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In this paper, we investigate the freshness of the vehicular status updates in space-air-ground integrated networks (SAGIN), where the status updates are generated by sampling a fixed-rate dynamic Markov process and delivered to the monitor over an unreliable channel instantaneously. The age of information (AoI) is adopted to capture the timeliness of the status updates. Two Hybrid Automatic Repeat Request (HARQ) schemes, namely, classical HARQ scheme and incremental redundancy HARQ (IR-HARQ) scheme, are taken into consideration to combat the errors occurred in the transmission. In this setting, once an update is not decoded successfully, one should carefully decide how to schedule the updates for optimizing the AoI. Especially, differential encoding scheme is introduced in the considered system to exploit the temporal correlations of the source. By differential encoding, each update can be actual or differential, based on the differential encoding level. To minimize the long-term average age, we formulate a Markov Decision Process (MDP), and prove that the optimal transmission policies for classical HARQ scheme and IR-HARQ scheme behave differently in threshold structures. Further, we jointly optimize the codeword length, differential encoding level and retransmission times to minimize the AoI. The performance comparison shows the advantages of IR-HARQ scheme over classical HARQ scheme from the age perspective.

In this paper, a novel differential space-time block coded spatial modulation (differential STBC-SM) is proposed for uplink multi-user massive multiple-input multiple-output (MIMO) communications, which combines the concept of differential coding and STBC-SM to enhance the diversity benefits in the absence of the channel state information (CSI). The transmission structure of the proposed system is on a block basis, where each block contains two sub-blocks. More specifically, the first sub-block only conveys amplitude and phase modulation (APM) symbol bits, since its transmit antennas (TAs) obey a pre-designed activation pattern, which do not carry any information bit. For the second sub-block, the input bits are modulated to STBC-SM matrices, which are then differentially coded between two adjacent sub-blocks. Moreover, a novel block-by-block based non-coherent detector is presented. Finally, we derive an upper bound on the average bit error probability (ABEP) by using the moment generating function (MGF). Our simulation results show that the proposed differential STBC-SM transmission structure is able to acquire considerable bit error rate (BER) performance improvements compared to both the conventional differential spatial modulation (DSM) and differential Alamouti schemes.

This article proposes a model-free lossless data compression method for time series in smart grids (SGs), namely, Lossless Coding considering Precision (LCP) method. The LCP method encodes the current datapoint only using the immediate previous datapoint by differential coding, XOR coding, and variable length coding and transmits the encoded data once generated. It does not use the dynamics (e.g., many previous datapoints) or prior knowledge (e.g., mathematical models) of the time series. It considers the patterns, potential applications, and associated precision to preprocess the time series and especially suits high-resolution time series with long steady periods. The LCP method features low-latency and generalizability which enables real-time data communication for different time-critical tasks. Sub-metered load profiles in REDD dataset, high-resolution LIFTED dataset, AMPds dataset and PMU dataset are used to evaluate the performance of the LCP method. The results show that the LCP method demonstrates high compression ratio, low latency, and low complexity compared to state-of-the-art Resumable Data Compression (RDC) method, DEFLATE based on LZ77 & Huffman coding, and Lempel-Ziv-Markov Chain Algorithm (LZMA).

Timely reception of information is of utmost importance in many cyber-physical systems. We study timely status update schemes for a single source. We consider a scheme which exploits the temporal correlation in source messages to send differential information to the receiver, over an unreliable channel. In this scheme, the source sends the true state information, interleaved with differential messages. We observe that the differential encoding improves the timeliness performance even in the absence of feedback, if the codeword lengths for both differential and true messages are chosen judiciously.

