Method and apparatus for determining the rate of received data in a variable rate communication system

Background of the Invention

I. Field of the Invention

The present invention relates to communications or communications. In particular, the present invention relates to a method and an apparatus for determining a transmission rate in a transmission system variable rate.

II. Description of the Related technology

The Using CDMA (Code Division Multiple Access) modulation techniques is one of several techniques to support a communication, in which a large Number of system users are present. Although other techniques, such as TDMA (Time Division Multiple Access), FDMA (Frequency Division Multiple access) and AM modulation schemes such as ACSSB (amplitude companded single Side Band) are known, CDMA has significant advantages over these other techniques. The use of CDMA techniques in a multiple access communication system is disclosed in US Pat. No. 4,901,307, entitled "SPREAD SPECTRUM MULTIPLE ACCESS COMMUNICATION SYSTEM USING SATELLITE OR TERRESTRIAL REPEATER "which the assignee of the present invention has been granted and by reference which is incorporated herein. The use of CDMA techniques in a Multiple access communication system is further disclosed in the US Pat. No. 5,103,459, entitled "SYSTEM AND METHOD FOR GENERATING SIGNAL WAVEFORMS IN A CDMA CELLULAR TELEPHONE SYSTEM ", which the applicant of the present invention has been granted.

CDMA provides due to its inherent feature a wideband signal a form of frequency diversity by Spreading the signal energy over a wide bandwidth. Therefore relates to a selective frequency fading only a small part of the CDMA signal bandwidth. A Space or path diversity is Providing multiple signal paths through simultaneous links from get a mobile user through two or more cell sites. Further can by a path diversity by exploiting the multipath environment a spread spectrum processing are obtained by a signal, that is arriving with different propagation delays, permits, to be received and processed separately. Examples of path diversity shown in US Pat. No. 5,101,501, entitled "METHOD AND SYSTEM FOR PROVIDING A SOFT handoff IN COMMUNICATIONS IN A CDMA CELLULAR TELEPHONE SYSTEM ", and in the US Pat. No. 5,109,390 entitled "DIVERSITY RECEIVER IN A CDMA CELLULAR TELEPHONE SYSTEM " both the assignee of the present invention have been issued.

CDMA systems frequently employ a "variable Rate "vocoder one, to encode data so that the data rate of a data frame to the next can be varied. An exemplary embodiment of a vocoder variable rate is described in U.S. Pat. No. 5,414,796 entitled "VARIABLE RATE VOCODER ", the the assignee of the present invention has been granted. The Usage a communication channel with variable rate reduces a mutual interference by Eliminating unnecessary transmissions, if there is no to be transmitted useful is language. Algorithms are used in the vocoder for generating a varying number of information bits in each frame in accordance with variations in the voice activity. For example, a vocoder with a rate set of four-20 millisecond data frames generate, containing 20, 40, 80, or 160 bits, depending on type the speaker. It is desirable each frame of data to be transmitted in a fixed amount of time by varying the transmission rate a communication. additional details about the formatting of the vocoder data into data frames are described in U.S. Pat. No. 5,511,073, entitled "METHOD AND APPARATUS FOR THE FORMATTING OF DATA FOR TRANSMISSION ", the assignee of the present Invention was granted.

A technology for the receiver, to determine the rate of a received data frame, will be described in US Pat. No. 5566206, entitled "METHOD AND APPARATUS FOR DETERMINING DATA RATE OF TRANSMITTED VARIABLE RATE DATA IN A COMMUNICATIONS RECEIVER "that the Assignee of the present invention has been granted. Another Technology is described in European Patent application 0720797 entitled "MULTI RATE SERIAL Viterbi DECODER FOR CODE DIVISION MULTIPLE ACCESS SYSTEM APPLICATIONS "the assignee of the present invention. According to these techniques, each received data frame with each of the possible rates decoded. Error metrics, what quality the the decoded symbols for describe each decoded with each rate frame, are to a Processor delivered. The error metrics may CRC (cyclic redundancy check - cyclic Redundancy check) results, Yamamoto Quality Metrics and symbol error rate include. These error metrics are in communication systems widely known. The processor analyzes the error metrics and determines the most likely rate at which transfer the incoming symbols were.

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Further Attention is drawn to the document US A 5,509,020, the decoding device a for received Data revealed that transmitted receives folded code data and decoded. The received data from a first channel, whose data rate is fixed, and formed a second channel whose Data rate is variable. The decoding device for received Data includes a "high probability (Most likelihood) "- decoder for decoding of the received data on the basis of a Viterbi algorithm and a data rate decision unit for obtaining a predetermined Data rate of the second channel, which determines in accordance with a path-metric value is, the decoder is a decoded output from the "highest probability".

