5 research outputs found
Determination of ADSL capacity in a generic exchange environment
Please read the abstract in the front matter this documentDissertation (M Eng (Electronic Engineering))--University of Pretoria, 2006.Electrical, Electronic and Computer Engineeringunrestricte
Design of a Gigabit DSL modem using super orthogonal complete complementary codes
This paper describes the preliminary design and simulation towards a gigabit digital subscriber line modem that provides multi-user interference-free communication in a far-end crosstalk dominated environment by incorporating super orthogonal complete complementary spreading into the existing xDSL modem architecture. This is in contrast to existing vectoring and dynamic spectral management techniques that use joint processing and pre-processing of each user's signal to mitigate far-end crosstalk. A novel code allocation algorithm is introduced to provide all users with equal data rate ratios, even with bad line profiles and high-required data rates. Preliminary simulation results show that 1 Gbps aggregate throughput can be obtained for the system over a single pair of 0.5 mm copper wire over a distance from 180 to 150 m, depending on whether ADSL2+ or VDSL2 Profile 30a service bands are avoided, if present.The National Research Foundation of South Africa (Grant reference TP1207183332), Telkom and Bytes Universal Systems.http://onlinelibrary.wiley.com/journal/10.1002/(ISSN)2161-39152017-11-30Electrical, Electronic and Computer Engineerin
Space-time precoded CDMA-OFDMA employing super-orthogonal complete complementary codes
This paper addresses and illustrates, both analytically as well as by means of simulation,
the equivalence of a cyclically rotated complete complementary coded (CRCCC) code division
multiple access orthogonal frequency division multiplexed (CDMA-OFDM) BPSK/QPSK system
and a narrowband uncoded BPSK/QPSK reference system. The equivalence can be attributed to
the MUI-free characteristic performance of CRCCCs. It is demonstrated that when employed in a
multiple-input multiple-output (MIMO) antenna configuration along with orthogonal space-time block
codes (OSTBCs), the maximum theoretical diversity order of NTxNRx is achieved. Most significantly,
simulations show that CDMA-OFDM using CRCCCs is capable of rendering additional multipath
diversity gain at no additional processing cost. This signifies improved performance when compared
with conventional ST-OFDM systems.This work is based on the research supported in part
by the National Research Foundation of South Africa
(Grant reference TP1207183332) and our industry partners
Telkom and Bytes Universal Systems.http://www.saiee.org.za/DirectoryDisplay/DirectoryCMSPages.aspx?name=Publications#id=1588&dirname=ARJ&dirid=337am2016Electrical, Electronic and Computer Engineerin
A multi-levelled OFDM-CDMA modem using complete complementary codes
In this paper, we introduce a novel multiple access
scheme based on a combination of a multi-levelled modem and
multi-carrier techniques with the use of complete complementary
codes. This modulation technique combines a multi-dimensional
code division multiple access (CDMA) modem with recent designs
of perfectly complete complementary orthogonal codes.
The rotational properties of the spreading codes are further
exploited to improve the modulation technique, throughput,
spectral efficiency, and capacity. Additionally, the system is
extended by making use of multiple carrier frequencies as in
OFDM, with the additional benefits of being able to spread
data in frequency and/or in time. The modem offers multiple
access interference MAI-free and multipath interference MI-free
operation in both asynchronous and synchronous communication,
due to perfect autocorrelation and zero cross-correlation properties
of the spreading codes. The unique multi-levelled multiple
access modulation technique together with the integration of
complete complementary codes, produces a spectrally efficient
output signal with high data throughput rates, better noise
tolerances in harsh channel conditions and an increased user
capacity.The Department of Trade and
Industry (DTI), South Africahttp://www.saiee.org.za//content.php?pageID=200#ai201
Performance evaluation of a Gigabit DSL modem using super orthogonal complete complementary codes under practical crosstalk conditions
This paper describes the unique performance evaluation results of a Gigabit Digital
Subscriber Line modem that provides Multi-user-interference-free communication, by incorporating
Super Orthogonal Complete Complementary spreading into the existing xDSL modem architecture.
The GDSL modem was tested under practical crosstalk conditions, using the Network Interface, Power,
and Protection (NIPP) Committee MIMO Crosstalk Model. It was found that the GDSL modem
provides acceptable bit error rate performance for a fully loaded system, even for very short twisted
pairs. A unique observation from these performance evaluation tests is than the non-linear behaviour of
NEXT and FEXT creates an orthogonality distortion effect on the correlation properties of the SOCC
code family.http://www.saiee.org.za/DirectoryDisplay/DirectoryCMSPages.aspx?name=Publications#id=1588&dirname=ARJ&dirid=337am2018Electrical, Electronic and Computer Engineerin