WMN for Rural Communities a Case Study

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					           SUMMER UNIVERSITY ON IT IN AGRICULTURE AND RURAL DEVELOPMENT – 2007 DEBRECEN, HUNGARY




                       WMN for Rural Communities: a Case Study
Miklós Kasza1, Vilmos Bilicki1
1 Department of Informatics, University of Szeged, 6720 Szeged, Hungary
kaszi@jokeman.hu, bilickiv@inf.u-szeged.hu
   Abstract. Wireless Mesh Network is a popular technology used for providing mobile and fixed data
connection in rural and urban areas. In our article we would like to give an overview about the
currently deployed larger WMN installations and the typical services on the top of these
infrastructures. Furthermore we would like to give an overview of our WMN solution that can provide
infrastructure for highly mobile broadband connections and services that need low response times and
mobility support. Our WMN infrastructure is designed to be usable by multiple competing internet
service providers as a common basis (just like telephone cables in the wired world). IPv6-based
protocols and software are also supported.
   Keywords. Wireless Mesh Network, wifi, living laboratory, OpenWrt
Introduction
   Wireless Mesh Network is a popular solution used for providing mobile and fixed data
connection to rural and urban areas. In the C@R project, it was shown that despite of the lack
of high gain antenna our target mobile device, the Nokia770 tablet is able, to participate in a
WMN. In the following section we would like to give an overview about the currently
deployed larger WMN installations and the typical services on the top of these infrastructures.
After this we introduce the hardware and software tools that were in the field of our interest
during the creation of our WMN test site. At the end we present the deployed test
infrastructure and share some results of our testing and measurements.
WMNs in Practice
  There are several communities and corporations in the world who dedicated themselves to
building, operating and experimenting with wireless mesh technology. Some of them provide
complete mesh solutions including wireless devices and software for operating them. Some
others provide only pretty and easy-to-use devices that can be installed by any home users.
Table 1 summarizes the publicly available WMN solutions and some of their most important
properties.
                               Table 1. Publicly available WMN solutions
        Solution          Offered products and services             Target audience                        Technology
   Cambridge Matrix       Free access to local content via   Any user equipped with a wifi    Multi-hop optimisation, IPsec security
                                        wifi                       network device
                             Paid Internet connection
      MIT Roofnet         WMN software (Linux-based,         Experimental WMN installation     High-throughput routes in the face of
                          kernel-mode) and experimental                                                    lossy links
                               network installation                                              Adaptive bit-rate selection (Click
                                                                                                   modular router Linux patch)
                                                                                              New protocols (SrcRR – based on DSR,
                                                                                               ETX metric) which take advantage of
                                                                                                    radio’s unique properties
      LocustWorld          WMN software and hardware            Any WMN implementors             Uses AODV as routing protocol
                                                             (commercial version available)
         Fonera           Wireless devices and multi-level Any FON members (worldwide         Fon devices use a modified version of
                               public Internet-access        access for free) and non-        OpenWRT with a well controlled web
                                    (worldwide)                  members (paid)                    interface for configuration
     Wireless Africa      Wireless-enabled devices, low-      African people, schools and         VSAT, Ethernet and T1 uplink
                               cost Internet-access                   companies
      Meraki Mini           Devices and configuration         Individuals, communities and Commercial version of SrcRR as routing
                                    software                          entrepreneurs                      protocol
                                                                                              Devices can use Power over Ethernet as




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                                                                                               power source
  Sparknet OpenSpark     Devices and configuration      Free hotspot usage for       Uses a modified version of OpenWrt
                                 software            members, membership for other
                                                              individuals



