In wireless mobile ad hoc networks (MANETs), packet transmission is impaired by radio link fluctuations. This paper proposes a novel channel adaptive routing protocol which extends the Ad hoc On-Demand Multipath Distance Vector (AOMDV) routing protocol to accommodate channel fading. Specifically, the proposed Channel-Aware AOMDV (CA-AOMDV) uses the channel average nonfading duration as a routing metric to select stable links for path discovery, and applies a preemptive handoff strategy to maintain reliable connections by exploiting channel state information. Using the same information, paths can be reused when they become available again, rather than being discarded. We provide new theoretical results for the downtime and lifetime of a live-die-live multiple path system, as well as detailed theoretical expressions for common network performance measures, providing useful insights into the differences in performance between CA-AOMDV and AOMDV. Simulation and theoretical results show that CA-AOMDV has greatly improved network performance over AOMDV.

In a virtualized system, the hypervisor may be forced to reclaim memory by swapping out pages of guest operating systems (OSes) when the regular memory balancing mechanisms, such as page sharing and ballooning, fail to revoke enough memory for reallocation purpose, which always leads to serious performance degradation. In this paper, we introduce Adaptive Swap Prefetcher (ASP) and Host Swapping Notifier (HSN), the effective and lightweight solutions to gracefully reduce the degradation in system performance when host swapping is triggered. ASP smartly prefetches more pages from the host swap file as long as the good spatial locality persists so as to reduce disk transfers. The guest OS will be notified by HSN when the hypervisor evicts pages, which then hides those pages from its memory reclamation routines to eliminate unnecessary guest swapping and to prevent the occurrence of double paging anomaly. Currently ASP and HSN are implemented in KVM, experimental results show that guest performance can be improved by a factory of 1.4x and 2x respectively using ASP and HSN.

Congestion in mobile ad hoc networks leads to transmission delays and packet loss, and causes wastage of time and energy on recovery. Routing protocols which are adaptive to the congestion status of a mobile ad hoc network can greatly improve the network performance. In this paper, we propose a congestion-aware routing protocol for mobile ad hoc networks which uses a metric incorporating data-rate, MAC overhead, and buffer delay to combat congestion. This metric is used, together with the avoidance of mismatched link data-rate routes, to make mobile ad hoc networks robust and adaptive to congestion.