Non-interfering Channels Research Articles

Multi-frequency complete optical isolation based on indirect interband transition

Indirect interband photonic transition is an important approach to achieve on-chip complete optical signal isolation. We demonstrate that the operational isolation bandwidth based on this effect can be increased by utilizing non-interfering transition channels obtained from the process of transition channel engineering. Multiple optical modes can be excited through non-interfering channels and be absorbed by matched filters without interfering with each other, thus achieving multi-frequency complete optical isolation. With two non-interfering transition channels, an optical isolator design that achieves complete isolation at two frequencies is proposed as an example. The potential design of multi-frequency isolator is also discussed. All the results are verified with finite-difference time-domain simulation.

Emergent reliability in sensory cortical coding and inter-area communication.

Reliable sensory discrimination must arise from high-fidelity neural representations and communication between brain areas. However, how neocortical sensory processing overcomes the substantialvariability of neuronal sensory responses remains undetermined1-6. Here we imaged neuronalactivity in eight neocortical areas concurrently and over five days in mice performing a visual discrimination task, yielding longitudinal recordings of more than 21,000 neurons. Analyses revealed a sequence of events across the neocortex starting from a resting state, to early stages of perception, and through the formation of a task response. At rest, the neocortex had one pattern of functional connections, identified through sets of areas that shared activity cofluctuations7,8. Within about 200 ms after the onset of the sensory stimulus, such connections rearranged, with different areas sharing cofluctuations and task-related information. During this short-lived state(approximately 300 ms duration), bothinter-area sensory data transmission and the redundancy of sensory encoding peaked, reflecting a transient increase in correlated fluctuations among task-related neurons. By around 0.5 s after stimulus onset, thevisual representation reached a more stable form, the structure of which was robust to the prominent, day-to-day variations in the responses of individual cells. About 1 s into stimulus presentation, a global fluctuation mode conveyed the upcoming response of the mouse to every area examined and was orthogonal to modes carrying sensory data. Overall, the neocortex supports sensory performance through brief elevations in sensory coding redundancynear the start of perception, neural populationcodes that are robust to cellular variability, and widespreadinter-area fluctuation modes that transmit sensory data and task responses in non-interfering channels.

Optimal Power Allocation for Multiple Channels With One-Bit Analog-to-Digital Converters

In this study, an optimal power allocation over multiple noninterfering channels is derived for the case in which each channel uses two separate one-bit analog-to-digital converters for the real and imaginary parts respectively of the complex received signal. The optimization problem is formulated to determine the optimal transmit power allocation over multiple channels that maximizes the sum capacity. The solution of the optimization problem is explicitly determined by exploiting the Karush-Kuhn-Tucker conditions. The essential strategy for optimal power allocation is described with the corresponding mathematical results. Simulation results demonstrate that the derived power allocation is indeed optimal, as expected, and it achieves a significant gain compared to the case where an appropriate power allocation has not been used.

Optimal power allocation for the multiple-sensor single-DF relay based IoT networks under transceiver hardware impairments

Accurate system modeling is a crucial requirement while realizing efficient and reliable communication over Internet of Things (IoT) infrastructure. The assumption of ideal hardware causes huge deviation in the performance of systems as estimated from such theoretical models and their practical implementations. In this paper, we study this fact over N pairs of source and destination IoT devices/nodes having non-interfering channels with a half-duplex decode-and-forward relay node. The relay assists the communication between N source–destination pairs. Specifically, we first derive the outage probability expression for the considered system with transceiver hardware impairments under independent but not identically distributed Rayleigh fading channels. Then, taking the transceiver hardware impairments and power and outage constraints into account, we formulate and investigate an optimal power allocation strategy in order to minimize the source-sum-power consumption using Karush–Kuhn–Tucker (KKT) conditions. With the aid of numerical investigations, the optimality of the proposed strategy is illustrated. It is observed that the power consumption depends on the number of sources and increases with the increased number of sources. In addition, the transceiver hardware impairments have detrimental impacts on the source-sum-power consumption of the considered system. Our results also reveal that the proposed scheme outperforms the uniform power allocation scheme for various involved parameters.

Traffic-predictive QoS on-demand routing for multi-channel mobile ad hoc networks

Mobile multimedia applications have recently attracted numerous interests in mobile ad hoc networks (MANETs) supporting quality-of-service (QoS) communications. Multiple non-interfering channels are available in 802.11- and 802.15-based wireless networks. Channel assignment depends on the available bandwidth at involved nodes and the bandwidth consumption required by a new flow. Predicting available bandwidth of a node in wireless networks is challenging due to the shared and open nature of the wireless channel. This paper proposes a traffic-predictive QoS on-demand routing(TPQOR) protocol to support QoS bandwidth and delay requirements. A distributed channel assignment scheme and routing discovery process are presented to support multimedia communication and to satisfy QoS bandwidth requirement. The proposed channel assignment and reuse schemes can reduce the channel interference and enhance channel reuse rate. The proposed bandwidth prediction scheme can estimate the bandwidth requirement of each node for future traffic by the history information of its channel usage. Unlike many existing routing protocols, we take the traffic prediction as an important factor in route selection. The simulation results show that TPQOR protocol can effectively increase throughput, reduce loss ratio as well as delay, and avoid the influences of future interference flows, as compared to AODV protocol for a different number of channels.

