QUALITY OF SERVICE DESIGN ISSUES IN MULTIMEDIA COMMUNICATIONS OVER POWER LINE NETWORKS SRINIVAS KATAR

Transcription

1 QUALITY OF SERVICE DESIGN ISSUES IN MULTIMEDIA COMMUNICATIONS OVER POWER LINE NETWORKS By SRINIVAS KATAR A DISSERTATION PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY UNIVERSITY OF FLORIDA 2006

2 Copyight 2006 by Sinivas Kata

3 I dedicate this wok to my paents, Katai Lakshmipathi Raju and Kishna Kumai

4 ACKNOWLEDGMENTS I would like to thank my paents fo thei suppot and encouagement ove all these yeas. None of this wok would have possible without them. I would also like to expess my heatfelt gatitude to my wife Keeti fo he suppot and undestanding thoughout this endeavo. I would especially like to thank Lay Yonge and Intellon Copoation fo allowing me to wok pat time on my PhD. I would like to thank my colleagues, Bent Mashbun, Kaywan Afkhamie and Manjunath Kishnam fo thei valuable feedback. Woking with them has always been a pleasue. Finally, I would like to thank my advisos, D Haniph Latchman and D Richad Newman, fo thei valuable guidance thoughout my studies. I would also thank D Osca Cisalle and D Tan Wong fo being pat of my PhD supevisoy committee. iv

5 TABLE OF CONTENTS page ACKNOWLEDGMENTS... iv LIST OF TABLES... viii LIST OF FIGURES... ix ABSTRACT... xiii CHAPTER 1 INTRODUCTION BACKGROUND Low Bandwidth PLC Regulatoy constaints Technologies X CEBus LonWoks High Bandwidth PLC Regulatoy constaints Channel chaacteistics Attenuation chaacteistics Noise chaacteistics Technologies HOMEPLUG 1.0 TECHNOLOGY DESCRIPTION AND PERFORMANCE EVALUATION Home Netwoking Solutions New wie solution Wieless solution No new wie solutions HomePlug 1.0 Technology HomePlug Physical laye HomePlug 1.0 MAC Fame fomats...25 v

6 Channel access mechanism Segmentation and eassembly mechanism HomePlug 1.0 Pefomance based on Simulations HomePlug 1.0 Field Test Results and Compaison with IEEE b/a Expeiment method Results IEEE a indoo pefomance IEEE b and HomePlug POWER LINE MULTIMEDIA NETWORKING CHANNEL ADAPTATION BASED ON CYCLO-STATIONARY NOISE CHARACTERISTICS Intoduction Channel Measuements Channel Adaptation Computation of Channel Capacity Discussion of Results Conclusions MAC FRAMING MAC Faming and Faming Efficiency MAC Faming Stategies Simple concatenation Concatenation with explicit demacation Level faming Efficiency Analysis Simple concatenation Concatenation with explicit demacation level faming Compaison of Pefomance between vaious Faming Schemes Conclusions ALLOCATION REQUIREMENTS FOR SUPPORTING LATENCY BOUND TRAFFIC Intoduction Allocation Requiements without Tansmission Oveheads Fixed Allocation, L = Fixed Allocation, L > Allocation Requiements with Tansmission Oveheads Fixed Allocation Aveage Allocation Effect of Tansmission oveheads on Allocation Requiements Conclusions...92 vi

7 8 BEACON SCHEDULE PERSISTENCE TO MITIGATE BEACON LOSS Intoduction Pesistent Beacon Schedules Efficiency Analysis Non-pesistent schedule Pesistent cuent schedules Pesistent peview schedules Pesistent cuent and peview schedules Efficiency compaison QoS Consideations Lowe Bound on PLEP Non-pesistent schedules Pesistent cuent schedules Pesistent peview schedules Pesistent cuent and peview schedules Lowe Bound compaison Makov Chain Analyses Non-pesistent beacon schedules Pesistent cuent schedules Pesistent peview schedules Pesistent cuent and peview schedules Compaison of Pesistent Scheduling Mechanism Conclusions CONCLUSIONS AND FUTURE WORK LIST OF REFERENCES BIOGRAPHICAL SKETCH vii

8 LIST OF TABLES Table page 3-1 Fame Contol infomation fields HomePlug 1.0 simulation esults Bandwidth and QoS equiements fo multimedia applications MAC faming oveheads...62 viii

9 LIST OF FIGURES Figue page 1-1 FCC and CENELEC fequency band allocation Powe line channel impulse esponse Channel fequency esponse Noise geneated by light dimme Noise geneated by yad light Noise geneated by halogen lamp Noise geneated by hai dye Long Fame fomat Shot Fame fomat Pioity esolution and backoff scheme IEEE a indoo pefomance HomePlug 1.0 and IEEE b indoo pefomance Channel measuement setup Pefomance gain in PHY data ates as a function of macoslot size Pefomance gain in MAC data ates as a function of macoslot size Aveage gain in MAC and PHY data ates MAC faming Pocess Simple concatenation Concatenation with explicit demacation Level MAC faming Simple concatenation- efficiency with vaying FEC block o ate and N = ix

