Summary. Date: September 14, Authors: Jim Zyren, Intersil, Jan Boer, Lucent Technologies, Donald C. Johnson, WLAN Consulting,

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1 Sepember 1999 doc.: IEEE /09-r1doc.: IEEE IEEE P80.11 Wreless LANs Proposal for a second leer for flng n e proceedngs of FCC OET Docke No Dae: Sepember 14, 1999 Auors: Jm Zyren, Inersl, Jan Boer, Lucen Tecnologes, Donald C. Jonson, WLAN Consulng, Summary Aaced s a proposal for a second leer for flng n e proceedngs of e FCC n NPRM, OET Docke Ts leer provdes addonal subsanve maeral o suppor e saemens n e frs leer fled on Augus 19, Te ex as been made by e expers menoned above, based on submssons and dscussons eld n meengs of e ad-oc regulaory group on Monday Sepember 13, Te nenon s o dscuss e ex on e Wednesday, Sepember 15, 1999 meengs of e ad-oc regulaory group w e am o recommend an and 80.0 combned e-mal ballo. Submsson (aorney revewed)submsson page 1

2 Sepember 1999 doc.: IEEE /09-r1doc.: IEEE /09 Sep 13, 1999 Magale R. Salas, Esqure Secreary Federal Communcaons Commsson S. SW Wasngon DC 0554 Re: Amendmen of Par 15 of e Commsson's Rules for Spread Specrum Devces, ET Docke No Dear Ms. Salas: IEEE 80, e LAN/MAN Sandards Commee ( e Commee ), s wrng n regard o ET Docke No : Amendmen of Par 15 of e Commsson s Rules for Spread Specrum Devces. On Augus 19, 1999, e Commee submed an ex pare leercommens n s proceedng expressng opposon o e proposed rules canges wc would allow wder cannels for FHSS sysems as descrbed n e Noce of Proposed Rule Makng (e Noce ) n s proceedng. Snce a me, e membersp as connued o analyse analyze e proposed rule canges. Te Commee respecfully subms ese addonal commens n s proceedng. Te Insue of Elecrcal and Elecroncs Engneers, Inc. (IEEE) s a USA-based nernaonal professonal organzaon w more an 35,000 members represenng a broad segmen of e compuer and communcaons ndusres. IEEE 80.11, a carered Workng Group under e Commee, as developed a sandard for Wreless Local Area Neworkng (WLAN) n e MHz band ( e 450 MHz band ). Te number of ndvduals and correspondng company sponsorsps n e IEEE Workng Group evdences e srong neres n wreless local area neworkng. Te Workng Group currenly as over 00 members employed by 86 companes Regardng e ssue of Rule canges o ncrease e cannel wd of FHSS rado cannel wd, e Commee as already commened on a number of pons n e correspondence of Augus 19, Tese commens are summarzed below: a. Te use of eavly overlapped cannels for Wde Band Frequency Hoppng (WBFH) sysems wll resul n sgnfcanly ncreased nerference among sysems employng s meod of cannel selecon. b. Increasng op rae for WBFH sysems wll no reduce e nerference rea o oer users of e band. In fac, s measure wll acually ncrease nerference w oer usersa. We noe a ere s no regulaory probon agans e use of sysems wc ave ger oppng frequences, bu we are of e opnon a e Commsson sould no make ger op raes mandaory. c. In addon, we fnd a e proposed reducons n ransmed RF power for WBFH sysems are no adequae o ensure a exsng sysems do no suffer ncreased nerference. d. We furer noe a e resulng ncrease n nerference descrbed above wll nder marke accepance of g speed wreless neworkng produc wc operae n e.45 GHz ISM band. Te Commee would lke o make e followng addonal commens relang o proposed canges n FHSS operang rules: a. Drec Sequence Spread Specrum (DSSS) sysems were able o aceve ger rougpu wou requrng a cange n e Commsson s Rules. More mporanly, ger daa raes were aceved w no cange n e Power Specral Densy (PSD) of e DSSS waveform. Terefore, ere s lle or no mpac n erms of ncreased nerference w oer users of e band. b. In e Noce, e FCC Commsson (please be conssen) asks for commens on (spell ou because frs me used) HWN s assumpon a wde band frequency oppng sysems wll be unable o conssenlcy aceve subsanally greaer daa raes an 1 MHz sysems. Ts commen by IEEE P80.11 (s reference s unclear, wc commen, commen a?) suppors HWN s vew n s maer. Te adverse effecs of mulpa on WBFH sysem rougpu are descrbed n deal n e followng paragraps. Submsson (aorney revewed)submsson page

3 Sepember 1999 doc.: IEEE /09-r1doc.: IEEE Currenly employed frequency oppng sysems complyng w Par 15 employ or 4 level FSK modulaon (1 or Mb/s) and ave a 0 db bandwd of 1 MHz. Te benefs of ese sysems are a ey can be manufacured a relavely low cos because ey ave nonlnear sgnal processng componens, wle ey manan a reasonable performance n a mulpa envronmen. Te narrow band FH sysems work sasfacorly n envronmens were e delay spread s n e range of nanoseconds wc are caracersc of large real sores and manufacurng facles. Te FH sysems work because of e frequency dversy capables neren o oppng. Narrow band frequency oppers experence s level of delay spread as fla fades. If, because of a fade no ransmsson s possble a e parcular frequency, e cance o be n a fade agan a e nex op (nex 1 MHz frequency cannel) s small. By wdenng e bandwd of e frequency opper o 3 or 5 MHz, e opper as o deal w n band mulpa dsoron nsead of fla frequency fadng. A e nex op (frequency) e cance a no ransmsson s possble because of mulpa remans g. Tere s a lnear relaonsp beween e nersymbol nerference caused by mulpa and e symbol leng; wdenng e bandwd of a ransmsson sysem w a facor x (wou cangng e modulaon meod) makes e sysem x mes more suscepble o mulpa. For a 5 MHz wde frequency oppng sysem employng or 4 level FSK s means a e sysem can only olerae delay spread spreads of up o 0-40 nanoseconds. Tese delay spreads are caracersc of ordnary rooms. Furer, n low cos mplemenaons, s amoun of n band dsoron can be nroduced by e ransm and receve flers, us reducng olerance o mulpa o almos zero. Suc sysems would no be vable from a user pon of vew. From above reasonng we conclude a a 5 MHz wde frequency opper employng 4 level FSK wll no work n a normal envronmen. To ge daa roug e frequency opper as o fall back o a narrower bandwd w a lower daa rae. Of course, a wde band FH sysem can be desgned o be more robus agans delay spread. If e same modulaon meod s mananed, en a form of equalsaon s necessary. Apar from e ger amoun of (sgnal) processng, wc ncreases componen cos, equalzaon also requres lnear processng n bo ransmer and recever ncreasng e cos of (lnear) componens. Oer modulaon meods a are more robus agans mulpa can be employed n wde band FH sysems. Tese meods owever requre lnear componens and a g amoun of sgnal processng. To brng e delay spread robusness for a wde band frequency opper o e level requred for normal operaon, ere s a cos (nong s free). Te requred componens (lnear power amplfers, lnear receve funcons (AGC), DSP componens) brng e cos o e level of currenly employed drec sequence sysems or ger. Drec sequence sysems are runnng a 11 Mb/s and w adequae robusness agans delay spread effecs. Te coss of s ype of equpmen are decreasng rapdly (refer o e Apple s Arpor produc announcemen n Augus s year). Based on above argumens, can be concluded a e HomeRF Workng Group clam a fuure wdeband FH servces can be mplemened a lower cos and w greaer mulpa robusness an can curren DS sysems operang a comparable speeds does no old and s msleadng. IEEE also subms addonal sudes n suppor of e saemens made n e earler leer of Augus 19, ) Te documen Inerference Poenal of WdeBand Frequency Hoppng Sysems on Packe Daa Sysems ncludes an analyss of e effec of e power level of e WBFH sysems..) Te documen Effecs of WBFH Power Reducons and Hop Rae presens analyss resuls sowng a ncreasng op rae ncreases e collson rae w bo DSSS and convenonal narrowband FHSS sysems. Te effecs of proposed power reducons s also descrbed n deal. In summary, e Commee opposes e canges o e operang rules for FHSS sysems as descrbed n e Commsson s Noce of Proposed Rule Makng n s proceedng. Te Commee reeraes commens made n e Augus 19, 1999 leer o e Commsson and addonally concludes a WBFH sysem wll suffer severe mparmen due o mulpa cannel dsoron. Te Commee s also forwardng wo papers as descrbed above n suppor of our earler commens n s maer. Respecfully, Submsson (aorney revewed)submsson page 3

