(Regular Paper) 19 4, 2014 7 (JBE Vol. 19, No. 4, July 2014) http://dx.doi.org/10.5909/jbe.2014.19.4.510 ISSN 2287-9137 (Online) ISSN 1226-7953 (Print) IEEE 802.11n WLAN A-MPDU a), a) Block Ack-based Dynamic A-MPDU Aggregation Scheme in IEEE 802.11n WLAN In Cheol Shin a) and Dong-Hoi Kim a) IEEE 802.11n MPDU PPDU(Physical Layer Protocol Data Unit) A-MPDU (Aggregate - MAC Protocol Data Unit) (MAC: Media Access Control). MPDU A-MPDU. A-MPDU MPDU BA A-MPDU MPDU BA A-MPDU. NS-2(Network Simulator-2) A-MPDU. Abstract By adopting the MAC(Media Access Control) protocol which enables to pack multiple MPDUs(MAC-level Protocol Data Units) into a single PPDU(Physical Layer Protocol Data Unit), IEEE 802.11n WLAN supports high throughput. Up to now, there have been a lot of existing channel information-based A-MPDU schemes dynamically determining the number of MSDUs according to the wireless channel condition information which is sent from the receiver to sender. However, the channel information-based scheme has a serious drawback having a high system overhead due to the frequent channel feedback information. To reduce the system overhead, the proposed BA-base dynamic A-MPDU scheme simply chooses the number of MSDUs to be retransmitted by not the frequent channel feedback information but the BA signal representing whether MPSUs belonging to the A-MPDU are received or not. Through NS-2(Network Simulator-2), we found that the proposed scheme had higher throughput and lower packet error rate than the existing fixed A-MPDU scheme. Keywords : IEEE 802.11n WLAN, A-MPDU, Block Ack, Throughput, Packet Error Rate
1 : IEEE 802.11n WLAN A-MPDU (In Cheol Shin et al. : Block Ack-based Dynamic A-MPDU Aggregation Scheme in IEEE 802.11n WLAN). (IEEE) IEEE 802.11 802.11, 802.11a, 802.11b, 802.11g, 802.11n,,, (QoS: Quality of Service).. IEEE 802.11b/g/a (MAC: Media Access Control) 2, 11, 54Mbps 100Mbps. IEEE 802.11n, [1]., IEEE802.11n (Frame Aggregation). A-MSDU(MAC Service Data Unit) A-MPDU(MAC Protocol Data Unit) 2. A-MSDU DA (Destination Address) MSDU MSDU A-MPDU MPDU [2][3][4][5]. A-MPDU. ACK BA A-MPDU MPDU BA A-MPDU. Rician Rayleigh. 2 A-MPDU 3 BA A-MPDU. 4 5.. IEEE 802.11n IEEE 802.11e DCF (Distributed Coordination Function) PCF HCF. HCF DCF PCF EDCA HCCA [6]. EDCA DCF. IP ToS(Type of Service) AC(Access Category) [7]. 1. MPDU A-MPDU a) IT (Dept. of Electronic Engineering, College of IT, Kangwon National University) Corresponding Author : (Dong Hoi Kim) E-mail: donghk@kangwon.ac.kr Tel: +82-33-250-6349 Manuscript received May 29, 2014 Revised July 21, 2014 Accepted July 21, 2014 A-MPDU IEEE802.11. 1 IEEE802.11 MPDU. 1 MPDU SIFS(Shortest
1. MPDU Fig 1. Transmission process of MPDU 2. A-MPDU Fig 2. ransmission process of A-MPDU IFS), DIFS(DCF Inter-Frame Space), ACK. MPDU PHY. IEEE802.11g 54Mbps. MAC HCF A-MPDU. 2 A-MPDU. PHY MPDU. BA(Block ACK) MPDU Ack BAR(Block Ack Request) A-MPDU. D(A-MPDU frame Delimiter) MPDU. A-MDU MDPU SIFS Ack [9]. 2. A-MPDU BA A-MPDU BA(Block Ack). DCF MPDU ACK. BA MPDU MPDU, 3. BA Fig 3. Structure of BA method
1 : IEEE 802.11n WLAN A-MPDU (In Cheol Shin et al. : Block Ack-based Dynamic A-MPDU Aggregation Scheme in IEEE 802.11n WLAN) SSN(Starting Sequence Number) BAR(Block Ack Request) MPDU ACK. MPDU, BAR BAR SSN MPDU MPDU, BA. BA, MPDU( MPDU ). 3 BA BAREQ. 3. A-MPDU A-MPDU MPDU. A-MPDU AC TxOP PPDU. 4 MPDU A-MPDU. MPDU 8 A- MPDU 2 MPDU MPDU MPDU 0 BA. BA BA MPDU EDCA A-MPDU [8]. A-MPDU. A-MPDU A-MPDU. A-MPDU MPDU MPDU (delimiter) (Unique Pattern Scan). A-MPDU 4. MPDU Fig 4. Operating example of the existing fixed scheme
