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Global connectivity, low latency, and ready-to-use infrastructure of next generation wireless (NGW) networks provide a platform for machine-to-machine (M2M) communications on a large scale. However, M2M communications over NGW networks pose significant challenges because of different data rates, diverse applications, and a large number of connections. In this paper, we address M2M challenges over NGW networks, and in particular, we focus on random access overload issue and diverse quality-of-service (QoS) requirements to enable M2M communications in the context of NGW networks. To enable massive M2M access while QoS guarantees, we propose group-based M2M communications on the basis of identical transmission protocols and QoS requirements. Furthermore, to guarantee low energy consumption for M2M devices in the same group, we propose a decentralized group-head selection scheme. In addition, a solution is proposed by using an effective capacity concept to provide QoS guarantees for M2M devices with a strict time constraint. A new random access approach based on different lengths super orthogonal codes is proposed to ease massive random access challenges with provisioning diverse QoS requirements of M2M communications in heterogeneous NGW networks. [ABSTRACT FROM AUTHOR]

Power amplifier (PA) is one of important components in wireless communication system. However, its non‐linear and memory characteristic cause harmful distortion, which significantly decreases the power efficiency and wastes electronic energy since the power of PA needs back off. To overcome the non‐linear and memory problems, a novel method based on distortion‐characteristic estimation algorithm is developed in this study. The main innovation of this study is manifested in two aspects: first, the authors use well designed training signals to estimate the distortion characteristic of the PA; second, a novel PA characteristic estimation algorithm is developed in order to calculate the optimal state of the ideal predistorter that behaves like the inverse characteristic of PA theoretically. Since this novel method does not require the error between original signals and feedback signals, it can avoid the significant errors caused by the time mismatch between source signals and feedback signals, and can increase the power efficiency of the PA. The simulation results validate the performance increase and the synchronisation‐error immunity over the existing simplified filter look up table method. [ABSTRACT FROM AUTHOR]

SUMMARY Resource reservation or the other prioritization strategies adopted by Call Admission Control (CAC) schemes in wireless networks lead to unfair resource allocation to users belonging to different service classes (SCs) due to high divergence among the respective call blocking probabilities (CBPs). In this paper, we propose dynamic optimization of probabilistic CAC (P-CAC) schemes to assure CAC fairness among users of different SCs in wireless networks. The approach is based on users utility combined with fairness optimization, aiming at dynamically determining the probability value in the P-CAC scheme. This optimal probability is adjusted to network ongoing traffic, CBPs of each SC, prioritization levels characterizing the SCs supported, and the users risk aversion, which reflects their behavior toward the perceived QoS. The existence and uniqueness of the optimal probability that leads to absolute fairness among the users of a wireless network are proven. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

SUMMARY Link adaptation (LA) plays an important role in adapting an IEEE 802.11 network to wireless link conditions and maximizing its capacity. However, there is a lack of theoretic analysis of IEEE 802.11 LA algorithms. In this article, we propose a Markov chain model for an 802.11 LA algorithm (ONOE algorithm), aiming to identify the problems and finding the space of improvement for LA algorithms. We systematically model the impacts of frame corruption and collision on IEEE 802.11 network performance. The proposed analytic model was verified by computer simulations. With the analytic model, it can be observed that ONOE algorithm performance is highly dependent on the initial bit rate and parameter configurations. The algorithm may perform badly even under light channel congestion, and thus, ONOE algorithm parameters should be configured carefully to ensure a satisfactory system performance. Copyright © 2011 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

SUMMARY A new video transport protocol for multicast agents in wireless mesh networks (WMNs) is proposed in this paper. The proposed protocol enables a significant reduction in the transmission overhead, while providing reliable communication for its use in multicast applications. This proposed reliable protocol provides a practical approach for an overlay peer-to-peer multicast facility supported within the application layer. This obviates the need to give upgraded routers capable of handling multicast broadcasting or modify the existing protocol stack. The protocol tolerates partial losses in multimedia transmissions, while supporting control of the delay sensitivity of such transmissions in WMNs. The key issue in this protocol is the ability to detect packet loss, anticipate retransmission requests, and use the anticipated retransmission requests to transmit the lost packets prior to requests from other receiving agents. The proposed protocol allows for the receiver to determine if retransmission of lost packets is required, ensuring the greatest flexibility needed for a reliable multicast protocol. Copyright © 2009 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

This paper addresses the issues on spectrum sharing in a cognitive radio network consisting of a primary user and a group of cognitive users. Each cognitive user may occupy a non-overlapped sub-band of the primary spectrum, but it needs to perform spectrum sensing independently before accessing the sub-band. To reduce the complexity of spectrum sensing and thus energy consumption, this paper proposes a scheduled spectrum sensing scheme. First, we consider a single spectrum sensing scenario where only one cognitive user is elected to perform spectrum sensing, and then it broadcasts its sensing results to the other cognitive users. The scheduled spectrum sensing scheme works in both network-centric and user-centric ways. Next, the scheduled spectrum sensing scheme is further generalized to work in a multiple spectrum sensing scenario. The results show the effectiveness of the proposed schemes compared with the traditional schemes where all cognitive users may perform spectrum sensing at the same time. Copyright © 2010 John Wiley & Sons, Ltd. This paper proposes a scheduled spectrum sensing scheme for spectrum sharing in a cognitive radio network consisting of a primary user and a group of cognitive users. Both single and multiple scheduled spectrum sensing schemes are considered. The results show that in general the proposed scheduling schemes are more efficient than the extreme case in terms of the number of sensing operations required with a given sum false alarm probability and the sum-missed detection probability. Copyright © 2010 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]