Comparing with the existed technology, TD-SCDMA technology has many advantages. As TD-SCDMA is a combination technology, it adopts advanced technology such as time division duplex, smart antenna, joint detection, baton handover, uplink synchronization and dynamic channel allocation (DCA).
Time Division Duplex：Time Division Duplex is a fundamental differentiator between TD-SCDMA and FDD. TD-SCDMA system, under TDD mode, enables uplink and downlink transmission in the same carrier, rather than symmetrical uplink and downlink spectrum as required by FDD. Apart from great improvement of the spectrum availability by fully leveraging spectrum resources, TDD mode also boasts the strength of flexible adjustment of uplink and downlink conversion point based on different service type, thus providing best service capacity and spectrum availability.
Smart Antenna: Smart Antenna system consists of a set of antenna array, its connected receiver and advanced digital signal processing algorithm, On the transmit side, the smart antenna produces phase difference on the antenna array based on the received signals, withdraws terminal location information, and effectively produces multiple beam forming, with each beam directing towards a specific terminal and moving with it automatically, thus reducing co-channel interference and improving downlink capacity. The space beam forming results in great deduction of the total RF transmission power with the cell coverage unchanged. It helps improve the space electro-magnetic environment on the one hand and reduce the cost of wireless base stations on the other. On the receiving side, the smart antenna, through space selection diversity, can greatly improve the receiving sensitivity and reduce co-channel interference of users in different locations. As a result, it can effectively consolidate multi-path component, offset multi-path fading and improve uplink capacity.
Joint Detection: Joint detection technology is an inhibitor to multi-user interference, a major technology for eliminating and reducing multi-user interference. It process all user signals as useful signals, thus fully utilizing information from user signal such as the spread code, amplitude, time setting and delay, greatly reduce multi-path and multi-access interference. Combining with smart antenna technology, the joint detection technology can achieve better desired results.
Baton Handover: Baton handover is one of the core technologies of TD-SCDMA mobile communications system. It is a new handover approach between hard handover and soft handover. The principle is to obtain information of transmission time and power in the uplink channel in advance by using uplink pre-sync technology during the handover measurement period, thus reduce handover time, improve success rate and reduce drop rate. The whole process is like a baton match in the field sports, so it is vividly granted a name of baton handover. Compared with hard handover and soft handover, baton handover boasts advantages of less handover time, requiring only one wireless link during the whole handover process, less wireless resources as compared with soft handover, higher success rate as compared with hard handover as the uplink and downlink handover run separately, and enabling harmless handover etc.
Uplink Synchronization: Uplink Synchronization refers to full synchronization of signals transmitted by various terminals at the uplink channel at the base station demodulator. This is enabled through software and physical layer design. It enables complete orthogonality of all path in orthogonal spread spectrum code during dispreading, thus producing no multi-access interference. It overcomes the bottleneck of asynchronous CDMA technology for interferences arising from non-orthogonal path due to different arriving time of signals transmitted by each mobile terminal to base stations, thus improving the TD-SCDMA system capacity and spectrum availability. It can also simplify hardware circuit and reduce cost. Dynamic Channel Allocation: Dynamic channel allocation technology adopted by TD-SCDMA enables flexible wireless allocation in time domain, space domain and code domain. This technology enables better avoidance of interference and minimum channel reuse distance of TD-SCDMA system, thus efficiently utilizing the limited wireless resources and improving the system capacity. In addition, dynamic channel allocation in time domain enables flexible allocation of time slot resources, dynamic adjustment of the number of uplink and downlink time slots, so as to support symmetrical and asymmetrical services flexibly.
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