1.  Field of the Invention
The present invention relates generally to a CDMA (Code Division Multiple Access) communication system, and in particular, to a device and method of multiplexing and demultiplexing between physical channels and logical channels in a multiplex (MUX) and Quality of Service s (QoS) sublayer. 
2.  Description of the Related Art
The CDMA 2000 system can simultaneously provide a terminal with a plurality of services.  To do so, it supports various logical channels.  The logical channels correspond to physical channels via a MUX and QoS sublayer.  Thus, transmission data directed from an upper service entity to a logical channel is processed into information bits of a frame of a physical channel selected for transmission by the MUX and QoS sublayer.  Upon reception of the information bits, the physical layer constructs an actual physical channel frame based on the physical layer and transmits the physical channel frame. 
The MUX and QoS sublayers have not to date been incorporated in the CDMA 2000 system.  Presently, an IS-95-B MUX and DEMUX (demultiplex) layer can be considered for use when required.  The IS-95 standard which focuses on voice transmission has been currently developed to the IS-95-B standard.  The CDMA 2000 standard should ensure reverse compatibility for a terminal following the IS-95-B standard.  However, the IS-95-B MUX and DEMUX layers are not suitable for the CDMA 2000 system due to lack of logical traffics and does not support physical channels defined in the CDMA 2000 system.  Therefore, there is a pressing need for a new MUX and QoS sublayer which support the functions of a CDMA 2000 system as well as the functions of the IS-95-B MUX and DEMUX layer. 
It is, therefore, an object of the present invention to provide a communication method in a MUX and QoS sublayer which can appropriately multiplex and demultiplex data blocks transmitted on each channel by mapping logical channels supporting various services to physical channels, and provide reverse compatibility for a terminal based on the existing communication standards. 
To achieve the above object, there is provided a communication device and method in a mobile communication system.  The mobile communication system includes a plurality of service entities and a plurality of logical channels mapped to each service entity.  According to one aspect of the present invention, a communication device at a reception side has a plurality of logical channel mappers for the respective logical channels and a plurality of physical channel multiplexers/demultiplexers for physical channels.  Each logical channel mapper converts a received data block mapped on a logical channel to a traffic in a predetermined format.  Each physical channel multiplexer/demultiplexer defines a traffic receivable from a logical channel mapper, receives the traffic from the logical channel mapper, and demultiplexes the traffic into a corresponding physical channel.