10 6-6 Simple concatenation efficiency with vaying numbe of FEC blocks and p = Explicit demacation based concatenation - efficiency with vaying FEC block eo ate and N = Explicit demacation based concatenation - efficiency with vaying numbe of FEC blocks and p = Level faming - efficiency with vaying FEC block eo ate and N = Level faming - efficiency with vaying numbe of FEC blocks and p = Pefomance compaison of vaious MAC faming stategies with vaying FEC block eo ate, N= 25, L msdu = Tansmission oveheads in HomePlug AV Illustation of delayed etansmission stategy State tansition diagam fo no MPDU ovehead case Excess allocation as a function of FEC block eo pobability when no tansmission ovehead pesent Aveage packet loss pe packet loss event when no tansmission oveheads ae pesent Tansmission oppotunities equied to achieve PLEP = 10-5 at vaious FEC block eo pobabilities Fixed Allocation estimation eo fo N = 100 and L = 1, 2, 3, 4, 6, and Pobability distibution function of the Fixed Allocation estimation eo Aveage packet loss pe packet loss event when tansmission oveheads ae pesent Aveage Allocation estimation eo fo N = 100 and L = 1, 2, 3, 4, 6 and Pobability distibution function of the Aveage Allocation estimation eo Pecentage diffeence in Fixed Allocation and Optimal Allocation fo N = [50, 200], p= [0.01, 0.10] Pecentage diffeence in Aveage Allocation and Optimal Allocation fo N = [50, 200], p= [0.01, 0.10] Effective tansmission ovehead fo Aveage Allocations with N = 50 and x

11 8-1 Example of 2-pesistent cuent schedules Example of 2-pesistence peview schedules Example of 2-pesistent cuent and peview schedules Efficiency loss compaison fo vaious scheduling stategies Illustation of elationship between latency and pesistent peview schedule State tansition diagam fo non-pesistence beacon schedules State tansition diagam fo 2-pesistence cuent schedules Illustation of state changes in Makov chain fo 2-pesistent peview schedule State tansition diagam fo 2-pesistence peview schedules State tansition diagam fo 2-pesistence cuent and peview schedules Minimum latency equied to achieve PLEP of {10-5, 10-7 } at vaious beacon loss pobabilities in a system with non-pesistent schedules Minimum latency equied to achieve PLEP of {10-5, 10-7 } at vaious beacon loss pobabilities in a system with -pesistent cuent schedules Minimum latency equied to achieve PLEP of {10-5, 10-7 } at vaious beacon loss pobabilities in a system with -pesistent peview schedules Minimum latency equied to achieve PLEP of {10-5, 10-7 } at vaious beacon loss pobabilities in a system with -pesistent cuent and peview schedules Compaison of minimum latency suppoted by vaious scheduling stategies at vaious beacon loss pobabilities fo PLEP = Compaison of minimum latency suppoted by vaious scheduling stategies at vaious beacon loss pobabilities fo PLEP = Minimum schedule pesistence equied to suppot L = 2 fo vaious scheduling stategies at PLEP = Minimum schedule pesistence equied to suppot L = 2 fo vaious scheduling stategies at PLEP = Ove allocation equied to suppot vaious latencies in a system with nonpesistent beacon schedules, N = 100, PLEP = Ove allocation equied to suppot vaious latencies in a system with 2- pesistent cuent schedules, N = 100, = 8,PLEP = xi

12 8-21 Ove allocation equied to suppot vaious latencies in a system with 2- pesistent peview schedules, N = 100, = 4,PLEP = Ove allocation equied to suppot vaious latencies in a system with 2- pesistent cuent and peview schedules, N = 100, = 4,PLEP = Latencies equied to suppot a steam with optimal ove allocation fo a system with non-pesistent schedules fo PLEP = {10-5, 10-7 } Latencies equied to suppot a steam with optimal ove allocation fo a system with -pesistent cuent Schedules fo PLEP = {10-5, 10-7 } Latencies equied to suppot a steam with optimal ove allocation fo a system with -pesistent peview schedules fo PLEP = {10-5, 10-7 } Latencies equied to suppot a steam with optimal ove allocation fo a system with -pesistent peview schedules fo PLEP = {10-5, 10-7 } Compaison of optimal latency suppoted by vaious scheduling stategies at vaious beacon loss pobabilities fo N = 100, PLEP = Compaison of optimal latency suppoted by vaious scheduling stategies at vaious beacon loss pobabilities fo N = 100, PLEP = Minimum schedule pesistence equied to suppot L = 2 with X = 1 fo vaious scheduling stategies at PLEP = Minimum schedule pesistence equied to suppot L = 2 with X = 1 fo vaious scheduling stategies at PLEP = xii

13 Abstact of Dissetation Pesented to the Gaduate School of the Univesity of Floida in Patial Fulfillment of the Requiements fo the Degee of Docto of Philosophy QUALITY OF SERVICE DESIGN ISSUES IN MULTIMEDIA COMMUNICATIONS OVER POWER LINE NETWORKS By Sinivas Kata May 2006 Chai: Haniph A. Latchman Cochai: Richad E. Newman Majo Depatment: Electical and Compute Engineeing Home Netwoking is one of the majo hudles in enabling ubiquitous data and multimedia distibution. Most houses ae not equipped with specialized wiing fo netwoking puposes and etofitting them with new wiing is pohibitively expensive. Hence, the use of existing in-home powe line infastuctue fo netwoking puposes can go a long way towads solving the in-home connectivity poblem. In this dissetation we fist investigate the viability of powe line communications (PLC) by evaluating the pefomance of HomePlug 1.0. Detailed event based simulation models wee used to show that HomePlug 1.0 can povide a maximum UDP and TCP data ates of 7.86Mbps and 5.90Mbps. Extensive field testing in 20 houses showed that HomePlug 1.0 povides an aveage of 2.3Mbps highe thoughput compaed to IEEE b. While HomePlug 1.0 is good enough fo data netwoking, it will not be able to suppot the newly emeging multimedia applications like audio and video steaming. We xiii

