System performance criteria in CDMA networks using gold codes

First, we have presented the autocorrelation and crosscorrelation properties for periodic and aperiodic binary sequences. The generation of binary sequences using shift registers with feedback was reviewed. We have also included correlation properties for the Gold codes. Next, we discussed Gold code generation for the balanced and unbalanced Gold codes. Thirdly, we investigated the number of simultaneous users in a CDMA system using Gold codes for the worst case and the average case of mutual interference. Finally, we simulated the probability of interference exceeding a threshold value, and the average crosscorrelation value caused by interference in a CDMA network which is using a Gold code. We compared probability and average crosscorrelation values simulated with theoretical bounds calculated. Here the simulation programs are done in C computer language

Binary matrices of optimal autocorrelations as alignment marks

We define a new class of binary matrices by maximizing the peak-sidelobe distances in the aperiodic autocorrelations. These matrices can be used as robust position marks for in-plane spatial alignment. The optimal square matrices of dimensions up to 7 by 7 and optimal diagonally-symmetric matrices of 8 by 8 and 9 by 9 were found by exhaustive searches.Comment: 8 pages, 6 figures and 1 tabl

Nonlinear Suppression of Range Ambiguity in Pulse Doppler Radar

Coherent pulse train processing is most commonly used in airborne pulse Doppler radar, achieving adequate transmitter/receiver isolation and excellent resolution properties while inherently inducing ambiguities in Doppler and range. First introduced by Palermo in 1962 using two conjugate LFM pulses, the primary nonlinear suppression objective involves reducing range ambiguity, given the waveform is nominally unambiguous in Doppler, by using interpulse and intrapulse coding (pulse compression) to discriminate received ambiguous pulse responses. By introducing a nonlinear operation on compressed (undesired) pulse responses within individual channels, ambiguous energy levels are reduced in channel outputs. This research expands the NLS concept using discrete coding and processing. A general theory is developed showing how NLS accomplishes ambiguity surface volume removal without requiring orthogonal coding. Useful NLS code sets are generated using combinatorial, simulated annealing optimization techniques - a general algorithm is developed to extended family size, code length, and number of phases (polyphase coding). An adaptive reserved code thresholding scheme is introduced to efficiently and effectively track the matched filter response of a target field over a wide dynamic range, such as normally experienced in airborne radar systems. An evaluation model for characterizing NLS clutter suppression performance is developed - NLS performance is characterized using measured clutter data with analysis indicating the proposed technique performs relatively well even when large clutter cells exist

Development of a set of optimum synchronization codes for a unique decoder mechanization

Synchronization requirements are specified for and a unique decoder mechanization is associated with a particular communication system. Optimum synchronization codes, defined as codes which are the least susceptible to false synchronization indications, are sought. Existing sets of optimum codes are investigated for applicability. This Thesis shows how these sets were developed from selected criteria and demonstrates why their theoretical nature produces unsatisfactory results in the present application wherein all parameters are known. A computer program was written to examine code pattern performance in the specified decoder under actual operating conditions. From an analysis of the results, a recommended set of optimum synchronization codes was developed --Abstract, page ii

Arithmetic crosscorrelation of binary mm-sequences with coprime periods

The arithmetic crosscorrelation of binary $m$-sequences with coprime periods $2^{n_1}-1$ and $2^{n_2}-1$\ ($\gcd(n_1,n_2)=1$) is determined. The result shows that the absolute value of arithmetic crosscorrelation of such binary $m$-sequences is not greater than $2^{\min(n_1,n_2)}-1$

PULSE COMPRESSION IN SEARCH RADAR

Pulse compression is a vvidely used method to maintain the range resolution ot radar while increasing the average power per pulse that can be placed on a target. Using all these methods a wideband modulation is added to the transmitted pulse and a filter matched to this modulation is used in the receiver. There are several kinds of these additional modulations, and each has different properties, therefore simulation of these methods is essential during design of modulation. In this article an overview of pulse compression techniques is given, the benefits and disadvantages of these methods are discussed. Biphase coded systems are detailed, because they are easy to implement with digital hardware. At the end, our simulation hardware and software tools are described, giving some illustrations from the results