Remote Broadcast Access
Newsletter Issue 8
Inside this issue:
- Comrex Comments
- Matrix GSM Module Debut
- Introduction to GSM
- How to Order GSM Wireless
- Codec Answer Guy
- TechTips
Comrex Comments
This issue of Access spotlights the new GSM Module for the Matrix. For years, we have been asked for a wireless codec. While the Matrix was designed from the start to work as a wireless unit, this involved a somewhat cumbersome interface to a limited number of external GSM phones. Also, audio quality was limited to a low bandwidth.
Enter the new GSM Module. This simple addition to the portable Matrix is set to revolutionize remote broadcasting. The module includes a built-in GSM wireless phone, compatible with any GSM carrier, now available in most of the US and the world.
The new algorithm gives improved frequency response (7 kHz at 9600 baud) and reduces digital artifacts. New error correction and modem technology mean better stability for your connection.
The GSM Module also gives excellent reception: the kit comes with an external mag-mount antenna, and is more powerful than handheld phones, because it is not limited by radiation concerns. Just insert your SIM card, attach the antenna to a metal surface, and you're ready to broadcast from anywhere!
After an exciting beta test this summer, the module begins shipping in September; we are taking orders today.
But don't take our word for it - try it for yourself. Contact us to schedule your demo of the new GSM Module.
Matrix GSM Module Debuts with Global Beta Test
Dozens of broadcasters around the world and across the US have taken part in the GSM Module beta test this summer, demonstrating a number of applications for the wireless codec.
In Uganda, as in many regions of the world, wired telephone service is very limited. Even in Uganda's urban areas, POTS lines are unavailable for broadcasters, says Radio Simba's Collin Mutambo, so wireless service enables many new broadcast opportunities. Sportscasters generally use mobile phones on Uganda's expanding GSM network, or when the rugged terrain permits, by RPU links.
Many Ugandan radio stations now broadcast soccer and run promotions from remote rural villages using handheld GSM phones. Simba has gone one step further by using the Matrix with GSM Module to broadcast sports events. "Our remote broadcasts are much clearer and fuller than the competition," says Mutambo.
During Simba's evening drive show, reporters go into the city to air listeners' comments on the day's news. The reporter interviews passers-by for the ten-minute segment.
"Previously, our reporter used a normal mobile phone," says Mutambo, "and had to go through the inconveniencing process of holding the phone to every interviewee's ear."
With the GSM Module, the guest could speak comfortably into a microphone.
In the US, Salem's WFSH Atlanta (The Fish) used the GSM Module for a live broadcast of their "Christmas in July" promotion, featuring twenty-two tons of manufactured snow.
The remote booth was a distance from the nearest building, so if not for the GSM Module, the station would have used a cell phone, says producer Shaun Kassity. The GSM Module improved the remote sound dramatically, without complicating the station's remote preparation, he says. "Setting up the Matrix is so simple."
Radio One Dallas broadcasts morning "Street Hits" features from around the city. The station has used RPUs on location in the past, demanding technical know-how from the promotional crew; often an RPU problem would force the remote talent onto a handheld cell phone. The Matrix GSM Module, says engineer Steve Walker, makes the morning stops more spontaneous and easier for the crew.
To hear sound clips from these and other remotes, visit www.comrex.com.
An Introduction to GSM
Worldwide, GSM (Global System for Mobile Communications) is the most common standard for digital wireless phones. In the US, while GSM is gaining popularity, there are also two other digital wireless standards (TDMA and CDMA) used widely. At this time, GSM is the only form of digital PCS that has a stable enough data spec to be suitable for audio codec use.
GSM is increasing its North American presence, with carriers now covering most cities in the US and Canada, plus many suburban areas and major highways. The two largest US carriers are T-Mobile and Cingular. (AT&T Wireless/mLife GSM service will not support data calls, rendering it useless for audio transmission.) Canada is covered by Microcell Telecommunications and Rogers Wireless, and Telcel covers much of Mexico.
You can check availability in your part of the world with the following maps. (Please note that many maps err on the conservative side; for example, Comrex headquarters in Massachusetts is shown with weak coverage, but a strong signal is actually present.)
For US GSM availability, T-Mobile maintains a map of its own coverage plus other GSM carriers: www.t-mobile/coverage.
For interactive maps covering the rest of the world: www.cellular-news.com/coverage.
To keep up with the ever-changing vocabulary of wireless, you can see Cingular Wireless' helpful glossary for wireless terms and technology: www.cingular.com/about/newsroom_glossary1.
How To Order GSM Wireless
To use the Matrix with GSM Module, you will need an account with a GSM wireless provider, which includes circuit-switched data.
Every GSM phone uses a SIM (Subscriber Information Module) card, a smart card containing a subscriber's phone number and account information. With GSM service, unlike other wireless technologies, the carrier needs to activate only the SIM card, not the phone itself. Once active, a SIM card can be moved to any GSM phone, taking the customer account information with it. The wireless carrier will provide a SIM card with the account.
