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High-Speed Downlink Protocol Access draadloos internet |
High-Speed Downlink Protocol Access
draadloos internett artikel
High-Speed Downlink Protocol Access draadloos internet
High-Speed Downlink Packet Access (HSDPA) (Sometimes known as High-Speed
Downlink Protocol Access) is a 3G mobile telephony protocol in the HSPA
family, which provides a roadmap for UMTS-based networks to increase their
data transfer speeds and capacity. Current HSDPA deployments now support 1.8
Mbit/s, 3.6 Mbit/s, 7.2 Mbit/s and 14.4 Mbit/s in downlink. Read also
HSDPA Wireless Internet
Further speed grades are planned for the near future. The networks are then
to be upgraded to HSPA Evolved, which provides speeds of 42Mbit downlink in
its first release.
In addition to supporting high data speeds, HSDPA greatly increases the
capacity of the network. Current HSDPA networks have the capacity to provide
each customer with 30 gigabytes of data per month in addition to 1000
minutes of voice and 300 minutes of mobile TV and HSDPA Wireless Internet.
telecommunicatie management
As of March 19 2007, 100 HSDPA networks have commercially launched mobile
broadband services in 54 countries. Near to 40 HSDPA networks support 3.6
Mbps peak data throughput (downlink direction). A growing number are
delivering 7.2 Mbps peak data throughput, leveraging new higher-speed
devices coming into the market. One network has been declared as “14.4 Mbps
(peak) ready” while several additional networks will have this capability by
end 2007. The first commercial HSUPA (uplink direction) network is launched,
with several more set to follow in 2007 CDMA-EVDO networks had the early
lead on performance, and Japanese and South Korean providers were the highly
successful benchmark for that technology. Lately the situations seems to be
changing in favour of HSDPA as an increasing number of providers worldwide
are adopting it. South Korea's KTF and SK Telecom built nationwide HSDPA
networks. KTF are selling HSDPA handsets to its customers on March 2007. SK
Telecom announcing that by first half of 2007 it will be selling HSDPA
handsets to its customers and that it will be cutting funding to its
CDMA2000 network. A similar situation occurred in Australia, with Telstra
announcing the closure of its CDMA-EVDO network and its replacement with a
HSDPA network. Rogers Wireless deployed HSDPA system 850/1900 in Canada on
April 1, 2007.
Fast Packet Scheduling HSDPA Wireless Internet
The HS-DSCH downlink channel is shared between users using channel-dependent
scheduling to take advantage of favourable channel conditions to make best
use of available radio conditions. Each user device periodically transmits
(as often as 500 times per second) an indication of the downlink signal
quality. The Node B uses this information received from all user devices to
decide which users will be sent data on the next 2 ms frame and, for each
user, how much data should be attempted. More data can be sent to users
which report high downlink signal quality.
The amount of the channelisation code tree, and thus network bandwidth,
allocated to HSDPA users is determined by the network. The allocation is
"semi-static" in that it can be modified while the network is operating, but
not on a frame-by-frame basis. This allocation represents a tradeoff between
bandwidth allocated for HSDPA users, versus that for voice and non-HSDPA
data users. The allocation is in units of channelisation codes for Spreading
Factor 16, of which 16 exist, and of which up to 15 can be allocated to
HSDPA.
When the Node B decides which users will receive data on the next 2 ms
frame, it also determines which channelisation code(s) will be employed for
each user, and this information is sent to the user devices over one or more
HSDPA "scheduling channels" (these scheduling channels are not part of the
HSDPA allocation previously mentioned, but are allocated separately). Thus,
for a given 2 ms frame, data may be sent to a number of users
simultaneously, using different channelisation code. The maximum number of
users to receive data on a given 2 ms frame is determined by the number of
allocated channelisation codes. This differs from CDMA2000 1xEV-DO, where
data is sent to only one user at a time.
Other Improvements HSDPA Wireless Internet
HSDPA is part of the UMTS standards from release 5 onwards, which also
accompanies an improvement on the uplink providing a new bearer of 384 kbit/s
(previous max bearer was 128 kbit/s).
As well as improved data rates that are associated with HSDPA one of the key
benefits that are seen is the reduction on latency, improving the round trip
time for applications.
Along with the HS-DSCH channel, three new physical channels are also
introduced. One is the High Speed-Shared Control CHannel (HS-SCCH) (HSDPA
Wireless Internet)which informs the user that data will be sent on the HS-DSCH
2 slots ahead. The second one is the Uplink High Speed-Dedicated Physical
Control CHannel (HS-DPCCH), which carries acknowledgment information and
current channel quality indicator (CQI) of the user. This value is then used
by the Node-B in calculating how much data to send to the UE on the next
transmission. The third downlink physical channel is the HS-PDSCH (High
Speed-Physical Downlink Shared CHannel). This is the physical channel mapped
to the above HS-DSCH transport channel that carries actual user data.
[edit] HSDPA UE categories
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