ITR: Collaborative Research:'Free' Bits: The Challenge of the Wireless Internet

第二代和第三代无线系统主要是为语音而设计的，因此它们是面向连接的、对延迟敏感的，并提供固定的比特率。 此外，由于服务是“随时/随地”所需的，这些系统必须提供无处不在的覆盖。 这种覆盖是通过相对均匀的小区站点网格来实现的，这些小区站点被放置以控制干扰并最小化中断，而不是最大化吞吐量。 因此，这种系统提供低比特率，并且当用于大量信息时相对昂贵。 与此同时，与因特网的有线连接鼓励了那些依赖于比特实际上是“免费的”的使用（和用户）。我们认为，有线和无线接入之间的这种“经济”不匹配是无线互联网急剧增长的主要障碍。 解决方案可能在于设计专门用于无线数据的系统，认识到数据服务通常是无连接的，延迟不敏感的，并且没有特定的比特率要求。 这些差异表明，无处不在的（随时/随地）覆盖不是无线数据网络的严格要求，并且使得可能的系统中，小的、分离的覆盖区域促进在几分之一秒内传输兆字节的数据，并且成本是与传统的无处不在的覆盖相关联的成本的一小部分。 通信理论和简单的链路预算计算告诉我们，建立这样的系统是可能的，但信号处理的挑战是众多的，不同于面向连接的无线服务所提供的历史挑战。 当一个移动的用户经过一个信息站时，将有一个机会窗口，也许只有几分之一秒，在这个窗口中，用户将有机会访问一个高速率的通信信道。 关键任务是识别窗口并以适当速率传输。 移动的必须基于宽带无线电信道的测量来做出这些决定，其中在衰落以及干扰中存在频率选择性和时间变化。 在Infostations系统的特定背景下，我们计划将我们的研究分为四个部分：无线电信道建模：典型Infostations无线电信道的表征。收发器设计：单载波和多载波系统的发射机和接收机的分析和性能评估。无线电资源管理根据接收机测量得出的发射机功率和速率自适应策略。算法开发测试床采用DSP和FPGA的平台发射机和接收机算法的实际评估技术。 该项目的活动将包括在新泽西州无线电信中心（NJCWT）主持下的新泽西的三个研究机构（新泽西理工学院、普林斯顿大学、罗格斯大学）。 NJCWT是一个机构间研究和教育组织，由新泽西州科学技术委员会赞助和资助。 该中心的重点是在计算，通信和信息系统的数字无线电技术的多年努力。 这项工作是支持和将加强目前拟议的无线网络项目。

Second and third generation wireless systems have been designed primarily for voice, so they are connection oriented, delay sensitive, and provide fixed bit rates. Additionally, since service is desired "any-time/anywhere," these systems must provide ubiquitous coverage. This coverage is achieved through relatively uniform grids of cell sites, which are placed to control interference and minimize outage rather than to maximize throughout. As a result, such systems deliver low bit rates and are relatively expensive when used for large amounts of information. At the same time, wireline connection to the Internet has encouraged uses (and users) that depend upon bits being virtually "free." We contend that this "economic" mismatch between wired and wireless access is the primary obstacle to the dramatic growth of a wireless Internet. The solution may lie in designing systems specifically for wireless data, recognizing that data services are often connectionless, delay insensitive and have no specific bit rate requirements. These differences suggest that ubiquitous (anytime/anywhere) coverage is not a strict requirement for wireless data networks and makes possible systems in which small, separated coverage areas facilitate transfers of megabytes of data in fractions of a second, and for a fraction of the cost associated with conventional ubiquitous coverage. Communication theory and simple link budget calculations tell us that it is possible to build such systems, but the signal processing challenges are numerous and distinct from the historical challenges offered by connection-oriented wireless services. When a mobile user passes an Infostation, there will be a window of opportunity, perhaps as short as a fraction of a second, in which the user will have access to a high-rate communication channel. A key task is to identify that window and transmit at an appropriate rate. The mobile must make these decisions based on measurements of a wideband radio channel in which there is frequency selectivity and time variation in the fading as well as in the interference. In the specific context of an Infostations system, we plan to divide our research into four components:Radio Channel Modeling: The characterization of typical Infostation radio channels.Transceiver Design: The analysis and performance evaluation of transmitters and receivers for bothsingle carrier and multicarrier systems.Radio Resource Management Transmitter power and rate adaptation policies derived from receivermeasurements.Algorithm Development Testbed A platform employing DSP and FPGA technology for the practicalevaluation of transmitter and receiver algorithms. The activities of this project will encompass three research institutions in New Jersey (New Jersey Institute of Technology, Princeton University, Rutgers University) under the auspices of the N.J. Center for Wireless Telecommunications (NJCWT). The NJCWT is an inter-institutional research and educational organization sponsored and funded by the N.J. Commission on Science and Technology. The focus of the center is a multi-year effort in Digital Radio Technology for Computing, Communications and Information Systems. This effort is supportive of and will enhance the present proposed project in wireless networks.