MACA-BI performance

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Transcript MACA-BI performance

MACA-BI(MACA By Invitation) A Wireless MAC Protocol for High Speed ad hoc Networking

컴퓨터 및 정보통신공학과 200730038 김 연주


■ 논문 소개 ■ Introduction ■ MACA-BI Illustrated ■ Collisions in MACA-BI ■ Predicting Traffic ■ MACA-BI Performance ■ Conclusion

논문 소개

논문 소개

■ Introduction to MACA-BI ■ Show that MACA-BI outperforms other multiple access protocol in high speed


Introduction (1/3)

■ MACA   Solves the hidden terminal problem Outperforms CSMA in a Wireless multi-hop network ■ MACA with Carrier Sensing (FAMA-NTR)  Can perform almost as well as CSMA in a single-hop wireless network ■ FAMA-PJ, CARMA  Achieve better performance at high load ■ MACAW   Five-way handshake Overhead cause low channel utilization!

• TX-RX turn-around time, preamble bits, control bits, checksum bits

Introduction (2/3)

■ In order to better appraise the turn-around overhead, every transmission should be delayed by TX to RX turn around time to give a chance to the previous transmitter to switch to receive mode.

■ The relative impact of turn-around time becomes more critical at high channel speed and low propagation delays.

 So turn-around time is important role in future high speed, indoor wireless LANs and, more generally, multihop ad hoc networks!!

Introduction (3/3)

■ MACA-BI (MACA By Invitation)  Reduces the turn-around time  Two handshake  Waits for an “ Invitation ” by the intended receiver in the form of an RTR (Ready to Receive) control packet

MACA-BI Illustrated

MACA-BI Illustrated (1/2)

■Three basic cycles of the MACA protocol  “ driven by the transmitter ”  The three-way handshake A RTS B C A CTS B C A DATA B C Blocked

MACA-BI Illustrated (2/2)

■Two basic cycles of the MACA-BI protocol  The two-way handshake ■Node B does not have exact knowledge of packet arrival times at Node A ■The each data packet carries the information  Backlog in transmitter: # of packet and their lengths, the average rate and future backlog ■Node A replies with the transmission of the requested number of packet and with new backlog information A RTR B C A DATA B C Blocked

Collisions in MACA-BI

Analysis of collision states (1/3)

■ Examination   6 node hidden terminal configuration Identify possible collisions  Node A and B issue RTRs at about the same time to different neighbors  Only three possible combinations ■ Two type of RTR collision  Direct collision • Between nodes within hearing distance (due to carrier sense failure)  Indirect collision • Between nodes hidden from each other and transmitting to a common neighbor

Analysis of collision states (2/3)

Analysis of collision states (3/3)

■ If node receives the RTR packet,  Knows the duration of the impending data packet data packet transmissions by its two-hop neighbors  Is able to decide if its transmission can disturb its neighbors reception

Data collision free property (1/2)

■ No collision among data packet in MACA-BI ■ Direct collision among data packet  A transmits data packet to B, then C cannot transmits data packet to B  Only if C did not hear the RTR from B to A, C can transmit a data packet to D • B transmitted RTR to A while C was transmitting-> impossible!

• B transmitted RTR to A while C was receiving a RTR from D -> impossible!

Data collision free property (2/2)

■ Hidden terminal problem은 여전히 control packet을 방해 ■ RTR과 Data packet간에 충돌 가능 ■ Carrier Sensing 실패로 Control Packet간에 충돌 가능 ■ MACA-BI는 이러한 충돌 가능성이 존재하지만, MACA는 이러한 충돌을 줄이려고 하지 않는다.

Comparing MACA & MACA-BI protocol states (1/4)

■ Assume  The channel is symmetric as in all other MACA protocols  Control packet can be corrupted by noise  Direction collision  Indirection collision

Comparing MACA & MACA-BI protocol states (2/4)

■ Direction Collision

Comparing MACA & MACA-BI protocol states (3/4)

■ Indirection Collision

Comparing MACA & MACA-BI protocol states (4/4)

■ If the protocols work properly, they are data collision free ■ Cannot speculate a priori on the probability of each configuration, but can qualitatively say that introducing the third pass in the handshake (as MACA dose) does not reduce the dangerous situations ■ 프로토콜은 channel noise나 fading등으로 control packet 방해를 받아 실패 할 수 있는데 MACA가 MACA-BI보다 훨 씬 취약!

Predicting Traffic

MACA-BI performance

MACA-BI performance (1/8)

■ MACA-BI multi-hop network는 시뮬레이션을 통해 조사 ■ 시뮬레이션  Four nodes  네트워크의 기본적인 기능, data link, MAC layer는 구현  Routing은 Bellman-Ford scheme  모든 node는 size 50의 buffer를 공유  Data link layer는 선택적인 반복을 가진 size 8의 sliding window • separate window는 각 pair node가 사용  Flow control은 sliding window mechanism을 통해 공급  Separate MAC protocol 시뮬레이션 모듈은 개발

MACA-BI performance (2/8)

■ 시뮬레이션 (계속)    Neighbor with highest buffer occupancy is invited to transmit Channels are error free Packet transmission can collide due to the hidden terminal problem and the non negligible propagation delay  방해받은 packet들은 sliding window mechanism에 의해 재 전송 -> packet loss는 오직 네트워크 레벨에서만 발생   FAMA-NTR은 매 handshake마다 하나의 data packet을 전송 Floor 충돌이 반복되는 것을 막기 위해 Poisson process를 가진 floor로 node들은 reschedule  Datagram traffic을 시뮬레이션하기 위해 Poisson process를 가진 모든 노드들에서 External packet들 발생

MACA-BI performance (3/8)

■ 첫 번째 시뮬레이션  Null propagation time의 1Mbps의 링크  Control packet 4 bytes  Data packet 1000bits  Floor generation interval 2.5ms

MACA-BI performance (4/8)

MACA-BI performance (5/8)

■ 두 번째 시뮬레이션  유한한 propagation time  전송 범위 3미터의 near-filed signal strength  Four node  10Mbps channel speed  Average floor generation interval 0.3ms

 Data packet size 53 bites  Control packet size 4 bytes

MACA-BI performance (6/8)

MACA-BI performance (7/8)

MACA-BI performance (8/8)



■ Eliminate RTS packet  Reducing the overhead for each packet transmission  Simplifying the implementation ■ More robust to hidden terminal collision, direct collision and noise corruption ■ Not very sensitive to the TX-RX turn-around time ■ In simulation, shows its superiority