CA2233723A1 - Apparatus and method for determining and using channel state information - Google Patents
Apparatus and method for determining and using channel state information Download PDFInfo
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- CA2233723A1 CA2233723A1 CA002233723A CA2233723A CA2233723A1 CA 2233723 A1 CA2233723 A1 CA 2233723A1 CA 002233723 A CA002233723 A CA 002233723A CA 2233723 A CA2233723 A CA 2233723A CA 2233723 A1 CA2233723 A1 CA 2233723A1
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/18—Phase-modulated carrier systems, i.e. using phase-shift keying
- H04L27/22—Demodulator circuits; Receiver circuits
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B7/00—Radio transmission systems, i.e. using radiation field
- H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
- H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
- H04B7/08—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the receiving station
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L1/00—Arrangements for detecting or preventing errors in the information received
- H04L1/02—Arrangements for detecting or preventing errors in the information received by diversity reception
- H04L1/06—Arrangements for detecting or preventing errors in the information received by diversity reception using space diversity
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L1/00—Arrangements for detecting or preventing errors in the information received
- H04L1/20—Arrangements for detecting or preventing errors in the information received using signal quality detector
Abstract
Apparatus and method for calculating the channel state associated with received signals are disclosed. The channel state is determined from the received signal by analyzing the received signals. Also, apparatus and method for performing erasures of the received signals and for selecting between diversity communication signals based on the channel state are disclosed.
Description
APPARATUS AND ~IETHOD FOR DETERMINING AND USING CHANNEL
STATE I~FORMATION
B~ck~,~ronnd Of The lnvention ., The present invention relates to wireless communications. More particularly, it relates to appa~ s and methods for determining the state of a frequency channel in a ~,vireless communication channel and for using the channel state illrC~I~llaLiOll.
As is well known, a frequency channel in a wireless communication channel is subject to many sources of degradation. Thus, communication signals will not always be communicated properly on a frequency channel. When operating a wi,~less communication system, it is desirable to be able to determine the "state" of a frequency channel in order to determine the li~;elihood of acceptable comm--nic~tic-n on the frequency channel. While channel estimators are known in the art, none ~deq~telyperforms the tasks of determining the state of a frequency channel. Another shortcoming of existing communication systems is found in the usage of channel state inro, Illalion~
Thus, apparatus and method for determining the state of a frequency channel are needed. Further, apparatus and method for using the channel state illrollllalion to control the operation of the communication system to achieve improved comml-ni~tion are also needed.
Snn-m~rv Of The ln~ention The present invention provides apparatus and method for determining and using channel state information. In accordance with one aspect of a ,vlerell~d embodiment of the present invention, channel state information is derived from a set of communication symbols received during an individual time slot, although any set of commllnic~tion signals or even a single communication signal can be used. For each of the received comm--nication symbols, QPSK modulated symbols are hard detected to determine the actual transmitted signal. Then, the in phase and quadrature components of the received communication symbols in the plane of the modulation points are determined. Next, the sum of the in phase components is determined and the sum of the absolute value of the quadrature components is determined. The channel state is then determined from the SUBSTITUTE SH EET (RULE 26) ratio of the sum of the in phase components to the sum of the absolute value of the quadrature components. The present invention also contemplates determining the channel state from the phase error of the received signals from the modulation points.
The present invention further contemplates determining the channel state from the distance error of received signals from the modulation points.
In accordance with another aspect of the present invention, method and apparatusfor erasing communication signals in accordance with the channel state are provided. In accordance with the method, the channel state is determined when the comm~nic~tion signal is received and then signals are erased if the channel state is not better than a predetermined level.
In accordance with a further aspect of the present invention, method and apparatus for selecting one of two communication signals for processing when diversity signals are received. In accordance with the method, a first channel state is determined when the first of two diversity communication signals is received and a second channel state is determined when the second of the two diversity communication signals is received.
Then, based on the values of the first and the second channel states, one of the two diversity communication signals is selected for further processing.
The invention will now be described in connection with certain illustrated embo~limçnts; however, it should be clear to those skilled in the art that various modifications, additions and subtractions can be made without departing from the spirit and scope of the claims.
Description Of The Dr~win~s FIG. 1 illustrates a wireless communication system in which the apparatus and method ofthe present invention is used;
FIG. 2 shows the steps used to determine channel state by using the in phase andquadrature components of a received communication signal;
FIG. 3 illustrate a modulation plane and the determination of channel state by using the in phase and quadrature components of received signals as in FIG. l;
FIGS. 4 and 5 illustrate an alternate process of determining channel state by using phase error of received signals;
SUBSTITUTE SHEET (RULE 26) , -FIGS. 6 and 7 illustrate a process for determining channel state by using the Euclidean distance error of received signals and the respective modulation points;
FIG. 8 illustrates the processing apparatus in the subscriber units used to determine charmel state in accordance with any of the above processes;
FIG. 9 illustrates the process in accordance with another aspect of the present invention wherein communication signals from one of two diversity ch~nnf~lc are selected for proceccinp FIG. 10 illustrates the process in accordance with one aspect of the present invention wherein communication signals are erased; and FIG. 11 illustrates a metric decision zone.
Description Of Tlle Pref~rred Embod iment FIG. 1 illustrates a wireless communication system I in which the apparatus and method of the present invention can be used. A base station 2 establishes communications with and between a plurality of mobile or portable subscriber units 4 and a plurality of dispatch stations 6. The subscriber units 4 have the ability to comm--nic~te with each other and with the dispatch station 6. The communication functions provided preferably include telephony, dispatch, one to one communications, data communications and other communication functions. The communication links are provided between the above described components and over the PSTN.
The system of FIG. 1 preferably establishes communications over a plurality of frequency ~.h~nnçlc and in a plurality of time slots. The communications over the frequency channels are preferably broken into packets which are "hopped" across the frequency channels -- thus, a communication is transmitted over more than one frequency channel in accordance with a predetermined sequence, as described in United States Patent No. 5,408,496, which is hereby incorporated by reference. Such a system is commonly referred to as a frequency hopping system.
The comml-nications can also be "hopped" across the plurality of time slots. In this case, different parts of a communication are transmitted in different time slots, again in accordance with a predetermined sequence. Further, the communication system 1 is shown as a sectorized system having three sectors 8 to 10. The hopping sequences used SUBSTITUTE SHEET (RULE 26) WO 97/13378 PCT/IL96/001~0 in the sectors 8 to 10 are preferably orthogonal, as explained in United States Patent No.
5,408,496. The present invention, however, is not limited to sectorized comm-lnic~tion systems or to frequency and/or time hopped communication systems.
When a subscriber unit 4, a dispatch station 6 or a base station 2 receives a signal, it is desirable to determine the state of the communication channel that the signal was received on. In FIG. 2, the preferred steps used to determine channel state, in accordance with a one embodiment of the present invention, are illustrated. In the first step 100, after the received signals are demodulated, communication signals from one of the plurality of time slots in the time slotted communication system of FIG. 1 are detected.
For illustrative purposes only, assume that communication signals received in the time slot consists of thirty-eight QPSK modulated symbols, each symbol falling into one of four quadrants in a modulation plane, the quadrant being specified by two bits. For example, in FIG. 3, a QPSK modulation plane having four modulation points 102 to 105 in quadrants 0 to 3, respectively, is shown. For each received symbol, the two bits in the symbol deterrnine which quadrant the symbol belongs in.
After demodulation, as part of step 100, hard detection -- a well known process --assigns each symbol to one of the four quadrants. This process simply deterrnines the value of the received symbol and makes the quadrant assignment. Thus, in FIG. 3,symbol S1, whose bits are 00, is assigned to quadrant 0. Symbol S2, whose bits are 01, is ~igned to quadrant 2. Symbol S3, whose bits are 11, is assigned to quadrant 3.
Symbol S4, whose bits are 10, is assigned to quadrant 1. This process is performed thirty-nine times, one time for each symbol in the time slot.
Next, in step 106, each symbol is rotated to a selected one of the four quadrants, preferably quadrant 0. This process allows uniform and simpler processing of thereceived communication signals in accordance with the present invention. If quadrant 0 is sPlected as the quadrant to which all symbols are rotated to, then the symbols are rotated according to the following:
(1) If the symbol is in quadrant 0, the symbol is not rotated;
STATE I~FORMATION
B~ck~,~ronnd Of The lnvention ., The present invention relates to wireless communications. More particularly, it relates to appa~ s and methods for determining the state of a frequency channel in a ~,vireless communication channel and for using the channel state illrC~I~llaLiOll.
As is well known, a frequency channel in a wireless communication channel is subject to many sources of degradation. Thus, communication signals will not always be communicated properly on a frequency channel. When operating a wi,~less communication system, it is desirable to be able to determine the "state" of a frequency channel in order to determine the li~;elihood of acceptable comm--nic~tic-n on the frequency channel. While channel estimators are known in the art, none ~deq~telyperforms the tasks of determining the state of a frequency channel. Another shortcoming of existing communication systems is found in the usage of channel state inro, Illalion~
Thus, apparatus and method for determining the state of a frequency channel are needed. Further, apparatus and method for using the channel state illrollllalion to control the operation of the communication system to achieve improved comml-ni~tion are also needed.
Snn-m~rv Of The ln~ention The present invention provides apparatus and method for determining and using channel state information. In accordance with one aspect of a ,vlerell~d embodiment of the present invention, channel state information is derived from a set of communication symbols received during an individual time slot, although any set of commllnic~tion signals or even a single communication signal can be used. For each of the received comm--nication symbols, QPSK modulated symbols are hard detected to determine the actual transmitted signal. Then, the in phase and quadrature components of the received communication symbols in the plane of the modulation points are determined. Next, the sum of the in phase components is determined and the sum of the absolute value of the quadrature components is determined. The channel state is then determined from the SUBSTITUTE SH EET (RULE 26) ratio of the sum of the in phase components to the sum of the absolute value of the quadrature components. The present invention also contemplates determining the channel state from the phase error of the received signals from the modulation points.
The present invention further contemplates determining the channel state from the distance error of received signals from the modulation points.
In accordance with another aspect of the present invention, method and apparatusfor erasing communication signals in accordance with the channel state are provided. In accordance with the method, the channel state is determined when the comm~nic~tion signal is received and then signals are erased if the channel state is not better than a predetermined level.
In accordance with a further aspect of the present invention, method and apparatus for selecting one of two communication signals for processing when diversity signals are received. In accordance with the method, a first channel state is determined when the first of two diversity communication signals is received and a second channel state is determined when the second of the two diversity communication signals is received.