Rapid increase of data-center traffic due to the growing use of cloud services and mobile broadband services requires a higher capacity Ethernet link based on an economical approach and high-performance short-reach optical transmission techniques based on intensity-modulation and direct-detection have been attracting huge interest. In the next-generation Ethernet such as 800GbE or 1.6TbE, a higher-baudrate signal will be necessary and the transmission performance will be limited by the transceiver bandwidth. In this article, we show a spectral-shaping technique for PAM signals based on a nonlinear differential coding which realizes the narrower signal spectrum and enhances the tolerance to bandwidth limitation. We theoretically investigate the characteristics of the proposed scheme and demonstrate 186-Gb/s 10-km transmission by means of an O-band experiment with a 3-dB bandwidth of 14 GHz in which the proposed technique is applied to a 93-Gbaud PAM4 signal. Furthermore, we propose a combination of nonlinear differential coding and LLR-based decoding and show that the combined scheme realizes 4-dB improvement in the required optical power. We also investigate the performance dependency on the parameters such as the number of taps in the equalizers utilized in the decoder.

Differential spatial modulation (DSM) is able to transmit additional data bits without increasing the number of radio-frequency chains and power consumption and also avoids pilot overhead. In this paper, we propose two new schemes of DSM to improve the original DSM. One is an increased-rate scheme that transmits one additional data bit per two blocks. The bit mapping and maximum-likelihood detection is particularly designed. The goal of the second scheme is to increase the diversity of DSM. By properly designing block coded modulation and complex antenna-index matrices, the proposed scheme can achieve the desired diversity order. Compared with the existing schemes with the same constellation of the transmitted signals, the proposed scheme achieves higher transmission rates.

In this paper, we propose a differential multiple-input multiple-output (MIMO) scheme based on the novel concept of chaos-based time-varying unitary matrices to demonstrate—for the first time in the literature—the ability of differential encoding in achieving practical physical layer security even without the need for using channel estimation. In the proposed scheme, an erroneous secret key, which is extracted from the wireless nature, is used to initialize a chaos sequence that is responsible for generating artificially time-varying unitary matrices capable of obfuscating the transmitted data symbols from illegitimate eavesdroppers. Contrary to conventional studies, the key agreement ratio in this study is assumed to be imperfect, which is often true and very realistic in high-mobility scenarios. Following this, we conceive a new calibration algorithm for reconciling the chaotic sequence generated at the legitimate parties, thus making this calibration algorithm a unique, novel solution to the key sharing problem of conventional chaos-based communication techniques, which has been overlooked over the past few decades. It is found out that differential encoding obviates additional complexity and insecurity in dealing with channel estimation, whereas an eavesdropper must tackle the complicated differentially encoded patterns, which have an exponentially increasing complexity order. In addition, the obtained simulation results demonstrate that the proposed scheme can outperform conventional chaos-based MIMO schemes that assume perfect channel knowledge.

In this correspondence paper, an adaptive turbo equalizer for differential OFDM systems in underwater acoustic communications is proposed. This scheme first reconstructs the demodulation symbols using the soft information fed back from the channel decoder, and then eliminates the residual intercarrier interference (ICI) induced by estimated symbols using an adaptive turbo equalizer. Moreover, a pilot-based differential encoding method is presented to mitigate the impact of the feedback error, thereby improving the convergence of turbo equalization. Theoretical analysis and simulation results demonstrate that, the proposed equalizer outperforms the linear minimum mean-squared error (MMSE) estimation-based turbo equalizer for coherent systems in medium-to-high signal-to-noise ratio (SNR) region, while enjoys significantly reduced computational complexity, and its performance is more robust against the change of Doppler frequency.

The problem of information transmission through water pipelines is addressed and a class of methods based on differentially encoded orthogonal frequency division multiplexing (OFDM) is proposed. Specifically, two methods are investigated; one based on conventional differential encoding with an estimation of the average time of arrival and another based on double encoding. Results show that the first approach improves performance in the low signal to noise ratio (SNR) region, while the second is better suited at high SNR. Adopting these techniques closes the performance gap between differential OFDM systems and coherent OFDM systems while retaining the benefits of computational simplicity.

