Patent Publication Number: US-10772153-B2

Title: Methods and apparatus for two-stage ACK/DTX detection

Description:
CLAIM TO PRIORITY 
     This application claims the benefit under 35 U.S.C. § 119 of U.S. Provisional Application No. 62/663,734, filed on Apr. 27, 2018, and entitled “METHOD AND APPARATUS FOR TWO-STAGE ACK DTX DETECTION FOR CARRIER AGGRESSION WITH SYMBOL DOMAIN METRIC AND MAJORITY LOGIC DECISION,” which is incorporated herein by reference in its entirety. 
    
    
     FIELD 
     The exemplary embodiment(s) of the present invention relates to telecommunications network. More specifically, the exemplary embodiment(s) of the present invention relates to receiving and processing data streams via a wireless communication network. 
     BACKGROUND 
     With a rapidly growing trend of mobile and remote data access over a high-speed communication network such as third generation (3G) or fourth generation (4G) cellular services, accurately delivering and deciphering data streams become increasingly challenging and difficult. The high-speed communication network which is capable of delivering information includes, but not limited to, wireless network, cellular network, wireless personal area network (“WPAN”), wireless local area network (“WLAN”), wireless metropolitan area network (“MAN”), or the like. While WPAN can be Bluetooth or ZigBee, WLAN may be a Wi-Fi network in accordance with IEEE 802.11 WLAN standards. 
     Typically, wireless network performance depends in part on the quality of the transmission channel. For example, if the channel conditions are good, the network may perform with higher speed and capacity than when the channel conditions are poor. To obtain the best network performance, wireless networks may rely on user devices (e.g., user equipment “UE”) to report control information back to the network. The control information includes parameters indicating the channel conditions and/or transmission parameters. 
     In the Third Generation Partnership Project (3GPP) Long-Term Evolution (LTE) standard, a Physical Uplink Control Channel (PUCCH) carries important control information, such as HARQ-ACK bits or SR bits for carrier aggregation. The performance of ACK messages play an important role in the overall downlink performance as the residual error rate of HARQ is in the same order of the feedback error rate of ACK bits. For example, after a user device receives a transmission from a network server, it generates acknowledgement (ACK) bits that indicates whether or not the transmission was properly received. The ACK bits are transmitted back to the network server through the PUCCH. The server can determine from the received ACK bits whether the transmission was properly received, and initiate a retransmission if necessary. 
     Discontinuous transmission (DTX) is a method of momentarily powering-down, or muting, a mobile or portable wireless UE when there is no voice input to the send. This optimizes the overall efficiency of the wireless voice communications system. During DTX mode, no ACKs are transmitted. However, it is then up to the receiver to determine whether ACK/NACK symbols have been received from a UE, or if the UE is in DTX mode. Unfortunately, conventional DTX detection may lead to detection errors and corresponding transmission inefficiencies. 
     Therefore, it is desirable to have a mechanism that efficiently detects DTX operation to enhance network performance. 
     SUMMARY 
     The following summary illustrates a simplified version(s) of one or more aspects of present invention. The purpose of this summary is to present some concepts in a simplified description as more detailed description that will be presented later. 
     In various exemplary embodiments, methods and apparatus are provided for efficiently detecting DTX operation for UE in LTE PUCCH format 3 uplink communications using Reed-Muller decoders and symbol regeneration. 
     In an exemplary embodiment, a method is provided that comprises determining a first stage DTX value from bit-domain correlation values, determining a second stage DTX value from symbol domain correlation values, and determining a DTX decision based on the first stage DTX value and the second stage DTX value. 
     In an exemplary embodiment, an apparatus is provided that comprises bit-domain decision logic that determines a first stage DTX value from bit-domain correlation values, symbol domain decision logic that determines a second stage DTX value from symbol domain correlation values, and DTX decision logic that determines a DTX decision based on the first stage DTX value and the second stage DTX value. 
     Additional features and benefits of the exemplary embodiment(s) of the present invention will become apparent from the detailed description, figures and claims set forth below. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The exemplary aspect(s) of the present invention will be understood more fully from the detailed description given below and from the accompanying drawings of various embodiments of the invention, which, however, should not be taken to limit the invention to the specific embodiments, but are for explanation and understanding only. 
         FIG. 1  is a block diagram illustrating a communication network configured to transmit and receive data streams using various embodiments of a DTX detector to detect discontinuous operation. 
         FIG. 2  shows an embodiment of a receiver that comprises an exemplary embodiment of a two-stage DTX detector. 
         FIG. 3  shows an exemplary embodiments of the bit extraction/deinterleaver. 
         FIG. 4  shows an exemplary block diagram of the two stage DTX detector shown in  FIG. 2 . 
         FIG. 5  shows a detailed exemplary embodiment of the Top-M survival candidate symbol regenerator shown in  FIG. 4 . 
         FIG. 6  shows an exemplary method for operating a two-stage DTX detector that uses majority logic. 
         FIG. 7  illustrates an exemplary digital computing system with various networking features. 
     
