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Multiple Access Techniques (MAT)

???????????? Multiple Access protocol ???????????? ??. 1970 ????????????????? ????? ???????????? Multiple Access protocol ?????????????? ALOHA protocol ????????????????? protocol ?????????????????????????????? ????????? protocol ??????????????? code division multiple access (CDMA) protocol

?????????????? Multiple Access Protocol

???????????????? ?????? ,??????? channel ???????? ??????????????? ??????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????? ???? Multiple Access Protocol ?????????????????????????????????????????????????????????????????????????????????????????

??????????? Multiple Access protocol ?????????

????????? protocol ?????????????????????????????????????????????????????????? protocol ??????????????????????????????????? ??????????????????????,????????????????? Multiple Access protocol ??????????? ????????????????????????????

  • 1. ????????????????????????? Multiple Access protocol ????????????????? share ?? channel ?????????????????????????????????????? ???????, protocol ??????????????????????????????????????? channel ?????????????????????????????????????????????????????????????? , protocol ???????????????????????????????? channel ?????????????????????
  • 2. protocol ???????????????????????????????????????????????????? ????????????????????????????????????? ?????????????????????? ????????????? (channel throughput) ?????????????????????????????? (delay of the transmissions)
  • 3. ????????????????????????????????????? ??????? ?????????????????????????????????????????????? ????????????????????????????????????????????????? channel ??????????????
  • 4. protocol ?????????????????????????????????????????? traffic (????., voice ??? data)
  • 5.protocol ???????????????? (stable) ???????????????????????????????????,?? load ???????????????????????????????????????,???? protocol ???????????????? (unstable)??????? load ????????? ??????????????????????????? load ?????????????????????????????????????????????????????????????? (lower throughput)
  • 6. protocol ?????????????????????????????????????????? failure ????????????????????????,??????????????????????????????????????????,?????????????????????????????????????????????????????????????

???????????? Multiple Access protocol

Multiple Access protocol ???????????? 3 ???????????????

  • 1.the contentionless protocols (scheduling)
  • 2. the contention protocols (random access)
  • 3.the class of CDMA protocols

Contentionless (scheduling) Multiple Access Protocols

Contentionless MA protocols ??????????????????????????????????????? channal ?????????????????????????????????????? (scheduling) ?????? ????????????? (channel transmissions) ???????????, ?????????????????????????????????????????? transmission ???? transmission ????????????????????????? ????????? scheduling ????? 2 ???

  • 1.Fixed assignment scheduling
  • 2.Demand assignment scheduling

Fixed Assignment

?????? MA protocol ??? fixed assignment ???????????? channel ???????????????????????????????? ???????????????????????????????????????????? channel ??????????? ????????????????????????????????? ????????????????????? Time ???? Frequency ????????? TDMA protocol ?? FDMA protocol ???????? ????????? [1] ???? 20,21

Demand assignment

?????? demand-assignment contentionless protocol ???????????????????????????????????????????????????????????????????????????????? channel ????????????????? ???????????????????????????????????????? (scheduled) ????????????????? ?????????????????????????????????????????????? ?????????????????????????????????????????????????? ??????????? protocol ???????????????????????????????????????????????????? schedule

scheduling ?????????????? central, ???????????????? centralized demand assignment protocol ?????? roll-call polling protocol ??????????????????????????????????????????????? distributed demand assignment protocol ?????? token-passing protocol

Roll-Call Polling

Roll-call polling protocol ?????????????????????? ???????, ??? central control ???????????????????????? ??????????????????????????????????????????????? ????????????????????? polling message ??? central control ????????? message ????????????????????? ????????? message ?????????????????????????? ?????????????? message ??????? ???????????????? “ready” ???? central control ?????? central control ???????????????? ??? controller ?????? polling message ??????????????????????

Token-Passing Protocol

????????????? token-passing protocol ??? token-bus protocol ?? protocol ??????? ????????????????????????? bus ???????? ??????????????????? address ??????????,?????? bus ?????????????????????????????????????????? ??????????????

successor’s address ?????????? address ????????? ??????????????????????? address ????????????????????? ??????????????? address ???? ?????????????????????????????????????????????????