According to the present Invention, a method for determining a current rate a current frame, as set forth in claim 1, a receiver, such as set forth in claim 17, and a communication system as in claim 34 set forth, is provided. Preferred embodiments of the present Invention are in the dependent claims claimed.

Summary the invention

The present invention provides a new and improved apparatus and a method for decoding data. The device and the method in a communication system having a Transmitter and a receiver used, wherein the receiver determines which ones of a plurality rate frames in a transmitted signal from the transmitter were. For example, when the transmitter employs four transmission rates, decodes the receiver each frame of the received signal based on the four rates, four CRC (cyclic redundanoy check) bits, four symbol error rate (SER - symbol error rate) values ​​and one or more Yamamoto check value (e) to create. If the CRC on two installments is true, then the receiver compares the SER values ​​for those two installments each other in order to determine with which of the two installments a current frame was transmitted. If the CRC on a rate is true, then the SER value for that rate is at a maximum SER threshold for this rate compared. additionally can SER values ​​for the other rates are compared to minimum SER thresholds. Further, the Yamamoto check values are analyzed to determine if each loose or tighter minimum and maximum SER thresholds should be used, if the Yamamoto values ​​for agree the current rate or not vote.

General expressed, incorporating the present invention a method for use in a communication system having a Transmitter and a receiver. The transmitter transmits a signal having an instantaneous rate, the current rate is one of a Variety of rates corresponds. The receiver generates a plurality of Prüffehlerwerten and error rate codes and at least one decoding code, each is based on whether the signal has one of the plurality of rates. the The method determines the current rate of said signal and comprises the Steps: (a) determining if only a first check value of a selected rate is positive, wherein the selected Rate is one of a plurality of rates; (B) determining if the selected rate a predetermined rate corresponds; (C) if the selected rate the predetermined rate corresponds to comparing a selected decoding code with an elected Value; (D) if the selected Rate does not correspond to the predetermined rate, comparing a selected error rate code with a first value based on a predetermined operational relationship, whereby the selected Rate Plan chosen Rate corresponds; (E) if the selected decoding code to the selected value equivalent, comparing the selected Error rate code to a second value predetermined based on the Operation relationship; (F) if the selected decoding code is not the selected Value corresponds to, comparing the selected error rate code with a third value based on the predetermined operational relationship; and (g) determining that said current rate of the signal the chosen rate is, if the selected Error rate code the predetermined operational relationship with the first, has second or third value.

General expressed, incorporating the present invention also a method for determining the current rate of the signal comprising the steps of: (a) determining that only first and second Fehlerprüfwerte of first and second rates are positive, wherein the first and second Rates of the plurality of rates; (B) comparing a first Error rate codes with a second error rate code plus a first Value based on a predetermined operational relationship, wherein the first and second error rate codes the first and second rates comply; and (c) determining that the current rate of the signal the second rate is, when the first error rate code the predetermined Operating relationship with the second Feh lerratencode plus a first value has, and otherwise determining that said current rate of the first Rate.

BRIEF DESCRIPTION OF THE drawings

The Features, objects and advantages of the present invention are apparent from the following detailed description in Conjunction with the drawings, in which like reference numerals corresponding identify and wherein:

<figref idrefs="S36">1</figref> a Block diagram of the commu&lt;?page 4?&gt;cation system of the present invention is;

<figref idrefs="S37">2</figref> on Flowchart illustrating a method for selecting the decoded Frame when the CRC for two different rates true;

<figref idrefs="S38">3</figref> on Flow chart an alternative method for selecting the decoded frame when the CRC for two different rates true;

<figref idrefs="S39">4</figref> on Flowchart illustrating a method for selecting the decoded Frame when the CRC for a rate determined;

<figref idrefs="S40">5</figref> on Flow chart an alternative method for selecting the decoded frame when the CRC agrees to a rate; and

<figref idrefs="S41">6</figref> a Representation of rate decision regions for symbol error rate i and j , if the CRC for both rates i and j is true.

Detailed Description of the Preferred Embodiments

Among with reference to <figref idrefs="S36">1</figref> transmits a remote sending system <figref>2</figref> data to a remote receiving system <figref>4</figref>, In an exemplary execution example the present invention in a wireless communication system implemented that, using spread spectrum modulation signals communicates. A communication using spread spectrum communication systems is detailed in US Patent 4,901,307 above and 5,103,459 described.

A Data Source <figref>6</figref> variable rate provides data frames with variable rate for transmission a CRC (cyclic redundancy check - cyclic redundancy check) - and Schlussbit generator <figref>8</figref>, In the exemplary embodiment, is the data source <figref>6</figref> a vocoder for variable rates for encoding of voice information with four variable rates as described in detail in the above mentioned US Pat. No. 5,414,796 is described. If, for example, in used a cellular telephone environment, the signal is with transferred the full rate, to transfer language (That is, when a user speaks), and is transmitted to the eighth rate, to transmit silence (Ie when the user is not speaking). The eighth rate saves on the number of transmitted Bits and thus saves energy. In general, 90% of from the transmitter <figref>2</figref> to the receiver <figref>4</figref> transmitted Signals either in full or eighth rate. The half and quarter Rates make the transition rates between full and eighth rates are.