4 Sepember 1999 doc.: IEEE /09-r1doc.: IEEE /09 James T. Carlo Vc Hayes Car, IEEE 80 LAN/MAN Sandards Car, IEEE 80.11, Wreless LANs Texas Insrumens Lucen Tecnology 908 Heaerdale Drve Zadelsede 1-10 Dallas TX JZ Neuwegen, e Neerlands cc: Carman Wllam E. Kennard Commssoner Susan Ness Commssoner Harold Furcgo-Ro Commssoner Mcael K. Powell Commssoner Glora Trasan Dale Hafeld Julus P. Knapp Neal L. McNel Karen Rackley Jon A. Reed Anony Serafn Submsson (aorney revewed)submsson page 4

5 Sepember 1999 doc.: IEEE /09-r1doc.: IEEE Annex 1 Inerference Poenal of WdeBand Frequency Hoppng Sysems on Packe Daa Sysems Dae: Sepember 13, 1999 Auor: Donald C.Jonson WLAN Consulng,Inc. Pone: Fax: e-mal: JonsDB@aol.com 1.0 Absrac Te effec of modfyng e 47 CFR Par frequency oppng spread specrum rules o perm a wder bandwd s nvesgaed relave o e nerference poenal on packe daa ransmsson sysems a conform o e curren rules. Te rules modfcaon would perm WdeBand Frequency Hoppng (WBFH) sysems w bandwds of 3 MHz and 5 MHz n addon o sysems operang under e curren rules a lm e bandwd o 1 MHz. Te probably of a WBFH ransmsson mulang a wreless daa packe s nvesgaed n erms of e WBFH and vcm power levels, e WBFH bandwd, e duraon of e vcm packe nerval and WBFH op nerval and poenal vcm recever parameers. A WBFH sysem operang n accordance w e proposed revsed rules and a poenal vcm wreless packe daa sysem conformng o e curren rules are consdered o operae n e same area. Te confguraon analyzed consss of a vcm packe daa sysem operang n a cenralzed mode and an nerferng WBFH sysem w ransmers evenly dsrbued wn and around e vcm sysem communcaon cell. Te proporon of WBFH ransmers a creae packe errors n e vcm recever s analyzed. I s sown a ncreasng e frequency oppng rae ncreases e probably of nerference o packe daa sysems. Te wder bandwd would, of self, ncrease e nerference probably, bu would also perm a ger opng rae. Te proposed rules modfcaon would place a lower lm on e oppng rae, bu would no mpose an upper lm. Te poenally ger oppng rae would furer ncrease e nerference probably. I s sown a ncreasng e bandwd of frequency oppng sysems o 3 or 5 MHz grealy ncreases e nerference o 1 MHz bandwd frequency oppng packe daa sysems. Te ncrease would requre e WBFH sysem o use a power level as muc as 0 db below e 1 MHz sysem o offse e effec of e wder bandwd alone. Te poenal ncrease n frequency oppng rae also produces a lke facor. Te effec on drec sequence packe daa sysems s less, bu s nevereless sgnfcan. I s sown a e cange would cause a 13 o 15 db effec on a packe daa sysem suc as one conformng o IEEE p Ta s, e WBFH power level would ave o be decreased by 13 o 16 db o ave e same nerference effec on s sysem as does a 1 MHz bandwd frequency oppng sysem. Submsson (aorney revewed)submsson page 5

6 Sepember 1999 doc.: IEEE /09-r1doc.: IEEE /09.0 Packe Overlap Dependence on Bandwd and Hop Tme Te relave overlap probably wll be nvesgaed ndependenly of e relave power level of e nerferng and vcm sysems. Ta s, wll be assumed a ere are a fxed number of WBFH ransmers near enoug o e packe recever o nerfere and a s number does no vary w bandwd. Ts wll laer be expanded o nvesgae e effec of e relave power levels of e wo sysems, ncludng e bandwd effecs on e nerference power level. Defne e followng parameers: B = Bandwd of e nerfered sgnal. B = Bandwd of e wdeband frequency oppng (WBFH) sysem (1, 3 or 5 MHz) B = Te nerference bandwd, e dfference frequency range over wc e WBFH sgnal nerferes w e vcm recever. B >= B + B 1 B = Toal bandwd of e WBFH sysem (75 o 85 MHz.) H = WBFH op me P = Packe ransmsson me. Refer o fgure -1 and consder a sngle acve wdeband WBFH ransmer wn range of a LAN packe recever. If one or more on-frequency ops sar n e nerval H + P, en overlap occurs. Probably op s on e packe frequency = Mean me beween sar of on-frequency ops = Packe B B + B B B H B B + B P H On-cannel opper H + P Fgure -1. Illusraon of WBFH Overlap w LAN Packe. Te mean number of ops a sar n e nerval H + P equals e duraon of s nerval dvded by e mean duraon beween ops. Le s mean number be m 1, en m 1 H + P B = H B H + P B + B H B If ere s one acve WBFH sysem n range of e packe LAN recever, en m 1 s e probably of overlap. If ere are more an one acve WBFH sysem n range, en e overlap probably can be modeled as a bnomal probably funcon w m 1 equal o e probably of success on eac ry (one ry per frequency op sysem). W N suc sysems n range, e overall probably of overlap s 1 1 m 1 Pr(overlap) = ( ) N 1 Reference 1 sows some measuremens of e nerference bandwd for wo frequency oppers usng e modulaon ecnque employed n e IEEE p80.11 frequency oppng wreless LAN. In e case of bo e 1 MHz and 5 MHz bandwd frequency oppers e 3 db nerference bandwd s approxmaely equal o e sum of e 0 db bandwds. Te frequency oppng sysems w a 0 db bandwd of 1 MHz ad a 3 db nerference bandwd of MHz and a w e 5 MHz bandwd ad a 3 db nerference bandwd of 9.5 MHz. Submsson (aorney revewed)submsson page 6

