Non-WiFi wireless
There’s much more to “wireless” than WiFi. 3G and EV-DO wireless IP networking is available from the major mobile carriers, while iBurst, Unwired and BigAir offer fixed or mobile wireless connectivity. Satellite links may be the only option in remote areas.
BigAir offers VoIP over its low-latency, QoS-enabled fixed wireless service, says CEO Jason Ashton. This is a business-grade service, he says, including PABX features such as voicemail, call transfer, call hold, conference calls and so on, although it can also be used with an existing PABX. With 25ms typical latency he claims VoIP calls match
landline quality.
Existing users are mainly SMEs requiring up to 50 in-dial numbers. The company has upgraded the system based on customer feedback, and may start targeting corporate accounts.
Streaming media and production company Viocorp recently moved into temporary offices, not yet wired so the company was not able to get service from Telstra or Optus. A fixed installation could have taken months but BigAir’s wireless broadband and VoIP services were set up in two days. The company will be moving again in six months and will be able to take the services to its new premises.
Sydney’s Luna Park also uses VoIP over the BigAir network with a mix of fixed and mobile handsets. Approximately 150 staff are equipped with Spectralink handsets that connect over the WiFi LAN that covers the premises. “Properly engineered it works fine,” says Ashton. BigAir hopes to extend this VoIP service to its iBurst customers in the near future.
3G data and EV-DO are relatively expensive but BigAir’s iBurst plans are capped and shaped, Ashton says, so there’s no risk of being charged for excess data while trying VoIP. In any case the amount of data needed for a voice call is quite small, so the marginal cost is effectively zero.
Ashton says Kyocera is expected to introduce an iBurst handset next year with a WiFi option that will allow it to act as a base station for the user’s PC and other devices. “People just want to cut the cord completely,” he says. “I use a SIP client on my notebook [to make VoIP calls over iBurst]. When [WiMax] becomes an embedded chipset [in PCs and PDAs], it’ll be fantastic.”
Zultys has trialled VoIP over iBurst, Warhurst says, adding that “the quality was absolutely brilliant”. The company is about to try CDMA and 3G wireless links, but Warhurst warns potential users to watch out for carriers that over-subscribe their access points.
PBA’s Withers says customers have been using unmanaged VoIP services over iBurst “but they’re in the mix with everything else” and so “you can’t guarantee the quality at times of high load”. iBurst normally guarantees packet delivery but PBA has been developing a managed VoIP service that is able to drop an occasional voice packet to maintain the latency required for good audio quality. Available soon, this service—which will include PABX function—will handle three or four simultaneous calls alongside data traffic. By the end of the year PBA plans to introduce header compression that will allow as many as 10 or 12 simultaneous calls.
PBA will offer a VoIP desk phone with a built-in iBurst modem and a data port to connect a PC or network switch. It’s aimed at the SOHO market: “in one device, you’ve got everything,”
says Withers.
Commander already has clients lining up for the VoIP service, he says, especially among small businesses. Since it can be deployed immediately it will be useful for businesses such as construction companies that move their operations from one location to another.
Talking of construction Thiess—the well-known construction and engineering provider—uses satellite links to communicate with its remote sites. Voice and data flow over the same link so it is important to make the best use of the restricted bandwidth and to prioritise the most time-critical traffic.
“We have to tailor a communications solution to the needs of each project which may include wireless or satellite communications, voice over IP, and different line of business applications. And all projects need to access mission-critical data applications including enterprise resource planning, knowledge management and transactional systems,” says corporate telecommunications manager Ben Creevey.
The company has eight satellite communications trailers that can be towed out to a new site and put into service within hours. Each is equipped with a Packeteer appliance to handle data compression and traffic shaping. “If we were to leave our applications unmanaged, then the use of Web applications would have a disastrous effect on voice,” Creevey says. “Yes, we want to get more bandwidth multiples out of our network and satellite links. But more important is being able to guarantee the consistent performance of mission-critical applications, including VoIP.”
Some data is more compressible than others. Creevey says compression rates of 80-90 percent are achieved with some applications but the average is about 45 percent. “We’re doing VoIP over satellite quite well. Packeteer’s ability to perform compression and manage bandwidth means we can get near equivalent performance of a 512Kbps link on a 256Kbps link.”
According to Bede Hackney, Packeteer country manager, it’s important to understand the traffic to get this sort of improvement. It would be easy to configure a network to simply send voice packets ahead of every other traffic type but you must ensure all applications run successfully.
Thiess’s satellite links combine low bandwidth with high latency and high utilisation, he says, so they needed to leave as much capacity as possible for voice traffic (through compressing and shaping other traffic), and optimise the voice traffic itself. Thiess recently switched to the MPLS protocol, which rules out the use of RTP header compression. Voice packets are so small that the header occupies more bits than the data, Hackney explains, but header compression and MPLS aren’t compatible. The latest version of Packeteer’s software provides RTP compression, which repacks the data from multiple voice packets into one packet for transmission across the WAN link.
Another useful feature is the ability to continually and independently monitor the latency and jitter on each link, he says. This allows an organisation to check that the service provider is delivering according to the SLA. If you’re running data, voice and video across a link you’re probably paying a premium for a realtime quality-of-service classification, so you need to check that you’re getting what you pay for.
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