14 study thee issues that the new geneation PLC systems need to ovecome to enable multimedia communications: (a) AC line cycle vaiation in noise, (b) Impulse noise, and (c) Beacon Loss. We use channel chaacteization measuements on 72 channels to investigate the pefomance enhancements that can be achieved by using a channel adaptation mechanism that is synchonized to the AC line cycle. The esults show that a 30% impovement in physical laye (PHY) data ates can be obtained by continuously adapting to the AC line cycle. A time slot based adaptation that is moe suitable fo pactical systems povided an aveage of 10% impovement in MAC data ates. To effectively ovecome impulse noise, we popose a novel 2-level MAC faming mechanism that enables efficient etansmissions. Ou simulations and analysis show that this mechanism povides linea degadation in pefomance even unde high FEC Block eos. Futhe investigation of the effect of tansmission oveheads on efficiency showed that low data ate, low latency QoS applications can incu significant loss in efficiency unde high FEC block eos. Hence, PLC channel adaptation should take into account the application QoS equiements to optimize the oveall system capacity. Due to the uneliable natue of the powe line channels, beacon eception cannot always be guaanteed. We investigate vaious pesistent scheduling appoaches to mitigate beacon loss. Ou analysis shows that using pesistent cuent and peview schedules, o pesistent peview schedules, up to 10% beacon loss can be toleated with minimal impact on MAC efficiency and QoS. xiv

15 CHAPTER 1 INTRODUCTION The explosive gowth of the Intenet is diving the need fo ubiquitous data and multimedia communications in the twenty-fist centuy. Majo hudles in ealizing this objective ae the last mile (access) and last hunded feet (in-home) connectivity poblems. Appoximately 50% of all netwok investments ae spent on poviding the last mile infastuctue. The high expense incued in laying new wiing fo boadband access to individual customes has foced sevice povides to use the existing cable and telephone lines. As much of the wold still awaits boadband access, thee is a need fo altenative viable appoaches to solving the last mile poblem. In addition in-home distibution of multimedia content is still a challenge paticulaly fo homes that ae not equipped with pope wiing to suppot high-speed data and multimedia communications. Retofitting the house with new wiing is pohibitively expensive and hence the need aises fo new LAN technologies that enable affodable connectivity within the home. With moe than a centuy of ongoing deployments thoughout the wold, electical powe lines epesent by fa the most pevasive netwok of wiing in the wold. The use of powe lines as a communications medium can come a long way towad solving the last mile and last hunded feet poblems. Seveal attempts wee made stating fom the ealy 1920 s to develop a eliable powe line communication (PLC) technology. Howeve, the lack of sophisticated digital signal pocessing technologies hampeed ealie PLC technologies fom gaining widespead acceptance. Fo seveal decades, thei applicability was limited to opeation 1

16 2 and maintenance of the powe supply gid. The explosive gowth of the Intenet in the ecent decades has efueled the inteest in developing high bandwidth (i.e., opeating in 1-30 MHz fequency band) PLC technologies fo in-home netwoking as well as fo boadband access. Howeve, the challenges to enabling high-speed communication ove the powe line ae many. Powe lines wee oiginally devised fo tansmission of powe at Hz and at most 400 Hz. At high fequencies the powe line is vey hostile fo signal popagation [1, 2]. Powe line netwoks opeate on standad in-building electical wiing and as such consist of a vaiety of conducto types and coss-sections joined almost at andom. Theefoe a wide vaiety of chaacteistic impedances will be encounteed in the netwok. This impedance mismatch causes a multi-path effect esulting in deep notches at cetain fequencies. While a typical channel may pesent an aveage attenuation of appoximately 40 db, it is not uncommon fo potions of the bands to expeience geate than 60 db of attenuation. Powe line netwoks ae also affected by intefeence. Electic appliances with bush motos, switching powe supplies and halogen lamps poduce impulse noise that can educe the eliability of communication signals. Due to high attenuation ove the powe line, the noise is also location dependent. Powe line channels also show stong dependence on the undelying AC line cycle. All these factos make the design of PLC technologies extemely challenging. In this dissetation we take a pactical appoach to undestanding the issues in enabling high bandwidth communication ove the powe lines and how the PLC technologies based on HomePlug 1.0 and HomePlug AV standads ovecome these challenges. A combination of analysis, simulations and field tests ae used to detemine

17 3 the effectiveness of the vaious appoaches used by these standads. The oganization of this dissetation is as follows. Chapte 2 builds the backgound on powe line communications. This chapte intoduces the two majo categoies of PLC devices, low-bandwidth PLC and highbandwidth PLC, and descibes the vaious egulations constaints unde which PLC devices should opeate. Technology choices cuently available fo low and high bandwidth PLC systems ae pesented. This chapte also includes a detailed desciption of the powe line channel chaacteistics at high fequencies (i.e., 1-30 MHz). The fist geneation of high-bandwidth PLC technology, HomePlug 1.0, is investigated in Chapte 3. A detailed desciption of HomePlug 1.0 standad was followed by simulation based evaluation of its pefomance. Simulation esults showed that HomePlug 1.0 povides a maximum thoughput of 7.86 Mbps and 5.90 Mbps fo UDP and TCP espectively. The MAC satuation thoughput showed gaceful degadation with incease in numbe of station in the netwok. Simulations with Voice ove IP taffic showed that the pioity contention mechanism in HomePlug 1.0 could guaantee low latencies fo delivey delay sensitive taffic. Extensive field tests wee also conducted to evaluate the pefomance of HomePlug 1.0 with competing home netwoking solutions, IEEE b and IEEE a. These esults show that the fist geneation PLC technologies povide a ubiquitous and eliable home netwoking solution. The HomePlug 1.0 standad was designed to tansfe data with a maximum MAC thoughput of 8 Mbps. While this is good enough fo file shaing and Intenet access, it will not be able to suppot newly emeging multimedia applications like audio and video steaming. Multimedia applications equie not only significantly lage bandwidths, but

