HSDPA is not the first technology to invent these approaches. You see
them in most new wireless technologies, including CDMA2000 EV-DO and
WiMAX, as well as in Wi-Fi. As for speeds, that's where things get a
bit tricky. The network does indeed support a peak rate of 14 Mbps,
but this is what you would get with the full capacity of the cell
sector at the highest modulation level and no error correction. In
other words, you'll never actually experience this speed, as you'll
never experience the peak rate of 2.4 Mbps quoted for EV-DO. Initial
devices are likely to have peak rates of 1.8 Mbps or 3.6 Mbps,
depending on their designs. Subsequent devices will be faster. As for
typical speeds you can expect, it will depend on the number of users
active in the network, but average speeds in the 500 kbps to 1 Mbps
range should be achievable in relatively lightly loaded networks.
However, speeds may go down a bit if people flock to the technology,
as is the case for all the 3G technologies. Of course, with the
somewhat slow adoption of cellular data as discussed in my last
column, this is a problem that operators would love to have, and one
they can manage through additional cell sites and new spectrum
allocations. HSDPA latency goals are also aggressive, and in initial
networks, latency will likely be in the 100 to 200 msec range.
As for how this lines up with EV-DO that Sprint and Verizon are
deploying, HSDPA will likely meet or exceed EV-DO performance. HSDPA
also allows simultaneous voice and data on the same device. However,
EV-DO operators will have broader coverage in the near term. Mobile
WiMAX specifications point to somewhat higher performance, but there
are a series of further enhancements planned for HSDPA.
In my view, HSDPA is a great thing for the wireless industry for a
number of reasons. First, it will offer a highly compelling broadband
wireless service over very large coverage areas. Second, it will
compete head to head with EV-DO, resulting hopefully in competitively
priced service plans. Third, it will keep the WiMAX people on their
toes, forcing them to deliver the best possible technology; otherwise,
it won't be competitive. The reciprocal case is also present, as WiMAX
has accelerated 3GPP (the organization that specifies GSM-UMTS
technology) efforts to start designing what comes after HSDPA,
currently called 3GPP Long Term Evolution.
From a usage point of view, even by the end of 2006, HSDPA won't be
everywhere. Coverage is likely to emphasize urban areas, and in less
densely populated areas, the fallback will be to EDGE for quite some
time. This means there's no reason to wait for HSDPA, as you should
probably plan for most applications you deploy to work over both HSDPA
and EDGE. The same is true for EV-DO, where the fallback is to 1xRTT.
As HSDPA gets closer, you're likely to see lots of hype about the
technology. But if you keep in mind its true capabilities, there's no
reason to not start incorporating HSDPA into your wireless planning.
