Upcoming PhD QE Progress

So I’ve been doing my PhD for over two years now, and I haven’t posted a reflective “state of the thesis” post in quite some time, so here it is. I have maxed out my 50 pages (not included ToC and references) for some time now, it’s just been in the process of revision for the last month or so! I have more or less settled on what my research actually is now and am getting a clearer picture of it in my head all the time.

Officially the topic is “Radio Resource Management for Quality of Service in Heterogeneous Wireless Networks”. This is quite the mouthful, I know. Really what it boils down to is: Making various wireless technologies (Bluetooth, WiFi, WiMAX, 3G, 4G, … , etc) seamlessly work together. Many devices are capable of connecting to many of these radio access technologies (RATs), but often it is not seamless. What do I mean by this? Well suppose I am inside a university building, deep in the basement (where they tend to put CS students :P) where there is no mobile reception (3G, 4G etc.). I start downloading a large file, or call someone via wifi. Now I want to walk to my car because it’s time to go home for the day. Many networks now are not able to handle this, and it is interrupted after you change networks. Furthermore, you often have to manually tell the device you want to leave one network and join another. Seamless means this should all happen without you noticing. This is the focus of my research.

The biggest problem that I am concerned with is called handoff or handover. This is when the switch between RATs occurs. Traditionally, this also occurs when a mobile device switches from one tower to another, and it usually involved predicting the motion of the device along with some other factors for Quality of Service (QoS). For a vertical handover, we may or may not need to predict motion. If the heterogeneous wireless network (HWN) is densely covered, many RATs are available throughout the coverage region (as opposed to a sparsely covered where a given location may have access to one technology at once). In a dense HWN, the problem becomes a multi-criteria question.

  1. Which network is most economical for me to connect to?
  2. Which configuration of (network, client) pairs is most profitable for the operator?
  3. Which network is able to provide me with the required QoS?

More technical details to follow…

Why Blanket Wireless Coverage in Waterloo Failed, and Potential Solutions

Today the KW Record ran an article entitled “Blanket Wi-Fi plans unplugged in Waterloo Region and Guelph, but growing in Stratford”. I thought I’d throw in my two cents since this issue is very related to some of my research. Overall to me, the biggest factor that contributed to the failure of blanket wireless access in the Region of Waterloo was the cost of the service for users. From what I remember, it was on part with many high speed Internet plans. Why would someone pay the same price to have potentially slower, less secure service than competing wired services?

The Atria plan used large WiFi cells, with very expensive antennas (see the apartment building near University Plaza, which I believe was one of them).

Many other cities (much larger ones) have been very successful in providing blanket WiFi, using a completing different coverage model and cost model. The best example is San Francisco where a company named Meraki provides free wifi for over 100,000 people using their Mesh Router devices. These devices cost between $399 and $1500 each, which is still expensive, but likely much cheaper than anything used by Atria. These devices likely have much lower range and handle dense areas compared with the atria cells which seem to be designed for large areas, and require many people to subscribe to pay for their costs. The argument in the article that WiFi coverage in metropolitan areas is difficult seems like a terrible attitude to have for an area that has a reputation as a high tech leader. San Francisco likely has much greater challenges in this regard compared to our tiny city.


Example coverage map in San Francisco

Instead of using these expensive devices, much cheaper devices such as linksys wrt routers could be used. These routers support linux, and because of this much customization is possible such as mesh networking. While these devices are less reliable than the previous more expensive solutions, it may be a good way to at least get the network started cheaply. Additionally, areas which are not used by as many people could be covered with cheaper routers, while areas with more dense traffic may be covered by expensive ones.

The argument in the article that WiFi networks are unnecessary because of cellular networks is ludicrous! If that is the case, why are every smartphone and other device including WiFi radios in them? It’s because data on cellular networks is way to expensive. Any place where a device can get free or low cost WiFi should be used instead of the cellular network. One large problem with this at the moment, however is that it is not seamless to go from a cellular network to a wifi network. For example, it is often not possible to carry on a phone call while switching networks, or continue downloading or steaming without interruption. This will change with much of the research in heterogeneous networks.

One potential model that hasn’t been explored much is community wireless networks. In this case, devices could be provided to anyone willing to provide access to their own home network for the community. The incentive could be either donations from users, or a very small fee (2 – 5 dollars per month) which is distributed to providers. Additionally, anyone who provides a part of the network is able to get on free to other parts of the network. Of course, there’s nothing to stop the larger companies like Rogers and Bell from creating the same type of value added service. Since so many people already have wireless in their home using Rogers and Bell, they could create some type of login where you take your bandwidth quota with you and have access to anyone else’s network who is also participating. This way, you are not using their bandwidth cap (only their “speed” – which may introduce a whole other range of problems :P)

Windows 7 – SP1, Multiple OS – Grub

A while ago I bought a Toshiba netbook which of course came with Windows 7 startup. Since I was going to be putting 4 OS’es on it (Windows, Ubuntu, Chromium and Meego), I was switching from the usual method of booting directly into Windows, into using Grub2. Of course now that the SP1 update has come out, it doesn’t install properly. This is the support page that the error pointed me to: http://windows.microsoft.com/en-US/windows7/windows-7-windows-server-2008-r2-service-pack-1-sp1-installation-error-0x800F0A12


Windows Disk Management Tool, used for setting active partition

Unfortunately, none of these options worked. It turns out, it is a simple fix (at least for me). In start menu, type “disk management” into the search, and click on “create and format hard disk partitions”. Right click on the partition that has Windows7 (likely the largest NTFS partition [don’t select the recovery partition] if you have a setup like mine) and click “Mark Partition as Active”. Then try to install SP1 again, and it should work fine.

