MAC Throughput Improvement Using Adaptive Contention Window

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1 Joural of Computer ad Commuicatios, 2015, 3, 1 14 Published Olie Jauary 2015 i SciRes. MAC Throughput Improvemet Usig Adaptive Cotetio Widow Chu Liag Li, Wei Tig Chag, Mi Huei Lu Departmet of Electrical Egieerig, Natioal Chug Hsig Uiversity, Taichug, Taiwa chuli@drago.chu.edu.tw Received 2 Jauary 2015; accepted 19 Jauary 2015; published 23 Jauary 2015 Copyright 2015 by authors ad Scietific Research Publishig Ic. This work is licesed uder the Creative Commos Attributio Iteratioal Licese (CC BY). Abstract HomePlug AV (HPAV) is a stadard developed by HomePlug Powerlie Alliace (HPA) for power lie commuicatio. I HomePlug AV, it uses a techology amed Carrier Sese Multiple Access with Collisio Avoidace (CSMA/CA) to reduce collisio happeed i etwork. However, whe etwork odes icrease, the cotetio widow umber may ot be wide eough. It will cause collisio probability to icrease. I this paper, we itroduce a ew idea of adaptive cotetio widow which will produce suitable cotetio widow uder actual etwork eviromet. Our method oly requires the iformatio of CSMA/CA parameters. It meas that oe does t eed to correct the origial CSMA/CA procedure but substitutes old parameters by the ew oes. Simulatio experimets coducted i the etwork simulator NS3 show that compared with HomePlug AV, our method promotes throughput sigificatly whe the ode umber icreases. Keywords CSMA/CA, Cotetio Widow, Power Lie Commuicatio 1. Itroductio Power-Lie Commuicatio (PLC) is developed rapidly i recet years. Because it does t eed to build additioal trasmit chael ad exists almost everywhere eve i the backward areas, it is mostly recogized as the solutio of last mile to the curret etwork commuicatio. Sice power lie was ot origially built for iformatio trasmissio, there are several problems. Oe of these is the data collisio. Whe chael trasmits multiple packets at the same time, packets will collide aturally causig packets to be destroyed. The statio has to retrasmit packets which will cause throughput decrease i the ed. Thus, HomePlug AV [1] uses CSMA/CA [2] to avoid collisio happeig. The priciple is as follows: each time the statio tries to sed package, it will detect chael s status. If the chael is idle, the statio seds the packets. Otherwise, it goes ito the cotetio How to cite this paper: Li, C. L., Chag, W. T. ad Lu, M. H. (2015) MAC Throughput Improvemet Usig Adaptive Cotetio Widow. Joural of Computer ad Commuicatios, 3,