    
    
     DETAILED DESCRIPTION 
     The purpose of the following detailed description is to provide an understanding of one or more embodiments of the present invention. Those of ordinary skills in the art will realize that the following detailed description is illustrative only and is not intended to be in any way limiting. Other embodiments will readily suggest themselves to such skilled persons having the benefit of this disclosure and/or description. 
     In the interest of clarity, not all of the routine features of the implementations described herein are shown and described. It will, of course, be understood that in the development of any such actual implementation, numerous implementation-specific decisions may be made in order to achieve the developer&#39;s specific goals, such as compliance with application- and business-related constraints, and that these specific goals will vary from one implementation to another and from one developer to another. Moreover, it will be understood that such a development effort might be complex and time-consuming but would nevertheless be a routine undertaking of engineering for those of ordinary skills in the art having the benefit of embodiment(s) of this disclosure. 
     Various embodiments of the present invention illustrated in the drawings may not be drawn to scale. Rather, the dimensions of the various features may be expanded or reduced for clarity. In addition, some of the drawings may be simplified for clarity. Thus, the drawings may not depict all of the components of a given apparatus (e.g., device) or method. The same reference indicators will be used throughout the drawings and the following detailed description to refer to the same or like parts. 
     The term “system” or “device” is used generically herein to describe any number of components, elements, sub-systems, devices, packet switch elements, packet switches, access switches, routers, networks, modems, base stations, eNB (eNodeB), computer and/or communication devices or mechanisms, or combinations of components thereof. The term “computer” includes a processor, memory, and buses capable of executing instruction wherein the computer refers to one or a cluster of computers, personal computers, workstations, mainframes, or combinations of computers thereof. 
     IP communication network, IP network, or communication network means any type of network having an access network that is able to transmit data in a form of packets or cells, such as ATM (Asynchronous Transfer Mode) type, on a transport medium, for example, the TCP/IP or UDP/IP type. ATM cells are the result of decomposition (or segmentation) of packets of data, IP type, and those packets (here IP packets) comprise an IP header, a header specific to the transport medium (for example UDP or TCP) and payload data. The IP network may also include a satellite network, a DVB-RCS (Digital Video Broadcasting-Return Channel System) network, providing Internet access via satellite, or an SDMB (Satellite Digital Multimedia Broadcast) network, a terrestrial network, a cable (xDSL) network or a mobile or cellular network (GPRS/EDGE, or UMTS (where applicable of the MBMS (Multimedia Broadcast/Multicast Services) type, or the evolution of the UMTS known as LTE (Long Term Evolution), or DVB-H (Digital Video Broadcasting-Handhelds)), or a hybrid (satellite and terrestrial) network. 
       FIG. 1  is a block diagram illustrating a communication network  100  configured to transmit and receive data streams using various embodiments of a DTX detector  152  to detect discontinuous operation. The network  100  includes packet data network gateway (“P-GW”)  120 , two serving gateways (“S-GWs”)  121 - 122 , two base stations (or cell sites)  102 - 104 , server  124 , and Internet  150 . P-GW  120  includes various components  140  such as billing module  142 , subscribing module  144 , tracking module  146 , and the like to facilitate routing activities between sources and destinations. It should be noted that the underlying concept of the exemplary embodiment(s) of the present invention would not change if one or more blocks (or devices) were added to or removed from diagram  100 . 
