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© Robert W. Heath Jr. 2015
Interference Statistics in Random mmWave Ad Hoc Networks Andrew Thornburg, Tianyang Bai, Robert W. Heath Jr. Wireless Networking and Communications Group Dept. of Elec. and Comp. Engr., The University of Texas at Austin
www.profheath.org
This work was supported in part by the Army Research Office under grant W911NF-14-1-0460
© Robert W. Heath Jr. 2015
Why millimeter wave wireless networks?
u Huge amount of spectrum possibly available in mmWave bands u Technology advances make mmWave possible for cheap consumer devices u Applicable for WLAN, cellular, device-to-device, and ad hoc networks
2
300 MHz 3 GHz
30 GHz 300 GHz
cellular WiFi
note: log scale so even smaller over here
UHF (ultra high frequency) spectrum !
© Robert W. Heath Jr. 2015
Differentiating features of mmWave communication
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Key Question: Is interference a significant design impairment
in mmWave ad hoc networks?
(1) use of directional antennas
@ RX and TX
(2) blockage can reduce interference
© Robert W. Heath Jr. 2015
Prior work u Few references on large-scale / outdoor mmWave ad hoc networks
ª Most related work is in the application of mmWave to indoor PAN
u Stochastic geometry with ad hoc networks ª Pioneering work [BacBla09] ª Directional antennas [HunAnd08]
u Claims on the interference for mmWave networks
ª Psuedo-wired for PAN [SinMud11] ª Noise limited cellular [AndBuz14] ª But can be interference limited [BaiHea14]
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© Robert W. Heath Jr. 2015
System model
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General network model
User Density
Building Density
random network with infinite # of user pairs
randomly located buildings
distant dependent pathloss
small-scale fading
© Robert W. Heath Jr. 2015
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Network model for interference analysis
User Density
Building Density
focus on the interference term
only consider typical receiver and all interferers
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Random ad hoc network with Boolean blockage
Length & width of building independently drawn from a
distribution
Typical receiver located at the origin
Center of each building forms a PPP independent of
the transmitter process
Transmitters form a Poisson point process
Link is LOS or NLOS depending on its blockage
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Sectored antenna model
Feasible w/ 32 element array
devise mainlobe and backlobe from measured antenna
parameters
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Interference CDF
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© Robert W. Heath Jr. 2015
Interference-to-noise-ratio (INR)
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random gain
gamma
path-loss intercept
noise power
random distance due
to PPP
random blockage
4
2
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u Let be the threshold to consider the INR noise limited
INR distribution
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constant but treat as a
Gamma RV with large N
approximate Gamma CDF
to help analysis
© Robert W. Heath Jr. 2015
Final result
u The instantaneous INR distribution of a mmWave ad hoc network can be tightly approximated by
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Constant Gamma parameter
Fading Gamma parameter
Approximation constant
© Robert W. Heath Jr. 2015
INR CDF with 9º antenna beamwidth
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INR CDF with 30º antenna beamwidth
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INR CDF with 90º antenna beamwidth
© Robert W. Heath Jr. 2015
INR CDF with LOS only vs LOS + NLOS users
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LOS interference only LOS & NLOS interference
NLOS interference is negligible
© Robert W. Heath Jr. 2015
Conclusions
u Derived an expression for INR CDF in mmWave ad hoc networks
u MmWave ad hoc networks can be interference limited ª All but sparsest network with narrowest beamwidth
u LOS interference in by far dominant ª Aggregate non-line-of-sight interference is negligible ª Line-of-sight interference avoidance likely worthwhile
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© Robert W. Heath Jr. 2015
References u F. Baccelli and B. Blaszczyszyn, Stochastic Geometry and Wireless Networks, Volume II - Applications. NoW
Publishers, 2009, vol. 2. [Online]. Available: http://hal.inria.fr/inria-00403040
u A. Hunter, J. Andrews, and S. Weber, “Transmission capacity of ad hoc networks with spatial diversity,” IEEE Trans. Wireless Commun., vol. 7, no. 12, pp. 5058–5071, 2008.
u S. Singh, R. Mudumbai, and U. Madhow, “Interference Analysis for Highly Directional 60-GHz Mesh Networks: The Case for Rethinking Medium Access Control,” IEEE/ACM Trans. Netw., vol. 19, no. 5, pp. 1513–1527, 2011.
u J. G. Andrews, S. Buzzi, W. Choi, S. V. Hanly, A. Lozano, A. C. K. Soong, and J. C. Zhang, “What Will 5G Be?,” IEEE Journal on Selected Areas in Communications, vol. 32, no. 6, pp. 1065–1082, June 2014.
u T. Bai and R.W. Heath, “Coverage and rate analysis for millimeter-wave cellular networks,” IEEE Trans. Wireless Commun., vol. 14, no. 2, pp. 1100–1114, Feb.2015.
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