2 mode. This method ca avoid too may statios trasmittig at a time hece to effectively reduce the chace of data collisio. A PLC architecture cosists of head ed (HE) ad user modem. HE erects at the trasformer side ad oe side is coected to the trasmissio backboe, like Etheret. Aother side is coected to the power lie to receive request from PLC users. The user modem coects to the commuicatio equipmet to commuicate through the power lie. If a PLC modem accesses the Iteret, it will receive packets from the head ed through the power lie. Although HomePlug AV stadard ca guaratee high throughput whe the umber of odes is very limited, whe the ode umber icreases, the value of cotetio widow settig i HomePlug AV will be big which leads throughput to decrease accordigly. I [3], iformatio theory ad data miig techique were applied for etwork traffic profilig. Some research tasks focused o ehacig throughput via the revised MAC layers [3] [4]-[8]. Amog which, the authors of [3] proposed a adaptive cotetio widow mechaism for HomePlug AV ad verified their desigs through experimets. They have coducted a experimet to reach the best successful trasmissio umber i a beaco period. That is, if the umber of successful trasmits is less tha the imal oe, it meas that the curret cotetio widow size is iappropriate. It will the chage it i the ext beaco period. I 2011, the authors of [4] foud the imal cotetio widow value for the situatio of differet odes. Both of them show that throughput ca be improved i a efficiet maer if the size of cotetio widow is imized. Eve though previous research ca achieve the desired effect, most of them require iformatio of all statios. That meas that they eed aother bit to trasmit that iformatio to each ode. Or, they have to modify the protocol. I this research, we propose a ew strategy of a adaptive cotetio widow mechaism that does t chage the origial CSMA/CA procedure or require statio s iformatio as a basis of modifyig the cotetio widow size. Our correctio factor icludes the CSMA/CA parameters. Soft experimets at the etwork simulator, NS3, show the improved effect i throughput. 2. Priciples of CSMA/CA For PLC, whe a statio tries to sed a packet, it first checks the chael coditio. If the chael is i idle, it trasmits data accordigly. Otherwise, it eters the cotetio mode. The cotetio period is a regio to coted the authority of usig chael by other statios. Before goig ito the cotetio period, the statio will allocate each packet priority. Packets with higher priority use the chael first. If there are several packets possessig the same priority, it will become the cotetio period. I priority resolutio, HPAV defie four parameters, CA0, CA1, CA2 ad CA3. CA3 preset the highest priority, ad CA0 is the lowest, etc. Each statio will be defied the packet s priority i two priority regios deoted PRS0 ad PRS1 respectively. At each PRSi, the statio chooses to sed or ot to sed sigals. Accordig to the PRS, we ca determie the packet s priority level. Differet priority level correspods to differet parameter settigs. Table 1 shows the role of it. After implemetig the settig of priority, each statio equips with a specific packet priority level. Higher priority level wis the cotetio ad possesses more chaces to sed the packet. If there are several statios with the same priority, it will proceed to the ext stage-radom backoff procedure. For the radom backoff procedure, we first itroduce cotetio widow ad three couters, backoff couter, deferral couter ad backoff procedure couter. 1) Cotetio widow (CW): Cotetio widow is a fixed umber defied i Table 2. It is used to determie the value of backoff couters. 2) Backoff couter (BC): Backoff couter s value chooses from a radom value of cotetio widow. It meas that CW is the maximal value of BC could be. BC will be decreased by oe, each time whe it seses a busy status i the chael util BC equals to zero. The statio will trasmit the packet. 3) Deferral couter (DC): Whe the umber of users i the local area etwork is large, usig oly BC to delay the trasmissio time is ot eough. Deferral couter is used to avoid collisio further. At the begiig, DC is fixed. Differet CAs have differet iitial values of DC correspodig to. If the chael status sesed is idle, DC remais uchaged. O the cotrary, if it is busy, DC will be decreased by oe. Whe DC reaches to zero, the time cotetio is declared fail. It will restart cotetio agai. 4) Backoff procedure couter (BPC): Backoff procedure couter is set to be zero iitially. Whe the statio 2

