Underwater Acoustic Sensor Network for Antisubmarine Warfare 조호신 hscho@ee.knu.ac.kr 경북대학교전자전기컴퓨터학부
수중 NCW 개요 기본개념 필요성 발표순서 NCW 수중센서네트웍발전전망 수중 MAC 설계를위한고려사항 수중환경에서의다중접속방식 수중환경에서의재전송기법 요약및결론 2 2
대잠전체계를위한수중 NCW 개요 기본개념 전투요소들을네트워크로연결 전장상황공유 지휘속도향상 신속한작전전개 공격치명성제고 Satellite Shipboard Command center 3
필요성 대잠전체계를위한수중 NCW 개요 대잠전탐지체계환경의변화 냉전시대대잠전환경 현대천해대잠전환경 ~2000 m ~200 m 1000m 이상심해 장거리음파전달특성양호 비교적시끄러운원자력잠수함 해상교통량작아매우조용한음파탐지환경 대륙사면구조 200m 이하천해 다중경로음파전달특성불량 매우조용한재래식잠수함 어로활동및상선교통량많아매우시끄럽고급변하는음파탐지환경 4
필요성 대잠전체계를위한수중 NCW 개요 수동소나 능동소나 Multi-Static 소나 NCW 소노부이 디핑소나 TAS 해저고정형센서 네트웍개념 탐지영역확장 은밀성향상 5
수중센서네트웍의구성 Satellite Control Station Shipboard Command center Buoy gateway node UUV (Mobile node) Telesonar repeater node 6 Bottom sensor nodes
NCW 수중센서네트웍발전전망 소규모 대규모 대잠작전범위확대 필요센서노드개수증가 소형, 저가, 고성능 지능적네트워킹 (MAC, Network, Transport protocol) Short-range commun. ( < 1 Km) 잠수함의정숙성, 은밀성향상 저전력통신 Not rechargeable sensor Low power transducer/hydrophone needed. 음향채널의문제점극복 설치및관리의용이성향상 Self-configuration Self-healing 7
NCW 수중센서네트웍발전전망 전송기술의향상 MIMO Cooperative Relay Cognitive Radio Support Mobile Nodes MAC protocol Network protocol 네트웍토폴로지 클러스터구조 에너지효율 고장감내 부하분산 트리구조 ( 클러스터내부 ) 다중홉전송 8
9 수중 MAC 설계를위한고려사항 Frequency-dependent transmission loss Transmission loss Urick propagation model d k f d f d TL ) ( ), ( α = absorption loss : ) ( path loss coeff. : distance between tx and rx : f k d α > < > < = B f B f df f N f d TL df f d S B d SNR,, 0 0 ) ( ), ( ), ( ), ( bandwidth : noise p.s.d of : ) ( transmitted signal p.s.d of : ), ( B f N f d S
Colored noise 수중 MAC 설계를위한고려사항 10
Multipath 수중 MAC 설계를위한고려사항 Source signal ~200 m Received signal 1mode 2mode 3mode Doppler frequency spread f d = v r c f 0 v r : velocity of f 0 the source relative to the receiver c :speed of : frequency of acoustic signal acoustic signal 11
수중 MAC 설계를위한고려사항 High and variable propagation delay 1500 m/s (acoustic wave in water) Five orders of magnitude higher than in RF terrestrial channel Extremely variable According to temperature, salinity, density Limited bandwidth Range [km] Bandwidth [khz] Very Long 1000 <1 Long 10-100 2-5 Medium 1-10 10 Short 0.1-1 10-50 Very Short <0.1 >100 12
Management 수중 MAC 설계를위한고려사항 Not easy to control Self-configuration & self-healing required. Not rechargeable Low power communication Energy efficient modem Energy efficient MAC protocol Energy efficient routing protocol 13
Multiple Access FDMA (Frequency Division Multiple Access) Narrow bandwidth TDMA (Time Division Multiple Access) Difficult timing synch CDMA (Code Division Multiple Access) Most promising candidate Near-far problem power control Code assignment OFDMA (Orthogonal Frequency Division Multiple Access) Doppler spread difficult freq. synch Not completely evaluated yet. 14
네트웍토폴로지 데이터수집형계층트리구조 L 1 CDMA 성능분석 L 2 L1 L 3 L K 15 15
