Design and Analysis of WDMA protocol for Passive Star-Coupled Lightwave Networks
Graduate student: Bin Wang, Hung-Ying Tyan
Faculty: Chao-Ju Jennifer Hou
Sponsors: partially under DARPA/ITO
Based on the POPSMAC protocol (developed as part of the RAINBOW project
at IBM), we propose an improved medium access protocol for wavelength
division multiple access (WDMA) photonic networks.
The photonic network is based on a passive star-coupled configuration
where high topological connectivity is achieved.
Using the same set of photonic devices as in POPSMAC, the proposed
protocol alleviates the drawbacks of the POPSMAC protocol, e.g.,
invalid data transmissions following receiver collisions and possible
acknowledgment packet collisions with header/data packets,
while retaining many advantages of the POPSMAC protocol.
As a result, the network performance in terms of the throughput and the
packet delay is improved.
We also develop analytical models based on the timing diagram
analysis, the continuous-time Markov chain, and the randomization
technique to investigate the performance of the proposed
protocol. The performance is evaluated in terms of channel
utilization, mean packet delay, and packet delay distribution
with variations in the number of nodes, the offered traffic,
the size of data packets, and the network propagation delay.
Numerical results show that the proposed protocol achieves
better channel utilization and incurs lower packet delays
than the POPSMAC protocol.
In this project, we devise a preallocation-based single-hop wavelength
division multiple access (WDMA) scheme
to support time constrained communication in star-coupled
optical networks.
We consider a star-coupled broadcast-and-select network architecture
in which the N stations are connected to a star coupler with W different
wavelength channels.
Each of the W wavelength channels is slotted and shared by the N
stations by means of time division multiplexing.
Depending on the tunability characteristics (tunable or fixed tuned)
of the transmitters/receivers, we classify the network architecture
as tunable transmitter/fixed tuned receiver (TT-FR),
fixed tuned transmitter/tunable receiver (FT-TR),
and tunable transmitter/tunable receiver (TT-TR).
We first characterize each real-time message stream M_i with two
parameters, relative message deadline D_i and maximum (total) message
size C_i that can arrive within any time interval of length D_i.
We then discuss a restricted case in a TT-FR (or FT-TR) system in
which the message streams from a source station are assumed to be all
destined for the same destination station.
Under this assumption, no source/destination conflicts may occur.
We propose a preallocation based slot assignment scheme
to pre-allocate slots to a set of isochronous
message streams, {M_i=(C_i,D_i) <= 1 \leq i \leq n}, in such
a way that in any time window of size D_i slots, at least C_i
slots on a wavelength channel are allocated to M_i for all i.
With the solution derived in the restricted case as a
basis, we then consider slot assignment in a (general) TT-TR system,
and propose a binary splitting scheme to
assign each message stream sufficient
and well-spaced slots to fulfill its timing requirement, subject to
source/destination conflict constraints.
We rigorously prove the invariant properties,
and the correctness, of the binary splitting scheme.
We also address the problem of dynamically
establishing/terminating real-time message streams in response to
call setup/clear requests
in single-hop star-coupled WDMA-based optical networks.
We consider a star-coupled broadcast-and-select network architecture
in which N stations are connected to a star coupler with W
different wavelength channels (W \leq N) and one control channel.
Each of the W data channels is slotted and shared by the $N$
stations by means of time division multiplexing.
The control channel is used for network stations
to coordinate on the call establishment and termination operations.
We propose a distributed, dynamic slot allocation scheme to
allocate/de-allocate, in response to call setup/clear requests,
time slots on each of the W data channels to message streams, with the
objective of meeting message deadlines.
To facilitate slot assignment,
the proposed scheme first decomposes each message stream into a
set of message sub-streams,
and groups the time slots on each wavelength channel into sub-channels.
In response to a call setup request, the proposed scheme then
allocates one or more empty sub-channels available over the $W$ data
channels to a message stream to fulfill its timing requirement,
subject to the source/destination constraints and that the timing
guarantees to existing message streams should not be violated.
On the other hand, in response to a call clear request, the proposed
scheme releases the slots allocated to the terminated
message stream, and merges, if appropriate, empty sub-channels
to facilitate future message stream establishment.
We formally prove the properties, and the correctness of,
the proposed dynamic slot allocation scheme.
MAC Protocol for High Performance
MAC Protocol for Supporting Time-Constrained Communications
Return
to Project Home Page