Interference considerations for the time division duplex mode ofthe UMTS Terrestrial Radio Access

The air interface of the UMTS Terrestrial Radio Access (UTRA) covers both a frequency division duplex (FDD) part for the paired bands and a time division duplex (TDD) part for the unpaired bands of the UMTS spectrum. The Universal Mobile Telecommunication System (UMTS) is the 3rd-generation mobile communication system. This paper presents an interference evaluation of the UTRA TDD. Since both uplink and downlink share the same frequency in TDD, the signals of the two transmission directions can interfere with each other. This interference can occur between two mobile stations or between two base stations within one carrier or between two operators. The interference between uplink and downlink is evaluated by system simulations. Synchronization and coordination requirements of UTRA TDD are evaluated based on the results     

Handover and Uplink Power Control Performance in the 3.84 Mcps TDD mode of UTRA Network

In this article we consider the performance of the 3.84 Mcpstime-division duplex (TDD) mode of UTRA (Universal TerrestrialRadio Access) network. We emphasize two of the radio resourcemanagement algorithms, handover and uplink power control, whoserole in the overall system performance is studied extensively.First, a handover algorithm used in WCDMA (Wideband Code DivisionMultiple Access) standard is considered in a TDD-mode operation.This gives rise to a careful setting of different handoverparameters, and the evaluation of the effects to the systemperformance. Secondly, the specified uplink power controlalgorithm is considered. Since it is based on several user-mademeasurements which may involve both random and systematic errors acareful study about the suitability of the power control scheme iscarried out.     

FLC-Based MBWIMA/UMTS Protocol for Multimedia Services in UTRA TDD Mode

An intelligent medium access control (MAC) protocol based on fuzzy logic control (FLC) is proposed and compared with a general packet radio system in UMTS (GPRS/UMTS), priority scheme and the movable boundary wireless integrated multiple access in UMTS (MBWIMA/UMTS) protocols. The integrated video/voice/data services of UMTS in UTRA TDD mode have different transmission properties. By fuzzy logic control, the resources of the wireless communication can be intelligent assigned for different types of mediums. The voice-video dropping probability and data packet delay are input to FLC to optimally select the maximum number of voice/video slots. Voice activity detector (VAD) and multiple access interference in single cell are also considered in the simulations.     

Signaled Step Size for Downlink Power Control of Dedicated Channels in UTRA TDD

This paper discusses downlink inner loop power control of dedicated channels in UTRA TDD. The current UTRA TDD downlink power control is similar to one in UTRA FDD mode, that comprises of closed inner loop and quality based outer loop. However, due to the time division feature and associated fexibility with asymmetry of TDD, the inner loop can not react as fast as in FDD and it is affected by rapid changes in environment. Therefore, the effect of the inner loop algorithm to the performance of UTRA TDD network is studied in this paper. Especially, the use of asymmetric step sizes for power up and power down commands is evaluated in contrast to the conventional symmetric power adjustment. Since it would be beneficial for the downlink inner loop power control to reach the target SIR as fast as possible, the power control step size based on the difference between the UE measured SIR and target SIR would be the most desirable power adjustment. Since the effectiveness of this type of an algorithm depends on available signaling bandwidth that is used, a study is carried out to find the tradeoff between the signaling bandwidth and related network performance.Janne Kurjenniemi was born in Jyväskylä, Finland, in March 1974. He received the M.Sc. in telecommunications in 2001 from the University of Jyväskylä, Jyväskyl, Finland. He is working as a Researcher at the Department of Mathematical Information Technology, University of Jyväskylä. His research interests include radio resource management for wireless communication systems.Otto-Aleksanteri Lehtinen was born in Tampere, Finland, in September 1971. He received the Master of Science in Technology in 1999 from the Helsinki University of Technology, Department of Electrical engineering (major in radio technology, minor signal processing and computer devices). His research interests include radio resource management for wireless communication systems.Tapani Ristaniemi was born in Kauhava, Finland, in 1971. He received the M.Sc. in mathematics in 1995, Ph.Lic. in applied mathematics in 1997, and Ph.D. in telecommunications in 2000 from the University of Jyväskylä, Jyväskylä, Finland. During 2001–2003 he was a professor of telecommunications at the Department of Mathematical Information Technology, University of Jyväskylä. In 2003 he joined the Institute of Communications Engineering in the Tampere University of Technology, Finland, where he has been a professor of wireless data communications. His research interests include signal processing for communications and radio resource management for wireless networks.     

