Softswitches

IP telephony is a different matter. Equipment costs thousands rather than millions of dollars,
and many manufacturers are already building broadband wireless radios with inherent support
for IP voice. Therefore, the barrier to entering the IP voice market is much lower than is the
case for traditional circuit voice. Still, it is a business not to be embraced without careful consideration
and one that demands hard choices in respect to basic infrastructure equipment.
Two fundamental equipment-related issues confront the broadband wireless operator
considering IP voice services. The first has to do with the choice of a platform, and the second
has to do with the scope and positioning of the services.
IP telephony today suffers not from a lack of standards but a plethora of them. H.323,
Universal Datagram Protocol (UDP), Session Initiation Protocol (SIP), Simple Object
Access Protocol (SOAP), Media Gateway Control Protocol (MGCP), and Media Gateway
Control (MEGACO), among others, vie for the allegiance of the IP voice carrier, and in no case
are these all supported on a single hardware platform. IP telephony also suffers from a diversity
of approaches in embodying those several standards in hardware. Often, though not always,
signaling and converting IP traffic into circuit traffic takes place within different devices,
and some manufacturers favor highly distributed architectures where numerous aggregation
boxes are scattered about the network. In the case of SIP-enabled networks, special telephone instruments are used that convert the voice signal to IP right at the deskset. Each approach
requires a different type of deployment with a different array of equipment components.
Wireless broadband operators face a choice of terminating local phone traffic over their
own networks at either a class 5 switch or a softswitch equivalent or, alternatively, ceding the
switching function to some other service provider. In most cases, the ownership of a traditional
class 5 switch is out of the question for the wireless operator, so a softswitch is the only real
choice unless the wireless operator chooses to route phone traffic through the exchange of the
local incumbent and utilize that carrier’s circuit switch.
If a softswitch is employed, the wireless operator will need to lease a circuit connection to
a class 4 or tandem switch operated by a long-distance service provider. Both long-distance
calls and local calls made to parties who subscribe to landline telephone services will then
have to be routed through that class 4 switch. The local calls to nonsubscribers will then be sent
back to the incumbent telco’s class 5 switch and from there to the designated party. Obviously,
some complex issues and difficult decisions are involved in setting up an IP voice service.
Quite a number of service models can be built around IP telephony, and I will discuss
them in detail in the next chapter. The long-term profitability of those models is at issue, however.
Voice is becoming an increasingly price-eroded, low-margin business, and IP telephony
will surely accelerate that trend because it reduces the cost of transit and because IP voice has
been positioned as a price-competitive product by those carriers offering it. To make matters
worse, various peer-to-peer Internet telephony programs have recently been disseminating
through the online community that completely eliminate the need for a local carrier and that
route all telephone traffic through the Internet service provider (ISP) with no billable minutes
being involved. IP voice services may be becoming cheaper to provision, but they also appear
likely to command lower prices over time and ultimately lower margins for the service provider.
Some industry analysts have concluded that voice telephony will eventually become a
no-charge amenity that is simply included in a basic service package. Figure 6-3 shows a voiceover
IP connection to the PSTN. If such a state of affairs comes to pass, then voice services could become just another overhead
expense for the wireless broadband operator. But, at least for the midterm, offering voice
still appears to represent a sound strategy for the wireless operator, if for no other reason than
it adds to the bundle of converged services.
Before I leave the topic of telephone switches in the central office, I will add this concerning
the issue of availability: Conventional plain old telephone service (POTS) has come to be
regarded as a lifeline service, something that will enable subscribers to summon aid in the
midst of emergencies, and indeed countless lives have been saved over the years because of
timely telephone calls. Naturally, the value of a telephone service as a lifeline depends on availability,
and at least in the United States, incumbent carriers have made every effort to ensure
the highest availability. One attribute of traditional analog phones that makes such availability
possible is that no outboard electrical power source is required. As long as the telephone is
connected to an active jack, it will operate even during a power outage.
In general, this is not true with broadband voice services such as voice over digital subscriber
line (DSL), cable telephony, or broadband wireless voice. They utilize AC or battery
power to operate the interface and thus are vulnerable to outages.
The cable industry has responded by designing customer premises telephony interfaces
with backup power, but I have not seen anything equivalent in the wireless broadband space.
For that reason operators should position their voice offerings as second-line services. I also
suggest that any IP switches be highly redundant and served with instantaneous backup electrical
power.