Wideband Wireless Networks Research Articles

On Beamforming Gain Models for Performance Evaluation and Analysis of Narrowband and Wideband Wireless Networks

Directional antennas and beamforming techniques that bring promising transmission gain to the wireless links are widely incorporated in the system-level analysis of wireless networks. In many existing studies, the beamforming gain model to calculate the beamforming gain considers beamforming pattern and aligned as well as misaligned cases. However, the channel properties, e.g., the $K$ factor and the spatial distribution of multi-paths, are neglected, which could significantly influence the beamforming gain. In this paper, a general beamforming gain model is appropriately defined, while the traditional beamforming gain model is proved to be only a special case in the proposed general model by considering an oversimplified channel with no angular spread. In light of this, expressions of the received signal amplitude and the beamforming gain are rigorously derived for narrowband fading and wideband statistical mmWave channels, respectively. Thorough comparison between the proposed beamforming gain model and the traditional beamforming gain is provided, which demonstrates and validates that the traditional model incorrectly captures the beamforming gain and thereby, leads to inaccurate system-level network analysis. To this end, the effectiveness and importance of the proposed general beamforming gain model are revealed, particularly for millimeter-wave wideband systems.

Multipath-Enhanced Device-Free Localization in Wideband Wireless Networks

State-of-the-art device free localization systems infer presence and location of users based on received signal strength measurements of line-of-sight links in wireless networks. In this letter, we propose to enhance device free localization systems by exploiting multipath propagation between the individual network nodes. Particularly, indoors, wireless propagation channels are characterized by multipath propagation, i.e., received signals comprise multipath components due to reflection and scattering. Given prior information about the surrounding environment, e.g., a floor plan, the individual propagation paths of multipath components can be derived geometrically. Inherently, these propagation paths differ spatially from the line-of-sight propagation path and can be considered as additional links in the wireless network. This extended network determines the novel multipath-enhanced device free localization system. Using theoretical performance bounds on the localization error, we show that including multipath components into device-free localization systems improves the overall localization performance and extends the coverage area significantly.

Статистическая модель широкополосного канала беспроводной сети для условий различных сред промышленного предприятия

The article describes a wideband wireless network channel for the an industrial enterprise conditions organization problem. It is shown that well-known multipath models are used to estimate the parameters of such channel, for example, the signal power at the receiver. It is noted that due to the complex characteristics of the industrial environment, such models are not always possible to use. The model presented in this work allows us to estimate power delay profile, taking into account the environment of an industrial enterprise. It is shown that this model allows to increase the accuracy of the estimation of the receiver location in comparison with the existing ones.

Fully Monolithic BiCMOS Reconfigurable Power Amplifier for Multi-Mode and Multi-Band Applications

A power amplifier (PA) supporting wideband code division multiple access, long-term evolution (LTE), and wireless local area network applications has been implemented in 0.18- $\mu{\hbox{m}}$ SiGe BiCMOS technology. The PA integrates a tunable input matching network, a broadband output matching network, and adaptive bias circuits in a single chip to achieve high linearity and high power in different modulation schemes and operating bands. The three-stage PA adopts a differential-type configuration without using through-silicon-via technology to deliver 4 1.3–42 dB of gain and 28.2–28.6 dBm of 1-dB compression output power with a 20.8–27.6% power-added efficiency (PAE) at 1.85–2.5 GHz. To further validate the usefulness of the proposed PA, the envelope-tracking PA is designed to improve the PAE by 6.5% within the linearity specification of a 24.7-dBm average output power and a $-$ 33-dBc adjacent channel leakage ratio for 2.35-GHz 16 quadrature-amplitude-modulation time-division LTE signal with 20-MHz bandwidth.

