Open Wireless Architecture - The Core to 4G Mobile
Communications


Abstract


Mobile communication is continuously one of the
hottest areas that are developing at a booming speed,
with advanced techniques emerging in all the fields of
mobile and wireless communications. Current times
are just the beginning for deploying 3G mobile
communication systems, while research on the next
generation of mobile communications, 4G wireless and
mobile networks begin to pave the way for the future.
This article studies the visions of 4G from a technical
perspective. After a brief review on the development
history and status of mobile communications and
related 4G perspectives, the article describes the
open Wireless Architecture (OWA) platform which is
used for high speed wireless access. OWA for fourth
generation (4G) mobile communications supporting
various different wireless radio transmission
technologies (or called air interfaces) and convergence
of wireless networks and wireline networks by
constructing an open architecture platform in the
systems of base-band processing, radio frequency,
controller, networking as well as service applications,
etc. With this said OWA model, a fourth generation
mobile communication system is defined and
developed.


INTRODUCTION


Mobile communications and wireless networks are
developing at an astounding speed, with evidences of
significant growth in the areas of mobile subscribers and
terminals, mobile and wireless access networks, and
mobile services and applications. According to 3G goals,
3G is necessary but not sufficient to the mobile
communication strategy, in which many problems are only
partly solved and there are still many problems left to be
solved in the next generation, i.e. 4G. Packet switched
wireless system with wide area coverage and high
throughput. It is designed to be cost effective and to
provide high spectral efficiency. The 4g wireless uses
Orthogonal Frequency Division Multiplexing (OFDM),
Ultra Wide Radio Band (UWB), and Millimetre wireless.
Features:
o Support for interactive multimedia, voice, streaming
video, Internet, and other broad band services
o IP based mobile system
o High speed, high capacity, and low cost per bit
o Global access, service portability, and scalable mobile
services
o Seamless switching, and a variety of Quality of Service
driven services
o Better spectral efficiency
o Seamless network of multiple protocol and air interface


MOBILE COMMUNICATIONS REVIEW


The history and status of mobile communications are
shortly listed in the following, together with the respective
evaluations on the chief contributions.
1) Traditionally, wireless systems were considered as an
auxiliary approach that was used in regions where it was
difficult to build a connection by wire line.
2) 1G was based on analogy technique and deployed in
the1980s. It built the basic structure of mobile
communications and solved many fundamental problems,
e.g. cellular architecture adopting, multiplexing frequency
band, roaming across domain, non-interrupted
communication in mobile circumstances, etc. Speech chat
was the only service of 1G.
3) 2G was based on digital signal processing techniques
and regarded as a revolution from analogy to digital
technology, which has gained tremendous success
during1990s with GSM as the representative. The
utilization of SIM (Subscriber Identity Module) cards and
support capabilities for a large number of users were 2Gâ„¢s
main contributions
4) 2.5G extended the 2G with data service and packet
switching methods, and it was regarded as 3G services for
2Gnetworks. Under the same networks with 2G, 2.5G
brought the Internet into mobile personal communications.
This was a revolutionary concept leading to hybrid
communications.
5) 3G is deploying a new system with new services instead
of only providing higher data rate and broader bandwidth.
Based on intelligent DSP techniques, various multimedia
data communications services are transmitted by
convergent 3Gnetworks.3G still leaves some unsolved
problems that it does not concern or concerns only partly.
The limitations and difficulties of 3G include:
Difficulty in continuously increasing bandwidth and high
data rate to meet multimedia services requirements,
together with the coexistence of different services needing
different QoS and bandwidth.
3G can provide down page link data rate up to 10Mbps;
4G will be able to support bit rate of up to 50-100Mbps for
urban outdoor, and 1Gbps for indoor, environments
Limitation of spectrum and its allocation.


