Coping with communication gray zones in IEEE 802.11b based ad hoc networks

Abstract

Our experiments with IEEE 802.11b based wireless ad hoc networks show that neighbor sensing with broadcast messages introduces "communication gray zones": in such zones data messages cannot be exchanged although the HELLO messages indicate neighbor reachability. This leads to a systematic mismatch between the route state and the real world connectivity, resulting in disruptive behavior for some ad hoc routing protocols. Concentrating on AODV we explore this issue and evaluate three different techniques to overcome the gray zone problem. We present quantitative measurements of these improvements and discuss the consequences for ad hoc routing protocols and their implementations.

ADHOCTCP: Improving TCP Performance in Ad Hoc Networks

“…As already discussed, if the TCP sender does not have indications on the route re-establishment event, the throughput and session delay will degrade because of the large idle time. Also, if the new route established is longer or shorter in term of hops, than the old route TCP will face a brutal fluctuation in round trip time (RTT) [13]. In addition, in ad hoc networks, routing protocols that rely on broadcast Hello messages to detect neighbors' reachability may suffer from the "communication gray zones" problem.…”

Comparison of two routing metrics in OLSR on a grid based mesh network

“…In order to avoid communication grey zones [18], which are illustrated in Fig. 15, the broadcast rate is locked to the data rate.…”

High Throughput Route Selection in Multi-rate Ad Hoc Wireless Networks

“…In [8] the authors show that the minimum hop path generally contains links which exhibit low reliability. In [9] and [10] the authors present routing protocols which are based on signal stability rather then just shortest path in order to provide increased path reliability. In our work, signal stability information is used not only to increase path reliability, but also to increase network throughput.…”