Time Division Synchronous Code Division Multiple Access System Research Articles

An Improved Channel Estimation in a TD-SCDMA System Based on the Threshold of Detect Energy and its Performance Analysis

B. Steiner estimator used in the time-division synchronous code-division multiple access (TD-SCDMA) system is a low cost estimator. The precision of the estimated channel impulse responses (CIRs) is affected by noises in the channel, which result in worse performance of the estimation. For the reason that there are many threshold processing algorithms based on Steiner algorithm, the optimal threshold value becomes a crucial factor. In this paper, based on statistical information of channel in the data field, an improved channel estimation algorithm is proposed by detecting energy of CIR's tap in time-domain, and the amplitude of estimated channel impulse response is adjusted by a gain coefficient. Simulation results prove the validity of the proposed technique for channel estimation good performance. Additionally, it is shown that the improved estimators outperform traditional channel estimators.

Performance Evaluation of the Joint Detection with Channel Estimation Error

In previous B. Steiner channel estimation algorithm adopted in Time DivisionSynchronous Code Division Multiple Access (TD-SCDMA) system, but there are some errors in estimated channel due to noise. However, due to using the short training sequences available, the resulting estimation of the channel and detected data suffer from unavoidable errors. In this paper, we analyze the effect of channel estimation error on joint detection and evaluate the performance of TD-SCDMA systems with channel estimation error. The simulation results are consistent with the theory analysis.

Doppler Shift Estimation for TD-SCDMA System over Railway Environments

In this paper, a new Doppler shift estimator is proposed for Time Division-Synchronous Code Division Multiple Access (TD-SCDMA) over railway environments. Different from other existing methods, which commonly assume that the fading channel coefficients are available for the Doppler estimators, the proposed estimator is developed based on the signals which contain unknown frequency selective fading channel coefficients, unknown Rice factor and random receiver noise; it contains three steps. The statistical properties of the training symbols which are called near independent identically distributed (i.i.d.) training sequences, i.e., midamble, are first analyzed. Afterwards, by the help of a training sequence, the second-order and fourth-order statistics of the received signals are calculated. Then, by exploiting these statistical results, the Doppler shift estimator is obtained. The proposed estimator employs a smoothing function with corrective factor. By optimizing the corrective factor, an accuracy solution is acquired within the Doppler shift range of possibilities. Simulation results indicate that the proposed estimator is greatly reliable and effective to estimate Doppler shift up to 400 Hz.

The Wireless Network Positioning Strategies Basing on Mobile Terminal

With the continuous development of terminal technologies, the use of mobile terminals is becoming more and more diverse. Many value-added services brought by such applications gradually become to be the firm's new profit opportunity. The location itself has great value; with the display of electronic map or with the support of geographic information database, a variety of information can be shown, tracked and handled. Such location-based services (LBS) is widely used in the field of public wireless data, and mobile location services is recognized as the most attractive wireless data value-added business in 3G network. This paper discusses three positioning standards of the 3GPP first; and then combined with the existing GSM/GPRS cellular radio communication network, it mainly gives specific positioning implementation strategies of single base station in the TD-SCDMA (Time Division Synchronous Code Division Multiple Access) system.

Frequency estimation for the downlink of the TD-SCDMA system over frequency flat Rician fast fading channels

In this paper, a new frequency estimation scheme is proposed for the downlink of Time Division-Synchronous Code Division Multiple Access (TD-SCDMA) system over frequency flat Rician fast fading channels. The proposed algorithm exploits the synchronous downlink sequence of the downlink pilot time slot in the sub-frame, and takes account of the case where the carrier frequency offset (CFO) and the Doppler shift coexist. The new approach first presents the second-order and fourth-order statistics of the signals which contain unknown CFO, unknown Rician fading coefficients with the Doppler shift, and additive white Gaussian noise. Then, by flexible parameters setting and concrete mathematical operations for above statistics, a new closed-form expression for frequency estimation (the CFO and the Doppler shift) is derived. The simulation results are finally provided to illustrate the accuracy and reliability of the proposed method within the expectative frequency estimation range.