3 Table 1. Relatioship betwee PRS ad CA. Low priority High priority CA0 CA1 CA2 CA3 PRS PRS Table 2. Parameter settig. BPC BPC = 0 BPC = 1 BPC = 2 BPC 3 CA3, CA2 High priority DC = 0 CW = 7 DC = 1 CW = 15 DC = 3 CW = 15 DC = 15 CW = 31 CA CA1, CA0 Low priority DC = 0 CW = 7 DC = 1 CW = 15 DC = 3 CW = 31 DC = 15 CW = 63 fails to trasmit packets (happeed collisio). Statio will attempt to coted agai ad BPC will be icreased by oe. Accordig to differet BPC, there are differet DC ad CW settigs to respod. We express the behavior through Markov chai [4] i Figure 1. Each time we begi the backoff procedure by settig the same probability to obtai the value of BC from zero to CW (=W). Therefore, each probability at the top statemet is 1/W. At each time slot (defied i HPAV is ms), the statio will detect the commuicatio chael. The probability is P to sese a busy, ad it is 1 P to sese a idle. Whe DC or BC is equal to zero but the chael status sesed is still i busy. BPC will be icreased by oe ad BC will be rechose. That meas that there are too may users occupyig the chael. The, DC ad BC eed to be icreased for loger waitig time for collisio avoidace. Whe BC reaches to zero ad the chael status sesed is idle, the statio ca the trasmit packets. The complete flow chart is illustrated i Figure 2. The time of successful trasmissio ca be expressed as i Figure 3. PRS0 ad PRS1 are regios to decide packets priority, a cotetio regio refer to the waitig time of the coteded chael before trasmittig packets, data trasmissio is the time of packets set i the PHY layer; RIFS refers to the time before sedig ackowledgemet, ACK is the time of trasmittig ackowledgemet, ad CIFS is time before startig the ext packet. Amog which, PRS0, PRS1, RIFS, ACKS, ad CIFS are fixed umbers i HomePlug AV, see Table Slot Utilizatio ad Relatio with Throughput Referrig to Figure 3, we defie rs t ad rc t respectively, the time required for a successful data trasmissio ad the time for a collisio happeed durig data trasmissio. The two terms ca be expressed by r t T, r t T where s s all c c all is the total slot time i the cotetio regio ad If we defie Ts frame all PRS0 PRS1 T RIFS ACK CIFS (1) Tc PRS0 PRS1 T CIFS (2) frame P b as the probability of slot sesed i busy. From [2], Pb P b ca be expressed by 1 1 (3) where is the probability of the statio trasmitted i a slot ad is the umber of statios. Sice P b reflects 3

4 Figure 1. Markov chai of CSMA/CA. Figure 2. Operatioal flow chart of the CSMA/CA procedure. 4

5 Figure 3. The process for a successful trasmissio. Table 3. HPAV system parameters. Parameters Beaco period CIFS RIFS PRS0 PRS1 Slot time MAX_FL Respose tieout Time ms 100 μs μs μs μs μs μs μs the probability of chael i busy status, it ca also be defied as busy slot umber P b busy slot umber idle slot umber (4) This is also referred as slot utilizatio [9]. We coduct several extesive simulatio experimets o the Network Simulator 3 (NS3) [10]. NS3 is a evet driver developed to mimic etwork eviromet. Compared with its predecessor NS2, NS3 is completely developed by C++ ad the system architecture is simpler tha that of NS2. We record slot utilizatio every 30 secods at various ode arragemet. There are four CW cases i the simulatio. The results are show i Figure 4(a) where T s defied i Equatio (1) is set to be 3500 μs ad the slot time is similar to that defied i Table 3. I Figure 4(a), red lie refers to HomePlug AV stadard which let CW = [ ]. Other lies are the situatio with differet CW values. Whe CW is set to be larger, the probability for obtaiig a larger BC is higher. Correspodigly, its slot utilizatio is comparatively smaller. However, eve the CW settig is as such, the slot utilizatio icreases cotiuously. This fact ispires us to cosider whether oe ca use slot utilizatio to relate the cogestio level. Aother simulatio bee coducted is to observe the variatio of throughput at the same settig, illustrated as i Figure 4(b). I Figure 4(b), HomePlug AV stadard has the highest throughput whe the umber of cotetio odes is small. However, whe the ode umber icreases, the throughput will decrease because of the higher collisio probability. O the cotrary, CW = [ ] settig possesses the worst throughput at the begiig. That s because it wastes too much time i the idle slot. However, it will cause low collisio probability whe the ode umber becomes larger. This why it possesses highest throughput whe the ode umber is more tha 35. Therefore, if oe ca assig the system a low CW settig whe the ode umber is few ad a high CW whe the ode umber is large the better throughput could be expected. This is the basic idea behid the adaptive cotetio widow mechaism proposed i this research. To compare Figure 4(a) ad Figure 4(b), from the ode umber 5 to 12, CW = [ ] has the highest throughput. From 13 to 35 odes, CW = [ ] possesses the highest throughput. After 35, CW = [ ] has the highest throughput. Most of their slot utilizatio are i 0.1 ~ 0.2 whe they possess the highest throughput. Oe ca thus ifer that the value of slot utilizatio i 0.1 ~ 0.2 would be the best settig i this case. 5