Difficult to roam across distinct service environment
indifferent frequency bands.
Lack of end-to-end seamless transport mechanism
spanning a mobile sub-network and a fixed one.
Table 1 summarizes the entire development of mobile
communications with the properties of each generation
including starting time, driven technique, representative
standard, radio frequency, bandwidth, multi-address
technique, cellular coverage, core networks, and service
type.
Different 4G feature frameworks have been defined from
the standpoints of service subscriber, service provider,
researcher and engineer. In the following we give some
representatives of 4G perspectives.
1) It is easy to say, based on the developing trends of
mobile communication, that 4G will have broader
bandwidth, higher data rate, smoother and quicker handoff,
wider mobile area, more various service, lower cost, etc.
Obviously these ideas do not make too much sense as
such.
2) Other than the words more, any and/or all are
preferred over expressions used by some others, e.g.
anyone can communicate with anyone else, anywhere and
anytime, or enjoy any service of any network operator,
through any network of any network service provider.
These sentences are
truly attractive from a subscriberâ„¢s viewpoint, and they
sound quite like advertisements or word games.
3) DoCoMo introduced the concept of MAGIC for the
vision of 4G [5]: Mobile multimedia; Anytime, anywhere,
anyone; Global mobility support; Integrated wireless
solution; and Customized personal service, which mostly
focused on public systems and treat 4G as the extension of
3G cellular service.
Figure 1 shows the wireless evolution to 4G mobile
communications based on OWA platfonn, where 3G,
Wireless LAN and other wireless access technologies
will be converged into 4G mobile platform to deliver the
best infrastructure of mobile communications with
optimal spectrum efficiency and resource management.
Open Wireless Architecture


The 4G Mobile communications will be based on the Open
Wireless Architecture (OWA) to ensure the single terminal
can seamlessly and automatically connect to the local
high-speed wireless access systems when the users are in
the offices, homes, airports or shopping centers where the
wireless access networks (i.e. Wireless LAN, Broadband
Wireless Access, Wireless Local Loop, HomeRF, Wireless
ATM, etc) are available
This converged wireless communications can provide the
following
advantages:
0 Greatly increase the spectrum efficiency
0 Mostly ensure the highest data-rate to the wireless
0 Best share the network resources and channel terminal
utilization
1.An open wireless architecture (OWA) for fourth
generation mobile communications system comprising:
a) A wireless communication terminal device supporting
various different wireless standards (air interfaces) in the
same device with same unique identifier and capable of
communicating with other devices, systems or networks
through a wireless medium or over-the-air network,
b) An advanced computer system equipped with full
networking facilities to access various different backbone
networks through wireline networking interfaces or
sometimes through broadband wireless access systems,
c) An advanced transceiver system supporting various
different air interfaces to interconnect with wireless
communication terminal device, etc through the air link,
d) transceiver system connected to computer system to
construct the base-station as a whole,
e) wireless terminal device can also connected to different
wireline networks through its networking interfaces in the
wireless terminal device,
f) base-station can connected to other base-station either
over the wireline networks or over broadband wireless
access system through computer system, or by over-the-air
networks through transceiver system,
g) wireless terminal device can also connected to other
wireless terminal device through the air page link in an ad-hoc
mode in case of special situations.
2. A method providing a smart antenna processing module
for OWA system, method comprising:
a) using antenna arrays to process radio signals in space,
not only time, to improve performance in presence of
wireless fading and interference,
b) using beam forming algorithm to increase received
signal-over-noise-rate (SNR) for desired directions,
c) using diversity algorithm to combat fading in order to
work at less SNR,
d) using interference mitigation method to maximally
reuse the channel frequencies,
e) using spatial multiplexing algorithms to increase data
speeds, for example, MIMO (multiple-in and multipleout),
etc.
An Open Wireless Architecture (OWA) for fourth
generation mobile communications system providing a
cost-effective business model and method for vendors,
operators and providers of various different wireless
standards, method comprising:
a) open spectrum management saving lots of investment in
spectrum allocation
b) open architecture saving lots of marketing costs of
different standards and services, lots of costs in
infrastructure investment, lots of costs on interoperability
issues, optimizing the network resource and system
capacity.
3. An OWA comprises: open processing engine decodes,
de-channelizes and demodulates the base-band channel
signals and control signals of said various air-interfaces
into detailed digital signalling, traffic and control
information, and vice verse
.
4. A system base station can be reconfigured and reprogrammed
as wireless router, mobile soft switch or
wireless gateway, etc.
Vertical handoff and Horizontal handoff


To support OWA architecture there are two kinds of
handoffs


Horizontal handoff


Horizontal handoff is performed when the terminal moves
from one cell to other cell with in the same wireless
system.