CDMA 성능분석 Power saving scheme : 엇갈림깨어남패턴 노드간의거리에기인하여시간차를두고연속적으로깨어나는패턴 효율적인다중홉전송으로전송지연시간을줄임 Awake Awake L k-1 Sleep Awake Awake L k Sleep Transmission Awake Awake Reception L k+1 Sleep Wakeup-time 16 16 Latency
CDMA 성능분석 신호대잡음비 L k 1 L k d j _ i+2 l l i i+ 3 node i node i+1 node i+2 node i+3 S P S γ = P t _ i li γ t _ i = S li out j _ i+ 2 = = P t _ i+ 2 d γ j _ i+ 2 γ γ ( li+ 2 S ) d j _ i+ 2 node j node j+1 17 17 ( E N ) b o k 1 = N B t w 123 thermal noise + S [ n S R in 14243 4 int ra-family k out ( j) 1] + S j _ m out m F ( j) 14243 inter-family B w
CDMA 성능분석 트리형계층구조에서의적용예 Rx Tx Rx Tx 18 18
CDMA 성능분석 모의실험환경 Parameter Value Topology [1 2 4 8] Acoustic speed 1500 m/s Node spacing ACK packet size RTS/CTS packet size Vertical: 1 km, Horizontal: 200 m 100 bits 100 bits Data packet size 2000 bits Path loss (γ) 1.5 Required (E b /N o ) 5 db Bandwidth 30 khz 19 19
CDMA 성능분석 비트오류율에따른데이터처리율 20 20
CDMA 성능분석 전송부하에따른데이터처리율 21 21
수중에서의 OFMDA 적용 AMC (Adaptive Modulation & Coding) 기본개념 SNR 16QAM -3/4 지상의경우 Freq. f 1 f 2 f 3 f 4 f k : Sub-carrier 16QAM -1/2 Minimum SINR requirements (AWGN channel, target BER: 10-6 )-WiMAX 20dB-5dB=15dB QPSK -3/4 QPSK -1/2 BPSK -3/4 SINR 5.0 db 8.0 db 10.5 db 14.0 db 18.0 db 20.0 db MCS QPSK- 1/2 QPSK- 3/4 16QAM- 1/2 SINR Graph Slop: -15dB/sub-band 대역 (khz) 16QAM- 3/4 64QAM- 2/3 64QAM- 3/4 22
수중에서의 OFMDA 적용 수중에서의 AMC 활용주파수대역및거리 Consider QPSK and 16QAM SINR graph slop: -10dB/sub-band 대역 AMC 적용가능범위 통신거리가짧을수록 -10dB 에대한대역폭증가요구되는파워감소 통신거리가늘어날수록 -10dB 에대한대역폭감소요구되는파워증가 23
수중에서의 OFMDA 적용 주파수자원활용방안 Grouping of Sensor Node 거리에따른센서노드의그룹화 균등분포의센서노드가정 각그룹별노드수일정 -> 그룹의넓이일정 Hello Message for Grouping Hello Message 의부반송파구성 S ( d, f )(db) = 10log [ Ad (, f ) N( f )] AN F = min{ f diff ( k, f ) = D(dB)} Hk 10 1 diff ( k, f ) = S ( d k, f ) S ( d k + 1, f ) AN AN d d 2 d 3 2d 24
거리별주파수할당예 수중에서의 OFMDA 적용 25
ARQ What is ARQ (Automatic Repeat request)? Retransmission of erroneously received packets Stop & Wait is Strong Candidate in UW. Current acoustic modem supports half-duplex mode But poor efficiency To Improve the S&W ARQ scheme Transmission of blocks of packets Algorithms for adaptive adjustment of packet size to maximize efficiency of ARQ scheme 26
Ideas 수중환경에적합한 ARQ Scheme Channel sharing property t r t p Two node can share the channel if the packet is scheduled such a way that the events of packet transmission and reception do not occur at the same time at each node 27
수중환경에적합한 ARQ Scheme Operation Tinter t g Source node A sequentially transmits the sub-packets from 1 to N Relay node B and C immediately forward the received sub-packet to the next node if no error is found The relaying causes a backward overhearing to the previous nodes and this backward overhearing could be recognized as an ACK Only the destination node D needs to transmit a normal ACK 28
