Non-uniform Bandwidth Research Articles

A Fixed Rate Speech Coder Based on the Filter Bank Method with Non-Uniform Bandwidths

A Fixed Rate Speech Coder Based on the Filter Bank Method with Non-Uniform Bandwidths

Bandwidth partition and allocation for efficient spectrum utilization in cognitive communications

Conventional cognitive communications rely heavily on the smartness of secondary (unlicensed) users (SUs) to achieve high spectrum utilization, which involves the optimization of the SUs' policies and behaviors for dynamic spectrum access, power allocation among multiple channels, etc. Due to the inherent randomness of the primary users' (PUs') transmission, those efforts inevitably increase the implementation complexity and sensing overheads of the SUs, and in turn lower the spectrum utilization efficiency. In this paper, we try to change the focus from SU to PU. A cooperative traffic allocation strategy for PU, together with the non-uniform bandwidth partition, is employed to regularize the PU's resource occupancy pattern without compromising its performance, and to maximize the spare bandwidth for the SU at the same time. We first study the capacity based optimization problem (COP) together with the fully polynomial time approximation scheme (FPTAS) for an approximation guarantee of the global optimum. Then we analyze the subcarrier based optimization problem as the surrogate problem of COP, which can be solved by a greedy algorithm exactly. Both the theoretical analysis and the numerical simulations demonstrate the effectiveness of those methods to achieve the performance that almost identical to that of the global optimum solution.

Optimizing Non-Uniform Bandwidth Reservation Based on Meter Table of Openflow

Optimizing Non-Uniform Bandwidth Reservation Based on Meter Table of Openflow

Nonuniform bandwidth reservation for tunnels in MPLS network using meter tables of OpenFlow

AbstractResource reservation protocol‐traffic engineering (RSVP‐TE) is one of the most widely used technologies to construct multiprotocol label switching tunnels across wide area network. In RSVP‐TE, along the path selected by the constrained shortest path first algorithm, resource is allocated using RSVP at each hop to provide deterministic end‐to‐end service quality, such as rate, delay, packet loss, and jitter. However, we argue that the flat and uniform bandwidth reservation mechanism of RSVP, which reserves the same bandwidth at each hop along the tunnel, ignore the difference of available bandwidth of these links, resulting in that the bandwidth of some congested links are quickly exhausted, whereas other links are not fully utilized. To further improve the load balancing and resource utilization of the network, a nonuniform bandwidth reservation (NUBR) method is proposed in this paper. With the proposed method, each node along the tunnel can flexibly reserve different bandwidth according to its own available resources. Thus, the reserved bandwidth at the congested links can be decreased by aggressively overreserving at idle links. In this paper, we introduce the concept of NUBR and explore the implementation based on the meter table of OpenFlow. The mathematical models and algorithms of NUBR have been studied under 2 application scenarios. At last, the simulation results show that the proposed method can allow more multiprotocol label switching tunnels than the traditional uniform bandwidth reservation method.

Cognitive wideband spectrum sensing using cosine-modulated filter banks

A multichannel joint spectrum sensing strategy based on cosine-modulated filter banks (CMFBs) was developed to improve sensing efficiency. The received wideband signal was split into several bands through the filters that are constructed by grouping continuous sub-band filters. Through flexibly designing prototype filter, not only the spectrum of non-uniform bandwidth can be estimated, but also the spectral leakage between adjacent channels can be adjusted. The probabilities of false alarm and detection for multichannel jointly spectrum sensing in the Rayleigh fading channel were deduced. The decision thresholds of different channels were obtained as regards the probability of false alarm. Simulation results show that compared with the traditional energy detector, the detection capability and sensing efficiency have been improved, especially at low signal-to-noise ratio. The CMFB-based multichannel joint sensing scheme not only increases the efficiency of detection, but also enhances the flexibility on the control of bandwidth and spectral leakage between neighbouring channels.

