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