A Novel Spectrally Efficient Asynchronous Multi-Channel MAC Using a Half-Duplex Transceiver for Wireless Networks

Multi-channel medium access control (MAC) protocols maximize network performance by enabling concurrent wireless transmissions over non-interfering channels. Despite physical layer advancements, the underlying IEEE 802.11 MAC standard cannot fully exploit features and support high-performance applications. In this work, we propose the novel spectrally efficient asynchronous multi-channel MAC (SA-MMAC) protocol for wireless networks using a single half-duplex transceiver. A full-duplex mode of operation on data channels reduces the signaling overhead and boosts the spectrum efficiency. A revamped contention mechanism of IEEE 802.11 addresses the multi-channel hidden terminal problem, and a jamming signal from the receiver addresses the collisions in control signals. Furthermore, the control channel is used for data transmissions to increase the bandwidth utilization but under a restricted half-duplex mode to avoid causing a bottleneck situation. The simulator is tested for correctness. The results suggest that the protocol can work well on 3, 4, or 12 concurrent channels with high node density, providing about 12.5 times more throughput than IEEE 802.11 and 18% to 95% more throughput than its multi-channel variants under saturated traffic conditions.

A QoS Routing Protocol with Bandwidth Allocation in Multichannel Ad Hoc Networks

Mobile multimedia applications have recently generated much interest in mobile ad hoc networks (MANETs) supporting quality-of-service (QoS) communications. Multiple non-interfering channels are available in 802.11 and 802.15 based wireless networks. Capacity of such channels can be combined to achieve higher QoS performance than for single channel networks. The capacity of MANETs can be substantially increased by equipping each network node with multiple interfaces that can operate on multiple non-overlapping channels. However, new scheduling, channel assignment, and routing protocols are required to utilize the increased bandwidth in multichannel MANETs. In this paper, we propose an on-demand routing protocol M-QoS-AODV in multichannel MANETs that incorporates a distributed channel assignment scheme and routing discovery process to support multimedia communication and to satisfy QoS bandwidth requirement. The proposed channel assignment scheme can efficiently express the channel usage and interference information within a certain range, which reduces interference and enhances channel reuse rate. This cross-layer design approach can significantly improve the performance of multichannel MANETs over existing routing algorithms. Simulation results show that the proposed M-QoS-AODV protocol can effectively increase throughput and reduce delay, as compared to AODV and M-AODV-R protocols.

Decentralized Constraint Satisfaction

We show that several important resource allocation problems in wireless networks fit within the common framework of constraint satisfaction problems (CSPs). Inspired by the requirements of these applications, where variables are located at distinct network devices that may not be able to communicate but may interfere, we define natural criteria that a CSP solver must possess in order to be practical. We term these algorithms decentralized CSP solvers. The best known CSP solvers were designed for centralized problems and do not meet these criteria. We introduce a stochastic decentralized CSP solver, proving that it will find a solution in almost surely finite time, should one exist, and also showing it has many practically desirable properties. We benchmark the algorithm's performance on a well-studied class of CSPs, random k-SAT, illustrating that the time the algorithm takes to find a satisfying assignment is competitive with stochastic centralized solvers on problems with order a thousand variables despite its decentralized nature. We demonstrate the solver's practical utility for the problems that motivated its introduction by using it to find a noninterfering channel allocation for a network formed from data from downtown Manhattan.

A gating mechanism for border node assisted association of wireless personal area networks

IEEE 802.15.4 based Wireless Personal Area Networks (WPANs) are envisioned to play a vital role in the application centric ubiquitous networks. In IEEE802.15.4 networks, the use of non-interfering logical channels in multiple PANs, operating in a Personal Operating Space (POS) ensures to control the scope of PAN-directed broadcasts, reduce received energy per PAN device, and minimize interference at the physical layer. At the downside the inter-PAN communication is not possible with this setup as PANs in the same region remain unaware of each other’s presence. This situation hinders sharing information of common interest amongst PANs and accessing infrastructure networks hopping through multiple PANs. In this paper, we present a comprehensive architecture enables neighboring PANs to communicate by diffusing into each other through border nodes. The basic idea is to time share logical channels to perform a gating operation by border nodes. Our contribution includes detection of border nodes, discovery of neighboring PAN(s), a common channel based gating protocol, interest diffusion and inter-PAN data transfer. We mathematically analyze the proposed architecture and carry out simulations in Network Simulator (ns2) for performance evaluation. Our simulations show that the proposed architecture gives optimal performance when multiple border nodes are able to perform gating.Electronic supplementary materialThe online version of this article (doi:10.1186/2193-1801-1-12) contains supplementary material, which is available to authorized users.