uShare autostart – Ubuntu 11.04

Previously, I installed ushare easily on Ubuntu following a process similar to this: https://help.ubuntu.com/community/Xbox360Media

I’ve recently become annoyed that ushare hasn’t been autostarting in Ubuntu 11.04. I suspect it may have something to do with the fact that I am using the same machine to host vpn so I have a bridged connection br0 as my main connection. The default script in /etc/init.d/ushare should be able to autostart, and I have tried adding it to rc.d using variation of this command “sudo update-rc.d ushare defaults 80”, however it fails to start. I have no trouble running it manually with the “/etc/init.d/ushare start” command however. So I’m guessing it is just trying to start before the network interfaces come up and failing. The workaround I found tries to solve this by explicitly running after the interface is up. The way to do it, is to add it to the “/etc/network/interfaces” file using something called “post-up”. Since I wanted to have ushare run after my br0 interface is brought up, I added it like at the bottom of the br0 section, see below:

iface br0 inet static
address 192.168.0.198
netmask 255.255.255.0
gateway 192.168.0.1
bridge_ports eth1
post-up /etc/init.d/ushare start

And, now on restart “ps ax | grep ushare” shows the process running. I am also able to connect on my xbox just as before 🙂

Sources: http://www.cyberciti.biz/tips/how-do-i-run-firewall-script-as-soon-as-eth0-interface-brings-up.html

MediaWiki + Ubuntu 11.04 & Customizations

Recently, I setup a personal wiki for myself since I’m always encountering more information than I have time to read, but always want to go back later. Its also a way for me to organize topics I don’t know as much about as I’d like so that I can remember to come back to those areas later on. (Inspired by fellow UoG Student Eddia Ma: http://eddiema.ca/wiki/) The default install from Ubuntu is pretty simple. I just installed it with the expected:

sudo apt-get install mediawiki

There are some simple steps to follow as you install with the package manager such as setting up the database and first configuration which should be easy enough to get through. However, the wiki required much customization before it would be good for what I was planning on using it for.

Citation Support

First of all, it had to support citations so that I could source the original papers, websites and others. This required the Cite Extension which can be downloaded here: http://www.mediawiki.org/wiki/Special:ExtensionDistributor/Cite (make sure you select the version that corresponds to the mediawiki version you have installed. Next extract to your extensions folder (likely /var/lib/mediawiki/extensions/ on Ubuntu 11.04). Finally add the following line to your mediawiki configuration file LocalSettings.php (likely in /etc/mediawiki).

require_once("$IP/extensions/Cite/Cite.php");

Attachments

I wanted to be able to attach papers directly into my wiki (pdfs and other documents from academic papers). For this I had to add the following line to my LocalSettings.php file (likely in /etc/mediawiki):

$wgFileExtensions = array('png','gif','jpg','jpeg','doc','xls','mpp','pdf','ppt','tiff','bmp','docx', 'xlsx', 'pptx','ps','odt','ods','odp','odg');

Additionally, I encountered problems uploading many larger pdfs since they are larger than the default php upload size. In ubuntu, this can be changed by modifying the php.ini file (likely located in /etc/php5/apache). Look for ‘upload_max_filesize’ and ‘post_max_size’ in order to change this to whatever size you like.

Math!

Of course being a CS student, I need to be able to add math equations into my wiki. The math formulas are entered using Latex which most CS grad students (and many undergrads) should know how to use. This one is in the Ubuntu repositories so it is easy to do:

sudo apt-get install mediawiki-math

Then you have to edit the LocalSettings.php file again (/etc/mediawiki) so that the wgUseTex flag is true:

$wgUseTeX = true;

Source Code – Syntax Highlighting

Again since I am a CS student, my wiki needs to be able to display source code easily in a readable way. For this I use the Ubuntu package manager again:

sudo apt-get install mediawiki-extensions-geshi

And edit the LocalSettings.php file (/etc/mediawiki) – For some reason, other instructions I have online have different paths and names for the plugin, so this will only work using the plugin from the repository. If you download it yourself directly, the name and location may be different:

require_once("$IP/extensions/SyntaxHighlight_GeSHi/SyntaxHighlight_GeSHi.php");

Wiki Privacy

Lastly, as I previously mentioned the wiki is private (at least for now). To do this it is quite simple. Just paste this into the bottom of your LocalSettings.php file. (There are other variations on how private you can make the wiki, but if you want to do that, check out the official mediawiki page)

# Disable reading by anonymous users
# See: http://www.mediawiki.org/wiki/Manual:Preventing_access#Restrict_viewing_of_all_pages
$wgGroupPermissions['*']['read'] = false;

# But allow them to access the login page or else there will be no way to log in!
# NOTE: You also need to provide access here to the .css and .js files that the
# allowed pages attempt to load; otherwise, users will get errors on the page
# when they attempt to load it (IE will complain about the errors;
# FF will show them in its error console)
# [You also might want to add access to "Main Page", "Wikipedia:Help", etc.)
$wgWhitelistRead = array ("Special:Userlogin", "MediaWiki:Common.css",
"MediaWiki:Common.js", "MediaWiki:Monobook.css", "MediaWiki:Monobook.js", "-");

# Disable anonymous editing
$wgGroupPermissions['*']['edit'] = false;

# Prevent new user registrations except by sysops
$wgGroupPermissions['*']['createaccount'] = false;