1. Distributed Dynamic Channel Allocation in Wireless Network

2. Cellular Network Cellular network consists of cells.
Mobile service station (MSS) is incharge of a cell.
MSS makes all decision for channel allocation.

3. Cellular Network
Message passing between MSS & its neighbors to avoid co-channel interference.
Time stamped requests are sent by MSS to neighboring MSS for channel allocation.
MSS
Neighbour
MSS
Time stamped Request

4. Message Types MSS REQUEST RESPONSE Neighboring MSS CHANGE_MODE RELEASE
ACQUISITION

5. Message Types REQUEST- requesting to acquire a channel.
RESPONSE- responding to the request from receiving node.
CHANGE_MODE- mode changed from local to borrowing or vice versa.
RELEASE- sending node has released the channel.
ACQUISITION- sending node has acquired a channel.

6. Node Class PR: set of primary channels.
Use: set of currently used channels
Iuse: Set of channel used by interfering node
Mode: represents mode of the node i.e. Local or borrowing.
Waiting: number of requests not received ACK.
Pending: check if any pending request.
Rounds: number of attempts to acquire channel in borrowing mode.

7. Implementation There are two types of request channel modes:
1. Local – have sufficient primary channel
2. Borrowing – borrow channel from other node (not implemented completely)
Long and Complex java coding.

8. Verification
Java PathFinder
Properties
Errors

9. Java PathFinder (JPF)
Explicit state software model checker for Java bytecode.
Focus is on finding bugs in Java programs
- concurrency related: deadlocks, (races), missed signals etc.
- Java runtime related: unhandled exceptions, heap usage, etc.
- and also: complex application specific assertions

10. Property to Verify 1 Deadlock free (theoretically)
local mode: all request proceed in parallel resulting no deadlock.
borrowing mode: requests are responded based on timestamp.
Verify
- No circular wait due to the use of timestamp.

11. Property to Verify 2 No Data Races (theoretically)
Any channel r is not acquired by two interfering cells.
Verify
- For no two node threads allocate(r) = true.

12. Errors! 1. no main method() navy 21 % jpf Node
[SEVERE] JPF exception, terminating: no main() method in Node
Add main method that invokes thread to request channel.

13. Errors! 2. Out of Memory [SEVERE] JPF out of memory
Increase maximum Heap size to 1024

14. Future Work Java implementation of borrowing mode.
Verify no violation (assertion error) occurred while checking both deadlock and race Condition using JPF.
Playing with JPF to check other properties.

15. Thank You Questions ?