Performance Analysis of Multi-Antenna TD-CDMA Receivers with Estimation and Consideration of the Interference Covariance Matrix

The use of adaptive antennas in cellular mobileradio systems is considered to be one of the mostimportant measures to increase capacity. The consideredadaptive antenna concept is applied to the well-known TD-CDMA mobile radio air interface. TD-CDMA isadopted by ETSI for the UTRA TDD mode and is one of thecandidates considered by ITU for IMT-2000. In thereceivers of a TD-CDMA system the intracell multiple access interference (MAI) is eliminated byjoint detection. This detection algorithm also offersthe advantageous possibility of considering theintercell interference covariance matrix in order toenhance system performance. In this paper, amulti-antenna receiver structure with the capability toestimate the covariance matrix of the received intercellmultiple access interference (MAI) is presented. The benefits of taking into account theinterference covariance matrix both in channelestimation and data detection are shown by simulations.The directional channel models applied in thesimulations are derived from measured channel impulseresponses.     

Slot-Splitting TDD-CDMA for Cellular Wireless Networks

This paper proposes an improved version of time-division duplex (TDD) mode called slot-splitting TDD (SS-TDD), which increases the average achievable capacity of a TDD cellular network by splitting a slot. The improvement results from partial relaxation of the restriction in the former versions of TDD, which requires an integer number of downlink slots. The proposed method can be implemented with no significant increase in computational complexity. In addition, with a few minor modifications, the proposed SS-TDD can be applied to two out of three burst types in UTRA TDD with a single-switching-point configuration. In a multi-cell environment with mixed traffic, our analysis shows that the proposed SS-TDD increases the average cell capacity (in Mbps) by up to 18.5-10.0%, and the Erlang capacity by up to 20.5-44.3%, for targeted SIRs in the range of 5-7dB.     

Intelligent MBWIMA/UMTS protocol using cascade fuzzy logic control for UTRA TDD mode

An intelligent medium-access-control (MAC) protocol based on cascade fuzzy-logic-control (CFLC), consisting of a fuzzy V/sub max/ (maximum number of voice/video slots) control and a fuzzy data-rate control for universal mobile telecommunications system (UMTS) terrestrial radio access time-division duplex (UTRA TDD) mode is presented. Voice, data, and video are integrated for transmission using CFLC-based movable-boundary wireless multiple access (MBWIMA) in the UMTS protocol. The performance of the CFLC-based MBWIMA/UMTS protocol with data-rate control is optimized by using the CFLC to generate the proper maximum number of voice/video slots and a suitable data rate. Simulation results demonstrate that the data-packet delay for the CFLC-based MBWIMA/UMTS protocol with data-rate control is less than that for the CFLC-based MBWIMA/UMTS protocol without data-rate control. The CFLC-based MBWIMA/UMTS protocol with data-rate control can greatly improve both the voice-video dropping probability and the data-packet delay of the MBWIMA/UMTS and general packet-radio system/UMTS protocols at the expense of a small decrease in the data-packet throughput. Voice-activity detector, single cell, and multicell environments are also considered.     

Analysis of random access channel in UTRA‐TDD on AWGN channel

The random access channel (RACH) in UTRA‐TDD systems is an uplink contention‐based transport channel that is mainly used to carry control information from mobile stations to base stations. In this paper, we study the performance of RACH on an additive white Gaussian noise (AWGN) channel whereby successful transmission of a burst requires the spreading code chosen to be collision‐free and the burst is error‐free after convolutional decoding. Based on this model, the code‐collision probability, the data bit error probability and the RACH channel capacity are derived. The random retransmission delay mechanism is not specified in UTRA‐TDD. We therefore choose an access mechanism with binary exponential backoff delay procedure similar to that in IEEE 802.11. Based on that mechanism, the blocking probability and the first two moments of the delay are also derived. Compared with the mean, the standard deviation is found to be very high. Copyright © 2004 John Wiley & Sons, Ltd.     

