Filtering strategies for TFC selection schemes in 3GPP W-CDMA systems

The selection of a suitable transport format combination (TFC) according to the system load condition is one important issue of the radio resource management (RRM) in 3GPP W-CDMA systems. Different TFCs specify different ways of transmitting user data input from logical channels. It is observed that data transmission with a higher data rate will suffer a higher bit error rate (BER). This paper investigates the impact of BER on the selection of optimal TFC for transmitting the user data. Two filtering strategies are proposed to filter out infeasible TFCs so that the optimal TFC can be selected to achieve high performance. Moreover, an imbedded Markov chain is developed to evaluate the proposed strategies. From the simulation results, the feasibility and the effectiveness of the proposed strategies are demonstrated as well. We are suggesting that, for the design of an optimal TFC selection algorithm, the proposed TFC filtering strategy shall be taken into consideration.     

Design and analysis of time-based code allocation schemes in W-CDMA systems

Efficient resource allocation for requests is an important issue in the radio resource management. In the third generation mobile communication systems, Orthogonal Variable Spreading Factor (OVSF) codes are used for spreading codes. In this paper, we consider the OVSF code allocation problem for supporting real-time services in which the service time of a request can be obtained a priori. The impact of the remaining time factor on the OVSF code allocation in W-CDMA systems is investigated. Two time-based allocation schemes are proposed for code assignment and reassignment. This paper represents the first attempt on addressing the remaining time impact on the OVSF code allocation. Simulation results show that the time-based allocation schemes have better performance on reducing the blocking probability and the reassignment cost.     

An emulator framework for a new radio resource management for QoSguaranteed services in W-CDMA systems

In the context of third-generation (3G) systems a mix of services with different requirements are expected. Consequently, packet scheduling mechanisms for quality of service (QoS) guarantees will play a key role. This paper proposes a new scheduling strategy that makes consistent the target quality in the radio link with the priority level assigned to each user. The performance of such a strategy is assessed by system level simulations and, in order to gain more insight into the difficulties of this optimization problem, it is compared to other alternatives. This work is part of the Wineglass project, within the Fifth Framework Program of the European Commission (IST), where a real time demonstrator including the radio resource management tasks is being developed. Thus, an implementation approach of the proposed scheduling is also described. The implementation is based on lookup tables and this approach is validated by simulation     

Dynamic resource allocation schemes during handoff for mobilemultimedia wireless networks

User mobility management is one of the important components of mobile multimedia systems. In a cell-based network, a mobile should be able to seamlessly obtain transmission resources after handoff to a new base station. This is essential for both service continuity and quality of service assurance. In this paper, we present strategies for accommodating continuous service to mobile users through estimating resource requirements of potential handoff connections. A diverse mix of heterogeneous traffic with diverse resource requirements is considered. The investigate static and dynamic resource allocation schemes. The dynamic scheme probabilistically estimates the potential number of connections that will be handed off from neighboring cells, for each class of traffic. The performance of these strategies in terms of connection blocking probabilities for handoff and local new connection requests are evaluated. The performance is also compared to a scheme previously proposed by Yu and Leung (see IEEE J. Select. Areas Commun., vol.15, p.1208-25, 1997). The results indicate that using dynamic estimation and allocation, we can significantly reduce the dropping probability for handoff connections     

Intelligent scheduling and planning systems for telecommunications resource management

This paper discusses the importance of resource management in the telecommunications industry. It argues for intelligent resource management systems (IRMSs) that are capable of providing flexible and dynamic resource management. It introduces the main requirements and benefits of an IRMS and describes the technical basis of current research activities which are leading towards the development of constraint technology based IRMS platforms.     

RF microelectronics for W-CDMA mobile communication systems

Third generation (3G) mobile communication systems are now just starting to be introduced. With a maximum data rate of 2 Mbit/s they will make wireless access to broadband data services like the Internet or video applications feasible. Most of the different physical layer technologies summarised under the acronym 3G are based on wideband-CDMA (W-CDMA), in contrast to existing second generation systems, which mostly use TDMA and FDMA. This has severe consequences for the design of the transceiver front-ends. During standardisation these were assumed to have an adequate RF performance yet they still present a performance bottleneck for the system. Starting with a short introduction to UMTS (Universal Mobile Telecommunications System)-the 3G standard to be deployed in Europe and already operating in Japan-this paper describes by way of example some of the test cases specified for UMTS and their impact on the analogue front-end. It is shown that accurate simulation of all the analogue and digital signal processing is necessary in order to predict the RF performance needed of today's commercial RFICs. The paper then presents and reviews some actual design examples. Finally, possible technologies and techniques for application in future mobile terminals are discussed     

TD-SCDMA系统混合业务下的无线资源管理算法研究

给出了智能天线技术在系统级研究的理论模型，推导了采用多用户检测和自适应智能天线技术后的容量和负载评估理论模型。基于该模型，给出了一种新的接入控制算法，并为实时多媒体业务提出了一种先进的动态信道分配算法。仿真结果表明，提出的理论模型和无线资源管理算法适用于TD-SCDMA系统，能够显著提高系统性能，用于实际TD-SCDMA网络的规划优化。     