Amplitude phase shift keying (APSK) aided differential spatial modulation (APSK-DSM) is a multiple-input-multiple-output wireless transmission technique which not only has the desirable features of differential spatial modulation (DSM) but also has a higher spectrum efficiency than DSM. However, the error propagation problem and the violation of the quasi-static channel assumption in conventional APSK-DSM design will cause significant performance loss, especially in undesirable channel conditions. Besides, the maximum-likelihood detection based on the traditional block-by-block search has a complexity that grows exponentially with the block size, which becomes intractable in systems with large transmit antenna numbers. To overcome those drawbacks, we propose a novel transmission scheme named the absolute amplitude differential phase spatial modulation (AADP-SM) in this paper. AADP-SM is able to alleviate the error propagation problem and achieve a near-coherent performance by invoking multiple previous blocks in the current detection. By taking into account the channel fading rate, AADP-SM is also more robust in fast-fading channels than APSK-DSM. A novel non-coherent detection algorithm is proposed for AADP-SM to reduce the exponential detection complexity to a polynomial order. Finally, we show through simulation that AADP-SM is tolerable to imperfect information about the channel statistics.

The combination of non-orthogonal multiple access (NOMA) and multi-input multi-output (MIMO) approaches has been considered as assuring multiple access for the fifth generation technology. In this study, the performance of a 2 × 2 MIMO–NOMA system with low-density parity check (LDPC) codes is investigated. Redundancy with randomly interleaved differential encoding (R-RIDE) is proposed and applied to LDPC encoded messages by two users. LDPC decoding is done using the sum-product algorithm (SPA), which has two types of decoding methods, hard-decision and soft-decision. For hard-decision, bit-flipping decoder is used and for soft-decision, probability domain, log-domain, and simplified log-domain decoders are used. Bit error rate (BER) versus signal-to-noise ratio (SNR) in (dB) and average mutual information (AMI) in (bps/Hz) versus SNR (dB) are evaluated to compare the performance of the proposed and conventional LDPC schemes in NOMA and MIMO–NOMA systems. Simulation results show that both AMI and BER of the proposed LDPC–R-RIDE in MIMO–NOMA system greatly outperforms conventional LDPC coded schemes in NOMA and MIMO–NOMA systems. Moreover, the proposed R-RIDE-LDPC in MIMO-NOMA system outperforms the proposed scheme in the NOMA system. From the simulation results, LDPC–R-RIDE with simplified log-domain decoder has the best AMI result and BER performance compared with other decoding methods.

Spatial modulation (SM) uses a single antenna for transmission each time to avoid synchronization and interferences among transmitter antennas, and differential SM (DSM) is a kind of SM technique that does not need pilot symbols and channel estimation. The original noncoherent detection for DSM is very complicated, so various low-complexity detectors have been proposed. However, they are still too complicated to be applied to DSM with many transmitter antennas. In this paper, low-complexity DSM schemes for dozens or hundreds of transmitter antennas are designed. Two bit-mapping schemes are proposed: one is group arrangement for maximizing data rates, and the other is full mapping so that DSM can be easily detected at the receiver. A low-complexity detection algorithm that is less complicated than all existing fixed-complexity detectors is proposed as well. In addition, two detection strategies for the proposed bit mapping methods are proposed. Simulation results show that the proposed low-complexity DSM schemes have satisfactory error performance.

We experimentally investigated differential precoding for dual polarization signals with two eigenvalues for a fiber link with Raman amplification, using QPSK and 8-PSK modulation schemes with symbol rates of 1 and 2 GBd. By using differential precoding in nonlinear domain for higher-order modulation schemes, we reduced the phase variance of the eigenvalues’ spectral amplitude by a factor of up to 5.4 and 7.4 for 1 and 2 GBd respectively, while LMMSE equalization provides a significant benefit for lower-order modulation schemes. With differential precoding we achieved bit error rates below SD-FEC limit at 8 Gbps for up to 5030 km link length. For 20 Gbps the range could be doubled to 1609 km. Adding LMMSE equalization to the proposed scheme also offers a tolerance to launch powers below the theoretical optimum for correct detection of the differential phase.

