CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Application No. 60/875,539, filed on Dec. 19, 2006 and entitled “scheme of header compression and ciphering in PDCP layer”, the contents of which are incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a method and apparatus for providing voice communication service in a wireless communications system, and more particularly, to a method and apparatus for effectively utilizing the contents of the voice packets with bit corruption, and enhancing voice quality. 
         [0004]    2. Description of the Prior Art 
         [0005]    The third generation mobile telecommunications system (called 3G system) provides high frequency spectrum utilization, universal coverage, and high quality, high-speed multimedia data transmission, and also meets all kinds of QoS requirements simultaneously, providing diverse, flexible, two-way transmission services and better communication quality to reduce transmission interruption rates. However, due to demand for high-speed and multimedia applications, the next generation mobile telecommunications technology and related communication protocols have been developed. 
         [0006]    Long Term Evolution wireless communications system (LTE system), an advanced high-speed wireless communications system established upon the 3G mobile telecommunications system (e.g. Universal Mobile Telecommunications System), supports only packet-switched transmission, and tends to implement both Medium Access Control (MAC) layer and Radio Link Control (RLC) layer in one single communication site, such as in Node B alone rather than in Node B and RNC (Radio Network Controller) respectively, so that the system structure becomes simple. 
         [0007]    The Universal Mobile Telecommunications System (UMTS) provides services of voice and packet transmission over a circuit-switched (CS) core network and a packet-switched (PS) core network. In comparison, the LTE system provides the same services over only the PS core network. Such transition simplifies the system structure, but induces different problems. 
         [0008]    In UMTS, the voice channel is operated in a Transparent Mode (TM), providing voice communication service over the CS core network. In TM, voice data packets with bit corruption, which fail in Cyclic Redundancy Check (CRC), are not discarded but delivered to the upper layer with a CRC error indication. As a result, for the voice decoder in the receiver, preserving data packets with bit corruption can recover voice with a quality better than discarding those data packets with bit corruption. 
         [0009]    In comparison, in the LTE system, voice application is transported over the PS core network and IP network. The PS voice application is also known as VoIP (voice over internet protocol) application. In addition, in the LTE system, the MAC layer provides Hybrid Automatic Repeat Request (HARQ) procedures on all transmissions as possible, so as to enhance transmission efficiency. Therefore, VoIP application is transported with HARQ. In such a situation, if the voice data packets are erroneous, or fail in CRC for example, the packets with bit corruption are discarded and will not be delivered to the upper layer. 
         [0010]    In short, since the LTE system uses HARQ when transmitting voice data packets, the receiver will discard voice data packets with bit corruption and will not deliver them the upper layer, causing waste of voice data. 
       SUMMARY OF THE INVENTION 
       [0011]    According to the present invention, a method for providing voice communication service in a receiver of a wireless communications system comprises activating a Hybrid Automatic Repeat Request, called HARQ hereinafter, process, receiving a first voice packet and storing the first voice packet in a buffer by the HARQ process, receiving a second voice packet and storing the second voice packet in the buffer before the first voice packet is successfully received by the HARQ process, and delivering the first voice packet to an upper layer with an indication to indicate that the first voice packet comprises erroneous data. 
         [0012]    According to the present invention, a communications device for enhancing voice quality when providing voice communication service in a wireless communications system comprises a control circuit for realizing functions of the communications device, a processor installed in the control circuit, for executing a program code to command the control circuit, and a memory installed in the control circuit and coupled to the processor for storing the program code. The program code comprises activating a Hybrid Automatic Repeat Request, called HARQ hereinafter, process, receiving a first voice packet and storing the first voice packet in a buffer by the HARQ process, receiving a second voice packet and storing the second voice packet in the buffer before the first voice packet is successfully received by the HARQ process, and delivering the first voice packet to an upper layer with an indication to indicate that the first voice packet comprises erroneous data. 
         [0013]    These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]      FIG. 1  is a function block diagram of a wireless communications device. 
           [0015]      FIG. 2  is a diagram of program code of  FIG. 1 . 
           [0016]      FIG. 3  is a flowchart of a process according to the embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0017]    Please refer to  FIG. 1 , which is a functional block diagram of a communications device  100  in a wireless communications system. The wireless communications system is preferably the LTE system. For the sake of brevity,  FIG. 1  only shows an input device  102 , an output device  104 , a control circuit  106 , a central processing unit (CPU)  108 , a memory  110 , a program code  112 , and a transceiver  114  of the communications device  100 . In the communications device  100 , the control circuit  106  executes the program code  112  in the memory  110  through the CPU  108 , thereby controlling an operation of the communications device  100 . The communications device  100  can receive signals input by a user through the input device  102 , such as a keyboard, and can output images and sounds through the output device  104 , such as a monitor or speakers. The transceiver  114  is used to receive and transmit wireless signals, delivering received signals to the control circuit  106 , and outputting signals generated by the control circuit  106  wirelessly. From a perspective of a communications protocol framework, the transceiver  114  can be seen as a portion of Layer 1, and the control circuit  106  can be utilized to realize functions of Layer 2 and Layer 3. 