18 4 also equie guaantees on QoS paametes like latency, jitte and packet loss pobability. To addess this new beed of applications, a new geneation of HomePlug Standad, HomePlug AV, was eleased by the HomePlug Poweline Alliance. In Chapte 4 we povide a bief oveview of the QoS equiements fo vaious applications multimedia applications and the salient featues of the HomePlug AV standad that enables it to suppot these applications. To achieve data ates necessay to suppot multimedia applications, HomePlug AV uses a channel adaptation mechanism that is synchonized to the undelying AC line cycle. In chapte 5, we use channel chaacteization measuements and analysis to investigate the pefomance enhancements that can be eceived by using AC line cycle based channel adaptation. These esults show that 30% impovement in the physical laye data ates can be obtained by continuously adapting to the undelying AC line cycle. Since continuous adaptation with espect to time is unduly complex fo pactical systems, we popose dividing the AC line cycle into multiple egions and adapting independently in each egion. Results show that using a 1-2 milliseconds egion size will povide optimal MAC pefomance on most paths tested. Impulse noise souces (like dimmes, halogen lamps, etc.,) ae vey common in powe line netwoks. Impulse noise will poduce tempoal effects in channel capacity. Between two impulse noise events, the channel capacity can be vey high, while duing the impulse noise the capacity is vey low. To obtain low FEC block eo ates, the channel has to be adapted close to the lowe end of its capacity (i.e., capacity nea impulse noise event) and hence is undesiable. Physical laye adapting to the highe end of the channel capacity hinges on the ability to efficiently etansmit coupted potions

19 5 of the data at the MAC laye. Chapte 6 pesents a novel 2-level MAC faming mechanism that enables efficient e-tansmission of coupt data. Both analytical and simulation esults ae used to compae the pefomance of the 2-level MAC faming with othe viable appoaches. These esults show that 2-level MAC faming povides linea degadation in pefomance even unde high eo conditions and it outpefoms othe appoaches. Apat fom the MAC faming oveheads, each tansmission will also incu oveheads due to physical laye heades, acknowledgments and intefame spacings. The impact of these tansmission oveheads on the TDMA allocation equiements and efficiency of multimedia steams is investigated in Chapte 7. Results show that the allocation has to be inceased by one o moe tansmission ovehead to suppot low latency applications. Futhe the incease the incease in allocation equiements is not highly dependent on the application data ate. Hence, low data ate applications can incu significant loss in efficiency. These esults show that channel adaptation should take into consideation the application data ate to impove the oveall capacity of the system. HomePlug AV uses a beacon based Time Division Multiple Access (TDMA) technique fo poviding guaanteed bandwidth to multimedia steams. Beacons in HomePlug AV cay TDMA allocation (o scheduling) infomation fo vaious active multimedia steams. Since a station that missed a beacon will not know the schedule fo that beacon peiod, it will not be able to tansmit. Due to the lage attenuation and impulse noise, beacon detection cannot always be guaanteed. To ovecome occasional beacon loss, HomePlug AV uses pesistent beacon schedules. Pesistent schedules ae valid fo multiple beacon peiods, thus enabling a station to tansmit even if it misses one

20 6 o moe beacons. In Chapte 8, we use a Makov chain based analysis to investigate the impact of beacon loss on systems with and without pesistent beacon schedule. Results show that by using pesistent cuent and peview schedule o pesistent peview schedules, HomePlug AV systems can toleate up to 10% beacon loss with minimum impact of MAC efficiency and QoS guaantees. A bief summay of the majo contibutions of this dissetation and the scope fo futue wok ae pesented in Chapte 9.

21 CHAPTER 2 BACKGROUND Powe line communications stands fo the use of powe supply gid fo communication pupose. Powe line netwok has vey extensive infastuctue in nealy each building. Because of that fact the use of this netwok fo tansmission of data in addition to powe supply has gained a lot of attention. Since powe lines ae devised fo tansmission of powe at Hz and at most 400 Hz, the use this medium fo data tansmission, at high fequencies, pesents some technically challenging poblems. Besides lage attenuation, powe line is one of the most electically contaminated envionments, which makes communication extemely difficult. Futhemoe, the estictions imposed on the use of vaious fequency bands in the powe line spectum limit the achievable data ates. Powe lines connect the powe geneation station to a vaiety of customes dispesed ove a wide egion. Powe tansmission is done using vaying voltage levels and powe line cables. Powe line cable chaacteistics and the numbe of cossoves play an impotant ole in detemining the kind of communication technology that needs to be used. Based on the voltage levels that ae used, powe lines can be categoized as follows: 1. High-tension lines: These connect electicity geneation stations to distibution stations. The voltage levels on these lines ae typically in the ode of hundeds of kilovolts and they un ove distances of the ode of tens of kilometes. 2. Medium-tension lines: These connect the distibution stations to pole mounted tansfomes. The voltage levels ae of the ode of a few kilo volts and they un ove distances of the ode of a few kilometes. 7

22 8 3. Low-tension lines: These connect pole-mounted tansfomes to individual households. The voltage levels on these lines ae of the ode of a few hunded volts and these un ove distances of the ode of a few hunded metes. High-tension lines epesent excellent caies fo RF enegy as we only find open wie equipment with vey few cossoves. A tansmission powe of about 10 watts is often sufficient to ovecome distances of moe than 500 kilometes. Aound the yea 1922 the fist caie fequency system (CFS) began to opeate on high-tension lines in the fequency ange of KHz [3, 4, 5]. Duing the past and even nowadays the main pupose of CFS was to maintain the opeability of the powe supply. While in fome times speech tansmission was dominant, today we have moe and moe digital data communications due to the apid pogess of oveall automation. Though the application of moden digital modulation and coding schemes, a significant enhancement of bandwidth efficiency could be achieved fo CFS. Medium- and low-tension lines ae chaacteized by a lage numbe of coss connections and diffeent conducto types (e.g., open wie and cable). Long distance RF signal popagation is extemely bad in this envionment because of high attenuation and impedance matching poblems. Aound the yea 1930 ipple caie signaling (RCS) began to opeate on these lines. These used a fequency ange below 3 KHz down to 125 Hz with amplitude shift keying (ASK) modulation technique. The data ate achieved by RCS is in the ode of a few bits pe second. Load management and automatic econfiguation of powe distibution netwoks wee among the most impotant tasks pefomed by RCS. We see that histoically the use of powe line communications was mainly fo use by the utility copoations (UCs) in maintaining the seamless powe supply. The UCs geneally egaded the powe distibution wiing as a natual medium fo thei

