A CPCH access method for prioritized services in W-CDMA

Common packet channel (CPCH) access is an efficient approach to support packet data transmissions in a wideband code-division multiple-access (W-CDMA) system. This letter introduces a simple access control method for CPCH, which results in higher throughput. This method also provides prioritized services for different traffic classes. Each traffic class is assigned a distinct transmit permission probability that is determined at the new call initiation stage based on the status of CPCH channel occupancy. The differentiated service qualities, which correspond to different transmit permission probabilities, are evaluated in terms of packet blocking rates. The overall system performance is also evaluated in terms of normalized throughput.     

Performance analysis of a combined random-reservation access scheme

Stability and throughput are investigated for a combined random-reservation access scheme employed in a satellite-based very small aperture terminal (VSAT) packet communication network. The analysis is based on the use of catastrophe theory by which the system behavior is characterized by the cusp catastrophe. A stable region is given in terms of system and user parameters such as packet generation rate, retransmission rate, channel division ratio and propagation delays. A numerical example is given to illustrate the analysis developed. Simulation results agree with the steady-state throughput of the model     

Steady-State analysis of a split-connection scheme for Internet access through a wireless terminal

TCP does not perform well in a connection that includes a lossy wireless link. Techniques intended to improve the performance of TCP for such connections can be grouped into three categories: end-to-end, link layer and split-connection approaches. Some simulations and experimental results indicate that split-connection protocols yield better performance than the other two approaches. Although analytical modeling of the end-to-end and link-layer approaches has been presented, no comparable performance analysis for split-connection protocols has been reported previously. In this paper, a stochastic model is developed and used to analyze the performance of a class of split-connection protocols which deploy TCP on the wire-line network and a light-weight transport protocol on the wireless final hop. The final hop is provided by a digital TDMA cellular system. The condition of heavy source traffic to the wireless terminal is considered. The model relates the throughput and some useful auxiliary performance measures to key system parameters such as propagation delays, the base-station buffer size, the ARQ protocol and channel-error process of the wireless link. The usefulness of the analysis is illustrated by its application to the problem of sizing the TCP receiving buffer in a base station.     

一种针对超短波电台接入网的混合信道接入方案

为超短波电台接入网提供了一种混合信道接入方案,方案借鉴了民用接入技术的一些先进理念,并结合军用跳频电台网络的特殊业务应用需求,采用了一种静态TDMA、动态TDMA和频分多址FDMA的混合信道接入策略,实现了多用户多业务传输的QOS保障,满足了军用业务的特殊传输需求。     

Supporting rate guarantee and fair access for bursty data trafficin W-CDMA

This paper presents a new protocol for statistical multiplexing of bursty data traffic in the forward (base-to-mobile) link of a wireless wideband code division multiple access (W-CDMA) system using orthogonal variable spreading factor (OVSF) codes. At the heart of the protocol is an efficient scheduling algorithm that dynamically assigns an OVSF code to a mobile user on a timeslot-by-timeslot basis and allows many users with bursty traffic to share a limited set of OVSF codes. An important feature of our protocol is that it can provide a heterogeneous data rate guarantee to each mobile user and fully utilize the system capacity. Moreover, the unreserved bandwidth of the network can be shared fairly among competing mobile users     

Discrete-time analysis of cell spacing in ATM systems

In this paper, an analysis of a general spacer mechanism as used in ATM systems and being part of the usage parameter control functions is developed. The cell process which is subject to spacing can be an arbitrarily chosen renewal process. The algorithm aims at the calculation of the spacer output process in terms of the cell inter-departure time distribution which gives insights to understand the traffic stream forming properties of the spacing mechanism. Two spacer variants are taken into account, where cell rejection and non-rejection versions of the spacing scheme are considered. It is shown that the state process of theGI/D/1 queue andGI/D/1 queue with bounded delay can be used to analyze the spacer process. Numerical results are presented to show the system performance for different traffic conditions and system parameters. Beyond the consideration of the pure spacing mechanism, we also take into account that the cell streams are changed between the ATM connection endpoints and the spacer. We model this by considering the output process of a discrete-timeGI/G/1 queue as the spacer input process. We also take the spacer output process as input for a discrete-timeG//G/1 queue to investigate how the spaced cell stream is again changed until reaching the private/public UNI.The work for this paper was performed while the author was with the Institute of Computer Science, University of Würzburg, Germany.     

