Reduced-Complexity Noncoherently Detected Differential Space-Time Shift Keying

Motivated by the recent development of Spatial Modulation (SM) and Differential Space-Time Shift Keying (DSTSK), we propose a reduced-complexity Conventional Differential Detector (CDD) as well as its reduced-complexity Multiple-Symbol Differential Sphere Detector (MSDSD) counterpart for DSTSK. Both schemes operate on a symbol-by-symbol basis in order to reduce the complexity of the classic block-by-block-based CDD and MSDSD, whilst still approaching the optimum performance of the full-search-based Maximum Likelihood (ML) detector. More explicitly, we carefully consider the objective function to be used for decoding the index of the specific antenna activated by taking into account the particular modulation scheme employed. Our simulation results demonstrate that the proposed CDD and MSDSD designed for DSTSK guarantee a significant complexity reduction compared to the classic block-based decoders, especially for high-rate DSTSK schemes, which is achieved without a performance penalty

Dispensing with Channel Estimation…

In this article, we investigate the feasibility of noncoherent detection schemes in wireless communication systems as a low-complexity alternative to the family of coherent schemes. The noncoherent schemes require no channel knowledge at the receiver for the detection of the received signal, while the coherent schemes require channel inherently complex estimation, which implies that pilot symbols have to be transmitted resulting in a wastage of the available bandwidth as well as the transmission power

Bit-Interleaved Coded Energy-Based Modulation with Iterative Decoding

This paper develops a low-complexity near-optimal non-coherent receiver for a multi-level energy-based coded modulation system. Inspired by the turbo processing principle, we incorporate the fundamentals of bit-interleaved coded modulation with iterative decoding (BICM-ID) into the proposed receiver design. The resulting system is called bit-interleaved coded energy-based modulation with iterative decoding (BICEM-ID) and its error performance is analytically studied. Specifically, we derive upper bounds on the average pairwise error probability (PEP) of the non-coherent BICEM-ID system in the feedback-free (FF) and error-free feedback (EFF) scenarios. It is revealed that the definition of the nearest neighbors, which is important in the performance analysis in the FF scenario, is very different from that in the coherent BICM-ID counterpart. The analysis also reveals how the mapping from coded bits to energy levels influences the diversity order and coding gain of the BICEM-ID systems. A design criterion for good mappings is then formulated and an algorithm is proposed to find a set of best mappings for BICEM-ID. Finally, simulation results corroborate the main analytical findings

Capacity -based parameter optimization of bandwidth constrained CPM

Continuous phase modulation (CPM) is an attractive modulation choice for bandwidth limited systems due to its small side lobes, fast spectral decay and the ability to be noncoherently detected. Furthermore, the constant envelope property of CPM permits highly power efficient amplification. The design of bit-interleaved coded continuous phase modulation is characterized by the code rate, modulation order, modulation index, and pulse shape. This dissertation outlines a methodology for determining the optimal values of these parameters under bandwidth and receiver complexity constraints. The cost function used to drive the optimization is the information-theoretic minimum ratio of energy-per-bit to noise-spectral density found by evaluating the constrained channel capacity. The capacity can be reliably estimated using Monte Carlo integration. A search for optimal parameters is conducted over a range of coded CPM parameters, bandwidth efficiencies, and channels. Results are presented for a system employing a trellis-based coherent detector. To constrain complexity and allow any modulation index to be considered, a soft output differential phase detector has also been developed.;Building upon the capacity results, extrinsic information transfer (EXIT) charts are used to analyze a system that iterates between demodulation and decoding. Convergence thresholds are determined for the iterative system for different outer convolutional codes, alphabet sizes, modulation indices and constellation mappings. These are used to identify the code and modulation parameters with the best energy efficiency at different spectral efficiencies for the AWGN channel. Finally, bit error rate curves are presented to corroborate the capacity and EXIT chart designs

High-speed and Robust Integrated Silicon Nanophotonics for On-Chip Interconnects

Optical interconnects offer advantages over electrical interconnects such as higher bandwidth, low power, reduced interconnects delay, and immunity to electro-magnetic interference and signal crosstalk. However, in order for optical interconnects to be widely adopted, the technology must be made cost effective and must be simple to implement with CMOS electronics. Silicon photonics offers a great promise due to its inexpensive material and its compatibility with the current CMOS fabrication technology. Moreover, Silicon as a platform has the ability to integrate with different types of the optical components such as photodetector, modulator, light source, and waveguide to form a photonics integrated circuit. The goal of this work is to develop and fabricate devices that utilize a hybrid electronic-photonic integration to enable high performance optoelectronic computing and communication systems that overcome the barriers of electronics and dramatically enhance the performance of circuits and systems. We experimentally demonstrate a novel broadband optical time division multiplexer (OTDM) on a silicon chip. The system has a footprint× 700 micrometer and is inherently broadband with a bandwidth of over 100nm making it suitable for high-speed optical networks on chip. Also, we propose and fabricate a novel design to demultiplex the high bit rates of OTDM data using two differentially operated 5Gb/s modulators. Moreover, we propose a high-speed hybrid optical-time-division-multiplexing (OTDM) and wavelength-division-multiplexing (WDM) system that seamlessly generates high bit-rate data (\u3e200Gbit/s) from a low speed (5Gbit/s) quantum-dot mode locked laser pulse source. By utilizing time and wavelength domains, the proposed design is a promising solution for high-speed, compact and low-power consumption optical networks on chip. And finally, we experimentally demonstrate a robust, low insertion loss, compact Silicon ring resonator electro-optic modulator for Binary Phase Shift Key (BPSK) coding/decoding that encodes data in the phase of light. Our design improves significantly over recently demonstrated PSK modulator designs in terms of insertion loss and stability

