UMTS/IMT-2000 based on wideband CDMA

The UMTS terrestrial radio access is based on wideband 4.096 Mchip/s DS-CDMA technology. UTRA will be connected to an evolved GSM core network for both circuit and packet services. A merger between ETSI/Europe and ARIB/Japan based on W-CDMA, a GSM core network, and a common frequency allocation according to the ITU Recommendation of 2 GHz makes a global IMT-2000 standard feasible. UTRA based on W-CDMA fully supports the UMTS/IMT-2000 requirements (e.g., support of 384 kb/s for wide-area coverage and 2 Mb/s for local coverage). Furthermore, the air interface has flexible support of mixed services, variable-rate services, and an efficient packet mode. Key W-CDMA features also include improved basic capacity/coverage performance compared to second-generation systems, full support of adaptive antenna arrays, support of hierarchical cell structures with interfrequency handover, and support of asynchronous inter-base-station operation. There have been no constraints due to the strong requirements for backward compatibility with second-generation systems. This has facilitated a high degree of flexibility and a future-proof air interface. Extensive evaluations by means of simulations and field trials have been carried out by a number of companies, and full system tests are ongoing. Consequently, W-CDMA technology can now be regarded as a mature technology, ready to provide the basis for UMTS/IMT-2000     

Wide-band CDMA for the UMTS/IMT-2000 satellite component

This paper describes the main aspects relevant to the development of a third-generation radio transmission technology (RTT) concept identified as satellite wide-band CDMA (SW-CDMA), which has been accepted by the International Telecommunications Union (ITU) as one of the possible RTTs for the satellite component of International Mobile Telecommunications-2000 (IMT-2000). The main outcomes of the extensive system engineering effort that has led to the above ITU RTT are described. In particular, we address propagation channel characteristics, satellite diversity, power control, pilot channel, code acquisition, digital modulation and spreading format, interference mitigation, and resource allocation. Due to its similarity with respect to the terrestrial W-CDMA proposal from which it is derived, the SW-CDMA open air interface solution is described briefly, with emphasis only on the major adaptation required to best cope with the satellite environment. Quantitative results concerning the physical-layer performance over realistic channel conditions, for both forward and reverse link, are reported. A system capacity study case for a low-Earth-orbit constellation is also provided     

An overview of air interface multiple access for IMT-2000/UMTS

The basis for any air interface design is how the common transmission medium is shared between users (i.e., multiple access scheme). The underlying multiple access method for all mobile radio systems is FDMA. The performance of TDMA and CDMA has been subject to vigorous debate, without any definitive conclusions. This article gives an overview of worldwide research and standardization activities related to the multiple access schemes for third-generation mobile communications systems IMT-2000 and UMTS     

A vision of UMTS/IMT-2000 evolution

A vision is presented for a fully IP-based mobile network which goes beyond UMTS/IMT-2000. A top-to-bottom design approach is introduced that is capable of offering new and innovative services and applications to both fixed and mobile users efficiently, cost effectively and in a user-friendly manner. Some issues and examples in the design steps following this new approach are discussed. It is clearly shown that the convergence of mobile and fixed networks will be achieved naturally through the use of an `all IP' based solution for both access and core networks     

基于CDMA的IMT-2000空中接口方案简介

围绕第三代移动通信系统IMT - 2 0 0 0标准 ,各国间正展开激烈的竞争 ,提交ITU的地面候选方案多达 10种。由于CDMA具有容量大、频谱利用率高、频率规划方便等优点 ,IMT - 2 0 0 0候选标准已基本上统一到基于CDMA方案上。本文先简要介绍了第三代CDMA空中接口的特征 ,然后分别介绍呼声最高的两种方案的空中接口标准 :W -CDMA和cdma2 0 0 0。     

Cross-Layer optimal connection admission control for variable bit rate multimedia traffic in packet wireless CDMA networks

Next generation wireless code division multiple access (CDMA) networks are required to support packet multimedia traffic. This paper addresses the connection admission control problem for multiservice packet traffic modeled as Markov modulated Poisson process (MMPP) with the quality of service (QoS) requirements on both physical layer signal-to-interference ratio (SIR) and network layer blocking probability. Optimal linear-programming-based algorithms are presented that take into account of SIR outage probability constraints. By exploiting the MMPP traffic models and introducing a small SIR outage probability, the proposed algorithms can dramatically improve the network utilization. In addition, we propose two reduced complexity algorithms that require less computation and can have satisfactory approximation to the optimal solutions. Numerical examples illustrating the performance of the proposed schemes are presented.     