A new access scheme in OFDMA systems

1 Introduction Orthogonal frequency division multiple access (OFDMA) technology has been emerged as one of the prime multiple access schemes for broadband wireless networks, for example, IEEE 802.16a-h [1, 2], IEEE 802.20 [3], and so on. On the other hand…     

Discrete-time, discrete-frequency, time-frequency analysis

A formulation of a discrete-time, discrete-frequency Wigner distribution for analysis of discrete-time, periodic signals is given using an approach involving group representation theory. This approach is motivated by a well-known connection between group theory and the continuous Wigner distribution. The advantage of this approach is that the resulting discrete distribution satisfies mathematical properties analogous to those satisfied by the continuous distribution. After outlining the relationship between group representation theory and time-frequency analysis, we derive the discrete distribution and exhibit many of its mathematical properties. These include time and frequency marginals, the Weyl correspondence, and covariance. In particular, the interpretation of covariance for the discrete distribution is shown to be different than that for the continuous distribution. Finally, we note some unusual features of this discrete distribution, which are a consequence of the group-theoretic derivation     

Performance analysis of cell search in W-CDMA systems over Rayleighfading channels

The three-step cell search has been considered for fast acquisition of the scrambling code unique to a cell in wideband code-division multiple-access (W-CDMA) systems. In this paper, the performance of the cell-search scheme is analyzed in Rayleigh fading channels. The system parameters for the cell-search scheme and the design parameters for the receivers are examined. Probabilities of detection, false alarm, and miss for each of the three steps are derived in closed form based on the statistics of CDMA noncoherent demodulator output. Through the analysis, the effect of threshold setting and post-detection integration for each step is investigated and the power allocation for the channels is considered. The optimal number of post-detection integrations for each step may depend on not only the power allocation for the channels related to the cell search, but also the false-alarm penalty time. Our analysis can be utilized for determining the values of the parameters. Also, the cumulative probability distribution of the average cell-search time is obtained. Finally, it is shown that the analysis could be used to obtain the distribution of the cell-search time graphically according to the distance between a mobile station and a base station by considering the propagation models for pass loss and the traffic distribution models     

Cell search in W-CDMA

In a CDMA cellular system, the process of the mobile station searching for a cell and achieving code and time synchronization to its downlink scrambling code is referred to as cell search. Cell search is performed in three scenarios: initial cell search when a mobile station is switched on, idle mode search when inactive, and active mode search during a call. The latter two are also called target cell search. This paper presents algorithms and results for both initial and target cell search scenarios for the wideband CDMA (W-CDMA) standard. In W-CDMA, the cell search itself is divided into five acquisition stages: slot synchronization, frame synchronization and scrambling code group identification, scrambling code identification, frequency acquisition, and cell identification. Initial cell search needs all five stages, while target cell search in general does not need the last two stages. A pipelined process of the first three stages that minimizes the average code and time acquisition time, while keeping the complexity at a reasonable level, is considered. The frequency error in initial cell search, which may be as large as 20 kHz, is taken care of by partial symbol despreading and noncoherent combining. Optimization of key system parameters such as the loading factors for primary synchronization channel, synchronization channel, and common pilot channel for achieving the smallest average code and time acquisition time is studied. After code and time synchronization (the first three stages), a maximum likelihood (ML)-based frequency acquisition method is used to bring down the frequency error to about 200 Hz. The gain of this method is more than 10 dB compared to an alternative scheme that obtains a frequency error estimate using differential detection     

Priority-based random access scheme for S-PCN

A novel random multiple access technique, priority-based fast access (PBFA), is proposed by the authors to reduce the access delay of delay-sensitive random access (RA) packets in S-PCNs. The approach, based on the concept of good channel transmission (GCT), can significantly improve the delay performance, in particular, for those delay-sensitive packets, of a slotted ALOHA (S-ALOHA) random access channel (RACH) in a satellite fading environment. In addition, the time capture effect is exploited to further improve the RACH performance     

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.     

一种基于MPLS的无线接入网微移动方案

将MPLS技术应用到基于IP的无线接入网络是近年越来越受到关注的新课题.本文提出了一种基于MPLS的微移动方案,方案采用在基站进行缓冲的方法降低切换时的分组丢失.最后对方案的性能从算法所产生的网络开销、切换时延与分组丢失几个方面进行了分析和讨论,结果表明本方案适用于高速微蜂窝及微微蜂窝的移动通信环境,并能满足一般的数据及实时业务的需求.     