Then, based on the values of the first and the second channel states, one of the two diversity communication signals is selected for further processing.
The invention will now be described in connection with certain illustrated embo~limçnts; however, it should be clear to those skilled in the art that various modifications, additions and subtractions can be made without departing from the spirit and scope of the claims.
Description Of The Dr~win~s FIG. 1 illustrates a wireless communication system in which the apparatus and method ofthe present invention is used;
FIG. 2 shows the steps used to determine channel state by using the in phase andquadrature components of a received communication signal;
FIG. 3 illustrate a modulation plane and the determination of channel state by using the in phase and quadrature components of received signals as in FIG. l;
FIGS. 4 and 5 illustrate an alternate process of determining channel state by using phase error of received signals;
SUBSTITUTE SHEET (RULE 26) , -FIGS. 6 and 7 illustrate a process for determining channel state by using the Euclidean distance error of received signals and the respective modulation points;
FIG. 8 illustrates the processing apparatus in the subscriber units used to determine charmel state in accordance with any of the above processes;
FIG. 9 illustrates the process in accordance with another aspect of the present invention wherein communication signals from one of two diversity ch~nnf~lc are selected for proceccinp FIG. 10 illustrates the process in accordance with one aspect of the present invention wherein communication signals are erased; and FIG. 11 illustrates a metric decision zone.
Description Of Tlle Pref~rred Embod iment FIG. 1 illustrates a wireless communication system I in which the apparatus and method of the present invention can be used. A base station 2 establishes communications with and between a plurality of mobile or portable subscriber units 4 and a plurality of dispatch stations 6. The subscriber units 4 have the ability to comm--nic~te with each other and with the dispatch station 6. The communication functions provided preferably include telephony, dispatch, one to one communications, data communications and other communication functions. The communication links are provided between the above described components and over the PSTN.
The system of FIG. 1 preferably establishes communications over a plurality of frequency ~.h~nnçlc and in a plurality of time slots. The communications over the frequency channels are preferably broken into packets which are "hopped" across the frequency channels -- thus, a communication is transmitted over more than one frequency channel in accordance with a predetermined sequence, as described in United States Patent No. 5,408,496, which is hereby incorporated by reference. Such a system is commonly referred to as a frequency hopping system.
The comml-nications can also be "hopped" across the plurality of time slots. In this case, different parts of a communication are transmitted in different time slots, again in accordance with a predetermined sequence. Further, the communication system 1 is shown as a sectorized system having three sectors 8 to 10. The hopping sequences used SUBSTITUTE SHEET (RULE 26) WO 97/13378 PCT/IL96/001~0 in the sectors 8 to 10 are preferably orthogonal, as explained in United States Patent No.
5,408,496. The present invention, however, is not limited to sectorized comm-lnic~tion systems or to frequency and/or time hopped communication systems.
When a subscriber unit 4, a dispatch station 6 or a base station 2 receives a signal, it is desirable to determine the state of the communication channel that the signal was received on. In FIG. 2, the preferred steps used to determine channel state, in accordance with a one embodiment of the present invention, are illustrated. In the first step 100, after the received signals are demodulated, communication signals from one of the plurality of time slots in the time slotted communication system of FIG. 1 are detected.
For illustrative purposes only, assume that communication signals received in the time slot consists of thirty-eight QPSK modulated symbols, each symbol falling into one of four quadrants in a modulation plane, the quadrant being specified by two bits. For example, in FIG. 3, a QPSK modulation plane having four modulation points 102 to 105 in quadrants 0 to 3, respectively, is shown. For each received symbol, the two bits in the symbol deterrnine which quadrant the symbol belongs in.
After demodulation, as part of step 100, hard detection -- a well known process --assigns each symbol to one of the four quadrants. This process simply deterrnines the value of the received symbol and makes the quadrant assignment. Thus, in FIG. 3,symbol S1, whose bits are 00, is assigned to quadrant 0. Symbol S2, whose bits are 01, is ~igned to quadrant 2. Symbol S3, whose bits are 11, is assigned to quadrant 3.
Symbol S4, whose bits are 10, is assigned to quadrant 1. This process is performed thirty-nine times, one time for each symbol in the time slot.
Next, in step 106, each symbol is rotated to a selected one of the four quadrants, preferably quadrant 0. This process allows uniform and simpler processing of thereceived communication signals in accordance with the present invention. If quadrant 0 is sPlected as the quadrant to which all symbols are rotated to, then the symbols are rotated according to the following:
(1) If the symbol is in quadrant 0, the symbol is not rotated;
(2) If the symbol is in quadrant 2, 90~ is added to the symbol phase to rotate the symbol to quadrant 0;
SUBSTITUTE SHEET(RULE ~6) CA 0 2 2 3 3 7 2 3 1 9 9 8 - 0 4 - o l (3) If the symbol is in quadrant 3, 180~ is added to the symbol phase to rotate the symbol to quadrant 0; and (4) If the symbol is in quadrant 1, 270~ is added to the symbol phase to rotate the syrnbol to quadrant 0.
Referring to FIG. 3, this process is illustrated with respect to symbols Sl to S4.
Since symbol S1 is in quadrant 0, nothing is done and symbol Sl remains in quadrant 0.
Since symbol S2 is in quadrant 2, 90~ is added to rotate symbol S2 to quadrant 0. Since symbol S3 is in quadrant 3, 1~0~ is added to rotate symbol S3 to quadrant 0. Since symbol S4 is in quadrant 1, 270~ is added to rotate symbol S4 to quadrant 0. Again, this process is performed thirty-nine times, one time for each symbol in the time slot.
Once all the symbols from a time slot have been rotated to the same quadrant, instep 108, the in-phase component of each symbol in the x-y plane, which has axesintersecting the modulation points in the modulation plane as shown in FIG. 3, is determined. Since the symbol is a complex number, this is preferably performed by taking the real component of each symbol, Re(Si), where Si are the symbols in a time slot. Then, in step 110, the quadrature component of each symbol in the x-y plane is determined. Again, since the symbols are complex numbers, this is preferably done by taking the im~in~ry component of each symbol in the time slot: Imag(Si). In FIG. 3, the calculation of the in-phase component, Real(S 1), and the quadrature component, Imag(Sl), for one symbol, S1, is illustrated. It is understood however that this process is preferably performed on each rotated symbol in a time slot.
In step 1 12, the channel state of the frequency channel during the time slot that the symbols were received on is determined from the ratio of the sum of the in-phasecomponents to the sum of the absolute value of the quadrature components. Thus, the in-phase component from each symbol in the time slot is summed. Then, the absolute value of the quadrature component from each symbol is summed. Then the channel state is the ratio of the sum of the in-phase components to the sum of the absolute value of the quadrature components. Thus, channel state, CS, is preferably determined as follows:
~ Real (Si) Cs = Slor l Im ag(Si)l slOI
SUBSTITUTE SHEET (RULE 26) , where Si are the symbols in the time slot. In the equation above, the absolute value is used to m~int~in channel state as a positive number. Other m~th~m~tic~l functions can be used to perforrn the same task. ~~
In the above equation, it is apparent that the higher the value of CS, the higher the quality of the channel state. Conversely, the lower the value of CS, the lower the quality of the channel state.
In accordance with the present invention, two points -- the norninal modulation point and the received signal point -- are compared to deterrnine channel state. In accordance u~ith this embodiment of the present invention, the calculation of the in-phase and quadrature components, therefore, provides a measure of the variance or error between the received symbol and the actual transmitted symbol as determined by hard detection. If the symbols in a time slot show a small deviation, the channel state is "good" since there was not much distortion. If, on the other hand, there is a lot of deviation in the received symbols, the channel state is "poor".
It will be appreciated that while the above describes a plefel~ed embodiment of determining channel state by processing the symbols in a time slot, the invention has broader applications. The above described processing can be perforrned on a single commllniç~tion signal to determine the state of the communication channel on which the signal was received, although the averaging of the received symbols yields a better indication of the channel state. Thus, it is apparent that the processing need not be restricted to the symbols in a time slot -- more or less symbols can be used as desired.
Also, the use of the previously described processing steps is not limited to frequency hopping and time hopping communication systems -- they may be used on any type of commllnic~tion system. In addition, if a plurality of symbols are used, they need not be rotated to one quadrant in the modulation plane as described above; instead the processing can be done within the quadrant that the symbol belongs to and the results averaged accordingly. Further, the processing of the present invention can be used with any modulation scheme.
FIGS. 4 and 5 illustrate the determination of the channel state via an alternateembodiment. Referring to FIG. 4, the first two steps 120 and 122 are the same as steps 100 and 106 previously described with respect to FIG. 2. Thus, in step 120, hard SUBSTITUTE SH EET (RULE 26) detection ofthe demodulated received symbols is perforrned to deterrnine the modulation point of the demodulated received signal and, in step 1 72, all of the received signals from a time slot are rotated to one quadrant in the modulation plane. The rotation of four '~ syrnbols S1 to S4 are illustrated in FIG. 5.
In step 124, the phase error of each rotated symbol is determined. Referring to FIG. 5, it is seen that the phase error, ~(lerr), for one demodulated received symbol, Sl, is the phase between modulation point 176, ~(mod), and the symbol Sl, ~(S1):
~(1 err) = ~(S I ) - O(mod) A~er the phase error for each demodulated received symbol is determined, in step128, the average phase error of the symbols within a slot is determined using the absolute value of the phase error:
~ (avg) = ~l~(ier~ (Si) - t~(mod) slO~ slO~
where i is the symbol number in a time slot and ~ (Si) is the phase of each rotated symbol Si within the time slot.
Alternatively, the average phase error of the symbols within a slot can be determined using the square of the phase error from each symbol:
~ ~avg)= ~ (~(ie77))~ (Si)-~(mod))2 slO~ .~lor where i is the symbol number in a time slot and ~ (Si) is the phase of each rotated symbol Si within the time slot.
Next, in step 130, the channel state, CS, is determined in accordance with ~(avg).
The exact relationship between the channel state and the average phase error (i.e. what is "good" and what is "poor") is preferably determined empirically for each communication system, but in general, the greater the average phase error, the worse the channel state and the lower the average phase error, the better the channel state.
FIGS. 6 and 7 illustrate the determination of the channel state via another alternate embodiment. Referring to FIG. 6, once again, the first two steps 140 and 142 are the same as steps 100 and 106 previously described with respect to FIG. 2. Thus, in step SUBSTITUTE SHEET (RULE Z6) -140, hard detection of the received symbols is performed to determine the modulation point of the received signal and, in step 142, all of the received symbols from a time slot are rotated to one quadrant in the modulation plane. The rotations of four symbols S 1 to S4 are illustrated in FIG. 7.