This article addresses the problem of coherent detection of acoustic orthogonal frequency division multiplexing (OFDM) signals using a sparse channel estimation method based on a physical model of multipath propagation. Unlike the conventional sample-spaced and subsample-spaced methods, such as least squares and orthogonal matching pursuit (OMP), which target the taps of an equivalent discrete-delay channel response, the path identification (PI) method targets the physical propagation paths in a continuous-delay domain, and focuses on explicit estimation of delays and complex amplitudes of the channel paths in an iterative fashion. When multiple receive elements are available, two situations are possible: one in which the array elements see uncorrelated channel responses, and another in which the channel responses are correlated. In the first case, channel estimation must be accomplished element-by-element. This is done simply by applying the PI algorithm to each element individually. In the second case, correlation between the elements can be exploited. In doing so, our goal is to reduce the signal processing complexity without compromising the performance. Toward this goal, an adaptive precombining method is proposed. Without requiring any a priori knowledge about the spatial distribution of received signals, the method exploits spatial coherence between receive channels by linearly combining them into fewer output channels so as to reduce the number of subsequent channel estimators. The algorithm learns the spatial coherence pattern recursively over the carriers, thus effectively achieving broadband beamforming. The reduced-complexity precombining method relies on differential encoding that keeps the receiver complexity at a minimum and requires a very low pilot overhead. Using synthetic data as well as 210 experimental signals transmitted over a 3–7-km shallow-water channel in the 10.5–15.5-kHz acoustic band during a 3.5-h experiment, we study the system performance in terms of data detection mean-squared error (MSE), symbol error rate, and bit error rate (BER), and show that the PI algorithm achieves excellent MSE performance while its complexity is considerably lower than that of the OMP algorithm. We also demonstrate that the receiver equipped with the proposed reduced-complexity precombining scheme requires three times fewer channel estimators while achieving the same MSE and BER performance as the full-complexity receiver.

In this chapter, we will discuss DPSK Transceiver hardware design which is based on π/4-DQPSK and 8-DPSK modulation-demodulation techniques, physical layer specifications for it, SIMULINK model for it, effect of using timing and carrier recovery on the transceiver performance, and finally synthesizable HDL model for the Bluetooth DPSK transceiver. The radio part of Bluetooth uses three kinds of digital modulation to transmit data, GFSK, π/4-DQPSK and 8-DPSK. Initially, the Bluetooth standard chose GFSK modulation due to its robustness against signal fading and interference, maintaining a good spectral efficiency, the maximum bit rate that can be obtained using GFSK is limited to 1Mbps. Two new modulation schemes were introduced to increase this. In the other version of Bluetooth a bit rate value of up to 2 Mbps can be achieved for π /4-DQPSK and up to 3 Mbps for 8-DPSK. However, the advantage of constant envelope is now lost and this behavior introduces some non-linear effects during modulation and transmission.

This article has indicated optical coherent differential polarization (DP) 16 quadrature amplitude modulation (QAM) transceiver systems with free-space optical (FSO) channel in the presence of differential coding scheme. The optical coherent DP 16-QAM receiver executes the reverse process conversion of the optical signal into an electrical one that is detected to the users. The proposed optical coherent DP-16 QAM transceiver systems based FSO channel model with differential coding has been presented and compared with the previous model. However, the simulation results have confidence realization about the superiority of the proposed simulation model. Hence the proposed optical coherent DP-16 QAM transceiver systems simulation model with differential coding is verified and validated the enhancement performance based on simulation performance parameters.

