Specific Systems: Broadband Powerline Communications Networks (PLCs) #16

Transcription

1 Specific Systems: Broadband Powerline Communications Networks (PLCs) #16 Victor S. Frost Dan F. Servey Distinguished Professor Electrical Engineering and Computer Science University of Kansas 2335 Irving Hill Dr. Lawrence, Kansas Phone: (785) FAX:(785) All material copyright 2006 Victor S. Frost, All Rights Reserved #16 1 Outline What is a PLC? Topology Channel characteristics Noise characteristics A MAC protocol for PLC networks Assumptions Operation MAC protocol is an example of: Earliest deadline first scheduling Scheduling algorithm that accounts for retransmissions #16 2

2 What is a Broadband PLC Network Powerlines have been used for: Low speed data transport for many years Control Telemetry In home power wiring have been used for networking Broadband PLC is an alternative for internet access-last mile #16 3 Broadband PLC topology Base station Internet Modified from: Design and performance evaluation of an hybrid reservation Polling MAC protocol for power-line communications G. Bianchi, Tinnirello, and G. Conigliaro, International Journal Of Communication Systems Int. J. Commun. Syst. 2003; 16: Access Units From: Distributed MAC protocols and priority oriented scheduling for a PLC access network Sundaresan, S. Anand, S. Srikanthn,y and C. N. Krishnan, International Journal Of Communication Systems Int. J. Commun. Syst. 2003; 16: #16 4

3 Broadband PLC System Architecture OM = outdoor master OR = outdoor repeater OAP = outdoor access point IA = Indoor adaptor IC = Indoor Controller From: Broadband PLC Access Systems and Field Deployment in European Power Line Networks Weilin Liu, Hanspeter Widmer, and Philippe Raffin, IEEE Communications Magazine, May #16 5 PLC Channel Time varying Frequency dependent EMC issues with amateur radio operators CENELEC (European Committee for Electrotechnical Standardization) * Europe khz 5 mw 144 kb/s Broadband PLC:1-30 Mhz *Niovi Pavlidou, Aristotle University of Thessaloniki A. J. Han Vinck, Javad Yazdani and Bahram Honary, Power Line Communications: State of the Art and Future Trends, IEEE Communications Magazine, April 2003 #16 6

4 Channel Transfer Function Characteristics * *Klaus Dostert, Powerline Communications, Prentice Hall, 2001 #16 7 PLC noise environment Colored background noise Source: Sum of low power noise sources Timescale: minutes to hours Narrowband noise Source: broadcast stations Timescale: varies with time of day Periodic impulsive noise asynchronous to the main frequency Source: Switching power supplies Timescale: ms (repetition rate Hz) Periodic impulsive noise synchronous to the main frequency Source: appliances Timescale: ms (repetition rate Hz or 60Hz and 120Hz), duration us Asynchronous impulsive noise Source: Switching transients in the power grid Timescale: duration us-ms and level 50dB above background noise level major source of errors #16 8

5 Estimation of Channel Capacity for Broadband PLC Networks Based on last mile capacity analysis in: Powerline Communications, Klaus Dostert, Prentice Hall 2001 Channel characteristics Noise characteristics Link Length m Theoretical Realizable Best Case 250 Mb/s 100 Mb/s Worst Case 14 Mb/s 5 Mb/s #16 9 A MAC protocol for Broadband PLC Networks Focus on protocol discussed in: Design and performance evaluation of an hybrid reservation Polling MAC protocol for power-line communications G. Bianchi, Tinnirello, and G. Conigliaro, International Journal of Communication Systems Int. J. Commun. Syst. 2003; 16: Assumptions Fast ARQ is better than FEC in impulsive noise environments like broadband PLC FEC has a constant bandwidth penality Fast ARQ is only invoked when errors, here induced via impulsive noise. Half duplex channel: same resources used for up and down stream communications Time division Frames Slots Minislots #16 10