     The network configuration illustrated by the communication network  100  may also be referred to as a third generation (“3G”), 4G, LTE, 5G, or combination of 3G and 4G cellular network configuration. MME  126 , in one aspect, is coupled to base stations (or cell site) and S-GWs capable of facilitating data transfer between 3G and LTE or between 2G and LTE. MME  126  performs various controlling/managing functions, network securities, and resource allocations. 
     In an embodiment, the S-GW  121  or  122 , in one example, coupled to P-GW  120 , MME  126 , and base stations  102  or  104 , is capable of routing data packets from base station  102 , or eNodeB, to P-GW  120  and/or MME  126 . A function of S-GW  121  or  122  is to perform an anchoring function for mobility between 3G and 4G equipment. S-GW  122  is also able to perform various network management functions, such as terminating paths, paging idle UEs, storing data, routing information, generating replica, and the like. 
     In an embodiment, the P-GW  120 , coupled to S-GWs  121 - 122  and Internet  150 , is able to provide network communication between user equipment (“UE”) and IP based networks such as Internet  150 . P-GW  120  is used for connectivity, packet filtering, inspection, data usage, billing, or PCRF (policy and charging rules function) enforcement, et cetera. P-GW  120  also provides an anchoring function for mobility between 3G and 4G (or LTE) packet core network(s). 
     Sectors or blocks  102 - 104  are coupled to a base station or FEAB  128 , which may also be known as cell site, node B, or eNodeB. Sectors  102 - 104  include one or more radio towers  110  or  112 . Radio tower  110  or  112  is further coupled to various UEs, such as a cellular phone  106 , a handheld device  108 , tablets and/or iPad®  107  via wireless communications or channels  137 - 139 . Devices  106 - 108  can be portable devices or mobile devices, such as iPhone®, BlackBerry®, Android®, and so on. Base station  102  facilitates network communication between mobile devices such as UEs  106 - 107  with S-GW  121  via radio towers  110 . It should be noted that base station or cell site can include additional radio towers as well as other land switching circuitry. 
     Server  124  is coupled to P-GW  120  and base stations  102 - 104  via S-GW  121  or  122 . In one embodiment, server  124  which contains a soft decoding scheme  128  is able to distribute and/or manage soft decoding and/or hard decoding based on predefined user selections. In one exemplary instance, upon detecting a downstream push data  130  addressing to mobile device  106  which is located in a busy traffic area or noisy location, base station  102  can elect to decode the downstream using the soft decoding scheme distributed by server  124 . One advantage of using the soft decoding scheme is that it provides more accurate data decoding, whereby overall data integrity may be enhanced. 
     When receiving bit-streams via one or more wireless or cellular channels, a decoder can optionally receive or decipher bit-streams with hard decision or soft decision. A hard decision is either 1 or 0 which means any analog value greater than 0.5 is a logic value one (1) and any analog value less than 0.5 is a logic value zero (0). Alternatively, a soft decision or soft information can provide a range of value from 0, 0.2, 0.4, 0.5, 0.6, 0.8, 0.9, and the like. For example, soft information of 0.8 would be deciphered as a highly likelihood one (1) whereas soft information of 0.4 would be interpreted as a weak zero (0) and maybe one (1). 
     A base station, in one aspect, includes one or more FEABs  128 . For example, FEAB  128  can be a transceiver of a base station or eNodeB. In one aspect, mobile devices such tables or iPad®  107  uses a first type of RF signals to communicate with radio tower  110  at sector  102  and portable device  108  uses a second type of RF signals to communicate with radio tower  112  at sector  104 . After receiving RF signals, FEAB  128  is able to process the received PUCCH transmissions using a DTX detector  152  that detects DTX operation of UE in LTE PUCCH format 3 uplink transmissions as described in greater detail below. 
     Table 1 illustrates PUCCH format 3 and specifies two coding scenarios depending on the number of ACK bits, [N A/N   PUCCH format 3 ≤11] using a single Reed Muller (RM) coding and [11&lt;N A/N   PUCCH format 3 ≤22] using interleaved dual RM coding. 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 Features of PUCCH format 3. 
               