6 (a) Figure 4. Simulatio o differet CW settig: (a) Slot utilizatio; (b) Throughput. (b) I summary, if oe ca cotrol slot utilizatio i a appropriate regio the better throughput could be expected. 4. Adaptive Cotetio Widow Mechaism From [11], it was kow that whe defied i Equatio (3) as the followig way, throughput of the etwork will exhibit the best performace: cavg. cavg 2 1 T T 1 T 2. cavg. where T cavg. is the average time of collisio trasmissio T c i the slot time as T cavg, Substitutig Equatio (6) ito Equatio (5) yields the ew as T c (6) 1 (7) T c 2 Substitutig Equatio (7) ito Equatio (3) gives the imal slot utilizatio which will lead to the imal throughput. We set this imal slot utilizatio as the stadard which is expressed as P b. : where 2. T c P b After recogized data received, every statio records the slot utilizatio by usig Equatio (4) for the last successful trasmissio packet. If slot utilizatio of the last packet is greater tha P b., it meas that the curret cotetio widow is ot big eough which may cause the cogestio. It will assig the system a larger cotetio widow. Otherwise, it will adjust the cotetio widow for reductio. Our adaptive cotetio widow architecture ca be illustrated as i Figure 5. I this figure, is expressed as slot utilizatio of the last packet. By the revised fuctio- f, it coverts the slot utilizatio to a revisig factor to multiply the origial cotetio widow (CW = [ ]). That is, f CW. the cotetio widow of the ext packet will be chaged to (5) (8) 6

7 Figure 5. System architecture of the proposed adaptive cotetio widow mechaism. We suppose that the revised fuctio f P, f is give i the form show i Figure 6. While the slot utilizatio is i betwee P b. ad 2 b. appears as a liear positive gai. Sice CW = [ ] is origially suitable for the case with oly a few odes, it does t eed to be small whe the slot utilizatio is apparetly too small. Therefore, we set fmi to be 1. O the other had, we defie M as the expressio of fmax to be a variable. Assume f is expressed by the followig form whe is i betwee P b. ad 2P b. : f m k (9) Substitutig P b.,1 ad 2 Pb., M ito Equatio (9) yields m ad k as M 1 m P b. k 2 M Fially, we obtai the complete form of the revised fuctio f : 1, Pb. M 1 f 2 M, P 2P Pb. M, 2Pb. b. b. The mai idea here is to icorporate slot utilizatio to determie cogestio level of the etwork. However, slot utilizatio determied by Equatio (4) leads to a large alteratio if the last packet is successfully trasmitted at BPC = 0 (Table 2). Uder this situatio, it will brig the ext packet with icorrect iformatio i the cogestio level. To tackle, we propose a virtual slot utilizatio istead of the previous slot utilizatio. A virtual slot utilizatio will lie i betwee P b. ad 2P b.. The eighborig two packets will ot exhibit large differece virtual slot utilizatio. The virtual slot utilizatio comes from the followig process. We defie vm ad vm 1 as the virtual slot utilizatio of the packets m ad m 1, respectively ad m is the slot utilizatio of the packet m, show as i Figure 7. The packet m + 1 uses vm as the previous slot utilizatio which ads Equatio (10) to obtai the revisig factor as its cotetio widow. vm is obtaied by the previous packet s virtual slot utilizatio vm 1 1 ad the slot utilizatio of the packet m. If m Pb., vm will be vm 1 2 Pb. vm 1 to icrease the 5 1 revisig factor. If m Pb., vm will be vm 1 vm 1 P b.. If m Pb., set vm vm 1 5. We replace the slot utilizatio by the virtual slot utilizatio accordig to Equatio (10): (10) 7