Tested Hardware
   The vast majority of the wireless routers on the market cannot be expanded to support more
features. That is, their firmware is static; end-users do not have access to the core system.
They can configure their router through the provided web interface, and what is not listed
there, it cannot be added or changed. If they want some specific extra functionality, they have
to buy a more expensive, high-end router.
   This is where third-party firmware is needed. These projects are based on open source
programs and the Linux kernel opening a new way to customize the wireless devices and add
features that are only present in high-end routers. Of course, there are some minimal
requirements which have to be met for the firmware to operate: 4MB of flash memory and at
least 8MB of RAM (16MB is a practical minimum).
                                      Linksys WRT54GL 1.1
   The Linksys WRT54GL is a Wi-Fi capable router (Access Point) from Linksys for sharing
Internet connections among several computers via 802.3 Ethernet (1 WAN, and 4 LAN ports)
and 802.11b/g wireless data links. It is cheap, compact; and by applying third-party firmware
the user can widen the number of tasks that can be managed.
   Linksys released the WRT54GL in 2005 to support third-party firmware based on Linux,
after the original WRT54G line was switched from Linux to VxWorks starting with version 5.
As of August 2006, version 1.1 appeared to be shipping worldwide. This step started the wave
of new firmware and activated open-source communities.
   The WRT54GL v1.1 uses a Broadcom 5352 CPU at 200MHz (ARM architecture) with
integrated switch; 16MB of RAM and 4MB of Flash memory. After flashing the default
OpenWrt firmware to the device, the router will have roughly 1.9MB of free space of flash
memory. No USB devices are supported.
                                    Asus WL-500G Premium
   The Asus WL-500G Premium router is much faster than the Linksys WRT54GL. It has one
WAN port and 4 LAN ports, both 10/100 capable of auto cross-over function (MDI-X). The
router also has 2 USB2.0 ports allowing the use of external hard disks, web cameras and
printers.
   The WL-500GP has an ARM processor running at 264MHz; 32MB of RAM, and 8MB of
Flash memory. This allows to deploy much more programs and utilities to the router’s flash
memory, as after flashing the default OpenWrt firmware; 6.2MB of free space will be present.
   The router has two antennas: one internal Inverted-F PCB antenna and one external dipole
antenna with Reverse-SMA antenna connector. The output power for 802.11g ranges from 14
to 16 dBm at normal temperature.
                                   Nokia 770 Internet Tablet
   The Nokia 770 is a wireless internet appliance designed for wireless Internet browsing and
e-mail functions. It does not have built-in cell phone capability, but once it is connected to a
network, VoIP comes into the picture.
   The device is based on a Texas Instruments OMAP 1710 CPU running at 252 MHz with
ARM architecture. The display has a resolution of 800×480 pixels. It is accessible via WLAN
(IEEE 802.11b/g), Bluetooth 1.2, dial-up access, and USB. The device contains a speaker and
a microphone. It comes with 64MB of DDR RAM and 128MB of internal FLASH memory,
of which about 64MB should be available to the user. The device also accepts MMC cards
expanding the storage space.