Radio resource management schemes for combined GSM/GPRS mobile systems

Data services like Web browsing, e‐mail and file transfer are becoming more and more popular in cellular systems. In contemporary systems like Global System for Mobile communications (GSM), data transfer has been circuit‐switched, that is, physical resources are allocated to a user for the entire call/session duration. However, this is inefficient in case of bursty traffic, where bursts are separated by long intervals of inactivity. This has been the main reason for the introduction of General Packet Radio Service (GPRS), which on the one hand acts as a mobile access network to the Internet, while on the other hand it enables the operator to offer a wide variety of value‐added services [Wireless Access Protocol (WAP) over GPRS, e/m‐banking, e/m‐commerce, push services, etc.] efficiently. However, in contemporary commercial implementations of GPRS the radio resource allocation algorithm does not take into account the Quality of Service (QoS)‐related service characteristics—although such information is exchanged between the terminal and the network—and consequently all service requests are treated the same way (‘best effort’). In this paper, we propose and evaluate via a simulation platform various Radio Resource Management (RRM) schemes capable of differentiating the handling of ‘service requests’ (in uplink and downlink), taking into account the GPRS‐related QoS parameters (precedence, reliability, delay, mean and peak throughput). The evaluation is performed for a range of voice (circuit‐switched) traffic loads, number of Transmit Receive eXchange (TRXs), offered data (packet‐switched) services characteristics, number of dedicated Packet Data Channels (PDCHs), and so on, taking into account the respective QoS requirements for both service types (circuit‐ and packet‐switched). Copyright © 2003 John Wiley & Sons, Ltd.     

Comparison of beamforming techniques for W-CDMA communication systems

Different beamforming techniques are employed in a wideband code-division multiple-access base station, and their uplink and downlink signal-to-interference-plus-noise ratio (SINR) performances are compared. It is found that the direction of arrival (DOA) method and the complex conjugate method have almost the same uplink SINR performance, but the complex conjugate method shifts the downlink main beam direction slightly due to the difference between the uplink and downlink carrier frequency. However, the degradation in the downlink mean SINR performance is less than 1 dB compared with that obtained by the DOA method. In the downlink, the SINR performances obtained by the single-beam method and multiple-beam beamforming technique are compared. It is found that the single-beam method has a poorer SINR performance in the low SINR region because it is more likely to suffer from deep fading. In the moderate or high SINR regions, the single-beam method has a much better SINR performance because it has a higher gain in the main path direction and a smaller angular coverage of the mainlobe, which results in a stronger signal level and smaller multiple-access interference at the mobile receiver.     

Low complexity resource allocation and scheduling algorithms for downlink SDMA systems

The downlink zero-forcing beamforming strategy in the case of random packet arrivals is investigated. Under this setting, the relevant fairness criterion is the stabilization of all buffer queues which guarantees a bounded average delay for all users. It has been shown that allocating resources to maximize a queue-length-weighted sum of the rates is a stabilizing policy. However, the high complexity of user selection and the feasible rates determination for optimal scheme may prevent the real-time scheduling operation. Two low complexity algorithms are provided taking the channel state, queue state and orthogonality into account. In particular, the authors pick the first user with the largest product between channel gain and queuing length, and select the remaining users to construct candidate user set based on the greedy user selection method or channel orthogonal user selection method. Then, the power and rate allocation for the selected users are implemented based on the modified water-filling method. The complexity of the proposed algorithms is analyzed. The average delay and average throughput are studied in homogeneous scenarios and heterogeneous scenarios, respectively. Simulation results show that the proposed algorithms can take full advantage of the multi-user diversity gain and provide average delay (or throughput) and fairness improvement compared with channel-aware-only schemes.     

Dynamic bandwidth allocation with fair scheduling for WCDMA systems

Dynamic bandwidth allocation (DBA) will play an important role in future broadband wireless networks, including the 3G and 4G WCDMA systems. A code-division generalized processor sharing (CDGPS) fair scheduling DBA scheme is proposed for WCDMA systems. The scheme exploits the capability of the WCDMA physical layer, reduces the computational complexity in the link layer, and allows channel rates to be dynamically and fairly scheduled in response to the variation of traffic rates. Deterministic delay bounds for heterogeneous packet traffic are derived. Simulation results show that the proposed CDGPS scheme is effective in supporting differentiated QoS, while achieving efficient utilization of radio resources.     

Multimedia Support for Wireless W-CDMA with Dynamic Spreading

The emerging multimedia communication needs more support in operating systems in order to be successful over a wireless environment. The system needs to support a seamless integration (i.e., transparent application switching) of voice, audio and conventional data (e.g., e-mails, and ftp). It should also support multiple users with a guaranteed quality. In this paper, we investigate effective protocol design with dynamic spreading factors such that various QoS based on different traffic types can be provided. Increasing spreading factors can benefit the system because it will increase the desired signal strength linearly. The measured bit error rate can be reduced 75 times with a long spreading factor. By taking advantage of this benefit, we propose some middle-ware solutions to monitor the network load and switch the spreading factors dynamically based on the current load with multimedia traffic. These middle-ware solutions are implemented in mobile and base stations and experiments are performed to measure the actual system performance. The preliminary results indicate that our proposed system can always maintain a desired quality for all the voice connections. We further extend our protocol to guarantee a balanced support among different traffic types. While the voice communication is still guaranteed to be non-interrupted, the data traffic is proved to be served with reasonable response time by our proposed system.     

