Parallel Use of Multiple Channels in Multi-hop 802.11 Wireless Networks

Abstract

We consider parallel use of multiple channels in a multi-radio, multi-hop 802.11 wireless network, with the goal of maximizing the total multi-hop throughput. We first quantify several fundamental forms of radio interference that cause performance degradation when the number of hops increases and that prevent total throughput from scaling up with number of radio interfaces at each node. We then evaluate three different methods of parallel channel use: Ad-Hoc, FrequencyDivision Multiplexing (FDM), and Time-Division Multiplexing (TDM). We measure their performance on a linearly connected multi-hop network of dual-radio nodes. Although theoretically these three methods should have comparable performance, their actual measured performances are quite different. We find that TDM has the best performance, followed by Ad-Hoc and then FDM. The performance differences are due to these methods' capabilities of combating interference. We conclude that interference, especially adjacent channel interference, has significant effect on the achievable performance of a multi-radio, multi-hop network and hence should be carefully taken into account in the design and deployment of such a network.

Maximizing Throughput of UAV-Relaying Networks with the Load-Carry-and-Deliver Paradigm

“…banking and traveling at relatively high speeds, as well as the relatively low tolerance of the 802.11 receivers to radio interference [1] [2].…”

“…First, LCAD can achieve high throughput performance by ensuring that UAV's communication with the source and destination ground nodes is free of interference from other nodes in the same networking system. In contrast, other 802.11-based multi-hop networks usually suffer from severe interference problems [1] [2]. Second, LCAD can scale its throughput by using multiple relaying UAVs in a pipelined fashion for data delivery, while other approaches often cannot due to interference and medium sharing constraints [9] [1].…”

Lessons learned from the deployment of a multihop IEEE 802.11g testbed using COTS devices

“…Despite the fact that it is well-known that multiinterface devices typically suffer from inter-card interference (see, e.g., [20], [22], [23]), and that the use of directional antennae may aggravate the adjacent channel interference as well (e.g. [24]), our results are indeed unexpected as devices are placed at distances much larger than the far field threshold.…”

“…Note that we are talking about relative distances between the sender, the intended receiver and potential interferer(s). Still, in all cases the absolute distances between each pair of devices are substantially larger than the far-field threshold, to prevent close-field interference (as reported by, e.g., [20]). This farfield threshold d is given by [21]:…”

Field Experimentation of Cots-Based UAV Networking

“…But uncertainties with these networks are also abundant. Beyond usual quality of service concerns about wireless mobile networks, there are UAV and COTS specific issues such as dynamically changing link quality due to UAV's movement and banking, and relatively low tolerance [5] of low-cost COTS wireless receivers to radio interferences.…”