1. Field of the Invention
The present invention relates to a mobile communication system, and more particularly to a method of transmitting emergency stop control information on an uplink common packet channel used in a mobile communication system of a wideband-code division multiple access (W-CDMA) type.
2. Description of the Related Art
In general, a reference specification of a Third Generation Partnership Project group(3GPP), which is one of the organizations establishing an IMT-2000 mobile communication standard, defines and describes transport channels and physical channels of an uplink (UL) and a down link (DL).
Of the transport channels defined in the 3GPP standard, a common packet channel (CPCH) is used in the uplink for transporting packets of relatively medium or small size. The CPCH is related to a dedicated physical control channel (DPCCH), which is one of the two types of the dedicated physical channel (DPCH) that is a physical channel of a DL physical channel to be explained later.
The DPCH generally comprises a three-layer structure: super frames, radio frames, and time slots. FIG. 1 shows a DPCH structure used in the Down Link.
The DPCH has two types: a dedicated physical data channel (DPDCH) for transferring data of an upper layer; and a DPCCH transferring control information of a physical layer.
FIG. 1 shows a structure of the DL DPCH in accordance with the 3GPP standard. Referring to FIG. 1, the DL DPCCH for transferring the control information comprises several fields such as a pilot field, a transport format combination indicator (TFCI) field, a feedback information (FBI) field, and a transport power control (TPC) field.
FIG. 2 shows relations between the DL DPCCH and the CPCH in accordance with the 3GPP interim standard. Referring to FIG. 2, the DL DPCCH is used to control power of the CPCH. When the DL DPCCH is used to control the transmission power of the CPCH, Only the DPCCH is transmitted without the DPDCH because no data are needed to be transmitted through the DPCH. At this stage in particular, the pilot bit and the transport power control (TPC) bit only are transmitted through the DPCCH. Table 1 below shows the channel information on the DPCCH and DL DPDCH in that case.
TABLE 1DPDCH ofDPCCH ofSpreadingBits/FrameBits/SlotBits/SlotKbpsKspsFactorDPDCHDPCCHTOTALBits/SlotNdata1Ndata2NTFCINTPCNpilot157.551260901501022024
The system adopting the 3GPP standard using the above channels is a asynchronous type which does not synchronize signals of other base station and even between signals down linked within a base station. Therefore, a random access manner is applied so that a plurality of user equipments (UE) can effectively transmit signals.
The universal mobile terrestrial radio access network (UTRAN) allocates an available Common Packet Channel (CPCH) to the UE, which transmits a packet in a random access manner.
Thereafter, the packet is transmitted through the UL CPCH. Prior to the transmission, a power control is performed with respect to the UL CPCH by the DPCCH only for a particular period of time.
The UTRAN measures a signal to inference ratio (SIR) with respect to the CPCH, and generates a transport power control (TPC) bit based on the measured value so as to be transmitted through the DL DPCCH.
The UE measures the SIR with respect to the DL DPCCH, and generates the TPC bit based on the measured value so as to be transmitted through the UL DPCCH. If the initial transmission power control is completed to be sufficient for packet transmission, the packet is transmitted through the UL CPCH.
While the packet is transmitted through the CPCH, the UE does not monitor other channels. Even during the transmission of the corresponding packets through the CPCH as described above, however, occasions arise to require interruption of the packet transmissions through the CPCH or release of the channel.
Nevertheless, the standard contributed in the 3GPP has failed yet to suggest any control procedures suitable for interrupting the packet transmission through the CPCH or an emergency stop to urgently release the CPCH, through which the packet is transmitted.
A considerable measure would be a method of transmitting emergency stop control information through a control channel. For instance, it is possible to receive emergency stop control information through other channels than the DL DPCH, e.g., a broadcasting channel (BCH), which is a transport channel, and a primary common control physical channel (PCCPCH), which is a DL physical channel, while the UE is transmitting the packets through the CPCH. However, the control information transmitted through the CCH can be restored as the original information only by undergoing a decoding procedure. Therefore, the period of time until obtaining the control information for an emergency stop becomes longer than the transport time interval (TTI) of the corresponding channel, which transmits the minimum control information.