Brevity is the soul of wit. William Shakespeare A cyclically permutable code is a set of codewords having the property that no codeword is a cyclic shift of another codeword. We study the problem of constructing cyclically permutable codes of large size and low correlation. Cyclically permutable codes are used in code-division multiple-access systems realized by e.g. direct-sequence modulation ...

The use of Code Division for Multiple Access or CDMA is well established. We know that it has advantages in multipath environment and increase in capacity due to sectoring antenna and voice activity factor. Here a step by step comparison is made among Frequency Division Multiple Access, Time Division Multiple Access and Code Division Multiple Access when capacity or SNR is of main concern. A de...

In this paper, the notion of quasi-orthogonal sequence (QOS) as a means of increasing the number of channels in synchronous code-division multiple-access (CDMA) systems that employ Walsh sequences for spreading information signals and separating channels is introduced. It is shown that a QOS sequence may be regarded as a class of bent (almost bent) functions possessing, in addition, a certain w...

An optical dynamic frequency hopping code division multiple access communication system is proposed. In this system, an electrically controlled tunable optical filter (TOF) is used to encode the modulated broadband light source. The code depends on the function set to the controller. The function defines the dynamic hopping pattern of the central wavelength of the transmitted narrowband optical...

The effect of using randomly selected sequence multisets for the uplink of a synchronous code-division multipleaccess channel is considered. A tight lower bound on the expected value of the sum capacity over the ensemble of randomly selected sequence multisets is given. For large systems, the sum rate penalty for using randomly selected multisets is shown to be at most 1 nat and to vanish as th...

In code-division multiple-access systems, simultaneous multiuser accessing of a common channel is made possible by assigning a signature waveform to each user. Knowledge of these waveforms enables the receiver to demodulate the data streams of each user, upon observation of the sum of the transmitted signals, perturbed by additive noise. Under the assumptions of symbol-synchronous transmissions...

A subcarrier spectral amplitude coding optical code division multiple access system using the Khazani-Syed code with Complementary subtraction detection technique is proposed. The proposed system has been analyzed by taking into account the effects of phase-induced intensity noise, shot noise, thermal noise and intermodulation distortion noise. The performance of the system has been compared wi...

In this study, the authors propose a novel collaborative multi-user transmission and detection scheme for the uplink of code-division multiple access (CDMA) that exploits the differences between users’ fading channel signatures to increase the user capacity well beyond the spreading length in multiple access interference (MAI) limited environment. The authors show that it is possible to achieve...

We consider multiuser communication on a binary input additive white Gaussian noise channel using Randomly Spread-Code Division Multiple Access. We show concentration of various quantities of the system including the capacity and the free energy. We also obtain a tight upper bound on the capacity of this system in the large user limit which matches with the replica solution. The method is quite...

Code Division Multiple Access Communications Sang Wu Kim1 and Andrea Goldsmith Dept. of Electrical Engineering California Institute of Technology Pasadena, CA 91125 Abstract We analyze the performance of the truncated power control scheme in code division multiple access communication systems, which compensates for fading above a certain cuto fade depth. We investigate the power gain as well as...