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   The operating system is a modified version of Debian GNU/Linux based on a Linux 2.6.12
kernel, but can be flashed with a newer, and even self-modified kernel (think about MIPv6
patched version, for example) including an X Window System-based graphical user interface in
the form of a window manager incorporating the GTK+ toolkit and Hildon user interface
widgets. The device includes the Opera web browser. Using the Package Manager, the user
can install many applications to the device.
   The development platform for the Nokia 770 is known as Maemo, and it is open source.
The most recent version is 2.2 (version 3.0 is for N800 only). The operating system is called
IT OS. The IT OS 2006 is the newest available for the Nokia 770.
   To cross-compile for the internet tablet, ScratchBox can be used. It’s a cross-compile toolkit
available for Debian GNU/Linux. It creates a virtual environment and with the Maemo SDK, it
is possible to develop programs for the ARMEL architecture, or even compile a patched kernel
to the Nokia 770.
Tested Software
  Most of the software we tested was run on the OpenWrt operating system. Primarily we
focused on the usability of AAA solutions and messaging (VoIP and instant messaging)
programs.
                            The OpenWrt Operating System
   After the release of the Linksys WRT54G router firmware source code, programmers started
to modify the firmware to change or add functionalities to the device. Several development
projects have been started to enhance the firmware for the WRT54G by mostly adding only a
few extra functionalities. It was difficult to find the most appropriate firmware with the
combination of functionality desired.
   OpenWrt takes a different route. Instead of starting out with the Linksys sources, the
development started with a clean slate rebuilt from the ground using the most recent versions
of software creating a really compact Linux for this embedded system. And what makes this
firmware unique is the fact that it employs a writable file system.
   The file system can be divided into two parts: The read-only ROM (SquashFS) where the
kernel and all the system files (that is, the firmware) could be found; and a writable one
(JFFS2). The first section of the flash memory is dedicated to the ROM; after flashing
OpenWrt to the device, it will stay the same. The remaining free space can be filled with
programs and utilities. The very last part of the flash memory is for the NVRAM where
special variables are stored. This section is reserved and stays intact even after a new flash;
but it can be changed.
   When installing programs to the device, the newly created executables and configuration
files will be stored in the JFFS2 partition. Also, when modifying base configuration files (the
ones that are present in the SquashFS), a new copy will be created in the JFFS2 partition; and
after that, the new copy will be the authoritative one.
   As of this design, after a defective installation or modification in the configuration files;
entering the failsafe mode can be handful. When booting in failsafe mode, only the files in the
SquashFS will be taken into account ignoring the JFFS2 partition. This means that the router
will behave in the same way as it would right after flashing the firmware again. When the
boot is finished after remounting the JFFS2 partition, the problem can be solved in most
cases.
   The OpenWrt also introduces a BuildRoot system. With this tool, it is possible to select the
packages present in the firmware, change their default configuration; select the Unix
commands we want to use; insert out own programs, and compile them to the ARM
architecture; or even change the final file structure. In this way, the OpenWrt firmware is
highly customizable and it gives us the power to do what we need with the cheap hardware.



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                                         WMN Services
   The raw data transfer capability of a wireless mesh network is not enough for the current
applications. High level services are needed to be able to utilize the unique physical and social
environment. A basic service set is the traditional AAA (Authentication, Authorization and
Accounting) services. As the infrastructure is implemented in a public space, a reliable AAA
framework cannot be ignored. In some places, the WMN infrastructure can compete with the
classical GSM based IN (Intelligent Network) services. The SIP and the XMPP protocol
families can provide a wide scale of IN and beyond IN services. The mobility in the IP word
is solved with the help of the Mobile IPv4 or Mobile IPv6 protocols. Depending on the
capabilities of the WMN routing and addressing capabilities, these services might be used on
the top of the WMN. The 802.11 protocol family supports the layer two roaming, but this can
be extended by a WMN based roaming scheme. In this section, there is a short overview of
these technologies.
                                               AAA
   Authentication, Authorization and Accounting (AAA) protocol serves to verify the identity
of an entity, determine whether a requesting entity will be allowed access to a resource and
collect information on resource usage for the purpose of capacity planning, auditing, billing or
cost allocation. AAA protocols are RADIUS, DIAMETER, TACACS, TACACS+. DIAMETER
is not directly backwards compatible, but provides an upgrade path for RADIUS. TACACS+
is based on TACACS, but in spite of its name, it is an entirely new protocol which is
incompatible with any previous version of TACACS. DIAMETER and TACACS+ have
generally replaced the earlier protocols in more recently built or updated networks. AAA is
widely used by VoIP service providers. It is used to pass the login credentials of a SIP end
point to a SIP registrar using digest authentication.
   There are several implementations of AAA, but most of them assume PCs as access points.
When it comes to ad-hoc networks consisting of routers with OpenWrt, only a few
possibilities can be found. Most of these initiatives are in early beta or testing stage, but some
are ready to be deployed on OpenWrt too.
                                      Chillispot + Radius




                         Figure 1. Sample ChilliSpot and Radius system
  ChilliSpot supports web based login which is today’s standard for public HotSpots.
Authentication, Authorization and Accounting (AAA) is handled by a radius server.
  To this setup (Figure 1), certain other programs are needed: authentication web server, and
a radius server. For the web server, the installation of Apache-SSL, MySQL and Perl is
necessary. All these resources must be merged together to work as desired.


