If you donâ€™t have any experience setting up a TCP/IP network, try to have a good friend that
knows the stuff onsite, or at least on the other end of a cell phone. Dozens of things can go
wrong in configuring a basic network connection on a regular wired Ethernet link. By adding
wireless to the mix, you could be in for a long day without proper support.
We are here to help. Try some of these basic solutions to common link problems:
Antenna alignment: Often, if the antenna mount is not secure, the alignment may skew
from its original position, causing a link disruption. Make sure that everything is mounted
securely, and that the antennas have been properly aligned. Double-check the link after
tightening down mounting bolts. Contents may have shifted during tightening.
Bad cables: Any pigtail cables in use as the connection between your laptop and the
antenna will likely have very fragile end connectors and often will break easily if not han-
dled properly. Ensure these cable ends are not damaged and are seated properly.
Network configuration: TCP/IP settings must be properly configured or you will not be
able to establish your network link. If you can detect the presence of the network from
the laptop, the link is probably fine. Ensure that all network settings are configured for
access across the wireless link, and make sure that both computers are fully configured to
receive traffic. Disable any firewalls.
Ping problems: Immediately check your wireless components and TCP/IP settings. These
settings can vary wildly based on your actual deployment. On a basic level, ensure that
the two computers are on the same IP subnet or can route to each other, and make sure
your gateway is set to the correct router device, if applicable.
Fresnel zone obstructions: Trees, buildings, and other obstructions in the Fresnel zone will
degrade your link quality severely, and appropriate actions must be taken to ensure a
322 Part IV â€” Just for Fun
clear Fresnel path. You may need to move the link, or raise the antennas above the
Intermittent signal: This toughest of all problems to troubleshoot can be caused by a
number of things. Check for some of these: bad wireless devices or poor configuration,
damaged antennas or connectors, bent or cut cables, too many connectors, RF design
errors, RF interference, other Wi-Fi radios, and possibly vehicular traffic, birds, or other
intermittent antenna obstruction. Also, check for water damage or any sign of seepage
into your electronics or antenna components. And finally, make sure you removed the
With all of these tips, you should have little trouble in making your link a success. Enjoy your
A long-distance wireless link bridges two remote locations and allows data to travel where it
has never traveled before. A high-speed Wi-Fi link can bring another building online, light
up a remote outpost, or establish a temporary uplink to the Internet. Beaming wireless signals
across long distances makes just about any personal, research, or business task much easier.
The technology has enabled researchers to keep in constant contact with each other and their
test subjects, businesses to save money by connecting multiple offices, and sharing of Internet
access to friends or relatives. Entirely new business models and research methods are being
revealed through long-distance wireless connectivity.
Creating a successful long-distance Wi-Fi link is certainly not unproblematic. Yet, as this
chapter has shown, a good design begins with an accurate survey, Fresnel zone and path loss
calculations, followed by level-headed link planning. If youâ€™re not up to the task mathemati-
cally, use the online link budget calculator at www.olotwireless.net/castella/
radio.htm. Also, remember that most, if not all, of the specifications required for the calcula-
tions in this chapter are available in your hardware manuals, on the manufacturer Web sites, or
through quick customer support phone calls. The task is not without challenges. The reward is
Now weâ€™ll lighten the subject a bit. Read on to Chapter 14, where we employ some unusual
wireless link tactics to create a car-to-car videoconferencing session. Prepare for a road trip
with a 1970s-style convoy, this time with Wi-Fi video instead of CB radio! 10-4 good buddy. I
mean, â€ślights, camera, action!â€ť
Deploy a Car-to-Car
Wireless Video Link
ouâ€™ve got high mobility wireless, a car with computer power on the
passenger seat, and your pals are following you down an obscure
back road. Their view is perpetually of your back bumper. The
conversation is limited to cell phones, two-way radio, or shouting out the
window. Ditch old-school analog communication and set up a Wi-Fi
in this chapter
Use a simple webcam or another video source and the folks in the trailing
car feel as if they are riding shotgun on point. With two cars on a road trip
sporting wireless and videoconferencing, you will have a virtual party on the
Selecting a camera
In this chapterâ€™s project, youâ€™re going to create a wireless videoconferenc-
ing system between two cars. The passengers in each car will be able to
Setting up the
see and talk to the people in the other car up to a distance of 300 feet
Before we get started, thereâ€™s a small amount of preparation and testing
youâ€™ll need to do. You will need the following:
âž¤ Video source compatible with Microsoft â€śvideo for Windowsâ€ť
(VFW), such as a USB webcam Setting up the cars
âž¤ Two Windows laptop computers (Windows 98 or higher)
âž¤ Wi-Fi card with external connector on each laptop
âž¤ Car-mounted Wi-Fi antenna on each car
âž¤ DC-to-AC inverter (optional)
âž¤ Mounting system (can be as simple as Velcro)
âž¤ Videoconferencing software (such as Microsoft NetMeeting)
Once the components are assembled and tested, install them in the car and
go for a road trip! (See Figure 14-1.)
