CDPD在智能交通系统中的应用

从介绍CDPD的原理及技术入手，以ITS中的道路信息提供系统的研究项目为背景，着重分析了选用CDPD的技术依据及其在ITS道路信息提供系统的实现方案，并给出了具体的软硬件实施细节。     

CDPD网络及技术浅谈

CDPD (Cellular Digital Packet Data,蜂窝数字分组数据 )是近年来新兴的一种无线数据传输技术 ,文中简要介绍了 CDPD的基本概念、系统组成及工作原理 ,并对其技术特点及在我国的使用进行了探讨。     

CDPD系统信道借用方法研究

CDPD网络利用现有的AMPS蜂窝网,传输无线分组数据业务。信道借用是CDPD系统的关键技术之一。为了不干扰AMPS的正常业务,CDPD网络通过信道借用充分利用AMPS的空闲信道进行数字传输。信道借用主要是通过频率跳变(channelhopping)实现的,频率跳变包括强迫跳变和定时跳变。文章论述了信道借用的原理、信道参数配置及实现。该思想也可用于其它网络,并延拓该网络功能。     

对偶基上改进CDPD系统RS编解码器的实现

以蜂窝数字分组数据系统(CDPD)中的RS(63，47)码为例，提出了一种建立在伽罗华域(Galois Fields)对偶基乘法器基础上的改进的Reed—Solomon绝解码器。针对CDPD系统的特点，对乘法器、欧几里德算法进行改进，并且应用流水线设计来优化系统，从而提高了编解码速度和性能，节省了硬件资源。该设计不但完全满足CDPD系统的设计要求，而且电路结构便于超大规模集成电路(VLSI)的实现，具有广泛的适用范围。     

CDPD系统中RS译码器的改进设计与实现

以蜂窝数字分组数据(CDPD)系统中的RS(63,47)码为例,提出了一种建立在伽罗华域(GaloisFields)广义三角基乘法器基础上的改进的Reed-Solomon译码器电路。在该译码器的设计中,针对CDPD系统中RS(63,47)码的特点,采用了改进的快速钱氏-BRS根搜索算法来求解它的根并且应用流水线等技术来优化系统设计,从而节省了硬件资源并且提高了速度,使得译码器的性能得到很大的改善。所设计的译码器不但完全满足CDPD系统的设计要求,而且电路结构易于超大规模集成电路(VLSI)的实现,具有广泛的适用范围。     

朗讯与南京邮电通信设备股份签CDPD项目

朗讯科技（中国）有限公司与南京邮电通信设备股份有限公司在北京签定了无线蜂窝分组数据(CDPD)项目合作协议．根据协议．南京邮电通信设备股份有限公司将为近千万的中国客户提供朗讯公司CDPD的组装生产、销售、安装、调试、维护及培训等一系列系统支持和服务。     

CDPD系统中MDBS信道器的实现

提出了CDPD (CellularDigitalPacketData)系统中MDBS (MobileDataBaseStation)信道器的软硬件实现方案。采用高速DSP芯片、ISP器件、GMSKModem芯片、 90 0MHz射频模块及其他相关器件 ,实现了MDBS中的MAC层协议和Physical层协议。提供了实验样机的测试结果 ,并对结果进行了分析。     

CDPD Modem设计与实现

本文主要介绍了基于蜂窝数字分组数据(CDPD)系统的无线Modem的一种实现方案.详细介绍了无线Modem的硬件模块划分与实现,CDPD协议中的媒质接入控制协议(MAC)、子网相关会聚协议(SNDCP)、移动数据链路协议(MDLP)的实现,并根据最新的ASIC技术的发展对如何改进硬件设计方案提出了建议.     

CDPD-GPS车辆监控系统移动终端的设计方案

介绍了基于CDPD网的GPS车辆监控系统上的移动终端的基本组成,给出了基于单片机和MODEM应用的具体实现方案。     

无线移动数据通信网——CDPD

CDPD系统以模拟AMPS公用移动通信网为基础,与AMPS共用同一频段,频宽30kHZ。CDPD将数据报文分成定长的数据段,每段加上收、发端地址和控制信息后,以分组为单位,在AMPS的空闲话音信道上传输,当话直用户要求占用该信道时,CDPD将重新寻找新的空闲信道,并利用信道跳频技术自动跳到新的空闲信道,如此反复直到数据传送完毕。系统的主要设备有移动数据终端（MES）、固定终端（FES）、移动数据基站（MDBS）、移动数据中介装且（MDIS）、管理服务器（AS）、分级服务器（PS）、网络名理系统（NMS）、路由器（Router）等（…     

