Search

This letter proposes a novel transport-layer encapsulation scheme, which integrates the permutation-based transmission and the packet grouping to improve spectral efficiency. For a group of packets, each data unit (DU) is divided into three portions: permutation-conveyed DU (PCDU), grouping-conveyed DU (GCDU), and conventionally conveyed DU (CCDU). The PCDU is conveyed through the selection among various lengths for GCDU plus CCDU. The GCDU is used for forming sub-groups so that, in each sub-group, the GCDU is encapsulated into the first packet only while removed from the other packets. Unlike CCDUs, the delivery of PCDUs and removed GCDUs does not consume any communication resource. To promote the improvement of spectral efficiency, an algorithm based on the binary search tree is proposed for the GCDU design in each sub-group, and a lower bound on the number of bits in the removed GCDUs is achieved in closed-form. Illustrative numerical results substantiate the spectral efficiency gain obtained by our permutation-based scheme in comparison with the conventional transport-layer encapsulation. [ABSTRACT FROM AUTHOR]

In this paper, a multi-vehicle multi-task non-orthogonal multiple access (NOMA) assisted mobile edge computing (MEC) system with passive eavesdropping vehicles is investigated. To heighten the performances of edge vehicles, we propose a vehicle grouping pairing method, which utilizes vehicles near the MEC to assist edge vehicles as full-duplex relays. For promoting transmission security, we employ artificial noise to interrupt eavesdropping vehicles. Furthermore, we derive the approximate expression of the secrecy outage probability of the system. The combined optimization of vehicle task division, power allocation, and transmit beamforming is formulated to minimize the total delay of task completion for edge vehicles. Then, we design a power allocation and task scheduling algorithm based on the genetic algorithm to solve the mixed-integer non-linear programming problem. Numerical results demonstrate the superiority of our proposed scheme in terms of system security and transmission delay. [ABSTRACT FROM AUTHOR]

In this paper, a decode-and-forward (DF) short-packet relaying model is developed to achieve timely status updates for intelligent monitoring within the Internet of Things (IoT), where the status updates generated at an IoT device are delivered to a remote server with the aid of a relay in both half-duplex (HD) and full-duplex (FD) modes. To characterise the data freshness of status updates, we exploit the age of information (AoI) as a metric, which is defined as the time elapsed since the generation of the latest successfully decoded status update. The average AoI is formulated and minimised for both HD-DF and FD-DF relaying IoT networks in finite blocklength regime. For the HD-DF relaying, we introduce a perfect approximation of the average AoI to solve the problem of average AoI minimisation with the optimal blocklengths in two phases. For the FD-DF relaying, we propose an iterative algorithm to solve the problem of average AoI minimisation by optimising the relay’s transmit power and the blocklength. Illustrative numerical results not only substantiate the validity of our proposed algorithms, but also provide useful references for the IoT monitoring network design, specifically for the transmit power thresholds at the IoT device and the relay. [ABSTRACT FROM AUTHOR]

In this paper, the concept of opportunistic bits (OBs) is developed in short-packet communications and investigated from a finite blocklength perspective. In the OB-based transmission, the data unit of a packet is divided into two parts: OBs and conventional bits (CBs). The OBs are not physically transmitted but used to indicate the index of the time slot (TS) when the packet containing CBs is transmitted. The loading of a bulk of OB-based packets into multiple TSs can be modelled as a Repeated Balls-into-Bins process with a multi-queue storage. If the bulk is not large enough, certain combination(s) of OBs will not appear, which leaves certain TS(s) empty and hence reduces the TS load efficiency. To evaluate the OB-based transmission performance, we formulate its maximal payload rate and TS load efficiency. With the aid of these two formulations, the energy gain, the goodput, and the latency of OB-based short-packet communications are derived and obtained in analytical forms. For achieving further insights, illustrative numerical results on the resource utilisation efficiency and the performance not only substantiate the advantages of the OB-based transmission over the conventional but also provide useful tools and specifications for its design in massive short-packet communications. [ABSTRACT FROM AUTHOR]

