Field Report: Comrex BRIC


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Broadcast Reliable Internet Codec (BRIC) technology has been under development by Comrex for some time. It holds the promise of a new and flexible way to deliver high-quality live remote broadcast audio over a variety of IP-based networks like DSL, cable modems, high-speed cellular and 802.11x (Wi-fi). It's the latter that is especially exciting, given the widespread deployment of hotspots in an increasing number of restaurants, bookstores, airports and other easily accessible locations.

To the Comrex engineering staff, the theory that BRICs would prove useful over Wi-fi was sound, but too often the real world leaves theory lacking. So on March 30, 2005, an unseasonably warm and sunny New England day, the engineering team set forth boldly to test BRIC on as many publicly available hotspots as possible.

The prototype system used for the field tests on public hotspots. The apparatus was carried in a laptop bag to hide its ominous appearance.

The final hardware for the Access codec (the first codec to truly be a BRIC) was still underway so we used a prototype system. Because the package resembles a typical incendiary device, and not desiring to alarm to public or the authorities with our testing, we placed the system in a laptop bag, which could be left discretely at our feet while the system was remote controlled by a harmless-looking laptop.

Getting started

Our first stop was Panera Bread Company in Chelmsford, MA, a popular coffee shop that has become the world's largest free Internet provider, with 537 stores offering unsecured Wi-fi access. Because we had limited battery power, we were pleased to have found a cherished table near an ac outlet.

Once we had ordered our coffee and pastries we prepared to connect to a public Wi-fi with BRIC for the first time in history. We had visions of Alexander Graham Bell at that moment his telephone first came alive, having spilled his drink and beckoned Mr. Watson for help over the invention. But our excitement was soon muted when we found that our wireless access card couldn't connect to the Panera access point. Inquiries about the health of the Wi-fi network among the baristas and bakers met with the expected quizzical looks and shrugs.

We decided as a last-ditch effort that a new Wi-fi card was in order. Luckily, the chosen Panera was adjacent to a Wal-Mart, retailer of all things useful and otherwise. I found the computer section of the giant store, and obtained the required hardware easily.

The replacement card did the trick and we were soon happily connected to the Panera Bread network. We connected to another prototype BRIC located at the Comrex lab, (which was wired in an analog loopback configuration) and sent audio across the link in full duplex. Our chosen audio source was a book-on-CD playing from a CD-walkman. So it was that day that the first sounds transmitted over this breakthrough technology were from Harry Potter and the Goblet of Fire.

The two key factors in using the public Internet for real-time audio are stability and latency. The nature of BRIC is that audio is broken into packets and sent off into the ether in hopes they will arrive at their destination quickly and in reasonable order. The only way to compensate for packets that are received late is to add a buffer at the input to the decoder, so that all packets will be received and ordered before decoding. The size of this buffer dictates the overall time delay of a particular link. Therefore it's important to find the sweet spot on these networks, balancing acceptable packet loss with reasonable delay.

At Panera we found that a solid connection was possible with a one-way audio delay of about 150ms. This put the delay in the same order of magnitude as a POTS codec, which seems workable for broadcasters. Optimism ensued as we headed toward our next destination.

Just up the road a few miles was the business district of Nashua, NH. Located on the state line, and benefiting from the lack of a sales tax, this area is a retail mecca. It also blossoms with wireless access points, we found out as we cruised the main throughway. Our laptop lit up with dozens of Wi-fi networks; some secure, but many wide open. Our destination was Borders Books, whose café includes a T-Mobile-provided hotspot. T-Mobile sports a subscription model, and we were taken aback a bit at paying $6 to $10 (based on package chosen) for our one-time test. But regular users get a better deal. The T-mobile connection was solid at a similar 150ms delay setting.

The test crew on the road and searching for the next hotspot.