Wireless Internet access for mobile subscribers based on theGPRS/UMTS network

With the advent of IP technologies and the tremendous growth in data traffic, the wireless industry is evolving its core networks toward IP technology. Enabling wireless Internet access is one of the upcoming challenges for mobile radio network operators. The General Packet Radio Service is the packet-switched extension of GSM and was developed to facilitate access to IP-based services better than existing circuit-switched services provided by GSM. We illustrate how a visited mobile subscriber on a GPRS/UMTS network can access his/her home network via the gateway GPRS support node (GGSN). We also propose some implementation ideas on wireless Internet access for a remote mobile subscriber based on a GPRS/UMTS network     

Energy efficient adaptive optical CDMA random access protocol based on particle swarm optimization

In this paper, an energy efficient adaptive optical code division multiple access (OCDMA) random access protocol based on particle swarm optimization (PSO) is described. This protocol is based on the S-ALOHA with power and rate allocation based on PSO. This scheme evaluates jointly optimal power and rate allocation PSO based under the random access protocol as a new and simplified scheme for high performance, high energy efficiency suitable for OCDMA systems. The aim is to maximize the aggregate throughput, subject to predetermined quality of service restrictions and energy efficiency constraint in terms of the signal-to-noise-plus interference ratio of each user class. Numerical results are discussed taking into account realistic network operation scenario.     

Adaptive traffic prediction based access control in wireless CDMA systems supporting integrated voice/data/video services

An access control protocol is proposed for integrated voice/data/video code-division multiple-access (CDMA) systems. The protocol involves predicting the residual capacity available for non-real-time data services in reverse link (mobile to base station). Two estimation schemes, a static estimation scheme and a dynamic estimation scheme, are proposed for predicting the residual capacity, the number or the data rate of data packets that could be scheduled at the next time slot. The performances of the proposed estimation schemes are evaluated in view of the outage probability and the mean data message delay.     

An access protocol for speech/data/video integration in TDMA-basedadvanced mobile systems

One key requirement in the radio access design of advanced, third-generation mobile systems is the ability to accommodate a variety of service types via flexible and efficient multiple-access protocols. This paper introduces a multiple-access protocol, SIR++ (service integration for radio access), which has the potential for meeting the service requirements of speech, video, and bursty data traffic in an efficient way. SLR++ is evolved from and generalizes a former protocol, SIR, which only considered the requirements of speech and data. The paper also evaluates the buffer occupancy distribution associated with an (H.263) video connection by solving a worst case model of the system     

A near-optimum MAC protocol based on the distributed queueingrandom access protocol (DQRAP) for a CDMA mobile communication system

This paper presents and analyzes a new near-optimum medium access control (MAC) protocol. The proposed access scheme is suitable for a CDMA mobile communication environment, and keeps under control and upper bounded the number of simultaneous transmissions. It has a delay performance approaching that of an ideal optimum M/M/K system, where K is the number of spreading codes being used (maximum number of simultaneous transmissions). The protocol is a free random access protocol when the traffic load is light, and switches smoothly and automatically to a reservation protocol when traffic load becomes heavier. It is based on distributed queues and a collision resolution algorithm. Moreover, a physical receiver structure is proposed and analyzed in order to preserve the robustness of the protocol in a wireless link. The results obtained show that the protocol outperforms other well known medium access protocols in terms of stability and delay, even when taking into account the loss caused by channel propagation conditions     

Online traffic smoothing for delivery of variable bit rate media streams

Traffic smoothing for delivery of online variable bit rate (VBR) media streams is one of the most important problems in designingmultimedia systems. Given an available client buffer, a window size, and a window-sliding size, previous window-based online smoothing methods have tried to reduce the peak bandwidth allocated in each window. However, as bandwidths allocated in different windows are minimized independently, these methods require a large peak bandwidth for transmitting an entire stream. In this paper, a new window-based method is proposed. It introduces two new ideas, the dynamic windowsliding size and the aggressive workahead, for delivery of online VBR media streams. Our aggressive and dynamic window sliding (ADWS) method can automatically decide on the suitable window-sliding sizes for different windows. Thus, the allocated peak bandwidth can be further reduced. By examining various media streams, ADWS is shown to be effective and efficient. Considering the online transmission of the movieStar Wars with a 90-kB client buffer, ADWS yields 13% less in peak bandwidth, compared with the bestknown window-based online smoothing algorthm SLWIN(1). Its computation cost (the window-sliding number) is 75% of that required by SLWIN(1).This work was partially supported by NSC, Taiwan, under grants. NSC88-2213-E-001-011, NSC88-2213-E-001-012, and NSC88-2213-E-001-025. A primitive version of this work appeared in IEEE INFOCOM'99 [7].     