????????????????????????????????????????????????????????????????? control information ??????????? token ??????????????????? ?????????????? token ??????????????????????????,???????????????????????????????????????????,????????? token ????????????????????? ????????????????????????????????????????????? ????????? token ??????????????????????????????? ?????????????????????? holds the token ????????????????????????????????????? ??????????????????? distributed demand assignment protocol

Contention (Random) Multiple Access Protocols

?????? contention multiple access ???????????????????????????????????????? ?????????????????????????????????? ???????????????????????????????????????????????????????????????????????????? ?????????????????????????????????????????????????????????????????????????????????????????? ??????????????????????????????????????????????????????????? ???????????????????????????????????????????? fail ????????????? failure ????????????????????????????????????????????????????????????? random process, ???????????????????? random process protocol ????????????????????????????? ??????????????????????????????????????

??????????? contention multiple access ??????? 2 ?????

  • 1.repeated random access protocols
  • 2.random access protocols with reservation

Repeated Random Access Protocols

???????????????????????????????????????????????? ?????????????????????????????????????????????????????????? ??????????????????????????????????????????????????????????????????????????? ???????????????????????????????????????????????? ??????????????????????????????????? start transmission ???????????????????????????? ????????????????????????????????????????????????,????????????????????????????????? ?????????????????????????????????????????????????????????????????????????????? repeated random access protocols ?????? pure (p)-ALOHA, slotted (s)-ALOHA, carrier sense multiple access (CSMA), inhibit sense multiple access (ISMA), ??? stack algorithm ?????? CSMA ??? ISMA ?????????? channel ?????? ?????? protocol ????????????????????????????????????????????????????????????????

p-ALOHA

pure ALOHA protocol ?????????????????? ALOHA system , a packet radio network ??????????????????????????????????????????????? 1970 ???????????? MA protocol ?????? ??? ALOHA protocol ?????????????????????????????????????? ALOHA ??????? protocol ????????????
pure (p)-ALOHA

p-ALOHA protocol ???? protocol ?????????????? central ??????????????????????? ???? base station ????? uplink channel ??????????????? base station ????? downlink channel ????????????? channel ?????? ?????????????????????? generated a packet ????????? packet ??? ???? uplink channel ??????????????????? ??? base station ????????????????????????????????????? ??? base station ?????????????????? (acknowledgment packet) ???? downlink channel ??????????????????????? acknowledgment ????????????????????????????????????????

????????????????? 2 ??????????????????????????? ???????????????????? (collision) ??? base station ????????????????????????????? ???????????????????????????????????????????????????????????????? acknowledgment , base station ???????????????????????????????????????????? ???????????????????????????????????

????????? [1] ???? 24,25

???????????????????????? [2] ???? 341-345

s-ALOHA

protocol ??? p-ALOHA ???? protocol ??????????????????????? ??????????????????????????????????????????????????????????????? 18% (very low channel throughput) ????????????????????????????????????????????????????????????????????????????????????????????????????? packet ?????????????????????????? ????????????????????? traffic ??????????????? ???????????????????????? p-ALOHA protocol ?????? ????????????????????????? packet ??????????????????????????????????????? ??????????????????????????????????????????? time slot ????????????????????????????? ???????? time slot ???????????????????????????? ???????????????????????????? packet ?????????????????????????????? p-ALOHA ????????????????????????????????????????????????????????? 2 ?????????? 36% protocol ??????????????????????????? s-ALOHA ;?????????[1] ???? 25-26 ??? ?????[2] ???? 345-347

Carrier Sense Multiple Access (CSMA)

CSMA ???????????? 2 ????? ?????? nonpersistent CSMA protocols ??? p-persistent CSMA protocols