Space-frequency channel pairing and power allocation for OFDM- based multi-pair two-way relay wireless networks

To improve multi-pair two-way relay wideband wireless networks using orthogonal frequency-division multiplexing, this paper proposes a space-frequency (SF) joint channel pairing (CP) that maximizes the sum-rate (MSR) after block diagonalization beamforming at a relay station (RS). Following this, a space-frequency (SF) joint water lling power allocation (WFPA) is designed to further improve the performance of the system. Simula- tion results illustrate that, compared to space channel pairing without CP, the proposed MSR-SFCP can achieve substantial performance gains, including improvements in the sum-rate and bit error rate (BER) for a given signal-to-noise ratio (SNR). In contrast, the SF-WFPA can improve BER performance in the low and medium SNR regimes, compared to equal power allocation.

Integer-linear-programing optimization in scalable video multicast with adaptive modulation and coding in wireless networks.

The advancement in wideband wireless network supports real time services such as IPTV and live video streaming. However, because of the sharing nature of the wireless medium, efficient resource allocation has been studied to achieve a high level of acceptability and proliferation of wireless multimedia. Scalable video coding (SVC) with adaptive modulation and coding (AMC) provides an excellent solution for wireless video streaming. By assigning different modulation and coding schemes (MCSs) to video layers, SVC can provide good video quality to users in good channel conditions and also basic video quality to users in bad channel conditions. For optimal resource allocation, a key issue in applying SVC in the wireless multicast service is how to assign MCSs and the time resources to each SVC layer in the heterogeneous channel condition. We formulate this problem with integer linear programming (ILP) and provide numerical results to show the performance under 802.16 m environment. The result shows that our methodology enhances the overall system throughput compared to an existing algorithm.

Theoretical analysis and simulation of a code division multiple access system (CDMA) for secure signal transmission in wideband channels

Theoretical analysis and simulation of a code division multiple access system (CDMA) for secure signal transmission in wideband channels

Fundamental Limits of Wideband Localization— Part I: A General Framework

The availability of position information is of great importance in many commercial, public safety, and military applications. The coming years will see the emergence of location-aware networks with submeter accuracy, relying on accurate range measurements provided by wide bandwidth transmissions. In this two-part paper, we determine the fundamental limits of localization accuracy of wideband wireless networks in harsh multipath environments. We first develop a general framework to characterize the localization accuracy of a given node here and then extend our analysis to cooperative location-aware networks in Part II. In this paper, we characterize localization accuracy in terms of a performance measure called the squared position error bound (SPEB), and introduce the notion of equivalent Fisher information (EFI) to derive the SPEB in a succinct expression. This methodology provides insights into the essence of the localization problem by unifying localization information from individual anchors and that from a priori knowledge of the agent's position in a canonical form. Our analysis begins with the received waveforms themselves rather than utilizing only the signal metrics extracted from these waveforms, such as time-of-arrival and received signal strength. Hence, our framework exploits all the information inherent in the received waveforms, and the resulting SPEB serves as a fundamental limit of localization accuracy.

A Jump Markov Particle Filter for Localization of Moving Terminals in Multipath Indoor Scenarios

This correspondence describes an efficient Bayesian framework for localization of moving terminals (MTs) in wideband wireless networks. In a previous paper, the authors have presented a grid-based technique, based on a hidden Markov model, that used the power delay profiles of the received signals to track the MT position. This grid-based Bayesian method has proved its efficacy in reducing localization errors in realistic indoor environments with multipath effects and mixed line-of-sight/non-line-of-sight (LOS/NLOS) conditions. However, the computational power and the memory storage requirements limit its use in practical wireless networks. To improve the computational efficiency, here we propose a jump-Markov particle-filter approach as an extension of the previous work; the LOS/NLOS sight process is the jumping feature that drives the MT motion dynamics, while the particle filter is used to track the MT position. Performance analyses, carried out for realistic multipath indoor environments, show that, with respect to the previous grid-based algorithm, this novel approach greatly reduces the tracking filter complexity still preserving the same localization accuracy. Simulation results prove also the robustness of the proposed method with respect to the uncertainty of sight statistics information.