Of the generator <figref>8</figref> generates a set of CRC bits for error detection at the transmitter, as is well known in the art. In addition, the generator depends<figref>8</figref> a Sequence of tail bits to the frame. In the exemplary embodiment the generator <figref>8</figref> the set of CRC and tail bits according to the "Telecommunications Industry Association's TIA / EIA / IS-95-A Mobile Stations - Base Station Compatibility Standard for Dual-Mode Wideband Spread Spectrum Cellular System ".

Of the Data frame is from the generator <figref>8</figref> to an encoder <figref>10</figref> delivered, of the data as symbols of an error correction and detection coded at the receiver. In the exemplary embodiment the encoder <figref>10</figref> 1/2-rate convolutional. The coded Sy Mbole be a interleaving or an interleaver <figref>12</figref> provided that the encoded symbols according to a predetermined interleaving reorders. In the exemplary embodiment the interleaver <figref>12</figref> a block interleaver, whose design are and implementation in art widely known.

Of the reordered frame is then provided to a modulator <figref>14</figref> delivered, of the frames for transmission modulated. In the exemplary embodiment, the modulator<figref>14</figref> on CDMA modulator, the implementation in detail in the aforementioned US patents describes 4,901,307 and 5,103,459. The modulated data frame is to a transmitter (TMTR or TX-transmitter) <figref>16</figref> delivered. The transmitter <figref>16</figref> converts the signal up and amplifies it for transmission through an antenna <figref>18</figref>,

The transmitted Signal from an antenna <figref>20</figref> a remote station <figref>4</figref>. such as a cellular telephone, receive, and to a receiver (RCVR - receiver) <figref>22</figref> delivered, the down-converts the received signal and amplified. The received signal is then provided to a demodulator (DEMOD) <figref>24</figref> delivered, which demodulates the signal. In the embodiment beispiehaften the demodulator <figref>24</figref> a CDMA demodulator <figref>24</figref>. its implementation in detail in the aforementioned U.S. Patents 4,901,307 and is described in 5,103,459.

the demodulated signal is then provided to a diversity combiner <figref>26</figref> delivered. The diversity combiner <figref>26</figref> combines the demodulated Signal from the demodulator <figref>24</figref> with demodulated signals from other demodulators (not shown), the same signal demodulate, except it on another transmission path is supplied. The design and implementation of the diversity combiner<figref>26</figref> becomes detail in the above-mentioned US Patent 5,109,390 describes. The diversity combined signal is a de-interleaver&lt;?page 5?&gt;ver <figref>28</figref> delivered, the symbols in the frame according to a predetermined reordering format that well known in the art is, reorders.

Of the reordered frame is then provided to a multi-rate decoder <figref>30</figref> delivered, the error correction for provides a framework of symbols. The decoder<figref>30</figref> decoded the data based on a predetermined set of rate hypotheses. In the exemplary embodiment, is the decoder <figref>30</figref> a multi-rate Viterbi decoder, as detailed in the above-mentioned co-pending US patent application Ser. No. 08 is / 126.477.

In decodes the exemplary embodiment, , the decoder <figref>30</figref> the symbols for each of the four possible Rates, separated by four decoded frames of data provided, each of which a CRC check detector or a CRC Tester <figref>32</figref> supplied is. The CRC check detector<figref>32</figref> certainly by conventional Techniques, whether the CRC bits for every frame of the decoded data is correct. The CRC check detector<figref>32</figref> performs a CRC check for the CRC bits in the four decoded frames through to assist in the determination, whether the currently received frame with the full, half, the quarter or the eighth transfer rate has been. As a result, delivers the CRC check detector<figref>32</figref> four check bits, C₁, C₂, C₄ and C₈Wherein a binary Show value of "1" for a given CRC check bit can that the CRC check coincided or a positive test result has, during a binary Value of "0" may indicate that the CRC bits no positive test have. As used herein generally corresponds to the subscript Index or the "1" full rate, "2" corresponds to half Rate, "4" corresponds to the quarter Rate and "8" corresponds to the eighth Rate.

In addition, supplies , the decoder <figref>30</figref> the decoded data to a symbol error rate (SER - symbol error rate) -Prüf detector. The SER detector <figref>34</figref> receives the decoded bits and an estimate of the received symbol data from decoder <figref>30</figref>, As known is encoded, the SER detector <figref>34</figref> the newly decoded bits and compares them to the estimate of the received symbol data from decoder <figref>30</figref>, The SER is a number of discrepancies between the re-encoded Symbol data and the received symbol data. Thus, the SER detector generates<figref>34</figref> four SER values: SER₁, SER₂. SER₄ and SER₈, For processing efficiency provides the SER detector <figref>34</figref> SER values ​​with a maximum value of 255. In addition, the CRC bits help the SER values, a determination of the rate of from the transmitter <figref>2</figref> transmitted current frame and whether the Frame error has to deliver.