Nonpersistent CSMA protocols,

???????????????? packet ??????????????????????????????????????????????????????? ????????????????????????????? (Idle) ???????????? ??????????????????????? ????????? protocol ?????????????????????????????????????? packet ?????????????????????????? ??????? packet ?????????? ?????????????????????????????????????????????? 2 ???????????????????????????????????????????? base station ????????????????? ?????????????????????????????????????????????????? ?????????? packet ??????????????????????????????????????? ??????????????????? packet ??????????????????

p-persistent CSMA protocols,

?????????????????? Nonpersistent CSMA protocols ?????????????????????????????????????????? (busy) ?? case ?????????????????????????????????????????????????????????????????? ??????????????????????? packet ?????????? ??????????????,???????????????????????????? (busy) ????????????????????????????????????????????????????????????????? ???????????????????????????????????????????????? packet ??????????????????????????????????????? packet ????????????? ?????????????????????? packet ??????? ?????????????????????? (busy) ??????????????????????????????? packet ???????????? ???????????????????????????????? packet ????? channel ???????????? (probability) ??????? p ???????? 1-p ??????????? t seconds ??????????????????????????? packet ????????????? ?????????????? packet ????????? t seconds ?????????? ?????????????????????? channel ??????? ?????????????????????????????????????????? ?????????????????? packet ?????????????????????????????????????????????? 2 ???????????????????????????????????????????? base station ????????????????? ??????????????????????? packet ????????????? ???????????????????? CSMA-CD (carrier sense multiple access with collision detect) protocol ?????????????? protocol ???????? monitoring ?????????????????? ????? detect ??????????? ???????????????????????????????? saving ????,1-persistent CSMA –CD protocol ??????????????????????? local area computer networks ????????????????? standard ??? IEEE in the 802.3 standard ;?????????[1] ???? 27-28 ??? ?????[2] ???? 348-350

Inhibit Sense Multiple Access (ISMA)

?? CSMA protocols ????????????????????????????? ( to sense ) ???????????????????????????????????????????????????????? ???????????,?????????? radio channels, ??????????????????????????????????????????????????????????????????????????????? channels ????????????? ?????? 2 ????? packet ?????????????????????????????????????????????????????????????? (hidden) ?????????????????????????????? packet ??????????????????? ???? ????????????? ????????????? CSMA ?????? ???????????????????? ISMA protocol ???????????????????? BTMA ( busy tone multiple access) ISMA protocol ???????????????????? CSMA protocol ??????????????????????????????????????????????????????????????????????????? ?? CSMA ???????????????????????????????????????????????????????????? ????? ISMA ??? base station ?????????? busy ???? ?????? Idle ????????????????????????????????????????????????????????????????????????????????????

?????????[1] ???? 28

Stack Algorithm

stack algorithm ??????????? Tsybakov ,?? stack algorithm ??????????????? feedback ????? feedback ???????????????????????????????????????????????????????????????????????????????? ??????????? packet ??????????????????????????????????????????????????? ????????????????????????????? packet ?????????????????????????????????????? packet , ????? packet ???????????????????????? ?????????????? 2 ??????? virtual stack ,??????????? 1 ????????????????????????? ??? packet ?????????????????? packet ????????????? stack algorithm ?????????????????????? ???????????????????????,????????????????????????????????? ( large throughput, about 0.4), ?????????????????????????????? ??????? feedback algorithms ??????????????? ????

  • (1) idle / success / failure feedback, (2) conflict / no conflict feedback, (3) idle / transmission feedback ???????????? algorithms ??? 3 ?????????????????? B.S. Tsybakov, “Survey of USSR contributions to random multiple access communications” IEEE Trans. Inf. Theory, Vol. IT-31, No. 2, pp. 143-145, March 1985. ???????? stack-algorithm ?????????????? mobile radio channels ?????????????????? J.A.M. Nijhof, R.D. Vossenaar and R. Prasad, “Stack algorithm in mobile radio channels” Proc. IEEE 44th Vehicular Technology Conference, Stockholm,Sweden,pp. 1193-1197,June 1994.

