Transfer Mode Local Area Networks Research Articles

Dynamic algorithm transformations (DAT)-a systematic approach to low-power reconfigurable signal processing

In this paper, dynamic algorithm transformations (DATs) for designing low-power reconfigurable signal-processing systems are presented. These transformations minimize energy dissipation while maintaining a specified level of mean squared error or signal-to-noise ratio. This is achieved by modeling the nonstationarities in the input as temporal/spatial transitions between states in the input state-space. The reconfigurable hardware fabric is characterized by its configuration state-space. The configurable parameters are taken to be the filter taps, coefficient and data precisions, and supply voltage V/sub dd/. An energy-optimal reconfiguration strategy is derived as a mapping from the input to the configuration state-space. In this strategy, taps are powered down starting with the tap with the smallest value [w/sub k//sup 2///spl Sigma//sub m/(w/sub k/)] (where w/sub k/ and /spl Sigma//sub m/(w/sub k/) are, respectively, the adders, redundant-to-binary conversion, tree adders, coefficient and energy dissipation of the kth tap). Optimal values for precision and supply voltage V/sub dd/ are subsequently computed from the roundoff error and critical path delay requirements, respectively. The DAT-based adaptive filter is employed as a near-end crosstalk (NEXT) canceller in a 155.52-Mb/s asynchronous transfer mode-local area network transceiver over category-3 wiring. Simulation results indicate that the energy savings range from -2% to 87% as the cable length varies from 110 to 40 m, respectively, with an average saving of 69%. An average saving of 62% is achieved for the case where the supply voltage V/sub dd/ is kept fixed.

A pipelined adaptive NEXT canceller

A near-end crosstalk (NEXT) canceller using a fine-grain pipelined architecture is presented. The performance of the proposed pipelined NEXT canceller is demonstrated in the 125 Mb/s twisted-pair distributed data interface and 155.52 Mb/s asynchronous transfer mode local area network applications. In addition, we analyze the computational complexity of the proposed pipelined NEXT canceller. It is shown that this architecture can be clocked at a rate that is 107 times faster than the serial architecture with a maximum loss of 2.0 dB in signal-to-noise ratio (SNR).

Reservation-based bandwidth allocation in a radio ATM network

The comparative performance of a number of reservation-based bandwidth sharing policies that could be used to maximize the link utilization and/or offer equally fair or preferential treatment to a class of supported users, is examined in the context of a radio asynchronous transfer mode local-area network (ATM LAN). Our analytical results, based an a recursion for the link occupancy distribution originally suggested by Kaufman (1981) and Roberts (1981) independently and subsequently extended to include finite source population models, are further extended in the cases of equal sharing of the resources with retries, and a dynamic sharing mechanism in which, when the available capacity is exceeded, weighted reductions for the active users' rates and queueing are employed. Next, examining the application of the above sharing schemes in an indoor radio environment, we apply switched diversity and a Reed-Solomon-based forward error correction (FEC) scheme to recover radio-related (Rayleigh fading) packet losses. The performance and the effects of the fading-mitigating switched-antenna-diversity mechanism and the required on a packet-basis coding protection are taken into account in order to establish the actual radio link throughput under the above conditions.

Space-diversity issues in the context of a B-ISDN-oriented indoor radio environment

A first assessment of the applicability and the tradeoffs involved in a switched (antenna) diversity approach is presented here as seen in the context of a future indoor wireless network operating in the mm-wavelength radio spectrum targeted to provide radio access to asynchronous transfer mode local area networks (ATM LAN's) and broadband integrated services digital networks (B-ISDN). Measurements conducted at 21.6 GHz are used to examine the gain variation of switched-diversity alternatives in terms of cumulative distribution functions. The performance of a two-branch post-detection code diversity combining scheme under Rayleigh fading conditions is also included for purposes of comparison. The results of our work here confirm the hypothesis that the choice of the employed antenna diversity technique in combination with the selected micro-cellular architecture have significant effects on both the throughput and the measured performance of future radio links.

Performance of an asynchronous transfer mode local area network switch with backpressure function‐maximum throughput analysis

AbstractAs an effective traffic control mechanism of the asynchronous transfer mode (ATM) local area network (LAN) which has been getting attention as the next‐generation high‐speed LAN, the reactive congestion control is considered. In this paper, to obtain such a traffic control mechanism, a scheme to add the function of backpressure to an ATM switch having buffers in both the input side and the output side is evaluated. Also in this paper, the maximum throughput of an ATM switch with backpressure function for burst traffic is analyzed mathematically. Further, a uniform traffic load and a mixture of such traffic occupying the bandwidth in a peak rate as voice and video are analyzed. Moreover, with some numerical data examples, the effect of the output buffer size and the burstiness of the arriving traffic on the system performance is analyzed.

Evaluating the performance of the dynamic bandwidth reservation method using link utilization information in automatic transfer mode local area networks

AbstractWith the improvement of the speed of computers in recent years, there is required a local area network (LAN) that can realize a high‐speed broadband communication. For this purpose, asynchronous transfer mode (ATM) LANs based on ATM technique is considered important.This paper considers the bandwidth reservation control as a means of traffic control in ATM LAN and evaluates the performance by simulation. The evaluation is made for the following methods of congestion control: ACK/NACK method, based on the ACK/NACK signal which is returned when the bandwidth reservation succeeds/fails; the dynamic ACK/NACK method, which is an improvement so that the control can be adapted to the traffic load; and control method based on the link information from the switch.It is shown for the single‐stage switching network that the dynamic ACK/NACK method has a better performance when the traffic is low but the control method based on the link information has the highest performance when the traffic is high. It also is shown for the three‐stage switching network that the control method based on the link information has the highest performance.