8 Figure 6. Correctio factor of the cotetio widow f. Figure 7. Sketch of slot utilizatio virtual slot utilizatio vm. m ad P 1 b. 1, m P vm vm b b., vm P vm vm m< Pb. (11) 1, vm m= P b. By this process, every statio CW will reach to a regio which the probability of every statio trasmittig packets will be close. The revisig factor f will be icreasig cotiuously whe P b. as well. While the previous method works i a efficiet way, there is a weakess, i.e. the cotetio widow mechaism shows lower throughput whe the ode umber is few. That s because if we modify the cotetio widow at BPC = 0 by the previous method, it teds to prompt a larger revisig factor whe the ode umber is few. Thus, it still exhibits a large cotetio widow causig lower throughput. It is expected that, at each time istat, ρ could really reflect the previous cogestio level. Thus, whe is large, we do t wat the statio trasmits at the first cotetio period time. It meas that oe still eeds a larger CW at BPC = 0 whe the ode umber is large. Therefore, oe has to defie a updated revisig factor for the state BPC = 0. Ulike the revisig factor characterized i Figure 5 usig a simple multiplicatio to modify the cotetio widow, the revisig factor at BPC = 0 should be updated i the way of additio. Comparig to the multiplicatio operatio, the amout of additio should be smaller. It will be more suitable for the case of BPC = 0 sice its deferral couter is 0. The modificatio is to itroduce a correctio factor, say 4 f vm M (12) where the operator miz x. By this way, we obtai a iteger, with its values i betwee 1 to 4, to idicate the cogestio level. Next, we record the couter of the backoff procedure of the last packet, deoted BPC m. To proceed, set the maximum value of BPC m to be 3 ad defie 8

9 BPC 1 Therefore, the value of will be from 1 to 4. Combiig ad forms a cogestio level idicator as where Table 4 lists all possible values of. We choose as our revisig factor whe BPC = 0. By this process, the statio will has less probability to trasmit at the first roud i the backoff regio whe the ode umber is large. It does t ifluece throughput whe the ode umber is fewer. The complete desig process of our adaptive cotetio widow process ca be summarized as follows: Step 1: Based o the give slot time, collisio trasmissio time T c ad ode umber obtai P b. as Step 2: Defie the revisig factor P b. f by P b. : m T c 1, Pb. M 1 f 2 M, P 2P Pb. M, Pb. b. b. Step 3: Cout the idle ad busy slot umbers of the last trasmissio packet to obtai the virtual slot utilizatio: busy_slot_umbers all_slot_umbers P, P P, P vm vm vm 1, P vm vm 1 b. vm 1 b. Step 4: Specify the revisig factor whe BPC = 0 i Table 2: Step 5: Update the cotetio widow via: 1) Backoff procedure is at BPC = 0: 2) Backoff procedure is at BPC > 0: 4 f M vm BPC 1 m * CW CW b. b. * CW CWf vm So far, our focus is oly i ow statio. However, the statio umber i Equatio (8) is ot fixed which is ukow i geeral. To resolve this problem, we calculate P b. Tc 3500 s with differet, see Figure 8. Whe the ode umber is i 1 ~ 200, its value will ot sigificatly affect P b.. To prove the ode umbers will ot ifluece P b. further, we calculate the sesitivity whe is larger tha Defie. It follows that the sesitivity fuctio of P b. with respect to the ode umber is give by T c b. 9