수중환경에적합한 ARQ Scheme Latency Analysis 3.5 3.4 3.3 simulation mathematical result 35 30 simulation (proposed, N=6) mathematical (proposed, N=6) simulation (S&W) mathematical (S&W) 3.2 25 Latency [sec] 3.1 3 Latency [sec] 20 15 2.9 10 2.8 2.7 5 2.6 0 2 4 6 8 10 12 14 16 18 Number of Sub-packets (N) 0 10-6 10-5 10-4 10-3 BER we can choose the number of sub-packet that minimizes the latency N = 6 29
Cooperative ARQ Scheme Operation of proposed Cooperative ARQ scheme a source node is transmitting to a destination node a neighbor node is listening to the ongoing communication the nodes in the cooperative region become cooperative node cooperative region (d DC < d SD ) & (d SC < d SD ) Cooperative region Destination node d SD Source node Cooperative node 30
Cooperative ARQ Scheme Operation of proposed Cooperative ARQ scheme the nodes in the cooperative region store a copy of the packet until the reception of a corresponding ACK destination node transmits the NACK to the cooperative node Destination node set by power control NACK NACK when a transmitted packet is NACK acknowledged by the destination ACK node, all cooperative nodes will remove their copy Source node Cooperative node 31
Retransmission Case 1 : Cooperative ARQ Scheme packet from source node to destination node is erroneous Case 2 : Destination NACK packet from cooperative node 1 to destination node is erroneous Cooperative1 NACK ACK Cooperative2 Source Case 3 : destination node does not receive the packet from cooperative node 1 within timeout 32
요약및결론 수중음향채널에적합한 MAC 프로토콜이필요함. Energy efficient Immune to long propagation delay 코드분할다중접속방식성능분석 트리토폴로지 단일코드방식유리 주파수할당및 OFDMA 적용방안 Considering frequency dependent path-loss 거리에따른센서노드그룹핑및주파수활용범위확대 채널공유 ARQ Long propagation delay 극복 협력형 ARQ Energy efficiency improved 33
34 감사합니다.
참고문헌 [1] R. J. Urick, Principles of Underwater Sound, MaGraw-Hill, 1983 [2] I. F. Akylidiz, D. Pompili, and T. Melodis, Underwater Acoustic Sensor Networks: Research Challenges, Ad hoc Networks (Elseviar), vol. 3, no. 3, pp. 257-279, May 2005. [3] M. K. Park, UWAN-MAC: An Energy Efficient MAC Protocol for Underwater Acoustic Wireless Sensor Networks, IEEE Journal of Oceanic Engineering, Vol. 32, No. 3, pp.710-720, 2007. [4] L. Freitag, M. Stojanovic, S. Singh, and M. Johnson, Analysis of Channel Effects on Direct-sequence and Frequency-hopped Spread-spectrum Acoustic Communication, IEEE Journal of Oceanic Engineering, vol. 26, no. 4, pp. 586-593, Oct. 2001. [5] Jae-Won Lee, Jong-Pil Kim, Ji-Hye Lee, Youn Seon Jang, Kyeong Cheol Dho, Kweon Son, and Ho-Shin Cho, An Improved ARQ Scheme in underwater acoustic sensor networks, Proc. OCEANS 08, April, 2008 [6] Jong-Pil Kim, Jae-Won Lee, Youn-Seon Jang, Kweon Son, and Ho-Shin Cho, A CDMA-Based MAC Protocol in Tree-Topology for Underwater Acoustic Sensor Networks, Proc. WUnderNet, Bradford, UK, May 2009. [7] M. Stojanovic, On the relationship between capacity and distance in an underwater acoustic communication channel, in Proc. ACM WUWNet, CA, pp. 41-47, Sept., 2006. 35