Improving the Cognitive Access Efficiency by Non-Uniform Bandwidth Allocation

In cognitive communication, dynamic sensing and opportunistic access enable secondary users to recognize and utilize the white spaces of the licensed bandwidth. Most present efforts focus on designing smarter channel sensing and access algorithms for secondary users, with the aim of optimizing the overall throughput and bandwidth utilization efficiency, under the condition of not interfering with primary users' communication. However, as the transmissions of the primary users are inherently random and unpredictable, sensing and sharing spectrum with the primary users inevitably make the cognitive process of the secondary users complex and ineffective. In this paper, a non-uniform bandwidth allocation scheme is proposed that regularizes the primary users' bandwidth occupancy pattern. The regularization is not designed to reshape the primary users's traffic, but to improve the sensing efficiency and throughput of the secondary users by optimizing the spectrum allocation. After the description of the new allocation scheme, we demonstrate its performance by theoretic analysis. Then we verify the validity of the non-uniform scheme with numerical simulations under non-fading and fading situations respectively. Through comparisons with the conventional uniform bandwidth allocation scheme, the non-uniform one shows higher sensing efficiency and better spectrum utilization due to lower sensing cost and reduced bandwidth loss.

Analysis and Design of Efficient and Flexible Fast-Convolution Based Multirate Filter Banks

In this paper, we investigate fast-convolution based highly tunable multirate filter bank (FB) configurations. Based on FFT-IFFT pair with overlapped processing, they offer a way to tune the filters' frequency-domain characteristics in a straightforward way. Different subbands are easily configurable for different bandwidths, center frequencies, and output sampling rates, including also partial or full-band nearly perfect-reconstruction systems. Such FBs find various applications, for example, as flexible multichannel channelization filters for software defined radios. They have also the capability to implement simultaneous waveform processing for multiple single-carrier and/or multicarrier transmission channels with nonuniform bandwidths and subchannel spacings. This paper develops an effective model for frequency response analysis and optimization for such filter banks, explores various practical issues of fast-convolution processing and reports the optimized frequency response characteristics versus direct raised cosine based designs. The fast-convolution approach is shown to be a competitive basis for filter bank based multicarrier waveform processing in terms of spectral containment and complexity.

Reconfigurable Low Area Complexity Filter Bank Architecture Based on Frequency Response Masking for Nonuniform Channelization in Software Radio Receivers

The most computationally demanding block in the digital front-end of a software defined radio (SDR) receiver is the channelizer which operates at the highest sampling rate. Channelizers are employed in the SDR receivers for extracting individual channels (frequency bands) from the digitized wideband input signal. Reconfigurability and low complexity are the two key requirements in an SDR channelizer. A new reconfigurable filter bank (FB) architecture based on frequency response masking (FRM) for SDR channelizers is proposed. The proposed FB offers reconfigurability at the architectural level and at the channel filter level and is capable of extracting channels of nonuniform bandwidths corresponding to multiple wireless communication standards from the digitized wideband input signal. Design examples show that the proposed FB offers multiplier complexity reduction of 84% over the conventional per-channel (PC) approach, which is best suitable for the extraction of channels of nonuniform bandwidth. The proposed FB has been synthesized on 0.18 μm complementary metal oxide semiconductor (CMOS) technology and compared with the PC approach. Synthesis results show that the proposed FB offers area reduction of 85%, power reduction of 48.5%, and improvement in speed of 56.7% over the PC approach. The proposed FB has been implemented on Xilinx Virtex 2v3000ff1152-4 FPGA and tested using real-time inputs from a vector signal generator.

An Area-efficient Non-uniform Filter Bank for Low Overhead Reconfiguration of Multi-standard Software Radio Channelizers

The channelizer in a software defined radio (SDR) base station extracts individual radio channels from the digitized wideband input signal at a very high sampling rate. The base station channelizer must be able to simultaneously extract multiple channels of non-uniform bandwidths corresponding to channel bandwidths of different communication standards. Reconfigurability and low complexity are the two key requirements in the SDR channelizer. A new reconfigurable filter bank (FB) architecture based on interpolation and masking technique for SDR channelizers is proposed in this paper. The proposed FB can be used for obtaining very narrow passband channels with extremely low complexity. Using a cascaded structure of the proposed FB, it is possible to extract channels of fractional passband widths by changing the interpolation factor. Design example shows that the proposed FB offers complexity reduction of 84% over the conventional per-channel (PC) approach. The proposed FB has been implemented and tested on Xilinx Virtex 2v3000ff1152-4 FPGA. Implementation results show that the proposed FB offers area reduction of 48.37%, speed improvement of 52.7% and power reduction of 75.9% over the PC approach.

