Primary Base Station Research Articles

Performance Analysis of Cognitive Radio Multiple-Access Channels Over Dynamic Fading Environments

In dynamically changing environments, the spectrum-sharing method is a promising method to address the spectrum underutilization problem for cognitive radio (CR) systems. This paper investigates the capacity of cognitive radio multiple-access channel (CR-MAC) over a dynamic fading environment. Multiple secondary users (SUs) transmit to the secondary base station under the transmit power (TP) and interference temperature (IT) at the primary base station constraints. In order to perform a general analysis, a theoretical dynamic fading model termed hyper-fading model, which is suitable to the dynamic nature of cognitive radio channel, is considered. The optimal power allocation method is employed to maximize the capacity of CR-MAC for hyper-fading channel with TP and IT constraints and full channel side information. Through the numerical simulations, the capacity of the hyper-fading channels are compared with that of other channel fading models such as Rayleigh, Nakagami-2, and with an additive white Gaussian noise channel. Additionally, the impacts of the number of SUs on capacity is investigated.

Cognitive Base Stations in LTE/3GPP Femtocells: A Correlated Equilibrium Game-Theoretic Approach

This paper considers downlink spectrum allocation in a long term evolution (LTE) system macrocell which contains multiple femtocells. By incorporating cognitive capabilities into femtocell base stations, the Home evolved Node Bs (HeNBs) can be formulated as secondary base stations seeking to maximize the spectrum utility while minimizing interference to primary base stations (evolved Node-Bs). The competition amongst cognitive HeNBs for spectrum resources is formulated as a non-cooperative game-theoretic learning problem where each agent (HeNB) seeks to adapt its strategy in real time. We formulate the resource block (RB) allocation among HeNBs in the downlink of a LTE system using a game-theoretic framework, where the correlated equilibrium solutions of the formulated game are being investigated. A distributed RB access algorithm is proposed to compute the correlated equilibrium RB allocation policy..

Design of Can Bus Clock Synchronous System Based on STM32

IEEE1588 Precision Clock Protocol is applied to Can Bus distributed system platform constructed of STM 32 chips to accomplish the clock synchronous system between primary and subsidiary base stations, thus ensuring the clock synchronization with the precision of millisecond.

Spectrum sensing and power/rate control in CDMA cognitive radio networks

In this paper, a two-phase algorithm for the spectrum sensing and power/rate control of a secondary user (S-user) or cognitive radio is proposed. In the first phase, the primary base station (P-BS), which is conscious of both the number and the data rate of primary active users (P-user), broadcasts theitusage capacity percentage (UCP) of its cell. Since knowing only the UCP is not enough to guarantee that the total load (of P-users and S-users) is less than a maximum permissible load, the S-user must measure the total interference received from both the P-users and other S-users. In this direction, using both the UCP and measurement of the interference received from the P-users and the S-users by the S-user or secondary base station (S-BS), we mathematically derive an equation for issuing data transmission permission, which if it is held then the second phase of the algorithm: the transmit power/rate control starts. In this phase, the S-user and the S-BS look for feasible values for the transmit power level and transmission rate. If there are feasible values, it starts its transmission at these feasible transmit power and rate. Since both the location of the S-user and the channel condition vary in time, the whole algorithm is iterated periodically with a period faster than the coherence time of the channel. Furthermore, we consider the down link of the above system with cooperation among neighboring S-users to overcome fading channels and we investigate the amount of improvement in the reliability of the issuing data transmission permission. As well, we consider the uplink of the system with multiple antennas in the S-BS to investigate the improvement in the same parameter over spatially correlated and independent fading channels. Theoretical analysis is validated using computer simulations. Both theoretical analysis and computer simulations show that the proposed cooperative spectrum sensing algorithm performs properly at SNR = −5dB in flat Nakagami-m fading channels with m = 1 even in correlated fading channels. We also address the improvement of the reliability of the issuing data transmission permission in the uplink in case of using multiple antennas only in the S-BS. Copyright © 2011 John Wiley & Sons, Ltd.

