1. LightRing with Tunable Transceivers
Kalai Rajah Narayanan
Optical Networks Advanced Research (OpNeAR) Lab
The University of Texas at Dallas
LightRing Architecture
Characteristics of LightRing
Node Architecture
Advantages
Contention free, on-demand bandwidth allocation
Token based – provides simple control approach
Destination stripping of messages
Frees resources after usage
Limitations
Number of transceivers increases in the order of the wavelengths  increase in cost, scalability issues
Message sizes have to be large (compared to ring latency) to achieve high efficiency
All-optical
Ring topology
Multi-wavelengths
Token-based access protocol
Loss-free
Bandwidth on-demand
Spatial Reuse l1 l2 l3 1 2 3 4 5 6 7 8
Tunable Transceivers
Transmitter Tuning Strategy
Receiver Tuning Strategy
Tuning Strategy Extensions
Pre-calculated tuning:
Transmitter tuned before appropriate token
arrival at node
Parallel tuning of transmitters
Runs as background process
Performance improvement with higher
number of transmitters
Reservation-based Tuning:
Transmitters tuned after token arrival at node
Small overhead – tunes only when necessary
Performance improvement with less number
of transmitters
Reduce transmitters and receivers at nodes
Efficient tuning algorithms
With reduced overhead
Adjustable with traffic flow
Distributed and distinct algorithms for
transmitters and receivers
Tokens used as receiver status indicators
No extra control overhead
Transmitter tuning strategies can be:
Chosen flexibly according to network
parameters
Applied to bi-directional rings with
cross-signaling or independent
signaling
Extended to accommodate band-limited
tuning
Used with varied Transmitter/ Receiver
node configurations
Idle receiver follows busy transmitter’s
wavelength
Receiver tuning overlaps with
signaling latency
Receiver status is advertised through
tokens
Only one receiver is tuned during one
token arrival at a node (computationally
less intensive)
Throughput vs. a/D
Summary
Throughput vs. Tuning Time
Analytical vs. Simulation Results
LightRing features still preserved
Transmitters and receivers can be reduced
without affecting performance significantly
Tuning strategies take advantage of ring
latency
Tuning algorithms can be run individually
for transmitters and receivers
Algorithms are simple, distributed
Algorithms work under non-uniform traffic
and are extensible to bidirectional rings,
band-limited tuning
N=32, W=16, R=16, T≤16,  = 0, Ring. Lat = 400µsec
N=32, W=16, R=T≤16, a/D=3, Ring. Lat = 400µsec
N=32, W=16, R=16, T≤16, a/D=3