22-08-2014, 12:33 PM
High Speed Data in Mobile Network Seminar Report
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INTRODUCTION
Currently, almost all network operators worldwide are upgrading
their GSM networks in order to provide high speed mobile data to their
subscribers. This subclause focuses on providing you with an overview of
some typical applications for high speed mobile data. We also would like to
make you aware of some of the general advantages and risks. When are
HSCSD and EDGE available for commercial applications? What are some of
the general aspects that all high speed mobile data options have in common?
ABSTRACT
Currently, almost all network operators worldwide are upgrading
their GSM networks in order to provide high speed mobile data to their
subscribers. The ever increasing growth rate of data applications such as e-mail
and the internet is confronting mobile network operators worldwide with the
challenge to upgrade their networks to high bandwidth capable "bit pipes" in
order to provide for all kinds of mobile data applications. High speed mobile
data will combine two of today's most rapidly growing technologies, mobility
and the internet.
GPRS (General Packet Radio Service), EDGE (Enhanced Data rates
for Global Evolution) and HSCSD (High Speed Circuit Switched Data) have
been designed primarily as upgrades to the well known and widely used GSM
standard. In the 1980s and early 1990s, when the GSM system was designed
and standardized, data transmission capabilities were of minor importance
compared to voice. Besides, at that time, the maximum transmission speed of
9.6 kbit/s that GSM offered, appeared to be sufficient and was comparable with
analog wireline modems.
THE NEED FOR HIGH SPEED MOBILE DATA
Why High Speed Mobile Data?
The ever increasing growth rate of data applications such as e-mail
and the internet is confronting mobile network operators worldwide with the
challenge to upgrade their networks to high bandwidth capable "bit pipes" in
order to provide for all kinds of mobile data applications. High speed mobile
data will combine two of today's most rapidly growing technologies, mobility
and the internet.
Let us compare the situation on the mobile side with the progress that
has been made on the fixed end. While even today's analog modems operate at
56 kbit/s and, indeed, ISDN transmits up to 128 kbit/s, mobile users are still
limited to 9.6 kbit/s in of GSM. The rollout of XDSL improves the situation
even further on the wireline side, thereby broadening the gap between wireline
and wireless
Bandwidth Requirements
The figure below presents the bandwidth requirements for some
typical data transfer applications. Note that these requirements apply to both
wireline and mobile usage. Obviously, GSM can barely cope with surfing the
web and video-conferencing is totally unfeasible.
Customer Potential
With regard to mobile data, not just the typical pattern of use by
today's businessmen on the move shall be addressed: Today's GSM-networks
are also used by many consumers for the largest growing mobile data
application of the late 1990's, SMS. Therefore, the new mobile data
technologies need to address both consumer groups, the private customer and
the business user. In the first instance, most network operators intend to attract
their high-end business subscribers, their long term goal being, however, to
bring high speed mobile data to the mass market
AN HISTORICAL VIEW
GPRS (General Packet Radio Service), EDGE (Enhanced Data rates
for Global Evolution) and HSCSD (High Speed Circuit Switched Data) have
been designed primarily as upgrades to the well known and widely used GSM
standard. In the 1980s and early 1990s, when the GSM system was designed
and standardized, data transmission capabilities were of minor importance
compared to voice. Besides, at that time, the maximum transmission speed of
9.6 kbit/s that GSM offered, appeared to be sufficient and was comparable with
analog wireline modems.
Starting with HSCSD, the first high speed mobile data upgrade to be
standardized, higher rates of transmission can be provided to mobile
customers. EDGE has a transmission speed of up to 384 kbit/s and GPRS is
able to support up to 160 kbit/s.
TELEMETRIC APPLICATIONS
Beverage or snack machines may be equipped with high speed
mobile data devices in order to transmit the remaining level of stock. Thus,
time-consuming and expensive "drive-ins" will only be carried out when
necessary. What is more, the customer will always find his/her preferred
choice. With the advent of high-speed mobile data and an underlying IP
protocol stack, the internet and packet-switched transmission can be used to
transfer telemetric information. This will keep prices low and makes telemetric
applications available to a wide range of new customers.
TOLL ROAD SERVICES
Nowadays, tolls are generally collected in a time-consuming and,
hence, costly fashion. In the future of high speed mobile data, cars may be
equipped with a mobile data device and rechargeable electronic cash in order
to pay the toll by merely passing through the toll station. Again, the underlying
IP protocol stack and the use of the internet will make this application cheap
and reliable.
TOLL ROAD SERVICES
Nowadays, tolls are generally collected in a time-consuming and,
hence, costly fashion. In the future of high speed mobile data, cars may be
equipped with a mobile data device and rechargeable electronic cash in order
to pay the toll by merely passing through the toll station. Again, the underlying
IP protocol stack and the use of the internet will make this application cheap
and reliable.
THE VALUE CHAIN TODAY AND WITH HIGH SPEED MOBILE DATA
With today's focus on speech services, it is mainly the network
operators and service providers who generate their revenue from the mass
mobile market. In future, there will be a third party who will enter the market:
This third party consists of the content providers who will provide the
applications for high speed mobile data. These applications will require all the
airtime of high speed mobile data networks.