            
           
           
               
               
               
            
               
                 Format 
                 Channel coding 
                 Modln (Bits) 
               
               
                   
               
               
                 Format 3 N A/N   PUCCH format 3  ≤ 11 
                 Reed Muller 
                 QPSK 
               
               
                 Format 3 11 &lt; N A/N   PUCCH format 3  ≤ 22 
                 Interleaved dual 
                 QPSK 
               
               
                   
                 Reed Muller 
               
               
                   
               
            
           
         
       
     
     For DTX detection, 3GPP specifies some major minimum performance requirements for ACK bits in format 3. The first performance requirement is the ACK missed detection probability, which is defined as the probability of not detecting an ACK bit when an ACK bit was sent on the particular bit position, with each missed ACK bit being counted as one error. For an example, the ACK missed detection probability shall not exceed 1% at the SNR given in table 8.3.6.1-1 and table 8.3.6.1-2, for 4 and 16 AN bits per sub-frame, respectively in the 3GPP TS36.104. 
     
       
         
           
               
             
               
                 TABLE 8.3.6.1-1 
               
             
            
               
                   
               
               
                 Minimum requirements for PUCCH format 3, 4AN bits 
               
            
           
           
               
               
               
               
               
            
               
                   
                   
                   
                 Propagation 
                   
               
               
                 Number 
                 Number 
                   
                 Conditions and 
                   
               
               
                 of Tx 
                 of RX 
                 Cyclic 
                 correlation matrix 
                 Channel Bandwidth/SNR [dB] 
               
            
           
           
               
               
               
               
               
               
               
               
               
               
            
               
                 antennas 
                 antennas 
                 Prefix 
                 (Annex B) 
                 1.4 MHz 
                 3 MHz 
                 5 MHz 
                 10 MHz 
                 15 MHz 
                 20 MHz 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
               
            
               
                 1 
                 2 
                 Normal 
                 EPA 5 Low 
                 — 
                 — 
                 — 
                 −3.7 
                 −3.8 
                 −3.8 
               
               
                   
                   
                   
                 EVA70 Low 
                 — 
                 — 
                 — 
                 −3.5 
                 −3.6 
                 −3.7 
               
               
                   
                 4 
                 Normal 
                 EPA 5 Low 
                 — 
                 — 
                 — 
                 −7.3 
                 −7.4 
                 −7.5 
               
               
                   
                   
                   
                 EVA70 Low 
                 — 
                 — 
                 — 
                 −7.2 
                 −7.3 
                 −7.3 
               
               
                   
                 8 
                 Normal 
                 EPA 5 Low 
                 — 
                 — 
                 — 
                 −11.1 
                 −10.9 
                 −11.1 
               
               
                   
                   
                   
                 EVA70 Low 
                 — 
                 — 
                 — 
                 −10.9 
                 −11.0 
                 −11.0 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 8.3.6.1-2 
               
             
            
               
                   
               
               
                 Minimum requirements for PUCCH format 3, 16AN bits 
               
            
           
           
               
               
               
               
               
            
               
                   
                   
                   
                 Propagation 
                   
               
               
                 Number 
                 Number 
                   
                 Conditions and 
                   
               
               
                 of Tx 
                 of RX 
                 Cyclic 
                 correlation matrix 
                 Channel Bandwidth/SNR [dB] 
               
            
           
           
               
               
               
               
               
               
               
               
               
               
            
               
                 antennas 
                 antennas 
                 Prefix 
                 (Annex B) 
                 1.4 MHz 
                 3 MHz 
                 5 MHz 
                 10 MHz 
                 15 MHz 
                 20 MHz 
               
               
                   
               
               
                 1 
                 2 
                 Normal 
                 EPA 5 Low 
                 — 
                 — 
                 — 
                 −1.3 
                 −1.2 
                 −1.2 
               
               
                   
                   
                   
                 EVA70 Low 
                 — 
                 — 
                 — 
                 −0.8 
                 −0.9 
                 −0.9 
               
               
                   
                 4 
                 Normal 
                 EPA 5 Low 
                 — 
                 — 
                 — 
                 −5.3 
                 −5.3 
                 −5.4 
               
               
                   
                   
                   
                 EVA70 Low 
                 — 
                 — 
                 — 
                 −5.0 
                 −5.1 
                 −5.1 
               
               
                   
                 8 
                 Normal 
                 EPA 5 Low 
                 — 
                 — 
                 — 
                 −8.8 
                 −8.8 
                 −8.9 
               
               
                   
                   
                   
                 EVA70 Low 
                 — 
                 — 
                 — 
                 −8.7 
                 −8.8 
                 −8.7 
               
               
                   
               
            
           
         
       
     
     Second performance requirement is the DTX to ACK probability, which is the probability that an ACK is detected when nothing was sent. This probability shall not exceed 1%, where the performance measure definition is as follows: 
               Prob   (       PUCCH   ⁢           ⁢   DTX     →     ACK   ⁢           ⁢   bits       )     =         #   ⁢     (     false   ⁢           ⁢   ACK   ⁢           ⁢   bits     )         #   ⁢     (     PUCCH   ⁢           ⁢   DTX     )     ×   #   ⁢     (       ACK   /   NAK     ⁢           ⁢   bits     )         ≤     10     -   2               
where:
 
1. #(false ACK bits) denotes the number of detected ACK bits.
 