23 9 communication needs, as all impotant stations ae connected. The lack of sophisticated signal pocessing techniques at affodable cost points limited the applicability of PLC technologies in the past. 2.1 Low Bandwidth PLC In the mid 90 s, data communications ove low-tension lines egained a lot of attention fo enabling smat houses. A smat house can be defined as a building equipped with numeous sensos and actuatos, whee fo example heating, aiconditioning and illumination can be automatically and emotely contolled and supevised. Futhemoe safety systems such as bugla o fie alams may be included [4, 6, 7]. New geneations of low bandwidth PLC systems wee designed fo addessing this maket Regulatoy constaints Fequency bands used by these devices ae esticted by the limitations imposed by the egulatoy agencies [8]. These egulations ae developed to ensue hamonious coexistence of vaious electomagnetic devices in the same envionment. The fequency estictions imposed in two of the main makets, Noth Ameica and Euope, ae shown in Figue 1-1. The Fedeal Communications Commission (FCC) and the Euopean Committee fo Electo technical Standadization (CENELEC) goven egulato ules in Noth Ameica and Euope espectively. In Noth Ameica fequency band fom 0 to 500 KHz can be used fo powe line communications. Howeve the egulatoy ules in Euope ae moe stingent. The spectum is divided into five bands based on the egulations. They ae 4. Fequency Band fom 3 9 KHz: The use of this fequency band is limited to enegy povides; howeve, with thei appoval it may also be used by othe paties inside consume s pemises.

24 10 5. Fequency Band fom 9 95 KHz: The use of this fequency band is limited to the enegy povides and thei concession-holdes. This fequency band is often efeed as the A-Band 6. Fequency Band fom KHz: The use of this fequency band is limited to the enegy povide s costumes; no access potocol is defined fo this fequency band. This fequency band is often efeed as the B-Band 7. Fequency Band fom KHz: The use of this fequency band is limited to the enegy povides customes; in ode to make simultaneous opeation of seveal systems within this fequency band possible, a caie sense multiple access potocol using cente fequency of KHz was defined. This fequency band is often efeed to as the C-Band 8. Fequency Band fom KHz: The use of this fequency band is limited to the enegy povide s customes; no access-potocol is defined fo this fequency band. This fequency band is often efeed to as the D-Band. FCC Geneal Use Fequency Band FCC Pohibited Fequency Band KHz (a) FCC Fequency Band Allocation fo Noth Ameica A-Band B-Band C-Band D- Ba nd CENELEC Pohibited Fequency Band KHz (b) CENELEC Fequency Band Allocation fo Euope Figue 1-1: FCC and CENELEC fequency band allocation Thus in Euope powe line communications ae esticted to opeating in the fequency ange fom KHz. Apat fom band allocation, egulatoy bodies also impose limits on the adiations that ae emitted by these devices. These eflect as estictions on the tansmitted powe in each of these fequency bands.

25 Technologies Vaious potocols have been developed fo use by low bandwidth digital devices fo communication on powe line. Each of these potocols diffeent in the modulation technique, channel access mechanism and the fequency band they use. Vaious poducts based on these potocols ae available in the maket and ae mainly used fo home automation puposes. A bief oveview of these potocols is pesented hee X-10 The X-10 technology is one of the oldest powe line communication potocol. It uses a fom of amplitude shift keying (ASK) technique fo tansmission of infomation. Although it was oiginally unidiectional (fom contolle to contolled modules) ecently some bi-diectional poducts ae being implemented. X-10 contolles send thei signals ove the powe line to simple eceives that ae used mainly to contol lightning and othe appliances. Some contolles available today implement gateways between the powe line and othe medium such as RF and infaed. A 120 KHz amplitude modulated caie, 0.5 watt signal, is supeimposed into AC powe line at zeo cossings to minimize the noise intefeence. Infomation is coded by way of busts of high fequency signals. To incease the eliability each bit of infomation is tansmitted sepaately, which limits the tansmission ate to 60 bits pe second. This epesents poo bandwidth utilization while the eliability of tansmission is seveely compomised in a noisy envionment. These ae the main easons why this technology has limited applications CEBus The CEBus potocol uses pee-to-pee communication model. To avoid collisions a caie sensed multiple access with collision esolution and collision detection

26 12 (CSMA/CRCD) is used. The powe line physical laye of the CEBus communication potocol is based on spead spectum technology patented by Intellon Copoation. Unlike taditional spead spectum techniques (that used in fequency hopping o time hopping o diect sequence), the CEBus powe line caie sweeps though a ange of fequencies as it is tansmitted. A single sweep coves the fequency band fom KHz. This fequency sweep is called a chip. Chips ae used fo synchonization, collision esolution and data tansmission. Using this chip technology data ate of about 10 KHz can be obtained. The fequency used by this technology esticts its use in only Noth Ameican maket LonWoks LonWoks is a technology developed by Echelon Copoation and povides a peeto-pee communication potocol, implemented using Caie Sensed Multiple Access (CSMA) technique. Unlike CEBus, LonWoks is a naowband spead spectum modulation technique using the fequency band fom 125 KHz to140 KHz. It uses multibit coelato intended to peseve data in the pesence of noise with a patented impulse noise cancellation. An advantage of the naowband signaling is that it can be used in both Noth Ameican and Euopean makets. 2.2 High Bandwidth PLC High-speed communication ove low-tension powe lines has ecently gained lot of attention. This is fueled by the unpaalleled gowth of the Intenet, which has ceated acceleating demand fo digital telecommunications. High bandwidth PLC devices ae designed to exploit this maket. Moe specifically, these devices use the existing powe line infastuctue within the apatment, office o school building fo poviding a local aea netwok (LAN) to inteconnect vaious digital devices. Some of the applications