In step 144, the Euclidean distance error of each rotated signal is deterrnined.Referring to FIG. 7, it is seen that the Euclidean distance error, El, for one received signal, S1, is the distance between the modulation point of the quadrant that the received signal is in -- in this case modulation point 146 -- and the signal S1. Then, in step 148, the absolute value of the Euclidean distance error for each received signal is determined. In step 150, the channel state, CS, is determined from the average distance error Ei of symbols within a time slot:
CS = ~ IEi s~O, In step 152, it is further preferred to normalize CS to the average absolute value of the symbols in a time slot:
-~ lSil s10, As before, the exact relationship between the channel state and the averageEuclidean distance error is preferably determined empirically for each communication system, but in general, the greater the average distance error, the worse the channel state and the lower the average distance error, the better the channel state.
Referring to FIG. 8, the receiving, processing and display equipment of the subscriber unit 4 is illustrated. The receive equipment of the base station 2 and the (lisp~t~l station 6 is substantially similar. The transmit circuitry, which is not important to the present invention, includes a transmitter 200 and a gain control circuit 202 which are controlled, in part, by a frequency s~ nthesizer 204. Signals are transmitted through a duplexer 206 and an antenna 208.
On the receive side, communication signals are received on the antenna 208 and on a second ~qntPnna 210. Two receivers 212 and 214 receive the signals from the antennas SUBSTITUTE SH EET (RULE 26) -208 and 210, respectively. The frequency channel of reception is progldl,ln,ed into the ,ecei~ 212 and 214 by the syntheci~er 204. The receivers 212 and 214 are gain and frequency controlled by a circuit 216.
The received signals from both ~ntenn~c 208 and 210 are preferably sent to the modem 218. The modem 218 converts the received signals to digital signals. The modem 218 ~leÇel~bly includes a digital signal processor (DSP), preferably Analog Devices 2111, 2171 or 2181, and a ASIC device 230. These devices process the signals received from both receivers 212 and 214 in accordance with the previously described steps.
The processing is controlled by a controller 220. The processed signals are further processed to extract voice and other info..l.&lion by a voice processing package (VPP) 222 and the processed communication signals are provided to a user interface 224through the interface 226. The user interface 224 incl~ s the usual devices found in subscriber units, inf.llltling a display, speakers and microphones.
The circuitry of FIG. 8, can be used to calculate the variation or error associated with received commnnic~tion signals in accordance with any of the previously described processes. Thus, the circuitry of FIG. 8 can calculate in-phase and quadrature components, phase error and/or distance errors associated with the received signals.
The channel state CS that is computed from received signals by the processing circuitry of FIG. 8 can be utilized to select between the two signals simult~neously received on the ~ntenn~c 208 and 210 and by the receivers 212 and 214, respectively.
This reception of dual signals is commonly referred to as "diversity" reception.Referring to FIG. 9, the steps for making the selection between the two diversity signals, which are received at the same time, are illustrated. In step 300, the charmel state for the first receive channel, CSI, which is generated by any of the previously described processes or by any other process, from the signals (or signal) received on ~ntenn~ 208, is determined. In step 302, the channel state for the second receive ~~.h~nnlol, CS2, which is generated as previously described or by any other process, from the signals (or signal) ,~ceived on antenna 210, is determined. Then in step 304, the channel states from each receive channel are compared. If we assume that the process of SUBSTITUTE SHEET (RULE 26) , FIGS. 2 and 3 are used to calculate the channel state for each receive çh~nnel~ then the following comparison is made:
CS1 > CS2?
If CS1 is greater than CS2, then in step 306, channel 1 is selected. Thus, the signals from antenna 208 are selected for processing. On the other hand, if CSl is not greater than CS2, channel 2 is selected so that the signals from the ~ntçnn~ 210 are selected for processing (step 308). As before, the processing is perforrned by the circuitry of FIG. 8, in particular, in the digital signal processor in the modem 218.
The selection of signals from one of two channels for processing is preferably done every time channel states are recalculated. Thus, where the channel states for the diversity channels are calculated for each time slot, it is the signals from the time slot of one of the channels that are selected for processing. A new selection is then made for every time slot. If channel state is determined from another period of signals, by way of example only, from a single signal, then the signals from the period that is used to calculate channel state are the ones selected for processing.
The channel state CS that is computed from received signals by the processing circuitry of FIG. 8 can also be utilized to erase signals which are not received with some minimurll confidence level. The confidence level is preferably determined in accordance with the channel state.
Referring to FIG. 10, the preferred steps for perforrning erasures of signals that are not received with some minimum confidence level are shown. In step 350, the channel state of a receive signal or of a group of receive signals -- for example, the signals in a selected time slot -- is determined. This can either be the channel state of the selected one of the two receive channels or it can be the channel state of a single receive çh~nnf~.l Then, in step 352, the channel state is compared to a threshold, th. If the comparison fails, that is, if the channel state is not better than some value represented by the threshold, it is preferred to erase the signal in step 354. If the comparison passes, that is if the channel state is better than some value represented by the threshold, in step 356, SUBSTITUTE SHEET (RULE 26) _ the signal is passed on for further processing. Whether "better" means greater or less than the threshold depends on the process used to determine channel state.
The number of signals erased plt:felably coincides with the number of signals used to c~lc~ te the channel state. Thus, where the channel state is calculated from signals in a time slot, it is the signals from the time slot of one of the rh~nn~lc that are erased in step 354. If channel state is determined from another period of signals, then the signals from the period that is used to ç~lc~ te channel state are the signals that are erased in step 354. So for example only, if channel state were c~lc~ te based on a single received signal, then it is pl~r~-led to erase only the single signal in step 354.
The preferred value of the threshold, th, depends on the method of calc~ ting channel state. If channel state is calculated via the in-phase and quadrature components of the received signals in a time slot, then the threshold is preferably 3.5 and the erasure is made in step 354 if the channel state of received signals in a time slot falls below that number. If the channel state is calculated via the phase error of the received signals in a time slot, then the threshold th is preferably 0.085 and the erasure is made in step 354 if the channel state of the received signals in the time slot exceeds that number.
In step 354, the erasure is preferably made by setting a metric, which is a number associated with each received signal that ,e,ult:senLs the confidence level that the received signal was properly received, to a predetermined value, typically the lowest value. When the circuitry of FIG. 8 processes the received signals, it preferably erases the signals with the lowest metric by setting those signals to zero.
In accordance with another embodiment of the present invention, a commllnic~tiondevice receiving a communication signal performs two measures of channel state and uses one of the channel states to perform diversity selection and the other channel state to perform erasures. In a preferred embodiment, the channel state determined by phase error measurements (FIGS. 4 and 5) is used to perform erasures of poorly received signals while the channel state determined by di~t~nce error measurements (FIGS. 6 and 7) is used to select one ofthe two diversity ch~nnPI~
SUBSTITUTE SHEET(RULE 26) Pseudocode The previously described steps of determining channel state from the in-phase and quadrature components of received signals from two ch~nn~?ls~ the steps of st?lectinE
between diversity signals and the steps of erasing signals which are not received with some .~ .- confi~ nr.e level, are further described by the following pseudocode:
Calculate Channel State CS X = 0.0 Tniti~1i7e channel state variables CS_Y = 0.0 for I: = l to 38 do For each symbol in a time slot Begin U:=R(I)R*(I-1) Perform for di~relenlial detection (di~ert;nl detection equations are used for di~el e"~ detection scht~ F,5) MSD, MHD:=according to routine Generate metrics, MSD and MHD, for so~ and hard decisions, lespc~Li~ely; see the metrics generation routine MET0[i] = TABLEl(MSD); Apply MSD to Table l (see below) which is an example of the metrics p,e~l,ed for a specific communication system. The table generates a 3 bit metric, MET0[i], where i is the symbol number within the time slot being processed. One bit of the metric MET0[i] is I and two bits are the confidence level.
METl [i] = TABLE2(MSD); Apply MSD to Table 2 (see below). The table generates a 3 bit metric, METl[i], where i is the symbol number within the SUBSTITUTE SHEET (RULE 26) , time slot being processed. One bit of the metric MET I [i] is Q and two bits are the confidence level.
If MHD = 0, then W:=U ~ (I j); Rotate to quadrant 0 based on hard decision If MHD = 1, then W:=U ~ (- l j);
If MHD = 3, then W:=U- (-l+j);
If MHD = 2, then W:=U- (l+j);
CS_X:=CS_X +Re(W) Sum in-phase components of rotated signal CS_Y:=CS_Y + IImag(W)I Sum absolute value of quadrature components of rotated signal end;
Perform Erasure If CS_X < CS_Y ~ CSmin, then CSmin is the threshold to which CS_X/CS_Y is compared to Begin For I:=l to 38 do For each symbol in a time slot, erase by setting confidence level bits to 00 Begin if MET0[i] < 4 then MET0[i] :=0 For I = O (represented by 0XX, i.e. < 4, where 0 is the bit and XX is the confidence level associated with the bit) erase by setting confidçnçe level to the minimllm value, 00, which causes the digital signal processor to erase the bit.
~ The result is MET 0[i] = 0.
if MET0[i] > 3 then MET0[i]:=4 For I = 1 (represented by lXX, i.e. > 3, SUBSTITUTE SHEET (RULE 26) where 1 is the bit and XX is the confidçnce level associated with the bit) erase by setting confidence 1evel to the minimllm value, 00, which causes the digital signal processor to erase the bit.
The result is METO[i] = 4.
if MET1[i] < 4 then MET1[i]:=0 For Q = O (represented by OXX, i.e. < 4, where O is the bit and XX is the confidence level associated with the bit) erase by setting confid~nçe level to the miniml-m value, 00, which causes the digital signal processor to erase the bit.
The result is MET lti] = O.
if MET1 [i] > 3 then MET1 [i]:=4 For I = 1 (represented by 1XX, i.e. > 3, where 1 is the bit and ~ is the confidence level associated with the bit) erase by setting confidence level to the minimnm value, 00, which causes the digital signal processor to erase the bit.
The result is M~TOti] = 4.
end;
end;
Perforrn diversity selection AO := CS_XO- CS_Y1 0 and 1 indicate the diversity ch~nnel~
A1 := CS_X1- CS_YO
For i=1 to 38 Set M~i] = MET1[i]:METO[i] M[i] becomes a six bit metric repr.osçn~ing I and Q and the confiAPnce levels. For each i, select the values from SUBSTITUTE SHEET (RULE 26) -channel 0 if A0 > Al and select the values from channel 1 if Al 2 A0.