Distributed Consensus Over Wireless Sensor Networks Affected by Multipath Fading

The design of sensor networks capable of reaching a consensus on a globally optimal decision test, without the need for a fusion center, is a problem that has received considerable attention in the last years. Many consensus algorithms have been proposed, with convergence conditions depending on the graph describing the interaction among the nodes. In most works, the graph is undirected and there are no propagation delays. Only recently, the analysis has been extended to consensus algorithms incorporating propagation delays. In this correspondence, we propose a consensus algorithm able to converge to a globally optimal decision statistic, using a wideband wireless network, governed by a fairly simple MAC mechanism, where each link is a multipath, frequency-selective, channel. The main contribution of the correspondence is to derive necessary and sufficient conditions on the network topology and sufficient conditions on the channel transfer functions guaranteeing the exponential convergence of the consensus algorithm to a globally optimal decision value, for any bounded delay condition.

Clear channel assessment in energyconstrained wideband wireless networks

This is intended as a tutorial review of the clear channel assessment (CCA) component of typical data link layers in wideband wireless networks that employ some form of channel sensing as part of their medium access mechanism. While channel sensing - the core component within CCA module - is implemented at the physical layer, its primary impact is on MAC throughput and energy efficiency, and this impact has not yet been adequately highlighted in the existing literature. We provide a description of CCA methods for wideband wireless networks like IEEE 802.11 and IEEE 802.15 followed by illustrations of their impact on the respective MAC protocols. We also demonstrate the need for a cross-layer consideration of MAC and CCA to optimize the performance of CSMA protocols.

Efficient MIMO channel estimation for linear precoded OFDMA uplink systems

A novel and simple uplink MIMO channel estimation technique based on spread pilots well suited to LP OFDMA schemes is proposed. The combination with Alamouti code is studied and two different approaches are compared. The performance evaluated over a realistic MIMO channel shows the efficiency of this novel scheme, which appears to be a promising channel estimation for the uplink of future wideband wireless networks.

MIMO Frequency Hopping Spread Spectrum Multi-Carrier Multiple Access: A Novel Uplink System for B3G Cellular Networks

In this paper, we propose and give the performance of a novel uplink system based on the combination of multi-carrier (MC), code division multiple access (CDMA) and multiple input multiple output (MIMO) techniques. First, we describe the interests of spread-spectrum multi-carrier multiple access (SS-MC-MA) scheme for uplink, especially compared to MC-CDMA. Classically, with SS-MC-MA, each user spreads its data symbols on a specific subset of adjacent or multiplexed subcarriers, to facilitate the channel estimation and reduce complexity at the reception. In order to compensate for the lack of frequency diversity of SS-MC-MA with adjacent subcarriers, we first combine it with an orthogonal space-time block code (STBC) and demonstrate the resulting spatial diversity gain. Then, we propose to allocate the subsets to the different users by applying a frequency hopping pattern (FH). In that case, each user benefits from the frequency diversity linked to the total bandwidth as with the multiplexed subcarriers solution, while keeping the advantages of the adjacent subcarriers solution. The gain provided by the use of the frequency hopping is stressed on. Finally, the performance of this scheme is evaluated over realistic MIMO channel with channel turbo coding for systems offering asymptotic spectrum efficiency of 1, 2, 3 and 4.5 bit/s/Hz. Thus, the efficiency of the novel proposed STBC FH SS-MC-MA system as a very promising multiple access and modulation scheme for the uplink of the future wideband wireless networks is successfully demonstrated.

Modeling Telecommunication Infrastructures Integrating Wideband Wireless and Wired Networks

Future telecommunication systems will integrate wireline and wireless networks in a single, advanced infrastructure. It is expected that such systems, in the wireless part, will exploit microcellular architectures in order to guarantee wideband multimedia services and to sustain the continuous growth of subscribers. In such a context, asynchronous transfer mode and Internet protocol are the basic technologies being considered by several studies and field implementations. In both cases, particular care has been devoted to cope with a large number of handoffs. This article considers some aspects of this integrated telecommunication infrastructure, proposing an improvement, for the wired part, of the virtual connection tree and shadow cluster concepts, whereas for the wireless part, a new model for the analysis of a dynamic channel allocation scheme is presented. The obtained analytical results, confirmed by simulation in a wide range of load conditions and user mobility, allow one to evaluate the main system performance parameters in terms of blocking probability of new calls, handoff-blocking probability, and forced termination probability.