27 13 include high-speed Intenet access, multimedia, smat appliances/emote contol, home automation and secuity; data back up, telecommunications, entetainment and IPtelephony Regulatoy constaints High bandwidth PLC devices fo communication on powe line use the fequency band between 1 MHz and 30 MHz. In contast to low bandwidth digital devices, the egulatoy standads fo this egion of the spectum ae still being developed. Cuently, United State is the only county whee the egulations fo High Bandwidth PLC systems ae well defined. In United States, PLC systems opeate unde FCC Pat 15 ules using the fequency band between MHz. Seveal sub-bands within this ange have to be notched to pevent intefeence with licensed sevices Channel chaacteistics Powe lines wee oiginally devised fo tansmission of powe at Hz and at most 400 Hz. At high fequencies powe line is vey hostile fo signal popagation [1, 2]. In the section that follows gives a bief oveview of powe line channel chaacteistics in the fequency band between 1 MHz and 30 MHz Attenuation chaacteistics High fequency signals can be injected on to the powe line by using an appopiately designed high pass filte. Received signal powe will be maximum when the impedance of the tansmitte, powe line and the eceive ae matched. Dedicated communication channels like Ethenet have known impedance, thus impedance matching is not a poblem. Howeve, powe line netwoks ae usually made of a vaiety of conducto types and coss sections joined almost at andom. Theefoe a wide vaiety of chaacteistic impedances will be encounteed in the netwok. Futhe, the netwok

28 14 teminal impedance will tend to vay both at communication signal fequencies and with time as the consume pemises load patten vaies. The multipath effect esulting fom impedance mismatch and the attenuation caused by the electic wiing makes powe line channels highly fequency selective [9]. While a typical channel may pesent an aveage attenuation of appoximately 40 db, it is not uncommon fo potions of the bands to expeience geate than 60 db of attenuation. Similaly, while most powe line channels have a significant delay spead of 1 to 2 µs, it is not uncommon fo some channels to exhibit a delay spead lage than 5 µs. Figue 2-1 and Figue 2-2 show a sample powe line channel impulse and fequency esponse. One of the unique chaacteistics of powe line channels is the dependence of channel chaacteistics on the AC line cycle. Electic appliances may tun on and off, and/o daw electic powe as a function of the AC line cycle. While this may change both the channel s fequency esponse and noise pofile, it is moe common to see changes in only the noise pofile. Figue 2-1: Powe line channel impulse esponse

29 15 Figue 2-2: Channel fequency esponse Noise chaacteistics The majo souces of noise on the powe line ae fom electical appliances, which geneate noise components that extend well into the high fequency spectum. Wose, thee ae often impulse noise souces. Impulse noise can be categoized as peiodic o continuous based on when it occus elative to the undelying AC line cycle. Figue 2-3, 2-4 and 2-5 espectively show peiodic impulse noise fom light dimme, yad light and halogen lamp in addition to the data signal (ectangula shape). Devices that contain bush motos (Figue 2-6) also poduce impulse noise. Induced adio fequency signals fom boadcast, commecial, militay, citizen band and amateu stations also impai cetain fequency bands. Because much of the noise expeienced by each node may be highly localized due to attenuation, the noise pofile seen by each PLC device may be significantly diffeent. Theefoe, powe line channels ae not typically symmetic.

30 16 Figue 2-3: Noise geneated by light dimme Figue 2-4: Noise geneated by yad light

31 17 Figue 2-5: Noise geneated by halogen lamp Figue 2-6: Noise geneated by hai dye

32 Technologies The fist geneation of high bandwidth PLC systems wee developed to enable high-speed data communications in a Small Office Home Office (SOHO) envionments. These technologies epesented a gain leap in exploiting the powe lines as a tue communication medium. The most widely deployed fist geneation PLC systems ae based on HomePlug 1.0 Standad. HomePlug 1.0 was developed by HomePlug Poweline Alliance; a non-pofit industy association that was fomed in Mach of 2000 by a goup of industy leading companies to enable standads based powe line netwoking poducts. In the next chapte, we take a detailed look at the technology behind HomePlug 1.0 and how it enabled it to ovecome the hash powe line envionment. The pefomance of this technology against othe popula SOHO netwoking options was also pesented. As home netwoks become moe and moe common, thee is inceasing demand fo enabling multimedia communications within the home. Multimedia applications not only equie high bandwidth but also need guaantees on vaious QoS elements like delay, jitte and packet loss pobability. A second geneation of HomePlug Standads, HomePlug AV was developed to addess this need. In Chaptes 5, 6, 7 and 8, we investigate some of the design choices made in HomePlug AV and evaluate thei pefomance.