Random Access with Reservation

Reservation protocols ????????????????????????????????? packet ??????? packet ??????; ?????????????????????? fixed ????????????????????????????????????????????????????? packet ?????? ????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????? ?????????? carried out ????????????????????????????????????????????????????? ????????????? packet ???????????????????????????????????????? ???????????????????????????????????????????????? ?????????????????????????????? packet ????????????? ??????????????????????????????????? packet ???????????????
????????? protocol ?? case ????????? Reservation ALOHA (r-ALOHA) ??? Packet Reservation Multiple Access (PRMA)

Reservation ALOHA (r-ALOHA)

????????? r-ALOHA protocol ????????????????????? slotted ALOHA protocol ?? slotted ???, ?? time slots ?????????????? ???? frames ????? frames ????????????? time slots ???????? ??????? frames????????????????????????????????????? slot ????? ?? 3 ???????????????????????
protocol ?????? 1 ????????? Robert ????????????????????????? frames ????? frames ??????? M+1 time slot ,M time slot ????? frames ???????????????????????????????? ??? M time slot ?????????????????????????????????????? ?? time slot ?????????????? V mini-slots ????? mini-slots ??????????????????????? time slot ,Roberts’ protocol ???????????? explicit reservation ?????????[1] ???? 30

protocol ?????? 2 ????????? Crowther, protocol ??????????????????? implicit reservation method ?? protocol ?????? ?? frames ????? ?????????????? time slot ????? ??? ????? time slot ??????????? 1 packet ?????????????? packet ??????????? ????????? packet ?????????? slot ?????? slotted ALOHA protocol ?? packet ?????????????????????????? ????????? slot ?????????????? packet ???????????????? packet ??????? ?????????[1] ???? 31

protocol ?????? 3 ????????? Binder, ?? protocol ?????? ?? N ??????? ????? time slot ??????? frames ??? M ??????????????????? N ???????????????? ???????????????????????????? time slot ??????????? frames ??????? ?? M < N , slot ?????????????????? protocol ???????????????? implicit reservation ?????????[1] ???? 31,32

Packet Reservation Multiple Access (PRMA)

Packet Reservation Multiple Access ???????????????? reservation ALOHA multiple access protocols ????????????????????????????? protocol ??????????????? protocol ??????????????????? ??? PRMA ???????????????? voice , PRMA protocol ?????????????? implicit reservation protocol ?? PRMA protocol ???????????????????????? frames ??????? frames ?????????????? time slot ????? ??? ??????????? frame ????????????????????? speech packets ?????? ????? speech ?????????? voice ????????????????????? ????????????????? speech packet ??????? speech packet ????? first-in / first-out buffer ?????????? packet ?????? buffer ??????? slotted ALOHA protocol ?? packet ?????????????????? buffer ????????? 40 ms ???????????????????? packet ???????????????????????????????????????????????????????? packet ???????? speech ??????????????????? ?????????????? packet ????????????????????? buffer ?????????????????? packet ??????? slotted ALOHA protocol ????????????? ????? packet ???????????? buffer??????? packet ???????????? buffer ??????????????????????????????????? ??????????????????? buffer ?????????? time slot ?????????? frames ????? ???????????? packet ???????????? buffer ????? ??????? packet ?????????????????????????????????????????????

?????????[1] ???? 32

CODE DIVISION MULTIPLE ACCESS (CDMA) PROTOCOLS

CDMA protocols ?????????????????? contentionless (scheduling) protocols ??? contention (random access) protocols

CDMA protocols ?????????? multiple access ???????????????????????????????????????????????? frequency ???? time ?????????????????????????????????????????????????? code ?? code ????????????????????????????????????? wideband signal (spread-spectrum signal) ??????????? ????????? multiple wideband signal ?????? ?????????? code ?????????????????????? wideband signal ????????? ??????????????????????????????????? ?????????????????? power ????????????????? ?????????? (compressed) ???? bandwidth ???????? original signal ???????????? wideband signal ??????????????????????????????????? wideband signal ?????????????? noise ?????????????????????????????????? ??????????????????????????????????????????????????????????? ?????? signal-to-noise ratio ??????????????????????????????????????????????? error ???????? case ??? protocol ?????????? protocol ?????? contentionless protocols ??????????????????????????????????????????????????????? ????????????????????????????????????????????????????????????????? ????????????????????,??????????????????????? protocol ???????????????????????, ?????? protocol ???????????????? contentionless protocols ?????????????????? access ??????????????????????????? protocol ???????? contention protocols ??????????????????? CDMA protocols ???? protocol ??????????????? contentionless protocols ??? contention protocols

?????? CDMA protocols ??????????????????????????? ????????????????????? modulation ???? wideband signal ?????????????????? 4 ?????? protocol ??????