Multidimensional PRMA with prioritized Bayesian broadcast-a MACstrategy for multiservice traffic over UMTS

Multidimensional packet reservation multiple access is proposed as a medium-access control (MAC) strategy for the uplink channel of the UTRA (UMTS terrestrial radio access) time-division/code-division multiple-access (TD/CDMA) mode to benefit from efficient statistical multiplexing on the large common pool of available resources (i.e., slots defined both in time and code domain). A prioritized Bayesian broadcast algorithm is derived to stabilize multidimensional packet reservation multiple access (MD PRMA) and to allow for access delay discrimination of four different access classes. Access delay spread can be selected, and trading voice-dropping ratio against data-access delay is possible. To control multiple-access interference, Bayesian broadcast can be combined with load-based access control. The performance of both frequency-division duplex (FDD) and time-division duplex (TDD) mode is evaluated, the latter particularly relevant for TD/CDMA. For mixed voice, Worldwide Web (WWW) browsing, and e-mail traffic, the UMTS WWW model is used, while the e-mail traffic model is derived here     

Low‐Cost High‐Performance TDD Synchronizer for WiBro RF Repeater

WiBro radio frequency (RF) repeater is used for solving the problem of partial shadow areas in the wireless communication field that uses time‐division duplexing (TDD) mode. In this paper, a method to efficiently generate TDD signals for WiBro RF repeater is proposed and its digital circuit is implemented. A TDD signal is detected from RF signals transmitted/received to/from RF repeater and then inputted again into the RF repeater, so that it can operate normally. First, the envelope of downlink signals is detected and then clamped to extract the basic form of a TDD signal using an operational amplifier circuit. Next, the TDD signal is generated by restoring and filtering the shape which has been distorted by the wireless channel. The algorithm and system to acquire TDD signal are developed with a goal to have simple but powerful functions with as little cost as possible. The proposed method is implemented as an RF‐digital integrated system and verified through the experiments under the same condition as actual WiBro service environment.     

A Non-Linear Multiuser Detector for UMTS

The family of international standards for mobile communications IMT-2000 includes amongst others the UMTS Terrestrial Radio Access (UTRA) proposal, which consists of two modes: Frequency Division Duplex (FDD) and Time Division Duplex (TDD). Both are wideband CDMA systems. CDMA systems are Multiple Access Interference (MAI) limited. Conventional detectors like the RAKE receiver do not decrease the MAI, this leads to a limited Bit Error Rate (BER) performance. For further improvement of system capacity Multiuser Detectors (MUD) should be applied. In this paper a non-linear approach employing Radial Basis Functions (RBF) is shown. The adaption of this algorithm to UTRA, its complexity and the BER-performance is discussed.     

Traffic and Interference Adaptive Scheduling for Internet Traffic in UMTS

In this paper we propose a scheduling strategy for the radio resources management when transmitting Internet traffic over third-generation systems. More precisely, we consider the UMTS Terrestrial Radio Access Network (UTRAN) Time Division Duplex (TDD) mode standardized by ETSI. UTRAN TDD uses a hybrid solution of code and time division multiple access, called TD-CDMA. In UMTS systems a key issue in developing access methodologies for the available spectrum is an optimal management of the rare radio resources. In this paper we present a fair and efficient scheduling algorithm that adapts its behavior to traffic and interference conditions. Specifically, our scheduling algorithm is able to manage the radio resources taking into account both the traffic fluctuations in the uplink and downlink direction and the variations of the system interference. The goal of our scheduler is the data-throughput maximization for an efficient utilization of available radio resources. The effectiveness of our scheduling algorithm is shown by exploiting analytical tools.     