6 Types of Slots: -Downlink -Uplink -Reservation F=Framing C i =Command -AU ID -Acks From: Design and performance evaluation of an hybrid reservation Polling MAC protocol for power-line communications, G. Bianchi, Tinnirello, and G. Conigliaro, International Journal Of Communication Systems Int. J. Commun. Syst. 2003; 16: #16 11 A MAC protocol for Broadband PLC Networks DLW Link layer at AU send ACK on a slot by slot basis fast retransmission UPL Supports one fixed length packet AU s request slots BS grants slots Acks for UPL from AU i are piggybacked in the control in next DLW even if slot not destine for AU i RSV AU has packet to send contending state Reservation slots are subdivided into minislots A random access protocol like ALOHA is used for contention When BS receives a minislot for AU i a grant for AU i is placed in a polling list The command in the next DLW contains a reservation ack #16 12

7 A connection set-up is used to identify all AU s that can access the channel AU s are given a connection ID AU s provide traffic/qos parameters Maximum tolerable delay (MD) Data Rate expressed as interarrival time (IT), maybe dynamically updated for VBR traffic For each AU the BS also tracks The remaining lifetime head-of-line packet = MD W; W is waiting time for HOL packet Number of retransmission attempts AU states Idle Active Contending #16 13 A MAC protocol for Broadband PLC Networks Active AU is granted slots according to scheduling rules Transition from Active Idle: AU notifies BS to stop sending grants Transition from Idle Active: AU enters contending state Controlling the frequency of RSV slots Too frequent uses capacity Not frequent enough high delay Proposed process Issue RSV slot every T sec If one collision of a minislot in RSV then send consecutive RSV slots subject to QoS constraint #16 14

8 The BS is designed to be an MD max -1 earliest deadline first scheduler Let MD max = Max MD of all AU s Set up a polling register that controls the order of polling the AU s k AU placed at position k in the polling register implies that the relevant packet must be transmitted on the channel in at most k slots, otherwise it expires Upon reservation the AU ID is placed a position MD-W or below. 0 ID for target AU transmission time #16 15 A MAC protocol for Broadband PLC Networks If no retransmissions then the scheduler issues grants for the AU in the lowest position in the polling register The AU in the bottom position of the polling register is always transmitted, it is that packets last opportunity. If retransmissions then the scheduler issues grants for the AU in the lowest position in the polling register and a retransmission counter #16 16

9 At the end of a transmission the BS learns Transmission successful If the AU is active the next grant is scheduled interarrival time (IT) slots later Transmission successful If the AU transitions from active to idle the AU is removed from polling register Transmission unsuccessful Leave in same position in polling register and increment the retransmission counter Note that MAC/scheduled deals with retransmissions #16 17 A MAC protocol for Broadband PLC Networks The polling register is shifted down each time slot. Note if packet in bottom of the polling register is corrupted then it is lost, that is a retransmission will exceed MD for that AU. Use of retransmission counter the transmission grant is assigned to the station in the lowest register position, among the ones with lowest retransmission counter value #16 18

10 A MAC protocol for Broadband PLC Networks Example: 3 AU s Assume W A = W b =W C = 0 Minislot for A arrives first MD = 5 so place in 5 th position in polling register Minislot for B arrives second MD = 4 so place in 4 th position in polling register Minislot for C arrives last MD = 4, 4 th position in polling register is full, so place in 3 rd position in polling register A B C RSV Slot Bold = New reservation #16 19 A MAC protocol for Broadband PLC Networks AU C is lowest in polling register so it is transmitted Assume this packet is corrupted Left in same position before shift down Increment retransmission counter shown by X #16 20

11 B granted next Lowest in polling register with lowest retransmission count Assume B successful #16 21 A MAC protocol for Broadband PLC Networks Using IT B = 3 MD = 4: a new reservation for B in placed in the 4 th Note A is next to be granted and assume it is corrupted Increment its retransmission counter So stays in polling register and after shift down is in the 2 nd location New reservation for A is not placed in the polling register until the previous one is cleared out #16 22

12 C is given a grant next because it is in the bottom position of the polling register Assume this is successful So a new reservation for C is place in the polling register because it has an MD = 4 #16 23 A MAC protocol for Broadband PLC Networks In time slot 5 a grant is given to AU B Assume this is transmission is successful #16 24

13 AU A is given a grant for slot 6 Assume this is successful Now new reservation for AU A can be placed on the polling register; should go in position 2, but after shift C is there so it goes in position 1 #16 25 A MAC protocol for Broadband PLC Networks #16 26