The United States' two largest carriers are T-Mobile and Cingular Wireless. The T-Mobile network is entirely GSM, while Cingular's network is increasingly offering GSM coverage. (Note that AT&T Wireless offers GSM service, but they have deactivated circuit-switched data for their customers, rendering their service useless for real-time audio transfer.) Many regional carriers also offer GSM.
Circuit-switched data (CSD) capability usually goes unadvertised and is not a common request at retail wireless stores, so store personnel may not be familiar with the service. They will likely try to sell you GPRS or wireless Internet, but you do not want these services. If they don't understand CSD, ask for standard non-GPRS data. You need the capability of making point-to-point data calls, like calling your office computer from the road. If the salesperson is still confused, you might call the carrier's customer service line directly. (Cingular Wireless: 1-866-246-4852, or 1-866-CINGULAR. T-Mobile: 1-800-937-8997.)
You can usually buy a SIM card by itself directly from the carrier. Given rebates and other sales, however, you may save money by purchasing a GSM phone package including the SIM card. The SIM card is then inserted into the GSM Module, allowing the Matrix to place calls over GSM service.
Ask the Codec Answer Guy
Q: What phone does the GSM Module use?
A: The phone is actually embedded in the module, so no external phone is necessary. Simply insert a SIM card to activate the phone.
Q: Why don't you support my CDMA or TDMA phones?
A: Unfortunately, the technology behind CDMA and TDMA does not support real-time audio transfer, as circuit-switched data technology is necessary for real-time audio transmission. TDMA only supports packet-switched data, which cannot be used, and CDMA technology is susceptible to buffering delays and network congestion. That leaves GSM as the only useful technology for transmitting real-time audio data.
Q: I hear a lot about GPRS and wireless Internet. Is this compatible?
A: Generally, no. GPRS uses the public Internet for data transfer, not point-to-point calls. Any data sent through the Internet is inherently in danger of network congestion and delays. Some packages may include both wireless Internet and circuit-switched data, but make sure you can make point-to-point data calls.
Q: How do I know my signal strength?
A: The Matrix displays the wireless signal strength, on a scale ranging from 0 to 32. We recommend a reading of at least 20.
Q: Can I use the phone for regular calls?
A: Using the Matrix GSM Module in Voice mode, you can use a microphone and headphones to call into a hybrid or a regular phone. And after the remote, use it to order a pizza.
How do I dial the phone when using the GSM module?
The phone is dialed from the Matrix keypad – for either enhanced (data) or voice calls. Just follow the menus.
Q: Can a Matrix improve my reception?
A: Yes. The GSM Module kit includes a small (3") external mag-mount antenna for optimal reception. Also, since the phone is not handheld, it can safely transmit more power than traditional handheld phones.
Q: Where should I place the antenna?
A: As high as possible. If you have trouble, try reorienting the antenna. Sometimes placement in the immediate area will change reception dramatically. Whenever possible, attach it to a steel surface, like a car body or even a pie pan, for a ground plane.
Q: AT&T Wireless offers GSM – why won't the Matrix work with them?
A: AT&T Wireless' GSM service has deactivated circuit-switched data for their subscribers. Subscribers of other companies can use CSD when roaming in AT&T areas, but AT&T customers are unable to use CSD anywhere.
Q: Will my older Matrix work on GSM?
A: Yes, but your Matrix units will require an upgrade. Call Comrex Tech Support for more information.
The Answer Guy is happy to respond to your questions. Send an email to answerguy@comrex.com or fax questions to 978-784-1717.
TechTips:
Improved Matrix Modem
Since early 2002, Matrix codecs have shipped with fully digital modem technology. Our field experience tells us that these newer modems provide significantly better stability — especially on difficult phone lines. We encourage older Matrix owners to take advantage of our offer for a free upgrade to the newer modem. Contact Comrex Tech Support for more details.
Comrex is constantly adding improvements to many of our products. So, even if your codec appears to be functioning perfectly, it may be a good idea to check out whether new capabilities have been added. Most upgrades are free, and most can be added to earlier units. For more information, check your serial number on the Comrex Upgrades web page: www.comrex.com/TechNotes/tn217.htm. If the information indicates that your product is due for an upgrade, call us at +1 978-784-1776. We will check our records to see if the work has already been done, and make arrangements if the unit should be sent in.
Avoid Overdriving
Many microphones may overdrive the input of a codec. Many sports headsets, in particular, use lavalliere-style mics that output a large amount of power. Even with very little gain on the codec, an overpowering mic can cause distortion. An in-line attenuator, such as the Whirlwind 10dB IMP PAD, will help you avoid this problem. Simply connect the attenuator between your microphone and codec input to drop the signal by 10dB. With this small investment (about $20), you can control your signal and avoid distortion.
Tech Tip of the Week
New at comrex.com, the Answer Guy presents the Tech Tip of the Week. Check back for new hints to help you get the most out of your Comrex equipment.
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