7 Sepember 1999 doc.: IEEE /09-r1doc.: IEEE Te process can be modeled as a Posson process f e mean number of overlaps s very low relave o e possble number. W N acve WBFH ransmers, e maxmum number of op sgnals a can sar wn e overlap nerval s m 1 N, us, f P + In N H P m << + In H were In(x) means e larges neger less an or equal o x. Te mean number s 1 e Posson process sould be a good approxmaon. Submsson (aorney revewed)submsson page 7 In e more general case ere s a larger populaon of WBFH ransmers, eac w a relavely low probably of beng acve. Tus, e mean number of overlaps s very low compared o e possble number and e Posson process apples. If ere are M frequency oppng ransmers n range and e mean probably a a ransmer s acve s p, en N s a random varable w mean Mp and e Posson dsrbuon s approprae. Le λ be e mean number of on-frequency ops sarng n e overlap nerval. In e former case λ 1 = Nm 1 and n e second case λ = Mpm 1. us, n e more general case = λ H + P B = Mp H B λ. (-1) Usng e Posson approxmaon, e probably of a leas one overlap s Snce Pr(overlap) 1 ε λ 3 λ λ 1 = λ + 6 ε λ, f λ << 1 en 1-e -λ λ and Pr(overlap) λ f λ << 1. Normally e packe error rae mus be less an 0.1 for a good qualy packe LAN. Te nformaon rougpu demand ends o rack e capably, us e facor Mp wll be relavely ndependen of e frequency oppng bandwd. Two facs are obvous from e expresson for λ. Frs, e overlap probably, and us nerference probably s ncreased w sor op mes. Te frs brackeed expresson approaces e value P /H as e op me approaces zero. Ts would mply a a mnmum op me would be a beer requremen an would be a maxmum op me. Oerwse, a cones s lkely o develop o opmze nerference robusness by sorenng e packe mes. Wreless packe daa sysems are neffcen w very sor packe mes, us a cones o mac packe mes o op mes would lead o neffcency. Second, ncreasng e frequency oppng bandwd ncreases e nerference poenal. Ts s parcularly severe wen e vcm bandwd s low, as s e case for packe daa frequency oppng sysems conformng o e presen bandwd rules (suc as ose operang n accordance w e IEEE pp80.11 sandard). Te curren rules requre a 1 MHz maxmum 0 db bandwd. Two frequency oppng sysems complyng w ese rules ave an nerference bandwd of less an MHz even f e frequences do no mac. Wdenng e frequency oppng bandwd o 5 MHz would ncrease e number of nerferers by a facor of a leas 3. Some examples of e overall effec are presened n secon Te Effec of e Inerference Power Level Te number of ransmers n nerference range of a vcm packe ransmsson sysem operang n a common area depends upon e power level dfference beween e poenal nerferer and e poenal vcm. Lowerng e WBFH power level s proposed as a means of equalzng e ncreased nerference effec of a wder frequency oppng bandwd. Te relave power level effec on nerference wll be nvesgaed ere. A ransmer wll nerfere w anoer sysem recever f s wn e range n wc e nerference power produces n e recever exceeds e requred carrer o nerference power margn. Ts nerference level depends n urn on e power level and ransmsson dsance of e poenally nerfered sysem. If e deploymen area of

8 Sepember 1999 doc.: IEEE /09-r1doc.: IEEE /09 e nerferer and vcm sysem s smaller an e medan nerference area, en e majory of e ransmssons wll creae nerference. A reduced power level only elps o e exen a e reduced level reduces e nerference area relave o e deploymen area. Te dependence of e nerference range on power level wll be esablsed. Defne e followng addonal parameers: p 1 = e ransm power of sysem 1 (e nerferer sysem) p 1 = e ransm power of sysem 1 wn e bandwd of sysem (e vcm sysem) p = e ransm power of sysem γ = e requred sgnal power o nerference power rao of sysem c = e sysem ransmsson range (e communcaon range) r = e sysem 1 ransmsson range (e nerference range) a = e ransm o receve power rao a dsance c (e sysem range) a 1 = e ransm o receve power rao a dsance r (e sysem o sysem 1 range) α = e aenuaon exponen. β = e proporon of nerferer power wn e bandwd of e vcm recever. B β = 10Log B B β = 0 oerwse. > B In e followng, upper case leers wll represen decbel quanes and lower case leers wll represen raos. Ta s, Γ = 10Logγ, A x = 10Loga x and P x = 10Logp x. c P r P 1 Fgure 3-1. Illusraon of e Inerference Range Compared o e Communcaon Range Te doed crcle n fgure 3-1 represens e nerference range of a ransmer of power level P 1 o a recever cenered n a LAN cell wen e ransmsson dsance s c. Te rao of e nerference range r o e communcaon range c wll be examned. Te necessary condon for creang nerference s p1a p a 1 γ. Submsson (aorney revewed)submsson page 8

9 Sepember 1999 doc.: IEEE /09-r1doc.: IEEE Te aenuaon exponen s commonly modeled as avng a value of up o a range of 5 o 10 meers and a larger value α beyond s range. In s model, w e α = range a 10 meers, e aenuaon n decbels can be expressed as () r = Af α + 10αLogr Av A + 10, (3-1). n wc A f s e aenuaon a 10 meers and A v s an approxmaely normally dsrbued random componen w mean zero. Te condon for avodng nerference can be expressed n decbel quanes and reduced o Logr = αlogc P ( A A ) α. (3-) Γ + v v1 On furer reducon r c P1 P +Γ Av 1 Av 10α 10α P = 10 *10 (3-3). Te frs exponenal s e medan nerference range o communcaon range rao and e las facor (ncludng e varable aenuaon) s a random mulpler. As an example, assume α = 3 and Γ = 13 db and equal power levels n eac sysem. Te medan nerference range s en.7 mes e communcaon range. Te mean ransmsson dsance o e cener of a cenralzed LAN cell s 0.75 mes e cell radus. Tus, e medan nerference dsance s approxmaely.7x0.75 =.0 mes e cell radus and e medan nerference area s approxmaely 4 mes e communcaon coverage area. Te effec of power level can beer be llusraed by compung e proporon of WBFH devces n a ypcal deploymen area a creae nerference o a vcm ransmer-recever combnaon. Te vcm sysem mg be a wreless LAN sysem, bu may also be anoer ype of packe based dgal communcaon sysem. Consder e regon oulned n fgure 3-. Here poenal vcm devces and poenally nerferng WBFH devces are evenly dsrbued over e area of radus r. Te vcm devces operae n a cenralzed mode n wc all ransmssons nvolve a cenralzed access pon (a n e dagram) and a moble devce (m n e dagram). Te nner concenrc crcle of radus 1 s e boundary of e vcm sysem cell, a s, e vcm devces wn s crcle communcae roug e access pon sown. A recangular deploymen area s more ypcal, bu a crcular deploymen area and cell sape lends self o a convenen evaluaon and wll serve o sow e power level effec. Buldng or offce area sze normally esablses e deploymen area dmensons. Usually, a sngle cell wll be suffcen o cover an area; a power level of 50 mw s suffcen o relably cover a communcaon radus of up o 50 meers. Te sngle cell deploymen area case s represened by r = 1. Fgure 3- llusraes e followng developmen. Esabls e proporon of nerferng devces a a dsance r from e moble recever (ose wn a small dfferenal of e doed lne n fgure 3-). Te recever s a dsance c from e desred ransmer. To do s rearrange equaon 3- as follows. A v1 A v = A v = P 1 P r + Γ 10αLog c Ts gves e necessary devaon from e mean of e wo dsance aenuaon values o make e nerference dsance equal r wen e communcaon dsance s c. A v1 and A v are e fadng and sadowng varaon n aenuaon. A v1 and A v are eac approxmaely normally dsrbued w mean zero. Te varance dfference s e sum of e varances of eac and e sandard devaon s e square roo of e varance. Le e sandard devaon of A v = A v1 - A v be A s. Ten A v /A s s a random varable of mean zero and sandard devaon 1. Submsson (aorney revewed)submsson page 9

