Binary Switching Algorithm Research Articles

Adaptive hierarchical coding and modulation scheme over satellite channels

In this study, a new scheme called adaptive hierarchical coding and modulation has been proposed, based on Adaptive Coding and Modulation (ACM) and hierarchical modulation (HM). The primary contribution of this study is summarised as the following aspects. Firstly, 16- to 64-APSK constellations with size and labelling optimisation method are proposed for HM, which can be adapted to transmitting multiple hierarchies with different QoS streams and to the non-linear satellite channels due to a lower peak-to-average power ratio compared to traditional hierarchical QAM modulation. Bit channel capacity and Chernoff error bound are introduced to optimise size and labelling of the constellation with interior-point algorithm and modified binary switch algorithm for a specific channel model to get a better performance. Secondly, combining with optimised constellations, coding and modulation modes set is obtained from using constellation design and optimisation method, with different modulation orders and code rates. And over satellite channels with rain and location attenuation, the proposed scheme is able to adapt itself to a changing channel condition and increase the transmission rate compared with ACM schemes of DVB-S2 and DVB-S2X standard.

Link-Adaptive Mapper Designs for Space-Shift-Keying-Modulated MIMO Systems

This work focuses on the design and analysis of link-adaptive bits-to-antenna-indexes mapping for closed-loop space-shift keying (SSK)-modulated multiple-input multiple-output (MIMO) systems. With the aim of achieving a lower bit error rate (BER), optimal mappers are designed under different transmission conditions. Assuming that perfect channel state information (CSI) is available at the transceivers, an original binary switch algorithm (OBSA) is proposed. For the case in which there is no CSI at the transmitter and the feedback channel is bandwidth limited, a restricted binary switch algorithm (RBSA)-based mapping design is proposed. Both of the proposed algorithms can bring considerable performance gains but are of high computational complexity if there are a large number of transmit antennas. To overcome this, algorithms with reduced computational complexity are proposed and investigated, which are named partial OBSA and partial RBSA. The performance improvement brought by all of the proposed mapping schemes in terms of BER performance enhancement and signal-to-noise ratio (SNR) gain in a high-SNR regime is theoretically given. Simulations are done to validate the theoretical analysis, and results show that the proposed schemes can improve BER performance considerably in a wide range of SNR regimes. In addition, all of the proposed mapping schemes can cowork with those existing transmit processing techniques and bring additional performance gain without incurring any extra cost on physical components (e.g., additional phase shifters or power amplifiers). All these make the proposed mapping schemes promising choices for the link-adaptive design of closed-loop SSK MIMO systems.

Mapping Optimization for a MAP Turbo Detector Over a Frequency-Selective Channel

In this paper, we consider a bit interleaved coded modulation (BICM) scheme over a frequency-selective channel. At the receiver, a turbo detector composed of a maximum a posteriori (MAP) detector and a MAP decoder is used. We propose to optimize the mapping choice in this context since it is well known that it has a significant impact on the performance of iterative receivers. We consider fixed and Rayleigh fading channels. Based on the Gaussian approximation, we give an analytical upper bound of the bit error probability (BEP) at the output of the detector for fixed channels. Then, we derive an approximate analytical expression of the BEP for both fixed and Rayleigh fading channels when the a priori information provided by the decoder is reliable, and then, most errors at the output of the detector are isolated. We find that the mapping minimizing this expression corresponds to a move away from the symbols differing by only one bit, unlike the Gray mapping. Since an exhaustive search to find this mapping is complicated for high-order modulations, we propose to use the binary switching algorithm (BSA) to approach the solution. Then, based on these results, we propose to adapt the mapping according to the signal-to-noise ratio (SNR) of the transmission.

Constellation Design for a Multicarrier Optical Wireless Communication Channel

A block-wise constellation design is presented for optical communication systems with multi-subcarrier modulation (MSM), intensity modulation (IM) and direct detection (DD). The DC-bias traditionally used only for compensating the negative peaks of the transmitter-side signals is treated as an information-carrying basis in our proposed scheme called MSM-JDCM. Designs are done for both flat-fading and frequency selective-fading scenarios, and following a principle of high dimensional sphere packing. To simplify the problem, we apply the following methods. First, we use bounds on the waveform's maximum and minimum. Second, we use the maximum and minimum constraints on a set of sufficient samples of waveforms. Third, we relax non-convex distance constraints into convex ones by iterative linearizations. With the MSM-JDCM, we minimize electrical power, optical power, and peak power with a common target bit error rate (BER). Analysis shows that the MSM-JDCM offers significant power gains over MSM-Normal and MSM-SPSS. The short-term peak to average power ratio (PAPR) and long-term PAPR constraints are combined with the MSM-JDCM to mitigate the nonlinear distortion caused by high power amplifier and laser diode, which is another novelty of our scheme. To attain lower BER, a binary switching algorithm (BSA) is applied to find the improved constellation labeling.

