1. A Two-Tier Heterogeneous Mobile Ad Hoc Network Architecture and Its Load-Balance Routing Problem C.-F. Huang, H.-W. Lee, and Y.-C. Tseng Department of Computer Science and Information Engineering National Chiao-Tung University IEEE VTC 2003. Speaker: Chung-Hsien Hsu Nov. 19, 2003

2. Outline Introduction System Model Solutions Boundary-Moving Solutions Host-Partitioning Solutions Simulation Conclusions

3. Introduction Most of the existing works have assumed a stand-alone MANET. It would be more attractive if one can simultaneously enjoy both: The flexibility provided by MANET The tremendous services/data provided in the Internet.

4. System Model Low-Tier ( 802.11...etc. ) High-Tier (PHS, GPRS, 802.11…etc.)

5. System Model – Problem Statement Assumption: The two-tier architecture is mainly used to support Internet access. Do not take intra-MANET communications into account. The key issue: How to utilize the bandwidths provided by the high-tier gateways efficiently. Load-balance routing.

6. System Model – Problem Statement (cont.) (a, T a ) (b, T b ) (c, T c ) (d, T d ) (e, T e ) (f, T f ) (g, T g ) (h, T h ) (i, T i ) (j, T j ) (k, T k ) (l, T l ) (m, T m ) (a, C a =384 Kbps) (b, C b =115.2 Kbps) (c, C c =11 Mbps)

7. System Model – Problem Statement (cont.) To evaluate how balanced a routing scheme can achieve Load Index (LI) Load-Balance Index (LBI) Goal: To reduce the LBI of the whole network.

8. Boundary-Moving Solutions The boundaries define the service range of each gateway host for low-tier hosts to route their traffics. Boundary-Moving Solutions Shortest-Path (SP) Routing Based on routing distances. Minimum Load-Index (MLI) Routing Based on gateways’ loads.

9. Boundary-Moving Solutions – Shortest-Path Routing The dominance of p over q: The service region of a gateway p:

10. Boundary-Moving Solutions – Shortest-Path Routing (cont.) i d m l n q e f p r b a c o g h j k Advertisement message: (a, 0) Serving gateway: a, 0 Default gateway: a Serving gateway: a, 0 Default gateway: a Serving gateway: a, 0 Default gateway: a Serving gateway: a, 0 Default gateway: a Advertisement message: (a, 1) Serving gateway: a, 1 Default gateway: e Serving gateway: a, 1 Default gateway: e Serving gateway: a, 1 Default gateway: e Serving gateway: a, 1 Default gateway: e Advertisement message: (c, 0) Serving gateway: c, 0 Default gateway: c Serving gateway: c, 0 Default gateway: c Serving gateway: c, 0 Default gateway: c Serving gateway: c, 0 Default gateway: c

11. Boundary-Moving Solutions – Shortest-Path Routing (cont.) i d m l n q e f p r b a c o g h j k

12. This scheme can not achieve the goal of load- balance routing in many cases. The traffic demands from hosts are not necessarily. Hosts may not be evenly distributed to all gateways.

13. Boundary-Moving Solutions – Minimum Load-Index Routing The boundaries between gateways will be adjusted dynamically. The scheme is fully distributed and is run by each host independently.

14. Boundary-Moving Solutions – Minimum Load-Index Routing (cont.) i d m l n q e f p r b a c o g h j k Advertisement message: (a, 0.7) Serving gateway: a, 0.7 Default gateway: a Serving gateway: a, 0.7 Default gateway: a Serving gateway: a, 0.7 Default gateway: a Serving gateway: a, 0.7 Default gateway: a Advertisement message: (a, 0.7) Serving gateway: a, 0.7 Default gateway: e Serving gateway: a, 0.7 Default gateway: e Serving gateway: a, 0.7 Default gateway: e Serving gateway: a, 0.7 Default gateway: e Advertisement message: (c,0.3) Assumption: Gateway-switch load threshold= 0.5 Check: (1) The serving time if over a time threshold T (2) = (0.7 – 5/20) / ( 0.3 + 5/20) = 0.81 > 0.5 Assumption: Gateway-switch load threshold= 0.5 Check: (1) The serving time if over a time threshold T (2) = (0.7 – 5/20) / ( 0.3 + 5/20) = 0.81 > 0.5 Serving gateway: c, 0.3 Default gateway: c Serving gateway: c, 0.3 Default gateway: c

15. Boundary-Moving Solutions – Minimum Load-Index Routing (cont.) i d m l n q e f p r b a c o g h j k

16. Dynamical boundaries: Lower traffic load will extend its service range. Higher traffic load will shrink its service range. This routing can lead to a more load-balanced status compared to the SP routing.