10 Sepember 1999 doc.: IEEE /09-r1doc.: IEEE /09 r r φ c a m 1 r Fgure 3-. Confguraon for Analyzng e Relave Number of WBFH Inerferers. Te moble devce (m) s recevng from e access pon (a). Te nner concenrc crcle s a cenralzed LAN cell for wc e radus s normalzed o 1. Te deploymen area s defned by e ouer crcle of normalzed radus r. Te normalzed communcaon dsance s c. Te doed lne s a crcular arc of radus r on wc all WBFH devces are equdsan from e moble recever. Inerferng and vcm devces are evenly dsrbued wn e area. If e nerferer bandwd s greaer an e vcm bandwd, e nerferer power receved by e vcm s reduced by e bandwd rao facor β. B β = 10Log B B β = 0 oerwse. Ten P 1 = P -β and > B P P 1 = P. Usng e above defnons, equaon 3- can be rearranged o A A v s P β + Γ 10α r = Log. A A c s s Te random varable A v /A s as a mean of zero and a sandard devaon of 1 and approxmaely obeys e normal probably dsrbuon. Defne X as e rg and sde of e equaon P β + Γ 10α r X = Log. A A c s s Le P n (X) be e value of e normal dsrbuon funcon for a varable of mean zero and sandard devaon 1, en P n A v ( X ) = Pr > X As equals e probably a a WBFH devce a dsance r wll nerfere wen e vcm communcaon dsance s c. In oer words, P n (X) s e proporon of devces a dsance r wc wll ave suffcen power level o nerfere w e vcm devce wen e communcaon dsance s c. (3-4) Submsson (aorney revewed)submsson page 10

11 Sepember 1999 doc.: IEEE /09-r1doc.: IEEE If N s e oal number of WBFH devces wn e deploymen area (e area bounded by r n fgure 3-), en N e densy of WBFH devces s. If ese devces are evenly dsrbued, e number of devces wn δr of π r e doed arc n fgure 3- s ( φrδr ) N πr. Furer, e number wc nerfere w e moble recever ( N m ) s N N φ ( r, c) r P n ( r, c, P, β Γ ) δr m =, πr (3-5) Te angle of e arc n fgure 3- (φ) can be esablsed o be φ = Cos φ = π 1 r r + c rc r < r c r r c Tus, e negral of equaon 3-5 from 0 o r +c s e oal number of WBFH devces a nerfere w e moble recever wen e communcaon dsance s c. Wen e LAN recever s a e access pon e number of devces a nerfere s defned as N a. In s case, φ s always π and e number of devces a nerfere w e access pon recever s e negral of equaon 3-5 from 0 o r w φ always equal o π. Te communcaon dsance wn e cell (c) s also a random varable and e number of nerferers mus be weged by e probably densy of c. Ts probably densy s ( x δx < c < x + x ) = 3x p( x) = Pr δ δx (3-6) Te overall proporon of devces a nerfere s deermned by e double negral c = x 3 c r x ( r, c ec) N N, were x s eer a or m. Annex 1 gves e full equaons and descrpon of e numercal negraon used. In a ypcal cenralzed wreless LAN, suc as an IEEE sandard LAN operang roug an access pon, e nformaon flow s balanced o and from e access pon. Some packes mus flow n e oppose drecon o e nformaon flow, bu ese are supervsory packes and are of sorer duraon an e nformaon packe. Te overall proporon of WBFH ransmers a nerfere wll be slgly ger because of e supervsory packe flow, owever s ncrease wll be small and wll be assumed ere a e overall proporon s (N a + N m )/N. A grap of s quany versus e power level relaed parameers s gven n fgure 3-3. Te parameers of e grap are ypcal values a can be expeced n a relavely open offce ype envronmen. Te propagaon exponen α s ypcally abou 3 n suc an envronmen and s s used n e grap. Te aenuaon varaon abou e regresson value predced by e exponen α s comprsed of a varaon due o sadowng and anoer due o mul-pa fadng. Te ypcal varaon due o sadowng s 3 o 4 db and a due o fadng s abou e same. Te fadng componen can be made neglgble n e desred communcaon pa by equalzaon and dversy ecnques. So, a reasonable value of e overall sandard devaon of e dfference aenuaon A s can be derved by assumng ree 4 db componens wc add n an RMS manner. Te value of 6.93 db used n e grap s 4 mes e square roo of 3. (3-7) Submsson (aorney revewed)submsson page 11

12 Sepember 1999 doc.: IEEE /09-r1doc.: IEEE / Percen Inerferng α = 3.0 A s = 6.93 db r = r = db IEEE 1 MHz Frequency Hoppng C/I-β = 16 db P-β+ β+c/i (db) Proporon Inerferng Vs. Dfferenal Power Level Fgure 3-3. Ts sows e quany (N a + N m )/N for varous raos of deploymen radus o cell radus. Typcal values of e parameers α and A s are used. Te vercal doed lne a 16 db corresponds o e case were an IEEE p80.11 sandard frequency oppng wreless LAN vcm sysem as e same power level as e nerferng WBFH sysem. Te curves of fgure 3-3 end o become fla as e C/I requremen of e vcm recever ncreases. Hg C/I requremens are caracersc of sysems w g modulaon effcency. Tus, e nerference effec due o power level dfference s relavely nsensve o reducng e nerferer power level n g modulaon effcency devces. 4.0 Compose Inerference Effec Te probably of packe overlap of a wde bandwd frequency oppng sysem on a packe daa sysem was developed n secon on e assumpon of a fxed populaon of nerferng ransmers all of wc ad suffcen power level o creae nerference. Secon 3 en sows e effec of power level and bandwd on e sze of s populaon. Te overall packe nerference probably can be consdered o be e produc of ree facors 1. A facor dependen on e oppng frequency or perod. Ts s e (H +P )/H erm of equaon -1.. A facor dependen on e relave bandwds. Ts s e B /B (B+B)/B erm of equaon A facor dependen on e nerference o vcm power level rao. Equaon -1 of secon gves e packe overlap probably (λ) dependence on e WBFH frequency oppng rae and bandwd. H + P B = Mp H B λ and secon 3 added e effec of power level. Te Hoppng Frequency Facor Ts s e facor H + P H of equaon -1. Ts erm ncreases w e oppng rae (1/H ) of e nerferng frequency opper. Increasng e bandwd as proposed for e WBFH perms e op me (H ) o be lowered and us perms a ger nerference facor. Submsson (aorney revewed)submsson page 1