We made a quick stop at a nearby Starbucks, which also supplies Wi-fi via T-mobile. Because this network had already been tested, we made a quick attempt to connect via the car. But shortly after we got our system booted and signal acquired, the caffeine took its toll as one of our engineers moved the laptop bag slightly the wrong way and dislodged the battery connector, killing power to the system. Rather than reboot and reconnect we went in search of a different network to try. Next stop: McDonalds.

Powered by a company called Wayport (which also provides access in many airports and hotels), the McDonald's Wi-fi network is perhaps the most ubiquitous. But our engineers rebelled against actually going in (vegetarians make lousy alpha testers) and we were relegated to the parking lot. Things went smoothly this time, however, and we were soon running our first mobile test. Delay and stability were reasonable on this link, as we could achieve solid performance with only slightly over 100ms latency. We tooled around the parking area a bit and lost our signal only when a large delivery truck passed between us and the restaurant. We found traffic able to block Wi-fi quite effectively. We thought the $4 daypass charge to use the network was still high, but a Wayport subscription could bring this cost down.

We lost the sounds of Harry Pottter as we re-entered the highway, but we continued on toward the UPS store where we tested their publicly available access point. Flush with our McDonalds success we opted to try it from the car, which worked quite well at the 250ms delay setting. This was the highest latency we found, and may have had more to do with the fact that we were parked 100 feet from the storefront than anything else. The UPS store access was also pay per use but had the advantage of allowing charges to a range of other Wi-fi subscription services, so if you already have an account elsewhere you can simply input that information to gain access.

A second network appeared on our laptop as available during this test. The ID shown on our laptop was simply “JT” but it was fairly strong throughout the area. We pinpointed the signal as coming from a local car dealer's parking lot. We surmised they offered free wireless to customers waiting for repairs. Because car dealers are popular sites for remote broadcasts we felt it our duty to run the test. We caught a few odd glances from the occasional salesman in the lot, but managed to secure a reliable connection with about 200ms delay.

Discrete snooping

We continued on sniffing commercial and residential areas alike, and found several wide open, accessible Wi-fi networks. With wireless routers costing less than $50, the number of systems online wasn't a surprise as much as the lack of security. It's not rocket science to set these routers so they can't be easily piggybacked. I suggested strongly that we resist the temptation to piggyback on any banks or law offices we found. But our laptop battery soon ran down anyway and we had to pack in our wireless adventure.

It should be noted that piggybacking on an unsecured private wireless network is probably deemed illegal in most jurisdictions, although the illegality of doing so without intent to hack anything really hasn't been tested in court. But this really shouldn't be necessary anyway, because legal public Wi-fi is now so widespread. And with the advent of BRIC, all these now become points of origin for remote broadcasts, news and sports with high-fidelity, full-duplex sound and reasonably low delay.


Hartnett is technical director of Comrex, Devens, MA.


What's a BRIC?

The telephone network is undergoing dramatic changes. As the popularity of voice-over-IP (VoIP) and broadband Internet explodes, telephone companies are finding significant cost savings in converting their networks away from the traditional circuit-switched data format to packet-based formats. This has profound implications for users of ISDN and POTS codecs, because in the coming years it may be difficult for telco networks to support these devices.

Meanwhile, a lot of work is being done to make voice transmission reliable over the public Internet. Although most systems only support telephone-quality audio, the coding algorithms used are quite resilient to the congestion problems that plague the Internet.

Broadcast Reliable Internet Codec (BRIC) borrows this resiliency from the VoIP world and blends it into wideband, low delay, broadcast-ready hardware. Wideband mono and stereo coding algorithms are supported. BRIC allows remote broadcasts to be generated from virtually any location where an Internet link can be established, whether wired or wireless. BRIC allows full-duplex transmission over cable, DSL, Wi-fi, dial-up and the increasing number of 3G cellular services becoming available.

Allowing backwards compatibility to legacy POTS codecs, BRIC provides a natural evolution allowing broadcasters to leverage the Internet for remote broadcasts while maintaining the ease-of-use and reliability they've come to expect from ISDN and POTS.




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