Design and implementation of multiplier-less tunable 2-D FIR filters using McClellan transformation

This paper proposes new structures for realizing tunable 2-D fan and elliptical filters with different spectral characteristics using McClellan transformation. The 1-D prototype is a variable digital filter obtained from the interpolation of a set of desirable impulse responses and is implemented using the Farrow structure. The coefficients of the sub-filters and the transformation parameters in the Farrow structure are represented in SOPOT, which can be easily implemented as simple shift-and-add operations. Furthermore, the transformation part can be shared between the sub-filters leading to significant saving in hardware complexity. Several design examples are given to demonstrate the effectiveness and feasibility of the proposed approach.published_or_final_versio

The design and multiplier-less realization of software radio receivers with reduced system delay

This paper studies the design and multiplier-less realization of a new software radio receiver (SRR) with reduced system delay. It employs low-delay finite-impulse response (FIR) and digital allpass filters to effectively reduce the system delay of the multistage decimators in SRRs. The optimal least-square and minimax designs of these low-delay FIR and allpass-based filters are formulated as a semidefinite programming (SDP) problem, which allows zero magnitude constraint at ω = π to be incorporated readily as additional linear matrix inequalities (LMIs). By implementing the sampling rate converter (SRC) using a variable digital filter (VDF) immediately after the integer decimators, the needs for an expensive programmable FIR filter in the traditional SRR is avoided. A new method for the optimal minimax design of this VDF-based SRC using SDP is also proposed and compared with traditional weight least squares method. Other implementation issues including the multiplier-less and digital signal processor (DSP) realizations of the SRR and the generation of the clock signal in the SRC are also studied. Design results show that the system delay and implementation complexities (especially in terms of high-speed variable multipliers) of the proposed architecture are considerably reduced as compared with conventional approaches. © 2004 IEEE.published_or_final_versio

Performance analysis of burst segmentation schemes supporting multiple traffic classes

Optical burst switching (OBS) with the support of multiple traffic classes is an important topic. Assuming traffic classes are maintained via choosing different offset times, a new OBS scheme called optical burst switching with burst splitting (OBSS) is proposed in this paper. OBSS provides high system throughput by taking advantages of the idle gaps on output wavelength channels when the Just-Enough-Time (JET) reservation scheme is used. Then an analytical model that supports N traffic classes is constructed and verified by simulations. The proposed model can be applied to the conventional OBS schemes as well as the OBSS scheme we proposed. Numerical results show that in our OBSS scheme, traffic classes can be effectively maintained via different offset times, and the packet loss probability is also much smaller than the conventional OBS. It is interesting to find that the choice of offset time for a specific traffic class affects the packet loss probabilities of classes higher than it, while the impact to classes below it is much smaller. © 2005 IEEE.published_or_final_versio

On the design and multiplier-less realization of digital IF for software radio receivers with prescribed output accuracy

This paper studies the design and multiplier-less realization of the digital IF in software radio receivers. The new architecture consists of a compensator for compensating the passband droop of the conventional cascaded integrator and comb (CIC) filter. The passband droop is improved by a factor of four and it can be implemented with four additions using the sum-of-powers-of-two (SOPOT) coefficients. The decimation factor of the multistage decimator is also reduced so that its output can be fed directly to the Farrow structure for sample rate conversion (SRC), eliminating the need for another L-band filter for upsampling. By so doing, the programmable FIR filter can be replaced by a half-band filter placed immediately after the Farrow structure. As the coefficients of this half-band filter, the multistage decimators and the subfilters in the Farrow structure are constants, they can be implemented without multiplication using SOPOT coefficients. As a result, apart from the limited number of multipliers required in the Farrow structure, the entire digital IF can be implemented without any multiplications. A random search algorithm is employed to minimize the hardware complexities of the proposed IF subject to a given specification in the frequency domain and prescribed output accuracy, taking into account signal overflow and round-off noise. Design results are given to demonstrate the effectiveness of the proposed method.published_or_final_versio

On the design and multiplierless realization of perfect reconstruction triplet-based FIR filter banks and wavelet bases

This paper proposes new methods for the efficient design and realization of perfect reconstruction (PR) two-channel finite-impulse response (FIR) triplet filter banks (FBs) and wavelet bases. It extends the linear-phase FIR triplet FBs of Ansari et al. to include FIR triplet FBs with lower system delay and a prescribed order of K regularity. The design problem using either the minimax error or least-squares criteria is formulated as a semidefinite programming problem, which is a very flexible framework to incorporate linear and convex quadratic constraints. The K regularity conditions are also expressed as a set of linear equality constraints in the variables to be optimized and they are structurally imposed into the design problem by eliminating the redundant variables. The design method is applicable to linear-phase as well as low-delay triplet FBs. Design examples are given to demonstrate the effectiveness of the proposed method. Furthermore, it was found that the analysis and synthesis filters of the triplet FB have a more symmetric frequency responses. This property is exploited to construct a class of PR M-channel uniform FBs and wavelets with M = 2 L, where L is a positive integer, using a particular tree structure. The filter lengths of the two-channel FBs down the tree are approximately reduced by a factor of two at each level or stage, while the transition bandwidths are successively increased by the same factor. Because of the downsampling operations, the frequency responses of the final analysis filters closely resemble those in a uniform FB with identical transition bandwidth. This triplet-based uniform M-channel FB has very low design complexity and the PR condition and K regularity conditions are structurally imposed. Furthermore, it has considerably lower arithmetic complexity and system delay than conventional tree structure using identical FB at all levels. The multiplierless realization of these FBs using sum-of-power-of-two (SOPOT) coefficients and multiplier block is also studied. © 2004 IEEE.published_or_final_versio