To achieve physical layer security (PLS) with a flexible implementation, a novel design named security-oriented trellis coded spatial-modulation (SO-TCSM) is proposed in this article, where the transmitter does not know the channel state information (CSI) of wiretapping channels and relies on the legitimate CSI to vary the mapping patterns for the antenna information and the radiated information, aiming at the optimisation of free Euclidean distances between the resultant SO-TCSM symbols. Eavesdroppers cannot decode the confidential information delivered in the legitimate link, as they do not know the legitimate CSI and, hence, have no basis to acquire the transmitter’s mapping pattern of the moment. Moreover, the SO-TCSM symbols are then compensated to maximise their Euclidean distances, which further improves the legitimate receiver’s decoding performance while enhancing the PLS. However, the compensation results in high transmit power when the legitimate channels are in deep fades. To boost the energy efficiency, a constraint is set to limit the transmit power. Under this constraint, the SO-TCSM performance is investigated in terms of bit error rate and transmit power consumption. The outcome of these investigations substantiates that, compared to conventional TCSM designs, our SO-TCSM achieves better performance in the legitimate link with lower decoding complexity. [ABSTRACT FROM AUTHOR]

To tackle the traffic congestion over channels, we propose a new transmission scheme, which is powered by the concept of index bit (IB), to increase the transmission efficiency. In this letter, the item of bit-unit (BU) is adopted to replace that of IP packet. Explicitly, every BU is divided into two parts: one is IB, and the other is conventional bit (CB). In specific, every IB is of equal length with its value representing the length of the corresponding CB. At the transmitter side, a storage is prepared for caching CBs temporarily, and has been divided into multiple sub-buffers in advance. Each CB is loaded into certain sub-buffer according to its IB, which is hidden during storing and transmission. To augment the benefit, a dynamic balancing method is proposed to adjust the width of each sub-buffer iteratively. Our numerical results demonstrate the achieved transmission efficiency gain. With the dynamic adjustment continues deeply, the utility function is increased in fluctuation to a saturated level. [ABSTRACT FROM AUTHOR]

Radio FD has emerged as an attractive technique capable of doubling the spectral efficiency over half duplex. However, for signal reception, an FD node needs to suppress its transmitter's signals quite significantly. In point to point communication systems, these transmitter signals are termed self-interference. When working with an FD mobile network, the self-interference problem becomes much more complicated because the receiver of an FD base station (BS) receives interference not only from its BS transmitter in its cell, but also from those in the surrounding cells. For the UL channel, self-interference extends to the problem of multiple interference. And, a similar interference problem can be found among the MSs over a DL channel. In both cases, the interference owing to the FD implementation spreads beyond the scope of the self-interference. This article describes the development of FD BSs that use antenna arrays to deal with the BSs' interference, and thus enable FD communication over the UL channel, where the theoretical focus is placed on how to use the antenna array to nullify the multiple interference and receive the signals of the desired MSs simultaneously. To complete the system construction, FD MSs have also been developed to enable DL transmission. A prototype system is described for the scenario of two cells and one FD MS for tests of FD communication over UL channels and DL channels in terms of video performance. Good video quality is demonstrated at both the BS and MS. [ABSTRACT FROM AUTHOR]

Due to the severity of self-interferences, analog interference canceller is an essential part of a full duplex radio system. As the self-interference can potentially be even much stronger than the received signal, it must be meritoriously suppressed before analog-to-digital conversion. This paper is aimed to provide an optimal radio frequency domain multi-tap interference cancellation design. To this end, the following two key problems are addressed: the hardware design problem and the adaptive weight adjusting problem. For optimal hardware design, a trade-off between widening effective delay range and maximizing the minimum cancellation capability is formulated. The principles and guidelines for optimal solution and hardware parameter design are derived. We also formulate adaptive weight adjusting as a multi-dimensional optimization problem, which is proved to be non-convex while adjusting the attenuators and phase shifters independently. By using a coordinate transformation technique, it is then converted into a convex optimization problem, and a convergent iterative algorithm based on the gradient descent method is applied to obtain the global optimum. The hardware implementation and experimental results substantiated the effectiveness of the proposed principles and algorithms. [ABSTRACT FROM AUTHOR]