PROBLEMS OF HIGH SPEED MOBILE DATA
High speed mobile data will certainly improve the existing mobile
networks greatly. GPRS and EDGE, in particular, will write a new chapter in
mobile communications history. However, there are various problems which
need addressing in order to make high speed mobile data a commercial
success.
Firstly, who shall provide all the necessary IP-addresses when many
people are permanently online? Even today, a shortage of IP addresses is
becoming evident. The only solution to this issue is an upgrade to IP version 6
but the question is when IP version 6 become a reality will.
Another problem is the short span between GPRS, EDGE and
UMTS. Even before the demand for GPRS has been proven, the technical
evolution has already found successors to GPRS, namely EDGE and UMTS.
Perhaps the market will not be ready for UMTS when it becomes available in
2002.
GPRS
GPRS is a packet-switched upgrade to GSM. What consequences
does packet-switching actually have on a mobile network? How does GPRS
perform in comparison with e.g. HSCSD? How will the GSM networks need
upgrading in order to implement GPRS ?
GPRS is Packet-Switched
GPRS or General Packet Radio Service is a packet-switched
technology based on GSM. As shown in the animation, the radio and network
resources are only accessed when data actually needs to be transmitted
between the mobile user and the network. Please note that in between
alternating transmissions, no network resources need to be allocated. Compare
this to the circuit-switched transaction where resources are being accessed
permanently, regardless of whether or not transmission is actually talking
place. Therefore, packet-switching saves resources, especially in the case of
bursty transactions.
Performance
GPRS Offers Bandwidths up to 160 kbit/s With the development of
HSCSD, the idea of timeslot bundling to achieve higher data rates was born.
GPRS also applies timeslot bundling but additionally, new channel coding
schemes have been defined. With 8 timeslots and coding scheme 4, GPRS is
able to provide a net throughput rate of 160 kbit/s. However, GPRS can not
change physical laws. In other words, the channel coding schemes that provide
for higher data transmission rates per timeslot sacrifice data protection for
speed. Therefore, the new coding schemes 2, 3 and 4 make less provision for
forward error correction and can only be applied when radio conditions are
good to excellent.
EDGE
EDGE will provide the highest speeds in the second generation of
mobile networks. However, how can EDGE achieve these high throughput
rates compared to GPRS or HSCSD? Is EDGE really the third alternative to
GPRS and HSCSD with regard to high speed mobile data? If EDGE is so
superior to HSCSD and GPRS, why not upgrade directly to EDGE, leaving out
HSCSD and GPRS? Indeed, why is the mobile industry in the US also talking
about EDGE ?
The EDGE-Family
Formerly, EDGE was the abbreviation for Enhanced Data rates for
GSM Evolution. Nowadays, with EDGE also being adopted by the North
American market, EDGE is the acronym for Enhanced Data rates for Global
Evolution. However, EDGE is not a single standard or protocol stack for high
speed mobile data. Instead, EDGE introduces a new modulation scheme which
is 8-PSK in addition to, e.g. GMSK in the case of GSM. As illustrated in the
figure below, three members of the EDGE family need to be distinguished.
There is EDGE for GSM which will migrate GPRS and HSCSD to EGPRS
and ECSD. There is also the North American EDGE extension for the IS-136
standard which is called IS-136 HS or EDGE Compact. Finally, there is UWC
136 which is the UWCC's proposal for IMT-2000.
EDGE and Interference
Tripling the data transmission rate on the Air-Interface by applying
8-PSK seems like an obvious step forward. However, it has some inherent
disadvantages, in particular, through the unpredictable environment of radio
transmission. With increasing interference, the clearly distinguishable symbols
of 8-PSK, as shown in the animation, become more and more diffused. At a
certain stage, the receiver is no longer able to distinguish between different
symbols. Obviously, 8-PSK with 8 different symbols is more vulnerable to
such interference than e.g. GMSK
CONCLUSION
High speed mobile data will certainly improve the existing mobile
networks greatly. GPRS and EDGE, in particular, will write a new chapter in
mobile communications history. Currently, almost all network operators
worldwide are upgrading their GSM networks in order to provide high speed
mobile data to their subscribers.
HSCSD is a circuit-switched technology. Therefore, one of its major
advantages is that the existing core network, mainly the MSC, is able to handle
HSCSD traffic. As opposed to GPRS, HSCSD neither requires a hardware
upgrade within the network, nor does it introduce new channel coding
technologies. Therefore, HSCSD is a rather simple upgrade of the standard
GSM, particularly in comparison with GPRS and EDGEGPRS also applies timeslot bundling but additionally, new channel
coding schemes have been defined. With 8 timeslots and coding scheme 4,
GPRS is able to provide a net throughput rate of 160 kbit/s. However, GPRS
can not change physical laws. In other words, the channel coding schemes that
provide for higher data transmission rates per timeslot sacrifice data protection
for speed