2. #(ACK/NACK bits) denotes the number of encoded bits per sub-frame
 
3. #(PUCCH DTX) denotes the number of DTX occasions
 
     One technique for ACK/DTX detection involves a threshold-based detection mechanism. When nothing is transmitted, the detection mechanism decides that the UE is in DTX mode instead of an ACK transmission mode, when a selected metric is lower than a selected threshold. However, the two detection performance requirements are conflicting (e.g., a low miss detection probability without increasing false alarm probability). 
     In an embodiment, a bit-level decorrelation value for all the possible information bit streams is calculated. A search for the maximum correlation result is performed and the bit stream with the maximum correlation value is considered as the transmitted information bit stream. The next correlation result after the maximum is called the submax correlation value. The bit-domain max and submax correlation values are reported. A reliability metric (I_dtx) can be derived from these bit level correlation values, such as (Metric=max_Corr−submax_Corr). In another embodiment, the metric is based on the maxCorr value, and then this metric is compared with a given threshold. Thus, a decision can be made according to the following conditions; 
                                If (I_dtx &gt; Threshold)                         DTX = 0; means it is not DTX mode, and the detected ACK bit           streams shall be considered                 Else if (I_dtx &lt;= Threshold) then                         DTX =1; which means there is no HARQ-ACK bits transmitted.                 End                    
where I_dtx is the metric and can be considered as a general function of f(max_Corr, submax_Corr).
 
     It can be seen that the threshold comparison plays a significant role in not only the accuracy of the DTX detection, but also the miss detection probability of the ACK bits. For example, if this threshold comparison leads to a DTX detection, this means that the detected bit packet will need to be dropped from counting toward the miss detection probability, and thus increases the miss detection probability. A more reliable DTX detection mechanism is desired. 
     Two Stage DTX Detection Mechanism 
     In various exemplary embodiments, a novel two-stage DTX detection mechanism is provided that can significantly increase the accuracy of the DTX detection performance and thus improve the miss detection probability under the false alarm probability requirements described above. 
     In an exemplary embodiment, DTX detection comprises an apparatus for generating metrics and a systematic method for calculating an optimal threshold for different scenarios based on, for example, the number of ACK bits, rank size, etc. 
       FIG. 2  shows an embodiment of a receiver  200  that comprises an exemplary embodiment of a two-stage DTX detector  220 . For example, the DTX detector  220  is suitable for use as the DTX detector  152  shown in  FIG. 1 . 
     The receiver  200  comprises front-end receiver  202  that receives uplink transmissions and performs front end fast Fourier transform (FFT) processing to extract data and pilot information. The data information is input to a data symbol processor  204  and the pilot information is input to a pilot symbol processor  208 . 
     A whitening coefficient calculator  206  generates whitening coefficients for both the pilot symbol processor  208  and the data symbol processor  204 . The pilot symbol processor  208  performs pilot AFC processing and whitening to generate processed pilot information that is input to a pilot channel estimator  212 . The pilot channel estimator  212  generates channel estimates that are input to a data channel compensator  210 . For example, in an exemplary embodiment, the pilot channel coefficients can be expressed as follows.
 
 Ĥ   Pilot   {tilde over (p)},q ( n   SS   ,l   P )
 
     The data symbol processor  204  performs DFT, despreading, and channel whitening to generate processed data symbols that also are input to the data channel compensator  210 . In an embodiment, the data symbol processor  204  outputs data symbol information  226  to the two stage DTX detector  220 . For example, the data symbol information  226  can be expressed as follows.
 
