Colouring Link-Directional Interference Graphs in Wireless Ad Hoc Networks

Abstract

In this paper, we clarify inter-link interference in wireless ad-hoc networks by using link-directional interference graphs (l-graph). Most of the interference graphs in the literature simply model the DATA and ACK traffic of a link by a single vertex. They fail to capture the link-directionalities. In fact, some instances of directional traffic can actually transmit simultaneously but are prohibited by the interference graphs. Thus, in our link-directional interference graph, a link is represented by two vertices, one for DATA traffic and the other for ACK traffic. We then apply a colouring algorithm in the l-graphs. The colouring results provide insights in order to boost network capacities in TDMA or FDMA ad-hoc networks. We show that the network capacities can be improved by 100% in a triangular topology and 33% in a lattice topology. Simulations also show that a distributed dual channel protocol assigning channels according to link-directionalities can boost the capacities by 70% in large-scale random networks. We believe this is a first paper in the literature to take into account link-directionalities in interference graphs.

Interference-Aware Scheduling for Connectivity in MIMO Ad Hoc Multicast Networks

“…A conflict (interference) graph was used to find the constraint conditions for the LP formulation. In [19], the authors proposed the construction of a link-directional interference graph to account for the directional traffic over each network link. They investigated a coloring algorithm with two colors on the interference graph to schedule transmissions in ad hoc networks employing TDMA or frequency division multiple access (FDMA).…”

“…In this section, we propose a scheduling algorithm that maximizes the connectivity metric defined earlier using the concept of coloring from graph theory [19], [20]. The algorithm is based on the use of the interference and collision graph (ICG) of the network [3], [18]- [20].…”

“…Since the nodes are energy limited, to extend the lifetime of the network and to reduce the mutual interference caused by the co-channel links, the transmit power of each link should be minimized under the constraint of the QoS requirement. Due to the approximation in (19), the use of the lower bound in (17), and the presence of outdated CSI, the actual SIN R k based on P and T will not be exactly equal to the threshold SIN R t . In most instances it will be greater than SIN R t due to the use of the lower bound in (17), but in some rare cases it can be below the threshold.…”

Scaling Capacity by Two Channels in IEEE 802.11 Ad Hoc Networks With an SIR Comparison Algorithm

“…See [18], which proposed the use of link-directional interference graphs to evaluate throughput improvements achieved by assigning channels according to link directionalities. Here, instead, we use the upper bound (best-case) analysis to compare the performance of the DCP and the SCA under various link-length scenarios to eliminate the impact of topology and traffic pattern.…”