1. The difference is that WCDMA on the wireless side adopts FDD (frequency division duplex) technology, so the carrier frequency interval is 5MHZ, so the effect is better than TD when moving at high speed, while TD adopts TDD (time division duplex) technology, which has higher spectrum utilization, but the effect is much worse when moving at high speed. At present, there is no other method that can be realized without a private network.
The main difference between FDD standard (WCDMA and CDMA2000) and TDD(TD-SCDMA) standard is whether the uplink and downlink use symmetrical dual-frequency or single-frequency, so Datang can't get rid of the patents of other competitors.
In addition, W developed early, so W should be relatively mature. At the beginning, China operators actually wanted to use W to develop 3G.
2. Compared with WCDMA, TD-SCDMA also has some shortcomings. For example, in the use of CDMA technology, TD-SCDMA is compatible with GSM cell, and the cell reuse coefficient is 3, which reduces the spectrum utilization. Due to the narrow frequency band of TD-SCDMA, multipath cannot be fully utilized, which reduces the system efficiency and makes it difficult to realize soft handover and soft capacity. In addition, TD-SCDMA system needs accurate timing and synchronization between cells, which requires high timing system. WCDMA, on the other hand, does not need inter-cell synchronization, and can be applied in different environments such as indoor, outdoor and even subway. In addition, WCDMA supports mobility better and is suitable for Hong Fengwo, cellular and microcellular networks, while TD-SCDMA is only suitable for microcells, and its support for high-speed mobility is also poor. Especially in the transition from GSM network to 3G, WCDMA has more obvious advantages. So from the current situation, although TD-SCDMA and WCDMA have their own advantages, WCDMA should become the mainstream standard of 3G.
3. Essentially, HSDPA is a collection of some wireless enhancement technologies. Using HSDPA technology can greatly improve the peak rate of downlink data on the basis of 3G existing technology. HSPDA is an important feature of 3GPPRelease5RAN. Compared with R4 TD-SCDMA and WCDMA systems, the introduction of HSDPA technology mainly enhances the system performance by modifying the air interface, which mainly works in the physical layer and MAC layer of UE and NodeB, while RLC (Radio Link Control) and packet data convergence protocol (PDCP) remain unchanged. The MAC-hs entity is mainly added to the MAC layer of UE and NodeB, and the MAC layer operations related to HS-DSCH are all completed here. In addition to the functions of flow control and priority processing, it is also necessary to complete the related operations of HARQ protocol, including scheduling, retransmission and rearrangement. In addition, RRC and NBAP protocols need to provide corresponding process support. HSDPA technology can be applied to both WCDMA and TD-SCDMA. In these two different systems, the implementation methods are very similar, and the basic principles and key technologies are basically the same.