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   Here is how it works: the wireless client requests an IP address and is allocated an IP
address by Chilli. When the user starts a web browser, Chilli will capture the TCP connection
and redirect the browser to the authentication web server. The web server queries the user for
his username and password. The password is encrypted and sent back to Chilli.
   This setup is widely used, but for OpenWrt several modifications are needed including the
changing of the firewall script, and providing a CGI wrapper. As ChilliSpot provides a DHCP
server, it can conflict with the built-in DHCP server of OpenWrt. Also, OpenWrt has a small
http server (for the web-admin interface) that only supports the use of shell script CGI
wrappers. The installation of another web server is necessary, which again, raises the problem
of conflicting services.
                                             WifiDog
   The WifiDog project is a premier open source captive portal solution. It was designed
primarily for wireless community groups. It has a simliar approach to that of ChilliSpot, but it
is much more lightweight. On the server side, for the authentication web server, Apache2,
PHP5 and PostgreSQL-8.1 are needed. On the client side, a small gateway for OpenWrt
exists.




                                Figure 2. Sample Wifidog system
   After installing the WifiDog gateway on the router, only a little change to the firewall script
and a light modification in the default WifiDog configuration are needed. Every connecting
wireless client is redirected to the captive portal when opening a browser window; and after
authentication, access is granted to them. The IP address of the clients can be given by the
built-in DHCP server of the OpenWrt, or in ad-hoc networks, it can be defined by the client
itself.
   WifiDog allows managing multiple networks and nodes; and through its web
administration, it is possible to edit existing users and their privileges. Complete and detailed
statistics can be generated for each individual user, or for each node.
   So far, this method has been proven to be the most lightweight solution for the OpenWrt-
based routers. As its full source code is available, it can be customized very well in the future.
Further information can be obtained from WifiDog Website.
                                      Other approaches
   There are other solutions for captive portals. The NoCatSplash is a C port of NoCatAuth
which is written in Perl. It is small, easy to install, but it is exceedingly unstable. Furthermore,
it does not support full user authentication, visiting clients are only presented by a single web
page where after clicking a button they can continue.
   A much more robust approach is the CoovaAP firmware. It is based on OpenWrt and it is


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modified to work as an access point. With this firmware, many methods can be selected for
AAA, but it depends on the use of external servers. Also, on weaker devices like the LinkSys
WRT54GL, the processor load and bandwidth consumption are too high to deal with.
                                  Instant messaging - VoIP
   Voice over Internet Protocol is the routing of voice conversations over the Internet or
through any other IP-based network. VoIP can facilitate tasks that may be more difficult to
achieve by using traditional networks. First, the ability to transmit more than one telephone
calls down the same line. Incoming phone calls are automatically routed to your VoIP soft
phone, regardless of where you are connected to the network - as VoIP is location
independent, only an internet connection is needed to get a connection to a VoIP provider.
Also, VoIP phones can integrate with other services available over the Internet including
video conversation, message or data file exchange in parallel with the conversation, audio
conferencing, managing address books and passing information about whether others (e.g.
friends or colleagues) are available online to interested parties.
                                         SIP / SIMPLE
   The Session Initiation Protocol (SIP) is an application-layer control (signaling) protocol for
creating, modifying, and terminating sessions with one or more participants. These sessions
include Internet telephone calls, multimedia distribution, and multimedia conferences.
SIMPLE is a set of extensions to the established SIP protocol that initiates, sets up, and
manages a range of media sessions including voice and video.
   One potential problem with SIMPLE is that it is a paging protocol meant to perform
signaling without carrying anything else. It can carry a brief conversation which is great for
single-session IM traffic and SMS traffic, but it is not very good for doing the heavy load to
carry things like data signals or video signals on top. Furthermore, SIMPLE is missing a core
IM-related functionality such as contact lists and group chat capabilities.
   Another potential pitfall with SIMPLE is that SIP uses both TCP and UDP as transport
layers. TCP includes congestion control, whereas UDP does not, thereby opening the door for
packet loss during the times of network congestion.
   Problems also arise when we want to deploy a SIP implementation to the Nokia 770. There
are only a few approaches and most of them are only in the porting phase. There is only one
solution that has been compiled and was able to run on the Internet Tablet: The Ekiga soft
phone; but the program’s size was above 40MB. This is extremely huge given the 64MB of
internal free space. Also, there were problems with accessing the sound card of the device.
                                        XMPP / Jabber
   The Extensible Messaging and Presence Protocol, or XMPP, is an open, XML-based
protocol for near-real-time, extensible instant messaging and presence information. XMPP is
also extended to handle signaling / negotiation for Voice over internet protocol (VoIP) and
other media sessions. This signaling protocol is called Jingle. Jingle is designed to be
consistent with the Google Talk service and interoperable with the Session Initiation Protocol.
   Proponents of XMPP contend that an XML-based data-transport technology is better suited
than a signaling technology to handle IM and presence. According to its designers, one major
benefit of XMPP is that it can be extended across disparate applications and systems because
of its XML base. Jabber’s extensibility and XML foundation is a considerable technical
advantage over SIMPLE.
   Contrary to SIP, setting up a Jabber server is easy; and the built-in Internet call application
in the Nokia 770 supports the XMPP/Jabber protocol by default. This means, with some small
configuration, in a few steps we have a complete and reliable VoIP system.
   Instant messaging (IM) and presence are core functionalities for XMPP, and they are a
stable technology defined in a protocol specification that has been approved by the relevant
standards development organization.