A-MPDU [4].. BA A- MPDU. BA A-MPDU A-MPDU ACK BA A-MPDU MPDU. BA A-MPDU BA A-MPDU MPDU., A-MPDU MPDU A-MPDU MPDU. A-MPDU MPDU A-MPDU MPDU. K-Factor. K-factor. LOS(Line Of Sight). K-factor LOS. K-factor LOS. 5 BA A-MPDU 5. BA A-MPDU Fig 5. Flowchat of the proposed BA based dynamic A-MPDU scheme
1 : IEEE 802.11n WLAN A-MPDU (In Cheol Shin et al. : Block Ack-based Dynamic A-MPDU Aggregation Scheme in IEEE 802.11n WLAN). BA_req_threshold A-MPDU MPDU. A-MPDU BA BA MPDU. MPDU BA_req_ threshold A-MPDU MPDU A-MPDU. A-MPDU 4. 6 BA A-MPDU. 6 7 MPDU A-MPDU A-MPDU MPDU BA-bitmap. MPDU A-MPDU. A-MPDU (BA_req_threshold) 3 2 MPDU A-MPDU A-MPDU 8. MPDU2 MPDU5. A-MPDU 5 MPDU BA_req_threshold 4 MPDU A-MPDU 7.. 1. NS-2(Network Simulator) [10] 6. Fig 6. Operating example of the proposed scheme
. 2 30. CBR 256Byte. EDCA 4 AC(Access Category). 1. Table 1. Simulation parameters Simulation tool Simulation time Simulation terrain Number of node Node distance Traffic type Packet size Packet interval Transmission rate BA_Req_threshold (Maximum # of pkts in an A-MPDU) Channel NS-2 30sec 670m x 670m 2 Node 40m when K-factor =-40dB (Rayleigh ) 50m when K-factor>=0dB (Rician ) CBR(Constant Bit Rate) 256byte 0.00001sec 54Mbps 10 ( ) Rician & Rayleigh EDCA queue size 500 K-factor(dB) 0, 3, 5, 7, 10 Doppler shifts 0, 2.5, 5, 7.5, 10 1. Rician K-factor. MPDU 10. 7 Rician Rayleigh. Rayleigh. (1). (2) Rayleigh LOS. Rician. 1 0 bessel 7. Fig 7. Probability density functions of Rician fading channel and Rayleigh fading channel LOS,. Rician Rayleigh. (1) K-Factor K-Factor K-Factor 0dB LOS 0. 0 (3) 0 (2), Rician Rayleigh. 7
1 : IEEE 802.11n WLAN A-MPDU (In Cheol Shin et al. : Block Ack-based Dynamic A-MPDU Aggregation Scheme in IEEE 802.11n WLAN) Rayleigh (3) Matlab K-factor 40dB Rician. K-factor -40dB Rician Rayleigh. Rayleigh K-Factor -40dB Rician [11]. 2. 8 9 Rician K-factor. K-Factor. K-factor. BA A- MPDU A-MPDU. K-Factor LOS. BA- A-MPDU A-MPDU MPDU A-MPDU.., K-Factor LOS A-MPDU MPDU A-MPDU. A-MPDU. 9. A-MPDU A-MPDU K-Factor Fig 9. Packet error rate between the proposed dynamic A-MPDU scheme and fixed A-MPDU scheme according to K-factor in Rician fading channel 8. A-MPDU A-MPDU K-Factor Fig 8. Throughput between the proposed dynamic A-MPDU scheme and fixed A-MPDU scheme according to K-factor in Rician fading channel 10 11 K-factor -40dB, Rayleigh. Rayleigh K-Factor
. A-MPDU A-MPDU. BA A-MPDU A-MPDU, A-MPDU. 10 11 BA A-MPDU A-MPDU 1.5Mbps 0.24%. 12 13 K-factor -40dB Rayleigh 10. A-MPDU A-MPDU (K-factor = -40dB) Fig 10. Throughput between the proposed dynamic A-MPDU scheme and fixed A-MPDU scheme in Rayleigh fading channel(k-factor = -40dB) 12. A-MPDU A-MPDU (K-factor = -40dB) Fig 12. Throughput between the proposed dynamic A-MPDU scheme and fixed A-MPDU scheme according to Dopploer spectrum in Rayleigh fading channel(k-factor = -40dB) 11. A-MPDU A-MPDU (K-factor = -40dB) Fig 11. Packet error rate between the proposed dynamic A-MPDU scheme and fixed A-MPDU scheme in Rayleigh fading channel(k-factor = -40dB) 13. A-MPDU A-MPDU (K-factor = -40dB) Fig 13. Packet error rate between the proposed dynamic A-MPDU scheme and fixed A-MPDU scheme according to Dopploer spectrum in Rayleigh fading channel(k-factor = -40dB)
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