  • 1.direct-sequence CDMA (DS-CDMA)
  • 2.frequency hopping CDMA (FH-CDMA)
  • 3.time hopping CDMA (TM-CDMA)
  • 4.hybrid CDMA

?? DS-CDMA protocol ?????? original signal ???? modulated ???? carrier ??????????????????????????? binary code sequence ???? bandwidth ?????????? bandwidth ?? original signal ???, ???? spectrum ???????? original signal, ??????????????? wideband signal ????????? wideband signal ????? modulated ?????????? channel ???????? modulated signal ??????????????? ?????????????????????????? ?????????????????????????????????????? ???????????????????????????? ???????????????????????????? code sequence ??????? original signal , ????????????? (correlation) ???????????????????????? code sequence ???????? original signal ??????????????????????????????????????????????????????????? generated ?????? code sequence, ?? cross-correlations ?? code sequences ?????????????????? code sequences ???????? original signal ?????????,??????????????????????? ????? power ratio ??????????????????????????????????????????????? ?????????????????????????? demodulated ??? original data ????????????????????????????? orrer

?????????[1] ???? 35

?? FH-CDMA protocol ,wideband channel ????????? frequency band ????????????? bandwidth ???????? original ???????? ??????????????????????????????,carrier frequency ???????????????????? ???????????????????pattern ???????????????????????????????????????? code ???????? ???????????? ??? demodulator ???????????????????? carrier frequency ?????????? demodulating ?????? ??????????? FH-CDMA protocol ??????? 2 ???? ??? fast frequency hopping protocols ??? slow frequency hopping protocols ?? fast frequency hopping protocols ??????????????? frequency band ????????????????????? ????????????????????????????? 1 bit ???????????????? frequency band ???????????????????? code ??????????????????????????????????????????????? frequency bands ??????????? bit ????????????????????????? ?????? power ?? bit ????????????????????????? power ??????????????? ?????? bit ?????????????????????????????? ?????? slow frequency hopping protocols ,??????????????????????? frequency band ???????? ??????????????????? frequency band ???????? ???? ???? bit ????????? ???????????????????? code ????? gain ?? bit ?????????????????????? frequency band ?????????????????????????? bit ?????????? ?????????????????????????????????????? ??????????????????? error-correcting code ???????????????? bit ?????????????? bit ??????????????? ?? frequency band ???????? bit ????????????????????????????????????

?? TH-CDMA protocols ????????????????????????????????? ????????????????????? (burst) ???????????????????? burst ???????? code ?????????????????? ????????????????????????????????? ??????????????? bandwidth ????????????????????????? ?????????????? FH-CDMA protocol ???????????? TH-CDMA protocol ????? wide-band spectrum ??????????????????????????? ???????????? spectrum ????????????? ??????????????????????????????????????????????????????????? ???????? code ?????????????????? ??????????????????????? ??????????????????????????????? ?????????????????????????????????????? ??????????????????? error-correcting code ,???????????????? bit ??????????????????? bit ??????????????????????????? bit ????????????????????????????????????

hybrid CDMA protocols ????????????????? modulation ?? direct sequence, frequency hopping, ???? time hopping protocols ????? modulated ?? wideband signal ???????????????????????? modulation ?????????????????????????????? modulation ????????????

?????????[1] ???? 34,35,36


???????????

  • [1] : CDMA for wireless personal communications; Ramjee Prasad; AH Artech House Publishers
  • [2] : Data and Computer Communications ,Third Edition ; William Stallings

 

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