24 of transmitting section 14 when the ascending (1111) and descending (1100) codes at 43 (see columns 111 and 112) are used to modulate the pilot symbols. Two different examples of pilot symbols are shown in Figure 10, namely, 1111 and 0000. The 0 in Figure 10 represent -l's. The receiver of the example of Figure 5 receives the composite signal from the air interface 15 through the antenna 20. The receiver section 16 processes the composite signal in the same conventional manner as it processes the conventional pilot symbols in Figure 2 of the previous technique. An extractor 51 has an inlet connected to the outlet of the conventional symbol 25 of the conventional receiving section 16. The extractor 51 extracts the original pilot symbols and the original power control information from the composite signal output at 25 from the receiving section 16. The extractor 51 sends the original pilot symbols to the receiving processing section 18 in the inlet 26 conventionally used to receive the pilot symbols in Figure 2. The extractor 51 provides conventional power control symbols to the input 28 which conventionally receives the power control symbols (see Figure 2). Figure 6 illustrates an example of the implementation of the extractor 51 of Figure 5. In the extractor of the example of Figure 6, the composite signal received from the output 25 of the receiving section 16 is applied to a pair of demodulators 61 and 63 Referring again to columns 111 and 112 of Figure 10, it will be seen that the demodulator 61 also receives the "rising power" code 111 with which the modulated pilot symbols are demodulated. Similarly, the demodulator 63 receives the "downstream" code 1100 with which the modulated pilot symbols are demodulated. The respective outputs of the demodulators 61 and 63 are coupled with the respective accumulators 62 and 64. Each accumulator calculates the sum of the output of the demodulated pilot symbols from the associated demodulator. The symbol T ~ in the feedback circuit of each accumulator 62 and 64 represents a delay of a symbol time, so that, as each symbol is received, it can be appropriately added to the partial sum currently stored in the accumulator . Making now - reference to columns 114 and 116 of Figure 10d M , these columns respectively illustrate the outputs of the demodulators 61 and 63 when the modulated pilot symbols, (i.e., the composite signals) of the column 113 are received at the respective inputs of the demodulators 61 and 63. For example, the pilot symbols modulated 1100 in row 119, column 113 will result in an output of 1100 from demodulator 61 in column 114, but will result in an output of 1111 from demodulator 63 in column 116. As shown in row 119, column 115, the output 1100 of the demodulator 61 is added to the accumulator 62 to provide a result of 0, representing 0, at 1100 the -l's. Similarly, row 119, column 117 of Figure 10 indicates that output 1111 of demodulator 63 accumulates a sum of 4 in accumulator 64. Because the ascending power code 1111 is orthogonal with respect to the descending code of power 1100, the outputs of the accumulators 62 and 64, as illustrated in Figure 10, are ideally different from one another maximum. Although orthogonal codes probably provide optimal performance, other appropriate codes may be used to practice the invention. In case, as in the example described above, the accumulator 64 produces a sum value greater in magnitude than the accumulator 62, then this indicates that the descending power code 1100 of the demodulator 63 was produced by the encoder 43 and it is used in the modulator 45 to modulate the pilot symbols. On the other hand, if the accumulator 62 accumulates a sum of greater magnitude, then this indicates that the ascending power code 1111 of the demodulator 61 was produced by the encoder 43 and was used in the modulator 45 to modulate the pilot symbols. Row 118 of Figure 10 illustrates an example where the rising power code 1111 (see row 118, column 112) is used to modulate the pilot symbols. The cumulative sum at 62 is 4 (row 118, column 115) and the cumulative sum at 64 is 0 (row 118, column 117). Referring again to Figure 6, a magnitude comparator 65 coupled with the accumulators 62 and 64 compares the magnitude of the respective sums calculated by the accumulators, and controls the selectors 66 and 67, correspondingly. When the accumulator 62 has the largest sum, then the output of the magnitude comparator selects a conventional rising power symbol that will pass through the selector 67 to the input 28 of the receiving processing section 18, and the content is selected of the buffer 68 which is to be passed through the selector 66 to the input 26 of the receiving processing section 18. On the other hand, if the sum accumulated by the accumulator 64 is greater than the sum accumulated by the accumulator 62, then the comparator output of magnitude 65 selects a conventional downstream power symbol to be passed through the selector 67 at the input 28 of the receiving processing section 18, and selects the contents of the buffer 69 to be passed to through the selector 67 to the input 26 of the receiving processing section 18. The buffers 68 and 69 are provided to buffer the outputs of the demodulators 61 and 63 until the comparator of magnitude 65 can determine, from the accumulated sums at 62 and 64, which of the demodulators 61 and 63 has output the original pilot symbols. That is, the demodulator 61 will output the original pilot symbols if the upstream power code 1111 was used to modulate the pilot symbols in the transmitter, and the demodulator 63 will send the original pilot symbols if the downstream power code 1100 was used to Modulate the pilot symbols on the transmitter. In this way, the demodulators 61 and 63 respectively define the ramifications of ascending power and descending power. These branches together indicate to the comparator 65 which power control code was used to modulate the original pilot symbols, and which demodulator has sent the original pilot symbols. When the sum of the accumulator 62 is greater than that of the accumulator .64, then the rising power symbol is selected at 67 and the output of the