| UMB Ultra-Mobile Broadband |
UMB Ultra-Mobile Broadband
key points, overview or tutorial about the basics of UMB, Ultra-Mobile
Broadband, the next generation evolution for CDMA2000 providing high data
transfer speeds and using both OFDM and MIMO.
Ultra-Mobile Broadband, UMB is the name for the next
evolution for the cdma2000 cellular telecommunications system which is run under
the auspices of 3GPP2. The UMB cellular system promises to provide very much
faster data transfer speeds, and enables the system to compete with other mobile
broadband systems including WiMAX and Wi-Fi.
The aims for UMB, Ultra-Mobile Broadband include making
significant increases to the user data rates when compared to the existing
cdma2000 cellular technologies, there will be increases to the system capacity,
a lowering the cost per bit of data transfer, enhancements to the existing
services, possibility of new applications, and the ability to use new spectrum
opportunities.
In order enable UMB to compete with other standards such as
WiMAX and preventing them from gaining a foothold in the market, the timescales
for UMB are very aggressive. The UMB, Ultra-Mobile Broadband standards are
expected to be complete by the end of 2007, and the first commercial launches of
UMB should take place around the middle of 2009.
UMB salient features
The UMB, Ultra-Mobile Broadband cellular telecommunications system offers has
many new features and techniques that enable it to fulfil the high expectations
for it, and to enable it to compete with other new and emerging technologies.
- Data rates of over 275 Mbit/s in the downlink (base station to mobile)
and over 75 Mbit/s in the uplink (mobile to base station).
- Uses an OFDM / OFDMA air interface
- Uses frequency division duplex (FDD).
- Possesses an IP network architecture
- Has a scalable bandwidth between 1.25 - 20 MHz (NB - OFDM / OFDMA
systems are well suited for wide and scalable bandwidths)
- Supports flat, mixed and distributed network architectures
It can be seen from the features and salient points, that the
UMB cellular system will provide a significant leap in terms of capability when
compared to the existing cdma2000 based systems. However UMB will operate
alongside cdam2000 1X and cdma2000 1X-EVDO, and it will offer seamless handoff
to and from these services. In this way a phased roll-out of the new UMB service
can be offered.
UMB air interface
There are a number of new technologies being used within the air interface of
UMB. One of the key technologies is OFDM, Orthogonal Frequency Division
Multiplex. The use of OFDM offers UMB the ability to carry high data rates as
well as providing the ability to use wide and variable bandwidths according to
the requirements of the link.
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Note on OFDM:
Orthogonal Frequency Division Multiplex (OFDM) is a
form of transmission that uses a large number of close spaced carriers
that are modulated with low rate data. Normally these signals would be
expected to interfere with each other, but by making the signals
orthogonal to each another there is no mutual interference. This is
achieved by having the carrier spacing equal to the reciprocal of the
symbol period. This means that when the signals are demodulated they
will have a whole number of cycles in the symbol period and their
contribution will sum to zero - in other words there is no interference
contribution. The data to be transmitted is split across all the
carriers and this means that by using error correction techniques, if
some of the carriers are lost due to multi-path effects, then the data
can be reconstructed. Additionally having data carried at a low rate
across all the carriers means that the effects of reflections and
inter-symbol interference can be overcome. It also means that single
frequency networks, where all transmitters can transmit on the same
channel can be implemented. Further information on OFDM can be found on
this site under the Cellular telecommunications section or by using the
Site Search facility. |
OFDMA, or orthogonal frequency division multiple access uses
OFDM as the basis of the modulation scheme, but it has been modified for
cellular telecommunications systems including UMB to provide a means of multiple
access. In this way it is possible for UMB to benefit from the advantages of UMB
in terms of its resilience to multipath effects while still being able to
provide a means of access to multiple users.
MIMO for UMB
In addition to introducing the use of OFDM for UMB, the system also uses MIMO,
Multiple Input Multiple Output (MIMO) as well as SDMA, Space Division Multiple
Access. These are advanced antenna techniques to provide even greater capacity,
coverage, and quality in deployments with multiple antennas. By using the
multiple paths present in any real radio path, they effectively enable the
channel capacity to be increased way beyond that predicted for the use of a
single path for that channel.
UMB Higher layers
The new UMB standard utilises sophisticated control mechanisms along with MIMO,
and SDMA to allow the transmission of variable length packets for each
application based upon the end-to-end system capabilities and the quality of
service (QoS). In this way the system can be optimised according to the
prevailing conditions and the requirements of each user.
To ease the introduction and roll-out of UMB, the system
inter-technology hand-offs to and from existing CDMA2000 1X and 1xEV-DO systems.
UMB IP based structure
In line with the move packet based data and IP (Internet Protocol), UMB is
following this trend. Its architecture has been drawn up to be able to support a
large variety of services that require extremely low latencies, low jitter and
increased spectral efficiencies. As a result, UMB is able to support a large
cross-section of advanced mobile broadband services by delivering low rate, low
latency, voice traffic at one end of the spectrum, and ultra-high-speed, latency
insensitive, broadband data traffic at the other. In this way it is able to
offer a better performance for many of the new services being conceived.
UMB summary
With UMB developments now moving ahead apace, news of the new technology will
start to appear increasingly within the literature. Although UMB, Ultra-Mobile
Broadband services are now due to be deployed until 2009, many preparations will
need to be made for UMB before this.
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