A programmable logic integrated circuit device (“PLD”) includes programmable logic and a dedicated (i.e., at least partly hard-wired) digital signal processing region for performing or at least helping to perform digital signal processing tasks that are unduly inefficient to implement in the more general-purpose programmable logic and/or that, if implemented in the programmable logic, would operate unacceptably or at least undesirably slowly. The digital signal processing region may include multiple digital signal processing stages. The digital signal processing region may include a multiplier stage and one ore more stages that can operate in combination with the multiplier stage. The digital signal processing region has a plurality of modes such as for providing multiply-and-accumulate operation, multiply-and-add operation, etc.

Devices and methods with programmable logic and digital signal processing regions

In a first embodiment of the invention, a concatenated preamble code is formed by a kronecker product between two subcodes of the same or different lengths. The subcodes have favorable correlation properties and may be Barker codes, minimum peak sidelobe codes, Gold codes, Kasami codes, Boztas codes, or other codes. At the receiver a two-stage processor is used to detect the concatenated preamble code. The two-stage processor comprises a series of two filters, one of which is preferably a mismatched filter. In another aspect of the invention, a repeated codeword preamble is formed from a series of the same repeated short subcode. The short subcode may be an augmented or truncated odd-length code. At the receiver a single matched filter is preferably used to generate a series of spikes separated by the period of the subcode. An alert/confirm detector non-coherently adds together individual correlation spikes and reject false alarms. The alert function measures total correlation energy and adjusts detection thresholds based thereon, while the confirm function ensures that the proper number of correlation spikes exceed a detection threshold at the correct times. The preamble codes and their means for detection are preferably employed in a TDMA spread spectrum communication system, wherein a plurality of user stations communicate with a base station, one in each time slot (or virtual time slot).

Preamble code structure and detection method and apparatus

We propose a novel coding scheme for the unsourced multiple access channel model introduced by Polyanskiy [1] This new paradigm is composed of four main ingredients: (i) the transmission period is partitioned into sub-blocks, thereby instituting a slotted framework; (ii) The message (data) is split into two parts and one part chooses an interleaver for a low density parity check (LDPC) type code This part of the message is encoded using spreading sequences or codewords that are designed to be decoded by a compressed sensing type decoder; (iii) The other part of the message is encoded using a low density parity check (LDPC) type code and decoded using a joint message passing decoding algorithm designed for the T-user binary input real adder channel; (iv) users repeat their codeword in multiple sub-blocks, with the transmission pattern being a deterministic function of message content and independent of the identity of the user When this coding scheme is combined with serial interference cancellation, the ensuing communication infrastructure can offer significant performance improvements compared to the recently proposed coding scheme in [2] and results in the best performing coding scheme to date

A user-independent serial interference cancellation based coding scheme for the unsourced random access Gaussian channel

In this paper, we present a performance analysis of microwave signal transmission by deploying digitized RF transport over a standard optical fiber link. The bandpass sampling technique is used to digitize the RF signal. An analytical model, which is transparent to any modulation format, was developed to assess the transmission performance of a digitized RF signal in M-level quadrature amplitude modulation (M-QAM) format. Using this analytical model, key design parameters such as bit resolution, link bit rate, receiver sensitivity, and link signal-to-noise ratio (SNR) were analyzed for a digitized 2.475 GHz RF signal with 16-QAM data modulation format and 6 MSymbols/s baud rate over a 20-km optical link. The analytical results show that the link SNR is predominantly determined by the performance of the analog-to-digital converter (ADC). We experimentally demonstrated the digitized RF transmission over a 20-km optical link. The analytical model and experimental results show that the performance of the link SNR is governed by jitter noise beyond 7 bits of resolution of the ADC. Using an ADC with 8-bit resolution, a 2.475 GHz RF signal with 16-QAM 6 MSymbols/s data was successfully transmitted and recovered with very good error vector magnitude of 1.77.

Design and Analysis of Digitized RF-Over-Fiber Links

Our studies have shown that a digitized radio- over-fiber system based on bandpass sampling with an analog-to-digital converter having a resolution of 8 b is sufficient to construct a high-performance, cost-effective link that can allow easy integration of wireless backhaul with optical communication infrastructure. We also show that the performance of the digitized system is predominantly limited by the performance of the analog-to-digital converter used, with its quantization noise limiting the performance for the lower values of resolution ( 7 b).

Digitized RF transmission over fiber

Requirements for future mobile communications systems are demanding. This paper presents techniques and a development system for the research, design & development of reconfigurable digital signal processing for software radio based systems. Software radio is an essential technology required for the realisation of 3G to meet requirements such as seamless global roaming and protocol independence. This development system ensures that the use of FPGA is practical and realistic when considering the high data rate and multifunctional requirements of 3G systems.

A new development system for reconfigurable digital signal processing

Superimposed codes for multiple-access communication in a binary adder channel are analyzed. The superposition mechanism used in this correspondence is ordinary addition. Each user is assigned a codeword from a superimposed code. It is proved that every constant-weight code C of weight w and maximal correlation c corresponds to a subclass of a disjunctive code D of order m >

Superimposed codes for the multiaccess binary adder channel

Methods of synthesising multilevel complementary sequence sets of both odd and even lengths are described, thus extending previous work which was restricted to even-length binary sets. Also, techniques for the synthesis of uncorrelated sets of multilevel complementary sequences are given. Possible application areas are then discussed briefly.

Synthesis of multilevel complementary sequences.

A new simple algorithm which allows the design of a trellis diagram for array codes is introduced. Based on this algorithm, the trellis decoding of array codes with maximum likelihood decoding (MLD) performance and relatively low complexity is proposed. It is shown that the trellis structure of array codes allows the application of combined coding and modulation (CCM) with higher information digit per channel symbol rate than for conventional CCM methods, based on convolutional codes. The bounds on the transmission rates for different types of CCM signals, based on convolutional and array codes, have been obtained and presented in the paper.

Maximum-likelihood decoding of array codes with trellis structure

Maximal length sequences over Gaussian integers are discussed. It is shown that there exist two sub-classes of maximal length sequences of length L whose periodic autocorrelation functions are zero everywhere except at the shifts 0, L/4, L/2, 3L/4.

Mike Darnell

Papers

A new development system for reconfigurable digital signal processing

Superimposed codes for the multiaccess binary adder channel

Synthesis of multilevel complementary sequences.

Maximum-likelihood decoding of array codes with trellis structure

Maximal length sequences over Gaussian integers