CDPD在公交电子站牌系统中的应用

介绍了ＣＤＰＤ的网络结构和基本特点,以及利用ＣＤＰＤ网络构建公交电子站牌系统的组成原理和主要功能。     

Performance of Connectionless Data Service in High Density Microcell

Two categories of commercial wireless packet services exist today – a standalone system where the entire bandwidth is dedicated to the transmission of data packets (e.g. ARDIS, Mobitex), and an overlay system, where the unused channels of an existing cellular phone system are used (e.g. CDPD, GPRS). This paper examines the performance of the overlay service in a high density Manhattan street grid microcell. This type of cell is common in central urban areas. A simple analytical model is derived to describe the channel occupancy distribution in the microcell. The model is used to examine the performance of CDPD, a connectionless data service operating over a cellular system. Throughput and latency are evaluated under the two existing channel assignment schemes currently in use. A new assignment scheme is proposed, and is found to give better performance with minimal changes to the CDPD specification.     

全国公用无线数据网(CDPD)

介绍了无线数据网（ＣＤＰＤ）的基本概念和工作原理,系统特点和系统组成以及应用范围,并介绍了ＣＤＰＤ一期工程在我国实施情况。     

Trading CDPD availability and voice blocking probability incellular networks

Cellular digital packet data (CDPD) offers mobile users access to a low-cost, ubiquitous, wireless data network. CDPD can be overlaid on existing AMPS analog cellular systems and share their infrastructure equipment on a noninterfering basis. Since CDPD utilizes the idle radio resources of AMPS, it is important to ensure that the normal AMPS activities are not affected by CDPD. Several timers and system parameters are defined in CDPD for this purpose. This article investigates how these timers and parameters affect the performance of AMPS/CDPD systems. Our study provides guidelines for the selection of input parameters to aid CDPD network planning. Specifically, we study the trade-off between CDPD availability and voice blocking probability. CDPD availability is defined as the proportion of time that the RF channels can be used to transmit CDPD data. We observe that selecting too large values for CDPD dwell time and the maximum number of CDPD channel streams will degrade the voice blocking probability without improving CDPD availability. On the other hand, selecting a too large value for the CDPD layoff time will degrade CDPD availability without improving voice blocking probability     

Performance of CDPD with Timed Hop and Forced Hop

Cellular Digital Packet Data (CDPD) offers mobile users access to a low-cost, ubiquitous, wireless data network. CDPD can be overlaid on existing AMPS analog cellular systems and share their infrastructure equipment on a non-interfering basis. To prevent interference with the voice activities, CDPD performs forced hop to a channel stream when a voice request is about to use the RF channel occupied by that channel stream. In addition, several timers and system parameters are defined in CDPD to ensure that the normal AMPS activities are not affected by CDPD. This article investigates how the channel selection algorithms, the timers and other parameters affect the performance of AMPS/CDPD systems. Specifically, we study the trade-off between mean CDPD channel holding time and voice incompletion probability. Our study indicates that if AMPS exercises the most-idle channel selection algorithm and CDPD exercises the least-idle channel selection algorithm, then the largest mean CDPD channel holding time is expected. On the other hand, if AMPS exercises the least-idle channel selection algorithm, then the smallest voice incompletion probability is expected.     

移动数据通信

本文介绍了移动通信发展的概况以及在现有模拟与数字移动网上进行数据通信的原理。同时还介绍了专用的无线分组交换数据网如ＣＤＰＤ和Ｄａｔａ ＴＡＣ。     

Cellular digital packet data network

Cellular digital packet data (CDPD) is a data network designed to meet growing mobile data transmission needs. CDPD networks can stand alone or overlay on the cellular voice system by drawing radio resources from the pool of unused or free cellular analog voice channels. Detection as to whether a channel is free or occupied is mechanized through channel sniffers. Once the CDPD network seizes a channel, it continues to use the channel as long as it is free and leaves the channel within 40 ms of initiation of any voice activity on the channel-the CDPD network then hops to another free channel, if available. CDPD follows slotted nonpersistent digital-sense multiple access with collision detection (DSMA/CD). In addition, it performs channel-error detection and channel-error recovery. We investigate several aspects of the CDPD network, namely, the: (1) effect of CDPD on cellular voice and (2) the delay-throughput performance due to DSMA/CD with error detection     

CDPD——未来个人通信的重要基石

计算机技术和无线通信技术的发展以及数据通信的市场需求推动了以ＣＤＰＤ为代表的无线数据通信技术的迅速发展。ＣＤＰＤ是以数字分组数据技术为基础，以蜂窝移动通信为组网方式来配置的。它采用ＴＣＰ／ＩＰ为基础的Ｉｎｔｅｒｎｅｔ协议，可视为Ｉｎｔｅｒｎｅｔ的延伸。优异的性能、强大的功能以及开放的系统平台使ＣＤＰＤ可适用多种业务，它将在“金卡”工程，现代化管理、电子商务和信息服务等领域大屏身手。