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                                          Mobile IPv4
   Mobile IP is a standard communications protocol that is designed to allow mobile device
users to move from one network to another while maintaining a permanent IP address. It is
described in IETF RFC 3344 and updates are added in RFC 4721. The Mobile IP protocols
support transparency above the IP layer including the maintenance of active TCP connections
and UDP port bindings. Besides the basic Mobile IPv4 (MIPv4) protocols, several other drafts
deal with concerns such as optimization, security, extensions, AAA support, and deployment
issues. Mobile IP provides an efficient, scalable mechanism for roaming within the Internet.
                                             Roaming
   Roaming is a general term in wireless telecommunications that refers to the extending of
connectivity service in a location that is different from the home location where the service
was registered. Roaming occurs when a subscriber of one wireless service provider uses the
facilities of another wireless service provider. This second provider has no direct pre-existing
financial or service agreement with this subscriber to send or receive information. A device
will usually indicate when it is roaming. The quintessential example of “roaming” is the case
of cellular phones when a phone is in a location where its wireless service provider does not
provide coverage (for example, another country). In some cases, roaming occurs in a phone’s
designated home area when it transmits via a different provider’s tower (sometimes at a
higher price). This is likely to occur when the service provider’s signal is too weak or if the
volume of callers is too high. In order for a mobile device to use a different carrier’s service,
the phone’s service provider must have a roaming agreement with that carrier. In 802.11
roaming can also mean subscriber mobility or handover (handoff) within the same network.
The most basic form of handover is when a phone call in progress is redirected from its
current cell and its used channel in that cell to a new cell and a new channel. The commonly
used wireless networking transmission methods are 802.11a, 802.11b, and 802.11g versions to
provide wireless connectivity today. Handoffs are supported under the “a”, “b” and “g”
implementations, but only for data. The handover delay is relatively long. Current roaming
delays in 802.11 networks average in the hundreds of milliseconds. The delay that occurs
during handoff cannot exceed about 50 milliseconds, the interval that is detectable by the
human ear. 802.11r will specify fast Basic Service Set (BSS) transitions and will be able to use
fast Roaming.
The Deployed Infrastructure
  In the Hungarian Living Laboratory, there are two pilot areas. The Mórahalom pilot area is
currently under deployment – 6 nodes are deployed and 4 others are under deployment. With
these 10 nodes we will be able to cover more than half of the city with mobile data network
service. On the top of this infrastructure, there is an AAA and an IM/VoIP service. In this
chapter, we will give an overview of the deployed infrastructure.
  In this pilot area, we have ten end users. The devices are mounted onto the rooftops of these
end users’ houses. They will use the network on a daily basis. Figure 3 shows the sites where
these nodes have been or will be deployed. The nodes are repacked Asus WL-500GP routers
with OpenWrt “White Russian” firmware and OLSR. On this WMN infrastructure there is an
AAA and an IM/VoIP service available.