33 CHAPTER 3 HOMEPLUG 1.0 TECHNOLOGY DESCRIPTION AND PERFORMANCE EVALUATION Affodable boadband Intenet communication to esidential customes is now available via Cable Modems and vaious flavos of Digital Subscibe Lines (DSL). In tun thee is a gowing need fo in-home netwoks to shae this single full-time Intenet access link, along with netwok connectivity fo vaious computes and pintes in the home. A good home netwoking solution should be easy to setup, zeo maintenance, cost effective and should also be able to povide eliable pefomance thoughout the house With multiple outlets in evey oom, esidential powe lines ae aleady the most pevasive netwoks in the home. Using this existing infastuctue to povide high speed netwoking capabilities povides seveal benefits. Fist of all, thee is no need fo expensive ewiing of the house. Secondly, almost all devices that need to be netwoked ae aleady connected to the AC wiing. Thus, home netwoking becomes as simple as plugging the device in the AC outlet. HomePlug 1.0 Standad was developed to enable ubiquitous, easy to use and affodable home netwoking. In this chapte we pesent detailed desciption of HomePlug 1.0 technology and evaluate its pefomance based on simulations and field tests. A moe thoough teatment of the mateial can be found in the following papes we published [10, 11, 12]. The oganization of this section is as follows. In Section 3.1 we povide a bief oveview of vaious options fo home netwoking and thei pos and cons. Details of HomePlug 1.0 technology and simulation based evaluation of its pefomance is 19

34 20 pesented in Section 3.2 and Section 3.3, espectively. Field test based pefomance compaison of HomePlug 1.0 and IEEE b/a ae pesented in Section Home Netwoking Solutions A vaiety of technological altenatives ae available to home netwoking. These technologies can be gouped into thee diffeent categoies based on the medium they use fo tansfe of data. They ae: 1. New Wie 2. Wieless 3. No New Wies New wie solution New Wied solutions use specialized cable to connect vaious devices. Thee ae the most matued technologies and have found wide spead acceptance in entepise, campus and industial netwoks. Some examples include Ethenet, Token Bus and Token ing. Ethenet is one of the most widely used netwoking solution inside the home these days. The majo dawback is that it would equie etofitting the house with these specialized cables. This is quite an expensive poposition as it could involve dilling holes in the walls. Futhe, most of the electicians have little o no knowledge on how to install these cables. Fo example, a simple mistake of impope temination of Ethenet wie will make the netwok useless. Anothe dawback of Ethenet is the lack of pope QoS povisions that ae vey citical fo any netwoking technology to be successful in the home netwoking maket. The ecently developed IEEE 1394b [13] specification also tagets the home netwoking maket. This is an extension of the popula IEEE 1394 [14] (also known as FieWie o i.link) that suppots cod lengths up to 100 metes. Using Cat 5 UTP cods, it can suppot data ate of 100 Mbps ove 100 metes distance. Using 50µm

35 21 fibe, data ates of up to 3200 Mbps can be suppoted fo cod lengths of up to 100 metes Wieless solution Wieless technologies use high fequency adio waves to tansfe data. The most pedominant technologies include, 1. IEEE b/a/g, 2. BlueTooth, 3. HomeRF, and 4. Ultawide band. The main benefit of using wieless netwoks is the feedom to move aound the house while maintaining netwok connection. IEEE x [15, 16, 17, 18] ae the most popula wieless home netwoking technology. IEEE b uses Diect Sequence Spead Spectum (DSSS) in the 2.4GHz Industial, Scientific and Medical (ISM) band and povides PHY ates of up to 11 Mbps. The extensions of this technology include IEEE g and IEEE a. IEEE g uses the same fequency bands as IEEE b, but with OFDM modulation and povides PHY ate of up to 54 Mbps. IEEE a uses the 5 GHz Unlicensed National Infomation Infastuctue (U-NII) bands along with OFDM modulation to povide up to 54 Mbps data ates. The main daw back of this technology has been coveage and quality of sevice. BlueTooth technology [19, 20] uses the 2.4GHz ISM band with fequency hopped spead spectum technology. This technology should be teated moe like a Pesonal Aea Netwoking solution athe than a Home Netwoking solution due to lowe tansmit powe equied by the kind of applications they seve.

36 22 HomeRF also uses the 2.4GHz ISM band with fequency hopped spead spectum technology. This technology had limited acceptance in the maket. The only advantage of this when compaed to IEEE b is a bette suppot fo VoIP taffic. The use of Ultawide Band (UWB) technology [21, 22] was ecently appoved by the FCC in Febuay UWB is defined as any adio technology having a spectum that occupies a bandwidth geate than 20 pecent of the cente fequency, o a bandwidth of at least 500 MHz. Thee ae two competing UWB standads. 1. Multi-Band OFDM (MBOA) UWB standad developed by WiMedia Alliance, and 2. Diect Sequence Code Division Multiple Access (DS-CDMA) UWB standad developed UWB Foum UWB technologies can enable data ates of up to 480Mbps. As with Bluetooth, Ultawide band signals have limited ange and ae moe suitable fo Pesonal Aea Netwoks No new wie solutions No New wie solutions use existing wiing inside the house to povide high-speed communication capabilities. These technologies include 5. HomePlug 1.0, HomePlug AV 6. HomePNA, and 7. MoCA HomePlug 1.0 and HomePlug AV technologies uses the existing powe line wiing inside the house and povide maximum PHY data ates of 14Mbps and 150Mbps, espectively. The ubiquity of powe outlets is the geatest advantage when compaed to othe wied technologies. HomePNA uses existing phone line as an infastuctue to povide home netwoking. The HomePNA 3.0 standad [23] eleased in 2003 enables data ates up to