 {tilde over (R)}   DeOC   {tilde over (p)},q ( n   SS   ,i ′)
 
     The data channel compensator  210  outputs compensated data to a diversity MRC block  214 , which generates scrambled data (e.g., {tilde over (d)}(0), . . . , {tilde over (d)}(23)) that is output to a demodulator/descrambler  216  that generates demodulated/descrambled data ({tilde over (b)} 0 , {tilde over (b)} 1 , {tilde over (b)} 2 , . . . , {tilde over (b)} 47 )  222 , which is input to bit extractor/deinterleaver  218 . 
     The bit extractor/deinterleaver  218  performs Reed Muller 32-bit decoding (RDEC32) for NACK&lt;=11 and dual Reed Muller 24-bit decoding (RDEC24) for 11&lt;NACK&lt;=22. In an embodiment, the bit extractor/deinterleaver  218  comprises a bit extractor and a Top-M list RM 32-bit decoder to generate candidate ACK bits (Ô i   ACK )  228  for NACK&lt;=11. In addition, the bit extractor/deinterleaver  218  comprises a dual RM deinterleaver, dual Top-M list RDEC24 decoders and dual bit demappers to generate the candidate ACK bits (Ô i   ACK )  228  for 11&lt;NACK&lt;=22. A more detailed description of the bit extractor/deinterleaver  218  is provided below. 
     In an exemplary embodiment, the two-stage DTX detector  220  receives pilot channel coefficients  224  output from the pilot channel estimator  212  and data symbol information  226  output from the data symbol processor  204 . The two-stage DTX detector  220  also receives the candidate ACK bits  228  and bit-domain correlation values  232  to generate a DTX detection result  230 . 
       FIG. 3  shows an exemplary embodiments of the bit extraction/deinterleaver  218 . The bit extractor/deinterleaver  218  comprises a first processing portion  302  and a second processing portion  304 . The first processing portion  302  comprises a 32-bit extractor  306  and a Top-M list RDEC32 decoder  308 . The second processing portion  304  comprises a dual RM deinterleaver  310 , a first Top-M list RDEC24 decoder  312 , a second Top-M list RDEC24 decoder  314 , a first Top-M bit demapper  316  and a second Top-M bit demapper  318 . 
     In an exemplary embodiment, the first processing portion  302  and the second processing portion  304  generate Top-M candidate ACK bits  228 , which are the Top-M (e.g., M is an integer) most probable candidates for the decoded ACK bits. In an embodiment, the first processing portion  302  and the second processing portion  304  comprise modified Reed-Muller decoders that produce the decoded ACK bits based on one or more metrics in the bit domain. For example, the Top-M candidate ACK bits can be denoted as:
 
[ b (0), b (1), . . . ,  b ( N− 1)]_[0, M− 1]=argmax Metric( j );
 
where the M bit sequences are the M most likely candidates that produce the highest M metrics for a Maximum-likelihood search.
 
     In an embodiment, two scenarios are handled by the bit extractor/deinterleaver  218  so that Top-M candidate ACK bits  228  are generated depending on the number of ACK bits. For example, for N A/N   PUCCH format 3 ≤11, the first processing portion  302  operates to generate Top-M candidate ACK bits  228 . For example, the 32-bit extractor  306  extracts soft bits from the received descrambled bits [{tilde over (b)} 0 , {tilde over (b)} 1 , {tilde over (b)} 2 , . . . , {tilde over (b)} 47 ]  222 . The 32 soft bits are passed to the Top-M list RDEC32  308  which generates the candidate ACK bits [ô i   ACK ]  228 . 
     For the case of 11&lt;N A/N   PUCCH format 3 ≤22, the received descrambled bits [{tilde over (b)} 0 , {tilde over (b)} 1 , {tilde over (b)} 2 , . . . , {tilde over (b)} 47 ]  222  are deinterleaved by the dual RM deinterleaver  310  to generate two sets of deinterleaved bits that are input to dual Top-M list RDEC24 decoders ( 316 .  318 ), respectively. Each decoder ( 316 .  318 ) produces corresponding decoded bits. The decoded bits are demapped by Top-M bit demappers ( 316 ,  318 ) to generate the candidate ACK bits [ô i   ACK ]  228 . 
       FIG. 4  shows an exemplary block diagram of the two-stage DTX detector  220  shown in  FIG. 2 . In an embodiment, the detector  220  comprises a Top-2 symbol regenerator  402 , correlation calculator  404 , symbol domain decision logic  406 , and DTX decision logic  408 . Also shown in  FIG. 4  is bit-domain decision logic  410  that receives bit-domain maximum correlation and sub maximum correlation values as described above and generates a bit-domain DTX decision  412  that is input to the DTX decision logic  408 . 
     In an embodiment, the Top-2 symbol regenerator  402  receives the Top-M candidate ACK bits  228  and generates Top-2 candidate symbols  414  that are input to the correlation calculator  404 . In an embodiment, the Top-2 candidate symbols are the regenerated symbols from each of the Top-M bit candidates. 
     The correlation calculator  404  receives data symbol information  226  and pilot channel coefficients  224  along with the Top-2 regenerated candidate symbols and generates one or both of a re-encoded maximum correlation value (renc maxCorr) and a re-encoded sub-maximum correlation value (renc sub maxCorr). These values are input to the symbol domain decision logic  406 . 
     For example, the following equations can be used to generate a joint channel estimate for the regenerated data symbol candidates.
 
