Energy Efficient MAC Protocols For Ad Hoc Networks by Vanitha SivaSubramaniam Distributed System Design Professor: Dr. Wu Jie 4/10/2003

2 OUTLINE Ad Hoc Networks Power Consumption Solutions For Power Limited Devices Energy Efficient MAC Protocols Conclusion

3 AD HOC NETWORKS Wireless terminals communicating with one another with no pre-existing infrastructure in place –Infrastructure-less network Application –Conferencing –Home networking –emergency services –sensor networks

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5 Problems in Ad Hoc Wireless Networks Hidden Terminal Exposed Terminal Energy of individual node and of the network as a whole Mobility

6 Power Usage in Different Modes ModelTransmitReceiveStandby GEC Plessey DE GHz 1.8 W0.6 W0.05 W Lucent’s 15 dBm 2.4 GHz Wavelan radio 1.75 W1.475W0.08 W

7 Power Consumption in Ad Hoc Networks Wireless hosts are powered by batteries which provide a limited amount of energy Third Generation wireless networks carry diverse multimedia traffic – Data, voice and video

8 Solutions for Power Limited Devices Low power system design focus on power usage in CPU, transmitter and receiver embedded in portable devices Network protocols are designed for energy efficiency Recent research has been devoted to low-power wireless access protocols like the MAC(Medium Access Protocols)

9 Protocol Stack of a Wireless System Application & Services OS & Middleware Network Data Link Physical MAC Protocol

10 Functions of Data Link layer Responsible for wireless link error control Security (Encryption and Decryption) Mapping network layer packets into frames Transmission and reception of frames over the air

11 Principles to Conserve Energy at DATA Link (MAC) Level Collision Avoidance Energy Conservation –Power saving in different mode –Switching between modes

12 Medium Access Control Protocol The MAC protocol simply determines when a node is allowed to transmit its packets and typically controls all access to the physical layer MAC protocol is responsible for allocating the time frequency space among the mobiles sharing the wireless channel

13 DATA Communication in AD Hoc Networks NODE A (Sender) NODE B (Receiver) NODE A Transmitting DATA to NODE B RTS- Request To Send CTS-Clear To Send ACK-Acknowledge

14 Energy Efficient MAC Protocols MACA Protocols –MACA ( Multiple Access with Collision Avoidance) –MACA-BI( By Invitation) CSMA Protocols –DFWMAC (Distributed Foundation Wireless MAC) –EY-NPMA (Elimination Yield – Non- Preemptive priority Multiple Access) –DBTMA ( Dual Busy Tone Multiple Access)

15 Continue.. Power Conserving MAC Protocols –MARCH (Media Access with Reduced handshake) –PAMAS (Power–Aware Multi-Access Protocol with Signaling) Power Control MAC Protocols –PCM ( Power Control MAC)

16 Multiple Access with Collision Avoidance (MACA) Three way handshake, RTS-CTS-DATA Power control feature: Inhibits a transmitter when a CTS packet is overheard to limit power Less DATA packet collisions Resolve the hidden terminal and exposed node problem

17 Handshake in MACA NODE A (Sender) NODE B (Receiver)

18 MACA-BI( By Invitation) Two way handshake. RTR (Ready To Receive)-DATA Receiver sends invitation to the sender Reduces transmit/receive turn around time ( ie., up to 25 microseconds) Less control packet collisions compared to MACA

19 Handshake in MACA-BI NODE A (Sender) NODE B (Receiver) RTR- Ready To Receive

20 DFWMAC ( Distributed Foundation Wireless MAC) Four way handshake RTS-CTS-DATA-ACK A sender node waits for DIFS( Distributed Inter-Frame Space) before making an RTS attempt A node enters a SIFS ( Short Inter Frame Space) before sending an ACK frame, DATA and CTS NAC (Network Allocation Vector) indicates the duration of the current transmission

21 Four Way Handshaking in DFWMAC Sender node Receiver node Others RTS CTS DIFS DATA SIFS ACK SIFS NAV(RTS) NAV(CTS) NAV(DATA) NAV- Network Allocation Vector

22 EY-NPMA (Elimination Yield-Non- Preemptive Priority Multiple Access) The node senses the medium and starts transmitting if it finds the channel idle Channel busy: The channel access has three Phases –Prioritization Phase: Priority is decided –Contention Phase : Nodes of same priority contend and one station wins Elimination Phase Yield Phase –Transmission Phase : DATA transmission

