The rapid proliferation of wireless systems makes interference management more and more important. This paper presents a novel cognitive coexistence framework, which enables an infrastructure system to reduce interference to ad-hoc or peer-to-peer communication links in close proximity. Motivated by the superior resources of the infrastructure system, we study how its centralized resource allocation can accommodate the ad-hoc links based on sensing and predicting their interference patterns.
Based on an ON/OFF continuous-time Markov chain model, the optimal allocation of power and transmission time is formulated as a convex optimization problem and closed-form solutions are derived. The optimal scheduling is extended to the case where the infrastructure channel is random and rate constraints need only be met in the long-term average. Finally, the multi-terminal case is addressed and the problem of optimal sub-channel allocation discussed. Numerical performance analysis illustrates that utilizing the superior flexibility of the infrastructure links can effectively mitigate interference.
On Scalable Video Streaming over Cognitive Radio Cellular and Ad Hoc Networks
预计在未来几年,通过无线网络的视频内容交付将大幅增长。在本文中,我们研究了具有挑战性的问题,视频认知无线电(CR)网络。虽然具有很高的潜力,但这个问题带来了新的技术挑战。回顾相关工作后,我们首先解决的问题,基于基础设施的CR网络的视频,然后扩展到非基于基础设施的ad hoc CR网络的视频问题。我们提出了跨层优化问题的公式以及有效的算法来解决问题。所提出的算法进行了分析,其最优性和验证与模拟。
New generation of radar systems will need to coexist with other radio frequency (RF) systems, anticipating their behavior and reacting appropriately to avoid interference. In light of this requirement, this paper designs, implements, and evaluates the performance of phase-only sequences (with constant power) for intelligent spectrum utilization using the custom built cognitive Multiple Input Multiple Output (MIMO) radar prototype. The proposed transmit waveforms avoid the frequency bands occupied by narrowband interferers or communication links, while simultaneously have a small cross-correlat…
In this paper we investigate the practical design for the multiple-antenna cognitive radio (CR) networks sharing the geographically used or unused spectrum. We consider a single cell network formed by the primary users (PU), which are half-duplex two-hop relay channels and the secondary users (SU) are single user additive white Gaussian noise channels. In addition, the coexistence constraint which requires PUs' coding schemes and rates unchanged with the emergence of SU, should be satisfied. The contribution of this paper are twofold. First, we explicitly design the scheme to pair the SUs to t…
Virginia Tech(弗吉尼亚理工大学);U.S Army Research Laboratory(美国陆军研究实验室)
This paper describes a sequential, or online, learning scheme for adaptive radar transmissions that facilitate spectrum sharing with a non-cooperative cellular network. First, the interference channel between the radar and a spatially distant cellular network is modeled. Then, a linear Contextual Bandit (CB) learning framework is applied to drive the radar's behavior. The fundamental trade-off between exploration and exploitation is balanced by a proposed Thompson Sampling (TS) algorithm, a pseudo-Bayesian approach which selects waveform parameters based on the posterior probability that a spe…
Performance Analysis of Spectrum Handoff for Cognitive Radio Ad Hoc Networks without Common Control Channel under Homogeneous Primary Traffic
认知无线电(CR)技术被认为是解决频谱稀缺问题的一种有效方法.由于CR网络的频谱变化性质,当授权用户重用频谱时,需要未授权用户执行频谱切换。在本文中,我们研究了频谱切换过程中的性能在CR ad hoc网络下均匀的主要业务。我们提出了一种新的三维离散时间马尔可夫链来描述频谱的衰落过程,并分析了非授权用户的性能。由于在真正的CR网络中,一个专用的公共控制信道是不切实际的,在我们的模型中,我们实现了一个网络协调方案,没有专用的公共控制信道是必要的。此外,在无线通信中,不能立即检测同时传输之间的冲突,并且需要重传整个冲突分组,这极大地影响了网络性能。有了这个观察,我们还考虑了在我们提出的离散时间马尔可夫链中的冲突数据包的重传。此外,除了随机信道选择方案,我们研究了不同的信道选择方案对频谱切换过程的性能的影响。此外,我们还考虑了频谱感知延迟在我们提出的马尔可夫模型,并研究其对网络性能的影响。我们验证了我们提出的马尔可夫模型对模拟和频谱切换场景中的其他参数的兴趣得到的数值结果。我们提出的分析模型可以应用于各种实际的网络场景。它也提供了新的见解的过程中的频谱衰减。目前,没有现有的分析认为,频谱切换的全面方面,我们认为在本文中。
On the Spectrum Handoff for Cognitive Radio Ad Hoc Networks without Common Control Channel
认知无线电(CR)技术是一种很有前途的解决方案,以提高频谱利用率,使非授权用户利用频谱的机会主义的方式。由于非授权用户是授权频谱的临时访问者,当授权用户收回频谱时,他们被要求腾出频谱。由于授权用户出现的随机性,对授权和非授权通信的中断通常难以防止。在本章中,提出了一个积极的频谱切换框架CR ad hoc网络,以解决这些问题。在所提出的框架中,信道切换策略和主动频谱切换协议,提出了让未授权用户腾出信道之前,授权用户利用它,以避免不必要的干扰。针对非授权用户的网络协调方案也被纳入到频谱切换协议的设计中,以实现信道会合。此外,提出了一种分布式信道选择方案,以消除非授权用户之间的冲突。在我们提出的框架中,未授权用户相互协调,而不使用公共控制信道。我们比较了我们提出的主动频谱切换协议与反应频谱切换协议,在该协议下,未授权用户切换信道发生冲突后,与授权传输。仿真结果表明,我们的主动频谱切换优于反应式频谱切换方法在更高的吞吐量和更少的冲突授权用户。此外,我们提出了一种新的三维离散时间马尔可夫链来描述反应性频谱中断的过程,并分析了非授权用户的性能。我们验证了我们提出的马尔可夫模型对模拟和频谱切换场景中的其他参数的兴趣得到的数值结果。
Distributed Optimal Beamformers for Cognitive Radios Robust to Channel Uncertainties
通过空间复用和分集,多输入多输出(MIMO)认知无线电(CR)网络可以显著提高传输速率和可靠性,同时通过波束赋形控制对对等节点和主用户(PU)的干扰。本论文优化了Ad Hoc CR网络的发射和接收波束形成器的设计时,CR到CR信道是已知的,但CR到PU信道不能准确估计。利用一个范数有界的信道不确定性模型,最优波束成形设计制定从所有数据流的总体均方误差(MSE)最小化,同时执行保护的PU系统时,CR到PU信道是不确定的。即使由此产生的优化问题是非凸的,可证明收敛到固定点的算法开发通过诉诸块坐标上升迭代,以及适当的凸逼近技术。有趣的是,这些新颖的方案也很自然地适用于分布式实现。数值试验证实了分析结果。