13 Sepember 1999 doc.: IEEE /09-r1doc.: IEEE Te fases oppng me s lkely o be e amoun of me necessary o ransfer one packe of nformaon. Ts wll usually nclude an excange of a long nformaon packe and one or more sor supervsory packes. Te vcm wll be suscepble o nerference on eac packe ransferred; f eer packe s mulaed e nformaon packe wll need o be reransmed. Consder e me for e complee packe excange assocaed w one nformaon packe o be e packe me. I s reasonable o assume a e frequency opper wll op as fas as praccal and s s afer eac of s nformaon packe excanges. In s case, e op me s e packe me of e frequency opper. I s also reasonable o consder a bo e op me and e packe me s nversely proporonal o e sgnalng speed. If eac sysem uses packes conanng e same amoun of nformaon (e same number of bs), en eac would ave a packe me bearng e same nverse proporonaly o sgnalng rae. Tus, H + P H k / Sr = k / k / S = k / S r r S = 1+ S r rv. S r and S rv are e sgnalng rae of e nerferer and vcm sysems respecvely. Te IEEE p80.11 frequency opng LAN as an upper sgnalng speed of MB/s. Ts s wo mes e 0 db bandwd, us wll be assumed a e sgnalng speed of a frequency opper s B were B s e 0 db bandwd as n secon. Te rao of s facor w a oppng bandwd of B o a wen e bandwd s 1 MHz s en Hoppng rae facor = Srv + B S + rv. Table 4-1 gves values of s facor for e curren sgnalng speeds of e IEEE p80.11 sandard. Te IEEE p80.11 frequency oppng op me s 100 mllseconds. Ts makes e oppng rae facor neglgble and makes e sandard frequency opper frendler o bo oer frequency oppers and o drec sequence sysems. Submsson (aorney revewed)submsson page 13

14 Sepember 1999 doc.: IEEE /09-r1doc.: IEEE /09 Vcm sgnalng speed S v (Mb/s) Frequency opper bandwd (B n MHz) Submsson (aorney revewed)submsson page 14 Hoppng rae facor any Table 4-1: Values of e Hoppng Rae Facor n Inerference Probably Te nerference probably of a frequency oppng sysem s ncreased by s facor f e frequency oppng bandwd s ncreased from 1 MHz o B, e frequency-oppng perod s equal o an nformaon packe ransmsson me and all packes conan e same amoun of nformaon. Even a e ges sgnalng speeds now used, e oppng rae facor s very sgnfcan. Te Hoppng Bandwd Facor Ts s e facor B B + B B B of equaon -1. Te curren frequency oppng bandwd s 1 MHz and e oal oppng band (B ) s proposed o say e same for e WBFH. Tus, e rao of e value of s erm w a wdeband frequency oppng sysem o e value w a 1 MHz bandwd frequency oppng sysem s Bandwd facor = B + B B +1. Table 4- compares s facor for e wo bandwds used n e IEEE p80.11 sandard. Te frequency oppng PHYscal layer (PHY), 0 MHz bandwd s 1 MHz and e drec sequence PHY bandwd s approxmaely 17 MHz. Vcm bandwd (B ) Frequency oppng bandwd (B ) Bandwd facor any 1 1 any Table 4-: Values of e Bandwd Facor n Inerference Probably Te nerference probably of a frequency oppng sysem s ncreased by s facor f e frequency oppng bandwd s ncreased from 1 MHz o B. 5.0 WBFH Inerference o IEEE p80.11 Sandard LANs Wreless packe daa sysems conformng o e IEEE p80.11 sandard for wreless LANs wll be used as example sysems o demonsrae e relave nerference poenal of wde bandwd frequency oppng sysems. Te IEEE p80.11 sandard specfes bo a frequency oppng and a drec sequence spread specrum wreless LAN PHYscal layer (PHY) usng e.4 GHz band. Mos sysems now n operaon follow s sandard. Te IEEE drec sequence PHY uses a cp rae of 11 Mcps/second. Te 0 db bandwd s no specfed bu s usually abou 17 MHz. Te drec sequence sgnalng speeds are 1,, 5.5 and 11 Mb/s. Te frequency oppng PHY uses a 0 db bandwd of 1 MHz and sgnalng speeds of 1 and Mb/s.

15 Sepember 1999 doc.: IEEE /09-r1doc.: IEEE Te IEEE p80.11 wreless LAN producs now ypcally use a power level of abou 16 o 0 dbm even oug e permssble level s 30 dbm. Te lower power level s easer o generae and s suffcen for e nsde communcaon dsances for wc e LANs are used. Te peoners seekng o ncrease e frequency oppng bandwd propose o lm e WBFH power level o 3 and 5 dbm. Snce s s above e levels now used, wll ave lkely ave lle effec on e WBFH power level. I can be expeced a WBFH LANs wll ave abou e same power level as curren LANs f e power level lm s lowered. Ts secon evaluaes e overall nerference effec caused by ncreasng e frequency oppng bandwd, akng no accoun e wo facors of secon 4 and e power level effec of secon 3. I can be expeced a e mos severe effec wll be on 1 MHz bandwd frequency oppng sysems as opposed o a on e drec sequence sysems. Ts s because e drec sequence sysems ave ger bandwd and sgnalng speed and are more ressan o nerference, a s, e nerference dsance of secon 3 s lower. Drec sequence spread specrum sysems are necessary, wn e curren rules, f sgnalng speeds above abou Mb/s are requred. Drec sequence sysems are very sensve o fas frequency oppng sysems. Te IEEE p80.11 sandard uses slow frequency oppng wc neuralzes e oppng rae facor beween e IEEE p80.11 sysems and us makes e sandard sysems more compable. Te oppng rae facor of able 4-1 s compared o a 1 MHz bandwd sysem a also uses fas frequency oppng. Te rao would be muc ger f a fas frequency oppng WBFH sysem was compared o e slow oppng sysem of IEEE p IEEE p80.11 Frequency Hoppng Sysem Wdenng e bandwd wou cangng e nerferer power level reduces e nerference power level wn a 1 MHz bandwd frequency oppng recever, us β of secon 3 s greaer an 1 for a 1 MHz bandwd frequency oppng vcm. Ts power reducon facor (β) for e proposed nerferng sysem bandwds s β = 0 db for e 1 MHz bandwd, β = 4.8 db for e 3 MHz bandwd and β = 7 db for 5 MHz bandwd. Te IEEE sandard frequency oppng LAN C/N requremen s 3 db for Mb/s and 0 db for 1 Mb/s and e wde bandwd sgnals nerceped by a narrow bandwd recever can be reaed as gaussan nose. Tus, e C/I (Γ of e equaons) requremen s approxmaely e same as e C/N requremen. Te probably of packe overlap s drecly proporonal o e bandwd facor of able 4- mes e oppng rae facor of able 4-1. Te approxmae value of e bandwd facor for 3 and 5 MHz bandwd sysems compared o 1 MHz bandwd sysems s and 3 respecvely (able 4-). Te facor due o e poenally ger oppng rae can also be or 3 respecvely (able 4-1). As an example, assume a e WBFH bandwd s 5 MHz and e produc of ese facors s 3. Ts s e mnmum value of e facor and would apply f e WBFH op me effec was neglgble due o a low oppng rae. Refer o fgure 3-3 o assess e power level effec. For a oal area equal o one communcaon cell (r = 1), 85.6 percen of e 1 MHz frequency oppers wll ave g enoug power level o nerfere w e Mb/s IEEE LAN ( P = 0, β = 0 and C/I = 3 db). 8.5 percen of e 5 MHz frequency oppers wll nerfere ( P = 0, β = 7 db and C/I = 3 db). Tus, e reducon n e proporon a nerfere due o e reduced level of nerceped power s 8.5/85.6 = 0.96, provded e sysems use e same power level. However, ree mes as many devces of equal power level generae overlappng ransmssons wen e bandwd s ncreased o 5 MHz. Te proporon of devces w suffcen power level o nerfere would need o be reduced o 1/3 o compensae. Ta s, e proporon nerferng would need o be no more an 85.6%/3 = 8.5%. Ts would requre a 1.0 db power reducon n e 5 MHz frequency opper ransmer relave o e 1 MHz sysem power level. If e power level dfference s 7 db (as requred by e proposed rules f all sysems operae a maxmum permssble power), e proporon of nerferers becomes 7.6%. Tus, an ncrease of e bandwd o 5 MHz accompaned by a 7 db power reducon ncreases e number of nerferers by a leas a facor of 7.6x3/85.6 =.5. Submsson (aorney revewed)submsson page 15

