1 National Research Council - Pisa - Italy Marco Conti Italian National Research Council (CNR) IIT Institute MobileMAN Architecture and Protocols 2nd MobileMAN Workshop - Sophie-Antipolis 6-7 March, 2003 IST - FET Initiative

2 Reference Architecture

3 Enhanced Legacy MANET Architecture Enhanced Wi-Fi cards (?) MANET Routing algorithms IP layer TCP Socket API MiddlewareServices location Existing Applications (SMS, chating, etc..) Cooperation Power Management Security (?) Wi-Fi cards

4 MANET approach: IP centric The problem is mainly concentrated on the IP layer and is related to “solve mobile routing problems at the IP layer” the main reason for doing work at the IP layer is to better support heterogeneity and networked interoperability of lower layer technologies support for a heterogeneous mix of technologies and devices is one of the great successes of IP IP layer software development often capitalizes on the rich variety of work done within IP protocol software stacks and operating systems therefore easing development, deployment costs, and simplifying redesign and replication efforts.

5 Ad Hoc network realistic view Networked communication dynamics favor smaller wireless networks or at least networks requiring fewer hops in order to access a fixed backbone For example, in ad hoc networks employing omni-directional antennas, recent research Piyush Gupta and P. R. Kumar, ``The Capacity of Wireless Networks,'' IEEE Transactions on Information Theory, vol. IT-46, no. 2, pp , March 2000.``The Capacity of Wireless Networks,'' has shown that as the network scales (assuming it is equally likely that any pair of network nodes wish to communicate) as the number of communicating network nodes grows, the achievable throughput per node pair goes to zero As such, the prospect of deploying very large-scale, ad hoc networks based on broadcast transmissions is not very promising.

6 Ad Hoc network realistic view (cont.) Small-medium scale ad hoc islands Ad hoc islands interconnected to the Internet MANET scales: small-scale (i.e., 2-20 nodes) moderate-scale (i.e., nodes) large-scale (i.e., 100+ nodes) very large-scale (i.e., nodes

7 Ad Hoc network realistic view (cont.) MANET etherogeneity is limited Bluetooth (too limited coverage area) family is de facto the standard for WLANs Ad hoc networking can be successful only if sufficiently dense network exists Our view of ad hoc network: based small-medium scale ad hoc islands homogeneous small (medium) scale Novel MobileMAN Architecture

8 The rationale to go in this direction: Problems pointed out by measurement studies of simple ad hoc networks: - Wi-Fi in ad hoc configurations has severe problems -TCP mechanisms made the Wi-Fi system more unstable -The 3-hop horizon for ad hoc networks made interesting to use simpler routing mechanisms 2, 2.5 Routing protocols, simplified TCP, cross-layers functions

9 Novel MobileMAN Architecture Wi-Fi or Enhanced Wi-Fi cards Subnetwork Forwarding and Routing Simplified Transport Protocol Socket API Applications and Middleware The Ad Hoc network is a subnet based on “ad hoc” protocols Proxy-based architecture for the connection to the Internet Wi-Fi or Enhanced Wi-Fi Subnetwork Forwarding and Routing Simplified Transport Protocol Socket API Proxy daemon Subnetwork IP TCP Socket API Ad Hoc Node Proxy

10 Novel MobileMAN Architecture Ad Hoc Node Interconnection to Internet without proxy Wi-Fi or Enhanced Wi-Fi cards Subnetwork Forwarding and Routing Simplified Transport Protocol Applications and Middleware IP TCP Socket API

11 Novel MobileMAN Architecture (Cont.) Current solutions are typically not “optimized”: solutions at one layer generally not exploit information/mechanisms available at lower layers Es. Localization services are designed independently by mechanisms already available at lower layers Our idea to exploit inter-layer coordination

12 Inter-layer coordination Let us assume that the network layer through the routing mechanism has a (partial) knowledge of the network topology. We can also assume that this knowledge is typically accurate for a 1-2 hop distance The MAC layer could exploit this information to reduce the impact of phenomena such as: exposed nodes, capture phenomena etc. Example: MAC - Network Layers coordination

13 Inter-layer coordination (cont.) On the other hand knowledge available at MAC layer can be used to select among alternative routes It might be worth avoiding one route because a link is currently blocked at MAC level (e.g., through the RTS/CTS mechanism, etc.) Example: MAC - Network Layers coordination (Cont.)

14 Inter-layer coordination (cont.) Let us assume that the network layer through the routing mechanism has a (partial) knowledge of the network topology. This may include Alternative routes for a given destination Other info on these routes (e.g., number of hops) The Cooperation layer by using these info can try to classify the reliability/performance/cooperation along these routes. A new nearness metric can be derived Example: Cooperation /Forwarding/Routing coordination

15 Inter-layer coordination (cont.) Packet Forwarding can exploit the closeness metric to select among alternative paths to perform a load balancing among the routes The feedbacks from this choice can be used to refine the nearness metric Example: Cooperation /Forwarding/Routing coordination (cont.)

16 Inter-layer coordination (cont.) The transport layer might use a redundant coding technique (see, e.g., FEC): a message is coded into n blocks but only k (k<n) need to be received. The redundancy level can be selected taking into account the reliability metric at the Cooperation layer Blocks can be forwarded on alternative links taking into consideration the closeness/reliability metric Finally, the results of this transmissions can be used to refine the reliability (nearness) metric. Example: Forwarding/Cooperation/Transport coordination (cont.)

17 Novel MobileMAN Architecture Enhanced Wi-Fi cards Routing (2) Users location Forwarding Simplified Transport Protocol Socket API Middleware Services location Shared memory Treasure hunting (with code mobility) Cooperation/ Performability Power Management