Online Controller Area Network message scheduling: analysis, implementation and applications

Message scheduling is a critical research issue in the Controller Area Network (CAN). Messages that fail to meet predefined deadlines may deteriorate system performance significantly. In this paper, we propose an online Message-Scheduling Controller (MSC), which is realised by the Radial Basis Function (RBF) network. The MSC exploits two novel learning algorithms to adaptively tune its internal parameters. The learning algorithms provide complementary effects to prevent possible causes of non-uniform bandwidth allocation among requesting messages and to reduce possibilities of Transmission Failures (TFs). Simulation results show that the proposed algorithm outperforms the existing scheduling methods.

A scalable, commodity data center network architecture

Today's data centers may contain tens of thousands of computers with significant aggregate bandwidth requirements. The network architecture typically consists of a tree of routing and switching elements with progressively more specialized and expensive equipment moving up the network hierarchy. Unfortunately, even when deploying the highest-end IP switches/routers, resulting topologies may only support 50% of the aggregate bandwidth available at the edge of the network, while still incurring tremendous cost. Non-uniform bandwidth among data center nodes complicates application design and limits overall system performance.In this paper, we show how to leverage largely commodity Ethernet switches to support the full aggregate bandwidth of clusters consisting of tens of thousands of elements. Similar to how clusters of commodity computers have largely replaced more specialized SMPs and MPPs, we argue that appropriately architected and interconnected commodity switches may deliver more performance at less cost than available from today's higher-end solutions. Our approach requires no modifications to the end host network interface, operating system, or applications; critically, it is fully backward compatible with Ethernet, IP, and TCP.

Design of Nonuniform Filter Bank Transceivers for Frequency Selective Channels

In recent years, there has been considerable interest in the theory and design of filter bank transceivers due to their superior frequency response. In many applications, it is desired to have transceivers that can support multiple services with different incoming data rates and different quality-of-service requirements. To meet these requirements, we can either do resource allocation or design transceivers with a nonuniform bandwidth partition. In this paper, we propose a method for the design of nonuniform filter bank transceivers for frequency selective channels. Both frequency response and signal-to-interference ratio (SIR) can be incorporated in the transceiver design. Moreover, the technique can be extended to the case of nonuniform filter bank transceivers with rational sampling factors. Simulation results show that nonuniform filter bank transceivers with good filter responses as well as high SIR can be obtained by the proposed design method.

DQDB/sup +/-/: a fair and waste-free media access protocol for dual bus metropolitan networks

A media access protocol that achieves a fair distribution of the bandwidth in one round-trip delay is presented. The protocol is based on a unique solution to a fair and waste-free bandwidth allocation. This bandwidth allocation can be implemented in a distributed manner. A comparison of the new protocol with the DQDB (distributed queue dual bus) protocol shows considerable advantages regarding the transmission delay of messages and the time a station needs to obtain a fair portion of the available bandwidth. The advantages of the protocol become more apparent for large networks and high transmission speeds. In addition, the new protocol can perform nonuniform bandwidth allocations. >

A contribution to the theory of short-time spectral analysis with nonuniform bandwidth filters

The mathematical representation of the short-time spectral analysis is extended from the case of uniform bandpass filters (that is, filters having the same complex envelope) to the case of nonuniform filters (that is, filters whose complex envelope depends upon their center frequency). This leads to an integral transform, formally similar to the Fourier transform, where the signal taken up to the observation time appears weighted by a function (namely, the complex envelope) depending on the frequency of analysis. Of course, for every choice of such a complex envelope (or of the equivalent set of filters), one has a corresponding integral transform to deal with. The particular case of complex envelopes as functions of the time-frequency product is studied here because of its great physical interest (it applies, for instance, to many existing real-time audio analyzers). The corresponding integral transform is shown to have two remarkable properties: 1) it admits an inverse integral transform; 2) it is form invariant under linear time scaling of the signal, and no other integral transform (that is, no other class of complex envelopes, even frequency independent) shares this property. The physical significance of such results is discussed, together with some ideas for applications and further theoretical work.