A vision from the future: beyond 3G TDD

This article introduces the visions and developments of Beyond 3G mobile communications in the China TDD Special Work Group. System structure, radio transmission design, radio resource management, and demonstration system implementation are covered. In system structure, the concept of group cell and the architecture of distributed antennas are introduced. The radio link transmission design presented in this article includes the radio frame structure, multiple access scheme, and promising key techniques. Link-level simulations prove the advantages of the design. The radio resource management strategies are introduced to optimize the system performance. The B3G TDD demonstration system being built by the TDD Special Work Group is also shown finally.     

一种基于FFT的Midamble码搜索算法

针对一种基于UTRA TDD LCR时隙结构的ad-hoc网络的通信特点,给出了一种可在DSP上实现的基于FFT的M idamble码搜索算法,并给出了基于该算法的多径搜索实现方案。分析表明,该算法充分利用了DSP的特点,且其运算效率相比于传统的匹配滤波有大大的提高。     

TDD CDMA系统无线资源管理真法的建模与仿真

无线资源管理是第三代移动通信系统中的重要组成部分,用于对业务需求、资源分配、系统容量和稳定性进行控制,而TDD CDMA系统特性及其中引入的智能天线技术使得无线资源管理算法需重新建模设计。本文利用OPNET仿真软件对TDD CDMA系统进行了建模,并且对我们提出的几种适用于TDD CDMA系统的新无线资源管理算法进行了仿真,与传统算法获得的仿真结果对比,验证了其性能增益。     

Optimum Joint Transmission (JT) Scheme in TD-SCDMA Downlink

1　Introduction　TD CDMAhasbeenselectedby 3GPPastheairin terfacestandardfortheTimeDivisionDuplexing(TDD)modeofthe 3GsystemInternationalMobileTelecommunications 2 0 0 0 (IMT 2 0 0 0 ) [1] .AlsotheChinese 3GairinterfaceTD SCDMAreliesontimeslot tedCDMAandTDDandiscloselyrelatedtoTD CD MA .TD SCDMAhasbeendecidedasthestandardforTDDmodeofthe 3rdGenerationmobileradiosystembyITU ,itisaimportantbreakthroughinacenturycom municationhistoryofChina .　InFDDmode ,Itneedawideenoughint…     

TDD无线通信系统中基于软件的AFC实现

提出了一种新颖的TDD无线通信系统中AFC实现方式。利用TDD无线通信系统中已有精确定时信号和MCU控制单元,通过程序控制MCU调节压控振荡器的输出频率,从而在未引入过多硬件的基础上以软件方式实现了自动频率控制(AFC),节约了成本。     

动态TDD技术HARQ时序冲突的解决方案

动态TDD技术的引入不仅能够很好地解决突发性业务需求增长较快的问题,还能提升小区通信系统的服务质量.在动态TDD系统中,无线帧配置可以通过系统中的负载量来改变.但是一些子帧可能会在重配后改变传输方向,导致一些HARQ进程出现时序冲突,影响系统性能.为了解决动态TDD系统中的HARQ时序冲突问题,提出了一种基于过渡无线帧的混合自动重传方案.当重配周期到来时,在重配点后增加一个过渡无线帧,使得HARQ时序以一种较简单、时序冲突较少的方式过渡到重配后的无线帧.在LTE系统仿真平台上建立HARQ模型进行性能验证,仿真结果表明,所提方案能有效地提升系统资源利用率,并给系统平均吞吐量带来增益.     

Schur algorithms for joint-detection in TD-CDMA based mobile radio systems

Third generation mobile radio systems will employ TD-CDMA in their TDD mode. In a TD-CDMA mobile radio system, joint-detection is equivalent to solving a least squares problem with a system matrix that exhibits some form of block-Toeplitz structure. This structure can be successfully exploited by using variations of the Schur algorithm for computing the QR decomposition of this system matrix. Together with a displacement representation, the Schur algorithm can be straightfonvardly adapted to a wide variety of matrix structures. In this paper we show this approach for two concrete manifestations of the TD-CDMA system matrix : first for a very compact, block-Toeplitz structure ; and second for the less favorable Toeplitz-block structure that arises when decision feedback is added to the data detection process.