Metrics Generation Routine Can be c~lall~ted via table but the following generator saves DSP memory Calculate III = IRe(lJ) C~lMll~te IQI = IIm~l Determine a section S in the first quadrant Referring to FIG. 11, there are 3 sectors in each quadrant. The sector that a symbol falls in is determined here. The 3 sectors are identified by S=0, 4, and 44.
- If IQI < lIl tan 30~, then S=44 If lIl ~ tan 30~< IQI ~ tan 60~ then S=0 If lIl ~ tan 60~ < IQI, then S=4 Calculate y = (Q2 + I2)'n Calculate rings:
R=3 0 < ~ < 1.225.10-3 The boundaries should be less than l;
see FIG. 11 for the generated metric decision zones, incllltiing the five possible rings.
R=2 1.225.10-3 <y < 4.9.10-3 R=1 4.9.10-3< y < 0.0196 R=0 0.0196 <~ < 0.49 - SUBSTITUTE SH EET (RULE 26) R=3 ~ > 0.49 C~lc~ te metrics:
MSD = S+R and MHD = 0: Q 2 O, I 2 0 The metrics (ME~) for hard detection and MSD for soft detectinn) are determined here based on the values of S and R.
MHD places the signal on one of four quadrants. MSD places the signal on the metric decision zone in FIG. 1. For example, if MHD
=1 (i.e. quadrant 1) and S = 44 and R =1, then MSD =17. See zone 17 in quadrant 1 of FIG. 11.
MSD = [(12-S) mod 48] + R and MHD = 1, mod indicates modular arithmetic for Q 2 O, I~O
MSD = [(24+S) mod 48] + R and ME~D =3, for Q~O, I<O
MSD = [(36-S) mod 48] + R and MHD =2, for Q<O, I > O
SUBSTITUTE SHEET (RULE 26) TABLEl-LSB Metrics IN OUT IN OUT
SUBSTITUTE SHEET (RULE 26) TABLE 2 - MSB Metr~cs rN ou r rN ou r SUBSTITUTE SHEET (RULE 26) An example will now be given that illustrates the processing of one symbol and the effect of an erasure on that symbol. Suppose that the first symbol in a time slot, Sl, is received and that, when applied to the metric generation routine, yields S = 44, R = 1 and MHD = 1. Applying these facts to the MSD equation:
MSD = [(12 - S) mod48] + R= [(12 - 44) mod 48] + 1 = 17 Thus, the symbol S 1 falls in zone 17 in quadrant 1 in FIG. 11.
Next MET0[1] and MET1[1] are generated by applying MSD to TABLE 1 and TABLE 2, respectively:
MET0[1] = 6 = 110 MET1[1] = 1 = 001 The first bit of MET0[1] specifies I = 1 and the next two bits, 10, specify a confidence level (00 is the lowest level, 11 is the highest). The first bit of MET1[1] specifies Q = 0 and the next two bits specify a confidence level.
Erasures are made, if at all, once all of the symbols in the time slot have beenprocessed. If the channel state falls below a threshold, CS min, then the confiden~e bits for all symbols in a time slot, Si, are set to "null values", which are of low level of confidPnce, like 00. The processing then changes the values of the I and the Q bits to null metrics which do not contribute to an erroneous decision at the error correcting SUBSTITUTE SH EET (RULE 26) process. F~enti~lly~ the erasure means that the I and Q information content from the time slot is not used. Thus, if an erasure needs to be made, the following occurs:
MET0[1] = 4 = 100 METl[l] = O = 000 This is repeated for all symbols in the time slot.
It is understood that changes may be made in the above description without departing from the scope of the invention. It is accordingly int~n~ed that all matter contained in the above description and in the drawings be interpreted as illustrative rather than limiting SUBSTITUTE SHFET (RULE 26)
SUBSTITUTE SHEET(RULE ~6) CA 0 2 2 3 3 7 2 3 1 9 9 8 - 0 4 - o l (3) If the symbol is in quadrant 3, 180~ is added to the symbol phase to rotate the symbol to quadrant 0; and (4) If the symbol is in quadrant 1, 270~ is added to the symbol phase to rotate the syrnbol to quadrant 0.
Referring to FIG. 3, this process is illustrated with respect to symbols Sl to S4.
Since symbol S1 is in quadrant 0, nothing is done and symbol Sl remains in quadrant 0.
Since symbol S2 is in quadrant 2, 90~ is added to rotate symbol S2 to quadrant 0. Since symbol S3 is in quadrant 3, 1~0~ is added to rotate symbol S3 to quadrant 0. Since symbol S4 is in quadrant 1, 270~ is added to rotate symbol S4 to quadrant 0. Again, this process is performed thirty-nine times, one time for each symbol in the time slot.
Once all the symbols from a time slot have been rotated to the same quadrant, instep 108, the in-phase component of each symbol in the x-y plane, which has axesintersecting the modulation points in the modulation plane as shown in FIG. 3, is determined. Since the symbol is a complex number, this is preferably performed by taking the real component of each symbol, Re(Si), where Si are the symbols in a time slot. Then, in step 110, the quadrature component of each symbol in the x-y plane is determined. Again, since the symbols are complex numbers, this is preferably done by taking the im~in~ry component of each symbol in the time slot: Imag(Si). In FIG. 3, the calculation of the in-phase component, Real(S 1), and the quadrature component, Imag(Sl), for one symbol, S1, is illustrated. It is understood however that this process is preferably performed on each rotated symbol in a time slot.
In step 1 12, the channel state of the frequency channel during the time slot that the symbols were received on is determined from the ratio of the sum of the in-phasecomponents to the sum of the absolute value of the quadrature components. Thus, the in-phase component from each symbol in the time slot is summed. Then, the absolute value of the quadrature component from each symbol is summed. Then the channel state is the ratio of the sum of the in-phase components to the sum of the absolute value of the quadrature components. Thus, channel state, CS, is preferably determined as follows:
~ Real (Si) Cs = Slor l Im ag(Si)l slOI
SUBSTITUTE SHEET (RULE 26) , where Si are the symbols in the time slot. In the equation above, the absolute value is used to m~int~in channel state as a positive number. Other m~th~m~tic~l functions can be used to perforrn the same task. ~~
In the above equation, it is apparent that the higher the value of CS, the higher the quality of the channel state. Conversely, the lower the value of CS, the lower the quality of the channel state.
In accordance with the present invention, two points -- the norninal modulation point and the received signal point -- are compared to deterrnine channel state. In accordance u~ith this embodiment of the present invention, the calculation of the in-phase and quadrature components, therefore, provides a measure of the variance or error between the received symbol and the actual transmitted symbol as determined by hard detection. If the symbols in a time slot show a small deviation, the channel state is "good" since there was not much distortion. If, on the other hand, there is a lot of deviation in the received symbols, the channel state is "poor".
It will be appreciated that while the above describes a plefel~ed embodiment of determining channel state by processing the symbols in a time slot, the invention has broader applications. The above described processing can be perforrned on a single commllniç~tion signal to determine the state of the communication channel on which the signal was received, although the averaging of the received symbols yields a better indication of the channel state. Thus, it is apparent that the processing need not be restricted to the symbols in a time slot -- more or less symbols can be used as desired.
Also, the use of the previously described processing steps is not limited to frequency hopping and time hopping communication systems -- they may be used on any type of commllnic~tion system. In addition, if a plurality of symbols are used, they need not be rotated to one quadrant in the modulation plane as described above; instead the processing can be done within the quadrant that the symbol belongs to and the results averaged accordingly. Further, the processing of the present invention can be used with any modulation scheme.
FIGS. 4 and 5 illustrate the determination of the channel state via an alternateembodiment. Referring to FIG. 4, the first two steps 120 and 122 are the same as steps 100 and 106 previously described with respect to FIG. 2. Thus, in step 120, hard SUBSTITUTE SH EET (RULE 26) detection ofthe demodulated received symbols is perforrned to deterrnine the modulation point of the demodulated received signal and, in step 1 72, all of the received signals from a time slot are rotated to one quadrant in the modulation plane. The rotation of four '~ syrnbols S1 to S4 are illustrated in FIG. 5.
In step 124, the phase error of each rotated symbol is determined. Referring to FIG. 5, it is seen that the phase error, ~(lerr), for one demodulated received symbol, Sl, is the phase between modulation point 176, ~(mod), and the symbol Sl, ~(S1):
~(1 err) = ~(S I ) - O(mod) A~er the phase error for each demodulated received symbol is determined, in step128, the average phase error of the symbols within a slot is determined using the absolute value of the phase error:
~ (avg) = ~l~(ier~ (Si) - t~(mod) slO~ slO~
where i is the symbol number in a time slot and ~ (Si) is the phase of each rotated symbol Si within the time slot.
Alternatively, the average phase error of the symbols within a slot can be determined using the square of the phase error from each symbol:
~ ~avg)= ~ (~(ie77))~ (Si)-~(mod))2 slO~ .~lor where i is the symbol number in a time slot and ~ (Si) is the phase of each rotated symbol Si within the time slot.
Next, in step 130, the channel state, CS, is determined in accordance with ~(avg).
The exact relationship between the channel state and the average phase error (i.e. what is "good" and what is "poor") is preferably determined empirically for each communication system, but in general, the greater the average phase error, the worse the channel state and the lower the average phase error, the better the channel state.
FIGS. 6 and 7 illustrate the determination of the channel state via another alternate embodiment. Referring to FIG. 6, once again, the first two steps 140 and 142 are the same as steps 100 and 106 previously described with respect to FIG. 2. Thus, in step SUBSTITUTE SHEET (RULE Z6) -140, hard detection of the received symbols is performed to determine the modulation point of the received signal and, in step 142, all of the received symbols from a time slot are rotated to one quadrant in the modulation plane. The rotations of four symbols S 1 to S4 are illustrated in FIG. 7.
In step 144, the Euclidean distance error of each rotated signal is deterrnined.Referring to FIG. 7, it is seen that the Euclidean distance error, El, for one received signal, S1, is the distance between the modulation point of the quadrant that the received signal is in -- in this case modulation point 146 -- and the signal S1. Then, in step 148, the absolute value of the Euclidean distance error for each received signal is determined. In step 150, the channel state, CS, is determined from the average distance error Ei of symbols within a time slot:
CS = ~ IEi s~O, In step 152, it is further preferred to normalize CS to the average absolute value of the symbols in a time slot:
-~ lSil s10, As before, the exact relationship between the channel state and the averageEuclidean distance error is preferably determined empirically for each communication system, but in general, the greater the average distance error, the worse the channel state and the lower the average distance error, the better the channel state.
