Research Conversazione 2010

This year's research conversazione was held on Friday 29 October 2010. This year, my poster is about the connectivity of 2-hop wireless networks with infrastructure support. Below are two selected photos:

Myself

(From left to right) Seh Chun Ng (me), Zijie Zhang (Jeffrey), Tao Yang

Workshop - Adelaide, South Australia

Recently ACoRN has organized a workshop (28-30 June 2010) held in Mawson Lakes, South Australia. I attended the workshop and presented my work, titled "On The Properties of Infrastructure-based Wireless Multi-hop Networks". You can find the workshop program here (http://www.acorn.net.au/event/mwnworkshop10/).

I also spent some time in Adelaide city. I used to study at the University of Adelaide. It is a good feeling to revisit the beautiful city again.

Some photos:

King William Street - Trams have replaced the 99B buses.

Victoria Park - the heart of Adelaide city.

Lollipops... I'm loving it!

Rundle Mall @ night time.

Conference - Cape Town, South Africa

I went to Cape Town, South Africa during 23-27 May, 2010 to attend IEEE ICC 2010. I presented my paper there, met some brilliant people in the conference. Although people say South Africa is not a safe place, I think it is beautiful. We can even see seals swimming around the harbour. See? Human can live peacefully with animals....

Here are some photos:

Johannesburg Airport - get ready for World Cup 2010

Cape Town & Table Mountain

Table Mountain Cableway

I am standing on top of Castle of Good Hope. Background is Cape Town City Hall. South Africa ex-president Mr. Nelson Mandela gave a historical talk there before.

Bo-Kaap district, where the Cape Town Malays stay.

Waterfront @ day time

Waterfront @ night time

Journal Paper - IEEE Journal on Selected Areas in Communications

Seh Chun Ng, Wuxiong Zhang, Yu Zhang, Yang Yang, and Guoqiang Mao, "Analysis of Access and Connectivity Probabilities in Vehicular Relay Networks," to appear in IEEE Journal on Selected Areas in Communications.

Abstract:

IEEE 802.11p and 1609 standards are currently under development to support Vehicle-to-Vehicle and Vehicle-to-Infrastructure communications in vehicular networks. For infrastructure-based vehicular relay networks, access probability is an important measure which indicates how well an arbitrary vehicle can access the infrastructure, i.e. a base station (BS). On the other hand, connectivity probability, i.e. the probability that all the vehicles are connected to the infrastructure, indicates the service coverage performance of a vehicular relay network. In this paper, we develop an analytical model with a generic radio channel model to fully characterize the access probability and connectivity probability performance in a vehicular relay network considering both one-hop (direct access) and two-hop (via a relay) communications between a vehicle and the infrastructure. Specifically, we derive close-form equations for calculating these two probabilities. Our analytical results,
validated by simulations, reveal the tradeoffs between key system parameters, such as inter-BS distance, vehicle density, transmission ranges of a BS and a vehicle, and their collective impact on access probability and connectivity probability under different communication channel models. These results and new knowledge about vehicular relay networks will enable network designers and operators to effectively improve network planning, deployment and resource management.

Conference Paper - Globecom 2010

Seh Chun Ng and Guoqiang Mao, “Analysis of k-Hop Connectivity Probability in 2-D Wireless Networks with Infrastructure Support”, to appear in IEEE Global Communications Conference (GLOBECOM), 2010.

Abstract:

Wireless multi-hop networks with infrastructure support have been actively studied to solve the scalability problem in large scale vehicular and sensor networks that the end-to-end throughput and other performance metrics decrease sharply with the increase in the number of nodes in the network. In the infrastructure-based networks, wireless nodes are allowed to access the base stations either directly or via a multi-hop path. In order to provide meaningful services, it is often desirable to limit the number of hops in the wireless multi-hop path. In this paper, we study a 2-D wireless network where users are Poissonly distributed in a square area and base stations are placed at the four corners of the square area as a typical component of a larger network where users are randomly distributed and base stations are regularly deployed. We obtain analytically the exact and approximate k-hop connectivity probability for k=2, i.e. the probability that all users can access to at least one base station in at most two hops, under a generic channel model. The results are verified by simulations and can be used in network planning, design and resource management.

Photos - The Entrance

The Entrance - 1.5 hours drive from Sydney, where Tuggerah Lake meets the Pacific Ocean.

Some part is so shallow that we can walk to cross the lake.

Pelicans are waiting for fish feeding...

Beautiful landing...

Notes - The Connectivity: What is missing?

For the connectivity of wireless ad hoc network, we have the following results:

1. In 1D, we used the following techniques to obtain the results (from less accurate to exact result).

a) Isolated node: Analyse the probability of the existence of an isolated node.
b) Occupancy theory: subdivide the interval into "cells" of length r (the transmission range). If there exists an empty cell separating two cells that each contains at least one node, then the network is disconnected.
c) Random Interval Graph: The existence of the big spacings. (exact result)

2. In 2D, we do not have the exact result. Instead, the following techniques are used to obtain the asymptotic results.

a) Isolated node: The existence of an isolated node

From 1D results, we can predict that using occupancy theory may improve the results obtained under 2D networks. From observing the occupancy theory methodology, I assume there are two directions that we can look into the connectivity problem.

a) Divide the 2D area into cells and start from here.
b) Look at nodes lying within a certain sector of angle but are not directly connected.

I could not tell any further until I have more concrete ideas on that.