3 research outputs found
Joint buffer management and scheduling for input queued switches
Input queued (IQ) switches are highly scalable and they have been the focus of many studies from academia and industry. Many scheduling algorithms have been proposed for IQ switches. However, they do not consider the buffer space requirement inside an IQ switch that may render the scheduling algorithms inefficient in practical applications.
In this dissertation, the Queue Length Proportional (QLP) algorithm is proposed for IQ switches. QLP considers both the buffer management and the scheduling mechanism to obtain the optimal allocation region for both bandwidth and buffer space according to real traffic load. In addition, this dissertation introduces the Queue Proportional Fairness (QPF) criterion, which employs the cell loss ratio as the fairness metric. The research in this dissertation will show that the utilization of network resources will be improved significantly with QPF. Furthermore, to support diverse Quality of Service (QoS) requirements of heterogeneous and bursty traffic, the Weighted Minmax algorithm (WMinmax) is proposed to efficiently and dynamically allocate network resources.
Lastly, to support traffic with multiple priorities and also to handle the decouple problem in practice, this dissertation introduces the multiple dimension scheduling algorithm which aims to find the optimal scheduling region in the multiple Euclidean space
THE APPLICATION OF REAL-TIME SOFTWARE IN THE IMPLEMENTATION OF LOW-COST SATELLITE RETURN LINKS
Digital Signal Processors (DSPs) have evolved to a level where it is feasible
for digital modems with relatively low data rates to be implemented entirely with
software algorithms. With current technology it is still necessary for analogue
processing between the RF input and a low frequency IF but, as DSP technology
advances, it will become possible to shift the interface between analogue and digital
domains ever closer towards the RF input. The software radio concept is a long-term
goal which aims to realise software-based digital modems which are completely
flexible in terms of operating frequency, bandwidth, modulation format and source
coding. The ideal software radio cannot be realised until DSP, Analogue to Digital
(A/D) and Digital to Analogue (D/A) technology has advanced sufficiently. Until
these advances have been made, it is often necessary to sacrifice optimum
performance in order to achieve real-time operation. This Thesis investigates practical
real-time algorithms for carrier frequency synchronisation, symbol timing
synchronisation, modulation, demodulation and FEC. Included in this work are novel
software-based transceivers for continuous-mode transmission, burst-mode
transmission, frequency modulation, phase modulation and orthogonal frequency
division multiplexing (OFDM).
Ideal applications for this work combine the requirement for flexible baseband
signal processing and a relatively low data rate. Suitable applications for this work
were identified in low-cost satellite return links, and specifically in asymmetric
satellite Internet delivery systems. These systems employ a high-speed (>>2Mbps)
DVB channel from service provider to customer and a low-cost, low-speed (32-128
kbps) return channel. This Thesis also discusses asymmetric satellite Internet delivery
systems, practical considerations for their implementation and the techniques that are
required to map TCP/IP traffic to low-cost satellite return links