A Feature Topic on B3G Wireless
The authors of this book were the Guest Editors for a Feature Topic on Multiple Access Technologies
for B3G Wireless Communications in the IEEE Communications Magazine, which was published in
the 2005 February issue [562]. That feature topic was published to serve as a stimulus to accelerate
the technological evolution of multiple access technologies for B3G wireless applications. Several
important issues on multiple access technologies that are suitable for B3G wireless systems have
been addressed in the feature topic. It should be mentioned that the call for papers for the feature
topic received an overwhelming response from the research community. More than forty high-quality
submissions were received from both the academia and the industry of different regions around the
world. This was a very positive sign, which showed that people around the world have been aware
of the importance of the research issues related to the feature topic. Unfortunately, because of limited
space and volume, only eight papers were accepted in the feature topic. In the following text, we give
a brief introduction to the eight articles published in that feature topic, as they addressed relevant
issues to what the B3G wireless needs in the perspective of multiple access technologies.
The first article was written by H. Wei, L-L. Yang, and L. Hanzo, titled Interference-Free Broadband
Single- and Multi-carrier DS-CDMA [563]. The article addressed a very interesting issue: the
choice of the DS spreading code for a DS-CDMA system. It was demonstrated in the article that the
family of codes exhibiting an interference-free window (IFW) outperforms classic spreading codes,
provided that the interfering multiuser and multipath components arrive within this IFW, which may
be ensured with the aid of quasi-synchronous adaptive timing advance control. The article further
showed that the IFW duration may be extended with the advent of multicarrier DS-CDMA proportionate
to the number of subcarriers. Hence, the resultant MC DS-CDMA system is capable of
exhibiting near-single-user performance without employing a multiuser detector. The authors also
addressed the limitations of the system, such as the number of spreading codes exhibiting a certain
IFW being limited, although this problem may be mitigated with the aid of novel code design principles.
This contribution was interesting because of the fact that all existing CDMA systems fail to
offer satisfactory performance and capacity, which is usually far less than half of the Processing Gain
(PG) of CDMA systems. Therefore, the work presented in the article can be a direction finder for
further research on the design of next generation CDMA systems, whose performance should not be
interference-limited.
The second article [564] in the feature topic was written by William C. Y. Lee, who proposed a
new up and down link duplexing scheme called code division duplexing (CDD), whose physical layer
scheme can work harmoniously with a 4G wireless architecture called code spreading (CS) orthogonal frequency-division multiple access (OFDMA). The CS technique used a set of smart codes with its
meritorious properties, which can eliminate both multipath and multiuser interferences. The article
showed that the same number of smart codes applied repeatedly in each subcarrier of OFDMA could
be used to increase the number of traffic channels. The author further illustrated that the scheme could
take advantage of both the attributes of CDMA and OFDMA toward a simpler and more spectrally
efficient system as applied in a CDD system.
The third article, Ultra-wideband for Multiple Access Communications [565], was contributed
by Robert C. Qiu, Huaping Liu, and Sherman Shen. This article offered a comprehensive review
of UWB multiple access and modulation schemes. It also included a comparison with narrowband
radios. The authors outlined other issues with Ultra-wideband (UWB) signal reception and detection,
and explored various suboptimal low complexity receiving schemes. The focus of the article was on
balancing the treatment of theoretical and practical designs. They also mixed the needs of two major
applications (IEEE 802.15.3a and 4a). They believed that UWB holds a promising future for wireless
multiple access, simply because of the unprecedented huge chunk of the unlicensed spectrum. The
article then pointed out that in the long run, UWB will change some of the basic ideas in the standard
wireless textbooks, and will enable the concept of gigabit wireless communications.
Next, Farooq Khan offered his opinion on a time-orthogonal CDMA high-speed up link data transmission
scheme, suitable for B3G wireless systems. In this article [566], the author presented a new
time-orthogonal CDMA approach called high-speed up link data burst transmission mode. The concept
was based on slot-synchronized slot-orthogonal transmissions, whereby high-speed data transmissions
take place in slots orthogonal to the slots used for physical layer control signaling and low-data-rate
transmission such as resource requests. Using this approach, very high data rates and capacity are
achieved during data burst transmission because of the availability of high signal-to-interference-plusnoise
ratio (SINR) resulting from the orthogonality of the transmissions. The simulation results given
in this article showed that the up link spectral efficiency of the proposed scheme was approximately
four times better than the up link spectral efficiency achieved with existing 3G systems.
The fifth article [567], written by Romano Fantacci et al., gave a review of the implementation of
future CDMA communication systems. More specifically, the authors highlighted the issues regarding
coping with the challenging requirements future systems ought to face. In the article, particular
attention was given to addressing some inherent weak points of current CDMA systems, and then
to suitable detection techniques to overcome major impairments in the channels. The article went on
to further point out that high-data-rate transmissions in B3G wireless require proper link adaptation
techniques. The article concluded by focusing on the design of suitable protocol strategies for new
heterogenous multimedia packet services, which are constrained by strict quality of service (QoS)
requirements.
The sixth article [568] discussed high-performance MIMO OFDM wireless LAN systems. The
article was jointly authored by S. Nanda et al., from Qualcomm, Inc. The article started by enumerating
valuable lessons to be learned from the design of wireless local-area networks (WLANs) that provide
data rates in excess of hundreds of megabits per second. In particular, they presented a MIMO WLAN
design and prototype that exploits these attributes to provide data rates in excess of 200 Mbps above
the medium access control (MAC). Although the design and prototype given in the article were
only focused on WLAN, it was demonstrated that very high data rates over wireless are feasible.
The article concluded with a summary of several key attributes of next generation high-performance
wireless networks.
The seventh article [569] offered a tutorial on multiple access technologies for beyond 3G mobile
networks, written by Abbas Jamalipour et al. In this article, the state-of-the-art technologies for multiple
access schemes that have been adopted in third-generation wireless cellular systems were reviewed,
and a path for the development of appropriate multiple access technologies for B3G mobile networks
was suggested. The authors provided an expression that could interconnect all those multiple access
schemes that are usually separated under time-division, frequency-division, and code-division techniques.
Several combinations of these multiple access schemes were discussed, and their application in different cellular mobile standards was addressed. The authors suggested that next generation networks
will be developed through the good management and combination of advanced multiple access
technologies, rather than the development of new schemes.
Finally, Markku Juntti et al., [570] proposed a MIMO system based on space�"time turbo coded
modulation and layered spatial multiplexing architectures for cellular multicarrier (MC) CDMA systems.
The authors discussed the issues related to the design of appropriate receiver algorithms, and
compared the performance of the new system with competing schemes in a single cell basis. The
performance evaluation of the proposed scheme was carried out for a seven-cell system with universal
frequency reuse. It was shown that the proposed MIMO scheme could significantly improve
the throughput compared to the corresponding single-antenna communication systems even in the
presence of spatial correlation.
It was hoped that by highlighting some of the current research work on multiple access technologies
for B3G Wireless Communications in the feature topic [562], the researchers would be
encouraged to consider some specific research issues raised therein. We believe that this feature topic
has triggered further interest in the research areas on multiple access technologies for B3G wireless
communications.
gigabit wireless
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