 {tilde over (H)}   Data   [0,M-1] ( n   SS   ,i ′)= {tilde over (R)}   Data   {tilde over (p)},q ( n   SS   ,i ′) ( n   SS   *N   SC   RB   +i ′) regen   [0,M-1] 
 
 i′∈ [0,11], n   SS ∈[0,1]
 
     For example, the following equations can be used for combining partial metric for the regenerated data symbols candidates and pilot symbols. 
     
       
         
           
             
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     The symbol domain decision logic  406  receives one or both of the renc maxCorr and renc sub maxCorr values and generates a symbol domain DTX decision  414  that is input the DTX decision logic  408 . 
     The DTX decision logic  408  also receives the bit-domain DTX decision  412  and the symbol domain DTX decision  414  and generates a final DTX decision  230 . For example, the DTX decision logic  408  uses majority logic to make the determination of the final DTX decision  230 . A more detailed description of the operation of the DTX decision logic  408  is provided below. 
       FIG. 5  shows a detailed exemplary embodiment of the Top-2 survival candidate symbol regenerator  402  shown in  FIG. 4 . In an embodiment, the regenerator  402  comprises channel coder  502 , scrambler  504 , and QPSK modulator  506 . 
     In an embodiment, the channel coder  502  receives the Top-M survival candidates ACKS  228  and performs channel coding using a RM32 or dual RM24 coders. For example, the channel coder  502  generate coded Top-M survival candidates and inputs these into the scrambler  504 . 
     In an embodiment, the scrambler  504  scrambles the coded Top-M survival candidates and performs a scrambling process to generate scrambled Top-2 candidates that are input to the QPSK modulator  506 . 
     In an embodiment, the QPSK modulator  506  modulates the scrambled Top-2 candidates to generate the Top-2 regenerated symbols  414 . As illustrated in  FIG. 4 , these regenerated symbols are input to the correlation calculator  404 . 
       FIG. 6  shows an exemplary method  600  for operating a two-stage DTX detector that uses majority logic. For example, the method  600  is suitable for use with the two-stage DTX detector  220  illustrated in  FIG. 2  and  FIG. 4 . 
     At block  602 , bit-domain correlation values are received. For example, in an embodiment, the bit-domain correlation values (maxcorr and sub maxcorr) are received by the first stage decision logic  410 . 
     At block  604 , a determination is made as to whether a delta (or difference) between the received bit-domain values is less than a threshold value. For example, a metric is defined as (delta_corr_bit-domain=maxCorr−sub maxCorr). If the metric is not less than the threshold value, the method proceeds to block  606 . If the metric is less than the threshold value, the method proceeds to block  608 . For example, the decision logic  410  makes this determination. 
     At block  606 , since the metric of the received bit-domain values is not less than a threshold value, a first stage parameter is set to zero. For example, the first stage parameter DTX_ACK_STAGE(0) is set to zero. For example, the decision logic  410  sets the first stage parameter value to zero. 
     At block  608 , since the metric of the received bit-domain values is less than a threshold value, a parameter is set to one. For example, the parameter DTX_ACK_STAGE(0) is set to one. For example, the decision logic  410  sets the first stage parameter value to one. 
     At block  610 , a determination is made as to whether the first stage parameter is set to zero or one. If set to zero, the method proceeds to block  612 . If set to one, the method proceeds to block  626 . For example, the decision logic  410  makes this determination. 
     At block  612 , bit extraction/deinterleaving is performed along with RM32 or dual RM24 decoding to generate Top-M candidate ACKS. For example, the bit extractor/deinterleaver  218  performs this operation. 
     At block  614 , Top-2 candidate symbols are generated from the Top-M candidate ACKS. For example, the Top-2 symbol regenerator  402  performs this operation. 
     At block  616 , one or both of renc maxCorr and renc sub maxCorr values are generated in the symbol domain. For example, the correlation calculator  404  performs this operation. 
     At block  618 , a delta RENC_corr value is computed. For example, the decision logic  406  performs this operation. 
     At block  620 , a determination is made as to whether the delta RENC_corr value is less than a threshold value. If so, the method proceeds to block  624 . If not, the method proceeds to block  622 . For example, the decision logic  406  performs this operation. 