Referring to FIG. 8, the receiving, processing and display equipment of the subscriber unit 4 is illustrated. The receive equipment of the base station 2 and the (lisp~t~l station 6 is substantially similar. The transmit circuitry, which is not important to the present invention, includes a transmitter 200 and a gain control circuit 202 which are controlled, in part, by a frequency s~ nthesizer 204. Signals are transmitted through a duplexer 206 and an antenna 208.
On the receive side, communication signals are received on the antenna 208 and on a second ~qntPnna 210. Two receivers 212 and 214 receive the signals from the antennas SUBSTITUTE SH EET (RULE 26) -208 and 210, respectively. The frequency channel of reception is progldl,ln,ed into the ,ecei~ 212 and 214 by the syntheci~er 204. The receivers 212 and 214 are gain and frequency controlled by a circuit 216.
The received signals from both ~ntenn~c 208 and 210 are preferably sent to the modem 218. The modem 218 converts the received signals to digital signals. The modem 218 ~leÇel~bly includes a digital signal processor (DSP), preferably Analog Devices 2111, 2171 or 2181, and a ASIC device 230. These devices process the signals received from both receivers 212 and 214 in accordance with the previously described steps.
The processing is controlled by a controller 220. The processed signals are further processed to extract voice and other info..l.&lion by a voice processing package (VPP) 222 and the processed communication signals are provided to a user interface 224through the interface 226. The user interface 224 incl~ s the usual devices found in subscriber units, inf.llltling a display, speakers and microphones.
The circuitry of FIG. 8, can be used to calculate the variation or error associated with received commnnic~tion signals in accordance with any of the previously described processes. Thus, the circuitry of FIG. 8 can calculate in-phase and quadrature components, phase error and/or distance errors associated with the received signals.
The channel state CS that is computed from received signals by the processing circuitry of FIG. 8 can be utilized to select between the two signals simult~neously received on the ~ntenn~c 208 and 210 and by the receivers 212 and 214, respectively.
This reception of dual signals is commonly referred to as "diversity" reception.Referring to FIG. 9, the steps for making the selection between the two diversity signals, which are received at the same time, are illustrated. In step 300, the charmel state for the first receive channel, CSI, which is generated by any of the previously described processes or by any other process, from the signals (or signal) received on ~ntenn~ 208, is determined. In step 302, the channel state for the second receive ~~.h~nnlol, CS2, which is generated as previously described or by any other process, from the signals (or signal) ,~ceived on antenna 210, is determined. Then in step 304, the channel states from each receive channel are compared. If we assume that the process of SUBSTITUTE SHEET (RULE 26) , FIGS. 2 and 3 are used to calculate the channel state for each receive çh~nnel~ then the following comparison is made:
CS1 > CS2?
If CS1 is greater than CS2, then in step 306, channel 1 is selected. Thus, the signals from antenna 208 are selected for processing. On the other hand, if CSl is not greater than CS2, channel 2 is selected so that the signals from the ~ntçnn~ 210 are selected for processing (step 308). As before, the processing is perforrned by the circuitry of FIG. 8, in particular, in the digital signal processor in the modem 218.
The selection of signals from one of two channels for processing is preferably done every time channel states are recalculated. Thus, where the channel states for the diversity channels are calculated for each time slot, it is the signals from the time slot of one of the channels that are selected for processing. A new selection is then made for every time slot. If channel state is determined from another period of signals, by way of example only, from a single signal, then the signals from the period that is used to calculate channel state are the ones selected for processing.
The channel state CS that is computed from received signals by the processing circuitry of FIG. 8 can also be utilized to erase signals which are not received with some minimurll confidence level. The confidence level is preferably determined in accordance with the channel state.
Referring to FIG. 10, the preferred steps for perforrning erasures of signals that are not received with some minimum confidence level are shown. In step 350, the channel state of a receive signal or of a group of receive signals -- for example, the signals in a selected time slot -- is determined. This can either be the channel state of the selected one of the two receive channels or it can be the channel state of a single receive çh~nnf~.l Then, in step 352, the channel state is compared to a threshold, th. If the comparison fails, that is, if the channel state is not better than some value represented by the threshold, it is preferred to erase the signal in step 354. If the comparison passes, that is if the channel state is better than some value represented by the threshold, in step 356, SUBSTITUTE SHEET (RULE 26) _ the signal is passed on for further processing. Whether "better" means greater or less than the threshold depends on the process used to determine channel state.
The number of signals erased plt:felably coincides with the number of signals used to c~lc~ te the channel state. Thus, where the channel state is calculated from signals in a time slot, it is the signals from the time slot of one of the rh~nn~lc that are erased in step 354. If channel state is determined from another period of signals, then the signals from the period that is used to ç~lc~ te channel state are the signals that are erased in step 354. So for example only, if channel state were c~lc~ te based on a single received signal, then it is pl~r~-led to erase only the single signal in step 354.
The preferred value of the threshold, th, depends on the method of calc~ ting channel state. If channel state is calculated via the in-phase and quadrature components of the received signals in a time slot, then the threshold is preferably 3.5 and the erasure is made in step 354 if the channel state of received signals in a time slot falls below that number. If the channel state is calculated via the phase error of the received signals in a time slot, then the threshold th is preferably 0.085 and the erasure is made in step 354 if the channel state of the received signals in the time slot exceeds that number.
In step 354, the erasure is preferably made by setting a metric, which is a number associated with each received signal that ,e,ult:senLs the confidence level that the received signal was properly received, to a predetermined value, typically the lowest value. When the circuitry of FIG. 8 processes the received signals, it preferably erases the signals with the lowest metric by setting those signals to zero.
In accordance with another embodiment of the present invention, a commllnic~tiondevice receiving a communication signal performs two measures of channel state and uses one of the channel states to perform diversity selection and the other channel state to perform erasures. In a preferred embodiment, the channel state determined by phase error measurements (FIGS. 4 and 5) is used to perform erasures of poorly received signals while the channel state determined by di~t~nce error measurements (FIGS. 6 and 7) is used to select one ofthe two diversity ch~nnPI~
SUBSTITUTE SHEET(RULE 26) Pseudocode The previously described steps of determining channel state from the in-phase and quadrature components of received signals from two ch~nn~?ls~ the steps of st?lectinE
between diversity signals and the steps of erasing signals which are not received with some .~ .- confi~ nr.e level, are further described by the following pseudocode:
Calculate Channel State CS X = 0.0 Tniti~1i7e channel state variables CS_Y = 0.0 for I: = l to 38 do For each symbol in a time slot Begin U:=R(I)R*(I-1) Perform for di~relenlial detection (di~ert;nl detection equations are used for di~el e"~ detection scht~ F,5) MSD, MHD:=according to routine Generate metrics, MSD and MHD, for so~ and hard decisions, lespc~Li~ely; see the metrics generation routine MET0[i] = TABLEl(MSD); Apply MSD to Table l (see below) which is an example of the metrics p,e~l,ed for a specific communication system. The table generates a 3 bit metric, MET0[i], where i is the symbol number within the time slot being processed. One bit of the metric MET0[i] is I and two bits are the confidence level.
METl [i] = TABLE2(MSD); Apply MSD to Table 2 (see below). The table generates a 3 bit metric, METl[i], where i is the symbol number within the SUBSTITUTE SHEET (RULE 26) , time slot being processed. One bit of the metric MET I [i] is Q and two bits are the confidence level.
If MHD = 0, then W:=U ~ (I j); Rotate to quadrant 0 based on hard decision If MHD = 1, then W:=U ~ (- l j);
If MHD = 3, then W:=U- (-l+j);
If MHD = 2, then W:=U- (l+j);
CS_X:=CS_X +Re(W) Sum in-phase components of rotated signal CS_Y:=CS_Y + IImag(W)I Sum absolute value of quadrature components of rotated signal end;
Perform Erasure If CS_X < CS_Y ~ CSmin, then CSmin is the threshold to which CS_X/CS_Y is compared to Begin For I:=l to 38 do For each symbol in a time slot, erase by setting confidence level bits to 00 Begin if MET0[i] < 4 then MET0[i] :=0 For I = O (represented by 0XX, i.e. < 4, where 0 is the bit and XX is the confidence level associated with the bit) erase by setting confidçnçe level to the minimllm value, 00, which causes the digital signal processor to erase the bit.
~ The result is MET 0[i] = 0.
if MET0[i] > 3 then MET0[i]:=4 For I = 1 (represented by lXX, i.e. > 3, SUBSTITUTE SHEET (RULE 26) where 1 is the bit and XX is the confidçnce level associated with the bit) erase by setting confidence 1evel to the minimllm value, 00, which causes the digital signal processor to erase the bit.
The result is METO[i] = 4.
if MET1[i] < 4 then MET1[i]:=0 For Q = O (represented by OXX, i.e. < 4, where O is the bit and XX is the confidence level associated with the bit) erase by setting confid~nçe level to the miniml-m value, 00, which causes the digital signal processor to erase the bit.
The result is MET lti] = O.
if MET1 [i] > 3 then MET1 [i]:=4 For I = 1 (represented by 1XX, i.e. > 3, where 1 is the bit and ~ is the confidence level associated with the bit) erase by setting confidence level to the minimnm value, 00, which causes the digital signal processor to erase the bit.
The result is M~TOti] = 4.
end;
end;
Perforrn diversity selection AO := CS_XO- CS_Y1 0 and 1 indicate the diversity ch~nnel~
A1 := CS_X1- CS_YO
For i=1 to 38 Set M~i] = MET1[i]:METO[i] M[i] becomes a six bit metric repr.osçn~ing I and Q and the confiAPnce levels. For each i, select the values from SUBSTITUTE SHEET (RULE 26) -channel 0 if A0 > Al and select the values from channel 1 if Al 2 A0.
Metrics Generation Routine Can be c~lall~ted via table but the following generator saves DSP memory Calculate III = IRe(lJ) C~lMll~te IQI = IIm~l Determine a section S in the first quadrant Referring to FIG. 11, there are 3 sectors in each quadrant. The sector that a symbol falls in is determined here. The 3 sectors are identified by S=0, 4, and 44.
