Huiting Cheng

Performance of broadcast transmission from multiple vehicles in vehicle-roadside-vehicle relay network

Vehicle to vehicle (V2V) communication is regarded as an essential means to avoid traffic accidents and increase vehicle safety. However, reliability of the communications severely suffers from wireless propagation on the road. A vehicle-roadside-vehicle relay communication scheme has been proposed to improve the reliability of the V2V communications. The packet broadcast transmission performance of the proposed scheme with large number of transmitting vehicle stations around intersection is evaluated by computer simulations that assume fading, corner loss attenuation and carrier sense range. The combinations of two frequency bands, 700 MHz and 5.9 GHz, are also compared for the direct and relay transmissions. Simulated results show that the average packet reception ratio is remarkably improved with the proposed scheme regardless of number of the vehicle stations. The frequency combination of 700 MHz as vehicular station transmission and 5.9 GHz as relay station retransmission shows better performance.

Reliable Inter-Vehicle Broadcast Communication with Sectorized Roadside Relay Station

Inter-vehicle broadcast communication is an effective means to achieve driving safety by exchange vehicle status information. The reliability of inter-vehicle communication around intersections suffers severely from shadowing effect caused by buildings at the corners. A broadcast relay network can extend the coverage of inter-vehicle communication around intersections. However its performance is affected by packet collision due to hidden terminal (HT) problem at the roadside relay station (RS). In this paper, the RS is sectorized with directional antennas to alleviate the impact of packet collision. Both the theoretical and simulation results show that the packet delivery rate is remarkably improved by the sectorization, especially in dense networks.

Performance Analysis of ITS V2V Broadcast Communication Using CSMA/CA and a Roadside Relay Station at Intersections

The reliability of Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) vehicle-to-vehicle (V2V) communication in real road environments suffers from fading, shadowing and the hidden terminal problem, especially for non-line-of sight (NLOS) areas such as intersections. In order to improve the communication reliability, a CSMA/CA based vehicle-roadside-vehicle broadcast relay network was proposed and its effectiveness has been shown through simulations. However, the potential of such a network has not been well analyzed and optimized. In this paper, a theoretical model is proposed to analyze the performance of the broadcast relay network in detail. In order to fit real vehicular environments, the model assumes a typical crossroad and takes into account fading, shadowing, the hidden terminal problem and the capture effect. The influence of system parameters including position of nodes, carrier sense threshold and RF frequency band on the reliability of the network is studied based on the model. The accuracy of the proposed analytical model is confirmed by simulations. The analytical model and the obtained results are useful for the design of vehicular broadcast networks to select appropriate system parameters.

Performance Analysis of CSMA/CA Broadcast Relay Network for ITS V2V Communications

The reliability of CSMA/CA vehicle-to-vehicle (V2V) communication under actual road environment suffers from fading, shadowing and hidden terminal (HT) problem. In order to improve the communication reliability, a V2V broadcast scheme with relay stations has been proposed and its effectiveness was shown by some simulations. However, the potential of the CSMA/CA broadcast relay network has not been well analyzed and optimized. In this paper, a theoretical model is proposed to analyze the performance of such network in detail. In order to fit the realistic vehicular environment, the model assumes a typical crossroad and takes into account fading, shadowing, hidden terminal problem and capture effect, as well as distances between nodes. The influence of system parameters including RF frequency band and carrier sense threshold on the reliability of the network is also studied through the analysis. The accuracy of the proposed analytical model was validated by simulations. Some suggestions to enhance the reliability of V2V communication are provided based on the results.

Efficient packet relay scheme with payload combining for ITS V2V communications

The reliability of CSMA/CA vehicle-to-vehicle (V2V) broadcast communication is seriously affected by propagation issues such as propagation loss, fast fading by multipath propagation, and hidden terminal problem. In order to improve the V2V communication reliability, a vehicle-roadside-vehicle relaying communication scheme has been proposed and its effectiveness has been shown. However, relaying increases air time occupancy ratio in a wireless channel which results in more chances of collision and limits the improvement by relaying. This paper proposes an improved V2V packet relay scheme with payload combining at relay station to save air time and mitigate the collision. Simulated results assuming an intersection show that the average packet delivery ratio is significantly improved with the proposed scheme.

Semi-Blind Gradient-Newton CMA and SDD Algorithm for MIMO Space-Time Equalisation

Semi-blind space-time equalisation is considered for dispersive multiple-input multiple-output systems that employ high-throughput quadrature amplitude modulation signalling. A minimum number of training symbols, approximately equal to the dimension of the space-time equaliser (STE), are first utilised to provide a rough initial least squares estimate of the STEs weight vector. A gradient-Newton-type concurrent constant modulus algorithm and soft decision-directed scheme is then applied to adapt the STE. The proposed semi-blind adaptive STE is capable of converging fast and accurately to the optimal minimum mean square error STE solution.

Adaptive Semi-Blind Space-Time Equalisation for Frequency Selective Rayleigh Fading MIMO Systems

An adaptive semi-blind space-time equaliser (STE) has recently been proposed based on a concurrent gradient-Newton constant modulus algorithm and soft decision-directed scheme for dispersive multiple-input multiple-output (MIMO) systems that employ high-throughput quadrature amplitude modulation signalling. We investigate the performance of this adaptive semi-blind STE operating in Rayleigh fading MIMO systems. Our results obtained show that the tracking performance of this semi-blind adaptive algorithm is close to that of the training-based recursive least squares algorithm. This study, therefore, demonstrates that the proposed semi-blind algorithm offers a practical means to adapt a STE in the hostile dispersive Rayleigh fading MIMO environment.