23 DBTMA (Dual Busy Tone Multiple Access) Two channels –Data Channel- Data packets –Control Channel- RTS and CTS Two out-of-band busy tones –Receive busy tone –Transmit busy tone Resolve Hidden terminal problem

24 Handshake in DBTMA NODE A (Sender) NODE B (Receiver) Receive Busy Tone Transmit Busy Tone

25 MARCH (Media Access with Reduced Handshake) Less number of handshakes : Reduces the control overhead by reducing the number of RTS’s along the multi-hop path Exploits overhearing by using omni directional antenna

26 Handshake Mechanism in MARCH RTS1 CTS1 DATA CTS2 DATA CTS2 AB C D

27 PAMAS ( Power Aware Multi- Access Protocol with Signaling) Separate signal channel Conserves battery power : Power off nodes not transmitting or receiving Wait-for CTS state : – After a node sends RTS Await DATA state: –After a node sends a CTS Transmit DATA state: – After a node gets a CTS Binary Exponential Backoff (BEB): Doubling wait time in sender node

28 Power Control MAC Protocol Power Control MAC (PCM) –PCM periodically increases the transmit power to max. power during the DATA packet transmission –PCM achieves throughput comparable to IEEE with less energy

29 CBD A E Transmission Range, Carrier Sensing Zone and Carrier Sensing Range Transmission Range Carrier Sensing Zone Carrier Sensing Range

30 Power Control MAC (PCM) Source and destination transmit the RTS and CTS using max. power. Source transmit DATA using a lower power level Source node periodically transmits DATA at max. power, to avoid collision Destination transmits ACK using minimum power required to reach the source node

31 A B DATA RTS CD CTS ACK DATA Transmission -Power Control MAC Protocol AB Sender NodeReceiver Node

32 CONCLUSION Of the many protocols existing only few of them focus on the conservation of battery power MACA Vs MACA-BI: MACA-BI reduces transmit/receive turn around time, hence saves power while changing the mode –MACA-BI has less control packet collisions compared to MACA –In CBR ( Constant Bit Rate) traffic MACA-BI has high efficiency, but in bursty traffic performance degrades compared to MACA

33 Continue DFWMAC Vs EY-NPMA: DFWMAC has more throughput than EY-NPMA [2] PAMAS : Power saving range 10%-50% [4] without affecting delay or throughput PCM: Power Control MAC requires a frequent increase and decrease in transmit power, hence implementation difficult [3]

34 References 1. Ad Hoc Mobile Wireless Networks: Protocols and Systems, C-K Toh. 2. Ajay Chandra V.Gummalla and John O. Limb, Georgia Institute of Technology, “Wireless Medium Access Control Protocol”, IEEE communications Survey, Eun-Sun Jung and Nitin H. Vaidya, “A Power Control MAC Protocol for Ad Hoc Networks”, MOBICOM’02, September 23 – 28, Suresh Singh and C.S.Raghavendra, “PAMAS-Power Aware Multi-Access Protocol With Signalling for Ad hoc networks”, in ACM Computer Communications Review, July C-K. Toh, Vasos Vassiliou, Guillermo Guichal and C-H. Shih,”March: A Medium Access Control Protocol for Multihop Wireless Ad Hoc Networks”, Proceedings of IEEE Military Communications Conference( MILCOM), Los Angeles,2000.

35 Continue 6. Fabrizio Talucci and Mario Gerla, “MACA-BI(MACA By Invitation): A Wireless MAC Protocol for High Speed Ad Hoc Networking”, Proc. IEEE ICUPC ’97, Kyu-Tae Jin and Dong-Ho Cho, “Optimal Threshhold Energy level of Energy Efficient MAC for Energy-limited Ad-hoc Networks, IEEE Jyh-Cheng Chen, Krishna m. Sivalingam, Prathima Agarwal, and Shalinee kishore, “ A Comparison of MAC Protocols for Wireless Local Networks Based on Battery Power Consumption”, IEEE INFOCOM, Mar J. Weinmiller et al., “Performance Study of Access Control in Wireless LAN’s – IEEE DFWMAC and ETSI RES 10 HIPERLAN”, Mobile Networks and Application,vol. 2, no1, 1997, pp

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