Announcements CMPE 257 Wireless and Mobile Networking n Sign up for demo slot Spring 2003 Lecture 14 CMPE 257 Spring 2003 1 Today n n CMPE 257 Spring 2003 2 CALM Tang2002 Reliable multicast cont d Bluetooth n n n Like AG e2e approach Initial study comparing SRM to UDP showed SRM performs badly in MANETs Why n n CMPE 257 Spring 2003 3 SRM is heavy duty No congestion control CMPE 257 Spring 2003 4 Impact of Congestion Control on Reliability n n n n CALM CALM uses rate based CC n Data is sent at application rate If congestion NACK sender clocks sending rate based on receivers experiencing congestion n n Congested receivers kept in receiverlist n n Source multicasts next data packet to selected receiver in receiver list Source explicitly requests problematic receiver to ACK If ACK received before time out receiver removed from receiver list When receiver list empty source reverts back to nominal application sending rate Feedback is unicast to the source n CMPE 257 Spring 2003 Evaluation n n n n Generated after N consecutive packets are missing 5 CMPE 257 Spring 2003 6 Results Simulations using QualNet Comparison between CALM SRM and multicast UDP ODMRP Metrics packet delivery overhead delay goodput CMPE 257 Spring 2003 n n CALM outperforms SRM UDP performs surprisingly well except under high traffic loads n n n 7 Proves need for congestion control SRM s main problem is extra load caused by its control packets Congestion control helps but still need relaibility CMPE 257 Spring 2003 8 Reliable Adaptive Lightweight Multicast RALM Tang03 n n n n RALM Operation Congestion control is really important to improve the reliability Simple source based congestion control and recovery Stop and wait rate control Favors reliability over throughput n n n Initially source starts sending at the application rate normal mode Whenever a receiver detects congestion by counting the missing sequence number it sends a NACK to the source Source adds the NACK ed receiver to the receiver list and enters the congestion control mode n CMPE 257 Spring 2003 9 RALM Operation cont d n n n n CMPE 257 Spring 2003 10 RALM Operation cont d While sending next new packet source selects feedback receiver from receiver list in roundrobin Indicates in the data packet that the feedback receiver should ACK back Limits sending rate and waits for ACK from feedback receiver before sending next packet Only feedback receiver replies preventing ACK NACK implosion and indicates the sequence number of lost packet for recovery CMPE 257 Spring 2003 Source maintains a receiver list which is a set of receivers that have reported congestion 11 n n n n Source then multicasts packet requested by feedback receiver Once all the packets are recovered source moves to next receiver in the receiver list The process continues until all the receivers in the receiver list are visited When the receiver list is empty source returns to normal mode CMPE 257 Spring 2003 12 RALM Example RALM Example n n n n CMPE 257 Spring 2003 13 Node 5 and node 7 detects congestion and sends feedback to the source missing sequence numbers are 22 23 24 and 25 for nodes 5 and 7 Source adds them to the receiver list Selects node 5 as the feedback receiver and sends new data Node 5 replies with an ACK requesting packet 22 CMPE 257 Spring 2003 14 RALM Example n n n n Source retransmits packet 22 by multicasting hence node 7 also receives it Finally after recovering all packets by stopand wait approach source removes node 5 from receiver list and moves to the next receiver which is node 7 Node 7 replies with ACK saying that all packets are received Node 7 removed from the receiver list and source returns back to normal mode CMPE 257 Spring 2003 15 Simulation Results CMPE 257 Spring 2003 16 Reliable Delivery Ratio over MAODV Experimental Setup n n n n n n n Qualnet simulator 802 11 MAC with 371m radio range 50 nodes in a 1500x1500 area Random node placement Two different underlying multicast routing protocols MAODV and ODMRP Application data size 512 bytes 5 sources and 10 group members CMPE 257 Spring 2003 17 Reliable Delivery Ratio over ODMRP CMPE 257 Spring 2003 CMPE 257 Spring 2003 18 Average Goodput MAODV 19 CMPE 257 Spring 2003 20 Average Goodput ODMRP Summary and Ongoing Work n n RALM reliability congestion control Make control mechanisms scalable n n n n n CMPE 257 Spring 2003 Select smaller set of receivers maybe 1 Use rate based CC instead of stop and go Interaction with MAC layer Comparison with AG and use different routing protocols Local recovery 21 CMPE 257 Spring 2003 22 Cable Replacement Bluetooth 1 Mb s n n CMPE 257 Spring 2003 23 Range 10 meters Single chip radio 1 Low power low cost Why not use Wireless LANs power cost CMPE 257 Spring 2003 24 Seamless Communication n Synchronization As soon as the Web browser is invoked on the mobile computing device link established with cellular phone ISP contacted user is connected n CMPE 257 Spring 2003 Automatic synchronization of calendars address books business cards 25 Cordless Headset CMPE 257 Spring 2003 Usage scenarios examples Cordless headset n n n n Multiple device access Hands free operation n n n n CMPE 257 Spring 2003 26 27 Data access points Synchronization Headset Conference table Cordless computer Computer speakerphone CMPE 257 Spring 2003 28 Bluetooth on the market PC cards Cell phones Head sets Chip sets Company Features Applications Cost Toshiba Motorola Digianswer File Transfer Dial Up Networking LAN access Fax File Transfer Dial Up Networking LAN access Fax File Transfer Dial Up Networking LAN access Fax E mail Unconscious connection File Transfer Dial Up Networking LAN access Fax E mail Unconscious connection 169 200 Basic BT Radio stack Embedded or Host stack Programmable 500 20 dBm 100 m Point to multipoint No Scatternet 0 dBm 10 m Point to multipoint No Scatternet 10 m user user 100 m user Base Station Point to multipoint SW FW upgradeable 10 m user user Point to point Connectivity Battery for the cell phone 10 m user user Point to point ARM processor USB RFCOMM ports IBM TDK 3COM Nokia Ericsson Sigma Bluetooth WG History n 169 n 149 n 149 n n 1500 CMPE 257 Spring 2003 n n n n 3Com Lucent Microsoft Motorola February 2000 1 800 adopters February 2001 version 1 1 out CMPE 257 Spring 2003 CMPE 257 Spring 2003 30 Goals May 1998 Public announcement of Bluetooth SIG July 1999 1 0A spec 1 500 pages published December 1999 version 1 0B released December 1999 promoters increases to 9 n n Promoter company