Further provides the decoder <figref>30</figref> Information to a Yamamoto detector test <figref>36</figref>. of a confidence metric (confidence metric) based on the difference between the selected Path down through a trellis and the next path through the trellis. While the CRC check dependent is of the bits in each of the four decoded frames, the Yamamoto check is dependent on the decoding process of the receiver <figref>4</figref>, The Yamamoto detector <figref>36</figref> supplies, such as the detectors <figref>32</figref> and <figref>34</figref>. four Yamamoto values ​​for each of the four possible Rates: Y₁, Y₂, Y₄ and Y₈, Although the detectors <figref>32</figref>. <figref>34</figref> and <figref>36</figref> as separate Elements are shown, the Detectors in the hardware of the decoder <figref>30</figref> integrated be.

On control processor <figref>38</figref> receives the CRC check bits, SER values and Yamamoto values ​​from the detectors in each case <figref>32</figref>. <figref>34</figref> and <figref>36</figref>, processor <figref>38</figref> then determines which of the four rates the currently received frame was sent. The decoder<figref>30</figref> provides four decoded frames for storage in a buffer <figref>40</figref> decoded Frames, each of the four frame by means of one of the four rates is decoded. Based on by the processor<figref>38</figref> certain Rate provides the control processor sends a signal to the buffer <figref>40</figref> decoded Frame, which outputs in response to the stored frames, decoded with the certain rate, or no frame outputs if a deletion is specified. In an alternative embodiment, the buffer is<figref>40</figref> decoded Setting a signal indicative of a frame erasure if an erasure indicated is.

In the communication system of <figref idrefs="S36">1</figref> can the signal from the transmitter <figref>2</figref> to the receiver <figref>4</figref> transfer will quickly change between the four installments. As a result, the transmitter <figref>2</figref> in the transmitted Signal no actual display the rate at which the signal is being transferred. This would unnecessary require bandwidth. Therefore the station sends<figref>2</figref> a frame with a current rate (of the four rates selected) and a control processor <figref>38</figref> and the decoder <figref>30</figref> of receiver <figref>4</figref> determine with the routines described hereinafter, which of the four rates the currently received frame was sent or whether an erasure displayed to be (ie, whether the current frame with the full, half, sent quarterly or eighth rate). The decoder<figref>30</figref> decoded the one of the four decoded frames which has the determined rate, and outputs a decoded signal. The match decoded signal may then, for example, a vocoder, amplifier and Speaker (not shown) are input to a speech signal output generated by a user of the receiver <figref>4</figref> is heard.

&lt;?page 6?&gt;

Of the control processor <figref>38</figref>, At least to the decoder <figref>30</figref> connected is, operates in conjunction with the processes in the flowcharts the <figref idrefs="S37">2</figref>-<figref idrefs="S40">5</figref> illustrated be to select the appropriate decoded frame to the user issued or delivered is, or for the current Setting a deletion condition be declared. While the control processor <figref>38</figref> and the decoder <figref>30</figref> as separate Elements are shown, the control processor and the decoder are taken together, to form a single decoder.

Among with reference to <figref idrefs="S37">2</figref> determines an exemplary routine <figref>100</figref>That by the processor <figref>38</figref> is carried out, in step <figref>102</figref>Whether the CRC positive for two of the four rates is. For example, if the processor<figref>38</figref> determined that the CRC of the full and eighth rate is positive (ie, bits C₁ = C₈ = 1), but the CRCs of the half and quarter rate are not positive (ie bits C₂ = C₄ = 0), then the processor <figref>38</figref>In that the step <figref>102</figref> is satisfied. If the CRCs in step <figref>102</figref> are positive for exactly two installments, then the current frame can have three possible interpretations: he could deleted be, he could transmitted i at a first rate have been corresponding to the first rate that meets its CRC, or he could transmitted j at a second rate have been equal to the second rate that fulfills its CRC.

If However, the CRCs for less than two or more than two of the rates are positive, then determined in step <figref>104</figref> the processor <figref>38</figref>, if she CRC exactly for a rate is positive. If so, then in step<figref>108</figref> the processor <figref>38</figref> a "CRC check routine" by how hereinafter will be described. However, if the CRCs are positive for any of the installments or if the CRCs for three or four rates are positive, then explained in step <figref>106</figref> the processor <figref>38</figref> the currently received frame as an erasure. In general, if the CRCs for none of the rates are positive, the current frame is erased. Alternatively, if the CRCs for three or four of the rates are positive, while the processor <figref>38</figref> still always determine the instantaneous rate of the currently received frame could, such determination computationally difficult, a higher probability of error have and generally requires too much processing overhead, the rate for the current frame to determine quickly and accurately. is why it for the processor <figref>38</figref> simple, the current frame as a cancellation to to explain.

