A supporting ability for high speed mobile packet data services is one of the most important characteristics of the 3G system. According to WCDMA R99, a peak rate of 2 Mbps can be provided, which is adequate for most of the traditional packet services. However, for data services requiring high on traffic and delay, such as video, streaming and download, the system is required to provide a higher transmission rate and a shorter delay.
HSDPA technology is introduced in 3GPP R5, which not only supports high speed unsymmetrical data services but also can increase the network capacity while minimizing the cost of the operator. It provides a smooth evolving path for higher data rate and capacity for the UMTS (Universal Mobile Telecommunications System). The HSDPA in R5 refers to the design idea and experience of CDMA20001X EV-DO and adds a high speed data sharing channel (HS-DSCH). The HS-DSCH makes the transmission power and the PN code etc. can be fully used and can be dynamically allocated according to the practice so that the resource utilization ratio is improved.
In a transmission process of a single carrier HSDPA in R5 specification, when a UE first accesses the network, it will be allocated a pair of uplink and downlink DPCHs (dedicated physical channel) and multiple pairs of HS-SCCHs and HS-SICHs to be monitored. The pair of uplink and downlink DPCHs is called uplink and downlink associate channels. Before the network transmits packet data to the UE through the HS-DSCH, it transmits corresponding control messages to the UE through one of the HS-SCCHs, such as the channel resource occupied by and the modulation method of the packet data, so that the UE can correctly receive data transmitted through the HS-DSCH and can notify through the HS-SICH the network to retransmit data. The HS-SCCH is at the downlink and mainly for transmitting necessary control messages for the HS-DSCH decoding. The HS-SICH is at the uplink and is for transmitting necessary control messages, which are mainly about the response to the packet transmission and the feedback information of downlink quality.
The uplink and downlink associate channels are for transmitting power control information, synchronous information, high-layer signaling and data response message and also for transmitting data. In practice, the uplink and downlink associate channels are mainly for transmitting high-layer control signaling, high-layer response message and messages for initiating power control and synchronous control of the HS-SCCH and HS-SICH. The UE can obtain the transmission power and synchronous control messages adopted by the HS-SCCH through the uplink and downlink associate channels so that the UE can receive the control message of the HS-SCCH and can feed back information through the HS-SICH in time so that the transmission of packet data can be established.
In order to further improve the performance of the system, a multi-carrier HSDPA technology is proposed to enhance the transmission ability of the packet data services. However, in the R5 specification, only the single carrier HSDPA technology is adopted and the allocation of control channels (HS-SCCH, HS-SICH and uplink and downlink associate channels) for controlling packet data transmission is simple can cannot support the multi-carrier HSDPA data transmission.