The very idea of a video screen operating in the car means that there
should be a driver and a passenger at a minimum. The passenger
will act as an electronics operator (EO) handling all of the equipment
and computer management.
324 Part IV â€” Just for Fun
FIGURE 14-1: Videoconferencing road trip!
Driver safety is paramount. A video system like the one you build here could be a distraction to
the driver. Ensure that all precautions are taken against driver distraction. When planning a trip
like this, extra care is essential.
Introduction to Videoconferencing
Videoconferencing is more than just video. It also includes audio and data sharing. In its high-
est form, videoconferencing enables multiple participants across the globe to share documents
and presentation materials, and perform instantaneous collaboration in a nearly transparent
â€świndowâ€ť to another part of the world.
There are systems that cost over $50,000 and use multiple flat-panel video displays for corpo-
rate boardroom meetings, like the incredible system by Tandberg shown in Figure 14-2. There
are also near-zero-cost person-to-person systems like Microsoft NetMeeting.
This chapter barely scrapes the surface of videoconferencing. To learn more, visit
www.packetizer.com and head to the â€śVoIP Informationâ€ť section.
Chapter 14 â€” Deploy a Car-to-Car Wireless Video Link
FIGURE 14-2: Tandberg 8000 boardroom videoconferencing system.
Whether the system being used is the free program like NetMeeting, a medium cost package
like the Polycom ViaVideo desktop system, or the high-end system like Tandbergâ€™s, they all
interoperate based on videoconferencing standards. These standards (developed by the
International Telecommunications Union, or ITU) define every aspect of the videoconferencing
experience. The ITU standards make it possible to use programs by different vendors on differ-
Some of the relevant videoconferencing standards:
H.320â€”Videoconferencing standard using Integrated Services Digital Network, ISDN
(a digital telephone service)
H.323â€”Videoconferencing standard used over packet-switched networks (LANs,
WANs, and Internet)
T.120â€”Real-time data conferencing protocol
326 Part IV â€” Just for Fun
CIFâ€”Video format standard, 352â€“288 pixels
QCIFâ€”Video format standard, 176â€“144 pixels
Multipointâ€”Three or more participants connect through a central server or multipoint
control unit (MCU).
Point-to-pointâ€”Two participants connecting directly.
This is just a snapshot. There are hundreds of protocols involved in a single videoconferencing
session. You can find more about these standards at www.packetizer.com by searching for
As the computer entrenches itself more firmly into every facet of entertainment and communi-
cations, you can bet that things will change rapidly. This chapter will introduce a single facet of
the video/computer integration and add a wireless link to make things interesting.
Microsoft NetMeeting will be used in a point-to-point videoconference over a point-to-point
wireless connection. That is, we will set up a NetMeeting session over a peer-to-peer wireless link.
The worlds of videoconferencing and wireless communications each use the terms â€śpoint-to-
pointâ€ť and â€śmultipoint.â€ť The definitions are as youâ€™d expect, one-to-one versus many-to-many.