Iterative power and subcarrier allocation in rate-constrained orthogonal multicarrier downlink systems based on hybrid harmony search heuristics

This paper presents a novel iterative hybrid algorithm for subcarrier and power allocation in a cognitive orthogonal frequency division multiple access (OFDMA) downlink. In the considered setup a primary base station forwards information to K distant receivers by using a single OFDM waveform, whereas a secondary base station – subject to stringent per-user rate constraints – interferes with the former by sending information from users to the same set of destinations. Power and user allocation at both base stations is jointly performed by the proposed algorithm to maximize the overall throughput of the setup while satisfying, at the same time, the imposed rate constraints. Our proposal, which stems from an hybridization of the harmony search (HS) and differential evolution (DE) algorithms along with a greedy local repair method, is shown – through computer simulations over the extended vehicular A ITU channel model – to be an effective and practical resource allocation procedure for cognitive OFDMA downlinks.

Capacity limits of spectrum‐sharing systems over hyper‐fading channels

ABSTRACTCognitive radio (CR) with spectrum‐sharing feature is a promising technique to address the spectrum under‐utilization problem in dynamically changing environments. In this paper, the achievable capacity gain of spectrum‐sharing systems over dynamic fading environments is studied. To perform a general analysis, a theoretical fading model called hyper‐fading model that is suitable to the dynamic nature of CR channel is proposed. Closed‐form expressions of probability density function (PDF) and cumulative density function (CDF) of the signal‐to‐noise ratio (SNR) for secondary users (SUs) in spectrum‐sharing systems are derived. In addition, the capacity gains achievable with spectrum‐sharing systems in high and low power regions are obtained. The effects of different fading figures, average fading powers, interference temperatures, peak powers of secondary transmitters, and numbers of SUs on the achievable capacity are investigated. The analytical and simulation results show that the fading figure of the channel between SUs and primary base‐station (PBS), which describes the diversity of the channel, does not contribute significantly to the system performance gain. Copyright © 2011 John Wiley & Sons, Ltd.

Auction-Based Spectrum Management of Cognitive Radio Networks

Cognitive radio (CR) technology is considered to be an effective solution to enhance overall spectrum efficiency, whereas a primary radio network (PRN) typically does not fully utilize an available spectrum. However, to realize the CR concept, it is essential to provide enough incentives to PRNs and extra revenue to the service provider such that CR mobile stations (CR-MSs) may accordingly utilize PRN spectrum bands, which provides a new challenge for spectrum management. In this paper, we consider a PRN consisting of a primary system base station (PS-BS) and multiple primary system mobile stations (PS-MSs), and we, therefore, construct a CR network (CRN) consisting of a PRN with multiple CR-MSs. We propose a spectrum-management policy framework based on the Vickrey auction such that CR-MSs can compete for utilization of the PRN spectrum bands available for opportunistic transmission of CR-MSs. PRN users are granted incentives at a discounting factor to access spectrum bands and are being compensated for possible operating interference from CR-MSs, whereas the interference is constrained under a tolerance level without losing satisfaction for the PS-MSs. Once CR-MSs are granted spectrum bands, they can utilize the spectrum bands for a certain duration with no spectrum handoff. Consequently, in addition to incentives to the PRN, the overall spectrum utilization, the profit of the service provider, and the opportunity to access the spectrum for the CR-MSs are enhanced to achieve a co-win situation for every involved party in CRNs. Realistic simulations by incorporating pretty bad channel conditions into system operations show the robust operation of our proposed system, which enables the CR concept.

