analyzing channel assignment with rearrangement in multi

Analyzing Channel Assignment with Rearrangement in Multi-Channel Wireless Line Networks

Sandeep Ahuja and Srinivasan Ramasubramanian

Department of Electrical and Computer EngineeringUniversity of Arizona


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


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


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


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


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


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


Omnidirectional case - details

Joint distribution of calls in a window (Yk = Vk - Xk)

8

i i+R



Steady-state probability distribution of number of channels in a window

Computation of steady-state probability

9



Success probability

10


Joint distribution of calls in a window (Zk = Wk - Xk)

Directional case - details

11

i i+R


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


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Performance results (1 channel)

13

R=1 R=2

R=3


Performance results (10 channels)

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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


Acknowledgment

National Science Foundation [Grants: CNS-0325979; CNS-0435490]Cisco Collaborative Research Initiative

analyzing channel assignment with rearrangement in multi

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