- If IQI < lIl tan 30~, then S=44 If lIl ~ tan 30~< IQI ~ tan 60~ then S=0 If lIl ~ tan 60~ < IQI, then S=4 Calculate y = (Q2 + I2)'n Calculate rings:
R=3 0 < ~ < 1.225.10-3 The boundaries should be less than l;
see FIG. 11 for the generated metric decision zones, incllltiing the five possible rings.
R=2 1.225.10-3 <y < 4.9.10-3 R=1 4.9.10-3< y < 0.0196 R=0 0.0196 <~ < 0.49 - SUBSTITUTE SH EET (RULE 26) R=3 ~ > 0.49 C~lc~ te metrics:
MSD = S+R and MHD = 0: Q 2 O, I 2 0 The metrics (ME~) for hard detection and MSD for soft detectinn) are determined here based on the values of S and R.
MHD places the signal on one of four quadrants. MSD places the signal on the metric decision zone in FIG. 1. For example, if MHD
=1 (i.e. quadrant 1) and S = 44 and R =1, then MSD =17. See zone 17 in quadrant 1 of FIG. 11.
MSD = [(12-S) mod 48] + R and MHD = 1, mod indicates modular arithmetic for Q 2 O, I~O
MSD = [(24+S) mod 48] + R and ME~D =3, for Q~O, I<O
MSD = [(36-S) mod 48] + R and MHD =2, for Q<O, I > O
SUBSTITUTE SHEET (RULE 26) TABLEl-LSB Metrics IN OUT IN OUT
SUBSTITUTE SHEET (RULE 26) TABLE 2 - MSB Metr~cs rN ou r rN ou r SUBSTITUTE SHEET (RULE 26) An example will now be given that illustrates the processing of one symbol and the effect of an erasure on that symbol. Suppose that the first symbol in a time slot, Sl, is received and that, when applied to the metric generation routine, yields S = 44, R = 1 and MHD = 1. Applying these facts to the MSD equation:
MSD = [(12 - S) mod48] + R= [(12 - 44) mod 48] + 1 = 17 Thus, the symbol S 1 falls in zone 17 in quadrant 1 in FIG. 11.
Next MET0[1] and MET1[1] are generated by applying MSD to TABLE 1 and TABLE 2, respectively:
MET0[1] = 6 = 110 MET1[1] = 1 = 001 The first bit of MET0[1] specifies I = 1 and the next two bits, 10, specify a confidence level (00 is the lowest level, 11 is the highest). The first bit of MET1[1] specifies Q = 0 and the next two bits specify a confidence level.
Erasures are made, if at all, once all of the symbols in the time slot have beenprocessed. If the channel state falls below a threshold, CS min, then the confiden~e bits for all symbols in a time slot, Si, are set to "null values", which are of low level of confidPnce, like 00. The processing then changes the values of the I and the Q bits to null metrics which do not contribute to an erroneous decision at the error correcting SUBSTITUTE SH EET (RULE 26) process. F~enti~lly~ the erasure means that the I and Q information content from the time slot is not used. Thus, if an erasure needs to be made, the following occurs:
MET0[1] = 4 = 100 METl[l] = O = 000 This is repeated for all symbols in the time slot.
It is understood that changes may be made in the above description without departing from the scope of the invention. It is accordingly int~n~ed that all matter contained in the above description and in the drawings be interpreted as illustrative rather than limiting SUBSTITUTE SHFET (RULE 26)
Claims
We claim:
A method of deriving the state of a channel on which communication signals are transmitted and received comprising the steps of:
determining the modulation point of the signal as transmitted;
determining the variance between the signal as received and the modulation point;
and determining the state of the channel in accordance with the variance.
The method of claim 1, wherein the phase variance between the signal as received and the modulation point is determined.
The method of claim 1 wherein the distance between the signal as received and the modulation point is determined.
Apparatus for deriving the state of a channel on which communication signals are transmitted and received, comprising:
means for determining the modulation point of the signal as transmitted;
means for determining the variance between the signal as received and the modulation point; and means for determining the state of the channel in accordance with the variance.
The apparatus of claim 4, wherein the phase variance between the signal as received and the modulation point is determined.
The apparatus of claim 4, wherein the distance between the signal as received and the modulation point is determined.
A method of deriving the state of a channel on which communication signals are transmitted and received, comprising the steps of:
for a plurality of signals, determining the modulation point of the signals as transmitted;
for each of the plurality of signals, determining the variance between the signal as received and the modulation point; and determining the state of the channel in accordance with the average variance of each of the plurality of signals.
The method of claim 7, wherein the signals from a time slot are used.
The method of claim 7, wherein the determined variance is the phase difference between the signal as received and the modulation point.
The method of claim 9, wherein the signals from a time slot are used.
The method of claim 10, wherein the state of the channel is determined in accordance with the following equation.
where .theta. (Si) is the phase of a received signal and .theta. (mod) is the phase of the modulation point of the transmitted signal.
12. The method of claim 7, wherein the determined variance is the distance between the signal as received and the modulation point.
13. The method of claim 12, wherein the signals from a time slot are used.
14. The method of claim 13, wherein the state of the channel is determined in accordance with the following equation:
wherein Ei is the distance between a received signal and the modulation point of the transmitted signal.
15. Apparatus for deriving the state of a channel on which communication signals are transmitted and received, comprising:
means for determining the modulation point of the signals as transmitted for a plurality of signals;
means for determining the variance between the signal as received and the modulation point for each of the plurality of signals; and means for determining the state of the channel in accordance with the average variance of each of the plurality of signals.
16. The apparatus of claim 15, wherein the signals from a time slot are used.
17. The apparatus of claim 16, wherein the determined variance is the phase difference between the signal as received and the modulation point.
18. The apparatus of claim 17, wherein the signals from a time slot are used.
19. The apparatus of claim 18, wherein the state of the channel is determined in accordance with the following equation:
where .theta. (Si) is the phase of a received signal and .theta.(mod) is the phase of the modulation point of the transmitted signal.
20. The apparatus of claim 15, wherein the determined variance is the distance between the signal as received and the modulation point.
21. The apparatus of claim 20, wherein the signals from a time slot are used.
22. The apparatus of claim 21, wherein the state of the channel is determined in accordance with the following equation:
wherein Ei is the distance between a received signal and the modulation point of the transmitted signal.
A method for processing a first communication signal and a second communication signal received by a communication device at approximately the same time on a first and second communication channel, respectively, comprising the steps of:
determining the state of the first communication channel;
determining the state of the second communication channel; and selecting between the first communication signal and the second communication signal based on the state of the first communication channel and on the state of the second communication channel.
The method of claim 23, wherein the first communication signal is selected for further processing when the state of the first communication channel is better than the state of the second communication channel and wherein the second communication signal is selected for further processing when the state of the second communication channel is better than the state of the first communication channel.
The method of claim 24, wherein the channel state is determined by determining the modulation point of a signal as transmitted on a communication channel, by determining the variance between the signal as received and the modulation point and then determining the channel state in accordance with the variance.
The method of claim 24, wherein the channel state is determined by determining the modulation point of each of a plurality of signals as transmitted on a communication channel, by determining the variance between each of the plurality of signals as received and the modulation points and then determining the channel state in accordance with the average variance.
The method of claim 26, wherein the selection of signals from the first or second communication channel is made based on the number of signals used to determine channel state.
The method of claim 26, wherein the plurality of signals used to determine channel state come from a time slot.
The method of claim 28, wherein the selection of signals for further processing is made every time slot.
The method of claim 24, wherein the channel state is determined by comparing the phase of a signal as received to the phase of the modulation point of the signal as transmitted.
The method of claim 30, wherein the channel state is determined by comparing the phase of a signal as received to the phase of the modulation point of the signal as transmitted for a plurality of signals and then using the average variation.
The method of claim 31, wherein the selection is made every time a new plurality of signals is used to determine channel state.
33. The method of claim 31, wherein the signals within a time slot are used to determine channel state and wherein the selection is made for every time slot.
34. The method of claim 24, wherein the channel state is determined by comparing the distance between a signal as received and the modulation point of the signal as transmitted.
35. The method of claim 34, wherein the channel state is determined by comparing the distance between a signal as received and the modulation point of the signal as transmitted for a plurality of signals and then using the average distance.
36. The method of claim 35, wherein the selection is made everytime a new plurality of signals is used to determine channel state.
37. The method of claim 35, wherein the signals within a time slot are used to determine channel state and wherein the selection is made for every time slot.
38. Apparatus for processing a first communication signal and a second communication signal received by a communication device at approximately the same time on a first and second communication channel, respectively, comprising:
means for determining the state of the first communication channel;
means for determining the state of the second communication channel; and means for selecting between the first communication signal and the second communication signal based on the state of the first communication channel and on the state of the second communication channel.
39. The apparatus of claim 38, wherein the first communication signal is selected for further processing when the state of the first communication channel is better than the state of the second communication channel and wherein the second communication signal is selected for further processing when the state of the second communication channel is better than the state of the first communication channel.
40. The method of claim 38, wherein the channel state is determined by determining the modulation point of a signal as transmitted on a communication channel, by determining the variance between the signal as received and the modulation point and then determining the channel state in accordance with the variance.
41. The apparatus of claim 38, wherein the channel state is determined by determining the modulation point of each of a plurality of signals as transmitted on a communication channel, by determining the variance between each of the plurality of signals as received and the modulation points and then determining the channel state in accordance with the average variance.
42. The method of claim 41, wherein the selection of signals from the first or second communication channel is made based on the number of signals used to determine channel state.
The apparatus of claim 41, wherein the plurality of signals used to determine channel state come from a time slot.
The apparatus of claim 43, wherein the selection of signals for further processing is made every time slot.
The apparatus of claim 38, wherein the channel state is determined by comparing the phase of a signal as received to the phase of the modulation point of the signal as transmitted.
The apparatus of claim 45, wherein the channel state is determined by comparing the phase of a signal as received to the phase of the modulation point of the signal as transmitted for a plurality of signals and then using the average variation.
The apparatus of claim 46, wherein the selection is made every time a new plurality of signals is used to determine channel state.
The apparatus of claim 46, wherein the signals within a time slot are used to determine channel state and wherein the selection is made for every time slot.
The apparatus of claim 38, wherein the channel state is determined by comparing the distance between a signal as received and the modulation point of the signal as transmitted.
50. The apparatus of claim 49, wherein the channel state is determined by comparing the distance between a signal as received and the modulation point of the signal as transmitted for a plurality of signals and then using the average distance.
51. The apparatus of claim 50, wherein the selection is made everytime a new plurality of signals is used to determine channel state.