14 Multiple classes of service Allow more than one AU per position in the polling register Low priority AU granted after all high priority AU View as multiple polling registers; when the high priority polling register is empty the low priority polling register is used to make grants Rearrange the polling register High priority AU s are substituted for low priority AU s in the polling register #16 27 A MAC protocol for Broadband PLC Networks Performance Evaluation* Focus on Packet voice with on/off model Ave on time = 1 sec Ave off time = 1.3 sec Durations ~ exponentially Slot time 576 bits payload Command Packet header Guard time Packet interarrival time = 16 ms Rates 720 Kb/s, 1.44 Mb/s and 2.88 Mb/s Noise Glibert model Good/Bad states Bad state models impulse noise IMT mean time between noise bursts * From: Design and performance evaluation of an hybrid reservation Polling MAC protocol for power-line communications, G. Bianchi, Tinnirello, and G. Conigliaro, International Journal Of Communication Systems Int. J. Commun. Syst. 2003; 16: #16 28

15 *, ** F=R/(576bits/16ms) * *From: Design and performance evaluation of an hybrid reservation Polling MAC protocol for power-line communications, G. Bianchi, Tinnirello, and G. Conigliaro, International Journal Of Communication Systems Int. J. Commun. Syst. 2003; 16: **Also see: Hrasnica H, Haidine A, Lehnert R. Reservation MAC protocols for powerline communications. Proceedings of ISPLC th International Symposium on Powerline Communications and its Applications, April 3 6, 2001, Sweden, #16 29 Conclusions MAC protocol is an example of: Earliest deadline first scheduling Scheduling algorithm that accounts for retransmissions PLC access networks operate in a harsh environment Available capacity is not very high Requires MAC protocols to overcome impulsive noise Standards still evolving #16 30

16 References Begain, K., et al., Modeling of a PLC access network, in First Polish-German Teletraffic Symposium. 2000: Dresden, Germany. Bianchi, G., I. Tinnirello, and G. Conigliaro, Design and performance evaluation of an hybrid reservation-polling MAC protocol for power-line communications. International Journal of Communication Systems, (5): p Klaus Dostert, Powerline Communications, Prentice Hall, 2001 Hrasnica H, Haidine A, Lehnert R. Reservation MAC protocols for powerline communications. Proceedings of ISPLC th International Symposium on Powerline Communications and its Applications, April 3 6, 2001, Sweden, Hrasnica, H. and A. Haidine. Modeling MAC Layer for Powerline Communications Networks,. in Internet, Performance and Control of Network Systems, part of SPIE's symposium on Information Technologies Boston, MA, USA. Hrasnica, H., A. Haidine, and R. Lehnert. Performance comparison of reservation MAC protocols for broadband powerline communications networks. in Proceedings of ISPLC th International Symposium on Powerline Communications and its Applications Malm.o, Sweden. Hrasnica, H., A. Haidine, and R. Lehnert, Broadband powerline communications networks : network design. 2004, Chichester, England ; Hoboken, NJ: Wiley. xiii, 275 p. Hrasnica, H. and R. Lehnert. Investigation of MAC protocols for broadband PLC networks under realistic traffic conditions. in 7th ISPLC Kyoto, Japan. #16 31 References Lin, Y.-J., et al. Periodic contention-free multiple access for power line communication networks. in 19th Internation Conference on Advanced Information Networking and Applications, Weilin Liu, Hanspeter Widmer, and Philippe Raffin, Broadband PLC Access Systems and Field Deployment in European Power Line Networks, IEEE Communications Magazine, May Majumder, A. and J. Caffery, Jr., Power line communications. Potentials, IEEE, (4): p Mollenkopf, J., Presentation to Cincinnati IEEE Meeting p Pavlidou, N., et al., Power line communications: state of the art and future trends. Communications Magazine, IEEE, (4): p Sundaresan, S., et al., Distributed MAC protocols and priority oriented scheduling for a PLC access network. International Journal of Communication Systems, (5): p Sutterlin, P. and W. Downey. A power line communication tutorial - challenges and technologies. in 1998 International Symposium on Power-line Communications and its Applications Tokyo, Japan. Weilin, L., H. Widmer, and P. Raffin, Broadband PLC access systems and field deployment in European power line networks. Communications Magazine, IEEE, (5): p #16 32