demodulator 61 (in the buffer 68) is selected at 66, while the descending power symbol is selected. and the output of demodulator 63 (in buffer 69) is selected at 67 and 66, respectively, if the sum of accumulator 64 is greater than the two sums. In this way, the magnitude 65 comparator and selectors 66 and 67 form a total selector that responds to accumulators 62 and 64 by making the appropriate selections at 66 and 67. Any desired pair of codes (optimally orthogonal codes) can be used to modulate / demodulate the pilot symbols. Also, any desired number of codes (ie, more than two codes) can be used to provide higher resolution power control than just the up and down power. This higher resolution would of course require additional modulator / accumulator ramifications such as those shown in 61-62 and 63-64, namely, a branch of the additional modulator / accumulator for each additional code beyond the two illustrated in Figure 6. This is illustrated in the extractor of the example of Figure 6A. In this example, comparator 65 will select the branch that has the largest sum of magnitude in its accumulator. Figure 7 illustrates the operation described above with respect to the transmitter of the example of Figure 4. It is first determined at 71 whether the pilot and power control symbols are ready from the transmitting processing section 12. When the pilot and control symbols of power are ready, the information of the power control symbol is coded at 73 using the encoder 41. Then at 75, the output of the pilot symbols at 23 of the transmit processing section 12, are modulated at 45 with the code of power control 43 sent from the encoder 41. Then, the modulated pilot symbols are transmitted through the air interface in a conventional manner at 77, and the control returns to await the arrival of more pilot and power control symbols at 71. Figure 8 illustrates the operation described above with respect to the demodular / aquatic branches of Figure 6. Taking the modulator branch 61 and the accumulator 62 as an example, when the information of the pilot symbol has been received (81) from the output 25 of the receiving section 16, then the accumulator 62 is marked to zero at 83, and the demodulator 61 tries to demodulate the first pilot symbol at 85. Then at 87, the output of the pilot symbol from the demodulator 61 is added to the contents of the accumulator 62, and it is also stored in the buffer 68. Then, steps 85 and 87 are repeated until the demodulator 61 has carried out its demodulation operation on all pilot symbols "received. When it is determined in 89 that the - l demodulator 61 has been operated on all received pilot symbols, then at 88 the contents of accumulator 62 is provided to the comparator of magnitude 65, and the control returns to await the arrival of more information of the pilot symbol at 81. Even though the operation of Figure 8 has been described with respect to the ascending power branch of the demodulator 61, the accumulator 62 and the buffer 68, the operation of Figure 8 is of course equally applicable to the downstream power branch of the demodulator 63, the accumulator 64 and buffer 69. Figure 9 illustrates the selection operation of the magnitude 65 comparator and multiplexers 66 and 67 to provide the desired power and pilot control symbols to the inputs 26 and 28 of the receiving processing section 18. It is first determined at 91 if the content (sums) of accumulators 62 and 64 have been received. If so, then at 93 the comparator of magnitude 65 compares the magnitude of the contents of the accumulator 62 with the magnitude of the contents of the accumulator 64. If the contents of the accumulator 62 are greater at 95, then at 97 the comparator 65 selects the ascending symbol in the multiplexer 67 and selects the buffer 68 in the multiplexer 66. If the contents of the accumulator 64 is greater than 95, then in 99 the comparator 65 selects the down symbol in the multiplexer 67 and selects the buffer 69 in the multiplexer 66 After appropriate selections have been made in the multiplexers at 98, the selected power control symbol of the multiplexer 67 and the selected pilot symbols of the multiplexer 66 are provided at the respective inputs 28 and 26 of the receiving processing section 18. Then , the comparator of magnitude 65 waits in 91 the next arrival of the sums from the accumulators 62 and 64. It will be evident for the workers in the art that the above described embodiments related to Figures 4 to 10 can be easily implemented as improvements in hardware, software or an appropriate combination thereof, in those portions of the conventional wireless communications transceivers that process the pilot symbols and the Power control symbols. Because the information of the power control symbol is embedded in the pilot symbol information to produce a composite signal according to the invention, there is no need to transmit any power control symbol information, so that the symbols of Power control shown in 32 in Figure 3 can be removed from the transmission, thereby allowing the aforementioned sights of increased available channel capacity (i.e., shorter transmission time through the transmission channel) to be achieved, decreased transmission power and decreased interference. The composite signal 100, including all the information of the pilot symbol and the power control symbol, is illustrated in Figure 11. As seen by comparison with Figure 3, the composite signal has exactly the same effect on the channel as the pilot symbols of Figure 3, but the composite signal of Figure 11 carries information of both the pilot symbol and the power control symbol. Although the examples described above involve embedding the power control information in the pilot symbols in a wireless communication system, the invention can also be used to embed in pilot symbols other types of control information for example regime information. of the frame, voice code information, integrated circuit rate information, commands to update position coordinates, etc. In addition, the above-described techniques of the invention are also applicable in wired communications systems. Many conventional wired communications systems such asi.