52. The apparatus of claim 50, wherein the signals within a time slot are used to determine channel state and wherein the selection is made for every time slot.
53. A method of processing communication signals, comprising the steps of:
determining the state of a communication channel on which a communication signal is received;
comparing the state of the communication channel to a threshold; and erasing the communication signal if the state of the communication channel does not exceed a threshold.
54. The method of claim 53, wherein the erasure is performed by setting the received communication signal to a null value.
55. The method of claim 53, wherein the channel state is determined by determining the modulation point of a signal as transmitted on a communication channel, by determining the variance between the signal as received and the modulation point and then determining the channel state in accordance with the variance.
56. The method of claim 53, wherein the channel state is determined by determining the modulation point of each of a plurality of signals as transmitted on a communication channel by determining the variance between each of the plurality of signals as received and the modulation points and then determining the channel state in accordance with the average variance.
57. The method of claim 56, wherein the number of signals erased corresponds to the number of signals used to determine channel state.
58. The method of claim 56, wherein the plurality of signals used to determine channel state come from a time slot.
59. The method of claim 58, wherein the decision to erase signals is made every time slot.
60. The method of claim 53, wherein the channel state is determined by comparing the phase of a signal as received to the phase of the modulation point of the signal as transmitted.
61. The method of claim 60, wherein the channel state is determined by comparing the phase of a signal as received to the phase of the modulation point of the signal as transmitted for a plurality of signals and then using the average variation.
62. The method of claim 61, wherein the decision to erase is made every time a new plurality of signals is used to determine channel state.
63. The method of claim 61, wherein the signals within a time slot are used to determine channel state and wherein the decision to erase is made every time slot.
64. The method of claim 53, wherein the channel state is determined by comparing the distance between a signal as received and the modulation point of the signal as transmitted.
65. The method of claim 64, wherein the channel state is determined by comparing the distance between a signal as received and the modulation point of the signal as transmitted for a plurality of signals and then using the average distance.
66. The method of claim 65, wherein the decision to erase is made everytime a new plurality of signals is used to determine channel state.
67. The method of claim 65, wherein the signals within a time slot are used to determine channel state and wherein the decision to erase is made every time slot.
68. Apparatus for processing communication signals, comprising:
means for determining the state of a communication channel on which a communication signal is received;
means for comparing the state of the communication channel to a threshold; and means for erasing the communication signal if the state of the communication channel does not exceed a threshold.
69. The apparatus of claim 68, wherein the erasure is performed by setting the received communication signal to a null value.
70. The apparatus of claim 68, wherein the channel state is determined by determining the modulation point of a signal as transmitted on a communication channel by determining the variance between the signal as received and the modulation point and then determining the channel state in accordance with the variance.
71. The apparatus of claim 68, wherein the channel state is determined by determining the modulation point of each of a plurality of signals as transmitted on a communication channel, by determining the variance between each of the plurality of signals as received and the modulation points and then determining the channel state in accordance with the average variance.
72. The apparatus of claim 68, wherein the number of signals erased corresponds to the number of signals used to determine channel state.
73. The apparatus of claim 68, wherein the plurality of signals used to determine channel state come from a time slot.
74. The apparatus of claim 73 wherein the decision to erase signals is made every time slot.
75. The apparatus of claim 68 wherein the channel state is determined by comparing the phase of a signal as received to the phase of the modulation point of the signal as transmitted.
76. The apparatus of claim 75 wherein the channel state is determined by comparing the phase of a signal as received to the phase of the modulation point of the signal as transmitted for a plurality of signals and then using the average variation.
77. The apparatus of claim 76, wherein the decision to erase is made every time a new plurality of signals is used to determine channel state.
78. The apparatus of claim 76, wherein the signals within a time slot are used to determine channel state and wherein the decision to erase is made every time slot.
79. The apparatus of claim 68 wherein the channel state is determined by comparing the distance between a signal as received and the modulation point of the signal as transmitted.
80. The apparatus of claim 79 wherein the channel state is determined by comparing the distance between a signal as received and the modulation point of the signal as transmitted for a plurality of signals and then using the average distance.
81. The method of claim 80, wherein the decision to erase is made everytime a new plurality of signals is used to determine channel state.
82. The apparatus of claim 80, wherein the signals within a time slot are used to determine channel state and wherein the decision to erase is made every time slot.
83. A method of processing a first communication signal and a second communication signal received by a communication device at approximately the same time on a first and a second communication channel, respectively, comprising the steps of:
determining the state of the first communication channel in accordance with a first process;
determining the state of the second communication channel in accordance with the first process;
selecting between the first communication signal and the second communication signal based on the state of the first communication channel and on the state of the second communication channel as determined by the first process;
determining the state of the selected communication channel in accordance with a second process;
comparing the state of the selected communication channel to a threshold; and erasing the signals of the selected communication channel if the state of the communication channel does not exceed the threshold.
84. Apparatus for processing a first communication signal and a second communication signal received by a communication device at approximately the same time on a first and a second communication channel, respectively, comprising:
means for determining the state of the first communication channel in accordance with a first process;
means for determining the state of the second communication channel in accordance with the first process;
means for selecting between the first communication signal and the second communication signal based on the state of the first communication channel and on the state of the second communication channel as determined by the first process;
means for determining the state of the selected communication channel in accordance with a second process;
means for comparing the state of the selected communication channel to a threshold; and means for erasing the signals of the selected communication channel if the state of the communication channel does not exceed the threshold.
A method of deriving the state of a channel on which communication signals are transmitted and received comprising the steps of:
determining the modulation point of the signal as transmitted;
determining the variance between the signal as received and the modulation point;
and determining the state of the channel in accordance with the variance.
The method of claim 1, wherein the phase variance between the signal as received and the modulation point is determined.
The method of claim 1 wherein the distance between the signal as received and the modulation point is determined.
Apparatus for deriving the state of a channel on which communication signals are transmitted and received, comprising:
means for determining the modulation point of the signal as transmitted;
means for determining the variance between the signal as received and the modulation point; and means for determining the state of the channel in accordance with the variance.
The apparatus of claim 4, wherein the phase variance between the signal as received and the modulation point is determined.
The apparatus of claim 4, wherein the distance between the signal as received and the modulation point is determined.
A method of deriving the state of a channel on which communication signals are transmitted and received, comprising the steps of:
for a plurality of signals, determining the modulation point of the signals as transmitted;
for each of the plurality of signals, determining the variance between the signal as received and the modulation point; and determining the state of the channel in accordance with the average variance of each of the plurality of signals.
The method of claim 7, wherein the signals from a time slot are used.
The method of claim 7, wherein the determined variance is the phase difference between the signal as received and the modulation point.
The method of claim 9, wherein the signals from a time slot are used.
The method of claim 10, wherein the state of the channel is determined in accordance with the following equation.
where .theta. (Si) is the phase of a received signal and .theta. (mod) is the phase of the modulation point of the transmitted signal.
12. The method of claim 7, wherein the determined variance is the distance between the signal as received and the modulation point.
13. The method of claim 12, wherein the signals from a time slot are used.
14. The method of claim 13, wherein the state of the channel is determined in accordance with the following equation:
wherein Ei is the distance between a received signal and the modulation point of the transmitted signal.
15. Apparatus for deriving the state of a channel on which communication signals are transmitted and received, comprising:
means for determining the modulation point of the signals as transmitted for a plurality of signals;
means for determining the variance between the signal as received and the modulation point for each of the plurality of signals; and means for determining the state of the channel in accordance with the average variance of each of the plurality of signals.
16. The apparatus of claim 15, wherein the signals from a time slot are used.
17. The apparatus of claim 16, wherein the determined variance is the phase difference between the signal as received and the modulation point.
18. The apparatus of claim 17, wherein the signals from a time slot are used.
19. The apparatus of claim 18, wherein the state of the channel is determined in accordance with the following equation:
where .theta. (Si) is the phase of a received signal and .theta.(mod) is the phase of the modulation point of the transmitted signal.
20. The apparatus of claim 15, wherein the determined variance is the distance between the signal as received and the modulation point.
21. The apparatus of claim 20, wherein the signals from a time slot are used.
22. The apparatus of claim 21, wherein the state of the channel is determined in accordance with the following equation:
wherein Ei is the distance between a received signal and the modulation point of the transmitted signal.
A method for processing a first communication signal and a second communication signal received by a communication device at approximately the same time on a first and second communication channel, respectively, comprising the steps of:
determining the state of the first communication channel;
determining the state of the second communication channel; and selecting between the first communication signal and the second communication signal based on the state of the first communication channel and on the state of the second communication channel.
The method of claim 23, wherein the first communication signal is selected for further processing when the state of the first communication channel is better than the state of the second communication channel and wherein the second communication signal is selected for further processing when the state of the second communication channel is better than the state of the first communication channel.
The method of claim 24, wherein the channel state is determined by determining the modulation point of a signal as transmitted on a communication channel, by determining the variance between the signal as received and the modulation point and then determining the channel state in accordance with the variance.
The method of claim 24, wherein the channel state is determined by determining the modulation point of each of a plurality of signals as transmitted on a communication channel, by determining the variance between each of the plurality of signals as received and the modulation points and then determining the channel state in accordance with the average variance.
The method of claim 26, wherein the selection of signals from the first or second communication channel is made based on the number of signals used to determine channel state.
The method of claim 26, wherein the plurality of signals used to determine channel state come from a time slot.
The method of claim 28, wherein the selection of signals for further processing is made every time slot.
The method of claim 24, wherein the channel state is determined by comparing the phase of a signal as received to the phase of the modulation point of the signal as transmitted.
The method of claim 30, wherein the channel state is determined by comparing the phase of a signal as received to the phase of the modulation point of the signal as transmitted for a plurality of signals and then using the average variation.
The method of claim 31, wherein the selection is made every time a new plurality of signals is used to determine channel state.
33. The method of claim 31, wherein the signals within a time slot are used to determine channel state and wherein the selection is made for every time slot.
34. The method of claim 24, wherein the channel state is determined by comparing the distance between a signal as received and the modulation point of the signal as transmitted.
35. The method of claim 34, wherein the channel state is determined by comparing the distance between a signal as received and the modulation point of the signal as transmitted for a plurality of signals and then using the average distance.
36. The method of claim 35, wherein the selection is made everytime a new plurality of signals is used to determine channel state.
37. The method of claim 35, wherein the signals within a time slot are used to determine channel state and wherein the selection is made for every time slot.
