1. Dynamic Source Routing -DSR DSR in Ad Hoc Wireless networks Presenter: Robert Gulde

2. Simple, efficient routing Self Organizing It determines how best to move packets around Self Configuring It determines the routes available w/o existing network structure w/o administration

3. Disconnected Uni-Directional Bi-Directional Network Connectivity Disconnected Uni-Directional Disconnected Uni-Directional Bi-Directional Mixed-Directional Source On Path Destination Disconnect

4. Advantages of DSR Trivially loop free nature of source routing by route information inspection Caching routing information from packets fowarded (ease dropping) Routes established on demand lend to scalability

5. Assumptions & Disadvantages Nodes participate fully Diameter or number of hops is small (5 – 10) Node velocity is small relative to transmission latency Errors are detectable and discarded Nodes may enable promiscuous receive mode (hardware layer passes packets & power consumption may be increased) Can operate without promiscuous mode on or in networks where it is unavailable. Bi & Uni directional capable once a route is established Only one address is used per node (Home Address) Entirely ON-DEMAND, no periodic packets, automatic scaling

6. The need to communicate Route Discovery – occurs when a node needs to send a message to another node and the path is not already known. Route Maintenance – occurs when the network topology has changed such that a route now results in an error. Two things can occur, a node can try a different route if know or try route discovery again.

7. Route Discovery Multiple replies are cached for future use Caching reduces work on new route requests A C D Z L J M N B AZ B,C,D B,J,D L,M,N B A,C,J J,D,Z,N,M,L,A C,D,Z,N,M,L,A A A,B,C,D,Z,N,M,L,A A,B,J,D,Z,N,M,L,A Free:

8. Source and destination in RREQ header Route record is initialized as empty list Unique route request ID, Hop Count If Relay node sees it’s own address or request ID in RREQ then discarded otherwise it is broadcast with its own address Route Discovery (RREQ/RREP) AZIDHCRelay node list,,,,CRC

9. Handling reply messages Relay nodes examine local cache for shorter route, if not it rebroadcasts adding its address to path Route Reply RREP contains outbound path info but may need to determine how to get message back to source (asymmetric problem). If it performs a RREQ to the original sender, it will piggy backs the initial RREQ on its own route discovery (RREQ). A C D Z L J M N B ? Is there a known path back? -Check routing cache -Else, perform Route Discovery (incl. original)

10. Data packets Are stored in sending buffer until a route is discovered This buffer fills and can wait for some time out before deleting the packet The buffer may act as a circular queue As packets remain in queue perform a new route discovery, cached routes deleted on time outs or route error replies

11. Route Maintenance Some what alluded to above: Packet retries, route error RERR responses Send buffer is full causes use of other cached routes, if routes don’t work they are pruned If no cached routes found Route Discovery performed

12. Error recovery RERR messages are used to update cache where link errors have occurred Intermediate links update their cache as well (perhaps recording statistics) Each node may request a ACK to each message or passive acknowledgement by listening for re-transmission or knowledge of underling link protocol - allowing the RERR to be generated

13. Relay node notes Don’t Cache Routes Unless bi-directional (IEEE 802.11, MACA, MACAW) RREP Speed up A C D Z L J M N B ? L BA C D Z J M N ?

14. More Relay node notes Fix-up of discovery process – Must not contain duplicates (the rule) If fails, then may not allow RERR message to get back to node attempting fix up, tables become stale A D Z J M B ? C JJ K

15. RREP Storm (BW) Transfer to Promiscuous before generating RREP t=K( HC - 1 + R ) A D E F C BG D,C,B,G C,B,G G F,B,G E,F,B,G HC=4 HC=3 HC=2 HC=1 B,G

16. Limitations DSR does not support true multicast Controlled flooding within some HC Nodes can employ address filtering in S/W Accomplished as piggy back to RREQ directed to multicast address DSR developed and tested OSI Level 3 However Layer 2 is possible

17. Simulation – Carnegie Mellon Tested using ns-2 on a 1500m X 300m Modeled: physical link layer – space and ground reflection, movement of nodes, power transmission, antenna gain, receiver sensitivity, propagation delay, carrier sense and capture effect 10, 20, or 30 nodes generating 4pkts/sec out of 50 Lucent WaveLAN RF characters approximated

18. Results 2m/sec 20m/sec

19. References David B. Johnson, David A. Maltz, and Josh Broch, "DSR: The Dynamic Source Routing Protocol for Multihop Wireless Ad Hoc Networks," Ad Hoc Networking, edited by Charles E. Perkins, Chapter 5, Addison-Wesley, (2001): 139-172.

20. TDMA Time Division Multiple Access Time division multiple access (TDMA) is digital transmission technology that allows a number of users to access a single radio-frequency (RF) channel without interference by allocating unique time slots to each user within each channel. The TDMA digital transmission scheme multiplexes three signals over a single channel. The current TDMA standard for cellular divides a single channel into six time slots, with each signal using two slots, providing a 3 to 1 gain in capacity over advanced mobile-phone service (AMPS). Each caller is assigned a specific time slot for transmission.

21. CDMA Code Division Multiple Access CDMA is a spread-spectrum technology that allows multiple frequencies to be used simultaneously. CDMA codes every digital packet it sends with a unique key. A CDMA receiver responds only to that key and can pick out and demodulate the associated signal

22. CDMA CDMA is a "spread spectrum" technology, which means that it spreads the information contained in a particular signal of interest over a much greater bandwidth than the original signal. When implemented in a cellular telephone system, CDMA technology offers numerous benefits to the cellular operators and their subscribers. The following is an overview of the benefits of CDMA. 1. Capacity increases of 8 to 10 times that of an AMPS analog system 2. Improved call quality, with better and more consistent sound as compared to AMPS system 3. Simplified system planning through the use of the same frequency in every sector of every cell 4. Enhanced privacy 5. Improved coverage characteristics, allowing for the possibility of fewer cell sites 6. Increased talk time for portables 7. Bandwidth on demand