BICM-ID-Based IDMA: Convergence and Rate Region Analyses

This paper considers uplink interleave division multiple access (IDMA), of which crucial requirement is the proper operability at a very low signal-to-interference-plus-noise power ratio (SINR) range. The primary objectives of this paper are threefold: (1) to demonstrate the achievability of near-capacity performance of bit interleaved coded modulation with iterative detection (BICM-ID) using very low rate single parity check and irregular repetition (SPC-IrR) codes at a very low SINR range, and hence the technique is effective in achieving excellent performance when it is applied for IDMA, (2) to propose a very simple multiuser detection (MUD) technique for the SPC-IrR BICM-ID IDMA which does not incur heavy per-iteration computational burden, and (3) to analyze the impacts of power allocation on the convergence property of MUD as well as on the rate region, by using the extrinsic information transfer (EXIT) chart. The SPC-IrR code parameters are optimized by using the EXIT-constrained binary switching algorithm (EBSA) at a very low SINR range. Simulation results show that the proposed technique can achieve excellent near-capacity performance with the bit error rate (BER) curves exhibiting very sharp threshold, which significantly influences the convergence property of MUD. Furthermore, this paper presents results of the rate region analysis of multiple access channel (MAC) in the cases of equal and unequal power allocation, as well as of a counterpart technique. The results of the MAC rate region analysis show that our proposed technique outperforms the counterpart technique.

Partially Coherent Constellation Design and Bit-Mapping with Coding for Correlated Fading Channels

The space-time (ST) constellation design problem and the related bit mapping schemes for multiple-input multipleoutput (MIMO) systems in spatially correlated Rayleigh fading channels with imperfect channel estimation at the receiver are considered. We assume that the channel estimation error covariance matrix, as well as transmit and receive correlation matrices are perfectly known both at the transmitter and at the receiver. We derive the cutoff rate (CR) and an upper bound (UB) on the average bit error probability (ABEP) expression for spatially correlated channels and propose them as the constellation design criteria subject to a given average transmit power constraint. Additionally, to use the resulting constellations together with forward error correction (FEC) codes requires efficient bit mapping schemes. Because these constellations lack geometrical symmetry in general, the Gray mapping is not always possible in the majority of the constellations obtained. Moreover, different mapping schemes may lead to highly different bit error rate (BER) performances. Thus, an efficient bit mapping scheme called the modified binary switching algorithm (MBSA) is proposed. It minimizes an upper bound on the ABEP (UB-ABEP) and is used to find the bit mapping schemes. Numerical examples show that the designed constellation and its optimized bit mapping together with turbo codes outperform the conventional constellations with respect to the frame error rate (FER).

EXIT-constrained BICM-ID design using extended mapping

This article proposes a novel design framework, EXIT-constrained binary switching algorithm (EBSA), for achieving near Shannon limit performance with single parity check and irregular repetition coded bit interleaved coded modulation and iterative detection with extended mapping (SI-BICM-ID-EM). EBSA is composed of node degree allocation optimization using linear programming (LP) and labeling optimization based on adaptive binary switching algorithm jointly. This technique achieves exact matching between the Demapper (Dem) and decoder's extrinsic information transfer (EXIT) curves while the convergence tunnel opens until the desired mutual information (MI) point. Moreover, this article proposes a combined use of SI-BICM-ID-EM with Doped-ACCumulator (D-ACC) and modulation doping (MD) to further improve the performance. In fact, the use of D-ACC and SI-BICM-ID (noted as DSI-BICM-ID-EM) enables the right-most point of the EXIT curve of the combined demapper and D-ACC decoder (Ddacc), denoted as DemDdacc, to reach a point very close to the (1.0, 1.0) MI point. Furthermore, MD provides us with additional degree-of-freedom in "bending" the shape of the demapper EXIT curve by choosing the mixing ratio of modulation formats, and hence the left most point of the demapper EXIT curve can flexibly be lifted up/pushed down with MD aided DSI-BICM-ID-EM (referred to as MDSI-BICM-ID-EM). Results of the simulations show that near-Shannon limit performance can be achieved with the proposed technique; with a parameter set obtained by EBSA for MDSI-BICM-ID-EM, the threshold signal-to-noise power ratio (SNR) is only roughly 0.5 dB away from the Shannon limit, for which the required computational complexity per iteration is at the same order as a Turbo code with only memory-2 convolutional constituent codes.

