Hello: A Generic Flexible Protocol

for Neighbor DiscoveryWei Sun, Zheng Yang, Keyu Wang and Yunhao Liu

CSE, Hong Kong University of Science and TechnologySchool of Software and TNList, Tsinghua University

Gaoyang Guan

Motivation• Neighbor discovery is crucial• Better trade-off between duty cycle and discovery

latency

Challenges• Existing protocols’ parameters are highly restricted• Reduce or take advantage of redundant discovery• Existing protocols cannot adjust well to application

demands

Contributions• A neighbor discovery protocol that exhibits the

highest degree of freedom.• An optimality analysis under a generic framework.• A flexible solution to applications dynamics.• Extensive evaluation through simulation and real

world experiments.

Design• A. Schedule Design

Design• A. Schedule Design• Possible solutions• Stay active in the first slots

• Our design• expand the period to cn slots• wakes up at the first slot of each cycle• wakes up at the consecutive slots indexed from 1 to

c/2 in the first cycle

Design• B. Symmetric Discovery Latency• Lemma 1.

The worst-case discovery latency Ls for Hello under symmetric duty cycles with parameter pair (c; n) is cn slots.

Design• C. Duty-Cycle Asymmetry

1) Same c, Different n:

2) Different c:

Design• D. A Generic Framework

Design• E. Optimality Analysis• 1) Optimum for symmetric duty cycles:

Searchlight

Design• 2) Optimum for asymmetric duty cycles:

This result well explains why Disco performs best under asymmetric duty cycles

Design• 3) A compromise:

worst-case latency

U-Connect

Design• G. Redundancy• 1) Redundancy from slot non-alignment

• beaconing at both the beginning and the end of an active slot leads to two discovery opportunities

• 2) Redundancy from repetitive patrols• each patrol is put at a randomly selected cycle (row) but at the

same relative position (column) within the cycle

Evaluation

Evaluation

Evaluation

Evaluation

Evaluation

IMPLEMENTATION

Q&A