dc.description.abstract | This thesis focuses on exploring a multicast communication protocol forWiFi Direct (WD) 802.11
networks. The aim is to improve reliability and efficiency of multicast communication in WD networks.
Multicast inWDhas numerous potential applications such as local content sharing, sharing
network services, playing multi-player games, and a number of other proximity based services in
various fields, viz. health, sports, agriculture, transportation, and gaming. The two major issues
with multicast, reliability and efficiency, have been extensively studied in literature for standard
WiFi 802.11 networks. However, multicast protocols used in standard WiFi 802.11 networks cannot
be straightforwardly used in WD networks because the two technologies are different. Some
of these differences include multicast group formation, group architecture, network topology, role
and capacity of multicast transmitter. As a result, a multicast protocol cannot achieve reliability
and efficiency without taking into account the specifications of the MAC and PHY layers of WD
802.11 networks.
Motivated from the leader based approaches of standard WiFi, an Enhanced Leader Based
Multicast (ELBM) protocol is proposed to achieve reliability in multicast communication in WD
networks. It reduces collision and interference in multicast data transmission by improving the
channel access mechanism and selecting an optimal representative multicast receiver. In order to
assess the performance improvement which results from early detection of packet collision, Early
Packet Loss Detection (EPLD) analytical model is proposed, which surpasses the standard protocol
in terms of system throughput. Similarly, a theoretical model is formulated to investigate the
new features of the MAC and PHY layers of 802.11ac, such as different Multiple In Multiple Out
(MIMO) configurations, Modulation and Coding Schemes (MCS), and wider channel bandwidths
under TGn channel models. Because hidden nodes can largely affect the throughput of WD networks,
therefore an improved analytical model known as Vidden is developed to analyse the Very
High Throughput (VHT) of 802.11ac in the presence of hidden stations. Vidden carefully calculates
the collision probability by taking into account both the contending, as well as, the hidden
stations
A novel adaptive algorithm is proposed to maximize the efficiency of WD 802.11 networks
under a TGn channel model by choosing optimal PHY parameters in accordance with targeted
Quality of Experience (QoE) for a particular application. The simulation results show that the
proposed method outperforms the standard method, thereby achieving an optimal performance in an adaptive manner. Thereafter, an efficient methodology is proposed to reduce the overall Packet
Error Rate (PER) based on the simulation results.
Finally, the problem of selecting the most favourable transmission channel and rate is investigated
for a multicast communication system in the context of WD 802.11 networks. To this end, a
novel Multi-rate Multi-channel Multicast (M3-Cast) protocol is proposed, which not only chooses
the most favourable communication channel and transmission rate but also takes into account the
implementation details of the underlying WD technology, thereby optimizing the overall system
performance. M3-Cast is formulated analytically and evaluated by a complete system level simulation.
The detailed results and analysis consider a number of performance metrics, such as bit
error rate (BER), multicast capacity, and system throughput under different MIMO configurations,
channel bandwidths, and various network radii. Consequently, the simulation and analytical results
show that M3-Cast protocol outperforms the standard multicast protocol of WD by almost two-fold in terms of system throughput. | |