10 Table 4. List of the values of ω Figure 8. Variatio of P b. o differet ode umbers. S P 1 l1 Pb Pb. b. Whe > 200, the terms 1 ad will be smaller tha 1. However, 11 l 1 1. Thus, S 0. 1 I the followig study, the etwork ode umber is set to be 10. Furthermore, if we cosider CW = [ ] as the largest cotetio widow, which will be approximately 15 times to the case of CW = [ ], the we set the maximum revisig fuctio M to be 15. The operatioal flow chart of the updated adaptive cotetio widow mechaism is illustrated i Figure Experimetal Results The goal of this research is to acquire higher throughput while maitaiig slot utilizatio. The simulatio experimets have bee coducted at the etwork simulator NS3. We set to be μs which remais the same as i HomePlug AV. Simulatio study is maily coducted for differet T s ad CW. Figure 10(a) shows slot utilizatio for various CW settigs. No matter HomePlug AV stadard or other CW settigs, their slot utilizatios exhibit large variatios whe the umber of odes icreases. However, there is 10

11 Figure 9. Operatioal flow chart of the proposed adaptive CW mechaism. oly slight differece amog differet cases i our proposed approach. This result shows that our method is effectively to cotrol slot utilizatio. Eve for a large scale etwork, it shows o sigificat differece. After verifyig slot utilizatio, the mai poit of this research is to get better throughput o the large scale etwork. We prove i the follows that the proposed approach exhibits the best throughput performace while comparig to other fixed CW settigs. Icludig the origial HomePlug AV (CW = [ ]). All packets are supposed to possess the same priority ad all statios are o the saturated situatio which meas that all statios have packets to trasmit at all time. We record the average throughput every 30 secods for each coditio. Figure 10(b) shows throughput of various CW settigs with T s equal to 3500 μs. HomePlug AV stadard exhibits the highest throughput at the begiig. Whe the ode umber becomes large, HomePlug AV stadard s CW settig is ot big eough because its throughput decreases seriously. O the other had, CW = [ ] has the lowest throughput at the begiig because the system wastes too much time o the idle slots. However, it rises subsequetly whe the ode umber become large. Our method shows the highest at all time sice its CW settig is ot fixed. Whe the ode umber is relatively few, it uses a small CW. Whe the ode umber icreases, it automatically icreases the CW value accordigly. Thus, whe the ode umber becomes large, it still exhibits low probability i etwork collisio. That s why it ca keep high throughput of the etwork over the whole commuicatio time. This is as expected before. Figure 10(c) shows that whe the ode 11

12 (a) (b) (c) Figure 10. Various CW settigs i differet simulatio cases: (a) Slot utilizatio; (b) Throughput (T s = 3500 μs); (c) Throughput (large ode umber ad large CW); (d) Throughput (T s = 5500 μs). umber is icreased to 95, it performs as the cases of CW = [ ] i the simulatio study. The simulatio result shows that whe the ode umber approaches to a large value, throughput will coverge to a small regio. Thus, settig a extremely large CW does t brig positive effect. That s also the reaso that we set a limit to f. To prove performace robustess of the preset mechaism, we coduct experimets for differet trasmissio time. Figure 10(d) illustrates that throughput of the successful trasmissio time equals 5500 μs. This shows the similar result, our method performs the best at all time. From Figure 10(b) ad Figure 10(d), it ca be see that if trasmissio time is less, the degree of CW affectig throughput is larger ad our adaptive CW mechaism performs better tha other cases as well. We also verify the case whe there is a abrupt chage i the ode umber ad examie if it still works. Cosider the etwork has 40 odes at the begiig. At 60 secods, it reduces to 10 odes. We compare the situatio with 10 odes at the begiig ad record throughput at each secod. The simulatio result is show i Figure 11(a). It displays that after 60 secods, throughput of the situatio 1 has bee improved ad quickly approaches to the lie of situatio 2. This edorses performace robustess of our proposed mechaism Fially, the umber i Equatio (8) was chaged to 10 at the previous simulatio test. To prove that it wo t sigificatly alter the result, we coduct extra tests with the umber of odes = 30 ad compare it to the case of = 10. See Figure 11(b) for the result. It clearly shows that the value of does t sigificatly affect throughput. That demostrates robustess of our proposed approach to the etwork complexity. (d) 12