Irregular Mapping and its Application in Bit-Interleaved LDPC Coded Modulation With Iterative Demapping and Decoding

This paper proposes an irregular mapping technique, where a new labeling searched via modified adaptive binary switch algorithm (ABSA), mixed with a pre-fixed labeling, can provide near-optimal match to a given outer channel code. By using the proposed technique, the bit-interleaved low-density parity-check (LDPC) coded modulation systems with iterative demapping/decoding (BILCM-ID) could achieve near-capacity performance. With a slight modification on the LDPC coded modulation scheme of DVB-T2 standard, the proposed technique can improve the iterative demapping system by exploiting significant iterative gain. The superior performance is verified via extrinsic information transfer (EXIT) chart analysis and bit error rate (BER) simulation.

Labeling Optimization for BICM-ID Systems

Labeling is crucial for bit-interleaved coded modulation with iterative demapping and decoding (BICM-ID) systems. Based on extrinsic information transfer (EXIT) charts, a novel adaptive binary switch algorithm (ABSA) in searching for labeling to well match the outer channel code is proposed. ABSA can be applied to arbitrary constellations, meanwhile it makes the proposed BICM-ID systems hold a near-capacity performance.

Sample-Adaptive Product Quantizers with Affine Index Assignments for Noisy Channels

When we design a robust vector quantizer (VQ) for noisy channels, an appropriate index assignment function should be contrived to minimize the channel-error effect. For relatively high rates, the complexity for finding an optimal index assignment function is too high to be implemented. To overcome such a problem, we use a structurally constrained VQ, which is called the sample-adaptive product quantizer (SAPQ) [12], for low complexities of quantization and index assignment. The product quantizer (PQ) and its variation SAPQ [13], which are based on the scalar quantizer (SQ) and thus belong to a class of the binary lattice VQ [16], have inherent error resilience even though the conventional affine index assignment functions, such as the natural binary code, are employed. The error resilience of SAPQ is observed in a weak sense through worst-case bounds. Using SAPQ for noisy channels is useful especially for high rates, e.g., > 1 bit/sample, and it is numerically shown that the channel-limit performance of SAPQ is comparable to that of the best codebook permutation of binary switching algorithm (BSA) [23]. Further, the PQ or SAPQ codebook with an affine index assignment function is used for the initial guess of the conventional clustering algorithm, and it is shown that the performance of the best BSA can be easily achieved.

Bit-Interleaved Sphere-Packing-Aided Iteratively Detected Space-Time Coded Modulation

We design a bit-interleaved space-time coded modulation scheme using iterative decoding (BI-STCM-ID) combined with a new multidimensional mapping scheme invoking sphere-packing (SP) modulation, which we refer to as the space-time block-coded sphere-packed bit-interleaved coded modulation (STBC-SP-BICM) arrangement. The binary switching algorithm (BSA) is used to optimize the cost function employed for deriving different mapping strategies, which are designed with the aid of EXtrinsic Information Transfer (EXIT) charts for the sake of improving the convergence behavior of the system. The resultant system is amalgamated with a unity-rate code (URC) as a precoder to enhance the attainable iterative detection performance. An irregular URC (IrURC) is invoked to create an open EXIT tunnel at low signal-to-noise ratios (SNRs). The complexity of employing the multidimensional SP scheme is also addressed.

Equivalent Capacity-Based Joint Multilevel Coding and Space–Time Transmit Diversity Design

A novel space-time block-coding-assisted and sphere-packed multilevel-coded (STBC-SP-MLC) modulation arrangement is proposed, which combines an MLC-based scheme with a twin-antenna-aided STBC for the sake of providing a transmit diversity gain. The SP modulation invokes a 4D D 4 constellation space. A new bit-to-SP symbol mapper is designed for the sake of improving the system's performance. This involves mapping the MLC bits to the SP symbols of Layer-1 and Layer-2 in D 4 space. The binary switching algorithm is used to determine the optimum cost function used for designing different mapping strategies. The so-called equivalent capacity-based design invoking the 4-D signal space is used to determine the optimum coding rate of the STBC-SP-MLC scheme's component codes. Finally, we investigate a hybrid bit-to-SP symbol-mapping strategy for the STBC-SP-MLC scheme, which is capable of providing unequal error protection.