But it can be a little confusing when not paying attention.
The steps for accomplishing a videoconferencing session over Wi-Fi are as follows:
1. Set up a camera
2. Obtain and configure the videoconference program
3. Develop a data transmission path
4. Mount into the cars
Although in-car data conferencing is quite possible, it wonâ€™t be explored in this chapter.
Possibilities include war drive program sharing, editing documents while driving to a meeting,
text chatting about the guys in the front seat, transferring files, and so on.
First things first: get a video source working on the laptop. There are several methods for
doing, this depending on whatâ€™s available to you.
Step 1: Choosing a Camera
A video source (more commonly called a camera) is obviously the first step in getting a video-
conference going. Here, a few of the most popular cameras are listed and the interaction with
your computer is explained. Most computer-capable cameras are digital and communicate
Chapter 14 â€” Deploy a Car-to-Car Wireless Video Link
directly with the computer. The more ubiquitous analog camera needs a capture device to con-
vert the analog into a digital format. And the Ethernet camera bypasses all of this by including
its own computer and serving Web pages with embedded video.
By far, the easiest cameras to get working on a modern Windows laptop are the USB cameras,
popularly marketed as webcams. These cameras bring in a video signal to the Windows video for
windows architecture. The VFW architecture is used by most video-capable Windows applica-
The downside to USB cameras is their relatively poor quality as compared to consumer video
products, like camcorders. USB webcams are designed for use over the Web at low bandwidth.
The largest USB camera picture size is 640 480 pixels. Figure 14-3 shows a Logitech webcam.
Camcorder Using IEEE1394
Some camcorders can display DVD-like video on the computer. With many newer camcorders
supporting the IEEE1394 standard (Apple FireWire and Sony i.LINK) the incoming video is
pure digital with no degradation of quality. Unfortunately, few videoconferencing programs
FIGURE 14-3: Logitech USB webcam.
328 Part IV â€” Just for Fun
directly support the IEEE1394 interface. The workaround is to use third-party software as an
IEEE1394 to VFW converter. One product that does this is WebCamDV by OrangeWare,
available at www.orangeware.com.
Gnomemeeting is an open source NetMeeting-like program for Linux systems. It is one of the
few programs that directly support IEEE1394 video. Find it at www.gnomemeeting.org.
Analog Video Cameras
Most cameras have outputs for composite video in the form of RCA connectors or analog
video using an S-Video connector. The computer will need a video capture device to work with
video in these popular analog formats. The Dazzle division of Pinnacle Systems makes several
products that capture video via USB. Find them at www.dazzle.com. There are also a few
PCMCIA cards that capture video, although they are harder to find.
The upside to analog video is the huge availability of cameras that support it. Composite video
is a format available for almost all televisions these days, so virtually all camcorders have com-
posite video at a minimum. Also, there are thousands of dedicated camera products that output
composite video. Security cameras, for example, tend to support output composite video. The
downside is the poor quality of composite RCA video.
Composite video generally uses the ubiquitous â€śRCA jackâ€ť connector while S-Video uses a spe-
cial 4-pin mini-DIN connector. When capturing, use S-Video if possible. Itâ€™s the highest quality
analog video format.
Ethernet cameras have built-in Web servers and do not generally include direct computer con-
nections. The method of use for an Ethernet camera is to attach the camera to an Internet con-
nection, then browse to the camera using a standard Web browser.
In effect, an Ethernet camera creates a video feed automatically. If you want a plug-and-play
car-to-car video feed try this: place a wireless Ethernet camera in each car, and connect to each
otherâ€™s camera via its Web browser. Figure 14-4 shows a diagram of how this more expensive
solution would work. By definition, this is not videoconferencing. But you can still see and hear
each other. Ethernet cameras usually cost from a couple hundred to several thousand dollars
depending on features and quality.
Ethernet cameras are often used in remote surveillance situations. Due to the stand-alone design
of Ethernet cameras, they are not generally suitable for videoconferencing.