For example, modems use signals called training sequences. These training sequences are used in wireline systems to carry out transmission evaluation functions analogous to those for which the pilot symbols are used in wireless systems. In this way, the training sequences are similarly available to embed in them other control information used in the wired systems. Although the exemplary embodiments of the present invention have been described in detail above, this does not limit the scope of the invention that can be practiced in a variety of embodiments.

Claims (30)

CLAIMS:

1. A transmitter for transmitting communication signals to a receiver through a transmission channel, comprising: an apparatus for providing a pilot signal and other control information to be used by the receiver; a composite signal generator capable of operating to embed the other control information in the pilot signal, which has an input coupled with the apparatus to receive the pilot signal and other control information, the composite signal generator has an output responsive to the pilot signal and other control information to produce a composite signal including composite information from which the receiver can determine the pilot signal and other control information; and a transmission interface coupled with the output of the composite signal generator to be interconnected between the composite signal generator and the transmission channel.

2. The transmitter of claim 1, wherein the composite signal generator includes a modulator coupled to the input to receive the pilot signal, and an encoder coupled to the input to receive the other control information, the encoder has an output for providing coded control information representative of the other control information, the modulator is coupled with the output of the encoder to modulate the pilot signal with the coded control information in order to produce the composite signal, the modulator is coupled with the output of the generator of the composite signal to provide the composite signal thereto.

The transmitter of claim 1, wherein the composite signal requires less transmission time through the transmission channel than it would need to transmit the pilot signal and the other control information as separate signals.

The transmitter of claim 1, wherein the composite signal requires less transmit power than would be necessary to transmit the pilot signal and the power control information as separate signals.

The transmitter of claim 1, wherein the composite signal creates less interference in the transmission channel than would be created by transmitting the pilot signal and the power control information as separate signals.

6. The transmitter of claim 1, wherein the transmission channel includes a CDMA transmission channel of a cellular telecommunications system.

The transmitter of claim 1, wherein the transmission channel is a radio channel and the pilot signal includes pilot signals used to evaluate the radio channel.

The transmitter of claim 7, wherein the other control information includes power control information used to control the transmit power in the radio channel.