Joint Design of Precoder and Power Allocation for Downlink Multi-Cell Multi-User Wireless Systems with Interference Alignment

In the paper, we propose a joint design of precoder and power allocation for downlink multi-cell multi-user wireless systems with interference alignment (IA). This non-iterative method is decomposed into two separate steps. First, we design the precoding and decoding matrices using IA, fully eliminating the interference between the effective channels. Then, on the basis of the pre-canceling, each base station performs equal power allocation among different users and adopts a joint optimization of precoding matrix and power allocation to maximize the information rate of the corresponding noninterfering effective channel. Meanwhile, we present the corresponding detection method for each noninterfering effective channel. It is analytically shown that the proposed IA scheme exploits less antenna resources than the search IA scheme does to achieve the same degrees of freedom. Moreover, the simulation results demonstrate that the proposed IA scheme shows better performance than the original IA scheme.

Design and evaluation of a fast MAC layer handoff management scheme for WiFi-based multichannel Vehicular Mesh Networks

Vehicular Mesh Networks (VMNs) are important components of the wireless metropolitan networks. Compared with traditional wireless networks, they are more efficient in terms of deployment, configuration, and maintenance. However, connecting all mesh routers through wireless connection in VMNs results in the network backbone's remarkably lower bandwidth. Multichannel technology, where non-interfering channels are used to enable mesh routers to send and receive packets simultaneously, can be adopted to improve the throughput of VMNs. Due to the limited radio range of mesh routers, mobile clients have to switch among different mesh routers to maintain wireless connections. Therefore, providing smooth roaming in multichannel VMNs has become an important topic in VMN research. In this paper, a novel MAC layer handoff scheme is proposed as a means of minimizing handoff latency for WiFi-based multichannel VMNs to provide smooth communication for real-time applications. By designing a dynamic grouping algorithm for channel selection and allowing mesh routers to switch their channels for probe response messages, our scheme can shorten the waiting time for the detection of available access routers, decrease the loss ratio of data packets during the handoff, and consequently achieve smooth handoff in the MAC layer.

Bandwidth provisioning in infrastructure-based wireless networks employing directional antennas

Motivated by the widespread proliferation of wireless networks employing directional antennas, we study the problem of provisioning bandwidth in such networks. Given a set of subscribers and one or more access points possessing directional antennas, we formalize the problem of orienting these antennas in two fundamental settings: (i) subscriber-centric, where the objective is to fairly allocate bandwidth among the subscribers and (ii) provider-centric, where the objective is to maximize the revenue generated by satisfying the bandwidth requirements of subscribers. For both the problems, we first design algorithms for a network with only one access point working under the assumption that the number of antennas does not exceed the number of non-interfering channels. Using the well-regarded lexicographic max–min fair allocation as the objective for a subscriber-centric network, we present a dynamic programming algorithm that achieves the fairest allocation. For a provider-centric network, the allocation problem turns out to be NP-hard. We present a greedy heuristic-based algorithm that guarantees almost half of the optimum revenue. We later enhance both these algorithms to operate in more general networks with multiple access points and no restrictions on the relative numbers of antennas and channels. A simulation-based evaluation using OPNET demonstrates the efficacy of our approaches and provides us further insights into these problems.

MIMO Gaussian Channels With Arbitrary Inputs: Optimal Precoding and Power Allocation

In this paper, we investigate the linear precoding and power allocation policies that maximize the mutual information for general multiple-input-multiple-output (MIMO) Gaussian channels with arbitrary input distributions, by capitalizing on the relationship between mutual information and minimum mean-square error (MMSE). The optimal linear precoder satisfies a fixed-point equation as a function of the channel and the input constellation. For non-Gaussian inputs, a nondiagonal precoding matrix in general increases the information transmission rate, even for parallel noninteracting channels. Whenever precoding is precluded, the optimal power allocation policy also satisfies a fixed-point equation; we put forth a generalization of the mercury/waterfilling algorithm, previously proposed for parallel noninterfering channels, in which the mercury level accounts not only for the non-Gaussian input distributions, but also for the interference among inputs.

Limits of Multicasting in a Packet-Switched WDM Single-Hop Local Lightwave Network

Wavelength division multiplexing (WDM) is a technique used to divide the tremendous optical bandwidth of a fiber into many non-interfering channels. A WDM single-hop local lightwave network can be designed by using two-way fibers to connect every node to a passive star coupler, and equipping the nodes with tunable transmitters and/or receivers. The passive star broadcasts data transmitted on each wavelength channel to all nodes in the system. This type of network, known as broadcast and select, is naturally suited to multicasting; every node in the network has the opportunity to receive any particular packet. In this study, we show how multicasting in a broadcast and select environment can dramatically increase the throughput of the network. Using a Markov model and a simulation, we show that multicasting significantly improves the limiting performance of both small and large networks, especially when each node is equipped with multiple receivers.

Joint optimisation of transmitter and receiver for digital transmission over multiple-channel systems

The optimum linear multiple transmitting and receiving filters are determined for noisy multiple-channel systems using a criterion of minimum output noise variance under the constraints of zero intersymbol interference (ISI) and interchannel interference and of fixed transmitting power. The optimum transmitter appears to generate orthogonal vector functions. For these vector functions the cascade connection of the multiple channel and its multiple matched filter behaves like noninterfering channels (NIC). In the optimum system the ISI is eliminated per NIC by a transversal filter.