With several advantages over conventional RGB cameras, event cameras have provided new opportunities for tackling visual tasks under challenging scenarios with fast motion, high dynamic range, and/or power constraint. Yet unlike image/video compression, the performance of event compression algorithm is far from satisfying and practical. The main challenge for compressing events is the unique event data form, i.e., a stream of asynchronously fired event tuples each encoding the 2D spatial location, timestamp, and polarity (denoting an increase or decrease in brightness). Since events only encode temporal variations, they lack spatial structure which is crucial for compression. To address this problem, we propose a novel event compression algorithm based on a quad tree (QT) segmentation map derived from the adjacent intensity images. The QT informs 2D spatial priority within the 3D space-time volume. In the event encoding step, events are first aggregated over time to form polarity-based event histograms. The histograms are then variably sampled via Poisson Disk Sampling prioritized by the QT based segmentation map. Next, differential encoding and run length encoding are employed for encoding the spatial and polarity information of the sampled events, respectively, followed by Huffman encoding to produce the final encoded events. Our Poisson Disk Sampling based Lossy Event Compression (PDS-LEC) algorithm performs rate-distortion based optimal allocation. On average, our algorithm achieves greater than 6x compression compared to the state of the art., 8 main pages

Minimum shift keying (MSK) shows better bandwidth efficiency than phase-shift keying due to its constant envelope property. The performance of block linear equalization (BLE), commonly used for MSK communication in radio communication systems, is limited in the complex time-varying underwater acoustic (UWA) channel because BLE cannot track channel changes within the data block. A time-domain adaptive decision feedback equalization (TD-ADFE) method based on Laurent’s decomposition is proposed to address issues pertaining to MSK communications over UWA communication. The method can effectively track the time-varying UWA channel through that the output of encoder updates the equalizer coefficient iteratively, which comprises matched filter, equalizer, differential decoding, and differential encoding. According to the numerical simulation results, the TD-ADFE performed better than FD-BLE over time-varying UWA channel by approximately 5.5 dB when the bit error rate (BER) was 10-3. The sea trial results over 28 hours demonstrated that the BER of TD-ADFE was 36.8% lower than FD-BLE.

Targeting both computing and coding efficiencies, we propose in this work a novel hierarchical bit-wise differential coding scheme to compress point cloud attributes. The encoder firstly quantizes and organizes the points into an octree structure and, for each internal node, picks its attribute(s) from a child named source child. Next, the encoder conducts a top-down scanning of the hierarchy. For each node with more than one child, it computes the bit-wise attribute difference between the current node and each non-source child by exclusive-OR and encodes the difference with an arithmetic coder. Further, a table look-up approach is proposed to accelerate the online source child identification. The proposed scheme produces superior computing and coding efficiencies for lossless point cloud attribute compression, outperforming the MPEG benchmark coders by large margins in our experiments.

In this paper, we investigate the feasibility of a Wavelength-Division Multiplexing Radio over Fiber system, using Differential Phase Shift Keying modulation with an Optical Double Side-Band Suppressed Carrier for long distance networks. The proposed system was implemented in Optisystem and evaluated based on the analysis of the Q-factor and the Bit Error Rate (BER). 60 GHz is chosen because it represents the future band of the 5G and its applications. The simulation results obtained indicate that the laser's power of 5 dBm allows the propagation over a distance of 2520 Km when the differential coding is used, and over distance of 1620 Km when it's not used.

This paper gives an overview of differential place marking phenomena and formulates a number of universals that seem to be well supported. Differential place marking is a situation in which the coding of locative, allative or ablative roles depends on subclasses of nouns, in particular place names (toponyms), inanimate common nouns and human nouns. When languages show asymmetric coding differences depending on such subclasses, they show shorter (and often zero) coding of place roles with toponyms, and longer (often adpositional rather than affixal) coding of place roles with human nouns. Like differential object marking, differential place marking can be explained by frequency asymmetries, expectations derived from frequencies, and the general preference for efficient coding. I also argue that differential place marking patterns provide an argument against the need to appeal to ambiguity avoidance to explain differential object marking.

