Scheduling light-trails on WDM rings

Abstract

a b s t r a c tWe consider the problem of scheduling communication on optical WDM (wavelength division multiplexing) networks using the light-trails technology. We seek to design scheduling algorithms such that the given transmission requests can be scheduled using a minimum number of wavelengths (optical channels). We provide algorithms and close lower bounds for two versions of the problem on an n processor linear array/ring network. In the stationary version, the pattern of transmissions (given) is assumed to not change over time. For this, a simple lower bound is c, the congestion or the maximum total traffic required to pass through any link. We give an algorithm that schedules the transmissions using O(c + log n) wavelengths. We also show a pattern for which Ω(c + log n/ log log n) wavelengths are needed. In the on-line version, the transmissions arrive and depart dynamically, and must be scheduled without upsetting the previously scheduled transmissions. For this case we give an on-line algorithm which has competitive ratio Θ(log n). We show that this is optimal in the sense that every on-line algorithm must have competitive ratio Ω(log n). We also give an algorithm that appears to do well in simulations (for the classes of traffic we consider), but which has competitive ratio between Ω(log 2 n/ log log n) and O(log 2 n). We present detailed simulations of both our algorithms.

An efficient resource management scheme in light-trail networks

“…Later, a scheme for throughput improvement in multi-splitting lighttrails was investigated [8] and a delay-aware MAC protocol based on multi-splitting concept was proposed [7]. Pal and Ranade [24] gave polynomial time algorithms for both static and dynamic scheduling problems in ring networks. Their work is the first one to exploit competitive analysis approach and approximation algorithms to solve the scheduling problem.…”

“…D 2 ATD_DBA uses S lk avg and buf lk avg as thresholds to categorize the four cases for node i (line [16][17][18][19][20][21][22][23][24][25][26][27][28] If the first condition holds, it means that the amount of buffered traffic of node i is larger than the mean size of buffered traffic of the whole light-trail. The other condition implies that node i accumulates traffic of the class min_type more than the mean volume of the same class in the whole light-trail.…”

“…Afterward, many variations of lighttrail architecture were proposed as well, such as bidirectional light-trail (BDLT) [22], strongly connected light-trail (SLiT) [11], waveband switching light-trail (WBS-LT) [27], and multicast-capable light-trails [12]. In addition to architecture design and MAC protocol proposals [3][4][5][6][7][8]17,24], there are other interesting issues like the routing problem and DBA problem [21]. The routing problem is an extensively investigated one in light-trails, e.g., the static routing problem [2,3,23,26,30], the dynamic routing problem [14,19,[28][29][30].…”

Fragmented coloring of proper interval and split graphs

“…If no interval of I properly contains another, set theoretically, then G is called a proper interval graph. As mentioned in [3], the light-trail scheduling problem is similar to the problem of scheduling in reconfigurable bus architectures [4,5], and hence component coloring applies there too.…”

MAC protocol with delay-aware adaptive round time for split light-trail

“…LT has been considered as an attractive solution for optical networks to support emerging services such as videoon-demand, pseudo-wires, data-centers, etc. Extensive researches have been devoted to addressing the problems in LT networks, such as traffic grooming [2][3][4], node architecture [5,6] and media access control (MAC) protocol [7][8][9][10][11][12][13].…”