Multi-Dimensional Mappings of M-ary Constellations for BICM-ID Systems

This paper studies bit-interleaved coded modulation with iterative decoding (BICM-ID) systems that employ multi-dimensional mappings of M-ary constellations to improve the error performance over Rayleigh fading channels. Based on the analytical evaluations of the asymptotic bit error probability (BEP), the distance criteria for the mapping designs can be obtained. A binary switching algorithm (BSA) is then applied to find the optimal mappings with respect to the asymptotic performance. Simulation and analytical results show that the use of multi-dimensional mappings of M-ary constellations can significantly improve the error performance.

Constellation mapping for space-time matrix modulation with iterative demodulation/decoding

The mapping from binary sequences to space-time matrices is an important issue in designing space-time coded multiple-antenna systems where different mapping schemes may lead to different bit-error-rate (BER) performance. In this letter, we use a binary switching algorithm to investigate the mappings of bit-interleaved coded modulation with iterative demodulation/decoding (BICM-ID) for space-time modulation. Both coherent and noncoherent space-time modulation in the cases of no a priori information and perfect a priori information of the coded bits for the demodulator are considered.

Design of constellation labelling maps for iteratively demapped modulation schemes based on the assumption of hard-decision virtual channels

A bit-interleaved coded modulation system can be regarded as a serially concatenated (SC) system with a modulation scheme as a full rate inner code. The labelling map of the modulation scheme is very important for the performance of iterative demapping and decoding, which is usually designed with the help of the extrinsic information transfer (EXIT) chart. In the paper an analytical approximate expression for the EXIT function (EF) of a maximum a posterior probability demapper over memoryless channels is derived, where the real channel is replaced with a hard-decision virtual channel to make the EF easy to be calculated. The hard-decision virtual channel is selected to have the same capacity as the real channel. Then a closed-form EXIT function is defined for each signal point, i.e. the single signal EXIT function (SSEF). A useful property is proved that the area under the SSEF for each signal is determined by the constellation itself and has nothing to do with the labelling map. Based on the property and the binary switch algorithm, a general method is proposed to design the labelling maps of modulation schemes with desirable EFs matching channel codes. SC systems can then be built with the desired convergence and asymptotic behaviour.

Optimization of symbol mappings for bit-interleaved coded Modulation with iterative decoding

We investigate bit-interleaved coded modulation with iterative decoding (BICM-ID) for bandwidth efficient transmission, where the bit error rate is reduced through iterations between a multilevel demapper and a simple channel decoder. In order to achieve a significant turbo-gain, the assignment strategy of the binary indices to signal points is crucial. We address the problem of finding the most suitable index assignments to arbitrary, high order signal constellations. A new method based on the binary switching algorithm is proposed that finds optimized mappings outperforming previously known ones.

Non-redundant VQ channel coding using tabu searchstrategy

The tabu search approach is applied to codevector index assignment for noisy channels for the purpose of minimising the distortion due to bit errors without introducing any redundancy. Experimental results demonstrate the robustness of this approach compared with the standard parallel genetic algorithm and the binary switching algorithm.

Pseudo-Gray coding

A pseudo-Gray code is an assignment of n-bit binary indexes to 2" points in a Euclidean space so that the Hamming distance between two points corresponds closely to the Euclidean distance. Pseudo-Gray coding provides a redundancy-free error protection scheme for vector quantization (VQ) of analog signals when the binary indexes are used as channel symbols on a discrete memoryless channel and the points are signal codevectors. Binary indexes are assigned to codevectors in a way that reduces the average quantization distortion introduced in the reproduced source vectors when a transmitted index is corrupted by channel noise. A globally optimal solution to this problem is generally intractable due to an inherently large computational complexity. A locally optimal solution, the binary switching algorithm, is introduced, based on the objective of minimizing a useful upper bound on the average system distortion. The algorithm yields a significant reduction in average distortion, and converges in reasonable running times. The sue of pseudo-Gray coding is motivated by the increasing need for low-bit-rate VQ-based encoding systems that operate on noisy channels, such as in mobile radio speech communications.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>