An Improved OCDMA/OCDMA Scheme Based on Displaced Orthogonal User Sets

Vanhaverbeke, F.; Moeneclaey, Marc

doi:10.1109/lcomm.2004.827453

Cited by 15 publications

(17 citation statements)

References 12 publications

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“…We have used the code cross-correlations from (9) and noted that ρ jk = ρ * jk . Factoring out b 1 , b 2 , ..., b N , and rearranging, we can rewrite (24) to get (25) at the top of next page.…”

Section: A Effective Channel Matrixmentioning

confidence: 99%

“…As for nonorthogonal code sets, numerous literatures exist regarding the design of code sequences when the number of users exceeds the processing gain in synchronous CDMA systems [20]- [25]. This problem statement parallels code selection for the CPMA receiver, where it is desired to accommodate N > G antennas to reduce BW requirements of the shared blocks.…”

Section: Code Selectionmentioning

confidence: 99%

“…This problem statement parallels code selection for the CPMA receiver, where it is desired to accommodate N > G antennas to reduce BW requirements of the shared blocks. Thus, the code set schemes in [20]- [25] can be used directly for our application to minimize code cross-correlations, thereby minimizing capacity degradation.…”

Section: Code Selectionmentioning

confidence: 99%

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Code-modulated path-sharing multi-antenna receivers: theory and analysis

Jahanian

Heydari

Tzeng

2009

IEEE Trans. Wireless Commun.

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Conventional multi-antenna receiver front-ends require multiple RF/baseband chains and analog-to-digital converters (ADC). This increases power consumption and chip area substantially. In this letter, we introduce a new Code-Modulated Path-Sharing Multi-Antenna (CPMA) receiver architecture suitable for any multi-antenna scheme including spatial multiplexing, spatial diversity, and beamforming. The receiver uses code modulation to distinguish the antenna signals before combining them in the analog domain. The combined signal propagates through shared-path blocks and all the original signals are later recovered in the digital domain for further processing. Due to the spread spectrum nature of code modulation, a larger bandwidth is needed for the blocks in the shared path. To alleviate this effect, the use of non-orthogonal coding is examined. An effective channel matrix is derived and the system capacity is evaluated in terms of the cross-correlation between signature codes. Implementation and code selection issues are discussed. Analysis and simulation results indicate that by properly selecting non-orthogonal code sets, the spreading factor, and therefore, the overall analog signal bandwidth is reduced while incurring minimal performance degradation.

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Section: A Effective Channel Matrixmentioning

confidence: 99%

Section: Code Selectionmentioning

confidence: 99%

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Code-modulated path-sharing multi-antenna receivers: theory and analysis

Jahanian

Heydari

Tzeng

2009

IEEE Trans. Wireless Commun.

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“…Many approaches with several diversities can be found such as those reported in literature [2][3][4][5][6][7]. The use of Welch Bound Equality (WBE) sequences though achieves a significant improvement in maximizing the total number of users, but it suffers from the problem related to scalability [1].…”

Section: Introductionmentioning

confidence: 99%

“…In another scheme known as Random Orthogonal/ Orthogonal (O/O) CDMA two sets of different orthogonal code are used for two sets of users [2]. In [3] a more improved random O/O CDMA has been proposed with displaced codes. In [2] [3] the use of non-linear multi user detectors with massive computations add extra complexity to the receiver side.…”

Section: Introductionmentioning

confidence: 99%

Synchronous overloaded system for the uplink of cellular CDMA with Unequal Chip Delay Spreading (UCDS)

Singh

2012

2012 5th International Conference on Computers and Devices for Communication (CODEC)

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Channel overloading in Code Division Multiple Access (CDMA) facilitates to accommodate more number of users than the assigned spreading factor N. Our proposal for a synchronous CDMA technique for the uplink of a cellular system over additive white gaussian noise (AWGN) channel achieves oversaturation by using the same set of orthogonal Walsh Hadamard codes and a receiver with lower complexity. The technique involves dividing the total number of active users into G groups, each with L users. Each user in a group is assigned the same signature sequence but with different chip duration. Users in a group can be classified as Primary and Secondary. The Primary user avails the spreading sequence with the maximum chip duration Tc. The rest L-1 (secondary) users are assigned the same code with chip duration as multiples of Tc/L. Unlike conventional Direct Sequence CDMA (DS-CDMA), all the users participate in spreading using the proposed Unequal Chip Delay Spreading (UCDS) technique. The receiver contains a switching unit to separate the received stream into L sub-streams followed by the detection process using a simple multi user detector. On the other hand, L levels of Unequal Error Protection (UEP) can be attained due to the unequal amount of multiple access interference (MAI) existing in alternate chip interval during transmission. Unequal chip delay spreading finally enables it to have a L-fold increase in the user data rate at the receiving end as compared to that of the transmission.

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Sequences with low total squared asynchronous correlation for chip‐unaligned CDMA systems

Vanhaverbeke

Moeneclaey

2007

Trans Emerging Tel Tech

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SUMMARYWe examine some properties of Chip-unaligned (Cu) CDMA systems with sequences that are obtained by means of an eigen update algorithm. We briefly refer to these systems as 'Cu systems with low total squared asynchronous correlation (TSAC)'. The notion of TS(A)C, which is well-known for Chip-aligned (Ca) systems, is extended to the Cu case. It is found that the TSAC of Cu systems with low TSAC is a nonsensitive function of the time shift set of the Cu system, but it is strongly dependent on the chip pulse. Similar to the Ca case, for high channel loads, the TSAC of some Cu systems with low TSAC appears to be proportional to the channel load and the number of users in the system, while the equally good property is valid. An examination of the maximum common signal to interference and noise ratio (SINR) target level max indicates that particular types of Cu systems with low TSAC allow for a significantly higher value of max than achievable in Ca systems.

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An Improved OCDMA/OCDMA Scheme Based on Displaced Orthogonal User Sets

Cited by 15 publications

References 12 publications

Code-modulated path-sharing multi-antenna receivers: theory and analysis

Code-modulated path-sharing multi-antenna receivers: theory and analysis

Synchronous overloaded system for the uplink of cellular CDMA with Unequal Chip Delay Spreading (UCDS)

Sequences with low total squared asynchronous correlation for chip‐unaligned CDMA systems

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