If in step <figref>102</figref> the CRCs for two rates are positive, then the processor compares <figref>38</figref> in step <figref>110</figref> the SER values ​​for the two rates in step <figref>102</figref> are positive. If the Example in step <figref>102</figref> the CRCs for the full and eighth Rates are positive, then the processor <figref>38</figref> in step <figref>110</figref>. if the SER value for the full rate (SER₁) Greater than or equal to the SER value for the eighth rate (SER₈) Plus a weighting value W is determined based on the full and eighth rate (W_1.8) Is determined. Generally compares the processor <figref>38</figref> in step <figref>110</figref> the SERs based on the following equation: <st32:df xmlns:st32="http://lighthouseip.com/">SER<st32:sub>i</st32:sub> ≥ SER<st32:sub>j</st32:sub> + W<st32:sub>i, j</st32:sub> (1)</st32:df>in which i and j are the two rates which respond to the two rates, in step <figref>102</figref> are positive.

Of the Weighting or scaling value W can one of six possible have values, since i and j can have one of four possible values ​​based on the four rates (ie W_1.2, W_1.4, W_1.8, W_2.4, W_2.8 and W_4.8). additionally the weighting value W can have a value in the range of -255 to +255 have since the SER values ​​have a maximum value of 255th Of the Weighting value W is generally necessary because of the different Probability densities of SERs for the possible rates and the differences in the ways the CRC check for the different current frame rate of the transmitter. The weighting value W is preferably formed based on empirical data come through experimentation. By forming an acceptable Target error rate and test the response of the communication system of <figref idrefs="S36">1</figref> among the four installments, be it used resulting empirical data, a weighting value W for each of the six combinations of rates to determine.

in the Generally provides the weighting value W is an increased level of confidence or a confidence level with which the two installments transfer the currently received frame has been. to determine only that the current rate equal to the rate is having the lower SER, can lead to a false determining the run rate of the current frame. Why must the SER_iits value is less than the SER_jValue plus a weighting factor, so that the processor <figref>38</figref> may determine that the rate of currently received frame is equal to the rate I is.

Sometimes it is less desirable to decode a current frame at an incorrect rate than the current frame as an erasure to explain. This is considered in the present invention. If a current frame is decoded at the wrong rate, the decoder <figref>30</figref> on disturbed or noisy signal, the amplified and at a user's ear can be broadcast. Such a disturbed signal may for a Users in the International&lt;?page 7?&gt;perception not be desirable. As a result, sacrifices the present invention provides a slightly higher frame erasure rate in exchange for no decode a current frame with the wrong rate. Nevertheless, the receiver attempts <figref>4</figref> preferably, a frame erasure rate maintaining less than 1%. Preferably, the probability that the wrong rate among the routines described herein determined is less than or equal to 10^-5,

If the SER_iValue greater than or equal to the SER_jValue plus the weighting value W_{i, j} is then determined in step <figref>112</figref> the processor <figref>38</figref>That the rate of the of the transmitter <figref>2</figref> received current frame rate is i (RX rate = Receiver rate or Receptions rate). Alternatively, if the SER_iValue is less than the SER_jValue plus W_{i, j} is, then determined in step <figref>114</figref> the processor <figref>38</figref>. that the rate of by the transmitter <figref>2</figref> received instantaneous Frame rate is equal to the j. In the above example, where i and j respectively the full and eighth match rate is when the SER₁-Value greater than or equal to the SER₈Value plus the weighting value W_1.8 is the rate of the currently received frame equal to the full rate in step <figref>112</figref>, Otherwise the Rate equal to the eighth rate in step <figref>114</figref>, After determining the rate of the current frame, the processor <figref>38</figref> on appropriate signal to the buffer <figref>40</figref>Which in response thereto the frame which is decoded according to the determined rate or no border issues when an erasure is declared.

On alternative embodiment according to the present Invention for determining the received signal rate where two of the vote four installments, is in <figref idrefs="S38">3</figref> as one routine <figref>120</figref> shown. This and other alternative embodiments, the are described below, are similar to the corresponding Embodiment described above, and common steps are identified by the same reference numerals. Only significant differences in operation are described in detail described.