         [0018]    Please continue to refer to  FIG. 2 .  FIG. 2  is a diagram of the program code  112  shown in  FIG. 1 . The program code  112  includes an application layer  200 , a Layer  3   202 , and a Layer  2   206 , and is coupled to a Layer  1218 . The Layer  2   206  comprises two sub-layers: a radio link control (RLC) entity  224  and a media access control (MAC) entity  226 . A primary function of the RLC entity  224  is providing different transmission quality processing, performing segmentation, reassembly, concatenation, padding, retransmission, sequence check, and duplication detection on transmitted data or control instructions based on different transmission quality requirements. The MAC entity  226  can match packets received from different logic channels of the RLC entity  224  to common, shared, or dedicated transport channels according to radio resource allocation commands of the Layer 3 (RRC layer)  202 , for performing channel mapping, multiplexing, transport format selection, or random access control. 
         [0019]    The LTE system supports only PS transmission, such that the program code  112  provides voice communication service by VoIP application, and uses HARQ when transmitter voice data packets, in order to enhance transmission efficiency. In such a situation, the embodiment of the present invention provides a voice communication program code  220  to effectively utilize voice data, and to enhance voice quality. Please refer to  FIG. 3 , which illustrates a schematic diagram of a process  30 . The process  30  is utilized for providing voice communication service in a wireless communications system, and can be compiled in to the voice communication program code  220 . The process  30  comprises the following steps:
       Step  300 : Start.   Step  302 : Activate an HARQ process.   Step  304 : Receive a first voice packet and store the first voice packet in a buffer by the HARQ process.   Step  306 : Receive a second voice packet and Store the second voice packet in the buffer before the first voice packet is successfully received by the HARQ process.   Step  308 : Deliver the first voice packet to an upper layer with an indication to indicate that the first voice packet comprises erroneous data.   Step  310 : End.       
 
         [0026]    According to the process  30 , in the HARQ process, if a first voice packet stored in the buffer comprises erroneous data (for example, the first voice packet fails in CRC), and the receiver receives a second voice packet, which is a new transmission, the embodiment of the present invention delivers the first voice packet to the upper layer with an indication to indicate that the first voice packet comprises erroneous data. In other words, when a voice packet comprises erroneous data and is to be discarded from the buffer, the embodiment of the present invention delivers the voice packet to the upper layer, so as to process the contents of the voice packet by the upper layer. As a result, the upper layer can process the contents of the voice packet, and determine to discard or utilize the voice packet accordingly. 
         [0027]    Preferably, if the first voice packet comprises a compressed header, the embodiment of the present invention can further perform decompression on the compressed header to get a decompressed header and a third voice packet, and perform a check procedure, such as CRC, on the decompressed header, or check if a field of the decompressed header comprises a value that is not allowed, to determine whether the decompressed header conforms to a predefined requirement. If the result of the check procedure indicates that the decompressed header conforms to the predefined requirement, the upper layer preferably delivers the third voice packet to another upper layer with another indication to indicate that the third voice packet comprises erroneous data. Oppositely, if the result of the check procedure indicates that the decompressed header does not conform to the predefined requirement, the upper layer preferably discard the first voice packet as never received. 
         [0028]    Similarly, if the first voice packet is ciphered, the embodiment of the present invention can perform deciphering on the first voice packet before the upper layer performs decompression on the header of the first voice packet. 
         [0029]    Therefore, via the process  30 , for voice packets with bit corruption, which is transmitted by HARQ, the embodiment of the present invention delivers the packets with bit corruption to the upper layer, and processes the packets by the upper layer, so as to achieve a better voice quality. In comparison, for voice packets with bit corruption, the prior art discards the packets with bit corruption and does not deliver them to the upper layer, causing waste of voice data. In other words, when providing voice communication service, the embodiment of the present invention can effectively utilize voice data packets with bit corruption, so as to enhance voice quality. 
         [0030]    In summary, for voice packets with bit corruption, the embodiment of the present invention delivers the voice packets with bit corruption to the upper layer, so as to effectively utilize the contents of the voice packets with bit corruption, and enhance voice quality. 
         [0031]    Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.
A method for providing voice communication service in a receiver of a wireless communications system includes activating a Hybrid Automatic Repeat Request, called HARQ hereinafter, process, receiving a first voice packet and storing the first voice packet in a buffer by the HARQ process, receiving a second voice packet and storing the second voice packet in the buffer before the first voice packet is successfully received by the HARQ process, and delivering the first voice packet to an upper layer with an indication to indicate that the first voice packet includes erroneous data