16 Sepember 1999 doc.: IEEE /09-r1doc.: IEEE /09 Table 5-1 sows e sows e resul of e above compuaon for a range of bandwd and nerference facors. Te able sows e amoun e WBFH power would ave o be reduced relave o e 1 MHz bandwd sysem power n order o manan e same nerference probably for e 3 and 5 MHz bandwd sysems as for a 1 MHz bandwd sysem. Te bandwd-oppng rae facor apples o a 1 MHz bandwd devce w a C/I value of 3 db. Te bandwd oppng rae facor (column 3) s sown a an nermedae and a maxmum value for eac WBFH bandwd. Te proporon of devces w suffcen power level o nerfere decreases w larger deploymen areas. However, even a very large deploymen areas e ncreased bandwd causes ncreased nerference unless e power level of e WBFH sysems s drascally lower an a of e 1 MHz bandwd sysems. Toal radus o cell radus rao (r ) Bandwd rao power reducon facor β (WBFH bandwd) Produc of bandwd and oppng rae facors Necessary WBFH power reducon db (3 MHz) 19.0 db > 6 db db (5 MHz) db > 6 db db (3 MHz) 14.5 db db db (5 MHz) db > 4 db db (3 MHz) 11.5 db db.0 7 db (5 MHz) db db Table 5-1: Necessary Power Level Dfference o Equalze Inerference Probably o a 1 MHz Bandwd Mb/s Sysem. Te nerference probably of a frequency oppng sysem of 3 and 5 MHz bandwd s compared o a of a 1 MHz bandwd sysem. Te wder bandwd sysem power level would need o be less an a of a 1 MHz bandwd frequency oppng sysem by e amouns of e able f e nerference poenal s o be equalzed. Te vcm sysem as a 1 MHz bandwd and a 3 db C/I requremen. Tese parameers approxmaely mac e IEEE p80.11 Mb/s frequency oppng PHY. Drec Sequence Sysem Te IEEE p80.11 drec sequence PHY uses an 11 Mcp/second sgnalng rae and as a 0 db bandwd of approxmaely 17 MHz. Tus, e bandwd facor affecng e number of overlappng ransmssons s 1.11 and 1. for e 3 MHz and 5 MHz WBFH sysems respecvely (able 4-) and e oppng rae facor s poenally 1.4 and 1.75 respecvely. Tus, e poenal bandwd oppng rae facor produc s 1.6 for e 3 MHz bandwd and.1 for e 5 MHz bandwd. A ypcal 11 Mb/s IEEE p80.11 drec sequence mplemenaon as a C/N requremen of 1.5 db and a C/I requremen for a sngle frequency one of abou 7 db. Wen a consan amplude nerferng sgnal as a bandwd n excess of a of e unspread drec sequence sgnal, e C/I requremen s ger an for a narrower bandwd sgnal. Tus, e C/I requremen for a 1, 3 and 5 MHz bandwd consan amplude modulaed sgnal s beween 7 db and 1.5 db f e nerferng sgnal s of consan amplude. Te requremen ncreases w ncreasng bandwd. Tere s no assurance a e WBFH sysem wll use a consan amplude sgnal. If e sgnal s no consan amplude, e C/I requremen could be as g as e C/N requremen of 1.5 db. A C/I requremen of 10 db wll be assumed for comparson purposes. Te nerference effec would be worse f e WBFH sgnal s no of consan amplude. Table 5- sows e sows e amoun e WBFH power would ave o be reduced relave o a of a drec sequence sysem power n order o manan e same nerference probably for e 3 and 5 MHz bandwd sysems as for a 1 MHz bandwd sysem. Te bandwd-oppng rae facor apples o devce suc as an IEEE p80.11 sandard drec sequence PHYscal layer (PHY) w a bandwd of 17 MHz, a sgnalng speed of 11 Mb/s and a C/I requremen of 10 db. Submsson (aorney revewed)submsson page 16

