Research On TD-SCDMA Evolution And Radio Resource Management Technologies

Time Division Synchronous Code Division Multiple Access (TD-SCDMA) evolution and advanced radio resource management (RRM) technologies are researched in this dissertation. The mainstream TD-SCDMA evolution can be categorized into two types:systems based on Code Division Multiple Access (CDMA) and systems based on Orthogonal Frequency Division Multiple Access (OFDMA). Several novel RRM technologies are involved here, such as the novel fast packet scheduling (FPS) algorithm considering feedback delay in TD-SCDMA High Speed Downlink Packet Access (TD-HSDPA) systems, the novel strategy of orthogonal variable spreading factor (OVSF) code reusing in TD-HSDPA, the packet scheduling and resource allocation schemes in TD-SCDMA Long Term Evolution (TD-LTE), the novel adaptive resource allocation (ARA) algorithm in OFDMA with insufficient guard interval. under fractional load, and the three-dimension scheduling and resource allocation scheme based on physical resource block (PRB) reusing. Moreover, the co-existence performance of TD-SCDMA and TD-LTE are studied.TD-SCDMA evolution not only needs the upgrade in system fundamental architecture, but also the innovation and optimization in key technologies on physical (PHY) layer and medium access control (MAC) layer. TD-HSPA/TD-HSPA+ based on CDMA and TD-LTE/TD-LTE+ based on OFDMA are introduced by this dissertation, while the standardization and key technologies of TD-SCDMA evolution are analyzed, such as smart antenna (SA), joint detection (JD), adaptive modulation and coding (AMC), hybrid auto repeat request (HARQ), multiple input multiple output (MIMO) antenna, and OFDM algorithm; the framework and schemes of future RRM are also mentioned. Through the analysis of the features and structures of TD-SCDMA evolution, the system level simulation methodology is discussed. The correlative simulation modules and assumptions of parameters are designed, and the simulator also takes the differences between TD-HSPA and TD-LTE into account. Our research work can be composed of following 6 parts:Firstly, TD-HSDPA adopts high speed downlink shared channel (HS-DSCH) as the traffic channel to transmit packet data for different users, and it has two shared control channels for interaction between base station (NodeB) and user equipment (UE):shared control channel for HS-DSCH (HS-SCCH) and shared information channel for HS-DSCH (HS-SICH). In TD-HSDPA, due to the timing relationship of high speed (HS) channels, the feedback information of channel quality indicator (CQI) are always delayed under the conventional scheduling schemes; especially, when the traffic load is heavy, the CQI received by NodeB can no longer represent the current channel condition for users. In order to maintain the efficiency of feedback information, a novel scheduling scheme for feedback delay control is proposed. As the new scheme utilizes users'scheduling and channel allocation, the interaction delay can be greatly shortened, and the system performance can be improved remarkably.Secondly, OVSF is adopted in TD-HSDPA for physical channel spreading, and the spreading codes can be up to 16. Similar to TD-SCDMA, TD-HSDPA is a kind of resource-limited systems whose spreading codes are finite in a given time slot. The proposed OVSF codes reusing algorithm introduces spatial domain into TD-HSDPA by using spatial filter of SA beam-forming, and the users who have passed the spatial filter can share same codes, which enhances the system capacity and improve the quality of service (QoS).Thirdly, OFDM is considered as one of the most promising technologies for future multimedia wireless systems that require reliable and high-rate data transmission. As subcarrier resource is exploited, more complicated scheduling algorithms are required to achieve richer multi-user diversity. We investigate the combined performance of HARQ aware cross-layer design RRM in TD-LTE downlink systems, which is generally composed of time domain packet scheduling (TDPS) at MAC layer and frequency domain resource allocation (FDRA) at PHY layer, and the simulation results shows that the cross-layer design algorithm can guarantee the users'fairness and bring more performance gain for TD-LTE downlink.Fourthly, a more practical scenario, in which multi-path delay is longer than the guard interval (GI), is considered in this dissertation, and the intra-cell inter-symbol interference (ISI) and inter-carrier interference (ICI) are re-analyzed. Most of the existing literatures focus on the digital signal processing (DSP) algorithms at the receiver for reducing the intra-cell interference of OFDMA systems. However, instead of the conventional complicated DSP algorithms, we propose a novel adaptive resource allocation scheme, in which RA flexibility of fractional load is utilized to avoid intra-cell interference.Fifthly, in TD-LTE, we adopt SA to improve spectrum utilizing efficiency. Through the beam-forming, spatial dimension resources are introduced into TD-LTE, and the RRM schemes are extended to three-dimension. The proposed scheme makes the users who have passed spatial filter reuse the same PRB, which enhances the system throughput remarkably.Finally, the co-existence performance of TD-SCDMA and TD-LTE are studied. By the cooperative simulation of double systems, we analyze the interference with different traffics, and find out the required adjacent channel interference power ratio (ACIR) value in different scenarios from the simulation results.