Low-complexity user pairing and power allocation algorithm for 5G cellular network non-orthogonal multiple access

Non-orthogonal multiple access (NOMA) is a candidate technology for the 5th generation cellular networks to reduce the big gap between network capacity and fast growing traffic. It applies superposition coding in transmitters and successive interference cancellation at the receivers to cancel intra-cell interference. The same frequency resource can be allocated simultaneously to multiple intra-cell users, holding large potentials on improving network performance. A major technical challenge of NOMA is on user pairing and power allocation (UPPA). Most of existing UPPA algorithms are based on exhaustive search with extensive computation. A new algorithm, which has the lowest computation complexity achievable for NOMA UPPA is proposed. The main idea is to pair the first users having the highest proportional fairness priority coefficient with potential second users having the highest channel conditions. A fixed power allocation strategy is adopted. The proposed algorithm is significantly faster than existing algorithms without sacrificing NOMA throughput gain

Fast and efficient user pairing and power allocation algorithm for non-orthogonal multiple access in cellular networks

Non-orthogonal multiple access (NOMA) is emerging as a promising multiple access technology for the fifth generation cellular networks to address the fast growing mobile data traffic. It applies superposition coding in transmitters, allowing simultaneous allocation of the same frequency resource to multiple intra-cell users. Successive interference cancellation is used at the receivers to cancel intra-cell interference. User pairing and power allocation (UPPA) is a key design aspect of NOMA. Existing UPPA algorithms are mainly based on exhaustive search method with extensive computation complexity, which can severely affect the NOMA performance. A fast proportional fairness (PF) scheduling based UPPA algorithm is proposed to address the problem. The novel idea is to form user pairs around the users with the highest PF metrics with pre-configured fixed power allocation. Systemlevel simulation results show that the proposed algorithm is significantly faster (seven times faster for the scenario with 20 users) with a negligible throughput loss than the existing exhaustive search algorithm

Point-to-point channel modelling within offshore wind farms

From the perspective of several measurement campaigns in the offshore environment, it has been reported that the sea surface reflections are the main source of fading. We present a novel solution to this problem, by investigating the analytical implications of the propagation model which best fits the offshore channel characteristics. We also present a novel and yet simple implementation of receiver diversity which can mitigate the fading caused by sea surface reflections and ensure that the link is always steady even under extreme turbulent conditions

Design and Optimization of Scheduling and Non-orthogonal Multiple Access Algorithms with Imperfect Channel State Information

Non-orthogonal multiple access (NOMA) is a promising candidate technology for 5G cellular systems. In this paper, design and optimization of scheduling and NOMA algorithms is investigated. First, the impact of power allocation for NOMA systems with round-robin scheduling is analyzed. A statistic model is developed for network performance analysis of joint scheduling of spectrum resource and power for NOMA algorithms. Then, proportional fairness (PF) scheduling for NOMA algorithms is proposed with a two-step approach, with its objectives to ensure low computational complexity, high throughput, and user fairness. In the first step, an optimal power allocation strategy is developed with an objective maximizing weighted sum rate. In the second step, three fast and scalable scheduling and user pairing algorithms with QoS guarantee are proposed, in which only a few user pairs are checked for NOMA multiplex. The algorithms are extended to the cases with imperfect channel state estimation and more than two users being multiplexed over one resource block. Numerical results show that the proposed algorithms are significantly faster and more scalable than the existing algorithms, and can maintain a higher throughput gain than orthogonal multiple access

Throughput-based rate adaptation algorithm for IEEE 802.11 vehicle networks

A key problem with IEEE 802.11 technology is adaptation of the transmission rates to the changing channel conditions, which is more challenging in vehicular networks. Although rate adaptation problem has been extensively studied for static residential and enterprise network scenarios, there is little work dedicated to the IEEE 802.11 rate adaptation in vehicular networks. Here, the authors are motivated to study the IEEE 802.11 rate adaptation problem in infrastructure-based vehicular networks. First of all, the performances of several existing rate adaptation algorithms under vehicle network scenarios, which have been widely used for static network scenarios, are evaluated. Then, a new rate adaptation algorithm is proposed to improve the network performance. In the new rate adaptation algorithm, the technique of sampling candidate transmission modes is used, and the effective throughput associated with a transmission mode is the metric used to choose among the possible transmission modes. The proposed algorithm is compared to several existing rate adaptation algorithms by simulations, which shows significant performance improvement under various system and channel configurations. An ideal signal-to-noise ratio (SNR)-based rate adaptation algorithm in which accurate channel SNR is assumed to be always available is also implemented for benchmark performance comparison

A Millimeter Wave based Sensor Data Broadcasting Scheme for Vehicular Communications

In recent years, vehicles are becoming smart with the aid of various onboard sensing, communication and computing capability, which is helpful to improve road safety and driving experiments. With data fusion technique, a vehicle can even increase the driving safety by obtaining sensor data from other vehicles. The millimeter Wave (mmWave) based Vehicle-to-Vehicle (V2V) communication technology has become a promising technology to transmit sensor data in huge size such as video streams. However, the high radio frequency of mmWave makes it vulnerable to obstacles. Furthermore, the directional propagation property is not efficient to broadcast information among vehicles. In this paper, we propose a broadcasting scheme to guarantee each vehicle to get the sensor data of all other vehicles. Head vehicles are selected to gather the information on the environment and decide those transmission vehicles and receiving vehicles in each time slot. A graph-based routing selection algorithm is proposed with relatively low complexity. Moreover, the upper bound of broadcasting delay for one dimensional platoon is analyzed based on the network calculus theory. Simulation results indicate that the proposed scheme has faster delivery rate compared to the traditional First-In-First-Out (FIFO) scheme. The maximum broadcasting delay of the proposed scheme is less than the traditional schemes about 30% in different scenarios

Achievable performance gain of IEEE 802.11 multi-rate link adaptation algorithm with cross-layer design

Link quality-based rate adaptation has been widely used for IEEE 802.11 networks. However, network performance is affected by both link quality and random channel access. Selection of transmit modes for optimal link throughput can cause medium access control (MAC) throughput loss. In this paper, we investigate this issue and propose a generalised cross-layer rate adaptation algorithm. It considers jointly link quality and channel access to optimise network throughput. The objective is to examine the potential benefits by cross-layer design. An efficient analytic model is proposed to evaluate rate adaptation algorithms under dynamic channel and multi-user access environments. The proposed algorithm is compared to link throughput optimisation-based algorithm. It is found rate adaptation by optimising link layer throughput can result in large performance loss, which cannot be compensated by the means of optimising MAC access mechanism alone. Results show cross-layer design can achieve consistent and considerable performance gains of up to 20%. It deserves to be exploited in practical design for IEEE 802.11 networks

Enhanced Collision Avoidance for Distributed LTE Vehicle to Vehicle Broadcast Communications

In this paper we investigate the distributed autonomous resource selection for LTE vehicle to vehicle (V2V) broadcast. The effectiveness of collision avoidance and location based resource allocation enhancements is examined. It is found that collision avoidance with multiple data resources reservation per schedule assignment (SA) is a key to improve broadcast reliability. However in the existing collision avoidance algorithm reserving multiple resources per SA can lead to many data packet collisions if a SA collision happens. We propose an enhanced collision avoidance to address this issue. The idea is to use selected data packets to disseminate the reservation of data resources and SA resources, which can provide better communication among neighbor vehicles on resource reservation and reduce data collisions. Simulation results show that the proposed collision avoidance enhancement can effectively improve SA and data transmission reliability. The network capacity in terms of supported vehicles under given V2V service requirements is largely increased by 17% at a negligible cost of added overhead