We consider the status updates of a physical process over an unreliable channel. In this setting, one may not be able to reliably transmit the current state at all times. Instead, one is interested in the timeliness of the accurately received information. This is a setting for several cyber-physical system applications that require real-time monitoring and control. In this paper, we study periodic data transmission schemes at a single source which exploit the temporal correlation in the source messages. When the source has no feedback, it can periodically send the actual information, interspersed with differential messages. On the availability of receiver's feedback at the source, it can decide to send either the differential or the actual information at each transmission opportunity. For a fixed length coding, we show that the differential encoding improves the timeliness performance only if the receiver's feedback is available.

The matrix-based differential encoding invoked by Differential Space-Time Modulation (DSTM) typically results in an infinite-cardinality of arbitrary signals, despite the fact that the Transmit Antennas (TAs) can only radiate a limited number of patterns. As a remedy, the recently developed Differential Spatial Modulation (DSM) is capable of avoiding this problem by conceiving a beneficial sparse signal matrix design, which also facilitates low-complexity single-RF signal transmission. Inspired by this development, the Differential Space-Time Block Code using Index Shift Keying (DSTBC-ISK) further introduces a beneficial diverstiy gain without compromising the DSM's appealingly low transceiver complexity. However, the DSTBC-ISK's performance advantage tends to diminish as the throughput increases, especially when an increased number of Receive Antennas (RAs) is used. By contrast, the classic Differential Group Code (DGC) that actively maximizes its diversity gain for different Multiple-Input Multiple-Output (MIMO) system setups is capable of achieving a superior performance, but its detection complexity grows exponentially with the throughtput. Against this background, we propose the Differential Space-Time Shift Keying using Diagonal Algebraic Space-Time (DSTSK-DAST) scheme, which is the first DSTM that is capable of achieving the DGC's superior diversity gain at high throughputs without compromising the DSM's low transceiver complexity. As a further advance, we also conceive a new Differential Space-Time Shift Keying using Threaded Algebraic Space-Time (DSTSK-TAST) arrangement, which is capable of achieving an even further improved diversity gain at a substantially reduced signal detection complexity compared to the best DGCs. Furthermore, in order to strike a practical tradeoff, we develop a generic multi-element and multi-level-ring Amplitude Phase Shift Keying (APSK) design, and we also arrange for multiple reduced-size DSTM sub-blocks to be transmitted in a permuted manner, which exhibits an improved diversity-throughput tradeoff.

In this paper a novel photonic digitization scheme with differential encoding based on orthogonal vector superposition (OVS) is proposed and demonstrated. A phase modulator (PM) and two delay-line interferometers (DLIs) with π/2 difference in bias phase are employed to generate two orthogonal modulated signals. By adjusting and combining the intensity of two orthogonal signals with an OVS module, the desired phase shifts among different transfer functions can be obtained. The proposed scheme can differentially encode the input signal with enhanced bit resolution. Compared with the existing photonic digitization schemes based on modulators, this scheme features its simple configuration, because only a single PM, two DLIs and an OVS module are required; moreover, since the desired phase shifts of transfer functions are realized by attenuating the signal intensities, the proposed scheme can effectively alleviate the problem of phase bias drift induced by modulators. Proof-of-concept experiments of 3- and 4-bit photonic digitization systems based on OVS are successfully carried out, which demonstrate the feasibility of the approach.

In this paper different channel coding and interleaving schemes in DS/CDMA system over multipath fading channel were used. Two types of serially concatenated coding were presented. The first one composed of Reed-Solomon as outer code, convolutional code as inner code and the interleaver between the outer and inner codes and the second consist of convolutional code as outer code, interleaved in the middle and differential code as an inner code. Bit error rate performance of different schemes in multipath fading channel was analyzed and compared. Rack receiver was used in DS/CDMA receiver to combine multipath components in order to enhance the signal to noise ratio at the receiver.