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                       Figure 3. Map of the deployed WMN test nodes
       (satellite image with WMN overlay and map with the nodes’ positions marked)
                              Management and Monitoring
   The management and monitoring takes a significant share of the total cost of the ownership
price of a telecommunication network. One approach to decrease this price is to use intelligent
self tuning self healing solutions. This could be complemented by a voluntary non-profit
based management and monitoring team. The public owned WMN goes on this road. In the
Hungarian Living Laboratory, we would like to establish a voluntary group for operating and
monitoring the deployed mesh. The business case behind this will be incorporated into the
global business case of the public owned mesh network. To be able to effectively monitor and
manage a network, intelligent tools are needed. We would like to use and extend the
capabilities of our Netspotter framework to monitor and manage wireless mesh networks. The
details of the needed capabilities will be defined during the manual monitoring and managing
of the WMN.
   Most of the devices are situated on the top of houses, and they are only accessible through
wireless interfaces. It is essential to monitor the accessibility, and if the device is not
accessible, it should change for a failsafe state. This is described in the following subsection.
                                         Fail-safe Mode
   Our goal was to provide a fallback state, so that after a short period of time the device could
sense the problem and go to a failover mode, if we brick the routers while testing or
measuring. What we need is to reach the router, no matter what the circumstances are.
   The most basic way is to guarantee that any router will be accessible from any point, if we
dedicate an IP address to every device and keep the number of the extra installed program
beyond the firmware to the minimum.
   In our case, we named our mesh “nlab_mesh” with 192.168.2.0/24 IP address domain. We
have only two programs installed: the OLSR daemon, and the wl package to manage the
wireless interface. Every router is shipped with a shell script that will be able to restore the
original state where the mesh is rock solid and all the devices are accessible.
   The operation method can be divided into three major parts: NVRAM (non-volatile random
access memory) settings, file system setup and wireless settings.

Measurements
  After 5 deployed routers in Mórahalom, we made some measurements and tests to verify
the integrity of the mesh network. We measured the coverage of each node; the bandwidth
between them; and the VoIP performance. We took 2 Nokia 770 and a laptop, and connected


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them to the mesh at various places. The laptop hosted a small jabber server for VoIP testing;
and the Nokia internet tablets were equipped with iper for bandwidth measurements. The
testing took place on a sunny day, with clear weather conditions.
                                      Physical Properties
   At the time of the testing, 5 routers were online: labeled .4, .5, .7, .11 and .14. We
connected a laptop (labeled .50) to the mesh with OLSR support and two Nokia 770 devices
(labeled .110 and .120), without being near .11. The olsrd_dot_draw plugin gave us the
following visualization.




                  Figure 4. OLSR setup visualized by olsrd_dot_draw plugin
   Thereafter, we made measurements with the Nokia 770 devices using iperf at the nodes
inside the hosting house and outside. As we moved farther and farther, the bandwidth was
slightly getting lower. We learned that if a building blocked the direct way of the beam, there
were some packet losses. But overall, the lowest bandwidth we encountered was
300Kbits/sec.
   The APs labeled .14 and.11 have larger antennas mounted, the peak bandwidth at these
routers is about 800Kbits/sec. The .7 is mounted at the top of a block of flats - there we had
3.6Mbits/sec. We were able to catch its signal from a distance of 6 km.