Microwave vs optical crosslink study

The intersatellite links (ISL's) at geostationary orbit is currently a missing link in commercial satellite services. Prior studies have found that potential application of ISL's to domestic, regional, and global satellites will provide more cost-effective services than the non-ISL's systems (i.e., multiple-hop systems). In addition, ISL's can improve and expand the existing satellite services in several aspects. For example, ISL's can conserve the scarce spectrum allocated for fixed satellite services (FSS) by avoiding multiple hopping of the relay stations. ISL's can also conserve prime orbit slot by effectively expanding the geostationary arc. As a result of the coverage extension by using ISL's more users will have direct access to the satellite network, thus providing reduced signal propagation delay and improved signal quality. Given the potential benefits of ISL's system, it is of interest to determine the appropriate implementations for some potential ISL architectures. Summary of the selected ISL network architecture as supplied by NASA are listed. The projected high data rate requirements (greater than 400 Mbps) suggest that high frequency RF or optical implementations are natural approaches. Both RF and optical systems have their own merits and weaknesses which make the choice between them dependent on the specific application. Due to its relatively mature technology base, the implementation risk associated with RF (at least 32 GHz) is lower than that of the optical ISL's. However, the relatively large antenna size required by RF ISL's payload may cause real-estate problems on the host spacecraft. In addition, because of the frequency sharing (for duplex multiple channels communications) within the limited bandwidth allocated, RF ISL's are more susceptible to inter-system and inter-channel interferences. On the other hand, optical ISL's can offer interference-free transmission and compact sized payload. However, the extremely narrow beam widths (on the order of 10 micro-rad) associated with optical ISL's impose very stringent pointing, acquisition, and tracking requirements on the system. Even if the RF and optical systems are considered separately, questions still remain as to selection of RF frequency, direct versus coherent optical detection, etc. in implementing an ISL for a particular network architecture. These and other issues are studied

Distributed Self-Concatenated Coding for Cooperative Communication

In this paper, we propose a power-efficient distributed binary self-concatenated coding scheme using iterative decoding (DSECCC-ID) for cooperative communications. The DSECCC-ID scheme is designed with the aid of binary extrinsic information transfer (EXIT) charts. The source node transmits self-concatenated convolutional coded (SECCC) symbols to both the relay and destination nodes during the first transmission period. The relay performs SECCC-ID decoding, where it mayor may not encounter decoding errors. It then reencodes the information bits using a recursive systematic convolutional (RSC) code during the second transmission period. The resultant symbols transmitted from the source and relay nodes can be viewed as the coded symbols of a three-component parallel concatenated encoder. At the destination node, three-component DSECCC-ID decoding is performed. The EXIT chart gives us an insight into operation of the distributed coding scheme, which enables us to significantly reduce the transmit power by about 3.3 dB in signal-to-noise ratio (SNR) terms, as compared with a noncooperative SECCC-ID scheme at a bit error rate (BER) of 10-5. Finally, the proposed system is capable of performing within about 1.5 dB from the two-hop relay-aided network’s capacity at a BER of 10-5 , even if there may be decoding errors at the relay

Comparison of direct and heterodyne detection optical intersatellite communication links

The performance of direct and heterodyne detection optical intersatellite communication links are evaluated and compared. It is shown that the performance of optical links is very sensitive to the pointing and tracking errors at the transmitter and receiver. In the presence of random pointing and tracking errors, optimal antenna gains exist that will minimize the required transmitter power. In addition to limiting the antenna gains, random pointing and tracking errors also impose a power penalty in the link budget. This power penalty is between 1.6 to 3 dB for a direct detection QPPM link, and 3 to 5 dB for a heterodyne QFSK system. For the heterodyne systems, the carrier phase noise presents another major factor of performance degradation that must be considered. In contrast, the loss due to synchronization error is small. The link budgets for direct and heterodyne detection systems are evaluated. It is shown that, for systems with large pointing and tracking errors, the link budget is dominated by the spatial tracking error, and the direct detection system shows a superior performance because it is less sensitive to the spatial tracking error. On the other hand, for systems with small pointing and tracking jitters, the antenna gains are in general limited by the launch cost, and suboptimal antenna gains are often used in practice. In which case, the heterodyne system has a slightly higher power margin because of higher receiver sensitivity