Interface placement in constructing widest spanning tree for multi-channel multi-interface wireless mesh networks

Proceedings of the IEEE Wireless Communications and Networking Conference, 2009, p. 2560-2564Widest spanning tree is a broadcast tree with its bottleneck link bandwidth maximized. It provides a cost effective broadcasting solution in multi-channel multi-interface wireless mesh networks. To find the widest spanning tree, existing algorithms jointly consider channel assignment, routing and scheduling while assuming the number of network interface cards (NICs) at each node is given. In this paper, we treat the number of NICs at each node as a design parameter, whereas the total number of NICs in the system is given. By properly placing more NICs to more "critical" nodes, the bandwidth of the spanning tree can be further increased. To this end, a new Integer Linear Programming (ILP) is formulated for solving the widest spanning tree problem based on joint optimization of interface placement, channel assignment, routing and scheduling. Numerical results show that interface placement provides a significant boost to the bandwidth of the widest spanning tree found. © 2009 IEEE.published_or_final_versio

Interface placement in constructing widest spanning tree for multi-channel multi-interface wireless mesh networks

Proceedings of the IEEE Wireless Communications and Networking Conference, 2009, p. 2560-2564Widest spanning tree is a broadcast tree with its bottleneck link bandwidth maximized. It provides a cost effective broadcasting solution in multi-channel multi-interface wireless mesh networks. To find the widest spanning tree, existing algorithms jointly consider channel assignment, routing and scheduling while assuming the number of network interface cards (NICs) at each node is given. In this paper, we treat the number of NICs at each node as a design parameter, whereas the total number of NICs in the system is given. By properly placing more NICs to more "critical" nodes, the bandwidth of the spanning tree can be further increased. To this end, a new Integer Linear Programming (ILP) is formulated for solving the widest spanning tree problem based on joint optimization of interface placement, channel assignment, routing and scheduling. Numerical results show that interface placement provides a significant boost to the bandwidth of the widest spanning tree found. © 2009 IEEE.published_or_final_versio

J-CAR: An efficient channel assignment and routing protocol for multi-channel multi-interface mobile ad hoc networks

In Session: Wireless Ad Hoc and Sensor Networks towards Anytime Anywhere Internetworking: WSN-15: Resource Allocation: article no. WSN15-2We propose an efficient joint channel assignment and routing protocol (J-CAR) for multi-channel multi-interface mobile ad hoc networks (MANETs). Aiming at overcoming the limitations of the existing channel assignment and routing algorithms, J-CAR negotiates a channel at each active link during the route setup process. It has the following major features: a) a pre-determined common control channel is used by every node for routing and channel negotiation; b) control packets for data transmission (RTS, CTS & ACK) are carried by the associated data channels; c) the spare capacity on the control channel can be used for data transmission; d) an interface is free to change its working modes between send and receive; and e) an interface can tune to any data channels for data sending or receiving at the cost of switching overhead. With J-CAR, a more flexible assignment of interfaces, channels, and the working mode of each interface can be rendered. The performance gain brought by J-CAR is substantiated by extensive simulation results. © 2006 IEEE.published_or_final_versionProceedings of the Global Telecommunications Conference, 2006 (GLOBECOM 2006), San Francisco, CA, USA, 27 November - 1 December 200

BGP ingress-to-egress route configuration in a capacity-constrained AS

The BGP ingress-to-egress route configuration problem is to find a set of paths in an ISP to carry the transit flows, such that the amount of network resources consumed is minimized without violating the bandwidth constraint on all network links. To solve the problem, we first formulate it using Integer Linear Programming (ILP). Due to the high complexity involved in ILP, a heuristic algorithm, called MPPF, is then proposed. MPPF is designed based on the idea that heavily-loaded destination prefixes should be given higher priority to select less expensive edge links and routes. Simulation results show that MPPF requires less network resources and edge link capacity than an alternative heuristic called BTF. © 2005 IEEE.published_or_final_versio

BGP ingress-to-egress route configuration in a capacity-constrained AS

The BGP ingress-to-egress route configuration problem is to find a set of paths in an ISP to carry the transit flows, such that the amount of network resources consumed is minimized without violating the bandwidth constraint on all network links. To solve the problem, we first formulate it using Integer Linear Programming (ILP). Due to the high complexity involved in ILP, a heuristic algorithm, called MPPF, is then proposed. MPPF is designed based on the idea that heavily-loaded destination prefixes should be given higher priority to select less expensive edge links and routes. Simulation results show that MPPF requires less network resources and edge link capacity than an alternative heuristic called BTF. © 2005 IEEE.published_or_final_versio