Cooperative spectrum sensing in cognitive radio networks: A survey

This document provides updates to IEEE Std 802.16's MIB for the MAC, PHY and asso- ciated management procedures in order to accommodate recent extensions to the standard.

IEEE Standard for Local and Metropolitan Area Networks Part 16: Air Interface for Fixed Broadband Wireless Access Systems Draft Amendment: Management Information Base Extensions

The Transmission Control Protocol.

With the rapid deployment of new wireless devices and applications, the last decade has witnessed a growing demand for wireless radio spectrum. However, the fixed spectrum assignment policy becomes a bottleneck for more efficient spectrum utilization, under which a great portion of the licensed spectrum is severely under-utilized. The inefficient usage of the limited spectrum resources urges the spectrum regulatory bodies to review their policy and start to seek for innovative communication technology that can exploit the wireless spectrum in a more intelligent and flexible way. The concept of cognitive radio is proposed to address the issue of spectrum efficiency and has been receiving an increasing attention in recent years, since it equips wireless users the capability to optimally adapt their operating parameters according to the interactions with the surrounding radio environment. There have been many significant developments in the past few years on cognitive radios. This paper surveys recent advances in research related to cognitive radios. The fundamentals of cognitive radio technology, architecture of a cognitive radio network and its applications are first introduced. The existing works in spectrum sensing are reviewed, and important issues in dynamic spectrum allocation and sharing are investigated in detail.

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Advances in cognitive radio networks: A survey

Intelligent reflecting surface (IRS) is an enabling technology to engineer the radio signal propagation in wireless networks. By smartly tuning the signal reflection via a large number of low-cost passive reflecting elements, IRS is capable of dynamically altering wireless channels to enhance the communication performance. It is thus expected that the new IRS-aided hybrid wireless network comprising both active and passive components will be highly promising to achieve a sustainable capacity growth cost-effectively in the future. Despite its great potential, IRS faces new challenges to be efficiently integrated into wireless networks, such as reflection optimization, channel estimation, and deployment from communication design perspectives. In this paper, we provide a tutorial overview of IRS-aided wireless communications to address the above issues, and elaborate its reflection and channel models, hardware architecture and practical constraints, as well as various appealing applications in wireless networks. Moreover, we highlight important directions worthy of further investigation in future work.

Intelligent Reflecting Surface-Aided Wireless Communications: A Tutorial

We consider power allocation in energy efficient OFDM (Orthogonal Frequency Division Multiplexing) or MIMO (Multiple-Input Multiple-Output) transmissions. An energy-per-goodbit (EPG) metric is used to gauge the average energy consumed for transmitting each bit. Existing works minimize EPG by searching for a set of dual variables which are used to compute the optimal power allocation in a Water-Filling (WF) expression. The searching process is complex and requires a long running time. In this paper, we propose a new algorithm to compute the optimal power allocation without searching any dual variables. Our algorithm is based on an iterative calculation of the total transmission power and it converges when the minimum EPG is reached. It takes WF as the basic building block. Unlike the conventional WF approach which needs to search for a Lagrange multiplier (i.e., the water level), we additionally propose a novel WF algorithm without searching the Lagarange multiplier. Numerical results show that our power allocation algorithm for EPG minimization, together with the embedded fast WF algorithm, can run multiple times faster than the existing ones.

Power allocation based on fast Water-Filling for energy efficient OFDM and MIMO transmissions

In this paper we study the interactions of TCP and IEEE 802.11 MAC in Wireless Mesh Networks (WMNs). We use a Markov chain to capture the behavior of TCP sessions, particularly the impact on network throughput performance due to the effect of queue utilization and packet relaying. A closed form solution is derived to numerically determine the throughput. Based on the developed model, we propose a distributed MAC protocol to alleviate the unfairness problem in WMNs. Our protocol uses the age of packet as a priority metric for packet scheduling. Simulation is conducted to validate our model and to illustrate the fairness characteristics of our proposed MAC protocol. We conclude that we can achieve fairness with only little impact on network capacity.

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MAC-layer protocol for TCP fairness in Wireless Mesh Networks

The past studies for survivable routing suffers from the scalability problem when the number of nodes or connection requests grows in the network. In this proposal, a novel path based shared protection framework namely Inter-Group Shared protection (I-GSP) is developed such that the traffic matrix can be divided into multiple protection groups (PGs) based on specific grouping policy. This novel scheme not only overcomes the scalability problem but also provides an upper bound on the affected working paths in case of link failure in the network. Experiment results show that I-GSP based integer linear programming model solves the networks in a reasonable amount of time for which a regular integer linear programming formulation becomes computationally intractable. For most of the cases the performance gap between the optimal solution and the proposed I-GSP ranges between (2-16)%. The proposed optimization model yields a scalable and near-optimal solution for the capacity planning in the survivable optical networks.

OPN02-2: Inter-Group Shared Protection (I-GSP): A Scalable Solution for Survivable WDM Networks

Joint source and channel coding (JSCC) has been widely reported for its superb capability in mitigating the legacy channel/user diversity problem in the wireless multicast/broadcast scenario, where the successively refined source information is manipulatively mapped with superimposed channel symbols via superposition coding (SPC). However, the use of SPC involves additional hardware in the physical layer, which may not be in compliance with most standard equipments and protocols. This paper introduces a novel framework of logical SPC (L-SPC) modulation for multicast/broadcast of successively refined sources via the JSCC approach. The framework is characterized by completely software-based L-SPC modulation at the sender, where the modulated signal is generated by mapping successively refined information bits onto a single signal constellation. At the receiving end, the proposed framework only needs simple modifications in the medium access control layer software, while the required demodulation schemes are completely compatible with the standard ones with uniform constellation. Generalized formulations on symbol error rate (SER) are derived for performance evaluation and comparisons with the conventional hardware-based approach for both the 2- and 3-layer cases.

Logical Superposition Coded Video Multicast/Broadcast

In this paper, we solve the survivable routing problem in dynamic WDM mesh networks under the framework of short leap shared protection (SLSP). A novel algorithm called cascaded diverse routing (CDR) is proposed. We also demonstrate a novel approach to solving the diverse routing problem in networks with dynamic traffic for the purpose of shared protection, called iterative two-step-approach (ITSA). Simulation is conducted using four different networks (22-, 30-, 79-, 100-node) for a comparison between ordinary shared protection schemes and the SLSP scheme. Simulation results show that the best performance can be achieved with well-design diameter of protection domains for every connection request according to the size and topology of the network.

Pin-Han Ho

Papers

Power allocation based on fast Water-Filling for energy efficient OFDM and MIMO transmissions

MAC-layer protocol for TCP fairness in Wireless Mesh Networks

OPN02-2: Inter-Group Shared Protection (I-GSP): A Scalable Solution for Survivable WDM Networks

Logical Superposition Coded Video Multicast/Broadcast

A novel strategy for protection domain allocation in dynamic mesh WDM networks