Among with reference to <figref idrefs="S38">3</figref> the routine <figref>120</figref> the same steps <figref>102</figref>. <figref>104</figref>. <figref>106</figref> and <figref>108</figref> by, the above with reference to the routine <figref>100</figref> described were. In step<figref>124</figref> sets if the CRCs in step <figref>102</figref> for two of the agree rates, the processor <figref>38</figref> a more accurate comparison between the SER values ​​for the two in step <figref>102</figref> identified by installments to further ensure that the current frame with the corresponding rate is decoded. In particular, the processor sets<figref>38</figref> in step <figref>124</figref> a multiplicative factor k_{i, j} in the above equation (1), the following comparative function to offer: <st32:df xmlns:st32="http://lighthouseip.com/">SER<st32:sub>i</st32:sub> ≥ k<st32:sub>i, j</st32:sub>· SER<st32:sub>j</st32:sub> + W<st32:sub>i, j</st32:sub> (2).</st32:df>

As the weighting value W is the multiplicative factor k_{i, j} preferably through experimentation based on empirical data for the four transmission rates certainly. Thus, there are six possible multiplicative factors based on the four possible transmission rates (ie k_1.2, k_1.4, k_1.8, k_2.4, k_2.8 and k_4.8). Of the multiplicative factor k can simply be a normalization factor, so that for example, if i is equal to full and j is equal to half, k_1.2 two would be to the "half rate" -SER₂-Value with regard to the SER₁-value Normalize. Alternatively, the multiplicative factor k not only a normalization factor include, but compensate for differences between the different transmission rates, is as described below.

Among with reference to <figref idrefs="S41">6</figref> is a simplified diagram of rate decision regions for SER values ​​SER_i and SER_j shown, the CRCs for the rates i and j agree. Generally, a dividing line separates SER_i = k_{i, j}· SER_j + W_{i, j} a SER_i-Area <figref>140</figref> of a SER_j-Area <figref>142</figref>, As a result, determines the multiplicative factor k_{i, j} the slope the line, while the weighting value W_{i, j} whose offset or Offset from the origin (its y-intercept) determined. In general vary the multiplicative factor k and weighting value W the judgment region the areas <figref>140</figref> and <figref>142</figref>, For example, if the SER_iValue is less for the current frame than the SER_jValue, provides this framework a point above the line SER_i = k_{i, j}· SER_j + W_{i, j} and in the SER_j-Area <figref>142</figref>, In such a For example, the rate of the received frame then probably equal to j.

It can Probability density curves based on the empirical data, collected through experimentation, to create and an acceptable target error rate are defined. can then for one Part of the probability density curves below the acceptable Target error rate, are integrated to minimum and maximum SER threshold values ​​(in the Hereinafter discussed) for to determine any rate. The empirical data can be entered in worksheets be and known numerical analysis techniques in the spreadsheets be used to optimized values ​​below the target acceptable error rate to deliver. In sum, by experimenting the probability be determined, with the current rate is i, based on given SER values, wherein the probability then based on the SER_i-Value and the SER values ​​for the other rates (eg SER_j) is pictured.

in the Generally set the routine <figref>120</figref> and the other here described routines Functions &lt;?page 8?&gt;based on two rates and two SERs, SER_i, SER_j. a (ie, f (i, j, SER_i, SER_j)). In the exemplary embodiment, the present invention employs linear equations such as the Equation (2) and as shown in <figref idrefs="S41">6</figref> illustrated is. The weighting value W, the multiplicative factor k and the maximum and minimum SER thresholds (discussed below) are preferably in memory as a lookup table (not shown) stored on by the processor <figref>38</figref> is accessed.

In step <figref>124</figref> the processor <figref>38</figref> essentially, on which side of the line in <figref idrefs="S41">6</figref> one point exists, that of the two SER values ​​(SER_i. SER_j) Is defined, thereby the most likely rate for to determine the currently received frame. If the SER_iis value is less than k_{i, j} time the SER_jValue plus W_{i, j}. then the processor <figref>38</figref> in step <figref>126</figref>. whether SER_j is greater than a maximum acceptable SER threshold for the rate i (ie MaxSER_i). In general there is a maximum SER threshold for the given rate, beyond which the probability of an error (Decoding with the incorrect rate) is unacceptable. As cited above, be the maximum SER thresholds in <figref idrefs="S41">6</figref> shown be determined based on empirical data obtained by experimentation be derived with the four installments. If the SER_i-Value less than the maximum SER_i-Threshold is, then the processor <figref>38</figref> in step <figref>128</figref>. that the rate of the currently received frame is equal to i. If However, the SER_iValue greater than or equal to the maximum SER_i-Threshold is, then the processor <figref>38</figref> in step <figref>130</figref>. that the current frame erasure is.

If in step <figref>124</figref> the processor <figref>38</figref> determined that the SER_iValue greater than or equal than k_{i, j} times the SER_j-Value plus W_{i, j}, Then the processor <figref>38</figref> in step <figref>132</figref>Whether the SER_jValue greater than or equal to a maximum SER threshold for rate j (ie MaxSER_j). If so, the processor<figref>38</figref> in step <figref>130</figref>That said current frame is erased. However, if the SER_jis value is less than the maximum SER_jThreshold, then determines in step <figref>134</figref> the processor <figref>38</figref>That the current transmitted frame j at the rate has been.