17. Host-Partitioning Solutions Hosts will be divided into groups, each to be served by a gateway. Host-Partitioning Solutions Centralized Assignment (CA) Distributed Assignment (DA)

18. Host-Partitioning Solutions – Centralized Assignment Assumption: There is a centralized server Gathering the traffic load information of all hosts. Assigning hosts to gateways. This problem is strongly related to the renowned number-partitioning problem.

19. Host-Partitioning Solutions – Centralized Assignment (cont.) Execution steps: Step 1: Sort all low-tier hosts into a list in a descending order of their traffic indices. Step 2: Sequentially assign each host x in the list to the gateway g with the minimum L’ g, where L’ g = L g + T x / C g, until the whole list is examined.

20. Host-Partitioning Solutions – Centralized Assignment (cont.) This scheme is costly There will be a lot of message exchanges in the network. Without considering the hop-count factor. The central server may assigns a host to a gateway which is far away from it.

21. Host-Partitioning Solutions – Distributed Assignment Basic idea: To configure a logical network to connect all gateways together. For gateways to exchange load and capacity information and to trade low-tier hosts. Logical links are constructed by low-tier links. The logical network can be of any topology, but must be connected.

22. Host-Partitioning Solutions – Distributed Assignment Low-tier hosts inform their traffic demands to their current serving gateways. Gateways delegate hosts to other gateways.

23. [Step 1] Each gateway periodically conveys its load and capacity information to its neighboring gateways. [Step 1] Each gateway periodically conveys its load and capacity information to its neighboring gateways. [Step 2] Gateway a to determine the candidate gateways to which it may delegate hosts. : 0.083/0.052 = 1.596 > 1 (assumption: load threshold = 1) [Step 2] Gateway a to determine the candidate gateways to which it may delegate hosts. : 0.083/0.052 = 1.596 > 1 (assumption: load threshold = 1) [Step 3] To compute the expected LBI if host i is delegated to gateway b. [Step 3] To compute the expected LBI if host i is delegated to gateway b. Host-Partitioning Solutions – Distributed Assignment (cont.) (a, 5) (b, 5) (c, 5) (d, 5) (e, 5) (f, 5) (g, 7) (h, 5) (i, 5) (j, 5) (k, 5) (l, 5) (m, 5) Load: 0.083 Capacity: 384 kbps Load: 0.083 Capacity: 384 kbps Load: 0.052 Capacity: 115.2 kbps Load: 0.052 Capacity: 115.2 kbps Load: 0.00136 Capacity: 11 Mbps Load: 0.00136 Capacity: 11 Mbps [Step 4] To choose a host which can reduce LBI greatly. In this example, host g will be chosen. [Step 4] To choose a host which can reduce LBI greatly. In this example, host g will be chosen. [Step 5] Gateway a notifies host g this decision with a Deldgate_to(b) message. [Step 5] Gateway a notifies host g this decision with a Deldgate_to(b) message. Deldgate_to(b)

24. [Step 5] Gateway a notifies host g this decision with a Deldgate_to(b) message. [Step 5] Gateway a notifies host g this decision with a Deldgate_to(b) message. [Step 6] Wait for one information-exchange interval and go to step 2. [Step 6] Wait for one information-exchange interval and go to step 2. Host-Partitioning Solutions – Distributed Assignment (cont.) (a, 5) (b, 5) (c, 5) (d, 5) (e, 5) (f, 5) (g, 7) (h, 5) (i, 5) (j, 5) (k, 5) (l, 5) (m, 5) Load: 0.083 Capacity: 384 kbps Load: 0.083 Capacity: 384 kbps Load: 0.052 Capacity: 115.2 kbps Load: 0.052 Capacity: 115.2 kbps Load: 0.00136 Capacity: 11 Mbps Load: 0.00136 Capacity: 11 Mbps

25. Simulation Environment: Area: 500 * 500 square area. Host: 100~200 hosts are randomly generated. Transmission distance: 100 units Traffic load: uniformly distributed between 1~20 kbps. Hosts can roam around randomly. Gateway: 4 hosts with no mobility.

26. Simulation (cont.) Four combinations of gateway capacities: (128 K, 128K, 128K, 128K) (128 K, 256K, 384K, 512K) (128 K, 256K, 512K, 1024K) (1024 K, 1024K, 1024K, 1024K) Dividing the network unit square area evenly into four 250 * 250 regions. The four gateways are each placed at the center of one region.

27. Simulation (cont.)

28. Conclusions In this paper: Extending the definition of ad hoc networks. Providing two-tier heterogeneous mobile ad hoc network architecture. Proposing several solution for load-balance routing in this architecture. Boundary-Moving solutions Easy to implement and compatible with current IP routing. But in many cases can not lead to a load-balanced status. Host-Partitioning solutions Able to handle situations very well by paying some more routing overheads.

29. i d m l n q e f p r b a c o g h j k