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                      Figure 5. Signal ranges of deployed WMN nodes
  Below is a table with the bandwidth between each pair of nodes.
       Table 2. Bandwidth measurements between each pair of deployed mesh nodes

                      Station      Station      TCP Transfer      TCP Bandwidth
                        .4           .5          0.45 Mbytes       0.35 Mbits/sec
                        .4           .7          0.61 Mbytes       0.48 Mbits/sec
                        .4           .11         0.66 Mbytes       0.54 Mbits/sec
                        .4           .14         1.62 Mbytes       1.33 Mbits/sec
                        .5           .7          0.67 Mbytes       0.54 Mbits/sec
                        .5           .11         3.32 Mbytes       2.77 Mbits/sec
                        .5           .14         0.25 Mbytes       0.19 Mbits/sec
                        .7           .11         4.90 Mbytes       4.06 Mbits/sec
                        .7           .14         1.13 Mbytes       0.91 Mbits/sec
                        .11          .14         0.72 Mbytes       0.58 Mbits/sec


  We measured with the Nokia770 in the building of node .11 and near node .11 through
Táncsics Mihály Street. Some terrain obstacles weakened the connection quality.




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             Figure 6. Map of measurements between node .11 and a Nokia 770

           Table 3. Bandwidth measurements between node .11 and a Nokia 770
                            Distance         TCP Transfer     TCP Bandwidth
                             indoors          0.72 Mbytes       0.58 Mbits/s
                            50 meters         0.94 Mbytes       0.75 Mbits/s
                            100 meters        0.42 Mbytes       0.33 Mbits/s
                            150 meters        0.77 Mbytes       0.62 Mbits/s
                            200 meters        0.85 Mbytes       0.68 Mbits/s
                            250 meters        0.44 Mbytes       0.35 Mbits/s

                                               AAA
  We tested the AAA service with two Nokia770 from indoor and outdoor. The Web based
authentication worked well.




                         Figure 7. Map of AAA service measurements
                                         VoIP measurements
   For VoIP testing we used the laptop as a jabber server connected to node .11. The two
Nokia 770 devices were used for the client side. One of them was connected to node .14 and
the other to node .7. The sound quality was fairly good even with background flood ping
between node .11 and .14.
   The test environment was set up quickly - we added two test users on the web admin
interface of the jabber server, we registered those users on the Nokia 770 devices, and we



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made a call. Whilst calling, we changed positions, but it did not affect the quality of the
conversation. However, moving far away from the host node, and behind a building blocking
the way of the beam, we experienced some short gap in the voice stream, or rarely a loss in
connection.




                              Figure 8. Map of VoIP measurements
Conclusion
   During the requirement capturing process for the Hungarian Living Laboratory, it turned
out that there is a need for a cheap mobile data communication infrastructure. Most of the
applications designed and developed in this LL will utilize the high level services of this
infrastructure. The philosophy behind the community owned wireless mesh network fits
perfectly into the philosophy behind the living laboratories. The field of WMN is in a phase of
very intensive research, development and deployment. In our case, we selected two pilot areas
where the end users can test the deployed infrastructure. In mid term, they will be involved
not only in the usage but in the maintenance of the infrastructure too. A work plan has been
elaborated with the stakeholders. The first milestone has been reached. The equipment and the
software environment have been selected and deployed in the site and in the testing laboratory
too. A group of end users provides place and electricity for the equipment. In turn, they get
free Internet access during the project. The network is and will be used on a daily basis.
Several measurements have been conducted to test the capabilities of the network. The
previous section gives an overview about the results of these measurements.
   As it was predicted with cheap hardware and free, open source software, we were able to
build a mobile data communication network. The cost of the network capable of providing
mobile wireless access to more than 1000 people is about 1000 Euro. The feedback from the
end users and the measurements showed that we are moving in the right direction. In the
future we are going to work on optimizing the capabilities of the network and to elaborate the
business case which will be used behind our community owned access network.
   Acknowledgements. We would like to say thanks to Sándor Kiss and Csaba Fodor from
Mórahalom for their help with the deployment and to the test end users who helped our work.
References
The OpenWrt Developers. OpenWrt Documentation. Available at:
  http://downloads.openwrt.org/kamikaze/docs/openwrt.html. Accessed June, 2007.
The OpenWrt Developers. OpenWrt Wiki Pages. Available at: http://wiki.openwrt.org/.
  Accessed June, 2007.
The WifiDog Developers Team. WifiDog Website. Available at: http://dev.wifidog.org/.
  Accessed June, 2007.


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