Motivated by the need for the fundamental increase of the spectral efficiency for the massive TCP/IP packet transmission, we propose a new method based on the concept of the opportunistic-bit (OB). The system design takes the advantage of the TCP/IP packet for its availability of sufficient information to the receiver to identify the address and interpret the contents. At the transmitter we specified a number of bits in each packet as the OB that is conveyed by a fixed sequential transmission index. The proposed scheme operates on the TCP/IP and the two additional specifications in the communication. As a result, we can achieve very high spectral efficiency gain and power gain as well. The theoretical analysis is confirmed by the numerical- and simulation results. [ABSTRACT FROM AUTHOR]

This correspondence proposes a novel multiuser computational offloading scheme for a fog-based scenario. Specifically, a controlling user (CU) distributes its computational tasks to multiple trusted helping users (HUs) by exploiting both nonorthogonal multiple access (NOMA) and beamforming. First, social relationships between the CU and HUs are exploited for the selection of trusted HUs. Then, the HUs having sufficient computing resources and high social trust are selected and grouped into multiple pairs. For the sake of improving the spectral efficiency, NOMA is invoked for simultaneously supporting several HUs. Meanwhile, a process of zero-forcing beamforming is used by the CU to completely eliminate the interpair interference, hence further enhancing the sum rate. By analyzing the achievable rate and energy consumption of the uplink and downlink transmission, an energy consumption minimization problem is formulated subject to the constraints of signal-to-interference plus noise ratio and transmission latency. We design a user-pairing and resource allocation algorithm for successively optimizing the power allocation and computational task distribution, while satisfying the classic Karush–Kuhn–Tucker conditions. Our numerical results demonstrate that by combining the social relationships, the computational capacities, and the channel conditions, the proposed multiuser computational offloading scheme relying on social trust, NOMA, and beamforming improves the energy consumption, sum rate, and transmission latency. [ABSTRACT FROM AUTHOR]

At the time of writing, vehicle-to-vehicle (V2V) communication is enjoying substantial research attention as a benefit of its compelling applications. However, the ever-increasing tele-traffic is expected to result in overcrowding of the available band. As a first resort, multiple input multiple output (MIMO) can be utilized to enhance the attainable bandwidth efficiency or link reliability. However, in hostile V2V wireless propagation environments, the achievable multiple-antenna gain is eroded by the channel correlation. As a promising MIMO technique, spatial modulation (SM) only activates a single transmit antenna (TA) in any symbol interval and, hence, completely avoids the inter-antenna interference, hence showing robustness against channel correlation. As a further powerful solution, non-orthogonal multiple access (NOMA) has been proposed for improving the bandwidth efficiency. Inspired by the robustness of SM against channel correlation and the benefits of NOMA, we intrinsically amalgamate them into NOMA-SM in order to deal with the deleterious effects of wireless V2V environments as well as to support improved bandwidth efficiency. Moreover, the bandwidth efficiency of NOMA-SM is further boosted with the aid of a massive TA configuration. Specifically, a spatio-temporally correlated Rician channel is considered for a V2V scenario. We investigate the bit error ratio performance of NOMA-SM via Monte Carlo simulations, where the impact of the Rician $K$ -factor, spatial correlation of the antenna array, time-varying effect of the V2V channel, and the power allocation factor is discussed. Furthermore, we also analyze the capacity of NOMA-SM. By analyzing the capacity and deriving closed-form upper bounds on the capacity, a pair of power allocation optimization schemes are formulated. The optimal solutions are demonstrated to be achievable with the aid of our proposed algorithm. Again, instead of simply invoking a pair of popular techniques, we intrinsically amalgamate SM and NOMA to conceive a new system component exhibiting distinct benefits in the V2V scenarios considered. [ABSTRACT FROM PUBLISHER]