Chapter 14 â€” Deploy a Car-to-Car Wireless Video Link
FIGURE 14-4: Wireless Ethernet cameras and wireless Web browsers watching each other.
Video Capturing in Windows
As we stated before, the computer needs to bring in a video signal. This is either done through
the USB port, or an analog capture device (which can also be USB). In any case, the camera or
capture device manufacturer must include Windows software to allow Windows to work with
the webcam. This is in the form of an â€śimaging deviceâ€ť driver.
A â€śdevice driverâ€ť is a small program that translates information from the software world of the
operating system to the hardware world of the camera, printer, network adapter, or whatever.
Windows has hundreds of built-in device drivers. New hardware products need to install
updated device drivers, usually from a CD-ROM packaged with the hardware.
Most video applications on Windows use yet another software layer called Video for Windows
(VFW). High-end applications like Adobe Premiere do not require VFW. But less expensive
or free programs like NetMeeting usually need it. Figure 14-5 shows the basic configuration of
a video and audio capture.
Up until the later versions of Windows, there was no way to see if your video source was work-
ing properly. Windows 98, for example, only included a â€śtest cameraâ€ť button in the Device
Manager. So, the easiest way to see if video is working in Windows is to use a video-capable
program and attempt to capture or display live video from the camera.
Most camera manufacturers include video capture programs. Follow the instructions with your
camera to get the program up and running. Then test the camera with that program. If it works
okay with the vendorâ€™s choice program, chances are good that it will work with Windows and
330 Part IV â€” Just for Fun
FIGURE 14-5: Diagram of how video capture works, including audio.
NetMeeting keeps getting mentioned because itâ€™s automatically installed with Windows. But
there are dozens of good videoconferencing programs available that go beyond NetMeetingâ€™s
very basic capabilities.
Two-party, or point-to-point, videoconferencing is the most common form of videoconferenc-
ing. This method only requires that each participantâ€™s computer have the software installed.
Calls are placed directly from one person directly to the other over a common medium (like the
Internet). Figure 14-6 shows a directly connected point-to-point videoconferencing session.
Videoconferencing products are merging (as with all technology) into video phones, instant
messaging plug-ins, and even cellular multimedia messaging services. Tracking this field is
becoming very difficult as definitions are changing.
That said, letâ€™s point out a few popular videoconferencing products:
Microsoft NetMeetingâ€”unsupported, easy to find, full-featured, free
CU-SeeMeâ€”unsupported, hard to find, features vary, free
Polycomâ€”full-featured fully supported hardware/software package, approximately $600
There are many more applications, but most of them cost more than $1000, and they certainly
fall outside the scope of this book. Many low-cost or free video chatting programs are entering
FIGURE 14-6: A point-to-point videoconference directly connects two callers.
Chapter 14 â€” Deploy a Car-to-Car Wireless Video Link
the market in the form of instant messaging clients (AOL IM and Microsoft MSN are the
biggest). These are not really videoconferencing products as they do not interoperate. Also,
many of the newer applications need full-time access to the Internet, so they are not a viable
option for high mobility video.
Videoconferencing software tends to disappear from the market after a time. This is, in part, due
to the expensive software technology licensing needed to employ the various interoperability
standards. By removing a product from â€śsupportedâ€ť status, a vendor can discontinue paying for
the technology but savvy users will keep using it.
The extremely popular CU-SeeMe software from Cornell University has changed ownership over
the years. The original software has evolved into more of an online chat service. The older soft-
ware is no longer supported but there is still a significant user base. Information and downloads
of the old CU-SeeMe can be found on the Internet using popular search engines.
Multi-party, or multipoint, videoconferencing is where multiple participants connect to each
other. The key element in multipoint videoconferencing is the central server, or multipoint
control unit (MCU). Calls are placed from each user to the MCU server. The MCU receives
calls from each participant and relays the video to every other participant. See Figure 14-7 for
an example of multipoint videoconferencing.
FIGURE 14-7: A multipoint videoconference connects
332 Part IV â€” Just for Fun