In order to increase the efficiency of dedicated frequency channels, i.e. to increase the specific data transfer rate, multipositional quadrature phase shift keying (QPSK, aka 4-PSK) should be used. The problems with QPSK signal demodulation is a rotation of the signal constellation plane by an angle multiple of 90° and a slow response of the carrier oscillation recovery scheme. The study considers the existing methods for eliminating the phase ambiguity of the recovered carrier frequency in typical QPSK modems, and identifies the shortcoming of a low-speed response oscillation recovery circuit. The authors propose a QPSK demodulator circuit with a fast adjustment of the reference oscillator, which is due to the fact that no loop filter is used in the feedback and that a digital calculator of the required phase shift is used. An algorithm for the frame synchronization restoration with the simultaneous elimination of the phase ambiguity multiple of 90° was also developed using synthesized binary sequences with an ideal non-periodic autocorrelation function (NACF) at even shifts that do not have the rotary symmetry property. The phase ambiguity elimination algorithm proposed in the article can be used as an alternative to standard modems with differential coding.

As the need for the deployment of Deep Learning applications on edge-based devices becomes ever increasingly prominent, power consumption starts to become a limiting factor on the performance that can be achieved by the computational platforms. A significant source of power consumption for these edge-based machine learning accelerators is off-chip memory transactions. In the case of Convolutional Neural Network (CNN) workloads, a predominant workload in deep learning applications, those memory transactions are typically attributed to the store and recall of feature-maps. There is therefore a need to explicitly reduce the power dissipation of these transactions whilst minimising any overheads needed to do so. In this work, a Differential Encoding of Feature-maps (DEF) scheme is proposed, which aims at minimising activity on the memory data bus, specifically for CNN workloads. The coding scheme uses domain-specific knowledge, exploiting statistics of feature-maps alongside knowledge of the data types commonly used in machine learning accelerators as a means of reducing power consumption. DEF is able to out-perform recent state-of-the-art coding schemes, with significantly less overhead, achieving up to 50% reduction of activity across a number of modern CNNs.

Common currency theories in neuroeconomics hold that neurons in specific brain regions specifically encode subjective values of offers and not stimulus-specific information. The rationale behind these theories is that abstract value encoding lets the decision maker compare qualitatively different options. Alternatively, expectancy-based theories hold that the brain preferentially tracks the relationship between options and their outcomes, and thus does not abstract away details of offers. To adjudicate between these theories, we examined responses of neurons in six reward regions to risky and safe offers while macaques performed a gambling task. In all regions, responses to safe options are unrelated to responses evoked by equally preferred risky options. Nor does any region appear to contain a specialized subset of value-selective neurons. Finally, in all regions, responses to risky and safe options occupy distinct response subspaces, indicating that the organizational framework for encoding risky and safe offers is different. Together, these results argue against the idea that putative reward regions carry abstract value signals, and instead support the idea that these regions carry information that links specific options to their outcomes in support of a broader cognitive map.

With wide application of RFID, backscatter communication has become a focus in academy and industry. Specially, ambient backscatter communication has attracted much attention due to its low energy consumption and low cost. In this paper, we study the signal detection of the ambient backscatter communication system and focus on the differential energy detection method. Specifically, we use the off-the-shelf differential encoding model to eliminate the necessity of channel state information (CSI). Differential energy detection method and ML detector are applied as well to make the detecting results more precise and to obtain better performance. Based on them, we improve the approximate threshold and propose optimal thresholds decision algorithm of signal detection, which is proved feasible and efficient. Corresponding BER expressions are derived to estimate the performance of the algorithm. Simulation results are then provided to corroborate the theoretical studies. It can be shown from the results that using two optimal thresholds will improve the performance of the system to some extent, it will also be more tolerant to longer transmitting distance, especially when the channel status are not good.