Multipath interference canceller for high-speed packet transmissionwith adaptive modulation and coding scheme in W-CDMA forward link

This paper proposes a multipath interference canceller (MPIC) associated with orthogonal code-multiplexing that achieves much higher peak throughput than 2 Mbit/s with adaptive data modulation for high-speed packet transmission in the wideband direct sequence-code division multiple access (W-CDMA) forward link, and evaluates its throughput performance by computer simulation. The simulation results elucidate that sufficient multipath interference (MPI) suppression is achieved by a four-stage MPIC with 6-12 orthogonal code-multiplexing using one iterative channel estimation with pilot and decision feedback data symbols and further that the interference rejection weight control according to the number of observed multipaths is effective in improving the throughput. It is also demonstrated that MPIC exhibits a superior MPI suppression effect to a chip equalizer in the lower received signal energy per bit-to-background noise spectrum density (E_b/N₀) channel around 0-3 dB owing to the successive channel estimation at each stage. We show that the maximum peak throughput using MPIC is approximately 2.1 fold that without MPIC in a two-path and three-path Rayleigh fading channel and that the peak throughput of 8.0 Mbit/s is achieved using 64 QAM data modulation in a two-path fading channel within a 5 MHz bandwidth. Furthermore, the required average E_b/N₀ for satisfying the same throughput with MPIC is decreased by more than 2.0 dB     

OCDMA在光接入网中的应用方案

文章对光接入网（OAN）中光码分多址（OCDMA）方式进行了研究分析,并进行了计算机模拟,结果表明,在OAN中引入OCDMA技术,不需网络同步,在下行方向有很好的安全性,用户和业务可随机接入,可构成灵活的通用接入网传输平台。     

On the analysis of switched-beam antennas for the W-CDMA downlink

Smart antennas are widely recognized as an enabling technology for addressing the demand of future wireless network capacity when employed in place of traditional fixed-coverage sector antennas. Furthermore, switched-beam antenna systems offer a robust implementation against multipath propagation effects and reduced complexity that is inherent with fully adaptive implementations. This paper introduces a simple closed-form expression for evaluating the capacity increase of W-CDMA cellular networks employing switched-beam antennas. The expression incorporates the effect of practical antenna patterns and the impact of multipath scattering on code orthogonality, as well as that of pilot signal power. The results show that a reduction in downlink interference of approximately 6 dB can be achieved by installing an eight-beam antenna system in a 120/spl deg/ sector configuration when representative values of these parameters are taken into account.     

Implementation of smart-card access control with threshold scheme

We describe an electronic implementation of a security scheme to control access to a building. Access to the building by a person alone is not possible but access by a group of authorized people whose number satisfies a prescribed threshold is permissible. The scheme makes use of the shared-secret symmetry cryptography together with smart-card technology. The access key of a person is carefully encoded and stored on a smart card which can also be used for many other purposes. Access records are kept on these smart cards in a distributive fashion and with duplication. Innocent people are able to present information regarding their recent accesses to the building and yet practically cannot be accused of fabricating these records. The scheme permits the use of a standalone controller and eliminates the need for expensive wiring to a remote central database of authorized users.     

一种TD-LTE系统内随机接入的实现方案

为了能更好地实现在不同的子帧配置下支持各种前导格式的上报,提出了一个一种集合了子帧配置0-6下支持前导格式0-4上报的实现方案,使得在更多的配置情况下,终端能完成随机接入。     

A multiple access scheme for wireless access to a broadband ATM LANbased on polling and sectored antennas

An adaptive polling scheme for multiple access in a broadband wireless local area networks (LANs) is proposed. It is designed to accommodate asynchronous transfer mode (ATM) traffic with a large and variable range of bit rates. The radio architecture is microcellular, with switched sectored-beam antennas and a small frequency reuse factor. Features of the multiple access scheme include polling rate depending on a terminal's average bit rate, fixed-length frames divided into segments corresponding to base antenna sectors, and automatic-repeat-request (ARQ) for error control, combined with randomized sector segment ordering. The steady-state performance (cell loss, call blocking and dropping probabilities, waiting time, and buffer occupancy) are evaluated by simulation for an open indoor environment, and for handoff, ARQ, and simple power control enhancements; focusing mainly on the effects of the propagation and interference conditions