The Infona portal uses cookies, i.e. strings of text saved by a browser on the user's device. The portal can access those files and use them to remember the user's data, such as their chosen settings (screen view, interface language, etc.), or their login data. By using the Infona portal the user accepts automatic saving and using this information for portal operation purposes. More information on the subject can be found in the Privacy Policy and Terms of Service. By closing this window the user confirms that they have read the information on cookie usage, and they accept the privacy policy and the way cookies are used by the portal. You can change the cookie settings in your browser.
Opportunistic access of licensed spectrum using a cognitive radio network (CRN) is getting research attraction due to its ability to improve utilisation of this scarce resource without affecting the primary users (PUs). To improve wide acceptability of CRN, it must be equipped with efficient protocols to deal with multiple primary networks to provision QoS guarantee for demand-driven applications...
The aim of this paper is to get an insight of the interference estimation for multi-layer multi-user multiple-input and multiple-output (ML-MU-MIMO) transmission for LTE-Advanced (long term evolution) systems. Different interference-aware receivers have been investigated in ML-MU-MIMO with the presence of co-layer, intra-cell and inter-cell interferences. User-specific reference signal (UE-RS) based...
In this paper, we propose a novel contention-aware channel selection algorithm that focuses on throughput and energy efficiency improvement in Cognitive Radio Ad-Hoc Networks (CRAHNs). Specifically, we study the operation and performance of a Secondary Network (SN) in a scenario where other non-cooperating CRAHNs are also using the primary resources. We prove that a channel categorization of the idle...
Interferences in cellular wireless networks (CWN) between central station (CS) and the terminal station (TS) have a direct impact on available throughput and represents the main capacity limitation, especially in networks with full frequency reuse among all CSs. More and more attention is being focused on a way of minimizing interferences. We are introducing a new Coordinated Channel Gain Estimation...
The terrestrial free space optical (FSO) link promises a number of advantages in terms of higher data rates and license free bandwidth, but is challenged by atmospheric propagation conditions. Designing a system for the worst channel conditions leads to an inadequate use of resources while opting for a system design based on clear sky conditions lacks reliability. The key idea behind this work is...
Limited feedback of channel state information (CSI), which is made up of rank indicator (RI), precoding matrix indicator (PMI) and channel quality indicator (CQI), is an important part in closed-loop transmission for 3GPP Long Time Evolution (LTE)/LTE-Advanced standard. In this paper, an efficient way, where PMI granularity selection method is used in PMI feedback mechanism, is presented to adaptively...
In this paper, we compare the energy efficiency of a single carrier multiple-input multiple-output communications in terms of the energy per data bit required to achieve desired performance level or throughput. The comparison on energy efficiency is done between traditional time-domain multiplexed training and a more recently introduced data-dependent superimposed training. We extend our earlier single-input...
IEEE 802.11 Wireless LANs (WLANs) use rate adaptation algorithms (RAAs) to dynamically switch data rates to accommodate the fluctuating wireless channel conditions. Classic RAAs such as ARF and ONOE suffer from rate poisoning and inability to distinguish between collision and packet losses caused by channel errors. Existing approaches in the literature are able to solve only one of the above two issues...
We propose a spectrum-sensing and data-transmission scheme that utilizes multiple-input and multiple-output (MIMO) technology to enable the spectrum to be sensed and data to be transmitted simultaneously. By using our proposed scheme, the degradation of quality of service (QoS) that is caused by spectrum sensing can be reduced and the system throughput of a cognitive radio (CR) system can be increased,...
Collaborative spectrum sensing among secondary users (SUs) in cognitive radio (CR) networks is shown to yield a significant performance improvement. However, much previous work in CR networks focus on single channel sensing performed by SU cooperatively while spectrum sensing on multiple channels is largely ignored. In order to overcome the foregoing shortcoming, coalition game theory is introduced...
In LTE-A or Rel. 10+, heterogeneous network deployments are supported to improve the user experienced link performance. However, such deployments give rise to new interference problems. In this study, macro-femto-cell interference scenarios for LTE-A downlink are investigated. We focus on the critical interference scenario of colliding cell-specific reference signals (CRSs). As conventional receivers...
In this paper, we tackle the problem of opportunistic spectrum access in cognitive radio networks where a number of unlicensed Secondary Users (SU) operating on the standard CSMA/CA protocol access a number of frequency channels partially occupied by licensed Primary Users (PU). We apply evolutionary game theory to model the spectrum access problem and derive distributed mechanisms to converge to...
In this paper we present a cooperative medium access control (MAC) protocol that is designed for a physical layer that can decode interfering transmissions in distributed wireless networks. The proposed protocol pro-actively enforces two independent packet transmissions to interfere in a controlled and cooperative manner with the help of a relay. To enable distributed, uncoordinated, and adaptive...
For reducing the channel switching frequency due to uncertain and frequent primary users' interruptions, we design a nonparametric channel allocation algorithm which can effectively manage the spectrum resources in distributed cognitive radio networks and serve for delay-sensitive data traffics. In the proposed algorithm, an infinite Gaussian mixture model is used to get the posterior decision from...
Multiple tags in Radio Frequency Identification (RFID) systems are scheduled by a medium access control layer using the Framed Slotted Aloha (FSA) or binary tree protocol. The focus of our research is on FSA and passive Ultra High Frequency (UHF) RFID. In current standards, only one tag can be acknowledged per slot. In this work we propose the increase of the theoretical throughput of FSA RFID systems...
We propose joint channel sensing, probing, and accessing schemes for secondary users in cognitive radio networks. Our method has time and space complexity O(N·k) for a network with N channels and k secondary users, while applying classic methods requires exponential time complexity. We prove that, even when channel states are selected by adversary (thus non-stochastic), it results in a total regret...
Cognitive radios hold tremendous promise for increasing the spectral efficiency of wireless communication systems. In this paper, an adaptive bit allocation algorithm is presented for orthogonal frequency division multiplexing (OFDM) CR systems operating in a frequency selective fading environment. The algorithm maximizes the CR system throughput in the presence of narrowband interference, while guaranteeing...
The partially observed Markov decision process (POMDP) is very important in cognitive radio network. We can formulate the opportunistic spectrum access in the framework of POMDP. However, no attention was paid to the algorithm in the presence of unknown environment. For the rapidly changing cognitive network with unknown environment, we firstly establish the channel state model based on MLA and prove...
At present, although the IEEE 802.11 MAC and PHY specifications provide multi-channel and multi-rate capabilities, exploiting data rates and available orthogonal channels is still a crucial issue to ensure high network performance in wireless mesh networks (WMNs). Most channel assignment schemes for WMNs assume that all links operate at an identical data rate; i.e., they ignore the existence of multi-rate...
In this paper, we present a rendezvous scheme for dynamic spectrum access (DSA) networks that can achieve approximately optimal throughput while not relying on a common control channel. Compared with existing rendezvous schemes for DSA networks that use a common control channel, the proposed scheme avoids congestion and jamming of the control channel, and also reduces control complexity and overhead...
Set the date range to filter the displayed results. You can set a starting date, ending date or both. You can enter the dates manually or choose them from the calendar.