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，并提供固定的比特率。此外，由于需要“随时随地”的服务，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蜂窝站点网格来实现的，这些网格的放置是为了控制干扰和最大限度地减少中断，而不是最大化吞吐量。因此，这样的系统提供低比特率，并且在用于大量信息时相对昂贵。与此同时，与互联网的有线连接鼓励了依赖比特的使用(和用户)，这些比特实际上是“免费的”。我们认为，有线和无线接入之间的“经济”不匹配是无线互联网戏剧性增长的主要障碍。解决方案可能在于专门为无线数据设计系统，认识到数据服务通常是无连接的，对延迟不敏感，并且没有特定的比特率要求。这些不同之处表明，无处不在(随时随地)覆盖并不是对无线数据网络的严格要求，并使这样的系统成为可能，在这种系统中，分散的小覆盖区域有助于在几分之一秒内传输兆字节的数据，并且成本仅为传统无处不在覆盖相关成本的一小部分。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，但信号处理挑战是众多的，与面向连接的无线服务提供的历史挑战截然不同。当移动用户通过信息站时，将会有一个机会窗口，可能只有几分之一秒，在这个窗口中，用户将有机会访问高速通信通道。一项关键任务是识别该窗口并以适当的速率进行传输。移动站必须基于对宽带无线信道的测量来做出这些决定，在该宽带无线信道中，衰落和干扰中存在频率选择性和时间变化。在信息站系统的具体环境下，我们计划将我们的研究分为四个部分：无线信道建模：典型信息站无线信道的特征。收发信机设计：对单载波和多载波系统的发射机和接收机进行分析和性能评估。无线电资源管理发射机功率和速率自适应策略由接收机测量得出。算法开发测试平台采用数字信号处理器和现场可编程门阵列技术，用于发射机和接收机算法的实际评估。该项目的活动将包括新泽西州的三个研究机构(新泽西理工学院、普林斯顿大学、罗格斯大学)，由新泽西州无线电信中心(NJCWT)赞助。NJCWT是一个由新泽西州科学技术委员会发起和资助的跨机构研究和教育组织。该中心的重点是用于计算、通信和信息系统的数字无线电技术的多年努力。这一努力支持并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 con-nection 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 rela-tively 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 differencessuggest 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 sys-tems, 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 contextof 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 both single carrier and multicarrier systems.Radio Resource Management Transmitter power and rate adaptation policies derived from receiver measurements.Algorithm Development Testbed A platform employing DSP and FPGA technology for the practical evaluation of transmitter and receiver algorithms. The activities of this project will encompass three research institutions in New Jersey (New Jersey In-stitute 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 or-ganization 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.