     At block  622 , since the delta RENC_corr value is not less than a threshold value, a second stage parameter is set to zero. For example, the second stage parameter DTX_ACK_STAGE(1) is set to zero. For example, the decision logic  406  performs this operation. 
     At block  624 , since the delta RENC_corr value is less than a threshold value, the second stage parameter is set to one. For example, the second stage parameter DTX_ACK_STAGE(1) is set to one. For example, the decision logic  406  performs this operation. 
     At block  626 , a DTX detection result is determined from the DTX_ACK_STAGE(0) and DTX_ACK_STAGE(1) values. For example, the DTX decision logic  408  performs this operation. For example, in one embodiment, a decision is based on majority logic. For example, if the first stage value is a 1 (DTX detection), then the second stage criteria are checked. If the second stage value is also a one (DTX detection), then the DTX detection is kept as the final result. Otherwise the first stage decision is reversed. 
     Thus, the method  600  operates a two-stage DTX detector using majority logic to make a DTX determination. In one aspect, results show that with the 2-stage symbol domain metric and majority logic decision, the miss detection probability performance is significantly increased while meeting the requirement of the false alarm detection (DTX−&gt;ACK) probability. 
       FIG. 7  illustrates an exemplary digital computing system  700  with various networking features. It will be apparent to those of ordinary skill in the art that other alternative computer system architectures may also be employed. 
     Computer system  700  includes a processing unit  701 , an interface bus  712 , and an input/output (“IO”) unit  720 . Processing unit  701  includes a processor  702 , main memory  704 , system bus  711 , static memory device  706 , bus control unit  705 , and mass storage memory  707 . Bus  711  is used to transmit information between various components and processor  702  for data processing. Processor  702  may be any of a wide variety of general-purpose processors, embedded processors, or microprocessors such as ARM® embedded processors, Intel® Core™2 Duo, Core™2 Quad, Xeon®, Pentium™ microprocessor, AMD® family processors, MIPS® embedded processors, or Power PC™ microprocessor. 
     Main memory  704 , which may include multiple levels of cache memories, stores frequently used data and instructions. Main memory  704  may be RAM (random access memory), MRAM (magnetic RAM), or flash memory. Static memory  706  may be a ROM (read-only memory), which is coupled to bus  711 , for storing static information and/or instructions. Bus control unit  705  is coupled to buses  711 - 712  and controls which component, such as main memory  704  or processor  702 , can use the bus. Mass storage memory  708  may be a magnetic disk, solid-state drive (“SSD”), optical disk, hard disk drive, floppy disk, CD-ROM, and/or flash memories for storing large amounts of data. 
     I/O unit  720 , in one example, includes a display  721 , keyboard  722 , cursor control device  723 , web browser  724 , and communication device  725 . Display device  721  may be a liquid crystal device, flat panel monitor, cathode ray tube (“CRT”), touch-screen display, or other suitable display device. Display  721  projects or displays graphical images or windows. Keyboard  722  can be a conventional alphanumeric input device for communicating information between computer system  700  and computer operator(s). Another type of user input device is cursor control device  723 , such as a mouse, touch mouse, trackball, or other type of cursor for communicating information between system  700  and user(s). 
     Communication device  725  is coupled to bus  712  for accessing information from remote computers or servers through wide-area network. Communication device  725  may include a modem, a router, or a network interface device, or other similar devices that facilitate communication between computer  700  and the network. In one aspect, communication device  725  is configured to perform wireless functions. 
     In one embodiment, DTX detector  730  is coupled to bus  711  and is configured to provide DTX detection. The DTX detector  730  comprises hardware, firmware, or a combination of hardware and firmware to perform all the DTX detection functions described herein. 
     While particular embodiments of the present invention have been shown and described, it will be obvious to those skilled in the art that, based upon the teachings herein, changes and modifications may be made without departing from these exemplary embodiments of the present invention and their broader aspects. Therefore, the appended claims are intended to encompass within their scope all such changes and modifications as are within the true spirit and scope of the exemplary embodiments of the present invention.