38. Apparatus for processing a first communication signal and a second communication signal received by a communication device at approximately the same time on a first and second communication channel, respectively, comprising:
means for determining the state of the first communication channel;
means for determining the state of the second communication channel; and means for selecting between the first communication signal and the second communication signal based on the state of the first communication channel and on the state of the second communication channel.
39. The apparatus of claim 38, wherein the first communication signal is selected for further processing when the state of the first communication channel is better than the state of the second communication channel and wherein the second communication signal is selected for further processing when the state of the second communication channel is better than the state of the first communication channel.
40. The method of claim 38, wherein the channel state is determined by determining the modulation point of a signal as transmitted on a communication channel, by determining the variance between the signal as received and the modulation point and then determining the channel state in accordance with the variance.
41. The apparatus of claim 38, wherein the channel state is determined by determining the modulation point of each of a plurality of signals as transmitted on a communication channel, by determining the variance between each of the plurality of signals as received and the modulation points and then determining the channel state in accordance with the average variance.
42. The method of claim 41, wherein the selection of signals from the first or second communication channel is made based on the number of signals used to determine channel state.
The apparatus of claim 41, wherein the plurality of signals used to determine channel state come from a time slot.
The apparatus of claim 43, wherein the selection of signals for further processing is made every time slot.
The apparatus of claim 38, wherein the channel state is determined by comparing the phase of a signal as received to the phase of the modulation point of the signal as transmitted.
The apparatus of claim 45, wherein the channel state is determined by comparing the phase of a signal as received to the phase of the modulation point of the signal as transmitted for a plurality of signals and then using the average variation.
The apparatus of claim 46, wherein the selection is made every time a new plurality of signals is used to determine channel state.
The apparatus of claim 46, wherein the signals within a time slot are used to determine channel state and wherein the selection is made for every time slot.
The apparatus of claim 38, wherein the channel state is determined by comparing the distance between a signal as received and the modulation point of the signal as transmitted.
50. The apparatus of claim 49, wherein the channel state is determined by comparing the distance between a signal as received and the modulation point of the signal as transmitted for a plurality of signals and then using the average distance.
51. The apparatus of claim 50, wherein the selection is made everytime a new plurality of signals is used to determine channel state.
52. The apparatus of claim 50, wherein the signals within a time slot are used to determine channel state and wherein the selection is made for every time slot.
53. A method of processing communication signals, comprising the steps of:
determining the state of a communication channel on which a communication signal is received;
comparing the state of the communication channel to a threshold; and erasing the communication signal if the state of the communication channel does not exceed a threshold.
54. The method of claim 53, wherein the erasure is performed by setting the received communication signal to a null value.
55. The method of claim 53, wherein the channel state is determined by determining the modulation point of a signal as transmitted on a communication channel, by determining the variance between the signal as received and the modulation point and then determining the channel state in accordance with the variance.
56. The method of claim 53, wherein the channel state is determined by determining the modulation point of each of a plurality of signals as transmitted on a communication channel by determining the variance between each of the plurality of signals as received and the modulation points and then determining the channel state in accordance with the average variance.
57. The method of claim 56, wherein the number of signals erased corresponds to the number of signals used to determine channel state.
58. The method of claim 56, wherein the plurality of signals used to determine channel state come from a time slot.
59. The method of claim 58, wherein the decision to erase signals is made every time slot.
60. The method of claim 53, wherein the channel state is determined by comparing the phase of a signal as received to the phase of the modulation point of the signal as transmitted.
61. The method of claim 60, wherein the channel state is determined by comparing the phase of a signal as received to the phase of the modulation point of the signal as transmitted for a plurality of signals and then using the average variation.
62. The method of claim 61, wherein the decision to erase is made every time a new plurality of signals is used to determine channel state.
63. The method of claim 61, wherein the signals within a time slot are used to determine channel state and wherein the decision to erase is made every time slot.
64. The method of claim 53, wherein the channel state is determined by comparing the distance between a signal as received and the modulation point of the signal as transmitted.
65. The method of claim 64, wherein the channel state is determined by comparing the distance between a signal as received and the modulation point of the signal as transmitted for a plurality of signals and then using the average distance.
66. The method of claim 65, wherein the decision to erase is made everytime a new plurality of signals is used to determine channel state.
67. The method of claim 65, wherein the signals within a time slot are used to determine channel state and wherein the decision to erase is made every time slot.
68. Apparatus for processing communication signals, comprising:
means for determining the state of a communication channel on which a communication signal is received;
means for comparing the state of the communication channel to a threshold; and means for erasing the communication signal if the state of the communication channel does not exceed a threshold.
69. The apparatus of claim 68, wherein the erasure is performed by setting the received communication signal to a null value.
70. The apparatus of claim 68, wherein the channel state is determined by determining the modulation point of a signal as transmitted on a communication channel by determining the variance between the signal as received and the modulation point and then determining the channel state in accordance with the variance.
71. The apparatus of claim 68, wherein the channel state is determined by determining the modulation point of each of a plurality of signals as transmitted on a communication channel, by determining the variance between each of the plurality of signals as received and the modulation points and then determining the channel state in accordance with the average variance.
72. The apparatus of claim 68, wherein the number of signals erased corresponds to the number of signals used to determine channel state.
73. The apparatus of claim 68, wherein the plurality of signals used to determine channel state come from a time slot.
74. The apparatus of claim 73 wherein the decision to erase signals is made every time slot.
75. The apparatus of claim 68 wherein the channel state is determined by comparing the phase of a signal as received to the phase of the modulation point of the signal as transmitted.
76. The apparatus of claim 75 wherein the channel state is determined by comparing the phase of a signal as received to the phase of the modulation point of the signal as transmitted for a plurality of signals and then using the average variation.
77. The apparatus of claim 76, wherein the decision to erase is made every time a new plurality of signals is used to determine channel state.
78. The apparatus of claim 76, wherein the signals within a time slot are used to determine channel state and wherein the decision to erase is made every time slot.
79. The apparatus of claim 68 wherein the channel state is determined by comparing the distance between a signal as received and the modulation point of the signal as transmitted.
80. The apparatus of claim 79 wherein the channel state is determined by comparing the distance between a signal as received and the modulation point of the signal as transmitted for a plurality of signals and then using the average distance.
81. The method of claim 80, wherein the decision to erase is made everytime a new plurality of signals is used to determine channel state.
82. The apparatus of claim 80, wherein the signals within a time slot are used to determine channel state and wherein the decision to erase is made every time slot.
83. A method of processing a first communication signal and a second communication signal received by a communication device at approximately the same time on a first and a second communication channel, respectively, comprising the steps of:
determining the state of the first communication channel in accordance with a first process;
determining the state of the second communication channel in accordance with the first process;
selecting between the first communication signal and the second communication signal based on the state of the first communication channel and on the state of the second communication channel as determined by the first process;
determining the state of the selected communication channel in accordance with a second process;
comparing the state of the selected communication channel to a threshold; and erasing the signals of the selected communication channel if the state of the communication channel does not exceed the threshold.
84. Apparatus for processing a first communication signal and a second communication signal received by a communication device at approximately the same time on a first and a second communication channel, respectively, comprising:
means for determining the state of the first communication channel in accordance with a first process;
means for determining the state of the second communication channel in accordance with the first process;
means for selecting between the first communication signal and the second communication signal based on the state of the first communication channel and on the state of the second communication channel as determined by the first process;
means for determining the state of the selected communication channel in accordance with a second process;
means for comparing the state of the selected communication channel to a threshold; and means for erasing the signals of the selected communication channel if the state of the communication channel does not exceed the threshold.
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| IL115476 | 1995-10-01 | ||
| IL11547695A IL115476A0 (en) | 1995-10-01 | 1995-10-01 | Apparatus and method for determining and using channel state information |
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| CA2233723A1 true CA2233723A1 (en) | 1997-04-10 |
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| CA (1) | CA2233723A1 (en) |
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| US5989289A (en) | 1995-10-16 | 1999-11-23 | Sdgi Holdings, Inc. | Bone grafts |
| ATE262863T1 (en) | 1996-10-23 | 2004-04-15 | Sdgi Holdings Inc | SPACER FOR SWIVELS |
| US6033438A (en) | 1997-06-03 | 2000-03-07 | Sdgi Holdings, Inc. | Open intervertebral spacer |
| GB9821385D0 (en) * | 1998-10-01 | 1998-11-25 | British Broadcasting Corp | Improvements relating to measuring channel state from a received signal and discriminating digital values from a received signal,suitable for use in cofdm |
| US6174311B1 (en) | 1998-10-28 | 2001-01-16 | Sdgi Holdings, Inc. | Interbody fusion grafts and instrumentation |
| US7106810B2 (en) | 1999-10-07 | 2006-09-12 | Matthew James Collins | Method and apparatus for a demodulator circuit |
| GB2355164B (en) * | 1999-10-07 | 2004-06-09 | Oak Technology Inc | Demodulator circuit |
| GB0110907D0 (en) | 2001-05-03 | 2001-06-27 | British Broadcasting Corp | Improvements in decoders for many carrier signals, in particular in DVB-T recievers |
| US20040062215A1 (en) * | 2001-07-13 | 2004-04-01 | Takaharu Sato | Cdma reception apparatus and cdma reception method |
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| EP0454585B1 (en) * | 1990-04-27 | 1994-08-03 | Nippon Telegraph And Telephone Corporation | An antenna selection diversity reception system |
| US5214675A (en) * | 1991-07-02 | 1993-05-25 | Motorola, Inc. | System and method for calculating channel gain and noise variance of a communication channel |
| US5351274A (en) * | 1993-08-20 | 1994-09-27 | General Electric Company | Post detection selection combining diversity receivers for mobile and indoor radio channels |
| US5530926A (en) * | 1993-10-04 | 1996-06-25 | Motorola, Inc. | Method for operating a switched diversity RF receiver |
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1996
- 1996-10-01 AU AU69994/96A patent/AU6999496A/en not_active Abandoned
- 1996-10-01 WO PCT/IL1996/000120 patent/WO1997013378A2/en active Application Filing
- 1996-10-01 CA CA002233723A patent/CA2233723A1/en not_active Abandoned
Also Published As
| Publication number | Publication date |
|---|---|
| IL115476A0 (en) | 1996-05-14 |
| WO1997013378A3 (en) | 1997-06-05 |
| WO1997013378A2 (en) | 1997-04-10 |
| AU6999496A (en) | 1997-04-28 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| FZDE | Discontinued | ||
| FZDE | Discontinued |
Effective date: 20000706 |