Among with reference to <figref idrefs="S39">4</figref> is used by the processor <figref>38</figref> a routine <figref>200</figref> conducted if the CRC for a rate determined. As with the step<figref>104</figref> (<figref idrefs="S37">2</figref>) the processor <figref>38</figref> in step <figref>202</figref> first, whether the CRC for exactly one rate agrees. If not, then explains the processor<figref>38</figref> in step <figref>203</figref> the current frame as an erasure or performs two CRC check routine <figref>100</figref> or <figref>120</figref> by how discussed above. If the CRC in step<figref>202</figref> just for a Rate true, the processor <figref>38</figref> in the routine <figref>200</figref> additional Steps a to confirm, that the rate which in step <figref>202</figref> was positive, actually the correct rate for is the current frame. Therefore, the processor<figref>38</figref> in step <figref>204</figref>. whether the rate which in step <figref>202</figref> was positive, the eighth Rate (ie, i = 8). If not, the processor<figref>38</figref> in step <figref>206</figref>Whether the SER value for the determined rate is greater than or is equal to a maximum SER threshold for that rate (ie SER_i ≥ MaxSER_i). If it is less than the maximum, then determined in step <figref>208</figref> the processor <figref>38</figref>. that the rate of the currently received frame is equal to i; otherwise declared the processor <figref>38</figref> in step <figref>210</figref> erasure.

If in step <figref>204</figref> the processor <figref>38</figref> determined that the indicated rate of eighth rate is equal, then examined in step <figref>212</figref> the processor <figref>38</figref> the Yamamoto value for the eighth rate (Y₈). As is known, has a Frame with eighth rate less CRC bits as a frame with the other Rates and as a result is the CRC often. Therefore, the routine sets<figref>200</figref> additional exams one to confirm, that the current frame was transmitted at the eighth rate. Consequently, in step <figref>212</figref>If the Yamamoto value for the eighth Rate true (ie a binary Value "1" to the decoder <figref>30</figref> supplies), the processor <figref>38</figref> an increased level of confidence or a confidence level that the rate of the current frame the eighth rate is. Therefore, the processor sets<figref>313</figref> in step <figref>214</figref> a larger or loosened maximum SER value for the certain rate a. Such loose maximum SER threshold elevated the probability that subsequent steps of the routine <figref>200</figref> correct determine that the current frame transfer rate with the eighth has been.

Vice versa, if the Yamamoto value in step <figref>212</figref> is wrong, then chooses the processor <figref>38</figref> in step <figref>216</figref> a smaller or tighter maximum SER value for the eighth rate. If the Yamamoto value is not correct, expect the processor <figref>38</figref>That the current frame is an erasure, and makes subsequent comparisons more stringent or more stringent in order ensure that the current frame only with the most stringent Comparison is determined to be transmitted at the eighth rate. In step <figref>206</figref> the processor sets <figref>38</figref> the loosened maximum SER value from step <figref>214</figref> or the narrower maximum SER value from step <figref>216</figref> and compares it with the eighth rate SER to determine whether the frame is erased (Step <figref>210</figref>), Or confirms that the current frame transmitted at the eighth rate was (step <figref>208</figref>).

Among with reference to <figref idrefs="S40">5</figref> is a more detailed analysis as a routine <figref>220</figref> shown. processor<figref>38</figref> results in routine <figref>220</figref> the steps <figref>202</figref>. <figref>204</figref> and <figref>206</figref> by, as discussed above. &lt;?page 9?&gt;Thereafter, however, the processor compares <figref>38</figref> in steps <figref>228</figref>. <figref>230</figref> and <figref>232</figref> the SER values for the three Rates, which in step <figref>202</figref> not were positive (ie, Rates j, k and l) with minimum SER thresholds. This reduces the opportunity that one of the decoded with a lower SER rates actually correct Rate, although the CRC for this rate has not voted. The steps<figref>228</figref>. <figref>230</figref> and <figref>232</figref> determine, whether the SER values ​​for the other rates are greater as minimum thresholds for this rate, and if so, declare an erasure, since the probability that the current frame with the transfer rate was, the probability prevails, that the current frame at the rate i was transferred.

