Transcript Ethernet and AFDX Presentation
Delay Sensitive TDMA Slot Assignment in Ad hoc Wireless Networks
Naresh Vattikuti, Himanshu Sindhwal, Mallesham Dasari Bheemarjuna Reddy Tamma
Uurmi Systems Pvt. Ltd. Department of CSE, IIT Hyderabad, India.
Hyderabad, India. Email: {vvsnaresh, himanshus, malleshamd}@uurmi.com [email protected] National Conference on Communication IIT Bombay, India 27 – 28 March 2015
Outline
• • • • • • • Introduction State of the art Problem statement Delay vs. Spatial reuse of slots Proposed Delay sensitive slot assignment Performance Evaluation Conclusions
Introduction
• • TDMA slot assignment Multi hop topology - Flows from A - F and C - G • Spatial reuse
Delay vs. Spatial reuse
• Spatial reuse approach • Minimum possible delay approach • Need to strike the balance between the two
• Delay analysis • Affect is more with longer hop flows
Problem Statement
• Selection of efficient slot based on the previous node’s slot so that the end-to-end delay in a long hop flow is minimized.
• Strike the balance between the delay and spatial reuse slots, given the Maximum delay for flow is known.
State of the art
• • • • Centralized: GSM, PDC, iDEN, PHS etcetera. Distributed: – – – – USAP, USAP/MA DRTDMA STDMA algorithms Applications???
Many algorithms: Effective handling of slot conflict, selection of best slot?
Opportunism with the cross layer advantage
Proposed Algorithm
• • • • The Algorithm restricts each node to select a slot such that it doesn’t breach D
max
/N (per hop-delay limit), where N is the number of hops in the flow.
Once delay for all the slots in S gave minimum delay and call it SspatialMin and the corresponding delay as spatialMin.
spatial
is calculated, we will find a slot which If this slot is inducing a delay less than D (=D
max
/N) then this slot will be selected and the algorithm completes else we will move to set S
other
and repeat the process to find the slot in S
other
which will give minimum delay among all the slots in S
other
, we will call it S
min
and the corresponding delay as фmin .
If ф
min
< spatialMin then we will select the slot S
min
(the idle slot giving minimum possible delay on this node) otherwise S giving minimum possible delay on this node and also spatially reused in the flow) will be chosen.
spatialMin
(the idle slot
Slot Selection Algorithm
I/P: Previous slots in the flow and idl slots.
O/P: Minimal delay aware slot S spatial S other = getIntersection(Sprev,Sidle) = S idle D = Dmax/n; For each S
if
i - S spatial in S spatial S i >P then ∆ i = S i P
else end if end for
∆ i = f- P+S i ∆ spatial_min = findMinimumOfAll∆ i ’s() S spatial_min = if ((∆ spatial_min * Slot_dur) <= D) then S selected slotCorrespondingTo∆ spatial_min () = S spatial_min
else
for each S
if
∆ i in S other set S i >P then i =
else
S i P f- P+S i
endif end for
∆ i = ∆ min = findMinimumOfAll∆ i ’s() S min = slotCorrespondingTo∆ min () if ∆ min < ∆ spatial_min
then
S selected = S min
else
S selected = S spatial_min
endif
Experimental Setup
Parameter
Number of Nodes Number of Slots Slot duration Number of Seeds Average Dmax Transmission Range Area
Value
20 32 1ms 15 200ms 1.5units
20x20units
We have analyzed three types of experimental results
1.
End-to-end delay with varying load 2.
3.
Call acceptance ratio with varying load Call acceptance ratio with different values of D
max
by keeping the load fixed
Algorithms for Performance Comparison
• • • Load Balancing approach proposed in [3], which is a traditional slot selection method Get the first available idle slot for reservation MPD approach Get the minimal delay aware slot out of all the idle slots available in the frame .
Delay Sensitive approach Strike the balance between delay and spatial reuse.
Call Acceptance vs. Load Random Topology
• Load = arrival rate *duration • Comparison sensitive of algorithm delay with Minimum approach.
possible delay approach and load balancing Call Acceptance vs. Load (Random Topology)
Call Acceptance vs. Load String Topology
• The curve Sensitive’ approach shows that, it achieves greater call acceptance ratio than MPD approach, because of spatial reusability.
of ’Delay Call Acceptance vs. Load (String Topology)
Delay vs. Load Random Topology
• as And also, MPD the ’Delay Sensitive’ approach’s curve shows that the delay with the increased load is as good approach and outperforms ’Load Balancing’ approach in the case of random topology.
Delay vs. Load (Random Topology)
Delay vs. Load String Topology
• The ’Delay Sensitive’ approach’s curve shows that the delay with the increased load is as good as MPD approach and outperforms the case of ’Load Balancing’ approach in string topology.
Delay vs. Load (String Topology)
Delay vs. Hop Count Random Topology
• Furthermore, the curves show that our approach giving better results in case of flows with more hop count as the probability of tradeoff between more frequently.
delay and spatial reuse happens Delay vs. Hop count (String Topology)
Call Acceptance vs. D
max
• Additionally, we calculated the call acceptance with varying the Dmax value. • The curve shows that, the Delay Sensitive approach gives more call acceptance with the increased Dmax, as the increase in Dmax lead to increase in maximum delay at each hop which will further enhance the spatial reuse.
Call Acceptance vs. D
max
(String Topology)
Conclusion
• • • • In this paper, an end-to-end delay sensitive approach is provided for slot selection by exploiting the spatial reusability in multi hop AWNs.
The results show that the developed algorithm balances well between the delay and spatial reusability metrics.
It is also shown from the results that, it performs well for long hop flows.
The tradeoff between the two metrics proposed in this paper can be expanded to other QoS metrics in distributed TDMA slot assignment process.
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