Vertical handoff


Vertical handoff, handles the terminal movement between
two different wireless system ( e.g. from WLAN to GSM)
.Moreover,4g networks are expected support real time
multimedia services that are highly time sensitive. It is
unacceptable if the Mobile IPv-6 handoff process
significantly degrades system performance, especially QoS
performance. In addition,it is hard to decide the correct
handoff time because measuring handoffs between
different wireless system is very complicated. Finally ,the
uncertain handoff completion adds to the complexity in
designing good handoff mechanism.
To over come these problems, researches are currently
investigating new handoff decision policies and new
algorithms for heterogeneous networks.


MIMO(Multiple Input Multiple Output)


Many enabling technologies have been proposed for 4G
wireless applications, and one of the most important
technologies is MIMO, which isof significant importance
due to the fact that it achieves its diversity gain and
multiplexing capability without extra spectrum. Therefore,
in order to improve spectral efficiency and system capacity
as a whole, multiple-antenna technology is almost a must
for 4G systems to support high data rate transmissions.
The proposed STCC MIMO scheme is able to provide a
joint diversity and multiplexing advantage (as shown in
Fig.4) with the help PCCs and OS spread spectrum. It also
offers an open MIMO architecture suited for different
wireless applications, which have distinct requirements on
diversity order and data throughput.


Adaptive Modulation and Coding (AMC)


The principle of AMC is to change the modulation and
coding format (transport format) in accordance with
instantaneous variations in the channel conditions,
subject to system restrictions. AMC extends the systems
ability to adapt to good channel conditions. Channel
conditions should be estimated based on feedback from
the receiver. For a system with AMC, users close to the
cell site are typically assigned higher order modulation
with higher code rates (e.g. 64 QAM with R=3/4 Turbo
Vertical
handoff
GSM
coverage
UMTS
coverage
WLAN
coverag
Horizontal
handoff
Codes). On the other hand, users close to the cell
boundary, are assigned lower order modulation with
lower code rates (e.g. QPSK with R=1/2 Turbo Codes).
AMC allows dflerent data rates to be assigned to
different users depending on their channel conditions.
Since the channel conditions vary over time, the receiver
collects a set of channel statistics which are used both by
the transmitter and receiver to optimize system
parameters such as modulation and coding, signal
bandwidth, signal power, training period, channel
estimation filters, automatic gain control, etc.


OFDM


OFDM is chosen over a single carrier solution due to
lower complexity of equalizers for high delay spread
channels or high data rates. A broadband signal is
broken down into multiple narrowband carriers (tones),
where each carrier is more robust to multipath. In order
to maintain orthogonality amongst tones, a cyclic prefix
is added which has length greater than the expected
delay spread. With proper coding and interleaving across
frequencies, multipath turns into an OFDM system
advantage by yielding frequency diversity


CONCLUSION


This aticle presents 4G visions from a technical
perspective. After a brief review of the history and status
of mobile communications, a 4G feature framework, in
which features of 4G mobile communications are defined.
The architecture (OWA) which helps in high speed
wireless access is explained in the article, OWA will
eventually become the global industry leading solution to
integrate various wireless air-interfaces into one wireless
open terminal where the same end equipment can flexibly
work in the wireless access domains as well as in the
mobile cellular networks. As mobile terminal (rather than
wireline phone) will become the most important
communicator in future, this single equipment with single
number and multiple air-interfaces (powered by OWA)
will definitely dominate the wireless communication
industries.
With the strong economy growth in China and the
neighbouring countries, the 4G mobile system based on
Open Wireless Architecture will become the next wave in
wireless communications. China, Japan, Korea,
Singapore as well as other Asian countries are investing
huge funds on this emerging 4G mobile core technology.