Therefore determined in step <figref>228</figref> the processor <figref>38</figref>, if he SER_jValue is less than or equal to the minimum SER threshold for the certain rate i and rate j (ie SER_{i, j}). If so, explain the processor <figref>38</figref> in step <figref>227</figref> the current Frame deletion. This is done so because the low SER of another rate (J) an increased likelihood indicating that the frame was transmitted at that rate (j). If not is so, then the processor compares <figref>38</figref> at steps <figref>230</figref> and <figref>232</figref> the last two SER values ​​(for the rates k and l) to corresponding minimum SER thresholds for the Rate i and rates k and l (SER_{j, k}, SER_{j, l}). At steps<figref>230</figref> and <figref>232</figref> the SER_k- Or SER_l-Values are lower than the minimum threshold, then explains the processor <figref>38</figref> in step <figref>227</figref> a current frame as an erasure. However, if such SER values ​​greater than the minimum is then determined in step <figref>234</figref> the processor <figref>38</figref>. that the current frame at the rate i was transferred.

As in the routine <figref>200</figref> verified the processor <figref>38</figref>When in step <figref>202</figref> positive Rate in step <figref>204</figref> as the eighth rate was determined, Yamamoto values for the eighth rate in step <figref>212</figref>, As discussed above. Thus recognized if the Yamamoto value for the eighth true rate of processor <figref>38</figref> in step <figref>238</figref> not only a more casual maximum SER threshold for certain rate (the eighth rate), but also sets loose Minimum SER thresholds for the specific and non-specific rates one (ie loosened min SER_{i, j}, SER_{i, k} and SER_{i, l}). Similar sets in step <figref>240</figref>If the Yamamoto value in step <figref>212</figref> not True, the processor <figref>38</figref> in step <figref>240</figref> not only closer maximum SER_iThreshold a, but also tighter minimum SER thresholds for the other rates (ie closer Min-SER_{i, j}, SER_{i, k} and SER_{i, l}). Thus, for the eighth rate includes the threshold lookup table by the processor <figref>38</figref> is used, two maximum thresholds the eighth rate, and two sets of three minimum threshold values ​​in steps <figref>238</figref> and <figref>240</figref> used will.

Various Alternatives to the various routines are available. To the For example, the processor <figref>38</figref>Rather than simply the specific and other SER values ​​in steps <figref>206</figref>. <figref>228</figref>. <figref>230</figref> and <figref>232</figref> the routine <figref>220</figref> compare the determined value with SER Compare a linear function by multiplying the minimum or maximum SER threshold with the multiplicative factor k and adding a appropriate weighting value W. For example, in step <figref>206</figref> the processor <figref>38</figref> the SER value SER_i with the function k_i· MaxSER_i + W_i compare, while in step <figref>228</figref> the processor the SER_j-Value with the function k_{i, j}· MINSER_{i, j} + W_{i, j} can compare. Further, a non-linear function in the steps of <figref>206</figref>-<figref>232</figref> used will. However, each supplies supplied from a non-linear function Improvement at best only a small advantage inkrementa len for routine <figref>220</figref> and leads to a processing complexity and thus increased Processing time.

While the Yamamoto values ​​for the eighth rate tested are, the routine <figref>220</figref> be modified so that the Yamamoto values ​​for the other rates also examined will. As a result, corresponding tighter or looser Maximum and minimum SER thresholds used for each of the other rates. A larger lookup table would thus for the processor <figref>38</figref> required in such an alternative embodiment. additionally can the routines <figref>100</figref>. <figref>120</figref>. <figref>200</figref> such use alternatives, such as inserting the Yamamoto check for each rate.

Instead of a lookup table having the weighting values ​​W, multiplicative Factors k and to use the minimum and maximum SER thresholds, can Such values ​​calculated using an algorithm with suitable equations will. However, such equations are complex and would have a significant Overhead of the processor <figref>38</figref> require. As a result, would at such alternative a faster and thus more expensive microprocessor <figref>38</figref> required.

Further can the routines of the present invention, the currently determined rate (Rate i) with previous Compare rates. As mentioned above, In the exemplary embodiment, 90% of the time the rate of the current frame, either the full or the eighth rate. Similar is in the exemplary embodiment, a high probability that the rate of the current frame equal to the rate of the previous frame is. When a person speaks, speaks probably continue (whereby the current frame a full rate has), while, when it is quiet, will likely continue to be quiet (maintaining of the current frame with eighth rate). As a result, the Routines described above, &lt;?page 10?&gt;determined rate of the current frame comparing the rate of the previous frame and loose maximum and apply minimum SER thresholds. Alternatively, if the momenta ne certain Rate differs from the previous rate, tighter thresholds be applied.

The teachings provided herein of the present invention may be applied other communication systems are used, not only on the exemplary spread spectrum communication system that described above has been. The present invention, the systems and methods use various above-described patents and applications.

These and other changes can with the invention in light of the above detailed description be made. In general, in the following claims, the Terms used, the invention not limited to the specific embodiments limit, the disclosed in the specification and claims be, but are intended to include any communication system that operates in accordance with the claims, to provide a rate determination. Accordingly, not by the invention limits the disclosure, but instead its scope is exclusively the following claims be determined.