A contention/reservation access protocol for speech and data integration in TDMA‐based advanced mobile systems

The performance of third generation mobile systems is greatly influenced by the multiple access protocols used in the radio access system. The paper introduces a multiple access protocol, SIR (Service Integration for Radio access), which has the potential for accommodating the requirements of speech and bursty data traffic in an efficient way. SIR is evolved from an access protocol (PRMA++) studied within the framework of the TDMA-based version of the European evolving standard for third generation mobile systems. In particular, SIR uses the same frame structure and in-band signalling but introduces a contention-free handling of data bandwidth requests while meeting speech service requirements via basic PRMA++ mechanisms. This revised version was published online in June 2006 with corrections to the Cover Date.     

Fair resource allocation with guaranteed statistical QoS for multimedia traffic in wideband CDMA cellular network

A dynamic fair resource allocation scheme is proposed to efficiently support real-time and non-real-time multimedia traffic with guaranteed statistical quality of service (QoS) in the uplink of a wideband code-division multiple access (CDMA) cellular network. The scheme uses the generalized processor sharing (GPS) fair service discipline to allocate uplink channel-resources, taking into account the characteristics of channel fading and intercell interference. In specific, the resource allocated to each traffic flow is proportional to an assigned weighting factor. For real-time traffic, the assigned weighting factor is a constant in order to guarantee the traffic statistical delay bound requirement; for non-real-time traffic, the assigned weighting factor can be adjusted dynamically according to fading, channel states and the traffic statistical fairness bound requirement. Compared with the conventional static-weight scheme, the proposed dynamic-weight scheme achieves capacity gain. A flexible trade-off between the GPS fairness and efficient resource utilization can also be achieved. Analysis and simulation results demonstrate that the proposed scheme enhances radio resource utilization and guarantees statistical QoS under different fairness bound requirements.     

Numerical analysis of joint CDMA/PRMA protocol based on equilibriumpoint analysis

Numerical expressions to assess the performance of a joint direct sequence code division multiple access/packet reservation multiple access (CDMA/PRMA) protocol are presented. Simulation of CDMA/PRMA systems with narrowbeam antennas is also applied to support the proposed technique     

Consistent estimation of Rayleigh fading channel second-orderstatistics in the context of the wideband CDMA mode of the UMTS

We address the problem of estimating the second-order statistics of a frequency-selective Rayleigh channel in the context of the wideband CDMA mode of the UMTS. The data to be transmitted are sent over slots on which the channel is assumed to remain constant. Each slot contains a pilot symbol sequence from which it is possible to estimate the current value of the channel. The covariance matrix of the channel is usually estimated by a denoised version of the empirical covariance matrix of the trained channel estimate. However, in the UMTS, this estimate is not consistent in the sense that if the number of slots used to estimate it tends to infinity, it does not converge to the true covariance matrix of the channel. We propose a new consistent estimate of the covariance matrix and evaluate the performances of two Wiener-like channel estimation schemes based on the proposed estimate. The performances of the new approach are evaluated by means of the bit error rate provided by a RAKE receiver based on the proposed channel estimates. It is shown that our estimate of the covariance matrix allows significant improvement in the performance of the RAKE receiver     

Delta modulation based prediction for access control in integratedvoice/data CDMA systems

In this paper, we propose access control protocols for integrated voice/data code division multiple access (CDMA) systems that are based on estimating the residual capacity available for data users. The data model considered in the analysis is suitable for non-transparent services (e.g., e-mail, file transfer, store-and-forward facsimile, etc.). The residual capacity is derived from the feasibility condition for power control using an adaptive prediction technique based on delta modulation. The analysis is extended for the case of imperfect power control. Two access control protocols are considered: modified delta modulation with scheduled access (MDM-S) and modified delta modulation with random access (MDM-R). Comparisons with earlier proposed protocols reveal a better performance in terms of average throughput for data for a given system capacity and outage probability     

Medium access control protocol for the integration of voice/data on a local area network

The analysis and performance of an integrated medium access protocol based on R-VT-CSMA for packet voice and data transmission on a broadcast-bus LAN is examined. This protocol, called adaptive R-VT-CSMA uses variable length packets and the strong correlation between successive voice frames to increase the throughput.<>