Cognitive Networks Achieve Throughput Scaling of a Homogeneous Network

We study two distinct, but overlapping, networks that operate at the same time, space, and frequency. The first network consists of $n$ randomly distributed \emph{primary users}, which form either an ad hoc network, or an infrastructure-supported ad hoc network with $l$ additional base stations. The second network consists of $m$ randomly distributed, ad hoc secondary users or cognitive users. The primary users have priority access to the spectrum and do not need to change their communication protocol in the presence of secondary users. The secondary users, however, need to adjust their protocol based on knowledge about the locations of the primary nodes to bring little loss to the primary network's throughput. By introducing preservation regions around primary receivers and avoidance regions around primary base stations, we propose two modified multihop routing protocols for the cognitive users. Base on percolation theory, we show that when the secondary network is denser than the primary network, both networks can simultaneously achieve the same throughput scaling law as a stand-alone network. Furthermore, the primary network throughput is subject to only a vanishingly fractional loss. Specifically, for the ad hoc and the infrastructure-supported primary models, the primary network achieves sum throughputs of order $n^{1/2}$ and $\max\{n^{1/2},l\}$, respectively. For both primary network models, for any $\delta>0$, the secondary network can achieve sum throughput of order $m^{1/2-\delta}$ with an arbitrarily small fraction of outage. Thus, almost all secondary source-destination pairs can communicate at a rate of order $m^{-1/2-\delta}$.

Schemes for Indoor Network Synchronization in UWB Positioning

Location Positioning is a major technology for ubiquitous computing. A research on Location Positioning using UWB is ongoing. In order to construct an indoor location network, synchronization of base stations is very important. NTP is popularly used as a clock synchronization protocol ranging from LAN to WAN. The Master-Slave scheme, however, is the simplest method for synchronizing an indoor network that uses UWB. In this paper, we compare and analyze the NTP and Master-Slave schemes according to the statistical channel model for an indoor multi-path propagation environment. Error ranges are calculated at various circumstances such as when the indoor network expands from one primary base station to several base stations. In particular, we compare the correctness of the NTP and Master-Slave synchronization methods. We have found that NTP is a more reasonable synchronization protocol in UWB positioning.

Report of the Special Committee on the Geophysical and Geological Study of the Continents, 1948–1949

During the year 1948 there was considerable geological and geophysical activity both in this country and abroad having a direct bearing upon the study of the continents. Of general interest is the critical evaluation of the world's primary gravity base stations values by Morelli at the Geophysical Institute in Trieste, and Hirvonen at the Isostatic Institute in Helsinki. An actual check using an improved gravity meter was also attempted by the Chairman of the Committee working under the auspices of the Office of Naval Research and the Woods Hole Oceanography Institution. The instrument used was a special Worden gravimeter having a range of 5400 mgal and a reading sensitivity of about 0.1 mgal. Approximately 82,000 mi were traveled in establishing one world‐girdling loop and four lesser trans‐oceanic loops. In all 165 stations were established and of these, 29 were reoccupation of old pendulum stations. Fourteen stations were national gravity base stations tied directly to Potsdam.

THE GRAVITY METER AS A GEODETIC INSTRUMENT

A special Worden temperature compensated gravity meter having a range of 5,500 mgals, and a reading sensitivity of 0.1 mgal was used to tie together various primary gravity base stations around the world and to establish new stations. Air transport was used and in a 3 month period over 80,000 miles were flown. Thirty‐three pendulum stations were reoccupied involving a change in gravity of 3,800 mgals, and 125 gravity stations were established. The investigation demonstrated that this instrument could be used satisfactorily for long range geodetic work and the results appear to be the equal of good pendulum observations. Drift was corrected for on the basis of the drift rate established immediately before and after flights. Closures after correcting for drift averaged less than 0.4 mgals, and the closure for the world girdling loop was 0.33 mgals. The probable error based upon the gravity values at the reoccupied pendulum station was ±0.5 mgals. Reoccupation of the absolute gravity stations at the U. S. Bureau of Standards in Washington, D. C. and the National Physical Laboratory in Teddington, England, indicated an approximate 5 mgal error in these pendulum determinations. Indirect ties to the absolute gravity base in Potsdam, Germany, through the primary national gravity bases tied to it, indicated a 15 to 19 mgal error in the Potsdam absolute value. Most of the primary national gravity bases tied directly to Potsdam were found to agree among themselves to within 1 mgal, and the U. S. Bureau of Standards Absolute Base in Washington, D. C. to have a perfect connection within the limits of accuracy of the present measurements. This investigation was made under the auspices of the Office of Naval Research.