Increasing the coverage and capacity of wireless networks using cognitive radio technology

像LTE(长期演进)这样的新标准承诺网络容量的多种增长。然而，对新多媒体应用的需求增长很可能会比预期更快地吞噬这种增加的容量。因此，更好地利用频谱对于未来一代的无线通信网络将是至关重要的。 根据多项研究，分配给传统服务的很大一部分频谱没有得到充分利用。2000年初，为了解决这一问题，S提出了认知无线电的思想。认知无线电(CR)感知频谱(发现频谱空洞)，分析频谱(发现空洞的属性)，并做出传输决策(数据速率、传输模式等)。在认知无线电环境中，有两种类型的用户：主用户(PU)，它是频谱上的遗留用户，具有比其他用户更高的优先权；以及次用户(SU)。后者是使用CR原则来使用否则浪费的带宽的那些。 在认知无线电中，PU通常比SU具有绝对优先权。也就是说，当主用户开始使用频谱时，次用户必须立即腾出它正在使用的频隙(S)。在这个研究项目中，我们的目标是通过使用先进的信道编码技术和多用户检测来允许PU和SU共存来提高频谱效率。 在蜂窝网络中，当移动台接近基站之间的边界以及离开最后一个基站时，覆盖范围恶化。临时情况也可能导致某些地区缺乏无线电能力。蜂窝系统可以使用认知无线电原理来提高其覆盖范围。LTE使用OFDMA作为接入方法。正交频分复用(Ofdm)是一种可以从码分多址中受益的调制技术，因为它具有灵活性和计算效率。 在这个项目中，我们将考虑认知无线电在LTE环境中的使用，LTE是主用户，WiFi是次用户。

New standards such as LTE (Long Term Evolution) promise manifold increase in network capacity. However, the increase in demand for new multimedia applications is more than likely to devour this increased capacity more quickly than anticipated. Therefore, better use of the frequency spectrum will be essential for the future generations of wireless communication networks. According to several studies, a large part of the spectrum allocated to conventional services is underutilized. In early 2000's the idea of Cognitive Radio was introduced for addressing this issue. A cognitive radio (CR) senses the spectrum (finds spectral holes), analyzes the spectrum (finds the properties of the hole) and makes transmission decision (data rate, transmission mode, etc.). In a cognitive radio environment there are two types of users: Primary Users (PU) who are the legacy users of the spectrum and have the priority over others and the Secondary Users (SU). The latter are the ones using CR principles to use the otherwise wasted bandwidth. In Cognitive Radio usually the PU's have absolute priority over SU's. That is, when a primary user starts using the spectrum, the secondary user has to immediately vacate the frequency slot (s) it is using. In this research project our goal is to increase the spectrum efficiency by allowing coexistence of the PU's and SU's through the use of advanced channel coding techniques and multiuser detection. In cellular networks, the coverage deteriorates as the mobile approaches the border between the base stations and when leaving the last base station. Temporary circumstances can also contribute to the lack of radio capacity in certain areas. Cellular systems can use principles of CR to improve their coverage. LTE uses OFDMA as the access method. Orthogonal Frequency Division Multiplexing (OFDM) is a modulation techniques that can benefit from CR due to its flexibility and computational efficiency. In this project, we will consider the use of cognitive radio in an LTE environment with LTE as the primary user and WiFi as the Secondary user.