Ghassan Abdalla | University of Khartoum (original) (raw)
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Papers by Ghassan Abdalla
The IEEE is working on a MAC standard (802.11p) for VANET based on 802.11e. Although the access f... more The IEEE is working on a MAC standard (802.11p) for VANET based on 802.11e. Although the access function of 802.11e supports QoS by using different backoff counters and interframe spaces for different QoS requirements, this reduces to a best effort service and low performance when the number of vehicles increases. Some applications of VANET, particularly safety related, have strict QoS requirements that cannot be guaranteed by 802.11p especially in heavy traffic conditions. To resolve these issues, we propose space-orthogonal frequency-time medium access control (SOFT MAC) protocol that can support QoS requirements and is compatible with 802.11 standard. The proposed MAC allocates guaranteed transmission slots via reservation and also has a random access period for best effort service. Reservations are allocated in a distributed manner without the need for a basestation or a cluster head. In this paper we analyse and discuss in details the rules and algorithms that govern SOFT MAC protocol and also explain its implementation using 802.11. The analysis of SOFT MAC proves it achieves higher saturation throughput than 802.11.
Eurasip Journal on Wireless Communications and Networking, 2009
Iet Intelligent Transport Systems, 2009
IEEE Vehicular Technology Magazine, 2009
Vehicular networks require accurate channel state information (CSI) to decode the received signal... more Vehicular networks require accurate channel state information (CSI) to decode the received signal. Such knowledge is usually obtained via a training sequence. However in vehicular networks, the channel coherence time is very small due to the high speeds of the nodes, therefore the channel estimate from the training is likely to become inaccurate as the decoding proceeds. Using shorter packets can improve the performance at the cost of increased overhead. In this paper we introduce a novel channel tracking algorithm for VBLAST in vehicular networks with relatively little change in the overhead. The algorithm uses first order Kalman filters therefore it has less complexity than available tracking algorithms. The algorithm uses the detected symbols and received signal after the interference cancellation and detection processes of the VBLAST decoder to improve the channel estimation. Simulation results show considerable improvement in mean square error (MSE) and BER when using this algorithm compared to channel estimation by training only with small increase in hardware complexity.
The IEEE is working on a MAC standard (802.11p) for VANET based on 802.11e. Although the access f... more The IEEE is working on a MAC standard (802.11p) for VANET based on 802.11e. Although the access function of 802.11e supports QoS by using different backoff counters and interframe spaces for different QoS requirements, this reduces to a best effort service and low performance when the number of vehicles increases. Some applications of VANET, particularly safety related, have strict QoS requirements that cannot be guaranteed by 802.11p especially in heavy traffic conditions. To resolve these issues, we propose space-orthogonal frequency-time medium access control (SOFT MAC) protocol that can support QoS requirements and is compatible with 802.11 standard. The proposed MAC allocates guaranteed transmission slots via reservation and also has a random access period for best effort service. Reservations are allocated in a distributed manner without the need for a basestation or a cluster head. In this paper we analyse and discuss in details the rules and algorithms that govern SOFT MAC protocol and also explain its implementation using 802.11. The analysis of SOFT MAC proves it achieves higher saturation throughput than 802.11.
Eurasip Journal on Wireless Communications and Networking, 2009
Iet Intelligent Transport Systems, 2009
IEEE Vehicular Technology Magazine, 2009
Vehicular networks require accurate channel state information (CSI) to decode the received signal... more Vehicular networks require accurate channel state information (CSI) to decode the received signal. Such knowledge is usually obtained via a training sequence. However in vehicular networks, the channel coherence time is very small due to the high speeds of the nodes, therefore the channel estimate from the training is likely to become inaccurate as the decoding proceeds. Using shorter packets can improve the performance at the cost of increased overhead. In this paper we introduce a novel channel tracking algorithm for VBLAST in vehicular networks with relatively little change in the overhead. The algorithm uses first order Kalman filters therefore it has less complexity than available tracking algorithms. The algorithm uses the detected symbols and received signal after the interference cancellation and detection processes of the VBLAST decoder to improve the channel estimation. Simulation results show considerable improvement in mean square error (MSE) and BER when using this algorithm compared to channel estimation by training only with small increase in hardware complexity.