17 Sepember 1999 doc.: IEEE /09-r1doc.: IEEE Toal radus o cell radus rao (r ) Produc of bandwd and oppng rae facors Necessary WBFH power reducon Table 5-: Necessary Power Level Dfference o Equalze Inerference Probably o a Drec Sequence Spread Sysem. Te nerference probably of a frequency oppng sysem of 3 and 5 MHz bandwd s compared o a of a 1 MHz bandwd sysem n wc e vcm sysem s a drec sequence spread specrum sysem of 17 MHz bandwd and 11 Mb/s sgnalng speed. Te wde bandwd frequency oppng sysem power level would need o be less an a of a 1 MHz bandwd frequency oppng sysem by e amouns of e able f e nerference poenal s o be equalzed. Te vcm sysem as a 10 db C/I requremen. Tese parameers approxmaely mac e IEEE p Mb/s drec sequence PHY. Te able does no ake no accoun e effec of e ger C/I needed for wder bandwd nerferers. Ts effec s lkely on e order of 1 o 3 db. Tus, e overall effec s 14 o 16 db on a drec sequence packe daa sysem w e parameers used n e able. Oer drec sequence sysems may use lower bandwd and ger C/I. Te effec would be worse on suc sysems. An ncreased bandwd for a drec sequence sysem would arm e nerference suscepbly from all frequency oppng sysems; ncreasng e drec sequence bandwd w ger spreadng would no be of benef. s would ad n e relave performance bu worsen e overall performance. Conclusons of Secon 5 Te specfc sysems evaluaed serve o llusrae e effec of a wder frequency oppng bandwd on a range of curren packe daa sysems. Te effec of ncreasng e frequency oppng bandwd s mos severe on e 1 MHz bandwd frequency oppng packed daa sysem because of e low bandwd and e g C/I rao. I s less on e drec sequence sysem because e bandwd s ger and e C/I s lower for s sysem. Tese specfc sysems are crcal owever. IEEE p80.11 as spen 8 years esablsng ese sandards based on e curren spread specrum rules. 6.0 Summary and Conclusons Te effec of e frequency oppng spread specrum bandwd and oppng rae on nerference generaon was frs analyzed separaely form power level, en e effec of power level was nvesgaed. A parcular pyscal confguraon ncludng a WBFH sysem and a poenal vcm sysem n a common area was analyzed for e nfluence of power level on nerference. Te necessary reducon n power level of a wde bandwd frequency oppng sysem compared o a sysem followng e curren rule n order o manan equal nerference probably was evaluaed. Lowerng e regulaon lms by 5 o 7 db for wder bandwd frequency oppng, as proposed, wll no ensure any relave power level reducon on curren sysems. Curren spread specrum wreless LANs ulze power levels 10 o 13 db below e allowable lms. Ts s all a s necessary o operae a e normal nsde ranges and propagaon condons now encounered. Te regulaons would need o lower e lms by a leas 10 db n addon o e values deermned ere n order o assure e nerference poenal of e wde bandwd sysems s no ger an a of e curren rules. I was sown a e nerference poenal ncreases w e frequency oppng rae as well as bandwd; and a ger bandwd perms a faser oppng rae. An upper lm on e frequency oppng rae would be beer an a lower lm. Te proper upper lm would lower e nerference poenal of 1 MHz bandwd sysems as well as a of ger bandwd sysems. Lowerng power as lle effec on sysems w g modulaon effcency. Suc sysems ave a g C/I requremen and e medan nerference range exceeds mos deploymen area szes. Submsson (aorney revewed)submsson page 17

18 Sepember 1999 doc.: IEEE /09-r1doc.: IEEE /09 Increasng e frequency oppng bandwd o 3 or 5 MHz, as proposed, was sown o ave a very severe effec on low bandwd sysems w a g C/I requremen suc as sysems conformng o e curren frequency opng rules. A packe daa sysem conformng o e IEEE p80.11 frequency oppng sandard was used as e example of suc a sysem. Te necessary power level reducon for s sysem w slow frequency oppng s on e order of 0 db compared o a 1 MHz frequency oppng sysem. I s n excess of 6 db for fas frequency oppng. Te effec on a ypcal drec sequence sysem was also evaluaed. Ts was sown o be abou 13 o 16 db. Mos of s effec s due o e poenal effec of fas frequency oppng. Tere s a severe effec on drec sequence sysems from any fas frequency oppng sysem. IEEE p80.11 allevaes s effec by requrng slow frequency oppng n e sandard frequency oppng PHY. Inerference from any frequency oppng sysem o a drec sequence sysem ncreases w ncreasng drec sequence bandwd, even oug relave nerference of wde bandwd sysems and 1 MHz bandwd sysems decreases w frequency oppng bandwd. Tus, ncreasng e spreadng gan s no a reasonable opon for lowerng e nerference effec. References 1. Effec of Overlappng Cannels on WBFH Sysems Relably. Jm Zyren, Don Sloan and Ad Kamerman, doc.: IEEE p /170, July, Annex 1 : Evaluaon of e Relave Numbers of Inerferers Ts secon sows e dealed equaons used o evaluae e proporon of WBFH devces a nerfere as a funcon of e power level, bandwd and vcm recever parameers. Te parameers below are defned n e man ex. Te quany P n (X) s common o e equaons for bo e moble and e access pon vcm devces n a cenralzed LAN cell. In eac case P β + Γ 10α r X = Log A A c s s and P n (X) s e normal probably dsrbuon funcon for a mean of zero and sandard devaon of 1. Te proporon of WBFH devces a nerfere w e moble devce was evaluaed usng e followng summaon. N N m n wc π r 3 N mx M φ NmxM mx n= 1 m= 1 mx () c ()( r r + c)( r, c) P ( X ) = (A1) m.5 r = M ( r c) + mx c n.5 = and N mx φ = Cos φ = π 1 r r + c rc r < r c, r r c Submsson (aorney revewed)submsson page 18. N mx and M mx deermne e number of seps used n e numercal negraon. Compuaons compared wn 1% w N mx, M mx = 10 and 5. N mx, M mx = 5 was used n e evaluaon. Te proporon of WBFH devces a nerfere w e access pon was evaluaed usng e summaon. N N a n wc = r N 6 mx M N mx mx n= 1 M mx () c rr P ( X ) m= 1 n n (A)

19 Sepember 1999 doc.: IEEE /09-r1doc.: IEEE m.5 r = r M N mx mx n.5 c = Equaon A dffers from equaon A1 n e defnon of r and e fac a φ s a consan equal o π radans for e access pon. Te able below was used o deermne P n (X). Lnear nerpolaon was used beween e pons of e able. X P n (X) P n (-X) = 1-P n (X) P n (X) = 1 for X >= 3.5. X P n (X) Submsson (aorney revewed)submsson page 19

20 Sepember 1999 doc.: IEEE /09-r1doc.: IEEE /09 Annex Effecs of WBFH Power Reducon and Hop Rae Dae: Sepember 13, 1999 Auor: Jm Zyren and Perre Gandolfo Inersl Melbourne, Florda, USA Pone: (407) Fax: (407) e-mal: Absrac In a recen NPRM (ET Docke 99-31), e FCC proposed o amend e rules for Frequency Hoppng Spread Specrum (FHSS) rados operang n e.45 GHz ISM band. Proposed rule canges nclude reduced ransm power levels and faser op raes for Wde Band Frequency Hoppng (WBFH) rados operang on 3 MHz or 5 MHz wde cannels. Te mpac of proposed power reducons s dscussed. An analyss demonsrang a ncreasng e requred mnmum op rae for WBFH rados acually ncreases nerference o oer users s presened. 1.0 Summary Inersl opposes canges n e operang rules governng operaon of FHSS rados n e.45 GHz band as proposed by e HomeRF Workng Group n a November, 1998 peon for rule makng. In a peon, HomeRF soug an ncrease n e FHSS occuped cannel wd. Ts ncrease would allow FHSS rados o operae w cannel wds of 1, 3, or 5 MHz. Sysems employng 3 MHz wde cannels or 5 MHz wde cannels are collecvely referred o as Wde Band Frequency Hoppng (WBFH) rados. HomeRF assered a e nerference resulng from e wder cannel wds could be offse by a combnaon of power reducon n proporon w e expanson n cannel wd, and an ncrease n e op rae. Te rules for e ree varaons of FHSS cannel wd are summarzed n Table Cannel Wd Max Power Max Dwell Tme Mnmum # Hops 1 MHz 30 dbm 400 msec 75 3 MHz 5 dbm 50 msec 75 5 MHz 3 dbm 0 msec 75 Table Proposed FHSS Cannel Parameers In e subsequen NPRM (ET Docke 99-31), e Offce of Engneerng and Tecnology (OET) ndcaed a was of e opnon a e proposed rule canges would no resul n ncreased nerference o Drec Sequence Spread Specrum (DSSS) sysems. However, OET specfcally soug commen on weer e reducon n power and ncrease n op rae as descrbed above would, n fac, preclude any ncrease n nerference o DSSS sysems. Due o e fac a nearly all porable FHSS and DSSS rados operang n accordance w Par 15, Secon 47 of e Commsson s Rules ransm a 0 dbm (100 mw) or less, e power reducons suggesed by HomeRF appear o offer lle or no proecon o exsng users of e.45 GHz ISM band. In addon, s sown by smple analyss a ncreasng e op rae as suggesed by HomeRF wll acually resul n an ncrease n nerference o exsng DSSS and FHSS sysems..0 Power Reducon Te reducon n power as proposed by HomeRF s no adequae o ensure a exsng users of e band, ncludng bo FHSS and DSSS rados, wll no suffer adverse effecs. Te reason s smple. Te reduced power levels sown n Table are above e ransm power levels of nearly all porable devces on e marke oday. Submsson (aorney revewed)submsson page 0