13 (a) Figure 11. Throughput at differet special case: (a) Situatio 1: 40 odes at etwork begiig. It remais 10 odes after 10 s. Situatio 2: 10 odes at all time; (b) Various settig of P b.. 6. Coclusio PLC is becomig mature i recet years. However, as the usual etwork commuicatio, the etwork cogestio problem is crucial whe cosiderig maitaiig commuicatio quality. While HomePlug AV is already a mature protocol i PLC, we propose here a adaptive cotetio mechaism istead of formulatig a ew protocol. The adaptive cotetio widow scheme oly eeds the iformatio from CSMA/CA i HomePlug AV. I additio, because the iformatio eeded is self-cotaied, oe does ot eed ot to correct the PHY layer settig to acquire extra iformatio from other statios. All eeded are to substitute the ew CW ad BC ito the origial HomePlug AV mechaism. This makes the approach more practical ad presets better feasibility. From the simulatio experimets coducted at NS3, it is foud that the proposed scheme ca effectively improve throughput. We have tested it with a variety of several scearios; satisfactory results have bee observed which show idetifiable improvemet of our proposed desig. Ackowledgemets This research was sposored by Natioal Sciece Coucil, Taiwa, uder the Grat NSC E MY3. Refereces [1] HomePlugPowerlie Alliace (2007) HomePlug AV Specificatio, Ver [2] Chug, M.Y., Jug, M.H., Lee, T.J. ad Lee, Y. (2006) Performace Aalysis of HomePlug 1.0 MAC with CSMA/CA. IEEE Joural o Selected Areas i Commuicatios, 24, [3] Velarde-Alvarado, P., Martiez-Pelaez, R., Ruiz-Ibarra, J. ad Morales-Rocha, V. (2014) Iformatio Theory ad Data-Miig Techiques for Network Traffic Profilig for Itrusio Detectio. Joural of Computer ad Commuicatios, 2, [4] Yoo, S.G. ad Bahk, S. (2011) Adaptive Rate Cotrol ad Cotetio Widow-Size Adjustmet for Power-Lie Commuicatio. IEEE Trasactios o Power Delivery, 26, [5] Krimiger, E. ad Latchma, H. (2011) Markov Chai Model of HomePlug CSMA MAC for Determiig Optimal Fixed Cotetio Widow Size. Proceedigs of IEEE Iteratioal Symposium o Power Lie Commuicatios ad Its Applicatios, Udie, 3-6 April 2011, [6] Liu, K.H., Hsieh, D.R., Hsu, J.Y. ad Chag, S.Y. (2012) Throughput Improvemet for Power Lie Commuicatio by Adaptive MAC Protocol. Proceedigs of IEEE Iteratioal Power Egieerig ad Optimizatio Coferece, Melaka, 6-7 Jue 2012, [7] Luca, D.B., Alessadro, S.D. ad Toello, A.M. (2013) MAC Ehacemets for G3-PLC Home Networks. Proceed- (b) 13

14 igs of IEEE Iteratioal Symposium o Power Lie Commuicatios ad Its Applicatios, Johaesburg, March 2013, [8] Tsokalo, I., Radeke, R. ad Lehert, R. (2013) Ehacemet of Backoff Algorithm i CSMA/CA Protocols for Broadbad PLC. Proceedigs of IEEE Iteratioal Symposium o Power Lie Commuicatios ad Its Applicatios, Johaesburg, March 2013, [9] Wu, H., Log, K. ad Heg, S. (2002) IEEE Distributed Coordiatio Fuctio (DCF): Aalysis ad Ehacemet. Proceedigs of IEEE Iteratioal Coferece o Commuicatios, 28 April-2 May 2002, [10] NS3. [11] Biachi, G. (2000) Performace Aalysis of the IEEE Distributed Coordiatio Fuctio. IEEE Joural o Selected Areas i Commuicatios, 18,

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