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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


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 !


Differentiating features of mmWave communication

Interference Statistics in Random mmWave Ad Hoc Networks 3

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


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]



System model




General network model

User Density

Building Density

random network with infinite # of user pairs

randomly located buildings

distant dependent pathloss

small-scale fading



Network model for interference analysis

User Density

Building Density

focus on the interference term

only consider typical receiver and all interferers



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



Sectored antenna model

Feasible w/ 32 element array

devise mainlobe and backlobe from measured antenna

parameters


Interference CDF



Interference-to-noise-ratio (INR)


random gain

gamma

path-loss intercept

noise power

random distance due

to PPP

random blockage

4

2


u  Let be the threshold to consider the INR noise limited

INR distribution


constant but treat as a

Gamma RV with large N

approximate Gamma CDF

to help analysis


Final result

u  The instantaneous INR distribution of a mmWave ad hoc network can be tightly approximated by


Constant Gamma parameter

Fading Gamma parameter

Approximation constant


INR CDF with 9º antenna beamwidth



INR CDF with LOS only vs LOS + NLOS users


LOS interference only LOS & NLOS interference

NLOS interference is negligible


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



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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