Complex Field Network Coding Scheme Research Articles

Precoding-based complex field network coding strategy for multi-source UAV cooperative system

Relay-based UAV swarm can further expand the surveillance range for more complex missions. Microsatellite swarms provide invulnerability and stability compared to conventional satellites and are selected for multi-UAVs multi-satellites systems. Determining how to recover more valuable information from the multi-source data is of significant importance. Considering that vast amounts of multi-source data from UAV swarm require higher throughput performance of transmission schemes, complex field network coding (CFNC) is selected for UAV cooperative system. However, adverse effects like inter-user interference of fading channels will limit the reliability performance of UAV cooperative system. To improve the reliability performance and recover more accurate valuable information, we propose a precoding-based CFNC strategy for multi-source UAV cooperative system. The proposed transmission scheme processes data through precoding matrix, which is obtained by the transformation of channel state matrix. Compared to conventional CFNC schemes, precoding-based CFNC scheme improves the accuracy of detections. Through theoretical analysis and experimental results, the precoding-based CFNC transmission scheme not only maintains high throughput, but also recover more valuable information and achieves better reliability performance.

Complex Field Network Coding for Multi-Source Multi-Relay Single-Destination UAV Cooperative Surveillance Networks

Relay-based cooperative communication for unmanned aerial vehicle (UAV) networks can obtain spatial diversity gains, expand coverage, and potentially increase the network capacity. A multi-source multi-relay single-destination structure is the main topology structure for UAV cooperative surveillance networks, which is similar to the structure of network coding (NC). Compared with conventional NC schemes, complex field network coding (CFNC) can achieve a higher throughput and is introduced to surveillance networks in this paper. According to whether there is a direct communication link between any source drone and the destination, the information transfer mechanism at the downlink is set to one of two modes, either mixed or relay transmission, and two corresponding irregular topology structures for CFNC-based networks are proposed. Theoretical analysis and simulation results with an additive white Gaussian noise (AWGN) channel show that the CFNC obtains a throughput as high as 1/2 symbol per source per channel use. Moreover, the CFNC applied to the proposed irregular structures under the two transmission modes can achieve better reliability due to full diversity gain as compared to that based on the regular structure. Moreover, the reliability of the CFNC scheme can continue to be improved by combining channel coding and modulation techniques at the expense of rate loss.

Physical Layer Network Coding for the K-User Multiple Access Relay Channel

We propose a Physical layer Network Coding (PNC) scheme for the K-user wireless Multiple Access Relay Channel, in which K source nodes want to transmit messages to a destination node D with the help of a relay node R. The proposed scheme involves (i) Phase 1 during which the source nodes alone transmit and (ii) Phase 2 during which the source nodes and the relay node transmit. At the end of Phase 1, the relay node decodes the messages of the source nodes and during Phase 2 transmits a many-to-one function of the decoded messages. To counter the error propagation from the relay node, we propose a novel decoder which takes into account the possibility of error events at R. It is shown that if certain parameters are chosen properly and if the network coding map used at R forms a Latin Hypercube, the proposed decoder offers the maximum diversity order of two. Also, it is shown that for a proper choice of the parameters, the proposed decoder admits fast decoding, with the same decoding complexity order as that of the reference scheme based on Complex Field Network Coding (CFNC). Simulation results indicate that the proposed PNC scheme offers a large gain over the CFNC scheme.

Optimal power allocation for complex field network coding scheme with the K- th best relay selection

Wireless relay and network coding are two critical techniques to increase the reliability and throughput of wireless cooperative communication systems. In this paper, a complex field network coding (CFNC) scheme with the K-th best relay selection (KBS) is proposed and investigated, wherein the K-th best relay is selected to forward the multiplexed signal to the destination. First, the upper bound of the symbol error probability (SEP), the diversity order, and the coding gain are derived for the CFNC scheme with KBS. Then, the coding gain is utilized as the optimized criterion to determine the optimal power allocation. It is validated through analysis and simulation that the CFNC scheme with KBS can achieve full diversity only when K=1, while the diversity order decreases with increasing parameter K, and the optimal power allocation can significantly improve the performance of the CFNC scheme with KBS.

무선 릴레이 시스템에서의 Complex Field Network Coding 기법 적용에 관한 연구

본 논문에서는 릴레이 기반 무선 통신 환경에서 기존의 CFNC (Complex Field Network Coding) 기법 적용 시 발생하는 문제점들을 개선하는 방안을 제시한다. CFNC 기법은 간단한 복소 덧셈 및 뺄셈 연산을 통해 상 하향 링크 신호 교환에 요구되는 시간 구간을 최소화함으로써 전송 효율을 극대화하는 장점을 가진다. 그러나, 기존의 CFNC 기법은 릴레이에서의 ML (Maximum Likelihood) 판정 과정에서 큰 폭의 성능 열화가 발생하는 단점이 있다. 또한, CFNC 기법 적용 시 릴레이의 수신 신호에 다중 주파수 오프셋이 발생함에 따라 릴레이의 미세 주파수 오프셋 추정 성능이 열화 되는 한편, 주파수 오프셋 보상 이후에도 잔류 주파수 오프셋으로 인한 성능 열화가 발생하는 문제점이 있다. 따라서 본 논문에서는 상향 링크의 송신 다이버시티를 이용함으로써 정확도를 개선 가능한 새로운 ML 판정 기법 및 다중 주파수 오프셋 환경에서 적용 가능한 새로운 미세 주파수 오프셋 추정, 보상 기법을 제안한다. 다양한 환경에서의 컴퓨터 모의실험을 통해 제안된 기법들이 CFNC 기법 적용 시 발생하는 문제점들을 효과적으로 개선 가능함을 입증한다. In this paper, a CFNC (Complex Field Network Coding) scheme is presented, which focuses on improving transmission efficiency by reducing time slots that are needed to exchange data frames. Conventional CFNC scheme has the advantage of minimizing the number of time slots required for information exchanges. However, there exists serious performance deterioration because the transmit signals are interfered with each other. Moreover, when CFNC scheme is applied, the estimation and compensation performance of fine frequency offset severely deteriorates due to the multiple frequency offsets in received signal of relay node. In order to overcome these critical problems, we propose an improved CFNC scheme with modified maximum likelihood decision method which uses uplink transmit diversity. Also, we propose an enhanced fine frequency offset estimation method and a corresponding compensation method to deal with the multiple frequency offsets. Corresponding simulation results verify that the proposed methods are able to effectively solve the problems of CFNC scheme.

Capacity Scaling of Wireless Networks with Complex Field Network Coding

Network coding in wired networks has been shown to achieve considerable throughput gains relative to traditional routing networks. For wireless multihop networks however, the ergodic capacity is unknown. In this context, the scaling of capacity with the number of nodes ( n ) has recently received increasing attention. While existing works mainly focus on networks with n source-destination pairs, this paper deals with capacity scaling in any-toany wireless links, where each node communicates with all other nodes. Complex field network coding (CFNC) is adopted at the physical layer to allow n nodes exchanging information with simultaneous transmissions from multiple sources. As n increases, a hierarchical CFNC-based scheme is developed and shown to achieve asymptotically optimal quadratic capacity scaling in a dense network, where the area is fixed and the density of nodes increases. This is possible by dividing the network into many clusters, with each cluster sub-divided into many sub-clusters, hierarchically. As a result, information is transmitted on multi-input multi-output based multiple access channels and broadcast channels. When generalized to extended networks, where the density of nodes is fixed and the area increases linearly with n , the hierarchical CFNC scheme is shown to scale as n 3 −α/ 2 for a path loss exponent α ≥ 2, which is asymptotically optimal when α 3.