9. A receiver for receiving communication signals from a transmitter through a transmission channel comprising: an extractor having an input for receiving a composite signal that was produced by the transmitter and including information indicative of an evaluation signal of channel and other control information to be used by the receiver, the extractor includes an output coupled with the input to provide the channel evaluation signal and the other control information in response to the composite signal; the extractor further includes a plurality of demodulators coupled with the input and also coupled with respective demodulation codes to demodulate the composite signal with each of the demodulation codes, the demodulation codes indicative respectively of a plurality of control indications included possibly in the other control information; and a receiver interface coupled with the input of the extractor to interconnect between the extractor and the transmission channel.

The receiver of claim 9, wherein the extractor includes accumulators respectively coupled with the demodulators to calculate the respective sums in response to the output signals received from the respective demodulators.

11. The receiver of claim 10, wherein the extractor includes a selector having an input coupled with the accumulators to receive the sums from them and in response to the sums to provide the channel evaluation signal and other control information, the selector is coupled with the output of the extractor to provide the channel evaluation signal and other control information thereto.

The receiver of claim 11, wherein the extractor includes a plurality of buffers respectively coupled with the demodulators to receive from them and store the respective demodulator output signals, wherein one of the output signals of the demodulator includes the channel evaluation signal, and wherein the selector compares the sums and provides a control output in response to the comparison to indicate which of the output signals of the demodulator in the buffers includes the channel evaluation signal.

The receiver of claim 9, wherein the transmission channel includes a CDMA transmission channel of a cellular telecommunications system.

The receiver of claim 9, wherein the transmission channel is a radio channel and the channel evaluation signal includes pilot symbols used to evaluate the radio channel.

15. The receiver of claim 14, wherein the other control information includes power control information used to control the transmit power in the radio channel.

16. A method for transmitting communication signals in a receiver through a transmission channel, comprising: providing a pilot signal and other control information to be used by the receiver; and generating in response to the pilot signal and other control information, a composite signal that includes information from which the receiver can determine the pilot signal and other control information, wherein the generation step further includes the step of embedding the other control information in the pilot signal.

The method of claim 16, wherein the step of generating includes modulating the pilot signal with the encoded information representative of other control information.

The method of claim 16, including sending the composite signal to the receiver through the transmission channel using less transmission time through the transmission channel than would be required to send the pilot signal and the other control information as separate signs.

The method of claim 16, which includes sending the composite signal to the receiver through the transmission channel using less transmit power than would be required to send the pilot signal and the other control information, as separate signals.

The method of claim 16, which includes sending the composite signal to the receiver through the transmission channel, wherein the sending step creates less interference in the transmission channel than would be created by sending the pilot signal and the other control information, as separate signals. - -

21. The method of claim 16, wherein the transmission channel includes a CDMA transmission channel of a cellular telecommunications system.

22. The method of claim 16, wherein the transmission channel is a radio channel and the pilot signal includes pilot symbols used to evaluate the radio channel.

23. The method of claim 22, wherein the other control information includes power control information used to control the transmit power in the radio channel.

24. A method for operating a receiver for receiving communication signals from a transmitter through a transmission channel comprising: receiving a composite signal produced by the transmitter and including information indicative of a channel evaluation signal and other information of control to be used by the receiver; and extracting the channel evaluation signal and the other control information from the composite signal, wherein the extraction step further includes demodulating the composite signal with respective demodulation codes, the demodulation codes are indicative of a plurality of possibly included indications. in other control information.

25. The method of claim 24, wherein the extraction step includes calculating the respective sums in response to the respective output signals produced in the step of demodulating the control signal with respective demodulation codes.

26. The method of claim 25, wherein the extraction step includes providing the channel evaluation signal and the other control information in response to these sums.

The method of claim 26, wherein the extraction step includes storing the respective output signals produced by the demodulating step and the composite signal with respective demodulation codes, the step of providing includes determining a comparison of the sums that one of the stored output signals includes the composite signal, and select a stored output signal.

The method of claim 24, wherein the transmission channel includes a CDMA transmission channel of a cellular telecommunications system.

29. The method of claim 24, wherein the transmission channel is a radio channel and the channel evaluation signal includes channel evaluation symbols used to evaluate the radio channel.

30. The method of claim 29, wherein the other control information includes power control information used to control the transmit power in the radio channel.