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Analyzing Channel Assignment with Rearrangement in Multi-Channel Wireless Line Networks
Sandeep Ahuja and Srinivasan Ramasubramanian
Department of Electrical and Computer EngineeringUniversity of Arizona
Analyzing Channel Assignment with Rearrangement in Multi-Channel Wireless Line Networks
Wireless infrastructure networks
Wireless infrastructure networks becoming more popular
Backbone may operate in 802.11a, while user interface may be on 802.11b/g
Increasing throughput in wireless infrastructure networks
Simultaneous transmission on multiple orthogonal channels
Use of directional antenna for improved spatial throughput
Contributions of this paper
Calls to be established over a single hop (needs channel assignment)
Analyze channel assignment with rearrangement
What is the probability that a given call is blocked/accepted?
Assuming we can rearrange all the existing calls
2
Analyzing Channel Assignment with Rearrangement in Multi-Channel Wireless Line Networks
Omnidirectional and directional transmission
Omnidirectional transmission
Directional transmission
Transmission and interference ranges are assumed to be the same
Ignore side and back lobes for now
3
i i+R
i i+R
Analyzing Channel Assignment with Rearrangement in Multi-Channel Wireless Line Networks
Network & traffic assumptions
Number of channels C; Range of transmission R
Call arrival process follows a Poisson process
Holding times are exponentially distributed with unit mean
All calls are one hop and bi-directional
Node i generates calls only for nodes i + R
Nodes i and i+R both act as transmitter and receiver
Number of calls originating at node i
Network may be viewed as an N-dimensional Markov Chain
Under what conditions a given call can be accommodated?
Assuming that existing calls can be rearranged
Treat the problem as a fresh channel assignment problem
4
Analyzing Channel Assignment with Rearrangement in Multi-Channel Wireless Line Networks
Spatial reuse of channels
5
A B C D E F G H J K L
A B C D E F G H J K L
When directional antennas are employed
When omnidirectional antennas are employed
Analyzing Channel Assignment with Rearrangement in Multi-Channel Wireless Line Networks
Omnidirectional case
Nodes i and i+R need to communicate
Number of calls originating in the window [k, k+2R]
Number of nodes in the window is 2R+1
Condition for call acceptance
6
i i+R
Analyzing Channel Assignment with Rearrangement in Multi-Channel Wireless Line Networks
Nodes i and i+R need to communicate
Number of calls originating in the window [k, k+R]
Number of nodes in the window is R+1
Condition for call acceptance
Directional case
7
i i+R
Analyzing Channel Assignment with Rearrangement in Multi-Channel Wireless Line Networks
Omnidirectional case - details
Joint distribution of calls in a window (Yk = Vk - Xk)
8
i i+R
Analyzing Channel Assignment with Rearrangement in Multi-Channel Wireless Line Networks
Omnidirectional case - details
Steady-state probability distribution of number of channels in a window
Computation of steady-state probability
9
Analyzing Channel Assignment with Rearrangement in Multi-Channel Wireless Line Networks
Omnidirectional case - details
Success probability
10
Analyzing Channel Assignment with Rearrangement in Multi-Channel Wireless Line Networks
Joint distribution of calls in a window (Zk = Wk - Xk)
Directional case - details
11
i i+R
Analyzing Channel Assignment with Rearrangement in Multi-Channel Wireless Line Networks
Directional case - details
Compute steady-state probability as before
Note that only window size changes from 2R+1 to R+1
Call success probability
12
Analyzing Channel Assignment with Rearrangement in Multi-Channel Wireless Line Networks
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Performance results (1 channel)
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R=1 R=2
R=3
Analyzing Channel Assignment with Rearrangement in Multi-Channel Wireless Line Networks
Performance results (10 channels)
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Analyzing Channel Assignment with Rearrangement in Multi-Channel Wireless Line Networks
Conclusion and future work
15
Analytical model for call blocking probability assuming
Rearrangement of calls
Interference and transmission ranges are identical
Simulation results validate analytical model
Future work
Assume that interference range is larger than transmission range
Eliminate rearrangement
Different transmission ranges over single-hop and multi-hop calls
Relation to optical networks - Routing and wavelength continuity constraint
Application to channel access protocols
Useful in quantifying the number of channels available at a node at any given time