Adaptive Modulation and Coding and Cooperative ARQ in a Cognitive Radio System

In this paper, a joint cross-layer design of adaptive modulation and coding (AMC) and cooperative automatic repeat request (C-ARQ) scheme is proposed for a secondary user in a shared-spectrum environment. First, based on the statistical descriptions of the channel, closed-form expressions of the average spectral efficiency (SE) and the average packet loss rate (PLR) are presented. Then, the cross-layer scheme is designed, with the aim of maximizing the average SE while maintaining the average PLR under a prescribed level. An optimization problem is formed, and a sub-optimal solution is found: the target packet error rates (PER) for the secondary system channels are obtained and the corresponding sub-optimal AMC rate adaptation policy is derived based on the target PERs. Finally, the average SE and the average PLR performance of the proposed scheme are presented

A Review of Cross-layer Design in Dynamic Spectrum Access for Cognitive Radio Networks

Cognitive Radio (CR) is an intelligent radio that can dynamically access the radio spectrum. Secondary users in Cognitive Radio Network (CRN) can access the licensed spectrum without causing harmful interference to primary users. The performance of cognitive radio networking functionalities depends on the properties of the spectrum band in use. This necessitates a crosslayer design in the entire CR networking protocol stack. Current researches are investigating different techniques of using cognitive radio to reuse more locally unused spectrums to increase the total system capacity. This paper provides a comprehensive survey of cross-layer design in cognitive radio network. The cross-layer design approach jointly considers the functions of the layers to maximize the performance of CR networks.</p

Truncated-ARQ aided adaptive network coding for cooperative two-way relaying networks: cross-layer design and analysis

Network Coding (NC) constitutes a promising technique of improving the throughput of relay-aided networks. In this context, we propose a cross-layer design for both amplifyand- forward (AF-) and decode-and-forward two-way relaying (DF-TWR) based on the NC technique invoked for improving the achievable throughput under specific Quality of Service (QoS) requirements, such as the maximum affordable delay and error rate.We intrinsically amalgamate adaptive Analog Network Coding (ANC) and Network Coded Modulation (NCM) with truncated Automatic Repeat reQuest (ARQ) operating at the different OSI layers. At the data-link layer, we design a pair of improved NC-based ARQ strategies based on the Stop-andwait and the Selective-repeat ARQ protocols. At the physical layer, adaptive ANC/NCM are invoked based on our approximate packet error ratio (PER). We demonstrate that the adaptive ANC design can be readily amalgamated with the proposed protocols. However, adaptive NC-QAM suffers from an SNR-loss, when the transmit rates of the pair of downlink (DL) channels spanning from the relay to the pair of destinations are different. Therefore we develop a novel transmission strategy for jointly selecting the optimal constellation sizes for both of the relay-to-destination links that have to be adapted to both pair of channel conditions. Finally, we analyze the attainable throughput, demonstrating that our truncated ARQ-aided adaptive ANC/NCM schemes attain considerable throughput gains over the schemes dispensing with ARQ, whilst our proposed scheme is capable of supporting bidirectional NC scenarios

Performance evaluation of cross-layer energy-efficient transmit antenna selection for spatial multiplexing systems

Abstract Multiple-input multiple-output (MIMO) and cognitive radio (CR) are key techniques for present and future high-speed wireless technologies. On the other hand, there are rising energy costs and greenhouse emissions associated with the provision of high-speed wireless communications. Consequently, the design of high-speed energy efficient systems is paramount for next-generation wireless systems. This thesis studies energy-efficient antenna selection for spatial multiplexing multiple-antenna systems from a cross-layer perspective, contrary to the norm, where physical-layer energy efficiency metrics are optimized. The enhanced system performance achieved by cross-layer designs in wireless networks motivates this research. The aim of the thesis is to propose and analyze novel cross-layer energy-efficient transmit antenna selection schemes that enhance energy efficiency and system performance - with regard to throughput, transmission latency, packet error rate and receiver buffer requirements. Firstly, this thesis derives the analytical expression for data link throughput for point-to-point spatial multiplexing multiple-antenna systems - which include MIMO and underlay CR MIMO systems - equipped with linear receivers with N-process stop-and-wait (N-SAW) as the automatic repeat request (ARQ) protocol. The performance of cross-layer transmit antenna selection, which maximizes the derived throughput metric, is then analyzed. The impact of packet size, number of SAW processes and the stalling of packets inside the receiver reordering buffer is considered in the investigation. The results show that the cross-layer approach, which takes into account system characteristics at both the data link and physical layers, has superior performance in comparison with the conventional physical-layer approach, which optimizes capacity. Secondly, this thesis proposes a cross-layer energy efficiency metric, based on the derived system throughput. Energy-efficient transmit antenna selection for spatial multiplexing MIMO systems, which maximizes the proposed cross-layer energy efficiency metric, by jointly optimizing the transmit antenna subset and transmit power, subject to spectral efficiency and transmit power constraints, is then introduced and analyzed. Additionally, adaptive modulation is incorporated into the proposed cross-layer scheme to enhance system performance. Cross-layer energyefficient transmit antenna selection for underlay CR MIMO systems, where interference constraints now come into play, is then considered. Lastly, this thesis develops novel reduced complexity versions of the proposed cross-layer energyefficient transmit antenna selection schemes - along with detailed complexity analysis - which shows that the proposed cross-layer approach attains significant energy efficiency and performance gains at affordable computational complexity

A novel cross-layer design for dynamic TXOP in IEEE802.11e

U radu se predlaže novi okvir za konstrukciju s poprečnim slojevima (cross-layer design) i optimizaciju bežičnih mreža kombiniranjem adaptivne modulacije i kodiranja (AMC) na fizičkom sloju (PHY) pomoću automatskog zahtjeva za ponavljanjem (automatic repeat request) i channel-aware multiuser scheduling protokola kod sloja za reguliranje povezivanja podataka - data link control (DLC). Predloženo se načelo zasniva na primjeni dvodimenzijskih Markovljevih lanaca diskretnog vremena - two-dimensional discrete time Markov chains (DTMCs) koji skupa modeliraju AMC shemu i amplitude contention window (CW). Predstavljen je novi algoritam za dinamičku konfiguraciju ispitivane mogućnosti prijenosa - polled transmission opportunity (TXOP) u IEEE 802.11e mreži s više brzina te se analizira njegova učinkovitost i uspoređuje sa zadanom konfiguracijom. Rezultati numeričke simulacije pokazali su visoku učinkovitost predložene metode u maksimiranju prosječnog protoka sustava.This paper proposes a novel framework for the cross-layer design and optimization of wireless networks combining adaptive modulation and coding (AMC) at the physical (PHY) layer by means of automatic repeat request and channel-aware multiuser scheduling protocols at the data link control (DLC) layer. The proposed framework is based on the use of two-dimensional discrete time Markov chains (DTMCs) jointly modelling the AMC scheme and the amplitude contention window (CW). A new algorithm for dynamic configuration of the polled transmission opportunity (TXOP) in multi-rate IEEE 802.11e network is presented and its performance is analysed and compared with default configuration. The numerical simulation results have indicated the high efficacy of the proposed method in maximizing the average throughput of the system