Dynamic multiuser resource allocation and adaptation for wireless systems

Driven by the increasing popularity of wireless broadband services, future wireless systems will witness a rapid growth of high-data-rate applications with very diverse quality of service requirements. To support such applications under limited radio resources and harsh wireless channel conditions, dynamic resource allocation, which achieves both higher system spectral efficiency and better QoS, has been identified as one of the most promising techniques. In particular, jointly optimizing resource allocation across adjacent and even nonadjacent layers of the protocol stack leads to dramatic improvement in overall system performance. In this article we provide an overview of recent research on dynamic resource allocation, especially for MIMO and OFDM systems. Recent work and open issues on cross-layer resource allocation and adaptation are also discussed. Through this article, we wish to show that dynamic resource allocation will become a key feature in future wireless communications systems as the subscriber population and service demands continue to expand.     

多业务MIMO-OFDMA/SDMA系统跨层调度与动态资源分配

对多业务MIMO-OFDMA/SDMA 系统下行链路跨层调度与动态资源分配问题进行了研究.首先,在满足各种约束条件的前提下,以最大化系统吞吐量为目标建立了相应的优化模型;然后,提出了一种基于业务类型和子空间距离的用户分组算法,该算法采用聚类分析的方法在每个子载波上对配置有多根接收天线的用户进行分组,从而降低了调度时所需搜索的用户空间的维数;接着,基于所提出的用户分组算法并结合不同业务的优先级提出了一种新的跨层调度和资源分配算法,该算法充分利用跨层信息为每个子载波调度相应的用户组,并为调度到的用户分配相应的系统资源,从而通过最大化每个子载波的吞吐量近似实现了系统整体吞吐量的最大化.仿真结果表明,与现有的方案相比,所提算法更好地满足了不同业务用户的QoS要求,并获得了更好的吞吐量性能.     

基于有限反馈的多用户MIMO系统调度方案分析

对两种基于有限反馈的多用户MIMO系统用户调度方案进行对比分析。两种调度算法均仅反馈1bit CSI,其不同之处是方法一中基站仅根据瞬时CSI随机调度用户,方法二中基站通过瞬时CSI结合空间相关信息来调度用户。先从算法实现过程对两个方案进行分析,再从空间相关性的利用、同时可通信的用户数和系统容量对两个方案的优缺点进行比较。     

Distributed resource allocation schemes

In this article, we discuss distributed resource allocation schemes in which each transmitter determines its allocation autonomously, based on the exchange of interference prices. These schemes have been primarily motivated by the common model for spectrum sharing in which a user or service provider may transmit in a designated band provided that they abide by certain rules (e.g., a standard such as 802.11). An attractive property of these schemes is that they are scalable, i.e., the information exchange and overhead can be adapted according to the size of the network.     

提高全局资源调度和本地资源调度的效能的云计算资源调度方案分析

设计分析可以提高当前全局资源调度、本地资源调度效能的云计算资源调度方案。在云计算资源调度中,能够优化分析,提高全局资源调度和本地资源调度的效能的调度方案,分析调度方案设计需求,设计实现提升云计算资源调度效能。结果证实,在云计算资源调度方案设计中,确保提高全局资源调度和本地资源调度的效能,全局资源调度效能提高20%,提高本地资源调度效能达到32%,发挥积极影响。结论表达出在进行云计算资源调度方案设计中,优化设计其全局资源调度、本地资源调度,可以提升资源调度效能,有助于提升云计算资源调度方案质量,发挥实用价值。     

Spline-based behavioural model for efficient analysis of large front-ends for W-CDMA systems

A new behavioural model suitable for the analysis of RF front-ends for W-CDMA systems is described. The model fully accounts for both linear and nonlinear dispersion effects, so that relatively by a band digitally modulated signals can be accurately dealt with. The linear front-end response is computed by means of the conversion admittance matrix. The relationship between the linear and nonlinear responses is characterised by a voltage and frequency-dependent describing function. The latter is evaluated by a cubic-spline-based two-dimensional interpolation scheme starting from a database generated by harmonic-balance analysis. In this way, front-end simulations that would require months of CPU time even by modern envelope-oriented techniques, can be performed in a matter of seconds without significant loss of accuracy.     

Adaptive selection combining for soft handover in OVSF W-CDMA systems

In W-CDMA, soft handover is supported at cell boundaries to maintain communication quality. The maximal ratio combining (MRC) and generalized selection combining (GSC) , are two possible approaches. However, soft handover is resource-intensive. In this letter, we propose an adaptive selection combining (ASC) scheme that can switch flexibly between MRC and GSC so as to take care of both channel loading and communication quality. The signal-to-interference-and-noise ratio (SINR) is kept as high as that of MRC while the blocking probability can remain at about the same level as that of GSC.