Phero-Trail: Bio-inspired Routing in Underwater Sensor Networks

Luiz F. Vieira, Uichin Lee, Mario GerlaUCLA

Application Scenario

Protecting critical installation such as harbor, underwater mining facility, and oil rigs. Mobile floating sensor nodes (they move with currents)

Autonomous Underwater Vehicles (AUV) or Submarines

AUV periodically “probes” sensors to check coverage and request “refills” of holes

SEA Swarm Architecture

Sensor Equipped Aquatic (SEA) swarm of mobile sensors: Span a Cube (say 1x1x1

km) under the ocean surface

Enable 4D (space and time) monitoring

Dynamic monitoring in face of ocean currents

Sensor nodes notify events to corresponding submarines

Z

X

Y

EventType A

EventType B

EventType A

EventType B

The Problem

Mobile sensors report events to submarines Must discover/establish route to submarine

Proactive (OLSR), Reactive Routing (AODV), or Sensor data collection (Directed Diffusion) All require route discovery (flooding) and/or maintenance

Not suitable for bandwidth constrained underwater mobile sensor networks (collision + energy consumption)

Geographical routing preferable, but expensive: U/W coordinate maintenance (no GPS) geo-location service to know the destination’s location

Goal: design an efficient routing protocol for a SEA swarm

Solution: Phero-Trail AUV uploads updates (pheromones) to sensors along its

projected trajectory on the “upper hull” of 1x1x1 cube Periodic updates create a pheromone trail We assume the trail length is = O(M), where M: number of

hops to travel width of network

Phero-Trail Routing

A mobile node routes the query packet vertically upwards to the convex hull

Node on convex hull performs a search to find a pheromone trail.

Once it finds the trail, the query travels to the end node (most recent update)

The packet is sent downward to the UAV (following the “bread crumbs” on the vertical path)

Event

1) Search Hull

Event

1) Search Hull

2) Ring Search

Event

1) Search Hull

2) Ring Search

3) Follow Trail

Event

1) Search Hull

2) Ring Search

4) Send Location

3) Follow Trail

Event

1) Search Hull

2) Ring Search

4) Send Location

3) Follow Trail

5) send alert

O/H Analysis Update

Length of a pheromone trail is assumed O(M) Up to M nodes remain connected in spite of current

Update O/H (pkt tx/sec) = MS/R = O(M) S = UAV speed and R = Tx range (uniform sensor distrib)

Routing Vertical routing O(M) - easy due to pressure gradient

Hull plane search for trail: random walk with step size =R Prob of success = 1/M (ie M pheromones among M2 sensors) Avg # of steps to find trail = M Travel until the end of trail = M Travel downwards to destination UAV = M

Total Routing O/H = O(M) pkt transmission

Related Work – Naïve Flooding Node periodically floods its current position to the entire network (M3 overhead)

M: number of hops to travel width of network

Z

X

Y

Simulation Results 1 Km x 1 Km x 1 Km

Submarine 5 m/s Vary network

size Compared with

flooding benchmark

O/H = Number of transmissions to deliver a

packet to UAV.

Simulation Results Number of pkt transmissions as a function of number of submarines (UAVs)

Related work - The ants

Ants can explore vast areas without global view of the ground.

Can find the food and bring it back to the nest.

Will converge to the shortest path.

How can they manage such great achievement ? By leaving pheromones behind them. Marking the area as explored

Communicating to the other ants.

Aging: pheromones evaporate

Double Bridge experiment

Food

AntHocNet: Ants-inspired routing Ants will start

from A the nest and look for D the food.

At every step, they will upgrade the routing tables and as soon as the first one reaches the food.

The best path will be known, thus allowing communication from D to A.

E

D

B

A

F

CNest

Food

AntHocNet (1/3)

(1) When a data session is started at node s with destination d, s checks whether it has up-to-date routing information for d.

(2) If not, it reactively sends out ant-like agents, called reactive forward ants, to look for paths to d.

AntHocNet (2/3)

(3) These ants gather information about the quality of the path they followed, and at their arrival in d they become backward ants which trace back the path and update routing tables.

(4) Once paths are set up and the data session is running, s starts to send proactive forward ants to d:

AntHocNet (3/3)

Packets are broadcast to alternate paths with some probability, so that new paths are explored.

(5) In case of link failures, nodes either try to locally repair paths, or send a warning to their neighbors such that these can update their routing tables.

VERY SIMILAR TO AODV

Related work: P2P Based Routing

FRESH (like Encounter w/out GPS coordinates): Target Node broadcasts its ID to all those it

encounters. Source “flood searches” for contacts, ie neighbors

with target ID Source forwards packet to most recent (FRESH)

contact Differs from Phero-Trail

FRESH relies on mobile “mules”; works best if destination is static

Phero Trail relies on static sensors and “moving” destination (AUV)

BreadCrumb:

Assume static wireless sensor networks (OK) The originator uses Bread Crumbs to retrace the

path Very similar to the down trace of the vertical

path to get to the AUV

Conclusion

Presented a novel bio-inspired Underwater Routing scheme (Phero Trail) efficient routing for a SEA swarm Optimal performance O (M) Outperforms naïve approaches Can perform as well as position aware schemes (eg Hydrocast) Yet, it does not require coordinates

Future Work

Phero Trail Study performance in presence of currents Study effect of multiple submarines Vary number of sensors/sinks, the speed of sensors/sinks, the deployment area size (including various depths).

Impact of coordinates - can do better with them?

Use Phero Trail as Location Server (PTLS) Compare performance of PTLS with High-Grade, XYLS