Wireless networks possess several distinct characteristics that render the methodologies developed for wired networks invalid and inefficient. Specifically, the scarce bandwidth resources call for prudent allocation to achieve efficient utilization and adequate user performance. Wireless links are volatile, error-prone, and link quality in terms of error probability and available bandwidth is time-varying. Wireless devices are often mobile, implying network topology changes over time, and constraints in their energy supply. More importantly, channel interference induced by the broadcast nature of the wireless transmissions needs to be judiciously taken into account when controlling the network, giving rise to nontrivial interdependencies across users and network layers.
Wireless networks predominantly operate on principles and protocols inherited from the wire-line world, or rely on purely empirical, ad-hoc resource allocation and parameter adaptation rules. Some prominent examples of shortcomings in currently employed protocols and mechanisms are:
1. The most widely used MAC protocol in wireless networks is based on CSMA, similarly to wire-line Ethernet protocol.
2. Transmission parameters such as transmission power and rate are adapted in an unsophisticated manner in cellular networks and WLANs,, mostly based on empirical rules (e.g., constant step power increase when link quality is deteriorated).
3. Wireless multi-hop routing protocols experience significant loss of throughput after a few hops even in semi-static situations.
4. Multi-cast traffic is not efficiently handled in wireless networks.
5. TCP, as inherited from wire-line networks, bears the major drawback that it cannot discriminate between congestion and packet errors in wireless environments.
6. Most protocols operate with little or no interaction with protocols in other layers of the stack.
OPNEX aims to rethink the protocol stack and essentially redesign wireless network protocols eliminating the inefficiencies in the currently used protocols and mechanisms.
Wireless networks predominantly operate on principles and protocols inherited from the wire-line world, or rely on purely empirical, ad-hoc resource allocation and parameter adaptation rules. Some prominent examples of shortcomings in currently employed protocols and mechanisms are:
1. The most widely used MAC protocol in wireless networks is based on CSMA, similarly to wire-line Ethernet protocol.
2. Transmission parameters such as transmission power and rate are adapted in an unsophisticated manner in cellular networks and WLANs,, mostly based on empirical rules (e.g., constant step power increase when link quality is deteriorated).
3. Wireless multi-hop routing protocols experience significant loss of throughput after a few hops even in semi-static situations.
4. Multi-cast traffic is not efficiently handled in wireless networks.
5. TCP, as inherited from wire-line networks, bears the major drawback that it cannot discriminate between congestion and packet errors in wireless environments.
6. Most protocols operate with little or no interaction with protocols in other layers of the stack.
OPNEX aims to rethink the protocol stack and essentially redesign wireless network protocols eliminating the inefficiencies in the currently used protocols and mechanisms.