21 Sepember 1999 doc.: IEEE /09-r1doc.: IEEE Te vas majory of IEEE WLAN devces ransm a 100 mw (+0 dbm) or less. Mos Blueoo devces wll radae a only 1 mw (0 dbm). Tese sysems use ransm power levels far below e lm permed under Secon of e Commsson s Rules n order o maxmze baery lfe n porable compung devces. Tecnologes suc as Blueoo and IEEE WLANs are nended o faclae wreless moble compung. Baery lfe s erefore a paramoun consderaon n ese ypes of devces. Based on HomeRF s presenaon o e FCC on Feb. 5, 1999 [1] s clear a e nended modulaon sceme s 4FSK. Delvery of 10 Mbps daa raes usng s form of modulaon n a 5 MHz wde cannel wll requre a very low ndex of modulaon ndex () of abou Ts s an exremely neffcen modulaon ecnque as demonsraed by e Eb/No curves sown n Fgure E-0 1.0E-03 B Error Rae 1.0E E-05 4FSK (=0.15) FSK (=0.3) DBPSK DQPSK 1.0E E Eb/No (db) Fgure.0-1 Eb/No vs. BER for FSK and PSK Waveforms In addon, e 4FSK waveform s also gly suscepble o mulpa. Due o e neffcency of e 4 FSK waveform and suscepbly o mulpa, WBFH rados wll be requred o operae a or near e maxmum allowable ransm power (+3 dbm). Even a s power level, s doubful a a WBFH sysem as proposed by HomeRF could provde a Qualy of Servce (QoS) adequae o suppor e ypes of mulmeda applcaons descrbed n er leer o e Commsson of November 11, Prevous Rulngs Te power reducons proposed by HomeRF are lnear n relaon o e ncrease n cannel wd. In a prevous rulng on a smlar proposal by Symbol (FCC 96-36), e Commsson commened on e poenal nerference o bo auorzed servces and oer Par 15 devces: Wle s ncrease n nerference poenal could be parally offse by a reducon n e oupu power of e frequency oppng ransmers, we are no convnced a a lnear power reducon alone s suffcen o offse s nerference poenal. Te Symbol proposal dffered from e HomeRF proposal n a called for a decrease n e number of FHSS oppng cannels n proporon o e ncrease n cannel wd. In s sense, e Symbol proposal was ecncally superor o e HomeRF proposal. Te use of overlappng cannels wll acually ncrease e collson rae among WBFH sysems, and n no way reduces nerference o oer Par 15 devces. In a proceedng relang o e reducon of e number of cannels n e 915 MHz band (FCC ), e Commsson graned e reques o reduce e number of oppng cannels o allow FHSS sysems operang n a band o avod nerferng w oer servces. However, e Commsson recognzed a suc a reducon oppng cannels would resul n an ncrease n collsons among FHSS sysems n e 915 MHz band. Submsson (aorney revewed)submsson page 1

22 Sepember 1999 doc.: IEEE /09-r1doc.: IEEE /09 In order o offse e poenal for ncreased nerference, e Commsson adoped rules wc requred sysems usng fewer oppng cannels o reduce power n proporon o e square of e reducon n e number of oppng cannels. Ts concluson was based on commens submed by TIA Wreless[]. In e 915 MHz ISM band, sysems usng 50 oppng cannels are permed o ransm a up o 1 Wa, wle sysems usng fewer cannels (bu no fewer an 5) are lmed o 50 mw. Te use of overlappng cannels obscures s ssue o some exen. However, n a prevous submsson o OET n s proceedng [3], e adverse mpac of allowng overlappng FHSS cannels as been demonsraed. Te number of overlappng FHSS cannels s largely rrelevan. Collson raes among FHSS sysems can be reduced only by ncreasng e number of orogonal (non-overlappng) cannels. In s sense, e HomeRF proposal conans e same number of orogonal cannels as e earler proposal by Symbol. I sould erefore become more apparen a e lnear power reducon proposed by HomeRF s nadequae o offse e ncreased poenal for nerference o oer users of e.45 GHz band. 3.0 Hop Rae In s leer o e Commsson of Nov. 11, 1999, HomeRF ndcaed a e reducon n me of occupancy s an effecve means of reducng nerference beween WBFH and oer users of e specrum. I mus be poned ou a a reducon n occupancy me requres a correspondng ncrease n op rae. However, even neglecng e expanson n bandwd, wen averaged over a 30 second perod e me of occupancy on any sngle cannel s uncanged. Te ne resul of e proposed ncrease n op rae s erefore more frequen collsons of a sorer duraon. Increasng e op rae of an FHSS sysem s NOT a means of reducng nerference w eer DSSS or oer FHSS sysems. In fac, ncreasng e op rae for an FHSS sysem ncreases e rsk of nerference o oer users. A model for predcng e collson rae w an FHSS sysem as been proposed [4]. Te model can be used o deermne e rae of collson beween a DSSS sysem and an FHSS sysem, or beween wo FHSS sysems. In e even of a collson, any b error wll cause e Cyclc Redundancy Code (CRC) of a packe ransmsson o fal, and e packe wll be los. Te model esmaes e probably of collson based on: 1.) Hop rae of e nerferng sgnal (HR).) Probably a FHSS nerferng sgnal ops no passband of desred sgnal (P op ) 3.) Probably a FHSS sysem acvely ransms wle on any gven op (P x ) 4.) Packe leng (n me) of desred sgnal ransmsson (L packe ) Te effec of op rae can be sown by sudyng e example of a DSSS sysem operang a 1 Mbps n e presence of a nearby FHSS sysem. Te bandwd of a DS sgnal s rougly 0 MHz. Terefore e probably a e FHSS sysem wll op no e DSSS passband s 0/79, or abou 5%. In s example, all parameers are eld consan w e excepon of op rae. In e frs case, e FHSS sysem s 18 ops per sec, wc resuls n an FHSS dwell perod ( dwell ) on any gven cannel of 781 usec. Case 1: HR = 18 ops/sec P op = 5% P x = 100 % L packe = 8370 usec FHSS Sysem Hops ousde DSSS passband FHSS Sysem Hops nsde DSSS passband (collson occurs) 1.07 dwell perods 1000 bye DSSS 1 Mbps (8370 µsec) Submsson (aorney revewed)submsson page