37 Mbps with optional extensions to 240 Mbps. It also has deteministic QoS, but suffes fom a limited numbe of available outlets in the house. Multimedia ove Coax (MoCA) [24] uses existing coax wiing to povide home netwoking. To avoid intefeence with video channels, MoCA uses 850MHz to 1500MHz fequency band. Simila to using existing telephone wiing, cable outlets ae typically limited to 3 o 4 in the aveage home and ae cetainly not pesent in all ooms. Use of splittes may also limit bi-diectional tansmission. As we have seen in this section, thee ae seveal technologies that have tageted the home netwoking technologies. Most of the technologies have gained limited acceptance due to coveage o ubiquity poblems. HomePlug and IEEE x ae the most impotant contendes at pesent due to thei ubiquity. 3.2 HomePlug 1.0 Technology HomePlug 1.0 technology [11, 12, 25, 26] ovecome the hash channel conditions on the powe lines by using an adaptive appoach that uses obust tansmission technique combined with sophisticated fowad eo coection (FEC) [27, 28], eo detection, data inteleaving, and automatic epeat equest (ARQ) [29] HomePlug Physical laye Othogonal Fequency Division Multiplexing (OFDM) is the basic tansmission technique used by the HomePlug. OFDM is well known in the liteatue and in industy [30]. It is cuently used in DSL technology [31], teestial wieless distibution of television signals, and has also been adapted fo IEEE's high ate wieless LAN Standads (802.11a and g). The basic idea of OFDM is to divide the available spectum into seveal naowband, low data ate sub-caies. To obtain high spectal efficiency the fequency esponse of the sub-caies ae ovelapping and othogonal,

38 24 hence the name OFDM. Each naowband sub-caie can be modulated using vaious modulation fomats. By choosing the sub-caie spacing to be small the channel tansfe function educes to a simple constant within the bandwidth of each sub-caie. In this way, a fequency selective channel is divided into many flat-fading sub-channels, which eliminates the need fo sophisticated equalizes. The OFDM used by HomePlug is specially tailoed fo powe line envionments. It uses 84 equally spaced sub-caies in the fequency band between 4.5MHz and 21MHz. Cyclic pefix and diffeential modulation techniques ae used to completely eliminate the need fo any equalization. Impulsive noise events ae ovecome by means of fowad eo coection and data inteleaving. HomePlug payload uses a concatenation of Vitebi and Reed-Solomon FEC. Sensitive fame contol data is encoded using tubo poduct codes. The powe line channel between any two links has a diffeent amplitude and phase esponse. Futhemoe, noise on the powe line is local to the eceive. HomePlug technology optimizes the data ate on each link by using channel adaptation. Channel adaptation is HomePlug 1.0 involves Tone Allocation, modulation selection and FEC selection. Tone allocation is the pocess by which cetain heavily impaied caies ae tuned off. This significantly educes the bit eo ates and helps in tageting the powe of FEC and Modulation choices on the good caies. HomePlug allows fo choosing fom diffeential binay phase shift keying (DBPSK), diffeential quadatue phase shift keying (DQPSK) on all the caies, with eithe ½ o ¾ FEC code ates. The end esult of this adaptation is a highly optimized link thoughput.

39 25 Cetain types of infomation, such as boadcast packets, cannot make use of channel adaptation techniques. HomePlug uses an innovative modulation called ROBO, so that infomation is eliably tansmitted. ROBO modulation uses a DBPSK with heavy eo coection with bit epetition in time and fequency to enable highly eliable communication. ROBO fames ae also used fo channel adaptation HomePlug 1.0 MAC The choice of Medium Access Contol (MAC) potocol povides a diffeent set of challenges. Home netwoks should be able to suppot a divese set of applications anging fom simple file tansfe to QoS demanding applications such as Voice-ove-IP (VoIP) and low data ate steaming media. The HomePlug MAC is built to seamlessly integate with the physical laye and addesses these needs. HomePlug MAC is modeled to wok with IEEE fame fomats. This choice simplifies the integation with the widely deployed Ethenet. HomePlug MAC appends the Ethenet fames with encyption and othe management befoe tansmitting it ove the powe line. A segmentation and eassembly mechanism is used to in cases whee the complete packet cannot be fit in a single fame Fame fomats HomePlug technology uses two basic fame fomats (efe Figue 5-1). A Long Fame consists of a Stat of Fame (SOF) delimite, Payload and End of Fame delimite (EOF). A Shot Fame consists of a Response Delimite and is used as pat of the Stopand Wait automatic epeat equest (ARQ) pocess. ARQ mechanism causes etansmission of coupt packets, thus educing the packet eo ate. All the delimites shae a common stuctue. A delimite consists of a Peamble and Fame Contol infomation field. The Peamble is a fom of spead spectum signal that is

40 26 used to detemine the stat of a delimite. This is followed by Fame Contol infomation, which is encoded using a obust Tubo Poduct Code and can be detected eliably even at seveal db below the noise floo. Among othe things, delimites convey timing infomation that is used by MAC to detemine the availability of the medium. The obust design of the delimite helps the nodes to obtain a vey high level of synchonization, thus educing unintended collisions. The details of the vaious field contained in the Fame Contol ae given in Table 3-1. The Payload of the Long Fame delimite is encoded based on the channel adaptation. The fist 17 bytes of the payload contain the Fame Heade. This field contains the souce addess, destination addess and segmentation infomation. HomePlug technology limits the maximum length of the payload field in the Long Fame to 160 OFDM Symbols (~1.3 msec). This manifests as bette guaantees of QoS as the delay incued by highe pioity taffic due to on going lowe pioity tansmission is educed. If the packet cannot be fitted into a Long Fame, a segmentation and eassembly mechanism is used to send it in multiple Long Fames. The fame heade contains infomation that is used by the eceive to popely econstuct the segmented packet. The Payload is potected by a Fame Check Sequence (FCS) to detect uncoected eos Channel access mechanism The channel access mechanism used by the HomePlug MAC is a vaiant of the well-known CSMA/CA potocol. A typical CSMA/CA potocol would equie nodes to sense the medium (this is the caie sensing pat) fo othe taffic. If the medium is busy, nodes will defe fom tansmitting until the medium becomes idle. When the medium becomes idle, nodes will wait fo a andomly chosen duation (this is the collision avoidance pat). A node will tansmit only if it detects no othe taffic on the medium