Effect of HARQ Gain for a Smart Antenna System and a Diversity Antenna System in a TD-SCDMA System

This paper presents a performance analysis of a beam forming smart antenna array system and a diversity antenna array system operating in a time division synchronous code division multiple access (TD-SCDMA) signal environment which adopts Hybrid Automatic Request (HARQ). Performance analysis was based on a receiver structure proposed in this paper which combined the HARQ with a smart antenna system or a diversity antenna system. When there was no HARQ, the diversity system outperformed the smart antenna system by about 4.2 dB for a given Frame Error Rate (FER) if the number of antenna elements was set to six for both the receiving systems. However, the performance difference was reduced to 2 dB when HARQ was appended in the receiver, as HARQ gain can be exploited more efficiently in a smart antenna system. Comparing the 6-antenna beamforming system with the 2-antenna diversity system (which is more realistic than a 6-antenna diversity receiver in practice), we found that the former outperforms the latter by 3 dB due to the contribution of HARQ gain. Performance analysis is shown in terms of FER and the required system complexities in a TD-SCDMA mobile communication system.

TD-SCDMA Evolution

This article focuses on the evolutional strategies (which can be divided into four phases) from the current commercial time division-synchronous code division multiple access (TD-SCDMA) to the future International Mobile Telecommunications (IMT)Advanced systems. The first evolutional phase is to develop an N-frequency technology to improve capacity and ease network planning of the current TD-SCDMA system. Singleand multicarrier high-speed packet access (HSPA) is specified in the second phase for providing high-rate packet services. Long-term evolution (LTE) technology is introduced in the third phase to provide a similar performance of mobile worldwide interoperability for microwave access (WiMAX). Finally, the fourth phase is to implement time division duplex (TDD)-based IMTAdvanced system, which is one of the alternative standards beyond third-generation (3G) systems. The advanced technologies to enhance spectral efficiency are the critical issues emphasized in all the four phases. The challenges and open issues in the different evolutional phases are identified in this article as well.

Evolution map from TD-SCDMA to FuTURE B3G TDD

The rapid growth of mobile applications in recent years has created a need for wideband wireless communication. The only predictable trend is that data-rate and QoS requirements will increase rapidly. This demand is pushing time-division-synchronous code-division multiple access (TD-SCDMA) to evolve in order to provide higher and higher data rates. This article presents the evolution map from TD-SCDMA to future terrestrial universal radio environment (FuTURE) TDD in China. The evolution includes four phases: low chip rate (LCR), high-speed downlink/uplink packet access (HSxPA)/TD-SCDMA EV 1x, long-term evolution (LTE) TDD, and FuTURE beyond 3G TDD. The main features of each phase are described in detail. By introducing the new technologies into the system step by step, for example, multiple input and multiple output (MIMO), orthogonal frequency-division multiplexing (OFDM), TD-SCDMA system can evolve to FuTURE B3G TDD smoothly, and provide high-data-rate services with low cost, low latency, and improved coverage and capacity.

Key techniques and radio network planning in TD-SCDMA systems

Receiving significant support from China's government and enterprises in themobile communication industry federation, Time Division Synchronous Code Division Multiple Access (TD-SCDMA) has become the fastest growing 3G technology standard in China. Since TD-SCDMA has adopted some key techniques, such as Time Division Duplex (TDD), joint detection, uplink synchronisation, Smart Antenna (SA), dynamical channel allocation and baton handover, the radio network design issues are distinguished from WCDMA and cdma2000. In this paper, the key techniques and issues impacting on TD-SCDMA radio network planning are introduced. The advanced radio network design issues, such as capacity planning, coverage planning, scrambling code planning, N frequency planning, inter-system interference cancellation and Radio Resource Management (RRM) schemes, are investigated. Particular planning strategies are also proposed, which include the network evolution architecture design and the base station co-sites design. Finally, some challenges for TD-SCDMA commercial deployments are presented.